Deformity Reconstruction Surgery for Blount's Disease

children

Review Deformity Reconstruction Surgery for Blount’s Disease

Craig A. Robbins

Paley Orthopedic & Spine Institute, West Palm Beach, FL 33407, USA; [email protected]; Tel.: +1-5618445255

Abstract: Blount’s disease is an idiopathic developmental abnormality affecting the medial proximal tibia physis resulting in a multi-planar deformity with pronounced tibia varus. A single cause is unknown, and it is currently thought to result from a multifactorial combination of hereditary, mechanical, and developmental factors. Relationships with vitamin D deficiency, early walking, and obesity have been documented. Regardless of the etiology, the clinical and radiographic findings are consistent within the two main groups. Early-onset Blount’s disease is often bilateral and affects children in the first few years of life. Late-onset Blount’s disease is often unilateral and can be sub-categorized as juvenile tibia vara (ages 4–10), and adolescent tibia vara (ages 11 and older). Early-onset Blount’s disease progresses to more severe deformities, including depression of the medial tibial plateau. Additional deformities in both groups include proximal tibial procurvatum, internal tibial torsion, and limb length discrepancy. Compensatory deformities in the distal femur and distal tibia may occur. When non-operative treatment fails the deformities progress through skeletal maturity and can result in pain, gait abnormalities, premature medial compartment knee arthritis, and limb length discrepancy. Surgical options depend on the patient’s age, weight, extent of physeal involvement, severity, and number of deformities. They include growth modulation procedures such as guided growth for gradual correction with hemi-epiphysiodesis and physeal closure to prevent recurrence and equalize limb lengths, physeal bar resection, physeal distraction, osteotomies with acute correction and stabilization, gradual correction with multi-planar dynamic external fixation, Citation: Robbins, C.A. Deformity and various combinations of all modalities. The goals of surgery are to restore normal joint and limb Reconstruction Surgery for Blount’s alignment, equalize limb lengths at skeletal maturity, and prevent recurrence. The purpose of this Disease. Children 2021, 8, 566. literature review is to delineate basic concepts and reconstructive surgical treatment strategies for https://doi.org/10.3390/ patients with Blount’s disease. children8070566 Keywords: Blount’s disease; infantile; early-onset; late-onset; juvenile; adolescent; tibia vara Academic Editor: Erich Rutz

Received: 16 May 2021 Accepted: 22 June 2021 1. Introduction Published: 30 June 2021 Blount’s disease is eponymous with non-physiologic tibia vara in skeletally immature Publisher’s Note: MDPI stays neutral patients. It is an idiopathic developmental abnormality affecting the medial proximal with regard to jurisdictional claims in tibia growth plate, resulting in a multiplanar deformity with pronounced tibia varus [1,2]. published maps and institutional afﬁl- The ﬁrst clinical and radiographic description of a single patient was by Erlacher in the iations. German literature in 1922 [3]. In 1937, Blount provided detailed histologic and radiographic descriptions of 13 original cases of tibia vara in the English literature [4]. He coined the term “osteochondrosis deformans tibiae” and characterized the early-onset form (herein referred to as infantile tibia vara (ITV)) that is clinically apparent before age four and the

Copyright: © 2021 by the author. late-onset form (herein referred to as late onset tibia vara (LOTV)) that develops in older Licensee MDPI, Basel, Switzerland. children prior to skeletal maturity [5]. In 1990, Thompson and Carter re-classiﬁed Blount’s This article is an open access article disease into three age-onset groups: (1) infantile: through three years of age, (2) juvenile: distributed under the terms and four to ten years of age, and (3) adolescent: 11 years or older before skeletal maturity [6]. conditions of the Creative Commons The juvenile form is the least common and exists with characteristics of the infantile and Attribution (CC BY) license (https:// late-onset forms. This discussion will utilize ITV and LOTV as the main categories of creativecommons.org/licenses/by/ Blount’s disease. 4.0/).

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ITVITV is is often often bilateral, bilateral, is is more more likely likely in in females, females, and and has has more more severe severe tibial tibial deformity deformity thanthan LOTV LOTV [ 7[7]] (Figure (Figure1 ).1). LOTV LOTV is is more more often often unilateral unilateral and and more more often often has has additional additional femoralfemoral deformitiesdeformities [[8].8]. Both Both are are more more prevalent prevalent in inBlacks, Blacks, Hispanics, Hispanics, and and Scandinavians Scandina- viansthan other than otherpopulations populations and nationalities, and nationalities, especially especially LOTV [9,10]. LOTV The [9,10 tibia]. The vara tibia is the vara pre- isdominant the predominant feature in feature limbs affected in limbs by affected Blount’s by disease Blount’s and, disease if left untreated, and, if left progresses untreated, to progressesknee deformity, to knee gait deformity, abnormalities, gait abnormalities, and premature and premature medial compartment medial compartment knee arthritis knee arthritis[11–13]. [ 11–13].

Figure 1. A 20-month-old child with ITV. Figure 1. A 20-month-old child with ITV.

2.2. Etiology Etiology and and Pathophysiology Pathophysiology AA single single cause cause for for Blount’s Blount’s disease disease is is unknown, unknown, and and it it is is currently currently thought thought to to result result fromfrom a a multifactorial multifactorial combination combination of of genetic, genetic, humoral, humoral, biomechanical, biomechanical, and and developmental developmental factorsfactors [14 [14–17].–17]. Early Early walking walking and and obesity obesity suggest sugge ast mechanical a mechanical contribution contribution to deformity to deformity in ITVin ITV [18]. [18]. LOTV LOTV is also is also linked linked with with obesity obesit [6,19y ].[6,19]. A relationship A relationship with vitaminwith vitamin D deficiency D defi- existsciency in exists all types in all [19 types–23]. Wenger[19–23]. etWenger al. proposed et al. proposed that age-related that age-related differences differences in osseous in physiologyosseous physiology lead to the lead clinically to the andclinically radiologically and radiologically distinct entities distinct of early-entities and of late-onsetearly- and diseaselate-onset [24]. disease In young [24]. children, In young the children, tibial ossification the tibial ossification center is cartilaginous center is cartilaginous and pliable; and in adolescence,pliable; in adolescence, however, the however, tibial epiphysis the tibial is well-formedepiphysis is well-formed and bony and and does bony not and deform. does Repetitivenot deform. compressive Repetitive forcescompressive across forces the medial across knee the medial in a predisposed knee in a predisposed young child young with physiologicchild with physiologic varus leads varus to a viciousleads to cyclea vicious of growth cycle of inhibition growth inhibition with worsening with worsening varus, delayedvarus, delayed ossification, ossifica andtion, deformity and deformity with characteristic with characteristic slopingof sloping the medial of the epiphysis medial epiph- [24]. Wengerysis [24]. et Wenger al. postulated et al. postulated that most casesthat most of LOTV cases occurof LOTV in children occur in with children mild with residual mild physiologicresidual physiologic genu varus. genu With varus. the With adolescent the adolescent growth growth spurt andspurt rapid and rapid weight weight gain, gain, the borderlinethe borderline varus varus suddenly suddenly worsens worsens due to adue similar to a mechanismsimilar mechanism of pressure-induced of pressure-induced growth- inhibitiongrowth-inhibition of the medial of the physis medial [24 physis]. [24]. RegardlessRegardless of of the the etiology, etiology, the the clinical clinical and and radiographic radiographic findings findings are are consistent consistent with with eacheach type type of of Blount’s Blount’s disease, disease, and and the the severity severity of of deformities deformities relates relates to to the the age age of of onset onset andand therefore therefore the the duration duration and and amount amount of growthof growth suppression suppression of the of medial the medial proximal proximal tibia physis.tibia physis. ITV is ITV characterized is characterized by more by more severe seve deformityre deformity of the of proximal the proximal tibia tibia with with medial me- plateaudial plateau depression. depression. Despite Despit the mediale the medial growth growth disturbance, disturbance, the lateral the lateral tibial physistibial physis and fibulaand fibula grow grow normally. normally. Because Because the fibulathe fibula is slightly is slightly inclined inclined in in the the sagittal sagittal plane plane (more (more posteriorposterior proximal proximal and and more more anterior anterior distal), distal), relative relative overgrowth overgrowth creates creates a a crank-shaft crank-shaft phenomenonphenomenon resulting resulting in in internal internal tibial tibial torsion torsion [5 [5].]. Schoeneker Schoeneker et et al. al. reported reported a a significant significant distaldistal femoral femoral valgus valgus in in four four of of seven seven children children with with advanced advanced ITV ITV [25 [25].]. Because Because they they begin begin atat a a later later age, age, the the deformities deformities in in LOTV LOTV are are often often less less pronounced, pronounced, and and there there is is not not the the medialmedial tibial tibial plateau plateau depression depression seen seen with with ITV ITV (Figure (Figure2). 2). Distal Distal femoral femoral varus varus is is common, common,

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andand Sabharwal Sabharwal reported reported that that it it contributes contributes up up to to one one third third of of the the total total varus varus deformity deformity in in LOTVLOTV [ 7[7–27].–27]. Increased Increased femoral femoral anteversion anteversion has has been been reported reported as as well well [ 28[28].]. As As the the knee knee deformitiesdeformities progress progress in in both both types, types, signiﬁcant significant strain strain is put is onput the on lateral the lateral collateral collateral ligament, liga- whichment, canwhich lead can to lead laxity, to jointlaxity, line joint divergence, line divergence, and knee and instability knee instability [29]. The [29]. pathologic The patho- changeslogic changes in Blount’s in Blount’s disease disease progress progress over time over todevelop time to complexdevelop complex multiplanar multiplanar deformities de- oftenformities with often additional with deformitiesadditional deformities in the same in limb. the same limb.

FigureFigure 2. 2.A A 14-year-old 14-year-old with with left-sided left-sided LOTV. LOTV.

3.3. ITV ITV Differential Differential Diagnosis Diagnosis and and Clinical Clinical Features Features Bow-legBow-leg deformity deformity in in infants infants and and children children is is common. common. The The differential differential diagnosis diagnosis inin- cludescludes metabolic metabolic conditions conditions such such as as Rickets Rickets and and renal renal osteodystrophy, osteodystrophy, congenital congenital deformity deform- suchity such as tibial as tibial hemimelia, hemimelia, genetic genetic conditions conditio suchns assuch bone as dysplasias,bone dysplasias, post-infectious post-infectious and post-traumaticand post-traumatic etiologies, etiologies, physiologic physiologic bowing, bowing, and and ITV ITV [30 [30].]. A A comprehensive comprehensive history history andand thorough thorough physical physical exam exam limit limit the the differential differential list; list; genetic genetic and and metabolic metabolic abnormalities abnormalities oftenoften involve involve additional additional organ organ systems systems and and can can affect affect the the entire entire skeletal skeletal system, system, and and the the historyhistory suggests suggests acquired acquired causes causes for for deformity. deformity. The The clinical clinical exam exam should should include include strength, strength, rotationalrotational profile, profile, joint joint range range of motion, of motion, joint stability,joint stability, neuromuscular neuromuscular function, function, limb length limb measurement,length measurement, gait pattern, gait pattern, and spine and alignment. spine alignment. PhysiologicPhysiologic bowing bowing and and ITV ITV are are often often difficult difficult to to distinguish distinguish from from each each other. other. The The combinationcombination of of hip hip flexion flexion and and external external rotation rotation with with increased increased internal internal tibial tibial torsion torsion worsenworsen the the appearanceappearance of genu genu varus varus with with kn kneeee flexion flexion in children in children with with physiologic physiologic bow- bowing.ing. TheThe salient salient clinical clinical features features in ITV in ITVare area painless a painless varus varus deformity deformity of the of theknee knee with withinternal internal tibial tibial torsion. torsion. In unilateral In unilateral cases there cases is there a leg is length a leg discrepancy. length discrepancy. There is Therea char- isacteristic a characteristic lateral thrust lateral with thrust gait, with and gait,knee andstability knee testing stability may testing show maylateral show ligamentous lateral ligamentouslaxity [15]. Often laxity there [15]. Oftenis a palpable there is prominence a palpable prominence on the medial on theproximal medial tibia proximal metaphysis tibia metaphysiscorresponding corresponding with the site with of thepathology. site of pathology. In general, In ITV general, has a ITVmore has abrupt a more deformity abrupt deformitycentered on centered the proximal on the tibia, proximal whereas tibia, phys whereasiologic physiologic bowing shows bowing a gentler shows curve a gentler affect- curveing the affecting entire leg the below entire the leg belowknee. the knee. TheThe Cover Cover Up Up test test described described by by Davids Davids et et al. al. is is an an accurate accurate clinical clinical screening screening tool tool to to differentiatedifferentiate between between physiologic physiologic bowing bowing and and ITV ITV [ 31[31].]. It It is is a a qualitative qualitative test test comparing comparing thethe clinical clinical alignment alignment of of the the distal distal thigh thigh to to the the top top portion portion of of the the leg leg with with the the child child supine supine andand the the legs legs rotated rotated so so the the patellae patellae are are forward. forward. The The middle middle portions portions of of the the thighs thighs and and legslegs are are covered covered up up so so only only the the knee knee is is visible. visible. Neutral Neutral or or varus varus alignment alignment at at the the lateral lateral kneeknee is is considered considered a a positive positive test test (Figure (Figure3) 3) and and suggests suggests the the possibility possibility of of ITV. ITV. Obvious Obvious

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valgusvalgus appearanceappearance at at the the lateral lateral knee knee is considered is considered negative negative (Figure (Figure 4) and4) andindicates indicates phys- physiologiciologicvalgus bowing.appearance bowing. In their at Inthe study, their lateralstudy, all knee patients allis considered patients with radiographic with negative radiographic (Figure ITV had 4) ITV aand positive had indicates a positivetest phys-(sen- testsitivityiologic (sensitivity =bowing. 1.00), =and In 1.00 their 18), of and study, 25 18children ofall 25 patients children with awith positive with radiographic a positivetest had testITVor developed hadhad ora positive developed ITV (positivetest ITV(sen- (positivepredictivesitivity = predictive 1.00), value and = 0.72). value 18 of A = 25 0.72).total children of A 43 total ofwith of50 43childrena positive of 50 children with test physiologic had with or physiologicdeveloped bowing ITV bowing had (positive a nega- had ativepredictive negative test (specificity testvalue (speciﬁcity = 0.72). = 0.86), A = totaland 0.86), allof and 43childre of all 50 childrenn children with a withnegative with a physiologic negative test had test physiologicbowing had physiologic had bowing a nega- bowing(negativetive test (negative (specificity predictive predictive =value 0.86), value=and 1.00). all = 1.00).childreRadiographic Radiographicn with aevaluation negative evaluation test and had androutine physiologic routine follow-up follow-up bowing are arewarranted(negative warranted predictivein any in any child childvalue with with =a 1.00).positive a positive Radiographic test test or suspicion or suspicion evaluation of ITV. of ITV. and routine follow-up are warranted in any child with a positive test or suspicion of ITV.

FigureFigure 3. 3.Positive Positive Cover Cover Up Up test test of of the the child child in in Figure Figu1re demonstrating 1 demonstrating neutral neutral or varus or varus alignment alignment at atFigure the lateral 3. Positive knee indicativeCover Up oftest ITV. of the child in Figure 1 demonstrating neutral or varus alignment the lateral knee indicative of ITV. at the lateral knee indicative of ITV.

Figure 4. Negative Cover Up test demonstrating valgus alignment at the lateral knee indicative of FigurephysiologicFigure 4. 4.Negative Negative genu varus. Cover Cover Up Up test test demonstrating demonstrating valgus valgus alignment alignment at at the the lateral lateral knee knee indicative indicative of of physiologic genu varus. physiologic genu varus. 4. Radiographic Imaging 4. Radiographic Imaging 4. RadiographicA standard ImagingX-ray series at our institute included full-length standing frontal and lateral Aradiographs.A standard standard X-ray X-ray For seriesthe series AP at at ourview, ou instituter theinstitute patellas included included are full-lengthrotated full-length in standinga forward standing frontal position frontal and (Figureand lateral lat- radiographs.5),eral the radiographs. beam is For centered theFor AP the at view, APthe view,knee, the patellas theand patellas bloc areks rotatedareare used rotated in under a in forward a a forward shorter position limbposition to (Figure level (Figure 5the), thepelvis.5), beamthe Inbeam islarge centered is patientscentered at it the at is the knee,often knee, necessary and and blocks bloc toks areimage are used used each under underleg individually a shortera shorter limb limb in the to to levelAP level view. the the pelvis.Weight-bearingpelvis. In In large large patients patients films may it it is is demonstrate often often necessary necessary knee to to joint image image laxity each each with leg leg individually individuallywidening of in thein the the lateral AP AP view.view. joint Weight-bearingspace.Weight-bearing Standing films APfilms and may may lateral demonstrate demonstrate images kneecenter knee joint jointed on laxity laxity the withknee with wideningon widening cassettes of of thelong the lateral lateral enough joint joint to space.includespace. Standing Standing the entire AP AP tibia and and are lateral lateral taken images images as well. centered center CT andedon MRIon the the can knee knee be onuseful on cassettes cassettes to define long long the enough enough anatomy to to includeofinclude joint thesurfaces the entire entire and tibia tibia physes. are are taken taken Rotation as as well. well. profile CT CT and and CT MRI MRIscans can can can be be quantify useful useful to to torsional define define the the abnormali- anatomy anatomy oftiesof joint joint above surfaces surfaces and below and and physes. physes.the knee. Rotation Rotation profile profile CT CT scans scans can can quantify quantify torsional torsional abnormalities abnormali- aboveties above andbelow and below the knee. the knee.

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Figure 5. Correct position for AP standing X-ray with patella rotated forward [32]. Figure 5. Correct position for AP standing X-ray with patella rotated forward [32]. 5. Radiographic Analysis 5. RadiographicA line drawn fromAnalysis the center of the femoral head to the center of the ankle deﬁnes the load-bearingA line drawn mechanical from the axis center of the lowerof the extremity femoral (Figure head6 ).to This the axis center is superior of the ankle defines to the historic tibial–femoral shaft angle (Figure7) described by Salenius and Vannka [ 33] thefor evaluationload-bearing of lower mechanical extremity alignmentaxis of the [34 lower]. Radiographic extremity deformity (Figure analysis 6). This begins axis is superior to thewith historic the malalignment tibial–femoral test to identifyshaft angle the mechanical (Figure 7) axis described deviation. by Joint Salenius orientation and Vannka [33] forangles evaluation are measured of lower to identify extremity the locations alignment and quantify [34]. Radiographic angular deformities deformity based on analysis begins withpopulation the malalignment norms [32,35]. Standardtest to identify coronal plane the mech measurementsanical axis include deviation. the mechanical Joint orientation an- axis deviation (MAD), femoro–tibial angle, neck shaft angle (NSA), mechanical lateral gles are measured to identify the locations and quantify angular deformities based on distal femoral angle (mLDFA), knee joint line congruency angle (JLCA), medial proximal populationtibial angle (MPTA), norms tibial[32,35]. metaphyseal–diaphyseal Standard coronal plane angle (MDA)measurements if very young, include medial the mechanical axistibial deviation plateau depression (MAD), angle femoro–tibial (if present), andangle, lateral neck distal shaft tibial angle angle (NSA), (LDTA). mechanical Standard lateral dis- talsagittal femoral plane angle measurements (mLDFA), include knee the anatomicjoint line posterior congruency distal femoral angle angle (JLCA), (aPDFA), medial proximal tibialanatomic angle posterior (MPTA), proximal tibial tibial metaphyseal–diap angle (aPPTA), andhyseal the anatomic angle posterior (MDA) distal if very tibial young, medial angle (aPDTA) [36]. tibial plateau depression angle (if present), and lateral distal tibial angle (LDTA). Standard sagittal plane measurements include the anatomic posterior distal femoral angle (aPDFA), anatomic posterior proximal tibial angle (aPPTA), and the anatomic posterior distal tibial angle (aPDTA) [36].

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FigureFigure 6. (Left): 6. (Left Coronal): Coronal plane plane illustration illustration of the of lo thewer lower extremity, extremity, demonstrating demonstrating the mechanical the mechanical axis axis deviation (MAD), the lateral distal femoral angle (LDFA), the joint–line congruency angle Figure 6. (Left): Coronal plane illustration of the lower extremity, demonstrating the mechanical (JLCA),deviation the medial (MAD), proximal the lateral tibial angle distal (MPTA), femoral an angled the (LDFA),lateral distal the tibial joint–line angle (LDTA). congruency (Right): angle (JLCA), axis deviation (MAD), the lateral distal femoral angle (LDFA), the joint–line congruency angle Sagittalthe medial plane illustration proximal tibialof the angle proximal (MPTA), part of and the thetibia lateral and the distal distal tibial part of angle the femur, (LDTA). demon- (Right): Sagittal (JLCA), the medial proximal tibial angle (MPTA), and the lateral distal tibial angle (LDTA). (Right): strating the posterior proximal tibial angle (PPTA) [29]. Sagittalplane plane illustration illustration of of the the proximal proximal part of the the tibia tibia and and the the distal distal part part of the ofthe femur, femur, demon- demonstrating the stratingposterior the posterior proximal proximal tibial tibial angle angle (PPTA) (PPTA) [29 [29].].

Figure 7. Illustration of the tibiofemoral angle as described by Salenius and Vankka [37]. FigureFigure 7. Illustration 7. Illustration of the tibiofemoral of the tibiofemoral angle as described angle as by described Salenius byand Salenius Vankka [37]. and Vankka [37].

6. Diagnosis Radiographic imaging can be used to diagnose ITV and help distinguish it from physiologic bowing, and metabolic, genetic, and acquired causes such as those due to trauma and infection in young children. A metabolic work-up may be indicated to evaluate for causative factors such a vitamin deﬁciency. True physiologic bowing is characterized by a varus mechanical alignment with otherwise normal appearing standing X-rays. ITV has a Children 2021Children, 8, x 2021FOR, PEER8, x FOR REVIEW PEER REVIEW 7 of 27 7 of 27

6. Diagnosis6. Diagnosis RadiographicRadiographic imaging imaging can be usedcan be to useddiagnose to diagnose ITV and ITV help and distinguish help distinguish it from it from Children 2021, 8, 566 physiologicphysiologic bowing, bowing, and metabolic, and metabolic, genetic, genetic, and acquired and acquired causes suchcauses as suchthose as due those to due7 of 25to trauma traumaand infection and infection in young in children. young children. A metabolic A metabolic work-up work-up may be mayindicated be indicated to evalu- to evaluate for causativeate for causative factors suchfactors a vitamin such a vitamin deficiency. deficiency. True physiologic True physiologic bowing bowingis character- is characterized by izeda varus by amechanical varus mechanical alignment alignment with otherwise with otherwise normal normalappearing appearing standing standing X-rays. X-rays. spectrum of characteristic radiographic changes (Figure8) including radiolucency, sclerosis, ITV hasITV a spectrum has a spectrum of characteristic of characteristic radiographic radiographic changes changes (Figure (Figure8) including 8) including radiolu- radiolu- apparent fragmentation, and angulation of the medial proximal tibia [4,38]. Levine and cency, sclerosis,cency, sclerosis, apparent apparent fragmentation, fragmentation, and angulation and angulation of the medialof the medialproximal proximal tibia tibia Drennan measured the metaphyseal diaphyseal angle (MDA) (Figure9) of the proximal [4,38]. Levine[4,38]. andLevine Drennan and Drennan measured measured the metaphyseal the metaphyseal diaphyseal diaphyseal angle (MDA) angle (MDA)(Figure (Figure tibia in standing radiographs and concluded that patients with angles ≥ 11◦ were more 9) of the9) proximal of the proximal tibia in standingtibia in standing radiogra radiographs andphs concluded and concluded that patients that patients with angles with angles likely to progress to ITV [39]. Feldman and Schoenecker reported that MDA angles ≤ 9◦ ≥ 11° were≥ 11° more were likely more to likely progress to progress to ITV [39].to ITV Feldman [39]. Feldman and Schoenecker and Schoenecker reported reported that that suggest physiologic varus, and angles ≥ 16◦ are indicative of ITV [37]. MDA anglesMDA ≤ angles 9° suggest ≤ 9° suggestphysiologic physiologic varus, and varus, angles and ≥ angles 16° are ≥ indicative16° are indicative of ITV [37]. of ITV [37].

Figure 8.FigureFigure Standing 8. 8.Standing Standing X-ray of X-ray X-raythe 20-month-old of of the the 20-month-old 20-month-old child in childFigurechild inin 1 Figure Figurewith 1bilateral 1with with bilateral bilateralITV; MDA ITV; ITV; right MDA MDA 22°, right right 22 22°,◦, MDA left 16°. MDA leftMDA 16°. left 16◦.

Figure 9.FigureFigure Illustration 9. 9.Illustration Illustration of the metaphyseal–diaphyseal of of the the metaphyseal–diaphyseal metaphyseal–diaphyseal angle (MDA) angle angle (MDA) of (MDA) Levine of Levineof and Levine Drennan. and and Drennan. Drennan. The an- The The angle angle lies liesbetweengle betweenlies betweena line a linedrawn a drawnline through drawn through throughthe themost most the distal most distal point distal point on point onthe the medial on medial the and medial and lateral lateral and beaks lateral beaks of beaks ofthe the of tibia the tibia metaphysis and a line perpendicular to the lateral cortex of the tibia [37]. tibia metaphysismetaphysis and and a line a line perpendicular perpendicular to tothe the lateral lateral cortex cortex of ofthe the tibia tibia [37]. [37 ].

7. Staging Langenskiöld described a radiographic classiﬁcation (Figure 10) of changes to the medial proximal tibia epiphysis, physis, and metaphysis in ITV [14,38,40]. Deformity progresses with age through six stages culminating with complete closure of the medial physis

and significant deformity. Although significant inter-observer variability has been reported, particularly in the middle stages (III–IV), the Langenskiöld classification system provides the clinician with a prognostic tool and general guidelines for treatment. In general, the Children 2021, 8, x FOR PEER REVIEW 8 of 27

7. Staging Langenskiöld described a radiographic classification (Figure 10) of changes to the medial proximal tibia epiphysis, physis, and metaphysis in ITV [14,38,40]. Deformity pro- Children 2021, 8, 566 gresses with age through six stages culminating with complete closure of the medial phy- 8 of 25 sis and significant deformity. Although significant inter-observer variability has been reported, particularly in the middle stages (III–IV), the Langenskiöld classification system provides the clinician with a prognostic tool and general guidelines for treatment. In gen- earliereral, stagesthe earlier (I–III) stages have (I–III) more have potential more potential for spontaneous for spontaneous resolution, resolution, and and the the latter latter stages (IV–VI)stages have (IV–VI) more have potential more potential for deformity for deformity progression progression [41–43 [41–43].]. MRI ﬁndingsMRI findings correlate cor- with radiographs,relate with butradiographs, the expense but the and expense need forand sedation need for insedation toddlers in toddlers make this make impractical this im- for practical for most diagnostic uses [44]. most diagnostic uses [44].

FigureFigure 10. Diagram 10. Diagram of radiographic of radiographic changes changes seen seen in the in infantile the infantile type ty ofpe tibia of tibia vara vara and and their their development development with with increasing increasing age [41]. age [41]. 8. Natural History 8. Natural History The natural clinical proﬁle of physiologic bowing (Figure 11) is maximal varus around The natural clinical profile of physiologic bowing (Figure 11) is maximal varus 16 months moving into valgus by age 3 to 4 years and then neutral alignment achieved around 16 months moving into valgus by age 3 to 4 years and then neutral alignment around age 6–8 years of age [33]. The natural history of ITV is towards deformity progres- achieved around age 6–8 years of age [33]. The natural history of ITV is towards deformity sionprogression in the majority in the ofmajority affected of children,affected child butren, spontaneous but spontaneous resolution resolution has been has reportedbeen re- [43]. Children 2021, 8, x FOR PEER REVIEW Asported varus [43]. deformity As varus increases, deformity theincreases, mechanical the mechanical axis moves axis moves further further from from midline midline9 of and 27 in-

creasesand increases forces across forces the across medial the compartmentmedial compartment of the of knee. the knee. This canThis lead can tolead development to devel- of osteoarthritisopment of osteoa [45–47rthritis]. [45–47].

FigureFigure 11. The 11. Thedevelopment development of the of tibiofemoral the tibiofemoral angle angle in children in children during during growth growth [33]. [33 ].

9. Non-Operative9. Non-Operative Treatment Treatment In aIn young a young child child with with suspected suspected ITV ITV but butno clear no clear clinical clinical or radiographic or radiographic diagnostic diagnostic criteria,criteria, a short a short trial trialof observation of observation is warran is warranted.ted. Spontaneous Spontaneous resolution resolution of early of ITV early has ITV beenhas described been described but the majority but the majority of cases progress. of cases progress. At the moment At the of moment any clinical of any or clinicalradio- or graphicradiographic evidence evidenceof progression, of progression, brace treatment brace treatment should be should initiated be immediately. initiated immediately. Gen- eralGeneral bracing bracingguidelines guidelines are for children are for childrenunder 3 underyears of 3 yearsage with of age early with ITV early (I or ITVII) in (I or whomII) ina brace whom can a be brace adequately can be adequately fit and regularly ﬁt and worn. regularly Birch’s worn. criteria Birch’s for anti-varus criteria forlong anti- leg bracing during ambulation is for patients aged ≤ 3 years with progressive deformity, clear radiographic evidence of ITV, or lateral thrust with ambulation [15]. Loder and John- son found a 50% brace failure in children with stage I and II infantile Blount’s disease. Their recommendations were for children between 1½–2 ½ years of age, worn during weight-bearing to decrease compressive forces, and if not corrected after one year to proceed with surgery [48]. Authors report limited success with bracing due to multiple factors including compliance and obesity [1,49,50]. Bracing is not indicated in stages III and higher as it is ineffective and delays surgery.

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varus long leg bracing during ambulation is for patients aged ≤ 3 years with progressive deformity, clear radiographic evidence of ITV, or lateral thrust with ambulation [15]. Loder and Johnson found a 50% brace failure in children with stage I and II infantile Blount’s disease. Their recommendations were for children between 11/2–21/2 years of age, worn during weight-bearing to decrease compressive forces, and if not corrected after one year to proceed with surgery [48]. Authors report limited success with bracing due to multiple factors including compliance and obesity [1,49,50]. Bracing is not indicated in stages III and higher as it is ineffective and delays surgery.

10. Surgical Planning The most common indication for surgery in ITV is progressive deformity with failure of conservative treatment in Langenskiöld I and II. With advanced stages, immediate surgery is indicated. The goals of surgery are to restore normal joint and limb alignment, equalize limb lengths at skeletal maturity, and prevent recurrence. The reconstructive surgical plan is formulated after a comprehensive evaluation of the patient clinically, radiographically, and psychosocially. Current problems are itemized and future problems such as acquired limb length discrepancy are predicted [51]. The patient’s age, weight, stage, severity, and number of deformities may indicate which procedures have the greatest chance for success. Psychosocial factors such as reliable transportation for routine follow-up may limit which procedures are feasible. Post-operative issues must be considered as part of the preoperative plan. These include the method of surgical site stabilization, patient mobilization, hygiene and grooming, prevention of joint contractures, and ability to understand and comply with complex instructions such as external ﬁxator care and adjustments. Surgical options for ITV include growth modulation such as guided growth for gradual correction with hemi-epiphysiodesis and physeal closure to prevent recurrence and equalize limb lengths, physeal arrest resection, physeal distraction, osteotomies with acute correction and stabilization, osteotomies with gradual correction with external ﬁxation, and various combinations of all modalities. To avoid under-correction, overcorrection, and creation of iatrogenic deformities, a thorough analysis of all deformities away from the proximal tibia is paramount [7]. The surgical plan should consider staging complex reconstructions to minimize and overlap surgical procedures. For example, guided growth of modest femoral deformity can be combined with acute or gradual correction of the tibia/fibula [52]. Acute correction is reserved for moderate deformities to avoid risk of soft tissue compromise or neurovascular insult with the understanding that internal fixation requires a more aggressive and invasive surgery, and postoperative adjustments are not possible. External fixation allows gradual correction and refinement of complex deformities.

11. Hemi-Epiphysiodesis Hemi-epiphysiodesis, also called “guided growth”, induces angular correction at the physis through the Hueter–Volkman principal, whereby compressive forces across a physis inhibit growth, and tensile forces across a physis stimulate growth [53–55]. Several open and percutaneous techniques exist, including irreversible partial growth plate destruction, staples, screws, and tension bands. The later techniques are considered reversible in that growth will resume after the hardware is removed [56]. Hemi-epiphysiodesis is contraindicated in conditions that will self-correct, and the surgeon must understand the differences between physiologic and pathologic deformities [52]. Hemi-epiphysiodesis is indicated for angular correction in early-stage infantile Blount’s disease prior to pathologic medial physeal bar formation. Over the past 15 years, lateral tension band hemi-epiphysiodesis with a two hole plate and cannulated screws (Figure 12) has become a popular method for guided growth [52]. This technique has beneﬁts over staples and open irreversible hemi-epiphysiodesis. The implants do not loosen or migrate, a common complication with staples, but early reports found a high failure rate with small diameter titanium screws in obese patients with Blount’s disease. Larger stainless steel screws are now available [57–59]. Because these Children 2021, 8, 566 10 of 25

implants are placed outside the periosteum and do not violate the physis, they maximize their effective fulcrum and are reversible if removed. Helfing reported on 27 patients under 4 years of age who had spontaneous resolution of tibial torsion with angular correction [60]. Scott reported an 89% success rate with lateral tension-band plating on 18 limbs in 12 children with Langenskiöld I or II ITV. Burghardt et al. reviewed the Blount’s disease literature and reported the main problems with lateral tension band are under-correction and poor predictability of correction amount. However they concluded that given the low technical difficulty and morbidity, guided growth with lateral tension band plating is the gold standard of care and should be the first treatment attempted; in the event of under-correction, osteotomies should be considered the salvage procedures [58]. Bushnel commented that the surgeon must weigh the safety and simplicity of this procedure against the much more extensive but much more predicable realignment obtained with osteotomy procedures [61]. Westburty et al. concluded that the goals of hemi-epiphysiodesis in ITV and LOTV include (1) correction of deformity to avoid need for osteotomy, and (2) prevention of progression of the deformity to facilitate subsequent surgery [62]. Assan asserted that guided growth Children 2021, 8, x FOR PEER REVIEWremains the best treatment for early ITV, and that the tibial osteotomy should be11 reserved of 27 for neglected forms or those close to skeletal maturity [63].

FigureFigure 12.12. TheThe child child in inFigure Figure 1 with1 with ITV ITV10 months 10 months after bilateral after bilateral lateral hemi-epiphysiodesis lateral hemi-epiphysiodesis showing interval correction of varus. showing interval correction of varus. 12. Physeal Arrest Resection 12. Physeal Arrest Resection The growth disturbance of the proximal medial tibia in ITV behaves initially like a The growth disturbance of the proximal medial tibia in ITV behaves initially like a partial growth arrest and progresses to form a medial physeal bar and ultimately complete partialmedial growth arrest [14]. arrest MRI and and progresses CT scan can to formbe used a medial to accurately physeal map bar the and location ultimately and completequan- medialtify the arrest size of [14 a]. physeal MRI and disturbance CT scan can[64]. beResection used to of accurately the pathologic map thearrest, location called and quantifyepiphysiolysis the size (Figure of a physeal 13), candisturbance theoretically [64result]. Resection in resumption of the of pathologic normal growth arrest, and called epiphysiolysisprevent additional (Figure deformity. 13), can theoretically result in resumption of normal growth and prevent additional deformity. Andrade reviewed 27 limbs in 24 patients aged 5–10 who underwent medial epiphysiolysis combined with valgus osteotomy. Epiphysiolysis was performed through a medial oblique incision and involved removing the pathologic Blount lesion (the medial extent of the metaphysis, physis, and epiphysis to the weight bearing portion of the medial tibial plateau) from anterior to posterior. They resected to healthy physis, interposed cranioplast over the denuded bone surfaces, and performed a closing wedge metaphyseal tibial

Figure 13. (A) A 6-year-old female with untreated stage IV ITV; the metaphyseal bone and Blount lesion to be excised is outlined; (B) 3D CT showing extent of abnormal depressed epiphyseal bone anteriorly. The "cleft" on the anterior surface of the metaphysis (arrow) is where the initial resection for epiphysiolysis begins. (C) After interposition of cranioplast at the site of resection and stabilization of a closing wedge tibial osteotomy. The bovie cord defines the lateral mechanical axis [65].

Andrade reviewed 27 limbs in 24 patients aged 5–10 who underwent medial epiphysiolysis combined with valgus osteotomy. Epiphysiolysis was performed through a medial

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Figure 12. The child in Figure 1 with ITV 10 months after bilateral lateral hemi-epiphysiodesis show- ingosteotomy interval correction into an over-corrected of varus. valgus alignment. The procedure was >80% successful in resuming growth and preventing recurrence in children under 7 years of age. They 12.recommended Physeal Arrest alternative Resection procedures in patients who failed previous procedures or who wereThe older growth than agedisturbance 7 [65]. Beck of the reported proximal favorable medial results tibia in threeITV behaves patients initially with stage like VI a partiallesions growth who underwent arrest and physeal progresses bar to resection form a medial with interposition physeal bar (twoand ultimately fat, one cranioplast) complete medialand valgus arrest producing [14]. MRI osteotomy and CT scan of the can proximal be used tibiato accurately and ﬁbula map [66 ].the Birch location reported and usefulquan- tifyresumption the size of of growth a physeal in 7 ofdisturbance 13 patients after[64]. resectionResection of of Stage the VIpathologic lesions [15 arrest,]. Loder called and epiphysiolysisJohnson resected (Figure physeal 13), barscan theoretically with methylmethacrylate result in resumption interposition of normal in three growth children and preventwith one additional good, one deformity. fair, and one poor result [48].

Figure 13. (A) A 6-year-old female with untreated stage IV ITV; the metaphyseal bone and Blount lesion to be excised is outlined; (B)) 3D3D CTCT showingshowing extentextent of of abnormal abnormal depressed depressed epiphyseal epiphyseal bone bone anteriorly. anteriorly. The The “cleft” "cleft on" on the the anterior anterior surface surface of of the metaphysis (arrow) is where the initial resection for epiphysiolysis begins. (C) After interposition of cranioplast at the metaphysis (arrow) is where the initial resection for epiphysiolysis begins. (C) After interposition of cranioplast at the the site of resection and stabilization of a closing wedge tibial osteotomy. The bovie cord defines the lateral mechanical site of resection and stabilization of a closing wedge tibial osteotomy. The bovie cord deﬁnes the lateral mechanical axis [65]. axis [65].

13. OsteotomiesAndrade reviewed with Acute 27 limbs Correction in 24 patients aged 5–10 who underwent medial epiphys- iolysisProximal combined tibia with and valgus fibular osteotomy. osteotomies Epiphysiolysis are indicated was for performed patients with through ITV who a medial have failed previous surgery or are not candidates for less invasive forms of surgery such as guided growth (Figure 14). These include patients with advanced stages (IV–VI) of pathology who have a functional medial physeal tether that would preclude correction with simple guided growth. In general, osteotomy is indicated when a rapid complete correction is desired or when it is preferable not to operate on the physis [67]. There is no consensus in the literature regarding the ideal alignment of the lower extremity after surgical reconstruction for Blount’s disease [7], but most authors recommend over- correcting ITV into valgus before age 4 to offload the medial physis [4,14,68–70]. The tibial osteotomy is performed below the tibial tubercle, and several options exist including opening wedge, closing wedge, dome-type, W/M serrated, and oblique. Tibial osteotomies can be open or percutaneous. Fibular osteotomies are performed under direct visualization in the proximal half to avoid peroneal nerve injury [71]. Percutaneous tibial osteotomies are safe, simple, quick, reliable, and minimally invasive [72]. Open tibial osteotomies require extensile exposure and require expert planning and carpentry to accurately correct multiplanar deformities. Closing wedges loose length, and open wedges may require bone grafting. Dome-type osteotomies make rotational correction difficult, whereas the obliquely inclined Rab-type osteotomy allows simultaneous correction of varus and internal torsion [73]. The serrated W/M osteotomy described by Khermosh and Wientraub [74] requires accurate pre-operative planning and intra-operative osteotomy carpentry to allow for correction of rotation and up to 25 degrees of angulation through an Children 2021, 8, x FOR PEER REVIEW 12 of 27

oblique incision and involved removing the pathologic Blount lesion (the medial extent of the metaphysis, physis, and epiphysis to the weight bearing portion of the medial tibial plateau) from anterior to posterior. They resected to healthy physis, interposed cranioplast over the denuded bone surfaces, and performed a closing wedge metaphyseal tibial osteotomy into an over-corrected valgus alignment. The procedure was >80% successful in resuming growth and preventing recurrence in children under 7 years of age. They recommended alternative procedures in patients who failed previous procedures or who were older than age 7 [65]. Beck reported favorable results in three patients with stage VI lesions who underwent physeal bar resection with interposition (two fat, one cranioplast) and valgus producing osteotomy of the proximal tibia and fibula [66]. Birch reported useful resumption of growth in 7 of 13 patients after resection of Stage VI lesions [15]. Loder and Johnson resected physeal bars with methylmethacrylate interposition in three children with one good, one fair, and one poor result [48].

13. Osteotomies with Acute Correction Proximal tibia and fibular osteotomies are indicated for patients with ITV who have failed previous surgery or are not candidates for less invasive forms of surgery such as Children 2021, 8, 566 guided growth (Figure 14). These include patients with advanced stages (IV–VI)12 of of pa- 25 thology who have a functional medial physeal tether that would preclude correction with simple guided growth. In general, osteotomy is indicated when a rapid complete correction is desired or when it is preferable not to operate on the physis [67]. There is no con- extensilesensus in approach the literature to the regarding tibia. Internal the ideal ﬁxation alignment is not needed of the aslower the metaphyseal extremity after osteotomy surgical fragmentsreconstruction are interlocked for Blount’s and disease are inherently [7], but most stable. authors The limb recommend is immobilized over-correcting in plaster ITV of Paris. Healing is rapid due to the large metaphyseal surface area. into valgus before age 4 to offload the medial physis [4,14,68–70].

FigureFigure 14. 14.A A 4-year-old4-year-old with with II/III II/III ITVITV withwith acuteacute over-correctionover-correction intointo valgus.valgus.

IfThe fibular tibial shortening osteotomy is is anticipated performed withbelow the the correction, tibial tubercle, an oblique and several fibular options osteotomy exist isincluding performed opening to allow wedge, for shortening,closing wedge, or a dome diaphyseal-type, W/M segment serrated, is removed and oblique. [36]. Tibial Care isosteotomies taken to avoid can be injury open to or the percutaneous. peroneal nerve Fibular and osteotomies its branches are [71 pe],rformed and a prophylactic under direct peronealvisualization nerve in decompression the proximal andhalf fasciotomyto avoid peroneal should benerve considered injury [71]. with Percutaneous rotational or largetibial angularosteotomies corrections are safe, [75 simple,]. The removed quick, reliable, fibular and segment minimally can be invasive used as an[72]. autograft Open tibial with os- a concomitant medial hemi-plateau elevation osteotomy. Angular and rotational deformities can be acutely corrected and stabilized with internal or external fixation. Coronal plane instability may improve after acute correction with realignment and fibular shortening [76]. Osteotomy stabilizing options range from simple casting, pins in plaster, internal fixation with plate and screws, to external fixation, or a combination. The choice of stabilization depends on the patient’s age, size, weight, and mobility. Complications from tibia and fibular osteotomies include vascular injury, compartment syndrome, delayed union, nonunion, hardware failure, infection, recurrence, and peroneal nerve palsy. With acute correction and internal fixation under-correction, overcorrection, and loss of correction can occur. In early stages of ITV, overcorrection into 5–10◦ of valgus is performed to unload the medial physis. Casting and protected weight bearing further unload the medial physis and may allow spontaneous correction of the physeal insult [15]. If an initial procedure fails or the child has advanced stage disease, the reconstruction becomes more complex as the articular and proximal tibial deformity progresses (Figure 15). The surgeon must perform epiphysiodesis of the lateral proximal tibia and entire proximal fibular physis to prevent recurrence of deformity. Limb length equalization must be planned with shoe lift, contralateral epiphysiodesis, ipsilateral lengthening, or a combination. If the valgus overcorrection does not spontaneously correct, a guided growth procedure can be performed at a later date to improve alignment. Prognostic factors for failure and recurrence of deformity in ITV include age > 4, increased stage (>II), obesity, and failure to over-correct into 5–10◦ of valgus [77]. Maré et al. Children 2021, 8, 566 13 of 25

reported that significant pre-operative medial plateau depression (>60◦) and post-operative knee instability with varus alignment increased the risk of recurrence [78]. Loder and Johnson reported that a single valgus osteotomy was successful in 60–75% of children under age 4, while in older children, repeat osteotomies are needed in 60–65% of cases [48]. Ferriter et al. also noted that the recurrence of deformity is higher above age 4 and occurs over time [79]. Andrade concluded that even though a discrete bony bridge cannot be demonstrated, there is significant enough growth disturbance of the medial physis in tibias with Langenskiöld III or greater, that unloading with valgus osteotomy will fail [65]. Although Rab had good short-term results with 15 months of follow-up, later studies showed a 60% recurrence rate with longer follow-up [63]. Percutaneous osteotomy with acute correction and external fixator does not allow length correction but it does allow immediate weight bearing with a minimally invasive technique. Depending on the type of fixator, alignment can be adjusted postoperatively in clinic or in the operating room. In 2000, Smith et al. performed acute correction on Children 2021, 8, x FOR PEER REVIEW23 extremities with an Orthofix fixator with overall good results [2]. In 2006, Feldman14 of 27

compared 14 patients with acute correction stabilized with an EBI external fixator to 18 who underwent gradual correction with a Taylor spatial frame hexapod fixator and concluded gradualgradual correction correction was was more more accurate accurate [80 [80].]. Current Current hexapod hexapod fixators fixators allow allow simultaneous simultaneous correctioncorrection of of multiplanar multiplanar deformities, deformities, including including length. length.

Figure 15. A 7-year-old child who failed acute valgus-producing osteotomy due to medial physeal Figure 15. A 7-year-old child who failed acute valgus-producing osteotomy due to medial physeal bar formation; note the medial tibial plateau depression and limb length discrepancy. bar formation; note the medial tibial plateau depression and limb length discrepancy. 14. Hemi-Plateau Elevation Osteotomy Depression of the medial tibial plateau can occur in the later stages of ITV when there is a functional or actual bridge across the medial physis. The deformity may appear worse on radiographs than it actually is due to the presence of unossified cartilaginous material [15]. MRI and intra-operative arthrography can be useful to define anatomy. Langenskiöld and Riska recommended hemi-plateau elevation osteotomy for late presenting ITV in 1964 [40]. Stanitski et al. did not. They evaluated 17 tibiae in 10 patients aged 3–8 with severe ITV (stage III or higher) and found no tibia had depressions on arthrograms in 11 knees or MRI in 17 knees. They reported the “empty” space seen radiographically had cartilage- density material [81]. This study has not been repeated. Several authors reported that medial plateau elevation osteotomy is an important reconstructive option in late-stage ITV [25,82,83]. The medial tibial plateau depression angle (Figure 16) can be measured and quantified with intra-operative fluoroscopy and arthrogram. The articular deformity is corrected with an oblique osteotomy originating in the axilla of the metaphyseal beak and extending into the intercondylar area (Figure 17). Increased posterior depression can be differentially corrected with rotation in the sagittal plane. Barka et al. recently described an "inside-out"

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14. Hemi-Plateau Elevation Osteotomy Depression of the medial tibial plateau can occur in the later stages of ITV when there is a functional or actual bridge across the medial physis. The deformity may appear worse on radiographs than it actually is due to the presence of unossified cartilaginous material [15]. MRI and intra-operative arthrography can be useful to define anatomy. Langenskiöld and Riska recommended hemi-plateau elevation osteotomy for late presenting ITV in 1964 [40]. Stanitski et al. did not. They evaluated 17 tibiae in 10 patients aged 3–8 with severe ITV (stage III or higher) and found no tibia had depressions on arthrograms in 11 knees or MRI in 17 knees. They reported the “empty” space seen radiographically had cartilage-density material [81]. This study has not been repeated. Several authors reported that medial plateau elevation osteotomy is an important reconstructive option in late-stage Children 2021, 8, x FOR PEER REVIEW 15 of 27 ITV [25,82,83]. The medial tibial plateau depression angle (Figure 16) can be measured and quantified with intra-operative fluoroscopy and arthrogram. The articular deformity is corrected with an oblique osteotomy originating in the axilla of the metaphyseal beak and extending into thetechnique intercondylar using area a (Figuregigli saw 17). to Increased perform posterior the oste depressionotomy to can avoid be differentially the risk of intra-articular correctedfracture with and rotation medial in thecondyle sagittal displacement plane. Barka et al. [8 recently4]. The described open-wedge an “inside-out” defect is bone-grafted, techniqueand the usingosteotomy a gigli saw stabilized to perform with the osteotomyinternal or to external avoid the riskfixation. of intra-articular This osteotomy is rarely fractureperformed and medial alone condyle and is displacementcombined with [84]. addition The open-wedgeal procedures defect is bone-grafted,to acutely or gradually cor- andrect the residual osteotomy deformities stabilized with such internal as tibia or external vara, tibial fixation. torsion, This osteotomy procurvatum, is rarely and limb length performed alone and is combined with additional procedures to acutely or gradually correctdiscrepancy. residual deformities In ITV, medial such as plateau tibia vara, elevatio tibial torsion,n osteotomy procurvatum, should and limb be combined length with lateral discrepancy.epiphysiodesis In ITV, of medial the plateauproximal elevation tibia osteotomyto complete should the be tibial combined physeal with lateralarrest and epiphysi- epiphysiodesisodesis of the of theproximal proximal fibula tibia to completeto prevent the tibial asymmetric physeal arrest growth and epiphysiodesis and deformity recurrence of(Figure the proximal 18). fibula to prevent asymmetric growth and deformity recurrence (Figure 18).

FigureFigure 16. 16.The The medial medial tibial plateau tibial depressionplateau depression angle (α) is measured angle (α between) is measured a tangent between to the lateral a tangent to the lat- plateaueral plateau and medial and plateau; medial the plateau; osteotomy the aims osteot towardsomy the aims intercondylar towards notch.the intercondylar notch.

Figure 17. The osteotomy is complete and held in a corrected position to restore the medial joint line; the iliac crest allograft is impacted in the opening wedge.

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technique using a gigli saw to perform the osteotomy to avoid the risk of intra-articular fracture and medial condyle displacement [84]. The open-wedge defect is bone-grafted, and the osteotomy stabilized with internal or external fixation. This osteotomy is rarely performed alone and is combined with additional procedures to acutely or gradually correct residual deformities such as tibia vara, tibial torsion, procurvatum, and limb length discrepancy. In ITV, medial plateau elevation osteotomy should be combined with lateral epiphysiodesis of the proximal tibia to complete the tibial physeal arrest and epiphysiodesis of the proximal fibula to prevent asymmetric growth and deformity recurrence (Figure 18).

Children 2021, 8, 566 15 of 25 Figure 16. The medial tibial plateau depression angle (α) is measured between a tangent to the lateral plateau and medial plateau; the osteotomy aims towards the intercondylar notch.

Children 2021, 8, x FOR PEER REVIEW 16 of 27 FigureFigure 17. 17.The The osteotomy osteotomy is complete is complete and held in and a corrected held in position a corre tocted restore position the medial to joint restore line; the medial joint theline; iliac the crest iliac allograft crest is allograft impacted is in impacted the opening in wedge. the opening wedge.

FigureFigure 18. The 18. osteotomy The osteotomy and allograft and are allograft stabilized with are screws; stabilized the proximal with tibia screws; epiphysiode- the proximal tibia epiphysiodesis sisis is completed completed by placingby placing a lateral tensiona lateral band totension prevent recurrence;band to aprevent percutaneous recurrence; ablative a percutaneous ablative epiphysiodesis of the proximal fibula was performed. epiphysiodesis of the proximal fibula was performed. 15. Combined Osteotomies 15.In Combined late-stage or neglected Osteotomies ITV, there is often significant depression of the medial tibial plateau in addition to procurvatum, tibial torsion, and tibia vara. Multiple authors have reportedIn good late-stage results performing or neglected combined ITV, osteotomies there andis often procedures significant including acutedepression of the medial tibial elevationplateau of thein medialaddition plateau, to metaphysealprocurvatum, osteotomy tibial of the to tibiarsion, (and fibula)and tibia for acute vara. Multiple authors have or gradual correction, lateral tibia epiphysiodesis, and proximal fibular epiphysiodesis (Figurereported 19). Gregosiewicz good results et al. performing reported on 13 casescombined in 10 children osteotomies with advanced and ITV procedures including acute (IV–VI)elevation with 8-year of the follow-up medial treated platea withu, double metaphyseal level osteotomy osteotomy with internal of fixation. the tibia (and fibula) for acute They performed a lateral closing wedge tibia osteotomy and used the resected bone to or gradual correction, lateral tibia epiphysiodesis, and proximal fibular epiphysiodesis (Figure 19). Gregosiewicz et al. reported on 13 cases in 10 children with advanced ITV (IV–VI) with 8-year follow-up treated with double level osteotomy with internal fixation. They performed a lateral closing wedge tibia osteotomy and used the resected bone to graft the medial tibial plateau elevation osteotomy. They reported good results in 11 of 13 patients [18]. In 2003, Accadbled et al. described a one-step treatment for ITV in four patients: percutaneous epiphysiodesis of the superolateral tibia and proximal fibula, elevation osteotomy of the medial tibial plateau, osteotomy of the fibula, and dome-shaped metaphyseal osteotomy of the tibia, followed by progressive lengthening with an Ilizarov frame [82]. They reported all patients had healed at an average of 6 months, and at follow- up (average 6 years 10 months) all had normal limb length and alignment with congruent joint surfaces.

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graft the medial tibial plateau elevation osteotomy. They reported good results in 11 of 13 patients [18]. In 2003, Accadbled et al. described a one-step treatment for ITV in four patients: percutaneous epiphysiodesis of the superolateral tibia and proximal ﬁbula, elevation osteotomy of the medial tibial plateau, osteotomy of the ﬁbula, and dome-shaped metaphyseal osteotomy of the tibia, followed by progressive lengthening with an Ilizarov frame [82]. They reported all patients had healed at an average of 6 months, and at follow- Children 2021, 8, x FOR PEER REVIEWup (average 6 years 10 months) all had normal limb length and alignment with congruent17 of 27

joint surfaces.

Figure 19. A 7-year-old with bilateral advanced ITV underwent staged acute correction and growth Figure 19. A 7-year-old with bilateral advanced ITV underwent staged acute correction and growth plate stoppage. plate stoppage. 16. Epiphysiodesis 16. Epiphysiodesis Epiphysiodesis procedures are used to completely stop growth of a physis. In unilat- Epiphysiodesis procedures are used to completely stop growth of a physis. In unilateral ITV it is most often performed on the contralateral limb at a calculated patient age to eral ITV it is most often performed on the contralateral limb at a calculated patient age equalize limb lengths at skeletal maturity [85,86]. In the ipsilateral limb proximal tibia and to equalize limb lengths at skeletal maturity [85,86]. In the ipsilateral limb proximal tibia fibula epiphysiodesis is combined with medial hemi-plateau elevation osteotomy in late- and ﬁbula epiphysiodesis is combined with medial hemi-plateau elevation osteotomy in late-stagestage ITV ITV to prevent to prevent recurrence recurrence and and overgrowth overgrowth of the of the proximal proximal fibula. ﬁbula. SeveralSeveral techniques techniques existexist for epiphysiodesis. epiphysiodesis. Irreversible Irreversible growth growth plate plate destruction destruction can canbe performed be performed percutaneously percutaneously with with drills drills and and curettes curettes or through or through more more invasive invasive open open tech- techniquesniques such such as the as thePhemister Phemister [87]. [87 Instrume]. Instrumentednted techniques techniques include include screws, screws, staples, staples, and andtension tension bands bands and and can can be be reversible reversible especially especially if if the the physis physis itself is notnot violated.violated.Open, Open, moremore invasive invasive techniques techniques have have a lowera lower rate rate of failureof failure at theat the cost cost ofadded of added morbidity, morbidity, but allbut techniquesall techniques report report good good to excellent to excellent results results [88– 91[88–91].].

17. Gradual Correction with External Fixation Dynamic external fixation allows for gradual correction of multiplanar deformities including angulation, translation, rotation, and length (Figures 20 and 21). Treatment is prolonged with frequent follow-up and demands significant commitment from the patient, family, and surgeon [15]. Preoperative discussions must clearly outline the frequency of visits, ensure comprehension of fixator mechanics, and delineate the prolonged treatment time in the fixator.

Children 2021, 8, x FOR PEER REVIEW 18 of 27

Children 2021, 8, 566 17 of 25 Perceived advantages of gradual deformity correction with external fixator include lower risks for deep infection and neurovascular compromise than with acute correction, the ability to fine tune the correction, early weight bearing, and lengthening [92]. Disad- 17. Gradual Correction with External Fixation vantages include the prolonged duration of treatment, need for frequent follow-up and radiographs,Dynamic risks external of pin fixation and wire allows infectio for gradualn, fixator correction malfunction/ of multiplanarhardware deformitiesfailure, and includingpotential angulation,loss of correction translation, or fracture rotation, after andfixator length removal. (Figures The 20 most and common 21). Treatment complica- is prolongedtions include with superficial frequent follow-up pin infections and demandsthat respond significant to oral commitmentantibiotics infrom a majority the patient, of pa- family,tients. andDespite surgeon these [ 15challenges,]. Preoperative gradual discussions correction must with clearly or without outline limb-lengthening the frequency of is visits,the procedure ensure comprehension of choice for patients of fixator with mechanics, severe or and complex delineate deformities the prolonged not amenable treatment to timeacute in correction the fixator. [93].

Figure 20. The patient in Figures 16–18; a hexapod was placed to correct tibia varus, internal torsion, Figure 20. The patient in Figures 16–18; a hexapod was placed to correct tibia varus, internal torsion, and procurvatum; 3 cm of length was gained due to the growth plate closures. and procurvatum; 3 cm of length was gained due to the growth plate closures.

Perceived advantages of gradual deformity correction with external fixator include lower risks for deep infection and neurovascular compromise than with acute correction, the ability to fine tune the correction, early weight bearing, and lengthening [92]. Disad- vantages include the prolonged duration of treatment, need for frequent follow-up and radiographs, risks of pin and wire infection, fixator malfunction/hardware failure, and potential loss of correction or fracture after fixator removal. The most common complications include superficial pin infections that respond to oral antibiotics in a majority of patients. Despite these challenges, gradual correction with or without limb-lengthening is the procedure of choice for patients with severe or complex deformities not amenable to acute correction [93]. Cheraskin et al. reported on external fixator treatment in 31 patients with complex deformities resulting from early- and late-onset Blount’s disease. Despite frequent and significant complications during treatment, they had 88% achievement of treatment goals [93]. In 2003, Feldman reported that 21 of 22 patients with ITV and LOTV achieved alignment within 3◦, and all had good results treated with a Taylor spatial frame. Sachs et al. concluded that LOTV correction in children with minimal LLD and without severe procurvatum or torsion (under 2 cm) did not need fibular osteotomy or fixation [36]. In patients with

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Children 2021, 8, x FOR PEER REVIEWlateral collateral ligament laxity and limb length discrepancy, the ﬁbula can be captured19 of 27 distally and pulled distally with tibial lengthening to retain the lateral collateral ligament.

Figure 21. The patient in Figures 15–18 6 months after frame removal showing maintained align- Figure 21. The patient in Figures 15–18 6 months after frame removal showing maintained alignment ment and length. and length. Cheraskin et al. reported on external fixator treatment in 31 patients with complex 18. Late-Onset Tibia Vara (LOTV) deformities resulting from early- and late-onset Blount’s disease. Despite frequent and significantLOTV presentscomplications at an during older age treatment, than ITV. they The had deformities 88% achievement include of tibia treatment vara with goals various[93]. In amounts 2003, Feldman of tibial reported torsion, procurvatum,that 21 of 22 patients limb length withdiscrepancy, ITV and LOTV and achieved sagittal plane align- kneement instability within 3°, indicative and all had of lateral good results collateral treated ligament with laxity. a Taylor The spatial differential frame. diagnosis Sachs et isal. similar to ITV, but in most cases the diagnosis is easily made based on the history, clinical concluded that LOTV correction in children with minimal LLD and without severe exam, and radiographs. LOTV has a different radiographic appearance than ITV; there is procurvatum or torsion (under 2 cm) did not need fibular osteotomy or fixation [36]. In often widening of the medial tibial physis, and ipsilateral deformity of the distal femur and patients with lateral collateral ligament laxity and limb length discrepancy, the fibula can tibia are common [40]. Medial tibial plateau depression is not present. There is no evidence be captured distally and pulled distally with tibial lengthening to retain the lateral collat- for bony bridge in LOTV and therefore no indication for physeal bar resection [24]. The eral ligament. patients are more often obese, the deformity is more often unilateral, and knee pain is more common (Figure 22). Ipsilateral femoral varus can contribute substantially to the overall 18. Late-Onset Tibia Vara (LOTV) varus alignment of the knee. Patients with compensatory distal tibia valgus can develop gastrocsoleusLOTV presents and subtalar at an joint older contractures, age than ITV. which The mustdeformities be assessed include preoperatively tibia vara with [26,29 var-]. Rotationious amounts proﬁle of CT tibial scans torsion, can quantify procurvatum, torsional limb abnormalities length discrepancy, above and and below sagittal theknee. plane Standardknee instability deformity indicative imaging of and lateral analysis collateral as described ligament for laxity. ITV The is performed. differential diagnosis is similar to ITV, but in most cases the diagnosis is easily made based on the history, clinical exam, and radiographs. LOTV has a different radiographic appearance than ITV; there is often widening of the medial tibial physis, and ipsilateral deformity of the distal femur and tibia are common [40]. Medial tibial plateau depression is not present. There is no

Children 2021, 8, x FOR PEER REVIEW 20 of 27

evidence for bony bridge in LOTV and therefore no indication for physeal bar resection [24]. The patients are more often obese, the deformity is more often unilateral, and knee pain is more common (Figure 22). Ipsilateral femoral varus can contribute substantially to the overall varus alignment of the knee. Patients with compensatory distal tibia valgus can develop gastrocsoleus and subtalar joint contractures, which must be assessed pre- Children 2021, 8, 566 operatively [26,29]. Rotation profile CT scans can quantify torsional abnormalities19 above of 25 and below the knee. Standard deformity imaging and analysis as described for ITV is performed.

Figure 22. A 16-year-old adolescent with unilateral LOTV; he has distal femur varus, proximal tibia Figure 22. A 16-year-old adolescent with unilateral LOTV; he has distal femur varus, proximal tibia varus, and distal tibia valgus. varus, and distal tibia valgus. The natural history of LOTV is unclear, and degenerative medial knee joint arthritis The natural history of LOTV is unclear, and degenerative medial knee joint arthritis in in the third decade is common in untreated patients [13,26,94]. There is no documented the third decade is common in untreated patients [13,26,94]. There is no documented role forrole non-operative for non-operative treatment treatment in LOTV, in and LOTV, surgery and is surgery the deﬁnitive is the treatment.definitive Thetreatment. goals are The to restore knee joint orientation and a neutral mechanical limb alignment, equalize limb lengths at skeletal maturity, and prevent recurrence. In obese patients, neutral alignment often gives the appearance of valgus due to fat-thigh gait, as described by Davids [68]. The patient’s large thighs necessitate walking and standing in hip abduction, which increases the inter-malleolar distance at the ankles and appearance of genu valgus. These patients often have additional deformities of the distal femur (most commonly varus) and/or tibia (most commonly valgus), and these must be independently evaluated for surgical correction via guided growth or osteotomy to avoid over-correcting one deformity to treat another [29]. There is no consensus on how much knee joint obliquity may predispose one Children 2021, 8, 566 20 of 25

to arthritis due to translational and shear forces, but it is agreed that over correcting the tibia to compensate for some amount of femur varus deformity is not recommended [29]. Cooke et al. reported on an analysis of adult bowlegged patients with osteoarthritis and found the pattern of distal femur valgus and proximal tibial varus will generate lateral subluxing forces and overload the medial compartment [95]. Gordon et al. recommended treating compensatory varus of the distal femur if mLDFA was >95◦ and distal tibia valgus if LDTA ≤ 86◦ [29]. De Pablos suggested guided growth for distal femoral varus >10◦ in skeletally immature patients [96]. The surgical options for LOTV include guided growth, physeal distraction, acute osteotomy, gradual correction, contralateral epiphysiodesis, and combined strategies. The treating surgeon must consider comorbidities of sleep apnea and dietary deficiencies [97,98]. There is no consensus in the literature regarding the ideal alignment of the lower extremity after surgical reconstruction for Blount’s disease [7], but most authors recommend correcting to neutral mechanical alignment for LOTV [4,14,68–70]. The use of custom 3D printed osteotomy guides has been reported [99]. As with ITV, guided growth with lateral tension-band hemi-epiphysiodesis is a first- line surgical option for skeletally immature patients with LOTV [58]. Despite reports of inadequate correction, hardware failure, and the need for subsequent procedures, the relatively low morbidity and potential improvement of deformity make this a safe and recommended first-line procedure [57–59,61,62,100,101]. Mackintosh reported that age greater than 14 years, BMI > 45 kg/m2, and more significant deformity were associated with failure [100]. Park et al. reported favorable results in hemi-epiphyseal stapling in LOTV [27]. An external fixator can be used to distract through an open proximal tibial physis in LOTV without the need for an osteotomy (Figure 23, 1–5). The correction occurs through the site of deformity and leads to physeal arrest after consolidation and thus prevents recurrence. It requires a stable external fixator, and the surgeon must be aware of the Children 2021, 8, x FOR PEER REVIEWepiphyseal pins’ close proximity to the joint and monitor for infection [102]. De Pablos22 of 27 reported complete correction in 12 of 12 patient with no recurrence [103].

Figure 23. Physeal distraction in LOTV. X-ray series of a case of LOTV gradually corrected by means Figure 23. Physeal distraction in LOTV. X-ray series of a case of LOTV gradually corrected by means of physeal distraction: (1) Pre-operative, (2) immediate post-operative, (3) 22 days post-operative ofangular physeal correction distraction: completed, (1) Pre-operative, (4) 2 months (2) immediate post-operative post-operative, after 2.5 cm ( 3lengthening) 22 days post-operative to compensate angulara discrepancy, correction (5) completed, 4 months post-operative (4) 2 months post-operative consolidation afterobtained 2.5 cm [96]. lengthening to compensate a discrepancy, (5) 4 months post-operative consolidation obtained [96]. Significant obesity (Figure 24) limits surgical treatment options due to the large ex- posures needed for internal fixation, risk of internal hardware failure secondary to challenges with mobilization and immobilization, and challenges obtaining stability. Percuta- neous or minimally invasive osteotomies with acute or gradual correction with hexapod external fixation is the mainstay of deformity correction in obese adolescents with LOTV who have failed guided growth or are not a candidate due to age or severity of deformities. The hexapod fixator allows for immediate weight bearing and mobility, offers rigid stabilization of the bones, and is very accurate.

Figure 24. A 400-pound (181 kg) adolescent with a hexapod fixator stabilizing gradual correction of LOTV.

Juvenile Blount’s disease was described by Thompson in 1984 in children aged 4–10 with pathologic tibia vara. Little is known about the etiology or natural history. It shares

Children 2021, 8, x FOR PEER REVIEW 22 of 27

Figure 23. Physeal distraction in LOTV. X-ray series of a case of LOTV gradually corrected by means Children 2021, 8, 566 of physeal distraction: (1) Pre-operative, (2) immediate post-operative, (3) 22 days post-operative21 of 25 angular correction completed, (4) 2 months post-operative after 2.5 cm lengthening to compensate a discrepancy, (5) 4 months post-operative consolidation obtained [96]. Significant obesity (Figure 24) limits surgical treatment options due to the large expo- Significant obesity (Figure 24) limits surgical treatment options due to the large ex- sures needed for internal fixation, risk of internal hardware failure secondary to challenges posures needed for internal fixation, risk of internal hardware failure secondary to chal- with mobilization and immobilization, and challenges obtaining stability. Percutaneous or lenges with mobilization and immobilization, and challenges obtaining stability. Percuta- minimally invasive osteotomies with acute or gradual correction with hexapod external neous or minimally invasive osteotomies with acute or gradual correction with hexapod fixation is the mainstay of deformity correction in obese adolescents with LOTV who have external fixation is the mainstay of deformity correction in obese adolescents with LOTV failed guided growth or are not a candidate due to age or severity of deformities. The who have failed guided growth or are not a candidate due to age or severity of deformi- hexapod fixator allows for immediate weight bearing and mobility, offers rigid stabilization ties. The hexapod fixator allows for immediate weight bearing and mobility, offers rigid of the bones, and is very accurate. stabilization of the bones, and is very accurate.

FigureFigure 24. 24.A A 400-pound 400-pound (181 (181kg) kg) adolescentadolescent withwith a hexapod fixator ﬁxator stabilizing stabilizing gradual gradual correction correction of ofLOTV. LOTV.

JuvenileJuvenile Blount’s Blount’s disease disease was was described described by by Thompson Thompson in in 1984 1984 in in children children aged aged4–10 4–10 withwith pathologic pathologic tibia tibia vara. vara. Little Little is is known known about about the the etiology etiology or or natural natural history. history. It It shares shares common pathology with early- and late-onset tibia vara. Because the patients are larger than those with ITV and can have signiﬁcant deformities, the surgical reconstruction strategies are similar to those for LOTV: guided growth and corrective osteotomy with internal or external ﬁxation depending on patient age, weight, and deformities.

19. Conclusions Blount’s disease represents a large spectrum of pathology from infantile (before age 4) to late-onset (after age 4) with a common mechanical pathogenesis leading to medial tibial growth suppression and deformity [104]. The deformity is often multiplanar and includes tibia vara, procurvatum, and tibial torsion. Distal femur and tibia deformities more often exist in the late onset form. Projected limb length discrepancy must be calculated and addressed. Non-operative treatment with bracing in young children has limited efficacy, and surgery is warranted in patients with documented clinical or radiographic progression. Surgical options depend on the patient’s age, extent of physeal involvement, severity and number of deformities, and the psychosocial family dynamics. Despite the unpredictable results and frequent failure, due to the low morbidity and potential to correct deformity or, at least, prevent progression, most authors recommend lateral tension- band hemi-epiphysiodesis as a first line of treatment for most patients regardless of age or weight [10,60,105]. If this fails, then corrective osteotomy is the salvage procedure, preferably before age 4 in ITV with options for acute or gradual correction depending on the patient’s age, size, severity, and complexity of deformity. Completion of lateral tibia and proximal fibula epiphysiodesis is required in late-stage ITV to prevent recurrence. The Children 2021, 8, 566 22 of 25

goals of surgery are to restore normal joint and limb alignment, equalize limb lengths at skeletal maturity, and prevent recurrence, as untreated deformity can progress to knee pain, instability, and degenerative arthritis [46,47,106,107].

Funding: This research received no external funding. Data Availability Statement: This is a literature review article; no data was accumulated. Acknowledgments: Thank you to my partner David Feldman for his editorial expertise, guidance, wisdom, and suggestions. Thank you to my partner Dror Paley for nearly two decades of mentorship and expanding my surgical and clinical acumen. Conﬂicts of Interest: The author declares no conﬂict of interest.

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