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A follow-up of 2 years or more on 105 patients with the Modular (Marmor) knee replacement revealed that 88 per cent of the patients had a successful result. The complications and failures are analyzed in depth. Late loosening of the components was not observed except with the 6 mm tibial plateau. Pain relief was dramatic as well as improved function, stability and motion.
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In a prospective study fo the incidence of deep-vein thrombosis in thirty patients undergoing total knee replacement, all patients had clinical examinations and 125I fibrinogen scanning, while those suspected of having deep venous thrombosis also had confirmatory venography. Sixteen (53 per cent) of the thirty patients had thromboembolic disease; nine had thrombi only in the limb operated on; four had bilateral deep venous thrombi; and three had pulmonary embolism. In nine patients who took aspirin regularly the incidence of thromboembolism was 11 per cent, while in the eight who did not take aspirin or any other antiplatelet drug the incidence was 88 per cent, a difference which was highly significant (p = 0.003).
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Early results of 76 geometric total knee replacements were reviewed with assistance from computer analysis. A 92% patient follow-up for one to three years showed an overall satisfactory result with substantial improvement, especially in relief of severe pain. However, several problems are noted, including fractures beneath the tibial plateau and loosening. The long-term results are still unknown. The indications for total knee replacements should remain conservative until long-term results and experience have been achieved.
Prosthetic cruciate ligaments are now used clinically. Long-term results are not yet available and for that reason an attempt has been made to reproduce the clnical situation in dogs. Post-traumatic osteoarthritis was inevitably noted following simple excision of the anterior cruciate ligament in a control group of 10 animals. Different prosthetic materials were used and their breaking point was compared with that of normal anterior cruciate ligaments. The longest follow-up period was 6 months. Although some animals had no clinically demonstrable instability, at autopsy all prosthetic ligaments were noted to have failed. The degree of post-traumatic osteoarthritis was directly related to the duration of follow-up. The causes of failure of the prosthetic ligament do not appear to be related to the method of anchorage to bone but rather to the type of prosthetic material used. Although the tensile strength may occasionally have been sufficient, the materials did not have the required elastic characteristics to meet the physiologic demands of a normal cruciate ligament.
Forty-two months follow-up examinations on 30 total knee arthroplasties revealed the following significant complications: phlebothrombosis, 13 knees (46%); pulmonary embolism 3 patients (11%); asymptomatic loosening, 8 knees (11.4%); symptomatic loosening, 3 knees (4.8%); superficial infections, 4 knees (5.4%); deep infections, 4 knees (5.4%); peroneal palsy, 3 patients (4.3%). Early detection of thrombophlebitis by 125I fibrinogen scan and possible aspirin prophylaxis were evaluated. In view of the limited number of encouraging results, e.g. excellent 58.6 per cent; good 28.5 per cent; fair 5.4 per cent and poor 7.1 per cent, caution is advocated until extensive time elapses for more clinical experience with total knee arthroplasty.
Thirty-six patients with arthrosis of the carpometacarpal joint of the thumb were treated, 19 patients by resecting the trapezium and interposing a tendon, 17 patients by replacing the resected trapezium with silastic prosthesis (Swanson). The follow-up time was in average 22 respectively 44 months; both groups were comparable. The patients treated by resection of the trapezium and tendon interposition were more satisfied and had less pain than those treated by implantation of a Swanson prosthesis. There was no difference in mobility and strength of pinch between the two groups. After resection of the trapezium and tendon interposition the authors found a proximal translocation averaging 7 mm (6 to 14), however these patients had a good functional result and no pain. Five patients had a luxation of the Swanson prosthesis, and four required a second operation.
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Patients with arthritis often want more information about their disease and surgery than physicians realize. They turn to the popular press, which focuses on recent, often untested innovations that capture the imagination. This information is not always consistent with the longer, more mundane perspective of science. There has been promising progress in uncemented arthroplasty, but conventional techniques remain useful. Revolutionary change awaits new materials. Particularly significant advances have enabled surgeons to prevent or rectify complications of reconstructive joint surgery.
The wear of joint prostheses generates wear particles that produce an inflammatory response in the surrounding tissues and may contribute to bone resorption resulting in prosthetic loosening. Although the effects of particles produced from prosthetic materials have been studied extensively in vitro and in vivo, little attention has been paid to the standardisation of methods for the generation and characterization of these particles. This paper describes a reproducible method for generation of metal particles by the abrasive shaking of joint replacement components. Particular attention was given to the production of metal particles that closely resembled particles found around solid and loose human prostheses. To achieve this, particle size, size distribution, chemical composition, and shape were characterized. Particles that were 0.5-3.0 microns in diameter were isolated by differential sedimentation, and the distribution of particle sizes was determined with use of a Coulter Multisizer. Chemical composition was measured by atomic absorption spectrophotometry, and transmission electron microscopy was used to characterize particle shape. The techniques were shown to be reproducible, since there was little variation between batches over a lengthy time period. These or similar methods of particle production and characterization should be an essential part of future in vitro and in vivo studies of wear particles.
Following loosening of total hip prostheses increasing bone resorption occurs around the prosthesis, which can lead to extensive bony defects. In this paper a revision prosthesis for the femur is presented, which is fixed in the distal marrow cavity without cement, bridging the damaged prosthesis bed and stabilizing the femur. Vigorous bony regeneration begins in the resorption defects, which makes good the loss of bone substance. The revision prosthesis described for the cup is also implanted without cement. It allows additional fixation with screws and also onlay grafting, so that even when the acetabulum is badly damaged it is possible to change the prosthesis to obtain a good functional result and also allow recovery of the bone.
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OBJECTIVE: To study the possibility of reconstructing TMJ with a modified three-dimensional adjustable condylar prosthesis (TDACP). METHODS: The modified TDACP was placed immediately after resection of the mandibular ramus and condyle in 3 adult rhesus monkeys. The results were evaluated by radiography, histological and anatomical examinations, as well as chewing function at 3, 6, and 14 months after surgery. RESULTS: Through adjustment the condyle prosthesis could fit exactly, the functions were good, every part of the prosthesis was firm, the screws were osteointegrated, there was no adverse soft tissue reactions and no pathological changes in the TMJ of non-operated opposite condyle. Problems were: the distribution of fixation stress of screws was somewhat unreasonable, the downward sliding of the condyle was limited, there was erosion of the posterior slope of the glenoid fossa, and the articular disc could not keep its in situ place and function. CONCLUSION: The results suggests that the prosthesis needs further improvement.
Reconstruction of the hip joint by a saddle prosthesis after excision of a malignant pelvic tumor is a relatively new method, which thus far has been mainly used for revision of infected hip arthroplasties. One patient with a metastatic cystosarcoma phyllodes and one patient with a chondrosarcoma of the pelvis were treated by local resection and reconstruction with a saddle prosthesis. Although the patient with the metastatic cystosarcoma phyllodes died 9 months after surgery due to metastatic disease, both patients had early recovery, with no difference in leg length and obtained early painless complete weight bearing with satisfactory functional result. These two case reports clearly illustrate the usefulness of the saddle prostheses in limb saving surgery for malignant tumors of the pelvis.
INTRODUCTION: Prosthetic replacement of the metacarpophalangeal joints of long fingers is a problematical technique for the surgeon. The aim of the present study was to examine and compare, by means of finite element analysis, stress distribution in a normal metacarpophalangeal joint and to compare this with the findings in a similar joint with a prosthesis in order to better determine the risk of aseptic loosening, and also to examine possible solutions to limit these risks. METHOD: Finite element modelling was carried out using Abaqus software. Various criteria were taken into account including anatomical data, stress distribution, mechanical characteristics of the materials used, and different positions of the phalanx. RESULTS: A comparison of the results showed two significant stress distribution factors, i.e., a reduction of normal stress in the cortical bone of the finger fitted with a prosthesis; and the appearance of a flexion moment which completely modified the stress distribution throughout the metacarpal and therefore also in the opposite phalanx. DISCUSSION: To reduce the risk of aseptic loosening, two solutions were proposed: a) to reduce Young's module. The problem which arises, as in the case of total hip prosthesis, is that of finding a material with a Young's module which is closer to that of cortical bone, and which at the same time has a high elastic limit and breakage point and good biocompatibility; b) to reduce the inertia of the prosthesis, which seems the more likely of the two propositions, as it is based on the results of the modelling. The inertia of the prosthesis on stress distribution can be reduced by modifying two parameters, namely by producing a hollow section and shortening the structure of the prosthesis.
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