Comparison of Intraoperative Radiation Exposure Between Minimally Invasive Chevron Akin (MICA) and Open Procedures for Hallux Valgus Correction

Abstract

Category: Bunion; Midfoot/Forefoot Introduction/Purpose: The minimally-invasive Chevron-Akin (MICA) procedure for hallux valgus correction is an increasingly popular technique that has yielded comparable radiographic and clinical outcomes to open procedures3–5. Intraoperative radiation dosages for certain foot and ankle surgeries have been reported relative to the international occupational radioprotection thresholds6. In particular, the mean intraoperative radiation exposure during the MIS Scarf osteotomy has been reported to be 14-times greater than open osteotomy7. However, no study to date has reported on the intraoperative radiation exposure during MICA procedures in relation to that of open procedures. Methods: This is a retrospective comparative study from a single institution. Patients underwent a MICA (n=25) or open (n=40) hallux valgus correction by a single foot and ankle fellowship trained surgeon. To account for the learning curve8, the number of intraoperative fluoroscopy shots for the first 50 consecutive MICA procedures were analyzed, and the first 25 procedures were excluded. Four data points were retrieved from the mini C-arm, including 1) number of fluoroscopy shots taken; 2) total fluoroscopy time (s); 3) total radiation dose (mGy); and 4) total dose area product (DAP; mGy*cm2). Preoperative and postoperative radiographs were referenced to measure the hallux valgus (HVA) and intermetatarsal angles (IMA) as previously described.9 Categorical variables were compared using the chi-square test, and continuous variables were compared using Student’s t-test or the Mann-Whitney U test. Analysis of variance was used to determine the statistical significance of differences in the fluoroscopy data between groups. Results: The average total dose absorbed (4.00 vs. 1.34 mGy, p< 0.001), total fluoroscopy time (226 vs. 48.5 s, p< 0.001), and number of fluoroscopy shots (125 vs. 22.3, p< 0.001) were 2.9, 4.6, and 5.6 times greater in the MICA versus the open group, respectively. The total DAP (4.22 vs. 2.56 mGy*cm2, p=0.175) was 1.6 times greater in the MICA group but the difference was not statistically significant. The mean preoperative and postoperative HVA and IMA were greater in the MICA cohort compared to the open cohort. However, there was no statistical difference in change in HVA (MICA -17.43 vs. Open -20.05, p=0.125) or IMA (MICA -8.08 vs. open -9.31, p=0.11) between the two cohorts, with each resulting in normal postoperative angles. Conclusion: In this single surgeon series, the MICA procedure demonstrated significantly greater dose absorbed, total fluoroscopy time, and number of fluoroscopy shots compared to the open procedure. The extent of radiation exposure to the surgeon and the patient in relation to the radioprotection thresholds must be closely monitored to specify the health risks involved with this procedure.