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.

   
   

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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).
   
   

3D planning in shoulder arthroplasty - what is its value?

Surgeon Acceptance of an Initial 3D Glenoid Preoperative Plan: Rates and Risk Factors

These authors point out that the effect of 3D planning on surgeon decision making has not been well studied. They conducted a retrospective review of 6,483 total shoulder cases (417 surgeons) for which the glenoid component was planned with a commercially available 3D computed tomography (CT) software program (VIP, Arthrex, Inc.) from 2016 to 2019.

Fifty-six surgeons and their 4,314 planned cases (67%) were included in a high-volume group (>30 cases/surgeon).

The glenoid version (Vtech) and inclination (Itech) of the VIP technician plan as well as the surgeon’s final plan for version (Vsurg) and inclination (Isurg) were extracted. When the version and/or inclination of the surgeon plan matched that of the technician, that variable was defined as “accepted”.

In approximately half of the cases (55%) there was matching of both version and inclination. In 18%  neither parameter of the glenoid plan matched that of the technician.

Surgeon acceptance of the initial plan was lower for greater degrees of retroversion.
Surgeon acceptance of the initial plan was lower for surgeons with higher case volumes.

The authors concluded that "Shoulder surgeons should be aware that an initial 3D preoperative plan provided by industry represents a potential source of cognitive bias in shoulder arthroplasty planning."

Comment: This paper suggests that in almost half of the cases, the surgeon selected a plan different than that provided by the technician and that this discordance increased with surgeon experience and glenoid retroversion.

The value of 3D planning with regard to patient outcomes is not provided. In that the cost of 3D planning is substantial* and the effect on the patient is unknown, it is important to asses the value of this technology as suggested here:
Rethinking How We Spend Healthcare Dollars During—and After—the Pandemic

*The cost of this 3D planning appears substantial, "For this 3D planning software, a CT submitted for 3D planning with the VIP system must meet certain FDA requirements and is screened and processed by a VIP Operations  team technician trained in the use of the software. The team is comprised of 11 employees  (Arthrex, Inc., Naples, FL, USA) trained in the segmentation, thresholding and implant  positioning of Arthrex anatomic and reverse total shoulder arthroplasty components in the VIP system."

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To see a YouTube of our technique for total shoulder arthroplasty without preoperative CT scan or 3D planning software, click on this link.

To see a YouTube of our technique for a reverse total shoulder arthroplasty without preoperative CT scan or 3D planning software, click on this link.

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To see our new series of youtube videos on important shoulder surgeries and how they are done, click here.

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

How you can support progress in shoulder surgery

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'

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'

Three-dimensional preoperative imaging for total shoulders

Trends and impact of three-dimensional preoperative imaging for anatomic total shoulder arthroplasty

These authors sought to determine the incidence in the United States of preoperative three dimensional imaging prior to anatomic total shoulder arthroplasty for osteoarthritis and to determine if preoperative imaging is associated with decreased complication rates.

They used a Medicare insurance database, to identify  patients who underwent computed tomography
(n.9380) and/or magnetic resonance imaging (n.15,653) prior to anatomic total shoulder arthroplasty for a diagnosis of osteoarthritis from 2005 to 2014.

The incidence of preoperative three-dimensional imaging significantly increased over time, with computed tomography increasing more than magnetic resonance imaging.

While the overall revision rate was 0.8% lower in the preop CT group, the reasons for the difference are not clear in that the rates of loosening/osteolysis, periprosthetic fracture, periprosthetic disclocation, dislocation/instability, mechanical loosening, implant wear/breakage, and cuff tear were not different between the preop CT group and controls.

Comment: It seems that the clinical benefit 3 dimensional preoperative imaging needs further study with respect to defining its advantages for specific diagnoses.

At present, we find that standardized plain films provide the information needed to plan and perform total shoulder arthroplasty (see this link).

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

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To see our new series of youtube videos on important shoulder surgeries and how they are done, click here.

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

How you can support progress in shoulder surgery

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'

Shoulder arthroplasty - is three dimensional planning helpful?

The influence of three-dimensional planning on decision-making in total shoulder arthroplasty

These authors evaluated the accuracy of glenoid version and inclination measurements using 2D CT scans compared with a validated 3D software program and its influence on decision making on implant selection.

They found that preoperative glenoid retroversion on reformatted 2D CT scans was 11.9° ± 9.6° and mean superior inclination was 10.7° ±  8.6°. When the 3D software was used the results were slightly different, glenoid retroversion averaged 15.1° ± 10.6° and superior inclination averaged 8.9° ± 9.9°. 

Surgeon observers decided from glenoid measurements and rotator cuff integrity whether to implant an anatomic or reverse shoulder arthroplasty. A reverse was selected if there was

(1) grade 3 and 4 fatty infiltration according to the Goutallier classification

(2) superior glenoid inclination greater than 10° or 

(3) glenoid retroversion greater than 27° of the neoglenoid as well as subluxation of the humerus greater than 80%.

Decisions based on the 2D analysis were compared to the decisions made according to the 3D planning. The hypothetical choice of anatomic versus total shoulder was changed in 7 of 50 patients after the 3D planning.  

In all cases where the decision was altered from an anatomic to a reverse prosthesis, 3D measurements demonstrated an increased glenoid retroversion of more than 8° compared with 2D.

In all cases where the decision was altered from a reverse to an anatomic prosthesis a decrease of more than 10° of glenoid inclination was observed on the 3D reconstructions.

Comment: In our practice, we do not depend on CT measurements to define the choice between anatomic and reverse total shoulders. Rather the choice is based on characteristics such as pseudoparalysis, instability, bone stock, and patient activity levels. We do not find arbitrary thresholds, such as 10° of inclination or 27° of inclination, to be of clinical utility.

In most cases the information necessary for prosthesis selection can be gathered from a good history, physical examination and standardized plain radiographs, avoiding the cost and radiation exposure of CT scans and complex reconstructions requiring proprietary software

Does a preoperative CT show the key information about the arthritic shoulder?

Another three dimensional drill guide tested in vitro

Testing of a novel pin array guide for accurate three-dimensional glenoid component positioning


These authors created polymer models of glenoids from computed tomography scans from 9 arthritic patients. They describe a novel pin array guide and method for patient-specific guiding of the glenoid central drill hole.

Each 3-dimensional (3D) printed scapula was shrouded "to simulate the operative situation".

Three different methods for central drill alignment were tested, all with the target orientation of 5° retroversion and 0° inclination: no assistance, assistance by preoperative 3D imaging, and assistance by the pin array guide.

Version errors using the pin array guide (3° ± 2°) were significantly lower than version errors associated with no assistance (9° ± 7°) and preoperative 3D imaging (8° ± 6°).

The authors suggest that "This method may ultimately provide a cost-effective solution enabling surgeons to obtain accurate orientation of the glenoid."

Comment: The data on the nine species point to the wide variety of glenoid pathoanatomy that may be encountered in shoulder arthroplasty.

What is not presented in this paper is the cost of the system, the time necessary to implement the system, and whether the exposure available in a human shoulder would allow use of the system. Some of this information could have been gathered by attempting to implement the system in a cadaver with a realistic surgical exposure, rather that what was available with a plastic scapula in a clamp. Without this information, we cannot determine the value of a system that 'improves' guide pin positioning by an average of less than 10 degrees.

Finally, it is not known whether glenoids with severe retroversion, such as the one represented on their model below, are best served by attempting to 'correct' the version. The photo shows that to change the version to 5 degrees of retroversion would require a massive posterior bone graft, removal of a huge amount of anterior bone, or the use of a massively augmented glenoid component.

As we've explained in a recent post as well as in an earlier post, our approach is to ream the glenoid conservatively to a single concavity without using a guidewire and use an anteriorly eccentric humeral head and rotator inverval plication as necessary to manage any tendency for posterior instability.

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Consultation for those who live a distance away from Seattle.

Check out the new Shoulder Arthritis Book - click here.

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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 including:shoulder arthritis, total shoulder, ream and run, reverse total shoulder, CTA arthroplasty, and rotator cuff surgery as well as the 'ream and run essentials'

See from which cities our patients come.

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Shoulder joint replacement arthroplasty - does three dimensional imaging and templating get us closer to the goal?

Three-dimensional imaging and templating improve glenoid implant positioning.

Preoperative quantitative assessment of glenoid bone loss, selection of the glenoid component, and definition of its desired location can be challenging. Placement of the glenoid component in the desired location at the time of surgery is difficult, especially with severe glenoid pathological conditions.

These authors randomly assigned 46 patients to three-dimensional computed tomographic preoperative templating with either standard instrumentation or with patient-specific instrumentation and were compared with a nonrandomized group of seventeen patients with two-dimensional imaging and standard instrumentation used as historical controls. All patients had postoperative three-dimensional computed tomographic metal artifact reduction imaging to measure and to compare implant position with the preoperative plan.

They found that three-dimensional imaging and templating with or without patient-specific instrumentation, yielded a significant improvement achieving the desired implant position within 5° of inclination or 10° of version when compared with two-dimensional imaging and standard instrumentation.

Comment: Consistent with our experience, these patients with primary osteoarthritis were categorized as showing a wide range of pathoanatomies. The issue is how these variations might best be managed. These authors indicate that one method is to 'correct' glenoid version and inclination between 0 and 10 degrees relative to the plane of the scapula, using augmented glenoid components if deemed necessary. As Figure 2 of this article demonstrates, this approach may lead to the removal of a substantial amount of glenoid bone and may require not only a special glenoid component, but also special instruments to guide and prepare the glenoid bone for the receipt of this component. The alternative, most commonly used in our practice, is to use nubbed reamers to convert the glenoid articular face to a single concavity while preserving the maximal amount of glenoid bone as described here.

If we accept the premise that glenoid version and inclination should be corrected, these authors found that glenoid inserted with three-dimensional imaging and  'three-dimensional intelligent reusable instruments' had a mean difference of 3 degrees in inclination (CI  2 - 4) from the planned position, while the two-dimensional imaging group had a mean difference of 11 (CI 8 - 14). The respective data for version were 4 (CI 3 - 5) and 7 (CI 5 - 9). The question becomes whether the differences of 7 and 3 degrees are worth the time and expense of the three-dimensional imaging and  three-dimensional intelligent reusable instrument system in terms of value to the patient. Time will tell.



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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 including:shoulder arthritis, total shoulder, ream and run, reverse total shoulder, CTA arthroplasty, and rotator cuff surgery as well as the 'ream and run essentials'



See from which cities our patients come.





See the countries from which our readers come on this post.

Three dimensional planning and patient specific glenoid guides: a virtual study in cadevaric scapulae without arthritis

Three-dimensional planning and use of patient-specific guides improve glenoid component position: an in vitro study.

These authors evaluated the reliability and precision of three-dimensional planning and use of patient-specific guides in the simulated placement of a glenoid guide pin in 18 normal dry cadaver scapulae.

Quantitative analysis of guide pin positioning demonstrated a good correlation between preoperative planning and the achieved position of the guide pin.

Comment: This study was performed in dry normal scapulae. It focused on pin placement - glenoid reaming and actual component placement were not included.  From the photographs, it appears that complete exposure of the perimeter of the glenoid is necessary to allow for insertion of the pin guide. Thus the ability to use this system in actual shoulder arthroplasty where exposure can be difficult  - particularly in cases of glenoid retroversion - is unknown. The cost of the system and the time necessary in its implementation are not provided in this manuscript - thus the value (benefit/cost) cannot be determined. See this related post.

We do not use a guide pin in shoulder arthroplasties out of concern for pin breakage or inadvertent pin advancement into the chest. Our technique for glenoid insertion is shown here.

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Consultation for those who live a distance away from Seattle.

Click here to see the new Shoulder Arthritis Book

Click here to see the new Rotator Cuff Book

To see the topics covered in this Blog, click here

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 including:shoulder arthritis, total shoulder, ream and run, reverse total shoulder, CTA arthroplasty, and rotator cuff surgery as well as the 'ream and run essentials'