Quasi-isometric points for the technique of lateral suture placement in the feline stifle joint

To evaluate the quasi-isometric points (nearest isometric points) between the distal aspect of the femur and fabella and the proximal aspect of the tibia for placement of a lateral suture in cats.

Radiographic study.

Cadaveric cat stifles (n = 7 cats; 14 stifles).

Specimens were secured in a mounting frame to maintain rigid fixation of the femur and allow free range of motion of the stifle joint and proximal tibia. Two anatomic landmarks were identified: the center of the lateral fabella (Ff) and a point 4 mm proximal to the insertion of the patellar tendon adjacent to the tibial cortex (Tt). Radiopaque spheres were placed at predefined landmarks in the femur (caudal aspect of the lateral femoral condyle distal [F1] and proximal [F2] to the lateral fabella) and in the tibia (caudal to the proximal aspect of the extensor groove [T1]; cranial to the proximal aspect of the extensor groove [T2]; 2 mm proximal and caudal to the insertion of the patellar tibial tendon [T3] and 3 mm caudal to the insertion of the patellar tibial tendon [T4]. For each stifle, 4 radiographic projections were made: in extension (166°), in flexion (45°), and 2 intermediate stance phases (90°, 130°). ANOVA was used to compare means of the distance between the point pairs and means of the percent change in variation of distance (VOD%) using the 45° measurement as a reference.

Mean VOD% nearest to zero, over all the different angles tested, was produced by Ff-Tt, which was statistically significantly different from each of the other point pairs.

Ff-Tt provides the best quasi-isometric points for placement of lateral sutures in cats, compared with all combinations tested. Further assessments with biomechanical studies are needed to evaluate the reproducibility of these landmarks for stabilization of CCL rupture in cats.