Symposium: lumbar spine fixation--the pedicle screw controversy.
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Bone Screws↗
Biomedical subjects
C C Edwards
Publications and source records attributed to C C Edwards.
Thoracic epidural abscess.
Twenty-one cases of thoracic spinal epidural abscess occurring over a 10-year period were retrospectively reviewed. Diagnosis was made by MRI or myelography and confirmed in the operative cases. A bacterial agent was isolated in 18 of the cases (86%). When measured, the erythrocyte sedimentation rate was elevated in all cases. Four patients who presented without neurologic deficits remained intact. All patients who presented with neurological deficits underwent surgical intervention in addition to intravenous antibiotics. Of the 15 patients who presented with a paraparesis of less than antigravity strength, five eventually were independent ambulators and continent. A good outcome resulted in 80% of those who underwent decompression within 24 h, as opposed to only 10% of the patients decompressed after 24 h. Good results can be obtained despite severe neurologic compromise when treated by rapid diagnosis and decompression of the spinal canal.
Abscess↗
Ribozyme-mediated modulation of human O6-methylguanine-DNA methyltransferase expression.
A synthetic oligonucleotide containing ribozyme sequences targeted to the 5' region of the human O6-methylguanine-DNA methyltransferase (MGMT) mRNA has been constructed. This ribozyme demonstrates cleavage activity in vitro in the presence of Mg2+. To determine whether this ribozyme can function in vivo, HeLa CCL2 cells were transfected with a mammalian expression vector containing the ribozyme sequence. Following selection and expansion of individual transfectants, a stable clone was isolated that lacks both MGMT mRNA and protein. Molecular analysis of this cell line indicates that in vivo cleavage of MGMT mRNA is responsible for the lack of MGMT activity.
Base Sequence↗
Shapes of cells spreading on fibronectin: measurement of the stellation of BHK21 cells induced by raising cyclic AMP, and of its reversal by serum and lysophosphatidic acid.
In common with many other animal cells in culture, BHK21, CHO and NIH-3T3 cells adopt bizarre stellate or arborized shapes when exposed, in the absence of serum, to agents which increase cytoplasmic cyclic AMP (cAMP). Dibutyryl cAMP, 3-isobutyl-1-methylxanthine, 5'-deoxy-5'-methylthioadenosine, cholera toxin and the invasive adenylate cyclase from Bordetella pertussis all induce similar shapes. Time lapse video recording of BHK21 cells spreading on fibronectin shows that stellate shapes are generated by outgrowth of neurite-like processes led by small fans of ruffling membrane. These structures stain strongly for F actin, and their outgrowth is completely inhibited by cytochalasin D. Thus if stellation is caused by microfilament depletion, this must be selective for subsets of microfilaments. We have quantified the shape changes of BHK21 cells using the parameter dispersion. They are prevented by low concentrations (1% by volume and below) of bovine sera. The inhibitory component of foetal bovine serum acts humorally, behaves as a macromolecule and is itself inhibited by suramin, but platelet-derived growth factor, insulin, vasopressin and bradykinin are inactive. The inhibitory activity of serum may be due to phospholipids, since it can be replaced by lysophosphatidic acid in the presence of serum albumin.
3T3 Cells↗
Identification of nitrosourea-resistant human rhabdomyosarcomas by in situ immunostaining of O6-methylguanine-DNA methyltransferase.
Cellular levels of O6-methylguanine-DNA methyltransferase (MGMT) correlate strongly with cellular resistance to carcinogenic and chemotherapeutic agents that produce adducts at the O6-position of guanine in DNA. Although biochemical and molecular assays can indicate the average MGMT content of tissues or tumors, they cannot distinguish mixed populations of cells, such as those that exist in tumor biopsy samples. We have determined MGMT at the cellular level in a panel of pediatric rhabdomyosarcoma xenografts by in situ immunostaining with a human MGMT-specific antibody employing a very sensitive procedure that involves biotin-avidin coupled horseradish peroxidase with silver-enhanced diaminobenzidine-nickel staining. Two xenograft tumor lines known to be MGMT-deficient were not stained, whereas the nuclei in three MGMT-expressing lines were clearly stained. This is the first demonstration of an in situ procedure that discriminates drug-sensitive MGMT-deficient tumors from drug-resistant MGMT expressing tumors. This procedure should prove useful, therefore, for predicting the susceptibility of tissues and tumors to O6-guanine alkylating agents.
Amino Acid Sequence↗
Predictors of participation in a school-based anti-tobacco activism program.
This study investigated the predictors of participation in a school-based, anti-tobacco activism program. Subjects in this study consisted of 7th grade students participating in the intervention component of Project S.H.O.U.T., a tobacco use prevention program in San Diego County, California. In the activism component, a newsletter containing an activism contest was distributed to each student. Small prizes were awarded to contest winners at each school. "Activism" included letter and petition writing, anti-tobacco poster contests, merchant education, peer surveys and magazine subscription cards. A total of 170 students participated in the activities, with 81.1 percent participating two or more times. Of those who participated, 59 percent were female and 60 percent were White, non-Hispanic. Two sets of logistic analyses were conducted. Variables such as SES, gender, ethnicity, friends' tobacco use and parental tobacco use were used to predict participation in activism activities. The choice of variables was intended to provide information regarding activism participation in reference to known tobacco risk factors. Results of the first analysis indicated that students with a higher SES, and in an urban vs. rural location were more likely to participate in the activism activities. The second analysis used the same set of characteristics to predict "ever-use" of tobacco. Results of this analysis indicated that male gender, low grades, White, non-Hispanic ethnicity, friends' and parents' tobacco use were positively associated with tobacco experimentation.
Adolescent↗
Chronic donor site pain complicating bone graft harvesting from the posterior iliac crest for spinal fusion.
To explore the relationship between surgical approach and chronic posterior iliac crest donor site pain, 151 bone graft harvests with follow-up periods longer than 1 year were evaluated using a detailed questionnaire and follow-up clinical visits. There was no difference in the incidence of chronic donor site pain between harvests performed through the primary midline incision versus a separate lateral oblique incision (28 vs 31%). Twice as many donor sites harvested for reconstructive spinal procedures were reported as having chronic pain as compared with those harvested for spinal trauma, regardless of approach used (39 vs 18%). The association of chronic donor site pain with residual back pain was also greater in the spinal reconstructive group. Thus, it appears that incidence of chronic donor site pain is more dependent on diagnosis than on surgical approach.
Bone Transplantation↗
Anatomic consideration for sacral screw placement.
Instrumentation of the lumbosacral spine increasingly involves screw fixation to the sacrum. Recommended locations and techniques for screw placement vary, particularly when bicortical purchase of the sacrum is performed. The purpose of this study was to describe the critical anatomy and potential injuries to neurovascular and visceral structures anterior to the sacrum. Lack of awareness can lead to life-threatening complications. The study included 22 fresh human cadavers with no prior spinal surgery. Specimens were placed in a prone position, and the lumbosacral spine was exposed. Two 6.5-mm screws were inserted using one of two techniques, respectively: Starting just inferior to the S1 facet one screw was angled 25 degrees caudally and 30 degrees laterally; in the second technique, lateral inclination was increased to 45 degrees. In addition, all specimens had screws placed in the S2 pedicles. An anterior dissection was performed to allow evaluation of the neurovascular and visceral structures at risk for injury by, or adjacent to, the screw tips. All significant neurovascular structures in the area of concern were constant in position. The internal iliac vein and the lumbosacral nerve trunk were most at risk for injury by the 30 and 45 degrees laterally directed screws. The sigmoid colon, though close to the S2 screw, was protected by its mesentery. Screws placed in the S1 pedicle were least likely to injure the neurovascular bundle. A lateral and a midline safe zone were identified.
Aged↗
Fractures of the atlas.
Thirty-four patients who had fractures of the atlas (the first cervical vertebra) were reviewed at an average follow-up of 4.5 years. Seventeen patients had bilateral fracture of the posterior arch of the first cervical vertebra. Eight were treated with immobilization in a cervical orthosis, with no long-term problems secondary to the injury. Nine of these patients had additional fractures in the first and second cervical vertebral complex, complicating the management of the fractures of the posterior arch. Two of the nine patients died, and the treatment of the other seven was dependent on the additional fractures. A second group of six patients had a fracture in the area of the lateral mass, with one fracture just anterior to or within the anterior portion of the lateral mass of the first cervical vertebra and a second fracture posterior to the lateral mass of the first cervical vertebra on the same side; resultant asymmetrical displacement of the lateral masses was seen on the open-mouth roentgenogram that was made for each patient. A third group of eleven patients sustained a Jefferson, or burst, fracture of the first cervical vertebra. These patients had either four fractures (two in the anterior arch and two in the posterior arch) or three fractures (one in the anterior arch and two in the posterior arch). Spreading of the lateral masses was relatively symmetrical on the open-mouth roentgenogram. Patients who had fractures with displacement of two to seven millimeters were treated with immobilization in a halo vest. Patients who had fractures with severe spreading of the lateral masses (more than seven millimeters) were treated with reduction of the lateral masses by axial traction until healing of the arch had occurred. No atlanto-axial instability was evident in any patient at follow-up.
Adolescent↗
Prevention of tobacco use among adolescents in public schools in San Diego County, U.S.A.
Project S.H.O.U.T. (which stands for "Students Helping Others Understand Tobacco") is a tobacco-use prevention project funded by the United States National Cancer Institute for preventing the use of cigarettes and smokeless tobacco (snuff and chewing tobacco) in public schools in San Diego County, California. Based on principles of behavior modification, Project S.H.O.U.T. teaches students how to anticipate and overcome negative peer pressure to use tobacco and reinforces them for having done so. Preliminary results indicate that the prevalence of tobacco use among students receiving peer pressure resistance skills training was somewhat but not statistically significantly lower than the control group after one year of intervention. In addition, students in a third lottery condition, who were reinforced for simply not using tobacco, showed lower prevalence rates compared to controls. Additional support for the efficacy of the intervention program was provided by the refusal skills assessment test, which indicated that students exposed to the intervention were able to refuse tobacco offers more effectively than the control students. Our results indicate that tobacco use prevention experts should do more than provide decision-making and behavioral skills for resisting tobacco use, but should also reinforce the non-use of tobacco.
Adolescent↗
Traumatic lesions of the occipitoatlantoaxial complex.
Injuries of the occipitoatlantoaxial complex are relatively rare but form a group of ligamentous and bony lesions that may unnecessarily confuse the clinician. Since fractures of the dens and traumatic spondylolisthesis of the axis have been well described in a number of large series, this article concentrates on the lesions less frequently seen and described. The ligamentous injuries are occipitoatlantal dislocation, rupture of the transverse ligament, and atlantoaxial rotatory fixation. The bony injuries are fractures of the occipital condyles, atlas, and the lateral masses of C2. The incidence, diagnostic criteria, and treatment modalities depend on the nature of localization of the traumatic lesions.
Atlanto-Axial Joint↗
Pneumocystis carinii antigenemia in acquired immunodeficiency syndrome.
The present study was conducted to determine the prevalence and significance of Pneumocystis carinii antigenemia in patients with acquired immunodeficiency syndrome (AIDS) and clinically or invasively diagnosed P. carinii pneumonitis. Single serum specimens from 20 AIDS patients invasively examined for P. carinii organisms and 106 AIDS patients with a clinical diagnosis only of P. carinii pneumonitis were blindly tested for P. carinii antigenemia by a counterimmunoelectrophoresis assay. In the 20 specimen-documented cases, the antigen test demonstrated a sensitivity of 75% and a specificity of 90%. The positive predictive value of the test was 90%, while the negative predictive value was 70%. In AIDS patients with specimen-documented P. carinii pneumonitis, the prevalence of P. carinii antigenemia coincided almost exactly with the prevalence of positive invasively obtained specimens (60 and 59%, respectively). In patients with a clinical diagnosis only of P. carinii pneumonitis, half as many (30%) were found to exhibit antigenemia. Sequential P. carinii antigen titers determined by a new latex agglutination technique on three AIDS patients with specimen-documented P. carinii pneumonitis demonstrated the influence of specific therapy upon P. carinii antigenemia and its potential prognostic application.
Acquired Immunodeficiency Syndrome↗
Low lumbar burst fractures. Reduction and stabilization using the modular spine fixation system.
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Bone Screws↗
Management of open fractures in the multiply injured patient.
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Connective Tissue↗
Bilateral facet dislocations in the thoracolumbar spine.
Bilateral facet dislocation represents approximately 11% of all thoracolumbar spine injuries requiring surgical stabilization. The injury can be caused by either flexion distraction (29/30 cases) or by pure distraction (1/30). Recognition of the injury is possible on plain radiographs, and confirmed by the empty facet sign on the computed tomography (CT) scan. In contradistinction to other major spine injuries, the majority of patients present with complete neurologic lesions (21/30). Recovery of patients with incomplete lesions is frequent (5/6); however, recovery from complete lesions did not occur. Compression instrumentation is recommended for patients with complete lesions because it is stable and requires no external immobilization. Distraction instrumentation that imparts significant extension is advised for patients with incomplete lesions. It is safe and reliable, and eliminates the posterior bulging of the injured disc that can occur with compression. For low lumbar injuries where compression is desirable in order to achieve the shortest possible instrumentation, a discectomy is recommended.
Adult↗
Pneumocystis carinii serologic study in pediatric acquired immunodeficiency syndrome.
Pneumocystis carinii antigen and IgG antibody profiles were prepared on 17 pediatric patients with acquired immunodeficiency syndrome (AIDS) with pneumonia who were examined by a variety of invasive methods for P carinii organisms. Overall, the accuracy of the antigen assay in invasively examined pediatric patients with AIDS with pneumonia was 94% (sensitivity, 100%; specificity, 90%), as antigen and invasive test results agreed in 16 of 17 patients. No statistically significant differences in IgG titer were observed between controls and patients invasively examined for P carinii, whether the organism was observed in the specimen or not. Since 38% of all serum samples referred were derived from "blood-borne" cases of AIDS, including patients who contracted AIDS as a result of both transfusion and hemophilia A, this suggests that P carinii pneumonia or P carinii pneumonia- like pneumonias may be more common in these individuals.
Acquired Immunodeficiency Syndrome↗
Severe open tibial fractures. Results treating 202 injuries with external fixation.
Grade III open tibial fractures are known for frequent complications and poor clinical results, yet published series are few and cite conflicting results. To address this dilemma, the authors report a prospective study of 202 consecutive Grade III tibial fractures. All injuries were treated under protocol at the authors' university with primary external fixation and serial debridement. Equinus deformity was prevented with a new tibiometatarsal frame extension. Severe injuries crossing the ankle or knee were temporarily stabilized with external fixation across these joints. Staged reconstruction of soft tissue and then bone was undertaken for 176 of these tibias in patients who survived their multiple injuries. Reconstructive procedures included skin grafts in 57%, muscle flaps in 32%, and bone grafts in 28%. Gastrosoleus myocutaneous flaps were successful in 92% of cases versus 66% for free flaps. Late follow-up data were obtained for 171 (97%). Infection occurred in 15% and led to amputation in 7%. The infection rate was reduced to 9% in the second half of the series largely by removal of all necrotic bone prior to wound coverage. Angulation (greater than 10 degrees) in 9% and delayed union were lessened with early posterolateral grafting followed by progressive fracture loading in the fixator. A 9% incidence of pin tract drainage or loosening was reduced with predrilling and diaphyseal half pins. The time to fixator removal averaged 87 days. Ninety-three percent of the fractures united (median time, nine months) but healing times varied widely according to the amount of tissue injury and bone loss. Eighty-nine percent had satisfactory late clinical function. Results from this study, the largest series of open Grade III tibial fractures reported to date, suggest that successful staged reconstruction is now a reasonable expectation for most of these severe injuries.
Adolescent↗
Evidence for depressed humoral immunity to Pneumocystis carinii in homosexual males, commercial plasma donors, and patients with acquired immunodeficiency syndrome.
Heterosexual controls were found to have significantly higher titers of immunoglobulin G antibody to Pneumocystis carinii than did patients with the acquired immunodeficiency syndrome (AIDS) and P. carinii pneumonitis, human immunodeficiency virus (HIV) antibody-positive or -negative homosexual male "gay bar" patrons, and HIV antibody-positive or -negative commercial plasma donors. The T-helper/T-suppressor lymphocyte ratios of HIV antibody-negative homosexual male gay bar patrons were slightly depressed (mean = 1.31 +/- 0.54) compared with those of heterosexual controls (mean = 1.79 +/- 0.32). In addition to other recognized factors, preexisting humoral as well as cell-mediated immune deficits before infection with HIV may help to explain the prevalence of and morbidity and mortality associated with P. carinii pneumonitis in AIDS patients.
Acquired Immunodeficiency Syndrome↗