title: What are the results using the modified trapdoor procedure to treat chondroblastoma of the femoral head?
abstract: BACKGROUND
  Treatment of chondroblastoma in the femoral head is challenging owing to the particular location and its aggressive nature. There is little published information to guide the surgeon regarding the appropriate approach to treating a chondroblastoma in this location. We developed a modified trapdoor procedure to address this issue. The primary modification is that the window surface of the femoral head is covered by the ligamentum teres rather than cartilage as in the traditional procedure.
  
  
  OBJECTIVE
  We assessed (1) the clinical presentation of chondroblastoma of the femoral head and treatment results with the modified trapdoor procedure in terms of (2) the frequency of local recurrence, (3) complications, and (4) functional outcomes using the Musculoskeletal Tumor Society (MSTS) score.
  
  
  METHODS
  Between 1999 and 2010, we treated 14 patients for chondroblastoma of the femoral head. All patients received the modified trapdoor procedure. Of those, 13 were available for followup at a minimum of 36 months (mean, 66 months; range, 36-117 months) and one patient was lost to followup. There were nine males and four females, with a mean age of 18 years (range, 9-29 years). Clinical features were ascertained by chart and radiographic review, and recurrence, complications, and functional outcomes (MSTS score) were recorded from chart review. Patterns of bone destruction were evaluated using the Lodwick classification, which ranges from IA (geographic appearance with sclerotic rim) to III (permeative appearance).
  
  
  RESULTS
  The symptoms at diagnosis were pain in nine patients and discomfort in four. The mean duration of symptom was 11 months (range, 1-36 months). The physis was open in two patients, closing in one, and closed in 10. The patterns of bone destruction were evaluated as Lodwick Class IA in six patients, Lodwick Class IB in five, and Lodwick Class IC in two. At latest followup, no local recurrence was observed. Two patients had postoperative complications. One had avascular necrosis of the femoral head and was treated with prosthesis replacement. The other had asymptomatic heterotopic ossification in the surgical field. The mean MSTS score was 29.6 (range, 28-30).
  
  
  CONCLUSIONS
  Based on this small series, we believe our modified trapdoor procedure is a safe, effective means of treating a chondroblastoma in the femoral head, but additional clinical evaluation with more patients is necessary to confirm our findings.
  
  
  METHODS
  Level IV, therapeutic study. See the Instructions for Authors for a complete description of levels of evidence.
authors.affiliation: Department of Orthopedic Oncology Surgery, Beijing Ji Shui Tan Hospital, Peking University, Beijing, China.
authors.forename: Hairong
authors.initials: H
authors.lastname: Xu
authors.forename: Xiaohui
authors.initials: X
authors.lastname: Niu
authors.forename: Yuan
authors.initials: Y
authors.lastname: Li
authors.forename: Odion T
authors.initials: OT
authors.lastname: Binitie
authors.forename: G Douglas
authors.initials: GD
authors.lastname: Letson
authors.forename: David
authors.initials: D
authors.lastname: Cheong
mesh_terms: D000293:Adolescent; D000328:Adult; D018771:Arthralgia / Q000209:etiology; D001696:Biomechanical Phenomena; D002648:Child; D002804:Chondroblastoma / Q000150:complications / Q000175:diagnosis* / Q000534:rehabilitation / Q000601:surgery*; D004434:Early Ambulation; D004551:Elbow Joint / Q000503:physiopathology; D019317:Evidence-Based Medicine; D005260:Female; D005266:Femoral Neoplasms / Q000150:complications / Q000175:diagnosis* / Q000534:rehabilitation / Q000601:surgery*; D005270:Femur Head / Q000601:surgery*; D005271:Femur Head Necrosis / Q000209:etiology / Q000601:surgery; D005500:Follow-Up Studies; D006801:Humans; D007593:Joint Instability / Q000209:etiology; D008297:Male; D009364:Neoplasm Recurrence, Local / Q000473:pathology; D019637:Orthopedic Procedures / Q000379:methods*; D009999:Ossification, Heterotopic; D016059:Range of Motion, Articular; D012086:Reoperation; D016896:Treatment Outcome; D055815:Young Adult