Tornier Perform Anatomic Augmented Glenoid Implants Correct Posterior Subluxation and Maintain Active Joint Reduction in Walch B2 Glenoids.

Abstract

Background: The Walch type B2 glenoid is characterized by retroversion, posteroinferior erosion and posterior humeral head subluxation. A surgical management option for a B2 glenoid is an anatomic total shoulder arthroplasty (aTSA) with a posteriorly augmented all-polyethylene glenoid (PAG) implant. However, little is known about what occurs actively at the glenohumeral articulation after aTSA with a PAG. Additionally, most studies on B2 glenoids, whether pre-aTSA or post-aTSA, assess subluxation statically. Presently, it is unknown if subluxation recurs after aTSA with a PAG or if it varies dynamically throughout active motion. Therefore, the primary objective of this study was to determine if Walch type B2 patients managed with an aTSA and a PAG (Tornier Perform Anatomic Augmented Glenoid Implant) would maintain correction of subluxation when examined statically and when stressed with active motion. The secondary objective was to analyze if a patient's range of motion (good or limited), magnitude of B2, or PAG implant size (15° or 25°) affect postoperative correction of subluxation.

Methods: Twenty Walch type B2 patients (mean age 68 years, range 54 to 83) underwent stemless aTSA with a 15° or 25° PAG implant and were assessed at a minimum 2-year follow-up. All patients underwent dynamic 4DCT scanning to actively track glenohumeral implant alignment and subluxation during a provocative active internal rotation motion protocol. Bone and implant 3D models of the humerus and scapula for each 4DCT scan were created using 3D Slicer. Landmarks were selected on the models to create coordinate systems that were then used in conjunction with a custom program (MATLAB) to determine subluxation preoperatively (statically), and postoperatively (dynamically).

Results: Posterior humeral head subluxation was significantly corrected (p<0.001) from an average of 66% (range 51%-98%) preoperatively to 54% (range 41%-77%) postoperatively. Concentric aTSA joint alignment was maintained throughout an active internal rotation (IR) motion protocol, as subluxation percentage only varied by 1% throughout IR movement (range 54% to 55%). Neither patient IR range of motion (good or limited) nor size of PAG (15° or 25°) had a significant effect (p>0.05) on subluxation postoperatively.

Conclusion: At short-term follow-up, aTSA with an all-polyethylene PAG (Tornier Perform Anatomic Augmented Glenoid Implant) was successful at restoring and maintaining glenohumeral alignment with correction of subluxation throughout a provocative active IR motion protocol. As such, recurrence of subluxation does not occur statically or actively in patients who have undergone glenoid reconstruction with correction of posteroinferior erosion with a half-wedge PAG implant. Thus, aTSA with a PAG implant is an acceptable option for patients with mild or moderate B2 glenoids.