Discrepancy Between the Desired Radiographic Advancement and True Advancement Required for Patellar Tendon-Tibial Plateau Angle Reduction to the Ideal 90° Using the Modified Maquet Technique in Dogs

Introduction:

Pre-operative measurements are one of the most critical components of the tibial tuberosity advancement procedures. The purpose of this study was to evaluate the validity of practiced radiographic advancement measurement methods to achieve PTA reduction to the ideal 90° using the MMT in dogs.

Material and Methods:

Radiographs of cadaveric stifles placed at 135° in the true lateral position were used to measure the desired advancement with two methods: AM, the advancement using the conventional method and AE, the advancement using the correction method. An MMT osteotomy was performed, and the tibial crest was successively advanced to AM and AE. Postoperative PTAs (PTAM and PTAE) were measured on mediolateral radiographs. If none of the measurements was close to 90°, the advancement was modified until the PTA was equal to 90 ±0.1°, and the true advancement (TA) was measured.

Results:

The mean AM and AE were 10.9 ±2.4mm and 11.9 ±2.7mm, respectively. The mean PTAM and PTAE were 93.5 ±0.5° and 92.4 ±0.4°, respectively; both were significantly different from 90° (p<0.05). The mean TA was 13.9 ±2.9mm.

Discussion:

According to the results of the present study, both methods failed to determine the true advancement required for PTA reduction to the intended 90° when an MMT was performed. The actual clinical significance of under estimating the required advancement is unknown. However, we recommend using the method that leads to the larger cage size recommendation and to always choose the larger cage in case of doubt between two sizes.