Abstract:
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Purpose: The current radiological assessment of total knee arthroplasty (TKA) alignment using plain radiographs is widely accepted as inadequate in providing essential information about alignment in the coronal, sagittal and axial planes. We describe a new CT method that fully defines the mechanical axis and analyses all the relative alignment characteristics (femoral varus/valgus/flexion/extension/rotation, tibial varus/valgus/rotation/posterior slope and femoral-tibial coupling) of a TKA.
Methods and Materials: A GE Light Speed multislice CT scanner performed a highspeed helical scan from the acetabular roof to the talus in 100 patients following TKA. The knees were scanned in a supine position with the legs in a neutral position. Scan time was 45 seconds and calculated radiation dose was 2.7mSv. The images were reformatted in coronal, sagittal and axial planes, and femoral and tibial component alignment measured.
Results: The technique has a low intraobserver error rate of 9%. The anatomical axis was defined with a 0.5mm error and an overall accuracy of 3mm in a three-dimensional plane, as determined against an independent FARO arm technique. The CT analysis of 100 patients shows normal tibial baseplate rotation to be 8-12 degrees from the tibial tuberosity
Conclusion: The Perth CT protocol for total knee arthroplasty provides the only currently available technique for measuring all the alignment characteristics required to fully assess the quality of a knee replacement. It will provide the radiologist and orthopaedic surgeon with quantitative information in assessing both the painful and malaligned knee replacement as well as being important in the planning of revision surgery.
Questions about this event email: rosiegscott50@hotmail.com
Scott MBBS, R,
The Perth CT Protocol for Assessment of Total Knee Replacement. Radiological Society of North America 2003 Scientific Assembly and Annual Meeting, November 30 - December 5, 2003 ,Chicago IL.
http://archive.rsna.org/2003/3104378.html
