Activation level of extensor carpi ulnaris affects wrist and elbow acceleration responses following simulated forward falls

What differences exist between the lead and trail wrist in extensor carpi ulnaris activity and golf swing joint kinematics in sub-elite golfers?

This study assessed the lead and trail arm peak and average extensor carpi ulnaris (ECU) muscle activity in association with tri-planar angular velocities of the lead and trail wrists during the golf swing. Fifteen sub-elite, male right-handed golfers (Mage = 34.7 years ±13.3, Mhandicap = 1.5 ± 2.2) were recruited to execute five shots each with their pitching wedge, 7-iron and driver clubs in an indoor golf simulator. Surface electromyography (EMG) sensors were placed over the ECU muscle belly and inertial measurement unit sensors were placed bi-laterally on the distal forearm and dorsum of the hand. There was a statistically greater recruitment of the trail ECU muscle during the downswing (p < 0.001) for all clubs. The lead ECU muscle was recruited more during the backswing (p < 0.001) and follow through (p < 0.024) phases. There were statistically different tri-planar movement patterns between the lead and trail wrist throughout all three phases of the golf swing. No significant relationships were found between downswing EMG data and clubhead kinematics at impact. In conclusion, differing wrist kinematics and associated muscle activity may contribute to the asymmetrical injury pattern seen clinically.

Test-retest reliability of the FALL FIT system for assessing and training protective arm reactions in response to a forward fall

The use of the hands and arms is an important protective mechanism in avoiding fall-related injury. The aim of this study was to evaluate the test-retest reliability of fall dynamics and evokd protective arm response kinematics and kinetics in forward falls simulated using the FALL simulator For Injury prevention Training and assessment system (FALL FIT). Fall FIT allows experimental control of the fall height and acceleration of the body during a forward fall. Two falls were simulated starting from 4 initial lean angles in Experiment 1 and with 4 different fall accelerations in Experiment 2. Fourteen younger adults (25.1±3.5 years) and 13 older adults (71.3±3.7 years) participated in Experiment 1 and 13 younger adults (31.8±5.7 years) participated in Experiment 2. Intraclass correlation coefficients (ICC) were used to the evaluate absolute agreement of single measures at each condition and averages across conditions. Average measures of fall dynamics and evoked kinematics and kinetics exhibited excellent reliability (ICC(A,4)>0.86). The reliability of single measures (ICC(A,1) > 0.59) was good to excellent, although 18% of single measures had a reliability (ICC(A,1)) between 0.00 and 0.57. The FALL FIT was shown to have good to excellent reliability for most measures. FALL FIT can produce a wide range of fall dynamics through modulation of initial lean angle and body acceleration. Additionally, the range of fall velocities and evoked kinematics and kinetics are consistent with previous fall research.•

The FALL FIT can be used to gain further insight into the control of protective arm reactions and may provide a therapeutic tool to assess and train protective arm reactions.

The infra-meniscal fibers of the anterolateral ligament are stronger and stiffer than the supra-meniscal fibers despite similar histological characteristics

PURPOSE

The purpose of the current investigation was to characterize biomechanical differences between the supra- and infra-meniscal sections of the anterolateral ligament (ALL). We hypothesized that the supra-meniscal fibers of the ALL would be stronger and stiffer than the infra-meniscal fiber.

METHODS

Nine cadaveric knee specimens [mean (SD) age = 79 (14.6) years] were dissected to identify the borders of the ALL while maintaining the anatomy of the lateral meniscus. The specimens were randomly assigned to either a supra-meniscal (the ALL below the meniscus was sectioned leaving only the supra-meniscal ALL intact) or an infra-meniscal (the ALL above the meniscus was sectioned leaving only the infra-meniscal attachment intact) group. The specimens were potted into dental cement such that the ALL was pulling laterally on the meniscus when the specimens were secured within an Instron materials testing machine. The specimens were subjected to a tensile failure test at 1 mm/s. The load at failure and stiffness were calculated from the force-displacement curves, while peak stress was calculated by normalizing the peak force to the cross-sectional area of the ALL. Furthermore, one intact knee specimen was used to perform a histological analysis on the two ALL sections using Masson's Trichome staining.

RESULTS

The infra-meniscal ALL had a significantly (p = 0.03) higher load to failure (195.0 vs. 132.1 N) and was significantly (p = 0.03) stiffer than the supra-meniscal fibers (24.8 vs. 12.3 N/mm). The relatively similar cross-section areas also resulted in the infra-meniscal sections having a greater peak stress (p = 0.04) (11.1 vs. 5.4 MPa). Histological analysis showed relatively consistent fiber orientation with similar organization noted throughout the fibers.

CONCLUSIONS

The ALL-meniscal construct that includes the infra-meniscal fibers was significantly stronger and stiffer than the construct that includes the supra-meniscal fibers. The infra-meniscal ALL is another important component of the anterolateral complex of the knee, and should be considered when presented with an ACL and/or meniscal injury.

The effect of asymmetrical body orientation during simulated forward falls on the distal upper extremity impact response of healthy people

The occurrence of distal upper extremity injuries resulting from forward falls (approximately 165,000 per year) has remained relatively constant for over 20years. Previous work has provided valuable insight into fall arrest strategies, but only symmetric falls in body postures that do not represent actual fall scenarios closely have been evaluated. This study quantified the effect of asymmetric loading and body postures on distal upper extremity response to simulated forward falls. Twenty participants were suspended from the Propelled Upper Limb fall ARest Impact System (PULARIS) in different torso and leg postures relative to the ground and to the sagittal plane (0°, 30° and 45°). When released from PULARIS (hands 10cm above surface, velocity 1m/s), participants landed on two force platforms, one for each hand. Right forearm impact response was measured with distal (radial styloid) and proximal (olecranon) tri-axial accelerometers and bipolar EMG from seven muscles. Overall, the relative height of the torso and legs had little effect on the forces, or forearm response variables. Muscle activation patterns consistently increased from the start to the peak activation levels after impact for all muscles, followed by a rapid decline after peak. The impact forces and accelerations suggest that the distal upper extremity is loaded more medial-laterally during asymmetric falls than symmetric falls. Altering the direction of the impact force in this way (volar-dorsal to medial-lateral) may help reduce distal extremity injuries caused when landing occurs symmetrically in the sagittal plane as it has been shown that volar-dorsal forces increase the risk of injury.

De Quervain’s syndrome: It may not be an isolated pathology

Introduction

This paper details a retrospective review of patients’ records diagnosed with de Quervain’s syndrome following a traumatic event but no history of repetitive strain.

Methods

Data analysis of 41 patients was performed. The inclusion criteria were pain over first dorsal compartment, pain on resisted extensor pollicis brevis and/or abductor pollicis longus, and a positive Finkelstein’s test. The assessment included a subjective history to establish a repetitive activity or a traumatic incident and diagnostic tests to establish possible instability or osteoarthritis.

Results

There were 13 men and 28 women with an age range from 20 to 72 years. Statistical analysis was undertaken using Fisher’s Exact tests. 46.3% ( n = 19) of 41 patients had a ligament injury diagnosed after the de Quervain’s. 94.7% ( n = 18) of 19 patients with ligament instability had a history of trauma, and this was statistically significant. Clinically significant was that 82.9% ( n = 34) of 41 patients demonstrated extensor carpi ulnaris (ECU) muscle weakness, but there was no statistical significant correlation between ECU weakness and ligament instability. Patients could have ECU weakness without ligament instability; however, patients with ligament instability appeared more likely to have ECU weakness.

Conclusions

The results would suggest that de Quervain’s syndrome, in a proportion of patients, could be secondary to underlying wrist pathology due to previous trauma. If the patient does not report a true repetitive strain history, a more thorough assessment may need to be undertaken to establish if there is any underlying pathology.

Anticipatory and Reactive Response to Falls: Muscle Synergy Activation of Forearm Muscles

We investigated the surface electromyogram response of six forearm muscles to falls onto the outstretched hand. The extensor carpi radialis longus, extensor carpi radialis brevis, extensor carpi ulnaris, abductor pollicis longus, flexor carpi radialis and flexor carpi ulnaris muscles were sampled from eight volunteers who underwent ten self-initiated falls. All muscles initiated prior to impact. Co-contraction is the most obvious surface electromyogram feature. The predominant response is in the radial deviators. The surface electromyogram timing we recorded would appear to be a complex anticipatory response to falling modified by the effect on the forearm muscles following impact. The mitigation of the force of impact is probably more importantly through shoulder abduction and extension and elbow flexion rather than action of the forearm muscles.

Predicting Distal Radius Bone Strains and Injury in Response to Impacts Using Multi-Axial Accelerometers

Measuring a bone’s response to impact has traditionally been done using strain gauges that are attached directly to the bone. Accelerometers have also been used for this purpose because they are reusable, inexpensive and can be attached easily. However, little data are available relating measured accelerations to bone injury, or to judge if accelerometers are reasonable surrogates for strain gauges in terms of their capacity to predict bone injuries. Impacts were applied with a custom designed pneumatic impact system to eight fresh-frozen human cadaveric radius specimens. Impacts were repeatedly applied with increasing energy until ultimate failure occurred. Three multiaxial strain gauge rosettes were glued to the bone (two distally and one proximally). Two multiaxial accelerometers were attached to the distal dorsal and proximal volar aspects of the radius. Overall, peak minimum and maximum principal strains were calculated from the strain-time curves from each gauge. Peak accelerations and acceleration rates were measured parallel (axial) and perpendicular (off-axis) to the long axis of the radius. Logistic generalized estimating equations were used to create strain and acceleration-based injury prediction models. To develop strain prediction models based on the acceleration variables, Linear generalized estimating equations were employed. The logistic models were assessed according to the quasi-likelihood under independence model criterion (QIC), while the linear models were assessed by the QIC and the marginal R2. Peak axial and off-axis accelerations increased significantly (with increasing impact energy) across all impact trials. The best injury prediction model (QIC = 9.42) included distal resultant acceleration (p < 0.001) and donor body mass index (BMI) (p < 0.001). Compressive and tensile strains were best predicted by separate uni-variate models, including peak distal axial acceleration (R2 = 0.79) and peak off-axis acceleration (R2 = 0.79), respectively. Accelerometers appear to be a valid surrogate to strain gauges for measuring the general response of the bone to impact and predicting the probability of bone injury.

Reliability of Impact Forces, Hip Angles and Velocities during Simulated Forward Falls Using a Novel Propelled Upper Limb Fall ARrest Impact System (PULARIS)

Previous forward fall simulation methods have provided good kinematic and kinetic data, but are limited in that they have started the falls from a stationary position and have primarily simulated uni-directional motion. Therefore, a novel Propelled Upper Limb fall ARest Impact System (PULARIS) was designed to address these issues during assessments of a variety of fall scenarios. The purpose of this study was to present PULARIS and evaluate its ability to impact the upper extremities of participants with repeatable velocities, hand forces and hip angles in postures and with vertical and horizontal motion consistent with forward fall arrest. PULARIS consists of four steel tubing crossbars in a scissor-like arrangement that ride on metal trolleys within c-channel tracks in the ceiling. Participants are suspended beneath PULARIS by the legs and torso in a prone position and propelled horizontally via a motor and chain drive until they are quick released, and then impact floor-mounted force platforms with both hands. PULARIS velocity, hip angles and velocities and impact hand forces of ten participants (five male, five female) were collected during three fall types (straight-arm, self-selected and bent-arm) and two fall heights (0.05 m and 0.10 m) to assess the reliability of the impact conditions provided by the system. PULARIS and participant hip velocities were found to be quite repeatable (mean ICC = 0.81) with small between trial errors (mean = 0.03 m/s). The ratio of horizontal to vertical hip velocity components (∼0.75) agreed well with previously reported data (0.70-0.80). Peak vertical hand impact forces were also found to be relatively consistent between trials with a mean ICC of 0.73 and mean between trial error of 13.4 N. Up to 83% of the horizontal hand impact forces displayed good to excellent reliability (ICC > 0.6) with small between trial differences. Finally, the ICCs for between trial hip angles were all classified as good to excellent. Overall, PULARIS is a reliable method and is appropriate for studying the response of the distal upper extremity to impact loading during non-stationary, multi-directional movements indicative of a forward fall. This system performed well at different fall heights, and allows for a variety of upper and lower extremity, and hip postures to be tested successfully in different landing scenarios consistent with elderly and sport-related falls.