Plantar plating the modified Lapidus arthrodesis

Abstract

Category: Midfoot/Forefoot Introduction/Purpose: Modified Lapidus arthrodesis is performed in the treatment of different pathologies, including hallux valgus and osteoarthritis of the 1C-MTT joint. Complications of this procedure include delayed union and non – union. To prevent them, several rigid fixation methods have been proposed. Biomechanically, plantar plate fixation may be the best solution. Therefore, we sought to investigate our clinical results and complications in patients operated on with a modified Lapidus arthrodesis using two different plantar plate fixation systems. Methods: After IRB approval, we reviewed our prospectively collected database for patients operated on with a modified Lapidus arthrodesis. Dedicated foot and ankle orthopaedic surgeons performed all procedures. Patients were included if they were older than 18 years, had a minimum FU of 1 yr and agreed to participate in the study. Patients with neuropathy, previous surgery, concomitant midfoot/hindfoot procedures or those which fixation method was different from a plantar plate were excluded. Preoperative and postoperative IM angle was evaluated. Two independent musculoskeletal radiologists assessed consolidation under CT scan at 12 weeks postop. Triaxial 2-mm reformatted CT slices were used to calculate joint fusion percentage. Each patient was assigned to a consolidation group considering joint fusion percentage: 0-24%, 25-50%, 51-74%, 75-100%. Intra/interobserver coefficients of variability were calculated. SF-36, SMFA, FAOS and FAAM were obtained preoperatively and at one year follow up. t-test was performed to address for functional outcomes differences in-between groups. Results: Twenty-three patients (35 feet) met inclusion criteria. Mean age was 47 years (13-65), 83% female and 17% male. Eleven patients had bilateral surgery. Mean preoperative/postoperative IM angle were 16+3 and 9+2, respectively (p<0.001). Ten feet achieved <24% consolidation (33%) and 20 feet >25% (67%). With the numbers available, consolidation rate didn´t differ in patients undergoing unilateral/bilateral surgery(p=1.0) or plating system(p=0.22). One patient had an anterior tibialis tendon rupture and 1 patient presented an infected non-union, prompting revision. Mean preoperative/postoperative values for SF-36 physical and mental component were 49 and 76(p<0.001); and 43 and 68(p<0.001), respectively. FAOS-pain were 60 and 81(p<0.001);FAOS-daily-life were 59 and 96(p<0.001);FAOS-sport were 43 and 74 (p<0.001);and FAAM-Daily-life score were 67 and 87(p<0.001). No significant differences were found for SMFA. Conclusion: Despite a low consolidation rate at 12 weeks post op, patients with plantar plated Lapidus arthrodesis presented a significant increase in functional outcomes and a low revision/complication rate at 1 yr FU. Consideration should be given to delay evaluation under CT scan to 24 weeks post op.