title: Prevalence of radiological findings related to femoroacetabular impingement in professional baseball players in Japan.
abstract: BACKGROUND
  Femoroacetabular impingement (FAI) is a known patho-mechanism that causes hip pain and osteoarthritis (OA) and is considered uncommon in Japan, while secondary OA due to hip dysplasia is considered common. However, no studies have specifically targeted athletes in Japan and/or Asia. This study aimed to determine FAI prevalence using radiological findings among baseball players playing on a professional, Japanese team.
  
  
  METHODS
  We retrospectively assessed 63 plain anteroposterior (AP) hip radiographs (126 hips from 47 [74.6%] Asian players and 16 [25.3%] non-Asian players) obtained for medical evaluations. Radiographs were used to measure lateral center-edge (LCE) angle; acetabular roof obliquity (ARO); and the presence of crossover sign (COS), posterior wall sign (PWS), coxa profunda, pistol grip deformity, herniation pits, and labral ossification. Further, the prevalence of radiographic indicators related to FAI was compared between Asian and non-Asian players.
  
  
  RESULTS
  In the 126 hips examined, 10 hips (7.94%) were classified as having hip dysplasia (LCE angles < 20°). Of the remaining 116 hips, eight (6.9%) had LCE angles > 40°, and 24 hips (20.7%) had AROs of <0°, indicating acetabular over-coverage. In Asian players, COS was identified in 47 hips (54.0%), positive PWS in 38 hips (43.7%), positive coxa profunda in 8 hips (9.2%), and pistol grip deformity in 37 hips (42.5%). Further, herniation pits and positive labral ossification were identified in 25 (28.7%) and 11 (12.6%) hips, respectively. A comparative review of COS prevalence (Asians vs. non-Asians) revealed that COS was significantly higher in Asian players. No differences were observed in the mean LCE angle, mean ARO, or other radiographic indicators.
  
  
  CONCLUSIONS
  Radiological indicators related to FAI were identified in 76.6% (72/94 hips) of the Asian professional baseball players; this prevalence was considerably higher than that reported for general Asian populations. We consider that elite Asian athletes may frequently show morphological deformities related to FAI.
authors.affiliation: Department of Orthopaedic Surgery, Kitasato University School of Medicine, Kanagawa 252-0374, Japan. Electronic address: kenfu@r4.dion.ne.jp.
authors.forename: Kensuke
authors.initials: K
authors.lastname: Fukushima
authors.affiliation: Department of Rehabilitation, Kitasato University School of Allied Health Sciences, 1-15-1 Kitasato, Minami-ku, Sagamihara, Kanagawa 252-0374, Japan.
authors.forename: Naonobu
authors.initials: N
authors.lastname: Takahira
authors.affiliation: Department of Orthopaedic Surgery, Yokohama Minami Kyosai Hospital, 1-21-1 Mutsuura-higashi, Kanazawa-ku, Yokohama, Kanagawa 236-0037, Japan.
authors.forename: Sousuke
authors.initials: S
authors.lastname: Imai
authors.affiliation: Department of Orthopaedic Surgery, Yokohama Minami Kyosai Hospital, 1-21-1 Mutsuura-higashi, Kanazawa-ku, Yokohama, Kanagawa 236-0037, Japan.
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Yamazaki
authors.affiliation: Department of Orthopaedic Surgery, Kitasato University School of Medicine, Kanagawa 252-0374, Japan.
authors.forename: Tomonori
authors.initials: T
authors.lastname: Kenmoku
authors.affiliation: Department of Orthopaedic Surgery, Kitasato University School of Medicine, Kanagawa 252-0374, Japan.
authors.forename: Katsufumi
authors.initials: K
authors.lastname: Uchiyama
authors.affiliation: Department of Orthopaedic Surgery, Kitasato University School of Medicine, Kanagawa 252-0374, Japan.
authors.forename: Masashi
authors.initials: M
authors.lastname: Takaso
mesh_terms: D000328:Adult; D017677:Age Distribution; D044466:Asian People / Q000706:statistics & numerical data; D001265:Athletic Injuries / Q000000981:diagnostic imaging / Q000453:epidemiology; D001484:Baseball / Q000293:injuries*; D015331:Cohort Studies; D057925:Femoracetabular Impingement / Q000000981:diagnostic imaging* / Q000453:epidemiology*; D006801:Humans; D007564:Japan; D008297:Male; D015588:Observer Variation; D015995:Prevalence; D011859:Radiography / Q000379:methods; D012189:Retrospective Studies; D055815:Young Adult