Metallosis-induced Iliopsoas Bursal Cyst Causing Venous Obstruction and Lower-limb Swelling after Metal-on-metal THA

The formation of iliopsoas bursal cystic lesions after total hip arthroplasty is an infrequently reported condition. This article describes an unusual complication of a current-generation metal-on-metal total hip arthroplasty.A woman presented with unilateral spontaneous lower-limb swelling that developed 5 years postoperatively. It occurred secondary to venous obstruction by a metallosis-induced iliopsoas bursal cyst associated with markedly elevated intralesional cobalt and chromium levels. Metal artifact reduction sequence magnetic resonance imaging showed that the bursal cyst was communicating with the hip joint and that it severely compressed the common femoral vein. Based on the findings of high local tissue metal ions and vertical cup positioning causing edge loading, the authors proposed an inflammatory reaction to metal debris that tracked into the iliopsoas bursa and formed a cyst. The patient underwent revision of the excessively vertical acetabular component and conversion to a ceramic-on-ceramic bearing interface, drainage of the bursal cyst, and synovectomy. No signs existed of local recurrence at 1-year follow-up.To the authors' knowledge, the occurrence of metallosis-induced iliopsoas bursitis with secondary pressure effects after contemporary metal-on-metal total hip arthroplasty has not been reported. When treating hip dysplasia, one must avoid maximizing cup-host bone contact at the risk of oververticalization. Iliopsoas bursal cystic lesions can lead to severe vascular compressive symptoms with no ominous radiographic findings. Physicians and orthopedic surgeons should be aware of the possibility of this complication in patients with unexplained unilateral lower-limb swelling.