Equivalent outcomes of ultra-congruent and standard cruciate-retaining inserts in total knee arthroplasty

No systematic review has compared the clinical outcome of anterior stabilized ultra-congruent and standard cruciate-retaining inserts in fixed-bearing primary total knee arthroplasty. This study aimed to compare the outcomes and establish the superiority or equivalence of these inserts.

Pubmed, EMBASE, Medline, AMED, ERIC, and Proquest databases were searched electronically. PRISMA guidelines were followed in the conduct of the study. The clinical outcomes compared in the meta-analysis were overall knee score, WOMAC, score for knee function, score for knee pain, SF-12 PCS, knee flexion, manipulation under anaesthesia for postoperative knee stiffness, revision total knee arthroplasty or change of polyethylene insert for post-operative instability (relative risk [RR]) and survivorship. Study quality was evaluated using the Newcastle Ottawa Scale and the Modified Jadad scale.

Fourteen studies comprising 9989 knees (three RCTs and 11 comparative case-cohort studies) were included for qualitative and quantitative analysis. The pooled analysis of the ultracongruent insert and the standard cruciate retaining insert was based on a cohort of 2860 and 7129 TKA, respectively. Knee pain was significantly better in patients that had standard inserts (p = 0.02; 95% CI - 1.06 to - 0.10), and the physical component of health-related quality of life was also significantly better in patients that had standard inserts (p = 0.02; 95% CI - 6.43 to - 0.64). There was a 72% lesser chance of revision TKA or change of insert for postoperative instability in knees that had been implanted with ultracongruent inserts (RR = 0.28; p = 0.0002; 95% CI 0.15-0.55). There was no difference in the otheroutcome measures. There was no significant difference between the two inserts, considering the minimal clinically important difference or absolute ratio.

Differences observed between the two types of inserts were not clinically significant. Therefore, based on current evidence, arthroplasty surgeons can use either of these inserts with cruciate-retaining knee prosthesis.

Therapeutic study, Level II.