Reliability of a novel method to assess orientation of the ACL in healthy and ACL reconstructed knees: A pilot study for future applications in orthopaedic surgery — The Association Specialists
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Reliability of a novel method to assess orientation of the ACL in healthy and ACL reconstructed knees: A pilot study for future applications in orthopaedic surgery (436)

Samuel Grasso 1 2 , Corey Scholes 1 , Joe Lynch 1 , Qing Li 2 , Brett Fritsch 1 , David Parker 1 , Myles Coolican
  1. Sydney Orthopaedic Research Institute, Chatswood, NSW, Australia
  2. School of Aerospace, Mechanical and Mechatronic Engineering, The University of Sydney, Sydney, NSW, Australia

Background

The ability to generate 3-dimensional computer models from MRI to assess graft orientation following arthroscopic reconstruction of the anterior cruciate ligament opens numerous opportunities for surgery. Although previous MRI-based methods have been described, they are limited by a reliance on anatomical landmarks to perform key measurements and a lack of reliability data. The purposes of this paper are to i) introduce a new method for assessing ACL graft orientation using MRI, ii) assess the intra and inter-observer reliability of this new approach and iii) report preliminary comparisons between ACL-reconstructed and native knees  with respect to ACL orientation.

Methods

Patients that underwent an arthroscopic ACL reconstruction (N = 3) were matched to healthy controls (N = 3) and imaged with 3.0T MRI. Scans were manually segmented and 3D models of the femur, tibia and ACL were created (ScanIP, Simpleware). A global reference system was then calculated by finding the centre of tibial plateau in 3 planee and the orientation of the ACL was determined mathematically. This was  repeated by 3 independent observers to determine intra- and inter-observer reliability.

Results

Test-retest differences in the sagittal plane ranged between -1.6 - 2.0o and  -0.3 – 2.9o in the coronal plane. Typical error was 1.0o across the two patient groups in both sagittal and coronal planes. The difference between ACL graft and native ACL orientation was 3.0±1.7o in the sagittal plane and 5.6±5.4o in the coronal plane.

Conclusion

These results agree with reported orientation data [1, 2], while the demonstrated ability to detect differences between reconstructed and native ACL orientation that exceed the measurement error suggests that this method of calculating ACL orientation is reproducible.  While further work is required to confirm reproducibility in a larger sample, the results indicate a potential for use in patient-specific surgical planning in knee reconstruction.


  1. Scanlan, S.F., et al., Variations in the three-dimensional location and orientation of the ACL in healthy subjects relative to patients after transtibial ACL reconstruction. Journal of Orthopaedic Research, 2012. 30(6): p. 910-918.
  2. Abebe, E.S., et al., The effect of femoral tunnel placement on ACL graft orientation and length during in vivo knee flexion. Journal of Biomechanics, 2011. 44(10): p. 1914-1920