title: Focal osteolysis in total hip replacement: CT findings.
abstract: OBJECTIVE
  To describe the CT findings of focal osteolysis following total hip replacement (THR).
  
  
  METHODS
  CT imaging features of 30 THRs with focal osteolysis visualized on follow-up radiographs and undertaken revision surgery were reviewed. On CT scans, the shape and anatomic location of osteolytic lesions was recorded, as well as their size and number. The presence of cortical disruption or expansion, liner wear, metallosis, and heterotopic ossification was also noted. In each case, surgical and histologic findings were correlated with imaging features.
  
  
  RESULTS
  Focal osteolysis was common in the superior part of acetabular and femoral components. CT features of focal osteolysis were multiple, expansile, oval, or round radiolucencies, which were conglomerated into multilobular shape. The cortex adjacent to the osteolytic lesions revealed irregular thinning and discontinuity (29/30, 97%) accompanied by a few tiny fragments. Liner wear was common (27/30, 90%), and metallosis was frequent (8/30, 26.7%). Pathologic results were foreign body reaction in 20 patients, chronic inflammation in eight, and fibrosis in two.
  
  
  CONCLUSIONS
  CT appearances of focal osteolysis following THR are multilobulated lucent areas with expansile periosteal reaction and cortical abnormalities, mimicking infection or tumor. We consider that CT is useful for the prediction and assessment of the nature and extent of focal osteolysis.
authors.affiliation: Department of Diagnostic Radiology, KyungHee University Medical Center, 1 Heokidong Dongdaemun-ku, 130-702 Seoul, Korea.
authors.forename: Ji Seon
authors.initials: JS
authors.lastname: Park
authors.forename: Kyung Nam
authors.initials: KN
authors.lastname: Ryu
authors.forename: Hoon Pyo
authors.initials: HP
authors.lastname: Hong
authors.forename: Yong Koo
authors.initials: YK
authors.lastname: Park
authors.forename: Young Soo
authors.initials: YS
authors.lastname: Chun
authors.forename: Myung Chul
authors.initials: MC
authors.lastname: Yoo
mesh_terms: D000077:Acetabulum / Q000000981:diagnostic imaging / Q000473:pathology; D000328:Adult; D000368:Aged; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects; D005260:Female; D005269:Femur / Q000000981:diagnostic imaging / Q000473:pathology; D005500:Follow-Up Studies; D005549:Foreign-Body Reaction / Q000000981:diagnostic imaging / Q000209:etiology; D006622:Hip Prosthesis; D006801:Humans; D008297:Male; D008875:Middle Aged; D010014:Osteolysis / Q000000981:diagnostic imaging*; D011475:Prosthesis Failure; D014057:Tomography, X-Ray Computed; D016896:Treatment Outcome