The stepped glenoid component

In their classic article, Stepped Augmented Glenoid Component in Anatomic Total Shoulder Arthroplasty for B2 and B3 Glenoid Pathology, the authors demonstrate that a stepped augmented glenoid component can restore premorbid glenoid anatomy in patients with asymmetric biconcave glenoid bone loss (Walch B2), with short-term clinical and radiographic results equivalent to those for patients without glenoid bone loss (Walch A1) treated with a non-augmented component. 

They found a greater risk of osteolysis around the central peg in patients with moderate-to-severe B3 glenoid pathology with this stepped augmented glenoid component. As demonstrated in the technique guide, use of this component involves reaming of the posterior glenoid to fit the step, which may diminish the bony support for the back of the component.

Should this component fail, the posterior bone stock available for conversion to a reverse total shoulder may be compromised. 

A recent paper, Total Shoulder Arthroplasty for Glenohumeral Arthritis Associated with Posterior Glenoid Bone Loss: Midterm Results of an All-Polyethylene, Posteriorly Augmented, Stepped Glenoid Component,  presented a 5 year followup of 35 shoulders receiving a stepped glenoid for the treatment of glenohumeral osteoarthritis with posterior glenoid bone loss. The average preoperative glenoid retroversion was 21.6˚. Although postoperative CT scans were obtained, the postoperative glenoid retroversion was not presented.
Two patients (6%) experienced prosthetic instability requiring revision.

The average Lazarus score (0 no radiolucency to 5 gross loosening) was 0.72. The average Yian score (0 no radiolucency to 18 radiolucent line around entire component) was 2.6. There was an increase in Lazarus score and decrease in Wirth score between 2- and 5-year follow-up. The severity of radiographic loosening correlated with patient-reported pain levels. 

The authors point out that these results are not inferior to those achieved with standard glenoid components in the treatment of glenohumeral arthritis with posterior bone loss.

Comment: Since posterior reaming removes posterior bone and the stepped component adds posterior polyethylene, it would be of interest to know the net change in glenoid retroversion in these patients.

Two figures from this series seem to suggest that substantial retroversion remains after insertion of the stepped component.

As pointed out in the two posts referenced below, future research is needed to determine the clinical value and means of "correcting" glenoid retroversion.

What happens when glenoid version and inclination are "corrected"?

Glenoid version: acceptors and correctors

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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).

B2 and B3 glenohumeral pathoanatomy - the stepped glenoid component

 Stepped Augmented Glenoid Component in Anatomic Total Shoulder Arthroplasty for B2 and B3 Glenoid Pathology A Study of Early Outcomes

These authors studied the use of a stepped augmented glenoid component for management of Walch B2 (n=29) and B3 (n=21) glenoids and compared the radiographic and clinical outcomes at short-term follow-up with those achieved with a non-augmented component of the same design in Walch A1 glenoids (n=42).

Sequential 3-dimensional (3D) computed tomography (CT) imaging was performed preoperatively, within 3 months postoperatively with metal artifact reduction (MAR) to define implant position, and at a minimum of 2 years postoperatively with MAR. 

Preoperatively, these images showed that the alignment of the humeral head to the glenoid (HGA - represented by the circles in the graph below) was independent of glenoid version. Type B3 (yellow circle) showed centering of the humeral head on the glenoid that was comparable to type A1 (blue circle). On the other hand, the alignment of the humeral head to the scapular body (HSA - represented by the triangles) was strongly related to glenoid version (black line).

Similarly at two years after surgery the humeroscapular alignment (but not the humeroglenoid alignment) was closely related to glenoid version.

Clearly the humeroscapular alignment is essentially a reflection of the amount of retroversion and is not a measure of the degree of subluxation or decentering of the humeral head on the face of the glenoid (see this link).

The implant placement desired by the authors was achieved in all (100%) of the 42 A1 glenoids, 27 (93%) of the 29 B2 glenoids, and 15 (71%) of the 21 B3 glenoids.

Radiographic followup at two years showed:

A1 glenoids: Central peg osteolysis (CPO) was present in 5% of the A1 glenoids. 40% had glenoid component shift.

B2 glenoids:  CPO was present in 10% of the B2 glenoids with the augmented component. 55% had glenoid component shift.

B3 glenoids: Central peg osteolysis (CPO) was present in 29% of B3 glenoids treated with the augmented glenoid component (29%). 62% had glenoid component shift.

The two year clinical outcome scores were not different for the three glenoid types.

Comment: This authors have continued their careful and thoughtful analysis of arthritic glenohumeral anatomy. Their observations on glenoid component shift and central peg osteolysis obtained with metal subtraction imaging provide knowledge that informs our understanding and management of shoulder arthritis.

Using their careful analytical approach, high percentages of the glenoid components were noted to shift in position for all three glenoid types (A1:40%, B2: 55%, B3: 62%).

They point out both the severity and the shape of glenoid bone loss are important when considering the type of glenoid component to use and its location in aTSA. Use of the stepped augmented glenoid component requires more anterior glenoid reaming to correct pathologic glenoid retroversion in moderate-to-severe B3 glenoids, resulting in implant medialization. These B3 glenoids had a higher rate of central peg osteolysis and persistent postoperative joint-line medialization relative to the premorbid joint line. They do  not recommend use of the stepped augmented glenoid component for correction of severe B3 glenoid retroversion that requires excessive anterior glenoid reaming.

Recognizing that high degrees of retroversion, bone loss and humeral head decentering on the glenoid are indicators of worse pathoanatomy and that each of these - separately or in combination - can negatively affect the durability of the arthroplasty, several questions arise:

(1) How important is it to re-establish a "normal" joint line; how much medialization of the the joint line be compensated for by modification of the prosthetic head curvature and thickness?

(2) How important is it to re-establish "normal" version in the B2 glenoid at the expense of removing sclerotic glenoid bone; how much abnormal glenoid retroversion can be compensated for by using soft tissue balancing and anteriorly eccentric humeral components to center the humeral head on the face of the glenoid?

(3) How important is it to re-establish "normal" version in the B3 glenoid at the expense of removing sclerotic glenoid bone; since the humeral head is centered in the glenoid is it necessary to change the version?

(4) How important is it to avoid peg perforation; might perforation of the glenoid neck by the central peg actually enhance fixation as it appears to do with many designs of reverse total shoulder?

(5) What is the best way to achieve centering of the humeral head on the glenoid while optimizing bone preservation?

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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).

This is a non-commercial site, the purpose of which is education, consistent with "Fair Use" as defined in Title 17 of the U.S. Code.          

Note that author has no financial relationships with any orthopaedic companies.

Management if the B2 and B3 glenoid types with an augmented glenoid component

Stepped Augmented Glenoid Component in Anatomic Total Shoulder Arthroplasty for B2 and B3 Glenoid Pathology A Study of Early Outcomes

These authors studied the use of a stepped augmented glenoid component for management of Walch B2 (n=29) and B3 (n=21) glenoids and compared the radiographic and clinical outcomes at short-term follow-up with those achieved with a non-augmented component of the same design in Walch A1 glenoids (n=42).

Sequential 3-dimensional (3D) computed tomography (CT) imaging was performed preoperatively, within 3 months postoperatively with metal artifact reduction (MAR) to define implant position, and at a minimum of 2 years postoperatively with MAR. 

Preoperatively, these images showed that the alignment of the humeral head to the glenoid (HGA - represented by the circles in the graph below) was independent of glenoid version. Type B3 (yellow symbols) showed centering of the humeral head on the glenoid that was comparable to type A1 (blue symbols). On the other hand, the alignment of the humeral head to the scapular body (HSA - represented by the triangles) was strongly related to glenoid version. 

Similarly at two years after surgery the humeroscapular alignment (but not the humeroglenoid alignment) was closely related to glenoid version.

The desired implant placement was achieved in all (100%) of the 42 A1 glenoids, 27 (93%) of the 29 B2 glenoids, and 15 (71%) of the 21 B3 glenoids.

Radiographic followup at two years showed:

A1 glenoids: Central peg osteolysis (CPO) was present in 5% of the A1 glenoids. 40% had glenoid component shift.

B2 glenoids: There was only a small difference in the frequency of CPO between B2 glenoids with the augmented component (10%) and A1 glenoids (5%) with the standard component. The short-term clinical and radiographic results were equivalent to those for patients without glenoid bone loss (Walch A1) treated with a non-augmented component. 55% had glenoid component shift.

B3 glenoids: Central peg osteolysis (CPO) with or without implant shift occurred in a higher percentage of B3 glenoids treated with the augmented glenoid component (29%) than A1 glenoids treated with a standard component (5%) B3 glenoids were associated with more component medialization relative to the premorbid joint line compared with A1 and B2 glenoids. 62% had glenoid component shift.

The two year clinical outcome scores were not different for the three glenoid types.

Comment: This authors have continued their careful and thoughtful analysis of arthritic glenohumeral anatomy. Their observations on glenoid component shift and central peg osteolysis obtained with metal subtraction imaging provide knowledge that informs our understanding and management of shoulder arthritis.

They point out both the severity and the shape of glenoid bone loss are important when considering the type of glenoid component to use and its location in aTSA. Use of the stepped augmented glenoid component requires more anterior glenoid reaming to correct pathologic glenoid retroversion in moderate-to-severe B3 glenoids, resulting in implant medialization. These B3 glenoids had a higher rate of central peg osteolysis and persistent postoperative joint-line medialization relative to the premorbid joint line. They do  not recommend use of the stepped augmented glenoid component for correction of severe B3 glenoid retroversion that requires excessive anterior glenoid reaming.

Recognizing that high degrees of retroversion, bone loss and humeral head decentering on the glenoid are indicators of worse pathoanatomy and that each of these - separately or in combination - can negatively affect the durability of the arthroplasty, several questions arise:

(1) How important is it to re-establish the premorbid joint line; how much medialization of the the joint line be compensated for by modification of the prosthetic head curvature and thickness?

(2) How important is it to re-establish the premorbid version in the B2 glenoid at the expense of removing sclerotic glenoid bone; how much abnormal glenoid retroversion be compensated for by using soft tissue balancing and anteriorly eccentric humeral components to center the humeral head?

(3) How important is it to re-establish the premorbid version in the B3 glenoid at the expense of removing sclerotic glenoid bone; since the humeral head is centered in the glenoid is it necessary to change the version?

(4) How important is it to avoid peg perforation; might perforation of the glenoid neck by the central peg actually enhance fixation as it appears to do with many designs of reverse total shoulder?

In sum, what is the best way to balance bone preservation vs "correction" of the pathoanatomy?

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 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).

Post operative glenoid component version - how much does it matter?

Clinical and Radiographic Outcomes of a Posteriorly Augmented Glenoid Component in Anatomic Total Shoulder Arthroplasty for Primary Osteoarthritis with Posterior Glenoid Bone Loss
These authors sought to evaluate the ability of a posteriorly stepped augmented glenoid component, used in 71 patients (mean 65 years of age) with primary glenohumeral osteoarthritis with B2 or B3 glenoid morphology, to correct preoperative retroversion and humeral head subluxation and to identify factors associated with radiographic radiolucency and patient-reported clinical outcomes.

At a median of 2.4 years (range, 1.9 to 5.7 years); the Penn Shoulder Score, range of motion, humeral head centering, and glenoid version were significantly improved. Patients with persistent posterior subluxation of the humeral head postoperatively had worse preoperative fatty infiltration of the teres minor and greater postoperative component retroversion. Patients with center-peg osteolysis had more preoperative joint-line medialization and posterior glenoid bone loss. Patients with more preoperative humeral head posterior subluxation had a lower PSS.

Postoperative humeral head centering on the glenoid component was measured as the anteroposterior humeral head glenoid alignment (HGA-AP) on an axillary radiograph as the amount of posterior displacement of the head center (black dot) with respect to the glenoid component centerline (solid green line) divided by the radius of curvature of the humeral head. In the example below the humeral head component is centered on the glenoid component centerline.

In the example below the humeral head center lies posterior to the glenoid component centerline

Comment: It was of interest to compare these results with those of another recent paper,
Does Postoperative Glenoid Retroversion Affect the 2-Year Clinical and Radiographic Outcomes for Total Shoulder Arthroplasty?

This study analyzed 71 patients having total shoulder arthroplasty with a conventional non-augmented glenoid component inserted with no specific effort to change the version of the glenoid. 

The authors compared the 21 shoulders in which the glenoid component was implanted in 15° or greater retroversion (mean ± SD, 20.7° ± 5.3°) with the 50 in which it was implanted in less than 15° retroversion (mean ± SD, 5.7° ± 6.9°). At the 2-year followup the mean (± SD) improvement in the SST (6.7 ± 3.6; from 2.6 ± 2.6 to 9.3 ± 2.9) for the retroverted group was not inferior to that for the nonretroverted group (5.8 ± 3.6; from 3.7 ± 2.5 to 9.4 ± 3.0). The percent of maximal possible improvement (%MPI) for the retroverted glenoids (70% ± 31%) was not inferior to that for the nonretroverted glenoids (67% ± 44%). 

No patient in either group reported symptoms of subluxation or dislocation. The radiographic results for the retroverted glenoid group were similar to those for the nonretroverted group with respect to central peg lucency (four of 21 [19%] versus six of 50 [12%]; p = 0.436. The mean percentages of posterior humeral head decentering were also similar (3.4% ± 5.5% versus 1.6% ± 6.0%; p = 0.223). The percentage of patients with retroverted glenoids undergoing revision (0 of 21 [0%]) was not inferior to the percentage of those with nonretroverted glenoids (three of 50; [6%]; p = 0.251).

The postoperative decentering was measured on an axillary view in essentially the same manner as in the other paper, except that the displacement is express as a percent of the head diameter rather than the radius. In the example below the humeral head is centered on the glenoid.

The following table attempts to compare the shoulders from each article with respect to postoperative glenoid component retroversion of less than 15 degrees and postoperative glenoid version of 15 degrees or more.

In both series the results appear similar for glenoid components inserted in more or less than 15 degrees of retroversion. There were no revisions for glenoid failure in either series.

It is recognized that long term studies will be needed to determine the relative effectiveness and longevity of different approaches to the retroverted glenoid.

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