Mechanical considerations in impaction bone grafting.
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In impaction grafting of contained bone defects after revision joint arthroplasty the graft behaves as a friable aggregate and its resistance to complex forces depends on grading, normal load and compaction. Bone mills in current use produce a distribution of particle sizes more uniform than is desirable for maximising resistance to shear stresses. We have performed experiments in vitro using morsellised allograft bone from the femoral head which have shown that its mechanical properties improve with increasing normal load and with increasing shear strains (strain hardening). The mechanical strength also increases with increasing compaction energy, and with the addition of bioglass particles to make good the deficiency in small and very small fragments. Donor femoral heads may be milled while frozen without affecting the profile of the particle size. Osteoporotic femoral heads provide a similar grading of sizes, although fewer particles are obtained from each specimen. Our findings have implications for current practice and for the future development of materials and techniques. (+info)
Total joint replacement: implication of cancelled operations for hospital costs and waiting list management.
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OBJECTIVE: To identify aspects of provision of total joint replacements which could be improved. DESIGN: 10 month prospective study of hospital admissions and hospital costs for patients whose total joint replacement was cancelled. SETTING: Information and Waiting List Unit, Musgrave Park Regional Orthopaedic Service, Belfast. PATIENTS: 284 consecutive patients called for admission for total joint replacement. MAIN MEASURES: Costs of cancellation of operation after admission in terms of hotel and opportunity costs. RESULTS: 28(10%) planned operations were cancelled, 27 of which were avoidable cancellations. Five replacement patients were substituted on the theatre list, leaving 22(8%) of 232 operating theatre opportunities unused. Patients seen at assessment clinics within two months before admission had a significantly higher operation rate than those admitted from a routine waiting list (224/232(97%) v 32/52(62%), x2 = 58.6, df = 1; p < 0.005). Mean duration of hospital stay in 28 patients with cancelled operations was 1.92 days. Operating theatre opportunity costs were 73% of the total costs of cancelled total joint replacements. CONCLUSION: Patients on long waiting lists for surgery should be reassessed before admission to avoid wasting theatre opportunities, whose cost is the largest component of the total costs of cancelled operations. (+info)
Extensible endoprostheses of the humerus after resection of bone tumours.
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We carried out extensible endoprosthetic replacement of the proximal or total humerus in 18 children aged between six and 12 years, after resection of primary bone tumours mainly for osteosarcoma and Ewing's sarcoma. In 11 patients we performed 44 lengthening procedures, with an average of two per child annually and a mean total extension of 29.9 mm per patient. We were able to achieve lengthening of the operated limb with few complications and a mean functional rating of 79.3% according to the Enneking system. Progressive lengthening of these prostheses does not adversely affect the overall function of the arm, and superior subluxation of the head of the prosthesis has not been a problem. (+info)
Screening for Staphylococcus epidermidis markers discriminating between skin-flora strains and those responsible for infections of joint prostheses.
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Fifty-four Staphylococcus epidermidis strains responsible for infections of joint prostheses and 23 strains isolated from skin flora were studied for markers of virulence, to discriminate invasive strains from normal flora. They were screened for binding to polystyrene and matrix proteins and for the presence of staphylococcal genes involved in adhesion. The ica operon involved in biofilm formation was the only marker discriminating between these 2 categories of strains. (+info)
Silicone lymphadenopathy mimicking a lymphoma in a patient with a metatarsophalangeal joint prosthesis.
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With lymph node enlargement, the possibility of a malignant process such as metastatic carcinoma or lymphoma needs to be excluded. This report describes a 47 year old woman with inguinal lymph node enlargement initially suspicious for lymphoma. Fine needle aspiration findings favoured reactive hyperplasia, but a malignant process could not be excluded. The final histological diagnosis was a foreign body granulomatous inflammatory response as a result of regionally disseminated silicone particles from an over looked metatarsophalangeal joint prosthesis. Because of the large number of joint prostheses world wide, it should be kept in mind that migration of wear particles can create granulomatous inflammation and node enlargement. (+info)
The management of local complications of total hip replacement by the McKee-Farrar technique.
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One thousand and forty-two McKee-Farrar prostheses of the present design inserted in Norwich from January 1965 to December 1972 have been reviewed retrospectively to determine the incidence of complications needing revision. Of prostheses implanted for more than two years, 6-6 per cent needed revision for loosening (cup 3-5 per cent; stem 2-2 per cent; both components 0-9 per cent). Of the total number, 2-3 per cent became infected and 1-9 per cent dislocated. Most dislocations needed only a single closed reduction but 0-8 per cent were revised. The outcome of revision operations was also assessed. Of revisions for loosening, 40 per cent needed no further operation but 23 per cent required excision; pelvic fracture or bone destruction around the components made success unlikely. Revisions for dislocation were disappointing. Of all revisions 17 per cent became infected. Excision arthroplasty is better than a series of failed revisions in an elderly patient. (+info)
The Walldius hinge arthroplasty.
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Eighty-three Walldius arthroplasties, performed by one surgeon as salvage operation on the knee joint between 1966 and 1972, were independently reviewed. The fifty-seven living patients with sixty-seven arthroplasties were interviewed and examined and the clinical records of the deceased patients were inspected. Sixty-seven arthroplasties (81 per cent) were successful and sixteen failed (19 per cent). Acrylic cement was used to secure the prosthesis on eight occasions only. There were two primary infections (2-4 per cent) and two delayed (2-4 per cent). Major loosening occurred in three arthroplasties (3-6 per cent). Minor loosening was compatible with a good result. Arthrodesis was successful on the two occasions on which it became necessary to remove the implant. There were no disasters. On the basis of these results it is considered that the Walldius arthroplasty can justifiably be offered as an alternative to primary arthrodesis of the knee. (+info)
Link arthroplasty of the metacarpo-phalangeal joints. A preliminary report of a new method.
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Link arthroplasty is a system of joint replacement in which the joint is left almost intact with no great removal of bone. It is based on a two-piece self-locking hinge slotted into the metacarpal head and phalangeal shaft. The operation is simple and no special instruments are needed. The preliminary follow-up of fifty-four metacarpo-phalangeal joint replacements showed thirty-five good and sixteen fair results. (+info)