PubMed Health⌕ Search

Biomedical subjects

S R Garfin

Publications and source records attributed to S R Garfin.

At least 91 records · Page 5Linked to original sources
PubMed1992

Morphology of the dens. A quantitative study.

Morphometric studies of the dens of the second cervical vertebra were performed on a sample of one hundred twenty bones from the Hamann-Todd Collection. Data were collected on the longitudinal and transverse dimensions of the dens, as well as the size of the dens relative to the centrum of C2. Relationships of dens dimensions to body size and sexual dimorphism were evaluated. In both longitudinal and transverse mean dimensions, the dens in males was slightly, but significantly larger (5-10%) than in females. The relative distributions of dens dimensions were consistently skewed toward the higher values in males and the lower values in females. Body height or weight were not significantly correlated with dens dimensions, and were therefore poor predictors of the size of the dens. Implications for screw fixation of fractures of the dens are discussed.

Adult↗
PubMed1992

Quantitative internal dens morphology.

Recent work has demonstrated the highly variable and unpredictable external dimensions of the dens (odontoid process). No data have been available regarding internal dimensions. Quantitative computed tomography analysis of 120 axis vertebrae allowed nondestructive measurement of external and internal dens dimensions. The external computed tomography measurements correlated well with caliper-derived data. Minimum internal dens dimensions and cortical thicknesses in the sagittal and transverse planes are reported. Some axis vertebrae may not be amenable to internal fixation of type II dens fractures. Preoperative planning should include quantitative computed tomography analysis of the dens.

Adult↗
PubMed1992

Experimental stretch neuropathy. Changes in nerve conduction under tension.

We developed an animal model of stretch injury to nerve in order to study in vivo conduction changes as a function of nerve strain. In 24 rabbits, the tibial nerve was exposed and stretched by 0%, 6% or 12% of its length. The strain was maintained for one hour. Nerve conduction was monitored during the period of stretch and for a one-hour recovery period. At 6% strain, the amplitude of the action potential had decreased by 70% at one hour and returned to normal during the recovery period. At 12% strain, conduction was completely blocked by one hour, and showed minimal recovery. These findings have clinical implications in nerve repair, limb trauma, and limb lengthening.

Action Potentials↗
PubMed1992

Can burst fractures be predicted from plain radiographs?

Plain radiographs of 67 acute spinal compression fractures in 49 patients were analysed by subjective and objective criteria, using CT scans as the diagnostic standard for the diagnosis of burst fracture. Discriminant analysis correctly predicted the type of fracture in 88% of cases. Burst fractures, however, were almost as frequently misdiagnosed as being wedge compression fractures using this technique, compared with the reading of 25 films from patients without previous information. A quarter of the injuries would have been misdiagnosed had reliance been placed solely on the plain radiographs. CT scans of all patients with acute spinal compression fractures should be considered to decrease this potentially serious diagnostic error.

Diagnosis, Differential↗
PubMed1992

Strain, stress and stretch of peripheral nerve. Rabbit experiments in vitro and in vivo.

Mechanical stretching is known to cause morphologic and functional changes in peripheral nerve. The points at which these changes occur, however, are not clearly defined and reported data are conflicting. The studies presented in this paper provide a basic understanding of the biomechanical properties, stretch-injury patterns, and changes of conduction properties of peripheral nerves due to stretching. Our studies showed that peripheral nerves exhibited non-linear stress-strain characteristics when placed under tension. Initially, under tension, the nerve had a low modulus that increased gradually with increasing strain until reaching a maximal value. When the nerve failed under tension, the perineurium inside the nerve ruptured, but the exterior of the nerve remained intact. Our results also show that a peripheral nerve in situ was under significant strain, but minimal in situ stress (less than 0.05 MPa). The in situ strain might vary with limb position, but did not appear to exceed the limit beyond which substantial tension or stress would be developed in the nerve. The time-dependent viscoelastic behavior of peripheral nerves were also characterized. The maintenance of small in situ stresses suggests that sustained increases in tension could be adversely affecting the electrophysiologic properties of the nerve. Indeed, marked alteration of conduction properties resulted from even a small stretch of 6 percent beyond the in situ length of the nerve, or stress less than 10 percent of the ultimate strength of the nerve.

Animals↗
PubMed1992

Complications of anterior intervertebral grafting.

Reconstruction of the spine after anterior decompression is essential to restore stability and function. A variety of materials and methods are available to reconstitute the vertebral column. Numerous complications of anterior grafting have been identified, and include failure of the graft, graft extrusion, nonunion, and infection. The clinical severity of these complications vary. The use of spinal instrumentation has helped to address some of these problems. Although certain problems are the result of faulty decision making or technical error, others are related to the severity of the patient's disease and the limitations of grafting materials. Some complications can be avoided while others can be anticipated and perhaps corrected early.

Bone Transplantation↗
PubMed1992

Disk herniations associated with compression instrumentation of lumbar flexion-distraction injuries.

Flexion-distraction injuries are often treated by open reduction and fusion using compression instrumentation. Three cases that were complicated by disk herniation at the injured level, with an acquired neurologic deficit, are reported. Middle-column failure through the annulus fibrosis (Gertzbein and Court-Brown Type A) appeared to be a common feature. This may be a permissive condition for this complication as compression is applied across the torn annulus. Preoperative magnetic resonance imaging and postreduction myelography may identify such herniations. Acquired neurologic deficits after reduction and instrumentation demand emergent evaluation and treatment.

Adolescent↗
PubMed1992

Postoperative posterior spinal wound infections.

The incidence of postoperative spinal infections increases with the complexity of the procedure. Diskectomy is associated with less than a 1% risk of infection; spinal fusion without instrumentation is associated with a 1%-5% risk; and fusion with instrumentation may be associated with a risk of 6% or more. Twenty-two postoperative posterior spinal infections that occurred during a three-year period were reviewed for this report. Staphylococcus aureus was the most frequent organism cultured (more than 50% of the cases). Other recurring organisms were Staphylococcus epidermis, Peptococcus, Enterobacter cloacae, and Bacteroides. Many patients had multiple organisms. Risk factors appeared to include advanced age, prolonged hospital bed rest, obesity, diabetes, immunosuppression, and infection at remote sites. Operative factors included prolonged surgery (greater than five hours), high volume of personnel moving through the operating room, and instrumentation. Postoperative contamination may occur and may be related to prolonged postoperative bed rest, skin maceration (thoracolumbosacral orthoses), and drainage tubes exiting distally from lumbar wounds (toward the rectum). Effective treatment includes early diagnosis, surgical debridement and irrigation, and parenteral antibiotics. Superficial infections were treated successfully with wound closure over outflow tubes, and deep infections with inflow-outflow systems. Maintaining the instrumentation in place was possible in most cases. Parenteral antibiotics were maintained for six weeks in every case.

Anti-Bacterial Agents↗
PubMed1992

Surgical management of cervical radiculopathy. Indication, techniques, and results.

Cervical radiculopathy can be surgically approached either posteriorly or anteriorly and the anterior approach has been described with or without fusion. The choice of approach and technique must be based upon anatomic, pathophysiologic, and biomechanical principles in addition to the familiarity of the surgeon with the procedures. The authors discuss the use of the posterior approach for lateral soft-disk disease because it minimizes disruption of soft and bony tissues and does not markedly disrupt the biomechanics of the cervical spine. The anterior approach is preferred for radiculopathy involving osteophytic hard-disk disease, and when properly and carefully performed, the addition of an interbody fusion holds significant advantages over diskectomy without fusion.

Cervical Vertebrae↗
PubMed1991

A new technique for the in vitro measurement of nucleus pulposus swelling pressure.

Swelling of the intervertebral disc nucleus pulposus may be a contributing factor in lower back pain syndromes. We have designed and tested a new osmometer for in vitro determination of nucleus pulposus swelling pressure. The functional principle of the osmometer involves compressing a sample of nucleus pulposus with nitrogen gas until saline pressure gradients across a 0.45-micron Millipore filter are eliminated. Swelling pressures of both pooled dog and pooled pig lumbar disc nucleus pulposus were measured on the new osmometer and were compared with swelling pressure determined using the equilibrium dialysis technique. The osmometer measured swelling pressures comparable to those obtained by the dialysis technique. This osmometer provides a rapid, direct, and accurate measurement of swelling pressure of the nucleus pulposus.

Animals↗
PubMed1991

Stress relaxation of a peripheral nerve.

This study determines the change in tension after an acute nerve lengthening, as would occur in peripheral nerve repair. Stress relaxation, a viscoelastic property, was studied with the use of 24 rabbit tibial nerves. The nerves were divided into three groups and were stretched 6%, 9%, or 12% beyond their original resting length. The mean 1-hour stress relaxations for the three groups were 48%, 34%, and 34%, respectively. Nerve stress relaxation was significantly greater at 6% strain than at 9% or 12% strain. These biomechanical findings have important clinical implications for nerve-stretch injury and for nerve repair.

Animals↗
PubMed1991

Effects of acute, graded compression on spinal nerve root function and structure. An experimental study of the pig cauda equina.

A well-controlled experimental model for analysis of compression-induced functional changes of the porcine cauda equina is presented. The model allows for electrophysiologic investigation of a variety of neurophysiologic changes induced by nerve root deformation. At an acute pressure threshold of 50-75 mm Hg, changes in both afferent and efferent conduction are induced. With higher compression pressure, a differential recovery in afferent and efferent conduction is seen.

Action Potentials↗
PubMed1991

Anatomic comparison of the Roy-Camille and Magerl techniques for screw placement in the lower cervical spine.

The Roy-Camille and Magerl techniques for screw placement in the lower cervical spine were compared under simulated operating room conditions. Three surgeons with varying years of spine surgery experience participated. The anatomic morbidity risks of each screw insertion technique were evaluated by anatomic dissection and radiographic examination. The spinal cord and vertebral arteries were not threatened by either method. Analysis of the pooled data revealed that the Roy-Camille technique had less risk of nerve root injury, nerve roots placed "at risk" for injury, and errors in "zone" of placement. The Magerl technique had less risk of facet joint violation. A learning curve was observed. Once the surgeons gained experience with the two techniques, there were no longer any statistically significant differences among them. The number of years of spine surgery practice did not influence the morbidity risk of either technique. The surgeons' ability to aim the screws was identical in the axial plane, but consistently less accurate in the sagittal plane for the Magerl screws because of the normal prominence of the cervicothoracic junction. Thorough familiarity with the regional anatomy and practice in the anatomy laboratory are recommended before performing these techniques in patients.

Bone Screws↗
PubMed1991

Acute compartment syndrome. Effect of dermotomy on fascial decompression in the leg.

Prompt surgical decompression is the only means of preventing the late sequelae of ischaemic contracture in post-traumatic compartment syndromes. However, controversy exists regarding the length of dermotomy required for adequate decompression in the lower extremity. This study investigated the skin envelope as a potential contributing factor. Wide fascial releases were performed through limited 8 cm incisions in eight cases of post-traumatic lower extremity compartment syndrome. In nine of 29 compartments the pressure remained greater than 30 mmHg. Lengthening the skin incisions to an average of 16 cm decreased intracompartmental pressures significantly. This study documents the skin envelope as a contributing factor in acute compartment syndromes of the leg. The use of generous skin incisions is supported and the need for intra-operative compartment pressure measurements in the treatment of this condition is emphasised.

Acute Disease↗
PubMed1991

The anatomy of the cauda equina on CT scans and MRI.

The nerve roots of the cauda equina may be visualised by contrast-enhanced CT scans and by surface-coil MRI. We have identified the pattern of anatomy from L2-L3 to L5-S1 in 10 human cadaver specimens and correlated this with anatomical dissections. Individual roots are slightly more distinct on contrast-enhanced CT than on surface-coil MRI. There is a crescentic oblique pattern of nerve roots at the lower lumbar levels which is still apparent in the more crowded proximal sections. In all cases, the axial images correlated precisely with the dissections. Current imaging modalities can help the clinical understanding and management of abnormalities in this region of the spine.

Adult↗