Objective: To establish by ultrasonography (US) the frequency of calcaneal entheses involvement in erosive osteoarthritis (EOA), nodal osteoarthritis (NOA), RA and PsA, and to compare these results in order to aid clinicians in the differential diagnosis among these diseases. A comparison between US results and radiography was also made.
Methods: The heels of 56 consecutive outpatients with EOA, 209 with NOA, 158 with RA and 125 with PsA were studied by US and radiography. A control group of 50 subjects was examined by US.
Results: US showed no significant difference in inferior calcaneal enthesophytosis among the four diseases. The frequency of posterioinferior enthesophytosis was lower in RA (34%) in comparison with the other diseases (57% in EOA, 47% in NOA, 49% in PsA). Achilles enthesitis was found in 8% of PsA and in 2% of RA. Retrocalcaneal bursitis was found in 18% of RA and in 6% of PsA. Posterior erosions were present in 12% of RA and 5% of PsA. Inferior erosions were present in 6% of RA and in 1% of PsA. Plantar fasciitis was found in 26% of RA, in 37% of PsA, and in 15% of NOA and 12% of EOA. Subcalcaneal panniculitis was observed in 10% of RA and in 1% of PsA. In the control group, only posterioinferior and inferior enthesophytosis (22% and 18% respectively) were found. Kappa statistics show excellent agreement between US and radiography in detecting posterioinferior (kappa = 0.89) and inferior enthesophytosis (kappa = 0.83), and entheseal erosions (kappa = 0.86).
Conclusions: The calcaneal lesions that could be found in EOA are similar to those observed in NOA. The frequency of calcaneal enthesophytosis is similar in EOA, NOA, and PsA, but inflammatory lesions of calcaneal entheses and of the adjacent bursae are more frequent in RA and in PsA. In terms of heel involvement, EOA seems to be similar to NOA. US shows an excellent concordance with radiography in detecting entheseal cortical bone abnormalities.