Arthroplasty Templating Guide
This OsiriX plugin has been designed for orthopedic surgeons. It allows the user to perform a filmless on-screen planification based upon an AP pelvis radiographic projection before the implantation of a hip athroplasty. The plugin, in its actual version, integrates templates for Medacta® hip arthroplasty implants. The plugin gives the surgeon full freedom to select and position the implants himself. The plugin will not in any way make any decisions or influence the choice or position of implants. The choice of implants and their positioning is totally left to the decision of the user. The designers of this plugin take no responsibility regarding any treatment choices linked to the use of this plugin.
Preferably, an AP radiograph centered on the pelvic symphysis is used and opened in the OsiriX viewer window.
When launched, the plugin will activate an interface window offering the sequential steps required to complete the preoperative templating. Steps are supposed to be used in sequence, but a backwards correction or modification is possible. To move from one step to the next, hit the Return key or click on the "Done" button.
This step requires the user to provide a calibration value. Since the projected image on an xRay film is usually larger than the patient, the size of the templates used to perform the planning need to be adjusted according to the calibration value. A standard value of 1.15 is set by default by the plugin. A different value can however be entered by the user at this stage if desired. The plugin also allows the user to trace a measuring line on the viewer window and then determine the calibration value by specifying the measuring line's real length.
This step requires the user to draw the horizontal axis. Any landmark such as the top of the iliac crest, teardrops, SI-joint, can be used. A second axis can optionally be drawn parallel to the femoral shaft to be addressed.
- Femoral landmarks
In this step the user defines the femoral landmarks by determining a height reference for the right and left femurs. Usually, the tips of the greater trochanters are used. This allows the plugin to calculate the leg-length discrepancy.
- Femur identification
This step allows the plugin to later produce a simulated post-op view, with implants in-situ and the hip reduced. The user draws a contour that grossly encircles the proximal femur to be adressed (metaphysis and proximal shaft area). It is not necessary to follow exactly the contours of the bone.
From the moment the femur is identified, an informational text box will be show, listing values such as leg length differences, lateral offset, implants choice. The user may move this listing, change its color or size by dragging or double-clicking on the text area.
This step provides a list of available implants for acetabular replacement. Choose one from the list and drag the chosen implant over the acetabulum to be replaced. Once the implant has been placed on the viewer window, the user can still move it (by dragging it) and rotate it (by pressing the option and command keys).
Rotation can also be done by using the left and right arrow keys (and / and * numpad keys), while the up and down arrow keys (and + and - numpad keys) will select a larger/smaller sized implant of the same family. This is also valid for the Stem implant.
This step provides a list of the available femoral components. Choose one from the list and drag it over the proximal femur. Position, rotation and implant size can be changed as described for the Cup phase.
When completing the step above, the plugin will reduce the hip by choosing the closest neck size (S, M, L, XL, XXL). The user may however select another neck size by dragging the proximal femur or by selecting a neck size directly on the interface menu.
The user may save a copy of the AP pelvis with the added templating data if he desires. The picture will be saved in the user's own OsiriX database.
The plugin icon can be placed on the viewer toolbar by right-clicking on the viewer toolbar and selecting customize toolbar. We have found it useful, in order to have the preop plan available in the operating room, to also save a copy as a jpg file (hit CMD-SHIFT-E) on a USB key or to simply print the image on paper, if possible using a color printer.