Glenoid pathoanatomy: what about the B Walch types?

In his classic paper, Morphologic study of the glenoid in primary glenohumeral osteoarthritis, Gilles Walch identified the B1 and B2 glenoids as being common of types of arthritic glenohumeral pathoanatomy in patients presenting for anatomic shoulder arthroplasty. 

An important characteristic of these glenoid types is the posterior decentering of the humeral head on the glenoid, a critical element in the evaluation and management of glenohumeral arthritis.  Note that the degree of decentering was (and remains) defined by the relationship of the humeral head to the face of the glenoid (and not the plane of the scapula), as seen from this figure from his classic article.

The decentering of the head on the glenoid can be evaluated on the standardized axillary "truth" view, as shown in the five examples below.

By the "truth" view, we mean an axillary view obtained with the arm elevated in the plane of the scapula that shows the spinoglenoid notch or "eye" (red arrow) as shown in this Steve Lippitt illustration:

The rationale for evaluating decentering with the arm elevated to a functional position is that CTs or MRIs obtained with the arm at the side may not reveal it, as shown in the two images of the same shoulder shown below. The MRI obtained with the arm at the side does not reveal decentering, whereas dramatic posterior decentering is shown when the arm is elevated to a functional position in the axillary "truth" view.

While often considered together, the B1 and B2 are not the same. The B1 has posterior decentering of the humerus on the glenoid without biconcavity of the glenoid from bony erosion. By contrast, the B2 has posterior decentering of the humeral head on the glenoid with biconcavity of the glenoid as shown in these illustrations from the classic article by Walch.

A third B was added by the authors of A modification to the Walch classification of the glenoid in primary glenohumeral osteoarthritis using three-dimensional imaging.

As can be seen from these figures, the B3 is monoconcave (i.e. no biconcavity) with substantial retroversion and without posterior decentering of the humeral head on the glenoid, i.e. the humeral head is centered with respect to the glenoid.

This point is emphasized by the authors of Quantitative measurement of bony pathology in advanced glenohumeral osteoarthritis who use the term "humeral-glenoid alignment (HGA)" to indicate centering or decentering of the humeral head on the glenoid. HGA is measured as the position of the humeral head center relative to the perpendicular line drawn from the glenoid center point (without reference to the scapular axis). This relationship is shown in a figure from their article showing the centering of the humeral head in a B3 glenoid (i.e. the humeral head is not decentered).

How does all this relate to the practice of anatomic shoulder arthroplasty? A recent article, Why do primary anatomic total shoulder arthroplasties fail today? A systematic review and meta-analysis, is relevant. The authors reviewed a total of 44 studies involving 35,168 aTSA procedures; 2744 failures were identified. The three most prevalent types of failure were: 

(1) implant loosening (26.1%), with 21.7% of failures attributed to glenoid component loosening. 

(2) Rotator cuff insufficiency (17.3%).  

(3) Instability (10.4%) 

Another recent article compared the types of failure in the Kaiser and the Australian Orthopaedic Association databases.Early revision in anatomic total shoulder arthroplasty in osteoarthritis: a cross-registry comparison.

The most common reasons for revision in the AOA experience were instability/dislocation (31.1%), rotator cuff insufficiency (24.2%), and loosening/lysis and implant breakage glenoid insert (11.0% each). The most common reasons in Kaiser experience were rotator cuff tear (32.3%), glenoid component loosening (29.0%), and dislocation and infection (12.9% each). 

While these articles did not study the relationship of glenoid type to loosening or instability, we can venture that because B1 and B2 glenoids demonstrate preoperative posterior decentering, they would be at risk for postoperative instability. The B3, being centered preoperatively would seem less at risk for instability as long as the centering was not disrupted by the arthroplasty.

There are a number of approaches for shoulders with each of the different B types, each of which has its proponents, advantages and limitations. As emphasized in Short-term outcomes of anatomic total shoulderarthroplasty with nonaugmented glenoidcomponent for Walch B2 and B3 glenoidmorphology, all B's are not the same. In fact, each patient and their shoulder is a one of a kind combination. We like to say that each patient is an N of 1.

Here's an approach we commonly use for effectively and durably restoring stability and mobility. Note that usually we do not attempt to "correct" preoperative glenoid version (see Does postoperative glenoid component retroversion following anatomic total shoulder arthroplasty affect clinical outcomes? A systematic review and meta-analysis) and judge the need for an anteriorly eccentric humeral head based on intraoperative testing at surgery with trial components in place (see Management of intraoperative posterior decentering in shoulder arthroplasty using anteriorly eccentric humeral head components).

We start with Anatomic total shoulder - preoperative planning and intraoperative decision making, recognizing the different characteristics among the 3 Bs

B1 - conservative reaming without attempting to alter version, preserving glenoid bone stock, excellent carpentry to assure perfect seating of the component, and use of an anteriorly eccentric humeral head to manage excessive posterior translation if that is evident on intraoperative examination with a concentric trial humeral head component in place.

B2 - conservative reaming - just sufficient to convert the biconcavity to a mono concavity without attempting to alter glenoid version, preserving glenoid bone stock, excellent carpentry to assure perfect seating of the component, and use of an anteriorly eccentric humeral head to manage excessive posterior translation if that is evident on intraoperative examination with a concentric trial humeral head component in place.

B3 - conservative reaming without attempt to alter glenoid version, preserving glenoid bone stock, excellent carpentry to assure perfect seating of the component. An anteriorly eccentric humeral head component is rarely necessary because of the absence of preoperative decentering.

For additional information on this approach see:

Anatomic Total Shoulder Arthroplasty with All-Polyethylene Glenoid Component for Primary Osteoarthritis with Glenoid Deficiencies

Does Postoperative Glenoid Retroversion Affect the 2-Year Clinical and Radiographic Outcomes for Total Shoulder Arthroplasty?

Does glenoid version and its correction affect outcomes in anatomic shoulder arthroplasty? A systematic review

Anatomic total shoulder arthroplasty for posteriorly eccentric and concentric osteoarthritis: a comparison at a minimum 5-year follow-up

Glenoid retroversion does not impact clinical outcomes or implant survivorship after total shoulder arthroplasty with minimal, noncorrective reaming

Pollination

Bumble Bee on Iris

Montlake Fill

Spring 2021

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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).

What's important in anatomic total shoulder arthroplasty?

Anatomic total shoulder arthroplasty reliably provides long term comfort and function for patients with osteoarthritis and an intact rotator cuff, even in patients with deficiencies in glenoid bone (see Anatomic Total Shoulder Arthroplasty with All-Polyethylene Glenoid Component for Primary Osteoarthritis with Glenoid Deficiencies). While some surgeons attempt to "correct" the patient's glenoid version, others "accept" it (see Glenoid Version, Acceptors and Correctors). It either case, one of the most important technical goals of anatomic total shoulder arthroplasty is excellent seating of the glenoid component (see Edge displacement and deformation of glenoid components in response to eccentric loading. The effect of preparation of the glenoid bone).

Good seating is achieved by reaming the glenoid bone to a single concavity

that matches the backside of the glenoid component

so that no cement is placed between the bone and the backside of the prosthesis to fill in the gaps,

backside cement indicates poor seating and risks cement failure

below is an example of a well-seated glenoid component. The only cement visible is in the peg holes.

To further investigate the technical factors associated with anatomic total shoulder (aTSA) outcomes, the authors of Anatomic total shoulder arthroplasty for posteriorly eccentric and concentric osteoarthritis: a comparison at a minimum 5-year follow-up evaluated 210 patients at a minimum of five years after aTSAs performed with conservative glenoid reaming with no attempt at version correction. 

Preoperatively, 98 (47%) had posteriorly decentered humeral heads and 108 (51%) had centered humeral heads. There were 77 shoulders with Walch type A glenoids and 122 with Walch type B glenoids. 

At a mean 8-year follow-up, the final SST score, change in SST score, and percentage of maximal improvement were not correlated with preoperative or postoperative humeral head centering, Walch classification, or glenoid version. 

Two patients (1%) underwent open reoperations during the study period. 

In patients with Walch B1 and B2 glenoids (n = 110), there were no differences in outcome measures between patients that had postoperative retroversion of more or less than 15°. 

Although 15 of 51 patients (29%) with minimum 5-year radiographs had glenoid radioluciences, these radiographic findings were not associated with inferior clinical outcomes. 

On multivariable analysis, glenoid component radiolucencies were most strongly associated with incomplete component seating.

Careful preparation of the glenoid bone. 

From the authors of Edge displacement and deformation of glenoid components in response to eccentric loading. The effect of preparation of the glenoid bone we learn that the wobble and warp of the polyethylene component is minimized by spherically reaming the bone to precisely match the back of the component.

Glenoid bone stock is preserved by reaming only enough to create a single concavity, rather than trying to "correct" glenoid version.

The adequacy of glenoid reaming can be evaluated by using a pegless trial with the same backside curvature as the actual component and assuring that there is no rocking with eccentric loading. The goal is complete congruency.

Assuring optimal seating and cementing of the component. 

From the authors of The radiographic evaluation of keeled and pegged glenoid component insertion we learn that poor seating and poor cement technique contribute to poor fixation as evidenced by radiolucent lines on the immediate postoperative x-rays. 

Poor seating is evidenced by the presence of cement between the glenoid bone and the backside of the component. 

Good seating is indicated by the absence of cement between the component and bone (below top), rather than using cement as putty in an attempt to compensate for inadequate reaming.

A thin layer of cement between the bone and component is brittle and subject to cracking, displacement and loss of support for the glenoid implant.

Optimal cementing is reflected by the absence of radiolucent lines on postoperative radiographs.

We have learned that this can be achieved by drying each fixation hole with a CO2 spray

Immediately before pressurizing the cement into the hole

Comment: The survivorship of cemented, pegged, all-polyethylene glenoid components has yet to be surpassed by other types of glenoid implants (see Total shoulder replacement stems in osteoarthritis-short, long, or reverse? An analysis of the impact of crosslinked polyethylene). Attention to the details of bone-preserving bone preparation, complete seating of the component and modern cement technique may further improve the clinical outcomes of anatomic total shoulder arthroplasty. Our technique for this procedure is shown in this link.

The complexities of glenohumeral arthritic pathoanatomy

 Glenohumeral arthritis comes in a wide variety of forms. While these are often described in terms of glenoid version, inclination, biconcavity, and bone loss, these terms only partially capture the complexity of each arthritic shoulder as exemplified by this 3D reconstruction

To further complicate things, changes in glenoid pathoanatomy may be associated with other important features of the shoulder. For example, superior inclination can be associated with rotator cuff dysfunction (see for example link, link, link) which may have a profound effect on anatomic glenoid component durability and post arthroplasty shoulder function.

The authors of Mid-term Radiographic Outcomes of Anatomic Total Shoulder Arthroplasty in Biplanar Glenoid Deformities sought to separate the effects of  combined retroversion ≥ 20 degrees + inclination ≥ 10 degrees in 28 shoulders from a matched set of 28 shoulders with retroversion ≥ 20 degrees alone. All shoulders were managed with "hi side reaming" and a standard glenoid component.

The goal at surgery was to achieve 80% glenoid component seating and final retroversion within 10-15 degrees of neutral with no specific attempts to correct glenoid inclination.

Using preoperative CT-based 3D planning software, they found that the biplanar shoulders had greater inclination (14.5 ̊ versus 5.3̊) and greater retroversion (30.0 ̊ versus 25.6 ̊)

Using postoperative plain radiographs, they found that biplanar shoulders had greater implant superior inclination (5.9 ̊ vs. 3.0 ̊). 

In that 2 different imaging methods were used it is difficult to know if 14.5̊ vs 5.9 ̊ represents the actual amount of change in inclination. 

The initial postoperative posterior decentering was 3.5% vs 1.8%.

On final follow-up plain radiographs, biplanar shoulders had higher Lazarus radiolucent scores (2.4 vs. 1.6) and higher proportion with glenoid radiolucency (68% vs. 39%). 

Preoperative biplanar deformity was the only significant predictor of glenoiod radiolucency (odds ratio 3.3).

Posterior decentering increased for both groups to 7.6% vs 4.0%.

Comment: This is an interesting paper calling attention to the variability in preoperative glenohumeral arthritic pathoanatomy.

In considering the possible contributing factors to the increased rate of glenoid lucencies in the biplanar shoulders one could consider (a) concomitant cuff dysfunction in the shoulders with increased inclination (see above), (b) the increased rate of posterior decentering, (c) the greater postoperative inclination risking rocking horse loosening from superiorly directed loading of the glenoid component, and (d) the increased amount of bone removal necessary to achieve 80% seating in the superiorly inclined shoulders.

Additional larger studies will help sort out the relative importance of these variables. It would be desirable if these future studies used the same method of measuring glenoid inclination, glenoid version, and humeral head centering preoperatively and postoperatively so that one could determine the amount of change in these two important variables.

Comments welcome at shoulderarthritis@uw.edu

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

26. 
    
    Follow on twitter/X: https://x.com/RickMatsen
    Follow on facebook: https://www.facebook.com/shoulder.arthritis
    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). 

27. 
    

The relationship of glenoid version and glenohumeral centering to clinical outcome in a series of 210 patients having anatomic arthroplasty followed for a mean of eight years.

Some shoulder surgeons devote substantial resources to correcting preoperative glenohumeral pathoantomy, while others are inclined to accepting features such as glenoid retroversion (see Glenoid version: acceptors and correctors). 

Recognizing that the surgeon is the method, it is interest to view the outcomes of different  approaches to anatomic total shoulder arthroplasty (ATSA).

The authors of Anatomic total shoulder arthroplasty for posteriorly eccentric and concentric osteoarthritis: a comparison at minimum 5-year follow-up present the average 8 year outcomes for a single-center series of 210 patients with refractory primary osteoarthritis treated with ATSA without attempt to correct glenoid version.

All cases were performed by one of three fellowship-trained shoulder surgeons. Preoperative 3D planning was not used for any of these cases. 

The shoulder was approached through the deltopectoral interval with a subscapularis peel. In cases with posteriorly eccentric wear, the humeral and glenoid sided capsular release during exposure was limited to the mid- sagittal plane (i.e. “6 o’clock”) to preserve posterior capsular tension. Glenoid reaming was limited to that necessary to create a single concavity, preserving bone stock without attempting to correct retroversion. 

Sufficient reaming was indicated by the absence of tipping when a pegless, round-backed trial component was loaded eccentrically. 

The glenoid component in the majority of cases utilized a fluted central peg for bone ingrowth with cemented peripheral pegs (Depuy-Synthes Anchor Peg; n = 204). Cementation technique involved meticulous drying with a pressurized carbon-dioxide spray

Particular attention was given to avoid cement on the backside of the implant.

A standard anatomic humeral arthroplasty was usually performed with conventional length stem (Depuy Global AP or Enovis Turon; n=204).

In cases in which excessive intraoperative posterior translation was identified with trial components in place, an anteriorly eccentric humeral head without or with rotator interval plication was considered to provide stability.

Preoperative and postoperative standardized axillary views were used to determine Walch classification, glenoid component seating, humeroglenoid alignment (HGA-AP) and version. 

The outcome measures included the Simple Shoulder Test, radiolucencies around the glenoid component, and revisions.

98 (47%) of the shoulders had posteriorly decentered humeral heads while 108 (51%) had centered humeral heads. 

77 shoulders had Walch type A glenoids and 122 had Walch type B glenoids. 

35 shoulders had preoperative glenoid retroversion >15 degrees

The mean preoperative SST score of 3.4 improved to a mean of 9.4 at 8 years after surgery. Two patients (1%) underwent re-operations during the study period. 

There was minimal change in glenoid version: the average postoperative retoversion was 7.0 degrees in comparison the preoperative average of 8.8 degrees.

Neither the final SST, change in SST or percentage of maximal improvement were correlated with pre- and postoperative humeral head centering, Walch classification or glenoid version. 

In patients with Walch B1 and B2 glenoids (n=110), there were no differences in outcome measures between patients with postoperative retroversion of more and less than 15 degrees.

While 15 of 51 patients (29%) with minimum 5-year radiographs had glenoid radioluciences, these radiographic findings were not associated with inferior clinical outcomes. 

On multivariable analysis glenoid component radiolucencies were most strongly associated with incomplete component seating (bottom two images below).

Comment: This study indicates that clinically significant and durable outcomes with low revision rates can be accomplished with a straightforward surgical technique in which glenoid bone preservation is prioritized.

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/X: https://x.com/RickMatsen
Follow on facebook: https://www.facebook.com/shoulder.arthritis
Follow on LinkedIn: https://www.linkedin.com/in/rick-matsen-88b1a8133/

Contact: shoulderarthritis@uw.edu

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).