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Biomedical subjects

C L Hamill

Publications and source records attributed to C L Hamill.

7 recordsLinked to original sources
PubMed1998

Neurogenic motor evoked potentials: a prospective comparison of stimulation methods in spinal deformity surgery.

Neurogenic motor evoked potentials (NMEPs) elicited by spinal cord stimulation via the spinous processes (SP-NMEP) have been widely accepted as a sensitive method of monitoring motor tract function. SP-NMEP requires additional surgical dissection as well as electrodes within the wound, making the method somewhat inconvenient. A less invasive percutaneous method of spinal cord stimulation (PERC-NMEP) has more recently been described. We prospectively compared the SP-NMEP and PERC-NMEP methods in 184 patients undergoing 225 surgical procedures. Although SP-NMEP responses were more readily obtainable than PERC-NMEP, the reliability of the two methods was not significantly different. Both methods were found to be sensitive to neurologic deficit. The present study suggests that when responses are obtained, the percutaneous method is reliable enough to obviate the spinous process method of monitoring the motor function of the spinal cord.

Adolescent↗
PubMed1997

Posterior arthrodesis in the skeletally immature patient. Assessing the risk for crankshaft: is an open triradiate cartilage the answer?

STUDY DESIGN: Thirty-three skeletally immature patients younger than 12 years of age and having posterior arthrodesis and evidence of solid posterior fusion without "adding on" were retrospectively reviewed. All patients had a minimum of 5 years of follow-up. OBJECTIVES: To ascertain factors associated with crankshaft and to determine how accurate a marker the triradiate cartilage was. SUMMARY OF DATA: All patients had Risser Stage 0 curves and all of the girls were premenarchal preoperatively. The average age was 9 years 3 months (range, 2 years-11 years 11 months). Preoperative diagnoses consisted of 14 idiopathic, 11 congenital, five dysplastic, and three neuromuscular etiologies. METHODS: Preoperatively, within 3 months after surgery, and at 2-year, 5-year, and final postoperative follow-up, the following radiographic parameters were reviewed: coronal Cobb, apical vertebral rotation, apical vertebral translation, rib vertebral angle difference, and trunkshift. RESULTS: The triradiate cartilage was open in 24 patients at the time of operation. Of those 24, only nine (37.5%) had documented proof of crankshaft. Patients with closed triradiate cartilage had no significant postoperative increase in radiographic parameters (0 of 9). The subgroup of patients with idiopathic scoliosis had an average age of 11 years 3 months (range, 9 years 2 months-11 years 11 months). Five of 14 patients had an open triradiate cartilage. All were followed up to skeletal maturity. None had significant progression in postoperative radiographic parameters. CONCLUSION: This study did not find an open triradiate cartilage to be an absolute prognostic indicator for the occurrence of crankshaft. Additional refinement of markers of maturity are needed to determine who requires anterior arthrodesis.

Cartilage, Articular↗
PubMed1997

Interobserver variability in grading lumbar fusions.

Inter- and intraobserver variability in grading lumbar fusion status radiographically was assessed. The objective was to determine the interobserver variability and intraobserver reproducibility in the assessment of two level noninstrumented lumbar fusions. Fifty sets of radiographs with anteroposterior, left and right bending, and flexion-extension lateral views were assessed by six observers of varying experience and background, with fusion status graded. Kappa statistical analysis revealed only fair interobserver agreement in grading lumbar fusion status. Intraobserver reproducibility was higher in more experienced observers. The results indicate only fair reliability in terms of interobserver agreement to grading of lumbar fusion status. Variability in assessing lumbar fusion radiographically may explain some of the variability in fusion rates reported in the literature and poor correlation that can be seen between clinical outcome and radiologic outcome.

Bone Transplantation↗
PubMed1996

The use of pedicle screw fixation to improve correction in the lumbar spine of patients with idiopathic scoliosis. Is it warranted?

STUDY DESIGN: A retrospective assessment of coronal, sagittal, and axial correction using convex lumbar pedicle screw constructs compared with hook constructs in patients with idiopathic scoliosis. OBJECTIVE: To determine if pedicle screw constructs can improve coronal, sagittal, and axial correction without increased complications and therefore warrant their use in the lumbar spine. SUMMARY OF BACKGROUND DATA: Although hooks have been the traditional fixation choice for posterior scoliosis correction of the lumbar spine, pedicle screws may offer advantages for improved correction of lumbar spinal deformity. METHODS: Twenty-two patients constituted Group A (hooks), in which 17 were double major and five were King Type IV curves. These patients had a minimum follow-up period of 2 years and an average of one hook per lumbar fusion segment. Twenty-two patients constituted Group B (screws), in which 20 were double major and two were King Type IV curves. These patients had a minimum follow-up period of 2 years, and screw configuration consisted of pedicle fixation on the convex side for correction and at times on the concave side for fixation. RESULTS: Pedicle screw fixation constructs had improved lumbar Cobb correction (P < 0.05), lowest instrumented vertebra tilt (P < 0.05), lowest instrumented vertebra translation (P < 0.01), and segmental sagittal alignment from T12 to lowest instrumented vertebra (P < 0.01). There was no significant change in axial rotation using either surgical method. CONCLUSIONS: The use of pedicle screw fixation on the convex portion of the lumbar spine in patients with double major idiopathic scoliosis allows for improved correction of the lumbar Cobb measurement, horizontalization and translation of the lowest instrumented vertebra, and improved segmental lordization over the instrumented levels without increased complications.

Adolescent↗
PubMed1985

The effect of varied stride rate upon shank deceleration in running.

The purpose of this study was to determine the effects of systematic changes in stride rate and length at a given running speed on the peak shank deceleration (PSD) experienced during ground contact. Data were collected from 10 well-trained subjects as they ran on a treadmill at a pace of 3.8 m s-1 (7-min mile-1). Shank deceleration was measured by a lightweight accelerometer which was tightly attached over the distal medial tibia. High-speed films (200 Hz) were taken from a side view to quantify modifications in sagittal plane movement which might have accompanied the stride rate changes. Five stride rate conditions were randomly presented - 10% slower, 5% slower, normal, 5% faster and 10% faster. Average PSD was computed from 10 steps during each condition and testing was repeated on three different occasions. For each session, PSD observed for each condition was normalized to that observed at the normal stride rate in order to minimize the effects of variations in attachment of the accelerometer between and within subjects. The normalized PSD results at each stride rate tested were - normal = 1.0, 10% slower = 1.09, 5% slower = 1.03, 5% faster = 0.96 and 10% faster = 0.91. Significant differences were found between all these means except normal and 5% slower. The kinematic analysis revealed non-significant results for hip, knee and ankle joint angles at touchdown for the various stride rates. Application of the findings to existing analytical models indicated that, for a given running speed, peak impact forces in the ankle and knee joints decreased as stride rate increased.

Acceleration↗
PubMed1983

The effects of shoe design parameters on rearfoot control in running.

Control of the amount and/or rate of pronation of the foot which occurs during distance running has been cited as an important consideration for runners when selecting a running shoe. In this study, high-speed movie film was taken from the rear while 10 subjects ran on a treadmill at a pace of 3.8 m X s-1. These subjects wore 36 different shoes in combinations of three midsole hardnesses, three heel flares, and four heel heights. The film data were digitized and used to determine the eversion or inversion of the heel relative to the lower leg throughout foot contact. Because eversion of the foot is a component of pronation it was used as a predictor of how much pronation was occurring. It was found that shoes with soft midsoles (25 durometer, Shore A scale) allowed significantly more maximum pronation (MP) and total rearfoot movement (TRM) than shoes with either medium (35 durometer) or hard (45 durometer) midsoles. Shoes with 0 degrees heel flare allowed significantly more MP and TRM than shoes with either 15 degrees or 30 degrees heel flares. Heel height was found to have no significant effect on either MP or TRM. These data provide guidelines for the construction of running shoes designed to limit rearfoot movement.

Biomechanical Phenomena↗