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Biomedical subjects

Evalina L Burger

Publications and source records attributed to Evalina L Burger.

5 recordsLinked to original sources
PubMed2005

The memory properties of cold-worked titanium rods in scoliosis constructs.

STUDY DESIGN: Time series monitoring changes in titanium and stainless steel rod curvature kept at a constant temperature of 37 C as a function of time. OBJECTIVES: To assess the possibility of loss of curvature in titanium rods after scoliosis surgery. SUMMARY OF BACKGROUND DATA: Titanium rods have gained use in scoliosis surgery due to their excellent biocompatibility, while allowing medical personnel to obtain undistorted magnetic resonance imaging scans following surgery. However, the impression of several clinicians has been that when screw pullout and/or loss of sagittal balance occurs, it may be due to the rods losing some of their curvature. METHODS: Five 6-mm rods of differing compositions and lengths (titanium 300 and 100 mm, stainless steel 300 and 100 mm, prebent titanium 85 mm) were bent at room temperature with a 3-point rod bender, then placed in an incubator at 37 C. Digital photographs were taken every 2 weeks and analyzed to extract the radius of curvature of each rod. RESULTS: The Ti rods had a significantly decreasing curvature with time. The prebent Ti and stainless steel rods did not exhibit significant change in curvature. CONCLUSIONS: Titanium rods bent at room temperature and then exposed to body temperature over time tend to exhibit "metal memory"; they gradually revert to their original shape. This may result in loss of sagittal balance and/or proximal screw pullout.

Bone Nails↗
PubMed2005

Short rest periods after static lumbar flexion are a risk factor for cumulative low back disorder.

The objective of this work was to study the effect of rest periods of various durations applied between six 10-min sessions of static flexion on the development of cumulative low back disorder (CLBD). Three experimental groups of a feline model were used, and the rest duration between sequential static load periods was set to 5, 10, and 20 min, with a corresponding load-to-rest ratio of 2:1, 1:1 and 1:2, respectively. The reflex electromyographic (EMG) activity from the multifidus muscles and supraspinous ligament displacement (creep) were recorded during the flexion periods and over 7 h of rest following the load-rest cycles. It was found that a minor disorder developed in all the groups whereas a severe neuromuscular disorder including a delayed hyperexcitability was observed only in the group subjected to 5 min rest. The two-way ANOVA showed a significant effect of time post loading (p<0.001) and rest duration (p<0.001) on the Normalized Integrated EMG (NIEMG) recovery data; a significant effect of time post loading on the Displacement data (p<0.001) was observed as well. The post hoc Fisher test performed on the NIEMG data during the recovery phase showed a significant difference between the group subjected to 5 min rest and the other two groups (p<0.001). These results suggest that while a short rest period of 2:1 load-to-rest ratio leads to CLBD, longer rest at 1:1 and 1:2 load-to-rest ratio are more favorable for preventing or attenuating the development of CLBD. Short rest periods between sessions of static lumbar flexion, therefore, are a risk factor for the development of CLBD.

Animals↗
PubMed2005

New tension band material for fixation of transverse olecranon fractures: a biomechanical study.

This study tested the use of braided polyethylene cable as an option for repairing transverse olecranon fractures. Six cadaveric elbows underwent a transverse olecranon osteotomy followed by fixation with tension band constructs using 18-gauge wire and Secure-Strand (U.S. Surgical, North Haven, Conn). Distraction forces up to 450 N were applied to the triceps tendon while measuring fracture displacement with an extensometer. The average maximal fracture gap with the standard AO tension band technique using stainless steel wire was 0.66 +/- 0.43 mm, as opposed to 0.68 +/- 0.45 mm with braided polyethylene cable. A paired t test indicated no significant difference between the two materials. These results support the feasibility of braided polyethylene cable as an alternative to the standard steel-wire tension band.

Biocompatible Materials↗
PubMed2004

Static load magnitude is a risk factor in the development of cumulative low back disorder.

Occupations requiring frequent periods of static lumbar flexion are known epidemiologically to be risk factors for the development of cumulative low back disorder. The impact of the load magnitude sustained during a series of short static lumbar flexions followed by an equally long rest period on the development of a cumulative low back disorder was addressed in an in vivo feline model. Static loads of 20, 40, and 60 N were applied over 10 min of flexion followed by 10-min rest sessions that were repeated six times (for a total of 2 h) while monitoring lumbar viscoelastic creep (laxity) and reflex electromyographic (EMG) activity from the multifidus muscles. Creep and EMG were also monitored over 7 h of rest following the six flexion-rest sessions. It was found that the creep developed in the 10-min flexion periods did not recover completely during the following 10 min of rest, giving rise to a large cumulative creep at the end of the work-rest session. Muscle activity demonstrated spasms during the static flexion periods as well as initial and delayed hyperexcitability during the 7-h rest period. Loads of 20 and 40 N did not result in delayed hyperexcitability, whereas loads of 60 N resulted in delayed hyperexcitability. Statistical analysis demonstrated that increased load significantly intensified the magnitude of the hyperexcitabilities (P < 0.05). Thus, repeated periods of static lumbar flexion were found to result in a transient neuromuscular disorder with an intensity directly related to the load magnitude, which should be considered a compounding risk factor.

Animals↗