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Biomedical subjects

R L Ferguson

Publications and source records attributed to R L Ferguson.

At least 19 recordsLinked to original sources
PubMed2000

Lower extremity deformities associated with thrombocytopenia and absent radius syndrome.

The cases of 11 patients with the syndrome of thrombocytopenia and absent radius (TAR syndrome) who presented at two institutions between 1970 and 1996 were reviewed. Knee deformities have been well documented in thrombocytopenia and absent radius syndrome, but an inordinate frequency of other lower extremity problems needing orthopaedic attention was seen. Five of the 11 patients with thrombocytopenia and absent radius syndrome studied had knee deformities, but seven of the 11 had 11 other lower extremity deformities. This article documents all of the lower extremity problems seen in the seven patients with thrombocytopenia and absent radius syndrome with anomalies other than those of the knee.

Child, Preschool↗
PubMed1998

A modified Harrington technique for scoliosis.

Post-Harrington techniques for adolescent idiopathic scoliosis have increased the complexity of scoliosis surgery while contributing only biomechanically more secure fixation and sagittal contour preservation. On the the basis of principles defined by Harrington, the authors developed a simplified technique that accomplishes equivalent outcomes.

Biomechanical Phenomena↗
PubMed1998

Distraction instrumentation outcomes in scoliosis.

The short-term outcomes of a new distraction technique using a small rod spinal instrumentation system (WRIGHTLOCK) are reported for adolescent idiopathic scoliosis. No caudally directed thoracic hooks were used. Seventy-four children aged 11.7 to 17.5 years who underwent consecutive posterior instrumentations are reviewed. Their curves improved from a mean of 55.6 degrees to 22.7 degrees (average of 59.2% correction). At 2.7 years mean follow-up, coronal curves lost an average of 4.2 degrees correction. Overall, there was a mean increase of 4.4 degrees in kyphosis. Children with the most preoperative hypokyphosis were afforded the greatest gains in kyphosis. Instrumentation resulted in a mean loss of 8.2 degrees lumbar lordosis. These results compare favorably with published results for other multihook systems.

Adolescent↗
PubMed1997

Efficacy of hyaluronic acid/nonsteroidal anti-inflammatory drug systems in preventing postsurgical tendon adhesions.

Tendon adhesion is acknowledged to be a function of both an overwhelming inflammatory response at the surgical site and the loss of physical separation that is normally present between the tendons and the synovial sheath. Adhesions bind the flexor tendons to each other and to surrounding structures, interfering with their normal gliding function. The clinical result of adhesion formation following flexor tendon surgery is poor digital function. This study investigated the effect of intraoperative treatments of high viscosity absorbable gels made of various combinations of hyaluronic acid and nonsteroidal anti-inflammatory drugs, on adhesion formation in a leghorn chicken flexor tendon model. Forty-eight mature, white leghorn chickens were used to verify the surgical model and to test five different gel treatments. The gels were formed from: 2% sodium hyaluronate in phosphate buffered saline alone or combined with 1 mg/mL tolmetin sodium; 1 mg/mL naproxen sodium; 0.216 g/mL calcium acetate; or 0.216 g/mL calcium acetate plus 1 mg/mL naproxen sodium. The gels were applied by injecting 0.2 mL of the specified composition into the intrasheath space near the conclusion of the surgical procedure. Gross and histological evaluations were conducted to analyze the efficacy. All of the treatments significant reduced the extent and severity of postsurgical tendon adhesion in this animal model as compared with the control (no gel treatment) (p < 0.05). The combination of naproxen sodium and calcium acetate in a high viscosity sodium hyaluronate carrier was the most effective composition. The combination of a high viscosity gel and nonsteroidal anti-inflammatory drugs appears to maintain the natural separation between the tendons and their sheaths and decrease the tissue inflammatory response through mediating two of the major stimuli in adhesion formation.

Animals↗
PubMed1997

Comparison of neurologic deficits with atlanto-dens intervals in patients with Down syndrome.

Eighty-four patients with Down syndrome had flexion-extension lateral roentgenograms of the C1-C2 articulation for the purpose of dividing the group into subluxators (> or = 4 mm atlanto-dens interval and 2 mm translation) and nonsubluxators (those who did not meet these criteria). Neurologic examinations and chart review were carried out on all patients to ascertain those with a positive neurologic finding or history. Seventeen (20%) were defined as subluxators and 67 (80%) as nonsubluxators. Five (29%) of the subluxators were found to have positive neurologic findings and 18 (27%) of the nonsubluxators had similar types of positive neurologic findings. These percentages are not significantly different. This led us to conclude that positive neurologic findings and an abnormal atlanto-dens interval are not alone adequate criteria to judge need for surgical stabilization of the C1-C2 articulation in patients with Down syndrome.

Adolescent↗
PubMed1994

The effect of site of implantation and animal age on properties of polydioxanone pins.

Absorbable polymeric orthopaedic pins (Orthosorb) of 2.0 mm diameter were implanted at different sites in mature (3.5 kg, > 5 months) and immature (5 weeks old) rabbits (total 36) for 2, 4, and 5 weeks. The sites of implantation were the medullary canal of the femur, muscles of the thigh and subcutaneous tissue of the dorsum. In mature rabbits, 1.3 mm diameter pins were also implanted in the medullary canal of the femur. The shear strength of the pins harvested from the rabbits, was measured at each time period using a fixture that shears the pins into three parts symmetrically about the load axis. In both mature and immature rabbits the rate of degradation in mechanical properties was higher in the medullary canal of bone than in the muscle and in the subcutaneous tissue (p < 0.05). The strength retention was lower in immature than in mature rabbits after 4 and 5 weeks. The 1.3-mm pins had higher initial strength (174.7 +/- 7 MPa), higher strength retention and slower degradation within the medullary canal of femur of mature rabbits as compared to the 2.0-mm pins (157.5 +/- 4.8). DSC and X-ray diffraction results of control and implanted pins showed higher initial crystallinity and a wider range of crystallite size in the 1.3-mm pins. After 5 weeks in vivo, the crystallinity increased indicating degradation within the amorphous phase. The smaller crystallites underwent recrystallization to form larger crystallites. The results indicate that site of implantation and age of recipient influence the degradation and associated effects on mechanical properties of absorbable implants. The size of the implant, though important in determining its properties, should be considered in association with its microstructure, which also plays an important role in determining strength and strength retention of absorbable polymeric systems.

Aging↗
PubMed1992

Treatment of slipped capital femoral epiphysis with a spica cast.

Thirteen patients who had seventeen slipped capital femoral epiphyses were managed with a spica cast between 1984 and 1986. The average time in the plaster cast was three months. Complications were noted in fourteen of the hips. Three pressure sores developed in two patients. Further slipping developed in three hips once the cast had been removed, and chondrolysis developed in one of these hips. Chondrolysis developed in eight additional hips, and the lesion was transient in four of them. Degenerative changes developed in all nine hips with chondrolysis, regardless of whether the chondrolysis was transient or permanent. The degenerative changes were Iowa Grade I in three of these hips, Grade II in two hips, and Grade III in four. Chondrolysis developed in six of the eight black patients and in four of the five black boys. Chondrolysis developed in six of the nine hips that had a Grade-II or III slip. These findings have led us to abandon the use of a spica cast as a mode of treatment for slipped capital femoral epiphysis.

Adolescent↗
PubMed1988

Biomechanical comparisons of spinal fracture models and the stabilizing effects of posterior instrumentations.

In this study, the authors evaluated the stiffness of motion segments in intact spines in two spine fracture models, and with each of five implant systems used for posterior fixation of thoracolumbar spine fractures. The devices represented a cross-section of types, including those employing sublaminar wires with and without laminar hooks, pedicle screws, plates, and rods. Two spine fracture models, one partially and one totally destabilized, were used in the tests of the instrumentation. Stiffness, or the magnitude of load needed to produce a unit displacement of the construct in the direction of the applied load, was measured in flexion, extension, lateral bending, and torsion in combination with a compressive force. Both horizontal plane shear and angular displacements were measured in the two fracture patterns. All evaluations were made by testing the difference in stiffness for statistical significance among groups. The results showed significant differences in stiffness without instrumentation among intact spines, partly destabilized spines (anterior two-thirds of disk and posterior ligaments removed), and totally destabilized spines (only anterior longitudinal ligament intact). The implant/spine constructs were least stiff relative to the intact spine in torsion, followed in increasing order of stiffness with flexion, lateral bending, and extension. In the Roy-Camille plate with six-screw fixation was found to produce the stiffest construct, followed by wired Harrington rods, C-rods and J-rods, and the Vermont internal fixator.(ABSTRACT TRUNCATED AT 250 WORDS)

Biomechanical Phenomena↗
PubMed1988

The Galveston experience with L-rod instrumentation for adolescent idiopathic scoliosis.

Eighty patients were treated with L-rod instrumentation (LRI) for adolescent idiopathic scoliosis at the authors' institution from 1978 through 1985. The percentage correction of Cobb angle, the fusion rate, and the neurologic injury rate were similar to that reported for Harrington instrumentation. Avoidance of postoperative casting or bracing, maintenance of secondary spinal contours, secure pelvic fixation when needed, and anterior thoracoplasty in a majority of patients were achievable goals with LRI.

Adolescent↗
PubMed1988

A 1988 perspective on the Galveston technique of pelvic fixation.

The Galveston technique for pelvic fixation was used in 40 patients who underwent scoliosis surgery with pelvic fixation at The University of Texas Medical Branch from February 1980 through June 1987. Analysis of the outcomes indicates that extension of a scoliosis fusion to the pelvis can be undertaken with excellent chance for success and without the necessity of routine postsurgical casting or bracing. Accurate contouring of the L-rod implant and meticulous fusion technique are essential to success.

Adolescent↗
PubMed1988

Considerations in the treatment of cerebral palsy patients with spinal deformities.

The natural history of spinal deformities in the cerebral palsy patient is different than that in the idiopathic patient. Consequently, the approach to the patient with cerebral palsy and the surgical decision-making are different from that in the idiopathic patient. The present article gives the UTMB approach to the treatment of the cerebral palsy patient and the unique considerations that must be taken into account when treating these patients. Specific references are made to the use of L-rod instrumentation to stabilize the spinal deformity in the cerebral palsy patient.

Adolescent↗
PubMed1987

Rib regeneration area as an indicator of fusion area in adolescent idiopathic scoliosis.

This retrospective study of 24 patients with adolescent idiopathic scoliosis who underwent L-rod instrumentation, posterior thoracoplasty, and rib-bone grafting analyzed the correlation between the quality of rib regeneration and the host response to the rib-bone grafts. A planimetric technique was used to quantitate the coronal plane area of the resected ribs and of an L1-L2 concave fusion area immediately after surgery and at the end of the first postsurgical year. Using computerized regression analysis, these and other variables such as age, Cobb angle, and grafting technique were studied. Rib regeneration correlated with spinal fusion but not with age or Cobb angle. A better host response with strip vs. morseled graft was suggested, but not statistically proven. The data strongly support the belief that systemic biologic factors are a major variable affecting the quality of the fusion procedure.

Adolescent↗
PubMed1987

The biomechanics of decompressive laminectomy.

The biomechanical effect of laminectomy as a means of relieving compression of the spinal cord-meningeal complex by an anterior mass was studied in ten grossly normal human cadaver spines. The basic experimental set-up involved drilling a sagittal plane hole transversely across a vertebral body to provide direct access to the anterior aspect of the neural canal. After securing a probe and linearly variable differential transformer (LVDT) assembly at each site to be tested, the probe was gently pushed into the neural canal; contact force against the tip of the probe as well as the depth of probe penetration was measured and recorded. Laminectomy did not alter the resulting contact force/anterior penetration plots at the fifth cervical, seventh thoracic, 12th thoracic, or third lumbar vertebra. Using the probe/LVDT assembly to measure anterior dural displacement and a cantilever displacement device to measure posterior dural displacement after laminectomy at the 12th thoracic vertebra, the authors found that although the anterior dura underwent gross displacement as the probe was pushed into the neural canal, the posterior dura displaced to a minimal degree. The extent of the laminectomy was not a factor. The study did not demonstrate any possible mechanism by which laminectomy could reduce the pressure exerted on the dura and neural elements by an anterior mass in a spine with otherwise normal neural canal dimensions.

Biomechanical Phenomena↗
PubMed1986

An algorithm for the treatment of unstable thoracolumbar fractures.

This article describes a fracture classification used at the University of Texas Medical Branch that takes into account the fracture mechanics and attempts to match the requirements of the fracture to the strong points of a particular spinal implant. The present algorithm for the treatment of thoracolumbar fractures is presented, and its efficacy is demonstrated by comparing it with an evolutionary group of spinal fractures cases

Biomechanical Phenomena↗
PubMed1985

Topics of interest in pediatric orthopedics.

This two-in-one article presents an overview of septic arthritis of the hip and school screening for adolescent idiopathic scoliosis--two problems commonly shared by the pediatrician and the pediatric orthopedic surgeon. The importance of aggressive diagnostic measures and treatment for the septic hip is emphasized and the basis for the rationale is given. In the section on scoliosis, the reader is introduced to the "scoliometer," and a rationale for management of most of these children by the primary physician is given.

Adolescent↗
PubMed1985

A biomechanical study of thoracolumbar spine fractures with bone in the canal. Part III. Mechanical properties of the dura and its tethering ligaments.

Experiments were performed to determine some mechanical properties of the spinal cord-meningeal (SCM) complex and its tethering elements with reference to factors contributing to contact pressure of an anterior mass on the SCM complex with spinal fracture and the development of some means to relieve the pressure. Measurements were made using a combined microload cell and displacement transducer that was passed posteriorly through a hole drilled in vertebra T12 through the interpedicular space and contacted the cord. Loss of nerve roots and anterior ligaments as dural tethers in the lumbar region permitted the SCM complex to fall out of the lordosis of the canal and fail to resist transverse loading. Head and neck flexion increased contact force for a given depth of penetration, particularly in the cervical region. This was consistent with measurements of strain along the dura that was greatest in the cervical region. The dura was found to be elastic, having a failure strain averaging 34% but was uniform in thickness, stiffness, and elastic modulus along its length. The study did not delineate any surgical manipulation other than removal of the anterior mass that would be beneficial when there is anterior compression of the spinal cord.

Biomechanical Phenomena↗