Evaluation of patellar height and measurement methods after valgus high tibial osteotomy

Abstract

Several controversies exist regarding the surgical difficulties and the results of total knee arthroplasty performed after failed valgus high tibial osteotomy (HTO), and the main subject is the change in patellar height that results as patella baja or infera. The purpose of this retrospective study was to evaluate patellar height after valgus HTO and the measurement methods that were actually used. Eighty-five knees that were subjected to valgus HTO were evaluated both preoperatively and postoperatively according to the Insall-Salvati Index (ISI), Blackburne-Peel Index (BPI), and Caton Index (CI) to assess any alteration of patellar tendon height that was present. All cases underwent closing wedge osteotomy with three staples or plate internal fixation and were allowed early range of motion. Significant decrease in mean patellar height ratios was detected according to all three indexes at 85 months of mean follow-up. The percentages of the decrease were 8.26% in ISI, 9.08% in BPI, and 6.34% in CI. Two knees showed patella infera according to ISI, one according to BPI and three according to CI. There were no significant correlations between the indexes and clinical status of the patients. Elevation of patella relative to the femur in closing wedge valgus HTO procedure due to the shortening of the segment between tibial tuberosity and joint line is normally expected. A significant decrease in patellar height according to ISI suggests that there should be patellar tendon shortening as patellar height cannot be changed. BPI and CI for determining patellar height in valgus HTO do not accurately measure the alteration of patella because they may affect the tibial inclination and antero-posterior translation of the proximal fragment. Another measuring system based on femoral reference points should be proposed to determine the exact change of patellar height in the valgus HTO procedure.

Comparison of five patellar height measurement methods in 90° knee flexion

“…To some extent, our study showed a similar distribution of patellae norma, alta and infera as reported in the literature at the site of different surgical indications [12,[30][31][32]. In some cases, our results demonstrated great variations in the determined values.…”

Patellar Height and Tibial Slope after Opening-Wedge Proximal Tibial Osteotomy

“…The decrease in patellar height observed was similar to the decrease in patellar height reported after closing-wedge proximal tibial osteotomy procedures. 13,26,38,41,43,47 We also found that this significant decrease in patellar height after opening-wedge proximal tibial osteotomies happens within the first 3 postoperative months. However, only when measuring the patellar height using the Insall-Salvati index was there a significant difference in patellar height ratio between the anteromedial and posteromedial plate positions.…”

“…§ Both decreased 24,26 and increased 6 tibial slope after proximal tibial osteotomies have been reported to have a significant association with reduced patellar height.…”

Radiological outcomes in a randomized trial comparing opening wedge and closing wedge techniques of high tibial osteotomy

“…However, these indexes are by some authors not recommended for use in HTO patients since the osteotomy changes proximal tibial anatomy including tibial slope [25,27,30]. Instead, the use of an index with a reference point within the femur is recommended, e.g.…”