Cadaveric Evaluation of MIS Akin Variation on Length and Angular Correction

Research Type: Level 4 – Case series Introduction/Purpose: Hallux abductovalgus, commonly known as a bunion, is a prevalent deformity of the forefoot with many described techniques for surgical correction. Minimally invasive surgery is gaining popularity in the foot and ankle community, but there is limited literature on the degree of correction achievable with akin osteotomies using these techniques. This study aims to compare the outcomes of oblique and transverse Akin osteotomies using two different burr sizes (2.0mm and 2.9mm) on cadaveric specimens to evaluate the effects of angular correction and bone length. Methods: Ten matched pairs (20 total) of thawed fresh-frozen cadaveric above-knee specimens were used. Each specimen had demographic data recorded, and pre-test dorsal-plantar X-ray images of the hallux proximal phalanx. The medial soft tissues were dissected, and proximal and distal points were measured with calipers. Five matched pairs received oblique osteotomies, and five received transverse osteotomies; left feet used a 2.0mm burr, right used a 2.9mm burr. A single MIS experienced surgeon performed all procedures. Post-test imaging, taken in the same orientation with the osteotomies in manually reduced positions. Caliper measurements were repeated, and images were analyzed with a Dicom viewer. Angular correction was determined by comparing pre- and post-test longitudinal axes. Results: For oblique osteotomies on cadavers 1–5 (left with 2.0 mm burr, right with 2.9 mm burr), post-test length differences measured 0.26 cm versus 0.45 cm. The average osteotomy angles were 57.78° and 58.26°, while degrees of correction averaged 4.43° (SD 1.66) and 9.40° (SD 5.62). For transverse osteotomies on cadavers 6–10, the 2.0 mm burr (left) produced a 0.34 cm length difference, an 85.43° angle, and 6.64° of correction (SD 4.38). The 2.9 mm burr (right) yielded a 0.52 cm difference, an 89.97° angle, and 14.87° of correction (SD 4.10). Conclusion: These findings suggest that burr size affects surgical correction in a predictable pattern, with the 2.9mm burr and transverse osteotomies providing greater change compared to the 2.0mm burr and oblique osteotomy. This study highlights the importance of preoperative planning and burr selection in achieving optimal and consistent results for patients undergoing minimally invasive Akin osteotomy procedures.