Brachymetatarsia

Etiology

Brachymetatarsia occurs due to the premature closure of the growth plate (epiphyseal plate) in the affected metatarsal, resulting in a significantly shorter bone than its counterparts. The etiology of brachymetatarsia may be genetic, traumatic, iatrogenic, or due to an underlying endocrinopathy.

Genetic Factors

Brachymetatarsia may be sporadic or inherited. Inherited brachymetatarsia may follow an autosomal dominant or autosomal recessive genetic pattern. Familial cases support the hypothesis of a hereditary predisposition, suggesting that certain individuals may be genetically more susceptible to developing this anomaly.[2][6][1] An association between congenital brachymetatarsia and Turner syndrome exists.[7]

Endocrinopathies

Pseudohypoparathyroidism is associated with the development of brachymetatarsia. This disorder disrupts normal bone growth and skeletal development, leading to the premature closure of growth plates and shortened metatarsals. This endocrinopathy contributes to abnormal foot morphology and impaired skeletal maturation by interfering with the hormonal regulation essential for bone elongation.[3]

Trauma

Although rare, trauma to the foot during critical growth phases can damage the growth plate, disrupting normal bone development. This trauma may occur in the intrauterine environment or after birth.[8] Traumatic disruption may lead to the premature closure of the growth plate, resulting in the shortening of the affected metatarsal and the onset of brachymetatarsia. Trauma during periods of rapid growth can have enduring effects on foot structure and function.[3][1] 

Iatrogenic Causes

Surgical and nonsurgical interventions or treatments, such as radiation therapy, can occasionally affect the growth plates, disrupting their normal development. This interference may lead to the premature closure of the growth plates, resulting in the shortened metatarsal bones characteristic of brachymetatarsia.[3][1]

Epidemiology

Brachymetatarsia is a relatively rare condition, with an estimated prevalence of 0.022% to 0.05% in the general population.[3][1] The condition disproportionately affects females, with studies indicating a striking female-to-male ratio of approximately 25:1.[9] In up to 72% of cases, brachymetatarsia affects both feet. The fourth metatarsal is most commonly impacted, followed by the first, although multiple metatarsals may be involved.[1]

Brachymetatarsia is occasionally associated with other congenital anomalies, such as syndactyly, which often manifests as partial webbing between the second and third toes.[10] Although brachymetatarsia can occur in isolation, it is also associated with certain syndromic conditions. This association emphasizes the need for a thorough clinical evaluation to identify any underlying genetic or developmental disorders that may contribute to the clinical presentation.[11]

Pathophysiology

The pathophysiology of brachymetatarsia is primarily attributed to the premature closure of the growth (epiphyseal) plate of the affected metatarsal. Growth plates at the ends of long bones are essential for bone lengthening during childhood and adolescence. When a growth plate closes prematurely, the affected metatarsal stops growing, resulting in a shorter bone than the surrounding metatarsals, which continue to develop normally. This length discrepancy creates the characteristic appearance of brachymetatarsia, where one or more toes appear shortened or elevated compared to adjacent toes. The abnormal bone length can disrupt foot biomechanics, contributing to functional and aesthetic concerns.[1]

History and Physical

Clinical Presentation 

Patients with brachymetatarsia typically present with a visibly shortened toe, often accompanied by a noticeable gap between the affected toe and the adjacent toes, creating the appearance of an elevated or retracted digit. The condition may occur unilaterally or bilaterally. Bilateral cases are more commonly associated with underlying genetic or systemic disorders, while unilateral presentations are generally sporadic.[2]

Symptoms of brachymetatarsia, resulting from the altered alignment of the foot, vary with factors such as age, gender, the number of metatarsals affected, and the degree of the deformity.[1] Mild cases may be asymptomatic, with patients reporting minimal to no discomfort. Clinical significance typically arises when the condition destabilizes the first ray axis, leading to excessive pronation and decreased push-off strength during gait.[8] Fourth metatarsal brachymetatarsia is easily identifiable and often presents with a dorsally displaced fourth toe, which may overlap the fifth toe.[12][6]

In severe cases, individuals may experience significant pain, difficulty walking, and challenges with shoe fitting. The altered foot mechanics resulting from the shortened metatarsal often lead to metatarsalgia and increased pressure on neighboring toes. This can cause secondary complications, such as calluses, corns, or other pressure-related issues.[1]

Evaluation

The diagnosis of brachymetatarsia is primarily clinical, based on a physical examination of the foot and the patient's medical history. Radiographic imaging is essential for confirming the diagnosis and assessing the extent of metatarsal shortening.

• X-ray: Standard anteroposterior x-rays of the foot are used to diagnose brachymetatarsia by evaluating the curvature of the metatarsal heads. A shortened metatarsal disrupts the normal, smooth curvature of the metatarsal arc, which is a significant diagnostic indicator. For a diagnosis of brachymetatarsia, the affected metatarsal must show a shortening of at least 5 mm compared to the normal arc (see Image. Metatarsal Head Parabolas Depicting Brachymetatarsia).[13]

• Computed tomography and magnetic resonance imaging: These advanced imaging modalities may be utilized in specific cases to provide a more detailed evaluation. These modalities are beneficial when there are concerns about concurrent anomalies or underlying pathological conditions that may influence the presentation of brachymetatarsia.[9]

Lamm Classification

The Lamm classification of brachymetatarsia focuses discrete deformities in the affected metatarsal ray into 3 broad categories or types.

• Type A refers to metatarsals that are purely shortened without any other structural abnormalities.
• Type B involves bowing or angulation of the metatarsal shaft.
• Type C is characterized by metatarsophalangeal joint (MTPJ) incongruency, such as joint deformity, arthritis, or dislocation.

The Lamm classification uses a number (1–5) to indicate the affected metatarsal, followed by letters (A, B, and C) to describe the specific deformities, including axial length deficiency, bowing, and MTPJ congruency, respectively. For example, "4ABC" indicates a shortened fourth metatarsal with shaft bowing and joint incongruency.[14]

Treatment / Management

The management of brachymetatarsia is tailored to the severity of the condition and the patient's symptoms.

Conservative Treatments

Conservative approaches may be sufficient for individuals who are asymptomatic or experiencing mild discomfort. These measures focus on alleviating symptoms and enhancing the patient's quality of life without requiring invasive procedures. The key objectives of conservative management are listed below. 

Pressure relief: Custom orthotics and padding can help distribute pressure more evenly across the foot, alleviating discomfort and preventing the exacerbation of symptoms.[15]

Improved comfort: Modifying footwear, such as shoes with a wider toe box, can accommodate the shortened toe and reduce friction, improving comfort, especially in cases where finding properly fitting shoes may otherwise be challenging.[15][6]

Functional support: Orthotic devices can provide additional support to the foot's biomechanics, helping maintain proper alignment and function, which can mitigate issues such as abnormal gait patterns.[15]

Prevention of secondary issues: Conservative treatment targets the primary symptoms of brachymetatarsia to prevent or minimize secondary complications, such as calluses, corns, or other pressure-related problems.

Surgical Treatments

For patients experiencing more pronounced symptoms, such as significant functional impairment, persistent pain, or cosmetic concerns, surgical intervention may be necessary. Several surgical techniques have been developed to address the challenges associated with brachymetatarsia.

Callus distraction (metatarsal lengthening): This technique involves gradually elongating the shortened metatarsal using an external fixation device. The procedure begins with an osteotomy, where the bone is surgically divided. An external fixation device is used to incrementally separate the bone ends at a rate of 1 mm per day, promoting new bone formation in the resulting gap with minimal risk of vasospasm. This method allows for precise control over the lengthening process and has demonstrated favorable outcomes in both functional and aesthetic aspects.[16] This is the most commonly used surgical procedure for brachymetatarsia, typically employed when more than 15 mm of lengthening is required.[15] 

Acute lengthening with bone grafting: Acute lengthening is commonly used for cases of minor metatarsal hypoplasia or shortening. The exact threshold for performing one-stage lengthening is debated but generally ranges from 1 to 2 cm.[15][11]. However, the general consensus is that acute lengthening is unsuitable for deformities exceeding 2 cm. Lengthening beyond this threshold can place excessive tension on the toe's tendons and, more critically, compromise tissue viability due to vasospasm in stretched neurovascular structures.[15] Acute lengthening commonly involves the use of autografts or allografts, with plate and screw fixation to stabilize the grafts. While this technique effectively addresses shorter metatarsals, it is constrained by the safe limits of achievable lengthening.[11] Additionally, acute one-stage lengthening with bone grafting demonstrates a complication rate of 19.5%, which is further discussed in the Complications section.[15] 

Combined techniques: In complex or severe cases of brachymetatarsia, a hybrid approach that combines callus distraction with bone grafting may be used. This combination provides a more comprehensive management strategy for the deformity, optimizing both functional and cosmetic outcomes.[16] 

Toe amputation: Toe amputation is typically considered a last-resort option for managing brachymetatarsia and is rarely performed due to its significant impact on both function and appearance. This procedure may be indicated in severe cases where conservative treatments and surgical lengthening techniques have failed to address persistent pain, functional limitations, or cosmetic concerns. The decision to proceed with amputation requires a thorough evaluation of the patient's overall health, functional needs, and quality of life.

While amputation of the affected toe can alleviate chronic pain and severe deformity, it carries significant consequences, including loss of toe function, altered gait, and potential psychological effects. As a result, this approach is typically reserved for cases where less invasive treatments have proven insufficient. Careful consideration of the potential benefits and drawbacks is essential to ensure that toe amputation aligns with the patient's long-term goals and overall well-being.

Surgical Treatment Algorithm Using the Lamm Classification Criteria

The Lamm brachymetatarsia classification provides a surgical treatment algorithm for addressing specific deformities.[14] 

• Type 4A (axial distance deficiency): Management options include acute lengthening with a bone graft for cases involving less than 1 cm of shortening or gradual lengthening through percutaneous distraction osteogenesis (PDO) with external fixation. Bone grafting involves the use of autografts or allografts, which are secured with plate and screw fixation. In PDO, external fixators with half pins are placed in the metatarsal and proximal phalanx, with additional stabilization potentially required for lengthening exceeding 15 mm.
• Type 4AB (axial distance deficiency and bowing): This approach involves using the PDO technique for axial lengthening combined with an acute realignment osteotomy to address bowing. The osteotomy is performed at the center of rotation and angulation (CORA), allowing for precise realignment of the metatarsal. The external fixator stabilizes the metatarsal and protects the MTPJ during lengthening and realignment.
• Type 4B (bowing of the metatarsal shaft): This involves a percutaneous acute realignment osteotomy at the CORA to correct the bowing, followed by stabilization with either internal or external fixation. The procedure aligns the distal and proximal axes of the metatarsal, restoring its normal structure.
• Type 4BC (bowing and congruency of MTPJ): This approach involves an osteotomy to correct bowing and a soft tissue release or osseous realignment for MTPJ relocation. The joint is held in a neutral position with an external fixator, and joint distraction is sustained for 6 to 12 weeks.
• Type 4AC (axial distance deficiency and congruency of MTPJ): This approach combines the PDO technique for axial lengthening with MTPJ realignment through reduction, soft tissue release, or joint resurfacing. An external fixator maintains neutral joint positioning, with joint distraction maintained for several weeks.
• Type 4C (congruency of MTPJ): MTPJ relocation is achieved through manual reduction, soft tissue release, or joint resurfacing, followed by stabilization with an external fixator. Joint distraction of 5 mm is maintained for 8 to 12 weeks to promote optimal healing.
• Type 4ABC (axial deficiency, bowing, and congruency of MTPJ): This comprehensive approach combines PDO for lengthening, acute osteotomy for bowing correction, and MTPJ relocation through soft tissue release or joint realignment. An external fixator stabilizes the metatarsal and joint in a neutral position, ensuring proper healing and restoration of function.

Differential Diagnosis

Congenital Curly Toe

Congenital curly toe is a deformity where one or more toes bend downward at the distal interphalangeal joint, often resulting in overlapping toes. This condition closely resembles brachymetatarsia, particularly when the affected toe appears shortened.[17] Although the fifth toe is most commonly involved in congenital curly toe, any toe can be affected. The hallmark feature is a flexion deformity at the distal interphalangeal joint, distinguishing this anomaly from other conditions.

Juvenile Bunions (Hallux Valgus)

Juvenile bunions are characterized by a medial deviation of the first metatarsal and a lateral deviation of the great toe, creating a visual gap between the toes that might resemble brachymetatarsia. This deformity primarily affects the first metatarsal and must be distinguished from isolated metatarsal shortening. The condition is further characterized by a prominent medial deviation of the first metatarsal and a lateral deviation of the great toe, which can lead to toe overlap.[18]

Turner Syndrome

Turner syndrome (45, XO) is a chromosomal disorder characterized by physical abnormalities such as short stature and various skeletal deformities. A potential manifestation of this syndrome is brachymetatarsia, which often involves multiple metatarsals in the foot. In addition to short stature, individuals with Turner syndrome commonly exhibit distinct physical features, such as a webbed neck; brachymetatarsia in patients with Turner syndrome commonly affects multiple metatarsals.[7]

Pseudohypoparathyroidism

Pseudohypoparathyroidism is an endocrinopathy marked by resistance to parathyroid hormone. This condition is often associated with skeletal abnormalities, including short stature and shortened metacarpals or metatarsals. Electrolyte abnormalities such as hypocalcemia and hyperphosphatemia further contribute to the clinical presentation.

Metatarsal Coalition

Metatarsal coalition is a condition where 2 or more metatarsals are fused by bone, cartilage, or fibrous tissue. This fusion can restrict foot movement and alter the foot's appearance, sometimes resembling brachymetatarsia. However, advanced imaging techniques can accurately identify these coalitions and differentiate them from isolated metatarsal shortening cases.[19]

Chronic Osteomyelitis

Chronic osteomyelitis can lead to growth disturbances and shortening of the affected bone. Clinical symptoms such as pain, swelling, and redness, along with elevated laboratory markers of infection, such as white blood cell count, erythrocyte sedimentation rate, or C-reactive protein, are key in distinguishing osteomyelitis from brachymetatarsia, which is primarily a structural deformity rather than an infectious process.

Prognosis

The prognosis of brachymetatarsia depends on the severity of the condition and any associated abnormalities. In many cases, brachymetatarsia is primarily a cosmetic or aesthetic concern, especially when the condition is mild and does not significantly impact foot function or cause discomfort. However, more severe presentations of brachymetatarsia can lead to significant complications, including pain, difficulty finding properly fitting shoes, and altered gait patterns due to biomechanical changes in the foot.

The abnormal alignment of the metatarsals can disrupt normal walking patterns, potentially leading to further foot problems and discomfort. Overall, the prognosis for individuals with brachymetatarsia is generally favorable, especially when appropriate management strategies are implemented. Treatment options can alleviate symptoms and improve function, thereby enhancing the patient's quality of life. Early intervention and individualized treatment plans are essential in addressing both the cosmetic and functional concerns associated with the condition.[2]

Complications

Brachymetatarsia can lead to complications that significantly affect a patient’s overall quality of life. These issues may be categorized into functional, aesthetic, psychological, surgical, and secondary orthopedic complications.

Functional Complications

Altered gait: The shortened metatarsal interferes with the normal foot mechanics, leading to an abnormal gait. This imbalance can result in compensatory movements, placing additional strain on other parts of the foot and potentially causing secondary issues.

Pain and discomfort: Many individuals with brachymetatarsia experience discomfort, particularly during walking or prolonged standing. The abnormal foot structure increases pressure on adjacent toes and metatarsals, contributing to pain.

Calluses and corns: Altered foot mechanics in brachymetatarsia often lead to the development of calluses and corns, especially on the undersides of the toes and metatarsal heads. These skin conditions can cause significant discomfort and frequently necessitate ongoing medical care.

Shoe-fitting challenges: The discrepancy in toe length can make it difficult to find shoes that fit properly. Ill-fitting footwear may exacerbate pain and lead to blisters and other related foot problems.[5]

Aesthetic and Psychological Complications

For many patients, the noticeable shortening of the toe raises significant cosmetic concerns. The visible gap or elevated position of the affected toe can be distressing, particularly for individuals who are self-conscious about the appearance of their feet. This aesthetic deformity, along with functional challenges, often leads to psychological stress, which can diminish self-esteem and cause feelings of social embarrassment. Patients may become reluctant to expose their feet in public, avoiding activities such as swimming or wearing open-toed shoes, contributing to increased isolation and emotional strain.[20]

Surgical Complications

While surgical interventions can effectively address brachymetatarsia, these procedures carry risks.

Infection: As with any surgical procedure, infection is a potential risk, particularly at the incision site. The external fixation devices used in certain surgeries may further elevate this risk by providing additional entry points for bacteria, which can lead to postoperative infections.

Nonunion or delayed union: Bone healing may be compromised in cases of nonunion, where the bone ends fail to fuse, or delayed union, where the healing process is abnormally slow. Both complications may necessitate further surgical interventions to support proper bone recovery.

Neurovascular injury: Surgical procedures on the foot risk damaging nearby nerves or blood vessels. This can lead to symptoms such as numbness, tingling, or, in severe cases, reduced blood flow to the affected area. 

Recurrence or residual deformity: Despite the success of surgery, there is always a possibility that the deformity may recur or that some malalignment may persist. In some cases, the resultant lengthening may be insufficient, or the toe may fail to align properly with the adjacent toes, leading to dissatisfaction with the outcomes.

Hardware complications: Procedures involving hardware, such as external fixation devices or internal implants, may be complicated by hardware failure, loosening, or irritation. These problems may necessitate additional surgeries for correction or adjustment.

Secondary Orthopedic Issues

Deformities in adjacent toes: The altered mechanics of the foot can cause secondary deformities in nearby toes, such as hammertoes or claw toes. These conditions can further complicate both functional and aesthetic outcomes.

Metatarsalgia: Increased pressure on the remaining metatarsals can lead to metatarsalgia, a condition marked by pain and inflammation in the ball of the foot. This condition can be particularly disabling and may require additional treatment.

Stress fractures: The altered weight distribution and changes in gait mechanics can elevate the risk of stress fractures. These fractures can be painful and usually require an extended period of rest and immobilization for healing.