33rd Annual Scientific Meeting proceedings

Objectives
Medial patellar luxation (MPL) is a common cause of lameness in dogs. The underlying mechanisms of patellar luxation are still not fully understood. The objective of this study was to evaluate the in vivo biplanar fluoroscopic kinematics of dogs with MPL.

Methods
Six client-owned dogs presented with MPL grades I-III were included. The dogs underwent fluoroscopic imaging while walking and trotting on a treadmill. A CT scan of both hindlimbs was obtained. 3D models of the bones were created, and a cartesian coordinate system was assigned. The 3D bone models were then shape-matched to the fluoroscopic images obtained from 3 gait cycles. Translation and rotation around three axes were calculated.

Results
The patella luxated during the late stance and early to mid-swing phase in all MPL grades and returned to the groove during the late swing phase. The patella of affected limbs moved more medially, distally, caudally, and was more externally rotated than in healthy dogs. The frequency of luxation did not match with MPL grade in 2/4 legs with MPL grade 0 and in 2/4 legs with grade 3.

Conclusions
The mediolateral, proximodistal, and craniocaudal position of the patella follows a gait-related pattern. The limbs affected with a more severe grade of MPL show more displaced and rotated patella than healthy limbs, although the patellar luxation frequency during the analyzed cycles is not directly correlated to the clinical grading of MPL.

Conclusions
A novel fixation technique using a single-length orthopedic wire demonstrated similar strength and stiffness as the 2Pins+TBW technique and was superior to the 2Pins technique.