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T W Bauer

Publications and source records attributed to T W Bauer.

At least 37 records · Page 2Linked to original sources
PubMed1999

Femoral bone regeneration subsequent to impaction grafting during hip revision: histologic analysis of a human biopsy specimen.

Cemented revision with impaction grafting shows encouraging early clinical results; postoperative biopsy specimens taken from the proximal femur in humans have demonstrated viable trabecular and cortical bone. Human radiographic studies also illustrate density changes within the proximal femur, consistent with remodeling of bone-graft. In an animal experiment, bone incorporation was shown in the proximal femur, but graft lysis was reported around the distal portion of the implant. We report on a patient who sustained a traumatic femoral fracture at the level of the tip of the femoral component 27 months after revision with impaction grafting and a collarless polished taper stem. At the time of open reduction and internal fixation of the fracture, we obtained circumferential biopsy specimens from the fracture site. Three distinct zones could be identified histologically: i) an inner zone consisting of bone-cement, fibrous tissue, and partially necrotic trabeculae with evidence of bone remodeling; ii) a middle zone consisting of viable trabecular bone and probable neocortex formation with fewer particles of bone-cement; and iii) an outer zone with viable cortex. Fibrous tissue was present around some of the incorporating bone-graft fragments, but no continuous fibrous membrane was present. Cement particles were identified, but no polyethylene debris was found by light microscopy. Biopsy specimens from the distal aspect of the prosthesis may not reflect changes seen proximally, but based on the available tissue, this case illustrated histological evidence of bone-graft remodeling after impaction grafting. These results are consistent with our expectations based on radiographic findings and clinical results.

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PubMed1999

Deformation of the acetabular polyethylene liner and the backside gap.

Polyethylene wear of acetabular components may cause osteolysis and aseptic loosening in total hip arthroplasty. Case reports of wear between the polyethylene liner and acetabular metal backing (backside wear) have promoted speculation on the clinical importance of debris generation at this site and the potential importance of insert conformity. We examined 90 retrieved nonconforming acetabular components from a single manufacturer. Twenty-four liners (27%) showed polyethylene deformation corresponding to screw holes on the backside surface. The location of screw-hole deformations corresponded to the direction of polyethylene deformation (wear) on the articular surface in all cases. The polyethylene liners with backside deformations were significantly thinner than the liners without deformation (P = .02). The presence of acetabular osteolysis did not significantly correlate with backside deformation, but there was a significant association between osteolysis and wear of the articular surface (P = .0004). In this implant design, backside deformation (wear) may not be due to micromotion at the interface but to the viscoelastic nature of ultra-high-molecular weight polyethylene.

Acetabulum↗
PubMed1999

Relationship between wear debris particles and polyethylene surface damage in primary total knee arthroplasty.

To study relationships between design and wear, particles were isolated from tissues around 75 failed primary total knee prostheses, and particle size and concentration were compared with the extent and distribution of wear on superior and inferior polyethylene surfaces of the corresponding implants. Twenty-four heat-pressed, posterior cruciate ligament (PCL)-retaining (group I: PCA knee), 19 non-heat-pressed, PCL-retaining with relatively flat surfaces (group II: AMK, Kinematic, Microloc, Ortholoc), 14 non-heat-pressed, PCL-retaining with relatively congruent surfaces (group III: Townley Arizona), and 18 PCL-resected implants (group IV: Insall-Burstein, Total Condylar) were evaluated. Groups III and IV had fewer particles, smaller particles, and less surface damage than groups I and II. Implants with third-body wear had relatively small debris particles; those with thinner polyethylene had more severe surface delamination and more wear between liner and metal base. Groups I and II had more rotationally asymmetric wear patterns than groups III and IV. The size and concentration of debris particles might reflect, in part, different dominant wear mechanisms among implants of different designs.

Adult↗
PubMed1999

Papillary clear cell adenocarcinoma of the groin arising from endometriosis.

A 67-year-old woman presented with rapidly enlarging right anterior thigh mass. Clinical impression was of a primary sarcoma, but the histologic analysis of an incisional biopsy specimen showed adenocarcinoma with clear cell differentiation. Initially thought to be a metastasis, the malignant tumor appears to have arisen from extraabdominal endometriosis of the right groin. This case shows clinical, radiographic, and histologic findings that may help the orthopaedic surgeon recognize an unusual complication of extrapelvic endometriosis.

Adenocarcinoma, Clear Cell↗
PubMed1998

Bone ingrowth to implant surfaces in an inflammatory arthritis model.

Many studies have shown enhanced bone apposition to implants coated with hydroxyapatite, but the optimum implant texture, especially in abnormal trabecular bone, is unclear. The purpose of this project was to evaluate the histological and mechanical properties of cylindrical implants with three different surface textures that were placed in the cancellous bone of the distal femur of the rabbit after the production of an inflammatory knee arthritis. The three implant surfaces included a beaded surface (Group A), a beaded surface coated with hydroxyapatite (Group B), and a smooth surface coated with hydroxyapatite (Group C). The right knees of 36 rabbits were injected with carrageenan twice a week for 2 weeks. Then bilateral implantations were performed, with 12 rabbits in each group receiving identical implants in the right and left knees. The rabbits were killed 6 weeks after surgery. Mechanical (push-out test) and histomorphometric analyses were performed to determine the quality and quantity of bone ingrowth. In Group A, there was virtually no direct contact (a 20-60-microm clearance) between the bone and the beaded surfaces. Direct contact between the bone and the implant surfaces was seen in Groups B and C. The thickness and number of trabeculae were smaller on the arthritic side than on the control side for all groups but were not different between groups for either the control or the arthritic side. Mechanical testing showed that the shear strength of the interface was weaker on the arthritic side in all groups. The results suggest that inflammatory arthritis induced by carrageenan may influence the quality of local bone (osteopenic changes) and hence compromise the bone apposition and mechanical stability of the interface between the implant and bone.

Animals↗
PubMed1998

Results of 2-stage reimplantation for infected total knee arthroplasty.

Optimum treatment of the infected total knee arthroplasty has not been clearly established. To clarify the efficacy of two-stage reimplantation, experience with 66 infected total knee arthroplasties in 64 patients who had been treated with 2-stage reimplantation total knee arthroplasty between September 1980 and October 1993 was reviewed. Of these, 55 knees in 54 patients were available for follow-up examinations at an average of 61.9 months (range, 28-146 months). The initial diagnoses were rheumatoid arthritis (14 knees) and osteoarthritis (41 knees). Reimplantation was successful in 80.0% of knees with low-virulence organisms (coagulase-negative Staphylococcus, Streptococcus), 71.4% with polymicrobial organisms, and 66.7% with high-virulence organisms (methicillin-resistant Staphylococcus aureus). Reimplantation was successful in 82% of patients with osteoarthritis and in 54% of patients with rheumatoid arthritis (P = .024). The success rate was 92% if infection occurred after primary arthroplasty but only 41% if after multiple previous knee operations (arthroscopy, osteotomy, or revision total knee arthroplasty) (P < .001).

Adult↗
PubMed1998

Actinomycosis of the cholecystic duct: case report and review.

Actinomycosis of the gall bladder, cholecystic duct or common bile duct is rare, with only 16 cases reported to our knowledge. We report a case of actinomycosis in the cholecystic duct remnant of an 80-year-old woman with a history of cholecystitis, choledocholithiasis and cholecystoduodenal fistula requiring cholecystectomy and fistula closure three years prior. Histologic sections of the cystic duct remnant showed several dense basophilic masses containing numerous, dark blue, Gram-positive branching bacilli compatible with actinomycotic granules. Fluorescent antibody staining was positive for Actinomyces naeslundii. Staining for acid-fast bacilli was negative. The pathogenesis, presentation, diagnosis and management of abdominal actinomycosis with specific reference to disease involving the gall bladder are discussed.

Actinomyces↗
PubMed1998

Biomechanical and histological evaluation of a calcium phosphate cement.

It is often difficult to achieve stable fixation of a comminuted fracture associated with a metaphyseal defect. The injection of a resorbable cement into an osseous defect may help to stabilize the fracture and to maintain osseous integrity as the cement is resorbed and replaced by bone. The purpose of the present study was to evaluate the repair of a metaphyseal defect after treatment with an injectable calcium-phosphate cement. The injectable cement undergoes isothermic curing in vivo to form a carbonated apatite (dahllite) with a compressive strength of twenty-five megapascals. Either the cement or allograft bone was placed in proximal tibial metaphyseal and distal femoral metaphyseal defects in seventy-two dogs and was evaluated from twenty-four hours to seventy-eight weeks postoperatively. Histological examination showed that the cement was osteoconductive; nearly the entire surface area was covered with bone two weeks after the injection. The resulting bone-cement composite underwent gradual remodeling over time in a pattern that was qualitatively similar to the remodeling of normal cortical and cancellous bone. Osteoclasts were found to resorb the cement and were usually associated with adjacent new-bone formation. With increasing time in vivo, the cement was penetrated by small blood vessels that became surrounded by circumferential lamellae of bone and that closely resembled evolving haversian systems. This process occurred more rapidly in the cortex than in the medulla. Mechanical testing showed that, by eight weeks, the tibiae that had been treated with cement had reached nearly 100 per cent of the torsional strength of the contralateral, control (intact) tibiae; this finding paralleled the histological observations of bone apposition to the cement and rapid restoration of the cortex. At no time was fibrous tissue present between the cement and the bone, and there was no evidence of acute inflammation. Small particles of cement were present within occasional macrophages during the process of cement resorption, but the macrophages disappeared over time and were not associated with fibrosis or unexpected resorption of bone. Resorption of the cement was incomplete in the medullary area at seventy-eight weeks, but the pattern of cement resorption and bone-remodeling suggested gradual restoration of a physiological proportion of bone and marrow in both the cortical and the medullary region with maintenance of mechanical function.

Animals↗
PubMed1998

Norian SRS cement augmentation in hip fracture treatment. Laboratory and initial clinical results.

Bone quality, initial fracture displacement, severity of fracture comminution, accuracy of fracture reduction, and the placement of the internal fixation device are important factors that affect fixation stability. New high strength cements that are susceptible to remodeling and replacement for fracture fixation may lead to improved clinical outcome in the treatment of hip fractures. Norian SRS is an injectable, fast setting cement that cures in vivo to form an osteoconductive carbonated apatite of high compressive strength (55 MPa) with chemical and physical characteristics similar to the mineral phase of bone. It can be used as a space filling internal fixation device to facilitate the geometric reconstruction, load transfer, and healing of bone with defects and/or fractures in regions of cancellous bone. Furthermore, this cement can improve the mechanical holding strength of conventional fixation devices. Use of this material potentially could improve fracture stability, retain anatomy during fracture healing and improve hip function, thus achieving better clinical outcomes. In vivo animal studies have shown the material's biocompatibility, and cadaveric studies have shown the biomechanical advantage of its use in hip fractures. Initial clinical experience (in 52 femoral neck fractures and 39 intertrochanteric fractures) showed the potential clinical use of this innovative cement in the treatment of hip fractures.

Aged↗
PubMed1997

Effect of femoral head diameter on tissue concentration of wear debris.

Although several studies have reported the physical properties of debris particles in tissues adjacent to failed total joint implants, few have correlated the results of particle analysis with other clinical and implant variables believed to influence implant wear. We retrospectively analyzed 41 fibrous membranes (from 35 patients) adjacent to failed acetabular cups from a single manufacturer and studied the relationship between three different femoral head sizes (26, 28, and 32 mm) and the characteristics of wear debris in the adjacent tissues. All total hip prostheses consisted of modular cobalt-chromium alloy femoral heads articulating with titanium-alloy-backed ultrahigh molecular weight polyethylene (UHMWPE) acetabular components from a single manufacturer. Large femoral head diameter (32 mm) was found to correlate significantly with large particle size (diameter and surface area, p < 0.05), high tissue concentration of particles (particle volume/gram of tissue, p < 0.01), and high rate of particle production (particles volume/month, p < 0.05). The results of these quantitative assays support the findings of radiographically based clinical studies that show higher volumetric wear associated with 32 mm femoral head components.

Adult↗
PubMed1997

Three-dimensional analysis of multiple wear vectors in retrieved acetabular cups.

The wear of polyethylene acetabular components is an important issue in total hip arthroplasty. The amount of wear has been measured in many studies, but few have addressed other mechanical aspects of wear in vivo. We used the shadowgraph method to measure the wear vectors in 104 retrieved acetabular cups that had been made by a single manufacturer, and we identified more than one wear vector in thirty-one cups (30 per cent). We hypothesized that the most likely explanation of multiple wear vectors was loosening of the acetabular implant with a change in the orientation of the implant in the pelvis. To test this hypothesis, we estimated the extent of motion of the cup in situ on the basis of differences in angles measured from serial radiographs of sixteen hips. We then used linear transformation of the three-dimensional vectors to compare the wear directions measured in the retrieved implants with the wear directions predicted from the radiographs. The change in wear direction predicted on the basis of in vivo motion of the cup never corresponded to the actual difference between wear vectors in the retrieved implants. Our results suggest that multiple wear vectors may be commonly found in retrieved implants, but loosening of the acetabular cup does not account for the multiple vectors. Additional observations suggest that impingement between the edge of the acetabular cup and the femoral component may be associated with multiple wear vectors. These results have implications for the investigation of the general mechanisms of wear in vivo and suggest that clinical or wear-testing scenarios that assume a single direction of wear may underestimate the over-all amount of volumetric wear.

Equipment Failure Analysis↗
PubMed1997

Paraarticular osteochondroma of the knee: report of 2 cases and review of the literature.

Paraarticular osteochondromas are unusual osteocartilaginous tumors that arise in the soft tissue adjacent to a joint. Their pathogenesis and classification are controversial, and worrisome histologic features make the distinction from chondrosarcoma difficult on morphologic grounds alone. Two cases of paraarticular osteochondroma of the knee arising in patients 66 and 75 years of age are reported in this study. Although the exact biologic nature of these tumors is not well characterized, limited data suggest that they will behave in benign fashion, similar to soft tissue chondromas. Paraarticular osteochondromas should be recognized to avoid unnecessarily aggressive surgical management.

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PubMed1996

Calcium pyrophosphate dihydrate crystal deposition disease as a cause of lumbar canal stenosis.

STUDY DESIGN: This study measured the incidence of calcium pyrophosphate dihydrate crystal deposition in specimens of ligamenta flava in consecutive patients undergoing decompressive laminectomy between 1984 and 1991. The results were compared to determine the difference between calcium pyrophosphate dihydrate-negative patients with lumbar canal spinal stenosis. OBJECTIVES: The results were compared with cadaver specimens and literature values to determine if calcium pyrophosphate dihydrate crystal deposition disease contributes to the thickening of the ligamentum flavum and thereby contributes to spinal stenosis. SUMMARY OF BACKGROUND DATA: Calcium pyrophosphate dihydrate crystal deposition disease has been described in the axial skeleton. Hypertrophy of the ligamentum flavum has been suggested to contribute to stenosis. The association of calcium pyrophosphate dihydrate disease and hypertrophied ligamenta flava has not been fully defined nor linked to neurologic symptoms and signs. METHODS: The incidence of calcium pyrophosphate dihydrate crystal deposition in specimens of ligamenta flava obtained from four groups was measured: specimens obtained during surgery from 102 consecutive patients undergoing decompression laminectomy between 1984 and 1991, 47 additional pathologic specimens of ligamentum flavum tested between 1984 and 1991, 222 calcium pyrophosphate dihydrate-positive Pathology Department specimens collected between 1980 and 1991, and, as control specimens from 20 cadavers. The associated patient histories were reviewed for the first two groups; no histories were available for the cadaver group. RESULTS: The incidence of calcium pyrophosphate dihydrate crystal deposition was 24.5% in the ligamentum flavum among the surgical patients, 31% among the Pathology Department specimens, 33.8% among the calcium pyrophosphate dihydrate-positive Pathology Department specimens, and 5% among the cadavers. No associated medical conditions with calcium pyrophosphate dihydrate crystal deposition were found among the medical histories. Patients with the symptoms of spinal stenosis who were also calcium pyrophosphate dihydrate-negative patients with symptoms of less than 6 months' and less than 24 months' duration (P < 0.001). Except for time to presentation, calcium pyrophosphate dihydrate-negative patients had similar signs and symptoms of lumbar canal spinal stenosis. Having previous spine surgery did not produce a statistically significant risk of having calcium pyrophosphate dihydrate crystal deposition. No specific laboratory tests were found to be of predictive value. CONCLUSIONS: These findings suggest that calcium pyrophosphate dihydrate crystal deposition may indeed be associated with the thickening of the ligamentum flavum, if so, patients may benefit from medical treatment before undergoing surgical treatment of lumbar canal spinal stenosis.

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