1.9 Gait analysis

The study of non-biological systems has been defined as ‘hard’ science and those of biological systems as ‘difficult science’. This is because biological systems fluctuate. Gait analysis is the study of walking, a process made up of a multitude of complex fluctuating parameters. Each pace that we take is slightly different from the last, and your gait is different from mine. This means that some differences that we may observe are merely the result of biological variability, while other equally subtle ones may be diagnostic of abnormality.

Many techniques for performing gait analysis have been developed in an attempt to qualify (what is the problem?) and quantify (how bad is it?). Some of the techniques available are listed in Table 1.9.1. Any useful measurement of gait will strive to achieve the following (Box 1.9.1):

Clinical utility is the concept of addressing the question of whether the test measures things which cannot be measured in any other way, and whether these measures actually lead to new clinical decisions being made which are ‘better’ than those made using the old methodology.

So far, no system of gait analysis has come close to these basic requirements.

Equipment used for gait analysis (Table 1.9.1) can be classified into four simple groups (Box 1.9.2). Those which:

If a combination of these techniques is used, complex calculations can be performed using computers to calculate the forces passing through the patient’s limbs and the body. From that it may even be possible to determine which muscle is contracting (or failing to relax) at each phase of the gait cycle. These calculations are complex and inevitably rely on some estimations (educated guesses). Any error in the data entered into the equations will be amplified by those calculations, so paradoxically the more complex the calculations the higher the chance of meaningless results being produced.

There are few conditions in which gait analysis is still considered as being of potential value in determining what treatment is most appropriate.

Myography can be used to determine whether muscles are active continuously or only during part of the gait phase. If muscles are found to be active through all phases of gait, then division or lengthening may improve gait but transfer will not. If, however, contraction only occurs during the swing phase of gait, then transfer may provide the best result. The situation is complicated by the fact that any change in the action of one muscle (by lengthening or transfer) may change the behaviour of other muscles.

To date, no method of gait analysis has proved invaluable in the assessment of a patient. No trials have yet demonstrated its benefit over simple clinical assessment. This may, in part, be because the surgical treatment options remain so crude in conditions such as cerebral palsy.