Complications in Canine Cranial Cruciate Ligament Surgery. Ron Ben-Amotz

1.11). The degree of joint effusion in some cases can be roughly correlated with the degree of CCL pathology. Generally, patients with competent partial CCL pathology will have less joint effusion than patients with incompetent or complete CCL pathology. Evidence of likely synovitis can be noted as subtle regions of sclerosis noted on the caudal aspect of the trochlear groove as seen on the lateral view.

Degenerative changes can readily be seen in patients with CCL pathology (Figure 1.12). In particular, changes will be noted at the proximal trochlear groove, lateral and medial femoral trochlea, distal pole of the patella (patella apex), caudal tibial plateau, medial and lateral aspects of the tibial condyle margins, and both fabellae. In some cases, the sesamoid bone of the popliteal muscle can be displaced proximally and/or caudally. The importance of taking contralateral radiographs at the time of initial diagnosis is for the evaluation of OA and joint effusion as well as detection of other pathologies that might exist. If noted on the contralateral stifle (even in the face of joint stability), one should assume there is already CCL pathology present and the likelihood of joint instability developing is high. If this is present, it is important to educate the owner regarding this finding.

Figure 1.9 A lateral radiograph documenting appropriate positioning of the stifle. Notice there is superimposition of the femoral condyles and the tibial plateau demonstrating a straight view in the sagittal plane.

Figure 1.10 A cranial‐caudal radiograph documenting appropriate position of the stifle. Notice how the calcaneus intersects the center of the trochlear ridge of the talus demonstrating a straight view in the frontal plane.

1.3 Treatment

      A number of methods for stifle stabilization exist. They are commonly characterized as extraarticular stabilization, intraarticular stabilization, and osteotomy modifying procedures. One of the complicating factors of stifle stabilization (and indeed, one of the reasons for the existence of so many surgical procedures) is the lack of definitive guidelines for what constitutes a successful postoperative outcome.

Figure 1.11 Evidence of joint effusion in the stifle of a patient with CCL pathology. In the caudal compartment, there is displacement of the joint capsule as can be noted by the red arrows. The opacity in the cranial compartment (blue arrows) is joint effusion that is displacing the fat pad cranially.

Figure 1.12 Evidence of degenerative changes in the stifle of a patient with CCL pathology. Commonly noted areas are the distal pole of the patella (blue arrow), cranial tibial plateau (orange arrow), caudal tibial plateau (yellow arrow), and fabella (red arrow). In addition, a small area of sclerosis can be seen around the trochlear groove (green arrow) indicative of synovitis or osteophytosis of the medial or lateral femoral trochlea.

      While all correctly executed surgical procedures can stabilize the stifle, not one of these procedures ultimately restores completely normal stifle kinematics or kinetics. In defining a good outcome, should we consider a stable stifle to be the predominant deciding factor? Interestingly, work has been completed that demonstrates ongoing instability following surgical stabilization [16, 25], yet retrospective and client assessment studies have shown high success rates with certain procedures. What about return to function? Success rates among all surgical procedures are in the high 80% to low 90% range when evaluating most retrospective studies. While this suggests that most surgical procedures do a good job of returning canines to “normal” function, probably the best way to tell would be return to sport or work for our canine athletes. Recent data have suggested that following TPLO, agility dogs have a good prognosis for return to sport [26].

Elimination of progression of OA has been stated as a possible determination of outcome and goal of treatment. This is likely not an achievable feat. Once the CCL has become damaged and instability in the stifle is present, there is abnormal joint loading. Thus, damage to the chondrocytes has occurred. Therefore, it is probably better to evaluate surgical stabilization procedures in terms of which are the most capable of slowing down and minimizing progression of OA, rather than which can eliminate it entirely.

1.4 Defining a Complication

      The ability to recognize and manage complications should be considered when choosing a surgical procedure. Generally, the complication rate of currently practiced surgical stabilization procedures is low, but individual techniques are associated with their own unique set of potential complications and it is of the utmost importance that the clinician is familiar with the management of these complications prior to undertaking the initial procedure. In the past, much focus has been on the actual surgical procedure and training of how to perform it. Unfortunately, what is missed is how to identify patients that might be at an increased risk of complications, how to identify intraoperative complications, decision making to avoid intraoperative complications, recognition of postoperative complications, and how to revise complications in the postoperative period should they occur.

      1.4.1 Assessment of Success and Complications

      Although a high success rate (intended outcome) is important when deciding to perform a surgery, the risk of an unintended outcome, severity of potential adverse events, and owner financial burden need to be considered and communicated to the owner. Avoiding iatrogenic harm should be an emphasis of all practicing veterinarians. In veterinary orthopedics, standardized definitions of complications have been suggested in an attempt to improve consistency and comparability in veterinary orthopedic research [27]. For example, a method to classify catastrophic, major and minor complications has been published so results between studies can be accurately translated and to allow the clinician to decide if an intervention causes unacceptable morbidity.

      One method to quantify success and harm factors is a ratio between the number of patients needed to treat (NNT) and number needed to harm (NNH). NNT is defined as:

      where attributable risk is the difference between the frequencies of a successful outcome between two interventions. The NNT assesses how many patients would have to be treated with one treatment compared to another before there would be one additional positive outcome. For example, if surgery A had a success rate of 75% and surgery B had a success rate of 67%, the NNT would be 13 (1/(0.75−0.65) = 12.5); the result of 12.5 was rounded up to the nearest whole number to make the result more clinically relevant and prevent overestimating the benefit of surgery A. This means that surgery A would have to be performed on 13 patients before one additional beneficial outcome would be seen. In human medicine, a single‐digit result is generally considered a good NNT [28].

      Conversely, NNH assesses how many patients need to