Does malalignment affect patient reported outcomes following total knee arthroplasty: a systematic review of the literature

Background: Total knee replacement is an effective treatment for knee arthritis. While the majority of TKAs have demonstrated promising long-term results, up to 20 % of patients remain dissatisfied with the outcome of surgery at 1 year. Implant malalignment has been implicated as a contributing factor to less successful outcomes. Recent evidence has challenged the relationship between alignment and patient reported outcome measures. Given the number of procedures per year, clarity on this integral aspect of the procedure is necessary. Objective: To investigate the association between malalignment and PROMS following primary TKA. Methods: A systematic review of MEDLINE, CINHAL, and EMBASE was carried out to identify studies published from 2000 onwards. The study protocol including search strategy can be found on the PROSPERO database for systematic reviews. Results: From a total of 2107 citations, 18 studies fulfilled the inclusion criteria, comprising of 2214 patients. Overall 41 comparisons were made between a malalignment parameter and a PROM, with 30 comparisons (73 %) demonstrating no association. However, 50 % (n = 9) of the studies with 'Low risk' radiological assessment methods have reported a statistically significant association between one or more parameter of malalignment and PROMS. Conculsion: When considering malalignment in an individual parameter, there is an inconsistent relationship with PROMs scores. Malalignment may be related to worse PROMs scores, but if that relationship exists it is weak and of dubious clinical significance. However, this evidence is subject to limitations mainly related to the methods of assessing alignment post operatively and by the possibility that the premise of traditional mechanical alignment is erroneous. Larger longitudinal studies with a standardised, timely, and robust method for assessing alignment outcomes are required.