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[Sensitivity to constituents of bone cement in a patient with joint prosthesis].

Failure to tolerate prosthetic material can lead to a variety of clinical findings. A 55-year-old woman had a total replacement of the right knee. Two weeks later she developed pruritic skin lesions over the joint, as well as pain and impaired function. Allergic testing showed clinically relevant Type IV sensitization to methylmethacrylate, as well as to various formulations of the bone cement, including one with an added antibiotic. The symptom complex of pruritic skin lesions in the area of the prosthesis, pain and disability, as well as relevant Type IV sensitization justified replacing the prosthesis.

Bone Cements↗

[What retropatellar changes result by implantation of a superficial knee joint prosthesis?].

The aim of this study was to evaluate the retropatellar pressure, force, and contact area in cases of knee arthroplasty compared to knees without arthroplasty. We examined six leg specimens before and after knee arthroplasty. The modified Thiel fixation was used, and arthroplasty was the Genesis I without patellar implant (Fa. Smith & Nephew, Schenefeld). Contact measurements were performed with pressure-sensitive film (Fuji Prescale type "super low") in 45 degrees, 60 degrees, 90 degrees, and 120 degrees knee flexion. The results were evaluated with special software, "Pressure Imaging and Analyzing System FPD-901 Series". The leg was exarticulated in the hip joint and the knee joint was opened from a suprapatellar approach. The film was placed at a defined area between the facies patellaris of the femur and facies articularis of the patella. Instantaneous pressure was measured during a time of 5-s pressure increase and a further 5 s. A force of 280 N was applied to the quadriceps muscle. Before knee arthroplasty, the contact area measured 154.3 mm2, the average pressure was 1.14 MPa, the force 182.13 N. After knee arthroplasty, the contact area was 119.94 mm2, the average pressure 1.522 MPa, the force 180.98 N. Following knee arthroplasty the contact area decreased significantly (P = 0.015), and the average (P = 0.0001) and maximum pressure (P = 0.0003) increased significantly. The force did not change significantly (P = 0.7642). The choice of the knee arthroplasty implant and approach to the knee joint should be considered in order to achieve an increased retropatellar contact area thus preventing smaller contact areas than before knee arthroplasty. The increased contact area could also prevent increasing retropatellar pressures after knee arthroplasty and further complications.

Aged↗

[Intraoperative Doppler ultrasound of the femoral vein for maintaining venous patency in hip joint prosthesis implantation].

PROBLEM: Is the femoral vein occluded during insertion of the stem? Can thrombembolic complications be reduced by avoiding occlusion? METHODS: In a prospective randomized study 160 cemented stems were implanted from the anterolateral approach: 76 patients had conventional figure-of-four positioning of the femur, 84 patients had a modified position according to the blood flow registered by intraoperative Doppler sonography. RESULTS: 68.7% of the 84 femoral veins were completely occluded in the figure-of-four positioning. Only by reduction of this position and soft tissue release, venous flow could be demonstrated by sonography. Increased body mass index (BMI) and age correlated with occlusion (p = 0.0001 and p < 0.05). In the 84 patients no thrombembolic complication was found. In the control group 3 deep thromboses were revealed by venography (p = 0.105). CONCLUSION: Doppler sonography helps guaranteeing venous drainage. A modified leg position should be aimed at especially in increased BMI and age.

Aged↗

[Knee joint prosthesis implantation after fractures of the head of the tibia. Intermediate term results of a cohort analysis].

A significant number of patients with operated tibial plateau fractures develop osteoarthritis and require total knee arthroplasty. In cases of primary osteoarthritis the results are generally good. However, it is not known whether patients with post-traumatic osteoarthritis obtain comparably favorable results. In a retrospective study we analyzed 72 patients who had undergone a self-aligning (SAL) total knee arthroplasty. Ten patients received arthroplasty due to sequelae of a tibial head fracture (group I). The median time to follow-up in this group was 30 months. Clinical and radiological evaluation was based on the Knee Society Clinical Rating System. The score comprises pain, range of motion, stability, and function. We defined the axis and possible loosening by radiological examination. For comparative descriptive statistics, a cohort of patients was chosen who had received an arthroplasty because of primary gonarthrosis (group II, 76 arthroplasties in 62 patients). The median time to follow-up in this group was 46.5 months. Three patients in group I underwent revision surgery, four patients displayed severe functional deficits and pain, and one patient had a varus deformity with good clinical function. This corresponded to an early complication rate of 27% and a late complication rate of 36%; a relevant instability or loosening of the components did not occur in this group. In group II the incidence of early complications was 10%. The patients in group I reached a mean value of 153 points using the rating system vs 167 points in group II. Analyzing the clinical parameters of the score, we found that patients in group I experienced significantly more pain, thereby affecting functions of daily living, such as walking and climbing stairs. Because of the small number of patients in group I, conclusions can only be drawn to a limited extent. However, we saw that these patients displayed a higher incidence of complications and performed less well. This has to be taken into consideration and discussed prior to surgery.

Activities of Daily Living↗

[Survival time of loosened cemented hip joint prosthesis].

With the help of survival curves we analysed in 111 aseptically loosened endoprostheses of the hip the function of the implants. We found a mediate rate of 6.04 years for the total survival time. We discussed two peaks after 2 years and between the 5. and 8. year after the implantation. There was a reduction of the survival time in the upper age and in the right side of the implantation. The second implantation had a worse prognosis compared with the first implantation (medial rate of 2.38 to 6.6 years). Important causes for the loosening were an enlarged angle of the hip socket and a varus position of the stem. But the survival curves showed in connection with these factors no statistical significance. We found a reduction of the survival time in the cases with no complete boundary of the bone cement in the proximal part of the stem.

Age Factors↗

An estimation of fatigue life for a carbon fibre/poly ether ether ketone hip joint prosthesis.

A fracture mechanics approach was applied to estimate the life of a prosthesis injection moulded from short carbon fibre reinforced poly ether ether ketone. Flexural modulus and strength, fracture toughness, fatigue endurance limit, fatigue crack growth rate and threshold stress intensity factor were determined. The dimensions of the test pieces were selected to yield fibre orientation and fibre length distributions similar to those obtained in the prosthesis. Stress levels generated in the prosthesis under different activities were estimated by conducting three-dimensional finite element analysis. It was shown by a fracture mechanics approach that a fatigue failure due to the propagation of an embedded elliptical slit, under these stresses, would be unlikely for a crack length smaller than 1.85 mm. However, the cement would fail under the same conditions, irrespective of the type of the prosthesis employed.

Benzophenones↗

[Correlation of electromyography and clinical results after bicondylar knee joint prosthesis implantation].

AIM OF THE STUDY: To investigate clinical findings in patients receiving bicondylar sledge prostheses, and their correlation with electromyographic measurements in comparison with healthy volunteers. MATERIAL AND METHODS: An average of 31.9 months after implantation of a bicondylar sledge prosthesis, 15 patients were clinically examined and compared with 11 control subjects. Electromyographic measurements of the rectus femoris, vastus medialis and lateralis, semitendinosus, biceps femoris, tibialis anterior, and gastrocnemius muscles were obtained. RESULTS: All clinical scores were significantly poorer in the patient group. The activity of the vastus lateralis was significantly reduced. The activity in the lower leg of the operated side was significantly higher than in the control group. Significant differences were found in the tibialis anterior and gastrocnemius muscles between controls and patients. Analysis of the correlation between the clinical scores and the electromyographic measurements showed no significance. CONCLUSION: The clinical results correlated only slightly with the electromyographic activity of the muscles investigated. The commonly presumed quadriceps insufficiency was not confirmed.

Aged↗

[Results of testing a non-protrusion hip joint prosthesis].

To prevent protrusion of the socket of an endoprosthesis into the pelvis, an experimental nonprotrusion endoprosthesis has been designed and tested. The endoprosthesis is of novel design; however, its production is rather simple. The efficiency of its use is strongly evidenced by reasonably long-term experiments. Comparing the results of use of a routine design endoprosthesis versus the nonprotrusion one under the same loading conditions has shown that the novel endoprosthesis is better.

Animals↗