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Biomedical subjects

W T Jackson

Publications and source records attributed to W T Jackson.

At least 91 records · Page 5Linked to original sources
PubMed1991

Anatomic considerations in posterior plating of the cervical spine.

We evaluated the anatomic structures at risk during posterior plating of the cervical spine and outlined a safe technique for screw insertion. Three cadaveric specimens were evaluated anatomically and radiographically. Screws and wires were inserted into the articular masses at different locations and angulations. The relationship of the neurovascular structures to the screws and wires was noted. To avoid injury to the nerve roots, vertebral artery, and spinal cord, the screw should be placed in the center of the articular masses perpendicular to the vertebral plane with 15 degrees lateral angulation.

Bone Plates↗
PubMed1991

Assessment of tibial fracture union by 35-45 degrees internal oblique radiographs.

Thirty-five to 45 degrees internal oblique radiographs were used in the assessment of tibial fracture healing. This view is particularly helpful when routine radiographic examinations (anteroposterior and lateral) are nondiagnostic in assessing tibial fracture healing. The technique was helpful in the diagnosis of four occult nonunions as well as in showing the position of a bone graft when used. The authors recommend this view when a decision about tibial fracture healing cannot be made from routine radiographs. They recommend this view before resorting to tomograms of the tibia.

Fractures, Ununited↗
PubMed1991

Radiological evaluation of peroneal tendon pathology associated with calcaneal fractures.

Review of MRI, CT, and radiographic views of 21 intraarticular calcaneal fractures revealed eight cases of peroneal tendon subluxation or dislocation. Routine radiographs were nondiagnostic for the soft tissue injury in five of these eight patients. The anatomic relationships between the tendons, retinaculum, and fibular groove could typically be identified easily on MRI or CT scan. In this combined injury, recognition of the peroneal tendon subluxation or dislocation and its proper management may reduce subsequent tendon dysfunction; it may also alter the calcaneal fracture management.

Adult↗
PubMed1991

A calcified ligamentum teres mimicking entrapped intraarticular bony fragments in a patient with acetabular fracture.

A motor vehicle accident victim presented with a fractured acetabulum and had apparent entrapped bony intraarticular fragments seen on computed tomography scanning. At surgery, these fragments were found to be a partially avulsed calcified ligamentum teres that was apparently caused by a previous injury of the same hip. Excision of the calcified ligament and surgical stabilization of the acetabulum were performed. A calcified ligamentum teres may be confused with entrapped bony fragments and therefore cause difficulty in the evaluation and management of acetabular fractures.

Acetabulum↗
PubMed1991

Anatomical and radiological considerations in compressive bar technique for posterior pelvic disruptions.

Sacral bar fixation is a well-recognized technique for the treatment of posteriorly unstable pelvic injuries, particularly sacral fractures. The sacral bars are placed in the iliac crest posterior to the sacrum. We reviewed 103 pelvic computed tomography (CT) scans and three cadaver pelves to measure the iliac crest prominence and its spatial relationship to the lamina of the sacrum. It was found that the best bony purchase for the bars is at the level of the L5-S1 junction. Lower placement of the bar increases the risk of violating the sacral canal and may also decrease the bony purchase of the bars. Some patients have an inadequate iliac crest posteriorly for proper placement; therefore, the pelvic CT scans should always be carefully evaluated preoperatively. The study also includes a description of a technique for percutaneous placement of sacral bars using fluoroscopic guidance.

Female↗
PubMed1991

Unilateral lumbosacral facet joint dislocation associated with vertical shear sacral fracture.

An 18-year-old woman involved in a motor vehicle accident sustained a vertical shear fracture of the sacrum accompanied by unilateral dislocation of the L5-S1 joint. Evaluation of the patient's injuries was defined by computed axial tomography. Through a posterior midline incision, open reductions of the dislocated L5-S1 joint and of the sacral fracture were performed. Reduction was followed by anterior stabilization of the symphysis pubis. The patient remained neurologically intact after surgery.

Adolescent↗
PubMed1991

Percutaneous computed tomography stabilization of moderate to severe slipped capital femoral epiphysis.

A percutaneous computed tomography (CT) guided pinning of experimentally reproduced slipped capital femoral epiphysis in five cadavers and one patient--who had bilateral pinning for moderate and severe grade chronic slip--was conducted. Prior investigations of cadavers revealed that this procedure can be performed in selected cases. The details of the technique are illustrated in this article.

Adolescent↗
PubMed1991

Effect of LTB4 receptor antagonists in endotoxic shock in the rat.

This study examined 1) the effects of infusion of LTB4 and 2) the potential role of LTB4 in the sequelae to endotoxic shock in the rat. Control rats were anesthetized with Ketamine/xylazine and given LTB4 (2 micrograms/kg) bolus i.v. followed by a 1 microgram/kg/min infusion for 10 min. LTB4 induced systemic hypotension and a three-fold increase in circulating band neutrophils which contributed to a 70% increase (P less than 0.05) in the total peripheral neutrophil count. LTB4 did not cause changes in circulating mature (segmented) neutrophils, lymphocytes, platelets, or hematocrits. Pretreatment (1 min) with LY233978, an LTB4 antagonist (10 mg/kg bolus i.v.), inhibited LTB4-induced systemic hypotension (-16.1 +/- 6.1 mmHg [n = 3] vs. -38.8 +/- 5.9 mmHg [n = 4], P less than 0.05). Salmonella enteritidis endotoxin (10 mg/kg bolus i.v.) induced systemic hypotension, hemoconcentration, leukopenia, and thrombocytopenia, which was greatest at 5 and 15 min postendotoxin. The leukopenia was characterized by lymphopenia, band neutropenia, and segmented neutropenia. LY233978 (10 mg/kg bolus i.v. immediately before endotoxin administration and followed by an infusion at 0.67 mg/kg/min for 90 min) attenuated endotoxin-induced hemoconcentration at 60 and 90 min postendotoxin (P less than 0.05), and systemic hypotension at 15 min postendotoxin (P less than 0.05). The LTB4-receptor antagonist LY255283 (10 mg/kg bolus i.v., 10 min before endotoxin followed by a 5 mg/kg bolus i.v. 30 min postendotoxin) completely inhibited endotoxin-induced systemic hypotension and partially attenuated endotoxin-induced hemoconcentration from 15 min to 90 min postendotoxin (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Limitations of radiography and computed tomography in the diagnosis of transverse sacral fracture from a high fall. A case report.

Transverse sacral fractures with sacral canal compression and neurologic deficit are rare sequelae of high falls. Nevertheless, a high index of suspicion is necessary as such an injury may present significant complications and may be missed on standard anteroposterior pelvic roentgenograms and pelvic computed tomography (CT) examinations obtained during the evaluation of multiple traumas. The saddle anesthesia, loss of bladder and sphincter function, and sexual dysfunction may be masked or unrecognized during the acute phase of polytrauma. Special attention must be directed to obtaining a lateral profile view of the sacrum, as this deformity may not be seen in any other view. Sagittal reconstruction images of the sacrum can be obtained during a pelvic CT examination if the initial lateral roentgenograms are technically inadequate because of the patient's obesity or limitations of portable radiographic equipment in the emergency department. The CT scoutview itself may show the acute sacral angulation if sufficient technique factors are employed. The roentgenographic suspicions can be confirmed with lateral multidirectional tomography or even with sagittal magnetic resonance imaging (MRI). Because this transverse sacral fracture is unstable in flexion, additional neurologic injury may result if the spine or hips are unwittingly manipulated in flexion.

Accidental Falls↗
PubMed1991

Aortic rupture complicating a fracture of an ankylosed thoracic spine. A case report.

A 34-year-old man was injured in a motorcycle accident and suffered both aortic rupture and thoracic spinal fracture, complicated by an underlying undetected ankylosing spondylitis. The latter disease can affect the integrity of vascular and spinal structure. Aortography is recommended as a high priority for the patient in an unstable cardiovascular condition requiring a definitive diagnosis. Aortic rupture and thoracic spine fracture may occur from high energy deceleration trauma. Motor vehicle passenger and pedestrian injuries are most commonly involved, although airline accidents and high falls also generate some cases. Mediastinal widening, displacement of esophagus and trachea, apical dissection of blood, and, especially, paravertebral pleural space widening are common to both injuries. Whereas most mediastinal hematomas are nonaortic in origin, a combined injury must be considered because clinical features may also overlap. These include hypotension (hypovolemic or spinal shock), paraplegia, and severe back pain. In light of the high mortality and time constraints associated with aortic rupture, immediate diagnostic resolution is necessary for appropriate management and priority of investigation.

Adult↗
PubMed1991

Ipsilateral radial head dislocation and radial shaft fracture. A case report.

Dislocation of the radial head in an adult is an uncommon injury. The mechanism of injury is considered to be due to hyperpronation of the forearm. Fracture-dislocations of the forearm are well described and involve both the radius and the ulna. A dislocation of the head of the radius with an ipsilateral fracture of the shaft of the radius seems not to have been reported; the mechanism of injury can only be postulated.

Adult↗
PubMed1991

Plating of the fibula. Its potential value as an adjunct to external fixation of the tibia.

There is added stability when plate fixation of the fibula supplements the external fixator used in treating tibial fractures associated with a segmental defect. An anatomic specimen model of a Grade III open fracture of the tibia with an associated fibular fracture was used in this study. Fibular internal fixation using an AO standard plate was performed on one of each of five matched pairs of legs. These were then subjected to identical loads in compression and torsion. The numeric values obtained during loading in all modes were converted to ratios between each of the tested pair to directly compare the effect of stabilization of the fibula. The final results showed that in each case, the preparation with fibular plating had improved resistance to deformation in axial loading. On average, the plated specimens were 2.2 times stiffer. In torsion, plating the fibula did not appear to affect the resistance of the construct to the applied load. Supplemental plate fixation of the fibula in fractures of the tibia with segmental defects may improve subsequent morbidity. The increased rigidity of the system may be sufficient to allow partial to full weight bearing immediately after surgery. This may have significant value in the management of the polytraumatized patient.

Biomechanical Phenomena↗
PubMed1990

Carpal tunnel changes and median nerve compression during wrist flexion and extension seen by magnetic resonance imaging.

Magnetic resonance imaging was done on the wrists of 14 volunteer subjects with the wrists in the neutral position, then flexed and extended at 45 degrees. Computer enhanced cross-sectional areas were measured on each subject at the level of the hook of the hamate. In the neutral position the distance between confining structures around the median nerve is 2.0 +/- 0.2 mm in the anteroposterior direction, and the mean cross-sectional area of the carpal tunnel is 1.52 cm2. With the wrist in the extended position the distance available for the median nerve measures 2.2 +/- 0.4 mm and the cross-sectional area increases to 1.75 cm2. When the wrist is flexed, the distance available for the median nerve between the flexor tendons and transverse carpal ligament decreases to 1.1 +/- 0.4 mm, and the cross-sectional tunnel area decreases to 1.36 cm2. Flexion of the wrist and/or fingers both produces a palmar rearrangement of the flexor tendons creating potential compression of the median nerve. The nerve responds to these forces by becoming interposed in various positions between the superficial flexor tendons.

Adult↗