title: Predictive factors for recurrence of simple bone cyst of the proximal humerus.
abstract: OBJECTIVE
  To evaluate factors predictive of recurrence following curettage of simple bone cysts (SBCs) in the proximal humerus.
  
  
  METHODS
  Records of 29 male and 3 female patients aged 3 to 22 (mean, 11) years who underwent curettage with or without bone grafting for a solitary SBC in the proximal humerus were reviewed. The appearance, size, location, activity level, and fracture pattern of each cyst were recorded. The cyst index indicated the risk of refracture. Recurrence was defined as a refracture or enlargement of the cyst.
  
  
  RESULTS
  31 patients presented with a pathological fracture. The main symptoms were pain (n=30), loss of function (n=22), and mass/swelling (n=15). 25 patients gave a history of trauma. The duration of symptoms was less than one month. 10 patients had recurrence after a mean of 10 (range, 4-27) months; 5 were refractures and another 5 were enlargement of the cysts. Six were treated conservatively and eventually healed, whereas 4 underwent further curettage. Factors predictive of recurrence were patient age 5 years or younger (p=0.014), right-sided cyst (p=0.01), larger cyst (p=0.039), multilocular cyst (p=0.004) and unimpacted fracture (p=0.04). Recurrence was not related to gender, cyst location, or cyst activity level.
  
  
  CONCLUSIONS
  Most SBCs heal even if the fracture is treated expectantly. SBCs should be left alone unless symptomatic. If curettage is performed, grafts or bone substitutes should be used. More aggressive treatment might be necessary for unimpacted fractures to minimise the risk of recurrence.
authors.affiliation: Department of Orthopaedic Surgery, University of Edinburgh, Royal Hospital for Sick Children, Edinburgh, UK. karhao@gmail.com
authors.forename: Kar Hao
authors.initials: KH
authors.lastname: Teoh
authors.forename: Adam C
authors.initials: AC
authors.lastname: Watts
authors.forename: Yu-Han
authors.initials: YH
authors.lastname: Chee
authors.forename: Robin
authors.initials: R
authors.lastname: Reid
authors.forename: Daniel Edward
authors.initials: DE
authors.lastname: Porter
mesh_terms: D000293:Adolescent; D001845:Bone Cysts / Q000175:diagnosis* / Q000453:epidemiology / Q000601:surgery; D002648:Child; D002675:Child, Preschool; D003475:Curettage; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D006811:Humerus; D008297:Male; D011379:Prognosis; D012008:Recurrence; D012189:Retrospective Studies; D012307:Risk Factors; D013997:Time Factors; D055815:Young Adult