Review Article Management of Extra-articular Deformity in the Setting of Total Knee Arthroplasty

Abstract Peter K. Sculco, MD Extra-articular deformities of the femur and tibia in conjunction with Cynthia A. Kahlenberg, MD advanced knee osteoarthritis pose unique challenges for the arthroplasty surgeon. Careful preoperative planning is needed to Austin T. Fragomen, MD evaluate both the intra- and extra-articular deformities and to S. Robert Rozbruch, MD determine the best route to total knee arthroplasty. An intra-articular compensatory correction can typically be performed if the extra- articular deformity is distant from the joint or if preoperative templating shows that bony cuts do not interfere with ligamentous attachments. Staged osteotomy followed by arthroplasty is beneficial in severe cases in which bony cuts are excessive or would interfere with soft- tissue structures and in cases with leg-length discrepancy. Osteotomies can be performed percutaneously and fixed with intramedullary nails, external fixators, or plate and screw constructs. Ligamentous laxity after correction and risk of peroneal nerve injury are increased in extra-articular deformity cases and must be considered during the knee arthroplasty procedure with increased implant constraint and patient counseling, respectively. Computer- assisted navigation has an emerging role in total knee arthroplasty in patients with extra-articular deformity.

ore than 700,000 total knee risk of ongoing pain and early implant Marthroplasties (TKAs) are per- failure.3 The purpose of this article is formed annually in the United States.1 to present treatment algorithms for Although correction of intra-articular the management of extra-articular pathology is a mainstay of TKA, less deformity in either the femur or has been published on the evaluation tibia and in the coronal, sagittal, or From the Adult Reconstruction and and management of extra-articular axial plane and to review the radio- Joint Replacement Service deformity in the setting of TKA. An graphic imaging, surgical planning, (Dr. Sculco), the Department of extra-articular deformity may be a and multidisciplinary approach nec- Orthopaedic Surgery essary to optimize clinical outcomes (Dr. Kahlenberg), and Limb result of previous trauma or skele- and minimize arthroplasty failure. Lengthening and Complex tal developmental abnormalities and Reconstruction Service (Dr. Fragomen and Dr. Rozbruch), may increase the risk of knee osteo- 2 Hospital for Special Surgery, New arthritis. Thus, orthopaedic surgeons Causes of Extra-articular York, NY. should be aware of the diagnosis and Deformity of the Femur and J Am Acad Orthop Surg 2019;00:1-12 treatment algorithms for extra- Tibia and Its Association DOI: 10.5435/JAAOS-D-18-00361 articular deformity in the setting of With Knee Osteoarthritis TKA. Performing a TKA without Copyright 2019 by the American Academy of Orthopaedic Surgeons. addressing underlying extra-articular Causes of extra-articular deformity malalignment may place the patient at of the femur and tibia are numerous

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Copyright Ó the American Academy of Orthopaedic Surgeons. Unauthorized reproduction of this article is prohibited. Extra-articular Deformity in Total Knee Arthroplasty and can lead to varying degrees of articular deformities and end-stage deformities of the tibia are not de- deformity. Specific causes include osteoarthritis necessitating TKA, and tected on short films of the knee. We metabolic bone diseases, congenital appropriate management of these de- routinely obtain full-length radio- abnormalities, posttraumatic malunion, formities at the time of TKA is critical graphs for all TKA patients to eval- and previous osteotomies.4 Fracture to a successful clinical outcome. uate the deformity and allow for malunion of the femur and/or tibia, one Another cause of extra-articular appropriate preoperative planning.10 of the most common causes of extra- deformity about the knee is con- Although positioning can be difficult articular deformities around the knee,5 genital or metabolic bone diseases.5 in cases of severe deformity, every may cause altered knee kinematics and These include osteogenesis imperfecta, attempt should be made to position asymmetric compartmental forces causing a bony bowing or thinning the patient in an anatomic fashion. relatedtothedeformity and resultant deformity, Blount disease, causing Correlation should be made between mechanical axis deviation (MAD) varus deformity of the proximal tibia the physical examination and the that may lead to early degenerative and distal femur, and hereditary hy- positioning of the radiographic im- changes in the knee joint.6,7 However, pophosphatemia or hyperparathy- ages. Several measurements are the direct link between fracture mal- roidism, which lead to worsened bone made on the calibrated full-length union and knee osteoarthritis has been quality and a variety of deformities. standing radiographs to evaluate the questioned because a study of femoral Tumors, both benign and malignant, location and extent of deformity shaft malunions with more than 20 are another cause of extra-articular (Table 1). years of follow-up did not find an deformity. Tumors themselves, and association between femur malunion the medications used in the manage- Coronal Plane and knee osteoarthritis.8 The severity ment of tumors, can lead to worsened Measurements of the deformity, not the malunion bone quality and deformity and should In the coronal plane, the MAD is itself, is likely the most important betreatedinconsultationwitha used to evaluate for varus or valgus determinant of overall knee function tumor surgeon. Finally, Paget disease deformity. The lateral distal femoral and risk of osteoarthritis progression. of bone occurs from a disorganized angle (LDFA) and the medial proxi- In a study of 237 patients with knee bony deposition that causes the bone mal tibial angle (MPTA) determine osteoarthritis, Sharma et al2 noted that to become sclerotic and thickened. whether the deformity is originating more than 5° ofvarusorvalgus Associated deformities include distal from the femur, the tibia, or both. The deformity had a five times greater risk femoral valgus and anterior bow- joint line convergence angle indicates of osteoarthritis progression over an ing of the tibia. Patients with Paget the amount of deformity coming 18-month period compared with disease are also at risk of increased from within the joint. The center of neutral controls. In addition, they blood loss during surgery, and rotation of angulation (CORA) is found that the magnitude of advanced planning should be done useful to determine the distance of the mechanical malalignment correlated for these patients before they deformity from the joint and can be with a decline in physical function and undergo TKA.5 used if osteotomy planning is being increase in osteoarthritis. These lon- considered. gitudinal studies demonstrating increasing osteoarthritis progression, Radiographic Evaluation particularly with mechanical deform- Sagittal and Axial Plane ities greater than 5°, suggest that Long leg hip-to-ankle radiographs in Measurements untreated fracture malunions may the AP and lateral planes are essential The posterior distal femoral angle require TKA at a higher rate than for accurate preoperative planning and the posterior proximal tibial normal controls. For this reason, it is and assessment of an extra-articular angle are the primary measurements likely that joint arthroplasty surgeons deformity. Alghamdi et al9 noted that used to evaluate the degree of will encounter patients with extra- more than 50% of extra-articular deformity in the sagittal plane.

Dr. Sculco or an immediate family member has received research support from Intellijoint. Dr. Fragomen or an immediate family member is a member of a speakers’ bureau or has made paid presentations on behalf of NuVasive, Smith & Nephew, and Synthes; serves as a paid consultant to Globus Medical, NuVasive, Smith & Nephew, and Synthes; and serves as a board member, owner, officer, or committee member of the Limb Lengthening Research Society. Dr. Rozbruch or an immediate family member has received IP royalties from Stryker; is a member of a speakers’ bureau or has made paid presentations on behalf of NuVasive, Smith & Nephew, and Stryker; serves as a paid consultant to NuVasive and Stryker; and serves as a board member, owner, officer, or committee member of the Limb Lengthening and Reconstruction Society. Neither Dr. Kahlenberg nor any immediate family member has received anything of value from or has stock or stock options held in a commercial company or institution related directly or indirectly to the subject of this article.

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Table 1 Radiographic Measurements for Preoperative Assessment of Deformity11 Normal Measurement Description Range Clinical Significance

Coronal plane measurements MAD Measured by drawing a line from the 0-8 mm Any line that is drawn laterally is center of the femoral head to the center medial considered a valgus deformity, and any of the ankle and drawing a second line line greater than 8 mm medial is from the center of the tibial spines to considered a varus deformity meet the first line LDFA Angle between a line from the center of the 85°-90° Angle outside of normal range indicates hip to the center of the knee and a second deformity originating from the femur line connecting the femoral condyles MPTA Angle between a line down the shaft of 85°-90° Angle outside of normal range indicates the tibia and a line across the top of the deformity originating from the tibia tibial condyles JLCA Angle between a line drawn across the 0°-2° Angle greater than normal range tibial condyles and a line across the indicates deformity originating from femoral condyles inside the joint, either from cartilage loss or ligamentous instability Sagittal plane measurements PDFA Angle between the sagittal distal femoral 79-83 Angle outside of the normal range joint line and the mid-diaphyseal line of indicates a sagittal plane deformity of the femur the femur PPTA Angle between the sagittal tibial joint line 77-84 Angle outside of the normal range and the mid-diaphyseal line of the tibia indicates a sagittal plane deformity of the tibia Axial plane measurements LLD Distance measured from the top of the NA Any discrepancy should be noted and femoral head to the center of the ankle accounted for in the correction of the joint on each limb deformity Deformity measurements CORA Location where the anatomic axes of the NA Often used as the basis for where to plan bone proximal to the deformity and the osteotomy if corrective surgery is distal to the deformity meet being considered

CORA = center of rotation of angulation, JLCA = joint line convergence angle, LDFA = lateral distal femoral angle, LLD = limb-length discrepancy, MAD = mechanical axis deviation, MPTA = medial proximal tibial angle, NA = not applicable, PDFA = posterior distal femoral angle, PPTA = posterior proximal tibial angle

Measurements should be made Leg-Length Measurements the top of the femoral head to the preoperatively, and any deviation Limb-length discrepancy (LLD) center of the ankle joint on each limb. from the normal range should be should also be measured and consid- Separate measurements of the femur considered in preoperative planning. and the tibia can be useful in deter- ered in planning for TKA, but the The CORA can also be determined mining the source of the structural patient should be advised that an and used to determine osteotomy LLD. Functional measurement of planning in the sagittal plane. For LLD may persist after TKA. Radio- LLD can be performed from the axial plane malalignment, a CT scan graphically, standing full-length umbilicus to the medial malleo- canalsobeusedtodeterminefem- radiographs are an accurate and lus.13,14 A clinical measurement of a oral version12 andshouldbeob- reproducible method for evaluating patient’s functional LLD can be tained in cases of concern for axial LLD. The true, or structural, limb- performed by placing blocks of malalignment. length difference is the distance from varying heights under the shorter

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Figure 1

Radiographs demonstrating the effects of deformity near and far from the knee joint. A, A large deformity near the knee joint has a severe effect on angulation at the knee joint. Anatomic axes and mechanical axis are shown. Severe deviation of the mechanical axis is noted. B, View of the same patient’s knee showing the tibial deformity. C, A deformity of the same magnitude further away from the knee joint has less of an effect on angulation at the knee joint. limb until the patient feels leg lengths from the knee joint, its effect on all femur or tibia length that the to be equal.13 overall mechanical alignment de- deformity moved closer to the joint, creases and the deformity becomes an additional 2° of overall limb easier to address with TKA alone.4 malalignment would be present.4 Preoperative Templating For example, a deformity of the same Furthermore, LDFA and MPTA for Total Knee Arthroplasty magnitude just a few centimeters measurements should be analyzed as With Extra-articular from the knee joint may require a further deviations from normal Deformity substantial correction, whereas a measurements and should be incor- larger deformity farther away from porated into the preoperative plan- Preoperative planning for TKA in ning for the correction. cases of extra-articular deformity in the knee joint may have a minimal the femur, tibia, or both should effect on bone resections and bal- Preoperative Planning for include (1) the magnitude (in degrees) ancing of the TKA (Figure 1). Wolff 4 of the extra-articular deformity and et al used geometric calculations to Total Knee Arthroplasty: The (2) the location of the deformity show that the magnitude of defor- Coronal Plane (CORA) in relation to the knee joint. mity increases linearly as it gets A key component of preoperative The location of the CORA de- closer to the joint. They showed that planning in the coronal plane is termines surgical treatment because for the same 20° extra-articular determining the location of distal as the CORA moves further away deformity, with every 10% of over- femoral and proximal tibial bone cuts

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Copyright Ó the American Academy of Orthopaedic Surgeons. Unauthorized reproduction of this article is prohibited. Peter K. Sculco, MD, et al in relation to the insertion sites of the the femoral resection. If the perpen- Figure 2 collateral ligaments because this will dicular line (proposed femoral bone determine whether the correction is resection) passes distal to the in- achievable with TKA alone or if os- sertions of the collateral ligaments (on teotomies are needed before TKA. average25mmproximaltothejoint Previous studies have reported that line), an intra-articular correction is an intra-articular compensatory cor- feasible. If the proposed femoral bone rection can usually be achieved with resection compromises the collateral TKA if the extra-articular deformity ligament insertion, an extra-articular is ,20° in the coronal plane on the correction must be performed before femoral side or ,30° on the tibial TKA (Figure 2). For the tibia, a line is side when the CORA is located drawn from the center of the talus up outside the metaphyseal region.11,15-17 the shaft of the tibia in the distal For deformities of greater severity or fragment of the deformed bone. Wang deformities close to the joint, an extra- and Wang reported that if this line articular osteotomy may be needed to passes through the top of the tibial achieve a well-aligned TKA. Femoral- plateau, correction with primary sided deformities are less well toler- arthroplasty is feasible. However, ated than tibial deformities in the larger tibial corrections may require coronal plane because a corrective cut bone grafting, extensive releases, and of the distal femur will change the constrained implants. If the tibial balance of the knee only in extension, bone resection is too radical or not whereas a corrective cut on the tibial possible with conventional implants, a side will change the balance of the corrective tibial osteotomy should be knee equally in flexion and extension.18 performed before arthroplasty.16,18,20 Therefore, intra-articular correction of It is often helpful to draw a line per- an extra-articular femoral-sided defor- pendicular to the mechanical axis to mity may lead to an unbalanced knee estimate the exact tibial resection that due to flexion-extension gap imbalance. will be performed. 16 As previously mentioned, the thresh- Wang and Wang applied their Radiograph of a 50-year-old woman old for performing an isolated intra- coronal plane planning methodology with previous trauma to left lower articular compensatory correction with to a series of 15 patients with fracture extremity demonstrating preoperative templating bony cuts for correction of a TKA is based on angular severity, malunions causing extra-articular extra-articular deformity. Ninety- CORA distance from the joint line, and deformity of the femur or tibia. Pre- degree cuts are drawn on the tibia concomitant sagittal plane deformity. operative planning predicted that an and femur to template for TKA. As angular severity increases and intra-articular correction would be Preoperative planning shows an acceptable distal femoral cut. On the CORA is in close proximity, the possible. In the case series, the mean tibial side, if a 10 mm cut is taken from extent of soft-tissue releases necessary preoperative femoral deformity was the lateral side, a large medial defect to achieve a well-balanced knee in- 15° in the coronal plane and 8° in the would be present. If a 90° cut was creases along with the need for either sagittal plane. The mean tibial defor- madewitha2mmtakenoffthemedial ° side, the lateral tibial cut would be an unlinked constrained or linked mity was 19 in the coronal plane. All excessive. Options in this case include 19 constrained (hinge) device. patients underwent primary TKA, and corrective osteotomy versus cutting Wang and Wang16 described the mean postoperative mechanical axis 10 mm of bone from the lateral side another simple methodology to de- angle was 0.3° varus. They reported a and filling the large medial defect with graft, cement, or augment. In this case, termine whether the coronal plane mean Knee Society Score improve- the authors would favor a corrective malalignment is correctable with TKA ment from 22.3 to 91.7 at a mean of tibial osteotomy, followed by primary alone or if osteotomies are needed. 38 months postoperatively and no TKA, without the need for augmenting The mechanical axis of the femur is complications in the patient cohort. the defect. TKA = total knee arthroplasty drawn first from the center of the Preoperative planning should also femoral head to the center of the include an assessment of stem or keel femoral notch. A second line is then fit on the tibia and stem fit on the femur. used, this must be included as part of the drawn perpendicular to the mechani- Implants should be chosen preopera- preoperative template. In cases in which cal axis line at the proposed level of tively and if stemmed implants are being intra-articular correction can be

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Figure 3 ittal deformity with a TKR without notching the anterior femoral cortex (Figure 3). Other authors have reported the successful intra-articular correction of sagittal plane deformity of up to 15° foreitherrecurvatumor procurvatum.21 Although no absolute degree of sagittal malalignment exists, generally guidelines suggest that when the sagittal deformity (either pro- curvatum or recurvatum) is greater than 20°, an osteotomy should be performed before TKA. In the setting of a sagittal deformity that is com- bined with a coronal plane defor- mity, hexapod frames are a useful tool that can be used to gradually correct the deformity in multiple planes22,23 (Figure 4).

Preoperative Planning for Total Knee Arthroplasty: Rotational Deformity Preoperative awareness and planning for an axial plane deformity is also important for a successful outcome of TKA. Rotational deformity may be evaluated clinically during examina- tion of a patient’s gait by assessing for asymmetry in foot progres- sion angle between the normal and malaligned limb.24 Hip range of motion, particularly internal and Radiographs of a 59-year-old man, who presented with right knee pain after a femoral fracture 40 years prior, demonstrating femoral recurvatum deformity (A). external rotation, should be as- Computer navigation (Orthoalign) was used for alignment of the femoral cutting sessed, and significant differences guide. Neutral alignment was obtained in both the coronal and sagittal planes between the normal and affected side using standard primary TKR implants (B). should raise suspicion for rotation abnormalities involving the hip. achieved but stems or keels will not fit deformity in the setting of patients Plain radiographs may demonstrate because of an extra-articular defor- undergoing TKA.19,21 The literature subluxation of the patella in the mity, consideration should be given is limited on this topic, but previous trochlea groove, which may also to either switching implants or studies have reported that an intra- indicate a rotational abnormality. performing a corrective osteotomy articular correction with TKA is Any rotational abnormality noted before TKA to avoid complications feasible if a procurvatum deformity on examination of plain radio- intraoperatively. is less than 10° or a recurvatum graphs should be further evaluated deformity less than 20°.19 Tolerance with cross-sectional imaging, typically of recurvatum deformity is greater a CT version study of the lower Preoperative Planning for than that of procurvatum deformity extremity. Total Knee Arthroplasty: because of the risk of femoral Unfortunately, TKA allows for Sagittal Plane notching with a procurvatum extra- minimal correction of rotational Sagittal plane deformity is typically articular deformity. In recurvuatum, deformity. Wang et al21 reported in a better tolerated than coronal plane it is possible to correct a larger sag- series of patients undergoing TKA

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Figure 4

Radiographs of a 50-year-old woman, who sustained multiple fractures when she was a pedestrian struck by a motor vehicle 30 years before presentation, demonstrating tibial varus and recurvatum deformities. She incurred a malunion of the left proximal tibial shaft. She reported pain and knee stiffness. The radiographs demonstrated 29° of recurvatum deformity extra- articularly and 22° of tibial varus deformity (A). To correct both the varus and recurvatum deformities, an osteotomy was performed and a hexapod frame was used, acting as a virtual hinge, with gradual adjustments made to correct the deformity (B). She was in the frame for a total of 3 months, initially making the daily adjustments and then allowing for consolidation of the bony regenerate. She was staged to total knee arthroplasty 2.5 years after frame removal using primary components (C). with a history of femoral fracture Preoperative Planning for withILNs.Caremustbetakento malunion and severe internal rotation Total Knee Arthroplasty: avoid impingement of blocking screws of the femur leading to unavoidable Limb-Length Discrepancy onto the ILN that will prevent the nail notching of the anterior-lateral fem- from lengthening appropriately.29 Extra-articular deformity in patients oral cortex during the TKA. They Kim et al30 reported the effect of seeking TKA can also be associated recommended the use of a wedge uncorrected leg-length discrepancy with an LLD, usually shortening of the cancellous bone graft in the notched on the outcome of TKA. They found affected limb. In cases of both LLD area in these cases. With femoral that a postoperative LLD of .15 mm and deformity, intramedullary internal malunion and excessive external was associated with markedly lower lengthening nails (ILNs) can simulta- rotation of the distal femur, no spe- scores on both the Knee Society neously correct both problems25-28 cial challenges were encountered at functional score and the ascending the time of TKA.21 Rotational de- (Figure 5). When using an ILN before stairs parameter of the WOMAC formities are a challenging issue or simultaneously with a TKA, the score. However, no difference was facing the arthroplasty surgeon. We surgeon must be aware of the deform- found in patient satisfaction results. do not recommend attempting to ities that ILNs can create as they correct a rotational deformity at the lengthen. Thinner-diameter ILNs have a time of TKA. Instead, the senior tendency to bend into varus, whereas Treatment Principles for authors prefer to correct any rota- stiffer nails are more likely to create a Correction of Extra- tional deformity in a separate staged valgus deformity as they lengthen along articular Deformity procedure before TKA to avoid the anatomic axis. Blocking screws are complications during the arthro- especially useful for allowing for cor- The surgical treatment options for cor- plasty procedure. rection of coronal or sagittal deformity rection of an extra-articular deformity

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Figure 5

Photographs and radiographs showing femoral varus deformity and LLD. A 51-year-old woman with a history of unknown metabolic disease presented with knee pain, bilateral hip pain, and back pain progressing since childhood. She felt comfortable with a 12.5-cm block under her left leg to compensate for her LLD (A). Preoperative planning showed a mechanical axis deviation of 98 mm medial and an overall alignment with 35° of varus deformity along with a procurvatum deformity of 26° (B). A retrograde intramedullary lengthening nail was used to correct the limb length, varus, and procurvatum deformity. Lengthening was performed on the magnetic intramedullary lengthening nail at a rate of approximately 1 mm daily (C). She was staged to a TKA with a constrained polyethylene insert one year later with removal of the retrograde nail at the time of surgery (D). Postoperative clinical photograph and standing alignment radiograph showing correction of the deformity (E). LLD = limb-length discrepancy, TKA = total knee arthroplasty

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Copyright Ó the American Academy of Orthopaedic Surgeons. Unauthorized reproduction of this article is prohibited. Peter K. Sculco, MD, et al include (1) primary TKA, (2) simulta- an osteotomy is deemed necessary, correction.33 Disadvantages of hexa- neous corrective osteotomy and TKA, there are also benefits to a simulta- pod frames include patient discom- and (3) staged corrective osteotomy and neous approach. If the surgeon is fort and risk of pin-site infection. delayed TKA. In cases in which an adept at both osteotomy and ar- Deep osteomyelitis has been reported osteotomy is deemed necessary, the throplasty and performs both simul- in up to 4% of patients undergoing decision must be made between either a taneously, the patient only undergoes external fixation, which is particu- staged or simultaneous osteotomy one surgical procedure and one re- larly concerning in patients requiring before TKA. Regardless of whether the covery period. However, the recovery arthroplasty.34 In staged cases in osteotomy is staged or simultaneous, may be longer and more difficult than which the osteotomy implant is the objective is to restore the mechani- the two recoveries after a staged removed either shortly before or in cal alignment of the femur and tibia to approach. Furthermore, in a simul- the same setting as the TKA, stem- accommodate the arthroplasty implant taneous approach, surgeons should med arthroplasty implants may be and to do this using the least possible be cognizant of blood loss manage- used to bypass the osteotomy site radical bone resection, soft-tissue re- ment and management of cement and stress risers created after implant leases, and reduce the need for con- during implantation of the total knee removal.35 strained implants. because cement may be prone to In patients with extra-articular de- There are pros and cons to both the extrude through the osteotomy site. forming in whom a subsequent TKA staged approach and the simulta- Comparing risks and benefits of is expected, osteotomy should focus neous approach for correcting extra- the staged versus simultaneous ap- on correcting the femur and tibia to articular deformity for TKA. A staged proach, we generally prefer a staged their respective anatomic and me- osteotomy allows for greater surgical osteotomy followed by subsequent chanical axes, rather than perfecting flexibility for optimizing deformity arthroplasty with potential removal the overall alignment of the entire correction because no concern exists of osteotomy implant as needed. limb. If an acute correction is feasible, with regard to interfering with imme- intramedullary nails are preferred diate TKA. If necessary, plates and because they may easily be removed screws can be used and later removed Surgical Technique and at the time of TKA. Antegrade fem- as needed. In addition, the oste- Implant Choice for Extra- oral nails are optimal because they otomy is given the opportunity for full articular Osteotomy can be left in place, and computer healing without the risk of cement Correction navigation or patient-specific cutting intrusion from TKA. In addition, guides are used instead of an intra- correction of underlying malalign- Multiple surgical techniques and medullary guide. In cases in which ment improves knee kinematics, and methods of fixation have been used gradual correction is needed, external symptoms may be alleviated, possibly for osteotomy correction includ- fixators are used. Surgeons must be delaying the need for TKA. The au- ing intramedullary nails, plate and aware of previous incisions and con- thors find this to be more common in screw constructs, or hexapod exter- sider the future TKA incision when preoperative mechanical valgus de- nal frames.32 Internal lengthening performing the deformity correction. formities. Lonner et al31 reported 11 intramedullary nails can be particu- A complete correction of axial plane knees with extra-articular deformity larly useful if there is both an angular deformity is also performed at the (10 fracture nonunions and one deformity and an LLD. Distal fem- time of osteotomy because TKA al- patient with hypophosphatemic rick- oral and proximal tibial plates can be lows for minimal correction in the ets) who underwent a simultaneous used and are frequently removed axial plane. femoral osteotomy followed by TKA before or at the time of the arthro- in the same surgical setting. Although plasty procedure (Figure 6). they reported significant improvements External fixation devices such as Special Considerations in in the Knee Society Score (KSS) out- the hexapod frame can also be used Total Knee Arthroplasty comes, the complication rate was 45% for deformity correction with oste- Associated With Extra- and included one osteotomy nonunion, otomy. Benefits of this fixation articular Deformity two manipulations under anesthesia method for deformity correcting os- for stiffness, one acute pulmonary teotomies include gradual correc- Computer-assisted navigation pro- embolism, and one case of symptom- tion and control in multiple planes. vides some valuable features when atic implant requiring removal.31 Gradual correction is beneficial for managing an extra-articular defor- Although it is the authors’ prefer- minimizing peroneal nerve injury, mity at the time of TKA, especially in ence to use a staged approach when which may be seen with acute angular the setting of a previous implant.

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Figure 6

Algorithm demonstrating suggested management of severe osteoarthritis of the knee in the setting of extra-articular deformity.

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Benefits of computer-assisted, ro- Furthermore, infection is a concern Special care should be taken to protect botic, or patient-specific cutting in patients with retained implant who neurovascular structures, especially guides include avoiding the use of an are undergoing TKA. Cross et al40 the peroneal nerve, in cases in which a intramedullary femoral alignment reported a 5% infection rate in a large deformity correction is per- rod and more reliable access to the small series of patients undergoing formed, and patients should be edu- mechanical axis without the use of conversion from high tibial oste- cated preoperatively of this increased fluoroscopy.36-39 Catani et al36 otomy to TKA. Higher infection risk. A thorough preoperative neu- reported the use of an image-free rates have been reported with the use rovascular examination and appro- navigation system (Stryker Naviga- of hexapod frames,34,41 so when priate studies to document the status tion) in a series of 20 patients with an using these devices before TKA, of the neurovascular structures may extra-articular deformity secondary surgeons should ensure that patients be indicated. Hexapod frames may to remote femur or tibia fracture. are free of any evidence of deep or be used for gradual correction to Computer-assisted navigation was superficial infection before proceed- protect neurovascular structures. In used to identify the center of the ing with arthroplasty with inflam- addition, an increasing role exists for femoral head, and the proximal tibia matory markers and joint aspiration computer navigation both for man- cut was also aligned with the if elevated. aging femoral malunions at the time mechanical axis of the tibia using Ligamentous contractures and lax- of TKA and for performing TKA navigation. The authors demon- ity may be present in the knee in cases after deformity correction. strated an improvement from a mean of extra-articular deformity.4 Sur- preoperative alignment of 10.4° 6 geons performing TKA in the setting 8.3° varus to a mean postoperative of extra-articular deformity should References alignment of 0.8° 6 1.2° varus and be prepared to perform ligamentous References printed in bold type are an improvement in the KSS from releases and use constrained im- those published within the past 5 48.4 to 91.4. In addition, they plants as needed. reported no complications in this years. more complex cohort.36 The use of 1. Kurtz S, Ong K, Lau E, Mowat F, Halpern computer technologies for extra- Summary M: Projections of primary and revision hip and knee arthroplasty in the United States articular deformity is a rapidly from 2005 to 2030. J Bone Joint Surg Am evolving field, and additional studies Preoperative full-length standing hip- 2007;89:780-785. are needed to define their role in the to-ankle radiographs are necessary 2. Sharma L, Song J, Felson DT, Cahue S, management of extra-articular for preoperative assessment of extra- Shamiyeh E, Dunlop DD: The role of knee articular deformity in the setting of alignment in disease progression and deformity. functional decline in knee osteoarthritis. In cases of complex extra-articular TKA. Measurements including MAD, JAMA 2001;286:188-195. LDFA, MPTA, posterior proximal deformity, the surgeon must also be 3. Thiele K, Perka C, Matziolis G, Mayr HO, aware of certain complications that tibial angle, posterior distal femoral Sostheim M, Hube R: Current failure are more prone to arise and must angle, JLOA, and CORA should be mechanisms after knee arthroplasty have changed: Polyethylene wear is less common counsel the patient appropriately. made to distinguish between intra- in revision surgery. J Bone Joint Surgery- In a case series of 12 patients with articular and extra-articular defor- American 2015;97:715-720. extra-articular deformity secondary mity and to plan for the correction. 4. Wolff AM, Hungerford DS, Pepe CL: to skeletal dysplasia who were Preoperative templating should be The effect of extraarticular varus and 33 used to assess bony cuts that will be valgus deformity on total knee arthroplasty. undergoing TKA, Kim et al Clin Orthop Relat Res 1991;271:35-51. reported that 3/12 required custom- needed for intra-articular correction. 5. Naqvi A, Mistry JB, Elmallah RK, ized implants, 5/12 required con- In cases of severe deformity in which Chughtai M, Mont MA: Management of strained polyethylene inserts, and TKA alone is not possible, there are extra-articular deformities in knee 2/12 experienced transient peroneal numerous advantages to staging the arthroplasty, in Mont MA, Tanzer M, eds: Orthopaedic Knowledge Update 5: Hip nerve palsies. In our experience, for osteotomy rather than performing a and Knee Reconstruction, ed 5. Rosemont, cases of particularly severe multi- simultaneous osteotomy correction IL, AAOS, 2017, pp 210-219. planar deformities, staged osteotomy and then arthroplasty in the same 6. Weinberg DS, Park PJ, Liu RW: Association and a gradual correction using a surgical setting. It is important to between tibial malunion deformity parameters and degenerative hip and knee hexapod frame is a useful tool that consider that ligamentous laxity is disease. J Orthop Trauma 2016;30: allows for accommodation of soft associated with extra-articular defor- 510-515. tissues and neurovascular structures mity, and constrained implants should 7. Kettelkamp DB, Hillberry BM, Murrish to correction of the deformity. be available and used appropriately. DE, Heck DA: Degenerative arthritis of the

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