Orthopedics

The 2nd World Veterinary Orthopedic Congress was held in conjunction with the 33rd meeting of the Veterinary Orthopedic Society (VOS) from February 25 to March 4, 2006, in Keystone, Colorado. The meeting heard more than 100 scientific presentations covering a wide range of orthopedic topics from investigations conducted all over the world.

A multicenter study uncovered some interesting information on metastasis and survival times following limb-salvage surgery for osteosarcoma of the distal part of the radius. While limb amputation or radiation therapy, with or without chemotherapy, has been used to treat osteosarcoma of the distal part of the radius, an alternate therapy, limb-sparing, consists of excising the distal part of the radius and incorporating a cortical bone allograft, fixed in place with a bone plate (1). “Limb-spare” patients are usually treated with a course of chemotherapy as well. Although the surgery is very demanding with many potential complications, it has yielded encouraging results in terms of survival times and patient function. Perhaps the most common potential complication is infection of the surgical wound, which occurs in at least half of all cases. This survey of 47 dogs, however, suggested that this complication may not necessarily be a bad thing! (1). In fact, postoperative infection was found to be positively associated with time to metastasis and overall survival time. Sixty-eight percent of the dogs in this study developed infections. These dogs lived significantly longer than those that did not develop infections, and the metastasis of their neoplasia was significantly delayed. In addition, the authors noted that a shorter initial length of the part of the radius affected by the tumor, and a lesser body weight were also positive prognostic indicators in terms of survival time (1).

Tibial plateau leveling osteotomy (TPLO) is now a mainstream treatment for cranial cruciate ligament rupture, especially in large dogs. The results of 438 cases treated with TPLO were presented (2). Ninety-four percent of the cases were deemed to have returned to normal function after TPLO; however, only about 70% had attained this level of function 6 mo postoperatively. No loss in joint range of motion was reported in any of the cases, and nearly 92% were judged to have no or minimal radiographic progression of osteoarthritis by the end of the 2-year study period. Degenerative joint disease that did develop tended to be present within the first 6 mo, postoperatively. These authors reported a 2% frequency/occurrence of postoperative meniscal tears (2).

The characterization of cranial cruciate ligament rupture as a degenerative disease with a genetic etiology, as opposed to a traumatic injury, has long been speculated. At the 2004 VOS meeting, researchers from Iowa State University presented the results of a pedigree analysis done on Newfoundland dogs in the United States that confirmed the genetic nature of cruciate ligament disease and indicated a recessive mode of inheritance with 59% penetrance for this breed (3). These results have subsequently been published in a more complete form (4). Some of the same researchers have pursued this topic further by performing a genome scan on 66 Newfoundland dogs. By correlating this genomic information with pedigrees and phenotypes of the dogs’ cranial cruciate ligaments, Wilkie et al (5) have identified a significant association between rupture of the cranial cruciate ligament and genetic markers on chromosome 3. This would appear to open the door to potential identification of genetically susceptible individuals. The significance of this cannot be overstated, since, in our practice, the average age at which cruciate ligament disease becomes clinically apparent is > 5 y (unpublished observations), well after the beginning of the active breeding life for these animals. Minimizing the genetic expression of this trait will rely on the successful identification of susceptible individuals long before they show signs of clinical disease.