December/January 2001

Gait Analysis Comes Out Ahead

By Liz Finch

Waahen Eadweard Muybridge settled a bet in the late 1880s by devising a technique to photograph a galloping horse, he not only set the cinema industry in motion, he also inspired the development of modern computer-based gait analysis systems. These systems, also referred to as motion analysis or biomechanics, have allowed researchers to identify both normal and abnormal characteristics of gait, and have been used to document the usefulness of various therapeutic inter- ventions.¹

While popular for years in the research setting, gait analysis is just now making inroads in clinical use. The highest level of acceptance is in treating cerebral palsy (CP) patients, for whom physical evidence of abnormal motor function is a key element in diagnosis. For clinicians, gait analysis is becoming an important objective tool to identify deviations from normal gait, to determine functional problems, and to formulate a treatment plan that will bring quantifiable results.¹

The application of gait analysis in a clinical setting was around before David H. Sutherland, MD, started the first Motion Analysis Laboratory at Children's Hospital and Health Center, San Diego, in 1974. Prior to that, clinicians watched their patients walk and used physicians' experience to judge the problems. Computerized gait analysis systems are far better at breaking down motion so it can be studied in detail, and have improved the surgical and nonsurgical management of CP patients. Advantages over clinical observation include identification of problems at multiple levels of involvement, and the ability to distinguish primary pathologic motions from compensatory motions. The system also allows clinicians to identify dynamic movement patterns that would not be evident in passive tests of movement.²

Patient Mix

The Motion Analysis Laboratory continues to be a pioneer in the field of gait analysis. Its recent expansion to a 5,500-sq ft facility makes it one of the largest such facilities for clinical studies and research in the world. The laboratory has the capability to conduct three different patient/research studies concurrently. It gets referrals from all over the world, though most patients come from the surrounding area—San Diego, Riverside, Imperial, and Orange Counties.

Patients come to the Motion Analysis Laboratory suffering from congenital abnormalities, head injuries, neuromuscular disorders, peripheral nerve injuries, central nervous system tumors, trauma to limbs or spine, muscular dystrophy, poliomyelitis, lower extremity limb deficiencies, and functional problems of the upper extremity. The largest number of patients, however, are CP patients, who typically range in age from 2 to 21.

"We also have 70- and 80-year-olds coming in with total joint replacement, amputations, and post-polio syndrome," says Henry G. Chambers, MD, medical director of the Motion Analysis Laboratory. Chambers is a board-certified orthopedic surgeon and member of the American Academy of Cerebral Palsy and Developmental Medicine who has been with the laboratory for 10 years, since he came to Children's Hospital on a fellowship to study with Sutherland. "And we see sports injuries—mostly running and throwing injuries, as well as injuries in golfers and professional athletes—but young CP patients make up the majority."

Individualized Analysis

Regardless of the source of the patient's gait problems, the analysis process is the same.

"Each patient is different so it is important to do individualized gait analysis," Chambers says. "We know the curves of ranges of motion for normal children, and so when a patient's gait falls out of those normal ranges, we can find out why." Gait is defined as the movement from heel strike to heel strike. Mature gait factors include duration of single limb support, walking velocity, cadence, step length, and ratio of pelvic span to ankle spread. In addition, mature gait exhibits stability of the weight-bearing foot throughout the stance phase, clearance of the non-weight-bearing foot during the swing phase, appropriate prepositioning during the terminal swing of the foot for the next gait cycle, and adequate step length.²

A therapist and a physician first conduct complete physical examinations of patients, who are then videotaped from different angles as they walk back and forth. The patient's gait is measured using 3-D computer software to figure out the ranges of motion, and force plates embedded in the floor tell what forces are at work as the patient walks. Reflective markers are placed at specific anatomical points, the patient again walks back and forth, and electromyographic (EMG) markers are used to measure muscle activity.

"Sometimes we have to insert a fine wire into the muscles that are deep and difficult to find, such as in the upper extremities and in the hips," Chambers says. "We also look at energy utilization by measuring how much oxygen the children use when they walk, because a primary problem with CP is increased energy utilization."

The laboratory's equipment includes a six-camera movement measurement system, four force platforms, two telemetry EMG systems, a three-camera color video system, an instrumented treadmill, and a foot pressure measuring system.

Once all the tests have been performed, a report is generated from the data, and Chambers and a therapist study it to determine deviations from normal gait. Once these are identified, the team decides on the cause of the deviations and determines a preferred treatment plan.

Gait and Cerebral Palsy Gait deviations are caused by either muscular weakness, abnormal joint position or range of motion, or muscle contractures. CP patients also are usually deficient in selective muscle control, which affects locomotion.2 While there are a variety of differences in the gait of CP patients, many of the same behaviors have been identified by gait analysis. Some children walk up on their toes, equinus, or cross over their legs, adductor crossing. Other gait problems typical of CP patients include a stiff-kneed gait, and rotational abnormalities of the femur, tibia, and foot. The laboratory also sees a lot of foot deformities.

"From the data, we come up with a problem list," Chambers says. "For instance, if there are problems with the hip, we recommend physical therapy, management of spasticity, different types of braces, or different types of orthopedic surgeries. The treatment for equinus ranges from doing bracing to serial casting, to injection of botulinum toxin, to four or five different types of operations.

"For a child who has muscle tightness as well as rotational abnormalities, you can do muscle surgery and bone surgery," Chambers says. "But if the patient does not have gait analysis first, it is hard to figure out exactly what to do."

Following therapeutic intervention, the laboratory again conducts gait analysis on the patient—typically 6 months to a year after treatment. The laboratory also does a large amount of research to verify the procedures, and has published approximately 20 outcome studies from its work.

"We have one on rectus femoris transfer, and we have done some research on the use of botulinum toxin, which partially denervates the muscles," Chambers says. "That toxin lasts for 4 to 5 months and eliminates spasticity so we can do therapy. That has been very successful—probably 85%."

Ankle equinus is one of the most common problems in CP patients. Gait analysis research has shown that gastrocnemius-soleus fascial releases generate improvements in the static heel cord range-of-motion as well as lead to a decrease in the abnormal energy generated around the ankle in mid-stance. As a result, gastrocnemius-soleus fascial releases are now the most common procedures performed in children with fixed equinus contractures.²

The Cost Issue

While there is little question as to gait analysis's ability to fine-tune the treatment of CP patients, the system's high cost can put it out of reach of many facilities.

"It is expensive technology," Chambers says. "Prices of the equipment can range from $100,000 to $500,000. Our building cost $750,000 and we have $450,000 worth of equipment.

"We do not make money on this service. We lose money each time we do a study. The analysis is billable, but it is reimbursed poorly," he says. Clinicians also need to have a lot of experience to do gait analysis correctly.

"It takes a lot of extra people to run the equipment and read all the data," he says. "The bare minimum staff needed to run a gait analysis lab are a medical director, an engineer, a kinesiologist, a physical therapist, and an administrative person.

"The equipment also needs to be updated regularly," he says. "It used to be run by a special mainframe, but we are using PCs now. In fact, we just got a whole new system 6 months ago. With faster cameras, we can collect better data, and we are using a lot of telemetry instead of wiring.

"Computers are so fast now," Chambers continues. "It used to take Sutherland 2 to 3 weeks to map out the data by hand. Now we have the results when the child walks out of the lab."

Technology advances have made clinicians able to get better outcomes as well, and evaluate more and more new treatment modalities.

"We are finding more applications for gait analysis. There are more sports activities gait analysis centers, more for outcome studies, and there are several big multicenter studies across the United States that will help treat children with disabilities," he says.

"Today there are probably 50 labs within the whole country offering gait analysis because it is an important procedure for evaluation," he continues. "It is like performing radiography for broken bones or electrocardiography when you have a heart attack. We know which patients benefit from which types of therapy, and that saves money and anguish for kids."

Liz Finch is a contributing writer for Rehab Management.

References

1. Gitter A, McAnelly R. The value of information resulting from instrumented gait analysis: the physiatrist. In: DeLisa JA, ed. Monograph 002: Gait Analysis in the Science of Rehabilitation. Washington, DC: Veterans Health Administration; 1998.
2. Chambers H, Sutherland D. Movement analysis and measurement of the effects of surgery in cerebral palsy. Mental Retardation and Developmental Disabilities Research Reviews. 1997;3:212-219.

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