Does Fibular Displacement Predict Tibial Malrotation in Simulated Tibia-Fibula Fractures

Introduction:Tibial malrotation can occur with medullary nailing of diaphyseal tibial fractures. Fibular alignment has been proposed as a surrogate for axial plane reduction intraoperatively. The purpose of this study was to determine whether fibular alignment is a reliable marker of accurate tibial rotation.Methods:Deidentified CT scans of 50 patients with normal tibial anatomy were selected. Using ImageJ software, we simulated osteotomies at three sites (proximal third, mid-diaphysis, and distal third). We overlaid adjacent CT slices and rotated them around the central axis of the tibia in 5 degrees increments of external rotation (ER) and internal rotation (IR). At each increment, measurements of fibular overlap (%) were obtained from anteroposterior (AP) and lateral views. To simulate fixation of the fibula, we repeated rotation around the axis of the fibula with and without a simulated medullary implant in the tibia.Results:A total of 50 patients were included. The mean age was 62 years, average BMI was 25.8, and 28 of 50 patients (56%) were male. Earliest loss of fibular contact occurred at 24 degrees ER and 22 degrees IR at the proximal site. Contact was lost at 26 degrees ER and 28 degrees IR on the AP view and 42 degrees ER and 29 degrees IR on the lateral view. The mean fibular contact at each 5 degrees increment was similar for ER and IR. Fibular contact was reduced to 50% at 10 to 15 degrees of rotation in ER and IR at all sites. Tibial canal contact was lost at 24 degrees in both ER and IR around the fibula. With a virtual medullary implant, the mean maximal rotation was 6 degrees.Discussion:Surgeons should be aware that 20 degrees or more of malrotation is likely present when fibular contact is lost during medullary nailing of the tibia. Greater than 50% loss of contact should raise suspicion for malrotation. A fixed fibula and medullary tibial implant theoretically preclude significant tibial malrotation.