Distal Chevron Osteotomy Increases Anatomic Intermetatarsal Angle in Hallux Valgus

Area of Science:

• Orthopedic surgery
• Foot and ankle reconstruction
• Biomechanical analysis

Background:

• Distal chevron osteotomy (DCO) is a common surgical technique for hallux valgus (HV).
• DCO involves coronal translation of the capital fragment, potentially altering the first metatarsal's native alignment.
• The impact of DCO on the anatomic versus mechanical axis of the first metatarsal requires further elucidation.

Purpose of the Study:

• To radiographically evaluate the effect of DCO on the anatomic and mechanical axes of the first metatarsal.
• To test the hypothesis that DCO improves the mechanical axis but worsens the anatomic axis.

Main Methods:

• Retrospective case series analysis of patients undergoing DCO for HV.
• Primary outcome measures included changes in anatomic (a1-2IMA) and mechanical (m1-2IMA) first-second intermetatarsal angles.
• Secondary outcomes assessed were hallux valgus angle (HVA) and medial sesamoid position.

Main Results:

• Significant increase in a1-2IMA (4.1 degrees) and significant decrease in m1-2IMA (4.6 degrees) post-DCO.
• Significant improvement in HVA (12.5 degrees) and medial sesamoid position in 52.5% of cases.
• Worsening of the anatomic axis correlated with poorer sesamoid position improvement.

Conclusions:

• DCO for HV leads to worsening of the first metatarsal's anatomic axis, despite improving the mechanical axis, HVA, and sesamoid position.
• Increased anatomic axis deviation is linked to less improvement in sesamoid positioning.
• Findings suggest potential intermetatarsal instability, which may affect DCO efficacy in severe HV cases and contribute to recurrence.