The Application of the Novel Femoral-Epiphyseal Acetabular Roof (FEAR) Index

INTRODUCTION: Femoral-epiphyseal acetabular roof (FEAR) index is a recently introduced tool. It was proposed to be able to identify instability of the hip. Moreover, its use has been studied for predicting the outcome of surgery. OBJECTIVE: We conducted a systematic review to evaluate the implication of FEAR index. METHODS: A systematic computerised database search (Pubmed, ScienceDirect, and ClinicalKey) was performed until July 31st 2022 for articles related to FEAR index. RESULTS: Eleven studies were included in this systematic review. The FEAR index showed a very good interobserver intraclass correlation coefficients (ICC) (range: 0.778-0.99). Five studies (553 hips) assessed the use of FEAR index for hip instability. All studies indicated that the FEAR index was associated with hip instability despite differences in diagnosis (three borderline dysplastic hip, one femoroacetabular impingement (FAI), one developmental dysplasia of hip (DDH)). Five other studies involving a total of 686 hips evaluated the relation of FEAR index and surgery outcome in borderline instability. Three studies demonstrated a significant relationship of FEAR index and surgery success, with two studies suggested combination of FEAR index with AWI and/or PWI and one study proposed the use of ≥4˚ as the cut-off value for predictor of failed surgery. Two remaining studies that dichotomised PENG block by the value of 2˚ failed to show a significant relationship between FEAR index and success of surgery. In addition, two studies reported that FEAR index was able to differentiate FAI from DDH and two others discovered that FEAR index was significantly different in types of received surgery. CONCLUSION: The FEAR index is a relatively new index and only few studies have been conducted. This index may become a useful tool; however, further studies with high-quality design are needed to confirm its utilities and determine cut-off values accordingly.