Biomechanics of Wheelchair Transfers

This is a laboratory-based study to evaluate the risk of shoulder injury associated with transfers between wheelchair and vehicle in persons with spinal cord injury. Four new devices will be compared against an unassisted transfer.

Specific Aims:

The purpose of this 3 year laboratory-based randomized crossover study is to evaluate the ergonomic effectiveness of four wheelchair/vehicle transfer assistive devices, including (1) standard transfer board, (2) Glide n' Go, ( 3) Easy Reach Lift, and (4) Ryno Lift, and to compare them to an unassisted manual transfer. We have targeted persons with paraplegia (level of injury T2-L5) to standardize physical capabilities. Our research questions are:

1. Evaluate the impact of vehicle/wheelchair transfers on objective measures of shoulder kinematics, kinetics, and muscle activity, for each of the participants.
2. Evaluate the impact of vehicle/wheelchair transfers on subjective measures of shoulder pain, spasticity, perceived comfort, ease, efficiency, and safety.
3. Examine the effects of covariates (patient characteristics, SCI characteristics and pain) on both objective and subjective outcome measures.

Background:

Upper limb pain and injury are highly prevalent in persons with a spinal cord injury (SCI) who use a manual wheelchair for mobility. Historically, persons with paraplegia did not long survive the trauma of their injury, but with advances in medicine and emergency services, persons with SCI now have a life expectancy approaching that of the general population. For persons with paraplegia, paralysis of the lower limbs necessitates an over reliance on the upper limbs for performing wheelchair propulsion, transfers in/out of the wheelchair, and other mobility-related tasks. Many years of overuse of the upper extremities leads to an increased incidence of pain and cumulative trauma to the shoulders, elbows and wrists. Over 50% of persons with SCI have upper extremity pain; rotator cuff tears have been reported in 59-73%; and 40% have clinical evidence of carpal tunnel syndrome. Upper extremity deterioration following years of compensating for the lack of functional lower limbs in addition to their usual loading reduces quality of life, function, independence, and even life expectancy following SCI. The two most stressful mobility tasks performed by persons with paraplegia are wheelchair propulsion and wheelchair transfers. Several investigators have examined upper extremity kinematics (joint motions) kinetics (joint forces and torques), and muscle activity as determined by electromyography (EMG) among individuals with SCI during wheelchair propulsion. Comparatively few studies have addressed wheelchair transfers none of which offer an integrated kinematic, kinetic and EMG approach to simultaneously examine joint angles, moments and muscle activity.

Methods:

Using Vicon motion analysis technology, we propose a laboratory-based randomized evaluation of five vehicle transfer approaches: unassisted manual transfer, standard transfer board, Glide n'Go, Easy Reach lift, and Ryno lift. The selected commercially-available products represent the range of assistive technologies presently available for this task.

A sample of 58 veterans with paraplegia, who use a manual wheelchair for mobility, will be recruited to participate in this study. Subjects will be recruited from the Tampa VA Hospital by means of poster advertisement. Participants will complete data collection activities during one four-hour session, for which they will be compensated. Subjects will be asked to perform a series of five randomized wheelchair-to-vehicle transfer tasks. Vicon markers placed on the participant's body will capture positional data. Dynamic external loads exerted during the transfer tasks will be measured using AMTI MC3A tri-axial load cells strategically mounted in a vehicle mock-up. EMG will be recorded bilaterally for major muscle groups. Participants will complete subjective rating scales upon completion of each of the transfers.

The results of this study will be used to develop a clinical algorithm to assist clinicians with the selection of the most appropriate assistive technology for persons with disabilities who use a manual wheelchair for mobility. This algorithm will facilitate the individualized selection of assistive technologies that minimize risk for injury and maximize patient compliance, comfort, and satisfaction. The ultimate goal of this program of research is to (1) promote successful adaptation to aging with a disability, (2) reduce morbidity and mortality associated with wheelchair use, (3) enhance health-related quality of life, patient freedom, function, independence, and confidence, and (4) reduce healthcare utilization and associated costs.

A sample of 58 veterans with paraplegia who use a rigid manual wheelchair will be recruited to participate in this study.

Inclusion Criteria:

• level of SCI will be limited to ASIA A classification at T2 through L5 level to standardize physical capabilities,
• SCI for at least 2 years (neurologically stable,
• use rigid manual wheelchair as a primary means of mobility,
• able to self-propel wheelchair,
• able to independently transfer between wheelchair and vehicle,
• between the ages of 18-65,
• living in the community within 100 miles of the Tampa VA hospital,
• able to follow simple instructions,
• free from acute upper extremity injury for at least six months (determined by chart review) to minimize risk of injury during task performance,
• comparable bilateral functional range of motion and strength of the shoulders, elbows and wrists (determined by physical evaluation) to minimize risk of injury during task performance.

Exclusion Criteria:

Candidates who present:

• progressive disease (e.g. spinal tumor),
• extended bedrest for more than 30 days,
• ventilator-dependent,
• any cardiac or respiratory condition that would limit subject's physical performance,
• unstable medical conditions,
• use of power wheelchair or scooter as primary means of mobility,
• pregnancy,
• clinical evidence of severe musculoskeletal disorders of the upper extremity will be precluded from participating in this study.