Abstract
PurposeTotal knee arthroplasty (TKA) is widely used as a treatment for knee osteoarthritis. However, still up to 20% of the patients are dissatisfied. Joint line elevation after TKA might be a contributing factor as it alters knee kinematics. The aim of this study was to investigate the effect of joint line elevation on outcome.MethodsA systematic review of the literature was performed to select studies that reported on joint line alterations after primary or revision TKA and outcome. Studies with comparable outcome parameters were included in a correlation analysis.ResultsIn total, 396 studies were identified, of which 27 met the inclusion criteria. 8 studies could be included in the correlation analysis. Mean joint line elevation after primary TKA was 3.0 mm and after revision TKA this was 3.6 mm. A statistically significant negative correlation was found between joint line elevation and the postoperative Knee Society Score (KSS) function score (ρ = − 0.496, p < 0.001). In a pooled analysis, the maintained joint line revision TKA group had statistically significant better postoperative KSS total scores compared to an elevated joint line group (p < 0.001).ConclusionIn this systematic review, a negative correlation between joint line elevation and outcome was found. Furthermore, revision TKAs with a maintained joint line have statistically significant better postoperative KSS scores compared to an elevated joint line group. To achieve optimal outcome after TKA, restoration of the joint line is one of the parameters that should be pursued and introduced elevation should not exceed 4 mm.Level of evidenceIV.
Highlights
Satisfaction after total knee arthroplasty ranges between 75 and 90% [8, 9, 13, 29]
A total of 18 studies reported on primary Total knee arthroplasty (TKA) and 9 on revision TKA
Revision TKA joint line alteration is defined as the joint line position postoperative compared to either the preoperative or the healthy contralateral knee joint line position
Summary
Different contributing factors for dissatisfaction after TKA have been identified like socioeconomic status, mental well-being, fulfilment of expectation, and the postoperative general physical health of the patient [12]. From a surgical point of view, joint line elevation, among other factors, is considered to have a negative effect on postoperative outcome, since it alters the biomechanics of the knee. As a consequence of the elevated joint line, the posterior condylar offset (PCO) is likely to be reduced, which negatively influences flexion angle and the extensor mechanism strength, and resolves in mid-flexion instability [6, 36, 37]. Mean joint line elevation after primary TKA varies between 1.1 up to 5.6 mm [44, 46]. Some studies report a correlation between a raised joint line and patient-reported outcome measures (PROMs) [10, 17, 40], while others do not find this correlation [49]. There is still debate if minor joint line elevation affects PROMs after TKA [44], and if so, what amount of joint line elevation is acceptable after TKA
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