Assessing the Accuracy and Reliability of the Fluoroscopic Ruler for Comminuted Femur Fractures: A Cadaveric Study.

Background: Fixation of comminuted femur fractures may result in limb length discrepancy. Intraoperative fluoroscopic measurement of the contra-lateral femur with a ruler is commonly performed to establish a reference for femoral length. No evidence regarding the reliability and accuracy of this technique exists. This study aimed to assess the accuracy and interrater reliability of a fluoroscopic ruler in obtaining correct femoral length in a comminuted femoral shaft fracture model.

Materials and methods: Approximately 5 cm of bone was removed from the left femoral diaphyses of 8 cadavers. Seven orthopedic surgery residents and 2 attendings measured the length of the intact contralateral femur using a ruler under fluoroscopy. The ruler was then applied to the "fractured" femur with manual traction applied until femoral length matched the measured length of the contralateral femur. The resulting gap in the "fractured" femur was compared with the length of bone that had been resected. Data were analyzed using means, SDs, and intraclass correlation coefficients (ICCs).

Results: Fifty-seven measurements were collected. The mean difference between the measured fracture gap and the length of bone removed was 8.0±5.8 mm (range, 0-22 mm). Femoral length was accurate to 5 mm in 40% of cases, 10 mm in 70%, 15 mm in 81%, 20 mm in 98%, and 25 mm in 100%. The overall interrater reliability was poor (ICC, 0.11; 95% CI, 0.001-0.44).

Conclusion: Despite poor interrater reliability, the fluoroscopic ruler resulted in a mean leg length discrepancy of 8.0±5.8 mm in this cadaveric study. [Orthopedics. 202x;4x(x):xx-xx.].