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Biomedical subjects

P X Montesano

Publications and source records attributed to P X Montesano.

At least 19 recordsLinked to original sources
PubMed2005

Application of nucleus pulposus to L5 dorsal root ganglion in rats enhances nociceptive dorsal horn neuronal windup.

Herniation of the nucleus pulposus (NP) from lumbar intervertebral discs commonly results in radiculopathic pain possibly through a neuroinflammatory response. NP sensitizes dorsal horn neuronal responses, but it is unknown whether this reflects a central or peripheral sensitization. To study central sensitization, we tested if NP enhances windup--the progressive increase in the response of a nociceptive spinal neuron to repeated electrical C-fiber stimulation--a phenomenon that may partly account for temporal summation of pain. Single-unit recordings were made from wide dynamic range (WDR; n = 36) or nociceptive-specific (NS; n = 8) L5 dorsal horn neurons in 44 isoflurane-anesthetized rats. Subcutaneous electrodes delivered electrical stimuli (20 pulses, 3 times the C-fiber threshold, 0.5 ms) to the receptive field on the hindpaw. Autologous NP was harvested from a tail disc and placed onto the L5 dorsal root ganglion after recording of baseline responses (n = 22). Controls had saline applied similarly (n = 22). Electrical stimulus trains (0.1, 0.3, and 1 Hz; 5-min interstimulus interval) were repeated every 30 min for 3-6 h after each treatment. The total number of evoked spikes (summed across all 20 stimuli) to 0.1 Hz was enhanced 3 h after NP, mainly in the after-discharge (AD) period (latency > 400 ms). Total responses to 0.3 and 1.0 Hz were also enhanced at > or = 60 min after NP in both the C-fiber (100- to 400-ms latency) and AD periods, whereas the absolute windup (C-fiber + AD - 20 times the initial response) increased at > or = 90 min after treatment. In saline controls, windup was not enhanced at any time after treatment for any stimulus frequency, although there was a trend toward enhancement at 0.3 Hz. These results are consistent with NP-induced central sensitization. Mechanical responses were not significantly enhanced after saline or NP treatment. We speculate that inflammatory agents released from (or recruited by) NP affect the dorsal root ganglion (and/or are transported to cord) to enhance primary afferent excitation of nociceptive dorsal horn neurons.

Action Potentials↗
PubMed1994

Treatment of kyphotic deformity in ankylosing spondylitis.

This article reviews the available literature on the surgical options for the correction of kyphosis in ankylosing spondylitis and presents the radiologic appearance of the post-operative spine. In the postsurgical evaluation of the spine, the focus is on appreciation of the patterns of correction, early and late determination of angular correction, recognition of various complications (infection, nonunion, improper location, or breakage of hardware), and alertness to the possibility of complications at all levels of the spine.

Adult↗
PubMed1992

Is there a role for diskography in the era of magnetic resonance imaging? Prospective correlation and quantitative analysis of computed tomography-diskography, magnetic resonance imaging, and surgical findings.

We herein report the results of a prospective study to define the role of diskography in the diagnosis of low back pain in an emerging era of magnetic resonance imaging (MRI). The study involved 32 patients (78 disks) with a clinical diagnosis of lumbar disk herniation; all were studied by computed tomography-diskography (CT-D), and 25 (51 disks) were also examined using MRI. The disks were graded on these studies according to a staging scheme modified from Modic. Ten of the patients (13 disks) having both CT-D and MRI underwent exploratory surgery, and the staging at surgery served as the standard against which the evaluative studies were judged. Surgical staging was compatible with the CT-D and MRI results in five disks, while in another five disks it was compatible only with the CT-D results. In the remaining three disks, both CT-D and MRI misidentified the stages. In six disks, CT-D more accurately defined the stage of disease than did MRI, whereas MRI was more precise than CT-D in only one disk. While having documented the value of CT-D as a source of information, particularly when surgery is contemplated, and as an effective means of staging disk herniation, we recommend MRI as the ideal screening test for lumbar radiculopathy and low back pain, reserving diskography for problematic cases.

Adult↗
PubMed1992

Unstable thoracolumbar and lumbar burst fractures treated with the AO fixateur interne.

Twenty-five consecutive patients with unstable thoracolumbar and lumbar burst fractures were surgically treated with the AO Fixateur Interne (Synthes USA, 1690 Russell Rd., Paoli, PA). Indications for surgery included a progressive neurologic deficit, spinal canal compromise greater than 50%, vertebral body collapse greater than 50%, or sagittal angulation greater than 20 degrees. Twenty males and five females ranging in age from 16 to 60 years (average 31) were treated surgically and prospectively followed. Twenty-one fractures occurred at the thoracolumbar junction (T10-L2) and 4 in the lumbar spine (L3-5). Twenty-four patients were followed for a minimum of 12 months, ranging from 12 to 38 months (average 22); one patient was lost to follow-up after 1 month postoperatively. Preoperatively, 12 patients had partial neurologic deficits; postoperatively, 11 improved at least 1 Frankel grade. Preoperatively, the 12 patients with partial neurologic deficits averaged 45 points (range 24-49) on the lower extremity motor index scale. After surgery, these patients improved an average of five points (range 1-23) on the motor index scale. Both patients with complete spinal cord injuries remained unchanged neurologically postoperatively; no patients deteriorated neurologically after surgery. The average preoperative sagittal kyphosis at the fracture site was +16 degrees (range +10 degrees to +31 degrees); the immediate postoperative sagittal angular correction averaged -4 degrees (lordosis) and ranged from +12 degrees (kyphosis) to -26 degrees (lordosis). At last follow-up, the sagittal angular correction remained unchanged in three patients and decreased in 21 patients to an average of +5 degrees (range +37 degrees to -14 degrees).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1992

Management of thoracolumbar fractures with accompanying neurological injury.

The optimal surgical approach for spinal canal reconstruction of thoracolumbar fractures is controversial, and the relationship between spinal canal reconstruction and neurological recovery remains unclear. To address these issues, 22 consecutive cases of thoracolumbar fracture with accompanying neurological deficit were reviewed. Neurological status was graded at the time of admission, postoperatively, and at a mean of 15 months postinjury. By using preoperative and postoperative radiographs and computed tomographic scans, the degree of spinal canal compromise was quantified in the sagittal, coronal, and axial planes. All fractures were stabilized by posterior instrumentation and fusion, and in 10 injuries, retropulsed vertebral body fragments were further reduced by posterolateral decompression. Spinal canal dimensions, neurological function, and operative approach were compared by using nonparametric statistical analysis. The greater the initial spinal canal compromise, the more severe the neurological deficit (P = 0.04). With injuries involving L1 and above, this relationship increased (P = 0.003). The extent of spinal canal reconstruction failed to correlate with neurological recovery. Compared with spinal instrumentation alone, transpedicular decompression showed no benefit in terms of postoperative canal dimensions or neurological outcome. On the basis of this experience, transpedicular decompression offers no advantage over spinal instrumentation alone. The relationship between initial spinal canal encroachment and neurological deficit demonstrates that the degrees of bony and neurological injury directly reflect the kinetic energy transferred at the time of impact. The lack of correlation between the extent of spinal canal reconstruction and neurological recovery suggests that ongoing neural compression/distortion contributes little to the overall neurological injury.

Adolescent↗
PubMed1991

Spinal canal decompression in traumatic thoracolumbar burst fractures: posterior distraction rods versus transpedicular screw fixation.

Although the benefit of spinal canal decompression of traumatic thoracolumbar burst fractures is controversial, it remains a desirable procedure, as many reports describe improved neurologic outcome with spinal canal reconstruction. The optimal type of posterior instrumentation for reconstructing the spinal canal is unclear. This study focused on the efficacy of posterior distraction rods versus transpedicular screw fixation implants in decompressing the spinal canal and on the relationship between the amount of canal decompression and subsequent neurologic recovery. A medical records review was conducted to identify all patients surgically treated for traumatic burst fractures of the thoracolumbar spine from January 1, 1987 to June 30, 1989. Sixty-seven patients were selected by this review, and, of these, 30 had had both preoperative and postoperative CT scans. We could find no bias among patients who received both preoperative and postoperative CT scans as compared to those who did not, therefore the 30 patients were considered to be a random sample of the total population of 67. A retrospective study was then conducted on the 30 patients with surgically treated burst fractures--15 treated with posterior distraction rods and 15 treated with AO Fixator Interne transpedicular screw fixation implants. Preoperative and postoperative spinal canal cross-sectional areas were measured directly from the scaled CT scans. The area of most severe compromise was compared with an internal standard defined as the next, caudal, uncompromised spinal level, and the percentage of preoperative and postoperative canal compromise was calculated.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1991

Biomechanics of cervical spine internal fixation.

Recent advances in the area of cervical spine internal fixation have resulted in important additions to the armamentarium of the spine surgery. However, a sophisticated knowledge of the biomechanics of these devices is important. This article discusses the biomechanics of odontoid screws, anterior cervical plates, posterior cervical plates, and posterior C1-C2 screw arthrodesis. It is hoped that this information will aid in implant selection.

Biomechanical Phenomena↗
PubMed1991

Odontoid fractures treated by anterior odontoid screw fixation.

While odontoid fractures are common injuries, disagreement exists regarding treatment. Some authors claim a high rate of pseudoarthrosis and have therefore recommended early posterior fixation and fusion. This, however, results in decreased cervical rotation. Therefore, it has been recommended that a more direct approach to the fracture be taken. Results on anterior screw fixation in 14 patients are reported. The technique was found to be especially useful in multiple trauma patients, patients who refuse halo treatment, and in some nonunions.

Bone Screws↗
PubMed1991

Posterior cervical arthrodesis with AO reconstruction plates and bone graft.

The efficacy of posterior arthrodesis of the cervical spine with AO reconstruction plates and autogenous bone graft was evaluated in a prospective study. The technique of surgical exposure and the application of the reconstruction plates fixed with screws to the lateral masses is described in detail. Of 30 patients with unstable cervical spines, all had solid fusions based on flexion and extension radiographs at follow-up averaging 17.8 months. No patient's neurologic function deteriorated. All incomplete spinal cord injuries improved at least one Frankel level. There were no neurologic or vascular complications. At follow-up, three patients had fusions extending one level longer than those instrumented. Three other patients had an increase in kyphosis compared with the operative reduction, which was not clinically significant. Although a single screw loosened in three other patients, none had an increased deformity, and all progressed to successful arthrodesis. This technique is particularly advantageous when spinous processes, laminas, and facets are injured or deficient, or when facet-type fusions are indicated.

Adolescent↗
PubMed1991

Anatomic and biomechanical assessment of transarticular screw fixation for atlantoaxial instability.

The purpose of this study is to elucidate anatomically the atlantoaxial transarticular screw fixation described by Magerl in 1979 and compare it biomechanically with Gallie wiring. Five human C1-C2 specimens were tested in flexion/extension and rotation intact, then after wiring and screw fixation. Mean screw length was 39 mm, 25 mm in the C2 lamina and 14 mm in the lateral mass. Angular displacement of screwed specimens was significantly less than control or wired groups. Stiffness at 0-0.5 Nm loads was significantly greater for screwed specimens than for wired or controls (101 +/- 49 Nm, 10.3 +/- 9.2 Nm, and 1.96 +/- 0.18 Nm, respectively). All specimens withstood 5 Nm in flexion and extension without failure. Screw fixation provides stability comparable to Gallie wiring and is stiffer at low-range forces and rotational angles.

Atlanto-Axial Joint↗
PubMed1991

Indirect spinal canal decompression in patients with thoracolumbar burst fractures treated by posterior distraction rods.

The ability of posterior distraction instrumentation to produce indirect reduction of retropulsed bone fragments was studied in 44 patients with thoracolumbar burst fractures. Using the Denis Classification, two predominate fracture types were identified: 13 patients had type A and 29 had type B fractures. Two others had Denis type D fractures. Spinal canal stenosis was reduced from a preoperative mean of 65% to 32.8% postoperatively. Denis type A fractures had significantly better reduction of 62.5% pre- to 19.2% postoperatively. Denis type B fractures reduced from 66.3% pre- to 38.9% postoperatively. The initial kyphotic deformity and the loss of vertebral height did not influence results of indirect decompression. Neurologic function at follow-up correlated with preoperative canal stenosis, but did not correlate with residual stenosis after instrumentation. This study demonstrated that posterior distraction instrumentation can achieve approximately 50% reduction in canal stenosis and that results will be influenced by fracture morphology.

Adult↗
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

Fatal cardiac tamponade resulting from a central venous catheter: a case for open-chest cardiac resuscitation.

A computer Medline search has failed to reveal any cases of cardiac tamponade secondary to central venous catheter placement in spinal deformity patients. It has become apparent that this complication should be thought of more frequently, however. The anatomic variation of spinal deformity patients may contribute to this problem. Spine deformity patients have abnormal chest-wall compliance secondary to their deformity, and abnormal position of their intrathoracic organs. This may alter the effectiveness of closed-chest cardiac resuscitation in this patient population.

Bone Nails↗
PubMed1988

Morphology and treatment of occipital condyle fractures.

During the last 4 years, the authors have had six cases of occipital condyle fractures, a very rare injury. Medline search yielded reports of 20 occipital condyle fractures in the literature. Of the six treated by the authors, one death (by pontine hemorrhage) occurred in a patient with a displaced avulsion fracture on the right occipital condyle (Type III). All others attained solid union with appropriate immobilization. Morphologically, one presented with an impacted fracture of the occipital condyle (Type I), one with a basilar skull fracture that included an occipital condyle fracture (Type II), and four had avulsion fractures of the occipital condyle. The latter are potentially unstable since loss of integrity of alar ligaments may coexist. Type I and II are stable, and the authors recommend treatment with a semiconstrained cervical orthosis. Type III injuries, which are potentially unstable, require rigid immobilization.

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↗