title: Aneurysmal bone cysts: do simple treatments work?
abstract: BACKGROUND
  Primary aneurysmal bone cysts (ABCs) are benign, expansile bone lesions commonly treated with aggressive curettage with or without adjuvants such as cryotherapy, methacrylate cement, or phenol. It has been reported that occasionally these lesions heal spontaneously or after a pathologic fracture, and we observed that some ABCs treated at our center healed after biopsy alone. Because of this, we introduced a novel biopsy technique we call "curopsy," which is a percutaneous limited curettage at the time of biopsy, obtaining the lining membrane from various quadrants of the cyst leading to consolidation (curopsy = biopsy with intention to cure).
  
  
  OBJECTIVE
  We asked whether (1) a curopsy results in comparable likelihood of healing of the ABC compared with more aggressive approaches involving curettage, (2) the two approaches differ in terms of the likelihood of recurrence after treatment, and (3) the two approaches differ in terms of complications after surgery.
  
  
  METHODS
  Between January 1, 1999 and June 30, 2012, 221 patients with a diagnosis of primary ABC were registered in our oncology database. Patients presenting with a pathologic fracture and those seeking a second opinion were excluded. One hundred ninety patients were included in the study. One hundred two (54%) were treated with curopsy and 88 (46%) were treated with curettage after a core needle biopsy. Complete followups were available for 88% (90 of 102) and 93% (80 of 88) of patients in those groups, respectively. During that period, a curopsy was performed for all patients with benign bone lesions with imaging suggestive of classic primary ABCs and for whom the core needle biopsy simply showed blood with no solid component. Curettage after a core needle biopsy was reserved for histologically confirmed primary ABCs, lesions with impending fractures, large lesions, if the ABC was thought to be a secondary disorder, and patients for whom the curopsy failed. All patients were followed up until consolidation of the lesion (mean, 9.6 weeks, range, 3-25 weeks, 95% CI, 8.32-10.9 for curopsy; mean, 11.4 weeks, range, 8-32 weeks, 95% CI, 10.6-12.3 for curettage). The median followup for all patients was 14 months (range, 6-36 months).
  
  
  RESULTS
  Of the 102 patients who had curopsy and observation, 83 (81%) required no additional treatment and the lesion resolved. Of the 88 patients who underwent curettage (with or without adjuvant therapy) after core needle biopsy, the success rate was 90% (79 of 88). Local recurrences in both groups (curopsy or curettage) were treated successfully with additional curettage in all but one case. Curopsy in comparison to curettage provided a mean shorter healing time (9.6 versus 11.4, p = 0.01) but there was a higher local recurrence and need for additional intervention rate (18.6% versus 10.2%, p = 0.04). There were no differences in the complications between the treatment groups.
  
  
  CONCLUSIONS
  A curopsy is a novel biopsy technique that was successful in resolving ABCs in 81% of the patients in our study. Curopsy, as a biopsy technique, for ABCs needs consideration as it potentially minimizes the number of patients needing a second procedure (a core needle biopsy being the first) as is the current practice. Furthermore, it does not disadvantage the patient or surgeon should additional intervention be needed in the form of curettage with or without adjuvants.
  
  
  METHODS
  Level III, therapeutic study. See the Instructions for Authors for a complete description of levels of evidence.
authors.affiliation: The Royal Orthopaedic Hospital Oncology Service, Royal Orthopaedic Hospital, Bristol Road South, Birmingham, B31 2AP, UK, k.reddy@nhs.net.
authors.forename: Krishna I A
authors.initials: KI
authors.lastname: Reddy
authors.forename: F
authors.initials: F
authors.lastname: Sinnaeve
authors.forename: Czar Louie
authors.initials: CL
authors.lastname: Gaston
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Grimer
authors.forename: Simon R
authors.initials: SR
authors.lastname: Carter
mesh_terms: D062005:Biopsy, Large-Core Needle; D017824:Bone Cysts, Aneurysmal / Q000175:diagnosis / Q000401:mortality / Q000601:surgery*; D003475:Curettage / Q000009:adverse effects / Q000379:methods* / Q000401:mortality; D018572:Disease-Free Survival; D006801:Humans; D053208:Kaplan-Meier Estimate; D019637:Orthopedic Procedures / Q000009:adverse effects / Q000379:methods* / Q000401:mortality; D012008:Recurrence; D012074:Remission Induction; D012189:Retrospective Studies; D013997:Time Factors; D016896:Treatment Outcome