Glenoid Preparation in Reverse Shoulder Arthroplasty: Robotic-Arm Assisted Preparation Compared to Manual Preparation and Patient-specific Guides.

Abstract

Background: Precise and accurate glenoid preparation is important for the success of shoulder arthroplasty. Despite advancements in preoperative planning software and enabling technologies, most surgeons execute the procedure manually. Patient-specific instrumentation (PSI) facilitates accurate glenoid guide pin placement for cannulated reaming; however, few commercially available systems offer depth of reaming control. Robotic-arm assisted bone preparation has gained popularity in knee and hip arthroplasty, but at the present time there is limited information available on the use of robotics for shoulder arthroplasty. The purpose of this study was to compare glenoid preparation and final implant position using three techniques: manual, manual assisted with PSI, and robotic arm assisted bone preparation.

Methods: Six shoulder surgeons participated in this study utilizing three preparation techniques: (1) manual reaming, (2) manual reaming over a pin inserted using PSI, and (3) preparation using a robotic arm assist with an end-effector burr and haptic boundaries. Each surgeon randomly conducted each technique on 2 separate Bone Matrix glenoid models, for a total of 36 glenoid models tested. To compare the techniques, the final prepared Bone Matrix models underwent a CT scan with 3D virtual model generation. The prepared 3D virtual glenoid models were then compared to the preoperatively planned models. Parameters compared included deviations in version, inclination, anterior-posterior (AP) translation, superior-inferior (SI) translation, and depth of reaming.

Results: Regarding glenoid version with values reported as mean deviations from the preoperative plan, the robotic-assisted technique (1°) was significantly better than manual (9°, p<0.001) and PSI (4°, p<0.001) techniques at executing the preoperative plan. Regarding inclination, the robotic-assisted technique (2°) was significantly better than manual (9°, p=0.003) but not significantly different than PSI (3°, p=0.211). The robotic-arm technique, with AP translation, resulted in significantly lower mean displacements (0.3mm) than the manual technique (2mm, p=0.001) and the PSI technique (2mm, p=0.002). With SI translation, the robotic-arm assisted technique (0.7mm) resulted in significantly lower mean displacements as compared to the manual (2mm, p=0.007) and PSI (1mm, p=0.011). The robotic-arm assisted technique (0.4 mm) did not result in significantly lower mean depth of reaming displacements compared to the manual technique (0.8 mm, p=0.051) but did when compared to PSI (0.8 mm, p=0.036).

Conclusions: Glenoid preparation using a robotic arm with an end-effector burr and haptic boundaries was significantly better in its ability to execute a preoperatively planned implant position than manual preparation in 4 of 5 glenoid metrics examined and was significantly better than PSI in 4 of 5 glenoid metrics.