An, Kai‐Nan

Material properties of the plantar aponeurosis were determined by a two-dimensional video tracking method to simultaneously measure the aponeurosis deformation. Failure loads averaged 1189 ± 244 N and were higher in men. Average stiffness of the intact fascia was 203.7 ± 50.5 N/mm at a loading rate of 11.12 N/sec and it did not vary significantly for the loading rates of 11.12 to 1112 N/sec. The high tensile loads required for failure were consistent with clinical and biomechanical studies and indicated the importance of the aponeurosis in foot function and arch stability.

Tendon disuse, or stress deprivation, frequently accompanies clinical disorders and treatments, yet the metabolism of tendons subject to stress deprivation has rarely been investigated systematically. The effects of stress deprivation on canine flexor tendon were investigated in this study. One adult canine forepaw was suspended for 21 or 42 days. Control forepaws were collected from dogs that had no intervention on their limbs and paws. The expression of collagen I and III was not significantly altered in the tendons disused for 21 days but was significantly decreased at 42 days ( P < 0.03). The expression of collagen II, aggrecan, decorin, and fibronectin was significantly decreased in the tendons in the suspended limbs at 21 days ( P < 0.002) and further reduced at 42 days. With stress deprivation, the expression of matrix metalloproteinase 2 (MMP2) was significantly increased ( P < 0.004) at 21 and 42 days. The expression of MMP3 was significantly decreased at 21 and 42 days ( P < 0.03). The expression of MMP13 was not altered with stress deprivation at 21 and 42 days. The expression of MMP14 was significantly increased at 21 days ( P = 0.0015) and returned to the control level at 42 days. Tissue inhibitor of metalloproteinase 1 (TIMP1) expression was decreased after the limbs were suspended for 42 days ( P = 0.0043), but not 21 days. However, TIMP2 expression was not significantly different from control at 21 or 42 days. Furthermore, the cross-sectional area of the stress-deprived tendons at 42 days was decreased compared with the control group ( P < 0.01). The intervention method in this study did not result in any alteration of stiffness of the tendon. Our study demonstrated that stress deprivation decreases the anabolic process and increases the catabolic process of extracellular matrix in flexor tendon.

In this pilot study, hypertonic dextrose solution was used to induce fibrosis of the subsynovial connective tissue (SSCT) and create an animal model of potential use in the study of carpal tunnel syndrome (CTS). The SSCT of the carpal tunnel in 15 New Zealand white rabbits were injected with 0.05 ml of 10% dextrose solution in 1 paw and 0.05 ml of saline in the contralateral paw, to serve as a control. The animals were killed at 1, 2, 4, 8, or 12 weeks. While the saline side showed minimal changes at any time period, the hypertonic dextrose side showed progressive noninflammatory SSCT fibrosis, with vascular proliferation and thickening of collagen bundles. Demyelination of the median nerve developed at 12 weeks after the injection on the dextrose side. These findings are similar to the progression of pathology noted in humans with CTS.

The purpose of this study was to investigate the rela tionship of isometric and isokinetic endurance of the forearm complex under maximum effort in a healthy population. Isometric and isokinetic endurance meas urements of elbow flexion and extension of the domi nant and nondominant sides were made in 32 healthy male subjects (age range, 21 to 39 years). Both fatigue rates and the amount of time elapsed in reaching fatigue were determined. Analysis of these data reveals that 1) isometric endurance of the forearm complex cannot be used as a predictor of isokinetic endurance, as there is no relationship between the two, 2) dominant and non dominant endurance are related, a result that supports the belief that in the assessment of the endurance of a single diseased upper extremity, the best available comparison is with the contralateral healthy extremity, and 3) healthy males in the age range tested have greater endurance in elbow extension than in flexion.

A fracture healing monitoring system with external fixators was analysed using the finite element method. Pin displacement and side bar strain under axial and side loading were evaluated at various stages of simulated fracture healing. In general, a recovery of rigidity at the fracture site of up of 25 percent of intact bone could be sensitively predicted. Effects of cross-sectional distribution and length of callus at the fracture site on pin displacement and side bar strain were studied. Alterations of fixation configuration, such as component failure during the healing process, were found to have relatively little effect on pin displacement but a rather larger effect on side bar strain. In general, the assessment of fracture healing by monitoring the deformation of external fixation devices is a useful idea. However, in practice, great care must be taken to fully understand the implication of the monitoring system before drawing conclusions on such measurements.

In biomechanics, the knowledge of accurate location of a joint center is essential because equilibration of the external loads and muscular forces about the joint is performed about this specific point. This paper focuses on the location of centers of gleno-humeral joint and scapulo-thoracic joint in a subject moving their arm in the scapular plane with a magnitude of 120°. Biplanar radiography with successive exposures has been used locating anatomical axes of bones. Geometric models of bones were defined allowing access to bone morphology by superposing model projections onto X-ray imaged bone contours. Functional models were used so as to represent the behavior in motion of shoulder joints. These techniques allowed us to access to results describing the linear and angular relative displacements of the shoulder bones between two different postures. The gleno-humeral and scapulo-thoracic finite joint centers (F H and F S ) are first defined through the location of the corresponding helical axis of motion (HAM) moving the joint from positions occupied in initial and final postures. The gleno-humeral and scapulo-thoracic mean joint centers (M H and M S ) are then calculated using a new technique, which defines that each joint center has the point having the smallest migrations while moving continuously from initial to final postures. This allows for the analysis of the linear and angular clearances, which affect joint center migration. The whole continuous movement has been parsed into several steps to test the stability of the mean joint center throughout the motion.

The tenosynovium in the human carpal tunnel is connected to the flexor tendons and the median nerve by the subsynovial connective tissue (SSCT). The most common histological finding in carpal tunnel syndrome (CTS), a compression neuropathy of the median nerve, is noninflammatory fibrosis of the SSCT. The relationship, if any, between the fibrosis and nerve pathology is unknown, although some have speculated that a change in the SSCT volume or stiffness might be the source of the compression. Yet, while animal models have been used to study the physiology of nerve compression, so far none have been used to study the relationship of the SSCT pathology to the neurophysiological abnormalities. The purpose of this study was to identify animal models that might be appropriate to study the interaction of SSCT and nerve function in the development of CTS. The front paws of a rat, rabbit, dog, and baboon were dissected. The carpal tunnel anatomy and SSCT of these animals were also examined by light and scanning microscopy and compared to the relevant human anatomy and ultrastructure. The carpal tunnel anatomy and contents of the baboon and rabbit are similar to humans. The canine carpal tunnel lacks the superficial flexor tendons and the rat carpal tunnel is very small. The human, baboon, and rabbit specimens had very similar organization of the SSCT, and content of the carpal canal. We conclude that, while both the baboon and rabbit would be good animal models to study the relationship of the SSCT to CTS, the rabbit is likely to be more practical, in terms of cost and animal care concerns.

The specific aim of this study was to develop a quantitative method and a kinematic method to evaluate the maximal workspace of the trapeziometacarpal (TM) joint. Six fresh-frozen human cadaver hands were disarticulated 4 cm proximal to the wrist joint and used in this experiment. The three-dimensional motion data of the TM joint was collected by an electromagnetic tracking device at 30 Hz. The workspace was reconstructed according to a complete set of motion data included circumduction, flexion-extension and abduction-adduction. A spherical fitting technique was used to obtain a sphere encompassing all the motion trajectories and estimating the centre of the sphere. The surface area of the maximal TM workspace, located on the one part of the sphere surface, was calculated by surface integration. The interclass correlation coefficient values for the reliability estimation of the repeated measurements of the radius and surface area of all specimens were 0.91 and 0.98 respectively. The mean coefficients of variance of the measured radius and the surface area were 2.04 per cent and 3.65 per cent respectively. The results also showed that using a spherical model to calculate the maximal workspace as an index for assessing TM joint impairment is practical.