Analysis of tibial component rotation following total knee arthroplasty using 3D high definition computed tomography.

Malrotation of the tibial component is associated with poor outcomes after total knee arthroplasty, yet the definition and evaluation of this problem remain controversial. Contributing factors to this controversy include inconsistent and cumbersome methods for measuring rotation, based upon transposed measurements from multiple computed tomography images. We developed and tested the reliability of a new, simple method for measuring tibial component rotation based upon a single, three-dimensional high definition, axial computed tomography image. Sixty individual knees after total knee arthroplasty were evaluated. The intra-reliability and inter-reliability both exceeded 0.9 whether the tibial component was made of titanium, cobalt-chrome or all-polyethylene. Based upon these findings we suggest that this technique be used for evaluating tibial component rotation in future studies.

An interactive teaching device simulating intussusception reduction.

Intussusception is relatively uncommon, occurring in 0.5 to 2.3 cases per 1,000 live births in the USA. Radiology residents, therefore, have few opportunities to participate in intussusception reduction during training, and practicing radiologists encounter it infrequently. Training is essential, as successful reduction avoids surgery. The judgment involved in reducing an intussusception is best gained with experience. We developed a training device that simulates fluoroscopic intussusception reduction with air. The device consists of a doll that contains a cylinder with similar stress and strain characteristics to the human colon. The trainee pumps air into the cylinder through a rectal tube using a standard hand-held air reduction pump. A sensor measures the pressure within the chamber and transmits readings to a computer, which displays images from actual intussusception reductions based on the pressure maintained within the device. A random component in the software gives the user a new experience each time and models uncertainties in the actual reduction process, including perforation. This intussusception reduction simulator can enhance resident education, giving residents the opportunity to practice this technique before employing it on a real patient. The simulator can also help practicing radiologists become more comfortable with intussusception air reduction.