Lapidus with 1st Metatarsal-Intermediate Cuneiform Fixation Improves Rotational Correction of Hallux Valgus

CATEGORY: Bunion INTRODUCTION/PURPOSE: The modified Lapidus procedure offers effective correction of the triplanar deformity of hallux valgus; however, complications such as nonunion and recurrence range up to 15% when using a crossing lag screw fixation technique. An alternative form of fixation using a dorsomedial plate and first metatarsal-intermediate cuneiform (1MT-IC) screw has been proposed. This construct may reduce complication rates, facilitate earlier weightbearing and maintain 3-dimensional correction, especially rotation of the first ray. We investigated single-surgeon Lapidus patient cohorts utilizing cross screws (CS) versus plate and 1MT-IC screw (PS) fixation to compare patient reported outcomes, radiologic parameters on pre- and postoperative weightbearing CT (WBCT) and complications. We hypothesized that patients undergoing PS fixation would experience improved correction of first ray pronation. METHODS: This single-center, IRB-approved retrospective study identified all patients who underwent first tarsometatarsal joint arthrodesis for hallux valgus by a single surgeon and divided them by CS or PS fixation. Patients were minimum 18 years old with at least 12 months of follow-up. Revision forefoot surgeries, concomitant flatfoot reconstruction or ankle replacement, and patients with history of rheumatoid arthritis or gout were excluded. PROMIS scores in six key domains were compared between groups both preoperatively and at one year postoperatively. Radiographic assessment of hallux valgus angle (HVA) and intermetatarsal angle (IMA) were performed on pre- and postoperative XR. Pronation of the first ray was measured on WBCT using the validated triplanar angle of pronation. Clinical notes were reviewed for complications and reoperations. The PS group began weightbearing at an average 3.6 weeks versus 6 weeks the PS group. RESULTS: We compared 44 patients who underwent Lapidus with PS and 43 with CS fixation. The age, BMI and gender distribution in the two groups were similar. Both groups had significant improvement in HVA and IMA following Lapidus, (p<0.001), with no difference between groups. Average first ray pronation among PS patients was corrected to 26.0 degrees (from 36.6 degrees preoperatively), which was lower than the final pronation of 30.5 degrees in the CS group, (p<0.001). Both cohorts experienced improvement in PROMIS physical function, pain interference, pain intensity and global physical function. There were no differences in PROMIS score improvements between the cohorts. Weightbearing commenced earlier in the PS group without increased complications. CONCLUSION: The plate and 1MT-IC screw technique for Lapidus fixation has been described to provide better biomechanical stability and potentially maintain the desired hallux valgus correction by spanning the intermetatarsal joint. Prior studies have reported durable radiographic IMA correction with low nonunion rates. We found similar patient-reported outcomes and rates of complications compared with a group of cross-screw fixation patients. However, there was a significant difference in final pronation of the first ray, 26 vs 31 degrees, observed by weightbearing CT. Earlier weightbearing and improved rotational correction are advantages associated with PS fixation of Lapidus bunionectomy.