When technology and clinical medicine merge, this intersection makes evidence-based physiatry fraught with nuance. Clinical motion analysis is one area where advancements in technology have changed the way we evaluate and understand gait and movement pathology, through the use of instrumented gait analysis (IGA). In the “gait laboratory,” three-dimensional kinematics (motion), three-dimensional kinetics (forces), and dynamic electromyography (muscle activations) provide quantitative data for multidisciplinary teams to make clinical decisions. Most commonly, patients with neuromuscular conditions, such as cerebral palsy, are evaluated using IGA before undertaking major interventions that may include clinical neurotoxins, baclofen, or rhizotomy for tone management and single-event multilevel orthopedic surgery to correct musculoskeletal deformities arising from these conditions. However, any disease or condition that alters movement biomechanics is a potential candidate for IGA.
Observational gait analysis in the clinic or the hospital hallway has been conducted by physiatrists since the inception of the specialty. IGA is not a replacement for observational analysis; rather, it provides precise quantification of movement necessary for comprehensive clinical assessment. When combined with systematic observational skills, IGA can provide clear physical evidence for developing clinical guidelines for treatment decisions and evaluating intervention outcomes. Much of the foundation for IGA came from the prosthetics research of Verne Inman at University of California to improve walking performance of world war II veterans with limb loss.1 Two of Dr. Inman’s orthopedic residents, Jacqueline Perry and David Sutherland, took these biomechanical principles and refined them for clinical use in stroke, spinal cord and brain injury, cerebral palsy, and congenital joint abnormalities at their respective laboratories in Los Angeles and San Diego.2,3 James Gage and colleagues in St. Paul, MN, further refined the methods in common use today.4 When performed properly, clinical recommendations driven by IGA methods have been shown to alter clinical decision-making and improve clinical outcomes.5–7
Like an electrodiagnostic laboratory, established independent standards for measurement systems, evaluation procedures, medical and technical team competency, and data integrity must be met to ensure accuracy and reliability of IGA measurements and the recommendations that result from them. Organizations, such as the Commission for Motion Laboratory Accreditation, can provide such laboratory certification.
WHAT HAS CHANGED RECENTLY?
Clinical gait analysis has always been driven by technologic advancement. However, what has changed is the growing interest in acquiring movement, activity, and IGA data outside of the traditional laboratory setting. For example, sensor-based or “wearable tech” for quantifying human performance has captured the interest of clinicians, the public, and large technology companies because they offer cost savings compared with traditional IGA techniques and can record data in either the clinic or in natural environments. The challenge with these innovative tools has been that their accuracy is rarely established before going to market through validation with established IGA methods or in individuals with gait pathology.
Another trend has been to extend instrumented movement analysis for other clinical applications, particularly within the field of sports medicine. Return-to-play decisions can be determined by data gained through IGA. Again, developing clear criteria based on quantitative evidence is needed before this application of motion analysis is widely accepted.
WHAT HAS NOT CHANGED?
Regardless of technology, a multidisciplinary team is needed to translate data into clinical decisions. A typical evaluation involves gathering medical history, physical examination data, three-dimensional kinematics and kinetics, dynamic electromyography, and data interpretation through team review. This team review is fundamental to the process and essential for making clinical recommendations.
WHY IS THIS RELEVANT TO PHYSIATRISTS?
Observational gait analysis can fool even the most seasoned clinician. When a major intervention is being considered, the additional data gathered from IGA can overcome the limitations of observation as it does not inherently quantify the severity of abnormalities. There is also a significant potential for error with observational analysis as three-dimensional deformity is difficult to analyze from multiple planes at the same time. For example, direct observation of genu valgum from the coronal or sagittal plane can be confused with hip and knee rotation because of parallax error associated with the perspective and point of view of the observer. In addition, understanding IGA can improve your observational skills because the interaction between coupled motions revealed by IGA becomes more apparent when accurate quantification is available.
KEY RESEARCH FINDINGS IN GAIT ANALYSIS IN CEREBRAL PALSY FOR LAST SEVERAL DECADES
In general, soft-tissue lengthening surgeries in young children and adolescents with excessive tone, especially at the ankle and knee, should be postponed or avoided altogether.4 Achilles lengthening in children with crouch gait reduces the plantar-flexion knee extension couple, which can potentiate or worsen the gait abnormality. Managing tone with chemodenervation and oral tone modifying agents coupled with bracing can delay the need for orthopedic procedures. Bony surgeries should be postponed as long as possible to avoid repeat surgeries as children grow. During growing years, “guided growth” surgery can be used to tether growth plates and correct coronal and sagittal plane deformities in lieu of osteotomies. When necessary, soft tissue and bony procedures should be combined (single-event multilevel orthopedic surgery) to minimize the anesthetic risk and improve rehabilitation potential and to avoid the so-called “birthday surgery” phenomenon. Finally, it has been noted that gait patterns are remarkably stable after skeletal maturity, so correction of gait abnormalities in adolescence is a high priority. Walking into adulthood has long-term health benefits and may reduce the early onset of health conditions, such as diabetes and cardiovascular disease.
WHAT FUTURE QUESTIONS NEED TO BE ANSWERED?
Advances in technology have led to a proliferation of simpler, less expensive data collection tools (markerless motion capture, sensor-based inertial measurement units) that hold great promise for increased access to IGA both within and outside the traditional gait laboratory. Nevertheless, current commercial systems using these technologies require further validation in clinical populations and against marker-based motion capture to clearly demonstrate that they are just as accurate and reliable in the coronal and transverse planes as laboratory based systems. The future of IGA will include a range of technologies matched to the measurement requirements of the clinical question, with lower fidelity solutions used as screening tools to identify those individuals who could benefit from laboratory based assessment.
1. Inman VT, Ralston HJ, Todd F: Human Walking
. Baltimore, MD, Williams & Wilkins, 1981
2. Perry J: Gait Analysis: Normal and Pathological Function
. Thorofare, NJ, Slack, Inc., 1992
3. Sutherland D: Gait Disorders in Childhood and Adolescence
. Baltimore, MD, Lippincott Williams & Wilkins, 1984
4. Gage JR, Schwartz MH, Koop SE, et al.: The Identification and Treatment of Gait Problems in Cerebral Palsy
. London, Mac Keith Press, 2009
5. Cook RE, Schneider I, Hazlewood ME, et al.: Gait analysis alters decision-making in cerebral palsy. J Pediatr Orthopedics
6. Lofterod B, Terjesen T, Skaaret I, et al.: Preoperative gait analysis has a substantial effect on orthopedic decision making in children with cerebral palsy: comparison between clinical evaluation and gait analysis in 60 patients. Acta Orthop
7. Wren TA, Otsuka NY, Bowen RE, et al.: Outcomes of lower extremity orthopedic surgery in ambulatory children with cerebral palsy with and without gait analysis: results of a randomized controlled trial. Gait Posture