Plateau-Patella Angle: An Option for Assessing Patellar Height on Proximal Tibia Osteotomy

Abstract

Objective: To compare the plateau-patella angle method to the methods already established for patellar height measurement in patients undergoing high tibial osteotomy.Methods: This is a retrospective study of 13 patients undergoing medial opening tibial osteotomy. The patellar height was measured in pre and post-operative radiographs by the methods from Insall-Salvati, Caton-Deschamps, Blackburne-Peel and patella-plateau angle, as well as the tibial slope and length of the patellar tendon. Measurements were performed by two knee surgeons at two different times.Results: The mean age was 41.33 ± 01.09 years old. The average rates of Caton-Deschamps, Blackburne-Peel, Insall-Salvati and plateau-patella angle were, respectively, 1.00; 0.89; 1.10; and 23.15° preoperatively, and 0.89; 0.78; 1.11; and 20.46°, postoperatively. The correlation of Caton-Deschamps, Blackburne-Pell, and Insall-Salvati indexes and plateau-patellar angle interobserver was 0.72 (p <0.001), 0:54 (p <0.001), 0.65 (p <0.001), and 0.67 (w <0.001), respectively.Conclusion: The plateau-patella angle method undergoes changes that are correlated with changes in tibial slope after osteotomy, unlike the classical methods. This fact may lead to overestimate the reduction of patellar height after osteotomy. Level of evidence IV. Case Series.

The effect of distal tibial tuberosity high tibial osteotomy on postoperative patellar height and patellofemoral joint degeneration

“…Because of the effect of HTO on the tibial plateau, the position of the tibial tubercle, and the patellar tendon adherence, it is necessary to consider whether the measurement can adequately represent the patella height. Some studies have suggested that when patellar height is measured, the tibial plateau plane rather than the patellar tendon should be taken as the reference [24]. BPI is difficult to measure accurately, resulting in scarring down or contractures of the patellar tendon, and the insertion point of the distal patellar tendon is difficult to identify by X-ray.…”

Changes of Sagittal and Axial Alignments of Patella after Open- and Closed-Wedge High-Tibial Osteotomy: A Systematic Review and Meta-Analysis

“…34 Although the various limitations of patellar height indexes were pointed out, the most important consideration related to the HTO is that the reference to the patellar height should be the joint line, not the length of patellar tendon. 21 It is because the length of patellar tendon does not directly change after HTO. The ISI refers to the length of patellar tendon and patellar tendon insertion site.…”

“…Four comparative studies showed the patellar height after both OW and CW HTO. 5,10,14,20 A total of 11 studies [2][3][4]9,15,16,[21][22][23][24][25] reported postoperative changes in patellar height or patellofemoral alignment only after OW HTO and five studies [26][27][28][29][30] reported changes only after CW HTO. The measured indexes used for the evaluation of patellar indexes in each study are shown in ►Table 1.…”

A Sagittal Patellar Angle Linear Equation Reflecting Patellofemoral Kinematics: Evaluation of Patellar Height at any Degree of Knee Flexion Angle

“…It was defined as an angle formed by the line connecting the posterior end of medial tibial plateau and lower pole of the articular surface of patella, and a tangential line of the medial tibial plateau. This method was validated to be an eligible method for assessing patellar height after HTO, but a −0.67 correlation was found between PPA reduction and tibial slop increase, therefore, PPA may overestimate patellar height after HTO 12 . Ellington and his colleagues indicated that PPA has a higher reproducibility and advantage of simpler implementation compared with IS, BP and CD index 9 .…”