Is first metatarsal shortening correlated with clinical and functional outcomes following the Lapidus procedure?

To correlate first metatarsal (M1) shortening with transfer metatarsalgia, and clinical and functional outcomes in patients who underwent the Lapidus procedure (LP).

A retrospective review of 29 patients who were submitted to the LP for HV correction. The average follow-up was 20 months. M1 length was analyzed using the Relative First Metatarsal Length (RML) measurement. Intermetatarsal angle (IMA) and hallux valgus angle (HVA) were also measured. Clinical and functional analyses were based on the visual analogue scale (VAS), Lower Extremity Functional Scale (LEFS), and Short-form 12 (SF-12) health survey. SF-12 is divided into physical (PCS-12) and mental health (MCS-12) composite scales. Transfer metatarsalgia was diagnosed by the clinical exam. Radiographic, clinical, and functional outcomes were compared using paired Wilcoxon's and Student's t tests. Inter-observer reliability of RML measures was calculated using Intraclass Correlation Coefficients (ICC). The correlation between RML and the clinical and functional questionnaires was assessed with the Spearman's Rho test.

There was a significant M1 shortening of 2.3 mm (p < 0.05), with mean preoperative RML of 3 mm and mean post-operative of 5.3 mm. None of the patients evolved with transfer metatarsalgia. ICC of the RML measures presented excellent reliability. IMA and HVA showed improvements (p < 0.05). Clinical and functional improvements were observed in all questionnaires applied, except in the MCS-12. In the linear regression, RML was inversely correlated to LEFS (p < 0.05), which means that LEFS scores increased as RML measurements decreased.

The present study demonstrated that M1 shortening led to a decreased LEFS following the LP.