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Biomedical subjects

T S Whitecloud

Publications and source records attributed to T S Whitecloud.

At least 19 recordsLinked to original sources
PubMed1992

Hydroxylapatite coating of porous implants improves bone ingrowth and interface attachment strength.

The effect of a plasma-sprayed hydroxylapatite (HA) coating on the degree of bone ingrowth and interface shear attachment strength was investigated using a canine femoral transcortical implant model. Cylindrical implants were fabricated by sintering spherical Co-Cr-Mo particles 500-710 microns in diameter; the nominal implant dimensions were 5.95 +/- 0.05 mm diameter by 18 mm in length. One half of each implant was coated with hydroxylapatite, 25-30 microns in thickness, by a plasma-spray technique. Using strict aseptic technique, the implants were placed through both femoral cortices into defects approximately 0.05 mm undersized. After 2, 4, 6, 8, 12, 18, 26, and 52 weeks, the implants were harvested and subjected to mechanical pullout testing and undecalcified histologic evaluation. The application of the HA coating to porous implants enhanced both the amount of bone ingrowth and the interface attachment strength at all time periods. These differences were statistically significant for the percent of bone ingrowth at the 4-, 6-, 12-, 18-, 26-, and 52-week time periods, and interface shear strength values were significantly different at the 6-, 8-, 12-, 18-, and 26-week time periods. The rate of development of interface strength and bone ingrowth was also more rapid for the HA-coated implants. No evidence of any disruption, mechanical failure, or biologic resorption of the HA coating was observed. The results of the present study--demonstrating a beneficial effect of the HA coating at all time periods--are believed to be due to the use of paired comparisons, which allow assessment of subtle differences that might otherwise have been obscured by normal biological variability.

Analysis of Variance↗
PubMed1992

Neurologic testing with somatosensory evoked potentials in idiopathic scoliosis.

A study was undertaken to determine if a somatosensory conduction delay is present in the posterior columns of adolescents with idiopathic scoliosis. Somatosensory evoked potentials were recorded after median and posterior tibial nerve stimulation in 12 adolescent subjects being followed for idiopathic scoliosis with an average age of 14.6 years (range, 12.0-16.6 years). Twelve normal controls matched for age, sex, race, and height underwent identical testing. Evoked potential peak latencies were measured and conduction velocities calculated. Results showed no difference between scoliotics and normal controls. Comparable posterior column conduction velocities were recorded in both groups. If a defect in posterior column function does exist in adolescent idiopathic scoliosis, as previously postulated, it is not reflected by a conduction delay as measured by somatosensory evoked potential testing.

Adolescent↗
PubMed1992

Tissue growth into porous-coated acetabular components in 42 patients. Effects of adjunct fixation.

Histologic examination was performed on 42 uncemented, porous-coated acetabular components removed for reasons not related to fixation. Included were 20 devices that had fixed pegs or spikes to aid in initial fixation and 22 devices that used screws through the component. The diagnoses and patient ages at insertion, times in situ, and reasons for removal were comparable for the two groups. Bone ingrowth was observed in 28 of the 42 acetabular components (67%). Of the 20 components with pegs or spikes, nine had no bone ingrowth, six had minimal bone ingrowth, four had moderate ingrowth, and one had extensive bone ingrowth. Of the 22 components with screws, five had no bone ingrowth, six had minimal bone ingrowth, six had moderate bone ingrowth, and five had extensive bone ingrowth. Two of the devices with screws also had external threads on the metallic shell; neither had any bone ingrowth, and the two accounted for two of the five devices having no bone ingrowth in this group. Bone ingrowth occurred more frequently, in greater amounts and was more evenly distributed anatomically in cups using screws for initial adjunct fixation. Roentgenographic and clinical findings were unreliable in predicting ingrowth of bone.

Acetabulum↗
PubMed1992

Postlaminectomy kyphosis. Causes and surgical management.

Postlaminectomy instability of the cervical spine can be managed either anteriorly or posteriorly. The posterior procedures that have been described are best performed at the time of the original decompressive procedure. Thus, the development of a kyphotic deformity is prevented. Generally, it is technically easier to achieve anterior stabilization and arthrodesis if a postlaminectomy kyphosis develops.

Cervical Vertebrae↗
PubMed1991

Vertebral aneurysmal bone cyst. A case report and review.

The case of a 16-year-old boy with an aneurysmal bone cyst of the fourth lumbar vertebra and a herniated nucleus pulposus of the L4-5 disc is presented. Symptoms included progressive lower back pain and bilateral lower extremity weakness. Roentgenographic studies were consistent with a vertebral aneurysmal bone cyst with an expansile lesion that compromised the neural canal and an L4-5 herniated nucleus pulposus. Surgical treatment included tumor excision, L4-5 discectomy, lumbar decompression, and posterolateral and anterior lumbar fusion. Postoperatively, the lower back pain and lower extremity symptoms resolved. The patient continues to do well at 1-year follow-up.

Adolescent↗
PubMed1989

Complications with the variable spinal plating system.

From January 1986 to June of 1987, 40 patients underwent transpedicle fixation and fusion using the variable spinal plate system. Nineteen patients had undergone surgery at the same level or levels, and 21 patients had undergone no previous surgery. Diagnostic categories include spondylolisthesis, thoracolumbar and lumbar fractures, internal disc derangement, spinal stenosis, pseudarthrosis, mechanical instability, and fracture mal-union. Minimum follow-up has been 14 months, with the average being 20 months. Overall results showed 13 excellent, 12 good, seven fair, and eight poor. The overall complication rate was 45%. In those patients undergoing no previous surgery, it was 29%, but with those patients having previous surgery, it was 63%. Most of these complications were minor in nature and resolved before discharge. Implant failure occurred in seven patients, and consisted of screw breakage. Design modifications currently available should help minimize this complication. Although this method of internal fixation and fusion is technically demanding and has a high complication rate, it is considered to be indicated in lumbar fractures, revision of pseudarthrosis, spondylolisthesis with or without reduction, and failed surgery with marked instability.

Bone Plates↗
PubMed1989

Roentgenographic measurement of pedicle screw penetration.

Potential complications due to pedicle screw penetration of the anterior cortex include injury to vascular, visceral, ureteral, sympathetic, and neural structures. This study examined the accuracy of lateral roentgenographic techniques in determining actual screw penetration in vertebral levels T12 through S1 of ten unilateral sets of pedicles in five anatomic specimens. A true lateral roentgenogram alone was inaccurate for determining the penetration of the anterior cortex by a pedicle screw. The greatest discrepancy between roentgenographically apparent and actual screw penetration was found at the L4 and L5 levels. Deviation from a true lateral roentgenographic axis resulted in the most pronounced change in roentgenographically apparent screw penetration at L4 and L5. The roentgenographic axes resulting in the closest approximation of actual screw penetrations were 5 degrees and 10 degrees above the true lateral axis for the T12-L3 and the L4-S1 levels, respectively. At 50% apparent penetration, the screw may be safely assumed to not be penetrating the anterior cortex using a true lateral roentgenogram. At 80% apparent penetration, 30% and 10% probabilities of actual screw penetration of the anterior cortex exist at L4 and L5, respectively. At 100% apparent penetration, there is an almost 100% probability that the screw is actually protruding through the anterior cortex.

Biomechanical Phenomena↗
PubMed1988

Anterior lumbar fusion utilizing transvertebral fibular graft.

In those instances of failed posterior arthrodesis for spondylolisthesis, iatrogenic spondylolisthesis due to posterior neural decompression or severe (grade III or IV) spondylolisthesis, anterior stabilization using a fibular strut graft appears to be feasible and successful. Eleven patients were treated with this technique and ten achieved solid anterior arthrodesi; the eleventh fused posterolaterally. All improved symptomatically with no postoperative complications, including sexual dysfunction in the male.

Adult↗
PubMed1988

Lower cervical spondylosis and myelopathy in adults with Down's syndrome.

Abnormalities in the upper cervical spine resulting in cervical myelopathy in patients with Down's syndrome have been well-documented. However, two adult Down's syndrome patients recently presented with cervical myelopathy secondary to abnormalities of the lower cervical spine. Because of this, 105 Down's syndrome patients with normal upper cervical spines were evaluated clinically and radiographically. They were found to have an increased prevalence of lower cervical spondylosis that significantly correlated with physical findings consistent with cervical myelopathy. Therefore, physicians dealing with Down's patients should closely monitor neurological function and obtain flexion/extension laterals of the cervical spine to evaluate C1-C2 instability and degenerative changes in the lower cervical spine if a change in neurologic status is noted.

Adult↗
PubMed1987

Cervical spondylotic myelopathy and myeloradiculopathy. Anterior decompression and stabilization with autogenous fibula strut graft.

Operative treatment for cervical spondylotic myelopathy and myeloradiculopathy by anterior decompression produced functional improvement of one grade (Nurick's rating system) in 16 of 21 patients evaluated at 32 months average follow-up period. The best results occurred in patients with symptoms for less than one year and classified as grades I-III. The anterior approach for decompression is preferred because it is directed toward the degenerative structures responsible for cord and root compression. The autogeneic fibula dove-tailed strut graft is favored over an iliac crest bone graft because with multilevel decompression in the cervical spine, it provided structural stability and a high union rate. There were no neurologic complications in this series of 21 cases.

Cervical Vertebrae↗
PubMed1987

Cervical discogenic syndrome. Results of operative intervention in patients with positive discography.

In order to determine the validity of cervical discography in the diagnosis and treatment of patients presenting with cervical discogenic syndrome, a retrospective analysis of 34 patients who underwent cervical arthrodesis on the basis of positive cervical discography was performed. The symptomatic cervical levels were selected by reproduction of the patient's symptoms at the time of injection. No patient had radicular symptoms, and other diagnostic modalities such as computed tomography (CT) scanning or myelography had been within normal limits. Seventy percent of patients who underwent surgical intervention had good or excellent results. With proper utilization, cervical discography is a valid diagnostic study.

Adult↗
PubMed1986

Evaluation of hydroxylapatite graft materials in canine cervical spine fusions.

The efficacy of ceramic hydroxylapatite implant materials as graft materials for cervical spine fusion was evaluated in canines. Bioresorbable and non-bioresorbable systems were evaluated at time periods ranging from 1 to 24 weeks. Implant interbody position and progression of fusion were evaluated radiographically and histologically. Implant fracture and extrusion into adjacent soft tissues occurred in nine of 23 cases. Implant fracture occurred in many of the remaining 14 cases, however, the implant materials remained within the interspace. Implant fracture occurred with both implant systems. Radiographically little evidence of fusion was observed at less than 6 weeks, however by 12 weeks evidence of fusion was noted and was confirmed histologically. No difference in fusion rate or degree of fusion was observed between the two implant systems.

Animals↗
PubMed1986

Vibratory response in idiopathic scoliosis.

Recent clinical studies have suggested that a neurological lesion may be a cause of adolescent idiopathic scoliosis and animal experiments have implicated the posterior column pathway. We have tried to determine if differences in neurological response could be detected and measured clinically, and have compared the threshold of detection of vibratory sensation in 20 girls with adolescent idiopathic scoliosis with that in 20 clinically normal age-matched controls. A highly significant reduction of the threshold of detection of vibration was seen in the scoliotic group compared to the controls (p less than 0.001). Curve magnitude did not correlate with this threshold for either the upper (r = 0.172) or lower extremity (r = 0.126). Significant asymmetry between right- and left-sided thresholds to vibration was demonstrated in the scoliotic group. Our study supports the concept that an aberration in the function of the posterior column pathway of the cord may be of primary importance in the aetiology of idiopathic scoliosis. A clinically practical test to measure this function is presented.

Adolescent↗
PubMed1986

Upper extremity proprioception in idiopathic scoliosis.

Twenty-three patients with idiopathic scoliosis were tested for upper extremity proprioceptive function. All subjects had documented progression of deformity, with an average curvature of 34 degrees. The average ages for scoliotics and 18 control subjects were 16.1 and 20.8 years, respectively. Controls had no spinal deformity and underwent identical test procedures. The test results showed that scoliotic subjects had significant asymmetry between right and left limbs in their threshold for detection of joint motion (p less than or equal to 0.005) and in their ability to reproduce angles to which their elbow joint had been previously positioned (p less than or equal to 0.025). Slight asymmetry also was observed in the reproduction tests of the control group (p less than or equal to 0.013); however, there was no significant asymmetry seen in this group for the threshold test. Performance of bilateral limbs was designated good and bad for both groups; the limb that performed better in proprioceptive function was designated good limb. Analysis of data showed that the scoliotics' good and bad limbs performed inferiorly in both threshold and angle reproduction tests when compared with normal controls. The results of this study imply, but do not localize, a neurologic deficit in scoliotic patients.

Adolescent↗
PubMed1985

An analysis of failed Harrington rods.

Eight mechanically failed Harrington rods have been retrieved and examined clinically, metallurgically, and biomechanically to characterize the mode of instrument failure and to determine how future failure rates might be minimized. The results of the study indicated fatigue to be the mode of mechanical failure in all cases, however, in only one case was any significant metallurgical defect observed. Failure occurred at the ratchet-shaft junction in seven of eight cases with the remaining failure occurring at the midshaft region. This occurred in the rod with the metallurgical defect. The possibility of fatigue failure can be lowered by implementing both clinical and design considerations. Clinically, stress on the rod can be lowered by placing the ratchet-shaft junction as close to the hook as possible and by using the shortest rod possible. Both of these will minimize the moment arm at the vulnerable ratchet-shaft junction. Design modifications, including increased rod diameter, polishing the ratchet-shaft interface and material changes, can also be used to lower the stress on the rods and thus reduce the risk of mechanical failure.

Equipment Failure↗
PubMed1985

Chronic atlanto-axial instability in Down syndrome.

We studied the radiographs of thirty-two patients with Down syndrome for evidence of atlanto-axial instability. One of the patients had instability in 1970 and seven had it in 1983. The interval between the atlas and the odontoid process in the patients who demonstrated motion at that interval radiographically averaged 2.78 millimeters in 1970 and 6.93 millimeters in 1983 (p less than 0.005). Four patients whose radiographs showed atlanto-axial motion in 1970 lost that motion by 1983, and in seven patients who did not show atlanto-axial instability in 1970 it developed by 1983. Atlanto-axial instability was more likely to develop in boys who were more than ten years old. Accessory upper-cervical ossicles became evident in three patients, none of whom had atlanto-axial motion. However, one of these three patients had an abnormally wide atlanto-axial interval.

Age Factors↗