Comparison of patellar position and moment arm between tibial plateau leveling osteotomy and cranial closing wedge ostectomy: An ex vivo study

Abstract

Background: Tibial plateau leveling osteotomy (TPLO) and cranial closing wedge ostectomy (CCWO) are common treatments for cranial cruciate ligament disease. These two techniques mainly differ in whether the proximal tibial fragment contains the attachment site of the patellar ligament. Currently, there are no reports comparing how these techniques affect the patellofemoral joint. Aim: This ex vivo study aimed to compare the effects of TPLO and CCWO on the patellar position and moment arm in healthy Beagles. Methods: TPLO and CCWO were performed on each stifle in six cadavers of Beagles. Pre- and postoperative mediolateral radiographs with the stifle angle at approximately 90° were obtained. The modified Blumensaat index (MBI), patellar ligament length to patella length ratio (PLL:PL), and patellar moment arm (PMA) were measured in each radiograph. Mixed-model multiple regression analyses for the MBI, PLL:PL, and PMA, with the surgical procedure as the independent variable, was then performed. The joint angle was included as an independent variable for MBI, and PMA. Results: The PLL:PL was decreased after TPLO. Additionally, the PLL:PL after TPLO was significantly lower than that after CCWO. The MBI decreased with flexion. Postoperative MBI values were decreased for both procedures, with lower values after CCWO than after TPLO. The PMA values decreased with flexion. Postoperative values for both procedures were decreased in the PMA, with the values being lower after CCWO than after TPLO. Conclusion: Both TPLO and CCWO affect the patellofemoral joint. Compared with TPLO, CCWO produced greater downward traction on the patella. Therefore, CCWO may be used to correct the patellar alta and treat cranial cruciate ligament disease.