Reassessing glenoid inclination in reverse total shoulder arthroplasty with glenosphere lateralization

Abstract

Aims Existing literature indicates that inferiorly inclined glenoid baseplates following reverse total shoulder arthroplasty (RSA) produce better outcomes compared to superiorly inclined baseplates. We aim to compare clinical outcomes for RSAs with superiorly and neutrally/inferiorly inclined lateralized glenospheres. Methods We retrospectively reviewed 154 consecutive patients undergoing RSA between July 2015 and July 2017 by one single-fellowship trained surgeon (AJ). Two raters (KAM and MVS) independently measured glenoid inclination in preoperative and minimum two year follow-up radiographs (anteroposterior/Grashey) using the RSA angle. Inclination was then compared to patient-reported outcomes, range of motion (ROM), and independently assessed degree of scapular notching and staging of heterotopic ossification at two year follow-up. Results Median postoperative inclination for each group was found to be -3.6° (interquartile range (IQR) -2.1 to -6.9) and 6.0° (3.2° to 10.1°) for the neutrally/inferiorly and superiorly inclined cohorts, respectively. Preoperative inclination was highly associated with postoperative inclination (p = 0.004). When comparing superiorly and neutrally/inferiorly inclined glenospheres, there were no differences in heterotopic ossification (p = 0.606), scapular notching (p = 0.367), American Shoulder and Elbow Surgeons score (p = 0.419), Single Assessment Numeric Evaluation (p = 0.417), Visual Analogue Scale (VAS) pain score (p = 0.290), forward elevation (p = 0.161), external rotation (p = 0.537), or internal rotation (p = 0.656). Conclusion Compared to neutral and inferior inclination, up to 6° ± 3° of superior glenoid baseplate inclination on a lateralized RSA design produces no differences in postoperative ROM or patient-reported outcomes, and produces similar levels of scapular notching and heterotopic ossification. Additionally, the degree of preoperative inclination represents an important factor in surgical decision-making as it is strongly associated with postoperative inclination. It is important to note that the findings of this study are only reflective of lateralized RSA prostheses. Cite this article: Bone Joint J 2021;103-B(2):360–365.

Relationship between the prosthesis scapular neck angle and clinical outcomes in reverse shoulder arthroplasty

“…Studies assessing other methods of glenoid inclination have similarly found little to no association between glenoid inclination and complications. 22,23 These results may reflect that glenoid baseplates were placed within an acceptable range of PSNA and did not extend to extreme inclinations which would result in unfavorable biomechanics and short-term complications. 28,39 Future studies are needed to investigate if an increased rate of complications in patients with certain baseplate inclination occur with longer follow-up.…”

“…These findings are consistent with recent retrospective reviews by Bechtold et al, Mahendraraj et al, and Werner et al that show inclination does not significantly influence outcomes. [22][23][24] The remaining literature insufficiently describes the impact of baseplate tilt on postoperative functional outcomes, with studies focusing solely on radiographic evidence of complication or inadequately documenting postoperative glenosphere inclination in relation to long-term functional outcomes. 10,15,18,[25][26][27][28] Minimal data exists to guide surgeons in determining the ideal glenosphere inclination or prosthesis scapular neck angle (PSNA) in order to optimize patient outcomes and limit complications.…”

Glenoid Inclination: Choosing the Transverse Axis Is Critical—A 3D Automated versus Manually Measured Study

“…Even if it concerns one case over 10 in our practice and clinical situations, we must warn surgeons about such inclination variations as they may use these measurements, provided by software, to decide on the glenoid implant positioning in anatomic or reverse shoulder arthroplasty based on current recommendations. Thus, the degree of preoperative inclination represents an important factor in surgical decision-making as it is strongly associated with postoperative inclination [ 29 ]. Moreover, recommendations for anatomic total shoulder arthroplasty are to not position the glenoid implants over 10° of superior inclination and studies of glenoid component malpositioning in TSA have linked excessive superior tilt with a risk of secondary rotator cuff dysfunction and worse outcomes [ 30 , 31 ].…”

Associations between radiographic parameters in the reverse shoulder arthroplasty and patient outcomes

“…Two recent studies showed that a small amount of baseplate superior tilt is tolerated with no significant effect on Scapular notching or PROMs. 31,32 To eliminate the effect of implant on Notching or postoperative outcomes the analysis was repeated within the Zimmer and Equinox implant groups as they were most frequently implanted (N = 75 and 56 respectively). Postoperative CSA was significantly correlated with…”

“…Two recent studies showed that a small amount of baseplate superior tilt is tolerated with no significant effect on Scapular notching or PROMs. 31,32…”