Outcome Measures for Cruciate Surgery

Kenneth A. Johnson

Radiology is valuable for the detection of bone healing and implant failure complications after tibial osteotomy procedures for canine cruciate ligament disease. However, improvement in signs of lameness is the principal means of monitoring return of limb function. There are various lameness-scoring systems for dogs, but these are subjective and inaccurate, especially when the data have been derived from medical records for retrospective clinical investigations.

It is encouraging to see the steady growth of use of force plates and pressure mats to record lameness in prospective clinical investigations of canine osteoarthritic diseases, to objectively measure outcome during the recovery. These are not easy studies to conduct well, and they are expensive. Amongst the four papers about cruciate ligament disease in this issue of the Journal, two are prospective clinical studies using force plate gait analysis of dogs after tibial plateau levelling osteotomy.

The first of these studies was of dogs weighing less than 15 kg with cranial cruciate ligament disease that underwent a tibial plateau levelling osteotomy stabilized with a locking plate. Gait analysis done before surgery, and then at four intervals up to 6 months found that hindlimb symmetry index was significantly improved 1 month after surgery, and near normal by 6 months. Also noted was that the remaining width of the tibial tuberosity, cranial to the osteotomy, was 6.9 mm and 26% of the overall craniocaudal width of the tibia. The mean preoperative tibial plateau angle was 30.9 degrees; consequently, the tibial plateau was rotated beyond the so-called safe point in 6/12 dogs, without any instances of complications, such as tuberosity fracture, once again failing to support the hypothesis that rotation of the tibial plateau beyond the safe point carries a risk of complications. Both gait analysis studies and tibial plateau levelling osteotomy are difficult to perform in small breed dogs, but these findings provide support for this approach in treating cranial cruciate ligament disease in small dogs.

The second randomized prospective force plate study compared outcome after tibial plateau levelling osteotomy with the modified Maquet procedure. Since cruciate disease requiring surgery was often bilateral, the force plate data of limb function were compared with a control group of unaffected Labrador dogs, and not the contralateral hindlimb. The greatest improvement in limb function after both surgical procedures was in the first 6 weeks. At 6 months, in comparison to the control group, the peak vertical force and vertical impulse for the tibial plateau levelling osteotomy dogs (94 and 86%, respectively) and modified Maquet procedure dogs (89 and 80%, respectively) were not significantly different. In the hands of these surgeons, either of these surgical procedures could be recommended for dogs weighing 20 to 35 kg. Of course, keeping in mind that the success of any surgical procedure is predicated on the skill and experience of the surgeon and not just the technical merit of the surgical procedure per se.