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Biomedical subjects

T W Bauer

Publications and source records attributed to T W Bauer.

At least 55 records · Page 3Linked to original sources
PubMed1996

Comparison and quantitation of wear debris of failed total hip and total knee arthroplasty.

To compare the physical properties of debris particles associated with failed total hip and total knee arthroplasty, we applied a recently developed assay to electronically characterize the size, number, and composition of debris particles isolated from tissues adjacent to failed implants. We identified 21 samples (from 20 patients) of hip synovia and 35 samples (from 32 patients) of knee tissues that had been obtained at the time of revision arthroplasty. There were 12 females and 9 males in the hip group, and 16 females and 19 males in the knee group. Primary arthroplasty was performed for osteoarthritis (OA, 15 cases) or rheumatoid arthritis (RA, 6 cases) in the hip, and for OA (23) or RA (12) in the knee. Patients ranged in age from 23 to 85 (mean 59 years) for total hip, and from 27 to 84 (mean 61 years) for total knee arthroplasty. Implantation duration was from 5 to 123 months (mean 37.8) for total hip, and from 11 to 123 months (mean 63.1) for total knee arthroplasty. All of the implants were composed of cobalt-chromium alloy articulating with ultrahigh-molecular-weight polyethylene. The number of particles smaller than 10 microns ranged from 1.04 x 10(8)/g to 1.91 x 10(10)/g in the hip, and from 6.69 x 10(8)/g to 2.13 x 10(10)/g in the knee. Energy-dispersive X-ray spectroscopy and polarized light analysis showed both polyethylene and metal particles in most cases. The mean diameter of particles smaller than 10 microns was 0.72 +/- 0.2 microns in the hip, and 0.74 +/- 0.1 microns in the knee. Evaluation of particles larger than 10 microns showed a larger range of particle size in knee tissues (maximum 6.1 mm, mean 283 microns), than in the hip tissues (maximum 826 microns, mean 81 microns) (p < 0.001). Very small particles are common in both groups, but it appears that a larger range of particle sizes is present adjacent to failed knee than to failed hip prostheses. The higher frequency of large particles in failed knee prostheses probably reflects the perceived higher rate of delamination and fragmentation of tibial and patellar compared to that of acetabular polyethylene.

Adult↗
PubMed1996

Influence of biomaterial surface texture on bone ingrowth in the rabbit femur.

The purpose of this study was to examine both the histologic and the mechanical characteristics of bone apposition to an experimental surface, arc-deposited titanium, in a rabbit model and to compare them with those of four previously studied surfaces: one layer of cobalt-chromium beads, three layers of cobalt-chromium beads, plasma-sprayed cobalt-chromium, and uncoated titanium alloy. Bilateral cylindrical implants were press-fit into the lateral femoral condyles of 70 adult New Zealand White rabbits, which were allowed unrestricted activity and then killed at 6 or 12 weeks. The distal femora were harvested, radiographed, and prepared for either mechanical or histologic evaluation. All of the implants with coated surfaces had significantly greater shear strength than the implants of grit-blasted titanium alloy after both 6 and 12 weeks. After 6 weeks, maximum bone apposition occurred in the beaded surfaces. After 12 weeks, the shear strengths and bone apposition of implants of arc-deposited titanium and of one and three layers of cobalt-chromium beads were significantly greater than those of implants of plasma-sprayed cobalt-chromium and grit-blasted titanium alloy. The histologic studies correlated with the mechanical results. After 12 weeks, the bone apposition and mechanical stability of arc-deposited titanium were similar to those of a single layer of beads. There appeared to be no advantage to multiple layers of beads, and the plasma-sprayed cobalt-chromium and grit-blasted titanium surfaces showed lower shear strength and bone apposition than the other groups.

Analysis of Variance↗
PubMed1996

Isolation and quantitation of debris particles around failed silicone orthopedic implants.

Silicone elastomer implants have a relatively low rate of complications, but inflammatory reactions to debris have been reported. To characterize the size and number of debris particles, we isolated and quantified the debris particles present in the periarticular tissues of 10 patients with failed silicone wrist, elbow, or finger implants. Five rheumatoid synovia without implants were used for negative controls. The number of particles ranged from 0.99 to 24.8 x 10(9) per gram (dry weight) of tissue, and nearly all particles were silicone, as determined by x-ray spectroscopy. The implantation duration ranged from 3.2 to 10.6 years, and for the five wrist implants, the number of particles correlated with duration in vivo. The particles were small (mode particle diameter was 0.59 +/- 0.057 micron). These results suggest that billions of particles, most of which are smaller than 1 micron, are present adjacent to failed silicone implants, and may be associated with inflammation and bone resorption.

Elbow Joint↗
PubMed1996

Dedifferentiated chondrosarcoma with rhabdomyosarcomatous differentiation.

Dedifferentiated chondrosarcomas are primary bone tumors characterized by the presence of both low-grade cartilaginous and high-grade sarcomatous components. The high-grade component usually shows histologic features of either malignant fibrous histiocytoma or fibrosarcoma. We are aware of only 10 published cases in which the high-grade component showed rhabdomyosarcomatous differentiation. To further clarify the clinical, radiographic, and pathologic features of this unusual variant, we report three additional cases of dedifferentiated chondrosarcoma with rhabdomyosarcomatous differentiation. The patients included two men and one woman; their mean age was 63 years. Tumors originated in the pelvis (ilium), scapula, and tibia. Two patients presented with radiographic findings typical of dedifferentiated chondrosarcoma, including a geographic, lytic lesion with areas of mineralization suggestive of cartilage in close association with a permeative component. The third patient presented with a primarily lytic, destructive lesion of the right iliac wing. Histologically, the tumors contained lobules of well-differentiated chondrosarcoma associated with a high-grade sarcoma with prominent rhabdomyoblasts. Immunohistochemical stains for actin and desmin were positive in all three tumors, and electron microscopy revealed evidence of skeletal muscle differentiation. All three patients died with metastatic disease, 1, 6, and 12 months postoperatively. This histologic variant of dedifferentiated chondrosarcoma is rare, but it shows radiographic and clinical features similar to "conventional" dedifferentiated chondrosarcoma, including a very poor prognosis.

Aged↗
PubMed1996

Osseous manifestations of SAPHO (synovitis, acne, pustulosis, hyperostosis, osteitis) syndrome.

The SAPHO (synovitis, acne, pustulosis, hyperostosis, and osteitis) syndrome includes a complex group of disorders characterized by peculiar bone lesions, most commonly involving the anterior chest wall, and sometimes accompanied by dermatologic manifestations. The clinical and radiographic features of this syndrome are well described, but few studies have examined the histologic features of the bone lesions. We describe the clinical, radiographic, and histologic features of the osseous lesions encountered in eight patients with a clinical diagnosis of SAPHO syndrome. The patients included five female and three male patients ranging in age from 5 to 63 years (mean, 35.3 years). The most common clinical presentation was pain related to the sites of osseous involvement. Two patients also had some form of pustular dermatosis. The radiographic features of the osseous lesions varied but often suggested the possibility of a neoplasm. Nine pathologic specimens were available for review, five from the clavicle, two from the first rib, one from the calcaneus/cuboid, and one from the tibia. The histologic features varied but seemed related to the duration of the patients' musculoskeletal symptoms. Early lesions contained acute inflammation, edema, and prominent periosteal bone formation, histologically indistinguishable from ordinary bacterial osteomyelitis, whereas late lesions demonstrated markedly sclerotic bone trabeculae with prominent marrow fibrosis and only mild chronic inflammation; one of these biopsies appeared virtually identical to Paget's disease. One biopsy was performed after an intermediate duration of symptoms and contained prominent chronic inflammation only. The histologic findings in SAPHO are variable and nonspecific and may depend on the duration of disease, but it is important to recognize the spectrum of histologic changes possible in the syndrome and to realize that clinicopathologic correlation is necessary to avoid misdiagnosis and unnecessary long-term antibiotic therapy.

Acne Vulgaris↗
PubMed1996

Characterization of debris adjacent to failed knee implants of 3 different designs.

Wear debris particles have been associated with bone resorption and loosening of total joint implants. To characterize the wear particles around failed knee prostheses, tissues adjacent to 47 implants of 3 different designs were evaluated: 29 were posterior cruciate ligament retention type (Group I), 12 were posterior cruciate ligament sacrificing or substituting (Total Condylar, Insall-Burstein), (Group II), and 6 were mobile bearing (posterior cruciate ligament retaining LCS), (Group III). Wear particles were isolated and evaluated using electronic particle quantitation and scanning electron microscopy. The corresponding implants were also evaluated, and the surface damage quantified. The number of particles smaller than 10 microm ranged from 8.9 to 45.8 x 10(9) per gram of tissue (dry weight). Particle number directly correlated with duration of implantation. Group I implants had larger particles, and showed greater surface damage than the other 2 designs. Polyethylene surface damage significantly correlated with particle size more than 10 microm in length. Particle number showed a significant inverse correlation with the thickness of the polyethylene. These results support previous mechanical and retrieval studies suggesting that increased wear may be associated with thinner polyethylene, and there are differing degrees and patterns of wear based on implant design.

Adult↗
PubMed1996

Wear of polyethylene cups in total hip arthroplasty. A study of specimens retrieved post mortem.

The wear of polyethylene components of total hip replacements has previously been studied radiographically and by analysis of retrieved components. The extent of wear, however, has largely been determined from components retrieved at reoperation and has therefore been based on a subset of patients in whom the prosthesis is more likely to show excessive wear. The study of cups retrieved post mortem provides a better indication of the extent of wear of well functioning components. Twenty-six polyethylene liners were retrieved at autopsy from nineteen patients, after a mean of ninety-one months (range, thirty-three to 206 months) in situ. Each component had articulated with a thirty-two-millimeter-diameter femoral head. The components were evaluated visually for evidence of polyethylene wear such as pitting, scratching, and burnishing. Additionally; a shadowgraph technique was used to examine molds of the inner surface of the liner to determine the direction and extent of wear. The mean extent of linear wear of the retrieved liners was 0.45 millimeter (range, 0.17 to 1.07 millimeters), and the mean rate of wear was 0.07 millimeter (range, 0.02 to 0.18 millimeter) per year. The mean volumetric wear was 245.3 cubic millimeters (range, 13.0 to 779.1 cubic millimeters), and the mean rate of volumetric wear was 39.8 cubic millimeters (range, 1.0 to 131.3 cubic millimeters) per year. The mean rate of wear for the twenty-six liners was 45 to 69 per cent less than the rates reported in the literature for polyethylene liners retrieved at reoperation. Examination of the articulating surface did not reveal gross evidence of surface failure such as delamination or fatigue cracks. In general, the surfaces were merely burnished and scratched. The rates of wear of press-fit, metal-backed liners were significantly higher than those of all-polyethylene cemented components (p < 0.05). Additionally, statistical analysis revealed no correlation between wear and the patient's age, weight, or gender; the duration of implantation; or the thickness of the polyethylene. These results indicate that wear of the polyethylene of well functioning hip replacements is not as excessive as reported previously.

Acetabulum↗
PubMed1996

Characterization and comparison of wear debris from failed total hip implants of different types.

Particles of wear debris have been associated with loosening of implants and with osteolysis, but few studies have examined the relationship between characteristics of the implant and clinical variables and the concentration of particles isolated from periarticular tissues. We isolated and quantified particles of wear debris from orthopaedic implants in 123 tissue samples that had been obtained adjacent to a failed total hip prosthesis from eighty-eight patients. The concentration of these particles in the tissue and the size of the particles were then analyzed in relation to patient and implant-related variables. The number of particles ranged from 8.5 x 10(2) to 5.7 x 10(11) per gram of tissue (dry weight). More particles were found adjacent to failed titanium-alloy stems that had a cobalt-chromium-alloy modular head and failed titanium-alloy-backed cups than were found adjacent to all-cobalt-chromium-alloy prostheses. In addition, fewer particles were found adjacent to implants with a twenty-eight-millimeter femoral head than were found adjacent to implants with other femoral head sizes. Univariate analysis also showed correlations between a high concentration of particles and fixation without cement, an implant that had been in situ for a long duration, a young patient age, and an initial clinical diagnosis of avascular necrosis. Biopsy specimens from the proximal femoral membranes had higher concentrations than those from the joint capsules or the acetabular membranes. Although only five specimens were obtained directly from osteolytic lesions, the concentration of particles in those specimens was higher than that in biopsy specimens from other sites. Although many univariate correlations were identified, stepwise correlation regression analysis showed that the composition of the implant and the size of the modular femoral head were most strongly related to the concentration of debris in tissue.

Adult↗
PubMed1995

Histological and mechanical comparison of hydroxyapatite-coated cobalt-chrome and titanium implants in the rabbit femur.

The purpose of this study was to compare hydroxyapatite (HA)-coated titanium (Ti) and HA-coated cobalt-chrome (CoCr) implants in the distal femur of the rabbit by evaluating bone apposition and interfacial shear strength. Bilateral cylindrical implants with a plasma sprayed 50-microns thick HA coating were press-fit into the metaphyseal cancellous bone of the lateral femoral condyles in a transverse fashion, and the animals were sacrificed at 2, 4, and 8 weeks postimplantation. Mechanical strength of the interface between HA and bone was measured using the pushout method. For histologic analysis, the fractional linear extent of bone apposition was quantitated. No differences were found in the interfacial shear strength between the Ti and CoCr at any time period. The amount of bone apposition increased significantly at each time interval for both substrate metals, but there were no significant differences between the two substrates at any of the time periods studied. The HA-coated CoCr implants performed in a similar manner to the HA-coated Ti implants, both mechanically and histologically, suggesting that HA-coated CoCr implants deserve further study as a viable alternative to Ti for the biological fixation of total joint components in orthopaedic surgery.

Animals↗
PubMed1995

Adamantinoma.

This is an unusual case of an adamantinoma in an early phase of evolution. It was much smaller than adamantinomas typically seen at presentation, although it was located in the usual anterior tibial cortical region. Slow growth and a prolonged period of symptoms are common with adamantinoma and were also observed in this patient. The multifocal presentation within the same bone is unusual. This case illustrated the need to consider adamantinoma in the differential diagnosis of any pre-tibial cortical lesion despite the small size, benign presentation, or the longevity of symptoms.

Adolescent↗
PubMed1995

Cemented collarless (Exeter-CPT) versus cementless collarless (PCA) femoral components. A 2- to 14-year follow-up evaluation.

The purpose of this study was to compare the intermediate results of total hp arthroplasty with a cemented, collarless, femoral prosthesis design (Exeter, Howmedica, Middlesex, UK and CPT, Zimmer, Warsaw, IN) with those of a cementless, collarless, porous-coated femoral component (PCA, Howmedica). A total of 151 hips in 128 patients were reviewed. In the cemented group, 85 Exeter-CPT prostheses were used in 71 patients with an average follow-up period of 6.5 years. In the uncemented group, 66 PCA prostheses were placed in 57 patients with an average follow-up period of 7 years. Harrington hip scores improved from 50.1 to 80.7 for the PCA group and from 49.5 to 87.3 for the Exeter-CPT group. The patient satisfaction rates were 89 and 96%, respectively. Sixty-eight patients with Exeter or CPT prostheses had excellent function and no significant thigh pain after 2 years. One Exeter stem was revised 10 years after the primary surgery because of aseptic osteolysis due to cement defect. Two Exeter sockets were revised because of aseptic loosening. In the PCA group, the incidence of thigh pain that persisted beyond 2 years was 39.4%, and there were high incidences of distal cortical hypertrophy (66.6%) and bead loosening (45.5%). Sixteen hips were revised for aseptic stem loosening of the socket. The cementless ingrowth stems failed earlier (around 5 years), whereas the cemented stems continued to perform well past 14 years. In this study, the cemented, collarless, tapered, femoral prosthesis gave results superior to those of the uncemented collarless, porous-coated anatomic design at an average follow-up period of 7 years (range, 2-14 years).

Aged↗
PubMed1995

Vocal fold medialization using autologous cartilage in a canine model: a preliminary study.

Unilateral vocal fold paralysis can alter phonation. Medialization of the vocal fold using cartilage augmentation dates to the early 1950s. Improved phonation after cartilage chordal augmentation has been reported, but no study has as yet documented cartilage viability or size in this setting over time. The authors of this study evaluated thyroid alar cartilage as a medializing material in three mongrel dogs. Grafts were inserted lateral to the inner thyroid perichondrium at the vocal fold level via a window in the thyroid cartilage. Changes in weight, size, and volume were assessed 6 months after implantation. The average graft weight declined by 15%, and the average square area declined by 3%. Importantly, the average volume maintained was 87%. The grafts remained rigidly fixed to the thyroid cartilage in their placement positions. Histologic examination documented minimal resorption. The data suggest that thyroid alar cartilage is a viable filler in type I thyroplasty procedures.

Animals↗
PubMed1995

Revision hip arthroplasty with the use of cement and impaction grafting. Histological analysis of four cases.

The findings of radiographic studies have suggested that the cementing of an implant with a polished tapered stem into a bed of impacted bone allograft may provide adequate function of the joint and may restore bone in the proximal part of the femur. However, radiographs of hips with cancellous bone graft adjacent to cement are difficult to interpret, and the viability of impacted bone graft that is adjacent to cement and its capability for remodeling are unclear. To evaluate this interface further, we obtained biopsy specimens from the proximal part of the femur at the time of removal of trochanteric wires from four patients eleven to twenty-seven months after revision hip arthroplasty with cement and impaction grafting. Three relatively ill defined zones were identified histologically: an inner zone consisting of bone cement, fibrous tissue, and partially necrotic trabeculae with evidence of bone-remodeling; a middle zone consisting of viable trabecular bone and probable formation of so-called neocortex with fewer particles of bone cement; and an outer zone consisting of viable cortex. Fibrous tissue was present around some of the incorporating fragments of bone graft, but no continuous fibrous membrane was seen. Particles of cement were identified, but no polyethylene debris was visible on examination with light microscopy. The results demonstrated remodeling of bone and at least partial restoration of bone stock in the proximal part of the femur after revision arthroplasty with cement and impaction grafting.

Aged↗
PubMed1994

Alteration of hydroxylapatite coatings exposed to chemicals used in histological fixation.

Histological evaluation of retrieved devices allows for assessment of the biological response to the implants. Interaction between the biomaterial and the fluids used in the processing may alter the appearance or composition of the device. This may result in artifacts due to processing which are misinterpreted as being caused by the biological response. Alteration by the fluids used in fixation may be particularly important with materials that have a propensity to interact with aqueous environments, as in the case of calcium phosphate ceramics. Therefore, we examined the effects of various standard histological fixation techniques on hydroxylapatite coated metal implants. Of the techniques examined, fixation with ethanol appeared to affect the surface morphology the least, whereas fixation in unbuffered formalin appeared to affect the bulk composition of these samples the least. Fixation in buffered formalin resulted in marked changes in both surface morphology and bulk composition.

Adhesiveness↗