Shoulder demands in manual wheelchair users across a spectrum of activities

Design and Development of a Powered Myoelectric Elbow Orthosis for Neuromuscular Injuries

INTRODUCTION

Recovering from neuromuscular injuries or conditions can be a challenging journey that involves complex surgeries and extensive physical rehabilitation. During this process, individuals often rely on orthotic devices to support and enable movement of the affected limb. However, users have criticized current commercially available powered orthotic devices for their bulky and heavy design. To address these limitations, we developed a novel powered myoelectric elbow orthosis.

MATERIALS AND METHODS

The orthosis incorporates 3 mechanisms: a solenoid brake, a Bowden cable-powered constant torque elbow mechanism, and an extension limiter. The device controller and battery are in a backpack to reduce the weight on the affected arm. We performed extensive calculations and testing to ensure that the orthosis could withstand at least 15 Nm of elbow torque. We developed a custom software effectively control the orthosis, enhancing its usability and functionality. A certified orthotist fitted a subject who had undergone a gracilis free functioning muscle transfer surgery with the device. We studied the subject under Mayo clinic IRB no. 20-006849 and obtained objective measurements to assess the orthosis's impact on upper extremity functionality during daily activities.

RESULTS

The results are promising since the orthosis significantly improved elbow flexion range of motion by 40° and reduced compensatory movements at the shoulder (humerothoracic joint) by 50°. Additionally, the subject was able to perform tasks which were not possible before, such as carrying a basket with weights, highlighting the enhanced functionality provided by the orthosis.

CONCLUSION

In brief, by addressing the limitations of existing devices, this novel powered myoelectric elbow orthosis offers individuals with neuromuscular injuries/conditions improved quality of life. Further research will expand the patient population and control mechanisms.

Preliminary feasibility and acute physiological effects of a single session of upper limb vibration training for persons with spinal cord injury

CONTEXT

Strong upper limb musculature is essential for persons with spinal cord injury (SCI) to operate a manual wheelchair and live independently. Targeted upper limb vibration may be a viable exercise modality to build muscle efficiently while eliminating some of the barriers associated with exercise for persons with SCI.

OBJECTIVE

The purpose of this study was to assess preliminary feasibility of completing a single exercise session of upper limb vibration and compare the acute physiological effects to a single session of standard dumbbell resistance exercise.

METHODS

Individuals with SCI performed seven upper limb exercises (1) isometrically using a vibrating dumbbell at 30 Hz for 60 s (n = 22) and (2) using a standard isotonic resistance protocol (n = 15).

RESULTS

Nineteen (86.4%) of 22 participants were able to perform all vibration exercises at 30 Hz but hold time success rates varied from 33% (side flies and front raises) to 95% (internal rotation). No significant differences were found between vibration exercise and standard resistance protocol for blood lactate, power output, and heart rate (P > 0.05). Perceptions of the training were positive, with most participants (>70%) expressing interest to train with vibration in the future.

CONCLUSIONS

Vibration training was not feasible for all participants, suggesting an individualized approach to starting weight and progression may be necessary. Similar acute physiological changes were seen between vibration exercise and standard resistance protocol, suggesting they could have similar benefits. Additional research is needed to determine if vibration exercise is feasible and beneficial to incorporate into a long-term training program.

Models of care for musculoskeletal shoulder pain in spinal cord injury: A scoping review

CONTEXT

Spinal cord injury (SCI) is a neurological condition that significantly impacts a person's lifestyle, health and well-being. Many individuals with SCI experience secondary musculoskeletal shoulder pain. This scoping review examines the current research on the diagnosis and management of shoulder pain in SCI.

OBJECTIVE

The aim of this Scoping Review was (1) to chart peer-reviewed literature regarding the diagnosis and management of shoulder pain as it relates to SCI and (2) identify gaps in this body of literature to inform future research priorities.

METHODS

Six electronic databases were searched from inception until April 2022. In addition, reviewers scanned the reference lists of identified articles. Articles from peer-reviewed sources that reported diagnostic or management procedures for musculoskeletal shoulder conditions within the SCI population were considered and 1679 articles were identified. Title and abstract screening, full text review, and data extraction were undertaken by two independent reviewers.

RESULTS

Eighty seven articles were included, covering diagnosis or management of shoulder pain in SCI.

CONCLUSION

Whilst the most commonly reported diagnostic procedures and management strategies reflect contemporary practice for shoulder pain, the entire body of literature demonstrates inconsistencies in methodologies. In places, the literature continues to perceive value in procedures inconsistent with best practice. These findings encourage researchers to pursue the development of robust models of care for musculoskeletal shoulder pain in SCI using a collaborative and integrated approach, combining best practice for musculoskeletal shoulder pain alongside clinical expertise in the management of SCI.

Effects of the SmartDrive on mobility, activity, and shoulder pain among manual wheelchair users with spinal cord injury - a prospective long-term cohort pilot study

PURPOSE

to investigate long-term effects of SmartDrive on mobility, everyday activity, and shoulder pain among spinal cord injured manual wheelchairs users.

MATERIAL AND METHODS

A prospective pilot intervention study was conducted at Spinalis/Aleris Rehab Station, Sweden. Participants were consecutively invited when evaluated for SmartDrive prescription. Assessments were done at baseline, intervention (use of SmartDrive), and after six months. A smartwatch registered wheelchair utilization including push intensity and pushes/day. Wheelchair Outcome Measure, pain rating instruments including Wheelchair User's Shoulder Pain Index, a wheelchair test, and semi-structured interviews were used. Descriptive statistics and content analysis approach were used.

RESULTS

Twenty-five persons were screened, six of 14 included completed the study. Drop-out reasons were not related to SmartDrive for five of the eight persons. After intervention, there was a tendency of decreased pain (median (IQR) 5/10 (2.6-6.6) vs 2.5 (2-3.2). All participants reported increased satisfaction of performance when "taking a walk", from median (IQR) 45/100 (27-70) at baseline to 95 (80-100) at 6 months. Two persons who could not ascend a slope at baseline could manage using the SmartDrive. Interviews revealed that the in general positive response persisted at six months. Also, with the SmartDrive the participants could go out despite pain, providing a sense of freedom and independence. Three incidents were reported.

CONCLUSION

This long-term pilot study indicates that a SmartDrive might be a valuable assistive device to promote mobility despite of shoulder pain. All participants considered it easy to use and experienced increased independence, however skills training and follow-ups are necessary. IMPLICATIONS FOR REHABILITATIONA Rear Drive Power Assist Device (RD-PAD) could increase satisfaction with self-selected activities.A RD-PAD could increase functional mobility by facilitating propelling longer distances and steeper slopes.A RD-PAD could improve perseverance of daily activities in spite of shoulder pain.A RD-PAD could be a valuable assistive aid for persons with paraplegia with different level of wheelchair skills but with good self-awareness regarding their abilities.Thorough assessment of initial wheelchair skills, training, and follow-up are important to enhance safety and maximize performance when using the RD-PAD.

Effect of power-assistance on upper limb biomechanical and physiological variables during a 6-minute, manual wheelchair propulsion test: a randomised, cross-over study

PURPOSE

Use of a power-assistance wheelchair could reduce the risk of musculoskeletal disorders (MSDs), however, a comprehensive biomechanical evaluation of these systems has not been carried out. This study aimed to evaluate and compare biomechanical UL propulsion variables, and physiological exercise-related variables during the use of a wheelchair with rear drive power assist device (RD-PAD) and a standard manual wheelchair (MW).

MATERIALS AND METHODS

Twenty-two adults with spinal cord injury were recruited. RD-PAD (SmartDrive system) was fitted to their own MW. An instrumented wheel was used to measure handrim forces, and gas exchange and heart rate were monitored. Participants performed repeated out and back runs for 6 min on a straight outdoor course.

RESULTS

Distance covered was significantly greater with the RD-PAD (538 ± 104 m versus 470 ± 124 m). Peak mechanical effort during the propulsion phase was significantly lower with the RD-PAD (p < 0.001). Heart rate, metabolic equivalent of task (MET), tidal volume, minute volume, oxygen consumption, and peak oxygen consumption were all significantly lower with the RD-PAD (p < 0.001).

CONCLUSIONS

The results showed that use of RD-PAD increased the distance covered by MW users and reduced the energy costs of propulsion. The biomechanical results indirectly suggest that RD-PAD may reduce the risk of MSD.Implications for RehabilitationUsing the SmartDrive system as propulsion assistance increases the travel autonomy.The SmartDrive system reduces the biomechanical constraints propelling the wheelchair on a slope and low slope.SmartDrive the system reduces the physiological solicitation related to the propulsion of wheelchair.

Classification of Wheelchair Related Shoulder Loading Activities from Wearable Sensor Data: A Machine Learning Approach

Shoulder problems (pain and pathology) are highly prevalent in manual wheelchair users with spinal cord injury. These problems lead to limitations in activities of daily life (ADL), labor- and leisure participation, and increase the health care costs. Shoulder problems are often associated with the long-term reliance on the upper limbs, and the accompanying "shoulder load". To make an estimation of daily shoulder load, it is crucial to know which ADL are performed and how these are executed in the free-living environment (in terms of magnitude, frequency, and duration). The aim of this study was to develop and validate methodology for the classification of wheelchair related shoulder loading ADL (SL-ADL) from wearable sensor data. Ten able bodied participants equipped with five Shimmer sensors on a wheelchair and upper extremity performed eight relevant SL-ADL. Deep learning networks using bidirectional long short-term memory networks were trained on sensor data (acceleration, gyroscope signals and EMG), using video annotated activities as the target. Overall, the trained algorithm performed well, with an accuracy of 98% and specificity of 99%. When reducing the input for training the network to data from only one sensor, the overall performance decreased to around 80% for all performance measures. The use of only forearm sensor data led to a better performance than the use of the upper arm sensor data. It can be concluded that a generalizable algorithm could be trained by a deep learning network to classify wheelchair related SL-ADL from the wearable sensor data.

Manual wheelchair biomechanics while overcoming various environmental barriers: A systematic review

During manual wheelchair (MWC) locomotion, the user's upper limbs are subject to heavy stresses and fatigue because the upper body is permanently engaged to propel the MWC. These stresses and fatigue vary according to the environmental barriers encountered outdoors along a given path. This study aimed at conducting a systematic review of the literature assessing the biomechanics of MWC users crossing various situations, which represent physical environmental barriers. Through a systematic search on PubMed, 34 articles were selected and classified according to the investigated environmental barriers: slope; cross-slope; curb; and ground type. For each barrier, biomechanical parameters were divided into four categories: spatiotemporal parameters; kinematics; kinetics; and muscle activity. All results from the different studies were gathered, including numerical data, and assessed with respect to the methodology used in each study. This review sheds light on the fact that certain situations (cross-slopes and curbs) or parameters (kinematics) have scarcely been studied, and that a wider set of situations should be studied. Five recommendations were made at the end of this review process to standardize the procedure when reporting materials, methods, and results for the study of biomechanics of any environmental barrier encountered in MWC locomotion: (i) effectively reporting barriers' lengths, grades, or heights; (ii) striving for standardization or a report of the approach conditions of the barrier, such as velocity, especially on curbs; (iii) reporting the configuration of the used MWC, and if it was fitted to the subject's morphology; (iv) reporting rotation sequences for the expression of moments and kinematics, and when used, the definition of the musculoskeletal model; lastly (v) when possible, reporting measurement uncertainties and model reconstruction errors.

Effect of Fatiguing Wheelchair Propulsion and Weight Relief Lifts on Subacromial Space in Wheelchair Users

Objective

This study aimed to identify targets of intervention for reducing shoulder pain in wheelchair users with spinal cord injury (SCI) by (1) examining changes in subacromial space [acromiohumeral distance (AHD) and occupation ratio (OccRatio)] with fatiguing wheelchair propulsion, and different loading conditions [unloaded position vs. weight relief lifts (WRL)]; (2) associating these changes with wheelchair user capacity, as well as (3) identifying subject characteristics associated with subacromial space, such as sex, lesion level, time since injury, body mass index and impaired shoulder range of motion.

Methods

Fifty manual wheelchair users with SCI [11 females, age = 50.5 (9.7) years, time since injury = 26.2 (11.4) years] participated in this quasi-experimental one-group pretest-posttest study. Ultrasound images were used to define AHD during an unloaded position, and during personal and instructed WRL before and after fatiguing wheelchair propulsion. Furthermore, supraspinatus and biceps thickness defined from ultrasound images were used to calculate OccRatios. Wheelchair user capacity was quantified as functional strength (maximum resultant force reached during maximum isometric forward push) and anaerobic work capacity (highest power output reached during 15-m sprint test). Multilevel mixed-effects linear regression analyses controlling for between subject variability and covariables were performed to address the research questions.

Results

AHD was significantly smaller during personal WRL (p &lt; 0.001) and instructed WRL (p = 0.009, AHD both 11.5 mm) compared to the unloaded position (11.9 mm). A higher wheelchair user capacity (higher anaerobic work capacity) reduced the impact of WRL on AHD decrease. The fatiguing wheelchair propulsion had no effect on AHD (p = 0.570) and on OccRatio of supraspinatus (p = 0.404) and biceps (p = 0.448). Subject characteristics related to a larger subacromial space were lower lesion level, shorter time since injury, impaired external rotation, a lower body mass index and a higher anaerobic work capacity.

Conclusion

This study showed a significant reduction in AHD during WRL with no effect of fatiguing wheelchair propulsion on the subacromial space in wheelchair users with SCI. A higher anaerobic work capacity was beneficial in stabilizing the shoulder during WRL. Our findings may assist clinicians in designing a shoulder injury prevention program.

Wheelchair backs that support the spinal curves: Assessing postural and functional changes

Objective: To compare outcomes using a wheelchair back designed to support the natural seated spinal curves versus an upholstered back that promotes posterior pelvic tilt and thoracolumbar kyphosis.Design: Cross-over intervention.Setting: Two free-standing spinal cord injury (SCI) model system hospitals.Participants: Fifty adults with motor complete SCI C6-T4, between the ages of 18-60 years who use a manual wheelchair for mobility were recruited from a convenience sample.Intervention: Each participant's wheelchair back support was removed and replaced by an upholstered back and a solid back in randomized order. Postural and functional outcomes, pain, and satisfaction were evaluated using each back.Outcome measures: Seated postural measurements included pelvic angle, spinal angle of kyphosis and linear measurement of spine. Functional outcomes included vertical forward reach, one stroke push, timed forward wheeling, ramp ascent and descent. Numerical pain rating and a satisfaction survey provided input pertaining to both backs.Results: The solid back demonstrated significance in seated postural measurements. Participants using the solid back trended to higher scores in functional outcome measures including vertical forward reach, one stroke push and timed ramp ascent. Participants reported increased satisfaction with comfort and stability with the solid back.Conclusions: This pilot study demonstrated that a wheelchair back, which supports the seated spinal curves improves upright posture, functional reach, and wheelchair propulsion skills. Further research is necessary to demonstrate statistical findings as well as to assess back height and lateral support.

A Primary Care Provider's Guide to Shoulder Pain After Spinal Cord Injury

Shoulder pain is a common occurrence after spinal cord injury (SCI) and can have significant negative effects on health and function as many individuals with SCI are reliant on their upper extremities for mobility and self-care activities. Shoulder pain after SCI can be caused by acute injury or chronic pathology, but it is most often related to overuse injuries of the rotator cuff. Both acute strain and chronic overuse shoulder injuries in persons with SCI typically result from increased weight bearing on the upper extremities during transfers, weight-relief raises, and wheelchair propulsion, which are often performed in poor postural alignment owing to strength deficits. This article discusses management of patients with SCI who present with shoulder pain from the perspective of primary care physicians including evaluation and diagnostic procedures, interventions appropriate for both acute and chronic shoulder pain, and strategies for prevention.

Pain and its impact on functioning and disability in manual wheelchair users with spinal cord injury: a protocol for a mixed-methods study

INTRODUCTION

Approximately 80% of people with spinal cord injury experience clinically significant chronic pain. Pain (whether musculoskeletal or neuropathic) is consistently rated as one of the most difficult problems to manage and negatively affects the individual's physical, psychological and social functioning and increases the risk of pain medication misuse and poor mental health. The aim of this study is to therefore determine the presence of pain and its impact on functioning and disability as well as to develop a framework for self-management of pain for South African manual wheelchair users with spinal cord injury.

METHODS AND ANALYSIS

Community-dwelling participants with spinal cord injury will be invited to participate in this three-phase study. Phase 1 will use a quantitative, correlational design to determine factors related to pain such as pectoralis minor length, scapular dyskinesis, wheelchair functioning, physical quality of life, community reintegration and pain medication misuse. Demographic determinants of pain such as age, gender, type of occupation, completeness of injury and neurological level of injury will also be investigated. Participants with pain identified in phase 1 will be invited to partake in a qualitative descriptive and contextually designed phase 2 to explore their lived experience of pain through in-depth interviews. The results of phases 1 and 2 will then be used with the assistance from experts to develop a framework for self-management of pain using a modified Delphi study. Data analysis will include descriptive and inferential statistics (quantitative data) and thematic content analysis (qualitative data).

ETHICS AND DISSEMINATION

Approval for this study is granted by the Faculty of Health Sciences Research Ethics Committee of the University of the Pretoria (approval number 125/2018). This study is registered with the South African National Health Research Database (reference GP201806005). This study's findings will be shared in academic conferences and published in scientific peer-reviewed journals.

Follow-up consultations through telerehabilitation for wheelchair recipients with paraplegia in a developing country: a case report

INTRODUCTION

Persons with disability (PWD) in the Philippines find it difficult to attend regular face-to-face rehabilitation due to distance, transportation and food expenses, disability, and time constraints. Being a developing country, Filipino rehabilitation doctors have to be resourceful to overcome these barriers and try alternative ways to reach out to their patients, such as through telemedicine, specifically telerehabilitation.

CASE PRESENTATION

After receiving free wheelchairs, two patients with paraplegia secondary to spinal cord disease were unable to report for in-clinic wheelchair reassessment. Telerehabilitation was attempted for the first time to conduct wheelchair follow-up using a commonly available social media application through synchronous and asynchronous methods. During the teleconsultation, the rehabilitation doctors used the wheelchair follow-up form from the World Health Organization translated into Filipino. There were apprehensions at first, especially from the side of the patients, regarding the method, effectiveness, and safety of telerehabilitation. In the end, the patients found telerehabilitation easy, safe, and convenient, and were satisfied with the practical wheelchair modifications and exercise recommendations.

DISCUSSION

Telerehabilitation is a viable alternative to provide universal access to rehabilitation care and overcome the barriers to in-clinic visits among indigent PWD in a resource-limited country. Unlike in developed countries, we do not have readily available customized telemedicine platforms and telemonitoring equipment to conduct telerehabilitation. Nonetheless, we can make use of what is locally available, affordable, and convenient to our patients.

Comparing supraspinatus to acromion proximity and kinematics of the shoulder and thorax between manual wheelchair propulsion styles: A pilot study

BACKGROUND

Repetitive glenohumeral joint movement during manual wheelchair propulsion has been associated with shoulder pain in individuals with spinal cord injury. Clinical guidelines for shoulder health maintenance encourage semi-circular over arc propulsion to reduce loading frequency. This study aimed to determine the difference in estimated supraspinatus to acromion compression risk, and shoulder, thorax kinematics between (1) arc and semi-circular propulsion; and (2) self-selected and coached strategies.

METHODS

Shoulder and thorax kinematics were captured during wheelchair propulsion, noting individually self-selected styles. Participants were then coached to perform the other style(s) of interest, arc and/or semi-circular. CT bone models of the humerus and scapula were animated using glenohumeral kinematics to estimate the minimum distance between the supraspinatus humeral attachment and the acromion. Compression risk was defined as the proportion of each propulsion phase where the minimum distance fell below 5 mm. Comparisons were made between conditions evaluating compression risk, minimum distances and kinematics at events throughout propulsion.

FINDINGS

Ten individuals with spinal cord injury (9 male) participated. Arc and semi-circular propulsion did not significantly differ in compression risk or minimum distance across propulsion phases. Self-selected styles yielded lower compression risk and larger proximity values compared to coached styles. Glenohumeral horizontal abduction and thorax flexion differed between arc and semi-circular propulsion. Multiple glenohumeral and humerothoracic differences emerged between self-selected and coached conditions.

INTERPRETATION

Supraspinatus compression was observed during both arc and semi-circular propulsion, suggesting risk may be unavoidable in this task. Self-selected styles yield less risk, likely related to coached style unfamiliarity.

Associations between health behaviour, secondary health conditions and quality of life in people with spinal cord injury

Background

The development of secondary health conditions (SHCs) after spinal cord injury (SCI) is common and can affect an individual’s emotional well-being, and his or her health-related quality of life (QOL). Little is known about relationships between performing health-benefiting behaviours and the presence (or absence) of SHCs and QOL, particularly in South Africa.

Objectives

This research study was conducted in order to determine the associations between health behaviour, SHCs and QOL in people with SCI (PWSCI).

Method

This cross-sectional study included 36 PWSCI discharged from a private rehabilitation facility in Pretoria, South Africa. The PWSCI completed questionnaires pertaining to lifestyle, independence, presence of SHCs, social support and QOL. Data were analysed using descriptive and inferential statistics such as correlation tests and chi-square test of independence (x²) using the SPSS v25. Moderate, moderately high and high correlations are reported (Pearson r ≥ 0.4). Results were significant if p < 0.05.

Results

Participation in health-benefiting behaviour was associated with increased QOL (r = 0.457, p < 0.01) and increased social support from family and friends (r = 0.425, p < 0.01), which was associated with increased QOL (r = 0.671, p < 0.001). Not participating in specific neuromusculoskeletal health behaviours was found to be associated with the overall presence of SHCs (r = -0.426, p < 0.01).

Conclusions

Participating in health-benefiting behaviour can reduce the development of SHCs and subsequently increase QOL in PWSCI. Health professionals must focus on minimising the development of SHCs by providing specific education on good health-benefiting behaviour.

Engineering and Technology in Wheelchair Sport

Technologies capable of projecting injury and performance metrics to athletes and coaches are being developed. Wheelchair athletes must be cognizant of their upper limb health; therefore, systems must be designed to promote efficient transfer of energy to the handrims and evaluated for simultaneous effects on the upper limbs. This article is brief review of resources that help wheelchair users increase physiologic response to exercise, develop ideas for adaptive workout routines, locate accessible facilities and outdoor areas, and develop wheelchair sports-specific skills.

Arm-trunk coordination in wheelchair initiation displacement: A study of anticipatory and compensatory postural adjustments during different speeds and directions of propulsion

Arm-trunk coordination during the initiation of displacement in manual wheelchair is a complex task. The objective of this work is to study the arm-trunk coordination by measuring anticipatory and compensatory postural adjustments. Nine healthy subjects participated in the study after being trained in manual wheelchair. They were asked to initiate a displacement in manual wheelchair in three directions (forward vs. left vs. right), with two speeds (spontaneous vs. maximum) and with two initial hand's positions (hands on thighs vs. hands on handrails). Muscular activities in the trunk (postural component) and the arms (focal component) were recorded bilaterally. The results show two strategies for trunk control: An anticipatory adjustment strategy and a compensatory adjustment strategy with a dominance of compensation. These two strategies are influenced by the finalities of displacement in terms of speed and direction depending on the hands positions. Arm-trunk coordination is characterized by an adaptability of anticipatory and compensatory postural adjustments. The study of this type of coordination for subjects with different levels of spinal cord injury could be used to predict the forthcoming displacement and thus assist the user in a complex task.

Scapular kinematics in professional wheelchair tennis players

BACKGROUND

Participating in wheelchair tennis increases the demands placed on the shoulder and could increase the risk of developing shoulder pain and injury that might be associated with differences in scapular kinematics. The aim of the study was to examine the presence of shoulder pain and scapular kinematics in professional wheelchair tennis players.

METHOD

Scapular kinematics were obtained in 11 professional wheelchair tennis players, 16 people with shoulder impingement and 16 people without shoulder impingement during humeral elevation and lowering. Clinical examination of the wheelchair tennis players was undertaken using the Wheelchair Users Shoulder Disability Index (WUSPI) and clinical signs of shoulder impingement.

FINDINGS

The WUSPI questionnaire (mean = 28 SD 13.8) demonstrated wheelchair tennis participants experienced little shoulder pain and clinical examination revealed negative impingement tests. Wheelchair tennis players had greater scapular posterior tilt during humeral elevation (3.9° SE 1.71; P = 0.048) and lowering (4.3° SE 1.8; P = 0.04) on the dominant compared to non-dominant side. The dominant scapulae of wheelchair tennis players were significantly (P = 0.014) more upwardly rotated (21° SD 6.7) than the scapulae of people with shoulder impingement (14.1° SD 7.0) during scapular plane humeral elevation.

INTERPRETATION

This first study of scapular kinematics in professional wheelchair tennis athletes demonstrated bilateral asymmetries and differences to able-bodied participants with shoulder impingement. Understanding the role of sport participation on shoulder function in wheelchair users would assist in the development of preventative and treatment exercise programmes for wheelchair users at risk of shoulder injury and pain.

The Weight-Bearing Shoulder

The shoulder achieves a wide spectrum of motion, and in a subset of patients, including those who use manual wheelchairs and upper extremity walking aids, the shoulder also serves as the primary weight-bearing joint. Because the weight-bearing shoulder is subject to considerable joint reaction forces and overuse, a broad spectrum of pathology can affect the joint. The combination of muscle imbalance and repetitive trauma presents most commonly as subacromial impingement syndrome but can progress to other pathology. Patients with high-level spinal cord injury, leading to quadriplegia and motor deficits, have an increased incidence of shoulder pain. Understanding the needs of patients who use manual wheelchairs or walking aids can help the physician to better comprehend the pathology of and better manage the weight-bearing shoulder.

Kinematic and ergonomic assessment of laparoendoscopic single-site surgical instruments during simulator training tasks

While laparoendoscopic single-site surgery (LESS) appears to be feasible and safe, instrument triangulation, tissue handling, and other bimanual tasks are difficult even for experienced surgeons. Novel technologies emerged to overcome LESS' procedural and ergonomic difficulties of "tunnel vision" and "instrument clashing." Surgeon kinematics, self-reported workload and upper body discomfort were used to compare straight, bent and two articulating instruments while performing two basic surgical tasks in a LESS simulator. All instruments resulted in bilateral elevation and rotation of the shoulders, excessive forearm motion and flexion and ulnar deviation of wrists. Surgeons' adopted non-neutral upper extremity postures and performed excessive joint excursions to compensate for reduced freedom of movement at the single insertion site and to operate the instrument mechanisms. LESS' cosmetic benefits continue to impact laparoscopic surgery and by enabling performance through improved instruments, ergonomic improvement for LESS can reduce negative impact on surgeon well-being and patient safety.

Validation of Inertial Measurement Units for Upper Body Kinematics

The purpose of this study was to validate a commercially available inertial measurement unit (IMU) system against a standard lab-based motion capture system for the measurement of shoulder elevation, elbow flexion, trunk flexion/extension, and neck flexion/extension kinematics. The validation analyses were applied to 6 surgical faculty members performing a standard, simulated surgical training task that mimics minimally invasive surgery. Three-dimensional joint kinematics were simultaneously recorded by an optical motion capture system and an IMU system with 6 sensors placed on the head, chest, and bilateral upper and lower arms. The sensor-to-segment axes alignment was accomplished manually. The IMU neck and trunk IMU flexion/extension angles were accurate to within 2.9 ± 0.9 degrees and 1.6 ± 1.1°, respectively. The IMU shoulder elevation measure was accurate to within 6.8 ± 2.7° and the elbow flexion measure was accurate to within 8.2 ± 2.8°. In the Bland-Altman analyses, there were no significant systematic errors present; however, there was a significant inversely proportional error across all joints. As the gold standard measurement increased, the IMU underestimated the magnitude of the joint angle. This study reports acceptable accuracy of a commercially available IMU system; however, results should be interpreted as protocol specific.

Evaluating the Functionality and Usability of Two Novel Wheelchair Anti-Rollback Devices for Ramp Ascent in Manual Wheelchair Users With Spinal Cord Injury

BACKGROUND

Difficulty ascending ramps and inclines with a manual wheelchair adversely affects the everyday mobility and overall quality of life of manual wheelchair users. Currently, various anti-rollback devices are available to assist manual wheelchair users to ascend ramps and inclines. However, these devices have 2 main shortcomings: restriction to backward motion limiting recovery from an overturning wheelchair, which is a safety concern; and difficulty in engaging/disengaging the device while on the ramp.

OBJECTIVE

To evaluate the functionality and usability of 2 novel wheelchair anti-rollback devices developed to address these shortcomings (prototypes "Wheel" and "Brake").

DESIGN

Cross-sectional.

SETTING

Rehabilitation research facility.

PARTICIPANTS

Twelve adult participants with chronic spinal cord injury.

METHODS

Participants completed training and tested with both the wheelchair anti-rollback devices on a 7.3-m-long ramp.

MAIN OUTCOME MEASUREMENTS

Number of stops, perceived physical exertion, pain, and ease of use of these devices as participants maneuvered their wheelchairs up a 7.3-m ramp were assessed. Participants also evaluated their satisfaction with the usability of both the devices using the Quebec User Evaluation of Satisfaction With Assistive Technology (QUEST 2.0).

RESULTS

Both prototypes evaluated overcame the limitations of the existing anti-rollback devices. Nonparametric statistical tests showed that participants rated both prototypes similarly for the overall functional and usability aspects. However, the participants' satisfactory rating were higher for the prototype "Brake" than for the prototype "Wheel" based on a functional aspect (ie, engaging/disengaging easiness), and higher for Wheel than for Brake, based on a usability aspect (prototype size).

CONCLUSIONS

The qualitative and quantitative outcomes of this investigation, based on the usability and functional evaluations, provided useful information for the improvement in the design of both anti-rollback devices, which may allow manual wheelchair users to manage ramp ascent more safely and easily. Further evaluations with a different SCI population is recommended.

LEVEL OF EVIDENCE

IV.

Effects of Seated Postural Stability and Trunk and Upper Extremity Strength on Performance during Manual Wheelchair Propulsion Tests in Individuals with Spinal Cord Injury: An Exploratory Study

Objectives. To quantify the association between performance-based manual wheelchair propulsion tests (20 m propulsion test, slalom test, and 6 min propulsion test), trunk and upper extremity (U/E) strength, and seated reaching capability and to establish which ones of these variables best predict performance at these tests. Methods. 15 individuals with a spinal cord injury (SCI) performed the three wheelchair propulsion tests prior to discharge from inpatient SCI rehabilitation. Trunk and U/E strength and seated reaching capability with unilateral hand support were also measured. Bivariate correlation and multiple linear regression analyses allowed determining the best determinants and predictors, respectively. Results. The performance at the three tests was moderately or strongly correlated with anterior and lateral flexion trunk strength, anterior seated reaching distance, and the shoulder, elbow, and handgrip strength measures. Shoulder adductor strength-weakest side explained 53% of the variance on the 20-meter propulsion test-maximum velocity. Shoulder adductor strength-strongest side and forward seated reaching distance explained 71% of the variance on the slalom test. Handgrip strength explained 52% of the variance on the 6-minute propulsion test. Conclusion. Performance at the manual wheelchair propulsion tests is explained by a combination of factors that should be considered in rehabilitation.

Intraoperative workload in robotic surgery assessed by wearable motion tracking sensors and questionnaires

BACKGROUND

The introduction of robotic technology has revolutionized radical prostatectomy surgery. However, the potential benefits of robotic techniques may have trade-offs in increased mental demand for the surgeon and the physical demand for the assisting surgeon. This study employed an innovative motion tracking tool along with validated workload questionnaire to assess the ergonomics and workload for both assisting and console surgeons intraoperatively.

METHODS

Fifteen RARP cases were collected in this study. Cases were performed by 10 different participants, six primarily performed console tasks and four primarily performed assisting tasks. Participants had a median 12 (min-3, max-25) years of surgical experience. Both console and assisting surgeons performed robotic prostatectomy cases while wearing inertial measurement units (IMUs) that continuously track neck, shoulder, and torso motion without interfering with the sterile environment. Postoperatively, participants completed a workload questionnaire (SURG-TLX) and a body part discomfort questionnaire.

RESULTS

Twenty-six questionnaires were completed from 13 assisting and 13 console surgeons over the 15 cases. Postoperative pain was reported highest for the right shoulder and neck. Mental demands were 41 % higher for surgeons at the console than assisting (p < 0.05), while physical demands were not significantly different. Assisting surgeons worked in demanding neck postures for 58 % of the procedure compared to 24 % for the console surgeon (p < 0.01). Surgeons at the console were primarily static and showed 2-5 times fewer movements than assisting surgeons (p < 0.01).

CONCLUSIONS

Postures were more ergonomic during console tasks than when assisting by the bedside; however, the console may constrain postures leading to static loads that have been associated with musculoskeletal symptoms for the neck, torso, and shoulders. The IMU sensors were effective at quantifying ergonomics in robotic prostatectomies, and these methods and findings have broad applications to other robotic procedures.

Impact of novel shift handle laparoscopic tool on wrist ergonomics and task performance

BACKGROUND

Laparoscopic tool handles causing wrist flexion and extension more than 15° from neutral are considered "at risk" for musculoskeletal strain. Therefore, this study measured the impact of laparoscopic tool handle angles on wrist postures and task performance.

METHODS

Eight surgeons performed standard and modified Fundamentals of Laparoscopic Surgery (FLS) tasks with laparoscopic tools. Tool A had three adjustable handle angle configurations, i.e., in-line 0° (A0), 30° (A30), and pistol-grip 70° (A70). Tool B was a fixed pistol-grip grasper. Participants performed FLS peg transfer, inverted peg transfer, and inverted circle cut with each tool and handle angle. Inverted tasks were adapted from standard FLS tasks to simulate advanced tasks observed during abdominal wall surgeries, e.g., ventral hernia. Motion tracking, video analysis, and modified NASA-TLX workload questionnaires were used to measure postures, performance (e.g., completion time and errors), and workload.

RESULTS

Task performance did not differ between tools. For FLS peg transfer, self-reported physical workload was lower for B than for A70, and mean wrist postures showed significantly higher flexion for in-line than for pistol-grip tools (B and A70). For inverted peg transfer, workload was higher for all configurations. However, less time was spent in at-risk wrist postures for in-line (47 %) than for pistol-grip (93-94 %), and most participants preferred Tool A. For inverted circle cut, workload did not vary across configurations, mean wrist posture was 10° closer to neutral for A0 than B, and median time in at-risk wrist postures was significantly less for A0 (43 %) than for B (87 %).

CONCLUSION

The best ergonomic wrist positions for FLS (floor) tasks are provided by pistol-grip tools and for tasks on the abdominal wall (ventral surface) by in-line handles. Adjustable handle angle laparoscopic tools can reduce ergonomic risks of musculoskeletal strain and allow versatility for tasks alternating between the floor and ceiling positions in a surgical trainer without impacting performance.

Biomechanics of Pediatric Manual Wheelchair Mobility

Currently, there is limited research of the biomechanics of pediatric manual wheelchair mobility. Specifically, the biomechanics of functional tasks and their relationship to joint pain and health is not well understood. To contribute to this knowledge gap, a quantitative rehabilitation approach was applied for characterizing upper extremity biomechanics of manual wheelchair mobility in children and adolescents during propulsion, starting, and stopping tasks. A Vicon motion analysis system captured movement, while a SmartWheel simultaneously collected three-dimensional forces and moments occurring at the handrim. A custom pediatric inverse dynamics model was used to evaluate three-dimensional upper extremity joint motions, forces, and moments of 14 children with spinal cord injury (SCI) during the functional tasks. Additionally, pain and health-related quality of life outcomes were assessed. This research found that joint demands are significantly different amongst functional tasks, with greatest demands placed on the shoulder during the starting task. Propulsion was significantly different from starting and stopping at all joints. We identified multiple stroke patterns used by the children, some of which are not standard in adults. One subject reported average daily pain, which was minimal. Lower than normal physical health and higher than normal mental health was found in this population. It can be concluded that functional tasks should be considered in addition to propulsion for rehabilitation and SCI treatment planning. This research provides wheelchair users and clinicians with a comprehensive, biomechanical, mobility assessment approach for wheelchair prescription, training, and long-term care of children with SCI.

Quadrupedal Locomotion-Respiration Entrainment and Metabolic Economy in Cross-Country Skiers

A 1:1 locomotion-respiration entrainment is observed in galloping quadrupeds, and is thought to improve running economy. However, this has not been tested directly in animals, as animals cannot voluntarily disrupt this entrainment. The purpose of this study was to evaluate metabolic economy in a human gait involving all four limbs, cross-country skiing, in natural entrainment and forced nonentrainment. Nine elite cross-country skiers roller skied at constant speed using the 2-skate technique. In the first and last conditions, athletes used the natural entrained breathing pattern: inhaling with arm recovery and exhaling with arm propulsion, and in the second condition, the athletes disentrained their breathing pattern. The rate of oxygen uptake (VO2) and metabolic rate (MR) were measured via expired gas analysis. Propulsive forces were measured with instrumented skis and poles. VO2 and MR increased by 4% and 5% respectively when skiers used the disentrained compared with the entrained breathing pattern. There were no differences in ski or pole forces or in timing of the gait cycle between conditions. We conclude that breathing entrainment reduces metabolic cost of cross-country skiing by approximately 4%. Further, this reduction is likely a result of the entrainment rather than alterations in gait mechanics.

Shoulder Strength and Physical Activity Predictors of Shoulder Pain in People With Paraplegia From Spinal Injury: Prospective Cohort Study

BACKGROUND

Shoulder joint pain is a frequent secondary complaint for people following spinal cord injury (SCI).

OBJECTIVE

The purpose of this study was to determine predictors of shoulder joint pain in people with paraplegia.

METHODS/DESIGN

A 3-year longitudinal study was conducted. Participants were people with paraplegia who used a manual wheelchair for at least 50% of their mobility and were asymptomatic for shoulder pain at study entry. Participants were classified as having developed shoulder pain if they experienced an increase of ≥10 points on the Wheelchair User's Shoulder Pain Index in the 3-year follow-up period. Measurements of maximal isometric shoulder torques were collected at study entry (baseline), 18 months, and 3 years. Daily activity was measured using a wheelchair odometer, and self-reported daily transfer and raise frequency data were collected by telephone every 6 weeks.

RESULTS

Two hundred twenty-three participants were enrolled in the study; 39.8% developed shoulder pain over the 3-year follow-up period. Demographic variables and higher activity levels were not associated with shoulder pain onset. Baseline maximal isometric torque (normalized by body weight) in all shoulder muscle groups was 10% to 15% lower in participants who developed shoulder pain compared with those who remained pain-free. Lower shoulder adduction torque was a significant predictor of shoulder pain development (log-likelihood test=11.38), but the model explained only 7.5% of shoulder pain onset and consequently is of limited clinical utility.

LIMITATIONS

Time since SCI varied widely among participants, and transfer and raise activity was measured by participant recall.

CONCLUSIONS

Participants who developed shoulder pain had decreased muscle strength, particularly in the shoulder adductors, and lower levels of physical activity prior to the onset of shoulder pain. Neither factor was a strong predictor of shoulder pain onset.

Evaluation of pediatric manual wheelchair mobility using advanced biomechanical methods

There is minimal research of upper extremity joint dynamics during pediatric wheelchair mobility despite the large number of children using manual wheelchairs. Special concern arises with the pediatric population, particularly in regard to the longer duration of wheelchair use, joint integrity, participation and community integration, and transitional care into adulthood. This study seeks to provide evaluation methods for characterizing the biomechanics of wheelchair use by children with spinal cord injury (SCI). Twelve subjects with SCI underwent motion analysis while they propelled their wheelchair at a self-selected speed and propulsion pattern. Upper extremity joint kinematics, forces, and moments were computed using inverse dynamics methods with our custom model. The glenohumeral joint displayed the largest average range of motion (ROM) at 47.1° in the sagittal plane and the largest average superiorly and anteriorly directed joint forces of 6.1% BW and 6.5% BW, respectively. The largest joint moments were 1.4% body weight times height (BW × H) of elbow flexion and 1.2% BW × H of glenohumeral joint extension. Pediatric manual wheelchair users demonstrating these high joint demands may be at risk for pain and upper limb injuries. These evaluation methods may be a useful tool for clinicians and therapists for pediatric wheelchair prescription and training.

Upper extremity biomechanics of children with spinal cord injury during wheelchair mobility

While much work is being done evaluating the upper extremity joint dynamics of adult manual wheelchair propulsion, limited work has examined the pediatric population of manual wheelchair users. Our group used a custom pediatric biomechanical model to characterize the upper extremity joint dynamics of 12 children and adolescents with spinal cord injury (SCI) during wheelchair propulsion. Results show that loading appears to agree with that of adult manual wheelchair users, with the highest loading primarily seen at the glenohumeral joint. This is concerning due to the increased time of wheelchair use in the pediatric population and the impact of this loading during developmental years. This research may assist clinicians with improved mobility assessment methods, wheelchair prescription, training, and long-term care of children with orthopaedic disabilities.

Novel approaches to objectively assess shoulder function

BACKGROUND

The purpose of this study was to evaluate the effectiveness of existing technologies implemented in a novel manner to objectively capture upper extremity function.

MATERIALS AND METHODS

Patients scheduled to undergo reverse shoulder arthroplasty were recruited for the study. Functional limb use was measured with triaxial accelerometers worn in the subjects' natural living environment. Functional reach area was captured by 3-dimensional motion analysis testing as subjects were asked to circumduct their limb, reaching as far as possible in a circular manner. Statistical testing (α ≤ .05) was performed by paired t tests to identify differences between limbs.

RESULTS

There was no difference in functional limb activity between sides for the lower (P = .497) or upper arm (P = .918) for inactivity time. Mean activity was greater for the uninvolved limb compared with the involved limb (lower arm, P = .045; upper arm, P = .005). Low-intensity activity was greater for the involved arm compared with the uninvolved arm (lower arm, P = .007; upper arm, P = .015), whereas high-intensity activity was greater for the uninvolved arm (lower arm, P = .013; upper arm, P = .005). Radius of the functional reach area was greater for the uninvolved limb compared with the involved limb (P = .006).

CONCLUSIONS

Novel methods of capturing function were effective in discerning differences in side-to-side abilities among patients scheduled to undergo reverse shoulder arthroplasty. These testing procedures may be used to capture function across a spectrum of shoulder diseases. These objective data are invaluable in assessing the impact of disease and recovery after intervention and obtaining reimbursement from third-party payers.

The accuracy of an external frame using ISB recommended rotation sequence to define shoulder joint angle

When investigating shoulder kinematics, it may be necessary to limit shoulder joint angles at a specific level. Previous studies used external frames or external surfaces to assist the participant to reach the shoulder joint angles of interest. The accuracy of these methods, however, has not yet been investigated. In the current study, an external frame was designed to assist in maintaining specific shoulder postures in a wide range. The three degrees of freedom of rotation of the proposed frame were designed to be consistent with the description of shoulder joint angles recommended by the International Society of Biomechanics. Six participants used this frame to perform 118 different shoulder postures. The reference joint angles measured by a motion tracking system were compared with the frame-defined angles. The angle differences among all the participants ranged from 12.7° to 85.6°, with an average of 32.2° (SD 15.1°) across all postures. For the postures with elevation angles on or below horizontal, the average angle difference was 23.7° (SD 8.5°). Findings suggest that errors exist when using an external frame to assist in reaching specific shoulder postures. Error is minimized at elevation angles close to -30°, and the performance is poor for extreme shoulder postures.

Glenohumeral rotational motion and strength and baseball pitching biomechanics

CONTEXT

Addressing loss of shoulder range of motion and rotator cuff weakness in injury-prevention programs might be an effective strategy for preventing throwing arm injuries in baseball pitchers. However, the influence of these clinical measures on pitching biomechanics is unclear.

OBJECTIVE

To evaluate the relationships among clinical measures of shoulder rotational motion and strength and 3-dimensional pitching biomechanics and to evaluate the presence of coupling between the shoulder and the elbow during pitching to provide insight into the influence of clinical shoulder characteristics on elbow biomechanics.

DESIGN

Cross-sectional study.

SETTING

Biomechanics laboratory.

PATIENTS OR OTHER PARTICIPANTS

A total of 27 uninjured male high school baseball pitchers (age = 16 ± 1.1 years, height = 183 ± 7 cm, mass = 83 ± 12 kg).

MAIN OUTCOME MEASURE(S)

Clinical measures included shoulder internal- and external-rotation range of motion and peak isometric internal- and external-rotator strength. Three-dimensional upper extremity biomechanics were assessed as participants threw from an indoor pitching mound to a target at regulation distance. Linear regressions were used to assess the influence of clinical measures on the peak shoulder internal and external rotation moments and the peak elbow-adduction moment.

RESULTS

We found a positive relationship between clinically measured internal-rotator strength and shoulder external-rotation moment (R(2) = 0.181, P = .04) during pitching. We also noted an inverse relationship between clinically measured external-rotation motion and the elbow-adduction moment (R(2) = 0.160, P = .04) and shoulder internal-rotation moment (R(2) = 0.250, P = .008) during pitching. We found a positive relationship between peak shoulder internal-rotation moment and the peak elbow-adduction moment (R(2) = 0.815, P < .001) during pitching.

CONCLUSIONS

This study provides insight into the effects of shoulder strength and motion on pitching biomechanics and how these clinical measures might contribute to throwing arm injuries in the baseball pitcher. A relationship also was identified between peak shoulder and elbow moments in the throwing arm during pitching, providing biomechanical support for addressing clinical shoulder characteristics as a potential strategy for preventing elbow injury.

Variability in bimanual wheelchair propulsion: consistency of two instrumented wheels during handrim wheelchair propulsion on a motor driven treadmill

Background

Handrim wheelchair propulsion is a complex bimanual motor task. The bimanually applied forces on the rims determine the speed and direction of locomotion. Measurements of forces and torques on the handrim are important to study status and change of propulsion technique (and consequently mechanical strain) due to processes of learning, training or the wheelchair configuration. The purpose of this study was to compare the simultaneous outcomes of two different measurement-wheels attached to the different sides of the wheelchair, to determine measurement consistency within and between these wheels given the expected inter- and intra-limb variability as a consequence of motor control.

Methods

Nine able-bodied subjects received a three-week low-intensity handrim wheelchair practice intervention. They then performed three four-minute trials of wheelchair propulsion in an instrumented hand rim wheelchair on a motor-driven treadmill at a fixed belt speed. The two measurement-wheels on each side of the wheelchair measured forces and torques of one of the two upper limbs, which simultaneously perform the push action over time. The resulting data were compared as direct output using cross-correlation on the torque around the wheel-axle. Calculated push characteristics such as power production and speed were compared using an intra-class correlation.

Results

Measured torque around the wheel axle of the two measurement-wheels had a high average cross-correlation of 0.98 (std=0.01). Unilateral mean power output over a minute was found to have an intra-class correlation of 0.89 between the wheels. Although the difference over the pushes between left and right power output had a high variability, the mean difference between the measurement-wheels was low at 0.03 W (std=1.60). Other push characteristics showed even higher ICC’s (>0.9).

Conclusions

A good agreement between both measurement-wheels was found at the level of the power output. This indicates a high comparability of the measurement-wheels for the different propulsion parameters. Data from both wheels seem suitable to be used together or interchangeably in experiments on motor control and wheelchair propulsion performance. A high variability in forces and timing between the left and right side were found during the execution of this bimanual task, reflecting the human motor control process.

Pitch velocity is a predictor of medial elbow distraction forces in the uninjured high school-aged baseball pitcher

Background:

Medial elbow injuries are common among baseball pitchers. Easily accessed methods to assess medial elbow stress may be useful in identifying individuals with increased injury risk.

Hypothesis:

Pitch velocity (PV) is positively associated with higher medial elbow adduction moments.

Study Design:

Cohort study; Level of evidence, 2.

Methods:

Participants included 26 uninjured high school pitchers, 15 to 18 years in age. Three-dimensional data and PV were collected as athletes threw 10 fastballs for strikes to a regulation-distance target. Variables of interest were the normalized peak internal elbow adduction moment and peak PV. Linear regression was performed to evaluate the influence of PV on the adduction moment.

Results:

For the group, mean PV was 71 mph (range, 58-81 mph), and the adduction moment was 0.558 Nm/Ht × mass (range, 0.378-0.723). PV was positively associated with the adduction moment (P < 0.01, R²= 0.373).

Conclusions:

Talented young pitchers may be more susceptible to elbow injuries as a consequence of a biomechanical coupling between PV and upper extremity joint moments.

Clinical Relevance:

PV may be measured easily and serve as an indicator of medial elbow stress.

Torque and power outputs on skilled and unskilled users during manual wheelchair propulsion

Manual wheelchair users are at a high risk of pain and injuries to the upper extremities due to mechanical inefficiency of wheelchair propulsion motion. The kinetic analysis of the upper extremities during manual wheelchair propulsion in various conditions needed to be investigated. We developed and calibrated a wheelchair dynamometer for measuring kinetic parameters during propulsion. We utilized the dynamometer to investigate and compare the propulsion torque and power values of skilled and unskilled users under four different conditions. Skilled manual wheelchair users generated lower torques with more power than unskilled users and reacted alertly and sensitively to changing conditions. We expect that these basic methods and results may help to quantitatively evaluate the mechanical efficiency of manual wheelchair propulsion.

Relationship between the medial elbow adduction moment during pitching and ulnar collateral ligament appearance during magnetic resonance imaging evaluation

BACKGROUND

Medial elbow distraction during pitching as the primary mechanism contributing to adaptations in ulnar collateral ligament (UCL) appearance during magnetic resonance imaging (MRI) evaluation has not been established.

HYPOTHESIS

Uninjured high school-aged pitchers with unilateral adaptations of the UCL exhibit a higher peak internal elbow adduction moment than those without UCL adaptations.

STUDY DESIGN

Cohort study (Prevalence); Level of evidence, 2.

METHODS

Twenty uninjured, asymptomatic high school-aged pitchers underwent bilateral elbow MRI examinations. Three-dimensional motion analysis testing was performed to collect throwing arm biomechanics as participants pitched from an indoor mound. Nonparametric tests were performed to compare peak internal elbow adduction moment in uninjured participants with and without adaptations in UCL appearance and to determine the nature of the relationship between the peak internal adduction moment and UCL appearance.

RESULTS

Uninjured participants with UCL thickening exhibited a higher peak internal elbow adduction moment of 53.3 ± 6.8 N·m compared with uninjured participants without adaptations in UCL appearance, 38.8 ± 10.9 N·m (P = .05), as higher moments were correlated with ligament thickening (correlation coefficient, 0.45) (P = .02).

CONCLUSION

This study establishes the association between medial elbow distraction captured by the internal adduction moment during pitching and UCL adaptations visible during MRI evaluation.

Scapula kinematics and associated impingement risk in manual wheelchair users during propulsion and a weight relief lift

BACKGROUND

Shoulder impingement syndrome is a common upper extremity pathology in manual wheelchair users. Central to impingement is the orientation of the scapula and humerus as they determine the available subacromial space. The purpose of this study was to examine the scapulothoracic and glenohumeral internal/external rotation kinematics during the time of peak shoulder loading of propulsion and weight relief lift conditions to assess possible risk of impingement.

METHODS

Scapula, humerus and trunk kinematics were measured for twelve manual wheelchair users over three conditions: level propulsion, ramp propulsion, and a weight relief lift. Scapulothoracic and glenohumeral kinematic variables were characterized for the full cycle of each condition as well as at the period of peak loading.

FINDINGS

Common to all activities was an externally rotated glenohumeral joint and an anteriorly tilted and internally rotated scapula. At peak loading, glenohumeral internal/external rotation showed a significant difference between conditions, and post hoc analysis revealed that the weight relief lift displayed significantly less external rotation at peak loading when compared to level and ramp propulsion.

INTERPRETATION

All activities placed the scapula in a potentially dangerous orientation for development of shoulder impingement. The weight relief lift, with a decrease in glenohumeral external rotation and large superior forces at the shoulder, potentially places the shoulder of the manual wheelchair user at the greatest risk for impingement soft tissue injury. Preventative strength training and activity modification may provide measures to slow progression of impingement development and associated pain in the manual wheelchair user.

Individual muscle contributions to push and recovery subtasks during wheelchair propulsion

Manual wheelchair propulsion places considerable physical demand on the upper extremity and is one of the primary activities associated with the high prevalence of upper extremity overuse injuries and pain among wheelchair users. As a result, recent effort has focused on determining how various propulsion techniques influence upper extremity demand during wheelchair propulsion. However, an important prerequisite for identifying the relationships between propulsion techniques and upper extremity demand is to understand how individual muscles contribute to the mechanical energetics of wheelchair propulsion. The purpose of this study was to use a forward dynamics simulation of wheelchair propulsion to quantify how individual muscles deliver, absorb and/or transfer mechanical power during propulsion. The analysis showed that muscles contribute to either push (i.e., deliver mechanical power to the handrim) or recovery (i.e., reposition the arm) subtasks, with the shoulder flexors being the primary contributors to the push and the shoulder extensors being the primary contributors to the recovery. In addition, significant activity from the shoulder muscles was required during the transition between push and recovery, which resulted in increased co-contraction and upper extremity demand. Thus, strengthening the shoulder flexors and promoting propulsion techniques that improve transition mechanics have much potential to reduce upper extremity demand and improve rehabilitation outcomes.

Shoulder model validation and joint contact forces during wheelchair activities

Chronic shoulder impingement is a common problem for manual wheelchair users. The loading associated with performing manual wheelchair activities of daily living is substantial and often at a high frequency. Musculoskeletal modeling and optimization techniques can be used to estimate the joint contact forces occurring at the shoulder to assess the soft tissue loading during an activity and to possibly identify activities and strategies that place manual wheelchair users at risk for shoulder injuries. The purpose of this study was to validate an upper extremity musculoskeletal model and apply the model to wheelchair activities for analysis of the estimated joint contact forces. Upper extremity kinematics and handrim wheelchair kinetics were measured over three conditions: level propulsion, ramp propulsion, and a weight relief lift. The experimental data were used as input to a subject-specific musculoskeletal model utilizing optimization to predict joint contact forces of the shoulder during all conditions. The model was validated using a mean absolute error calculation. Model results confirmed that ramp propulsion and weight relief lifts place the shoulder under significantly higher joint contact loading than level propulsion. In addition, they exhibit large superior contact forces that could contribute to impingement. This study highlights the potential impingement risk associated with both the ramp and weight relief lift activities. Level propulsion was shown to have a low relative risk of causing injury, but with consideration of the frequency with which propulsion is performed, this observation is not conclusive.