Citations

The physical attributes of the three capitohamate interosseous ligaments were tested in a computer-controlled multi-axis testing machine using 12 human cadaver specimens. After an intact test run, selected ligaments were cut in random sequence and the test repeated. The remaining ligaments were tested to failure with servohydrolic stress at 5 mm/second. In the intact joint complex, the average dorsopalmar rotational displacement was approximately 9° in each direction. Under the load limit, the dorsopalmar translational displacement averaged 0.9 mm and 0.5 mm respectively, proximal–distal translational displacement averaged 0.8 mm and 0.4 mm respectively, and distractional displacement averaged 0.3 mm. Based on the sequential sectioning it was found that the dorsal ligament provided 76% (SD 14) of the rotational resistance with palmar rotation of the capitate and 44% (SD 19) of translational constraint with palmar translation of the capitate. The deep ligament provided 51% (SD 15) of the rotational resistance with dorsal rotation of the capitate and 63% (SD 24) of translational resistance with dorsal translation of the capitate. With proximal—distal translation, the dorsal ligament was the most important constraint in each direction. In resisting distraction, each of the three ligaments was equally effective. Failure testing showed the deep ligament was strongest at 289 N, followed by the palmar at 171 N and the dorsal at 133 N.

Flexor tendon repair remains one of the more difficult technical tasks facing the hand surgeon. A good repair must be both strong and able to glide smoothly through the tendon sheath. The purpose of this study is to present a model that allows surgeons to improve their technique of flexor tendon repair by receiving feedback on these important biomechanical parameters. The set-up requires testing equipment found in most biomechanical laboratories and should be available in many academic medical centres. Preliminary data suggest that receiving feedback about the strength and smoothness of a flexor tendon repair may be a very useful tool in helping surgeons improve the overall quality of their tendon repair technique.

Muscle physiological cross-sectional area, as defined and measured by dividing the volume of the muscle by its fibre length, is proportional to the maximum strength of the muscle. It is one of the important parameters when considering muscle mechanics in sports science and, clinically in tendon transfer procedures. This study reports that tendon cross-sectional area correlated well with the physiological cross-sectional area of associated muscles.

In order to determine the mechanical properties of the fibro-osseous pulleys in the hand, the diaphyseal annular pulleys, the volar plate annular pulleys and the cruciate or condensable portions were tested. A custom-made loading device provided proper fit of the soft tissues for a uniform distribution of the pulley load during testing. The A2 pulley was found to be the strongest of the pulleys; the A1 and A4 were the next strongest. The A3 pulley was nearly equal in mean breaking strength to the other annular pulleys, but in absolute breaking load was considerably weaker because of its shortness. The A4 was the least compliant of the pulleys. We concluded that the fibro-osseous A2 and A4 were mechanically stronger and stiffer pulleys than the A1, A3, A5 (volar plate) pulleys. In testing one type of pulley reconstruction, we found that the “belt loop” technique of Karev nearly matched the annular pulleys in strength and energy absorption.

The complex modulus E* and elastic modulus E′ of agarose gels (2% to 4%) are measured with a dynamic mechanical analyzer in frequency sweep shear sandwich mode between 0.1 and 20 Hz. The data showed that E* and E′ increase with frequency according to a power law which can be described by a fractional derivative model to characterize the dynamic viscoelasticity of the gel. The functions between the model parameters including storage modulus coefficient H and the power law exponent (β) and the agarose concentration are established. A molecular basis for the application of the fractional derivative model to gel polymers is also discussed. Such an approach can be useful in tissue culture studies employing dynamic pressurization or for validation of magnetic resonance elastography.

This study combines an ergometric wheelchair, a six-camera video motion capture system and a prototype computer graphics based musculoskeletal model (CGMM) to predict shoulder joint loading, muscle contraction force per muscle and the sequence of muscular actions during wheelchair propulsion, and also to provide an animated computer graphics model of the relative interactions. Five healthy male subjects with no history of upper extremity injury participated. A conventional manual wheelchair was equipped with a six-component load cell to collect three-dimensional forces and moments experienced by the wheel, allowing real-time measurement of hand/rim force applied by subjects during normal wheelchair operation. An Expert Vision™ six-camera video motion capture system collected trajectory data of markers attached on anatomical positions. The CGMM was used to simulate and animate muscle action by using an optimization technique combining observed muscular motions with physiological constraints to estimate muscle contraction forces during wheelchair propulsion. The CGMM provides results that satisfactorily match the predictions of previous work, disregarding minor differences which presumably result from differing experimental conditions, measurement technologies and subjects. Specifically, the CGMM shows that the supraspinatus, infraspinatus, anterior deltoid, pectoralis major and biceps long head are the prime movers during the propulsion phase. The middle and posterior deltoid and supraspinatus muscles are responsible for arm return during the recovery phase. CGMM modelling shows that the rotator cuff and pectoralis major play an important role during wheelchair propulsion, confirming the known risk of injury for these muscles during wheelchair propulsion. The CGMM successfully transforms six-camera video motion capture data into a technically useful and visually interesting animated video model of the shoulder musculoskeletal system. The CGMM further yields accurate estimates of muscular forces during motion, indicating that this prototype modelling and analysis technique will aid in study, analysis and therapy of the mechanics and underlying pathomechanics involved in various musculoskeletal overuse syndromes.

Abstract The compliance, capacity, and the position of minimum intraarticular pressure were measured in 13 thawed, fresh‐frozen human elbows. The capacity of the joint capsule was 23 ± 4 ml. The intraarticular pressure was the lowest at 80° of flexion. Capsular rupture occurred at relatively low intraarticular pressures—80 ± 42 mm Hg. Knowledge of the capacity of the normal elbow joint combined with the fact that this joint capsule tends to rupture or permit extravasation of fluid into the periarticular soft tissues should be considered when infusing fluids during arthroscopy. Finally, the “resting position” of 80° of flexion minimizes capsular tension and therefore might contribute to the development of joint contracture associated with prolonged immobilization in this position. This would be consistent with the observation that patients with posttraumatic elbow stiffness have an average arc of flexion of 60–90°.

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.