Correlation of first metatarsal sagittal alignment with clinical and functional outcomes following the Lapidus procedure.

ABSTRACT

BACKGROUND: The purpose of this study was to evaluate the effect of the variation of the first metatarsal (M1) sagittal alignment after the Lapidus procedure (LP) on clinical and functional outcomes, and transfer metatarsalgia. METHODS: Twenty-nine patients who underwent a LP, with a mean follow-up of 20 months, were reviewed. Radiographic, clinical and functional measurements were compared. Clinical and functional questionnaires applied were the visual analogue scale (VAS), American Orthopaedic Foot and Ankle Society (AOFAS) scale, lower extremity functional scale (LEFS) and SF-12, which is divided in physical (PCS-12) and mental-health (MCS-12) scales. Radiographic analysis of M1 sagittal alignment was based on the first metatarsal declination angle (FMDA) and Meary Angle (MA). Intermetatarsal angle (IMA) and hallux valgus angle (HVA) were also measured. RESULTS: FMDA, IMA and HVA showed significant variation, but MA did not. Clinical and functional improvements were observed, except in MCS-12. No patient developed transfer metatarsalgia. A direct correlation was found between Δ-FMDA with Δ-PCS-12 and Δ-LEFS, meaning that excessive M1 dorsiflexion as measured by FMDA led to a decrease in PCS-12 and LEFS. Patients with Δ-FMDA of up to 3.2° of dorsiflexion were those who had significant improvements. CONCLUSION: Dorsiflexion of M1 can lead to decreased outcomes as measured by PCS-12 and LEFS. However, satisfactory outcomes can be obtained even with some dorsal deviation of the M1. LEVEL OF EVIDENCE IV, retrospective case series.