Pack-Size-Dependent Effects of Bone Cement Use in Unicompartmental Knee Arthroplasty: A Prospective Randomized Trial

Excess bone cement is often discarded in unicompartmental knee arthroplasty (UKA), increasing costs and potentially cement-related complications. Although cement inefficiency is recognized in total knee arthroplasty (TKA), no prospective randomized trial has assessed the effect of cement pack size in UKA. We compared 20-g and 40-g cement packs for cement utilization, radiographic fixation, and 1-year outcomes.

In this prospective single-center randomized trial (from September 1, 2022 to June 30, 2024), patients undergoing medial UKA were allocated to 40-g (n = 98) or 20-g (n = 100) cement packs. Outcomes included cement used, wastage rate, penetration depth, radiolucent lines, extrusion, and 1-year implant survival. Groups were compared using appropriate parametric or nonparametric tests, and survival was analyzed using the Kaplan-Meier method with the log-rank test.

Cement used was similar (≈8.1 g; P = 0.173), but the 40-g group had a higher wastage rate than the 20-g group (85.76% vs. 71.49%; P < 0.001). Cement penetration (≈1.5 mm femur, ≈2.5 mm tibia), radiolucent lines (≈18-20%), and extrusion (≈12-18%) were comparable. One patient in the 40-g group developed infection requiring debridement, antibiotics, and implant retention (DAIR). One-year implant survival was 100% in the 20-g group and 99.0% in the 40-g group (P > 0.3).

In UKA without substantial bone defects, a 20-g cement allocation strategy reduces cement waste while maintaining comparable short-term radiographic fixation and clinical outcomes to a 40-g strategy. Under institutional pricing assumptions, smaller packs were associated with estimated cement acquisition cost savings, so 20-g allocation may be considered in routine UKA when substantial defects are absent.