Monday, January 19, 2015

Computer-assisted reverse total shoulder baseplate placement in model scapulae

Comparing conventional and computer-assisted surgery baseplate and screw placement in reverse shoulder arthroplasty.

These authors used a custom-designed system allowing computed tomography-based preoperative planning, intraoperative navigation, and postoperative evaluation.  Each of five surgeon performed 3 computer-assisted and 3 conventional simulated procedures on 3-dimensional CT reconstructed cadaveric shoulders. The 3-dimensional CT reconstructed postoperative units were digitally matched to a preoperative model for evaluation of entry points, end points, and angulations of screws and baseplate.

They found no difference in accuracy or precision of screws or baseplate entry points. Accuracy and precision were improved with the use of navigation for end points and angulations of 3 of the four screws. Navigated baseplate end point precision (but not the accuracy) was significantly improved.

The authors point out that the study was performed in a highly controlled in vitro environment with use of plastic and foam models representing a shoulder without exposure issues and without any significant bone deformity or bone loss.

These results relate to a specific baseplate system. Other designs have parallel screws, so screw angulation is not an issue. Screw length is usually not an issue unless it is excessive.

In our practice we rarely obtain CT scans before reverse total shoulder arthroplasty except in cases of severe deformity or bone loss. This research did not include such pathoanatomy.

From this paper we do not know the additional cost or time necessary for the CT scans, the preoperative planning, or the making of the navigation tools. From the information presented it is not possible to determine the value (benefit/cost) of such a system or its utility in actual surgery.


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