Using flexible carbon fiber insoles for 1^st metatarsophalangeal arthritis lead to pain reduction and high compliance rate: A Randomized Controlled Trial

Abstract

Introduction Shoe modification and orthotics play an important role in non-operative management for 1st metatarsophalangeal (MTP) arthritis. However, compliance can be low due to pain and discomfort. We hypothesized that patients who wear a flexible carbon fiber insole for 1st metatarsophalangeal arthritis will report reduced pain, and higher physical function and compliance rate when compared with a rigid Mortons extension insole. Methods Four males and nine females (mean age of 56 years; range 35-79) diagnosed with 1st metatarsophalangeal arthritis were included in this randomized controlled trial. Participants randomly received either bilateral flexible carbon fiber insoles (VKTRY®) (n=7) or unilateral Mortons extension insole (n=6). Outcome measures included patient compliance, comfort rate, and Patient-Reported Outcomes Measurement Information System (PROMIS) questionnaires Global Health, pain interference, v1.0 pain intensity, v2.0 Physical Function, and v1.0 Depression. Participants filled out questionnaires at baseline and at two, six, and twelve weeks follow-up. Results Compared to Mortons extension insole, use of flexible carbon fiber insole led to reduction of pain interference score at 6 and 12 weeks (median 𝝙 -9.5 vs 0.0 p=0.015; and median 𝝙 -15.1 vs -2.3 p=0.015, respectively), as well as reduction of pain intensity score at 6 and 12 weeks (median 𝝙 -11.9 vs -2.3 p=0.018; and median 𝝙 -11.9 vs -2.3 p=0.010, respectively). The compliance rate in flexible carbon fiber insole group was 100% at 2, 6, and 12 weeks, compared to 83%, 83%, and 50% in the Morton group. In addition, patients wearing carbon fiber insoles experienced higher comfort levels (p-values ranging from <0.001 to p=0.007). There were no differences between the comparison groups at 2, 6, and 12 weeks in terms of global health, physical function, and depression scores. Conclusion Patients diagnosed with 1st metatarsophalangeal arthritis may benefit from wearing flexible carbon fiber insoles, compared to commonly used rigid orthotic insoles, such as Mortons extension. This insert can be used safely for nonoperative treatment of hallux rigidus and is another option for nonoperative treatment.