Thursday, March 22, 2018

Reverse patient specific guides - what is the cost and are they worth it?

Accuracy of Patient-Specific Guided Implantation of the Glenoid Component in Reversed Shoulder Arthroplasty

These authors performed 32 reverse shoulder arthroplasties  using pre-operative 3D planning and 4 patient-specific guides in the preparation of the glenoid and in the positioning of the glenoid component.

Prior to surgery, patients underwent a preoperative standard 2-dimensional CT scan of the full scapula (0.5 mm thickness cuts). The scapula was was reconstructed into a 3D model. The patient-specific 3D model of the scapula was uploaded into an interactive surgical planning software program enabling the surgeon to virtually plan the position of the glenoid component preoperatively.

From this surgical plan, a patient-specific glenoid replica was created to allow the surgeon to visualize the optimal PSI guide position during the surgery. Additionally, four patient-specific polyamide guides were manufactured to control the position and orientation of baseplate component and screws intraoperatively.

The native glenoid was compared with the PSI bone model to ensure that all of the soft tissue was removed and that the PSI pin guide has a good fit on the glenoid.

Subsequently, the PSI guides were used to execute the pre-operative planning for glenoid component implantation. 

Baseplate version, inclination and entry point as well as angulation of the screws were compared to the pre-operative plan measured on CT by independent observers.

The mean deviation in baseplate version from the preoperative plan was 4.4° + 3.1° (range, 0.3°-13.7°), in baseplate inclination 5.0° + 4.2° (range, 0.1° to 14.5°) and in baseplate entry point 2.4 mm + 1.4 mm (range, 0.4° to 6.3°). The average screw superior-inferior angulation deviation for the superior screw was 2.8° + 2.6° (range, 0.0° - 10.1°) and 2.8 + 2.6° in the anteroposterior plane (range, 0.1° - 11.6°). For the inferior screw the superior-inferior angle deviation was 5.3° + 3.8°(range, 0.1°- 15.2°); the anteroposterior angle deviation was 4.1°+ 3.1°(range, 0.0° - 9.8°).

Comment: As with previous articles on CT-based preoperative planning and patient specific guides, the cost of the system and the cost of each application and the time necessary for the additional steps and the effect on clinical outcomes are not presented in this paper, which was authored by surgeons having consultancy agreements with the company making these devices (Zimmer). Furthermore, the authors do not suggest whether they recommend such a system for all reverse total shoulders or only for special ones. Finally, the training necessary to use such a system is not presented.

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