Survivorship, Clinical and Radiographic Outcomes of a Novel Cementless Metal-Backed Patella Design

Enhanced implant longevity through biological fixation is achievable using cementless total knee arthroplasty but concerns about patellar component failure have lingered because of prior experiences with older component designs. A new metal-backed patella (MBP) design was released which features a 3-dimensional printed porous titanium metal backing to improve biologic fixation potential and a unique compression molding technique to create a stronger interlock layer between the polyethylene and metal backing. Our study purpose was to determine the clinical and radiographic outcomes and survivorship of this novel cementless MBP.

Our institutional registry identified 388 cementless MBP with minimum 2-year and 80 with minimum 5-year follow-up. Knee Injury and Osteoarthritis Outcome Score for Joint Replacement and 12-item Veterans RAND/Short Form Health Survey (VR/SF-12) scores were used to evaluate clinical outcomes. Aseptic loosening noted on radiographs as well as revision for any reason were the end points used to determine survivorship.

Improvement in the preoperative Knee Injury and Osteoarthritis Outcome Score for Joint Replacement, VR/SF-12 physical health and mental health scores were all statistically significant at 2-year follow-up and the VR/SF-12 mental health score at 5-year follow-up. By radiologic criteria, biologic fixation of the patellar component was present in all except 1 case at 2 years (99.6%) and at 5 years (97.7%). Radiolucent lines were present in 15 cases (6.2%) at 2 years and in 6 cases (14%) at 5 years, but progressive increase in radiolucent lines was seen in only 4 cases. No component was revised for loosening; aseptic survivorship was 100%.

This 3-dimensional printed cementless patellar component shows excellent survivorship at 2-year and 5-year follow-up. We are hopeful about the long-term durability of this implant.