Comparison of Two Preoperative Radiographic Methods for Assessing Tibial Tuberosity Advancement to Achieve a Postoperative Patella Tendon Angle of 90° in Dogs

SIMPLE SUMMARY: In dogs, the current techniques for the preoperative planning of tibial tuberosity advancement do not appear to restore joint stability due to under-advancement after surgery. This cadaveric study compared the tibial-anatomy-based method and the common tangent method for measuring tibial tuberosity advancement. The postoperative patellar tendon angle was not significantly different between the two methods. However, the tibial-anatomy-based method yielded advancement similar to the sizes of commercially available wedges. Both techniques yielded a tibial tuberosity advancement within the suggested range. However, TAM resulted in a mean value of the postoperative patellar tendon angle corresponding to 90°. This study paves the way for developing intraoperative methods capable of achieving a patellar tendon angle that may not be influenced by preoperative variables. ABSTRACT: Previous studies have suggested that the preoperative methods used to plan tibial tuberosity advancement in dogs may result in under-advancement. Therefore, this cadaveric study compared the effectiveness of the common tangent method and the tibial-anatomy-based method for achieving a target patellar tendon angle (PTA) of 90° after the modified Maquet procedure. Twenty stifle joints of mesomorphic dogs were randomly assigned to the two measurement methods. Radiographs taken in the mediolateral projection were used to measure tibial tuberosity advancement, and the wedge size was selected accordingly. For each surgical procedure, a custom-made three-dimensional wedge matched to an OrthoFoam wedge was used as a spacer. Postoperative radiographs were used to measure the PTA and to evaluate the position of the wedge. The measured advancement was not significantly different between the two methods. For 60% of the cases, the advancement measured using the common tangent method was <5.3 mm and the wedge size was increased to match that of commercially available wedges. Consequently, there was a significant difference between the measurements and wedges selected between the two procedures. The postoperative PTA did not differ significantly between the two methods and was 90° ± 5° in 80% of the stifles. The position of the wedge relative to the osteotomy was not significantly different between the methods. In conclusion, the advancement determined using the tibial-anatomy-based method was generally consistent with the size of commercially available wedges, and the method yielded a mean postoperative PTA of 90°.