In vivo three-dimensional isometry analysis of suture attachment sites for extracapsular suture stabilization of the canine stifle

Background: The study aimed to perform isometry analysis of a selection of suture attachment points for extracapsular stabilization with three-dimensional (3D) measurements and normal gait kinematics of the stifle joint. Methods: Thirteen client-owned dogs were recruited. Fluoroscopic images of the stifle during treadmill walking and computed tomography of the same joint were acquired. Stifle kinematics were reconstructed using 3D model-based fluoroscopic analysis. Variability of the distance between the femoral and tibial attachment sites across gait cycles was evaluated. The maximum length variation (MLV) and maximum length percent variation (MLPV) were quantified and used to determine the level of isometry of the attachment site combinations. Results: A selection of combinations with lower mean MLV (<2.5 mm) or MLPV (<8%) was identified from 315 combinations, and all the combinations involved femoral attachment sites near the distal pole of the lateral fabella. The combinations also involving tibial attachment sites near the proximal tibial crest showed improved isometry, with an MLPV < 6%. Conclusion: Combinations using attachment sites around the distal pole of the lateral fabella and proximal tibial crest or caudal to the long digit extensor groove appeared to have improved isometry.