Summary
Patellar tendon thickening (PTT) and patellar tendinosis (PTS) have been discussed
in the veterinary literature as a post-operative complication of tibial plateau leveling
osteotomy (TPLO). The purpose of this study was to define radiographic PTT, determine
the frequency of and risk factors for PTT and PTS, and describe the clinical and histopathological
findings of PTS after TPLO. We hypothesized that the location of the osteotomy alters
forces placed on the patellar tendon resulting in PTT or PTS. Radiographs and medical
records from 83 dogs undergoing 94 TPLO procedures were retrospectively evaluated.
Two months post-operatively, 19 dogs (20.2%) had a normal patellar tendon or mild
PTT, 51 (54.3%) had moderate PTT, and 24 (25.5%) had severe PTT. Seven of the 24 dogs
(7.4%) with severe PTT had clinical signs consistent with PTS. Only dogs with severe
PTT developed PTS (p < 0.0001). The risk factors for the development of PTT include:
a cranial osteotomy, a partially intact cranial cruciate ligament (CCL) in conjunction
with a cranial osteotomy, and post-operative tibial tuberosity fracture. The only
risk factor identified for the development of PTS was a partially intact CCL. Four
dogs with PTS improved with conservative therapy and one improved with surgical treatment.
Two dogs had tendon biopsies with histopathological review that showed tendon degeneration
with lack of inflammation. As only the dogs with severe PTT develop PTS, a caudal
osteotomy for the prevention of PTT and subsequent PTS is recommended.
Keywords
TPLO - patellar - tendonitis - thickening