Management of bone deficiency by metal augmentation in total knee arthroplasty

Abstract

Background Inadequate bone stock is frequently encountered in total knee arthroplasty and may be found in primary and revision procedures. Different techniques and devices for their management include additional bone resection, shifting of the components, filling the defect with cement with or without reinforcing screws or mesh, bone grafting, modular metal augmentation, or custom components. The modular augmentations are particularly useful in restoring the proper anteroposterior dimension as well as distal positioning of the joint line. In this study, the authors evaluate the use of metal augmentation for the management of deficient bone stock in total knee arthroplasty. Patients and methods A prospective study was done through the period between June 2014 and June 2017 on 30 knee arthroplasties, both primary and revision cases in 28 patients with bone deficiency consistent with Anderson Orthopedic Research Institute type II, treated by metal augmentation using different types of tibial and femoral augments applied to a posterior-stabilized prosthesis. The mean follow-up was 19 months. Eighteen cases (60%) were primary knee arthroplasties, and 12 cases (40%) were revision knee arthroplasties. Assessment at follow-up included clinical assessment through the knee society clinical rating system and radiographic assessment through the knee society roentgengraphic evaluation system. Results At the last follow-up, the average clinical knee society score was 80.4 (range from 16 to 93) compared with the average preoperative knee society score of 32 (range from 6 to 51). Only tibial radiolucent lines appeared in zones 1, 2 (nine cases), zones 3, 4 (four cases), and zone 5 in one case. All were nonprogressive radiolucent lines, except for two cases that progressed to aseptic loosening, and only one of them to a varus subsidence of the tibial implant. Conclusion Modular metal augmentation is a successful way for reconstruction of bone defects encountered in total knee arthroplasty through preservation of joint line and bone stock.