Abstract
We have investigated whether the pattern of subchondral acetabular cyst formation reflects hip pathology and may provide a prognostic indicator for treatment.
A single surgeon series of sequential hip arthroscopies was reviewed to identify the most recent 200 cases undertaken on a previously un-operated joint with pre-operative plain radiographs and computed tomography or magnetic resonance scan available for review. Also, serial “non-arthritic hip scores” (NAHS) recorded pre-operatively, at 6 weeks and 3 months post-surgery. The acetabular Lateral Centre Edge Angle, the Acetabular Index, the FEAR index and the Kallgren and Lawrence grade were determined. All images were reviewed by two independent assessors and divided into four groups according to acetabular subchondral cyst distribution. NC - No cysts - 74 cases (mean: 40.1 years), SPC - a Single Peripheral Cyst – 58 cases (mean: 43.1 years), SDC - a Solitary Dome Cyst – 32 cases (mean: 33 years) and MC - Multiple Cysts – 36 cases (mean: 42.7 years).
No association was identified between gender and patient reported outcomes.
SDC patients were significantly younger than the other three groups (p <0.001). At three months after surgery, the average increase of the NAHS in the four groups was 25.3, 23.5, 4.2 and 4.9 respectively. Acetabular dysplasia was identified in 72% of the SDC group compared to 18%, 16% and 33% in NC, SPC and MC groups. Degenerative change was identified in 86% of the MC group compared to 18%, 40% and 41% of the NC, SPC and SDC groups.
The early patient reported outcome following hip arthroscopy was significantly affected by the location and number of acetabular subchondral cysts. A Solitary Dome Cyst is indicative of underling hip dysplasia. Multiple Cysts are indicative of degenerative disease. The majority of patients in these groups have poor three-month outcomes after hip arthroscopy.
