this was thought to play a minimal role in the CCL‐deficient stifle. While significant changes in internal rotation were not noted immediately following transection of the CCL, 2 months following transection the range of abduction and adduction in the stifle was increased. These rotary changes remained increased 2 years following tran section [15]. Recognition of the importance of preventing excessive internal rotation has led to the idea and development of augmentation to prevent excessive internal rotation following certain osteotomy procedures such as the TPLO (Figure 1.1).
Interestingly, a population of CCL‐deficient canines will exhibit persistent internal rotation following surgical stabilization. This persistent internal rotation likely falls under the umbrella term of “pivot shift.” Unfortunately, to date, it is not possible to predict which population of patients will exhibit persistent internal rotation following surgical stabilization. In the authors' opinion, patients with acute CCL rupture, large medial meniscal bucket handle tears, and lack of periarticular fibrosis tend to have persistent internal rotation following certain surgical procedures such as the TPLO. Recently, it was shown that the use of a lateral fabellotibial suture in combination with a TPLO was effective for managing CCL instability in patients with excessive internal rotation identified either preoperatively or intraoperatively [17]. Therefore, the authors recommend the use of adjunct lateral fabellotibial suture in identified patients with excessive internal rotation or “pivot shift” (Figure 1.1).
Figure 1.1 An immediate postoperative radiograph of stifle stabilization via a TPLO. Intraoperatively persistent excessive internal rotation was noted so a lateral fabellotibial suture was placed. Note the metallic crimp (red arrow) that has been added.
1.2 Diagnosis
The diagnosis of CCL pathology is made based on signalment, history and clinical signs, orthopedic examination findings, and diagnostic imaging. While the old saying “a hindlimb lameness in a mature dog is cruciate disease until proven otherwise” holds true, it is important to ensure that the lameness is due to CCL pathology and not another underlying pathological condition of the stifle or another anatomical structure of the pelvic limb.
Signalment information in canines with CCL pathology varies, with most affected dogs presenting for evaluation between 2 and 10 years of age. However, the authors have seen dogs as young as 12 weeks (Figure 1.2) and as old as 16 years present for CCL pathology. The authors (DD and RBA) have also observed a high incidence of 9–13‐month‐old American Pit Bull Terriers and American Staffordshire Terriers presenting with bilateral CCL pathology. The reason for this is unknown but could be due to demographics and possible breeding practices. Virtually any breed can be affected with CCL pathology; one study revealed the highest prevalence in the Rottweiler, Newfoundland, and Staffordshire Terrier [18]. Another study revealed that breeds at risk for suffering CCL rupture before 2 years of age included the Neapolitan Mastiff, Mastiff, St Bernard, Rottweiler, Akita, Newfoundland, Chesapeake Bay Retriever, Labrador Retriever, and American Staffordshire Terrier [19]. Female dogs have an increased prevalence of CCL pathology (similar to human female athletes), as do neutered canines compared to sexually intact canines [19].
Figure 1.2 Radiograph of a 12‐week‐old dog that suffered a traumatic CCL injury.
Historical findings of patients with CCL pathology may include an acute or chronic onset of hindlimb lameness that may range in severity from mild to nonweight bearing. Some patients may only exhibit stiffness when rising or after heavy activity or may offload the affected limb at a stance (Figure 1.3). When questioning owners, it is important to obtain a timeline of abnormalities they have noticed even when the lameness appears acute. The authors have found that when questioning owners, many patients have a longer standing history of subtle clinical signs before an acute lameness develops. This further emphasizes the degeneration of the CCL. The common scenario following complete rupture of the CCL is a nonweight‐bearing status for several days. As the inflammatory phase starts to subside, patients will begin to toe touch and use the limb with a noticeable weight‐bearing lameness. Many owners perceive this as their dog improving, when in reality this is consistent with the normal progression of CCL pathology.
Figure 1.3 Representation of offloading the left pelvic limb at a stance. This patient was diagnosed with a left CCL rupture. Notice when the dog is standing full weight is not applied to the left pelvic limb.
The orthopedic examination is aimed at demonstrating stifle instability; however, other aspects of the stifle and pelvic limb should be evaluated. Pending the severity of the condition as well as the timeframe, there may be pain upon flexion and extension of the stifle, in particular with hyperflexion and hyperextension. In chronic cases of CCL pathology, there may be thickening of the proximal medial tibial or the so‐called “medial buttress” which is development of periarticular fibrosis. The periarticular fibrosis can limit range of motion in the stifle, which may ultimately result in loss of active range of motion. A loss of active range of motion can translate into loss of limb function [20]. In cases with more advanced OA, crepitus may be noted as range of motion is evaluated, and in cases in which meniscal pathology is present, there may be either a consistent or intermittent clicking (“meniscal click”) during range of motion of the stifle. A recent study concluded that a meniscal click in CCL‐deficient stifles carries a high specificity for a bucket handle tear of the meniscus. In addition, the presence of a meniscal click during examination is strongly indicative of a meniscal tear being diagnosed at surgery. However, a lack of meniscal click carries a low sensitivity in diagnosing the absence of meniscal tear [21, 22]. This emphasizes the need for meniscal evaluation in every joint undergoing CCL stabilization.
Figure 1.4 A patient with instability of the left pelvic limb secondary to a CCL rupture. Notice the degree of muscle loss on the left hindlimb compared to the right.
Loss of function of a limb will ultimately lead to loss of muscle strength. Unfortunately, in the canine, loss of muscle strength has never been reported but loss of muscle mass has [23] (Figure 1.4). Therefore, it is important to measure mass at the time of the initial consultation as well as at each follow‐up visit. Additional information on measurement of hindlimb muscle mass can be found in Chapter 15. In addition, measurement of joint motion of the stifle should be performed
