The effect of dynamic ankle-foot orthoses on the balance and gait of stroke patients
The present research aimed to assess the effects of a novel type of orthosis, the Dynamic Ankle Foot Orthosis (DAFO), on the balance and gait characteristics of hemiparetic subjects. The DAFO is a low splint with a custom-moulded insole, which is believed to support foot alignment, ankle supination-pronation and provide minimal restriction of the ankle joint flexion-extension. It was hypothesised that DAFOs improve motor behaviour after stroke involving the acquisition of standing balance (hypothesis I) and gait (hypothesis II) compared with using shoes. It was proposed that users' subjective opinions of DAFOs would support the findings of the device's ability to modify human performance such that they are beneficial when used as a part of rehabilitation management for stroke patients (hypothesis III). Twenty-two stroke subjects were randomly allocated to experimental (with DAFO and shoes-only) and control (using shoes-only) groups. Subjects followed twelve weeks of experimental trials comprising three data collections. The testing procedure was developed from preliminary work, which involved a pilot study and reliability tests. Standing balance was measured using forceplatform apparatus. The parameters investigated were: the velocity and sway index of the CoP, and F(mean), F(sd) and F(slope) of shear forces. Kinematic gait performance was assessed using a 3-D four-camera motion measurement system. The parameters studied were: the gait velocity, stride length, step length, cadence, and single stance phase, together with the minimum/maximum values of the angular displacement and velocity of the foot, shank, and thigh segments in the saggittal plane during two strides. An open questionnaire was used to evaluate subjects' opinions regarding the use of DAFOs. Overall, the quantitative studies did not identify consistent and statistically significant differences between the two experimental situations for these groups of patients. In the studies of balance, none of the parameter comparisons analysed within- and between- groups achieved statistical significance. In the studies of gait, statistically significant differences were identified for some (but not all) parameters. It is unknown whether any single or combination of balance and gait variables can be used to describe human gait entirely. On this basis, hypotheses I and II were rejected. However, these are tentative conclusions. Thus, difficulties in maintaining the stroke subject cohort number for these studies meant that the analyses probably lacked sufficient statistical power to detect small but potentially important differences in DAFO mediated actions. Furthermore, in several cases, clear differences in the magnitude of balance and gait parameters between DAFO and shoe users were apparent, and these differences were often consistent with nearer normal levels associated with use of the device (suggesting potentially beneficial influences). Thus, positive effects of the DAFO on lateral velocity of sway and variability of the spectral frequency were evident for some subjects. The gait velocity, stride length and single stance phase were also nearer normal values using DAFOs than without them. In addition, the maximum foot velocity value was improved in the middle of swing phase on the affected side, which may indicate improvement to the ankle dorsiflexion function using these devices. In contrast to the inconclusive balance and gait findings, the outcome of the questionnaire assessments was clear. The majority of subjects provided very positive feedback with regard to DAFO use. Most subjects expressed confidence in the splint, which they perceived as helpful for their walking ability in day life. Some difficulties were noticed with donning and doffing the DAFO, but the perceived benefits outweighed this consideration. These qualitative studies therefore provide the most convincing evidence to support the idea that DAFOs improve stroke patients' balance and gait, and that this type of orthosis may form a useful adjunct to rehabilitation strategies. However, as the proposals set out for this research were related, acceptance of hypothesis III requires that at least one of the preceding hypotheses be accepted. On this basis, hypothesis III was also rejected. In conclusion, although this work failed overall to demonstrate a significant effect of DAFOs on the rehabilitation of stroke patients, the anecdotal evidence obtained adds to knowledge in this field. The research identified some parameters of balance and gait, which might be influenced by the device in a beneficial manner. These parameters may be more useful to use in future investigations. The reasons for the discrepant outcomes of the quantitative and qualitative studies are unclear. However, it is suggested that there may be uncontrolled variables within either the patient group or in the DAFOs (or both) which mean that some DAFOs work better than others. It is proposed that further studies of the DAFO are warranted.