Identification of Tibial Malrotation After Nailing Using Unique CT Scan Reference Line, and Influence of Position of Leg for Distal Locking on Rotation.

INTRODUCTION: Tibial torsion can be measured by various clinical and radiological methods. Computed tomography (CT) scan measurement is currently the investigation of choice. The purpose of our study was to compare the clinical and CT scan methods to reveal malrotation after nailing of tibia and also to find out if leg position for distal locking has any influence on incidence of malrotation.
MATERIALS AND METHODS: We have included 106 patients (21-68 years) of tibia nailing, and categorised them as category A (figure of four position n = 54) and category B (knee straight position n = 52) based on limb position for distal locking. The plumb line measurement, Thigh Foot Axis (TFA) and CT scan measurement (using new reference line) were documented and compared with the uninjured limb.
RESULTS: We observed plumb line measurement to be the most inaccurate method followed by TFA method. CT scan measurement was the most accurate method showing external rotations (> 10º) in 32 cases (30.1%) and internal rotation (> - 10º) in five cases (4.71%). The TFA method had a sensitivity of 44% and specificity of 86% in identifying malrotations. The interobserver reliability for CT scan measurement was 0.96. Even though statistically not significant (P value), figure of four position for distal locking leads to larger number of malrotations (both external and internal rotation).
CONCLUSION: CT scan is the most accurate method of measuring malrotation. The new reference line used in our study provides accurate measurement of malrotation. The two different positions of leg for distal locking do not have a statistically significant influence on incidence of malrotation. © Indian Orthopaedics Association 2020.