3D reconstruction of cartilage geometry from multidetector CT data a good preoperative planning tool

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3D reconstructions of cartilage geometry from multidetector CT arthrographic data can be used as an effective preoperative surgical planning tool for patients with hip pain, according to a study in the May issue of Radiology.

According to Bryce Allen, MD, Department of Orthopedics, Harold K. Dunn Orthopedic Research Laboratory, University of Utah, and colleagues, the accurate quantification of cartilage thickness is a “critical factor” to address when deciding on the best treatment for patients with hip pain.

Because of the geometrically complex nature of the hip, visualization of the cartilage thickness relative to the underlying three-dimensional (3D) morphologic characteristics could, the authors write, prove essential to the diagnosis and treatment of hip joint cartilage pathologic anomaly. It could be useful, then, to quantify cartilage thickness by using CT arthrography in patients who complain of pain that may be related to osteoarthritis but do not have direct evidence of radiographic thinning or localized defect.

While CT arthrography has been shown to be more accurate than MR arthrography for estimating cartilage thickness in the hip, the accuracy of measuring hip cartilage thickness from 3D reconstructions of multidetector CT arthrographic image data hasn’t been assessed, the authors point out. The purpose of their study was to quantify the accuracy of the hip cartilage thickness estimated from 3D surfaces, generated by segmenting multidetector CT arthrograms, by using direct physical measurements of cartilage thickness as the reference standard.

The researchers obtained four fresh-frozen hip cadavers from two male donors for purposes of the study. Six holes were drilled perpendicular to the cartilage of four cadaveric acetabula. The hip capsules were surgically closed, injected with contrast material and scanned by using multidetector CT.

After scanning, 5.3-mm cores were harvested concentrically at each drill hole and cartilage thickness was measured with a microscope. Cartilage was reconstructed in 3D by using commercial software. Segmentations were repeated by two authors. Reconstructed cartilage thickness was determined by using a published algorithm.

The authors' results demonstrated that cetabular cartilage thickness can be estimated to approximately ±0.5 mm of the true value with 95% tolerance when cartilage geometry is semiautomatically reconstructed from multidetector CT arthrographic data by using commercial segmentation software. So, assuming that accuracy of plus or minus 0.5 mm is sufficient, reconstruction of acetabular cartilage geometry from multidetector CT arthrographic data could potentially be used as a preoperative planning tool.