Biomechanical Comparison of 2 Common Techniques of Minimally Invasive Hallux Valgus Correction.

BACKGROUND: Hallux valgus is one of the most common surgically corrected forefoot deformities. Compared to open procedures, minimally invasive (MIS) treatment of hallux valgus has resulted in decreased operative time, reduced complication rates, and greater patient satisfaction. Historically, distal chevron osteotomies are the standard for moderate hallux valgus correction. To our knowledge, no studies have evaluated biomechanical strength of transverse and chevron distal first metatarsal osteotomy (DMO) constructs. The purpose of this study was to evaluate the biomechanical strength of these techniques.

METHODS: Eighteen cadaveric specimens (9 matched pairs) were randomized to transverse or chevron DMO. Each technique was performed by a separate fellowship-trained orthopedic foot and ankle surgeon. Radiographic images were analyzed. Biomechanical testing was performed using Instron Mechanical System. Ultimate load to failure, yield load, and stiffness were assessed. A 10-N preload was applied to the sesamoid bones for stability. A coaxial compression rate (10 mm/min) was applied until failure was observed. Mean and standard deviations were compared. All cadaveric specimens were male.

RESULTS: There was no significant difference in percent metadiaphyseal shift between osteotomies ( P = .453). The most common mode of failure was fracture at screw insertion site (55.6%), followed by failure at osteotomy site (44.4%). A trend toward increased ultimate load to failure ( P = .480), yield load ( P = .054), and stiffness ( P = .438) among transverse compared to chevron osteotomy was observed, but this difference was not statistically significant.

CONCLUSION: Biomechanical testing demonstrated no significant difference in ultimate load, yield load, and stiffness between MIS transverse and chevron osteotomy constructs; a trend toward increased strength in the transverse osteotomy cohort was observed. Chevron osteotomies may result in early failure by relative ease of cutout through cancellous bone compared to transverse osteotomies in which failure requires cortical cutout.

CLINICAL RELEVANCE: Use of MIS techniques for hallux valgus correction is gaining clinical traction. Although various clinical studies have evaluated outcomes of these MIS techniques, biomechanical studies have been minimal. Specifically, the potential biomechanical benefits of various MIS hallux valgus osteotomy techniques have not been delineated to date. The content of this manuscript is quite timely, given the rise in use of these MIS techniques.