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From March 2006 to August 2008, 93 subjects (186 knees) underwent simultaneous bilateral total knee arthroplasty performed by eight surgeons at North American centers. This randomized study was conducted to determine whether non-weight-bearing passive flexion was superior for knees receiving a posterior stabilized high flexion device compared to a posterior stabilized standard device in the contra-lateral knee. Weight-bearing single leg active flexion was one secondary endpoint. Follow-up compliance was 92.5%. Results show small, but significant superiority in the motion metrics for the high flexion device compared to the standard device 12 months after surgery, especially for a subgroup of patients with pre-operative flexion less than 120° in both knees. Thus, the ideal candidate for the high flexion device may be one with lesser pre-operative flexion., (Copyright © 2013 Elsevier Inc. All rights reserved.)

An 11.1% incidence of femoral osteolysis (30 cases in 28 patients) was identified in a series of 271 primary total knee arthroplasties. Two minimally constrained total knee designs (Synatomic [Depuy, Warsaw, IN] and Porous-Coated Anatomic [PCA, Howmedica, Rutherford, NJ] were used in this patient population. Femoral osteolysis was observed in 26 Synatomic and 4 PCA knees. The average follow-up period was 52 months (range, 24-96 months). Osteolytic lesions were identified radiographically, adjacent to the nonporous-coated (smooth) regions of the anterior and posterior flanges of the Synatomic and PCA femoral components. The average time to the diagnosis of femoral osteolysis was 31 months (range, 7-96 months). The average patient age at the time of primary total knee arthroplasty was 63 years (range, 43-83 years) and the average weight was 180 lb. (range, 107-278 lb.). Sixteen of the 30 cases were in men. All of the cases with femoral osteolysis had cementless implantation. Tissue specimens were obtained from the 18 cases requiring revision. Implants remained in situ an average of 66 months (range, 15-96 months) prior to revision. In 16 of the 18 cases revised, the femoral component was clinically and radiographically stable. Six of 18 cases were revised for severe osteolysis. The remaining 12 cases were revised for failed metal-backed patellae, failed cementless tibial fixation, or advanced polyethylene wear. Wear of the thin tibial inserts and patellar components were the two sources of particulate polyethylene. Polyethylene debris was observed in all tissue specimens. In cases with failed metal-backed patellae or impingement of the tibial locking pin-and-clip, fine metallic debris was also noted in tissue specimens. Microscopic evaluation of the osteolytic tissue revealed a florid histiocytic response with occasional giant cells. Intracellular submicron particulate polyethylene was identified with polarized light microscopy and oil-red-O staining techniques. In the study population, statistically significant factors associated with femoral osteolysis included male gender (P < .05), younger age (P < .05), increased patient weight (P < .05), positive tibial osteolysis (P < .001), osteoarthritis (P < .07), and length of time in situ (P < .001). In addition, patients with a Synatomic prosthesis were at increased risk for osteolysis compared to patients with a PCA device (P < .02). The authors postulate that histiocytic granuloma gained access to the proximal femur primarily via the unbonded interface between the smooth metal and bone.