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The zero-plus first metatarsal and its relationship to bunion deformity
John E Mancuso1, Steven P Abramow, Mark J Landsman
1Medical Arts Center Hospital, New York, NY, USA. DrMan86@aol.com
Summary
A longer first metatarsal bone, defined as a zero-plus first metatarsal, is significantly linked to hallux valgus (HV) or bunion development. This finding suggests its importance in preoperative evaluations for bunion surgery.
Area of Science:
- Orthopedics
- Podiatry
- Radiology
Background:
- Hallux valgus (HV) is a common foot deformity.
- The etiology of HV is multifactorial, with anatomical variations playing a role.
Purpose of the Study:
- To investigate the association between first metatarsal length and the presence of hallux valgus deformity.
- To determine if first metatarsal morphology is an independent risk factor for HV.
Main Methods:
- Retrospective review of 210 radiographic files (110 HV feet, 100 control feet).
- Analysis of first metatarsal length relative to the second metatarsal (zero-plus first metatarsal).
- Measurement of first metatarsal protrusion distance and assessment of metatarsal head shape.
Main Results:
- A zero-plus first metatarsal was present in 77% of HV patients versus 28% of controls (P <.001).
- Mean first metatarsal protrusion was significantly higher in HV patients (+1.58 mm) than controls (-2.05 mm) (P <.001).
- HV patients predominantly had round first metatarsal heads (91%), while controls had square/square-with-ridge heads (80%) (P <.001).
Conclusions:
- A zero-plus first metatarsal is significantly associated with hallux valgus formation.
- First metatarsal morphology, including length and head shape, is a key factor in HV etiology.
- The zero-plus first metatarsal should be considered in preoperative assessments for bunion deformity.