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Biomedical subjects

Timothy A Damron

Publications and source records attributed to Timothy A Damron.

29 records · Page 2Linked to original sources
PubMed2003

CD99 positive adamantinoma of the ulna with ipsilateral discrete osteofibrous dysplasia.

An adamantinoma is a rare, low-grade malignant, osteolytic bone tumor occurring predominantly in the diaphysis of the tibia. Osteofibrous dysplasia has been suggested as a precursor lesion to adamantinoma. Evidence for the relationship between these two tumors is based on their similar histologic features, immunohistochemistry, shared clonal abnormalities, overlapping skeletal distribution, and simultaneous occurrence in the tibia and fibula. The ulna is an unusual site of involvement by adamantinoma and osteofibrous dysplasia. Simultaneous involvement of the ulna by adamantinoma and ossifying fibroma has not been previously reported. A case is presented of an adamantinoma of the distal ulna with unique pathologic features occurring with an ipsilateral discrete focus of osteofibrous dysplasia as additional evidence of the relationship between these two lesions.

12E7 Antigen↗
PubMed2003

Critical evaluation of Mirels' rating system for impending pathologic fractures.

This project examined the hypothesis that Mirels' rating system for impending pathologic fractures is reproducible, valid, and applicable across various experience levels and training backgrounds. Twelve true clinical histories and corresponding radiographs for patients with femoral metastatic lesions were reviewed by 53 participants from five experience levels: orthopaedic residents, musculoskeletal radiologists, orthopaedic attendings, fellowship-trained practicing orthopaedic oncologists, and radiation or medical oncologists. Each examiner provided individual and total Mirels' scores and independent determination of impending fracture using clinical judgment. A subset of seven histories without prophylactic fixation provided a natural history group. There was highly significant agreement across experience categories for overall Kappa and for the concordance for individual and overall scores. Kappa analysis showed good agreement for site, moderate agreement for type, and fair agreement for size and pain. There was no significant difference in overall scores across experience levels. The pooled odds ratio favored Mirels rating system over clinical judgment regardless of experience level. Overall sensitivity was 91% and specificity was 35%. Mirels' system seems to be reproducible, valid, and more sensitive than clinical judgment across experience levels. However, although the system is a valuable screening tool, more specific parameters are needed.

Adult↗
PubMed2003

Precision and accuracy of DXA and pQCT for densitometry of the rat femur.

Measurements of bone mineral density and bone mineral content are key data in the study of osteoporosis and pathologic skeletal disease. Dual-energy X-ray absorptiometry and peripheral quantitative computed tomography are used in human and small animal studies. The purpose of this study was to evaluate the precision, accuracy, and systematic bias of measurement of the rat femur. Comparing machine-measured parameters with standard, nonradiographic measurements, we assessed validation of relative and absolute accuracy. Regression analysis and calculations of percent difference from standard values were used to determine the accuracy of each densitometry technique. Machine-specific and subject-specific precision was evaluated for each densitometer using repeated scans to calculate coefficients of variation. Each of the methods of densitometry examined in this study produced comparable results and was sensitive to small changes following experimental stimuli. Further, our assessment of the precision and accuracy observed between methods of scanning excised rat femurs validates our data acquisition method and serves as a foundation for future densitometry studies.

Absorptiometry, Photon↗
PubMed2003

Sequential histomorphometric analysis of the growth plate following irradiation with and without radioprotection.

BACKGROUND: The availability of radioprotectant drugs that selectively protect normal cells but not tumor cells has rekindled interest in the effects of irradiation on the growth plate. The purpose of the present study was to quantitatively examine the sequential histomorphometric effects of irradiation and pretreatment with a free radical scavenger radioprotectant, amifostine, on the growth plate over time. METHODS: Sixty four-week-old male Sprague-Dawley rats were randomized into five groups of twelve animals that were to be killed at 0.5, one, two, three, or four weeks after irradiation. One-half of the animals also received amifostine (100 mg/kg) prior to irradiation. In all animals, the right knee was treated with a single 17.5-Gy dose of radiation. End points were assessed with quantitative histomorphometric analysis of the growth plate, BrdU labeling for evidence of proliferation, evaluation of chondroclast cellularity, and determination of growth rates by means of oxytetracycline labeling. RESULTS: The mean lengths of the femur, tibia, and hind limb continued to increase at each time-interval following treatment, but by one week the mean limb length was 4% less on the irradiated side than on the control side, and this difference remained significant for four weeks (p < 0.05). The proximal tibial growth rate decreased during the first week to 18% of the control level. Nevertheless, growth continued even at the earliest time-periods, began to return toward normal at two weeks, and ultimately returned to at least 80% of normal by four weeks after irradiation. The area fraction of matrix in the hypertrophic zone increased initially and returned to control levels at three and four weeks. The administration of the radioprotectant resulted in significant increases in growth, growth rate, growth plate height, hypertrophic zonal height, and chondroclast profiles compared with the values for limbs in which irradiation had not been preceded by treatment with amifostine. CONCLUSIONS: We found an initially profound but transient direct inhibitory effect of irradiation on growth plate chondrocytes. Recovery of growth plate function after irradiation corresponded temporally with the appearance of newly formed islands of proliferating chondrocytes. Accumulation of matrix led to a transient increase in overall growth plate height, which was most pronounced in the hypertrophic zone. This was due, in part, to the sensitivity of chondroclasts to irradiation. The radioprotectant amifostine reduced these effects on growth rate, growth plate height, matrix accumulation, and limb length.

Age Factors↗
PubMed2003

Recurrent amyloidoma of soft tissue with exuberant giant cell reaction.

Amyloidoma (localized tumorlike amyloidosis) in the soft tissues is rare. We present an instructive case of recurrent amyloidoma in the soft tissue of the ankle in a 45-year-old man with multiple surgical procedures and chronic osteomyelitis of the underlying bones. The lesion evaded diagnosis because of a florid giant cell reaction that led to various misdiagnoses, including giant cell tumor of tendon sheath, foreign body reaction secondary to surgery, and pseudogout. This case demonstrates the importance of considering the possibility of amyloidoma when a giant cell-rich lesion is encountered in the soft tissues.

Amyloidosis↗
PubMed2002

Calcific myonecrosis: keys to early recognition.

Calcific myonecrosis is a rare, late sequela of trauma occurring almost exclusively in the lower extremity which may be confused with an aggressive primary neoplasm. The platelike mineralization pattern seen on radiographs is characteristic but not widely recognized by clinicians. Three cases of calcific myonecrosis are reported, unique in that two presented for care following infection and that one had extended to involve the muscle compartments of the foot, a previously unreported site.

Adult↗
PubMed2002

Tuberculosis of the hip as the presenting sign of HIV and simulating pigmented villonodular synovitis.

A 36-year old man, with no prior known exposure to human immunodeficiency virus (HIV) or tuberculosis, presented with monoarticular pain and a decreased range of motion in his left hip. Radiography and magnetic resonance imaging revealed bony erosive lesions, juxta-articular cysts, a large effusion, and juxta-articular edema. The initial clinical and radiographic diagnosis was pigmented villonodular synovitis (PVNS) of the left hip. However, what was initially felt to be a chronic proliferative inflammatory process was later determined to be tuberculous arthritis. This case emphasizes the importance of including tuberculous arthritis in the differential diagnosis of patients with monoarticular destructive joint disease radiologically suggestive of PVNS.

AIDS-Related Opportunistic Infections↗
PubMed2002

Adverse clinical events during cemented long-stem femoral arthroplasty.

The occurrence and risk factors for adverse clinical events associated with cemented long-stem femoral arthroplasty were studied. The hypothesis was that patients with femoral metastatic disease and previously uninstrumented canals were at higher risk for such adverse events. Fifty-five consecutive patients requiring long-stem femoral arthroplasty at two institutions were retrospectively reviewed. Adverse clinical events including hypotension, sympathomimetic administration, and O 2 desaturation were subclassified according to the timing of their occurrence. Adverse events occurred in 34 of 55 patients (62%), including coma in two patients and death in a third patient. The three catastrophic events occurred in patients with metastatic disease involving previously uninstrumented femoral canals. Desaturation was more frequent in patients with metastatic disease and previously uninstrumented canals compared with patients who had revision arthroplasty and patients with previously instrumented femoral canals. Preexisting medical illness was a significant risk factor in total adverse clinical events that included cement-associated adverse clinical events and cement-associated and postoperative hypotension. In long-stem cemented femoral components risk factors for adverse clinical events included metastatic disease, uninstrumented femoral canals, and preexisting medical conditions. These findings underscore the importance of appropriate patient selection, patient and family education, and anesthesia preparation before long-stem cemented femoral arthroplasty.

Adult↗
PubMed2002

Biomechanical analysis of humeral diaphyseal segmental defect fixation.

With disseminated malignancies, segmental defects of the humeral diaphysis may occur from surgical resection or as a complication of failed prior internal fixation. This study directly compared the biomechanical properties of a second generation titanium modular intercalary humeral spacer (segmental defect replacement prosthesis) with those of a modern locked humeral nail combined with methylmethacrylate (intramedullary nail) or with an intercalary allograft spacer (allograft nail composite) for fixation of segmental defects of the humeral diaphysis. Eighteen matched pairs (36 specimens) of fresh-frozen humeri were prepared in a standard fashion to create a 5-cm middiaphyseal defect and were divided randomly into three groups of 12 specimens each, using three different reconstructive methods. Specimens were tested in external torsion to failure on a Materials Testing System machine. The segmental defect replacement specimens had statistically greater peak torque (mean, 41.4 N-m) and stiffness (mean, 2.1 N-m/ degrees) than the intramedullary nail specimens (mean peak torque, 23.1 N-m) (mean stiffness, 1.6 N-m/ degrees) or the allograft nail composite specimens (mean peak torque, 12.4 N-m) (mean stiffness, 0.6 N-m/ degrees). The intramedullary nail specimens also had a statistically greater peak torque at failure and stiffness than the allograft nail composite specimens. For segmental defects of the humeral diaphysis, reconstruction with a cemented metallic intercalary spacer provides significantly greater immediate stability than interlocked intramedullary nail fixation supplemented with segmental methylmethacrylate or intercalary allograft reconstruction.

Biomechanical Phenomena↗
PubMedDate not supplied

Effects of irradiation on the appositional and longitudinal growth of the tibia and fibula of the rat with and without radioprotectant.

The effect of therapeutic levels of irradiation on appositional bone growth was compared with its effect on longitudinal growth in the skeletally immature rat model. The widths and lengths of the tibiae and fibulae of young rats were studied at 2, 4, 6, and 12 weeks after exposure to 17.5 Gy x-irradiation to the knee region of the right leg, with and without the aminothiol radioprotectant amifostine 20 minutes before radiation. Irradiation retarded growth in the width of the tibia to a greater extent (19%-27%) than longitudinal growth (9%-21%). The appositional growth discrepancy decreased over time, whereas the length discrepancy increased. The proximal fibula, in contrast, undergoes a normal decrease in width over time, and irradiation retarded this contraction by 14%. Appositional growth does not appear to be spared from the damaging effects of irradiation, but a catch-up phenomenon is observed that is not seen in longitudinal growth. Amifostine reduced the radiation-induced loss in tibial width by 40% to 50% and in length by 12% to 30%.

Amifostine↗