Inclusion and Exclusion Criteria in the Diagnosis of Femoroacetabular Impingement Takuma Yamasaki, M.D., Ph.D., Yuji Yasunaga, M.D., Ph.D., Takeshi Shoji, M.D., Ph.D., Sotaro Izumi, M.D., Susumu Hachisuka, M.D., and Mitsuo Ochi, M.D., Ph.D.
Purpose: The 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. Methods: A 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. Results: The 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. Conclusions: Common 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 Evidence: Level IV, systematic review of Level I through IV studies.
ecently, there have been many reports on the diagnosis or treatment of femoroacetabular impingement (FAI), which has been widely described as a possible cause of osteoarthritis.1-3 Overcoverage of the acetabulum could induce pincer impingement, whereas bone abnormality at the femoral head-neck junction could induce cam impingement.4-6 However, the correlation between radiographic FAI-related ﬁndings and the actual phenomenon of impingement remains unclear. Pincer-type FAI is usually diagnosed from such ﬁndings as the crossover sign, the posterior wall sign, the prominence of the ischial spine sign, or coxa profunda.6,7 However, cases of mild pelvic tilt or
From the Department of Orthopaedic Surgery, Graduate School of Biomedical Sciences, Hiroshima University (T.Y., T.S., S.I., S.H., M.O.); and Hiroshima Prefectural Rehabilitation Center (Y.Y.), Hiroshima, Japan. The authors report that they have no conﬂicts of interest in the authorship and publication of this article. Received July 9, 2014; accepted December 30, 2014. Address correspondence to Takuma Yamasaki, M.D., Ph.D., Department of Orthopaedic Surgery, Hiroshima University, 1-2-3 Kasumi, Minami-ku, Hiroshima, 734-8551, Japan. E-mail: [email protected]
Ó 2015 by the Arthroscopy Association of North America 0749-8063/14574/$36.00 http://dx.doi.org/10.1016/j.arthro.2014.12.022
developmental dysplasia of the hip (DDH) could induce false-positive results.8 Cam-type FAI is diagnosed from such ﬁndings as the alpha angle, pistolgrip deformity, or femoral head-neck offset.6,9,10 However, the condition of the radiographic images and measurement methods of the observers could cause these FAI-related ﬁndings to change. Therefore over-diagnosis of FAI may occur regardless of actual impingement in daily life activities. Meanwhile, insufﬁcient coverage of the acetabulum could induce hip instability.11 In Japan, the prevalence of DDH is high in patients with hip disorders, which has contributed to the development of surgical treatments for DDH including joint-preserving surgery. However, in cases with mild DDH, it has been unclear whether this symptom is derived from impingement or from instability of the hip.12,13 The purpose of this study was to clarify the criteria of FAI by means of a systematic review of FAI-related articles, as well as to revise the deﬁnition of FAI to avoid over-diagnoses or excessive treatments. We hypothesized that the pathology of FAI comes into existence with sufﬁcient acetabular coverage and that different pathologies such as hip instability could be a cause of groin pain even in the case of a shallow acetabulum with a normal center-edge angle.
Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol
(Month), 2015: pp 1-8
T. YAMASAKI ET AL.
Fig 1. Flow diagram showing method of article selection for study inclusion.
Methods A systematic review of FAI-related articles was performed to clarify the diagnostic criteria for FAI. We searched Web of Science for articles published between January 2008 and July 2013. Relevant articles that we located in the database included the term “femoroacetabular impingement.” These articles were investigated with the aim of removing duplicate studies. A total of 684 articles were identiﬁed in our search, and each abstract was reviewed by 2 of the authors (T.Y. and T.S.). Articles that mentioned the reason patients were selected to undergo FAI diagnosis were extracted. Of the 684 total articles, 93 qualiﬁed for full-text inspection. We included only studies that were published in English and reported on clinical FAI research involving more than 50 patients. Articles in which patients had previous hip disorders such as slipped capital femoral epiphysis, Legg-Calvé-Perthes disease, osteoarthritis of more than grade 1 by the Tönnis classiﬁcation, osteonecrosis, or post-traumatic deformity were excluded. Thirty-two articles met the inclusion and exclusion criteria. Sixty-one articles did not meet the inclusion criteria, comprising 40 articles with fewer than 50 patients, 10 review articles, 6 articles with healthy subjects who did not have any symptoms in the groin, and 5 articles with patients who had had previous hip disorders (Fig 1). In these articles we investigated the justiﬁcation for the FAI diagnosis, including radiographic FAI-related ﬁndings and physical examination ﬁndings. Furthermore, we also focused on the exclusion criteria for FAI in these articles, such as
previous hip disorders, previous hip surgery, patient age, and presence of hip dysplasia.
Standard conventional radiographic ﬁndings for the diagnosis of FAI were used in the reviewed articles. The crossover sign, the posterior wall sign, the prominence of the ischial spine sign, coxa profunda, protrusio acetabuli, the acetabular index (acetabular roof obliquity), and the lateral center-edge (LCE) angle were used to estimate pincer impingement with single or multiple ﬁndings evaluated in the articles. The alpha angle, pistol-grip deformity, triangular index,14 head-neck offset, and herniation pit were used to estimate cam impingement with single or multiple ﬁndings evaluated in the articles. In addition, the presence of previous hip disorders including osteoarthritis, positive ﬁndings of physical examinations for FAI, previous hip operations, age at surgery, and intra-articular disorders such as labral tears and chondral pathology were investigated in the diagnosis of FAI (Table 1). As for the prevalence of FAI-related ﬁndings, the crossover sign was used in 23 articles (72%), coxa profunda in 10 articles (31%), and the posterior wall sign in 7 articles (22%) (Table 2). Regarding acetabular coverage, the LCE angle was mentioned in 13 articles (41%), and 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%), with 50 or 55
Table 1. Participant Demographic Data for Studies of Femoroacetabular Impingement
Study DiazLedezma et al.15 Tibor et al.16
Level of Evidence Prognostic study, IV
No. of Patients (No. of Hips) 108
Information of FAI-Related Findings Coxa Herniation Mean Crossover Posterior Sign Wall Sign Profunda Pit Age, yr 36 Yes
Alpha Angle, >50 >55
Steppacher et al.17 Monazzam et al.18
Prognostic study, III Prognostic study, IV
53 (53) 225
Fraitzl et al.19
Diagnostic study, III Prognostic study, III Prognostic study, IV
646 188 (204)
Impellizzeri et al.25 Byrd and Jones26
Therapeutic study, IV Therapeutic study, IV
Diagnostic study, IV Diagnostic study, II Diagnostic study, I
Xp Xp, CT, MRI
Xp, MRarthro Xp, MRI
Xp, Gdenhanced MRI Xp
LCE angle 20 LCE angle 25 LCE angle 20
Femoral head asphericity by 3D CT
LCE angle 20
Evaluation Method Xp, MRI
Prognostic 167 (180) study, III Therapeutic 60 (65) study, IV Therapeutic 201 study, IV
Femoral version, acetabular version, neck shaft angle Retroversion index, PRIS sign LCE angle 40 , Tönnis angle 25
Radial MRI, Xp Radial MRI
LCE angle 20
LCE angle >25
Study Larson et al.30
Hartoﬁlakidis et al.31
Kivlan et al.32 Paliobeis and Villar33 Chen et al.34
Kim et al.36
Pollard et al.37 Horisberger et al.38 Takeyama et al.39 Lohan et al.40 Allen et al.41 Brunner et al.42 Philippon et al.43 Panzer et al.44 Larson and Giveans45 Tannast et al.46
No. of Information of FAI-Related Findings Patients Pistol-Grip Head-Neck (No. of Mean Crossover Posterior Coxa Herniation Alpha Level of Deformity Offset Other Findings Sign Wall Sign Profunda Pit Angle, Evidence Hips) Age, yr Prognostic 210 (227) 35.1 Yes Yes >50 Femoral head study, IV asphericity by 3D CT, protrusio acetabuli Prognostic 96 (96) 49.3 Yes Yes >68 Yes LCE angle 35 and study, IV (men)or acetabular index >50 0 (women) Therapeutic 72 29.9 Yes >50 Yes study, IV Diagnostic 76 34.6 Yes Yes Yes study, IV Diagnostic 1,128 Yes Yes study, IV Prognostic 338 (355) 36.8 Yes Yes >50 LCE angle >39 , study, III acetabular index 39 , study, IV acetabular index 50 Yes Yes study, IV Prognostic 817 (946) study, IV Diagnostic 78 study, III Prognostic 113 study, IV Therapeutic 53 study, IV Therapeutic 112 study, IV Diagnostic 200 study, IV Therapeutic 96 (100) study, IV Diagnostic 55 study, II
PRIS sign, coxa protrusio
Xp, MRarthro Xp Xp Xp, CT
Xp, Gdenhanced MRI Xp
>50 or 55
Evaluation Method Xp, MRI
Information on Acetabular Coverage
3D CT Yes
Xp, CT, MRarthro Xp, CT
CEA, enter edge angle; CT, computed tomography; FAI, femoroacetabular impingement; LCE, lateral center edge; MRI, magnetic resonance imaging; PRIS, prominence of ischial spine; 3D, 3dimensional.
T. YAMASAKI ET AL.
Nepple et al.35
Table 1. Continued
INCLUSION AND EXCLUSION CRITERIA FOR FAI Table 2. Frequency of Radiographic Parameters for FAI Diagnosis Frequency Pincer-type FAI Crossover sign (Xp) Coxa profunda (Xp) Posterior wall sign (Xp) Protrusio acetabuli (Xp) CE angle (Xp) (CE >40 or CE >30 þ ARO