Arthroscopic Treatment of Labral Tears in Acetabular Dysplasia: The Role of the Tonnis Angle and its Effect on the Outcomes (SS-40)

Abstract

Labral tears are a common finding in patients with acetabular dysplasia. Currently, the role of arthroscopic treatment and the factors that might influence the outcome of labral treatment are still uncertain. The aim of this study is to assess if the size of the Tonnis angle influences the clinical outcomes in patients with acetabular dysplasia receiving arthroscopic treatment for labral tears. Retrospective study of 30 patients with acetabular dysplasia, with an associated labral tear treated with hip arthroscopy. Inclusion criteria were centre edge (CE) angle < 25, Tonnis grade 0, lateral sourcil height ≥2mm. The Tonnis angle was measured. Intraoperative findings were recorded and the type of labral treatment: resection or repair. Patients were assessed using a 100 point Modified Harris Hip Score (MHHS) pre- and post-operatively after an average of 2 years. A linear regression model was used to assess the relation of the difference in MHHS (preop-postop) and the Tonnis angle (explanatory variable). A linear regression model was also fitted within each of the treatment groups separately. 30 patients; 23 females and 7 males (mean age 37 years, range 23-51) were assessed pre-operatively and at 2 year follow up. The average CE angle was 21 degrees (range 15- 24). The average Tonnis angle was 13.8 degrees (6-25). 11 patients had a labral debridement and 19 patients a labral repair. Our study demonstrates a significant (p=0.0013) relation between the reduction in MHHS score difference (preop-postop) as the Tonnis angle increases. This study demonstrates that in patients with dysplasia who received arthroscopic treatment for labral tears, the surgical outcome (MHHS) is depending on the Tonnis angle. Patients with an increased Tonnis angle, independent of the type of treatment, have a poorer outcome and possibly, a different treatment option should be considered.