Determination of isometric points for placement of a lateral suture in treatment of the cranial cruciate ligament deficient stifle.

Complete or partial rupture of the cranial cruciate ligament (CCL) is a common injury of the canine stifle. While numerous techniques have been developed for surgical treatment, extra-articular methods with placement of a lateral suture remain a popular treatment method. The purpose of this study was to determine the potential isometry of the six suture-paired sites; two on the femur and three on the tibia. In six femoro-tibial specimens with intact passive joint restraints, femoral sites adjacent to the proximal (F1) and distal (F2) poles of the fabella, and tibial sites adjacent to the patella insertion (T1), immediately cranial to (T2) and caudal to (T3) the long digital extensor tendon, were identified. A suture from one femoral site to one tibial site was placed under 0 or 5 N of preload, and tension was measured at joint angles of 150 degrees , 130 degrees , 90 degrees and 50 degrees . The F2-T3 combination was found to be most isometric. Isometry was re-assessed in the same specimens with the suture in the F2-T3 position, and under 5 N, 10 N and 15 N of preload, and after transection of the CCL. The suture pair retained its isometric pattern in the CCL transected specimens. There was no effect of preload on isometry patterns.