The incidence, location and distribution of degenerative subchondral acetabular cysts in primary osteoarthrosis of the hip.

Degenerative subchondral acetabular cysts are a common finding in patients with primary osteoarthritis of the hip. These mainly occur in the superior weight-bearing region of the acetabulum. The aim of this study was to identify the presence and distribution of degenerative acetabular cysts in patients with primary osteoarthritis of the hip. The radiographs of 100 consecutive patients who had a total hip replacement for primary osteoarthritis of the hip were retrospectively analyzed. Eighty-two patients had degenerative subchondral cysts. Of these 44% were solitary. All the cysts occupied the superior zone of the acetabulum with a proportion extending into the middle zone. None involved the inferior zone, the medial acetabular wall. The radiological presence of an acetabular cyst in the inferior zone (medial acetabular wall) warrants further investigation, and should not be presumed to represent a feature of osteoarthritis, even if osteoarthritis is present. (Hip International 2004; 14: 24-7).