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[The history of Metasul].

The first generation, metal-on-metal articulation from cobalt-chromium-molybdenum alloy produced by Sulzer Ltd. has been in use for 40 years. Former drawbacks concerning geometry, tolerance or metallurgy have been eliminated in the second generation METASUL components used since 1988. These are also free of disadvantages, such as potential fracture, shown by other hard-on-hard bearing couples. For 14 years now METASUL components have not been responsible for any repeat operation due to loosening. Both clinical and experimental outcomes show that yearly wear has been negligible (in the order of microns) and this allows us to expect the metal-on-metal coupling to function for periods not a achieved so far by any other hip prosthesis. Hip replacements based on METASUL are better than those involving metal-on-polyethylene or ceramic-on-polyethylene. Up to now the need for repeat operations has not been associated with the MATASUL coupling system. Loosening has always been due to other reasons. It can therefore be expected that, in choosing prosthetic devices and surgical techniques, METASUL hip replacements will play a leading role.

Arthroplasty, Replacement, Hip↗

[Uncemented total prosthetics as exemplified by a carbon-fiber prosthesis of the hip joint].

A new artificial total hip joint was designed and tested in animals and human patients up to five years. For implant combined carbon material (Endocarbone) was used. The primary anchorage was achieved by a hydraulic pin system without bone cement. The follow-up of bone growth at the implant bone border line was proved by X-ray, computer-tomography, arthrography and histo-morphological tissues. The Endocarbone hip prosthesis has been proved as a biological implant. The good bonely incorporation justifies a more intensive clinical testing.

Animals↗

Priorities for surveillance and cost-effective control of postoperative infection.

We estimated costs of major postoperative infections (wound infection, 1.2%; bacteremia, 0.2%; pneumonia, 0.9%; and symptomatic urinary tract infection, 0.2%) in patients with common elective operations done in 22 community hospitals during 1985 to mid-1987 by review of 3936 medical records randomly drawn from 17,500 postoperative patients. Calculations based on observed rates of major infection by class of operation and hospitalization days beyond diagnosis related group assignments assumed that daily costs for infection management would be $750. Potential savings per 100 patients from infection control efforts was $13,230 to $47,970 for large-bowel operations, laminectomy, total hip prosthesis, other hip prosthesis, and hip fixation operations and $480 to $4455 for cholecystectomy, hysterectomy, and transurethral prostatectomy. Determination of infection surveillance and control priorities should include consideration of differences in prolongation of hospitalization among various operations by similar infections.

Age Factors↗

Technical note: validation of a motion analysis system for measuring the relative motion of the intermediate component of a tripolar total hip arthroplasty prosthesis.

Tripolar total hip arthroplasty (THA) prosthesis had been suggested as a method to reduce the occurrence of hip dislocation and microseparation. Precisely measuring the motion of the intermediate component in vitro would provide fundamental knowledge for understanding its mechanism. The present study validates the accuracy and repeatability of a three-dimensional motion analysis system to quantitatively measure the relative motion of the intermediate component of tripolar total hip arthroplasty prostheses. Static and dynamic validations of the system were made by comparing the measurement to that of a potentiometer. Differences between the mean system-calculated angle and the angle measured by the potentiometer were within +/-1 degrees . The mean within-trial variability was less than 1 degrees . The mean slope was 0.9-1.02 for different angular velocities. The dynamic noise was within 1 degrees . The system was then applied to measure the relative motion of an eccentric THA prosthesis. The study shows that this motion analysis system provides an accurate and practical method for measuring the relative motion of the tripolar THA prosthesis in vitro, a necessary first step towards the understanding of its in vivo kinematics.

Algorithms↗

[Clinical and radiological results with the spherical Mecring as acetabulum prosthesis in hip joint diseases].

The recent experiences which the university hospital in Heidelberg has made with the spherical Mecring must be valued positively. Clinical, radiological and subjective dates from 147 patients were worked up retrospectively. Indeed, the positive results must be considered as relative because of the short respectively medium-term period of control. Nevertheless, the repeated improvement in the second group after a period of postexamination on a average of 3.05 years lets hope for positive long-term results. In the period between 1985 and 1990 three sockets had to be changed. The reasons that the sockets loosened were not specific for the screwing but depending on the individual patients or on the implantations and technical circumstances. The negative results achieved by Engh et al. 1990 could not be recognized (8). He measured a radiological instability of 18% and a technical instability of 28%. What Engh did was measuring simple review photographs and extracting valuable material from them while using geometrical methods. This method shows various measuring mistakes. Therefore Engh's conclusion that the screwing should not be used for implantation because of its displacement in the bones is doubtful. The doubts seem to be supported by the results of our comparison of two series of X-ray photographs with defined different pelvis positions of the same patient. The screwing seemed to be significantly displaced in cranio-medial direction. This was proved by experimental photographs with a pelvis raised to 6 cm in contralateral direction. But the results were a matter of radiological illusion. Radiological migration of the screwing is only provable by complicated X-ray analyses steered with the computer. These big X-ray series are not accessible at the time.

Acetabulum↗

[The cement-free modular revision prosthesis MRP-hip revision stem prosthesis in clinical follow-up].

INTRODUCTION: We present prospective medium-term results of the modular revision prostheses "MRP-TITANIUM". MATERIAL AND METHODS: 45 patients (n = 48 prostheses) were evaluated. The mean follow-up was 4.7 years (min.-max.: 1.0-9.0 years). Pre- and postoperatively the Harris hip score (differentiated to Paprosky I-III) was examined. 66.67 % of the cases had extensive bony defects (> or = Paprosky II b). By means of X-ray examinations, the stability of the prostheses, periprosthetic bone remodelling, the presence of radiolucent lines as well as bone defect regeneration were assessed postoperatively. RESULTS: The mean Harris hip score improved from 25.6 preoperative to 71.4 postoperative (p < or = 0.05). In 44 cases the X-ray showed stable fixation without secondary migration. In one case the stem (stand time 2.36 years) was revised due to secondary migration (> or = 5 mm). The survival rate (Kaplan-Meier) was 97 %. Bone transplantation with consecutive defect regeneration was (n = 30) complete in all cases. In six cases (12.5 %) a postoperative dislocation occurred with subsequent successful closed reposition four times (8.3 %). In two cases (4.2 %) an open reposition was done with correction of the antetorsion angle of the prostheses. CONCLUSION: The "MRP-TITANIUM modular revision prostheses" has proved to be reliable in cases of revision surgery with extensive bony defects. The failure rate was 2.1 % for 48 prospectively examined prostheses.

Aged↗

[Replacement of loose cemented total prosthesis of the hip by cementless prosthesis of the madreporic type (author's transl)].

The authors have inserted 77 cementless prosthesis of the madreporic type in cases of loosening of previously-inserted cemented prosthesis. 66 p. 100 of satisfactory results have been obtained with a follow up of one to six years. The analysis have shown that those with good results achieved stability in the course of time. The technique is fully described. In some cases bone grafting was necessary. In five cases a fracture of the femur was done during the operation. The possibility of a flare-up of infection is discussed. The authors consider that the absence of cement diminishes the liability to septic complications.

Acetabulum↗

[Infected hip joint prosthesis. Viewpoints for 1-stage and 2-stage prosthesis exchange].

When treating an infected hip prosthesis, there are a number of medical, technical and biomechanical considerations. No ideal solution for all problems is available. In individual cases an optimal compromise must be found. The means for curing the infection and the one for maintaining hip stability can counteract each other. Basically, three options are available: removal of the prosthesis without replacement and one- or two-stage replacement. With all three options thorough surgical debridement is vitally important. The introduction of antibiotic cement and cementless titanium implants, together with very effective local antiseptics, has remarkably improved our treatment of this problem. Therefore, removal of infected prostheses without replacement is not as well accepted now as it has been in the past.

Anti-Bacterial Agents↗

Operating room surveillance: a new approach in reducing hip and knee prosthetic wound infections.

A prospective study of surgical wound infections (SWI) in hip prosthesis surgery and total hip and knee replacements at two community hospitals with common surgical staffs was begun in May 1982. The rates of SWI during the first 7 months for four orthopedic surgeons were 9% (3/32) for hip prosthesis surgery and 16.7% (3/18) for total hip and knee replacement, with 12% (6/50) overall. To reduce infections, each orthopedic surgeon agreed to intraoperative surveillance (IOS) of two procedures (hip prosthesis or total hip or knee replacement) by the infection control nurse at each hospital. Significant IOS findings were too many persons in the operating room (five to nine persons), operating room doors opened frequently (25 to 50 times), inconsistent use of prophylactic antibiotics, and excessive conversation. In January 1984, IOS data and recommendations were shared with each orthopedic surgeon, the operating room staff, and the anesthesia personnel. Subsequently, a statistically significant drop in SWI was realized for total hip and knee replacement (1/36 versus 5/36, p = 0.05) and overall (3/73 versus 14/116, p = 0.05). The drop in SWI for hip prosthesis surgery was not statistically significant (2/37 versus 9/80, p greater than 0.10). IOS and individualized communication were effective in reducing SWI.

Aged↗

Investigation of hip joint prosthesis damage.

Following total hip arthroplasty the durability of a prosthetic implant depends on many factors but is generally limited by two types of damage: wearing of frictional surfaces of the acetabular and femoral component as well as the loosening and migration of the "rosthesis-cement-bone" system. Since it is possible to establish a cause-and-effect relationship between these two damage types, the aim of this research is to investigate the phenomena related to the contact surface and their influence on the prosthesis-bone relationship in general for various sizes and conditions of loading of the hip joint. The experimental study was conducted using a Timken testing device modified in such a way that simulation of relative movements of the joint elements was achieved using a mechanism that produces conditions similar to those in the human hip joint. The analysis of obtained measurements showed that actual radii of friction of the hip prosthesis did not correspond to the theoretical ones and that only a small portion of the total friction surface is realized. Variations of the radius of friction for the examined prosthesis type were very large, which changes the hypotheses on the ability of the prosthetic head and the "prosthesis-cement-bone" system to bear a certain amount of load. The construction and design of prosthetic implant components has a significant influence on both the amount of wear at the site of contact and the loosening of prosthesis.

Arthroplasty, Replacement, Hip↗