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S R Garfin

Publications and source records attributed to S R Garfin.

At least 73 records · Page 4Linked to original sources
PubMed1994

Preventing postlaminectomy adhesion. A new experimental model.

STUDY DESIGN: The efficacy of various interpositional membranes for prevention of extradural adhesion was investigated by a new animal model that quantified the biomechanical effect of scar formation. Twenty-one dogs were treated with autologous free fat graft, hyaluronic acid or no interpositional membrane after undergoing two-level laminotomy, nerve root exploration, and disk injury. An additional 11 dogs that did not undergo spine surgeries served as control animals. OBJECTIVES: Inter-animal variability in inherent propensity to form scar was first measured before any spine surgery. Twelve weeks after spine surgery, the lumbosacral spine of each dog was harvested en bloc for biomechanical testing of extradural adhesion ultimate load. Scar stiffness coefficient was also calculated. SUMMARY OF BACKGROUND DATA: Adhesion ultimate load was significantly less in the nonoperative control group when compared with the fat graft and no interpositional membrane group, but not when compared with the hyaluronic acid group. A beneficial effect of hyaluronic acid in lowering adhesion ultimate load was demonstrated, although a statistically significant difference from the fat graft and no interpositional membrane groups was not reached. No difference in scar stiffness coefficient was found between the four groups. METHODS: A new experimental model allowing objective biomechanical quantification of the effect of postoperative scar was described. Ultimate load of adhesions to both nerve roots and dura was measured. A biochemical assay that determined collagen content was also used to assess inter-animal propensity to form scar after a standardized surgical insult. Results were compared with other relevant studies. RESULTS: Findings suggest a beneficial effect of hyaluronic acid in decreasing the biomechanical strength of extradural adhesions following laminotomy, nerve root exploration, and disk injury when compared with use of fat graft or no interpositional membrane. These results support other recent investigations that study the use of hyaluronic acid treatment in a laminectomy model. The adverse consequence of intraoperative epidural bleeding was also demonstrated. CONCLUSIONS: The new experimental model described in the current study was reproducible and permitted objective quantification of the effect of postoperative adhesion rather than measuring its mere presence. A beneficial effect of hyaluronic acid treatment and a lack of such beneficial effect of free fat graft interpositional membrane was suggested. The importance of avoiding active epidural bleeding was also evident.

Adipose Tissue↗
PubMed1994

Metallic spinal artifacts in magnetic resonance imaging.

STUDY DESIGN: The magnetic resonance artifact susceptibility of traces of surgical aluminum, titanium, and stainless steel in a human spine model was investigated. Metallic filings were deposited in noncontiguous disc spaces in five human thoracic spines before magnetic resonance imaging with spin echo and gradient echo sequences. OBJECTIVES: Spin echo and gradient echo sequences were used for quantitate and compare void artifact produced by commonly used surgical metals. This was compared to a liquid paraffin control. SUMMARY OF BACKGROUND DATA: No significant susceptibility artifact was seen with any metal in all spin echo sequences, including T1 (TR 600, TE 12), T2 (TR 2000, TE 30), proton density (TR 2000, TE 80), and fast T2 scanning (TR 3800, TE 96, Ef). METHODS: Sagittal magnetic resonance imaging permitted void artifact quantification and comparison between different metallic alloys. Two neuroradiologists, working on a blinded basis, evaluated all data and rated the void susceptibility artifact on a scale of 1 (least) to 4 (greatest). RESULTS: In general, the magnitude of an imaging artifact during magnetic resonance imaging correlated with the magnetism of the metal. Nickel, found in a larger concentration in 316L than in 304 stainless steel, decreases the magnetic resonance artifact of specific metals because of its ability to stabilize iron in a non-magnetic state. Therefore, the 316L stainless steel yielded less artifact production than 304 stainless steel on gradient echo imaging. CONCLUSION: If upon gradient echo imaging in the postoperative period significant artifact production is noted, stainless steel deposition should be suspected as the causative agent. In this situation, spin echo techniques should be the first approach for attempting optimal visualization of the spinal cord and soft tissue structures.

Aged↗
PubMed1994

Acute calcific retropharyngeal tendinitis. Clinical presentation and pathological characterization.

Acute calcific retropharyngeal tendinitis is an underrecognized cause of pain and stiffness in the neck associated with odynophagia and retropharyngeal soft-tissue swelling. We report on five patients in whom an initial misdiagnosis of this entity as a retropharyngeal or nasopharyngeal abscess, a neoplasm, or a fracture-dislocation of the cervical spine led to interventions such as admission to the hospital and parenteral administration of antibiotics. An open biopsy was performed in one patient because of a suspected neoplasm. Evaluation of the tissue specimen with routine and polarized light microscopy, scanning electron microscopy, and energy-dispersive spectrometry demonstrated a foreign-body inflammatory response to deposited crystals of hydroxyapatite. In all five patients, the correct diagnosis was established only after retrospective review of the radiographic studies by a physician who was familiar with acute calcific retropharyngeal tendinitis. The computed tomographic findings of acute calcific retropharyngeal tendinitis are distinctive and consist of prevertebral calcification localized to the insertion of an edematous tendon of the longus colli muscle. Symptomatic relief was provided with anti-inflammatory and analgesic medications. The symptoms resolved, without sequelae, within one to two weeks for all of the patients. We hope that an increased awareness of hydroxyapatite deposition in the tendon of the longus colli muscle will result in improved early diagnosis of acute calcific retropharyngeal tendinitis.

Abscess↗
PubMed1993

The effects of induced hypertension and acute graded compression on impulse propagation in the spinal nerve roots of the pig.

Injuries caused by compression of spinal nerve roots are frequently encountered clinically. Experimental studies show that several different factors affect the pathophysiologic changes that occur after these injuries. However, the effect of hypertension in conjunction with graded compression of spinal nerve roots is yet unclear. A previously established porcine model was employed, in which the spinal nerve roots were exposed and compressed by an inflatable balloon. Impulse propagation across the compressed nerve segment was studied by the recording of efferent and afferent nerve action potentials, and nerve conduction velocity. The systemic blood pressure was increased by administration of Neo-Synephrine hydrochloride (phenylephrine HCl) (Winthrop Pharmaceuticals, New York, NY) and elevated 40 +/- 5 mm Hg above the normal (100 +/- 5 mm Hg), and electrophysiologic baseline values were recorded. The spinal nerve roots were then compressed for 2 hours with either 0 (control), 50, 100, or 200 mm Hg. The balloon was deflated and the nerve roots were allowed to recover for 1.5 hours. Impulse propagation was studied every 15 minutes and hypertension was maintained throughout the experiment. The results showed no significant changes of the efferent and afferent nerve action potentials at 0.50 or 100 mm Hg. At 200 mm Hg, efferent and afferent nerve action potentials decreased rapidly and were almost abolished within 20 minutes of compression. Some but not significant recovery was seen of the nerve impulse. Compared to data from normotensive pigs in an earlier experiment, the current study showed that hypertension significantly decreases the susceptibility of the spinal nerve roots to compression at and below 100 mm Hg.(ABSTRACT TRUNCATED AT 250 WORDS)

Action Potentials↗
PubMed1993

The effects of depth of penetration, screw orientation, and bone density on sacral screw fixation.

Obtaining adequate sacral fixation is an important and challenging clinical problem. Bicortical screw fixation has been used to provide improved mechanical strength. The goal of this study was to evaluate the effects of depth of penetration (unicortical versus bicortical), orientation (medial versus lateral), and bone density on the strength of the bone-screw interface. Seven-millimeter Steffee screws (Acromed, Cleveland, Ohio) were placed in human cadaveric sacra. The screws were placed either medially into the centrum of the S1 body or laterally into the sacral ala. The fixation systems used, either bicortical or unicortical, were tested on a Universal testing machine. The specimens were loaded to failure and biomechanical parameters were measured. Medially oriented screws sustained the highest load to failure. In an older population, unicortical fixation sustained load to failure and initial compliance findings were similar to those for bicortical fixation. The regional bone density in the centrum of the first sacral body was denser than that in the lateral alar region, and also provided more rigid bone screw fixation.

Aged↗
PubMed1993

Straight leg raising. Anatomical effects on the spinal nerve root without and with fusion.

Straight leg raising (SLR) is a useful clinical test to demonstrate an inflammatory compressive process across a spinal nerve root. Several previous studies have attempted to evaluate the effect of SLR on nerve root motion, but the exact direction and amount of this motion is still unclear. Components of the SLR test that have not been adequately addressed include the effect of SLR on the intact dural-nerve root system, motion of the nerve tissues as distinct from the dura, and nerve root strain. Separately, spinal fusion is occasionally used as an adjunct to discectomy to decrease instability and subsequent "nerve root irritation." The effect of a one-level fusion on in situ nerve root biomechanics, however, has not been evaluated. Ten fresh human cadavers underwent posterior lumbar laminectomies. Spinal nerve root motion was studied while a SLR maneuver was performed. Data was recorded photographically and statistically analyzed. The results were as follows: 1) SLR induced both linear motion (0.5-5 mm) and strain (2-4%) in spinal nerves L4, L5, and S1; 2) The dura moved less than the intrathecal nerve root at the pedicle and experienced more strain (P < .05). 3) The nerve roots moved laterally toward the pedicle and thus would move into a posterolaterally herniated disc. 4) Rigid anterior stabilization did not decrease nerve root motion or strain.

Aged↗
PubMed1993

Upper lumbar disc herniations.

This study reviews the presentation, diagnosis, and outcomes of upper lumbar disc herniations (L1-2, L2-3, L3-4). One hundred forty-one patients operated upon at three centers between 1980 and 1990 were analyzed (102 men, 39 women; 3 L1-2, 21 L2-3, 117 L3-4; average age 51.6 years; 10.4% of all lumbar discectomies performed). Preoperative signs and symptoms were highly variable. Sensory, motor, and reflex testing was variable and potentially misleading in suggesting a level of herniation. In analyzing radiographic studies (noncontrast CT, myelography, MRI) individually and using other radiographic studies and operative findings as a standard for comparison, a high false-negative rate was found for all studies when considered individually, especially at the higher L2-3 level. Intraoperative radiographs were employed with increasing frequency as the level of herniation ascended. Six operative complications (4.3%) were identified, all of which were treated and were resolving at the time of discharge. Follow-up obtained at an average of 2.2 years in 87% of patients by chart review showed no reoperations or late complications. Noncompensation patients had a significantly higher percentage of good/excellent results (86%) than those with compensation or legal claims pending (45% good/excellent results). Based upon these data, we recommend myelogram with postmyelogram CT and/or MRI in the workup of these patients and intraoperative radiographs in all cases when decompressing an upper lumbar disc herniation. Patients with compensation/legal claims should be approached cautiously, because their subjective results are significantly worse than those of noncompensation patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Effects of acute graded strain on efferent conduction properties in the rabbit tibial nerve.

This study examines effects of acute stretch on electrophysiologic properties of rabbit tibial nerve. Compound motor action potentials (CMAP) were measured in 30 rabbits, during and after two hours of acute, graded strain. The rabbits were assigned to one of three groups defined by the degree of stretch (0%, 8%, or 15%) beyond original resting length. These groups were subdivided according to ankle position during nerve strain (ankle dorsiflexion or ankle plantar flexion). Two hours of 8% strain did not significantly decrease CMAP amplitude. Fifteen percent strain with the ankle in dorsiflexion produced a significant and profound drop (99%) in CMAP amplitude. These findings are clinically relevant to nerve stretch injuries and to surgical procedures that induce acute nerve strain.

Action Potentials↗
PubMed1993

Length dependence of a halo orthosis on cervical immobilization.

This study was designed to observe the length dependence of a well-molded fiberglass body cast attached to a halo on motion restriction in an unstable cadaveric cervical spine. Also, by using this technique, comparison between the immobilization provided by a body cast and that provided by a standard premolded polyethylene halo vest could be made. Extreme cervical instability was created on adult cadavers. A halo ring was applied and then attached to a fiberglass body cast or to a polyethylene halo vest. Sequential lateral cervical radiographs were obtained during maximum flexion as the body cast was shortened from the level of the iliac crests to the level of the xiphoid process. Radiographic motion was also assessed within the polyethylene halo vest. Results revealed minimal motion difference as the fiberglass body cast was sequentially shortened. In contrast, motions within the polyethylene halo vest were variable. These results suggest that cervical immobilization may be relatively independent of support structure length and that immobilization can be maintained by a well-fitting halo vest extending to the level of the xiphoid process.

Cadaver↗
PubMed1992

Effects of reperfusion intervals on skeletal muscle injury beneath and distal to a pneumatic tourniquet.

To date there have been no experimental studies specifically directed at effects of reperfusion intervals on skeletal muscle injury beneath the tourniquet. 99mTechnetium pyrophosphate (Tc 99) incorporation and correlative histology were used to assess injury 2 days after tourniquet application in muscles beneath (thigh) and distal (leg) to the cuff. Tourniquets were applied to rabbit hindlimbs for a total of either 2 or 4 hours. In the 4-hour series, tourniquet compression (either 125 mm Hg or 350 mm Hg cuff inflation pressure) was either continuous or interrupted by 10-minute reperfusion intervals after 2 hours or after every hour of cuff inflation. In the 2-hour series, tourniquet compression (350 mm Hg) was either continuous or interrupted by 10-minute reperfusion intervals after 2 hours or after every hour of cuff inflation. In the 2-hour series, tourniquet compression (350 mm Hg) was either continuous or interrupted by a 10-minute reperfusion interval after 1 hour. Pyrophosphate incorporation (Tc 99 uptake) was significantly greater in the thigh region than in the leg region in all of the 4-hour tourniquet groups. Tc 99 uptake was significantly reduced by reperfusion after each hour of cuff inflation. With 350 mm Hg tourniquet pressure, a reperfusion interval after 2 hours of cuff inflation tended to exacerbate tourniquet compression injury. Reperfusion intervals did not significantly affect Tc 99 uptake in the leg region of these groups. With a 2-hour tourniquet time, Tc 99 uptake in the thigh was significantly decreased by reperfusion after 1 hour of cuff inflation. Previous clinical recommendations, based on serum creatine phosphokinase abnormalities after experimental tourniquet ischemia, probably reflected tourniquet compression injury. Hourly reperfusion limits skeletal muscle injury during extended periods of tourniquet use.

Animals↗
PubMed1992

Effects of magnitude and duration of compression on spinal nerve root conduction.

Spinal nerve root compression occurs commonly in conditions such as herniated nucleus pulposus, spinal stenosis, and trauma. However, the pathophysiology of the symptoms and signs related to spinal nerve root compression is poorly understood. The purpose of the present study was to assess and compare effects of various pressures and durations of acute compression on spinal nerve root conduction in the pig cauda equina. Efferent conduction (compound motor action potentials) and afferent conduction (compound nerve action potentials) were monitored during compression for 2 or 4 hours with compression pressures of 0 (sham), 50, 100, or 200 mm Hg. Recovery from compression was monitored for 1.5 hours. No significant deficits in spinal nerve root conduction were observed with 0 or 50 mm Hg compression, compared to significant conduction deficits induced by 100 and 200 mm Hg compression. Three-way analysis of variance demonstrated significant effects of compression pressure and duration on conduction at the end of compression and recovery, with a significant difference between efferent and afferent conduction at the end of the recovery period. These observations suggest an interaction between biomechanical and microvascular mechanisms in the production of nerve root conduction deficits. Such information may relate to the motor and sensory dysfunction in clinical conditions associated with spinal nerve root compression.

Action Potentials↗
PubMed1992

Screw fixation in the human sacrum. An in vitro study of the biomechanics of fixation.

A load-to-failure test was used to study the biomechanical properties of sacral screw fixation in human cadaveric specimens. The goals of this study were 1) to determine the effects of the two commonly chosen sacral screw orientations of fixation characteristics; 2) to determine the effects of selected screw-instrumentation linkages on the biomechanics of sacral screw fixation; 3) to correlate the biomechanical properties with a noninvasive assessment of sacral bone density; and 4) to correlate the torque during screw insertion with these biomechanical properties. The bone density of each specimen was measured with quantitative computed tomography. A screw was inserted from the dorsal surface either anteromedially or anterolaterally into the body of S1, and the torque needed to insert each screw was measured. The screw head was attached to a constrained or semiconstrained loading linkage. Force was applied to the screw in an inferior direction until the maximum load was achieved. The maximum load, screw translation, rotation at maximum load, and initial compliance of the bone-screw interface were determined. It was found that the anteromedial screw orientation, combined with a rigidly constrained loading linkage, resulted in the greatest maximum load to failure, the least screw rotation, and the least initial compliance of the four groups studied. The maximum load and the initial stiffness of bone-screw fixation increased significantly with bone density. Torque measurements correlated significantly with maximum load to failure, initial interface stiffness, and bone density. It was therefore concluded that bone density and torque measurements can be useful in assessing sacral screw fixation.

Aged↗