Metal block augmentation for bone defects of the medial tibia during primary total knee arthroplasty

BACKGROUND: Stable and well-aligned placement of tibial components during primary total knee arthroplasty is challenging in patients with bone defects. Although rectangular block-shaped augmentations are widely used to reduce the shearing force between the tibial tray and bone compared with wedge-shaped augmentations, the clinical result remains unclear. This study aimed to evaluate the outcome of primary total knee arthroplasty with metal block augmentation. METHODS: We retrospectively reviewed the 3- to 6-year follow-up results of 33 knees that underwent total knee arthroplasty with metal block augmentation (metal-augmented group) for bone defects of the medial tibia and 132 varus knees without bone defects as the control group. All surgeries were performed using posterior-stabilized cemented prostheses in both groups. Cemented stems were routinely augmented when the metal block was used. RESULTS: There were no differences in implant survival rates (100% in metal-augmented and 99.2% in control) or knee function scores (82 points in metal-augmented and 84 points in control) between the two groups at the final follow-up examination (P = 0.60 and P = 0.09, respectively). No subsidence or loosening of the tibial tray was observed. Of 33 metal-augmented total knee arthroplasties, a nonprogressive radiolucent line beneath the metal was detected in 10 knees (30.3%), and rounding of the medial edge of the tibia was observed in 17 knees (51.5%). CONCLUSIONS: The clinical results of total knee arthroplasty with metal augmentation were not inferior to those in patients without bone defects. However, radiolucent lines were observed in 30.3%.