Abstract
Objective: Medial patellar luxation (MPL) is a common orthopedic condition in dogs. After surgical correction, the recurrent rates appear to be higher and outcomes worse in grade IV than in lower grade MPL. To describe the outcomes of surgical correction of canine grade IV MPL.
Methods: This retrospective study analyzed the medical records of 16 dogs (11 females, 5 males; mean age 5.05 years) with 22 stifle joints (8 left and 14 right) that underwent MPL surgery at Rakuno Gakuen University between May 2015 and October 2020. The procedures included capsulorrhaphy, trochlear block recession, tibial tuberosity transposition, medial retinacular release, and lateral fabellotibial suturing. The types of postsurgical complications, including a recurrence of MPL, were recorded.
Results: Twelve of the 16 (75 %) dogs had concurrent contralateral MPL, and two dogs (12.5 %) had concurrent cranial cruciate ligament rupture. The mean follow-up was 12.1 months. No lameness was observed. The outcomes of surgery for grade IV MPL were not associated with bilateral surgery, age, sex, body weight, or the preoperative quadriceps angle. Although none of the dogs showed any major or catastrophic complications following surgery, postoperative minor and major complications were observed in eight of the 22 stifle joints (36.4 %).
Clinical significance: Grade IV MPL is a complex orthopedic disease in dogs that requires surgical patellar realignment to improve limb function. The surgical techniques used in this study were associated with a good prognosis without a surgical revision.

Key words: Canine diseases; cranial cruciate ligament; medial Patellar Luxation; outcomes assessment; postoperative complications