A 135° SHORT INLAY HUMERAL STEM LEADS TO COMPARABLE RADIOGRAPHIC AND CLINICAL OUTCOMES COMPARED WITH A STANDARD-LENGTH STEM FOR REVERSE SHOULDER ARTHROPLASTY
Figure 1 - (A) Image demonstrating the short stem press-fit humeral component, Revers Apex (Arthrex, Naples FL, USA). (B) Image demonstrating the standard-length stem press-fit humeral component, Univers Revers (Arthrex, Naples FL, USA).
Background: Humeral stem length in reverse total shoulder arthroplasty (RTSA) has decreased in recent years in an attempt to preserve more bone and facilitate stem removal in the revision setting. The purpose of this study was to compare the clinical and radiographic outcomes of a short- to standard-length stem RTSA. The authors hypothesized that there would be no difference in radiographic or clinical outcomes at short-term follow-up.
Methods: Patients who underwent RTSA using a press-fit standard- or short-length humeral component with a consistent geometry (Univers Revers, or Revers Apex; Arthrex, Inc., Naples, FL, USA) were evaluated in a multicenter retrospective review. The minimum clinical follow-up was 2 years. Immediate postoperative radiographs were used to assess initial alignment and filling ratios. In addition, radiographs at 2 years were evaluated for signs of stress shielding and/or loosening. Clinical outcome scores and range of motion were evaluated at the final follow-up and compared between groups.
Figure 2 - Initial postoperative radiograph demonstrating a stem that was placed into valgus alignment. Note the difference of more than 9° between the alignment of the prosthesis and humerus.
Figure 3 - Initial postoperative radiograph demonstrating a stem that was placed into varus alignment. Note the difference of more than 6° between the alignment of the prosthesis and humerus.
Results: A total of 220 patients with short-stem RTSA and 357 patients with standard-length stem RTSA were analyzed. There was no difference in baseline function between short- and standard-length stem patients. Patients in the short stem group had higher postoperative American Shoulder and Elbow Surgeons (84.6 vs. 80.8; P = .014) and Western Ontario Osteoarthritis of the Shoulder (86.5 vs. 82.7; P = .025). Patients in the short stem group also had greater postoperative active forward flexion (139° vs. 132°; P = .003) and internal rotation with the arm at 90° of abduction (43° vs. 32°; P < .001) than patients in the standard-length group. Radiographically, there was a higher metaphyseal (P = .049) and diaphyseal (P < .001) fill ratio in the short stem group, although there was no difference in postoperative alignment, radiographic signs of loosening, or revision for loosening between groups (all P > .05).
Figure 4 - Initial postoperative radiograph demonstrating a stem that was placed into neutral alignment. Note the difference of less than 5° between the alignment of the prosthesis and humerus. The varus/valgus is calculated by drawing a line that is in line with the lateral aspect of the implant and a separate line that goes along the lateral border of the humerus. The angle between these 2 lines is the amount of varus/valgus that the implant is in.
Figure 5 - Measurements of metaphyseal and diaphyseal filling ratios. Metaphyseal filling ratio was calculated by dividing the metaphyseal length of the stem (green line) by the length of the metaphyseal bone (purple line). The diaphyseal filling ratio was calculated by dividing the diaphyseal length of the stem (orange line) by the length of the diaphyseal bone (red line).
Conclusion: A short inlay stem leads to comparable radiographic findings and revision-free survival compared with a standard-length stem when placed with a press-fit technique for RTSA. Clinical outcomes are also equivalent or slightly improved with a short stem compared with a standard-length stem.
Click on the link for the full print article:
Published June 2, 2022 in the Journal of Shoulder and Elbow Surgery International.