Effect of the Centre of Rotation in Tibial Plateau Levelling Osteotomy on Quadriceps Tensile Force: An Ex Vivo Study in Canine Cadavers

Objective  The aim of this study was to determine the effect of the centre of rotation in tibial plateau levelling osteotomy (TPLO) on the tensile force of the quadriceps. Materials and Methods  Tibial plateau levelling osteotomy was performed on the left pelvic limbs from 20 normal adult Beagle cadavers. To replicate the tensile force of the quadriceps, gastrocnemius and stifle flexor muscles, these muscles were replaced with wires. The tensile force of each wire, cranial tibial displacement and internal tibial rotation were measured under the following conditions: intact cranial cruciate ligament, transected cranial cruciate ligament, ideally centred osteotomy TPLO (ICO group) and distally centred osteotomy TPLO (DCO group). The ratios of the tensile forces for the wires divided by the vertical force were used for analyses. Results  The mean intact and post-TPLO tibial plateau angles (TPA) in the ICO group were 30.3° ± 1.9° and 6.1° ± 1.6°, respectively, and those in the DCO group were 29.8° ± 2.4° and 6.8° ± 0.9°, respectively. The mean quadriceps tensile force after TPLO was significantly greater in the DCO group (3.9 ± 0.3) than the ICO group (3.3 ± 0.4) ( p  = 0.006). Both groups exhibited tibial caudal displacement after TPLO. Clinical Relevance  The tensile force of the quadriceps muscles changed in accordance with the centre of the osteotomy in TPLO. The DCO group had increased tensile force, which may cause patellar ligament thickening after TPLO. Setting the postoperative TPA at 6° may cause excessive rotation in patients with a normal tensile force of the stifle flexor muscles.