Heat Generation during Minimally Invasive Calcaneal Osteotomy: A Cadaveric Study
Authors: Hall SarahRose , Bakaes Yianni , Encinas Rodrigo , Jackson J. Benjamin , Gonzalez Tyler 
Published: December 2023

Category: Hindfoot; Ankle Introduction/Purpose: Minimally invasive percutaneous (MIS) calcaneal osteotomy has become more popular due to low risk of nerve injury and wound complications. The Shannon burr is often used to perform these osteotomies despite concern for the heat generation. Temperatures above 50oC may lead to osteonecrosis of bone. A recent MIS calcaneal cadaveric model study showed that cool irrigation led to less heat generation than room temperature irrigation. However, questions remain if irrigation is needed at all. This study evaluates heat generation during MIS calcaneal osteotomies and analyzes whether the use of cooled irrigation significantly decreases the temperature of the burring process compared to no irrigation at all. Our hypothesis was that cool irrigation would lead to overall lower heat generation compared to no irrigation. Methods: 5 matched paired cadavers (10 legs) were used to simulate a MIS calcaneal osteotomy for all trials. Prior to the osteotomy, 4 temperature probes were inserted as to the border where the Shannon burr would travel along the osteotomy site (Image 1). Probes were secured by suture and temperature was recorded using K-type thermocouples. All trials were complete using a pulse technique of 20 seconds on, 5 seconds off with a Shannon Burr and fluoroscopic guidance. Trials were complete with continuous cold irrigation (N=5) and without any irrigation at all (N=4). Temperatures were evaluated at baseline, during burring, and after burring to assess total heat generation and dissipation. A two-tailed t-test was used to analyze differences in heat generation and dissipation between procedures completed with irrigation and without irrigation (P < 0.05). Results: 5 cadavers with a mean age of 86.2 were evaluated for a total of 10 simulations, 9 analyzed. All cadavers underwent 1 trial with irrigation, and 1 without on opposite feet. Average drill time was 124±24.5 seconds with irrigation, and 118.8±43.9 seconds without (P=0.915). 77.8% of procedures showed heat generation below the level of bone necrosis (50 oC). 2 procedures without irrigation generated heat above this threshold (54.3 oC, 54.7 oC). Average change in temperature was 15.1±4.6 and 22.9±8.7 during drilling, 8.4±1.7 and 10.7±5.3 after drilling in procedures with and without irrigation, respectively. There was no significant difference detected between heat generation during or after burring in irrigated vs non-irrigated procedures (P = 0.426, 0.661). Conclusion: This cadaveric study found that the use of cooled irrigation compared to no irrigation did not lead to a significant difference in the heat generation during a MIS calcaneal osteotomy. However, 2 out of the 9 samples used in this study showed a heat generation above 50o C, and both were done without the use of irrigation. This may be useful information for a surgeon when considering the usage of cooled irrigation to reduce the potential risk of osteonecrosis when performing a MIS calcaneal osteotomy.