Accuracy of Humeral Articular Surface Restoration in a Novel Anatomic Shoulder Arthroplasty Technique and Design: A Cadaveric Study

Abstract

Introduction Accurate restoration of the humeral joint line during shoulder arthroplasty is critical to maximizing outcomes. However, clinical studies show that both resurfacing and stemmed arthroplasty systems routinely do not restore the articular surface accurately, even by experienced surgeons. The purpose of this study was to evaluate surgeons’ ability to recreate the 3-dimensional geometry of the proximal humerus using a newly developed arthroplasty system. Methods The difference in articular surface location before and after arthroplasty was measured using a new nonspherical arthroplasty system which uses a calibrated multiplanar osteotomy technique matching bone removal thickness to implant thickness. Eight human cadaver specimens were measured at 9 separate point locations over the articular surface from a fixed reference point on the lateral humerus. We repeated the measurements after bone preparation with the implant trial. Articular surface points >3.0 mm from their original location were considered outliers, based on literature. Results Average absolute deviation of each point on the articular surface measured 0.9 ± 0.7 mm (range: 0.0–2.7 mm) from preoperative to postoperative articular surface location. All (72/72) points measured were below the 3.0 mm outlier threshold from their original location. Conclusion Surgeons using the new system, ie, using a nonspherical head design and a calibrated multiplanar osteotomy surgical technique, were able to restore the joint line accurately with minimal (<1.0 mm) change from preop, with no outliers. Arthroplasty systems matching bone removal directly to implant thickness potentially may improve the reproducibility of arthroplasy and improve shoulder kinematics compared to traditional systems.