Functionally optimized orthoses for early rheumatoid arthritis foot disease: a study of mechanisms and patient...

To investigate the mode-of-action and patient experience of functionally optimized foot orthoses in patients with early rheumatoid arthritis (RA).

We conducted an investigation of 2 functionally optimized foot orthoses (selective laser sintering [SLS] and fused deposition modelling [FDM]) in 15 patients with RA of <2 years duration. The novel devices were optimized for 3 biomechanistic targets exploiting computer-aided design and additive manufacturing. A third standard device was used as the comparator (standard foot orthosis [SFO]). Foot and ankle biomechanical effects were compared. Adverse reactions, orthotic fit and comfort, and short-term symptom benefits were also monitored.

Both FDM (P = 0.028) and SLS (P < 0.0001) orthoses significantly reduced peak rearfoot motion in comparison to shod. The average ankle internal moment was significantly decreased in the SFO (P = 0.010) and approached significance in the SLS (P = 0.052) orthosis. SFO, FDM, and SLS orthoses significantly increased the peak height of the medial foot arch between 3.6 to 4.4 mm (P < 0.001). Peak pressures in the medial (P = 0.018) and lateral forefoot (P = 0.022) regions of interest were significantly reduced for the SLS orthosis. SFO, FDM, and SLS orthoses significantly increased midfoot contact area (P < 0.001 for all conditions). In comparison to SFO, SLS and FDM orthoses provided equivalent or better patient experience. No adverse reactions were reported.

Functional optimization is a feasible approach for orthoses prescription in early RA and has the potential to provide superior mode-of-action responses for biomechanical therapeutic targets compared to standard devices.