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Category: Midfoot/Forefoot; Other Introduction/Purpose: Minimally invasive (MIS) bunion correction is growing in popularity as a treatment option of hallux valgus deformities. This technique has been shown to help with post-operative pain and improve functional outcomes. Despite these benefits there are concerns that the Shannon burr may lead to excess heat generation, thermal necrosis of bone and potentially increase the risk of nonunion. The purpose of our study was to assess the heat generation while using a Shannon burr during MIS first metatarsal osteotomies. Methods: Four below knee cadavers were utilized and osteotomies of the distal and proximal aspects of each of the first metatarsal were performed utilizing a 2mm x 20mm Shannon burr under fluoroscopic guidance. 3 K-type thermocouples were placed in each metatarsal, one distal, one in between and one proximal to the osteotomy sites. Temperatures were evaluated during the entire burring process and after to assess heat dissipation and total heat generated. Three different techniques of burring were utilized, 1. Continuous without irrigation, 2. Continuous with irrigation and 3. Pulse burring technique with irrigation (20 seconds on, 10 seconds off). Results: The pulse burring technique with irrigation showed the overall lowest max temperature and change in temperature compared to the other techniques. Average burr time, maximum heat generation and overall change in heat was 86.2 seconds, 102.4 °F and 78.9 °F for all trials. Conclusion: The pulse burr technique with irrigation generated less heat than both continuous burring with and without irrigation. There was an overall trend toward higher heat generation with longer burr times regardless of irrigation and burring technique. Utilizing a Shannon burr with pulse burring and irrigation can minimize heat generation and potentially decrease the risk of thermal necrosis of bone. [ABSTRACT FROM AUTHOR]

Category: Bunion; Midfoot/Forefoot Introduction/Purpose: Bunions are one of the most common pathologies treated by orthopedic foot and ankle surgeons. The usage of minimally invasive and percutaneous surgical techniques continues to rise due to evidence of less pain, improved functional outcomes and low recurrence rates. Still, concern regarding heat generation during these procedures, osteonecrosis of bone, and nonunion persists. Literature suggests cool irrigation is superior to room temperature irrigation, but the question remains if irrigation is needed at all. This study evaluates the heat generation during percutaneous bunion surgery and analyzes the use of cooled irrigation compared to no irrigation at all. This study tested the hypothesis that cool irrigation would lead to overall lower heat generation compared to no irrigation at all. Methods: 5 matched paired cadavers (10 legs) were used to simulate MIS first metatarsal distal transverse osteotomy for all trials. Prior to 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 completed 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 (10 total simulations, 9 analyzed). Cadavers underwent 1 trial with irrigation, and 1 without on opposite feet. 88.9% of patients showed heat generation below the level of bone necrosis (50 oC). One trial with irrigation temperature rose to 79.1oC. Matching specimen without irrigation had probe failure and no temperature was obtained. Average burr time was 51.2±2.4 seconds with irrigation, and 35±0.5 seconds without. Irrigation was associated with a significant increase in burr time (P=0.002). Average temperature change was 13.62±11.9 and 0.7±0.5 during burring, 7.1±1.8 and 5.8±0.3 after burring in procedures with and without irrigation, respectively. No significant difference was detected between heat generation in irrigated vs non-irrigated procedures (P = 0.371, 0.548). Conclusion: This study found that in a cadaveric model the use of cooled irrigation, compared to no irrigation, did not lead to a significant difference in the heat generation during MIS first metatarsal distal transverse osteotomy. However, 1 out of the 9 samples used in this study showed a heat generation above 50 oC. Additionally, to our surprise the use of irrigation led to a significant increase in burring time. 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 first metatarsal distal transverse osteotomy. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]