title: Variability of magnification on digital pelvic radiographs from patients with fractures of the femoral neck - a retrospective audit.
abstract: OBJECTIVE
  To determine the variability in magnification of radiographs in an emergency setting.
  
  
  METHODS
  The retrospective study was conducted at Aga Khan University Hospital, Karachi, and comprised records of patients who underwent Austin Moore hemiarthroplasty over a two-year periodfrom 1st January 2006 to 31st December 2007. Magnification factor was determined using measurements obtained from preoperative and postoperative radiographs and comparing them with the actual size of implant used. Intra-observer and inter-observer reliability of measurements were calculated. SPSS 19 was used for data analysis.
  
  
  RESULTS
  Of the 63 patients studied, 25(39.7%) were males and 38(60.3%) were females with an overall mean age of 69.8±12 years. The mean implant size used was 46mm±4mm. Preoperative magnification was 8%±4%, resulting in an overestimation of implant size by 4.2±2.3mm. Postoperative magnification was 13%±4%, resulting in an overestimation of 5.9±1.9mm.Prediction using fixed scaling of 15% resulted in a correct estimation of implant size for only 15(24%) patients.
  
  
  CONCLUSIONS
  Digital radiographs of the pelvis exhibited variable amount of magnification along with an inconsistency in magnification on repeat examination.
authors.affiliation: Section of Orthopaedics, Department of Surgery, Aga Khan University Hospital, Karachi.
authors.forename: Akbar
authors.initials: A
authors.lastname: Zubairi
authors.affiliation: Section of Orthopaedics, Department of Surgery, Aga Khan University Hospital, Karachi.
authors.forename: Tashfeen
authors.initials: T
authors.lastname: Ahmad
keywords: Total hip replacement, Femoralneck fractures, Radiographic magnification.