Abstract
BackgroundThe purpose of this study was to evaluate the effect of patellar facet angle on pre- and postoperative patellofemoral alignment and the progress of arthritis of the patellofemoral joint in posterior-stabilized total knee arthroplasty (PS TKA) without patellar resurfacing.MethodsPatients who had a PS TKA for a varus osteoarthritic knee who were followed up for more than 2 years were included in this study. The radiologic and clinical outcomes were compared between 72 knees (group A) whose patellar facet angle was greater than 126° (> 126°) and 32 knees (group B) whose patellar facet angle was smaller than or equal to 126° (≤ 126°). For the radiologic assessment, the Kellgren-Lawrence grade, mechanical femorotibial angle, Insall-Salvati ratio, patellar tilt angle, patellar displacement and the osteosclerosis of the patellar ridge were evaluated. The range of motion (ROM) and patient-reported outcomes (the Knee Society knee score, the Knee Society function score, the Feller patellar score, and the Kujala patellofemoral score) were used for the clinical assessment.ResultsThe preoperative patellar tilt angle was 9.8° (standard deviation [SD] 5.5) and 14.6° (SD 4.1) in group A and group B, respectively, a significant difference (p < 0.001). Other preoperative radiologic parameters and preoperative patient-reported outcomes and ROM showed no significant difference between the two groups (all parameters (p > 0.05). At the last-follow-up, 22 knees (30.6%) showed progression of osteosclerosis of the patellar ridge in group A and 13 knees (40.6%) showed progression of osteosclerosis in group B (p = 0.371). The postoperative radiologic and clinical outcomes showed no significant difference between the two groups (all parameters, p > 0.05).ConclusionsAlthough a narrow patellar facet angle was related to an increase of lateral tilting of the patella, it showed no impact on the preoperative clinical assessment. The radiologic and clinical outcomes evaluated after the PS TKA showed no statistical difference according to the patellar shape. Although the patellar shape evaluated by the patellar facet angle can partially affect the preoperative patellofemoral alignment, this study result indicated insignificant clinical relevance of the patellar shape in the PS TKA.
Highlights
The purpose of this study was to evaluate the effect of patellar facet angle on pre- and postoperative patellofemoral alignment and the progress of arthritis of the patellofemoral joint in posterior-stabilized total knee arthroplasty (PS TKA) without patellar resurfacing
The Patient-reported outcome (PRO) and range of motion (ROM) evaluated before the surgery showed no significant differences between the two groups
HKA hip-knee-ankle, KL Kellgren-Lawrence, KSFS Knee Society function score, KSKS Knee Society knee score, ROM range of motion a A negative value means medial displacement and a positive value means lateral displacement b Evaluated at the patellar central ridge it can affect the patellofemoral alignment before the surgery
Summary
The purpose of this study was to evaluate the effect of patellar facet angle on pre- and postoperative patellofemoral alignment and the progress of arthritis of the patellofemoral joint in posterior-stabilized total knee arthroplasty (PS TKA) without patellar resurfacing. Previous studies have suggested that a variety of surgery and prosthesis-related factors, including implant design, resurfacing of the patella, implant malpositioning, jointline changes, and soft tissue impingement, are related to the anterior knee pain [4, 5] To solve these problems, the design of the femoral and patellar component of the implant has been improved, making it more “patellafriendly”. In terms of the surgical technique, procedures, such as patellar resurfacing and lateral patellar facetectomy, are presently being tried [4,5,6,7] Despite these efforts, anterior knee pain is still one of the main causes of dissatisfaction after TKA [8]. The patientrelated factors related to anterior knee pain deserve particular attention because the anatomy of the patellofemoral joint, alignment and kinematics differ between patients [9, 10]
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