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Background: There is no consensus on the most appropriate method to assess patellar height following medial unicompartmental arthroplasty (UKA) or open-wedge high tibial osteotomy (HTO). The purpose of this study was to evaluate the difference between pre- and post-operative patellar height in patients receiving UKA or HTO using three indices of patellar height.
Methods: The authors retrospectively analysed pre- and post-operative radiographs of 44 patients that received medial UKA (n=21) or open-wedge HTO (n=23). Pre- and post-operative radiographs were standardised between patients, including anterior-posterior, and lateral in 30° flexion images. Postoperative radiographs were obtained at 6 weeks. Patellar height was assessed according to the Insall-Salvati index, Blackburne-Peel index, and Caton-Deschamps index.
Results: Patients that received UKA (67.4±5.8 years) were significantly older than patients that received HTO (51.3±9.0 years, p<0.001). Preoperative patellar height was similar between patients that received UKA or HTO according to all three indices. Postoperative patellar height was similar among the two groups according to the Insall-Salvati index, but was significantly greater following UKA according to the Blackburne-Peel index (0.95±0.13 vs. 0.75±0.24, p=0.003) and Caton-Deschamps index (1.09±0.17 vs. 0.93±0.26, p=0.019). According to all three indices, UKA tended to increase patellar height, whereas HTO tended to decrease patellar height. The differences between pre- and post-operative patellar heights were however not significant, except for the Caton-Deschamps index following UKA (p=0.043).
Conclusion: According to all three indices, medial UKA tended to increase patellar height, whereas open-wedge HTO tended to decrease patellar height.
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