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[The role of the alloy-specific elements iron, cobalt, chromium and nickel in aseptic loosening of total hip joint prosthesis].

The cause of aseptic loosening of total hip joint prostheses is still largely unexplained. In addition to mechanical forces, material factors may also be instrumental. In 16 patients with loosened hip prostheses who underwent re-operation (8 X Huggler-Weber, 8 X McKee-Farrar), the concentration of the alloy-specific elements cobalt, chromium, nickel and iron were determined in 58 tissue samples by means of neutron activation and emission spectrum analysis. An increase in the element concentrations was found in all the tissue samples, and this was unrelated to the time elapsed since implantation. The chromium concentration in particular was significantly elevated in all the tissue samples, in some patients with McKee-Farrar prostheses up to 10,000 times the norm. In view of the known toxicity of cobalt, chromium and nickel in high doses it seems that the presence of unphysiologically high concentrations of these elements in the vicinity of total hip joint prostheses represents an explanation of some of the loosened prostheses.

Chromium Alloys↗

[The femoral neck fracture in the elderly patient - cemented or cementless hip arthroplasty?].

This is a report on the treatment results of femoral neck fractures with a cemented (group 1) and cementless (group 2) type of hip prosthesis, resp. 72 patients were enrolled. 35 patients were treated with a cemented hip prosthesis (mean age: 78 years), and 37 patients with a cementless modular hip prosthesis (mean age: 77 years). In the cemented group we observed 5 cases of hypotension during insertion of the prosthesis in the femoral shaft. One of these patients required mechanical resuscitation during surgery. In the second group 3 cases of proximal femur fissure and one case of distal femoral fracture were recorded. One year after surgery 43 patients presented for follow up evaluation (cemented group: n = 24; cementless group: n = 19). Both groups revealed comparable results according to the Harris Hip Score (75 versus 78,3 points). No prosthesis loosening was observed in either group. In our view the cemented hip prosthesis is the treatment of choice for femoral neck fractures among the old and very old, if no stabile osteosynthesis can be performed. Patients with cardiopulmonary risk factors, however, may profit from cementless hip arthroplasty to avoid the well known cardiodepression during surgery.

Aged↗

[Hand on composite prosthesis after resection of peri-acetabular sarcoma].

PURPOSE OF THE STUDY: To improve function after pelvic resection involving theacetabulum we have used an anatomic composite implant built with screws and cement. MATERIAL AND METHOD: Since 1990, 27 patients with peri-acetabular bone sarcoma have been treated by extensive resection followed by "hand on innominate prosthesis with constrained total hip prosthesis. The hand on innominate prosthesis was made of a titanium cup, a set of long titanium screws and 2 or 3 packs of gentamycin loaded ciment. RESULTS: Many postoperative complications were observed; deep infection (15 p. 100), hip prosthesis dislocation (33 p. 100) and local recurrence (17 p. 100). Nine patients (33 p. 100) had to be reoperated. Nevertheless at last follow up 24 patients still had their composite prosthesis. The mean functional result, rated according to a modified Enneking's staging system, was 83 p. 100 with unlimited walking without support, average hip flexion 100 degrees, length discrepancy less than 1 centimeters. DISCUSSION: These results were similar to those described in the literature for custom made innominate prosthesis and much better than those of alternative reconstructive procedures. Hand on composite prosthesis is cheaper, easier, more adaptable and enables better anchorage than custom-made prosthesis. Such a procedure can be used even after total iliac wing resection. CONCLUSIONS: The advantages of such procedure pleads for using it extensively after acetabular resection. But long term follow up is necessary to validate indications.

Acetabulum↗

[Results of implantation of uncemented porous metal hip prostheses].

72 patients having cementless spongy-metal hip prosthesis were reexamined by clinical and radiological check up two to seven years after implantation (average 43 months). In case of five patients hip prosthesis had to be changed due to loosening (no bony ingrowth n = 2, loosening of acetabular component due to technical faults n = 3). In correlation to clinical results 88% could be considered as excellent or good, 9% acceptable and 3% as inadequate. 10% of the patients complained about thigh pain. The typical radiological bony reactions of the surrounding bone are described. An evaluation of the radiological results can only be done under consideration of the clinical problems involved. In view of the positive results obtained in the recent time the use of spongy-metal hip prosthesis can be recommended for cementless hip joint replacement in case of younger patients. Especially in case of cemented hip joints which have become loose it will be an advantage to use spongy-metal hip prosthesis.

Adult↗

[Design and first clinical results with the ZMR taper revision prosthesis].

AIM: The purpose of this study was to survey and to evaluate the first clinical and radiological results with the cementless ZMR taper hip prosthesis. METHOD: The modular distal-tapered stem was designed with a roughened titanium surface and sharp splines to achieve secure distal fixation and rotational stability. 90 ZMR taper hip prostheses were implanted between October 1999 and July 2002. Out of these, 4 interventions were primary and 86 were revision procedures. In 43 cases a complete hip prosthesis revision and in 43 cases a stem revision was necessary. The mean age of the 90 patients (42 males, 48 females) was 67.1 years. The mean follow-up period was 7.6 months (3 to 25 months). RESULTS: The stem displayed an excellent distal fixation. The mean subsidence could be measured with 4.3 mm. Furthermore, most cases showed a particularly favourable remodelling of the proximal femoral bone stock. Complications associated with revision included intraoperatively 4 femur fractures, 3 femur fissures, 5 femur perforations, 2 trochanter fractures and postoperatively 19 dislocations, 5 superficial wound infections, 2 transient palsies, 1 pulmonary embolism, 1 stem rotation and 4 wound healing failures. Considering these complications 15 re-revisions were necessary and the ZMR taper hip prosthesis had to be exchanged in 3 cases. CONCLUSION: On the one hand the ZMR taper hip prosthesis proved its value, particularly with regard to the stem modularity, the excellent distal fixation in conjunction with the possibility of partial body weight bearing and the rapid bone remodelling of the femur. On the other hand an increased number of postoperative complications and re-revisions occurred. Further long-term studies seem to be essential.

Aged↗

Numerical and experimental stress analysis of a polymeric composite hip joint prosthesis.

A comparative stress analysis of a polymeric composite hip joint replacement was performed. A prototype short carbon-fiber reinforced PEEK (CF/PEEK) prosthesis was manufactured by injection molding. Finite element (FE) analysis was conducted on intact femurs and femurs fitted with the CF/ PEEK and the titanium prostheses under various loading conditions. FE models were validated by experimental strain gauge measurements by using synthetic femurs. There was a good agreement between the two methods except in the hoop strain of the femur in the calcar region because of the assumption of the isotropic material properties. The stem stresses were lower for the CF/PEEK prosthesis than for the titanium prosthesis. The maximum stress was in the spigot of the CF/PEEK prosthesis, but in the middle third of the stem of the titanium prosthesis. Stress generated in the cement was almost equal for both prostheses although more load was transferred, via cement, to the femur with the CF/ PEEK prosthesis because the load transfer took place over a larger area. An out-of-plane component of the joint load causes higher prosthesis and cement stresses.

Benzophenones↗

[FE-analysis of surface stresses for the tribological system in total hip prostheses].

The implantation of a total hip prosthesis is an operation which is performed frequently due to advanced hip joint damage both in humans and in veterinary medicine in dogs. The long-term result of a hip prosthesis is mainly determined by aseptic loosening of the prosthesis; among other causes, abrasion particles of the tribological pairing are responsible for the loosening. For the analysis of the surface stresses with different tribological pairings, a finite element model was generated which was based on the CAD data of a commercial total hip prosthesis. After transmission of a physiological force in the components of the three tribological pairings ceramic/polyethylene, ceramic/ceramic and metal/polyethylene, stresses were calculated. Stresses in the ceramic/ceramic tribological pairings were conspicuously higher than in the other material pairings. In the future adapted prostheses have to be developed that ensure optimal friction and absorption characteristics of the components.

Arthroplasty, Replacement, Hip↗

[Immunoscintigraphy for the detection of inflammation foci in bone and joint diseases].

We evaluated the monoclonal antibody MAb, BW 250/183, which is easy to label with Tc-99m, with respect to its clinical application for the detection of inflammatory processes in bone and joint diseases. This monoclonal antibody is a murine immunoglobulin (IgG1 isotype), directed against NCA 95 (nonspecific cross-reacting antigen), which is also present on the surface of neutrophil granulocytes. We investigated patients with acute (n = 9) and chronic (n = 3) osteomyelitis, with coxitis (n = 3) and coxarthrosis (n = 2), with septic hip prosthesis (n = 8) and loosening hip prosthesis (n = 14), with low back pain (n = 4), with spondylitis (n = 5) and with postoperative spondylodiscitis (n = 9). With reference to the total number of patients examined in this study we found 29 true positive results, 22 true negative results, 4 false negative results and 2 false positive results. This gives a sensitivity of 88% and a specificity of 92%. The lesions were already visualized within 4 to 6 hours, but 24 hour pictures are desirable. SPECT pictures are mandatory in patients with diseases of the hip or of the spine because sensitivity is considerably improved thereby.

Adolescent↗