Mid-Term Functionality and Survival of 116 HemiCAP® Implants for Hallux Rigidus

Hallux rigidus can be treated with a proximal hemiarthroplasty (HemiCAP®) to preserve the motion in the first metatarsophalangeal joint and reduce pain. This study examines the functionality, and survival rates of HemiCAP® implants, with or without a dorsal flange. One hundred and five patients were treated with a HemiCAP® (N = 116 HemiCAPs®) between 2006 and 2014. Revision rates, arthrosis score, hallux valgus (HV), intermetatarsal (IM), distal metaphyseal articular angle (DMAA), visual analog scale (VAS) (1-10 points), American Orthopaedic Foot and Ankle Score (AOFAS) MTP-IP (AOFAS 0-100 points), SF-12, range of motion (ROM), and radiographs were analyzed pre- and postoperatively. Statistics: Kaplan-Meier survival analysis, Cox-regression, and paired t tests. At 2, 4, and 6 years, the implant survival was 87%, 83%, and 81%, respectively. All revised due to pain. Dorsal flange, gender, arthrosis, HV, IM, and DMAA did not influence the results. At the mean 5-year follow-up (n = 47) median (range) dorsal ROM was 45° (10°-75°), AOFAS was mean 87.2 ± 10.8, VAS was 2 ± 1.6, and SEFAS was 42 ± 6 points. The dorsal flange made no significant difference for ROM or patient-reported outcome measures compared to the HemiCAP® with no dorsal flange. Twenty-three patients with preoperative data were re-examined, and preoperative dorsal ROM mean difference (confidence interval [CI]) increased 20.7° (13.9°-27.4°), VAS decreased with a mean difference (CI) of -4.7 (-5.8 to 3.5), and AOFAS increased with a mean difference (CI) 26.2 (20.2-32.2) (for all p < .001). The 6-year survival rate of the HemiCAP® implant was 81%. The design change to dorsal flange was not evident clinically. Unrevised patients had significantly less pain, greater ROM, and better foot and ankle function than preoperatively.