title: Osteoid osteoma: factors for increased risk of unsuccessful thermal coagulation.
abstract: OBJECTIVE
  To retrospectively identify risk factors that may impede a favorable clinical outcome after thermocoagulation for osteoid osteoma.
  
  
  METHODS
  Informed consent (permission for the procedure and permission to use patient data for analysis) was obtained from all patients who met study criteria, and institutional review board did not require approval. Analysis included age, sex, size and location of osteoid osteoma, presence of calcified nidus, number of needle positions used for coagulation, coagulation time, accuracy of needle position, learning curve of radiologist, and previous treatment in 95 consecutive patients with osteoid osteoma treated with thermocoagulation. With chi(2) analysis, Fisher exact test, or unpaired Student t test and logistic regression analysis, 23 unsuccessfully treated patients were compared with 72 successfully (pain-free) treated patients.
  
  
  RESULTS
  Parameters associated with decreased risk for treatment failure were advanced age (mean age, 24 years in treatment success group vs 20 years in treatment failure group) and increased number of needle positions during thermocoagulation. Estimated odds ratios were, respectively, 0.93 (95% confidence interval: 0.88, 0.99) and 0.10 (95% confidence interval: 0.02, 0.41). Patients with a lesion of 10 mm or larger seemed at risk for treatment failure (odds ratio = 2.68), but the 95% confidence interval of 0.84 to 8.52 included the 1.00 value. Needle position was inaccurate in nine of 23 patients with treatment failure; only one needle position was used in eight of these nine patients. Lesion location, calcification, sex, coagulation time, radiologist's learning curve, and previous treatment were not risk factors.
  
  
  CONCLUSIONS
  Multiple needle positions reduce the risk of treatment failure in all patients and should especially, but not exclusively, be used in large (> or =10-mm) lesions or lesions that are difficult to engage to reduce the risk for unsuccessful treatment.
authors.affiliation: Departments of Radiology and Orthopaedic Surgery, Leiden University Medical Center, Albinusdreef 2, PO Box 9600, NL-2300 RC Leiden, the Netherlands.
authors.forename: Geert M
authors.initials: GM
authors.lastname: Vanderschueren
authors.forename: Antoni H M
authors.initials: AH
authors.lastname: Taminiau
authors.forename: Wim R
authors.initials: WR
authors.lastname: Obermann
authors.forename: Annette A
authors.initials: AA
authors.lastname: van den Berg-Huysmans
authors.forename: Johan L
authors.initials: JL
authors.lastname: Bloem
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D001859:Bone Neoplasms / Q000473:pathology / Q000601:surgery*; D002114:Calcinosis / Q000473:pathology; D002648:Child; D002675:Child, Preschool; D016001:Confidence Intervals; D004564:Electrocoagulation / Q000295:instrumentation / Q000379:methods; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009339:Needles; D016017:Odds Ratio; D010017:Osteoma, Osteoid / Q000473:pathology / Q000601:surgery*; D011871:Radiology; D012086:Reoperation; D012307:Risk Factors; D012737:Sex Factors; D013997:Time Factors; D017211:Treatment Failure