title: Limited range of motion caused by heterotopic ossifications in primary total knee arthroplasty: a retrospective study of 27/191 cases.
abstract: BACKGROUND
  Heterotopic ossification (HO) following primary total knee arthroplasty is a rare complication and may be symptomatic if massive enough. Especially the range of motion (ROM) is essential for the function and durability of the implant. The aim of the study was to evaluate the influence of HO on ROM using clinical and radiological parameters.
  
  
  METHODS
  We reviewed 191 primary total knee arthroplasties according to the clinical preoperative and postoperative parameters of the Knee Society Score with special interest paid to the ROM. Standardized radiographs were taken at three levels and the implant position compared. The patients were divided into group 1 (with HO) and group 2 (without HO). The clinical and radiological parameters were compared.
  
  
  RESULTS
  We found an incidence of HO in 14.1% (n = 27). Group 1 showed a decreased ROM postoperatively (p = 0.003) and worse flexion contracture (p = 0.04) compared with group 2. The evaluated radiological parameters showed no significant difference between the two groups.
  
  
  CONCLUSIONS
  We found a significant limitation of ROM because of HO in our study. We found no correlation between HO and component alignment or component position. Local irritation has to be considered the main reason for limited ROM.
authors.affiliation: Department of Orthopaedic Surgery, University of Essen, Pattbergstr. 1-3, 45239 Essen, Germany. thomas_sterner@yahoo.de
authors.forename: T
authors.initials: T
authors.lastname: Sterner
authors.forename: G
authors.initials: G
authors.lastname: Saxler
authors.forename: B
authors.initials: B
authors.lastname: Barden
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019645:Arthroplasty, Replacement, Knee / Q000009:adverse effects*; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000000981:diagnostic imaging / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D009119:Muscle Contraction / Q000502:physiology; D018482:Muscle, Skeletal / Q000503:physiopathology; D009999:Ossification, Heterotopic / Q000000981:diagnostic imaging / Q000209:etiology* / Q000503:physiopathology*; D011859:Radiography; D016059:Range of Motion, Articular / Q000502:physiology*; D012189:Retrospective Studies