Identification and Fixation of Intermetatarsal Coronal Plane Instability Following Modified Lapidus Procedure

Abstract

Category: Bunion; Midfoot/Forefoot Introduction/Purpose: There are many described techniques to approach surgical correction of bunion deformity and prevention of recurrence is still a topic of interest. Coronal plane instability evidenced by intermetarsal angle (IMA) widening with weight bearing is a cause for concern with respect to recurrence. The identification of patients who are at risk for recurrence intraoperatively is challenging and currently there are few described tests that guide physician treatment. The aim of this study was to demonstrate an intraoperative intermetarsal coronal plane 'squeeze stress test' utilized by the senior surgeon along with the clinical and radiographic outcomes of patients who underwent fixation for their identified instability following the modified Lapidus procedure for hallux valgus correction. Methods: All patients included in this study presented with clinical and radiographic documentation of hallux valgus that was treated by a first tarsometatarsal arthrodesis with additional middle column fixation following widening on intraoperative fluoroscopy 'squeeze stress test' (Figure 1) by a single senior surgeon from 2015-2020. Fixation of the middle column was achieved via endobutton (5), screw (23), or endobutton plus screw (5). Clinical descriptions were reviewed for the presence of symptomatic recurrence and for the need of revision surgery. A single observer measured the HVA and the IMA angle of the preoperative and final post-operative weight-bearing radiographs, respectively. A total of 33 patients were included with an average age of 58.5 (range, 40-80) years of age and a mean follow-up of 8.3(range, 1.5-30) months. Mean BMI was 29 (range, 19- 54). Statistical analysis of this data set utilized the chi-square test and two sample t-test. Results: Pre-operatively, the patients with identified coronal plane instability had a mean HVA and IMA of 33 (range, 16-74) and 14 (range, 7-23) degrees, respectively. At final follow-up, these patients maintained a mean HVA of 9.8 (range, 0-32) and IMA of 4.5 (range, 0-15). No patients sustained clinical recurrence. Two patients underwent elective removal of hardware. One patient sustained a deep infection that required removal of hardware and formal debridement, this subsequently resolved. Conclusion: Coronal plane instability remains one of the unsolved facets of effectively treating symptomatic hallux valgus. Vigilance is the first step in prevention of recurrence in these patients and the 'squeeze stress test' is a simple, quick option for their identification. Our case series demonstrates satisfactory outcomes in terms of clinical recurrence for these patients utilizing this new evaluation technique. We believe further investigation of the squeeze stress test as an instability identifier is warranted in all types of bunion correction procedures.