16 Measurement Techniques
Clinical gait analysis has developed to a well-established method in centers specialized for the treatment of complex movement disorders in children and adults. With a set of different tools, the aim is to gain a better understanding for the human movement disorders of a patient, including the individual reasons and underlying causes for functional limitations that may have been caused by developmental disorders, diseases, or traumata.
While gait analysis requires considerable instrumental and personnel efforts, its value and efficacy is still subject to discussion. More recent reports underline the applicability for quality control issues as well as the importance for influencing clinical decision-making and planning of surgical interventions. 1, 2
The following clinically relevant aims may be addressed or achieved with clinical gait or motion analysis:
Support of diagnostic possibilities
Choice of the appropriate conservative or operative therapy
Quality control of therapeutic interventions
Follow-up of the course of the disease or healing process
Prediction of the outcome of the chosen treatment option
Objective outcome assessment in clinical trials
16.1 Methods and Technologies
16.1.1 Instrumented Three-Dimensional Gait Analysis
The standard tool for clinical movement analysis is the instrumented three-dimensional gait analysis. With the help of kinematic and kinetic parameters, it describes the gait characteristics of individual patients in detail and identifies potential gait asymmetries or movement impairments (i.e., it describes the quality of gait).
In instrumented gait analysis, the movement of a subject is typically being captured by an array of cameras that record the position of body-attached markers. The markers are applied at specific positions of predefined marker models (e.g., the two traditionally used Helen-Hayes (Fig. 16.1) or Cleveland Clinic marker sets that have been described and extensively validated). 3, 4 Recently, new models were proposed in order to prevent the known limitations or uncertainties of the traditional models by anatomically or functionally improved calibrations. 5
Key Concepts: Markers to Detect Body Movement
Passive markers usually use reflective spheres that are attached to defined anatomical landmarks with adhesives and do not require any energy supply. Advantage is the cable-free attachment, disadvantage is that markers cannot be unequivocally identified (i.e., markers can be confused inadvertently).
Active markers are usually light-emitting diodes that need an energy supply and are therefore cable-bound and more obstructive. However, due to a predefined order or frequency of the light signals, markers can always be identified unequivocally.
More recently, new approaches have been introduced that try to prevent the limitations that are involved in the use of markers by development of markerless tracking solutions. With standard video cameras, the outline of the moving object is automatically recognized against the invariable background of the image, and various directions of view eventually allow for a combination into a three-dimensional shape recognition of the moving subject. 6 The expectation was to use fairly low-cost instrumentation and apply it in normal environments (i.e., not necessarily laboratory-based) but to date, these systems are just beginning to appear on the commercial market.
The kinematic information obtained from image- or marker-based analysis can be combined with the assessment of ground reaction forces that describe the interaction between the human body and the environment during ground contact. The combination of kinematic or movement data with external loads enables the determination of the kinetic information. The external loads imposed on the body can be combined with the known position of the joint centers and the body′s inertial properties (mass and moment of inertia) to calculate or estimate the joint moments and powers in the hip, knee, and ankle joint by using the inverse dynamics approach. For each phase of the gait cycle, the size and direction of the force vector as well as the location of the joint center are known and can be used to determine the external moments. Using optimization algorithms (see Chapter 19), the internal (muscular) moments can also be computed. This approach works typically very well in the sagittal (flexion/extension moments) and frontal (abduction/adduction moments) plane but usually not in the transverse plane.
16.2 Advanced Technologies
Highly interesting data were obtained by in vivo measurements of patients equipped with instrumented prostheses of the hip and knee joint, and more recently also of the shoulder or spine implants. By telemetric transmission of strange gauge data imbedded in the prosthetic component, the information of implant loading during daily life activities, physiotherapy exercises, and sports was recorded from within the body and gave detailed insight based on direct measurements rather than model-based assumptions 7, 8 so that comparisons between calculated and measured hip joint contact forces were possible. 9
Further methods allow for a more detailed description of the movement of the joint components but usually require some kind of imaging that may mean potentially harmful exposure to ionizing radiation. The imaging is being used to create a three-dimensional model of the joint partners. In fluoroscopic images, the outline of the bone or joint prosthesis is being detected and matched to the three-dimensional model for each captured image. This technology was initially developed for the assessment of knee joint replacements and relied on the engineering data of the prosthetic components, but it can now be used with computed tomography or magnetic resonance imaging of the anatomical joints (e.g., Chen et al 10). Here, two fluoroscopic images with different views are necessary to recreate the exact joint position in space. These systems are mostly used for measuring kinematics of the knee joint or knee replacement, with recent approaches being developed for foot and ankle assessments. A limitation is the temporal resolution of the fluoroscope as well as the limited space that either restricts measurements to detecting only one step/movement cycle or requires a treadmill for stationary recording of a sequence of steps.
The modeling world is trying to advance from general models (often based on data on the Visible Human Project) toward developing personalized neuromuscular-skeletal models, also based on imaging, which can be used for predictions (e.g., Viceconti et al 11). However, this very elaborate approach is probably quite some distance away from being easily incorporated into something like a clinical routine application.
Related posts:
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
