The Impact of Each Burr Pass on Gap Size and Hindfoot Alignment in Minimally Invasive Zadek Osteotomy

Category: Hindfoot; Sports Introduction/Purpose: While MIS Zadek osteotomy offers numerous advantages, it does come with a significant drawback as it impedes the direct measurement of the planned resection, depending solely on the surgeon's perception. This reliance can result in either insufficient or excessive resection of the calcaneus. The aim of this study is to elucidate the impact of each burr pass on the extent of correction, gap size, and calcaneal morphology following MIS Zadek osteotomy. Methods: en cadaveric specimens devoid of apparent foot pathology underwent a minimally invasive Zadek osteotomy utilizing a 3.1 mm Shannon burr. The osteotomy initiation point was anterior to the attachment of the calcaneal plantar fascia, preserving the plantar cortex and extending dorsally to the anterior aspect of the posterosuperior tubercle of the calcaneus. Following each burr pass, the created defect was closed and maintained in a reduced state during subsequent burr passes. This sequence was reiterated five times, and neutral lateral x-rays were captured before and after each burr pass to quantify the impact of individual passes. Measurements were calibrated using markers placed during radiological examination. These measurements encompassed the defect size formed with each burr passage, determined by the change (shortening) in the overall length of the dorsal calcaneal cortex. Additionally, alterations in various foot alignment parameters were assessed, including Böhler angle, Calcaneal X/Y ratio, and Fowler Philip angle. Results: The dorsal calcaneal cortical length exhibited an average reduction with each burr pass as follows: 2.1 mm during the 1st pass, 1.9 mm during the 2nd pass, 1.6 mm during the 3rd pass, 1.2 mm during the 4th pass, and 0.9 mm during the 5th pass. The Böhler Angle (°), X/Y Ratio (%), and Fowler Philip Angle consistently decreased with each successive burr passage. Conclusion: Our research showcased that employing a percutaneous 3.1 mm burr in Zadek osteotomy sequentially can result in a 10 mm dorsal wedge size after 5 burr passes. The calcaneal geometry, assessed through the X/Y ratio, Fowler-Philip angle, and Böhler angle, exhibited gradual alterations with each burr pass. The insights gained from this study offer valuable information for foot surgeons, deepening their comprehension of the influence of each burr pass on gap size and foot alignment parameters in minimally invasive Zadek osteotomy.