Femoral prosthetic heads and their significance in polyethylene wear.
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We used scanning electron microscopy to perform an ultrastructural analysis and two optical interferometric profilers to measure roughness on 40 prosthetic femoral heads. We expressed roughness as Ra (roughness average) value and Rsk (roughness skewness) value. Our results show that in order to obtain an ideal surface finish a low or not very high Ra value and a negative Rsk value are needed. The presence of depressions or holes (rather than scratches) with smooth (rather than sharp) edges seems to improve the lubrication and wettability properties. (+info)
Comparison of in vivo wear between polyethylene liners articulating with ceramic and cobalt-chrome femoral heads.
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At yearly intervals we compared the radiological wear characteristics of 81 alumina ceramic femoral heads with a well-matched group of 43 cobalt-chrome femoral heads. Using a computer-assisted measurement system we assessed two-dimensional penetration of the head into the polyethylene liner. We used linear regression analysis of temporal data of the penetration of the head to calculate the true rates of polyethylene wear for both groups. At a mean of seven years the true rate of wear of the ceramic group was slightly greater (0.09 mm/year, SD 0.07) than that of the cobalt-chrome group (0.07 mm/year, SD 0.04). Despite the numerous theoretical advantages of ceramic over cobalt-chrome femoral heads, the wear performance in vivo of these components was similar. (+info)
The role of subchondral insufficiency fracture in rapid destruction of the hip joint: a preliminary report.
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OBJECTIVE: The pathophysiology of rapidly destructive arthrosis of the hip joint (RDA) is unknown. The purpose of this study was to document cases of subchondral insufficiency fracture of the femoral head, which has similar clinicoradiologic features to those of early-stage RDA. METHODS: This study was based on a retrospective review of 11 cases of subchondral insufficiency fracture of the femoral head that were confirmed histopathologically and for which radiographs both at the onset of hip pain and at the time of surgery were available. RESULTS: All patients were > 60 years of age (range 61-78 years, mean age 69), and 9 were women. On plain radiographs, the normal joint space had undergone rapid narrowing and/or disappeared within 9 months (mean 5.8 months). Magnetic resonance imaging, available in 2 cases, showed a pattern of bone marrow edema from the upper portion of the femoral head to the intertrochanteric region, with an associated focal low-intensity band on T1 paralleling the articular surface. In all cases, evidence of subchondral insufficiency fracture was confirmed histopathologically. In addition, in the marrow space, there were several round-to-oval granulomatous foci, which consisted of amorphous debris, fragmented bone, and articular cartilage surrounded by reactive histiocytes and giant cells. All 11 patients were osteopenic, as shown both radiologically and histopathologically. CONCLUSION: Subchondral insufficiency fracture resulting from osteopenia may lead to a rapid breakdown of the hip joint. (+info)
Ultrastructural evidence for vulnerability of hip region to fracture in the aged.
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OBJECTIVE: To probe ultrastructurally into the mechanism why hip region is the predilected site of fracture in aged people, yet with femoral head exempted. METHODS: Proximal femoral ends were collected from 14 aged people, who had undergone endoprosthetic replacement for intra-capsular fracture of the femoral neck, and from 7 young men died of brain injury. These specimens were processed and subjected to scanning electron microscopic and transmission electron microscopic observation for bone resorption. RESULTS: As compared with the specimens from young men, there were three types of bone resorption in the proximal femoral ends of aged people, i.e. osteoclastic resorption and osteocytic resorption of the trabeculae of cancellous bone, and osteoclastic resorption of Haversian systems of the cortical bone. In the proximal femoral ends of the young men, the arch structures composed of trabeculae in the femoral head showed a round or roundish configuration, while those at the femoral head-neck junction revealed an oval profile and those in the femoral neck exhibited a narrow oval contour. In the proximal femoral ends of the aged people, the morphological characteristics of the trabecular arch remained unchanged despite overt bone resorption. CONCLUSIONS: Vulnerability of hip region to fracture in aged people is due to a decline in the structural strength of bone tissues of the proximal femoral ends resulting from osteoclastic and osteocytic resorption. The round and roundish trabecular arch of the femoral head can bear external forces from different directions, so that no fracture occurs here, while the oval and narrow oval arches at the head-neck junction and in the neck region fail to stand the horizontal external forces (abduction and adduction injuries), thereby fracture easily happens. (+info)
Therapeutic benefit of a dissociated glucocorticoid and the relevance of in vitro separation of transrepression from transactivation activity.
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Glucocorticoids (GCs) are the mainstay of asthma therapy; however, major side effects limit their therapeutic use. GCs influence the expression of genes either by transactivation or transrepression. The antiinflammatory effects of steroids are thought to be due to transrepression and the side effects, transactivation. Recently, a compound, RU 24858, has been identified that demonstrated dissociation between transactivation and transrepression in vitro. RU 24858 exerts strong AP-1 inhibition (transrepression), but little or no transactivation. We investigated whether this improved in vitro profile results in the maintenance of antiinflammatory activity (evaluated in the Sephadex model of lung edema) with reduced systemic toxicity (evaluated by loss in body weight, thymus involution, and bone turnover) compared with standard GCs. RU 24858 exhibits comparable antiinflammatory activity to the standard steroid, budesonide. However, the systemic changes observed indicate that transactivation events do occur with this GC with similar potency to the standard steroids. In addition, the GCs profiled showed no differentiation on quantitative osteopenia of the femur. These results suggest that in vitro separation of transrepression from transactivation activity does not translate to an increased therapeutic ratio for GCs in vivo or that adverse effects are a consequence of transrepression. (+info)
Physeal dysplasia with slipped capital femoral epiphysis in 13 cats.
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Separation of the femoral capital epiphysis is associated with severe trauma in most species. This report describes 13 cats with slipped capital femoral epiphysis characterized by a distinctive lesion in the physeal cartilage. The lesion consists of irregular clusters of chondrocytes separated by abundant matrix on both the epiphyseal and metaphyseal side of the cleavage site. The affected population in this study is 85% male, 90% overweight, 23% Siamese, and 4.5-24 months old. The histopathology and demographics are similar to slipped capital femoral epiphysis in humans, which most often affects overweight adolescent boys. (+info)
Avascular necrosis of the femoral head: MR imaging with radiological and histological correlation.
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OBJECTIVE: To assess the value of MR in the diagnosis of avascular necrosis (AVN) of the femoral head. METHODS: MR images in 34 consecutive patients (26 men and 8 women) with AVN (57 hips) were reviewed. All lesions were confirmed by radiographic, radionuclide, computed tomographic, and/or histologic examination. Eleven specimens were obtained after total replacement of the hip. Four hips underwent biopsy. All MR images were obtained using a 0.35 T superconductive imaging unit with SE sequence. Specimens were cut coronally into 5 mm thick section and radiographs were obtained. RESULTS: There were four types of MR patterns of AVN. Type one appeared liner or patchy low signal area in the superoanterior portion of the femoral head. In type two, a band or ring of low signal intensity was found surrounding a central area of high signal intensity on T1WI and intermediate signal intensity on T2WI. The low signal band or ring consisted of thickened trabecular bone, mesenchymal and fibrous tissue, and amorphous acidophilic cellular debris. The central zones within the ring were composed of necrotic bone and marrow that had not been reached by the repair process. In type three, the focal subchondral region showed intermediate signal intensity on T1WI and high signal on T2WI surrounded by a low signal ring. The low signal ring consisted of thickened trabecular bone and little mesenchymal tissue. The central area was composed of mesenchymal tissue rich in capillaries and cystic necrotic zones. In type four, the signal intensity of femoral head was inhomogeneous on both T1WI and T2WI. There were low signal bands in the femoral neck surrounding the necrotic zone. Only limited areas of some lesions had signal intensity isointense with fat on T1WI and T2WI. The inhomogeneous area of low signal intensity consisted of a mixture of necrotic bone and marrow, amorphous cellular debris. The first type of MR pattern corresponded to the early stage of radiograph, and the third type of MR pattern to stage 5. The second and fourth type of MR patterns correlated less with the radiographic stage. CONCLUSIONS: MR imaging plays an important role in the diagnosis of AVN of femoral head especially in the early detection of AVN. The MR patterns of AVN is not correlated with radiographic stages exactly. (+info)
Trochanteric rotational osteotomy for osteonecrosis of the femoral head.
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The rate of success of transtrochanteric rotational osteotomy for osteonecrosis of the femoral head may be improved if patients are preselected using MRI. We have used three criteria for selection for osteotomy (i) minor collapse of the infarcted area, loss of congruity or the crescent sign, without narrowing of the joint space or acetabular involvement (ii) patients younger than 55 years and with a painful hip (iii) patients with an intact area constituting an arc of more than 120 degrees between the central vertical line of the femoral head and the posterior or anterior margin of the necrotic portion as seen on a midsagittal MRI. Seventeen patients were selected, with a follow-up of more than 42 months. A bone scan four weeks after operation showed adequate perfusion of the proximal segment in all hips. The hip score of Merle d'Aubigne et al improved from 13.5 points before operation to 17.2 points at the latest follow-up. Further collapse of the femoral head did not occur. The use of MRI instead of plain radiographs for the selection of patients has improved the success rate of transtrochanteric rotational osteotomy. (+info)