title: Evaluation of a new leg length measurement algorithm in hip arthroplasty.
abstract: Leg length inequality after hip arthroplasty is a major source of patient dissatisfaction and dysfunction. Despite numerous reported methods to intraoperatively determine leg length change, it remains a challenge. We developed a reliable and reproducible method to measure leg length change using surgical navigation. The method measures the change in position of the femur relative to the pelvis and the pelvic coordinate system without the need to establish a femoral coordinate system. We replaced 112 hips in 107 patients using the new leg length measurement algorithm. Leg length change measured at surgery was compared with leg length change as measured on magnification-corrected pre- and postoperative radiographs. Compared with radiographically measured leg length change, the leg length changes measured intraoperatively had a mean difference of -0.5 +/- 1.77 mm (range, -5-3.9 mm). We found no difference between radiographic data and navigation data. Leg length change measured using surgical navigation, measuring the change in position of the femur relative to the pelvic coordinate system, without establishing a femoral coordinate system is easy and reliable.
authors.affiliation: Center for Computer Assisted and Reconstructive Surgery, New England Baptist Hospital, Boston, MA, USA. tecker@caregroup.harvard.edu
authors.forename: Stephen B
authors.initials: SB
authors.lastname: Murphy
authors.forename: Timo M
authors.initials: TM
authors.lastname: Ecker
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D019644:Arthroplasty, Replacement, Hip / Q000379:methods*; D005260:Female; D005269:Femur / Q000000981:diagnostic imaging / Q000473:pathology; D006621:Hip Joint / Q000000981:diagnostic imaging / Q000473:pathology* / Q000601:surgery; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D007866:Leg / Q000000981:diagnostic imaging / Q000473:pathology*; D007870:Leg Length Inequality / Q000175:diagnosis* / Q000517:prevention & control; D008297:Male; D008875:Middle Aged; D019060:Minimally Invasive Surgical Procedures; D016343:Monitoring, Intraoperative / Q000379:methods; D010384:Pelvic Bones / Q000000981:diagnostic imaging / Q000473:pathology; D011859:Radiography; D015203:Reproducibility of Results