Does Navigation Improve Implant Placement Accuracy in Reverse Total Shoulder Arthroplasty?

re: Navigation improves accuracy of implant placement in reverse total shoulder arthroplasty, a commentary on “Short-term clinical and radiologic outcomes of reverse total shoulder arthroplasty with navigation system in the Asian population: a retrospective comparative study” by Jae Soo Kim, Su Cheol Kim, Jong Hun Park, et al., in JSES International 9(2025) 422-430.

Reverse total shoulder arthroplasty (rTSA) has revolutionized the management of complex shoulder conditions, especially in cases where rotator cuff integrity is compromised. Complication rates for early generations of prostheses were originally reported to be as high as 50%, but improved knowledge on surgical techniques, implant design, and optimal implant placement have decreased this significantly. Enabling technology, including artificial intelligence, robotics, and computer-assisted navigation, is at the forefront of orthopaedic surgery. Currently, while robotics are just being introduced to shoulder arthroplasty, navigation has a 10-year history in shoulder surgery. Navigation systems play an increasingly pivotal role, aiming to enhance the accuracy of implant placement. The recent article published by Kim et al. in JSES International (9[2025]: 422-430) provides valuable insight into short-term clinical and radiographic outcomes of rTSA with navigation in a specific population and adds to the growing literature on the benefits of navigation.

Brief Review of Kim et al., JSES International 2025

Kim and colleagues conducted a retrospective comparative study to evaluate the short-term clinical and radiographic outcomes of rTSA with navigation in an Asian population¹. Proper implant positioning can be challenging in this population due to the generally smaller glenoid morphology. The authors reviewed cases performed by a single surgeon, with the goal of comparing the clinical and radiographic outcomes of patients that underwent placement with surgical navigation versus those who had placement without navigation. The final cohort included 33 patients in the navigation (NAV) group versus 40 patients in the conventional (CON) group. Although the selection criteria for each category are not provided, there were no significant differences preoperatively in patient demographics or radiographic measurements. All patients had preoperative CT scans. The NAV group used preoperative planning software, while the CON group performed planning directly off the CT scans without specific planning software.

Key findings include:

• The NAV group had more augmented baseplates utilized.
• The NAV group had significantly lower superior inclination of the glenoid component, significantly lower incidence of perforation of the central cage, and significantly longer superior and inferior screws.
• In the NAV group, superior screws showed more inferior orientation of the superior screws, more anterior orientation of the inferior screws, and lower rate of superior screw penetration into the suprascapular fossa
• Range of motion and patient-reported outcomes improved significantly in both groups except for rotation, with no significant differences between groups.
• Complication rates were low: There were no significant increases in intraoperative or short-term postoperative complications attributable to navigation.
• The operative time was longer in the NAV group, though other studies have shown that with experience it can be time neutral².

The study’s strengths include its analysis of results of a single surgeon with examination of complications, outcomes, and radiographic positioning of the implant, including the use of postoperative CT scans. Another is its focus on an Asian population—addressing a gap in the literature. Weaknesses include its small sample size, relatively short-term follow-up, and lack of criteria for the use of navigation, which could introduce selection bias. Furthermore, as preoperative planning software was only utilized in the NAV group, it is difficult to determine how much of the difference is due to planning versus navigation. Iannotti has previously shown the benefit of preoperative planning alone. However, planning and execution of the plan are two separate entities. The findings are consistent with broader literature suggesting that navigation systems can improve key radiographic outcomes in shoulder arthroplasty³.

Outcome Summary: Navigation vs. Conventional rTSA
To contextualize these findings, the table below highlights the key comparative metrics and statistical endpoints from the Kim et al. cohort¹

Evaluated Feature / Metric	Navigation (NAV) Group (n=33)	Conventional (CON) Group (n=40)	Verified Radiographic & Clinical Outcomes
Superior Inclination of Glenoid Component	Significantly lower superior inclination	Higher superior inclination	Statistically significant difference favoring the NAV group.
Glenoid Vault Perforation by Central Cage	Significantly lower incidence of perforation	Higher incidence of perforation	Statistically significant reduction in structural vault breach within the NAV group.
Fixation Screw Length	Significantly longer superior and inferior screws	Shorter superior and inferior screws	NAV group allowed for longer screw insertion
Operative Time	Longer operative time	Shorter operative time	Operative time was increased in the NAV group, though literature demonstrates this can be time-neutral with experience.
Clinical Outcomes & Complications	No significant difference	No significant difference	Both cohorts demonstrated significant functional improvement with no significant differences in short-term complications.

Goals of Reverse Shoulder Implant Placement

In reverse total shoulder arthroplasty, proper implant placement can minimize the risk of component loosening, optimally improve patient range of motion, and minimize complications. The key goals in reverse shoulder implant placement include:

• Proper restoration of glenoid version
• Avoidance of superior inclination
• Maximizing backside contact while preserving as much subchondral bone as possible
• In a medialized glenoid component, inferior overhang of the glenosphere to avoid scapular notching
• Maximizing screw length in a safe direction to improve initial fixation
• Optimizing joint biomechanics and stability – implant dependent

Consequences of Improper Implant Placement

Conversely, even minor deviations in implant orientation or position can have profound consequences. Some of the most clinically significant complications include:

• Instability and dislocation: Implant malposition may compromise soft tissue tension or joint mechanics, increasing the risk of early or recurrent instability.
• Impingement and limited range of motion: Poor alignment may result in impingement on surrounding bony or soft tissue structures.
• Increased wear and risk of loosening: Off-axis loading can accelerate polyethylene wear and lead to aseptic loosening, reducing implant longevity.
• Scapular notching: Incorrect placement can cause repetitive impingement between the humeral cup and scapular neck; a common radiographic finding associated with functional decline.
• Acromial and scapular spine fractures: These may result from improper positioning or tension.

The Promise and Evidence for Navigation in Shoulder Arthroplasty

Navigation systems are increasingly being adopted in shoulder arthroplasty. These systems provide real-time intraoperative feedback, allowing surgeons to visualize component orientation, depth, and version relative to patient-specific anatomy, while leaving the surgeon in control. Navigation may help address the technical challenges of rTSA, especially in patients with abnormal glenoid morphology or bone loss.

Conclusion

Navigation technology, as Kim et al.’s study highlights, has the potential to improve the precision and consistency of implant placement, reduce technical errors, and support better patient outcomes, and the learning curve has been shown to be as short as 7 cases. Long-term studies will be needed to show that the improved implant placement translates to longer implant survival and greater long-term outcomes.

 

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References

1. Kim, Jae Soo et al. “Short-term clinical and radiologic outcomes of reverse total shoulder arthroplasty with navigation system in the Asian population: a retrospective comparative study.” JSES international vol. 9,2 422-430. 18 Oct. 2024, doi:10.1016/j.jseint.2024.09.025
2. Wang, Allan W et al. “Computer navigation of the glenoid component in reverse total shoulder arthroplasty: a clinical trial to evaluate the learning curve.” Journal of shoulder and elbow surgery vol. 29,3 (2020): 617-623. doi:10.1016/j.jse.2019.08.012
3. Youderian, Ari R et al. “Two-year clinical outcomes and complication rates in anatomic and reverse shoulder arthroplasty implanted with Exactech GPS intraoperative navigation.” Journal of shoulder and elbow surgery vol. 32,12 (2023): 2519-2532. doi:10.1016/j.jse.2023.05.021