Biomedical subjects

Rama Ramakrishnan

Publications and source records attributed to Rama Ramakrishnan.

2 recordsLinked to original sources

PubMed2006

Crosslinked polyethylene compared to conventional polyethylene in total hip replacement: pre-clinical evaluation, in-vitro testing and prospective clinical follow-up study.

BACKGROUND: Polyethylene wear-induced osteolysis is a major cause of implant loosening in total hip arthroplasty. New crosslinked polyethylenes are presumed to give lower wear rates, but no long-term clinical results are available yet. PATIENTS AND METHODS: We compared basic material characteristics and MTS hip joint simulator wear rates of a crosslinked polyethylene (Duration) to those of conventional polyethylene. In a randomized double-blind 5-year clinical follow-up study, 133 hips (67 conventional, 66 Duration) in 127 patients were followed-up for an average of 5 (3-6) years. Wear rates were measured using a computer-based edge detection method. The radiographic appearances of wear-related phenomena were recorded. RESULTS: The Duration polyethylene showed a significantly lower in-vitro wear rate in the simulator study (mean 22 (SD 2.3) vs. 40 (SD 1.5) mm3/106 cycles). Also, the in-vivo wear was lower for Duration (mean 0.083 (SD 0.056) mm/year) than for conventional polyethylene (mean 0.123 (SD 0.082) mm/year). All radiographic signs of osteolysis were less frequent in the Duration group. INTERPRETATION: Our study has given a substantial body of evidence--from lower wear rates, less frequent signs of osteolysis, and higher survival rates after a mean follow-up of 5 years--that Duration provides better clinical outcomes than conventional polyethylene.

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PubMed2005

Five-year experience with Crossfire highly cross-linked polyethylene.

UNLABELLED: Our purpose was to compare the clinical wear performance of highly cross-linked (Crossfire) polyethylene with conventional (N2Vac) polyethylene total hip bearings. We implanted 56 hips (47 patients) with Crossfire acetabular bearing liners and compared their wear performance with 53 conventional polyethylene inserts. Wear and clinical data were collected retrospectively at a minimum 4-year and average 5-year followup. The linear femoral head penetration rate measured from plain radiographs was 0.055 mm/year +/- 0.022 mm/year for the Crossfire polyethylene and 0.138 mm/year +/- 0.073 mm/year for the control, a reduction of 60% for the Crossfire components. Calculated annual wear was 0.036 mm/year for the Crossfire components and 0.131 mm/year for the controls, a reduction of 72%. Radiographic review at most recent followup showed a reduction in erosive osteolytic lesions of the proximal femur for the Crossfire components compared with controls, also suggesting a reduction in debris release for the Crossfire components. Complications leading to revision were not seen in the Crossfire or control groups. These clinical findings suggest that this particular highly cross-linked polyethylene can provide wear reduction and an alternate bearing surface for active patient populations. LEVEL OF EVIDENCE: Therapeutic study, Level III (retrospective comparative study). See the Guidelines for Authors for a complete description of levels of evidence.

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