Biomechanical comparison of Mitchell versus Chevron osteotomy with the third generation minimally invasive screw fixation technique.

BACKGROUND

The Mitchell and Chevron osteotomies are two widely performed surgical techniques for the correction of hallux valgus deformities. While both approaches are commonly used, there remains limited biomechanical evidence comparing their structural stability, particularly when paired with advanced fixation techniques. This study aims to evaluate and compare the biomechanical properties of these procedures when utilizing the third-generation minimally invasive (MIS) screw fixation technique.

METHODS

Sixteen synthetic first metatarsal (Sawbones Pacific Research Laboratories, Vashon, WA) were divided into two groups. The Mitchell osteotomy (n = 8) and the Chevron osteotomy (n = 8) were performed to simulate hallux valgus correction surgery. Both osteotomy groups were fixed using an identical technique. Two parallel, fully threaded, headless screws were positioned separately: one in a three-points fixation and the other in an intramedullary pattern. Each specimen was tested using a cantilever bending model. Following a 20-N preload, 500 cycles loading test was applied with the force ranging from 20 to 200 N (valley to peak). Interfragmentary displacement was recorded after the cyclic loading test. Finally, all specimens were subjected to destructive loading until catastrophic failure occurred.

RESULTS

In terms of construct stiffness, there were no significant differences (p = 0.12). The value was 321.8 ± 91.4 N/mm in the Mitchell osteotomy group and 224.3 ± 95.2 N/mm in the Chevron osteotomy group. All specimens completed the whole cyclic loading test without catastrophic failure, and the fragment displacement after 500 cycles was 1.2 ± 0.7 mm for the Mitchell osteotomy and 1.9 ± 1.1 mm for the Chevron osteotomy group (p = 0.20). No significant differences were observed between the groups regarding the ultimate failure load and failure mode.

CONCLUSIONS

The third generation MIS screw fixation technique provides comparable construct stability in both Mitchell and Chevron osteotomies, particularly in conditions requiring substantial correction. The current study offers biomechanical evidence supporting its clinical application.