Damage to the Cranial Cruciate Ligament (CCL; analogous to the ACL in humans) is among to most common disorders of the knee in veterinary medicine. While more common in dogs, it is also seen in cats. In dogs, especially large breed dogs, surgical correction of CCL rupture is recommended in order to improve return to function and long term prognosis and decrease the future development of arthritis. In cats, the benefit of surgical correction is less clear as they are smaller animals with different weight-bearing patterns than dogs. The purpose of this study was to determine the long term prognosis of cats with conservative management of their ruptured CCL compared to cats that are surgically corrected.
The study was designed as a retrospective cohort study of cats presenting to two university hospitals over a 6 year period. Medical records were examined for cats presenting with a ruptured CCL diagnosed by a positive cranial drawer test where follow up was available. Signalment information, medical records, surgical logs, and follow up information were obtained. Cats that were alive at the time of data collection had their owners contacted and asked to complete the Feline Muscluloskeletal Pain Index (FMPI) questionnaire.
60 cats had a diagnosis of CCL rupture during the time period, of which 50 had complete follow up information available. There was an even sex distribution and a median age of 9years. Presenting complaints were usually acute onset lameness.
28 cats were treated conservatively, and 22 received surgical intervention. The lateral fabellotibial suture technique was used in all cats. Arthrotomy was performed in 19 of the 22 cats and complete rupture of the CCL confirmed. Of these cats, 9 had concurrent meniscal injury, 4 had collateral ligament injury, and 3 had rupture of the caudal cruciate ligament. No cat treated conservatively required conversion to surgery. 6 of the surgical group cats had post-operative complications, 3 of which required a second surgery.
29 cats were alive at the time of follow up, of whom 24 (83%) had the FMPI questionnaire completed. The FMPI is scored on a numerical scale, with higher numbers representing more severe pain. The surgically treated cats reported a median score of 5, while conservatively treated cats were 0.5. This was a statistically significant difference, and significance was maintained even when cats with multi-ligament injuries were excluded.
Two of the conservatively treated and 5 surgically treated cats developed CCL rupture of the contralateral limb.
The retrospective nature and lack of complete follow up represent limitations to this study. Further, while long term pain was assessed, no data was collected on shorter term return to functionality and pain scoring.
The authors conclude that, based on the results of this study, surgical repair of CCL rupture in cats is of no benefit and may actually worsen long term arthritis. While prospective studies are indicated to investigate this in more detail, it would appear that surgical intervention may not be indicated in cats with CCL rupture, and that conservative management may be the preferred option.