Tibial component sizing and alignment of TKR components does not significantly affect patient reported outcome measures at six months. A case series of 474 participants.

Objectives: Total knee replacement (TKR) is an effective means of alleviating the symptoms of end stage osteoarthritis. However, 20% of patients report dissatisfaction one year post-operatively. Previous literature has demonstrated contradictory evidence regarding the relationship between alignment and tibial component sizing with patient reported outcome measures (PROMs). We aim to investigate the association between alignment of TKR components and effect of tibial component sizing on PROMs.

Method: A prospective, multicentre case series was performed at six centres. Baseline characteristics were collected at recruitment. Coronal and sagittal plain films were taken day one post-operatively. Trained medical professionals blinded to outcome measured the alignment and degree of over/underhang of the tibial component in the coronal and sagittal place, with Oxford Knee Score (OKS) measured six months post-operatively.

Results: 474 patients were recruited. Malaligned TKRs caused no significant difference in mean OKS change at six months (independent t-test) (p > 0.05). A multivariate regression model taking into account age, gender, body mass index and baseline OKS also demonstrated no significant difference (p > 0.05). With regards to tibial component sizing, 125 (27%) of patients had appropriately sized tibial components, 120 (26%) had overhang and 219 (53%) had underhang with no significant difference in OKS between the groups (p > 0.05).

Conclusion: Tibial component sizing and alignment does not significantly affect short-term function, as measured by OKS, after total knee replacement. Dissatisfaction after TKR is likely due to other factors other than alignment of implant.