The HAR-index: a reliable method for evaluating the risk of total hip arthroplasty conversion after hip arthroscopy for femoroacetabular impingement.

purposeHip arthroscopy is a growing technique in the treatment of femoroacetabular impingement (FAI), but can sometimes lead to unsatisfactory results such as the early conversion to total hip arthroplasty (THA). The purpose of this study is to describe a new tool for assessing the preoperative risk of THA conversion after hip arthroscopy in patients with FAI.

methodsThis study is a retrospective analysis of a prospective cohort of 584 patients with FAI who underwent hip arthroscopy at a single centre with a minimum 2 years follow-up. The preoperative variables of these patients were analysed to calculate the risk of each variable for THA. By selecting variables with an area under the receiver operating characteristic (ROC) curve greater than 0.7, a calculator was created to provide a risk index for each patient.

resultsFour variables (age, body mass index, Tönnis score and ALAD) were associated with an increased risk of THA conversion. The optimal cut-off points for each variable were determined, and a risk index was created. The Hip-Arthroplasty-Risk Index (HAR-Index) is a 0-4 points scale obtained from four binary scores of 0 or 1 depending on whether the cut-off point for each variable was reached or not. The increased risk of THA for each HAR-Index value was 1.1%, 6.2%, 17.9%, 55.1% and 79.3% respectively. The HAR-Index showed a very good predictive capacity with an area under the ROC curve of 0.89.

conclusionThe HAR-Index is a simple and practical tool for practitioners to make more informed decisions about performing hip arthroscopy in patients with FAI. With a very good predictive capacity, the HAR-Index can help to reduce the rate of conversion to THA. LEVEL OF EVIDENCE: Level III.