Arthroplasty planning: CT-based and CT-free

Different approaches are used for planning shoulder arthroplasty. Some focus on "reconstructing pre-morbid anatomy" while others seek to optimize the kinematics of the reconstructed joint.  This prentation, co-authored by one of our two outstanding shoulder fellows, Jake Checketts, provides some thoughts on planning for the reader's consideration.

See: 

Projected Lifetime Cancer Risks From Current Computed Tomography Imaging

Computed Tomography for Preoperative Shoulder Arthroplasty Planning: Lifetime Malignancy Risk 

An alternative to CT-based planning

Make a plan, adjust the plan

Short-eared owl

Skagit, Washingtion

March, 2025

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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).

Planning: accuracy, precision, outcome and the goal post.

The ten most memorable made and missed field goals in NFL history

It goes without saying that preoperative planning coupled with surgical experience, technique, and intraoperative adaptability are key ingredients to the successful outcome of shoulder arthroplasty. Preoperative planning allows the surgical team to grapple - before scrubbing in - with the anticipated pathoanatomy and the decisions that will have to made at surgery .

Traditionally, preoprerative planning was based on the physical examination and standard imaging of the shoulder, including standardized plain films with the addition of CT and MRI as necessary.

Recently introduced innovations in preoperative planning and plan implementation include three-dimensional simulation software, image guided navigation, patient specific instrumentation, virtual reality, and mixed reality.

While the effectiveness of these innovations in improving clinical outcomes for the patient remains to be rigorously demonstrated, the advocates of these innovations point to the improved accuracy and precision of component placement that can be achieved:

Accuracy and Reliability of Computerized Surgical Planning Software in Anatomic Total Shoulder Arthroplasty

Reliability and accuracy of 3D preoperative planning software for glenoid implants in total shoulder arthroplasty

Accuracy and precision of placement of the glenoid baseplate in reverse total shoulder arthroplasty using a novel computer assisted navigation system combined with preoperative planning: A controlled cadaveric study

The Value of Computer-Assisted Navigation for Glenoid Baseplate Implantation in Reverse Shoulder Arthroplasty: A Systematic Review and Meta-Analysis

High intraoperative accuracy and low complication rate of computer-assisted navigation of the glenoid in total shoulder arthroplasty

1. Precision refers to the degree of reproducibility or repeatability of the placement - doing it the same way each time. Accuracy, on the other hand, refers to the degree of closeness between the desired and the actual placement - how close do we need to be to what target?

2. 
   

   If we think of the field goal in American football, we note that the ball doesn't need to be accurately positioned in the center of the uprights nor does it need to be reproducibly positioned, it just needs to pass between the uprights to get the team three points.

   
   

   

   
   

   
   

   With respect to accuracy, the outcome (number of points generated) for each of the two sets of six kicks shown below would be the same.

   
   

   
   
   
   
   
   
   
   

   

   
   

   
   

   We need to learn how much accuracy is needed to get our patients the outcome they want. This is difficult, because we have yet to learn where the goal posts are, for example with respect to version correction and reverse total shoulder component position.

   
   

   As shown below, precision in and of itself cannot be the goal.

   
   

   
   
   

   
   

   As we design studies to determine the clinical value of planning innovations, we need define the degree of accuracy and precision needed to achieve the desired outcome for the patient. Do we know where goalposts are - where is the target - and how wide apart are the uprights? As pointed out in Influence of Backside Seating Parameters and Augmented Baseplate Components in Virtual Planning for Reverse Shoulder Arthroplasty, surgeons vary widely in their targeted position for total shoulder arthroplasty components.

   
   

   You can support cutting edge shoulder research and education that are leading to better care for patients with shoulder problems, click on this link.
   
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   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).
   
   

Do patients benefit from preoperative CT planning?

3D CT planning is a resource-consuming preoperative exercise, the primary goal of which is to help guide the placement of the glenoid component in a pre-determined position. It is currently used in cases of complex pathoanatomy as well as in routine cases of glenohumeral arthritis. 

The appropriate use and clinical effectiveness of this technology for different glenoid pathologies have not been rigorously evaluated.

The authors of The Influence of Computed Tomography Preoperative Planning on Clinical Outcomes after Anatomic Total Shoulder Arthroplasty: A Matched Cohort Analysis sought determine the effectiveness of 3D CT planning in improving the clinical outcomes of anatomic total shoulders (aTSA).

Using a multicenter shoulder arthroplasty registry, they identified patients having two year clinical followup after aTSA. The patients of seven surgeons were included. Surgeon preferences differed with respect to subscapularis management (peel vs lesser tuberosity), type of glenoid component (vault lock vs pegged vs keeled), use or non-use of 3D CT planning, and use or non-use of patient specific instrumentation (PSI). 

Those cases in which 3D CT planning was used constituted a "study" group. Patients not having 3D CT planning were matched to the study patients 1:1 based on age +/- 3 years, sex, and preoperative ASES score within 10 points. Matching for other variables, such as the type of preoperative glenohumeral pathoanatomy, surgeon identity, technique of subscapularis management, and type of glenoid component used was not carried out because there were insufficient potential control patients.

The study group consisted of 84 patients with 3D CT preoperative planning (51 with PSI, 33 without) and 84 matched control patients without CT-based planning. A comparison of these two groups is shown below. Improvement from baseline for the ASES was statistically significantly greater in the CT-based planning group compared to matched controls; however the average amount of improvement (6.4) failed to meet the threshold for clinically significant improvement (the minimal clinically important difference for the ASES score is 17). 

Within the 3D CT cohort, there were no significant differences in PROs or ROM between aTSAs performed with or without PSI. 

The authors concluded that the clinical significance of these finding is unclear, as the differences failed to meet a clinically significant threshold.

Comment: One philosophy in total shoulder arthroplasty is to use 3D CT planning and patient specific software to guide "correction to normal anatomy" of preoperative glenohumeral pathoanatomy using eccentric removal of glenoid bone   

and/or glenoid component augmentation.

Another philosophy is to ream the glenoid bone only to the extent needed to create a single concavity, accepting some glenoid retroversion and preserving as much glenoid bone stock as possible; this approach is based on intraoperative observation rather than on preoperative 3D CT planning.

Extensive clinical research will be required to find the balance between these two philosophies in optimizing the long term outcomes for patients with glenohumeral arthritis. Specifically, it will be important to determine whether certain patients with specific pathoanatomies may achieve clinical benefit from the added resources required for 3D CT planning.

You can support cutting edge shoulder research that is leading to better care for patients with shoulder problems, click on this link.

Follow on twitter: https://twitter.com/shoulderarth

Follow on facebook: click on this link

Follow on facebook: https://www.facebook.com/frederick.matsen

Follow on LinkedIn: https://www.linkedin.com/in/rick-matsen-88b1a8133/

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).

Preoperative computer planning and patient-specific instrumentation: "The long-term clinical benefit is unknown and requires further examination prior to the widespread acceptance of these technologies"

Computer-Assisted Preoperative Planning and Patient-Specific Instrumentation for Glenoid Implants in Shoulder Arthroplasty

These authors reviewed the literature on computer-assisted preoperative planning and patient specific instrumentation for glenoid implants in shoulder arthroplasty.

Their bullet points were:

» Glenoid component positioning affects implant survival after total shoulder arthroplasty, and accurate glenoid-component positioning is an important technical aspect.

» The use of virtual planning and patient-specific instrumentation has been shown to produce reliable implant placement in the laboratory and in some clinical studies.

» Currently available preoperative planning software programs employ different techniques to generate 3-dimensional models and produce anatomic measurements potentially affecting clinical decisions.

» There are no published data, to our knowledge, on the effect of preoperative computer planning and patient-specific instrumentation on long-term clinical outcomes.

The last of the above statements is most critical in that the value of these innovations is determined by the   benefit to the patient divided by the cost. See New technologies in anatomic total shoulder: what is their value to the patient? In terms of the value of these innovations, the authors state "high-level clinical outcomes studies are needed to justify the additional time and cost related to the universal use of CT scans, preoperative planning, and the production of PSI guides".

These authors point out that, "planning software is used in other areas of joint arthroplasty, most commonly for total knee arthroplasty. However, published reports have not reached consensus regarding the utility, accuracy, and reproducibility. Various studies have reported more accurate implant positioning with software assisted planning in total knee arthroplasty, but without impacting patient reported outcomes."

Comment: "Precision" and "accuracy" are terms often used in describing the benefits of computer assistance. Precision means the ability to reproduce the same result each time, while accuracy refers to the ability to hit a predefined target. These characteristics are of critical importance in the assembly of microchips or automobiles where the targets are clearly specified and the configuration of the structure entering the assembly line is always identical. In dealing with an arthritic shoulder, neither of these is true: (1) No two arthritic shoulders are the same and (2) while average ± standard deviation values for glenoid version and joint line position in normal shoulders can be defined, evidence is lacking that "reproducing normal anatomy" leads to better outcomes for the patient.

Consider an example from the review where three-dimensional planning was used.

Note that pre-operatively, the arthritic humeral head was centered in the glenoid fossa in both the superior-inferior direction and in the anteroposterior direction.

While the patient-assessed clinical outcome of this case was not presented, the postoperative x-rays show what appears to be superior decentering of the prosthetic humeral head on the glenoid in the AP view and anterior decentering of the humeral head on the glenoid on the axillary view.

Since the value of an innovation is determined by the health outcome that matters to the patient divided by the cost of delivering that outcome, each innovation needs to be put to the test by tracking patient reported measures of comfort and function combined with tracking of the cost of care from the initial encounter through a period of followup that is long enough to capture most adverse outcomes (n.b. this is likely to be 7-10 years for total shoulder arthroplasty). 

The potential divergence between the goal of the surgeon to restore "normal anatomy" and the patient's desire for durable comfort and function is reminiscent of the work of the late Wilton Bunch, who demonstrated that the goal of many scoliosis surgeons was to achieve a straight spine, while the goal of most scoliosis patients was to have a durably comfortable and functional back.

Follow on twitter: https://twitter.com/shoulderarth

Follow on facebook: https://www.facebook.com/frederick.matsen

Follow on LinkedIn: https://www.linkedin.com/in/rick-matsen-88b1a8133/

How you can support research in shoulder surgery Click on this link.

Here are some videos that are of shoulder interest

Shoulder arthritis - what you need to know (see this link)

The smooth and move for irreparable cuff tears (see this link)

The total shoulder arthroplasty (see this link).

The ream and run technique is shown in this link.

The cuff tear arthropathy arthroplasty (see this link).

The reverse total shoulder arthroplasty (see this link).

Shoulder rehabilitation exercises (see this link).

How reliable is preoperative planning software for shoulder arthroplasty?

 Does commercially available shoulder arthroplasty preoperative planning software agree with surgeon measurements of version, inclination, and subluxation?

These authors used commercially available software from 4 companies (Blueprint: Wright Medical, Memphis, TN, USA; GPS: Exactech, Gainesville, FL, USA; Materialise: DJO, Vista, CA, USA; and VIP: Arthrex, Naples, FL, USA) to evaluate 81 consecutive shoulder computed tomography scans obtained for preoperative planning purposes for shoulder arthroplasty. The results were compared to the analysis of  5 fellowship-trained sports medicine/shoulder surgeons. 

Surgeon reliability was acceptable for version, inclination, and the relationship of the humeral head to the plane of the scapula .

Significant differences were found between surgeon and commercial software measurements in version, inclination, and the relationship of the humeral head to the plane of the scapula (not to be confused with glenohumeral subluxation). Note in the example below, the humeral head is centered in the glenoid (i.e. not subluxated), even though a substantial percentage of the humeral head lies posterior to the plane of the scapula.

The authors concluded that preoperative planning software for shoulder arthroplasty has limited agreement in measures of version, inclination, and the relationship of the humeral head to the plane of the scapula, whereas surgeons have high inter-reliability. They recommend that surgeons should be cautious when using commercial software planning systems and when comparing publications that use different planning systems to determine preoperative glenoid deformity measurements.

Comment: The authors point out that reliance on planning software to determine the type of procedure, the need for special implants, and the position of the components may lead to decisions different from what a surgeon would make. For example, it may lead some surgeons to change from an anatomic shoulder replacement to a reverse shoulder replacement or to use glenoid augmentation when it is not necessary. As they say, surgical decisions should be made based on intraoperative findings, preoperative plan, quality of patient tissue, surgeon experience, and evolving evidence-based outcomes associated with implant longevity and patient function.

From recent aviation history, we are all too aware of what happens when the pilot relinquishes control to a computer.

How you can support research in shoulder surgery Click on this link.

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 total shoulder arthroplasty (see this link).

The ream and run technique is shown in 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).

Shoulder Arthroplasty Preoperative Planning Software - what is its value?

Does Commercially Available Shoulder Arthroplasty Preoperative Planning Software Agree With Surgeon Measurements Of Version, Inclination and Subluxation?

81 consecutive shoulder computed tomography (CT) scans obtained for preoperative planning purposes for shoulder arthroplasty were analyzed by commercially available software from four companies (Blueprint – Wright Medical; GPS – Exactech; Materialise; and VIP – Arthrex), and by 5 fellowship trained sports medicine/shoulder surgeons.

Inclination, version and subluxation of the humerus were measured in a blinded fashion on axial and coronal sequences at the mid-glenoid.

Surgeon measurements were analyzed for agreement, and were compared to the 4 commercial programs.

Surgeon reliability was acceptable for version, inclination, and subluxation. 

Significant differences were found between surgeon and commercial software measurements in version, inclination, and subluxation. 

Software measurements tended to be more superiorly inclined (average -2° to 2° greater), more retroverted (average 2°-5° greater) and more posteriorly subluxed (average 7°-10° greater) than surgeon measurements. 

The authors concluded that "preoperative planning software for shoulder arthroplasty has limited agreement in measures of version, inclination and subluxation measurements while surgeons have high interreliability. Surgeons should be cautious when using commercial software planning systems and when comparing publications that use different planning systems to determine preoperative glenoid deformity measurements."

They caution further, "if the templated preoperative  plan is inaccurate, the glenoid component can be placed in inappropriate alignment, or, the actual glenoid procedure may be altered or deviate from current best-practice recommendations. Although surgeon input is necessary to create the final preoperative plan in these various software platforms, many surgeons attempt to follow the templatned plan without adjusting intraoperatively. If the software is under or overestimating version, inclination, or subluxation, it is possible to direct the surgeon into improper component placement. Even more concerning is that some surgeons may use these measurements to decide between anatomic and reverse  arthroplasty.""final decisions should be predicated on multiple factors including intraoperative findings, preoperative plan, quality of tissue, surgeon experience, and evolving evidence-based outcomes associated with implant longevity and patient function."

Comment: Preoperative CT scans, 3-D planning software and patient specific instrumentation are costly in terms of health care dollars and provider time. Especially during these years when health care budgets are and will continue to be severely stressed by the COVID19 pandemic, we must ask whether these technologies add value in terms of measured improvements in the outcome patients realize from shoulder arthroplasty.

As pointed out by these authors, the type of arthroplasty, the type of components, the size of the components, and the position of these components need to be decided in large part based on intraoperative findings - including the nature of the soft tissues and the dynamic stability - factors that cannot be determined by preoperative static images of the bones. Reliance on 3D planning software may lead to choices that an experienced surgeon would not make.

In the great majority of cases, standardized preoperative plain films provide all the necessary information about the bony anatomy necessary to plan and perform the arthroplasty.

When the axillary view is obtained with the arm elevated in the plane of the scapula it can reveal instability not seen on CT scans obtained with the arm at the side.

This view reveals the key details of the glenohumeral pathoanatomy.

It also enables preoperative to sequential postoperative comparisons that would otherwise require repeated CT scans.

In today's climate, it may be time to reassess the measured (not theoretical) clinical value of 3D planning software to the patient.

As a basis for comparison, the lower line on the graph below from the Australian Orthopedic Assocation registry show a very low ten year revision rate for anatomic total shoulders using an all cross-linked polyethylene glenoid component inserted without 3D planning. Can the results of 3D planning be shown to be better than that?

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To see a YouTube of on how we do total shoulder arthroplasty, click on this link.

To see a YouTube of our technique for a reverse total shoulder arthroplasty, click on this link.

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How you can support research in shoulder surgery Click on this link.

We have a new set of shoulder youtubes about the shoulder, check them out at this link.

Be sure to visit "Ream and Run - the state of the art" regarding this radically conservative approach to shoulder arthritis at this link and this link

Use the "Search" box to the right to find other topics of interest to you.

You may be interested in some of our most visited web pages  arthritis, total shoulder, ream and run, reverse total shoulder, CTA arthroplasty, and rotator cuff surgery as well as the 'ream and run essentials'