Search PubMed⌕ Search

Biomedical subjects

R R Jacobs

Publications and source records attributed to R R Jacobs.

At least 37 records · Page 2Linked to original sources
PubMed1989

Enhancement of lumbar spine fusion by use of translaminar facet joint screws.

From January 1983 to March 1986 the authors have performed 88 consecutive lumbosacral spine fusion, enhanced with translaminar facet screws, as described by F. Magerl of St. Gallen, Switzerland. Forty-three patients have a follow-up of 12 months or greater, for a mean follow-up time of 16 months. The median time to fusion in this group was 6 months, with a range of 6 weeks to 10 months. Ninety-three percent of the patients were found to be clinically improved, and 91% of patients were judged solidly fused on evaluation of motion radiographs. Compared with our previously reported results for lumbar fusion without internal fixation, supplementation of lumbar fusion by translaminar facet screw fixation significantly improved the clinical results, as well as the time required for fusion, with no significant increased risk.

Adult↗
PubMed1989

The neuroradiographic diagnosis of lumbar herniated nucleus pulposus: I. A comparison of computed tomography (CT), myelography, CT-myelography, discography, and CT-discography.

The accuracy of five imaging modalities for the diagnosis of lumbar herniated nucleus pulposus (HNP) is compared prospectively in 124 patients, all of whom underwent surgical exploration. All tests were read independently of each other and the level of confidence in each diagnosis was recorded. The results are based on negative (106) as well as positive (125) findings at the 231 disc sites (level and side) explored. Computed tomography-discography (disco-CT) was the most accurate test (87%) compared to 77% for CT-myelography (myelo-CT), 74% for CT, 70% for myelography, 64% for disc injection pain, and 58% for discography. The false positive rate was lower for disco-CT (19%) than for myelo-CT (24%), CT (24%), and myelography (30%). The false negative rate was also lower for disco-CT (8%) than for myelo-CT (22%), CT (29%), and myelography (30%). Disco-CT was the most accurate test (94%) in patients who had prior disc surgery compared with 81% for myelo-CT, 80% for CT, and 74% for myelography. Disco-CT was also the most accurate test for patients with foraminal HNP (91% compared with 71% for CT, 65% for myelo-CT, and 58% for myelography). Disc injection reproduced the patient's clinical pain pattern in only 36% of herniated discs. This test has high specificity (89%), but low sensitivity (43%). The risks from myelography followed by discography within a 72-hour period are similar to those reported for myelography alone. Disco-CT is the most accurate of these tests (P less than 0.05) for the diagnosis of lumbar HNP.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

The neuroradiographic diagnosis of lumbar herniated nucleus pulposus: II. A comparison of computed tomography (CT), myelography, CT-myelography, and magnetic resonance imaging.

The accuracy of computed tomography (CT), myelography, CT-myelography (myelo-CT) and magnetic resonance imaging (MRI) for the diagnosis of lumbar herniated nucleus pulposus (HNP) is compared prospectively in 59 patients, all of whom underwent surgical exploration. All tests were read independently of each other and the level of confidence in each diagnosis was recorded. The results are based on the negative (61) as well as positive (59) findings at the 120 disc sites (level and side) explored. Magnetic resonance imaging was the most accurate test (76.5%) compared with myelo-CT (76.0%), CT (73.6%), and myelography (71.4%). The false positive rate was lowest for MRI (13.5%) followed by myelography (13.7%), CT (13.8%), and myelo-CT (21.1%). The false negative rate was lowest for myelo-CT (27.2%) followed by MRI (35.7%), CT (40.2%), and myelography (44.1%). In that subset of 19 patients who had prior surgery, myelography was the most accurate means of diagnosing lumbar HNP (88.8%), followed by MRI (83.3%), myelo-CT (78.4%), and CT (72.6%). The false positive rates in these patients were 11.6% for myelography, 13.2% for MRI, 14.5% for CT, and 16.4% for myelo-CT; the false negative rates were 22.7% for MRI, 24.4% for myelography, 29.5% for myelo-CT, and 47.7% for CT. Magnetic resonance imaging compares very favorably with other currently available imaging modalities for diagnosing lumbar HNP. Magnetic resonance imaging is painless, has no known side effects or morbidity, no radiation exposure, and is noninvasive. The authors recommend it as the procedure of choice for the diagnosis of most lumbar disc herniations.

Adolescent↗
PubMed1988

Decompression and circumferential stabilization of unstable spinal fractures.

A technique of anterior decompression of the spinal canal with anterior strut grafts, followed by posterior instrumentation and local fusion, is described in a group of 18 patients with unstable thoracolumbar fractures. All patients were found to have greater than 50% encroachment of the spinal canal and a preoperative kyphosis of 21.8 degrees. At follow-up 81% of patients with incomplete neurological lesions improved at least one Frankel Grade. Residual encroachment on the spinal canal was 4.6% and at follow-up the kyphotic angle was 17.1 degrees. Complications included one anterior graft loosening (not requiring revision), three loosened rods, only one of which required revision, and one fractured Harrington rod which did not require revision. The authors conclude that this technique is an effective and safe method for treating unstable thoracolumbar injuries and is recommended if anterior instrumentation is unavailable.

Adult↗
PubMed1988

1988 Volvo award in clinical sciences. Facet joint injection in low-back pain. A prospective statistical study.

From January 1980 through December 1984, 454 patients were evaluated with facet joint injections. All had the chief complaint of low-back pain, normal neurologic examinations and no root tension signs. Three hundred and ninety completed the protocol, which included a lumbar motion pain assessment before and after facet injection. A total of 127 variables were studied. There were 229 males and 161 females with a median age of 38. Facet joint arthrograms were performed prior to intra-articular injection of local anesthetic and cortisone. Initial mean pain relief was only 29%. Variables correlating significantly (P less than 0.05) with more postinjection pain relief were older age, prior history of low-back pain, normal gait, maximum pain on extension following forward flexion in the standing position, and the absence of leg pain, muscle spasm and aggravation of pain on Valsalva. Greatest pain relief immediately after injection was seen with lumbar extension and rotation, motions reported to stress the facet joints or aggravate pain of facet joint origin. Patients with more pain on lumbar extension and rotation as a group, however, did not get more pain relief. From this study we were not able to identify clinical facet joint syndromes or predict patients responding better to this procedure. The facet joints were not commonly the single or primary source for low-back pain in the great majority (greater than 90%) of patients studied.

Adolescent↗
PubMed1988

The neurological outcome following surgery for spinal fractures.

Sixty consecutive patients with spinal injuries and encroachment upon the spinal canal of greater than 20% were assessed for neurological outcome. The patients were divided into two groups, those undergoing posterior surgery alone, and those undergoing anterior surgery for formal decompression with or without anterior or posterior instrumentation. In those patients undergoing posterior surgery, an improvement rate in the neurological function of 83% was noted in patients with incomplete lesions, whereas an 88% improvement rate was found in those undergoing the anterior procedure. There was no statistical difference in outcome between these two groups. Positive correlations were found between the level of injury and Frankel grades. The cord lesions tended to demonstrate more severe neurological deficit, whereas the cauda equina lesions were associated with a lesser severity of neurologic deficit. A component of dislocation to the injury also resulted in a more severe neurological deficit. There was no apparent difference between the degree of bony encroachment of the spinal canal and the initial Frankel grade, nor was there a clear difference between those patients undergoing anterior versus posterior surgery.

Adolescent↗
PubMed1988

Irreducible sacroiliac dislocation of the pelvic ring with caudal displacement. A case report.

An irreducible sacroiliac dislocation of the pelvic ring with resultant caudal displacement of the injured hemipelvis occurred in a 15-year-old female. Because of interposed soft tissue and bone, closed reduction was not possible. Early open reduction through a posterior approach and internal fixation resulted in a painless pelvis. Sacral root avulsion resulted in permanent neurologic deficit that has been successfully managed with an orthosis.

Adolescent↗
PubMed1987

Strategies for prevention of byssinosis.

Cotton dust is a heterogeneous mixture of plant parts and contaminants from the soil, weeds, and microorganisms. Research to control byssinosis has focused on methods to reduce the trash associated with harvested fiber and control the dust in the textile mill environment. Dust control has been effective in reducing the prevalence of byssinosis, but because cotton dust is a heterogeneous mixture of components, simple reduction in dust levels does not always assure the prevention of byssinosis. Research to identify the agents that cause byssinosis and development of methods to eliminate those agents from cotton is needed to prevent new cases of byssinosis.

Byssinosis↗
PubMed1987

The effect of Harrington rod contouring on lumbar lordosis.

The effect of Harrington rod sagittal plane contouring, or lack of it, on total lumbar, segmental lumbar, and lumbosacral lordosis was studied retrospectively in a series of 36 patients operated on for idiopathic scoliosis. Regardless of contouring, there was a decrease in total lumbar lordosis and lordosis above L4, with an increase in lordosis below L5. Although not statistically significant, patients with contoured rods had less loss of segmental (L1-4) lordosis and less increase in segmental lumbosacral lordosis (L4-S1) than the noncontoured group. Although helpful, additional steps beyond concave rod contouring appear to be necessary to consistently preserve lumbar lordosis.

Adolescent↗
PubMed1986

Biomechanical studies of an anterior pelvic external fixation frame intended for control of vertical shear fractures.

Biomechanical testing of an experimental pelvic external fixation frame incorporating a large tubular horizontal member was carried out on formalin-fixed cadaver pelves with simulated vertical shear injuries. The device was tested with 5 mm standard and 6 mm experimental pins, and was compared to a Pittsburgh triangular (PT) frame constructed of standard Hoffmann components. Tested by vertical loading, the experimental frame with 5 mm standard pins was 1.9 times as stiff as the PT frame, and with the 6 mm experimental pins it was 2.4 times as stiff as the PT frame. Clinical trials are needed to determine efficacy in vivo.

Aged↗
PubMed1986

Internal fixation in lumbosacral spine fusion. A biomechanical and clinical study.

While the posterolateral technique is the accepted fusion method for chronic mechanical back pain, the results are variable and the indications are narrow. In an attempt to resolve this problem the role of internal fixation has been explored. Relative stiffness and strength under flexion loading of four lumbosacral fixation systems--(1) translaminar facet joint screws, (2) Luque rectangular box, (3) Luque fixation to the pelvis via the Galveston technique, and (4) two-part pelvic spinal rod system--were evaluated and compared to the normal spine with and without posterior ligaments. The stiffness of the normal intact spine was found to be nonlinear: the bending moment is a function of the square of the flexion rotation. Internal fixation resulted in a twofold increase in stiffness. Facet screws were 20% stiffer and the pelvic-spinal system 2.3 times stiffer (p = 0.001) than the Luque systems but all had similar strength. A retrospective study of 135 consecutive posterolateral lumbosacral spine fusions was conducted to determine what factors improved the fusion rate, clinical results, and time to fusion. Diagnosis and previous surgical treatment, discectomy or fusion, were of no significance. The radiographic and clinical results were highly correlated (p = 0.0001). Electrical stimulation failed to improve the results. Internal fixation with facet joint screws or rods to the pelvis was found to statistically decrease the pseudarthrosis rate and reduce the time required for spine fusion (p = 0.02). The surgical technique consists of translaminar facet screws and segmental fixation to the pelvis using a new implant system.

Adolescent↗
PubMed1986

Biomechanical evaluation of the Ender's pins, the Harris nail, and the dynamic hip screw for the unstable intertrochanteric fracture.

While intramedullary fixation may have less operative morbidity than sliding plate systems, there also may be a loss of stability and strength of the fixation. In a biomechanical study with simulated unstable intertrochanteric fractures in cadaver femurs, multiple Ender's pins were 18% stronger than the single Harris nail. Compression hip screws were three times stronger than the Harris nail and two and one-half times stronger than Ender's pins. The compression hip screw was five times more rigid than either condylocephalic system.

Biomechanical Phenomena↗
PubMed1985

Long bone defects treated with demineralized bone.

This study was undertaken to determine the potential of demineralized bone alloimplant (DBA) for healing long bone defects. We removed 25 mm of bone from the junction of the proximal and middle thirds of both ulnas in seven adult male mongrel dogs. On one side of each animal the devascularized bone was replaced as a cortical autograft (CA) and on the other side, the defect was filled with DBA. Because of implant error, there were only five CAs to evaluate, of which two had achieved clinical union. Of the seven DBAs only one achieved union. The bone in and around the defect was quantified on each specimen roentgenogram and was compared to the size of the original defect. The CA defects were filled 139% +/- 11% with bone that was partly new and partly remnants of the replaced autograft. The demineralized alloimplant defects were filled 143% +/- 45% with bone which, of course, was all newly formed. The difference between the two groups was not significant. We concluded that the DBA was an excellent osteogenic stimulant, but that it did not prevent nonunion in this model.

Animals↗
PubMed1984

A study of external skeletal fixation systems for unstable pelvic fractures.

This study was undertaken to determine the feasibility of constructing an anterior pelvic external fixator capable of resisting displacement of vertical shear fractures. Newly designed tapered thread pins for cancellous bone had better bone pin fixation and their greater 6-mm diameter provided more than twice the stiffness of Hoffmann 4-mm pins when tested in clusters. Using these pins and a more rigid anterior frame as one model, various pelvic fixators were tested to determine their resistance to vertical shear forces. These tests determined that this new fixator was 16 times stiffer than a Bonnel single anterior frame and five times stiffer than a double anterior frame (both constructed of Hoffmann components). Extrapolation from the data shows that 13 mm of posterior fracture displacement would occur with loads of one half body weight using the new fixator. Additionally it was noted that Hoffmann frames constructed with two 5-mm pins performed as well as those using three 4-mm pins.

Bone Nails↗
PubMed1984

Acute bronchoconstriction induced by cotton dust: dose-related responses to endotoxin and other dust factors.

Fifty-four healthy humans, selected for their acute airway responsiveness to cotton dust, had spirometric tests immediately before and after 6 hours of exposure to card-generated cotton dust from seven different cottons (of several grades and growing regions). During exposures, we measured airborne concentrations of viable fungi and bacteria (total and gram negative), vertically elutriated gravimetric dust, and vertically elutriated endotoxin. Correlation between each of these five exposure indices and exposure-related acute changes in forced expiratory volume in 1 s showed a statistically significant relationship between all of the indices except concentration of viable fungi. Of the other four indices, endotoxin was the most highly correlated (r = -0.94; p less than 0.00001), and gravimetric dust was the least correlated (r = -0.34; p less than 0.05). These findings suggest that gram-negative endotoxin may play a major role in the acute pulmonary response to inhaled cotton dust.

Adolescent↗