解剖学的全肩関節形成術における上腕骨コンポーネント長の比較（Equinoxe; Exactech, Inc.）

There has been a trend towards the use of shorter humeral components with the goal of preserving bone, decreasing operative time, and a theoretical decrease in stress shielding. The purpose of this study was to compare the clinical and functional outcomes of anatomic total shoulder arthroplasty (aTSA) between standard-length stems, short, and stemless humeral components with a minimum of 2-year follow-up.

A retrospective review of a multi-center international database was performed for aTSA with 2-year minimum follow-up between 2018-2021 using Standard Equinoxe stems, Equinoxe Preserve (Short) stems, or Equinoxe Stemless components (Exactech, Inc., Gainesville, FL, USA). Outcome measures included range of motion (ROM) and patient reported outcome measures (PROMs). Postoperative radiographic findings including presence of glenoid and humeral radiolucent lines in zones specific to the stem design were evaluated. Complication and revision rates were recorded.

825 patients were included (164 standard-length length stem, 356 short stem, and 305 stemless). The mean follow-up was 37.9 ± 12.6 months. There was no significant difference in previous shoulder surgeries, or medical comorbidities between the groups. The mean final forward elevation for standard-length, short, and stemless components was 156°, 158°, and 156°, respectively (p = 0.636). Final external rotation for standard-length, short, and stemless components was 58°, 57°, and 51°, respectively (p < 0.001). Final internal rotation scores were similar across groups (p= 0.090). Final PROMs did not meet the minimal clinically important difference (MCID) across cohorts. The mean operative time for the standard-length stem group was 101.8 minutes, for the short stem group was 92.7 minutes, and for the stemless group was 89.2 minutes (p < 0.001). There was no statistically significant difference in complication rate, or revision rate. The rate of humeral component radiolucent lines was greater for standard-length stems (p < 0.001) with a rate of 11.9% for standard-length, 1.7% for short stems, and 1.6% for stemless components. Patient satisfaction was also similar between the 3 cohorts (p = 0.757).

Our findings demonstrate similar postoperative motion and PROMs scores irrespective of the humeral stem component utilized. Complication and revision rates were similar for all 3 cohorts. Radiolucent lines were lowest with the stemless component. Early data supports the use of stemless and short stemmed humeral components which may be advantageous in decreasing operative time and preserving humeral bone for potential revision. Longer term studies are needed to confirm the survivability and durability of these shorter components.