Sunday, April 19, 2026

Component malposition and clinical outcomes in shoulder arthroplasty - are they related?

It seems intuitive that substantial malposition of shoulder arthroplasty components can lead to poor clinical outcomes.  


The assumption that malposition drives poor outcomes has become the rationale for investment in three-dimensional planning, patient-specific instrumentation, navigation, augmented reality, and robotics. However, examination of published evidence indicates that the relationship between measured component position and patient-reported outcomes is weaker than this narrative implies. For example Negligible Correlation between Radiographic Measurements and Clinical Outcomes in Patients Following Primary Reverse Total Shoulder Arthroplasty concluded that the relationship between measured component position and clinical outcomes is limited. Does postoperative glenoid component retroversion following anatomic total shoulder arthroplasty affect clinical outcomes? A systematic review and meta-analysis found no clinically significant difference in patient-reported outcome scores, range of motion, or complications for anatomic total shoulder arthroplasty glenoid components implanted with <15° versus ≥15° of postoperative retroversion across 15 studies and 1,190 shoulders. 

Humeral and glenoid component malposition in patients requiring revision shoulder arthroplasty: a retrospective, cross-sectional study measured component positions for TSA and RSA on pre-revision radiographs of patients having revision arthroplasty and compared these measures to "ideal" values for glenoid inclination, critical shoulder angle, glenosphere overhang, change in center of rotation, humeral head height, acromio-humeral interval, and humeral stem alignment. These measurements were not made on radiographs obtained immediately after the index arthroplasty, so the extent of postoperative component shift is not known.

The article found that the majority of glenoid components in these revision cases were malpositioned in relation to the "ideal" values for both TSA (51%) and RSA (93%) when all of the measures were considered. Similarly, there was humeral component malposition in 57% of TSA cases and 62% of RSA cases when all of the measures were considered.  

The prevalence of malpositioning in unrevised arthroplasties was not presented in this study.

Data such as that shown in graph A  (showing hypothetical values for unrevised shoulders) would suggest that malposition was not an important driver of revision.



On the other hand, data such as that shown in graph B would suggest that malposition was an important driver of revision.

This article did not provide data on the relationship of the degree of malposition to the rate of revision.

Data such as that shown in hypothetical graph C would suggest that the degree of malposition was tightly related to the revision rate.

Data such as that shown in hypothetical graph D would suggest that smaller degrees of malposition did not affect revision rate, whereas substantial degrees of malposition were clinically important.

What the literature does provide is evidence against a meaningful dose-response relationship. 

Below is a Forest plot of some key published studies relating glenoid component version to patient-reported clinical outcomes for aTSA and RSA. The effect sizes near zero with confidence intervals crossing the null line suggest the lack of a clinically meaningful dose-response relationship between glenoid component version and clinical outcome.



Below is a scatterplot showing the lack of a relationship between SANE and ASES scores and glenoid component version (data from Glenoid retroversion does not impact clinical outcomes or implant survivorship after total shoulder arthroplasty with minimal, noncorrective reaming).





Conclusion: A search of the currently available literature did not show a relationship between immediate postoperative radiographic measures of component position on one hand and clinically meaningful measures (such as patient-reported outcomes and revision rates) on the other. Such data will be important in demonstrating the potential clinical value of preoperative plan transfer technologies such as robotics, patient-specific instrumentation, navigation, and virtual/augmented reality. The thought that "continued improvements in component positioning technologies for both the glenoid and humeral implants are needed" will need to be supported by these analyses.

References
1. Checketts JX, Sanchez B, Norris G, Williamson TK, Hachadorian ME, Hsu JE, Schiffman CJ, Matsen FA III. Does postoperative glenoid component retroversion following anatomic total shoulder arthroplasty affect clinical outcomes? A systematic review and meta-analysis. J Shoulder Elbow Surg. 2026;35(5):1103–1116.
2. Sperling JW, Anderson MB, Jobin CM, Verborgt O, Duquin TR. Humeral and glenoid component malposition in patients requiring revision shoulder arthroplasty: a retrospective, cross-sectional study. J Shoulder Elbow Surg. 2025;34(8):1886–1896.
3. Service BC, Hsu JE, Somerson JS, Russ SM, Matsen FA III. Does postoperative glenoid retroversion affect the 2-year clinical and radiographic outcomes for total shoulder arthroplasty? Clin Orthop Relat Res. 2017;475(11):2726–2739.
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