Biomedical subjects

Trevor C Hearn

Publications and source records attributed to Trevor C Hearn.

7 recordsLinked to original sources

PubMed2006

A new versatile hand dynamometer.

This paper describes the design and testing of a new hand strain-gauge based dynamometer. The design is portable and capable of measuring grip strengths from 12.5 to 800N. The dynamometer is independent of point of application of the grip force. Finite element modelling and experimental testing were used to verify the mechanical system's suitability. The dynamometer was designed for input to a PDA to allow full portability of the device.

Biomechanical Phenomena↗

PubMed2004

Measuring grip strength in normal adults: reference ranges and a comparison of electronic and hydraulic instruments.

PURPOSE: To determine reference ranges for peak, average, and final adult grip strength over 10 seconds by using an electronic dynamometer, and to compare results from hydraulic and electronic dynamometers. METHODS: The hand-grip strengths of 476 healthy adult subjects were tested using the electronic (Grippit; AB Detektor, Goteborg, Sweden) and hydraulic (Jamar; Smith and Nephew, Memphis, TN) dynamometers. RESULTS: Age- and gender-specific reference ranges for the Jamar and Grippit dynamometers are presented. Bland-Altman analysis of the differences between the results obtained using the 2 instruments revealed a bias (mean difference) of 22 N (Jamar - Grippit) and limits of agreement of -86 to 129 N (mean +/- 2 SD), which indicates that grip measurements may vary by up to 215 N between instruments. CONCLUSIONS: The study yielded population reference ranges of peak, average, and final strength over a 10-second grip assessment using an electronic dynamometer. Results from the Grippit and Jamar dynamometers are similar; however, the dynamometers cannot be interchanged. The Grippit provides information about endurance and fatigue of grip over 10 seconds, showing differences between right- and left-dominant adults.

Adolescent↗

PubMed2003

Ultimate tensile strength of a Leeds-Keio/autograft ACL reconstruction utilizing PLLA tibial staple fixation.

An ovine model of anterior cruciate ligament reconstruction was utilized to evaluate the biomechanical and histological response of a polylactic acid tibial fixation staple (Gunze Ltd., Japan/Zimmer, Japan). This was performed in a comparison with metallic staples, currently utilized for this procedure. The prosthesis consisted of autograft combined with a Leeds-Keio (L-K) ligament. Early post-operative mobilization was followed by retrieval of specimens at 6, 12 and 24 weeks post-reconstruction. Evaluation of the mechanical characteristics of the graft reconstructions (tensile strength) showed no significant differences (P>0.05) between the staple types for each time period. The histological response to the polylactic acid staple was minimal over the time period studied, with no adverse tissue reactions observed. The mode of reconstruction failure was observed to change with time (P<0.05) presumably as the graft characteristics alter. Overall the absorbable staples performed at a comparable level with the metallic staples within the scope of the study.

Animals↗

PubMed2003

Number, incidence, and projections of distal forearm fractures admitted to hospital in Australia.

BACKGROUND: This study documents the number, incidence, and relative risk (RR) of distal forearm fractures requiring admission to hospital in Australia in 1997 and estimates of the projected numbers for 2021. METHODS: Distal forearm fracture numbers from 1993 to 1998 were obtained. The incidence and RR were calculated by gender and 5-year age groups for 1997. Projected numbers for 2021 were estimated using population projection data. RESULTS: In 1997, fracture numbers were 12357 for male patients and 19319 for female patients. The incidence was 152 per 100000 for male patients and 157 per 100000 for female patients. The highest incidence and RR was in the 10- to 14-year age group for male patients and in the 85 years and over age group for female patients. If fracture incidence remains constant (on the basis of predicted population changes in Australia), by 2021, it is estimated that fracture numbers for people 50 years of age and over will increase by 81%, compared with 11% for people under 50. In the older age group, the number for women will be 4.7 times higher than for men. CONCLUSION: This study quantifies the potential disproportionate increase in distal forearm fractures requiring admission in Australia, particularly for female patients, because of an aging population.

Adolescent↗

PubMed2002

The effect of hydration on the stiffness of intervertebral discs in an ovine model.

OBJECTIVE: To determine the hydration-over-time behaviour of ovine intervertebral discs and intact joints in a saline bath at body temperature and the effect this has on their stiffness compared to air at ambient temperature. DESIGN: The hydration-over-time behaviour and stiffness of the ovine functional spinal unit and disc were quantified. BACKGROUND: The fluid content of an intervertebral disc is not constant but varies with external load and load history. The stiffness of ovine functional spinal units in a hydrated environment and how this compares to testing in air have not been quantified. METHODS: Intervertebral discs and functional spinal units were weighed and soaked in a saline water bath at 37 degrees C and reweighed each hour for 6 h. They were then allowed to stand in air at room temperature while the time to return to initial weight was recorded. Functional spinal units were randomly assigned to two groups. Axial compression, flexion, extension, lateral bending and axial torsion tests were performed on both the intact functional spinal unit and isolated disc. Group 1 was tested in air then in a saline water bath at 37 degrees C with the testing order reversed for Group 2. RESULTS: Hydration of the disc reached a plateau after an average 3-4 h of soaking with the largest increase seen in the first hour. Four hours, standing in air at room temperature, was required to return specimens to their initial weight. The functional spinal unit stiffness was significantly lower for those specimens tested in the bath compared to air. CONCLUSIONS: Ovine intervertebral discs show similar hydration-over-time behaviour when compared to human discs. Stiffnesses in different modes of loading were significantly different when tested in a hydrated environment compared with the standard method of testing in air. RELEVANCE: It has been shown that there are biomechanical and biochemical similarities between sheep and human intervertebral discs. Despite these similarities, no studies have looked at how ovine intervertebral discs behave over time in a hydrated environment. In humans, hydration levels are an important aspect of intervertebral disc degeneration. There is also a relationship between decreased hydration levels and increased stiffness. This study demonstrates the similarities between human and ovine hydration-over-time behaviour. The importance of intervertebral disc hydration and its effects on stiffness under different modes of loading were also demonstrated and have not been previously shown using the ovine model. In this context, the results from this study provide further support for the use of the ovine model.

Analysis of Variance↗

PubMedDate not supplied

Biceps tenodesis: a biomechanical study of fixation methods.

Rupture of the biceps tendon occurs predominantly in the middle-aged and elderly, being predisposed through bicipital tendinitis and rotator cuff lesions. Surgical repair may be an option for those requiring strength in supination. This study compared the initial fixation strength of keyhole tenodesis (n = 7) and interference screw fixation by use of cadaveric specimens. Two interference screws were evaluated (n = 7 x 2): the round-headed cannulated interference screw (RCI) and a bioresorbable screw (Sysorb). All specimens failed at the fixation site but one. This study found that overall there was a significant effect as a result of study group (keyhole vs Sysorb vs RCI, P =.034). The post hoc comparisons revealed that the keyhole was significantly stronger than the RCI screw (P =.033) but not significantly different compared with the Sysorb screw (P =.129). No significant difference was observed between the Sysorb and RCI screws (P =.762). Interference screw fixation failed by tendon slippage at the screw-tendon-bone interface; keyhole fixation failed by tendon splitting and slippage out of the restraining keyhole. Keyhole tenodesis may permit earlier postoperative mobilization when compared with tenodesis by use of interference screw fixation.

Animals↗

PubMedDate not supplied

The accuracy of three-dimensional reconstructions of the ovine knee: dissectional validation.

A single, complete, ovine knee was imaged using conventional MRI then dissected allowing comprehensive dimensional measurement of the intra-articular structures. A three-dimensional (3-D) computer model of the knee was generated from the MR sections. Thirty-two individual structural measures were recorded from the image output for which there was an available surgical measure for direct comparison. The results of Pearson's correlation testing show a rounded score of 1.00, suggesting an exceptional linear correlation between direct anatomical measurement and the 3-D image output. Further analysis of the data revealed an average error of measurement of 0.2mm across the 32 measures. The findings of this preliminary study suggest that 3-D reconstruction from MR data may be an appropriate, and accurate, means for making dimensional measurements of the bony and soft tissue structures of the ovine knee. It is unlikely that the measurement error would be of any great clinical significance. There is evidence in the literature to suggest that an ovine knee may be considered an acceptable model for substitution for the human knee in diagnostic assessment studies. Therefore, such findings may be considered clinically relevant in the field of human knee assessment.

Animals↗