Total knee arthroplasty using ultra-congruent inserts can provide similar stability and function compared with cruciate-retaining total knee arthroplasty.

PURPOSE: Recently, ultra-congruent (UC) inserts have shown successful outcomes following total knee arthroplasty (TKA). It was hypothesized that patients in the UC group would not show significantly different in vivo stability or functional outcomes from those in the cruciate-retaining (CR) group.

METHODS: The prospective study enrolled patients who had been treated with either CR or UC TKAs (38 cases in each group), after a minimum 3-year follow-up. The same surgical technique was used with the same femoral components in both groups except for the polyethylene inserts (CR or UC). The clinical outcome measures were knee range of motion (ROM), Hospital for Special Surgery (HSS) score, Knee Society (KS) score, and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) subscale score. The mediolateral laxity at full extension and anteroposterior laxity at 90° flexion were measured in stress radiographs and compared between the two groups.

RESULTS: Both the CR and UC groups showed significant improvements in post-operative ROM, HSS, KS, and WOMAC scores without inter-group differences between two groups. Moreover, there were no differences in mediolateral or anteroposterior laxity between the two groups (p > 0.05).

CONCLUSION: TKA with posterior cruciate ligament (PCL) resection using the UC design showed comparable functional outcomes with those of CR TKA and provided similar in vivo stability. Therefore, UC inserts can be a good option in TKA without bony box cut when the PCL is damaged during an operation.

LEVEL OF EVIDENCE: II.