[Periprosthetic bone loss after total hip endoprosthesis. Dependence on the type of prosthesis and preoperative bone configuration].

The changes of the periprosthetic bone density were examined with DEXA in 81 patients over a period of 1 year after implantation of cementless total hip endoprosthesis. Four types of endoprostheses (Vision 2000/Duraloc, ALPHA-Fit/ALPHA-Lock Plus, CLS/Allofit, Mayo/Trilogy) were implanted. Information on the changes of the periprosthetic bone density depending on the type of the prosthesis and the bony situation at the femur before operation was expected from these measurements. In all types of stems the strongest reduction of the bone density was found in the region of the calcar femoris, and the smallest changes were found distally and medially of the tip of the prostheses. In the prosthesis with shorter stem the change of the bone density was altogether clearly lower than in prostheses with longer stem. With increasing size of the prosthesis with proximally porous coating made from cobalt-chrome alloy, proximal atrophy was observed more frequently, whilst in the prosthesis made from titanium alloy with completely rough-blasted surface the distal hypertrophy increased. A low preoperative corticalis-bone marrow index strengthened the proximal atrophy in proximally porously coated prosthesis made from cobalt-chrome alloy and led in the prosthesis with completely rough-blasted surface more often to distal hypertrophy of the bone.