Current concepts in patient specific implants for reverse shoulder arthroplasty

Abstract

In light of the increasing prevalence of reverse shoulder arthroplasty, it has become clear that standard off the shelf implants provide insufficient glenoid fixation in challenging primary and revision cases. Recent advancements in computed tomography scanning, software automation tools, and additive manufacturing have paved the way for patient specific implants in difficult cases for reverse shoulder arthroplasty. This review article aims to provide an overview of the current state of patient specific implants in reverse shoulder arthroplasty, discussing their design principles, manufacturing techniques, short-term clinical outcomes, and future directions.

Keywords: 3D printing; Custom implants; Glenoid bone loss; Manufacturing; Patient-specific orthopedics; Reverse total shoulder arthroplasty.

Figure 1

(A) Lateral view of preoperative glenoid with severe bone loss. (B) Intraoperative picture showing glenoid exposure. (C) Implantation of baseplate demonstrating the use of contoured femoral allograft to reconstruct the glenoid vault. (D) Anteroposterior Gashey radiographs postoperatively show a stable implant.

Figure 2

(A) Lateral view of preoperative glenoid anatomy and (B) anteroposterior of design plan for a revision rTSA with contoured PS implant without needing to remove extra glenoid bone. rTSA, reverse total shoulder arthroplasty; PS, patient specific.

Figure 3

(A) Lateral view of preoperative glenoid anatomy and (B) anteroposterior of design plan for a primary rTSA with PS implant demonstrating a severe modified Walch-Favard B3/E3 glenoid defect with medialization. rTSA, reverse total shoulder arthroplasty; PS, patient specific.

Figure 4

Optimized screw trajectories shown on a design plan for a revision rTSA with PS implant allowing fixation in remaining bone. rTSA, reverse total shoulder arthroplasty; PS, patient specific.

Figure 5

Step-wise patient-specific reconstruction technique is demonstrated via intraoperative images. The patient is positioned in modified beach chair position with extensile deltopectoral approach. The glenoid exposure is performed with circumferential retractor placement with unobstructed glenoid view (A). A preprinted 3D glenoid model is compared to the intraoperative visualization (B). The first glenoid drill guide is placed on the model to verify optimal guide position (C) and then positioned over the patient glenoid intraoperatively (D). Two pins are inserted for the central post and as a derotational pin (E). A cannulated drill is used to prepare for the central post and then the implant is impacted over the derotational pin (F). Next, the implant seating is confirmed (G) and peripheral screws are inserted (H). The optimal glenosphere (standard or lateralized) is inserted and impacted (I and J).

Figure 6

Postoperative radiograph with patient-specific implant is overlayed with the preoperative surgical plan. Intraoperative execution is verified with near same positioning of the actual implant.