Tibial Plateau Leveling Osteotomy & Osteosarcoma

Implant- or fracture-associated neoplasia has been reported in humans and dogs, but the mechanism is unknown. Possible theories include metal implants acting as a nidus for continuing inflammation or corrosion of metal causing altered host reaction. In this study, the medical records of dogs undergoing tibial plateau levelling osteotomy (TPLO) at 2 different institutions (Clinics A and B) were reviewed to determine the incidence of osteosarcoma at the TPLO site and other sites. Records of 472 Clinic A dogs and 1992 Clinic B dogs with >1 year of follow-up were available for analysis. Both institutions used multiple plate manufacturers, although the majority of the plates were from 2 manufacturers. Of the dogs from Clinic A and Clinic B, 5 and 6 dogs developed osteosarcomas at the surgery site, and 7 and 22 dogs developed osteosarcoma at other sites, respectively. The incidence rate at the TPLO site was 30.4 and 10.2 per 10000 dog-years at risk and at other sites was 42.6 and 37.5 per 10000 dog-years at risk, respectively. For Clinic A, the median time for development of osteosarcoma at the TPLO site was 4.6 years; at other sites, it was 2.9. At Clinic B, median time was 4.4 years and 3.4 years. The authors concluded the risk for osteosarcoma development following TPLO surgery is low.

Although overall risk for OSA following TPLO was deemed low in this study, the results should be interpreted cautiously. Dogs were followed for a minimum of 1 year; however, average interval between TPLO and OSA is reported to be 5.3 years.¹ Thus, the reported incidence here may be artificially low given the short follow-up in some dogs. Further, although OSA seems to be most common following use of the Slocum cast stainless steel plates, OSA is reported to develop in some cases in which other brands of wrought stainless steel plates were used. Thus, one should not presume 

the risk for OSA to be zero when non-Slocum TPLO plate brands are used.¹ It should be recognized that this paper did not compare OSA incidence rates in dogs that had a TPLO vs dogs that did not. Thus, this study does not answer the question of whether TPLO increases the risk for OSA in dogs that have had a TPLO relative to the general population. The important take-home message is that OSA should always be considered a differential diagnosis in a dog that presents with hindlimb lameness, regardless of whether the dog has a history of TPLO performed years previously. Further, OSA is still considered a relatively rare event following TPLO, and there is not enough information to preclude recommending TPLO as an option for treatment of canine cranial cruciate ligament disease.—Sara A. Colopy, DVM, PhD, DACVS