Understanding the biomechanics of the forearm during the dart thrower's motion.

This study investigated the contribution of different forearm muscles, namely the flexor carpi ulnaris, extensor carpi radialis longus and brevis, extensor carpi ulnaris and flexor carpi radialis, during the dart thrower's motion. Thirteen healthy participants were recruited. The forearm muscle activation patterns during the dart thrower's motion were measured using surface electromyography. The average root mean square for the extensor carpi ulnaris was found to be the highest during the dart thrower's motion. Muscle activations during the dart thrower's motion were heterogeneous among the participants. The results suggest the rehabilitation protocol for patients with wrist injuries should be reconsidered.

The right turn around: Penrose tourniquet application in paediatrics.

INTRODUCTION: Commercially available tourniquets are ill-suited for paediatric patients with limb circumferences smaller than the required mechanism, forcing surgeons to improvise. This study aimed to quantify pressures exerted by the Penrose tourniquet when applied on a phantom model and evaluate the intra-/inter-rater reproducibility of the technique previously proposed. METHODS: Eight calibrated pressure sensors were distributed evenly along the inner and outer circumference of a silicon-based model. A 30cm-by-3.2 cm ARGYLE Penrose drain, 4-by-4 gauze, marker and ruler were used. The optimal interval for arterial occlusion was determined to be 70% of limb circumference. The tourniquet was secured using two half-knots formed by gauze. RESULTS: Two-turns of the tourniquet about the model generated mean pressures (SD) of 209.43 (SD:35.98 mmHg) (95%CI: 195.85-224.00 mmHg) (outer-sensor) and 246.32 (SD:61.92 mmHg) (95%CI: 221.02-273.49 mmHg) (inner-sensor). Three-turns generated mean pressures of 302.07 (SD:23.98 mmHg) (95%CI: 292.29-312.53 mmHg) (outer-sensor) and 314.44 (SD:56.70 mmHg) (95%CI: 291.25-338.25 mmHg) (inner-sensor). CONCLUSION: The Penrose tourniquet has clinical utility, particularly for patients where commercially available tourniquets are not suitable. Current application techniques generate inconsistent pressures. Using the existing model, further refinement can be done to improve the consistency and safety of the application. We recommend using intervals of slightly more than 70% of limb circumference and only two turns of the Penrose tourniquet during application. LEVEL OF EVIDENCE: V.

Which is the most ergonomic mop? A comparison of three domestic mopping systems.

PURPOSE: To assess musculoskeletal risk factors (repetitions, posture, forces) of the upper limb during domestic floor mopping tasks. METHODS: Two hundred women were surveyed to determine the most common mopping system, mopping patterns and type of flooring used in their homes. The biomechanical demands of the three most common mopping systems were then evaluated in the laboratory. Participants were also asked to rate their perceived levels of exertion and cleanliness of each mopping system. RESULTS: The use of wet wipes had the highest repetition count and exertion rates during mopping and scrubbing tasks. Higher peak scrubbing forces were noted for the plunge mop. All participants found the cotton fibre mop to be the cleanest. All 3 mops had medium postural risk. CONCLUSION: The advantages and disadvantages of each mopping system were outlined and may be used by occupational therapists when providing ergonomic advice to patients with upper limb musculoskeletal conditions.

Computational Simulation of Synovial Fluid Kinematics of the Scapholunate Joint.

Background: The interaction between wrist kinematics and synovial fluid pressure has yet to be studied. To our knowledge, this is the first study to determine the effect of scapholunate joint kinematics on synovial fluid pressure change using finite volume method. Methods: The carpal bones of a cadaveric hand were obtained from Computed Tomography (CT) scans. CT images of the carpal bones were segmented and reconstructed into 3D model. The 3D synovial fluid model between the scaphoid and lunate was constructed and then used for computational simulations. The kinematics data of scapholunate joint obtained from radioulnar deviation of the wrist was investigated. Results: It was found that the pressure in synovial fluid varied from -1.68 to 2.64 Pa with maximum pressure located at the scaphoid-fluid interface during the radial deviation. For ulnar deviation, the pressure increased gradually from the scaphoid-fluid interface towards the lunate-fluid interface (-1.37 to 0.37 Pa). Conclusions: This new computational model provides a basis for the study of pathomechanics of ligament injury with the inclusion of synovial fluid.

Normative data on functional grip strength of elderly in Singapore.

STUDY DESIGN: Cross-sectional study for clinical measurement. INTRODUCTION: Most daily tasks require individuals to exert grip strength with torque, which can be challenging for elderly as their strength diminishes with age. We postulate that to assess the functional capacity of an individual, it is important to evaluate the functional grip strength instead of the maximal static grip strength. PURPOSE OF THE STUDY: The objective of this cross-sectional study is to establish normative data for the functional grip strength of elderly aged 60 years and older in the Singapore population. METHODS: In this study, 233 healthy subjects aged 60 years and older were recruited. Using a custom-made hand strength measurement device, the following measurements were recorded: grip strength at neutral position, grip strength with resistive pronation torque, and grip strength with resistive supination torque. RESULTS: Grip strengths measured for both genders decreased by 13% and 16% for males and females respectively, when pronation torque was exerted, and with supination torque, the strength decreased by 18% and 17% for males and females respectively. CONCLUSION: Normative data for the elderly population in Singapore had been established. The findings from this study can complement the existing ergonomic hand data in designing better assistive tools to improve the independent living of elderly. LEVEL OF EVIDENCE: NA.

A Biomechanical Comparison of Different Knots Tied on Fibrewire Suture.

BACKGROUND: Synthetic sutures such as Fiberwire used in flexor tendon repairs have high tensile strength. Proper application allows early mobilisation, decreasing morbidity from repair rupture and adhesions while preserving range of motion. Suture stiffness can cause poorer knot holding, contributing to gapping, peritendinous adhesions or rupture. Previous studies recommended more throws in knots tied on Fiberwire to prevent knot slippage. These larger knots are voluminous and prominent. In tendon repairs they can cause "catching", increase friction and work of flexion. Other studies advocated certain complicated knots as being more secure. We evaluated several knots and their biomechanical properties with the aim of finding a compact knot with less potential for slippage to maximise strength potential of flexor tendon repairs using Fiberwire. METHODS: A series of different knots tied on Fiberwire 4-0 sutures were pulled to failure on a mechanical tester. Mean tensile strengths, knot volumes and tensile strength to knot volume ratios were compared. RESULTS: Tensile strengths and knot volume increased with more throws and loops. Four variations of the square knot (the 4=4=1, 2=2=2=2, 1=1=1=1=1, 2=1=1=1=1 knots) had tensile strengths greater than 35N. The specialised anti-slip knot had highest tensile strength and suture volume but lower strength-to-volume ratio. CONCLUSIONS: The anti-slip knot had highest tensile strength but it also had the highest volume. The greater strength of repair may not translate into improved clinical outcome. The 1=1=1=1=1 knot has superior knot strength-to-volume ratio with good knot strength adequate for early active mobilisation in flexor tendon repairs.

A method for carpal motion hysteresis quantification in 4-dimensional imaging of the wrist.

INTRODUCTION: Carpal bones motions exhibit hysteresis that is dependent on the direction of wrist motion, which can be seen during 4-dimensional (3D plus time) imaging of the wrist. In vitro studies have demonstrated the phenomenon of carpal hysteresis and have reported that hysteresis area increases with carpal instabilities. However, their techniques required implantation of bone markers and thus cannot be used clinically. The objective of this study is to use noninvasive 4-dimensional computed tomography (4 DCT) technique to quantify carpal hysteresis, and to determine the reliability of this method. METHOD: A cadaveric wrist mounted on a custom motion simulator was imaged using a dual-source CT scanner while undergoing periodic radioulnar deviation. Ten image phases of this motion was reconstructed through retrospective cardiac gating. The rotational angles of scaphoid, lunate and triquetrum in each phase were derived through manual registration using Matlab after segmenting the bones in Analyze 8.1. These angles were then plotted against global wrist positional angles to produce the hysteresis curves and the area was calculated. The image segmentation and measurements were repeated by 2 raters to derive intra- and inter-rater reliability assessments. RESULTS: The hysteresis area was found to be larger in the lunate (96.5 deg(2)) followed by triquetrum (92.3 deg(2)) and scaphoid (67.5 deg(2)). The measurement of the total hysteresis area of the scaphoid had the highest reliability with intra- and inter-rater reliability of 95.5% and 95.4% respectively. DISCUSSION: We have demonstrated that our approach of using 4 DCT imaging can be used to assess and quantify the hysteresis of the carpal motion with good reliability.

Dynamic imaging with dual-source gated Computed Tomography (CT): implications of motion parameters on image quality for wrist imaging.

OBJECTIVE: Dynamic Computed Tomography (CT) promises insights into the pathophysiology of carpal instability by recording images of the carpus while it is in motion. The purpose of this study was to investigate the effect of motion velocity on image quality for dynamic carpal imaging applications using a clinical dual-source CT (DSCT) scanner. METHODS: A phantom with targets in the axial, coronal and sagittal planes was attached to a motion simulator and imaged using a 64-slice DSCT scanner. Data was acquired when the phantom was stationary and during periodic linear motion. Spatial resolution, motion artifacts and banding artifacts were assessed. RESULTS: Mean spatial resolution was 0.82 mm at 36 mm/s and 0.79 mm at 18 mm/s. Banding artifacts were mild at 36 mm/s and minimal at 18 mm/s. Motion artifacts were minimal at motion velocity of up to 36 mm/s in both the coronal and sagittal planes. Axial plane motion artifacts were moderate at 36 mm/s and mild at 18 mm/s. DISCUSSION: Sub-millimeter resolution is achievable with commercially available DSCT scanners with mild to moderate amounts of motion artifacts at velocities of 18 mm/s and 36 mm/s respectively.