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Rupture of the cranial cruciate ligament (CCL) is the most common orthopedic condition in the dog… and nearly every paper written on the topic begins with that line! The demographics of this problem within our practice have been examined on 2 previous occasions, covering cases treated from 1983 to 1994 (1) and from 1997 to 2002 (2). This article analyses cases from October 1, 2002, to September 30, 2007, and makes comparisons to the previous 2 studies.
Records were examined from 421 surgical procedures on 328 dogs. One hundred and thirty-one procedures were done on 100 small breed dogs, while 290 procedures were done on 228 large breed dogs. Fifteen kilograms was used as the dividing line between large and small breed dogs; however, some obese small breed dogs, > 15 kg, were still considered to be in the small breed category. All small breed dogs were treated surgically by using an extracapsular suture technique (3), fastened with a locking loop knot (4) or a crimp clamp (5). Of the large breed cases, 232 were treated surgically with a tibial plateau leveling osteotomy (TPLO) (6) and 58 received an extracapsular repair. In total, 232 TPLOs and 189 extracapsular repairs were performed.
The original survey showed a predominantly female (65%, female or female spayed) and small breed (65%) population with CCL ruptures (1). In the 2nd survey, these figures shifted significantly to 61% large breed dogs with 53% females or female spayed (2). In the current survey, 69% of cases were in large breed dogs, of which 53% were females or female spayed. In the small breeds, 58% were males or male neutered. Considering small and large breed cases in total, the distribution between the sexes was exactly equal.
The breed distribution in our patients was similar to that in the past surveys, with 23% of large breed cases occurring in Labradors or Labrador crosses. Rottweilers and rottweiler crossbreds, German shepherds and shepherd crossbreds, along with golden retrievers made up 11.4%, 10.7%, and 7.6% of our large breed cases, respectively. We observed that 9% of large breed cases occurred in dogs identified as huskies or husky crossbreds; a percentage much greater than the proportion of huskies in our practice population. Similarly, chow chows and their related crossbreds accounted for 2.8% of cases, while Great Pyrennes, Saint Bernards, mastiffs, springer spaniels, and related crossbreds each accounted for 2.4% of cases; numbers in excess of their frequency in our general population. Bichon frises (35%), cocker spaniels (17%), poodles (19%), lhasa apsos, (7%), and crossbreds of these breeds accounted for nearly 8 out of 10 of our small breed cases.
The mean weight of our large breed cases was 38 kg with a range of 16.8 to 89.5 kg. Small breed cases averaged 10 kg with a range of 3.6 to 22.2 kg.
The mean age of our large breeds was 5.5 y, with a range of 9 mo to 13 y. The small breeds averaged 7.4 y, but the range was worthy of note. Our oldest case was 15 y, but none were younger than 4 y. One might view these numbers in light of published theories on the etiology and pathogenesis of cruciate rupture. Degeneration of the CCL has been described as an aging change in many dogs (7). Conversely, “cruciate disease” has been a phrase coined to describe the genetically determined degeneration and rupture that occurs at a relatively early age, especially in large breed dogs (8). These data suggest that the generally older profile of small breed cruciate patients is consistent with aging degeneration, while the occurrence of cruciate disease in a generally younger population of large breed dogs, some under 1 y of age, supports the suggestion of a genetic etiology. An overwhelming number of small breed cases trace lineage to 4 breeds, making a genetic component in these dogs highly likely as well.
Another statistic that may be interpreted as contributing to the idea of a genetic etiology for CCL rupture is the proportion of dogs that subsequently rupture the CCL in the contralateral limb. The 2 previous surveys (1,2) identified 30% and 27% of dogs that ruptured their contralateral CCL. In this survey, 37% of large and 45% of small breed dogs ruptured their contralateral CCL. As significant as these latest figures are, they certainly understate the problem. There are undoubtedly dogs that were lost to follow-up that ruptured their contralateral CCL and there will be dogs that rupture their other CCL after the end of this study period.
Meniscal tears, especially to the medial meniscus, were noted in 37% of small and 42% of large breed dogs. This is similar to the 48% of dogs in the 1997–2002 survey noted to have meniscal pathology (2), and similar to previously published estimates (9–12). Again, as in the previous studies, there was not a significant difference between small and large dogs in the incidence of meniscal lesions.
A feature of cruciate disease that has received increasing attention in recent years has been partial CCL tears. In the 1997–2002 study (2), 13% of total cases were categorized as partial tears at surgery. In this review, 16% of total cases were partial tears; however, the breakdown between large and small breeds was significant. Twenty-one percent of large breed cases were confirmed as partial tears, while only 5% of small breed cases fell into this category.
The previous 2 studies only examined 1 complication, lameness, that was noted in the medical record more than 2 mo postoperatively (1,2). Such lameness, of varying degrees, was noted in 30% and 23% of large and 7% and 11% of small breed dogs, respectively. All cases in those previous 2 studies were treated with an extracapsular repair. The latest study looked more closely at complications since the majority of large breed cases (232 of 290) were treated with TPLO. Overall, 9% of large and 4% of small breed dogs had lameness, as reported by the owner, more than 2 mo postoperatively. Suture line infections occurred in 5.9% of large breed cases and 4.6% of small breeds. The criterion used to determine the presence of a postoperative infection was where the follow-up veterinarian deemed the prescribing of antibiotics to be warranted. In an additional 6% of large breed cases, a variety of other complications were reported, including seroma formation, postoperative bleeding, lick granuloma formation at the surgery site, and patellar fracture.
Comparing the occurance of complications in large dogs treated with TPLO with that in those treated with extracapsular repair, 15.5% of TPLO dogs experienced at least 1 complication, while 24% of extracapsular dogs experienced 1 or more complications. Complications in the TPLO group included infections, lick granulomas, lameness more than 2 mo postoperatively, seroma, excessive bleeding postoperatively, patellar fracture, and osteotomy/surgical hardware failure. Postoperative lameness beyond 2 mo was seen in 7.3% of TPLO cases compared with 15.5% of extracapsular cases, while infections occurred in 5.2% of TPLO cases compared with 8.6% in extracapsular cases; these differences are noteworthy. These figures compare favorably with published post-TPLO complication rates that exceed 20% (13,14); however, our numbers certainly underestimate the true complication rate since no effort was made to formally survey owners or referring veterinarians to determine complications that we were not informed of or did not note in our records. The limited number of extracapsular repairs done on large dogs during this period may also affect the validity of these results; however, the greater rate of complications in the extracapsular group is interesting and runs contrary to conventional wisdom, if not statistical analysis, in this review.