children Article Cross-Union Surgery for Congenital Pseudarthrosis of the Tibia Claire E. Shannon * , Aaron J. Huser and Dror Paley Paley Orthopedic and Spine Institute, West Palm Beach, FL 33407, USA; [email protected] (A.J.H.); [email protected] (D.P.) * Correspondence: [email protected] Abstract: Congenital Pseudoarthrosis of the Tibia (CPT) is a rare condition with a reputation for recurrent fractures and failure to achieve union. A large variety of surgical procedures have been attempted for the treatment of fractured cases of CPT with an average rate of union without refracture of only 50%. Intentional cross-union between the tibia and fibula has been reported to improve these results to 100% union with no refractures. This is a retrospective study of 39 cases of CPT in 36 patients treated by the Paley cross-union protocol with internal fixation, bone grafting, zoledronic acid infusion and bone morphogenic protein 2 (BMP2) insertion. All 39 cases of CPT united at the tibia and developed a cross-union to the fibula. Two patients had a persistent fibular pseudarthrosis, one that was later treated at the time of planned rod exchange and one that has remained asymptomatic. There were few postoperative complications. There were no refractures during the up to 7-year follow- up period. The most common problem was the Fassier-Duval (FD) rod pulling through the proximal or distal physis into the metaphysis (66.7%). This did not negatively affect the results and was remedied at the time of the planned rod exchange. The Paley Cross-Union Protocol is very technically demanding, but the results have radically changed the prognosis of this once sinister disease. Keywords: congenital pseudarthrosis of the tibia (CPT); congenital pseudarthrosis of the fibula; neurofibromatosis 1; NF1; cross-union; anterolateral bowing; hamartoma; bisphosphonate; zoledronic Citation: Shannon, C.E.; Huser, A.J.; acid; bone graft; BMP Paley, D. Cross-Union Surgery for Congenital Pseudarthrosis of the Tibia. Children 2021, 8, 547. https:// doi.org/10.3390/children8070547 1. Introduction Congenital Pseudoarthrosis of the Tibia (CPT) is a rare condition with an incidence Academic Editor: Reinald Brunner between 1:140,000 to 1:250,000 live births [1]. A diagnosis is often made early in life due to an anterolateral bowing deformity of the affected leg or a pathologic fracture of the Received: 2 June 2021 tibia and/or fibula. CPT is most commonly associated with neurofibromatosis (NF) in Accepted: 21 June 2021 Published: 24 June 2021 50–90% of cases [2]. Associations with fibrous dysplasia and osteofibrous dysplasia have been reported [3,4]. Non-operative management with protective bracing is considered the standard of care in cases that have not yet broken. Once the bone has fractured, surgical Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in management is indicated to achieve union and prevent refracture. A wide variety of published maps and institutional affil- surgical treatments have been tried for the management of CPT, with variable success. As iations. a result of these factors, there has been a general acceptance that refracture or failure to achieve union is a common pathway in this condition’s natural history, with failure rates (lack of union or union followed by refracture) as high as 68% [5,6]. The average rate of union without refracture for all of these methods is approximately 50% [2,7]. Persistent nonunion or refracture leads to additional surgery and secondary changes in the leg, Copyright: © 2021 by the authors. including ankle and knee contractures, malalignment, leg length discrepancy, calcaneo- Licensee MDPI, Basel, Switzerland. This article is an open access article cavus foot deformity, foot length shortening, calf muscular atrophy, gait alterations, coxa distributed under the terms and valga, and even hip dysplasia [8]. Beyond the physical and mental trauma that results from conditions of the Creative Commons the interruption of childhood with repeated surgery, the likelihood of failed treatment may Attribution (CC BY) license (https:// lead to the recommendation for amputation as a primary or secondary treatment [9]. creativecommons.org/licenses/by/ In 2011, Choi et al. [10] and in 2012, Paley [11] independently published their respective 4.0/). methods of treating patients with CPT by creating an intentional cross-union between the Children 2021, 8, 547. https://doi.org/10.3390/children8070547 https://www.mdpi.com/journal/children Children 2021, 8, 547 2 of 25 from the interruption of childhood with repeated surgery, the likelihood of failed treat- ment may lead to the recommendation for amputation as a primary or secondary treat- ment [9]. Children 2021, 8, 547 2 of 24 In 2011, Choi et al. [10] and in 2012, Paley [11] independently published their respec- tive methods of treating patients with CPT by creating an intentional cross-union between the tibia and fibula. Choi et al. did this by converging the fibula towards the tibia, bone graftingtibia and between fibula. Choi them et and al. did fixing this the by convergingtibia by IM therodding fibula across towards the the ankle tibia, joint bone and grafting circu- larbetween external them fixation and fixing (4-in-1 the technique). tibia by IM Paley rodding achieved across this the by ankle rodding joint and both circular bones externalstraight withoutfixation crossing (4-in-1 technique). the ankle and Paley bone achieved grafting this between by rodding the tibia both and bones fibula straight to create without a wide bridgecrossing of thebone, ankle applying and bone a circular grafting external between fixator, the tibia using and fibulabone morphogenic to create a wide protein bridge 2 (BMP2)of bone, intraoperatively applying a circular and using external Zoledronic fixator, using Acid bonepreoperatively morphogenic and 3 protein months 2 postop- (BMP2) erativelyintraoperatively (Paley cross-union and using Zoledronic protocol) (Figure Acid preoperatively 1A). Both achieved and 3 monthsunion in postoperatively all cases with- out(Paley refracture. cross-union This protocol) 100% success (Figure rate1A). of Both union achieved without union refracture in all cases was without double refracture.that of all previousThis 100% methods. success rate Furthermore, of union without the age refracture at the time was of double treatment that ofwas all not previous a limitation methods. to success.Furthermore, In 2019, the Paley age published at the time a ofmodification treatment wasof his not original a limitation method to substituting success. In a 2019,mal- leablePaley publishedplate on the a modification tibia for the ofcircular his original external method fixator substituting [8] (Figure a malleable1B). The Paley plate oncross- the uniontibia for protocol the circular was published external fixator with step-by-step [8] (Figure1B). illustrations The Paley cross-unionin the supplement protocol to wasthis articlepublished [12]. with The step-by-steppurpose of illustrationsthis study is in to the examine supplement the early to this results article of [ 12the]. ThePaley purpose cross- of this study is to examine the early results of the Paley cross-union protocol using only union protocol using only internal fixation (no external fixation). internal fixation (no external fixation). (A) Figure 1. Cont. Children 2021,, 8,, 547547 3 3of of 25 24 (B) Figure 1. ((A)) AP AP and and lateral lateral radiographs radiographs that that we werere taken postoperatively of a patient who underwent a Paley cross-union procedure performed with a circularcircular external fixator.fixator. (B) AP and lateral radiographs that were taken postoperatively of a patient who underwent a Paley cross-union procedureprocedure performedperformed withwith allall internalinternal fixation.fixation. 2.2. Materials Materials and and Methods Methods InstitutionalInstitutional review review board approval was obtained for a retrospective retrospective review of charts andand radiographs radiographs from from February February 2014 2014 to to April April 2 2019.019. Patients Patients were were included included if ifthey they had had a diagnosis of CPT, underwent the Paley cross-union protocol with all internal fixation, and Children 2021, 8, 547 4 of 25 Children 2021, 8, 547 4 of 24 had chart/radiographic documentation to support a minimum of 24-month follow-up. aThere diagnosis was a oftotal CPT, of 39 underwent cases of CPT the in Paley 36 patients cross-union treated protocol by the Paley with allcross-union internal fixation, internal andfixation had that chart/radiographic met the inclusion documentation criteria. No patients to support in the a minimum treatment of group 24-month were follow-up. excluded Therefrom the was study. a total There of 39 caseswere 16 of CPTboys inand 36 20 patients girls. The treated mean by age the Paleyat the cross-uniontime of surgery internal was fixation3.3 years that (range met 12 the months–13.5 inclusion criteria. years). No The patients mean follow-up in the treatment was 35 groupmonths were (range excluded of 24– from85 months). the study. Sixty-four There percent were 16 of boys patients and 20had girls. a clinical The meandiagnosis age of at NF1, the time 6% had of surgery a diag- wasnosis 3.3 of yearsosteofibrous (range 12dysplasia, months–13.5 and 30% years). were The idiopathic mean follow-up or without was a diagnosis. 35 months Seven (range of ofthe 24–85 36 patients months). (19%) Sixty-four had undergone percentof previous patients failed had a surgery clinical for diagnosis CPT. of NF1, 6% had a diagnosisAll cases of osteofibrous of CPT were dysplasia, classified and radiographically 30% were idiopathic using or the without Paley aclassification diagnosis. Seven (Fig- ofure the 2). 36 There patients were (19%) five hadtype undergone 1, one type previous 2a, six type failed 2b, surgery eight type for CPT. 3, six type 4a, twelve type All4b, casesand one of CPT type were 4c. All classified patients radiographically were given an using infusion the Paley of Zoledronic classification acid (Figure infusion2 ).