A supra-tuberosity anterior closing wedge proximal tibial osteotomy increases patellar height: a simulated time zero uniplanar radiographic study.

PURPOSE: The purpose of this time-zero radiographic study was to simulate the effect of supra-tuberosity tibial anterior closing wedge osteotomy (ACWO) in knees with posterior tibial slope (PTS) ≥12° on patellar height when aiming for a target PTS of 5°.

METHODS: The authors retrospectively reviewed true lateral radiographs of the knees of skeletally mature patients scheduled for primary anterior cruciate ligament reconstruction (ACLR), and included all knees with excessive PTS (≥12°). Coordinates of 11 landmarks were digitized to calculate patellar height (Caton-Deschamps index, CDI) and mid-shaft posterior tibial slope (mPTS). The change in patellar height following a simulated supra-tuberosity ACWO was calculated and compared for knees with patella norma versus alta. A linear univariable regression model predicted the effect of change in mPTS on CDI.

RESULTS: In the final cohort of 83 patients, a simulated supra-tuberosity ACWO increased CDI from 1.13 (range, 0.73 to 1.74) to 1.29 (range, 0.84 to 1.91; p<0.001). In 56 patients with patella norma, a simulated supra-tuberosity ACWO increased CDI from 1.02 (range, 0.73 to 1.19) to 1.18 (range, 0.84 to 1.41; p<0.001), whereas in patients with patella alta, a simulated supra-tuberosity ACWO increased CDI from 1.33 (range, 1.20 to 1.74) to 1.52 (range, 1.36 to 1.91; p<0.001). The linear regression model revealed that a 1° decrease in mPTS increased CDI by 0.02.

CONCLUSION: Simulation of a supra-tuberosity ACWO revealed that the procedure increases patellar height in all knees, but did not induce significant differences in patellar height characteristics between knees with patella norma versus alta. A linear regression model revealed that a 1° decrease in mPTS could theoretically increase CDI by 0.02.