Assessing torsion of the medial cortex of the canine tibia using computed tomography multiplanar reconstruction

OBJECTIVES To describe a protocol for the measurement of tibial rotational alignment using CT multiplanar reconstructions. To establish the feasibility of producing general guidelines for the amount of torsional contouring to apply to a bone plate applied to the medial aspect of the tibia during repair of a non-reducible tibial fracture. METHODS CT scans of the pelvic limbs of 15 chondrodystrophic and 34 non-chondrodystrophic dogs were studied. Medial tibial cortex torsion angle and distal medial tibial cortex angle were determined from CT multiplanar reconstructions. Medial plate application was simulated using a plate contoured to the group mean medial tibial cortex torsion angle and post-simulation tibial rotational alignment was assessed. RESULTS Mean medial tibial cortex torsion angles were 23° (chondrodystrophic) and 26° (non-chondrodystrophic). Following simulated plate application the change in medial tibial cortex torsion was less than 10° in 73% of chondrodystrophic and 93% of non-chondrodystrophic tibias. In total, 93% of chondrodystrophic and 97% of non-chondrodystrophic tibias had post-simulation distal medial tibial cortex angle less than 10° from the group mean pre-simulation distal medial tibial cortex angle. CLINICAL SIGNIFICANCE Medial tibial cortex torsion and tibial rotational alignment can be measured using the protocol described in this study. 26° of internal torsional tibial plate pre-contouring may be appropriate for non-chondrodystrophic dogs, but further clinical validation is required.