34th Annual Scientific Meeting proceedings

Objectives:

Research is lacking regarding surgical treatment guidelines for feline medial patellar luxation (MPL). This cadaveric study investigated the force required to cause MPL at different stifle angles and assessed the effect of wedge and block recession trochleoplasty (BRT or WRT), with and without partial parasagittal patellectomy (PPP), on this force.

Methods:

Twelve feline pelvic limbs with preserved quadriceps extensor mechanism were mounted on a custom-built jig with the patella attached to a load cell. The force required for luxation (Newtons) was measured in extension, neutral and flexion positions before and after the limbs underwent WRT or BRT; and after PPP combined (WRT+PPP or BRT+PPP). The maximum force to luxation was recorded once identified on the force-displacement graphs.

Results:

Before surgery, the force inducing luxation was significantly higher in flexion (22.38±15.33N) than neutral (11.47±5.83N) (p=0.026) and extension (8.44±5.53N) (p=0.014). In extension, no significant difference was found between all the groups (p>0.05). In neutral, the force in the BRT+PPP group (66.36±20.48N) was significantly higher than in the control (11.47±5.83N) (p=0.002), WRT (9.76±4.05N) (p=0.002), BRT (20.83±11.85 N) (p=0.004) and WRT+PPP (24.3±10.37 N) (p=0.008) groups. In flexion, the force to luxation after BRT+PPP (64.7±41.77 N) was significantly higher than WRT+PPP (30.22±14.91N) (p=0.045).

Conclusions:

The force required to cause MPL in cadaveric cats increased significantly when the stifle was in flexion. The combination WRT or BRT with PPP also significantly increased the force required to cause luxation. The highest force causing luxation was identified with the combination of BRT+PPP in neutral and flexed positions.