title: Variability associated with assessing changes in position of a canine uncemented femoral stem prosthesis.
abstract: OBJECTIVE
  Evaluate variability associated with assessing changes in the position of uncemented femoral stems.
  
  
  METHODS
  Stem level, canal fill, stem angle, and version angle were measured on craniocaudal horizontal beam (CCHB) and open leg lateral (OLL) radiographic projections of the femur of 20 dogs that had uncemented total hip replacement. Intraobserver and interobserver repeatability were determined on immediate postoperative (PO) images. Differences in position were calculated between the first (3 months - R1) and second (6 months - R2) re-evaluation (R1-R2) time points, and between PO and R1.
  
  
  RESULTS
  The measurement process was very repeatable. For R1-R2, the stem appeared to subside 0.8 ± 1.4 mm for measurements based on the greater trochanter on the CCHB images, but there was a wide range (-3.9 to 2 mm; positive values indicate proximad movement). Measurements based on the intertrochanteric crest on the OLL images had the same mean, and also a wide range (-4.4 to 2.1 mm; negative values indicate proximad movement). For PO-R1, the stem appeared to subside 1.8 ± 2.0 mm (CCHB, based on the greater trochanter, range -7.7 to 2.2 mm), 1.6 ± 1.5 mm (CCHB, based on the intertrochanteric crest, range -0.7 to 4.3 mm); and 2.1 ± 2.1 mm (OLL, based on the intertrochanteric crest, range -1.6 to 6.8 mm).
  
  
  CONCLUSIONS
  The position of a stable stem can appear different on subsequent re-evaluations, but this may be due to variability associated with inconsistency of positioning of the patient and limb.
  
  
  CONCLUSIONS
  Documenting subsidence in individual patients should not rely on calculations based on a single measurement.
authors.forename: H M
authors.initials: HM
authors.lastname: Korani
authors.forename: D J
authors.initials: DJ
authors.lastname: Marcellin-Little
authors.affiliation: Prof. Simon Roe, North Carolina State University, College of Veterinary Medicine, Department of Clinical Sciences, 1052 William Moore Drive, Raleigh, NC 27606, United States, Phone: +1 919 513 6334, Fax: +1 919 513 6336, E-mail: Simon_Roe@ncsu.edu.
authors.forename: S C
authors.initials: SC
authors.lastname: Roe
mesh_terms: D000818:Animals; D019644:Arthroplasty, Replacement, Hip / Q000662:veterinary*; D004283:Dog Diseases / Q000601:surgery*; D004285:Dogs; D006622:Hip Prosthesis / Q000662:veterinary*; D013314:Stress, Mechanical
keywords: Uncemented total hip replacement; measurements; stem level; variability