Evidence Update–Is Surgery Really Necessary for Dogs with Cruciate Ligament Ruptures?

A couple of years ago, I wrote about the question of whether or not surgery was better than medical management for dogs with cranial cruciate ligament (CCL) disease. Here was my conclusion at that time:

As is almost always the case, the evidence is not of the highest possible quality or unequivocal, but this does not exempt us from having to draw conclusions and make recommendations to our clients. My interpretation of the available evidence is that overall, cruciate ligament disease causes significant arthritis and loss of function when untreated. For most dogs under 15kg, conservative management (primarily restricted activity for 3-6 weeks, achieving and maintaining and appropriate body weight, and possibly physical therapy and pain medication) can achieve acceptable comfort and function. In larger dogs, significant arthritis is inevitable and dysfunction is extremely likely without surgical treatment. No single surgical technique is clearly superior, so the choice of specific surgery should be determined by the judgment of the individual surgeon and the needs of the owner.

A recent research article has added an important piece of evidence concerning this subject, and while supporting the value of surgery it does weaken somewhat the case against medical treatment for large dogs.

Wucherer, KL. Conzemius, MG. Evans, R. Wilke, VL. Short-term and long-term outcomes for overweight dogs with cranial cruciate ligament rupture treated surgically or nonsurgically. Journal of the American Veterinary Medical Association 2013;242(10):1364-72.

The authors interpretation of the results supports the argument that both surgical and nonsurgical treatment can be successful, even in overweight large-breed or giant-breed dogs, but that surgery appears to provide a better outcome.

Overweight dogs with CCLR treated via surgical and nonsurgical methods had better outcomes than dogs treated via nonsurgical methods alone. However, almost two-thirds of the dogs in the nonsurgical treatment group had a successful outcome…

Overall, I agree with their conclusion, though I would probably place less confidence in it than the authors do.

The Study
Forty overweight large-breed or giant-breed dogs with unilateral rupture of a CCL were recruited and randomized to either medical therapy alone (a weight loss program, individualized physical therapy, and daily use of a nonsteroidal anti-inflammatory medication) or medical therapy plus surgical therapy (TPLO). Outcomes were assessed at 6 weeks, 12 weeks, 24 weeks, and 52 weeks after the beginning of the study.

There was a high rate of drop out (5 digs by 6 weeks, 11 dogs by 24 weeks, and 17 dogs by 52 weeks). The majority of these dogs (11/17) dropped out due to CCL rupture in the opposite leg, and there was no overall difference in dropouts between the two groups (9 in surgical group and 8 in non-surgical group).

Both subjective outcome measures (surveys of owner perception of their dogs’ pain and lameness and pain scores generated by the investigators) and objective outcome measures (body weight, body fat, body condition scores, and several measures generated by force-plate analysis) were evaluated at the beginning of the study and in the dogs still participating at each follow-up point.

The Results
No adverse effects were reported for the weight loss diet, the NSAID therapy, or the physical therapy. A few minor complications associated with TPLO surgery were reported at rates consistent with those reported in other studies.

The weight loss program did result in decreases in body condition score and percent body fat for both groups, and there were no significant differences between the two groups. Interestingly, while total body weight did decline slightly for both groups, the decrease was not statistically significant for either, and there was no difference between the groups.

Subjective measures, both owner and investigator assessed, improved significantly for both groups. There were no differences between the groups in the subjective outcomes assessed by the investigators. The surgery group had significantly lower scores for pain severity and interference than the non-surgical group only at the 52-week evaluation. Some differences between the groups in visual analog pain scale assessment by owners were reported, but how many measures were assessed and which ones differed were not reported, and no statistical analysis of these differences was reported, so it is difficult to assess this outcome measure.

Of the several force-plate measures assessed (5 or 6 measures; it isn’t clear from the paper), only one differed between the groups, and this difference was significant only at two of the four assessment points (24 weeks and 52 weeks).

The investigators also created a composite measure of “successful outcome,” defined as achieving both a specific force-plate measure that was >85% that of a normal dog and a subjective, owner-assessed improvement in lameness and quality of life >/= 10%. The dogs in the surgical group had higher “successful outcome” scores at all assessment points, but this only reached statistical significance at 24-week evaluation.

Strengths of the Study
Overall, this was a well-designed study. The use of both subjective and objective outcome measures, random assignment of treatment, an aggressive and consistent medical therapy program, and partial standardization of surgical treatment all reduce the risk of bias, confounding, and other error in the study. The consistency of several reported variables (such as surgical complication rate) with those reported in other studies increases the confidence one can have in the results. And the attempt to verify compliance with the weight loss aspect of medical therapy is an important part of any study employing this therapeutic approach.

Limitations and Caveats
A significant limitation is the lack of blinding of owners or investigators to treatment group. While blinding would be difficult, and possibly unethical due to the need for a sham surgery component, the lack of blinding introduces significant risk of information bias, particularly in the subjective outcome measures.

There was some individualization of surgical procedure and physical therapy treatments employed, which means not all subjects had the same treatment. If some techniques used work better than others, or if the selection of technique to be used is associated with the likelihood of a good or bad outcome, this could generate an erroneous impression of the differences between the surgical and non-surgical treatment groups.

The biggest limitation of the study was probably the high dropout rate. In general, dropout rates greater than about 20% are considered to severely compromise the data, and the overall dropout rate was 42.5% in this study. Though the number of dropouts were evenly distributed between the two groups, this does not mean the dropouts did not introduce bias into the results. If those patients who dropped out, most because they developed a second CCL rupture in their other leg, differed in terms of their underlying disease or response to treatment from the subjects who stayed in the study, this could have significantly altered the findings.

Also, as the authors themselves point out, the dropouts caused a significant loss of power in the study (though no power analysis is presented in the report), and this could lead to a failure to detect a difference between the groups. Overall, the dropouts significantly weaken the confidence we can place in these results.

Bottom Line
This study does provide some support for the contention that overweight, large-breed or giant-breed dogs have better long-term outcomes when treated with both surgery and non-surgical therapy rather than with non-surgical therapy alone. However, the limitations in these data are great enough that the case for preferring surgical intervention is not strong. The non-surgically treated patients had overall very good outcomes that, at most time points and by most measures, did not differ significantly from the patients who received surgical treatment. Additional evidence would be required to make a strong statement that overall surgery is superior to aggressive medical therapy.

While it is reasonable to tell dog owners that there is some evidence their pets will benefit more from having surgery than not having it, we must also inform them that most dogs will have a good long-term outcome even without surgery. And it is important to emphasize that even with surgery, aggressive management of weight and physical therapy are important elements of  comprehensive and successful treatment. For those owners who cannot afford surgery, or those patients who are not good candidates, there are still effective therapies that can be offered.

Share on Facebook

Tweet

Follow us