[Skin and nail changes in foot deformities]

Area of Science:

• Podiatry
• Biomechanics
• Dermatology

Context:

• Hallux valgus involves the lateral deviation of the first metatarsophalangeal joint, commonly known as a bunion.
• This deviation significantly alters the biomechanical forces during gait, particularly during the foot's roll-off phase.

Purpose:

• To explain the biomechanical consequences of hallux valgus on the foot.
• To describe the resulting pathological nail and toe conditions associated with altered pressure distribution.

Summary:

• Hallux valgus causes the big toe to deviate laterally, changing the longitudinal axis of the toe.
• This deviation redirects forces during foot unrolling, leading to increased pressure on specific areas of the toe tip.
• Consequently, conditions such as subungual clavus (corns under the nail), ingrown toenails (unguis incarnatus), involuted nails (unguis convolutus), and corkscrew-like nail deformities (onychogryphosis) can develop.

Impact:

• Understanding these biomechanical shifts is crucial for diagnosing and managing hallux valgus complications.
• This knowledge aids in developing targeted treatments to alleviate pain and prevent further nail and toe pathology.
• Highlights the link between foot deformities and secondary dermatological and podiatric issues.