Preservation of joint line obliquity is not a critical factor for improving patient satisfaction

Purpose: This study has aimed to evaluate the clinical outcomes in paired bilateral posterior stabilized (PS) TKAs with significantly different degrees of joint line obliquity (JLO) change. Methods: A retrospective review was conducted on 128 patients who underwent paired bilateral PS TKAs, with greater and smaller JLO changes (G-ΔJLO and S-ΔJLO knees; difference between greater and smaller JLO change >3°). The mean follow-up period was 3.9 years (minimum 2 years). Radiographic changes in JLO were measured according to the Coronal Plane Alignment of the Knee (CPAK) classification. Maintenance of the CPAK type and JLO direction (apex distal, neutral, and apex proximal) was investigated. Clinically, the preferred TKA out of greater and smaller JLO changes was investigated. The Hospital for Special Surgery and Western Ontario and McMaster Universities Osteoarthritis Index were evaluated. Results: The average JLO change was 10.5° in the G-ΔJLO knees and 5.5° in the S-ΔJLO knees (p < 0.001). The CPAK type and JLO direction was better maintained in the S-ΔJLO knees (p < 0.001, repsectively). Regarding preference, 40 patients (31.2%) were satisfied with bilateral TKAs without a specific preference, while 44 patients (34.3%) preferred TKAs of the G-ΔJLO knee and 44 patients (34.3%) preferred the S-ΔJLO knee (p = 1.000). No significant differences were found in the patient reported outcomes between the G- and S-ΔJLO knees. Conclusion: The degree of JLO preservation did not significantly affect clinical outcomes of PS TKAs. JLO preservation will not be a critical factor in improving patient satisfaction for PS TKA. Level of evidence: III