Biomechanical properties of heel-pad and metatarsal head soft tissue and foot ulcers in patients with systemic sclerosis – a case control study

Abstract

Systemic sclerosis is a chronic connective tissue disease accompanied with skin and inner organ fibrosis and increased risk of foot ulcers. Biomechanical indexes (soft tissue thickness and compressibility) could affect the risk of this phenomenon. This study aimed to assess the heel pad and first metatarsal head soft-tissue thickness and compressibility index in scleroderma patients with and without foot ulcers and compare them with those of healthy individuals. Heel pad thickness in standing (loaded) and lying (unloaded) positions was measured in 40 scleroderma patients (diagnosed based on American College of Rheumatology classification criteria) by means of lateral foot radiography. The compressibility index was measured as the ratio of loaded to unloaded thickness. Also, soft-tissue thickness of the first metatarsal head was measured with ultrasound. Results were compared with 40 healthy controls of matched age and body mass index. Among 40 scleroderma patients (36 females, 4 males) with a mean age of 45 (±12) years, a mean body mass index of 25.5 (±4), and a mean disease duration of 10 years (±9.6), 8 (20%) patients had foot ulcers. Heel pad thickness (P value= 0.03) and the compressibility index (P value= 0.005) in the dominant side and the metatarsal head soft-tissue thickness on both sides (P value<0.0001) had significant differences with the control group. When comparing patients with and without foot ulcers, the soft-tissue thickness in both heels was significantly different (P value 0.01 for the right side and 0.007 for the left side). Thicknesses were negatively related to, but no relationship between the compressibility index and disease duration was observed. Plantar soft-tissue thickness decreases in scleroderma patients and could be a risk factor for foot ulcers.