Mid- and Long-Term Outcomes Are Favorable for Patients With Borderline Dysplasia Undergoing Primary Hip Arthroscopy: A Systematic Review

To evaluate midterm outcomes, long-term outcomes, and survivorship in the borderline dysplastic population after primary hip arthroscopy.A systematic review of current literature was performed with the following key words: "hip, "arthroscopy," "borderline dysplasia," "borderline hip dysplasia," "developmental dysplasia," "ten-year," "survivorship," "10-year," "5-year," "five year," "mid-term," "long-term," "outcomes," "arthroscopic," and "femoroacetabular impingement" in PubMed, Cochrane, and Scopus in March 2022 using the Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines. The following information was recorded: title, author, publication date, study design, demographic, number of hips, follow-up time, study period, indications for hip arthroscopy, patient-reported outcomes (PROs), characteristics of patients converting to total hip arthroplasty (THA), and rates of secondary surgeries and conversion to THA were recorded. Survivorship was defined as not converting to THA. Kappa values for the title/abstract and full-text screening were calculated. Forest plots were created for PROs that were included in 3 or more studies.Six articles comprising 413 hips were included in the study. Three studies were Level III evidence, and 3 studies were Level IV evidence. Average follow-up ranged from 5.7 to 12.2 years. One study defined borderline hip dysplasia as lateral center-edge angle 18-25° and 5 defined it as lateral center-edge angle 20-25°. All studies included PROs and reported significant improvement after surgery in at least one PRO. Three studies reported clinical benefit and across the studies at least 70% of patients achieved minimum clinically important difference in at least one PRO. Rates of undergoing revision hip arthroscopy and THA ranged from 2.1% to 7% and 0% to 24%, respectively. Tönnis grade 2, Tönnis angle >15, and Outerbridge Grade IV cartilage damage were identified as predictors of conversion to THA.Patients with borderline hip dysplasia undergoing primary hip arthroscopy demonstrated significant improvement in PROs at midterm and long-term follow-up. Survivorship at midterm follow-up was 98.2% (328/334 hips) and 76.3% (29/38 hips) at long-term follow-up.Level IV, systematic review of Level III and Level IV studies.