Is Robotic Shoulder Replacement Worth It?

A shoulder replacement has two parts: a ball on the upper arm bone (humerus) and a socket on the shoulder blade (the glenoid, the shallow cup of the shoulder blade). In an anatomic replacement, the ball and socket are rebuilt in their natural positions. In a reverse replacement, they are switched, with the ball fixed to the shoulder blade and the cup on the arm bone. Reverse replacement is used for arthritis with a damaged rotator cuff and for many other conditions.

The hardest step is placing the socket side. The glenoid is small, it is often worn unevenly by arthritis, and much of it is hidden from the surgeon’s view during the operation. The angle at which that part is placed matters. In anatomic replacements, a socket left tilted too far backward has been linked to bone loss around the implant.⁵ In reverse replacements, a baseplate placed too high or tilted upward has been linked to scapular notching, wear of the shoulder blade bone where the arm-bone component rubs against it, which was associated with lower strength and less overhead motion in a large French series.⁶

Every technology described below is aimed at this one step: getting the socket where the surgeon planned to put it.

3D planning predicts the implant well, but plans can change

In a study of 200 shoulder replacements, the implant planned on 3D software matched the implant actually used in 85% of anatomic and 90% of reverse replacements, with a complete mismatch in only 2% to 3%.⁸ That leaves some cases in which the plan changed during surgery, usually because bone quality or soft tissue looked different in person than on the scan. Patients in online forums sometimes report surprise that their “planned” implant was not the one used. A 3D plan is a strong starting point, not a promise, and the surgeon has to be ready to adjust.

There is a second caution. In a study of 6,483 cases from 417 surgeons using one company’s planning software, surgeons kept the initial plan prepared by the company’s technicians for both key socket angles in 55% of cases.⁹ The authors warned that a ready-made plan can anchor a surgeon’s judgment. Planning software helps most when the surgeon reviews and changes the plan, rather than accepting it.

Guides and navigation improve position, especially in difficult shoulders

An early randomized trial of 31 patients found that patient-specific guides reduced the average error in socket tilt from 11.6 degrees with standard instruments to 2.9 degrees. The benefit was largest in badly worn shoulders.¹⁰ Later work clarified where that gain comes from. In 173 anatomic replacements that all had 3D CT planning, adding patient-specific guides of various types did not consistently improve accuracy over standard instruments.¹¹ A 2026 randomized trial of 106 reverse replacements at seven centers found no difference in baseplate angles between guides and freehand placement after planning, though guides improved screw placement.¹² Taken together, much of the accuracy gain appears to come from detailed planning itself.

For navigation in reverse replacement, a meta-analysis of 10 studies and 667 shoulders found better control of baseplate tilt, no improvement in its rotation, and operations about 12 minutes longer. The authors described the clinical impact as still unknown.¹³

Better position has not yet meant better shoulders

A 2025 meta-analysis of patient-specific guides in shoulder replacement found no difference in complications, reoperation or shoulder function scores compared with standard instruments.¹⁴ A randomized trial of 47 reverse replacements found more accurate placement with guides but no difference in patient-reported results at two years.¹⁵ Even the link between position and long-term results is not settled. The study that tied a backward-tilted socket to bone loss found no difference in shoulder scores or reoperation.⁵ A separate two-year study found no difference in function or revision between patients whose socket ended up tilted back 15 degrees or more and those with better position.¹⁶

The robotic data so far

The largest robotic accuracy study, published in July, compared 61 robotic and 42 conventional reverse replacements by one surgeon, all planned with the same 3D software.¹⁷ The average gap between planned and achieved baseplate tilt was 2.7 degrees with the robot and 3.9 degrees without, a difference that was not statistically significant. The robot did eliminate large misses: no robotic case was more than 10 degrees off the plan, compared with 4 of 42 conventional cases (10%).

The study published on October 7 compared 39 robotic and 38 conventional reverse replacements by the same surgeon after excluding the first 23 robotic cases as a learning period.³ Average operating time was the same (about 74 versus 79 minutes), but robotic operations were more predictable in length. The robot’s learning curve was real: in another series, the first 10 robotic cases averaged about 106 minutes, falling to about 68 minutes by cases 21 to 30.¹⁸

Early users have also reported practical problems. In a survey of 14 surgeons who used the system during its limited release, 6 (43%) had at least one case in which they stopped using the robot and finished by hand, all because of problems registering the bone or fixing the tracking markers. The surgeons rated the robot as useful, and the authors described its clinical benefits as “yet to be realized.”¹⁹

Finally, an economic analysis asked how many revisions the robot would need to prevent to pay for itself. Assuming $1,500 in added cost per case and a 2.1% early revision rate, the robot would need to prevent about one revision for every 15 patients, which the authors concluded cannot be achieved under typical conditions.²⁰

What this means for you: the robot appears to make socket placement more consistent. Whether that consistency leads to a better or longer-lasting shoulder is not known, and it will take years of follow-up to find out.

• The robotic evidence comes mostly from one group. Most published robotic shoulder studies share an author who is a consultant for the manufacturer. The studies disclose this, and the findings are measured and cautious, but independent replication is still needed.
• No robotic study reports patient outcomes. The measured endpoints are angles on X-rays, operating time and surgeon workload. Those are surrogate measures, not pain, function or implant survival.
• The sample sizes are small. Ten percent of 42 conventional cases is four patients. A difference that size can shift with a few more cases.
• The robot is limited to reverse replacement. The anatomic replacements, where socket tilt has the clearest link to bone loss, are not yet part of the robotic option in the US.
• Large misses can be avoided without a robot. Experienced surgeons using 3D planning with or without guides also achieve low outlier rates. The robot’s added value over careful planning is the open question.