The Intermalleolar Method for Intraoperative Rotational Assessment of the Tibia – A Prospective Clinical Validation Study

Abstract

OBJECTIVES: To determine the accuracy of the intermalleolar method, an intraoperative fluoroscopic method for assessing tibial rotation in patients undergoing intramedullary nail fixation for tibial shaft fractures, by comparing it to the gold standard, computed tomography (CT). METHODS: Design: Prospective cohort study Setting: Academic Level 1 trauma center Patient Selection Criteria: Consecutive patients, age 18 years and older, with unilateral tibial shaft fractures who underwent intramedullary fixation from September, 2021 to January, 2023. Outcome Measures and Comparisons: Intraoperatively, tibial rotation measurements were performed using the intermalleolar method on both the uninjured and injured limbs. Postoperatively, patients underwent bilateral low-dose lower extremity rotational CT scans. CT measurements were made by four blinded observers. Mean absolute rotational differences and standard errors were calculated to compare the injured and uninjured limbs. Subgroup analysis was performed assessing accuracy relating to injured versus uninjured limbs, BMI, AO/OTA fracture pattern, tibial and fibular fracture location, and distal articular fracture extension requiring fixation. RESULTS: Of the 20 tibia fractures, the mean patient age was 43.4 years. The intermalleolar method had a mean absolute rotational difference of 5.1 degrees (SE 0.6, range 0 – 13.7) compared to CT. Sixty percent (24/40) of the measurements were within 5 degrees, 90% (36/40) of the measurements were within 10 degrees, and 100% (40/40) were within 15 degrees of the CT. No patients were revised for malrotation postoperatively. CONCLUSION: The intermalleolar method is accurate and consistently provides intraoperative tibial rotation measurements within 10 degrees of the mean CT measurement for adult aged patients undergoing intramedullary nail fixation for unilateral tibial shaft fractures. This method may be employed in the operating room to accurately quantify tibial rotation and assist with intraoperative rotational corrections. LEVEL OF EVIDENCE: Diagnostic Level II. See Instructions for Authors for a complete description of levels of evidence.