Barry Meadows

Affordable clinical gait analysis: an assessment of the marker tracking accuracy of a new low-cost optical 3D motion analysis system

BACKGROUND 3D motion analysis represents a method of collecting objective, accurate and repeatable gait data, however the high cost of equipment inhibits its widespread use in routine clinical practice. OBJECTIVE To determine the marker tracking accuracy of a new low-cost optical 3D motion analysis system. DESIGN Comparative between-system study. SETTING Clinical motion analysis laboratories. METHODS A rigid cluster of four reflective markers was used to compare a low-cost Optitrack 3D motion analysis system against two more expensive systems (Vicon 612 and Vicon MX). Accuracy was measured by comparing the mean vector magnitudes (between each combination of markers) for each system, and reliability was measured through the coefficients of variation (CV). Gaps in the marker trajectories, which are considered undesirable, were also counted. RESULTS In terms of accuracy, the largest disagreement between mean vector magnitudes for Optitrack and Vicon MX was 2.2%. The largest disagreement between Vicon 612 and Vicon MX was 2.1%. Regarding reliability, the mean CV was lowest in Vicon MX (0.3%) and similar in the Vicon 612 (2.5%) and Optitrack (2.3%) systems. The number of trajectory gaps for the Vicon MX, Vicon 612 and Optitrack systems were; zero, six and 11 respectively. CONCLUSIONS The Optitrack system provides a low-cost 3D motion analysis system that can offer marker tracking accuracy and reliability which is comparable with an older and still widely used system (Vicon 612). Further development work is required before Optitrack can be used for full 3D gait analysis by physiotherapists and other health professionals.

Biomechanics of the hip, knee and ankle

Forming part of section 4 on lower limb orthoses, this chapter focuses on the biomechanics of the hip, knee and ankle

The immediate effects of fitting and tuning solid ankle–foot orthoses in early stroke rehabilitation

Background: Ankle-foot orthoses are known to have a generally positive effect on gait in stroke, however the specifc type of AFO and the time point at which it is provided are highly variable in the currently available literature. Objective: The objective was to determine the immediate spatiotemporal and kinematic effect of custom-made solid ankle–foot orthoses in early stroke rehabilitation, compared to shod walking. Methods: Five male and three female participants were recruited to the study (n = 8), with a mean age of 57 (16) years who were 3.5 (3) weeks post-stroke. Each received a custom-made solid ankle–foot orthosis to a predefined set of design criteria and tuned using heel wedges to control the shank inclination angle during shod walking. Repeated spatiotemporal and three-dimensional gait measures were taken pre- and immediately post-intervention. Study design: A pre–post-test experimental study. Results: With the solid ankle–foot orthosis, walking velocity increased from 0.22 (0.2) to 0.36 (0.3) m/s (p < 0.05), overall average step length increased from 0.28 (0.1) to 0.37 (0.1) m (p < 0.05), cadence increased from 45 (19) to 56 (19) steps/min (p < 0.05) and step length symmetry ratio increased from 0.65 (0.2) to 0.74 (0.2) (not significant). No clear changes were observed in the joint kinematics of the hip and knee. Conclusion: In our small group of early stroke patients who were fitted with a solid ankle–foot orthosis, immediate significant improvements occurred in walking speed, step length and cadence, when compared to walking with shoes only. Clinical relevance This study provides evidence about the immediate effects of custom solid ankle–foot orthoses on gait of early stroke survivors. Ankle–foot orthosis design specifications are fully described for replication. This study suggests that observing global segment orientation may be more useful than joint angles when fitting and tuning ankle–foot orthoses for optimal ankle–foot orthosis/footwear alignment.

Tuning of rigid ankle-foot orthoses is essential

I write with reference to the excellent review by Eddison and Chockalingam on ankle–foot orthosis (AFO) tuning in the April 2013 issue of Prosthetics and Orthotics International. While I agree that further research is needed on the effect of tuning, I am very concerned that the conclusions listed in the article might dissuade clinicians from undertaking tuning of rigid AFOs in the meantime. When I first described the tuning process with AFOs for young children with cerebral palsy (CP) (actually, I called it ‘fine-tuning’ which perhaps more closely describes the sensitivity of the process), one of the interesting outcomes was facilitation of stability in mid to late stance.1 In normal gait, this is achieved by forward inclination of the thigh and alignment of the ground reaction force (GRF) in front of the knee joint centre and, crucially, behind the hip joint centre (Figure 1). Thus, stabilising external extension moments are applied at these joints, and the second peak of the vertical component of GRF is greater than body weight. Research has shown that reduced second peak of GRF, and thus instability, in CP is a common problem.2 In my opinion, when using AFOs, one objective is to achieve, as closely as possible, similar segment, joint centre and GRF alignments as in normal gait. From my research and clinical experience, it is clear to me that this process requires correct AFO design and fabrication – accommodating gastrocnemius contracture/tone, adequate stiffness, choice of initial shank to vertical angle (SVA) and so on – followed by tuning, in particular alteration of the SVA by the addition of small heel wedges between AFO and shoe. This process can be highly sensitive. The significance of the fact that a 3-mm wedge can increase SVA by 2° with a ‘typical’ child’s AFO (mentioned in one of the reviewed articles) is that this can move the hip joint centre forwards by approximately 20 mm.3 This can potentially change the alignment of the GRF from in front of the hip joint centre to behind, thus changing an unstable situation to stable. It appears to me that much that has been written about tuning tends to suggest that this is a highly complex process, often requiring access to gait analysis facilities and is costly in time and money. The conclusions in the review appear to support this opinion. However, from clinical experience, most rigid AFOs can be successfully tuned using small heel wedges and visual gait analysis. This is not particularly time-consuming, is inexpensive and a good way to start tuning. In more complex cases (e.g. severe crouch gait), there are greater challenges and significant footwear modifications may be necessary. In addition, other forms of intervention such as contracture reduction, Botox or surgery may be necessary prior to successful tuning. No prosthetist will deliver trans-tibial prostheses (I hope) without undertaking bench and dynamic alignments. This is ‘prosthetic tuning’. Similarly, I believe no orthotist should deliver rigid AFOs without confirming they have been optimally aligned. AFO tuning is essential and can create significant clinical benefits from relatively minor modifications.

Visualisation to enhance biomechanical tuning of ankle-foot orthoses (AFOs) in stroke: study protocol for a randomised controlled trial

BackgroundThere are a number of gaps in the evidence base for the use of ankle-foot orthoses for stroke patients. Three dimensional motion analysis offers an ideal method for objectively obtaining biomechanical gait data from stroke patients, however there are a number of major barriers to its use in routine clinical practice. One significant problem is the way in which the biomechanical data generated by these systems is presented. Through the careful design of bespoke biomechanical visualisation software it may be possible to present such data in novel ways to improve clinical decision making, track progress and increase patient understanding in the context of ankle-foot orthosis tuning.MethodsA single-blind randomised controlled trial will be used to compare the use of biomechanical visualisation software in ankle-foot orthosis tuning against standard care (tuning using observation alone). Participants (n = 70) will have experienced a recent hemiplegia (1-12 months) and will be identified by their care team as being suitable candidates for a rigid ankle-foot orthosis. The primary outcome measure will be walking velocity. Secondary outcome measures include; lower limb joint kinematics (thigh and shank global orientations) & kinetics (knee and hip flexion/extension moments, ground reaction force FZ2 peak magnitude), step length, symmetry ratio based on step length, Modified Ashworth Scale, Modified Rivermead Mobility Index and EuroQol (EQ-5D). Additional qualitative measures will also be taken from participants (patients and clinicians) at the beginning and end of their participation in the study. The main aim of the study is to determine whether or not the visualisation of biomechanical data can be used to improve the outcomes of tuning ankle-foot orthoses for stroke patients.DiscussionIn addition to answering the primary research question the broad range of measures that will be taken during this study are likely to contribute to a wider understanding of the impact of ankle-foot orthoses on the lives of stroke patients.Trial registration numberISRCTN: ISRCTN52126764

The use of biomechanical visualisation in neurorehabilitation and its effect on ankle-foot orthosis (AFO) tuning in stroke

Background: Difficulties interpreting the biomechanical data captured by 3D gait analysis (3DGA) systems mean that it is rarely used in routine clinical practice for gait rehabilitation of stroke patients. Biomechanical visualisation software has been designed to make data clinically useful in the context of AFO fitting and tuning for stroke patients. Therapists can use objective quantitative data to assist clinical decision-making. Participants receive an improved understanding of their condition/treatment, and it allows progress tracking. Objective: Test the hypothesis that stroke patients will receive improved outcomes when biomechanics visualisation is used in the AFO fitting and tuning process. Patients and methods/material and methods: An RCT is being used (ISRCTN52126764). The intervention arm receive AFO fitting and tuning using 3DGA and visualisation, and the non-intervention arm receive an AFO by standard care (clinicians using observation). Walking velocity, 3D kinematics and kinetics, step length, gait symmetry, mRMI and EuroQol (EQ-5L-5D) are measured at four time points (baseline, AFO provision, three months and six months). Ten participants, 5.7(6) weeks post-stroke, with an average age of 56.4(17) years have been recruited. Results: Walking velocity improvement (before/after AFO provision) data for the intervention group (n = 5) was 22(21) cm/s versus 1.6(6.4) cm/s for the non-intervention group (n = 5). The difference is significant (p < 0.05, Mann–/INS;Whitney U Test). More extensive results will be available at the time of presentation. Conclusion: Early data indicate that the visualisation of biomechanical data appears to assist the AFO tuning process, providing stroke patients with better immediate improvements in walking velocity.