title: Accessory navicular bone incidence in Chinese patients: a retrospective analysis of X-rays following trauma or progressive pain onset.
abstract: BACKGROUND
  Optimal treatment of symptomatic accessory navicular bones, generally asymptomatic 'extra' ossicles in the front interior ankle, remains debated.
  
  
  OBJECTIVE
  Incidence and type of accessory navicular bones in Chinese patients were examined as a basis for improving diagnostic and treatment standards.
  
  
  METHODS
  Accessory navicular bones were retrospectively examined in 1,625 (790 men and 835 women) patients with trauma-induced or progressive symptomatic ankle pain grouped by gender and age from August 2011 to May 2012. Anterior-posterior/oblique X-ray images; presence; type; affected side; modified Coughlin's classification types 1, 2A, 2B, and 3; and subgroups a-c were recorded.
  
  
  RESULTS
  Accessory navicular bones were found in 329 (20.2%) patients (143 men and 186 women; mean age, 47.24 ± 18.34, ranging 14-96 years). Patients aged 51-60 exhibited most accessory navicular bones (29.7%), with risk slightly higher in women and generally increasing from minimal 10.9% at ages 11-20 to age 51 and thereafter declining to 0.4% by age 90. The incidence was 41.6% for Type 1 (Type 1a: 9.1%, Type 1b: 15.5%, and Type 1c: 19.4%), 36.8% for Type 2 (Type 2Aa: 2.1%, Type 2Ab: 13.7%, Type 2Ac: 5.1%, Type 2Ba: 2.1%, 2Bb: 2.1%, and 2Bc: 11.6%), and 21.6% for Type 3 (Type 3a: 4.5%, Type 3b: 14%, and Type 3c: 3.0%).
  
  
  CONCLUSIONS
  Approximately one-fifth (20.3%) of ankle pain patients exhibited accessory navicular bones, with Type 2 most common and middle-aged patients most commonly affected. Thus, accessory navicular bones may be less rare than previously thought, underlying treatable symptomatic conditions of foot pain and deformity.
authors.affiliation: Department of Orthopedics, Huashan Hospital Fudan University, Shanghai, 200040, People's Republic of China.
authors.forename: Jiazhang
authors.initials: J
authors.lastname: Huang
authors.forename: Yijun
authors.initials: Y
authors.lastname: Zhang
authors.forename: Xin
authors.initials: X
authors.lastname: Ma
authors.forename: Xu
authors.initials: X
authors.lastname: Wang
authors.forename: Chao
authors.initials: C
authors.lastname: Zhang
authors.forename: Li
authors.initials: L
authors.lastname: Chen
mesh_terms: D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D002681:China; D005534:Foot Diseases / Q000000981:diagnostic imaging* / Q000453:epidemiology*; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D011859:Radiography; D012189:Retrospective Studies; D017678:Sex Distribution; D013639:Tarsal Bones / Q000002:abnormalities* / Q000000981:diagnostic imaging; D055815:Young Adult
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