Preoperative planning for reverse total shoulder using plain films.

A major component of the success of reverse total shoulder arthroplasty is the position and orientation of the base plate on the glenoid bone. While many different planning systems are available, the challenge is transferring the plan to the patient without relying on expensive and time-consuming approaches, such patient specific instrumentation or augmented reality.

Our usual target is to have the inferior edge of the baseplate at the inferior aspect of the reamed glenoid and tilted inferiorly with the central screw or peg inclined so that it is parallel to the floor of the supraspinous fossa. 

For routine cases, we plan for rTSA using plain x-rays obtained in the plane of the scapula (Grashey view). The scaled image is uploaded to the universally available PACS (Picture Archiving and Communication System). PACS tools are used to find the location of insertion point and the inclination of the drill for the central screw or post. These scaled measurements are then used to position and orient the drill on the patient's glenoid in the operating room. This generic approach does not encourage the surgeon to select implants from any particular company.

Here's an example: a 70 year old man with a massive irreparable cuff tear and pseudo paralysis. 

On the PACS screen a line segment (yellow) with a length equal to the radius of the base plate is drawn perpendicular to the floor of the supraspinatus fossa (red line) from the glenoid articular surface to the glenoid neck. The upper end of this line is the insertion point (yellow dot)

The distance of this point along the glenoid articular surface (green line) from the inferior glenoid lip is measured on the scaled PACS image. The insertion point can be found at surgery by measuring this distance using a flexible ruler.

The angle of drill insertion (dotted gold line) relative to the joint surface at the insertion point (black line) is noted on PACS and duplicated at surgery.

 

Favard et al have described four types of glenoid pathoanatomy in cuff tear arthropathy.  

For some cases, such as types E1 and E3, this planning approach may indicate that excessive reaming of inferior glenoid bone would be necessary to achieve the desired baseplate position and orientation. In such cases superior bone grafting or an augmented baseplate may be called for.

While more sophisticated proprietary systems can be used for more complex pathoanatomy, this generic approach can be effective for a large percentage of rTSA cases.

We use a similar plain films/PACS approach to planning a stemless anatomic arthroplasty - see this link.

Sometimes a convenient solution is staring right at us

Sooty Grouse

Mt. Rainier

July 4, 2025

You can support cutting edge shoulder research that is 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).

Reverse total shoulder - the complication of baseplate failure

Here are some cases of failure of the baseplate fixation to the scapula in reverse total shoulders performed with several different modern prosthesis systems. What do these failures have in common?

The answer, of course, is that in each case the glenosphere has been rocked up superiorly. This is because the major loads on the glenoid component - whether from deltoid contraction, from a fall, or from pushing up from the bed -  exert a superiorly directed force on the glenosphere that challenges the base plate's fixation to bone.

The ability of the glenoid component to resist these major loads depends on (1) secure bony fixation of the inferior screws in bone (green arrows) to resist failure in traction and (2) compression of the superior aspect of the baseplate against glenoid bone (yellow arrow) to prevent its rocking upwards as pointed out in Factors affecting fixation of the glenoid component of a reverse total shoulder prothesis. 

If either of these is insecure, upward loads on the glenosphere can cause the baseplate to rock upwards away from the bone.

It's all about good carpentry: (1) preparing the glenoid bone so that there is maximal contact between the superior baseplate and host bone and (2) secure screw placement in good quality bone. If the quality of the bone suboptimal, insertion of the baseplate central screw without tapping may provide better fixation (see Avoiding Glenoid Baseplate Fixation Failure by Altering Surgical Technique for Varying Bone Densities). 

Bone graft may not be a perfect substitute for host bone; see Early radiographic failure of reverse total shoulder arthroplasty with structural bone graft for glenoid bone loss

The authors of How to Avoid Baseplate Failure: The Effect of Compression and RSA Baseplate Design on Implant Stability recognize that immediate, secure fixation of the baseplate is essential: patients may fall or otherwise load the glenosphere soon after surgery - long before any ingrowth has taken place. Furthermore, high compression of the central screw dramatically improves the initial (T=0) stability of the baseplate.

In Revision Reverse Shoulder Arthroplasty for the Management of Baseplate Failure: An Analysis of 676 Revision RSA Procedures the importance of maximizing the contact between the baseplate and supporting bone is again emphasized for both primary and revision reverse total shoulders.

Finally, the stability of the baseplate on the bone of the glenoid is optimized by inferior inclination of the glenosphere, which results in a compressive force on the baseplate against bone when the glenoid is loaded by the humerus (note the obtuse angle between the arrows)

 

...as opposed to the distracting force that results when the glenosphere is superiorly inclined  (note the acute angle between the arrows). (see Biomechanical comparison of component position and hardware failure in the reverse shoulder prosthesis)

It's about good carpentry

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).

Reverse total shoulder failure from baseplate loosening

Incidence and risk factors for aseptic baseplate loosening of reverse total shoulder arthroplasty

These authors analyzed 202 shoulders that underwent primary or revision RTSA using 1 implant system and evaluated baseplate loosening at a minimum 2-year follow-up. They found that baseplate loosening occurred in 6 shoulders (3.0%). 

Four of the cases of baseplate failure occurred in the 39 revision RTSAs (10%) while only 2 occurred in the 163 primary arthroplasties (1.2%). 

Five of the cases of baseplate failure were among the 25 patients receiving structural bone graft.

Two of the cases of baseplate failure were among the 11 patients who did not have fixation with all locking screws. 

Comment: These data suggest that in this individual surgeon, individual prosthesis design series, baseplate failure was associated with inferior quality of glenoid bone (resulting from prior failure or necessitating bone graft or non-locking screws.

In the two examples from the article shown above, it is evident that the failure results from an upwards directed force applied to the laterally offset glenosphere by the humeral component. As emphasized in this article, Factors affecting fixation of the glenoid component of a reverse total shoulder prothesis, this force is best resisted by secure screw fixation and by solid contact between the upper aspect of the baseplate and the carefully prepared native glenoid bone.

The rates of complications after an arthroplasty are related to the patient, the prosthesis, and the physician performing the surgery. Here we have an analysis of 202 of 256 shoulders treated between 2008 to 2014 by an individual surgeon using an individual reverse total shoulder design. We can anticipate that the rate of complications, such as baseplate failure, in these experienced hands would be less than in the hands of less experienced surgeons. In fact a recent article Analysis of 4063 complications of shoulder arthroplasty reported to the US Food and Drug  Administration from 2012 to 2016, found that baseplate failure was the fourth most common cause of failure among 2390 revised reverse total shoulders:

The difference is that the data in the table above represent cases from occasional as well as from frequent shoulder arthroplasty surgeons.

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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'

Reverse total shoulder - safe baseplate fixation

Scapula fracture incidence in reverse total shoulder arthroplasty using screws above or below metaglene central cage: clinical and biomechanical outcomes

Scapular spine fractures are serious complications of reverse total shoulder arthroplasty.

These authors reviewed 318 reverse total shoulder arthroplasties (RTSAs) to identify scapular spine fractures.
Of 206 patients in the superior screw group, 9 (4.4%) experienced scapula spine fractures.

Of 112 patients in the inferior screw group, 0 had scapular spine fractures.

They also implanted RTSAs in 17 cadaveric scapula specimens with 2 screw configurations: inferior screws alone (group 1INF) vs. inferior screws with one additional superior screw (group 2SUP). 

Biomechanically, superior screw constructs (group 2SUP) demonstrated significantly (P < .05) lower load to failure (1077 N vs. 1970 N) compared with constructs with no superior screws (group 1INF). 

They concluded that the risk of scapular fractures was significantly (P < .05) for patients with no screws placed above the central cage compared with patients with superior metaglene screws.

The superior screw may not add substantially to the quality of the fixation. In an article entitled, Factors affecting fixation of the glenoid component of a reverse total shoulder prothesis, the relatively greater importance of the inferior screw in contrast to the relatively lower importance of the superior screw was emphasized.

In this type of design,  superiorly directed loads applied to the glenosphere by the humeral component are resisted primarily by the inferior screw.

Our approach to reverse total shoulder arthroplasty is to use a fixation system that uses a large central compression screw, avoiding the risks of a superiorly directed screw.

Here are some related posts.

Scapular fracture in reverse total shoulder arthroplasty

Scapular fractures after reverse total shoulder

Scapular spine fractures after reverse total shoulder 2

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Consultation for those who live a distance away from Seattle.

Check out the new Shoulder Arthritis Book - click here.

Click here to see the new Rotator Cuff Book

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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Reverse total shoulder arthroplasty - tilting the baseplate

Accuracy of the Subchondral Smile and Surface Referencing Techniques in Reverse Shoulder Arthroplasty.

These authors point out that inferior glenoid baseplate tilt relative to the coronal axis of the scapular body has been associated with improved results and fewer postoperative complications in reverse shoulder arthroplasty. They evaluated the accuracy of the "subchondral smile" and cannulated surface guide techniques in achieving inferior glenoid baseplate tilt by using 3-dimensional preoperative planning software. Virtual glenoid baseplate preparation and implantation were performed using computed tomography scans of 16 shoulders with rotator cuff deficiency. Two techniques were used: a subchondral smile technique that preferentially reams the interior glenoid, resulting in the appearance of a smile, and a cannulated surface guide technique that references the native glenoid face to place the baseplate in 10° of inferior tilt. 

Using the subchondral smile technique, the glenoid baseplate was implanted at a mean of 8.9° of superior tilt relative to the transverse scapular axis. Using the surface guide technique, the glenoid baseplate was implanted at a mean of 2.8° of superior tilt. 

Neither the subchondral smile technique nor the 10° cannulated surface guide technique is a reliable method to produce inferior glenoid tilt relative to the transverse axis of the scapula. 

They suggest that three-dimensional preoperative planning software may be useful for glenoid baseplate positioning in reverse shoulder arthroplasty.

Comment: Our practice is to obtain a preoperative true anteroposterior radiograph in the plane of the scapula and then use that image to envision a line perpendicular to the glenoid center.  At surgery, the drill for the central screw of the baseplate is oriented by eye with a slight inferior tilt in reference to this perpendicular to the glenoid center. No guides or special instrumentation is used. In cases where the preoperative true anteroposterior radiograph in the plane of the scapula indicates a superior inclination of the perpendicular to the glenoid center, the angle of the drill is adjusted accordingly.

This approach is shown for the left and right shoulders of a patient having had a failed hemiarthroplasty on one side and pseudo paralysis on the other. 

Our approach to reverse total shoulder arthroplasty is shown in this link. Our goal, whenever possible, is a cementless impaction grafted humeral stem with a 135 degree angle and a laterally offset glenopshere securely fixed with screws in the high quality bone at the base of the subscapularis fossa with minimal inferior placement to avoid excess tension on the acromion and the brachial plexus. The use of a glenosphere with lateral offset makes the exact inclination of the component less critical.

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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

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.

Glenoid baseplate micromotion - variation among different designs

Glenoid Baseplate Micromotion in Reverse Total Shoulder Arthroplasty

This author used osteopenic sawbones scapulae to model the force required to cause initial loosening of the glenoid baseplate and the force required to cause ultimate failure of the baseplate, and secondly, to distinguish trends in the design parameters resulting in increased fixation in order to optimize baseplate design.

An Instron was used to apply a load to cause displacement of the baseplate and record the applied loading; a Linear Variable Differential Transformer (LVDT) was used to measure and record the micro motion of the implant experiences. Each specimen was loaded in the  inferior to superior direction until 150 μm of motion occurred for 30 cycles at 1 Hz. The assumption was made that if more than 150 μm of motion occurs between the implant and bone, ingrowth will not occur to permanently stabilize the baseplate.

As shown below, there were differences among the implants, they were not statistically significant.

Conclusion: This thesis includes a very comprehensive review of reverse total shoulder baseplate failure and is recommended reading.
The high variability and lack of significant differences in this sawbones model suggests that even greater variation may be expected in clinical practice. It is unclear how important bone ingrowth is to the fixation of the different reverse implants - some of which use large compression and locking screws without an ingrowth central post. The quality of the patient's bone and the surgical technique may be at least as important to preventing baseplate failure as the implant design.

Our approach to reverse total shoulder arthroplasty is shown in this link.

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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

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.