Pathokinesiology
The Pathokinesiology Laboratory at Rancho Los Amigos National Rehabilitation Center is a world-renowned Gait and Motion Analysis Center. Clinical services are provided to the patients of Los Angeles County and to the private sector. Physicians refer their patients to the Pathokinesiology Laboratory to obtain a detailed evaluation of their function and recommendations for surgical and therapeutic interventions that could not be determined by standard clinical procedures.
The causes and treatments of patients with deformities,
pain, and gait disturbances are frequently not clinically
apparent. This is especially true for patients with
neuromuscular diseases and spinal cord/brain injuries who
have complex deformities that have multiple potential
causes. These patient populations often require surgical intervention
to optimize or permit function (i.e. enable a
patient to walk or use an arm for feeding or dressing).
The data obtained by the Pathokinesiology Laboratory is used to:
- Identify which muscles/structures are contributing to the patient’s deformity;
- Determine if a patient would benefit from reconstructive surgery;
- Delineate what surgery should be performed;
- Prevent inappropriate surgery;
- Decide if additional therapeutic programs are necessary to optimize function such as bracing or orthotic support, assistive devices and muscle strengthening by exercise or electrical stimulation.
This detailed approach maximizes patients’ outcomes and minimizes complications, unsuccessful surgeries, and multiple procedures.
The Pathokinesiology Laboratory is equipped to study a wide variety of activities including walking, running, stair climbing, ramp walking, bicycling, and arm function during wheelchair propulsion, crutch walking, walker use and selfcare activities. Our facility is unique in its expertise in gait and motion analysis for the adult patient, while the majority of other motion analysis laboratories serve only children. In addition, few clinical motion analysis laboratories have the capability to evaluate movement dysfunction of the arms. The Pathokinesiology Laboratory also is unique in its exclusive use of dynamic fine wire electromyography (EMG) to record the patient’s muscle function. Other clinical laboratories without this expertise must rely on surface recordings of muscle activity that cannot differentiate signals from nearby muscles. Decisions regarding which muscles to operate on must be made with the accurate information provided by fine-wire EMG to prevent inappropriate surgeries.
The specific clinical questions for each patient are addressed at the Pathokinesiology Laboratory by a tailored quantitative analysis of the patient’s impairment during walking or other activities of daily living. Depending on the patient’s needs, this may include analysis of muscle activity, joint motion, joint forces, foot pressures or energy expenditure. Muscle dysfunction is a common, but often unsuspected, source of pathology.
Research Endeavors
The research endeavors of the Pathokinesiology Laboratory originate from the desire to improve patient care. Consequently, the findings of past research have had direct application to the practice of rehabilitation. The Pathokinesiology Laboratory has been dually funded with outside federal grants for research and county funds for clinical services. The clinical service has directly benefitted from our research endeavors. Grant funding over the past 40 years has enabled us to acquire instrumentation and develop the skills for diagnosing the underlying muscle and joint impairments contributing to functional loss in patients with stroke, spinal cord injury, traumatic brain injury, post-polio, cerebral palsy, diabetes mellitus, amputation, orthopaedic trauma, and arthritis.
Over time, among the Pathokinesiology Laboratory’s most significant achievements resulting from our clinical research program has been the refinement of dynamic electromyography (EMG), the study of muscle contractions during movement. This work resulted in the development of the “EMG Analyzer” computer software that analyzes EMG patterns during gait, and compares them to normal muscle patterns, thereby providing the clinician with a printed report describing how much the patient’s muscle activity deviated from normal. This software is used at many centers around the country. Additionally, research on the dynamics of wheelchair propulsion for persons with spinal cord injuries resulted in the development of a force-measuring ergometric system used widely today to clinically evaluate shoulder pain experienced by people during wheelchair propulsion. Similarly, our research on crutch and walker use by persons with spinal cord injury has resulted in the development of “state-of-the-art” force-measuring crutches and a force-measuring walker.
Early Studies
Early Studies of abnormal muscle activity patterns during walking in patients with cerebral palsy, stroke, spinal cord injury and brain injury have led to surgical interventions including tendon tranfers that are the standard in patient care today, such as the Split Anterior Tibialis Tendon Transfer or SPLATT.
Survivors of the polio epidemics of the 1940’s and 1950’s experienced new problems thirty to fifty years later when symptoms resurfaced, leaving them with muscle weakness and paralysis. Renown Rancho physician Jacquelin Perry, M.D. undertook a comprehensive study revealing that these patients’ muscle and nerve units were simply wearing out from years of overuse, creating a basis for appropriate treatment to lessen these symptoms and prolong function.
In a series of research projects on the gait of persons with amputation of the leg, the relationship between muscle strength and function was identified as a critical determinant of the energy cost and the biomechanics of walking with a prosthesis. Specific features of the prosthesis were identified as requirements to normalize the forces on the other leg to prevent a second amputation.
After a stroke, many patients have long-term deficits in walking ability. These deficits manifest in a variety of walking patterns that require individualized rehabilitation approaches. The Pathokinesiology Laboratory undertook a longitudinal study of the recovery patterns of walking following a stroke to identify specific muscles with insufficient and excessive activity. This project led to a classification system that documented the most common walking patterns after stroke and the most appropriate muscles to target for strengthening and bracing for each walking pattern.
The Rancho Spinal Cord Injury Model Systems project headed by former Medical Director, Robert Waters, M.D. documented a marked increase in the incidence of shoulder joint pain in persons with spinal cord injury. Shoulder pathology is particularly devastating for this population of individuals who depend on use of their arms for locomotion as well as self-care activities. The Pathokinesiology Laboratory took the challenge and conducted groundbreaking research documenting the biomechanics of the shoulder during wheelchair propulsion, transfers and weight-relief raises. The unique capability of the Pathokinesiology Laboratory to successfully record the muscle activity of the deep shoulder muscles with fine-wire EMG in a large population of patients led to the establishment of EMG patterns for each functional level of spinal cord injury. This information documented the reason for the high demands of wheelchair propulsion in persons with tetraplegia and helped to identify targets for intervention to reduce the load on the shoulder.
While each of these projects provided numerous immediate clinical applications, they also formulated the basis for the continuing research efforts of the Pathokinesiology staff.
Current Highlights
In a recently completed research effort, we investigated the impact of varied styles of braces on walking in stroke patients. A common therapeutic approach to improving the hemiplegic patient’s walking ability is the use of an ankle-foot orthotic device (AFO). The objective of this study is to help us establish criteria for brace design and selection for stroke patients. Rancho Los Amigos stroke rehabilitation patients served as test subjects for the orthotics study. Typical braces provide stability by restricting motion, but normal walking motion is impaired in the process. An inappropriate design can make walking more difficult, yet clinical criteria for the selection of orthosis type is lacking. The purpose of this research effort was to compare stride characteristics and motion for individuals with hemiplegia while they’re wearing varied different plastic AFO designs. Finding the proper ankle/foot orthotic device that provides foot clearance during leg swing and adequate support without overly restricting motion during stance is a challenge. Study participants walk faster using the flexible design than when using the rigid design. The rigid AFO causes excess knee flexion during loading response, and restrains the tibia from progressing forward during stance, leading to inadequate knee flexion for swing. We have found that the typical ankle/foot orthotic brace is too rigid for most stroke patients. They need more flexibility to achieve optimum walking results. In this way, deterioration of joints and tissues can be minimized.
As part of a four-year National Institutes of Health (NIH) study, staffers are investigating the effects of two specific interventions on safeguarding shoulder function in wheelchair propulsion. Shoulder strengthening exercises to prevent pain and injury are being explored, as is the impact of adjusting wheelchair seat position to reduce damaging forces on the shoulder.
Shoulder biomechanics is also the focus of another NIH-funded study, which is testing individuals with incomplete spinal cord injuries who rely on crutches or walkers. We are trying to measure and document how strong the arms need to be to use crutches and avoid injuries like torn rotator cuffs. A goal of rehabilitation therapy is, whenever possible, to move SCI patients from wheelchairs to crutches or walkers. We need to know if increased mobility results in long-term damage to the shoulders.
In a research study funded by the National Institute of Disability and Rehabilitation Research, we are investigating the pressures under the foot of persons with diabetes. Structural irregularities in the forefoot are a common cause of injurious pressure concentrations during walking. Persons with normal sensation recognize these areas of high pressure as painful and quickly seek relief. Persons with diabetes, who lack sensation in their feet, frequently develop foot ulcers, which often lead to infection and amputation. Preservation of the patient’s limb depends on reducing the foot’s injurious pressure experienced while walking. Today’s techniques of shoe and insert production are inconsistent and varied because no objective criteria for an effective shoe system has been developed. This project is designed to identify the footwear factors that will reduce plantar pressures in the diabetic foot to a safe walking level.
As part of a Rehabilitation Engineering Research Center project recently funded by the National Institute of Disability and Rehabilitation Research, we are investigating and designing methods of manual wheelchair propulsion that are less stressful to the shoulder structures of individuals with spinal cord injury. The incidence of shoulder joint pain in the SCI population was found to be significantly greater than that seen in the normal population for any age group. To prevent further loss of functional independence, it is imperative to find ways to reduce the strain and joint deterioration that may occur with prolonged wheelchair use. A combined approach using dynamic modeling and computer simulation, and experimental assessment techniques is being used to develop alternative hand propulsion methods that reduce stress on the shoulder during manual propulsion. The outcome of this project will provide the biomechanical guidelines beyond the conventional hand-pushrim propulsion for optimum non-stressful shoulder function while preserving portability and ease of use.
Patients Served
We evaluate adults and children with impairments in walking, arm use or difficulty with performance of activities of daily living. The most frequent diagnoses of our patients include stroke, spinal cord injury, brain injury, cerebral palsy, post-polio, total joint replacement, orthopedic injuries, and amputation.
For additional information contact:
Sara Mulroy, PhD, PT
Director
E-mail: PKLab@rancho.org
Tel: (562) 401-7177