title: Measurement of leg length discrepancy after total hip arthroplasty. The reliability of a plain radiographic method compared to CT-scanogram.
abstract: OBJECTIVE
  To measure the interobserver reliability and intraobserver reproducibility of post total hip arthroplasty (THA) leg length discrepancy (LLD) measurement on radiographs as well as to evaluate its accuracy by comparing it with LLD measurement on computed tomographic scanogram (CT-scanogram).
  
  
  METHODS
  In this prospective study, postoperative LLD measurements in ten THA patients were made by four observers on anteroposterior radiographs of the pelvis (inter-teardrop line to the tip of lesser trochanter) and compared to LLD measurements made on CT-scanogram scout views of the lower limb. Two observers repeated the LLD measurements on radiographs 8 weeks after the first measurements. The interobserver reliability of the LLD measurement on plain radiographs was evaluated by comparing the measurements of the four observers and the intraobserver reproducibility by comparing the two repeated measurements made by the two observers.
  
  
  RESULTS
  We found excellent interobserver reliability (mean ICC 0.83) and intraobserver reproducibility (ICC 0.90 and 0.88) of the LLD measurements on plain radiographs. There was a moderate to excellent agreement, but with wide variation of measurements among the four observers, when plain radiographic measurement was compared with CT-scanogram (ICC 0.58, 0.60, 0.71, and 0.82).
  
  
  CONCLUSIONS
  Despite the excellent interobserver reliability and intraobserver reproducibility of LLD measurement on radiographs, clinicians should be aware of its limited accuracy when compared to CT-scanogram.
authors.affiliation: Department of Orthopaedics, Sundsvall Hospital, Sundsvall, Sweden. martin.kjellberg@lvn.se
authors.forename: Martin
authors.initials: M
authors.lastname: Kjellberg
authors.forename: Bariq
authors.initials: B
authors.lastname: Al-Amiry
authors.forename: Erling
authors.initials: E
authors.lastname: Englund
authors.forename: Göran O
authors.initials: GO
authors.lastname: Sjödén
authors.forename: Arkan S
authors.initials: AS
authors.lastname: Sayed-Noor
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects*; D005260:Female; D006801:Humans; D007870:Leg Length Inequality / Q000000981:diagnostic imaging* / Q000209:etiology*; D008297:Male; D015588:Observer Variation; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed; D014962:X-Ray Film