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Biomedical subjects

W T Jackson

Publications and source records attributed to W T Jackson.

At least 55 records · Page 3Linked to original sources
PubMed1994

Leukotriene B4 (LTB4) receptor antagonists: a series of (hydroxyphenyl)pyrazoles.

A series of (hydroxyphenyl)pyrazoles was designed by molecular modeling comparison with the LTB4 structure and prepared for evaluation as LTB4 receptor antagonists, culminating in 4-ethyl-5-[[6-methyl-6-(1H-tetrazol-5-yl)heptyl]oxy]-2-(1H-pyrazol -3- yl)phenol (2). Using an assay for inhibition of specific [3H]LTB4 binding to human PMN, it was found that the pyrazole ring could be methylated at N(1) with little loss of activity while methylation at N(2) reduced activity significantly. The structure-activity relationship of the terminal acid group was investigated. Good activity was found with o- and m-phenylalkanoic acids, chromane carboxylic acid, and tetrazole groups. The best in vitro activity was realized with the pyrazole nitrogen unsubstituted and with a six-carbon chain linking the phenyl ether oxygen to the tetrazole group. Compound 2, having an IC50 of 6.4 +/- 0.8 nM in the binding assay, was selected for further preclinical evaluation.

Animals↗
PubMed1994

Thoracic and lumbar fractures associated with femoral shaft fractures in the multiple trauma patient. Occult presentations and implications for femoral fracture stabilization.

Two-hundred-and-one patients with femoral shaft fractures were identified in a 5 year period at three institutions. Seven patients (3.5%) were found to have associated thoracic or lumbar fractures of various types. All resulted from high-velocity trauma. Four (57%) of these patients had thoracic or lumbar fractures that were undiagnosed on admission and before femoral fracture stabilization. A neurologic deficit persisted in four patients, and the possible contribution of femoral intramedullary rodding with positioning and traction must be considered. A high index of suspicion for thoracic and lumbar fractures is required when evaluating the high velocity trauma patient with a femoral shaft fracture. Presence of the thoracic or lumbar fracture may require initial spine stabilization or alter the method of femoral fracture treatment.

Adult↗
PubMed1994

Preoperative CT determination of angles for sacral screw placement.

Placement of screws in the sacrum is essential for assuring rigid fixation during instrumentation of the lumbosacral spine. However, the safest approach to obtaining sacral fixation has not been clearly delineated and is complicated by significant interpatient variation in sacral morphology. In the present study, CT evaluation of the S1 pedicle and sacral ala was performed in 10 cadavers and established "average" angles for screw placement. Placement of screws at the "averages" was undertaken and verified on CT. Violation, or near violation, of important anatomic landmarks was found in 4 of 10 specimens. As a result of this study, the authors contend that placement of screws in the sacrum at average angles presents unnecessary risks to important structures. The authors propose that each patient should undergo individualized preoperative CT evaluation to determine safe angles to minimize these risks.

Bone Screws↗
PubMed1994

Determination of wrist kinematics using a magnetic tracking device.

The objective of this work is to present a method to determine the three-dimensional kinematics of the human wrist joint under physiological loading conditions using a magnetic tracking device. Euler angles were used to determine wrist extension-flexion, radial-ulnar deviation and supination-pronation. The screw displacement axis (SDA) method was used to describe the relative motion between carpal bones. Computer graphics were also used to obtain a better visualization of the three-dimensional motions of the carpal bones. This was accomplished by combining motion data and digitization data describing the geometry of the articular surfaces of the carpal bones. Geometric data included the locations of several points located on the articular surfaces forming the radio-scaphoid and radio-lunate joints. The SDA axes describing the motions of the capitate or the lunate or the scaphoid with respect to the radius during flexion-extension were found almost parallel to the medial-lateral direction. Translations along any SDA did not exceed 2 mm. One can thus consider the motion of each carpal bone as a pure rotation about a screw axis. Also, the SDA axis describing the motion of the capitate with respect to the radius was found to pass through the proximal end of the capitate. The graphical display of carpal motions shows that, as the wrist is flexed, the surface of the lunate within the radio-lunate articulation moves from palmar to dorsal. On the other hand, the palmar-dorsal location of the proximal surface of the scaphoid within the radio-scaphoid articulation remains almost unchanged.

Biomechanical Phenomena↗
PubMed1994

Evaluation of process fractures of the talus using computed tomography.

Coronal computed tomography (CT) scan was used in the evaluation of a fractured process of the talus in 10 patients. Because routine radiographs failed to determine either the size or comminution of the fractured process, CT imaging was used to accurately assess the size, displacement, and comminution of the fractured process. CT scans also showed the extent of subtalar joint involvement, any associated tendon pathology, or additional fractures. In two patients the nature of the injury was initially missed, and CT scan diagnosed a nonunion of the lateral process. In all patients, CT scan altered the management of the fracture or helped in selecting the surgical approach. The authors recommend that coronal CT scans be used in the evaluation of a fractured process of the talus.

Adolescent↗
PubMed1994

Percutaneous computed tomography-guided stabilization of posterior pelvic fractures.

Nineteen patients with 21 unstable fractures of the posterior pelvic complex were treated with percutaneous computed tomography (CT)-guided posterior stabilization. CT allowed satisfactory visualization of the fracture and direction and length of the screw. It also allowed the authors to perform the procedure percutaneously, while causing only minimal blood loss. CT cuts that showed the best and safest sites for screw placement were selected. The length and direction of the screw was identified, and the skin entry site was determined. The guide pin was inserted across the fracture or disrupted sacroiliac joint; its correct position was confirmed and a cannulated screw was inserted over the pin. In the majority of patients, a pelvic external fixator was applied in the CT suite. Although assessing the deformity was possible, reduction was difficult but ultimately acceptable. All patients maintained reduction of their sacroiliac complex without loss of fixation, and all fractures healed without clinical or radiographic signs of pelvic instability. This technique was not associated with neurologic injury or deep infection. All but 2 patients returned to preinjury levels of activity and function. Two patients had associated injuries that affected their final functional outcome.

Adolescent↗
PubMed1994

Subluxation of the cervical spine caused by 3-point seat belt.

Cervical spine injuries associated with 3-point (lap-sash) seat belt restraint systems are uncommon and usually without serious sequelae. However, the potential for unstable subluxation or dislocation due to severe flexion-extension mechanism is present and may result in severe disability if not promptly recognized and treated. Such an unstable injury is reported here and was treated with internal fixation. Further attention should be given to the ability of headrests, air bags, and other restraints to protect the cervical spine.

Adult↗
PubMed1994

Anatomic and radiographic considerations in the placement of anterior pelvic external fixator pins.

Anatomic and radiographic studies were performed on three cadaveric pelves to define recommendations for better anterior pelvic external fixator pin placement. A thick zone of bone was identified for pin purchase beginning along the iliac crest 2-3 cm posterior to the anterior superior iliac spine (ASIS), and extending 6-8 cm posteriorly along the crest. This zone is hourglass-shaped, and follows the superior gluteal ridge to the superior acetabular region. This zone has a maximal thickness of 4 cm in the supra-acetabular region, and a minimum of 8 mm at the isthmus. Cortical pin penetration is more likely to occur if pin placement begins in the lateral third of the iliac crest, or if the pin is advanced beyond the isthmus of this zone, 5 cm from the crest. Acetabular penetration occurs when the pins are advanced farther than 10.5 cm. Radiographic evaluation demonstrates that only the pelvic outlet view gives the proper orientation of the iliac tables to guide the angle of the pin placement (24 degrees from vertical) and to confirm proper pin placement. Computed tomography (CT) evaluation with "inlet" positioning of the gantry gives complementary information for pin placement.

Bone Nails↗
PubMed1994

The perioperative management of protein S deficiency in total hip arthroplasty.

Protein S is an antithrombotic plasma protein that serves as a cofactor for another plasma protein, activated protein C. Patients who express a deficiency of protein S have an increased propensity to experience thromboembolic events. These events are often precipitated by factors that may cause thrombosis in nondeficient individuals, particularly in cases of trauma, pregnancy, or surgery. Anticoagulation therapy was instituted in a 45-year-old woman with known protein S deficiency and bilateral total hip arthroplasties.

Female↗
PubMed1993

Design, synthesis, and pharmacological evaluation of potent xanthone dicarboxylic acid leukotriene B4 receptor antagonists.

In an effort to develop increasingly potent and specific leukotriene B4 (LTB4) receptor antagonists, several xanthone dicarboxylic acids were synthesized and evaluated. Two separate synthetic routes were used to construct a xanthone nucleus containing a regiospecific orientation of each carboxylic acid pharmacophore. These compounds represent the major conformationally-restricted analogues of benzophenone dicarboxylic acids previously shown to antagonize the activation of human neutrophils by LTB4. The most potent agent was compound 32, which inhibited the specific binding of [3H]LTB4 to receptors on intact human neutrophils (IC50, 6.2 +/- 0.1 nM), LTB4-induced luminol-dependent chemiluminescence (IC50, 55 +/- 11 nM), aggregation (IC50, 133 +/- 42 nM), and chemotaxis (IC50, 899 +/- 176 nM). The compound was a poor antagonist of N-formyl-L-methionyl-L-leucyl-L-phenylalanine-induced chemiluminescence (IC50, 1599 +/- 317 nM) and aggregation (IC50, 2166 +/- 432 nM), indicating specificity in the inhibition of LTB4-stimulated events. Compound 32 (LY210073), which was completely devoid of agonist activity, appears to be one of the strongest inhibitors of LTB4 receptor binding reported so far.

Benzophenones↗
PubMed1993

Magnetic resonance imaging evaluation of the spine with metal implants. General safety and superior imaging with titanium.

We studied the cases of 15 patients who underwent postoperative magnetic resonance imaging evaluation after being treated with metal spinal implants. Spine stabilization was required in traumatic injuries for eight patients, cancer destruction in four patients, late cervical subluxation in one patient, spondylosis in one patient, and spondylolisthesis in one patient. A variety of stainless steel and titanium spinal implants were used. The images were evaluated for spinal and implant positioning and artifact production. Both stainless steel and titanium implants were imaged safely and there was no evidence of implant migration of local tissue-heating effect. The titanium spinal implants allowed postoperative spine imaging without the significant image distortion characteristic of the stainless steel implants. The stainless steel implants created significant artifact that impaired the usefulness of the magnetic resonance imaging evaluation.

Adult↗
PubMed1993

The location of the sacroiliac joint on the outer table of the posterior ilium.

Ten cadaveric sacroiliac joints were cleaned of soft tissue and analyzed to determine the average location of the sacroiliac joint on the outer table of the posterior ilium. The superior and inferior limbs of the joint were characterized according to length and width. The longitudinal axis for each limb was determined and located on the outer table of the posterior ilium. The location of the sacroiliac joint was then characterized with respect to established anatomic landmarks. The average lengths of the superior and inferior limbs were 4.4 and 5.6 cm, respectively. The width of each limb averaged 2.0 cm. The average distance from the longitudinal axis of the superior limb to the posterior superior iliac spine was 5.5 cm. The average longitudinal axis of the inferior limb was 1.2 cm superior to the inferior margin of the posterior inferior iliac spine. The angle between the two axes averaged 93 degrees.

Cadaver↗
PubMed1993

Comminuted fracture of the calcaneus associated with subluxation of the talus.

Two cases of complex fracture dislocation of the calcaneus having an unusual pattern of injury are described. The cases exhibit the following special characteristics: (1) fracture dislocation of the calcaneus where the primary fracture line separates the calcaneus into an anteromedial fragment that maintains its normal relationship to the talus and a posterolateral fragment that is dislocated from the subtalar joint. This posterolateral fragment moves laterally and lies adjacent to the fibula; (2) a secondary fracture line separating the lateral portion of the posterior facet from the tuberosity of the calcaneus. Both fragments are dislocated from their normal anatomical position; (3) talar tilt as shown on AP view of the ankle caused by inversion of the talus due to rupture of the lateral collateral ligament. Also, the posterolateral fragments impinging on the fibula pushes the heel downward and contributes to the talar tilt; (4) involvement of the calcaneocuboid joint; (5) dislocation of the peroneal tendons. This fracture pattern is unusual and has not been described before. Recognition of this unusual injury with subsequent and proper management may prevent major disability to the patient. Conservative treatment by casting or early range of motion is contraindicated. Closed reduction should be attempted immediately, and if not successful, a lateral approach with open reduction and internal fixation is the treatment of choice for this complex injury.

Adult↗
PubMed1993

Internal fixation of the thoracic and lumbar spine using Roy-Camille plates.

Thirty patients underwent fixation of the thoracic and lumbar spine from 1986 to 1990 using the Roy-Camille pedicular screw fixation system. The spine was stabilized for a variety of pathologic entities including fracture, tumor, spondylolisthesis, postlaminectomy instability, and pseudarthrosis. All but one patient obtained solid fusion based on radiographic and clinical criteria with an average follow up of 19.5 months. All patients reported subjective improvement in preoperative pain levels. There were no neurologic complications associated with the surgical procedure. Roy-Camille plate fixation appears to offer a stable surgical construct in the treatment of thoracic and lumbar spine instability.

Adolescent↗
PubMed1993

Fibular nonunion in combination with fractures of the tibia.

Seventeen cases of fibular nonunion or delayed union were seen in our institution from 1985 to 1990. All but one of these cases were associated with nonunion of the tibia which was diagnosed radiologically and/or surgically. The fibula characteristically heals before the tibia; therefore, if the fibula is slow in healing or showing nonunion, more intensive investigation of the tibia for occult nonunion, or delayed union, should be done to determine whether early surgical intervention would be necessary to avoid prolonging the course of treatment. Nonunion of the fibula may indicate instability of the fractured tibia. The authors have examined the relationship of this mutual nonunion and recommend careful observation of the fibular healing in associated fractures of the tibia and fibula.

Adolescent↗
PubMed1993

Partial scapulectomy for snapping scapula syndrome.

Snapping scapula is a relatively uncommon source of scapular pain. A survey of the literature reveals a variety of causes of this syndrome. In the case presented here, the symptoms of this syndrome were immediately and permanently relieved by surgical excision of scapular abnormalities and part of the medial scapular border.

Adult↗