Zeitschrift für Orthopädie und ihre Grenzgebiete
-
Z Orthop Ihre Grenzgeb · Mar 1998
[An in vitro model for producing femoral fractures and for the study of primary stability of cerclage].
Intraoperative femoral fracture is a well recognized intraoperative complication of cementless total hip arthroplasty (THA). This study was designed to establish an in-vitro model for initiation of fractures of the femur in cementless THA and to assess the effect of fracture fixation by cerclage wiring using steel wire (Protasul). ⋯ During insertion of a conical stem the orthopaedic surgeon should look for fractures of the medial cortex of the femur which is the most frequent location for fractures. This in-vitro model provides a reproductable method for the initiation and propagation of longitudinal femoral fractures in press-fit noncemented THA system and to assess the effect of fracture fixation in the form of cerclage wiring.
-
Z Orthop Ihre Grenzgeb · Mar 1998
[Comparative periprosthetic bone density measurements of the proximal femur shaft using dual energy x-ray absorptiometry (DEXA) with experimental "Press Fit-gliding Stem Prosthesis"].
Periprosthetic bone atrophy caused by stress shielding is one of the problems of non-cemented femoral stems of hip arthroplasty. Stress shielding and thus the loss of bone mass and their dissemination in the proximal part of the femur of conventional non-cemented femoral stems depends on stiffness (E-modules of the material and the geometry) of the implant and on the bonding between implant and bone. All currently implanted non-cemented femoral stems lead to proximal bone loss which goes up to 40-50% of the original bone mineral content. The senior author (E. M.) developed a femoral stem (Press Fit-Gliding Stem PFGS) which shifts relative movements of force-transmission from the bone-implant interface into the interior of the prosthetic system (Inner Bearing-System) and which only transfers forces proximal into the femur. ⋯ The Press Fit-Gliding Stem is still in the clinical test-program.
-
Z Orthop Ihre Grenzgeb · Mar 1998
[MRI-controlled outcome after core decompression of the femur head in aseptic osteonecrosis and transient bone marrow edema].
We evaluated the signal changes of avascular necrosis and transient bone marrow oedema before and after core decompression of the femoral head to deduce prognostic factors for this operative procedure. ⋯ In the case of transient bone marrow oedema, a restitutio ad integrum can be achieved with core decompression. In stage I and II of avascular necrosis, the successful outcome depends on the lesion size of the femoral head. Necrotic lesions less than 30% seem to have the best prognosis. In stage III and IV, core decompression cannot be recommended.