Comparison of trochlear block recession and trochlear wedge recession for canine patellar luxation using a cadaver model

Objective-To compare trochlear block recession (TBR) to trochlear wedge rec ession (TWR) with regards to patellar depth (percentage of patellar volume under the trochlear ridges), patellar articular contact, percentage of rece ssed trochlear surface area,and resistance to patellar luxation. Study Design-In vitro computed tomography (CT) and biomechanical evaluation using a cadaver model. Sample Population-Twelve normal, large-breed canine cadavers. Methods-Bilateral pelvic limb specimens with intact stifle joints were moun ted on a positioning device. The femoral trochlear ridges were reduced to p rovide a standard shallow trochlea. TBR or TWR was performed to a standard depth randomly on paired specimens. CT and biomechanical evaluations were p erformed pre- and postoperatively in both an extended (148 degrees) and fle xed (113 degrees) stifle position. CT images were digitized and measurement s made using an image-analysis software program. Biomechanical testing cons isted of applying 40 degrees of internal tibial rotation and documenting pa tellar luxation. Results-The change in trochlear depth (depth of recession) was not signific antly different between groups. In the extended stifle position (patella in the proximal trochlea), patellar depth and patellar articular contact with the recessed trochlea were significantly greater after TBR compared with T WR. The percentage of recessed trochlear surface area was significantly gre ater after TBR compared with TWR. In the extended position, a smaller perce ntage of the patellae luxated within 40 degrees of internal tibial rotation after TBR compared with TWR. Conclusions-TBR increases proximal patellar depth, increases patellar artic ular contact with the recessed proximal trochlea, recesses a larger percent age of trochlear surface area, and results in a greater resistance to patel lar luxation in an extended position as compared with TWR. Clinical Relevance-TBR may help limit the development of stifle DJD in dogs treated for canine patellar luxation. (C) Copyright 2001 by The American C ollege of Veterinary Surgeons.