Evaluation of a computerized measurement technique for joint alignment before and during periacetabular osteotomy

Robert S. Armiger, Mehran Armand, Jyri Lepisto, Davneet Minhas, Kaj Tallroth, Simon C. Mears, Matthew D. Waites, Russell H. Taylor

Research output: Contribution to journalArticlepeer-review

28 Scopus citations


Periacetabular osteotomy (PAO) is intended to treat a painful dysplastic hip. Manual radiological angle measurements are used to diagnose dysplasia and to define regions of insufficient femoral head coverage for planning PAO. No method has yet been described that recalculates radiological angles as the acetabular bone fragment is reoriented. In this study, we propose a technique for computationally measuring the radiological angles from a joint contact surface model segmented from CT-scan data. Using oblique image slices, we selected the lateral and medial edge of the acetabulum lunate to form a closed, continuous, 3D curve. The joint surface is generated by interpolating the curve, and the radiological angles are measured directly using the 3D surface. This technique was evaluated using CT data for both normal and dysplastic hips. Manual measurements made by three independent observers showed minor discrepancies between the manual observations and the computerized technique. Inter-observer error (mean difference ± standard deviation) was 0.04 ± 3.53° for Observer 1; -0.46 ± 3.13° for Observer 2; and 0.42 ± 2.73° for Observer 3. The measurement error for the proposed computer method was -1.30 ± 3.30°. The computerized technique demonstrates sufficient accuracy compared to manual techniques, making it suitable for planning and intraoperative evaluation of radiological metrics for periacetabular osteotomy.

Original languageEnglish (US)
Pages (from-to)215-224
Number of pages10
JournalComputer Aided Surgery
Issue number4
StatePublished - Jul 2007


  • Acetabular coverage
  • Cartilage segmentation
  • Inter-observer error
  • Periacetabular osteotomy
  • Preoperative planning
  • Radiographic angles

ASJC Scopus subject areas

  • Surgery
  • Radiology Nuclear Medicine and imaging


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