Clinical presentation of intra-articular osteoid osteoma of the hip and preliminary outcomes after arthroscopic resection: a case series.

Intra-articular osteoid osteoma (IAOO) of the hip is a relatively rare diagnosis, but one that can closely mimic symptomatic presentation of femoroacetabular impingement (FAI). Although there are multiple case reports of osteoid osteoma (OO) in the hip, we present the largest case series of hip IAOO treated with hip arthroscopy and discuss limited patient-reported outcomes after treatment with hip arthroscopy. We retrospectively identified patients diagnosed with IAOO of the hip with confirmatory computed tomography, magnetic resonance imaging or biopsy diagnoses of OO. We analyzed lesion location, main presenting symptoms, symptom duration and treatment undertaken. For the patients who underwent hip arthroscopy for treatment of their IAOO, we reviewed patient-reported outcome scores when available. Forty patients with confirmed IAOO were identified. Thirteen underwent excision with hip arthroscopy. The most common presenting symptom was groin pain. In limited patients who had pre- and post-operative outcome scores, we found significant improvements in modified Harris Hip Score (mHHS), Hip Outcome Score-Activity of Daily Living (HOS-ADL) and international Hip Outcomes Tool (iHot33) scores. Compared with patients undergoing hip arthroscopy for FAI alone, baseline mHHS, HOS-ADL, Hip Outcome Score-Sport-Specific Subscale and iHot33 scores were almost identical. We found that the presenting symptoms of hip IAOO closely mimic symptomatic FAI, including groin pain and anterior hip pain, so it is important to keep IAOO of the hip in the differential diagnosis of hip pain. Based on our experience, arthroscopy can be an effective treatment option for excision of intra-articular OO and is especially effective in patients with concomitant FAI in treating both pathologies.