➢ Calcaneonavicular and talocalcaneal coalitions account for 90% of all tarsal coalitions in the pediatric population.
➢ Computed tomographic (CT) or magnetic resonance imaging (MRI) scans identify tarsal coalitions that are unrecognized on radiographs and provide more information regarding the size, content, and location of coalitions. They are a mandatory component of the evaluation.
➢ Nonoperative measures represent the first line of treatment and may consist of activity modification coupled with nonsteroidal anti-inflammatory medications, the use of shoe inserts or orthotics to elevate the medial arch and to preserve hindfoot alignment, and immobilization in a below-the-knee walking cast to reduce joint stresses and to permit microfractures to heal.
➢ Operative treatment should be considered after nonoperative measures have been exhausted. The selection of the operative procedure should depend on the location of the pain, whether or not the tarsal coalition can be resected, the presence of marked hindfoot alignment, and the presence of arthritis in the Chopart joint.
➢ Patients with talocalcaneal coalitions that are >50% of the size of the posterior talocalcaneal facet and have excessive hindfoot deformity should be counseled, before undergoing coalition resection, about the higher chance of having a poor outcome and requiring a secondary procedure.
A tarsal coalition is a congenital foot anomaly that consists of a fibrous, cartilaginous, or osseous connection between tarsal bones. Originally described in 1764 by de Buffon et al.1 and a century later by Zuckerkandl2 and Holl3, tarsal coalitions have an estimated prevalence of 1% to 2% in the general population4,5 and the majority either are asymptomatic or cause only minor symptoms6. Tarsal coalitions have received considerable attention in the medical literature because of their association with peroneal spastic flatfoot7 as well as with a number of congenital conditions that affect the lower extremity. Although operative treatment is generally advocated for symptomatic tarsal coalitions that have not responded to conservative treatment, the indications as to which operative procedure to perform remain controversial because of conflicting results from small retrospective series and a lack of prospective comparative studies. The purposes of this review are (1) to provide an overview of the current understanding of the pathogenesis and natural history of tarsal coalitions, (2) to review the presentation, diagnosis, and radiographic methods for the evaluation of tarsal coalitions, and (3) to provide evidence-based recommendations based on the existing literature for the most commonly described surgical interventions.
The most common and clinically important type of tarsal coalition is congenital. Although tarsal coalitions can arise as a result of traumatic injuries, inflammatory arthropathies, degenerative joint disease, infections, and neoplasia, such acquired coalitions are rare, typically occur more often in adults8-10, and will not be discussed in this review. Congenital tarsal coalitions occur as the result of a failure of segmentation in embryonic mesenchyme that leads to a fibrous anlage between two or more tarsal bones6,11. This anlage, which forms as early as the fetal stage11, can develop into a fibrous coalition (syndesmosis) or can undergo metaplasia to cartilage (synchondrosis) and finally to bone (synostosis)9,10,12,13. The two most common sites of tarsal coalition, accounting for 90% of all coalitions14, are between the calcaneus and the navicular and at the middle facet of the talocalcaneal joint. The frequent finding of tarsal coalitions in first-degree relatives has led to their characterization as having an autosomal dominant pattern of inheritance6,10,11. However, phenotypic expression of tarsal coalitions is variable, with different members of the same family exhibiting coalitions between different tarsal bones6,10,13,15. Therefore, the genetic inheritance of this condition is likely to be more complicated than a simple Mendelian model and potentially involves more than one gene responsible for terminal limb development16. Tarsal coalitions also are associated with syndromes arising from genetic mutations, including fibular hemimelia, carpal coalition, clubfoot, arthrogryposis, Apert syndrome, and Nievergelt-Pearlman syndrome6,8,10,12,15,17.
Despite the detailed descriptions of the pain and deformity that occur secondary to tarsal coalition, the complete pathophysiology of this condition remains incomplete because of the inability to explain why as many as 75% of affected individuals are asymptomatic6. Furthermore, it is also unknown why similar-appearing coalitions can lead to a wide range of deformities, from planovalgus to even varus hindfoot alignment. During normal stance phase, the subtalar joint rotates as much as 10° internally, keeping the foot facing forward and accommodating for tibial external rotation18. In the presence of either a talocalcaneal or calcaneonavicular coalition, this internal rotation does not occur across the subtalar joint and is transferred to the calcaneocuboid and talonavicular joints. This transfer results in flattening of the longitudinal arch, abduction of the forefoot, and the creation of a planovalgus deformity10. This rigid flatfoot associated with hindfoot valgus initially was thought to occur secondary to spasm of the peroneal muscles, leading to the inaccurate and thus less frequent use of the term peroneal spastic flatfoot19. Pain following the development of this deformity is believed to arise either from ossification of a previously fibrous or cartilaginous coalition, microfractures at the coalition-bone interface, or chondral damage and secondary degenerative changes associated with the increased biomechanical stresses on adjacent structures9,13,20.
Patients with tarsal coalitions often present in early adolescence, most commonly for the evaluation of foot and/or ankle pain. The pain, typically insidious in onset, is exacerbated with weight-bearing and activity and is relieved with rest9,10,15,20,21. A history of recurrent ankle sprains or difficulty walking on uneven surfaces may be reported10,13,20. Pain may be diffuse, may be localized to a specific area related to the coalition, or may be due to the resulting hindfoot deformity. Pain that is localized to the sinus tarsi and inferior to the fibula is suggestive of a calcaneonavicular coalition8,10,13,21, whereas pain distal to the medial malleolus, deep within the subtalar joint, or along the medial aspect of the foot is suggestive of a talocalcaneal coalition10,13,20,21. In addition, pain over the medial arch or in the sinus tarsi can occur because of the presence of a planovalgus deformity, whereas lateral hindfoot pain can be associated with hindfoot varus. Tarsal coalitions presenting in association with syndromes usually are not the primary manifestation of these conditions, but an awareness of the relationship may assist the physician when evaluating foot pain or deformity in affected patients.
Examination should focus on the mobility and alignment of the hindfoot as well as the localization of pain. Observation of gait may demonstrate antalgic limp, shortened stance phase, equinus, and persistent hindfoot eversion throughout the gait cycle20,22. Inspection of the lower extremity with the patient standing frequently reveals hindfoot valgus, pes planus, forefoot abduction, and more distant genu recurvatum9,15,20,21. This spectrum of findings, however, is not always present, and a neutral or varus hindfoot does not rule out the presence of a tarsal coalition23. Pes planus should be evaluated for flexibility by asking the patient to stand on the toes. If the medial arch reconstitutes, then the patient has flexible pes planus, is less likely to have a tarsal coalition, and should be evaluated for gastrocnemius-soleus tightness as a source of the symptoms21,24. If the medial arch does not reconstitute, then the patient has rigid pes planus and the clinical suspicion of tarsal coalition remains elevated. The next step is to assess for loss of subtalar motion.
The patient is asked to perform a heel rise while standing, with the hindfoot being observed from behind. Normally, the hindfoot internally rotates and inverts through the subtalar joint into varus as the heel is lifted; if subtalar motion is restricted, the hindfoot will not assume its normal varus position, and the hindfoot valgus and diminished appearance of the medial plantar arch will persist. A reverse Coleman block test25 also can be used to evaluate for subtalar rigidity. With the patient standing, a 1-in (2.54-cm) block is placed under the medial aspect of the forefoot while the heel and the lateral border are kept in contact with the floor; if hindfoot valgus is not corrected with block placement, the test is positive and indicates that the deformity is rigid. With the patient sitting or supine, passive evaluation of subtalar motion is performed with the foot in 20° of dorsiflexion in order to minimize movement at the ankle joint. Provocative testing of subtalar and midfoot range of motion may reproduce symptoms and reveal stiffness in eversion and inversion. All areas of the ankle, hindfoot, and midfoot should be thoroughly palpated in an attempt to elicit pain. The contralateral extremity also must be examined, both for comparison and because of the known presence of bilateral coalition in at least 50% of patients6,10,13,15,20,21.
Positive findings on history and physical examination should prompt additional diagnostic tests. The differential diagnosis for pain in the context of a rigid flatfoot deformity includes infectious, inflammatory, and neoplastic processes. A laboratory evaluation, including a complete blood-cell count, determination of the C-reactive protein level and the erythrocyte sedimentation rate, a rheumatoid factor test, and anti-nuclear antibody counts should be considered.
Radiographic evaluation is critical and includes standing anteroposterior, lateral, internal oblique, and Harris long axial radiographs of the affected foot. Radiographic signs that are specific to certain tarsal coalitions can be identified, and hindfoot alignment can be measured.
Talocalcaneal coalitions most often involve the middle facet and exhibit several features that are not present on normal radiographs (Fig. 1, A). The lateral radiograph should be scrutinized for several signs: the C-sign, the dysmorphic sustentaculum tali, and the blunted lateral process of the talus (Fig. 1, B). The C-sign is formed by the continuity of the inferomedial border of the talus with the sustentaculum tali. As reported by Kernbach, this sign is more indicative of the proximity of the talus and sustentaculum tali due to hindfoot valgus and pes planus rather than coalition21. A dysmorphic sustentaculum tali is considered to be present when the contour of the rectangular block-like sustentaculum becomes enlarged and rounded22. Reliable findings on the Harris view that suggest the presence of a coalition include abnormal bone overgrowth of both the sustentaculum tali and the adjacent talus as well as a narrow or irregular joint line with sclerosis and subchondral cysts8,26 (Fig. 1, C).
Calcaneonavicular coalitions can be best observed on the internal oblique view and are represented by the so-called anteater sign, in which the elongated anterior process of the calcaneus attaches to the lateral aspect of the navicular27 (Fig. 1, D). The sign also can be viewed on the lateral radiograph but is less visible on that view8. A reverse anteater sign has also been described26, wherein an osseous process extends from the navicular toward the anterior process of the calcaneus. A talar beak may be observed in association with either a calcaneonavicular or talocalcaneal coalition. The beak occurs as a result of increased compensatory motion at the talonavicular joint and is best appreciated on the lateral radiograph10.
Hindfoot alignment can be defined and quantified on radiographs with use of either the hindfoot alignment view as described by Saltzman and el-Khoury28 (Fig. 2, A) or the long axial view initially described by Kleiger and Mankin29 (Fig. 2, B). Both views involve positioning the patient for a standing posteroanterior radiograph and then inclining the beam by either 20° (hindfoot alignment view) or 45° (long axial view) relative to the floor. Alignment can then be quantified by measuring the angle between the mid-diaphyseal axis of the tibia and the mid-diaphyseal axis of the calcaneus. Both views have been shown to be correlated with one another20, but the long axial view has been reported to have better inter-rater reliability30.
Despite the multitude of radiographic views that are available, advanced imaging modalities, including computed tomography (CT) and/or magnetic resonance imaging (MRI), are mandatory components in the evaluation of tarsal coalitions. In addition to providing more accurate information regarding the size31, content, and location of a coalition through multiplanar imaging17, both modalities have been shown to identify additional coalitions that are unrecognized on radiographs (Fig. 3)32,33. The minimum requirements for appropriate CT evaluation include 3-mm coronal and axial cuts with sagittal reconstructions34. On CT scans, non-osseous coalitions are identified as subtle sclerotic and cystic changes that are not evident on the normal side34. Three-dimensional CT scans recently have been examined as an additional way to better evaluate the size, location, and orientation of talocalcaneal coalitions7. MRI is useful for identifying fibrous or cartilaginous coalitions as well as arthrosis in adjacent joints, which could affect the long-term outcome after surgery. Fat-suppressed and short tau inversion recovery (STIR) sequences are recommended to delineate inflammatory changes, which could be an indication of other causes of pain such as coalition fractures or associated tendinitis35. Multiple techniques for quantifying coalition size and hindfoot alignment with use of coronal CT images have been described (Fig. 4)34,36, but reliability studies and correlation with measurements on radiographs or other imaging modalities are lacking.
The two main goals of treatment of tarsal coalitions include the relief of pain and the restoration of function. Therefore, the general consensus is that treatment of any kind is indicated solely for symptomatic tarsal coalitions. Nonoperative measures constitute the first line of treatment5,8,13,21,24,37-41. Such measures include activity modification coupled with nonsteroidal anti-inflammatory medication, the use of shoe inserts or orthotic devices to elevate the medial arch and to preserve hindfoot alignment, and immobilization in a below-the-knee walking cast to reduce joint stresses and to permit microfractures to heal. Prospective studies comparing each form of nonoperative treatment are lacking. Better outcomes after nonoperative treatment are expected for patients with no evidence of degenerative changes41. A commonly cited figure is that as many as 30% of symptomatic patients become pain-free following six weeks of cast immobilization13,41, but the report in which that value was cited did not include a sample size42 and the only other published report in which nonoperative treatment led to successful results included only fourteen patients31.
Operative treatment is indicated when symptoms persist despite prolonged nonoperative measures. The operative treatment of calcaneonavicular coalitions most commonly involves excision of the coalition and interposition with muscle, fat, or bone wax. It should be stressed that hindfoot deformities also may be present and that coalition excision alone does not necessarily restore hindfoot alignment. The treatment of talocalcaneal coalitions is less clear and is dependent on specific features of the coalition and hindfoot alignment. Multiple coalitions in the same foot in otherwise healthy patients (Fig. 3) have been reported43-48, but treatment recommendations are limited given the small number of reported cases and the variable results following either resection of the coalitions or triple arthrodesis.
In addition to the planned coalition resection, a customized approach for addressing associated hindfoot, midfoot, and forefoot deformities should be considered. Gastrocnemius recession or Achilles tendon lengthening should be considered if intraoperative ankle dorsiflexion is not past neutral. Forefoot malalignment that is represented by incomplete reduction of the talonavicular joint can be addressed through a combination of several procedures, depending on the severity and flexibility of deformities. Such procedures may include lengthening of the peroneus brevis, lengthening of the abductor digiti minimi, release of the dorsolateral talonavicular capsule, plication of the plantar-medial talonavicular capsule, plication of the posterior tibialis tendon, and closing-wedge osteotomy of the medial cuneiform when appropriate.
Preliminary evaluations of the long-term effects of operative treatment of tarsal coalitions have been positive. Khoshbin et al. examined twenty-four patients at an average of fourteen years after the treatment of tarsal coalition49. The authors found that patients who had undergone resection were more likely to have returned to sports and had greater levels of activity. Despite these promising results, coalition resection does not necessarily improve subtalar kinematics50, normalize dynamic plantar pressures, or restore muscular coordination51. Therefore, assessment of additional characteristics such as hindfoot alignment and degenerative disease affecting adjacent joints may be necessary.
Early investigators recommended triple arthrodesis for the treatment of calcaneonavicular coalitions because of concerns regarding associated transverse tarsal joint arthrosis and a high rate of recurrence of coalition following resection52,53. However, this recommendation was challenged by the results of several subsequent studies19,54 demonstrating that pain relief could be maintained at intermediate to long-term follow-up after isolated resection of a calcaneonavicular coalition. Our preferred method for the resection of a calcaneonavicular coalition is similar to the original description53. The surgical technique involves an anterolateral approach over the coalition, retraction of the extensor digitorum brevis and inferior extensor retinaculum, resection of a 1-cm block of the coalition, and interposition of a portion of the extensor digitorum brevis (Fig. 5). Andreasen reported that this technique was associated with satisfactory outcomes for twenty-two of thirty patients who were followed for as long as twenty-two years postoperatively52, Chambers et al. noted a 100% rate of satisfactory results in a study of twenty-nine patients who were followed for three to fourteen years55, Cowell reported good or excellent outcomes for twenty-three (88%) of twenty-six patients56, and Gonzalez and Kumar reported good to excellent outcomes for fifty-eight (77%) of seventy-five patients who were followed for an average of three years following resection and interposition54. A minimally invasive method of performing a coalition resection with use of arthroscopy57,58 recently has received attention, with good short-term results being observed in studies involving very small sample sizes59. The main concern regarding arthroscopic resection involves adequate identification of the deeper aspect of the osseous coalition bridge, which, if not adequately resected, can facilitate recurrence of coalition. Larger sample sizes and longer follow-up are required to determine if this approach could serve as a viable alternative to open surgery.
Alternative options to interposing a portion of the extensor digitorum brevis within the space at the site of the resected coalition include placing nothing, fat, or bone wax. Mitchell and Gibson, in a study of forty-one patients who underwent resection of a calcaneonavicular coalition without the use of any interposition material, reported a 68% rate of success in terms of the resolution of symptoms at the time of the six-year follow-up60. One drawback was the finding that the coalition had recurred in one-third of the patients, leading subsequent investigators to recommend the use of some form of interposition material. A concern related to transfer of the head of the extensor digitorum brevis is that it results in an osseous prominence along the lateral border of the foot, which can lead to difficulties with shoe wear61, although the incidence of this complication has not been reported, to our knowledge. Tachdjian62 indicated a preference for interposing fat that has been harvested from either the gluteal cleft or the abdomen, and Mubarak et al. recently evaluated that technique in a study of sixty-nine patients61. Although the duration of follow-up in that study was only one year, 87% of the patients returned to the same level of sports and had an excellent outcome. The remaining 13% of the patients exhibited recurrence of the coalition, with only three of them requiring revision resection. The authors concluded that the revision rate in their study was comparable, if not lower, than the rates in previous series involving the use of extensor digitorum brevis interposition, but longer-term evaluation of this patient cohort is still needed. Cohen et al. evaluated the use of bone wax interposition in a study of twelve patients and reported results that were comparable with those of extensor digitorum brevis transfer, but that study involved adults, most of whom already had preexisting hindfoot arthritis, and the average duration of follow-up was only thirty-six months63.
With regard to the identification of factors that are prognostic for a good outcome following the resection of a calcaneonavicular coalition, better results tend to be observed in young patients and in patients with cartilaginous or nonossified coalitions52,54,55. Jayakumar and Cowell suggested that the best long-term results are achieved in patients under the age of fourteen years42, but Cohen et al., in a series of adults, found that resection did provide at least short-term relief of symptoms in patients over the age of thirty years63. Talar beaking, initially considered to represent early talonavicular arthritis42,64, instead has been shown to occur secondary to increased motion at this interface, does not represent degenerative changes when inspected intraoperatively, and should not be considered as a contraindication to resection19,65.
On the basis of the results of multiple retrospective studies, excision is considered to be the operative treatment of choice for calcaneonavicular coalitions, with good-to-excellent results expected for the majority of patients after intermediate to long-term follow-up. Because of concern regarding coalition recurrence, the interposition of soft tissue is advised, with a portion of the extensor digitorum brevis being the most commonly utilized material as reported in the literature19,63. Recurrences are often treated with revision resection, whereas triple arthrodesis is utilized as a salvage procedure41. Hindfoot malalignment in the context of a calcaneonavicular coalition is an additional factor that must be considered. The literature regarding hindfoot malalignment and recommendations regarding its treatment are addressed jointly with talocalcaneal coalitions in the next section.
The optimal surgical treatment for talocalcaneal coalitions remains unclear because of a lack of comparative studies in the literature as well as an ongoing debate of how to address poor prognostic factors. Prior to the regular use of CT, resection of a talocalcaneal coalition was perceived to be associated with poor results because of inadequate intraoperative visualization and poor surgical technique19. On the basis of this perception, triple arthrodesis became the traditional treatment42. More recent investigations have demonstrated that, with adequate identification of the coalition with use of advanced imaging modalities and minimal degeneration in the posterior facet, resection of a talocalcaneal coalition via a medial incision and interposition of either a split flexor hallucis longus tendon, fat, or bone wax produces good to excellent outcomes for the majority of adolescent patients (Fig. 6). Our preferred technique involves a horizontal incision over the medial aspect of the hindfoot, centered over the sustentaculum tali and utilizing the interval between the tibialis posterior and the flexor digitorum longus (Fig. 7). The posterior neurovascular bundle is then identified and protected. Two 22-gauge needles are placed to identify the borders of the coalition and the slope of the subtalar joint to guide the plane of resection. The coalition is then resected, and a portion of the flexor hallucis longus tendon is interposed. Olney and Asher, in a study of ten patients who underwent resection of a talocalcaneal coalition followed by interposition of either fat or bone wax, reported an 80% rate of good or excellent results at an average of 3.5 years of follow-up66.Takakura et al., in a study involving thirty-three patients who underwent resection of a talocalcaneal coalition (representing one of the largest published series to date), reported a 94% rate of good or excellent results at an average of 5.3 years postoperatively67.
Predictive factors for poor outcome following talocalcaneal resection were first described by Wilde et al., who reported a success rate of only 50% in a series of twenty patients who were managed with resection and fat interposition34. The ten patients who had a poor outcome all had (1) a talocalcaneal coalition with an area that was >50% of the size of the posterior talocalcaneal facet, (2) hindfoot valgus of >16° as measured on CT scans with use of the mid-diaphyseal axis of the tibia and the mid-diaphyseal axis of the calcaneus, and (3) narrowing of the posterior talocalcaneal facet, indicating degenerative changes. That series provided justification for the earlier suggestion, made by Scranton, to avoid resection and to consider subtalar arthrodesis instead for the treatment of coalitions with an area that is >50% of the size of the posterior talocalcaneal facet31.
The factors that were found by Wilde et al. to be predictive of a poor outcome were evaluated by Luhmann and Schoenecker in a study of twenty patients with twenty-five talocalcaneal coalitions for which surgical resection had failed40. Although the authors found an association between poor results and a coalition size >50% of the posterior facet as well as hindfoot valgus of >21°, 50% of the patients with this degree of excessive hindfoot valgus reported good or excellent results following resection of the coalition. This heterogeneity of the results led the authors to conclude that although coalition size and hindfoot valgus can increase the risk of a poor outcome following resection, isolated resection should still be attempted first (with appropriate patient counseling) followed by a calcaneal osteotomy or lateral column lengthening if symptoms persist. Other investigators38,40 have challenged this conclusion and have proposed alternative strategies, collectively yielding mixed results.
Gantsoudes et al. recently reported the results of a study of forty-nine talocalcaneal coalitions that were treated with resection and fat interposition38. With use of a treatment strategy similar to what was suggested by Luhmann and Schoenecker40, patients with severe hindfoot valgus were counseled prior to resection and underwent a staged second procedure to properly align the hindfoot. At 3.5 years of follow-up, patients who had undergone a realignment procedure had foot and ankle functional scores similar to those for patients with normal alignment after coalition resection. Giannini et al. proposed instead to simultaneously address the talocalcaneal coalition and hindfoot malalignment by means of coalition resection and subtalar arthroereisis with a bioabsorbable implant68. The twelve patients (fourteen feet) in the study had fair-to-excellent results after as long as four years of follow-up, and all had preservation of hindfoot alignment. Conversely, Cain and Hyman reported excellent outcomes in a study of fourteen tarsal coalitions that were treated solely with hindfoot osteotomies and concluded that correction of hindfoot alignment and concluded that attaining proper alignment sufficiently restored hindfoot kinematics without the need for resection or arthrodesis69.
Recently, Mosca and Bevan carefully scrutinized the literature and reviewed their own series of cases to develop a treatment algorithm for talocalcaneal coalitions36. They revised the method of assessing hindfoot alignment described by Wilde et al.34 and compared the surface area of the coalition with the dimensions of the middle and posterior talocalcaneal facets on coronal CT slices. The novelty of this proposed algorithm is that treatment is based first on positive physical examination findings and then on how such findings fit in the context of hindfoot malalignment, the location of the tarsal coalition, and articular surface degeneration in the surrounding joints. The authors also advocated adding a calcaneal neck lengthening osteotomy distal to the location of the talocalcaneal coalition, citing a three-dimensional cadaveric study that showed that such an osteotomy reliably corrects all components of hindfoot valgus and eversion70. Although the study by Mosca and Bevan was limited by a very small sample size and the radiographic parameters require validation, the proposed algorithm is a logical extension of findings that have been reported in the literature and deserves prospective evaluation.
The optimal treatment of tarsal coalitions in the pediatric population remains controversial, and the lack of prospective or adequately powered comparative studies in the literature limits the grades of recommendation for management (Table I). Nonoperative treatment is consistently regarded as first-line treatment and should be exhausted before operative measures are considered. When operative treatment is indicated, the location of the pain, whether or not the coalition can be resected, the amount of hindfoot malalignment, and the presence of degenerative changes in the Chopart joint are the most important factors that should be utilized to guide decision-making (Fig. 8). In the presence of a normally aligned hindfoot and no surrounding arthritis, the treatment of calcaneonavicular coalitions most commonly involves resection of the coalition and the use of interposition material, usually a portion of the extensor digitorum brevis. Talocalcaneal coalitions also may be treated with resection; however, patients with larger coalitions and/or substantial hindfoot malalignment should be advised of the higher chance that that may require a subsequent procedure. Preliminary investigations into the long-term effects of operative treatment of tarsal coalitions have demonstrated positive effects in terms of pain relief and activity level. Additional long-term studies are needed to fully evaluate the effects of different operative procedures on foot kinematics, muscular activity, and overall outcome.
The authors would like to acknowledge Mr. Mark Lepik for his assistance in the creation of the surgical procedure figures.
Source of Funding: No external funds were received in support of this study.
Investigation performed at the Division of Orthopaedics, Shriners Hospital for Children, Montreal Children’s Hospital, McGill University, Montreal, Quebec, Canada
Disclosure: None of the authors received payments or services, either directly or indirectly (i.e., via his or her institution), from a third party in support of any aspect of this work. None of the authors, or their institution(s), have had any financial relationship, in the thirty-six months prior to submission of this work, with any entity in the biomedical arena that could be perceived to influence or have the potential to influence what is written in this work. Also, no author has had any other relationships, or has engaged in any other activities, that could be perceived to influence or have the potential to influence what is written in this work. The complete Disclosures of Potential Conflicts of Interest submitted by authors are always provided with the online version of the article.
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