Effect of sequential burr passes on osteotomy magnitude and calcaneal morphology in minimally invasive Zadek osteotomy

Purpose: This study aimed to evaluate the impact of each burr pass on degree of correction, gap size and calcaneal morphology in MIS Zadek osteotomy. Methods: MIS Zadek osteotomy was performed on ten cadaveric specimens using a 3.1 mm Shannon burr. After each burr pass, the osteotomy gap was manually closed, and the subsequent burr passes were carried out with the foot held in dorsiflexion, which was repeated five times. Lateral X-rays were taken before and after each burr pass. Two independent reviewers measured the dorsal calcaneal length after each burr passage, as well as changes in several calcaneal parameters including X/Y ratio, Fowler Philip angle, and Bohler angle. Results: The average decrease in dorsal calcaneal cortical length with each burr pass was as follows: 2.6 +/- 0.9 mm at the 1st pass, 2.4 +/- 1 mm at the 2nd pass, 2 +/- 1 mm at the 3rd pass, 1.6 +/- 1 mm at the 4th pass, and 1.4 +/- 0.7 mm at the 5th pass. The Fowler Philip and Bohler angles consistently decreased while the X/Y ratio consistently increased following each consecutive burr pass. Interobserver reliability analysis demonstrated good agreement for all parameters. Conclusion: The results revealed the trends of length and anatomical changes in the calcaneus with each burr pass. On average, a dorsal wedge resection of 10 mm was achieved after 5 burr passes. This data can aid surgeons in determining the optimal number of burr passes required for a particular amount of resection, ensuring the attainment of the desired patient-specific surgical outcome. (c) 2023 European Foot and Ankle Society. Published by Elsevier Ltd. All rights reserved.

Automated summary

This study evaluated the impact of each drill pass in MIS Zadek osteotomy on the calcaneus, including the degree of correction, gap size, and morphological changes. The results showed a gradual decrease in the dorsal cortical length of the calcaneus with each drill pass, along with decreases in the Fowler Philip and Bohler angles and an increase in the X/Y ratio. A 10mm dorsal wedge resection was achieved after 5 drill passes.