Radiologic features in symptomatic/asymptomatic heels of patients with ankylosing spondylitis

Most heel pain occurs at the posterior or plantar aspect, where main entheses of the heel are located. However, simple radiographs as basic work-up tools, their features based on their association with local symptoms in the heel in ankylosing spondylitis (AS) patients, have rarely been described.

Forty patients with AS and unilateral heel pain were enrolled to evaluate radiographic differences between symptomatic and asymptomatic heels. The two groups were assessed according to symptom location: posterior (group PS) or plantar (group PL). Typical abnormalities in bone and/or soft tissue on the heel due to inflammation were compared.

In group PS (20 cases), 19 (95%) symptomatic feet and 7 (35%) asymptomatic feet showed abnormal findings on the posterior heel and symptomatic feet showed 6 (30%) plantar abnormalities. Erosion of the posterior calcaneal tuberosity, obliteration of the retrocalcaneal recess (RR), and swelling shadows with increased thickness on posterior soft tissue were observed more frequently and significantly in symptomatic feet in group PS (P < 0.05). In group PL (20 cases), 11 (55%) symptomatic feet and 8 (40%) asymptomatic feet showed abnormalities on the plantar heel and symptomatic feet showed 14 (70%) posterior abnormalities, and none showed significant differences between symptomatic and asymptomatic feet.

Among simple radiographic alterations on heels with AS, such changes around the enthesis of the Achilles as bony erosion and RR obliteration with swollen posterior soft tissue are strongly related to current painful posterior heels. Assessment of enthesitis of the Achilles tendon in AS using plain radiography seems to be valid.