The acetabular labrum tear has been considered the most common cause of groin pain and the most frequent hip pathology. We have performed arthroscopic treatments for the labrum tear without obvious hip dysplasia. The purpose of this study is to investigate clinical outcomes of arthroscopic treatments in patients with labrum tear and to clarify the character of failure cases of hip arthroscopy for the labrum tear.

Seventy-four patients (78 hips) with CE angle more than 20°, who had labrum tear and were treated arthroscopically, were included in this study. The mean age at the primary hip arthroscopy was 42 years (12–68 years), and the mean follow-up period was 40 months (24–90 months). The labrum tear was treated with labrum debridement in 31 hips and labrum re-fixation in 47 hips. Clinical outcomes were evaluated using modified Harris Hip Score (mHHS), and fair or poor cases were investigated. FAI-related findings including crossover sign (COS), angle, pistol grip deformity (PGD), head/neck offset ratio were radiographically observed.

The mean mHHS revealed improvement from 71 points to 89 points after surgery. Progression of osteoarthritis was observed in 8 hips. Radiographical evaluation revealed mild COS in 22 hips, PGD in 10 hips. The mean angle was 63° and the mean head-neck offset ratio was 0.14. Overall, FAI-related findings were positive in 43 hips (55%). Ten patients (14%) including 4 patients with osteoarthritis were regarded as poor cases due to the pain score less than 20 points, and their symptoms occurred on long walking or the motion of external rotation without reference to FAI-related findings or procedures for the labrum tear. Four poor cases without FAI-related findings and osteoarthrisis had partial labrum tear and groin pain on walking or mild external rotaion. Moreover, extra-articular injection was effective in these cases.

Ten patients (14%) was considered poor cases after hip arthroscopy for the labrum tear. Even if the labrum tear is suspected on preoperative examinations, the cause of groin pain is not necessarily derived from the torn labrum. Surgeons should take not only intra-articular pathology but also extra-articular pathology into consideration before decision of arthroscopic treatment. Understanding genuine cause of groin pain in each patient would help to improve the results of hip arthroscopy.