Etiology of acquired hammertoe deformity

Area of Science:

• Podiatry
• Biomechanics
• Geriatric Medicine

Background:

• Acquired hammertoe deformity is characterized by proximal phalanx hyperextension.
• This condition results from an imbalance in the forces acting on the metatarsophalangeal joint, particularly the intrinsic flexors and extensors.
• Age-related decline in the efficiency of plantar structures (intrinsic flexors, plantar joint capsule, plantar aponeurosis) disrupts joint balance.

Purpose of the Study:

• To investigate the biomechanical factors contributing to acquired hammertoe deformity.
• To explore the role of age-related changes in plantar structures in the development of this deformity.
• To examine the potential influence of footwear on the progression of hammertoe deformity.

Main Methods:

• Clinical observations and measurements from lateral weight-bearing roentgenograms of feet across different age groups.
• Analysis of the antagonistic actions of toe extensors and intrinsic flexors.
• Assessment of the contribution of the plantar joint capsule and aponeurosis to joint stability.

Main Results:

• Dorsiflexion of lesser toes in older adults (mean 33-39 degrees) was significantly greater than in younger adults (mean 23-25 degrees).
• These findings suggest elongation of plantar structures beyond physiological limits in older individuals.
• Hyperextension of the proximal phalanx may be the primary deformity, leading to loss of the long extensor's tendodesis effect and subsequent proximal interphalangeal joint flexion deformity.

Conclusions:

• Age-related inefficiency of plantar structures is a key factor in acquired hammertoe deformity.
• Prolonged use of high-heeled shoes may contribute by maintaining toe dorsiflexion and stretching plantar structures.
• Restoring tension in plantar structures offers a potential corrective approach for hammertoe deformities.