Plantar forces mid-term after hemiarthroplasty with HemiCAP for hallux rigidus

Background: The aim of this study was to examine the biomechanical gait effects and range of motion following a proximal hemiarthroplasty with a HemiCap®. Methods: Forty-one HemiCAP-operated participants with a mean follow-up time of 5 years had plantar force variables (PFVs) examined and compared with their non-operated foot and a control group. PFVs were compared to the MTPJ1 range of motion (ROM), and pain measured by Visual Analog Scale (VAS). Results: The HemiCAP participants’ operated feet had higher PFVs laterally on the foot and lower PFVs under the hallux. Dorsal ROM of the operated feet was a median 45° (range 10–75) by goniometer and 41.5 (range 16–80) by X-ray. An increase in ROM decreased the forces under the hallux. Most participants were pain-free. No correlation between pain and PFVs was found. Conclusions: Increased dorsiflexion decreased the maximum force under the hallux. A mid-term HemiCAP maintains some motion. The decreased PFVs under the hallux may reflect a patient reluctance to load the first ray, although no correlation between plantar forces and pain was found. © 2019 European Foot and Ankle Society