Relative First Metatarsal Length Variation Following Hallux Valgus Surgery and Association with Postoperative Metatarsalgia

CATEGORY: Bunion; Midfoot/Forefoot INTRODUCTION/PURPOSE: The hallux valgus surgery can be associated with first metatarsal shortening increasing the occurrence of postoperative transfer metatarsalgia. There is no consensus regarding the acceptable degree of shortening and it relation with metatarsalgia. Besides shortening, there are other factors that could be associated with metatarsalgia like sagittal alignment, deformity correction and surgical technique. The primary objective of the study was to analyze the relative first metatarsal length variation following hallux valgus surgery and its association with postoperative metatarsalgia. The secondary objective was to analyze de first metatarsal length variation and postoperative metatarsalgia by type of surgical technique. METHODS: We performed a retrospective cohort study of all adult patients who underwent hallux valgus corrective surgery between 2017 and 2019 in our clinical center. The inclusion criteria were patients with at least 1 year follow up, without simultaneous lesser metatarsal procedures or referred preoperative metatarsalgia, and that could be contacted for the study. For the analysis we evaluated the incidence of post operative metatarsalgia via phone call and the relation with first metatarsal length variation which was determined by the relative first metatarsal length (RML) measurement according to Nilsonnne/Morton technique. All radiographs were measured by two foot and ankle surgeons. We analyzed the association of postoperative metatarsalgia according to the RML variation. A total of 85 feet were included in the study, with 5 different surgical techniques (16 promo, 19 chevron, 18 scarf, 14 lapidus and 18 MICA) RESULTS: The average preoperative and postoperative RML were + 0.03 mm and -2.92 mm, respectively. The average global postoperative RML shortening variation was -2.98 mm (min -10, max +5), and by surgical technique were -4.09 mm, -3.11 mm, - 3.05 mm, -2.93 mm and -1 mm for lapidus, chevron, scarf, promo and MICA, respectively. Only 9.1% of patients presented postoperative metatarsalgia, and the average postoperative RML shortening in those patients was - 4.63mm (min 0, max -10). There was a statistically significant correlation between RML shortening and postoperative metatarsalgia in patients with shortening higher or equal to 4 mm (p value <0.05). In relation to the 8 patients with metatarsalgia, 3 of them had a postoperative elevated first metatarsal (1 promo, 1 chevron and 1 lapidus) and 1 had recurrence of the deformity associated (lapidus). CONCLUSION: We found a postoperative RML shortening in hallux valgus correction, regardless of the selected surgical technique. The RML shortening was associated with postoperative metatarsalgia in patients with shortening higher or equal to 4 mm. However, in some of those patients, we found other concomitant factors, such as first metatarsal elevation or recurrence of the deformity. Therefore, even though we consider that shortening of the first metatarsal is an important factor, it seems relevant to assess all other potentials factors in patients with postoperative metatarsalgia.