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Biomedical subjects

Thomas W Bauer

Publications and source records attributed to Thomas W Bauer.

At least 19 recordsLinked to original sources
PubMed2007

Brief ultrasonication improves detection of biofilm-formative bacteria around a metal implant.

Biofilms are complex microenvironments produced by microorganisms on surfaces. Ultrasonication disrupts biofilms and may make the microorganism or its DNA available for detection. We determined whether ultrasonication could affect our ability to detect bacteria adherent to a metal substrate. A biofilm-formative Staphylococcus aureus strain was used for an in vitro implant infection model (biofilm-formative condition). We used quantitative culture and real time-polymerase chain reaction to determine the influence of different durations of ultrasound on bacterial adherence and viability. Sonication for 1 minute increased the yield of bacteria. Sonication longer than 5 minutes led to fewer bacterial colonies by conventional culture but not by polymerase chain reaction. This suggests short periods of sonication help release bacteria from the metal substrate by disrupting the biofilm, but longer periods of sonication lyse bacteria prohibiting their detection in microbiologic cultures. A relatively short duration of sonication may be desirable for maximizing detection of biofilm-formative bacteria around implants by culture or polymerase chain reaction.

Biofilms↗
PubMed2006

A prospective randomized study of posterolateral lumbar fusion using osteogenic protein-1 (OP-1) versus local autograft with ceramic bone substitute: emphasis of surgical exploration and histologic assessment.

STUDY DESIGN: A prospective, randomized and controlled study. OBJECTIVES: To evaluate the osteoinductive property of Osteogenic Protein-1 (OP-1 or BMP-7) and fusion rate in human instrumented posterolateral lumbar fusion through radiographic examination, surgical exploration, and histologic assessment. SUMMARY OF BACKGROUND DATA: The use of osteoinductive agents is a current topic in spinal fusion. Numerous preclinical investigations have demonstrated efficacy of osteoinductive proteins in spinal fusion, but few human clinical studies have been reported. METHODS: Nineteen patients with L3-L4 or L4-L5 degenerative spondylolisthesis underwent posterolateral lumbar fusion using pedicle screw instrumentation. The patients were randomized to receive either OP-1 Putty (3.5 mg OP-1/g of collagen matrix per side) alone (n = 9), or local autograft with HA-TCP granules (n = 10). Fusion status was evaluated using plain radiography and CT scan. Radiographic fusion criteria included less than 5 degrees of angular motion, less than 2 mm of translation, and evidence of bridging bone in the posterolateral lumbar area in which the graft materials were placed following decortication. After a minimum 1-year follow-up, the patients who showed radiographic evidence of fusion underwent instrumentation removal and surgical exploration of the fusion site. Biopsy specimens were taken from the fusion mass and evaluated histologically. RESULTS: Radiographic fusion rate was 7 of 9 OP-1 patients and 9 of 10 control patients. Based on surgical exploration of these 16 patients, new bone formation was macroscopically observed in the posterolateral lumbar region in all cases; however, solid fusion was observed in 4 of 7OP-1 and 7 of 9 HA-TCP/autograft patients. Histologic assessment demonstrated viable bone in 6 of 7 OP-1 patients. All the control (HA-TCP/autograft) specimens contained viable bone and fibrous tissue surrounding ceramic granules, suggesting slow incorporation of the graft material. CONCLUSIONS: In a human posterolateral lumbar spine trial, OP-1 reliably induced viable amounts of new bone formation, but the fusion success rate evaluated by surgical exploration was only 4 of 7.

Aged↗
PubMed2006

The use of newly developed real-time PCR for the rapid identification of bacteria in culture-negative osteomyelitis.

We report a case of a culture-negative osteomyelitis in which our newly developed real-time polymerase chain reaction (PCR) could differentiate Staphylococcus aureus from Staphylococcus epidermidis. This is the first report that described the application of this novel assay to an orthopedics clinical sample. This assay may be useful for other clinical culture-negative cases in a combination with a broad-spectrum assay as a rapid microorganism identification method.

Bacteriological Techniques↗
PubMed2006

The incidence of imaging findings, and the distribution of skeletal lymphoma in a consecutive patient population seen over 5 years.

OBJECTIVE: To determine the imaging incidence, distribution, and prognosis of primary and secondary osseous lymphoma from a consecutive, single-institution patient population seen over a 5-year period. DESIGN AND PATIENTS: Of 1098 newly diagnosed consecutively seen patients with lymphoma between 1996 and 2000, 975 comprised the study group. From the electronic medical records and imaging studies, age, gender, date of diagnosis of lymphoma, bone involvement, location in bone, multifocality in bone, histopathologic type of the lesion and patient survival were recorded. Primary lymphoma of bone was defined as osseous disease with or without regional node involvement and no evidence of systemic disease for 6 months. Secondary osseous lymphoma was considered present when osseous lymphoma was associated with systemic disease or the appearance of systemic disease within 6 months of osseous disease. RESULTS: Ninety-eight patients had osseous lymphoma (10%, 95% confidence interval [CI] 8.2, 11.9). Ages ranged from 9 to 92 years (mean 54) and gender 6:4 (M:F). Ten patients (1%) had primary lymphoma of bone. Eighty-eight patients (9%) had secondary lymphoma of bone. The vertebral column was the favored site for secondary osseous lymphoma. At 5 years, there were no deaths in the primary osseous lymphoma group and a 51% mortality rate in the secondary osseous lymphoma group. CONCLUSIONS: Primary lymphoma of bone remains a rare primary malignancy, favors the appendicular skeleton, and has a significantly better 5-year prognosis than secondary lymphoma of bone.

Adolescent↗
PubMed2006

Radiographic and histologic findings of vertebral augmentation using polymethylmethacrylate in the primate spine: percutaneous vertebroplasty versus kyphoplasty.

STUDY DESIGN: Animal study. OBJECTIVES: To investigate the gross behavior and the histologic effect(s) of polymethylmethacrylate (PMMA) in primate vertebral bodies after percutaneous vertebroplasty and kyphoplasty. SUMMARY OF BACKGROUND DATA: PMMA is known to induce thermal osteonecrosis in exposed bone during tumor surgery and total joint arthroplasty, and barium sulfate as well as PMMA are known to induce a foreign body reaction, but the effects of PMMA on vertebral cancellous bone have not been well documented. Furthermore, little is known about the mechanisms of cement extravasation that occasionally occur during these procedures. Lastly, it is not known if differences exist between vertebroplasty and kyphoplasty with regards to the above occurrences. METHODS: Six living, elderly, female baboons were used in this study. Seven vertebrae from T12 to L6 were investigated in each animal. Two levels underwent vertebroplasty, two underwent kyphoplasty, and one underwent cavity creation only without cement augmentation in each animal. Three animals were killed at 24 hours and three at 26 weeks after surgery. The specimens were examined macroscopically for cement migration, and histologically for evidence of thermal necrosis, foreign body reaction, cement migration, and intravascular extravasation. RESULTS: Small zones of osteonecrosis were observed histologically at the bone-cement interface in only two kyphoplasty (2 of 6) and two vertebroplasty specimens (2 of 5) at 26 weeks after surgery. All of these necrotic segments of bone were associated with new bone formation. Foreign body reactions were observed in all specimens at 26 weeks after surgery, yet none of them was associated with bone resorption. The incidence of cement leak into the spinal canal and adjacent soft tissues was 6 of 11 and 4 of 11 in vertebroplasty specimens and 5 of 12 and 3 of 12 in kyphoplasty specimens, respectively. There was no statistical difference in the incidence of cement leakage into the spinal canal (P = 0.54) and adjacent soft tissues (P = 0.55) between vertebroplasty and kyphoplasty specimens. The incidence of intravascular cement was significantly greater in vertebroplasty (11 of 12, 91%) than in kyphoplasty (5 of 12, 42%) (P = 0.013). CONCLUSIONS: PMMA caused relatively little necrotic exothermal effect. The presence of PMMA with barium sulfate induces a mild foreign body reaction. The use of a balloon tamp creates a void by displacing pieces of bone, which may result in a lower incidence of intravascular cement leak.

Animals↗
PubMed2006

The comparison of pyrosequencing molecular Gram stain, culture, and conventional Gram stain for diagnosing orthopaedic infections.

We have developed a combined real-time PCR and pyrosequencing assay that successfully differentiated the vast majority of gram-positive and gram-negative bacteria when bacterial isolates were tested. The purpose of this study was to evaluate this assay on clinical specimens obtained from orthopedic surgeries, and to prospectively compare the results of "molecular Gram stain" with culture and conventional direct Gram stain. Forty-five surgical specimens were obtained from patients who underwent orthopedic surgery procedures. The DNA was extracted and a set of broad-range PCR primers that targeted a part of the 16S rDNA gene was used for pan-bacterial PCR. The amplicons were submitted for pyrosequencing and the resulting molecular Gram stain characteristics were recorded. Culture and direct Gram staining were performed using standard methods for all cases. Surgical specimens were reviewed histologically for all cases that had a discrepancy between culture and molecular results. There was an 86.7% (39/45) agreement between the traditional and molecular methods. In 12/14 (85.7%) culture-proven cases of bacterial infection, molecular Gram stain characteristics were in agreement with the culture results, while the conventional Gram stain result was in agreement only for five cases (35.7%). In the 31 culture negative cases, 27 cases were also PCR negative, whereas 4 were PCR positive. Three of these were characterized as gram negative and one as gram positive by this molecular method. Molecular determination of the Gram stain characteristics of bacteria that cause orthopedic infections may be achieved, in most instances, by this method. Further studies are necessary to understand the clinical importance of PCR-positive/culture-negative results.

Base Sequence↗
PubMed2006

Reconstruction of intraosseous hemangiomas of the midface using split calvarial bone grafts.

BACKGROUND: Intraosseous hemangiomas are benign lesions that usually occur in the vertebral column and the calvaria. They are rare in the midface, with only 22 zygomatic and 26 nasal bone hemangioma cases described in the literature. Methods of reconstruction of craniofacial defects after surgical removal of these tumors have been inconsistent. METHODS: The authors report long-term follow-up in three cases of midface intraosseous hemangiomas all treated in a similar fashion: surgical excision of the tumor with a small margin of normal bone and primary reconstruction using split calvarial bone grafts. RESULTS: Clinical, photographic, and computed tomographic assessment (cases 1 and 2) documents no recurrence and maintenance of the result with a mean 5-year follow-up. To the authors' knowledge, this represents the longest follow-up of a patient series with hemangiomas of bone treated with primary reconstruction in the plastic surgery literature (Wolfe and Berkowitz did report on a single case with 4-year follow-up without recurrence). We recommend replacing like with like. Primary bone grafting with autogenous cranial bone was used to replace areas where original bone was thin, but full-thickness bone was used in areas where original bone was thick. Full-thickness cranial bone grafts may be superior to split cranial bone with regard to long-term volume maintenance. CONCLUSIONS: Preoperative computed tomographic scanning should lead to the appropriate diagnosis. Proper diagnosis should lead to appropriate treatment, which includes total excision and primary bone grafting of the defect to prevent soft-tissue contraction.

Adult↗
PubMed2006

Diagnosis of periprosthetic infection.

Periprosthetic infections are rare, but there is evidence to suggest that their frequency may be underestimated. No single laboratory test has perfect sensitivity and specificity for diagnosing infection. Most tests have better specificity when they are performed for patients in whom infection is suspected clinically rather than when they are used as screening tests. Screening test results that may suggest the possibility of infection include elevation of the erythrocyte sedimentation rate and/or serum C-reactive protein level more than three months after an arthroplasty. Most serologic tests are difficult to interpret when the patient has an underlying inflammatory arthropathy. Cultures of aspirated joint fluid can be especially helpful for patients who have symptoms suggestive of infection, but their results are best interpreted two weeks after administration of antibiotics has been discontinued. Joint fluid cell counts may also be helpful, but Gram stains of joint fluid have poor sensitivity and specificity. Criteria for diagnosing infection on the basis of frozen sections of implant membranes have not yet been standardized, but in many laboratories more than five neutrophils per high-power field in five or more fields (excluding surface fibrin) has been found to be suggestive of infection. Most polymerase chain reactions that detect the universal 16S rRNA bacterial gene have problems with false-positive results, but combining a universal polymerase chain reaction with subsequent bacterial sequencing can help improve specificity. Polymerase chain reactions can detect necrotic bacteria, so the clinical importance of positive results of this analysis in the absence of other features of infection remains to be determined.

Humans↗
PubMed2006

The use of real-time polymerase chain reaction for rapid diagnosis of skeletal tuberculosis.

We identified Mycobacterium tuberculosis DNA using real-time polymerase chain reaction on a specimen from an osteolytic lesion of a femoral condyle, in which the frozen section demonstrated granulomas. The process was much more rapid than is possible with culture. The rapid detection of M tuberculosis and the concomitant exclusion of granulomatous disease caused by nontuberculous mycobacteria or systemic fungi are necessary to appropriately treat skeletal tuberculosis. The detection and identification of M tuberculosis by culture may require several weeks using traditional methods. The real-time polymerase chain reaction method used has been shown to be rapid and reliable, and is able to detect and differentiate both tuberculous and nontuberculous mycobacteria. Real-time polymerase chain reaction may become a diagnostic standard for the evaluation of clinical specimens for the presence of mycobacteria; this case demonstrates the potential utility of this assay for the rapid diagnosis of skeletal tuberculosis.

Antitubercular Agents↗
PubMed2005

Histological and radiographic evaluation of polymethylmethacrylate with two different concentrations of barium sulfate in a sheep vertebroplasty model.

Percutaneous vertebral augmentation with PMMA has been widely performed and usually provides good pain relief and stabilization of fractured vertebrae. Adequate visualization of PMMA during injection is desirable to minimize cement extravasation, so contrast agents such as barium sulfate are commonly added to the PMMA. The aim of this study was to evaluate the differences of histology and radiographic visualization when different concentrations of barium sulfate are mixed with PMMA. Six sheep were utilized in this study. Three vertebrae of each animal were exposed via retroperitoneal approach, and a cavity was created and then filled with either 10% or 30% BaSO4/PMMA, or left empty. Vertebrae were harvested and analyzed radiographically and histologically 12 and 90 days after surgery. Average CT value of the 30% BaSO4/PMMA group was 2.4-fold higher than that of the 10% BaSO4/PMMA group. Foreign-body giant cells were recognized around BaSO4particles at 90 days in the 30% BaSO4 group, whereas few particles were recognized in the 10% group at 90 days, or in either group at 12 days. A very mild giant-cell reaction is induced by a higher concentration of BaSO4 in PMMA, but the marked improvement in cement visualization by increased BaSO4 may be important to minimize more serious complications of cement extravasation during PMMA injection.

Animals↗
PubMed2005

Histological evaluation of biopsies obtained from vertebral compression fractures: unsuspected myeloma and osteomalacia.

STUDY DESIGN: A histological evaluation of biopsies obtained from presumed osteoporotic vertebral compression fractures (VCF) to confirm possible osteomalacia after tetracycline labeling. OBJECTIVE: To describe the results of a series of biopsies obtained at the time of vertebral augmentation in presumed osteoporotic VCF, with special reference to the presence of unmineralized bone (osteomalacia) and occult or unconfirmed plasma cell dyscrasia. SUMMARY OF BACKGROUND DATA: Vertebral augmentation is now widely performed as a method to treat osteoporotic or osteolytic VCF. However, the influence of underlying pathology on the effect of treatment is unclear. METHODS: As of October 2003, 178 biopsies were obtained from 142 patients with VCF during 246 kyphoplasty procedures. There were 110 one-level, 28 two-level, and 4 three-level biopsies. Patients included 41 men and 101 women, with an average age of 72 years (range 40-90). The patients consented to this procedure, and 25 received tetracycline (1g/day, in 2 doses separated by 6 days). Vertebral body biopsies were taken using a trephine just before the kyphoplasty procedure. The biopsies were fixed, embedded, and stained with toluidine blue and hematoxylin eosin, and were viewed with transmitted light. Unstained sections were viewed under fluorescent light to detect tetracycline labels. RESULTS: The 178 biopsy levels included: T4 (3), T5 (1), T6 (4), T7 (13), T8 (12), T9 (8), T10 (11), T11 (17), T12 (28), L1 (25), L2 (14), L3 (13), L4 (17), and L5 (12). All specimens showed fragmented bone with variable amounts of unmineralized bone (osteoid), suggesting bone remodeling and/or fracture healing. Woven bone and cartilaginous tissue were often present, representing fracture callus formation. The biopsies obtained from 30 patients (21%), including 4 who received tetracycline, showed significantly increased osteoid, suggesting either increased bone remodeling activity or mineralization defect (osteomalacia). One sample from these 4 patients who received tetracycline showed no tetracycline labels, essentially diagnostic of osteomalacia. The biopsies also provided definitive diagnoses for one case of unsuspected and 3 cases of unconfirmed plasma cell dyscrasia. CONCLUSIONS: The majority of biopsies from this series of patients revealed findings consistent with various stages of fracture healing. Osteoid seams were increased in 30 patients, representing either increased bone remodeling or osteomalacia. More cases with tetracycline labeling will help elucidate the true incidence of osteomalacia in this population. As we confirmed 4 cases of plasma cell dyscrasia, we advocate a biopsy during each first-time vertebral augmentation procedure.

Adult↗
PubMed2005

Analytical technique for quantification of selected resorbable calcium phosphate bone void fillers with the use of polarized-light microscopy.

Synthetic calcium phosphate bone void fillers promote varying rates of bone formation and material resorption depending on chemistry, porosity, pore structure, and implant site. The objective of this study was to quantify the resorption of a novel ultraporous beta-tricalcium phosphate cancellous bone void filler with simultaneous quantification of bone formation in a canine humerus model. Potential measurement error involved in conventional histomorphometry using Von Kossa stains inspired the development of a new technique. This technique utilizes bright-field and polarized-light microscopy in conjunction with image analysis software, allowing more accurate histomorphometry. This technique was validated with two separate controlled experiments. Scanning electron microscopy further supported the results. The findings suggest that the use of polarized-light microscopy combined with image analysis software can be an effective tool in simultaneously quantifying calcium phosphate resorption and bone formation.

Animals↗
PubMed2005

A molecular gram stain using broad range PCR and pyrosequencing technology: a potentially useful tool for diagnosing orthopaedic infections.

The bacteria associated with orthopaedic infections are usually common gram-positive and gram-negative bacteria. This fundamental grouping of bacteria is a necessary first step in the selection of appropriate antibiotics. Since polymerase chain reaction (PCR) is more rapid and may be more sensitive than culture, we developed a postamplification pyrosequencing method to subcategorize bacteria based on a few nucleotide polymorphisms in the 16S rRNA gene. We validated this method using well-characterized strains of bacteria and applied it to specimens from spinal surgery cases with suspected infections. Lysates of 114 bacteria including 75 species were created following standard cultivation to obtain DNA. The DNA was amplified by a broad-range real-time PCR. The amplicons were evaluated by pyrosequencing and were classified as gram-positive, gram-negative, or acid-fast bacilli based on the first three to five nucleotides sequenced. In addition, clinical cases of suspected infection were obtained from spinal surgery. The results of the "molecular Gram stain" were compared with the results of traditional Gram stain and culture. The lysates of 107 (93.9%) of the bacteria extracts tested were appropriately categorized as gram-positive and gram-negative or as acid-fast bacilli on the basis of this assay. The sensitivity and specificity of this assay were 100% and 97.4% for gram-positive and 88.3% and 100% for gram-negative isolates. All of the five clinical samples were appropriately categorized as containing gram-positive or gram-negative bacteria with this assay. This study demonstrates that high sensitivity and specificity of a molecular gram stain may be achieved using broad-range real-time PCR and pyrosequencing.

Bacterial Infections↗
PubMed2005

Histologic and mechanical evaluation of impaction grafting for femoral component revision in a goat model.

A goat model of revision hip arthroplasty was used to examine the histology and mechanical performance of impaction grafting using two femoral stems varying in stem surface finish. There were no significant mechanical or qualitative histologic differences between smooth, tapered, polished stems and step-cut, grit-blasted stems. Allograft distribution, bone incorporation, and cement mantle thickness were not uniform within the femoral canal. Efforts to improve the impaction grafting technique may be more important than stem design.

Animals↗
PubMed2004

Preclinical evaluation of a poly (vinyl alcohol) hydrogel implant as a replacement for the nucleus pulposus.

STUDY DESIGN: An in vivo investigation into the safety of a novel hydrogel implant designed to replace the diseased nucleus pulposus. OBJECTIVES: To determine the local and systemic safety of this new implant in a nonhuman primate model. SUMMARY OF BACKGROUND DATA: A poly (vinyl alcohol) (PVA) hydrogel has been developed as a prosthetic replacement for the diseased nucleus pulposus. METHODS: PVA implants were inserted into discectomy defects created in the L3-L4 or L4-L5 intervertebral disc in 20 male baboons. Empty discectomy defects served as a surgical control in 8 additional animals. Routine follow-up evaluations included radiography, magnetic resonance imaging, gross pathology, and histopathology of both local and remote tissues. RESULTS: Insertion of the PVA hydrogel from an anterior direction produced extrusions in 5 animals from the first series of 15 surgeries (33%). A modified surgical technique, involving an anterolateral rather than anterior approach, was used in 5 animals, but the extrusion rate remained high (20%). Despite these surgical complications, the PVA implants were well tolerated over 24 months in vivo, with no evidence of device-related pathology in the adjacent disc tissue, spinal cord, or remote tissues. CONCLUSION: Implantation of the PVA implant for periods of up to 24 months produced no evidence of local or systemic toxicity. Additional studies are now needed to determine the efficacy of the device in its intended application.

Animals↗
PubMed2004

Recommendations for the reporting of bone tumors. Association of Directors of Anatomic and Surgical Pathology.

The diagnosis of a bone tumor is often an arduous task, even for the most experienced orthopedic pathologist. As a starting point, the classification of bone tumors is based on a histogenetic perspective encompassing the type of matrix produced (or not produced) by the tumor. In general, the surgical pathology report should include data pertinent to the treatment and prognostication of an individual patient, and the report should be delivered to the clinician in a clear, concise fashion. Reporting of most bone tumors is similar and includes such information as the type of surgery done, anatomic site, histological type and grade of the tumor (if applicable), and the adequacy of surgical margins. Special emphasis is needed for those tumors with distinct and well-established prognostic and therapeutic features such as osteosarcoma and Ewing's sarcoma/peripheral neuroectodermal tumor. Our recommendation emphasizes a standardized protocol for these sarcomas, especially in light of evidence that postchemotherapeutic tumor necrosis is of prognostic significance. It is also important to note that radiographic imaging plays a very important, often critical, role in allowing the pathologist the opportunity to reach the best final diagnosis. This is especially true when a malignant interpretation is contemplated and in subtyping lesions. We recommend close collaboration between musculoskeletal radiologists, clinicians, and pathologists when dealing with complicated neoplasms of bone.

Bone Neoplasms↗