Systematic Review| Volume 39, ISSUE 4, P1074-1087.e1, April 2023

Download started.


The Radiographic Femoroepiphyseal Acetabular Roof Index Is a Reliable and Reproducible Diagnostic Tool in Patients Undergoing Hip-Preservation Surgery: A Systematic Review

Published:January 10, 2023DOI:


      To assess the utility of the femoroepiphyseal acetabular roof (FEAR) index as a diagnostic tool in hip-preservation surgery.


      MEDLINE, EMBASE, and PubMed were searched from database inception until May 2022 for literature addressing the utility of the FEAR index in patients undergoing hip-preservation surgery, and the results are presented descriptively.


      Overall, there were a total of 11 studies comprising 1,458 patients included in this review. The intraobserver agreement for the FEAR index was reported by 3 of 11 studies (intraclass correlation coefficient range = 0.86-0.99), whereas the interobserver agreement was reported by 8 of 11 studies (intraclass correlation coefficient range = 0.776-1). Among the 5 studies that differentiated between hip instability and hip impingement, the mean FEAR index in 319 patients in the instability group ranged from 3.01 to 13.3°, whereas the mean FEAR index in 239 patients in the impingement group ranged from –10 to –0.77° and the mean FEAR index in 105 patients in the control group ranged from –13 to –7.7°. Three studies defined a specific cutoff value for the FEAR index, with 1 study defining a cutoff value of 5°, which correctly predicted treatment decision between periacetabular osteotomy versus osteochondroplasty 79% of the time with an AUC of 0.89, whereas another defined a cutoff of 2°, which correctly predicted treatment 90% of the time and the last study set a threshold of 3°, which provided an AUC of 0.86 for correctly predicting treatment decision.


      This review demonstrates that the FEAR index has a high agreement and consistent application, making it a useful diagnostic tool in hip-preservation surgery particularly in patients with borderline dysplastic hips. However, given the variability in FEAR index cutoff values across studies, there is no absolute consensus value that dictates treatment decision.

      Level of Evidence

      Level IV; Systematic Review of Level II-IV studies.
      To read this article in full you will need to make a payment

      Purchase one-time access:

      Academic & Personal: 24 hour online accessCorporate R&D Professionals: 24 hour online access
      One-time access price info
      • For academic or personal research use, select 'Academic and Personal'
      • For corporate R&D use, select 'Corporate R&D Professionals'


      Subscribe to Arthroscopy
      Already a print subscriber? Claim online access
      Already an online subscriber? Sign in
      Institutional Access: Sign in to ScienceDirect


        • Hanke M.S.
        • Schmaranzer F.
        • Steppacher S.D.
        • Lerch T.D.
        • Siebenrock K.A.
        Hip preservation.
        EFORT Open Rev. 2020; 5: 630-640
        • Kivlan B.R.
        • Nho S.J.
        • Christoforetti J.J.
        • et al.
        Multicenter outcomes after hip arthroscopy: Epidemiology (MASH Study Group). What are we seeing in the office, and who are we choosing to treat?.
        Am J Orthop (Belle Mead NJ). 2017; 46: 35-41
        • Novais E.N.
        • Coobs B.R.
        • Nepple J.J.
        • Clohisy J.C.
        • ANCHOR Study Group
        Previous failed hip arthroscopy negatively impacts early patient-reported outcomes of the periacetabular osteotomy: An ANCHOR Matched Cohort Study.
        J Hip Preserv Surg. 2018; 5: 370-377
        • Marland J.D.
        • Horton B.S.
        • West H.S.
        • Wylie J.D.
        Association of radiographic markers of hip instability and worse outcomes 2 to 4 years after hip arthroscopy for femoroacetabular impingement in female patients.
        Am J Sports Med. 2022; 50: 1020-1027
        • Lynch T.S.
        • Minkara A.
        • Aoki S.
        • et al.
        Best practice guidelines for hip arthroscopy in femoroacetabular impingement: Results of a Delphi process.
        J Am Acad Orthop Surg. 2020; 28: 81-89
        • McClincy M.P.
        • Wylie J.D.
        • Williams D.N.
        • Novais E.N.
        Standardizing the diagnostic evaluation of nonarthritic hip pain through the Delphi method.
        Orthop J Sports Med. 2021; 92325967121991213
        • Wyatt M.
        • Weidner J.
        • Pfluger D.
        • Beck M.
        The femoro-epiphyseal acetabular roof (FEAR) index: A new measurement associated with instability in borderline hip dysplasia?.
        Clin Orthop Relat Res. 2017; 475: 861-869
        • Hunziker E.B.
        Mechanism of longitudinal bone growth and its regulation by growth plate chondrocytes.
        Microsc Res Tech. 1994; 28: 505-519
        • Pauwels F.
        • Maquet P.
        Biomechanics of the locomotor apparatus: Contributions on the functional anatomy of the locomotor apparatus.
        Springer-Verlag, Berlin Heidelberg1980
        • Moher D.
        • Shamseer L.
        • Clarke M.
        • et al.
        Preferred reporting items for systematic review and meta-analysis protocols (PRISMA-P) 2015 statement.
        Syst Rev. 2015; 4: 1
        • Landis J.R.
        • Koch G.G.
        The measurement of observer agreement for categorical data.
        Biometrics. 1977; 33: 159-174
        • Slim K.
        • Nini E.
        • Forestier D.
        • Kwiatkowski F.
        • Panis Y.
        • Chipponi J.
        Methodological index for non-randomized studies (MINORS): Development and validation of a new instrument.
        ANZ J Surg. 2003; 73: 712-716
        • Shah A.
        • Kay J.
        • Memon M.
        • et al.
        What makes suture anchor use safe in hip arthroscopy? A Systematic review of techniques and safety profile.
        Arthroscopy. 2019; 35: 1280-1293.e1
        • Šimundić A.M.
        Measures of diagnostic accuracy: Basic definitions.
        EJIFCC. 2009; 19: 203-211
        • Batailler C.
        • Weidner J.
        • Wyatt M.
        • Pfluger D.
        • Beck M.
        Is the Femoro-Epiphyseal Acetabular Roof (FEAR) index on MRI a relevant predictive factor of instability in a borderline dysplastic hip?.
        Bone Joint J. 2019; 101-B: 1578-1584
        • Meyer A.M.
        • Schaver A.L.
        • Cohen B.H.
        • Glass N.A.
        • Willey M.C.
        • Westermann R.W.
        FEAR index in predicting treatment among patients with femoroacetabular impingement and hip dysplasia and the relationship of femoral version.
        J Hip Preserv Surg. 2022; 9: 84-89
        • Smith J.T.
        • Jee Y.
        • Daley E.
        • Koueiter D.M.
        • Beck M.
        • Zaltz I.
        Can the Femoro-Epiphyseal Acetabular Roof (FEAR) index be used to distinguish dysplasia from impingement?.
        Clin Orthop Relat Res. 2021; 479: 962-971
        • McClincy M.P.
        • Wylie J.D.
        • Yen Y.M.
        • Novais E.N.
        Mild or borderline hip dysplasia: Are we characterizing hips with a lateral center-edge angle between 18° and 25° appropriately?.
        Am J Sports Med. 2019; 47: 112-122
        • Truntzer J.N.
        • Hoppe D.J.
        • Shapiro L.M.
        • Safran M.R.
        Can the FEAR index be used to predict microinstability in patients undergoing hip arthroscopic surgery?.
        Am J Sports Med. 2019; 47: 3158-3165
        • Kuroda Y.
        • Hashimoto S.
        • Saito M.
        • et al.
        Femoro-Epiphyseal Acetabular Roof (FEAR) index and anterior acetabular coverage correlate with labral length in developmental dysplasia of the hip.
        Arthroscopy. 2022; 38: 374-381
        • Urup Tønning L.
        • Schmid M.
        • Barroso J.
        • et al.
        Is the femoral-epiphyseal acetabular roof (FEAR) index associated with hip pain in patients with hip dysplasia?.
        Acta Radiol. 2022; 112841851221093840
        • Wong S.E.
        • Newhouse A.C.
        • Wichman D.M.
        • Bessa F.
        • Williams J.
        • Nho S.J.
        Patients with a high femoroepiphyseal roof with concomitant borderline hip dysplasia and femoroacetabular impingement syndrome do not demonstrate inferior outcomes following arthroscopic hip surgery.
        Arthroscopy. 2022; 38: 1509-1515
        • Zimmerer A.
        • Schneider M.M.
        • Nietschke R.
        • Miehlke W.
        • Sobau C.
        Is hip arthroscopy an adequate therapy for the borderline dysplastic hip? Correlation between radiologic findings and clinical outcomes.
        Orthop J Sports Med. 2020; 82325967120920851
        • Garabekyan T.
        • Ashwell Z.
        • Chadayammuri V.
        • et al.
        Lateral acetabular coverage predicts the size of the hip labrum.
        Am J Sports Med. 2016; 44: 1582-1589
        • Kamenaga T.
        • Hashimoto S.
        • Hayashi S.
        • et al.
        Larger acetabular labrum is associated with hip dysplasia, joint incongruence, and clinical symptoms.
        Arthroscopy. 2020; 36: 2446-2453
        • Kraeutler M.J.
        • Garabekyan T.
        • Pascual-Garrido C.
        • Mei-Dan O.
        Hip instability: A review of hip dysplasia and other contributing factors.
        Muscles Ligaments Tendons J. 2016; 6: 343-353