**3. Results**

*3.1. Subjects*

Ninety-four rTSAs meeting the study criteria were performed during the study period. Of those, 61 were available at final follow-up (Figure 6). The mean age of patients was 69.2 ± 8.2 years (range: 53–88) with a mean follow-up of 3.1 ± 0.7 years (range: 2.0–4.2) years. Most patients were female (55.7%). Patient demographics are demonstrated in Table 1.

**Figure 6.** Flowchart displaying inclusion criteria.


**Table 1.** Patient demographics (*N* = 61).

## *3.2. Clinical Outcome*

Post LHO

Glenoid inclination

Baseplate inclination

LSA

Overall, there was significant improvement in all clinical outcome measures from pre- to postoperative. SST improved from 2.5 ± 1.8pre to 8.0 ± 2.6post, SANE improved from 28.9 ± 22.7pre to 80.7 ± 20.1post, VAS improved from 6.0 ± 2.2 pre to 1.4 ± 2.3post, ASES improved from 37 ± 14.5pre to 78.1 ± 21.6post. At final follow-up, there was no significant difference in SST, SANE, VAS, and ASES when comparing patient populations of the different institutions.

In addition, there was significant improvement in ROM from pre-to postoperative. AFE improved from 92 ± <sup>36</sup>◦pre to 131 ± <sup>27</sup>◦post, AABD improved from 69 ± <sup>35</sup>◦pre to 109 ± <sup>38</sup>◦post, AER improved from 29 ± <sup>18</sup>◦pre to 42 ± <sup>19</sup>◦pos<sup>t</sup> at final follow-up (*p* < 0.01, respectively). When comparing ROM of patients at the different institutions, no significant difference was found for AFE, AABD, or AER.

#### *3.3. Inter-Rater Reliability of Radiographic Analysis*

Inter-rater reliability was calculated for COR, Pre-CSA, Pre-AHD, Post-AHD, DSA, Pre-LHO, Post-LHO, LSA, glenoid inclination, baseplate inclination, Hamada and Notching grades. Reliability was found to be good for most of the radiographic measurements. However, Pre-AHD (ICC = 0.37; CI: 0.18–0.55) showed only poor reliability. Moderate to good ICC was found for COR (ICC = 0.68; CI: 0.51–0.8), DSA (ICC = 0.66; CI: 0.32–0.82) and glenoid inclination (ICC = 0.66; CI: 0.47–0.79). Mean values of radiographic measurements with corresponding inter-rater reliability are demonstrated in Table 2.

**Mean** ± **SD ICC ICC 95% CI Reliability** COR 20.9 ± 3.9 mm 0.68 [0.51, 0.8] Moderate-Good Pre CSA 35.2 ± 4.5 deg 0.9 [0.9, 0.94] Good Pre AHD 5.1 ± 3.2 mm 0.37 [0.18, 0.55] Poor Post AHD 26.3 ± 9.5 mm 0.88 [0.82, 0.93] Good DSA 38.6 ± 9.6 deg 0.66 [0.32, 0.82] Moderate-Good Pre LHO 9.9 ± 5.7 mm 0.86 [0.79, 0.91] Good

**Table 2.** Inter-rater reliability for all radiographic measurements and mean values for radiographic analysis.

 Abbreviation: COR = center of rotation; Pre CSA = preoperative critical shoulder angle; Pre AHD = preoperative acromiohumeral distance; Post AHD = postoperative acromiohumeral distance; DSA = distalization shoulder angle; Pre LHO = preoperative lateral humeral offset; Post LHO = postoperative lateral humeral; LSA = lateralization shoulder angle.

 0.84

 0.84

 0.66

0.79

 [0.75, 0.89]

 [0.47, 0.79]

 [0.69, 0.86]

 [0.73, 0.9]  Good

 Good

 Good

Moderate-Good

 9.5 ± 6 mm

 89.2 ± 11.9 deg

 81.2 ± 6.8 deg

 83.2 ± 6.4 deg

#### *3.4. Correlation between Preoperative Radiographic Measurements and Clinical Outcomes*

Pre-AHD was found to have a significant correlation with final AER (*p* = 0.016; *r* = 0.314). Additionally, Pre-LHO showed a significant correlation with final ASES (*p* = 0.032; *r* = −0.277). COR, CSA, and glenoid inclination had no significant influence on clinical outcomes at terminal follow-up (*p* > 0.05, respectively) (Appendix A Table A1).

#### *3.5. Correlation between Lateralization and Clinical Outcomes*

Post-LHO was found to significantly correlate with final ASES (*p* = 0.03; *r* = −0.281). Further, there was a significant correlation of LSA with final SST (*p* = 0.001; *r* = −0.41), final pain score (*p* = 0.034; *r* = 0.272), final SANE (*p* = 0.018, *r* = −0.308), and final ASES (*p* = 0.011; *r* = −0.327). Further, there was a significant correlation between LSA and final AFE (*p* = 0.033; *r* = −0.276). Correlations of LSA with final AER (*p* = 0.471; *r* = −0.096) and AABD (*p* = 0.824; r = 0.030) were found to be non-significant (Appendix A Table A1).

#### *3.6. Correlation between Distalization and Clinical Outcomes*

Post-AHD had a significant correlation with final SST (*p* = 0.025; *r* = 0.293). On the contrary, DSA showed no significant correlation to any clinical outcome measures. Post-AHD demonstrated a significant correlation to final AER (*p* = 0.002; *r* = 0.398). In addition, DSA significantly influenced final AFE (*p* = 0.02; *r* = 0.299). No significant correlations were found between DSA and final AER (*p* = 0.317; *r* = 0.133) and AABD (*p* = 0.283; *r* = 0.145).

#### *3.7. Prediction of Active ROM*

The highest degree in AFE was observed in patients presenting with a postoperative DSA between 40◦ and 60◦. Patients with an AFE < 100◦ (n = 5) were further shown to have a DSA smaller than 40◦ (Figure 7). When looking at the LSA, patients with an AFE < 100◦ (n = 4) had an LSA greater than 95◦. The highest degree in AFE was observed in patients having an LSA between 75◦ to 95◦ (Figure 8). However, there was no statistically significant correlation between distalization (*p* = 0.317) and lateralization (*p* = 0.471) to AER at final follow-up.

**Figure 7.** Scatterplot showing the linear correlation between DSA and LSA for final AFE. Good final AFE could be seen for DSA between 40 and 60◦ and LSA between 80 and 100◦; Abbreviations: DSA = distalization shoulder angle; LSA = lateralization shoulder angle; AFE = active forward elevation.

**Figure 8.** Scatterplot showing the linear correlation between LSA and DSA for final AFE. Good final AFE could be seen for DSA between 40 and 60◦ and LSA between 80 and 100◦. Abbreviations: DSA = distalization shoulder angle; LSA = lateralization shoulder angle; AFE = active forward elevation.
