Glenoid component version in anatomic total shoulder arthroplasty- does it matter?

 

Almost 30 years ago Gilles Walch called our attention to arthritic glenoid retroversion. Morphologic study of the glenoid in primary glenohumeral osteoarthritis

From that point on, there has been great interest in the version of the arthritic glenoid: what is it?, how should it be measured?. 

And in the execution of an anatomic total shoulder (aTSA),  should the version of the glenoid component be "corrected" to some particular value?, if so what value?, how should this correction be achieved? and does changing the preoperative version affect the clinical outcome of aTSA?

It goes without saying that a lot of time and money can go into the evaluation and management of arthritic glenoid retroversion. Perhaps it's time to see how much glenoid component matters to the patient.

About 15 years ago, Patterns of loosening of polyethylene keeled glenoid components after shoulder arthroplasty for primary osteoarthritis: results of a multicenter study with more than five years of follow-up pointed out that posterior tilting of the glenoid component was associated with preoperative posterior decentering and with excessive reaming. The authors suggested that preserving subchondral bone may be important for long-term longevity of the glenoid component.

Glenoid component retroversion is associated with osteolysis found that osteolysis around the center peg of a glenoid component was correlated with component retroversion of ≥15°, the paper clearly stated that "the presence of osteolysis around the center peg was not correlated with a worse clinical outcome defined by shoulder scores or a reoperation due to glenoid loosening". 

Nevertheless, achieving component retroversion of <15° has become a goal for many surgeons and an opportunity for orthopaedic companies who have made substantial investments in three-dimensional planning platforms, patient specific instrumentation, navigation, augmented / virtual reality and robotic assisted glenoid preparation.

A recent paper,  Does postoperative glenoid component retroversion following anatomic total shoulder arthroplasty affect clinical outcomes? A systematic review and meta-analysis assessed the clinical importance of implanting the glenoid component in <15° of retroversion. After screening 2,457 articles, 15 studies comprising 1,190 shoulders met inclusion criteria. Patients were stratified by whether postoperative glenoid component retroversion was <15° or ≥15°. The principal finding was that no clinically significant differences were observed between the two groups in patient-reported outcome scores, range of motion, or complications. 

An unexpected and important finding in this meta-analysis was that shoulders with ≥15° of postoperative retroversion were actually more likely to have no radiolucency (a Lazarus grade 0 radiographic score) than those with <15° retroversion (76.9% vs. 55.6%; P = .00021). This finding argues against the presumption that retroversion promotes loosening. 

Does Postoperative Glenoid Retroversion Affect the 2-Year Clinical and Radiographic Outcomes for Total Shoulder Arthroplasty? directly addressed the question in a case-control study. At 2-year follow-up, patients with glenoid components implanted in ≥15° retroversion had similar improvement in Simple Shoulder Test (SST) scores, similar final outcome scores, and similar radiographic findings compared to those with <15° retroversion. Notably, none of the patients with retroverted glenoid components underwent revision surgery, compared to 3 of 50 patients in the non-retroverted group.

Anatomic Total Shoulder Arthroplasty with All-Polyethylene Glenoid Component for Primary Osteoarthritis with Glenoid Deficiencies reported outcomes of aTSA with conservative, noncorrective reaming in shoulders with glenoid deficiencies, including those with significant retroversion. Mean postoperative retroversion in this series was 16°, yet mean postoperative SST was 9 out of 12, consistent with the excellent results achieved in shoulders without glenoid deformity. The revision rate was zero in 143 shoulders at mean follow-up of 34 months.

Anatomic total shoulder arthroplasty for posteriorly eccentric and concentric osteoarthritis: a comparison at a minimum 5-year follow-up compared outcomes of aTSA for posteriorly eccentric (Walch B) versus concentric osteoarthritis at minimum 5-year follow-up, finding no significant difference in ASES scores, revision rates, or radiographic loosening between groups. These durable results were achieved without attempting retroversion correction.

Does glenoid version and its correction affect outcomes in anatomic shoulder arthroplasty? A systematic review analyzed 16 studies and 1,211 shoulders finding that 8 of 11 reports found no significant association between pre- or postoperative glenoid retroversion and clinical results, including patient-reported outcomes, range of motion, and revision rates.

Total shoulder arthroplasty outcomes after noncorrective, concentric reaming of B2 glenoids reported a 95% implant survivorship at a mean of 4.9 years in a series treated with noncorrective reaming with a mean postoperative retroversion of 19°.

The Effect of Version Correction Techniques

If clinical outcomes are equivalent regardless of postoperative retroversion, the question becomes whether correction efforts add value without adding risk.  Does postoperative glenoid component retroversion following anatomic total shoulder arthroplasty affect clinical outcomes? A systematic review and meta-analysis compared three correction strategies: posteriorly augmented glenoids, eccentric (“high-side”) reaming, and conservative noncorrective reaming. Eccentric reaming was associated with a significantly higher complication rate than noncorrective reaming (9.3% vs. 3.1%; P = .043, OR 3.22) and a significantly higher revision rate (7.4% vs. 1.2%; P = .015, OR 6.18). 

Loss of the dense subchondral bone layer from corrective reaming may result in reduced glenoid component support, increased micromotion, and greater loosening risk over time. 

Implications for 3D CT Planning and Technology Transfer

CT-based three-dimensional preoperative planning, patient specific instrumentation, intraoperative navigation, augmented/virtual reality, and robotic glenoid preparation are all predicated on the same clinical logic: that achieving a glenoid component position closer to neutral version will improve patient outcomes. As reviewed above, the available evidence indicates that differences in postoperative glenoid component retroversion do not produce clinically detectable differences in pain relief, function, or implant survival at the follow-up intervals studied.

Use of Preoperative CT Scans and Patient-Specific Instrumentation May Not Improve Short-Term Adverse Events After Shoulder Arthroplasty: Results from a Large Integrated Health-Care System compared aTSA with and without preoperative CT scanning and PSI. These technologies expose patients to additional radiation from CT scanning and incur substantially greater costs of care. Use of CT scans and PSI did not reduce the rate of short-term adverse events following shoulder arthroplasty. Patients receiving PSI may be at greater risk of deep vein thrombosis or deep infection, possibly reflecting the additional operative time this technology requires. 

Three-dimensional computed tomography analysis of pathologic correction in total shoulder arthroplasty based on severity of preoperative pathology analyzed 152 shoulders with 3D CT postoperatively and found that while glenoid component shift occurred in 51% of patients, neither component shift nor central peg osteolysis was associated with worse clinical outcomes at minimum 2-year follow-up. 

What the Evidence Does Suggest About Optimizing aTSA outcomes?

The available evidence points to factors other than retroversion that drive aTSA results. 

See: Below left-poor glenoid seating with cement interposed between the glenoid component and the bone. 

Below right-posterior decentering due to poor glenoid preparation and ill-advised use of a posteriorly eccentric humeral head component.

Surgeons may wish to consider 6 aspects of aTSA that are relevant to the glenoid side of the arthroplasty.

(1) conservative reaming to retain the maximal amount of quality host bone

(2) rather than "correcting" glenoid retroversion (A, below), consider "accepting" it (B, below)

(3) component seating — good carpentry with complete backside contact of the glenoid implant against prepared bone; no cement between the component and the bone.

(4) humeral head centering on the glenoid achieved through soft tissue balancing and the possible us of an anteriorly eccentric humeral component.

(5) awareness that technologies can lead surgeons to prioritize postoperative glenoid component retroversion <15° retroversion (without acknowledging the potential risks)

(6) recognition that specialized (e.g. augmented) glenoid components may have downstream risks (see chart below from the 2025 AOANJRR)

Here is a thought provoking case in which substantial glenoid retroversion was accepted

Function at 14 years

Conclusion:

Glenoid component version may not be as critical to the outcome of aTSA as secure seating of the glenoid component on quality host bone and centering of the humeral head on the prosthetic glenoid. 

Rather than improving outcomes, there is evidence that "corrective reaming" can be associated with a significantly higher complication rate than noncorrective reaming (9.3% vs. 3.1% ) and a significantly higher revision rate (7.4% vs. 1.2%).

Seating and balance

Yellow-headed blackbird

Malheur

2024

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B3 glenoid in a 73 year old woman, 12 year followup

A 73 year old woman presented with pain and stiffness of the left shoulder. Her radiographs showed glenohumeral arthritis with a retroverted monoconcave (B3) glenoid. Her Simple Shoulder Test indicated that she could not sleep comfortably, reach the small of her back, lift eight pounds, toss, throw, wash back of her opposite shoulder or do her usual work. She had 120 degrees of active elevation with grade 5 strength.

       

After a discussion of the surgical options, she elected an anatomic total shoulder. This was performed without preoperative MRI, CT scan, 3D planning or brachial plexus block. The long head tendon of the biceps was preserved. Conservative glenoid reaming was performed with no attempt to alter glenoid version. A standard (non-augmented) glenoid component was used. A standard length smooth humeral stem was impaction-grafted into the humeral canal.

At 12 years after her arthroplasty at the age of 85, she reported being able to perform 8 of the 12 functions of the Simple Shoulder Test and was pleased with the outcome of her surgery.

Her x-rays at that time show secure fixation of the humeral and glenoid components with bony ingrowth between the fins of the central glenoid peg. Penetration of the anterior glenoid vault by the central peg is seen on the axillary view.

Comment: As pointed out by the authors of Anatomic Total Shoulder Arthroplasty with All-Polyethylene Glenoid Component for Primary Osteoarthritis with Glenoid Deficiencies, this standardized economical approach (minimal reaming, standard, non augmented, glenoid component) is effective across the range of glenoid types:

Humeral centering on the glenoid can be achieved

without change in glenoid version.

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

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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). 

Of mousetraps and anatomic glenoid components.

Ralph Waldo Emerson is credited with the saying, "build a better mousetrap and the world will beat a path to your door". 

A similar sentiment may drive the marketing of many different types of glenoid components in anatomic shoulder arthroplasty. Almost all have a polyethylene surface for articulation with the humeral component. The difference lies in the mechanism for fixation to the bone of the glenoid. Below are a few of the many.

One innovation uses porous metal into which bone can grow for fixation. The question is "does this innovation improve outcomes for patients?"  A recently study, A multicenter, randomized controlled trial comparing a second-generation uncemented trabecular metal-backed vs. cemented polyethylene glenoid component in total shoulder arthroplasty: 5-year results compared cemented all polyethylene glenoid components to uncemented trabecular metal glenoid components.

This study found no statistical or clinically relevant advantage of the trabecular metal-backed cementless component over the all polyethylene cemented component. No glenoid implant failures were reported, and complication rates were similar between groups. Metal debris was observed in 11 (23.9%) of the patients receiving trabecular metal components (see circle on x-ray below).

In addition, on the x-ray above it is not clear how much of the original polyethylene remains between the metal backing and the humeral component (red arrows).

The problem of accelerated polyethylene wear with metal backed components was pointed out in Metal-backed glenoid implant with polyethylene insert is not a viable long-term therapeutic option, the authors of which concluded "uncemented MB [metal backed] glenoid resurfacing is not a viable long-term therapeutic option because of accelerated PE [polyethylene]wear leading to early revision surgery". See also

Metal-Backed Glenoid Components Have a Higher Rate of Failure and Fail by Different Modes in Comparison with All-Polyethylene Components: A Systematic Review

The authors of Comparable low revision rates of stemmed and stemless total anatomic shoulder arthroplasties after exclusion of metal backed glenoid components: a collaboration between the Australian and Danish national shoulder arthroplasty registries found that "The adjusted hazard ratio for revision of total shoulder arthroplasties with metal backed glenoid components compared to all-polyethylene glenoid components was 2.54 (95% CI 1.70-3.79, p < 0.001) in the Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR) and 4.1 (95% CI 1.92-8.58, p<0.001) in the Danish Shoulder Arthroplasty Registry (DSR). The authors concluded "We advocate that metal-backed glenoid components should be used with caution and not on a routine basis."

The Australian Orthopaedic Association National Joint Replacement Registry further studied cumulative percent revision rates by glenoid type including modular metal backed (orange), non-modular metal backed (red), cemented all poly (green), and all poly with a modified central peg (blue). 

An example of an all poly glenoid component with a central peg modified to allow bone ingrowth is shown below.

It is apparent that long term, population-based studies are the key to tracking the outcome of different glenoid component designs. In the meanwhile, we should be prepared for the continued marketing of new glenoid prostheses, such as the 'inset' design shown below.

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).

Where should we put the glenoid component in shoulder arthroplasty?

Currently many surgeons find it interesting to use CT-based 3D software to help plan shoulder arthroplasty. The planning software program requires a defined target that specifies the desired values for six degrees of glenoid component freedom: version, inclination, rotation, superior-inferior position, anteroposterior-postion and medial-lateral position. The software then suggests the size and position of the glenoid component, as well as the amount of bone removal and the augments or bone graft that might be used to achieve the target position.

So the question becomes, how should the target for the glenoid be determined?

Premorbid Glenoid Anatomy Reconstruction from Contralateral Shoulders 3D-measurements: A CT scan analysis of 260 shoulders suggests that "Total shoulder arthroplasty (TSA) aims to reconstruct the premorbid anatomy of a pathologic shoulder". In the Introduction, it states that "It seems clear that the objective after anatomic TSA is to restore the preoperative anatomy of the patient". One notes that for most arthritic shoulders, premorbid anatomy and preoperative anatomy are not the same.

The paper goes on to suggest that one way to determine the premorbid anatomic of the glenoid is using a reconstruction of the CT of the contralateral shoulder. To support this concept they compared the 3D anatomy of the right and left shoulders of patients without shoulder pathology or injury. From this study they found that paired right and left scapulae were similar but not statistically symmetrical regarding glenoid version, inclination and width. Yet they concluded that "healthy contralateral shoulders can be a useful template in TSA preoperative planning."  One notes that most patients having shoulder arthroplasty on one side do not have a normal shoulder on the contralateral side for comparison.

Furthermore as explained in Glenoid version: acceptors and correctors, the clinical benefit to the patient of "correcting" glenoid version has get to be rigorously demonstrated. 

In the example below an arthritic shoulder in which the humeral head was nearly centered on the face of a retroverted glenoid was 3D planned to "correct" glenoid retroversion with posterior bone removal and insertion of a posteriorly augmented glenoid component.

Is this approach to reconstruction more effective and robust than the example below of a posteriorly decentered humeral head on a retroverted biconcave glenoid treated with a bone conserving standard glenoid component inserted with "accepting" the glenoid retroversion?

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).

Does the innovation of trabecular metal backed glenoid component improve 5 year total shoulder outcomes?

A Multi-Centre, Randomized Controlled Trial Comparing a Second-Generation Uncemented Trabecular Metal-backed versus Cemented Polyethylene Glenoid Component in Total Shoulder Arthroplasty: Five-year Results reports quality of life, clinical, patient-reported, and radiographic outcomes at five years from a randomized controlled trial comparing a second-generation uncemented trabecular metal-backed glenoid (TM, 46 patients, below right) versus a cemented non-ingrowth polyethylene glenoid (POLY, 47 patients, below left) in patients undergoing a total shoulder arthroplasty (TSA).

There were no preoperative differences between groups with respect to age, sex, or WOOS scores.
At followup, there were no statistical or clinically relevant differences in WOOS or patient-reported outcomes between the two groups.

Metal debris was observed in 11 (23.9%) of the TM shoulders without apparent impact on clinical outcomes.

One TM patient experienced glenoid loosening in the setting of an infection. 

One POLY patient had a minor intraoperative periprosthetic fracture of the glenoid which resolved non-operatively. 

Otherwise there was no radiographic evidence of glenoid loosening in either group.

Comment: This randomized clinical trial showed a minimal rate of glenoid component failure at five years after anatomic total shoulder arthroplasty for both the uncemented trabecular metal-backed glenoid and the cemented non-ingrowth polyethylene glenoid in patients undergoing a total shoulder arthroplasty. They noted no differences in outcome between the two glenoid components.

The authors point out that the osseous integration seen with the TM glenoid has the negative consequence that occurs in the revision setting where prosthesis removal can be extremely challenging and lead to extensive bone loss.

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).

The glenoid component in total shoulder arthroplasty: getting it done right.

Glenoid component loosening has been and remains an important cause of failure of anatomic total shoulder arthroplasty (data below from AOANJRR)

However, the survivorship of a pegged, cemented, cross linked, all-polyethylene glenoid component is excellent, with a 13 year cumulative percent revision rate of less than 5%. No metal backed or hybrid glenoid component has matched this outcome.

This type of glenoid arthroplasty serves shoulders across the range of glenoid types, with the lowest revision rates being for the B1 and B2 glenoids.

So, how might surgeons make the good results with the cemented, pegged all-polyethylene component even better? Here are some important concepts that can be put into action.

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.

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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).