Ankle-foot orthoses for improving walking in adults with calf muscle weakness due to neuromuscular disorders

Calf muscle weakness is a common symptom in slowly progressive neuromuscular disorders that lead to walking problems like instability and increased walking effort. The mainstay of treatment to improve walking in this population is the provision of ankle-foot-orthoses (AFOs). Since we are not aware of an up-to-date and complete overview of the effects of AFOs used for calf muscle weakness in slowly progressive neuromuscular disorders, we reviewed the evidence for the effectiveness of AFOs to improve walking in this patient group, in order to support clinical decision-making.

To review the evidence for the effects of ankle-foot orthoses (AFOs) for improving walking in adults with calf muscle weakness due to slowly progressive neuromuscular disorders.

On 10 February 2023, we searched the Cochrane Neuromuscular Specialised Register, CENTRAL, Embase, MEDLINE, ClinicalTrials.gov, and WHO ICTRP.

We looked for randomised controlled trials (RCTs), including randomised cross-over studies and quasi-RCTs, and non-randomised studies (NRSs) that examined the effects of AFO interventions compared with shoes-only walking in adults with calf muscle weakness due to neuromuscular disorders.

We used the methodological procedures described in the Cochrane Handbook for Systematic Reviews of Interventions. We summarised findings for the primary outcome (objectively measured walking effort, assessed as walking energy cost) and secondary outcomes (perceived walking effort, physical mobility, gait parameters, AFO use, satisfaction with the AFO, and adverse events). We grouped results according to the type of AFO material and synthesised them in meta-analysis where possible. We used the GRADE approach to rate the certainty of the evidence.

We included four randomised cross-over studies and six NRSs with 186 participants in total (the smallest study had 8 participants and the largest had 37). All studies were designed as self-controlled studies and examined the effects of custom-made and/or prefabricated AFOs. The AFOs were made of carbon (5 studies), polypropylene (5 studies), silicone (1 study), metal (1 study), elastic materials (2 studies), or leather combined with other materials (1 study). Outcome measures with AFOs were assessed during a single session (in some studies, people already used the study AFO in daily life), when the AFO was delivered, or at three-week or three-month follow-up. We judged one study to be at moderate risk of bias, and nine studies to be at high or serious risk of bias, primarily due to bias arising from period and carryover effects, selection bias, the inability to blind participants and assessors, missing data, and selective reporting. We found that carbon AFOs may reduce walking energy cost (mean difference (MD) -0.86 J/kg/m, 95% confidence interval (CI) -1.33 to -0.39; 2 studies, 45 participants; low-certainty evidence), and may increase walking speed (MD 0.19 m/s, 95% CI 0.11 to 0.27; 4 studies, 71 participants; low-certainty evidence) compared to shoes-only walking. We found that leather AFOs may increase walking speed (MD 0.25 m/s, 95% CI 0.07 to 0.43; 1 study, 11 participants; low-certainty evidence). Little or no effect on walking speed was found with polypropylene AFOs (MD 0.00 m/s, 95% CI -0.11 to 0.11; 2 studies, 25 participants; low-certainty evidence) and elastic AFOs (MD 0.03 m/s, 95% CI -0.12 to 0.18; 1 study, 14 participants; low-certainty evidence). Carbon AFOs may also enhance satisfaction while walking (1 study, 16 participants; low-certainty evidence). We were unable to draw conclusions about perceived walking effort (one study, 8 participants), balance (two studies, 21 participants), and AFO use (two studies, 51 participants), as the evidence is very uncertain. Finally, two studies (45 participants) reported on adverse events (low-certainty evidence).

The available evidence for ankle-foot orthoses (AFOs) to improve walking in adults with calf muscle weakness comes from a limited number of small studies with heterogeneity in intervention characteristics and outcome assessment, and is of low to very low certainty. The evidence suggests that carbon AFOs may reduce walking energy cost (effort), increase walking speed, and enhance satisfaction, and leather AFOs may increase walking speed, while polypropylene and elastic AFOs may make little or no difference to walking speed. We are unable to draw conclusions about the effects of AFOs on perceived walking effort, balance, and use. Nor can we draw conclusions about adverse effects of using AFOs. The variety in the findings for AFOs made of different materials suggests further investigation is warranted to explore how different AFO materials impact walking improvement in people with calf muscle weakness due to slowly progressive neuromuscular disorders.