Hybrid stem fixation in revision total knee arthroplasty (TKA)

The purpose of this study was to retrospectively compare the clinical and radiographic results of the Maxim Posterior Stabilized Constrained (PCS) (Biomet Orthopaedics, Inc., Warsaw, IN, USA) knee system using the hybrid fixation versus the fully cemented fixation of stems of the same length. The cohort in this study included 115 knees in 104 patients, with a minimum 2-year follow up postoperatively. All patients were evaluated with the Knee Society clinical rating score and roentgenographic evaluation. Of the 115 revision total knee arthroplasty (TKA) cases, the hybrid-fixation technique was used on both the femoral and tibial components of 75 (Group I-hybrid femur, hybrid tibia); the fully cemented technique was used on both components of 24 (Group II-cemented femur, cemented tibia); the hybrid-fixation technique was used on the femoral component and full cement on the tibial component of 13 (Group III-hybrid femur, cemented tibia); the femoral component was fully cemented, and tibial component had the hybrid-fixation technique used on 3 (Group IV-cemented femur, hybrid tibia). The average follow up was 44 (range: 24-126) months. At the most recent evaluation, the Knee Society score improved from an average preoperative value of 51.7 to 76.7, the pain score improved from 14.0 to 33.3, and the functional score improved from 40.5 to 47.0. The average stem-to-canal fill ratio was 80% in the femur and 85% in the tibia (p<0.05). Stem-to-canal fill ratio did not appear to influence clinical outcome. Radiolucent lines less than 2 cm were observed more frequently in the hybrid-cemented stems (89%) than the fully cemented stems (58%) at an average 8-year follow up postoperatively (p<0.05). A lower, but not statistically significant, failure rate was observed in the hybrid group in comparison with the cemented group.