First reported case of brachymetatarsia treated with a hexapod external fixator: a case report

Abstract

Introduction and importance:

Brachymetatarsia is a rare deformity characterized by abnormal shortening of one or more metatarsals due to premature physeal closure. If conservative treatment fails, surgical options such as one-stage lengthening or progressive distraction with an external fixator are the usual alternatives. This report presents the case of a patient with type 1 Rubinstein–Taybi syndrome and first-metatarsal brachymetatarsia, who was treated by progressive distraction with a hexapod external fixator. This is the first such case reported in the literature.

Presentation of case:

An 11-year-old girl presented with plantar pain and central metatarsal keratosis in the left foot. After 1 year of unsuccessful conservative treatment, progressive distraction with a hexapod external fixator was indicated to achieve multiplanar correction. Distraction began 7 days later at a rate of 1 mm per day. Premature healing required a second osteotomy, while a metatarsophalangeal subluxation was corrected by fixator adjustment. Two superficial infections were resolved with antibiotic therapy. The fixator was removed at 6 months after achieving 40 mm of lengthening and 12 mm of plantar translation, with a homogeneous regenerate. At 24 months, the patient had complete symptom resolution and substantially normalized function.

Clinical discussion:

Progressive distraction using a hexapod external fixator can serve as an effective alternative in cases requiring extensive lengthening and multiplanar corrections.

Conclusion:

This is the first documented case in which brachymetatarsia was treated using a hexapod system, achieving a healing index of 45 days per centimeter and a final AOFAS score of 85.

Introduction

Brachymetatarsia is a rare – congenital or acquired – foot malformation characterized by an abnormal shortening of one or more metatarsals due to premature physeal closure^[1^]. The condition is considered clinically significant when the shortening is 5 mm or more compared with Lelièvre’s metatarsal parabola^[2^]. Its incidence is estimated to be between 0.002% and 0.05%, with a predominance in females and bilateral involvement^[3^]. Although the main reason for consultation is cosmetic, some patients may develop transfer metatarsalgia, calluses, or difficulties wearing shoes^[4^].

Initial treatment is conservative and typically consists of orthopedic measures. If such measures fail, various surgical options are available, the most frequent of which are one-stage lengthening with bone grafting and progressive distraction with an external fixator, which allows gradual correction and greater lengthening at the expense of a higher rate of complications ^[5,6^].

HIGHLIGHTS

• Metatarsal lengthening in brachymetatarsia can restore function and foot alignment.

• Progressive distraction enables greater lengthening while preserving soft tissues.

• Hexapod external fixators allow precise multiplanar correction in complex cases.

Although monolateral fixators have been widely used in metatarsals, reports on circular fixators remain scarce. This report presents the first case of first metatarsal brachymetatarsia treated with a hexapod external fixator in a pediatric patient with Rubinstein-Taybi syndrome. This case report has been prepared in line with the SCARE checklist^[7^].

Case presentation

An 11-year-old girl with molecularly confirmed type 1 Rubinstein-Taybi syndrome presented to the clinic with intermittent pain during gait and keratosis beneath the central metatarsal heads of the left foot. Physical examination revealed shortening of the first metatarsal, with a 2-cm discrepancy relative to the second ray and a 5-mm discrepancy relative to the first metatarsal on the contralateral side (Fig. 1). A three-dimensional computed tomography (CT) scan confirmed the diagnosis of brachymetatarsia, with a baseline first metatarsal length of 31 mm and an interphalangeal hallux valgus angle of 28° (Fig. 1). Rehabilitation treatment was initiated immediately. However, after 1 year without improvement, a decision was made to perform surgical lengthening of the first metatarsal (Table 1).

Figure 1.

Clinical and radiological preoperative appearance of the left foot: (A) Plantar view showing keratosis under the central metatarsal heads. (B) Dorsal view showing shortening of the first metatarsal. (C) Preoperative anteroposterior three-dimensional computerized axial tomography (CAT) reconstruction confirming first metatarsal brachymetatarsia.

Table 1.

Case timeline.

Timeline	Event/procederé	Result/action
Day 0	Lengthening: Osteotomy + TrueLok	Start of distraction osteogenesis (7-day latency, 1 mm/day, target: 40 mm)
Week 3	Follow-up CAT scan	Premature healing: new osteotomy and distal reinforcement
During lengthening	Subluxation of the first metatarsophalangeal joint	Corrected under sedation by adjusting fixator assembly
Month 3	Calcaneal pin tract infection	Positive Staphylococcus epidermidis culture: treatment with amoxicillin-clavulanic acid
Month 4	Proximal tibia pin tract infection	Positive Staphylococcus aureus and Staphylococcus lugdunensis cultures: treatment with cefadroxil
Month 6	Follow-up X-ray	Formation of a homogeneous bone callus with proper metatarsal alignment removal of the fixator and application of a short brace
Month 6.5	Physical therapy	Removal of short brace: recovery of mobility, proprioception and muscle strength
Month 7.5	Follow-up	Patient started walking without crutches: retraining of unassisted gait
Month 8	Follow-up X-ray	Confirmation of complete healing, restoration of the metatarsal formula and slight subluxation
Month 10	Clinical assessment	Gait without pain or keratosis. Residual hypersensitivity
Month 16	Clinical assessment	Normal gait and ability to run, slight hallux stiffness
Month 24	Final assessment	American Orthopaedic Foot & Ankle Society (AOFAS) score: 85 points

The procedure was carried out under general anesthesia and fluoroscopic guidance. A hexapod external fixator (TrueLok Hexapod System, Orthofix S.r.l., Verona, Italy), capable of correcting deformities in multiple planes (Fig. 2), was selected to allow simultaneous metatarsal lengthening, along with controlled plantar translation and abduction of the first metatarsal. The assembly included a footplate connected to a tibial ring by six telescopic struts and was stabilized by two tibial screws and two crossed calcaneal Kirschner wires, in addition to two Kirschner wires placed distal to the osteotomy. A proximal percutaneous metaphyseal osteotomy was performed of the first metatarsal. Final fluoroscopic analysis confirmed proper alignment and no soft-tissue compromise.

Figure 2.

Assembly of the TrueLok Hexapod System (Orthofix S.R.L., Verona, Italy) for progressive lengthening of the first metatarsal.

A distraction protocol was started after a 7-day latency period. A lengthening rate of 1 mm/day was selected, following classical Ilizarov distraction osteogenesis principles^[8^], with a target lengthening of 40 mm. However, a follow-up CT scan performed at three weeks revealed premature healing, with only 5 mm of lengthening. This required a new osteotomy and reinforcement of the distal fixation, followed by a new distraction program after a second latency period. During the ensuing lengthening procedure, the patient experienced a subluxation of the first metatarsophalangeal joint, which was corrected under sedation by adjusting the fixator assembly, without the need for further surgery. Following the second osteotomy, the distraction phase lasted 48 days.

After 3 months with the fixator, the patient developed a calcaneal pin-tract infection caused by Staphylococcus epidermidis, which was resolved with amoxicillin-clavulanic acid (500/62.5 mg/8 h). A new pin-tract infection occurred the following month in the proximal tibia. Staphylococcus aureus and Staphylococcus lugdunensis were eradicated within 14 days after treatment with cefadroxil (1 g/12 h, then 1 g/8 h). No implants required removal or exchange.

At 6 months, a follow-up X-ray showed homogeneous bone callus formation with satisfactory overall alignment despite residual metatarsophalangeal subluxation, allowing fixator removal. A total lengthening of 40 mm and plantar translation of 12 mm were achieved. Subsequently, the patient wore a short brace for 2 weeks, followed by physical therapy. Six weeks later, she was walking without crutches. At 8 months, complete healing of the regenerate and restoration of the metatarsal formula were observed, with slight metatarsophalangeal subluxation of the hallux. At 16 months, pain, keratosis, limping, and calluses had resolved, with only mild hallux stiffness remaining (Fig. 3). At 24 months, the American Orthopedic Foot & Ankle Society (AOFAS) score was 85 points.

Figure 3.

Preoperative and final radiographic evaluations. (A) Preoperative weight-bearing anteroposterior radiograph showing shortening of the first metatarsal. (B) Weight-bearing anteroposterior radiograph at 16-month follow-up demonstrating restoration of the first metatarsal length. (C) Weight-bearing lateral radiograph of the left foot at 16-month follow-up showing satisfactory overall alignment.

Discussion

Brachymetatarsia is a relatively infrequent deformity that may cause both cosmetic and functional concerns. Surgical treatment usually takes one of two forms: one-stage lengthening with bone grafting, and progressive distraction with an external fixator–the latter being the most commonly used strategy in clinical practice^[6^]. In the present case, progressive distraction using a hexapod external fixator was selected to achieve extensive metatarsal lengthening together with controlled plantar translation and abduction of the first metatarsal through progressive multiplanar correction.

One-stage lengthening avoids external fixation and reduces bone-healing time, improving patient comfort and quality of life^[9^]. Nevertheless, this technique is generally indicated for lengthening procedures of less than 15 mm, as greater acute corrections increase the risk of neurovascular impairment and joint stiffness. Another significant drawback is donor-site morbidity^[10^]. According to recent reviews, one-stage lengthening with bone grafting is associated with an overall complication rate of approximately 19.5%^[6^]. Sliding osteotomy techniques have also been described as alternative one-stage procedures for moderate lengthening (~10 mm), potentially reducing donor-site morbidity, although reports in brachymetatarsia remain limited^[11^].

Progressive distraction osteogenesis is the preferred technique, particularly for corrections exceeding 15 mm, as it can overcome the limitations related to one-stage procedures^[9^]. Progressive distraction allows greater lengthening through callotasis and histogenesis while preserving soft tissues and joint mobility^[12^]. However, it requires longer healing times and may result in complication rates of up to 52%, including postoperative joint stiffness in 17% of cases, pin tract infection in 8%, and poor callus formation, malalignment, or joint dislocation in 12.6%^[6,11^].

Most publications on the treatment of brachymetatarsia employ monolateral external fixators^[4,5,12–14^], with reports on semi-circular^[9,15^] or circular fixators^[16^] being in the minority. This is noteworthy, as some of the aforementioned complications, particularly malalignment and joint dislocation, may be partly related to the reduced stability of monolateral systems compared with circular ones, a key factor highlighted by Ilizarov^[17^]. Barbier et al^[9^], using a semicircular external fixator, reported an overall complication rate of 48.1%, although only 1.8% were severe complications and no metatarsophalangeal dislocations or subluxations were observed. Similarly, Kumar et al^[16^] reported no significant complications using a circular external fixator. These findings contrast with the complication rates of up to 52% reported in monolateral series^[6,11^].

The present case introduces the use of a hexapod external fixator, which combines the structural stability of circular fixators with precise three-dimensional correction through dedicated software. Unlike conventional fixators, the hexapod system allows simultaneous or sequential multiplanar corrections without the need to reoperate or make major frame adjustments, facilitating a more precise restoration of foot anatomy^[18^]. Although hexapod systems are generally more expensive than conventional fixators, fewer reinterventions may partially offset these costs. Additionally, they are available worldwide^[18^] and have a relatively short learning curve compared with classical Ilizarov frames^[19^].

In our patient, the hexapod system was selected to allow simultaneous metatarsal lengthening together with controlled plantar translation and abduction of the first metatarsal, while preserving the possibility of progressive postoperative adjustment without reoperation. This strategy aimed to achieve a more anatomical forefoot alignment and potentially reduce transfer metatarsalgia. With this approach, 12 mm of plantar translation and 40 mm of lengthening (healing index: 45 days/cm) were achieved, exceeding the 10-20 mm typically reported in series using monolateral or semicircular fixators^[5,6,9,10,15^] and being over 40% longer than the initial metatarsal length.

According to some authors, lengthenings of this magnitude tend to be associated with more complications^[20,21^], which may explain the occurrence of pin-tract infections, premature healing of the osteotomy, and metatarsophalangeal subluxation observed in the present case. The patient’s young age and delayed family adherence to the distraction protocol may also have contributed to the premature consolidation. According to the Paley classification, pin-tract infections were considered problems, premature osteotomy healing an obstacle, and mild residual metatarsophalangeal subluxation a true complication, although without significant functional impairment^[22^]. Despite these complications, the patient obtained 85 points on the AOFAS score, very close to the value reported by Schneider and Jurenitsch^[23^] for the healthy population (≈88 points).

To the best of the authors’ knowledge, this is the first reported case of brachymetatarsia treated with a hexapod external fixator. This system may represent a safe and effective alternative for extensive lengthening procedures and multiplanar corrections, although larger series are required.

Conclusions

Hexapod external fixators offer a viable option for complex brachymetatarsia requiring extensive multiplanar correction. In the present case, satisfactory functional and radiological outcomes were achieved despite the occurrence of characteristic complications of distraction osteogenesis, all of which were successfully managed without compromising the result. Further studies are required to better define the indications and advantages of this fixation system.

Patient perspective

According to the patient’s parents, the treatment substantially improved the patient’s quality of life, mobility, and confidence. They highlighted the disappearance of pain while walking and an improvement in balance. The family expressed high satisfaction with the final outcome.

Ethical approval

Not required, since the article depicts clinical practice not constituted as research by the IRB of Hospital Universitario 12 de Octubre.

Consent

Written informed consent was obtained from the patient’s parents or legal guardian for publication and for any accompanying images. A copy of the written consent is available for review from the Editor-in-Chief of this journal upon request.

Sources of funding

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Author contributions

J.M.G.L.: conceptualization, methodology, formal analysis, investigation, writing – original draft preparation, writing – review and editing. J.A.G.S.: conceptualization, methodology, validation, writing – review and editing. A.H.R.: conceptualization, methodology, validation, writing – review and editing. R.M.C.: conceptualization, methodology, validation, writing – review and editing. J.C.G.B.: conceptualization, methodology, formal analysis, writing – review and editing. all authors have read and agreed to the published version of the manuscript.

Conflicts of interest disclosure

J.C.G.B. has worked as a medical consultant for Orthofix S.R.L.

Research registration unique identifying number (UIN)

Not applicable.

Guarantor

José María García López.

Provenance and peer review

Not commissioned; externally peer reviewed.

Data availability statement

Data sharing is not applicable to this article as no datasets were generated or analysed during the current study.