Abstract
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Brachymetatarsia involves a reduction in length of one or more metatarsals.
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The affected metatarsal is shortened by 5 mm or more, altering the normal metatarsal parabola.
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In addition to being an aesthetic deformity, it can present with pain due to transfer metatarsalgia.
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A possible association with genetic disorders needs to be investigated during clinical evaluation.
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Surgical treatment may involve a one-stage lengthening procedure or progressive distraction, each having its advantages and limitations.
Introduction
Brachymetatarsia is a congenital malformation or developmental disorder, characterized by a reduction in length of one or more metatarsals. It is defined as shortening of the metatarsal by 5 mm or more, that alters the normal metatarsal parabola (1).
Its etiology is explained by premature closure of the metatarsal physis owing to various factors; the acquired causes include trauma, tumors, and bone and iatrogenic infections. A relationship has been reported with syndromic disorders, such as bone tumors, pseudohyperparathyroidism, Down syndrome, Turner syndrome, Apert syndrome, sickle cell anemia, and osteodystrophy (2).
The fourth metatarsal is the most affected, followed by the first. It has an incidence of 0.022% to 0.05% in the general population and is more frequent among female individuals (demonstrating a ratio of 25:1). Bilateral involvement has been described in up to 72% of cases; some cases have associated syndactyly (which is generally incomplete) between the second and third toes.
The malformation becomes more evident when the child reaches adolescence, and the growth plate closes permanently. In addition to an aesthetic deformity, it can present with pain due to transfer metatarsalgia and even alterations in the gait cycle. Despite the functional impairments associated with this pathology, consultation is mainly sought for aesthetic reasons (owing to the considerable psychological impact in some cases).
Embryology
Bone tissue begins to form in the foot at approximately 14 days of gestation. It begins with the formation of 3 rays, the longest being the ray of the third toe. The limb axis is divided into two parts, namely, pre-axial and post-axial. The preaxial portion gives rise to the outline of the first and second toes, talus, navicular, the three cuneiforms, and the first two rays. The post axial portion gives rise to the third, fourth, and fifth toes, along with their metatarsals, calcaneus, and cuboid. Chondrification of the phalanges and metatarsals begins at 44 days of gestation and the ossification nuclei appear between the 9th and 15th week. It should be noted that until 9 months of gestation, the second metatarsal is longer than the first; however, the final lengths are 0.80 mm and 0.85 mm, respectively (3).
Anatomy and biomechanics
Lelievre's formula is based on the studies by Maestro (4). Lelievre (2) affirmed that among the three types of metatarsal formulas (Fig. 1), the ‘index plus–minus’ and the ‘index plus’ are ideal and offer better static and dynamic stability of the foot.
Metatarsal formulas. (A) Index plus–minus foot (Roman foot). (B) Index minus foot (Morton’s foot type or Greek foot). (C) Index plus foot (Egyptian foot).
Citation: EFORT Open Reviews 9, 4; 10.1530/EOR-23-0011
These two formulas deliver a parabola, aligning the metatarsal heads. This alignment allows the metatarsals to be at the same height during gait, particularly in the second and third rocker phases of the gait cycle. Shortening of one of the metatarsals leads to an elongation of their transverse ligaments; this alters the pattern of contact between the forefoot and ground and increases pressure on the former, thereby generating transfer metatarsalgia (5).
Clinical presentation
During patient evaluation, it is important that a possible association with genetic disorders is evaluated in addition to the obvious deformity in the metatarsals (Fig. 2). Other signs including toe deformities, plantar hyperkeratosis (translating transfer metatarsalgia), soft tissue contractures, and signs of concomitant pathologies (such as hallux valgus) warrant evaluation (6). The contralateral side should always be examined, as up to 72% cases may present with bilateral alterations.
Clinical aspect of the foot of a 15-year-old girl with left fourth-ray brachymetatarsia.
Citation: EFORT Open Reviews 9, 4; 10.1530/EOR-23-0011
It should be noted that the main reason for consultation is aesthetic discomfort, which is particularly distressing in adolescence. The presence of a distorted self-image may have a psychological impact on these patients (5).
Initial study
A radiographic study of both weight-bearing feet is essential for confirming the diagnosis (Fig. 3), as the height of the metatarsals may be measured on radiographs. Shortening by 5 mm or more confirms the diagnosis and allows evaluation of other foot deformities (as brachymetatarsia may be associated with some previously mentioned syndromes). Investigations should extend to the family to identify other members with the pathology; this may help identify hereditary syndromic disorders.
Weight-bearing dorsoplantar foot X-ray of a 14-year-old girl with bilateral fourth-ray brachymetatarsia.
Citation: EFORT Open Reviews 9, 4; 10.1530/EOR-23-0011
It is important to perform a comprehensive assessment of the patient before recommending a surgical procedure. It is also necessary to measure the serum levels of vitamin D, calcium, and phosphorus; perform nutritional evaluation; and inquire regarding tobacco or alcohol consumption and other habits.
Classification
In 2022, Lamm et al. (7) published a review of 166 cases including a total of 300 feet with brachymetatarsia. The findings suggested that this deformity involves shortening of other bones along with the metatarsal; the head, diaphysis, and even joint congruence is affected. The authors suggested an alphanumeric classification system, which is anatomical and comprehensive and helps guide surgical strategies. The number of the metatarsal is noted, and the shape is classified into three categories, as follows: type A, metatarsal shortening; type B, diaphyseal and metaphyseal compromise with angulation; and type C, incongruity in the metatarsophalangeal joint (Fig. 4). This classification can be applied before and after surgery. For example, in a case with shortening of the second metatarsal with angulation of the diaphysis, the code would be 2AB. This provides three surgical possibilities: type A necessitates the performance of a lengthening procedure, type B necessitates identification and correction of the apex of the deformity, and type C requires a soft tissue procedure or surface resurfacing. As pure deformities are rare, it may be necessary to combine these procedures in most cases.
Lamm’s classification of brachymetatarsia. (A) Type A, metatarsal axial deficiency. (B) Type B, bowing. (C) Type C, incongruity in the metatarsophalangeal joint. These different types can be combined in one deformity.
Citation: EFORT Open Reviews 9, 4; 10.1530/EOR-23-0011
Treatment
Conservative management
Conservative treatment is initially recommended in the case of young patients who present with biomechanical alterations and pain. The objective is to reduce pain in the forefoot, discomfort with footwear, and plantar hyperkeratosis. Orthopedic devices such as retro-capital button insoles and wide shoes are used with the aim of reducing pressure on the forefoot.
Surgical management
The ideal time for performing lengthening surgery is between 12 and 14 years of age, as growth plate closure occurs at this time and postoperative rehabilitation is more efficient (8). Two types of elongation techniques are mostly employed: one stage and progressive. The degree of shortening is the main factor that determines the type of lengthening, with cutoff values of 10–15 mm. This recommendation is based on expert opinion, as there is no high-level evidence to guide decision-making.
One-stage lengthening, initially described by McGlamry et al. in 1969 (9), consists of a transverse metatarsal osteotomy, acute distraction, and filling of the space with a calcaneal autograft. Various techniques have been subsequently described; these use autografts from the iliac crest, navicular, fibula, tibia, or the adjacent metatarsal. Some surgeons prefer the use of allografts or synthetic materials. Internal fixation with plates or Kirschner wire is recommended for fixing the osteotomy and maintaining metatarsal stability (Fig. 5).
A 12-year-old girl with third- and fourth-ray brachymetatarsia. (A) Preoperative clinical picture. (B) Preoperative dorsoplantar foot X-ray view. One-stage lengthening procedure with autologous bone graft interposition and K-wire fixation was performed. (C) Postoperative clinical picture; (D) Postoperative oblique foot X-ray view.
Citation: EFORT Open Reviews 9, 4; 10.1530/EOR-23-0011
The surgical approach may involve use of an open technique, such as the Weil technique, triple osteotomy, or percutaneous osteotomy. One of the percutaneous osteotomy techniques to consider is the distal metaphyseal metatarsal osteotomy (DMMO) (10), which offers good functional results, good rates of patient satisfaction, and a low rate of complications (11).
One-stage elongation has certain limitations. In cases with shortening of >15 mm, elongation may lead to vasospasm and stretching of the nerve bundle peripheral to the affected metatarsal; this affects the distal vasculature and leads to loss of sensation of the toe. This technique may also lead to stiffness or instability at the level of the metatarsophalangeal joint. In addition, it is not possible to obtain bone tissue for interposition in some cases. Although shortening of the adjacent metatarsals is considered as a valid alternative, there is no consensus on the ideal degree of shortening.
The sliding osteotomy, initially described by Marcinko et al. in 1984 (12), is another option. The use of a ‘Z’ osteotomy has also been reported; the main advantage of this technique is that it does not require the use of a bone graft, thus eliminating donor site morbidity. One of the issues with this technique is that it offers elongation to a limited extent.
Progressive lengthening is another technique; it is based on the principle of callotaxis, as described by Ilizarov. In this technique, the affected segment is stabilized using a distraction external fixator and a subperiosteal metaphyseal osteotomy is performed. The bone callus that forms in the osteotomy focus is elongated progressively. This technique is usually selected in cases where the desired elongation is greater than or equal to 15 mm.
The advantages of this technique include the progressive elongation of tissues, which prevents vasospasm, and avoidance of iatrogenic damage to the neurovascular bundle. In addition, the final length can be achieved in a predictable and controlled manner.
In this technique, two threaded pins each are inserted percutaneously into the proximal and distal segments. The first pin to be placed is fundamental (Fig. 6), as it directs the plane of elongation, and guides the next pins insertion (Fig. 7). A small dorsal incision of 5 mm is placed for performing the osteotomy, taking care not to damage the extensor apparatus of the toe (Fig. 8). Some surgeons recommend fixation of the proximal interphalangeal joint with a Kirshner wire to reduce the risk of dislocation or subluxation due to lengthening. It is necessary to wait between 5 and 7 days (the latency period) before performing the lengthening procedure to allow initiation of bone callus formation (Figs. 9 and 10). However, the latency period should not exceed 10 days, as this may lead to premature consolidation at the osteotomy site; the recommended rate of elongation is 0.5 mm/day.
Intraoperative images of first pin insertion for the application of an external fixator for progressive distraction. (A) Skin incision of 2 mm. (B) Pin insertion perpendicular to the metatarsal. (C) Intraoperative X-ray images with the insertion point and final perpendicular position, perpendicular to the axis of the metatarsal.
Citation: EFORT Open Reviews 9, 4; 10.1530/EOR-23-0011
Intraoperative images of sequential pin insertion. (A) The external fixator is used as a guide, fixed over the first pin inserted. (B) Distal pin insertion to establish the direction of the lengthening, in the axis of the fourth ray. (C) Two more pins are inserted, one in the proximal, and one in the distal clamp. (D) Intraoperative X-ray image with the external fixator applied.
Citation: EFORT Open Reviews 9, 4; 10.1530/EOR-23-0011
Intraoperative images of percutaneous osteotomy of the metatarsal. (A) Percutaneous drilling. (B) Intraoperative X-ray with the complete osteotomy.
Citation: EFORT Open Reviews 9, 4; 10.1530/EOR-23-0011
Images of a 12-year-old girl with bilateral brachymetatarsia. (A) preoperative dorsoplantar foot X-ray. (B) Immediately postoperative X-ray showing percutaneous osteotomy of the fourth metatarsal and external fixator positioning.
Citation: EFORT Open Reviews 9, 4; 10.1530/EOR-23-0011
Images of a 12-year-old girl with bilateral brachymetatarsia (continuation). (A) Dorsoplantar foot x-ray after 10 days latency period and 30 days lengthening, showing distraction callus formation. (B) Dorsoplantar foot x-ray after 3 months postoperatively, after removal of the external fixator.
Citation: EFORT Open Reviews 9, 4; 10.1530/EOR-23-0011
It is important that the pins are placed in a manner that maintains the distractor parallel to the floor and not in the anatomical axis of the bone. This attains particular importance in case of lengthening of the first metatarsal, as a poor lengthening position could generate excessive plantar flexion and lead to a compensatory varus deformity (13).
In relation to this surgical technique, lengthening by callotasis using a small external fixator (14) is preferable; it has offered excellent functional results and patient satisfaction at our center since 2012 (Fig. 11).
Images of clinical cases treated with lengthening by callotaxis. (A–B) Preoperative and postoperative clinical pictures of a 13-year-old girl with left fourth-ray brachymetatarsia. (C–D) Preoperative and postoperative clinical pictures of a 15-year-old girl with bilateral fourth-ray brachymetatarsia. Bilateral simultaneous progressive lengthening with an external fixator was performed.
Citation: EFORT Open Reviews 9, 4; 10.1530/EOR-23-0011
However, this lengthening procedure is associated with complications, with rates as high as 50% in some case series. Stiffness of the metatarsophalangeal joint and contracture of the intrinsic plantar muscles are among the frequent complications. The procedure may also lead to overlengthening or shortening, which alters the biomechanics of walking and causes transfer metatarsalgia. Another complication is infection, which is inherent to the use of external fixators and may occur in up to 8% cases.
Conclusion
Brachymetatarsia is a rare disorder that occurs more frequently in childhood and adolescence. The persistence of pain despite previous conservative treatment or aesthetic reasons are indications for surgery. Two surgical methods, each having specific inherent complications, are recommended for this pathology; selection depends on the affected metatarsal and the desired final length. There is no global standard among foot surgeons for selection of the surgical technique; decisions are made mainly based on the degree of shortening, lengthening objective, and surgeon preferences (15). The series consulted for this review showed similar results regardless of the selected technique, with high rates of patient satisfaction and good functional results.
ICMJE Conflict of Interest Statement
The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported.
Funding Statement
This research did not receive any specific grant from any funding agency in the public, commercial, or not-for-profit sector.
Author contribution statement
M Sepulveda: conception and design of the study, interpretation of data, drafting of manuscript, approval for publishing, and accountability for the work. G Orellana: acquisition of data, critical review of the manuscript, approval for publishing, and accountability for the work. F Sanchez: acquisition of data, critical review of the manuscript, approval for publishing, and accountability for the work. E Birrer: conception of the study, drafting and critical review of the manuscript, original images, approval for publishing, and accountability for the work.
Acknowledgement
The authors would like to acknowledge the help provided by the Vicerrectoría de Investigación, Desarrollo y Creación Artística, and by the Escuela de Graduados of the Facultad de Medicina, Universidad Austral de Chile in order to publish this work.
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