A patient-specific guide for optimizing custom-made glenoid implantation in cases of severe glenoid defects: an in vitro study

Background: Glenoid component and screw malpositioning in cases of severe glenoid defects might result in complications. We examined the efficacy of a surgical method to treat severe glenoid defects, including a custom-made glenoid component and accurate screw positioning, using a patient-specific positioning guide. Methods: Glenoid defects were created in 10 cadaveric shoulders. Computed tomography images were used to plan reversed shoulder arthroplasty and design patient-specific glenoid components. A patient-specific positioning guide was designed for 5 specimens. The remaining 5 specimens were implanted without the guide. Computed tomography images were used to determine the postoperative glenoid component and screw positions. Differences from the preoperatively planned implant and screw positions were calculated. Results: The patient-specific positioning guide significantly reduced the angular deviations from the planned glenoid implant positioning (P<.05) and also significantly improved the positioning of the screws (P<.001). In the group without the guide, the average total intraosseous screw length was 52% of the ideal preoperatively planned length compared with 89% for the group with the guide. A strong correlation (r = -0.85) was found between the orientation of the implant and the postoperative total intraosseous screw length. Conclusions: A patient-specific positioning guide significantly improves the position and fixation of a custom-made glenoid component in cases of severe glenoid defects. Level of evidence: Basic Science Study, Surgical Technique, Cadaver Model. (C) 2016 Journal of Shoulder and Elbow Surgery Board of Trustees.