Arthroscopic Bone Grafting of Deep Acetabular Cysts in Hip Preservation Surgery: A Matched Case-Control Study

Background: Acetabular subchondral cysts are commonly identified signs of joint degeneration and arthritis. This pathology is generally considered a relative contraindication for hip preservation surgery. Purpose: To investigate the effect of arthroscopic bone grafting for the treatment of acetabular subchondral cysts. Study Design: Cohort study (diagnosis); Level of evidence, 3. Methods: We completed a retrospective analysis of hip arthroscopies performed by the senior author between 2013 and 2021. Patients with radiologic evidence of acetabular cysts who underwent arthroscopic bone grafting, with or without subsequent periacetabular osteotomy (PAO) and/or derotational femoral osteotomy with a minimum of 2-year follow-up, were included in the analysis. Patients undergoing surgical treatment for diagnoses of slipped capital femoral epiphysis, Legg-Calves-Perthe disease, osteochondromatosis, or postdislocation syndrome, as well as patients who refused to participate in the study, were excluded. We compared the patient-reported outcomes (PROs) for patients who underwent arthroscopic bone grafting with a case-matched control group without acetabular cysts with the same surgical route (hip arthroscopy or hip arthroscopy followed by PAO). An "inside-out" arthroscopic bone grafting technique was utilized, which allowed for precise access to the cystic cavity through the articular side. We analyzed postoperative PROs at a minimum of 2 years postoperatively using the international Hip Outcome Tool (iHOT-12) and Nonarthritic Hip Score (NAHS). Results: In total, there were 44 hips in the experimental group and 78 hips in the control group. The mean PRO interval in the experimental group was 3.4 years (range, 2-5 years postoperatively), with 20 patients reaching PROs 5 years postoperatively. The experimental group reported significant improvement of iHOT-12 and NAHS scores postoperatively (both P < .001). Postoperative iHOT-12 and NAHS scores did not significantly differ between groups over a 5-year follow-up interval (P = .26 and .17, respectively). Radiographic evidence of cyst healing was achieved in all 7 patients who underwent postoperative magnetic resonance imaging, with 3 cases of complete resolution. Conclusion: Acetabular subchondral cysts treated with an inside-out method of arthroscopic bone grafting in the setting of hip preservation surgery with or without PAO was associated with a significant improvement in midterm PROs, comparable with a control group of patients without acetabular cysts who did not undergo bone grafting. Our results support the use of arthroscopic grafting in appropriately selected patients and suggest that hip preservation is not contraindicated in patients with acetabular subchondral cysts.