Comparison between pulsed ultrasound and low level laser therapy on experimental haemarthrosis.

The use of pulsed ultrasound (PUS) and low level laser therapy (LLLT) in patients with haemophilia has been recommended for supportive treatment of acute and chronic phases of haemarthrosis but its role has not been supported by experimental evidence. The purpose of the present study was to evaluate the effect of these modalities on joint swelling, friction and biomechanical parameters of articular cartilage. An experimental rabbit knee haemarthrosis model was used to test the hypothesis that LLLT and PUS favourably impacted on the biotribological and biomechanical properties of cartilage after joint bleeding. To test this, 35 male albino rabbits weighing 1.5-2 kg were used. The left knee of 30 rabbits was injected with 1 mL of fresh autologous blood two times per week for four consecutive weeks to simulate recurrent haemarthrosis; five rabbits served as non-bleeding controls. Ten rabbits were treated with PUS and 10 with LLLT and the remaining 10 were not treated. The treatments were started after 2 days and the treatment duration was planned for 5 days (sessions) in ultrasound and laser groups. A low level Ga-Al-As laser was applied with an 810 nm wavelength, 25 mW power, and 1 J cm(-2) dosage for 200 s duration. The PUS treatment was applied with a duty cycle of 1/9, frequency of 1 MHz, and power of 0.4 W cm(-2) for 150 s. Joint perimeter was measured before the procedure at the beginning of therapies and after cessation of the procedure. Friction and biomechanical parameters were measured immediately after the killing of the animals. The results demonstrate that PUS was more effective in reducing knee joint swelling than LLLT. Moreover, PUS had the unique ability of reducing the joint friction below normal values. However, it was not successful in returning the articular cartilage force and stiffness to normal state. LLLT was more effective in increasing equilibrium force of the articular cartilage than PUS, however, neither therapy normalized this parameter. From these data, we conclude that PUS is more effective than LLLT in reducing joint swelling and articular joint friction after experimental haemarthrosis.

Biotribological and biomechanical changes after experimental haemarthrosis in the rabbit knee.

Changes in articular cartilage after haemarthrosis have not been completely elucidated in haemophilic arthropathy. Insights into the pathophysiological mechanisms of blood-induced joint damage mainly derived from histological, inflammatory and biochemical investigations. A structure-function relationship is another reasonable way to determine the joint overall health status. Cartilage, a viscoelastic connective tissue, is at least a biphasic material that should also work under minimal friction. Pendulum friction tester measures the mechanical aspects of joint lubrication and quantifies the biotribological properties of the joint. Indentation test is an in situ method characterizing the biomechanical properties of the cartilage. Gross, biotribological and biomechanical properties were determined in a rabbit model of experimental haemarthrosis. A sample of 1 mL of fresh autologous blood was injected in the left knee of rabbit's joint twice weekly for four consecutive weeks. The right knee and animals in the control group were left untreated. After 8 days, joint perimeter, biotribological and biomechanical tests were performed. In a consistent manner, all data showed detrimental effects of the blood on the overall cartilage function under loading. Non-weight bearing and early blood aspiration seem wise to be considered after haemarthrosis.

Abnormal viscoelastic behaviour of passive ankle joint movement in diabetic patients: an early or a late complication?

AIMS/HYPOTHESIS: The goal of the present study was to compare the range of motion and both the viscous and elastic components of passive ankle joint movement in short- and long-term diabetic patients with that of a control population. METHODS: Thirty-four diabetic patients and 16 control subjects entered into the study. Patients with a history of over 15 years of diabetes were considered as a long-term diabetic group. In order to quantify the passive ankle joint movement, a device was designed to measure the dorsi- and plantar-flexion angle and the net moment at the ankle. Elastic behaviour was examined as the separate slope of regression lines (stiffness) of plantar and dorsal components in the loading moment-angle curve. It was also examined as the slope of the regression line in the final 10% of each component. Hysteresis, a characteristic of viscoelastic materials that indicates loss of energy during unloading, was corrected for range of motion and used to examine viscous behaviour of the ankle joint. RESULTS: Total and plantar ranges of motion were significantly lower in long-term diabetic patients than in short-term diabetic and control groups (p < 0.05). Plantar-flexion stiffness was significantly lower in short-term diabetic patients than in control subjects and long-term diabetic groups (p < 0.05). Corrected hysteresis was significantly higher in long-term diabetic than in short-term diabetic and control (p < 0.05) groups in the dorsal range of motion. CONCLUSIONS/INTERPRETATION: This study shows that both decreased plantar and total ankle joint ranges of motion, and increased viscous component of passive ankle joint movement are among the late complications of diabetes.

A dynamic model of the hand with application in functional neuromuscular stimulation.

Potential hand function in people with tetraplegia was evaluated using a three-dimensional dynamic mathematical model. The model was used to evaluate hand positioning, grasp force, and the outcome of surgeries such as tendon transfers and joint fusion, in situations typical of those encountered when using functional neuromuscular stimulation to restore function in people with tetraplegia. In the model, the hand is treated as a jointed multibody system. Each joint is subjected to muscle moments, passive joint moment, and moments due to grasp forces. Model simulations showed that function was highly dependent on both muscle strength and joint passive moments. The potential for tendon transfers, such as the Zancolli-lasso and intrinsicplasty, plasty, to improve hand function was demonstrated, but their value is subject-dependent. It was also shown that activation of multiple thumb muscles (adductor pollicis, abductor pollicis brevis, and flexor pollicis longus) without interphalangeal joint fusion can provide convenient lateral pinch posture with approximately 70% more grip force than a currently used method, which includes joint fusion but requires only one muscle. Finally, a grasp protocol was introduced and shown successful in palmar grasp and hold of movable cylindrical objects using only extrinsic muscles, provided the fingers could be extended sufficiently to enclose the object.

An experimentally based nonlinear viscoelastic model of joint passive moment.

Previous investigations have not converged on a generally accepted model of the dissipative part of joint passive moment. To provide a basis for developing a model, a series of measurements were performed to characterize the passive moment at the metacarpophalangeal joint of the index finger. Two measurement procedures were used, one in moment relaxation over a range of fixed joint angles and the other at a series of constant joint velocities. Fung's quasi-linear viscoelastic theory motivated the development of the passive moment model. Using this approach, it was not necessary to make restrictive assumptions regarding the viscoelastic behavior of the passive moment. The generality of the formulation allowed specific functions to be chosen based on experimental data rather than finding coefficients which attempted to fit a preselected model of the data. It was shown that a nonlinear viscoelastic model described the passive stiffness. No significant frictional effects were found. Of particular importance was the nonlinear behavior of the dissipative part of the passive moment which was modeled by joint speed raised to a power less than one. This result could explain the differing findings among previous investigations, and may have important implications for control of limb movement.

Biomechanical, radiologic, and histopathologic correlations in the pathogenesis of experimental intervertebral disc disease.

STUDY DESIGN: The desert sand rat, an animal model for spinal degenerative disc disease, was studied for biomechanical, histologic, and radiographic characteristics. Load deformation curves with peak force and force decay, hematoxylin-eosin-stained sections, and lateral radiographs were correlated. OBJECTIVES: The hypothesis that the subchondral bone response preceded or contributed to the degenerative disc disease seen in the desert sand rat was tested. SUMMARY OF BACKGROUND DATA: Intervertebral disc disease spontaneously develops in the desert sand rat during its lifetime. Approximately 50% will have significant disc disease by age 18 months. Previous studies have found metabolic and histologic changes associated with intervertebral disc degeneration in the sand rat. METHODS: Desert sand rats were killed at 3-, 9-, 15-, and 18-month intervals and tested in Rheometrics Solid Analyzer with nondestructive step strain loading to obtain a load deformation curve. Radiographs and histologic sections of each animal were compared. Peak force and force decay were analyzed by level and by age. Analysis of variance and Tukey's methods were applied to data. RESULTS: There were no statistically significant differences in biomechanical data. No histologic changes were noted in the study groups up to 18 months of age. Radiographic differences characterized by subchondral bony sclerosis were noted by 18 months of age. No trends were noted when radiographic grades were compared with force data. CONCLUSIONS: The absence of biomechanical histologic changes in the intervertebral disc per se from 3 through 18 months, with radiographic changes in the subchondral bone, supports the hypothesis that the earliest changes in intervertebral disc disease in this animal model are related to the subchondral bone response.