Reliability of computer-assisted periacetabular osteotomy using a minimally invasive approach

  • Sepp De RaedtEmail author
  • Inger Mechlenburg
  • Maiken Stilling
  • Lone Rømer
  • Ryan J. Murphy
  • Mehran Armand
  • Jyri Lepistö
  • Marleen de Bruijne
  • Kjeld Søballe
Original Article



Periacetabular osteotomy (PAO) is the treatment of choice for younger patients with developmental hip dysplasia. The procedure aims to normalize the joint configuration, reduce the peak-pressure, and delay the development of osteoarthritis. The procedure is technically demanding and no previous study has validated the use of computer navigation with a minimally invasive transsartorial approach.


Computer-assisted PAO was performed on ten patients. Patients underwent pre- and postoperative computed tomography (CT) scanning with a standardized protocol. Preoperative preparation consisted of outlining the lunate surface and segmenting the pelvis and femur from CT data. The Biomechanical Guidance System was used intra-operatively to automatically calculate diagnostic angles and peak-pressure measurements. Manual diagnostic angle measurements were performed based on pre- and postoperative CT. Differences in angle measurements were investigated with summary statistics, intraclass correlation coefficient, and Bland–Altman plots. The percentage postoperative change in peak-pressure was calculated.


Intra-operative reported angle measurements show a good agreement with manual angle measurements with intraclass correlation coefficient between 0.94 and 0.98. Computer navigation reported angle measurements were significantly higher for the posterior sector angle (\(1.65^{\circ }\), \(p=0.001\)) and the acetabular anteversion angle (\(1.24^{\circ }\), \(p=0.004\)). No significant difference was found for the center-edge (\(p=0.056\)), acetabular index (\(p=0.212\)), and anterior sector angle (\(p=0.452\)). Peak-pressure after PAO decreased by a mean of 13% and was significantly different (\(p=0.008\)).


We found that computer navigation can reliably be used with a minimally invasive transsartorial approach PAO. Angle measurements generally agree with manual measurements and peak-pressure was shown to decrease postoperatively. With further development, the system will become a valuable tool in the operating room for both experienced and less experienced surgeons performing PAO. Further studies with a larger cohort and follow-up will allow us to investigate the association with peak-pressure and postoperative outcome and pave the way to clinical introduction.


Hip dysplasia Computer-assisted surgery Surgical Navigation Intra-operative angle measurements 



This study was funded by the Danish Rheumatism Association (Gigtforeningen). We would like to acknowledge Netherlands Organisation for Scientific Research (NWO). The BGS was previously developed under grant number R01EB006839 from National Institutes of Health National Institute of Biomedical Imaging and Bioengineering.

Compliance with ethical standards

Conflict of interest

The authors declare that they have no conflict of interest.

Ethical approval

All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Declaration of Helsinki and its later amendments or comparable ethical standards.


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Copyright information

© CARS 2018

Authors and Affiliations

  • Sepp De Raedt
    • 1
    Email author
  • Inger Mechlenburg
    • 1
    • 2
  • Maiken Stilling
    • 1
    • 2
  • Lone Rømer
    • 3
  • Ryan J. Murphy
    • 4
  • Mehran Armand
    • 4
    • 5
  • Jyri Lepistö
    • 6
  • Marleen de Bruijne
    • 7
    • 8
  • Kjeld Søballe
    • 1
  1. 1.Department of OrthopaedicsAarhus University HospitalAarhus CDenmark
  2. 2.Department of Clinical MedicineAarhus UniversityAarhus NDenmark
  3. 3.Department of RadiologyAarhus University HospitalAarhus CDenmark
  4. 4.Research and Exploratory Development DepartmentJohns Hopkins University Applied Physics LaboratoryLaurelUSA
  5. 5.Department of Mechanical EngineeringJohns Hopkins UniversityBaltimoreUSA
  6. 6.ORTON Orthopaedic HospitalHelsinkiFinland
  7. 7.Departments of Radiology and Medical InformaticsBiomedical Imaging Group RotterdamErasmus MC RotterdamThe Netherlands
  8. 8.Department of Computer ScienceUniversity of CopenhagenCopenhagenDenmark

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