Radiological characteristics of the calcaneal spurs in psoriatic arthritis

Inflammation at the entheses is a distinguishing feature of psoriatic arthritis (PsA). Enthesitis at the heel is the most common location at the Achilles and plantar fascia insertions on the calcaneus. This study aimed to 1) describe the morphological features and measurements of plantar calcaneal spurs in subjects with PsA and controls and 2) determine radiological features that differentiate between inflammatory and non-inflammatory calcaneal spurs.

Weight bearing lateral foot radiographs of 101 subjects with PsA and 38 control subjects without inflammatory arthritis were examined for plantar calcaneal and Achilles spurs. Three measurements were taken from each radiograph: plantar spur base, mid-segment, and length in millimeters. The differences in radiographic measurements, and the presence of fluffy periostitis of the plantar spurs were then compared between PsA patients and controls.

Of the 101 subjects with PsA, 76 (75%) had at least one plantar calcaneal spur and 32 (31.5%) had at least one Achilles tendon spur, compared to 18 (47%) and 3 (8%) respectively in control group (p=0.004). Fluffy plantar periostitis was identified in 14 PsA subjects and none of the controls (p=0.01). The dimensions of plantar spurs were significantly different between groups - longer mid-segment distinguished patients with PsA from controls.

Calcaneal spurs are more common in subjects with PsA than controls. Longer mid-segment measurement was associated with PsA. This study indicates that the presence of fluffy plantar periostitis and broad based and longer mid-segment dimensions are radiological features for inflammatory spurs.