title: Absorption of the bone fragment in shoulders with bony Bankart lesions caused by recurrent anterior dislocations or subluxations: when does it occur?
abstract: BACKGROUND
  Recently, bony defects of the glenoid in patients with traumatic anterior shoulder instability have been increasingly noticed. The bone fragment of a bony Bankart lesion is often utilized for Bankart repair, but the fragment is at times smaller than the glenoid defect. The reason for this mismatch in size is unknown.
  
  
  OBJECTIVE
  The bone fragment of a bony Bankart lesion might gradually be absorbed over time.
  
  
  METHODS
  Case series; Level of evidence, 4.
  
  
  METHODS
  A total of 163 shoulders were prospectively examined by computed tomography. In shoulders with bony Bankart lesions, glenoid defects and bone fragment absorption were assessed, and findings were compared with the time elapsed after the primary traumatic episode. When a bone fragment was not detected despite loss of the normal contour of the glenoid rim, the findings were classified as erosions if the rim appeared round and slightly compressed and classified as complete bone fragment absorption if the rim appeared straight and sharp.
  
  
  RESULTS
  There were no glenoid defects in 55 shoulders, erosions in 16 shoulders, and glenoid defects in 92 shoulders. The size of the glenoid defect was 0% to 10% in 15 shoulders, 10% to 20% in 44, 20% to 30% in 26, 30% to 40% in 6, and 40% to 50% in 1. The average defect size was 7.9% in shoulders scanned at <1 year, 10.7% between 1 and 2 years, and 11.3% at >2 years, indicating no relationship with time after trauma. Regarding bone fragment absorption, all 92 shoulders with glenoid defects showed absorption to some extent. The extent of absorption was <50% in 32 shoulders, >50% in 45, and 100% in 15. The average extent of absorption was 51.9% in shoulders scanned at <1 year, 65.3% between 1 and 2 years, and 70.0% at >2 years, indicating a significant relationship with time after trauma.
  
  
  CONCLUSIONS
  Bone fragment absorption was seen in all of the shoulders with bony Bankart lesions. Most bone fragments showed severe absorption within 1 year after the primary traumatic episode. Before arthroscopic Bankart repair, not only glenoid defects but also bone fragment absorption should be assessed.
authors.affiliation: Department of Orthopaedic Sports Medicine, Yukioka Hospital, 2-2-3 Ukita, Kita-ku, Osaka 530-0021, Japan. nakagawa@yukioka.or.jp
authors.forename: Shigeto
authors.initials: S
authors.lastname: Nakagawa
authors.forename: Naoko
authors.initials: N
authors.lastname: Mizuno
authors.forename: Kunihiko
authors.initials: K
authors.lastname: Hiramatsu
authors.forename: Yuta
authors.initials: Y
authors.lastname: Tachibana
authors.forename: Tatsuo
authors.initials: T
authors.lastname: Mae
mesh_terms: D000293:Adolescent; D000328:Adult; D001862:Bone Resorption / Q000000981:diagnostic imaging; D001842:Bone and Bones / Q000000981:diagnostic imaging / Q000293:injuries / Q000502:physiology*; D002648:Child; D005260:Female; D061165:Glenoid Cavity / Q000000981:diagnostic imaging / Q000293:injuries*; D006801:Humans; D021621:Imaging, Three-Dimensional; D007593:Joint Instability / Q000209:etiology; D008297:Male; D008875:Middle Aged; D012008:Recurrence; D012783:Shoulder Dislocation / Q000150:complications*; D000070599:Shoulder Injuries; D012785:Shoulder Joint / Q000000981:diagnostic imaging; D013997:Time Factors; D014057:Tomography, X-Ray Computed; D055815:Young Adult
keywords: 3-dimensional reconstructed CT; arthroscopic bony Bankart repair; bone fragment absorption; bony Bankart lesion; glenoid defect; inverted pear glenoid; recurrent anterior shoulder dislocation/subluxation