Inclusion and Exclusion Criteria in the Diagnosis of Femoroacetabular Impingement

PurposeThe purpose of this study was to clarify the criteria for femoroacetabular impingement (FAI) by way of a systematic review of FAI-related articles, as well as to define more appropriate inclusion or exclusion criteria in the diagnosis of FAI.MethodsA systematic review of FAI-related articles was performed using Web of Science. Thirty-two articles met the inclusion and exclusion criteria. In these articles we investigated radiographic findings for the diagnosis of FAI and the prevalence of each FAI-related finding.ResultsThe crossover sign was used in 22 articles (69%); acetabular index, 9 articles (28%); posterior wall sign, 7 articles (22%); and prominence of the ischial spine sign, 3 articles (7%). Regarding acetabular coverage, the lateral center-edge (LCE) angle was described in 13 articles (41%), in which an LCE angle either of more than 40° or of more than 30° combined with an acetabular index of less than 0° was considered an inclusion criterion for pincer impingement. Meanwhile, the alpha angle was used in 28 articles (88%), in which 50° or 55° was recommended as a positive finding of cam impingement.ConclusionsCommon findings of pincer or cam deformity were used to select FAI patients with sufficient coverage of the acetabulum with an LCE angle of more than 25°. Patients with an LCE angle of less than 25° or those with local acetabular deficiency regardless of having a normal LCE angle should be excluded from the FAI criteria, even if the FAI-related findings are positive.Level of EvidenceLevel IV, systematic review of Level I through IV studies.