Hydroxyapatite crystal deposition disease around the hip: a rare cause of piriformis syndrome and ischiofemoral impingement

Abstract

Hydroxyapatite crystal deposition disease (HADD) around the hip is typically described involving the gluteal tendons. However, HADD can occur in any location and result in varied clinical presentations. Even with small deposits, symptoms can be significant and imaging findings may appear aggressive, mimicking infection and malignancy particularly when in an atypical location. We illustrate cases of both common and rare locations of HADD around the hip, in particular presenting as greater trochanteric pain syndrome, piriformis syndrome and ischiofemoral impingement. The latter two manifestations have not been previously described in the literature. Low signal deposits were identified on MRI at the greater trochanter (gluteus medius tendon), proximal piriformis (adjacent to the sciatic nerve), and quadratus femoris (in the ischiofemoral space), respectively. Associated inflammatory changes with tendinopathy, bursitis and oedema were also demonstrated. The patient with piriformis syndrome underwent steroid injections and shockwave therapy with significant symptom improvement. HADD should be within the differential diagnosis for hip pain and nerve compression syndromes. Knowledge of tendon anatomy and correlation with radiographs or CT, even after MRI, is crucial in recognising unusual manifestations and preventing unnecessary investigation. Therefore, we review the spectrum of imaging features of HADD, as well as the current evidence on its management, to confidently diagnose this condition.

A Case Report: Calcific Piriformis Tendinitis in a Patient with Known Sarcoidosis

“…Calcific tendinitis of the piriformis is scarce in medical literature with a recent review finding only two available cases reported [6]. A recent paper also reports a case of piriformis syndrome, diagnosed on MRI with findings of a calcific deposit with surrounding oedema within the proximal piriformis muscle adjacent to the sciatic nerve [7]. In this case, the patient gained significant symptoms improvement with steroid injection and low-energy shockwave therapy.…”