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 Table of Contents  
Year : 2021  |  Volume : 7  |  Issue : 1  |  Page : 26-30

A re-examination of the patterns of foot and ankle deformities in congenital limb deficiencies

1 Oxford University Hospitals NHS Foundation Trust, John Radcliffe Hospital, Headley Way, Headington Oxford, England
2 The Hospital for Sick Children, 555 University Avenue, Toronto, Canada

Date of Submission10-Apr-2021
Date of Decision10-Jun-2021
Date of Acceptance11-Jun-2021
Date of Web Publication30-Jun-2021

Correspondence Address:
Dr. Alpesh Kothari
Oxford University Hospitals NHS Foundation Trust, John Radcliffe Hospital, Headley Way, Headington, Oxford, OX3 9DU
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/jllr.jllr_13_21

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Purpose: The aim of this study is to evaluate foot deformities and anomalies present in congenital limb deficiencies (CLDs). We sought to define the relationship between the type of limb deficiency and foot posture, patterns of ray deficiencies, and association between tarsal coalition (TC) and ball-and-socket ankle. Materials and Methods: This is a single institution, retrospective radiograph, and medical record review of patients with CLD, comprising congenital femoral deficiency (CFD), tibial hemimelia (TH), and fibular hemimelia (FH) from January 2000 to January 2019. Data extracted included patient demographics, predicted leg length discrepancy, associated deformities and anomalies, and specifics of the foot deformity. Surgical procedures were recorded. Data were reported using descriptive statistics. Fisher's exact test analyses of contingency tables were used for the exploratory components of this study. Results: Eighty-one patients with 97 limb deficiencies were identified (16 – CFD, 18 – TH, and 63 – FH). Isolated CFD was not associated with foot and ankle deformity and TH was associated with an equinocavovarus foot in all limbs. In FH, an equinocavovarus deformity was present in 15/63 (24%) feet, most requiring foot surgery. Of 48 patients with FH and absent rays, two lacked lateral rays, whereas the remainder missed one or more intermediate rays. TC was unrelated to the presence of ball-and-socket ankle. Conclusions: This study demonstrates heterogeneity in the spectrum of foot and ankle deformity in CLD, particularly in FH. Recognition of this phenotypic variation is critical for surgeons to formulate a comprehensive treatment plan and ensure optimal functional outcomes. Level of Evidence: IV.

Keywords: Congenital femoral deficiency, congenital limb deficiency, fibular hemimelia, tibial hemimelia

How to cite this article:
Kothari A, Kelley SP, Bouchard M. A re-examination of the patterns of foot and ankle deformities in congenital limb deficiencies. J Limb Lengthen Reconstr 2021;7:26-30

How to cite this URL:
Kothari A, Kelley SP, Bouchard M. A re-examination of the patterns of foot and ankle deformities in congenital limb deficiencies. J Limb Lengthen Reconstr [serial online] 2021 [cited 2022 Aug 17];7:26-30. Available from: https://www.jlimblengthrecon.org/text.asp?2021/7/1/26/320030

  Introduction Top

Congenital lower-limb deficiencies consist of a constellation of deformities and deficiencies of variable severity from absence to hypoplasia. These are rare conditions. The most common limb deficiency, fibular hemimelia (FH), has an incidence of only 5.7–20 cases/million live births.[1]

The entire limb, or a segment of it, may be affected. Deficiencies such as FH, tibial hemimelia (TH), and congenital femoral deficiency (CFD) have the primary clinical problem of shortening or absence of the respective bone. Associated deficiencies of the affected limb are common and typically conform to recognizable patterns. These can include a dysplastic acetabulum, coxa vara and femoral bowing, hypoplastic lateral femoral condyle, hypoplastic cruciate ligaments, bowing of the tibia, ball-and-socket ankle joint, tarsal coalitions (TCs), equinovalgus or equinovarus foot deformities, and absent or additional rays. The extent and severity of these associated differences is variable and typically depend on the primary bony deficiency.[2]

The classically reported foot and ankle anomalies associated with FH include a ball-and-socket ankle, an equinovalgus foot deformity, TCs, and absent lateral rays.[3],[4],[5],[6] There are reports in the literature that the spectrum of FH can be more heterogeneous, including clubfoot-like equinocavovarus foot postures, and missing intermediate rays instead of lateral rays[7],[8] CFD occurs concurrently with FH in up to 80% of cases with the concomitant foot and ankle pathology.[9],[10] CFD is seldom associated with an isolated foot and ankle abnormality.[10] TH is associated with syndactyly, polydactyly, TCs, and an equinocavovarus foot posture.[11],[12]

Deformity correction and lengthening of the congenitally deficient limb has become more refined and predictable with good outcomes.[13],[14] The success of any limb deficiency treatment is often linked to length of consolidated bone regeneration achieved, however, success is also critically dependent on the function of the foot and ankle, as this is the interface between the lower limb and the ground.[15] Achieving a stable, plantigrade, and shoeable or braceable foot is essential when considering patients with limb deficiencies for reconstructive versus ablative procedures.

Given the importance of identifying, correcting, and retaining foot and ankle function during treatment of congenital limb deficiencies (CLDs), we aimed to evaluate the spectrum of foot deformities and combinations of anomalies present in a large cohort of longitudinal limb deficiencies. We hypothesized that equinocavovarus foot posture would not only be exclusive to TH but also be commonly observed in FH where the fibula is present providing an intact lateral buttress. We also hypothesized that central ray deficiency is more common in FH than previously reported and that TCs would predispose to a ball-and-socket ankle joint as a compensation for a rigid subtalar joint.

  Materials and Methods Top

This is a research ethics board-approved retrospective observational study reviewing the electronic medical records and radiographs of patients with longitudinal limb deficiencies seen at a single institution between January 1, 2000, and January 1, 2019. Patients were identified within the institutional radiology database by keyword search in the diagnosis fields or reports. Keywords included fibular/fibula hemimelia, tibial/tibia hemimelia, congenital limb deficiency, femoral deficiency, short femur, proximal femoral (focal) deficiency, and variants of the spelling of each term. Inclusion criteria were children between the age of 0 and 18 years at the time of X-ray, a congenital lower-limb deficiency confirmed on radiographs and in the medical records, a complete set of anteroposterior (AP) and lateral radiographs of the foot and ankle, and at least an AP view of the whole lower limb and pelvis of the affected side. Only patients with a definitive treatment and minimum of 12-month follow-up were included. The exclusion criteria were inadequate foot and ankle X-rays, foot or ankle deformity without other findings confirming lower-limb deficiency, and insufficient follow-up.

Data extracted included patient demographic details, descriptive details of their CLD including limb length discrepancy, associated limb deformities and anomalies, and specifics of the foot deformity (foot posture, ankle joint morphology, ray deficiency, presence and nature of coalitions, and presence of syndactyly). The surgical procedures undertaken and the use of any braces/prostheses were also recorded. Evaluation of the radiographs was performed by a fellowship-trained pediatric orthopedic surgeon and pediatric orthopedic fellow. In ray-deficient feet, we applied the criteria described by Reyes et al., assuming that the presence of a cuboid or calcaneocuboid coalition with articulating lateral metatarsal was surrogate evidence of a central rather than lateral ray deficiency [Figure 1].[8] For reference, limb deficiencies were described according to commonly used classifications [Appendix 1].
Figure 1: An anteroposterior radiograph of a foot with an intermediate ray deficiency as evidenced by preservation of the cuboid articulating with the lateral most rays. The most lateral ray flares like a classic 5th metatarsal. There is a central tarsal bone representing a cuneiform that does not have an adjacent articulating metatarsal. This patient also has coalitions between the navicular and talus and cuboid and calcaneus

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Most data were analyzed with descriptive statistics. Fisher's exact test analyses of contingency tables were used for the exploratory components of this study. Alpha was set at 0.05. Statistical analyses were performed using SPSS (version 25.0; SPSS Inc., Chicago, Illinois, USA).

  Results Top

After applying exclusion criteria, 81 patients with 97 limb deficiencies were included. There were 16 cases of CFD in 16 patients. Nine patients (56%) had concurrent FH. The left limb was affected in 7 (44%) cases and the right in 9 (56%) cases. In children with isolated CFD, there were no foot and ankle abnormalities. All limbs with concurrent CFD and FH had a foot deformity.

There were 18 cases of TH in 13 patients [Table 1]. The right side was affected in five (38%) patients, left in three (23%), and bilateral involvement in five patients (38%). All TH feet presented with an equinocavovarus foot posture [Table 1] and [Figure 2]a. Limb ablation was undertaken in seven cases (five through knee, one Boyd, and one Chopart amputations). Of the preserved limbs, nine had corrective foot and ankle surgery.
Table 1: Characteristics of limbs affected by tibial of fibular hemimelia, including frequency, gender, concomitant foot and ankle deformities, and whether limb ablation was undertaken

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Figure 2: Radiographic examples of range of foot and ankle deformities noted in congenital limb deficiency. (a) Equinocavovarus foot deformity observed in tibial hemimelia with associated anteromedial bow. (b) Equinocavovarus foot deformity noted in fibular hemimelia. (c) Planovalgus foot deformity noted in fibular hemimelia. Note, in fibular hemimelia cases, intermediate rays are absent. Reference lines are shown to further illustrate segmental alignment

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There were 63 cases of FH in 61 patients including 9 limbs with concurrent CFD, 24 (39%) left lower limbs, and 39 (64%) right lower limbs. Two patients had bilateral FH. Fifteen of 63 feet (24%) presented with a clubfoot-like equinocavovarus foot posture, three feet (5%) with a neutral foot posture, and the remaining 45 feet (71%) equinovalgus [Table 1] and [Figure 2]. All patients with an equinocavovarus foot posture had initial treatment with a Ponseti-like casting regime. Twelve of these 15 limbs subsequently required surgery of the foot and/or ankle, excluding percutaneous Achilles tenotomy performed as part of Ponseti management. These reconstructive procedures were predominantly soft-tissue releases (posterior or posteromedial release), tibialis anterior tendon transfer, or midfoot osteotomies. Nineteen (42%) of the limbs with an equinovalgus foot posture required surgical intervention, with the most frequent procedure being the SUPERankle (Systematic Utilitarian Procedure for Extremity Reconstruction).[16] A neutrally aligned hindfoot or equinocavovarus foot posture was only encountered when a fibula was present (47 limbs, 75%), even if partly deficient. When the fibula was absent (16 limbs, 25%), an equinovalgus foot posture was always observed.

Forty-eight (76%) of 63 feet had absent rays. Thirty feet (63%) had four rays, 14 (29%) had three, 2 (4%) had two, and 2 (4%) had one ray. Of the feet with missing rays, 46 of 48 (96%) were missing one or more intermediate rays as per the Reyes et al. criteria. The two feet missing lateral rays were feet with a single 1st ray.

Having a coalition was unrelated to the presence of a ball-and-socket ankle (P = 0.296). There was an inverse relationship between the number of rays and the presence of coalitions, i.e., the fewer the rays present, the more likely to have a TC (P = 0.019).

Surgical limb reconstruction was performed in 60 FH limbs. Of the three limbs undergoing amputation, two had a Syme's amputation and one a Boyd.

  Discussion Top

We report on the wide spectrum of foot and ankle deformities in a large cohort of CLDs. The case mix observed in our study is consistent with the previously reported incidence of CLD, with FH forming the largest subgroup of our population.[1] Coexisting multisegment longitudinal deficiencies were also often observed, especially in the context of CFD and FH.

The most important findings were in the FH population. First, in contrast to long-held assumptions, an equinocavovarus foot posture was a common observation seen in almost a quarter of cases. Second, when rays were deficient, they were more likely to be intermediate and not lateral rays. The relationship between TC and ball-and-socket ankle was also assessed, but no statistically significant association was found.

In FH, the predominant foot posture has classically been considered equinovalgus.[3],[4],[17] In this study, 24% of feet presented with a clubfoot-like equinocavovarus foot posture. This particular deformity in FH is only sporadically mentioned in the literature, and often with a low prevalence. Birch et al. reported 12 of 146 limbs with equinocavovarus, and Achterman and Kalamchi described only four from 97 limbs.[18],[19] The highest rate of FH presenting with an equinocavovarus foot was reported as 16% by Caskey et al., and one percent of all their clubfoot referrals, which still remains less than seen in this study.[7] As hypothesized, an equinocavovarus foot posture was not observed in Achterman and Kalamchi type II FH where the fibula was completely absent. This contrasts the observations of Caskey et al., although type II FH was only observed in 3/23 limbs with equinocavovarus.[7] It seems logical that an equinovalgus foot posture would predominate when the fibula was absent as there is no longer a lateral buttress in the ankle mortise.

It is not clear why there is such variability in foot posture in FH but recognizing the potential for equinocavovarus foot deformities is important. First, one should be mindful not to automatically label an equinocavovarus foot as idiopathic clubfoot in the context of a mild LLD and other foot anomalies like deficient rays, as this could represent FH. Caskey et al. found that when the LLD was subtle, it sometimes was not immediately evident to the treating surgeon that this was a case of FH.[7] Indeed, a third of equinocavovarus feet in this study did not have deficient rays, and the LLD similarly was not immediately evident.

These patients are important to recognize as they may require a limb reconstructive plan spanning their entire childhood and not just Ponseti treatment in infancy. In cases where other atypical limb features are noted alongside clubfoot, we would advocate long leg radiographs to further investigate whether there is an underlying longitudinal limb deficiency.

Second, while Ponseti is not an unreasonable approach to begin with, to improve the foot posture, these “clubfoot-like” feet may also be more resistant to Ponseti treatment and have a higher likelihood of requiring foot surgery. Twelve of 15 limbs of patients in this cohort with equinocavovarus and FH required surgery after failing foot deformity correction with the Ponseti method. There is no literature commenting on the success of Ponseti in the context of equinocavovarus feet in limb deficiency patients. Thus, from the outset, parents should be counseled on the significant likelihood of needing future foot surgery. From the authors' perspective, even if Ponseti alone cannot completely ameliorate the foot, preoperative casting as a general principle is often helpful to facilitate the subsequent surgical reconstruction.

Sixty-five percent of feet in FH limbs in this series had TCs, and 41% had a ball-and-socket ankle, which is consistent with rates observed in other series.[20],[21],[22] It has been hypothesized that stiffness of the subtalar joint caused by TC could drive the ankle to develop ball-and-socket morphology.[23],[24] Rodriquez-Ramirez et al. also looked into this relationship and failed to find such an association, and this may relate to the hypothesis of Thompson et al. that the ball-and-socket ankle may have a separate congenital origin.[20],[25] With the advent of routine whole-genome sequencing, the relationship between genotype and a ball-and-socket ankle joint is likely to be further clarified.

FH is classically associated with absent lateral rays.[3],[5],[6],[7] This observation alongside other skeletal anomalies like hypoplastic lateral femoral condyle led Stevens and Arms to coin the term “postaxial hypoplasia of the lower extremity” to use in preference to FH.[26] The findings in this study, however, are that in ray-deficient feet, it is commonly the central rays that are deficient. This contradicts many postulated theories on limb bud failure in FH and how the pattern of deficiency is dictated by the location and timing of insult occurring in a paraxial manner.[19],[27] However, intermediate ray deficiency in the context of fibular deficiency has been observed before. Lewin and Opitz theorized that intermediate ray deficiency was not necessarily part of the dysplasia, but incipient or mild ectrodactyly, and this association has been observed in more contemporary literature.[28],[29] Reyes et al. have also demonstrated central ray deficiency in FH with plain radiography and also with MRI confirming the attachment of peroneus brevis to the base of a remaining metatarsal.[8] A similar protocol to Reyes' et al. was applied in our study to define foot ray deficiencies, but we did not have MRI to confirm the presence of ancillary lateral structures.[8] The clinical significance of the nature of ray deficiencies is unclear, but conceivably, a plantigrade foot with a solid tripod between the first metatarsal head, heel, and most lateral metatarsal head would be more readily achievable in a foot missing central rays versus lateral rays. The only feet in our cohort missing lateral rays, were single-rayed feet that could not achieve a stable plantigrade position.

Our cohort demonstrated an inverse relationship between the number of rays and present and coalitions. This has not previously been described, but a similar pattern is observed in other genetic conditions where absent rays and coalitions are coincidentally described such as in Apert's syndrome. The clinical implications of this are unclear.

Fifty-six percent of children with CFD in our cohort had coexistent features of FH with clear anomalies of the foot and ankle. The coexistence of CFD and FH is well documented, with a variable prevalence of 45%–80%.[9],[10] Lewin and Opitz hypothesized that the proximal half of the femur is part of the “fibular field” which is critical to the development and growth of the limb bud.[28]

The foot and ankle phenotypes observed in TH patients in this study were consistent with published literature.[2],[11],[12] The foot posture was always clubfoot-like equinocavovarus. TCs, preaxial polydactyly, and complex syndactyly were also observed in a minority of cases. There were no ray deficiencies observed in our cohort, but published reports suggest that this is less frequent an observation than duplication of foot constituents.[11],[12] In the TH cohort, limb ablation was undertaken in almost half the limbs in contrast to only 5% of those affected by FH. The observation that limb reconstruction is more readily achievable in FH than TH is consistent with published literature.[11],[18]

There are limitations to this study. First, the identification of TCs was solely made on plain imaging and the true incidence may have been higher if MRIs were available on all feet such to enable detection of fibrous or cartilaginous coalitions, and better assess the skeletally immature foot. MRI would have been additionally useful to assess the presence of lateral structures (e.g., Peroneus brevis insertion) to irrefutably confirm cases of intermediate ray deficiencies. Second, due to the study design and the lack of patient-reported outcomes, it is impossible to comment further on the validity of the surgical decision-making process, and it is not possible to elucidate prerequisites for successful reconstruction. Finally, although our numbers of patients with each CLD type are relatively low, our cohort is large relative to existing publications in the literature and reflects the incidence of these conditions.

  Conclusions Top

This study demonstrates marked heterogeneity in the spectrum of foot and ankle deformity in CLDs, particularly with respect FH. Knowledge of this phenotypic variation is critical for surgeons to expediently identify a congenital limb deficiency, the first step to formulate a comprehensive treatment plan and ensure optimal functional outcomes.

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Conflicts of interest

There are no conflicts of interest.

  References Top

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Kelikian H, Kelikian AS. Disorders of the Ankle: Saunders; 1985. Chapter 20 The Ankle in Complex Disorders.  Back to cited text no. 23
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  [Figure 1], [Figure 2]

  [Table 1]


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