Annual change of the periprosthetic bone density in total hip arthroplasty using extensively porous coated femoral stem

초록

Purpose : For investigating the annual change of bone mineral density around femoral stem and the factors which would influence to the stress shielding effect in patients who had been operated by using the extensively porous coated cementless stem. Materials and Methods : We reviewed seventy-four patients who underwent unilateral primary total hip replacement arthroplasty with extensively porous coated cementless femoral stem, from June 1996, to June 1998, could be followed up at least for three years. All hips were stable bone ingrowth stem in radiographically. The proximal portion of the femur were divided six areas into zone 1, 2, 3, 5, 6, 7 according to Gruen zone. The bone mineral density(BMD) was measured at each area annually for longitudinal analysis with DEXA QDR 4500 . The BMD of opposite femurs were measured as same method. The difference of BMD between unoperated side and operated side was calculated. Then we analyzed relationship between the results and sex, patient's age, stem size, preoperative Singh's index for periprosthetic bone remodeling. For statistics, the ANOVA test and Student's t-test were used. Results : In first year after operation, the bone mineral density of all areas of Gruen zone were decreased significantly compared with those of unoperated side. From second year to fourth year after operation, bone mineral densities in Gruen zone 1, 2, 7 were decreased significantly, but those in Gruen zone 3, 5, 6 were increased significantly compared with those of unoperated side. The change of bone mineral density were stabilized in all areas with time. The changes of BMD were correlated with the following clinical variables: sex, patient's age, stem size, preoperative Singh's index. Especially the stem size has a strong predictable value. Conclusion : Our findings suggest that periprosthetic BMD was decreased at all area in first year after surgery, after then the BMD was decreased in Gruen zone 1, 2, 7 and was increased in Gruen zone