title: Magnetic resonance imaging appearances following hindquarter amputation for pelvic musculoskeletal malignancy.
abstract: OBJECTIVE
  To describe our experience of the magnetic resonance imaging (MRI) appearances after hindquarter amputation, focusing on the normal pattern of time-related changes in signal intensity within the amputation flap and appearances of local disease recurrence.
  
  
  METHODS
  This was a retrospective review of the records of patients identified on our orthopaedic oncology database who had undergone hindquarter amputation at our centre. Examinations were divided into one group consisting of 'normal' postoperative findings and another group demonstrating local recurrence. 'Normal' postoperative findings were assessed for signal intensity, morphology and presence of the 'muscle texture sign' within the amputation flap. Examinations were grouped according to time from surgery. Examinations demonstrating local recurrence were assessed for site, signal intensity, morphology and axial dimensions of recurrent tumour. Comparison was made to pre-operative imaging.
  
  
  RESULTS
  Thirty-five patients with postoperative MR images were identified. Seventy-seven examinations were reviewed (range 1-18 per patient). The 'normal group' comprised 18 patients (seven female, 11 male, mean age 44 years, range 16-75 years), with 47 examinations reviewed. The 'muscle texture sign' was preserved in all examinations in this group. Up to 6 months after surgery, 100% (10) of examinations showed hyperintense T2- and short-tau inversion recovery (STIR-weighted) signals within the muscle flap, indicating oedema. Only after 4 years was the muscle flap signal isointense in all cases (13). Up to 6 months after surgery, 50% (5 of 10) of examinations demonstrated flap swelling, but after 1 year, 100% (28) showed atrophy. Twenty percent (2 of 10) of examinations 0-6 months from surgery showed hyperintense T1-weighted signal within the muscle flap, consistent with fatty infiltration, but after 2 years, 100% (20) showed a hyperintense T1-weighted signal. The 'local recurrence' group comprised 20 patients (six female, 14 male, mean age 45.7 years, range 14-69 years), with 30 examinations demonstrating recurrent disease or metastasis. There were 23 recurrent tumours, of which 43% (10) were in the muscle component of the amputation flap, 13% (3 of 23) were in subcutaneous tissues of the flap, 13% (3 of 23) were at the posterior margin of the bone resection and 13% (3 of 23) were paraspinal. All recurrent tumours demonstrated hyperintense T2 and STIR signals. The signal intensity pattern of recurrence closely followed that of the original tumour. The 'muscle texture sign' was absent in all examinations demonstrating recurrence in muscle flap.
  
  
  CONCLUSIONS
  A pattern of time-related signal intensity and morphological changes is observed within normal hindquarter amputation flaps on MRI. Recurrent disease is most likely to occur within the muscle flap, typically of high T2-weighted signal intensity and characteristically follows the signal pattern of the original tumour.
authors.affiliation: Department of Radiology, The Royal Orthopaedic Hospital Foundation Trust, Bristol Road South, Northfield, Birmingham B312AP, UK. nkotnis@hotmail.com
authors.forename: Nikhil A
authors.initials: NA
authors.lastname: Kotnis
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Grimer
authors.forename: A M
authors.initials: AM
authors.lastname: Davies
authors.forename: Steven L J
authors.initials: SL
authors.lastname: James
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000672:Amputation Stumps / Q000473:pathology*; D001859:Bone Neoplasms / Q000473:pathology* / Q000601:surgery*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D019042:Muscle Neoplasms / Q000473:pathology* / Q000601:surgery*; D010386:Pelvic Neoplasms / Q000473:pathology* / Q000601:surgery*; D011379:Prognosis; D012189:Retrospective Studies; D016896:Treatment Outcome; D055815:Young Adult
references.citation: Am J Surg. 1989 Nov;158(5):404-8
references.pmid: 2817220
references.citation: Cancer Imaging. 2008 Feb 27;8:8-18
references.pmid: 18331968
references.citation: AJR Am J Roentgenol. 1985 Dec;145(6):1233-9
references.pmid: 3877428
references.citation: J Bone Joint Surg Br. 2008 Apr;90(4):484-7
references.pmid: 18378924
references.citation: Semin Surg Oncol. 1999 Jul-Aug;17(1):83-7
references.pmid: 10402642
references.citation: AJR Am J Roentgenol. 1995 Apr;164(4):989-93
references.pmid: 7726063
references.citation: Radiology. 1993 Nov;189(2):511-5
references.pmid: 8210383
references.citation: Magn Reson Imaging. 1990;8(6):771-7
references.pmid: 2266804
references.citation: Radiology. 1992 Jun;183(3):845-8
references.pmid: 1584945
references.citation: Radiology. 1987 Jul;164(1):243-5
references.pmid: 3588913
references.citation: AJR Am J Roentgenol. 2006 Sep;187(3):800-6
references.pmid: 16928948
references.citation: Radiology. 1989 Dec;173(3):755-8
references.pmid: 2813782
references.citation: Br J Radiol. 1992 Dec;65(780):1093-6
references.pmid: 1286416
references.citation: Magn Reson Imaging Clin N Am. 1995 Nov;3(4):695-712
references.pmid: 8564690
references.citation: Am J Surg. 1983 Feb;145(2):273-7
references.pmid: 6297327
references.citation: Ann Plast Surg. 1997 Jan;38(1):23-8
references.pmid: 9015535
references.citation: J Clin Oncol. 1985 Mar;3(3):353-66
references.pmid: 3973646