Stem Alignment With the Tapered Wedge Cementless Stem "Accolade II" Does Not Affect Bone Mineral Density Over 5 Years After Total Hip Arthroplasty

Abstract

Background: This study aimed to investigate the relationship between 3-dimensional (3D) alignment and postoperative bone mineral density (BMD) changes with Accolade II tapered wedge stems, which have a different proximal shape from other tapered wedge stems, up to 5 years after primary total hip arthroplasty.

Methods: We retrospectively analyzed the hips of 89 patients who underwent total hip arthroplasty using the second-generation proximally coated cementless stem (Accolade II; Stryker Orthopedics, Mahwah, NJ) at our institution from 2014 to 2018 over a 5-year follow-up. We evaluated the relationship between stem alignment, measured using 3D-templating software, and BMD changes in the 7 Gruen zones and compared the data with those from a former study using other short taper-wedge stems.

Results: BMDs in zones 1 and 7 continued to decrease gradually every year after surgery, and BMD in zone 7 showed the largest decrease (21%) from baseline over 5 years. No correlation was found between stem alignment (varus/valgus, flexion/extension, and anteversion/retroversion) and changes in BMD in each zone over 5 years.

Conclusions: Our data showed no correlation between 3D stem alignment and changes in BMD in each Gruen zone over 5 years. This suggests that the Accolade II stem may fit better into any shape of the proximal medullary canal because of its unique characteristics.

Keywords: Bone mineral density; Stem alignment; Tapered wedge cementless stem; Total hip arthroplasty.

Figure 1

Changes in BMD in each Gruen zone. Changes in BMD in zones 1 and 7 gradually decreased over time, and those in zone 3 were >100% at 5 years postoperatively. BMD, bone mineral density; Z, zone.

Figure 2

Difference of the proximal medial shape between Accolade II and a standard taper-wedge stem.