title: Patellar fractures after total knee replacement.
abstract: OBJECTIVE
  The objective of our study was to describe the patterns of patellar fracture after total knee replacement and assess their clinical significance.
  
  
  METHODS
  A retrospective review of patellar fractures after total knee replacement was performed. Seventeen cases were identified over a 10-year period. Radiographs, radiology reports, medical records, and operative notes were reviewed and analyzed. The clinical analysis included the time to fracture, the patient's symptoms and signs, whether the extensor mechanism was disrupted, and the treatment administered for the fracture. The radiographic analysis included fracture pattern, displacement, patellar position, presence of patellar osteonecrosis, and presence of soft-tissue abnormality.
  
  
  RESULTS
  The incidence of patellar fractures after total knee replacement was 1.14%. The mean time from total knee replacement to patellar fracture was 17.5 months. Nine fractures were asymptomatic and identified on routine follow-up radiographs. The patterns of fracture were diverse: Transverse (n = 6), comminuted (n = 2), vertical (n = 5), and avulsion (n =4) fractures were seen. Thirteen fractures were displaced. Patellar osteonecrosis was suspected in four fractures, and three fractures were associated with disruption of the quadriceps tendons. Thirteen fractures were treated nonoperatively, and four were treated surgically.
  
  
  CONCLUSIONS
  Patellar fractures are an uncommon, but important, complication after total knee replacement. Radiologists should be familiar with the imaging features of these fractures and their clinical significance.
authors.affiliation: Department of Radiology, The University of Iowa Hospital and Clinics, Iowa City, IA 52242, USA. ka1000@catholic.ac.kr
authors.forename: Kyung Ah
authors.initials: KA
authors.lastname: Chun
authors.forename: Kenjirou
authors.initials: K
authors.lastname: Ohashi
authors.forename: D Lee
authors.initials: DL
authors.lastname: Bennett
authors.forename: Georges Y
authors.initials: GY
authors.lastname: El-Khoury
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D019645:Arthroplasty, Replacement, Knee; D005260:Female; D050723:Fractures, Bone / Q000000981:diagnostic imaging* / Q000453:epidemiology / Q000209:etiology; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D010329:Patella / Q000000981:diagnostic imaging*; D011183:Postoperative Complications / Q000000981:diagnostic imaging*; D011859:Radiography; D012189:Retrospective Studies