Long-term results of cemented arthroplasty. Analysis of complications fifteen years after operation.

Three retrospective long-term studies were initiated to analyze aseptic loosenings in cemented total joint arthroplasties. The 15-year results of more than 3566 total hip arthroplasties show different causes for cup and stem loosening and different loosening behavior in the various age and diagnosis groups. The excellent long-term results of total knee arthroplasty show that bone cement alone cannot be made responsible for the many revisions required in this type of surgery. The authors observed and confirmed statistically that long-lasting duration of the implant depends to a great extent on the surgeon's own experience and care while using a highly developed prosthesis system.

[Follow-up of hip endoprostheses following completion of true stress conditions over a 10-year period]. / Verlaufsbeobachtung von Hüftendoprothesen nach Abschluss realer Belastungsbedingungen von 10 Jahren.

Results of a long term followup with total hip-replacement of the Endo-Klinik are presented. The analysed data-material exhibits a relative homogeneity because of a large series of one system of prostheses and homogeneous technique in surgery. Thus, analytic statistical methods (life-tables and regression models) could be used. In this way, prognostic factors on the durability of total hip replacement could be determined. These are essentially: long practical experience of the surgeon with one matured prosthesis-system, type of hip-joint disease, and the age of the patient. It is assumed, that in well organized special centres for joint replacement the failure rate could be reduced generally.

[Early experiences with the total mini hip-joint endoprosthesis (St. George Mini model) in dysplasia coxarthrosis]. / Früherfahrungen mit der Mini-Hüftgelenkstotalendoprothese (Modell "St. Georg-Mini") bei Dysplasie-Coxarthrose.

The results of 106 patients with osteoarthritis secondary to severe congenital hip dysplasia and dislocations of the hip operated at the Endo-Klinik were evaluated after an average follow up of 21 months. 142 "St. Georg-Mini" total hips were implanted employing Refobacin-Palacos R. The clinical results were graded as "combined performance" which considered hip pain, walking distance, hip mobility and walking aids. In 93% of the cases "combined performance" was improved at follow up and 91.7% of the patients were satisfied with the result. The early (during hospitalization) and late (after discharge from hospital) complication rate which had an influence on the result at follow up was 2.1% (n = 3) and 3.5% (n = 4) respectively. There were no deep infections. An extended indication for total hip arthroplasty also for younger patients with severe osteoarthritis secondary to hip dysplasia is discussed and can be advocated.

Antibiotic-loaded acrylic cement: current concepts.

Antibiotic-loaded acrylic cement has been used routinely since 1972 at the authors' hospitals, where a series of some 22,000 joint arthroplasty operations was performed from 1964-1983. The current status of the material is presented with up-to-date follow-up statistics on prophylactic therapy and on established deep infections. The results of 869 exchange arthroplasties are compared with results published in 1981. In the future, results will be presented in the form of survival curves. The method by which survival tables and curves are constructed is critical. Investigators should use survival curves for ease of comparison and because of the wide range of possibilities in an analysis of covariable factors. A retrospective actuarial analysis was made of 825 one-stage reimplantations in which antibiotic-loaded acrylic cement was used for infected total hip arthroplasties. Staphylococcus aureus was the most commonly encountered organism. Failure rates of prostheses infected by S. aureus, S. species, and anaerobic corynebacteria did not differ statistically. A factor that significantly contributed to failure of this method of treatment was Pseudomonas infection. By actuarial analysis five years after operation, a success (survival) rate of 77% was calculated.

Pharmacokinetic study of gentamicin-loaded cement in total hip replacements. Comparative effects of varying dosage.

A randomised, double-blind study was performed in two groups of 15 patients undergoing total hip replacements, using antibiotic-loaded acrylic cement containing 0.5 g and 1.0 g gentamicin base respectively per 40 g pack of powdered polymer. Postoperatively, the gentamicin levels in the blood, in the urine and in the wound drainage fluid were measured. In both groups of patients, the serum gentamicin concentrations were low whereas the wound drainage fluid contained highly effective antibacterial concentrations. Serum, urine and wound secretion levels showed approximately two-fold higher concentrations in the group of patients receiving the higher gentamicin load.

Management of infected prostheses.

A retrospective actuarial analysis of 825 onestage reimplantations using antibiotic-loaded acrylic cement for infected total hip replacements is presented. Staphylococcus aureus was the most commonly encountered organism. Failure rates of prostheses infected by S. aureus, Staphylococcus species, and anaerobic Corynebacteria did not differ statistically. A factor that significantly contributed to failure of this method of treatment was Pseudomonas infection. By actuarial analysis (with a twoyear minimum followup) at five years after operation 23% of the implants had failed, and at 11 years, 50%. This compares to a 77% success rate implied by conventional arithmetic.

Management of deep infection of total hip replacement.

Exchange operation is recommended as the treatment of choice for most deep infections involving a total hip replacement. This revision arthroplasty comprises, in one stage, excision of soft tissue, removal of implant and cement, replacement with an appropriate implant using Palacos R acrylic cement loaded with an appropriate antibiotic and, more recently, systemic antibiotics. During our first 10 years without systemic antibiotics we have achieved an overall 77 per cent success rate from a first attempt in 583 patients and a 90 per cent success rate after subsequent exchange procedures. Morbidity is significant but acceptable. Success is defined as control of infection, no loosening, and useful function. The factors associated with failures include, in particular, specific infections (Pseudomonas group, Streptococcus group D, Proteus group, and Escherichia coli), delay in operation and inadequate antibiotic dosage in the cement.

[Release of 14c-chloramphenicol in the rabbit femur implanted with polymethylmetacrylate (author's transl)]. / Uber die Freisetzung von 14C-Chloramphenicol aus in den Kaninchenfemur implantiertem Polymethylmethacrylat

In vitro studies and animal experiments were started for the purpose of following the migration of chloramphenicol marked with 14C from polymerised polymethylmetacrylate cylinders. Test-cylinders were submerged in a physiological saline solution and the 14C concentration followed over a period of 34 days. Two series were started with the cylinders being submerged at intervals of 5 and 40 min after the start of polymerisation. These in vitro studies showed that initially the migration of active substances marked with 14C from the plastic cylinders was extremely high but remained then constant over the whole test period. Over a period of at least 20 days a higher 14C migration was evident in those cylinders submerged in the elution 5 min after the start of polymerisation. In our in vivo studies we implanted test-cylinders into the femur of rabbits. The migration of active substances marked with 14C resulted in 14C-concentrations being present in the surrounding tissues. During the phase of exudation, depending on the operative process, the concentration increased and reached values that remained constant during the phase of recanalisation of the surrounding tissues over a period of up to 6 weeks. Thereafter the concentration of active substances fell. The max. concentration rates of active substances within the boundary layer were between 15 and 20 mug/g humidity weight. After 8 weeks we found concentration rates of approx. 1 mug/g humidity weight. On examining the 14C distribution within the implanted plastic cylinders we observed that in the course of time the boundary layer increased in thickness and a concentration gradient towards the centre had developed. The spread of diffusion gradually seized the deeper layers so that a long-lasting presence of active substances may be expected.

Statistics of total knee replacement: partial and total knee replacement, design St. Georg: a review of a 4-year observation.

Since 1969, we have used 2 different types of knee prostheses to reconstruct arthritic knees. The surface replacement prosthesis (sledge) is indicated where ligamentous stability is present and angular deformity is not severe. In addition, the sledge prosthesis may be implanted with good results in selected acute comminuted tibial plateau fractures. The total hinged prosthesis of metal design is recommended in knees which are severely deformed, and unstable, and therefore not suitable for the sledge prosthesis. Marked relief of pain was the most significant result in our patients. Residual knee pain was most frequently due to patello-femoral pain and, when severe, this was satisfactorily controlled by performing a patellectomy. Motion was usually maintained at the preoperative range or improved, mainly by reducing or eliminating the knee flexion contracture. In a high percentage, the unicompartmental sledge prosthesis has given excellent results. However, we tend to insert a bi-compartmental sledge prosthesis because experience has shown that even slight damage of the articular surfaces of the opposite side is likely to further deteriorate rapidly. Although a significant number of complications occurred, these have been minimized by further conservative and operative treatment. We anticipate a further reduction in complications based on our initial experience, and prosthetic revisions.