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Biomedical subjects

P A Robertson

Publications and source records attributed to P A Robertson.

At least 19 recordsLinked to original sources
PubMed2001

Natural history of posterior iliac crest bone graft donation for spinal surgery: a prospective analysis of morbidity.

STUDY DESIGN: A prospective study was conducted to examine bone graft donor site morbidity in 106 consecutive patients undergoing posterior spinal fusion. OBJECTIVES: To perform a prospective analysis of donor site morbidity, to document the incidence of major complications, and to collect information on the impact of autologous bone graft harvesting from the posterior iliac crest on the overall outcome of spinal surgery. SUMMARY OF BACKGROUND: Bone graft harvesting from the posterior iliac crest for spinal fusion is a source of significant morbidity. Previous retrospective case studies indicate that minor complications are common, but they do not define the natural history and complications of posterior iliac crest bone graft harvesting. METHODS: A standardized harvesting technique was used. At 3, 6, and 12 months after surgery, the patients completed a proforma questionnaire rating symptoms on a visual analog scale and underwent a postoperative examination by the surgeon. Finally, overall surgical outcome was assessed at 12 months. RESULTS: The major component of morbidity is donor site pain. Mean pain scores were 1.640 at 3 months, 1.812 at 6 months, and 1.207 at 12 months. The pain at 12 months was significantly less than at 3 and 6 months (P = 0.005), with a trend toward the highest scores at 6 months. A pain score of 0 was reported by 55% of the patients. Local sensory loss was found in 10% of the patients. Outcome assessment showed significant differences in morbidity for surgery performed at different spinal levels (P = 0.001), with lumbosacral surgery resulting in worse outcomes than either cervical (P < 0.05) or thoracolumbar (P < 0.05) surgery. Significantly higher visual analog scores were observed at 6 months in patients with poorer overall outcomes. CONCLUSIONS: According to this study, it is reasonable to reassure patients that a good result from spinal surgery will not be compromised by severe symptoms or major morbidity secondary to posterior iliac crest bone graft donation. Before surgery, patients may be advised concerning the risks of donor site pain, which improves significantly by 12 months, local tenderness, and uncommonly localized sensory loss.

Adolescent↗
PubMed2001

Biomechanical factors influencing nuclear disruption of the intervertebral disc.

STUDY DESIGN: A disc model with full anular division was used to investigate how different biomechanical parameters influence the severity of nuclear disruption during compressive loading. OBJECTIVE: To quantify the manner in which flexion, hydration, and loading rate contribute to the breakdown in the intrinsic cohesive structure of the nucleus pulposus. SUMMARY OF BACKGROUND DATA: The risk of disc herniation is known to increase when the disc is loaded in flexed positions. However, there is a lack of experimental data showing how a combination of flexion with different loading rates and hydration levels affects the extent of nuclear disruption. METHODS: A reproducible state of full hydration was established for isolated bovine caudal discs. A period of static preloading at an applied stress of 1 MPa was used to obtain a consistent state of partial hydration. Then 96 discs were subjected to a full-thickness division of the anulus fibrosus and compressed while hydration level, degree of flexion, and rate of loading were varied systematically. RESULTS: A full spectrum of nuclear damage was observed in the tests, ranging from no detectable disruption to sudden sequestration of the entire nucleus. These results were quantified, and a general correlation was established between the severity of disruption and the different loading parameters. CONCLUSIONS: The degree of flexion and the level of hydration were shown to play an important role in influencing the tendency of the nucleus to break loose and extrude through a preexisting anular division. Interestingly, the rate of loading appeared to have only a minor effect on the severity of damage induced in discs that incorporated a full depth anular division.

Analysis of Variance↗
PubMed2001

A Staphylococcus aureus paraspinal abscess associated with epidural analgesia in labour.

A case is described in which a parturient developed a Staphylococcus aureus paraspinal abscess following epidural analgesia in labour. We compared this case with other reported cases of paraspinal abscesses in obstetric patients. The presentation, diagnosis and management of these cases were reviewed. Anaesthetists need to be aware that non-spinal-epidural abscesses can occur in patients with an associated labour epidural.

Abscess↗
PubMed2000

Radiation exposure during fluoroscopically assisted pedicle screw insertion in the lumbar spine.

STUDY DESIGN: An experimental model to assess radiation exposure during lumbar pedicle screw insertion. OBJECTIVES: To measure skin (patient) and scatter (surgeon) doses of radiation during lumbar spine fluoroscopy to assess safety of the procedure for both the surgeon and patient and determine best practice. SUMMARY OF BACKGROUND DATA: Fluoroscopy assists with accuracy of pedicle screw placement, yet the optimal technique of C-arm use and risk to both patient and operating room staff from radiation exposure are unknown. METHODS: Entry- and scatter-dose recordings were made using a digital dosimeter while screening an anthropomorphic phantom prone on a radiolucent operating table. The source was positioned both superiorly and inferiorly with the height varied in the latter orientation to create a working space under the C-arm. The senior author's fluoroscopy records were reviewed in 140 consecutive cases. RESULTS: In a series of 140 patients who underwent pedicle screw fixation, the fluoroscopy time was 1.4 minutes per case or 0.33 minutes per screw. In the source-superior position, the effective dose received by the patient was approximately 2.3 mSv per case. In the source-inferior position with a working space of 300 mm, the effective dose was 6.8 mSv. Scatter dose to the surgeon was higher in the source-superior position but was still less than 10% of recommended limits for the hand, thyroid, and eyes. CONCLUSIONS: The source-superior position is the preferred position for pedicle screw screening if a working space is required. Patient exposure is minimized, and surgeon dose is well within current recommendations.

Bone Screws↗
PubMed2000

The radiologic anatomy of the lumbar and lumbosacral pedicles.

STUDY DESIGN: An anatomic and radiologic study of lumbar and lumbosacral pedicle anatomy. OBJECTIVES: To define the radiologic anatomy of the lumbar and first sacral pedicle in the coaxial projection. SUMMARY OF BACKGROUND DATA: Fluoroscopic assistance for pedicle screw placement requires radiologic landmarks. The radiologic landmarks have previously been assumed. Detailed study of the correlation between anatomy and radiology is required. METHODS: Lumbar vertebrae and sacra were marked with radiopaque material to demonstrate the pedicle cortical borders. The vertebrae were then imaged in the coaxial projection to determine the correlation between the pedicle cortex and the radiologic image. Pedicle dimensions were recorded. RESULTS: Pedicle dimensions were consistent with known measurements, yet the long axis of the L4 and L5 pedicle ellipse was oblique to the vertical. Consequently, the minor diameter of the pedicle ellipse was considerably less than the measured pedicle width at L5. The radiologic pedicle image was consistently within the true pedicle cortex, by up to 3 mm, and probably represents the inner cortical border of the pedicle. The S1 pedicle has reliable anatomic landmarks, yet only the medial and superior borders were visualized. CONCLUSIONS: The radiologic pedicle image in the lumbar and lumbosacral spine is a reliable guide to the true bony cortex of the pedicle. At S1 the pedicle image is less well correlated with the cortical borders of the pedicle, yet other reliable anatomic landmarks exist.

Bone Screws↗
PubMed2000

ACC and back injuries: the relevance of pre-existing asymptomatic conditions.

The purpose of the ARCI (1992) and AI (198) Acts is to cover those who suffered from personal injury by accident. This purpose should not be distorted. This review does not aim to suggest that cover be extended to victims of disease. Equally it is inappropriate that imaging be used to detect asymptomatic, age-related change--or reveal asymptomatic abnormalities that do not place the patient at increased risk of symptoms over the general population--so as to unfairly deny coverage to the victims of accidents. This is particularly important to those who suffer personal injury to the lumbar spine where the cause is wholly or substantially an accident, and in whom, without the specified accident having occurred, personal injury (symptoms and disability) would have not been likely to occur. Physicians managing spinal disorders must correlate clinical findings with imaging studies when planning treatment. Those considering entitlement for cover under third party/ACC provisions must pay close attention to the history and clinical evaluation, correlating these with the investigation findings, and not assume that the abnormalities found on sensitive investigations are the cause of the symptoms.

Aging↗
PubMed2000

Serial salivary estriol to detect an increased risk of preterm birth.

OBJECTIVE: To evaluate serial measurements of salivary estriol (E3) to detect increased risk of spontaneous preterm labor and preterm birth. METHODS: A masked, prospective, multicenter trial of 956 women with singleton pregnancies was completed at eight United States medical centers. Saliva was collected weekly, beginning at the 22nd week of gestation until birth, and tested for unconjugated E3 by enzyme-linked immunosorbent assay. Women were separated into high-risk and low-risk groups using the Creasy scoring system. RESULTS: A single, positive (at or above 2.1 ng/mL) salivary E3 test predicted an increased risk of spontaneous preterm labor and delivery in the total population (relative risk [RR] 4.0, P <.005), in the low-risk population (RR 4.0, P < or =.05), and in the high-risk population (RR 3.4, P =.05). Two consecutive positive tests significantly increased the RR in all study groups, with a dramatic improvement in test specificity and positive predictive value but only a modest decrease in sensitivity. In women who presented with symptomatic preterm labor, salivary E3 identified 61% of those who delivered within 2 weeks, using a threshold of 1.4 ng/mL. CONCLUSION: Elevated salivary E3 is associated with increased risk of preterm birth in asymptomatic women and symptomatic women who present for evaluation of preterm labor.

Adult↗
PubMed2000

Chitinases from Vibrio: activity screening and purification of chiA from Vibrio carchariae.

Fourteen species of Vibrio were screened for chitin-induced chitinase activity in culture medium. V. carchariae, V. alginolyticus 283 and V. campbellii showed high levels of activity. Screening on agar plates containing swollen chitin showed high levels of chitinase activity by the same three species, and also by V. fischeri and V. alginolyticus 284. An affinity purification procedure was developed for the chitinase from V. carchariae. The purified chitinase was active as a monomer with M(r) 63,000-66,000, and displayed activity toward polymeric chitin from acetylated chitosan or from crab shells. N-terminal sequence analysis and immunological cross-reactivity confirmed that the enzyme belongs to the group A/chiA family of bacterial chitinases.

Amino Acid Sequence↗
PubMed2000

Factors influencing obstetric and gynecologic patients' decisions toward medical student involvement in the outpatient setting.

OBJECTIVE: We sought to determine the reasons for obstetric and gynecologic patients' acceptance or refusal of medical student participation in their outpatient care. STUDY DESIGN: A descriptive and analytic cross-sectional study of 180 patients at the University of California, San Francisco, was done to identify factors involved in patient acceptance or refusal of medical student participation in their outpatient obstetric-gynecologic visit. Responses were analyzed by Cochran-Mantel-Haenszel tests for rank order tests of factors involved in the decision to accept or decline medical student participation and chi(2) or Fisher exact tests for comparison of data among different groups. RESULTS: Reasons for accepting medical student involvement included the desire to contribute to the training of future physicians and the desire for the highest standard of care. Reasons for refusing medical student involvement included the protection of patient privacy and the low comfort level with the examination. The acceptance rate for medical students during the obstetric visits was 89.1%, and that during the gynecologic visits was 81.4%. CONCLUSION: Private faculty patients, as well as Medicaid patients, have a high acceptance of both male and female medical students in the obstetric-gynecologic outpatient setting.

Ambulatory Care↗
PubMed2000

Medical malpractice: the effect of doctor-patient relations on medical patient perceptions and malpractice intentions.

OBJECTIVE: To examine the causal effects of doctor-patient relations and the severity of a medical outcome on medical patient perceptions and malpractice intentions in the event of an adverse medical outcome. DESIGN: Randomized between-subjects experimental design. Patients were given scenarios depicting interactions between an obstetric patient and her physician throughout the patient's pregnancy, labor, and delivery. PARTICIPANTS: One hundred twenty-eight postpartum obstetric patients were approached for participation, of whom 104 completed the study. Main outcome measures Patients' perceptions of physician competence and intentions to file a malpractice claim. RESULTS: Positive physician communication behaviors increased patients' perceptions of physician competence and decreased malpractice claim intentions toward both the physician and the hospital. A more severe outcome increased only patients' intentions to sue the hospital. CONCLUSION: These results provide empiric evidence for a direct, causal effect of the doctor-patient relationship on medical patients' treatment perceptions and malpractice claim intentions in the event of an adverse medical outcome.

Adolescent↗
PubMed1999

Determining the sagittal dimensions of the canal of the cervical spine. The reliability of ratios of anatomical measurements.

The ratio of the sagittal diameter of the cervical canal to the corresponding diameter of the vertebral body has been described as a reliable means for assessing stenosis of the canal and detecting those at risk of cervical neuropraxia. The use of ratio techniques has the advantage of avoiding variation in magnification when direct measurements are made from plain radiographs. We examined the reliability of this method using plain lateral radiographs of unknown magnification and CT scans. We also assessed other possible ratios of anatomical measurements as a guide to the diameter of the canal. Our findings showed a poor correlation between the true diameter of the canal and the ratio of its sagittal diameter to that of the vertebral body. No other more reliable ratio was identified. The variability in anatomical morphology means that the use of ratios from anatomical measurements within the cervical spine is not reliable in determining the true diameter of the cervical canal.

Adolescent↗
PubMed1999

Recurrent perinatal loss: a case study.

To date, investigators have not demonstrated a clear relationship between a parent's history of prior perinatal losses and intensity of grief response following a subsequent perinatal loss. Examining this relationship for low-income, African-American parents is important because they are a vulnerable population due to the high incidence of perinatal mortality in Blacks and their other life stressors that can impact on grief response and caring needs. The purpose of this case study was to examine the impact of recurrent perinatal loss on a low-income African-American parent. The research design for this study was case report, using interview data collected from a mother who had recently experienced her fourth perinatal loss, which occurred at twenty-five weeks of gestation. Transcripts from two open-ended interviews were analyzed. The theoretical framework used to guide analysis of this case study was Lazarus and Folkman's stress and coping theory. Results demonstrated that the prior perinatal losses did not appear as critical components of the way the mother responded to her most recent loss. Instead, perception of the care she received from healthcare providers and how that care related to her experiences with her one living child who was born at the same gestational age was an important determinant in how she responded to her loss. The results of this case study demonstrate the importance assessing a person's perception of their experience and those factors which contribute to the way they respond.

Journal Article↗
PubMed1999

Pedicle screw placement at the sacrum: anatomical characterization and limitations at S1.

Anatomical and biomechanical data have suggested that pedicle screw fixation at the sacrum is optimum in the anteromedial direction into the S1 vertebral body, yet the possibility of posterior iliac crest interference with this screw pathway has been considered but not defined. This study aimed to determine if the anteromedial direction of screw placement into the vertebral body is possible in all cases at S1 and to assess the limiting effect of the posterior iliac crest. Computed tomography scans of the upper sacrum at the S1 pedicle parallel to the sacral endplate were examined in 100 patients. Analysis using a digitizer allowed characterization of an ideal screw pathway with variable screw and screw head diameters in an anteromedial direction into the S vertebral body. The effects of the posterior iliac crest upon these pathways were studied. The study demonstrated that anteromedial placement with bicortical fixation at the vertebral body was theoretically possible in almost all (98.5%) cases. Because the sacral body is often wider than the sacral spinal canal, a straight-ahead screw direction will often achieve placement into the S1 vertebral body, if the starting point for the screw allows screw placement adjacent to the medial border of the S1 pedicle with only 1.5 mm of cortical bone separating the canal and the screw. The space between the posterior iliac crest and the lateral aspect of the screw corridor ranges from a maximum of 52.4 mm to a minimum of 12.8, 6.2, and 0 mm for the 7-, 10-, and 12.5-mm screw corridors. On only three occasions (1.5%) was the ideal screw corridor not possible because of posterior iliac crest overlap. In each case, this occurred only unilaterally and when the widest of the screw corridors (12.5 mm) was used. Both the distance between the posterior iliac crests and the space available for optimum screw placement are greater in females than males.

Bone Screws↗
PubMed1998

Reliability of axial landmarks for pedicle screw placement in the lower lumbar spine.

STUDY DESIGN: Measurements were made on transverse-plan, computed tomography scans from three different patient groups. OBJECTIVE: To describe the correlation between two previously described pedicle screw entry points to the pedicle axis and the predicted frequency of pedicle breakthrough from the use of a 6.5-mm screw placed parallel to the pedicle axis. SUMMARY OF BACKGROUND DATA: Fluoroscopic assistance improves the accuracy of pedicle screw placement. Whether this is a result of improved accuracy of the starting point or correct directional guidance is unclear. No morphologic studies have been done to assess the accuracy of previously described entry points. METHODS: Computerized digitizing and mathematic superimposition of the images from computed tomography scans of the low lumbar spine were used to quantify facet and pedicle anatomy and the correlation between two previously described entry points and the pedicle axis. RESULTS: The two previously described entry points are significantly medial to the pedicle axis. They are most medial at the L5 pedicle in patients with L4 degenerative spondylolisthesis. CONCLUSIONS: The two previously described entry points for pedicle screws in the low lumbar spine that were studied here are not reliable and tend to direct screw placement medial to the pedicle axis enough to lead to a substantial frequency of pedicle breakthrough for screws parallel to this axis. Surgeons implanting screws should take this tendency into account and use alternative methods to obtain accurate entry to the pedicle.

Adolescent↗
PubMed1998

Is there an association between water baths during labor and the development of chorioamnionitis or endometritis?

OBJECTIVE: Our purpose was to determine whether water baths during labor are associated with the development of chorioamnionitis or endometritis. STUDY DESIGN: One hundred ten cases of chorioamnionitis or endometritis and 97 controls were identified among singleton term gestations from the University of California at San Francisco perinatal database. Medical record review and patient interviews provided information on membrane rupture, history of bathing during labor, and relaxation and pain relief perceived by patients who experienced water bathing during labor. RESULTS: There was no statistically significant association between water baths during labor and the occurrence of chorioamnionitis or endometritis (odds ratio 0.93 [95% confidence interval 0.53 to 1.63]). CONCLUSIONS: Water baths during labor are not associated with chorioamnionitis or endometritis.

Adult↗
PubMed1998

Supporting parents during and after a pregnancy subsequent to a perinatal loss.

The experience of perinatal loss can be devastating for couples who want children. The decision and desire to attempt another pregnancy may be too much for parents to bear, yet the majority of women who experience perinatal loss do become pregnant again soon after the loss. A pregnancy after a perinatal loss can be mentally, emotionally, and physically taxing. The anxiety experienced by mothers during a subsequent pregnancy has been documented consistently by investigators, but less is known about the effects of perinatal loss on parenting subsequent children. Perinatal and neonatal nurses play a critical role in supporting parents during and after a subsequent pregnancy and need an understanding of the research to direct their practice.

Adult↗
PubMed1997

The Women's Health Curriculum by a problem-based learning method for medical students at the University of California, San Francisco.

OBJECTIVES: Our objectives were to (1) expand and strengthen the women's health curriculum at the University of California, San Francisco, and (2) evaluate the responses of both medical students and faculty to this curriculum. STUDY DESIGN: A written evaluation of the curriculum in women's health was completed by both students and faculty. Variables studied included mean scores of cases, the overall course score, and the preferences of medical students for faculty specialty in teaching the small groups. RESULTS: The overall course evaluation score was 7.81 (range 1 to 10). For those students who had both faculty from internal medicine or family medicine and obstetrics and gynecology, there was a strong preference that obstetrician-gynecologists teach the majority of the cases. CONCLUSIONS: The new case-based curriculum in women's health was enthusiastically received by both medical students and faculty.

Adolescent↗