Description

• Plantar flexion deformity of the proximal interphalangeal (PIP) joint with varying degrees of hyperextension of the metatarsophalangeal (MTP) and distal interphalangeal (DIP) joints (1). Occurs primarily in sagittal plane.
• Can be flexible, semi-rigid, or fixed:
  • Flexible: Passively correctable to neutral position
  • Semi-rigid: Partially correctable to neutral position
  • Fixed: Not passively correctable to neutral position

Epidemiology

Most common deformity of lesser toes, typically affecting only 1–2 digits:

• 2nd toe most commonly involved

• Undefined, with limited data
• Increases with age, duration of deformity (from flexible to rigid)

• Female > Male (2):
  • Female predominance from 2.5:1– to 9:1, depending on age group
• Can range from 1–20% of population studied
• Blacks more affected than whites (2)

Risk Factors

• Pes cavus and planus
• Hallux valgus
• Metatarsus adductus
• Ankle equinus
• Neuromuscular disease (rare)
• Trauma
• Improperly fitted shoes (e.g., with narrow toe box) and/or hosiery
• Abnormal metatarsal and/or digit length
• Inflammatory joint disease (e.g., rheumatoid arthritis [RA])
• Connective tissue disease
• Diabetes mellitus

• Specific genetic markers not identified
• Seen more frequently in families

General Prevention

• No documented means of prevention
• Modification of shoe wear using pressure-dispersive devices reduces pain (1).
• Foot orthoses modulate biomechanical dysfunction and muscular imbalance, thereby preventing progression (2).
• Control of predisposing factors (e.g., inflammatory joint disease) may slow progression.

Pathophysiology

• Any biomechanical dysfunction that results in loss of function of extensor digitorum longus (EDL) tendon at PIP joint and the flexor digitorum longus (FDL) tendon at the MTP joint; the intrinsic muscles sublux dorsally as the MTP hyperextends. This results in plantar flexion of the PIP joint and hyperextension of the MTP joint (2).
• Specific pathomechanics vary by etiology:
  • Toe length discrepancy or narrow toe box induces PIP joint flexion by forcing digit to accommodate shoe wear.
    • May also lead to MTP joint synovitis secondary to overuse, with elongation of plantar plate and MTP joint hyperextension.
  • RA causes MTP joint destruction and resultant subluxation

Etiology

• Congenital
• Acquired:
  • Any condition that compromises intra-articular and periarticular tissues, such as 2nd ray longer than 1st, inflammatory joint disease, improper fitting shoes, and trauma (1).
  • Damage to joint capsule, collateral ligaments, or synovia leads to unstable PIP joint or MTP joint.

Commonly Associated Conditions

• Hallux valgus
• Cavus foot
• Metatarsus adductus
• Dorsal callus