Is First Metatarsal Shortening Correlated with Clinical and Functional Outcomes Following the Lapidus Procedure?

Abstract

Category:Bunion; Midfoot/ForefootIntroduction/Purpose:Lapidus procedure (LP) is a powerful technique to correct hallux valgus (HV) deformities, with good long-term outcomes. However, postoperative complications may arise, as undercorrection of the deformity, nonunion, elevation and shortening of the first metatarsal (M1). The objective of this study was to correlate M1 shortening with transfer metatarsalgia, and clinical and functional outcomes in patients who underwent the LP.Methods:a retrospective review of 29 patients (36 feet) who were submitted to the LP for HV correction was performed. The average follow-up was 20 months. M1 length was analyzed using the Relative First Metatarsal Length (RML) measurement (Figure 1). When M1 shortens in relation to the second metatarsal, the RML measurements increase. The intermetatarsal angle (IMA) and hallux valgus angle (HVA) were also measured. Clinical and functional analyses were based on the VAS for pain, AOFAS, LEFS and SF-12 health survey. SF-12 is divided into physical and mental health composite scales (PCS-12 and MCS-12, respectively). Transfer metatarsalgia diagnosis was based on the clinical exam. Radiographic, clinical and functional measurements were compared using paired Wilcoxon signed-rank test and Student t test. Interobserver reliability of RML measurements was calculated using Intraclass Correlation Coefficients (ICC). A linear regression was performed to assess the correlation between RML and the clinical and functional questionnaires.Results:There was a significant M1 shortening of 2.28mm after the LP (p<.001), with mean preoperative RML of 3.06 mm and mean postoperative of 5.34 mm (Table 1). No patient developed transfer metatarsalgia. Intraclass Coefficient Correlation (ICC) of the RML measures showed a excellent reliability of 0.94 and 0.98 in the pre- and postoperative setting, respectively. IMA and HVA presented significant improvements (p<.001) (Table 1). Clinical and functional improvements were observed in all questionnaires applied, except in the MCS-12 (Table 2). In the linear regression, RML was inversely correlated to LEFS (p=<.05), which means that LEFS scores increased as RML measurements decreased (Table 3). There was no significant correlation with the other questionnaires.Conclusion:The present study demonstrated that M1 shortening led to a decreased LEFS following the LP. Comparative studies with prospective design and larger populations are required to assess the role of M1 shortening on clinical and functional outcomes.