Treatment of patellar luxation with polyethylene sulcal ridge prostheses in 44 feline stifles: a retrospective study.

Objectives: The aim of this study was to assess the complication rates and long-term outcomes, as well as to refine case selection criteria for cats undergoing trochlear ridge augmentation (TRA) using an ultra-high molecular weight polyethylene implant (UHMWPEI) for the treatment of patellar luxation (PL).

Methods: The clinical records from two referral veterinary hospitals were searched for cases that fitted defined inclusion criteria. A short-term assessment was based on examination and radiography at 8 weeks postoperatively. The long-term assessment was carried out at least 2 years postoperatively through examination and radiography, and less commonly via questionnaire.

Results: A total of 44 stifles in 39 patients with PL grade 2 (n = 19), 3 (n = 22) or 4 (n = 3) met the inclusion criteria. TRA using UHMWPEI was associated with minor complications in 20% of cases and major complications in 7% of cases. Minor complications included seroma formation (n = 5), superficial wound infection (n = 2), prolonged discomfort for a few weeks postoperatively (n = 1) and transient postoperative azotaemia (n = 1). After surgical correction of medial PL, one skeletally immature case developed transient grade 1 lateral PL, which resolved without intervention. Major complications comprised implant removal for ongoing lameness (n = 3). Degenerative joint disease, with mineralisation that was often marked, was noted in 26/35 (74%) cases that were available for radiographic follow-up 2 years or more after TRA. Nevertheless, good or very good long-term functional outcomes were achieved for 93% of cases.

Conclusions and relevance: The currently available UHMWPEIs were shown to be suitable for treating PL grades 2, 3 or 4 in cats weighing ⩾3 kg. Delaying TRA until growth is completed is advised. The long-term follow-up suggested that the correction of PL in cats with UHMWPEI was sustained and that good function could be expected in the long term. Mineralisation overlying implants was common, but this was not appreciably correlated with adverse functional consequences.