Thursday, December 18, 2025

CT-free planning for reverse total shoulder arthroplasty - why and how to do it

The most recent Australian Orthopaedic Association's Joint Replacement Registry reveals that the use of CT scans prior to shoulder arthroplasty is increasing rapidly.

This use needs to be considered in light of five factors
(1)  Evidence is lacking that preoperative CT planning improves patient-reported outcomes, complication rates, or revision rates for common arthroplasty cases:

Use of Preoperative CT Scans and Patient-Specific Instrumentation May Not Improve Short-Term Adverse Events After Shoulder Arthroplasty: Results from a Large Integrated Health-Care System found "no reduction in the risk of aseptic revision was observed for patients having preoperative CT scans".

The influence of computed tomography preoperative planning on clinical outcomes after anatomic total shoulder arthroplasty: a matched cohort analysis found the differences in clinical outcomes between the CT and non-CT scan groups failed to meet a clinically significant threshold.

Templating in shoulder arthroplasty - A comparison of 2D CT to 3D CT planning software: A systematic review did not find evidence demonstrating differences in time, cost, functional outcomes, complications, or patient satisfaction.

3D CT-Based Preoperative Planning and Intraoperative Navigation in Reverse Shoulder Arthroplasty: Early Clinical Outcomes did not find statistically significant benefit of CT-based navigation with respect to complication rate, radiographical glenoid notching, and clinical outcomes

Assessing the Value to the Patient of New Technologies in Anatomic Total Shoulder Arthroplasty did not find evidence that the patient outcomes for shoulder arthroplasty were statistically or clinically improved with the use of advanced technologies, such as CT based planning.


(2) CT scanning and 3D planning increase the cost of healthcare by dint of their own costs. But they also initiate a "cost cascade" by driving the use of more expensive implants, and by driving the use of expensive "transfer technologies", such as patient specific instrumentation, virtual and augmented reality, and robotics. Because planning software packages are proprietary, they can drive the use of the implants associated the software, rather than the implants that may be more cost effective.


Impact of preoperative 3-dimensional planning and intraoperative navigation of shoulder arthroplasty on implant selection and operative time: a single surgeon's experience. found an almost three-fold increase in the use of the more expensive augmented components when using 3D preoperative planning 

Computer navigation re-creates planned glenoid placement and reduces correction variability in total shoulder arthroplasty: an in vivo case-control study. found that patients undergoing computer-assisted shoulder arthroplasty had more than twice as many augmented glenoid components as the conventional group 

However, none of these studies presented costs or clinical outcomes comparisons and thus it cannot be ascertained whether the use of augmented components was a cost-effective intervention or not.

Preoperative planning in reverse shoulder arthroplasty: plain radiographs vs. computed tomography scan vs. navigation vs. augmented reality concluded that further research is needed to determine the added value of these technologies in terms of improving clinical outcomes for the patients. The scarce evidence comparing short-term clinical outcomes of RSA with and without the use of these technologies show no or marginal benefits "Any benefit should be balanced against the increased costs and the 200 to 1,000-fold increase in radiation exposure associated with the CT scans in comparison with radiographs ".  

(3) Thus, In addition to its cost, CT scanning is associated with an increased lifetime risk of cancer

Computed Tomography for Preoperative Shoulder Arthroplasty Planning: Lifetime Malignancy Risk: The current reliance on preoperative shoulder CT for arthroplasty planning needs to be weighed against the potential lifetime cancer risks.

Projected Lifetime Cancer Risks From Current Computed Tomography Imaging found that at current utilization and radiation dose levels, CT examinations in 2023 were projected to result in approximately 103 000 future cancers over the course of the lifetime of exposed patients. If current practices persist, CT-associated cancer could eventually account for 5% of all new cancer diagnoses annually.


(4) Reverse shoulder arthroplasty (RSA) is a highly successful operation in the population-based study by the Australian Orthopaedic Association with 10 year revision rates under 6%. Note that these national data include all cases performed by all surgeons, not only "high volume" surgeons.




Complications and revision of reverse total shoulder arthroplasty found that 40% of revisions were for infection, 20% for instability/dislocation, 20% for loosening, and 10% for fracture. Evidence is lacking that CT scans, CT-based planning, and associated technologies have a substantial impact on these common reasons for RSA revision. 

(5) In most cases, cost-effective preoperative planning can be efficiently carried out without a CT scan. 

Here's a way to it in under ten minutes using the Picture Archiving and Communication Systems (PACS) tools applied to two standardized preoperative plain films (AP view in the plane of the scapula and axillary view). This approach is generic and is not tied to any commercial company, allowing surgeons to have their choice of implant. It can be used by essentially all shoulder surgeons. It provides an approach for transferring the plan to the patient. It is cost-effective - an important feature, especially at this time when many are having difficulty affording health care.

Step 1, on the AP view, draw a line along the base of the supraspinatus fossa (yellow line in right hand image).

Step 2, draw a line segment  equal to the radius of the base of the glenosphere from the inferior glenoid at a right angle to the supraspinatus fossa line so that it intersects the glenoid face (yellow line on left image below). This intersection will be the starting point for the drill for the central scew of the baseplate. This point will be located at surgery by measuring the distance from this point to the inferior lip of the glenoid (yellow line on right image below). Note that the amount of bone that will be removed by reaming is represented by the triangle in between these two lines.

Step 3 Draw a line parallel to the supraspinatus fossa line that intersects the glenoid face at the insertion point (yellow line on left image); this is the trajectory of the drill. Measure the angle between this line and the face of the upper glenoid (yellow line on right image) to guide the tilt of the drill at surgery.

Step 4 On the axillary view, draw the desired trajectory of the central screw so that it will just penetrate the anterior cortex of the subscapularis fossa when fully inserted (central image). Note the angle of this line with the gleniod face (right image) to guide version of drill at surgery.

The resuling arthroplasty closely approximates the plan.


Another example






And another



CT-free planning is consisted with the philosophy expressed in the preface of Practical Evaluation and Management of the Shoulder (1994): "This book is directed at the type of practice we see evolving for the coming decades, when resources will not be as plentiful and increasing premiums will be placed on economy and effectiveness. In this spirit, we emphasize what can be accomplished with the basics: the clinical history, the physical examination, a few plain radiographs, simple patient-conducted rehabilitation programs, and well-characterized surgical procedures. "

Thanks to our two shoulder fellows, Jake Checketts and Dave Daniels, for their help with this post. They easily mastered this method and routinely apply it to all but the unusual cases of reverse shoulder arthroplasty (i.e. those with severe bone loss, complex revision cases, significant deformity).

Making a Plan


Osprey 
Union Bay Natural Area
2024







Here are some videos that are of shoulder interest
Shoulder arthritis - what you need to know (see this link).
How to x-ray the shoulder (see this link).
The ream and run procedure (see this link)
The total shoulder arthroplasty (see this link)
The cuff tear arthropathy arthroplasty (see this link).
The reverse total shoulder arthroplasty (see this link).
The smooth and move procedure for irreparable rotator cuff tears (see this link)
Shoulder rehabilitation exercises (see this link).
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