Effect of Forefoot Width Variation on Clinical and Functional Outcomes Following the Lapidus Procedure

Abstract

Category: Midfoot/Forefoot Introduction/Purpose: The Lapidus procedure (LP) is a powerful technique that often provides significant corrections of the hallux valgus (HV) deformities. In addition, it is described that forefoot width alters considerably with this technique, impacting in shoe wear. However, it has not yet been reported whether foot narrowing reflects on clinical and functional outcomes. This study aimed to evaluate the effect of variations in bony and soft tissue foot widths (BSFW) on clinical and functional outcomes after HV correction with the LP. Secondarily, we also tried to assess the relationship of standard radiographic measurements of HV with changes in BSFW. Methods: Forty-three feet in 35 patients with a mean follow-up of 18.5-months who underwent the LP were retrospectively reviewed. Bony width was measured from the most medial extent of the first metatarsal head to the most lateral extent of the fifth metatarsal head. Soft tissue width was measured considering the most medial and lateral shadow of the foot (Figure 1). Clinical and functional data were assessed with the VAS for pain, AOFAS, LEFS and SF-12. SF-12 comprises physical and mental health scales (PCS-12 and MCS-12). HV radiographic parameters as intermetatarsal-angle (IMA), HV-angle (HVA) and sesamoid- subluxation (SS) were assessed. Intraclass Correlation Coefficients (ICC) were calculated for BSFW. Clinical, functional and radiographic measurements were compared. Linear regression was used to assess the correlation of Δ-BSFW with clinical, functional and radiographic results. We also evaluated our sample at the cut-off point of quartile-50% to assess whether a given measure of Δ-BSFW was related to clinical and functional outcomes. Results: Pre- and postoperative ICC was 0.95 for bony and soft tissue width measurements. Bony width changed significantly from 95.5mm to 84.2mm (11.8%) and soft tissue width from 107.12mm to 100.84mm (5.86%) (p<.001 and p<.001). IMA, HVA and SS improved significantly. Significant clinical and functional improvements were observed, except in MCS-12. In simple linear regression, a correlation was found between variations of bony width with Δ-AOFAS and Δ-PCS-12, meaning that as the forefoot narrows, their values increase (p=.02 and p=.005). It was also related to Δ-IMA and Δ-SS, meaning that the forefoot narrows as these parameters improve (p<001 and p<0.001). Soft tissue width was related only to Δ-PCS-12 and Δ-IMA. In multiple linear regression, the strongest correlation observed was between bony width variation and Δ-IMA (P=.029,r2=0.22). At the quartile- 50%, in which our sample was divided equally, we have not found a given measure of Δ-BSFW that was significantly related to the clinical and functional questionnaires (Figure 2). Conclusion: The present study showed that narrowing of the forefoot after the LP improves clinical and functional outcomes, as measured by AOFAS and PCS-12. Besides, it also presented that correction of the radiographic parameters of the HV, mainly IMA, reflects on a significant decrease of the forefoot width. Further prospective and comparative studies with larger populations are required to evaluate the effects of forefoot width changes on clinical and functional outcomes.