Vet360 Vet360 Vol 05 Issue 03 - Page 8

SURGERY Article sponsored by Petcam ® Extra-articular repair techniques utilise synthetic materials to traverse and stabilise the stifle joint. The most commonly performed techniques include the lateral fabellar suture, bone anchor techniques and the Tightrope technique. In all cases, material is anchored at relative isometric points outside the joint on the distal femur and proximal tibia. Given that there are no true isometric points in the stifle due to the cam-shaped femoral condyles, the synthetic material is subjected to cyclic loading that eventually results in implant fatigue and failure. The goal of these repair options is to stabilise the stifle long enough to allow for periarticular fibrotic tissue to develop and mature over a 16-week period. This periarticular fibrosis becomes the long-term stabiliser of the stifle joint. The main complications of these techniques include implant infection along with premature implant failure. 8 Biomechanical techniques, also known as osteotomy procedures, involve cutting and manipulating the tibia in various ways that result in biomechanical neutralis ation of cranial tibial thrust in the CCL-deficient stifle. The most common procedures used today are the tibial plateau leveling osteotomy (TPLO), the tibial tuberosity advancement (TTA) and, more recently, the center of rotation angulation (CORA)-based leveling osteotomy (CBLO). Of these, the TPLO is probably the most widely used osteotomy technique. With the TPLO procedure (Figure 2) the 90-degree flexed lateral radiograph of the tibia (including stifle and hock) allows for measurement of the tibial mechanical axis, and a bisecting joint line of the stifle allows for measurement of the needed tibial plateau angle (TPA). Average TPAs in dogs range from 25 to 30 degrees (see text box). 9 Once the patient’s TPA is measured, a dome osteotomy of the proximal tibia is performed and the proximal tibial fragment is rotated a predetermined distance based on the patient’s specific TPA. This results in a reduction of the tibia slope to approximately five degrees, thus neutralising cranial tibial thrust. A bone plate with screws is then used to bridge and stabilise the fracture on the medial tibia. The patient is then limited in activity over the next six to eight weeks while the osteotomy heals. The TTA (Figure 3) is a technique that involves a linear cut in the tibial tuberosity and advancement (cranial displacement) of the tibial tuberosity fragment in a cranial direction to achieve and maintain a patellar tendon angle of approximately 90 degrees with respect Editor: There are specific radiographic positioning techniques to obtain the image and measurements are made from very specific points on the radiographs. In essence the vertical line is drawn connecting the tibial bony attachment of the cruciate down to the middle of the tibio-talar joint. The horizontal line is drawn perpendicular to the vertical line. The tibial plateau angle (TPA) is determined by drawing a line through the intersection of these two lines which runs parallel to the tibial plateau. The angle thus created is the TPA. vet360 Issue 03 | JULY 2018 | 8