THE CEMENT MANTLE IN TOTAL HIP-ARTHROPLASTY - ANALYSIS OF LONG-TERM RADIOGRAPHIC RESULTS

The correlation between the thickness of the cement mantle, the medull ary canal fill, and the orientation of the stem and the long-term radi ographic outcome of 836 cemented femoral components in patients who ha d a primary total hip replacement was assessed with use of survival an alysis over a twenty-one-year follow-up period. The femoral stems of h ips that had a two to five-millimeter-thick cement mantle in the proxi mal medial region had a better outcome than stems implanted with a thi cker or thinner cement mantle. Stems in femora with less than two mill imeters of proximal medial cancellous bone had a better outcome than s tems in femora with thicker cancellous bone. Stems that filled more th an half of the medullary canal had better radiographic results than th ose that filled half or less. Progressive loosening, fracture of the c ement, and radiolucent lines at the stem-cement or bone-cement interfa ces were more likely to develop in stems that were oriented in more th an 5 degrees of varus than in those in neutral or valgus. The noted co rrelations were true whether the stem was made of titanium alloy or of stainless steel. The results of this study emphasize the importance o f careful preoperative planning in total hip arthroplasty done with ce ment and provide guidelines for the selection of the shape, size, and position of the stem.