Hip arthroplasty using a cemented collarless polished tapered stem has been proven to yield excellent results in over forty years of clinical trials. Traditional implants of this design employ a double taper, in the coronal and sagittal planes, in contrast to the collarless polished cemented stem (CPCS) system, which is also tapered in the medial-lateral plane. This design has been shown to decrease cement stains in photoelastic studies. The aim of this investigation is to report early results of the CPCS system with respect to stem engagement into the cement mantle (subsidence) and proximal femoral changes following implantation. Eighty-six patients (34 males, 52 females; mean age, 68.45 years) underwent primary THA using the CPCS system between November 2000 and May 2003 at UMC Hospital in Tucson, AZ, by one orthopedic surgeon. The diagnosis for which the arthroplasty was performed was degenerative joint disease in 75 patients (87.2%), inflammatory in 5 (5.8%), avascular necrosis in 4 (4.7%), and dysplasia (DDH) in 2 (2.3%). Patients were evaluated with standardized radiographs post-op and at regular intervals. Stem subsidence was measured by the change in stem tip position relative to the stem centralizer. The mean follow-up was 19.5 months (range 12-46 mo). The CPCS stem demonstrated<1 mm subsidence in 31% of patients, 1-2 mm in 56%, and>2 mm subsidence in 13%. There was a single patient with 3 mm subsidence measured at 3 years follow-up. Proximal femoral changes were classified as no change, rounding, and resorption. Radiographs were also examined for decrease in bone density. No change was noted in 7% of patients, rounding in 69%, resorption in 28%. Resorption was minimal with the medial femoral cortex losing 1-3 mm of height with respect to the medial cement column. Decrease in bone density in the medial femoral cortex was seen in 58% of patients. Bone lysis was not seen in any patients. These findings are consistent with long-term reports on implants with dual taper designs. The CPCS system, with its triple taper design, performs in a similar fashion to dual taper stems. The addition of the 3rd taper does not appear to have any unexpected deleterious effects on implant performance in vivo.
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