Cranial cruciate ligament (CCL) rupture is common in dogs. Onset is more often insidious due to gradual ligament deterioration than acute due to traumatic rupture. Left untreated, degenerative changes in the stifle joint occur, especially in dogs weighing more than 15 kg. Tibial plateau-leveling osteotomy (TPLO) is one surgical technique that has been reported to minimize progression of osteoarthritis (OA) after CCL rupture. In this study, 29 dogs over 15 kg (average 33.6 kg) were evaluated for progression of OA and clinical function at least 1 year after TPLO. Radiographs taken before and at least 1 year after surgery were scored by 3 investigators for signs of stifle joint OA. A questionnaire given to owners was used to assess clinical function. The study found 6 of the 29 dogs (21%) had decreased evidence of OA, 1 dog (3%) showed no change, and 22 dogs (76%) showed measurable progression of OA. Despite this, clinical function as assessed by the client questionnaire was reported to be significantly improved after TPLO surgery when compared with preoperative function. Radiographic OA scores were not significantly predicted by clinical improvement in function.

COMMENTARY: The belief that TPLO stops or reverses radiographic signs of progression of stifle joint OA after CCL injury is widespread. However, this study found that a large percentage of dogs had significant progression of radiographic evidence of OA after TPLO. The difference in the results of this study might be explained by several factors: the radiographic scoring system used (which took into account parameters other than just osteophyte production), the longer follow-up time in the current study, or possibly the subjects used in the study-many of which already had evidence of OA at the preoperative evaluation. Still, the TPLO technique might result in less radiographic progression of OA in comparison with other techniques. A randomized, prospective clinical study would help determine this. In addition, despite the radiographic progression seen, client satisfaction with clinical outcome was good. This lack of a relationship between clinical function and radiographic OA has been seen in a number of studies and is well worth keeping in mind when evaluating surgical options.

Radiographic and functional evaluation of dogs at least 1 year after tibial plateau leveling osteotomy. Boyd DJ, Miller CW, Etue SM, Monteith G. Can Vet J 48:392-396, 2007.