Posteriorly augmented glenoid components - computing how much bone is lost on insertion

Augmented glenoid component designs for type B2 erosions: a computational comparison by volume of bone removal and quality of remaining bone

These authors used a computational modeling was to compare the volume of glenoid bone that would need to be removed in the implantation of three different designs of posteriorly augmented glenoid components in the management of B2 genoid erosion. They 'virtually implanted' a full-wedge, a posterior-wedge, and a posterior-step in 3-D reconstructions of 16 patients with B2 glenoids, correcting retroversion to 0° and 10°.

Importantly the amount of bone removed with these implants ranged from 1500 to 3000 cubic millimeters. When correcting to 0°, the posterior-wedge implant removed less bone than the posterior-step and the full-wedge. 

The residual glenoid bone density with the posterior-wedge was significantly greater than with the posterior-step.

Comment: This is an interesting study, suggesting that bone removal is necessary for fitting posteriorly augmented glenoids to the pathoanatomy encountered in glenohumeral arthritis. 

We have posted this concern previouslyl

Their implant fitting was virtual and not actual: implants could be manipulated to rotate (clockwise/ counterclockwise and superoinferior) and to translate (anteroposterior and superoinferior). The instrumentation for fitting the glenoid bone to the back of the glenoid component would seem to be quite complex. While the authors suggest that it would be best to use computerized

preoperative planning software making use of 3D CT-based models of the glenoid with properly sized implants, the problem of developing instrumentation to implement the plan remains.

While the authors conclude that " Augmented components can provide a bone-preserving option for B2 glenoid management." that statement is only correct if B2 glenoid management involves correction of retroversion. Our approach is manage the B2 glenoid by conservatively reaming only enough to convert the biconcavity to a single concavity without attempting to change version. See also this related article. this one, and this one as well.

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Glenoid bone density in A2 and B2 glenoids, implications for pathogenesis and treatment

Regional bone density variations in osteoarthritic glenoids: a comparison of symmetric to asymmetric (type B2) erosion patterns.

These authors compared the erosion patterns of 25 symmetric and 25 asymmetric glenoids using computed tomography-based imaging software.

For the symmetric cohort, there were no significant differences in bone density between the four quadrants at depths of 0 to 2.5 mm and 2.5 to 5 mm. For the asymmetric cohort, bone density was significantly higher in the posterior quadrants compared with the anterior quadrants, especially posteroinferiorly at both depths. The bone beneath the pathological posterior concavity also had lower void fraction compared with the bone beneath the normal anterior concavity.

This study demonstrates that osteoarthritic glenoids with symmetric erosion have uniform subarticular bone density. However, asymmetric (B2) erosion patterns have potentially important regional variations in bone density and porosity, with the densest bone with the least porosity found posteroinferiorly beneath the pathological concavity.

Comment: The condensation of bone beneath the pathological posterior glenoid is a response to posterior loading that occurs with functional decentering, that is the posterior subluxation that occurs when the arm is placed in a functional position, a decentering that is not seen on CT scans taken with the arm at the side as further explained here and here. This is one of the many reasons we do not get preoperative CT scans, preferring instead the 'truth view'.

The recognition of the variance in bone quality has lead some to question the advisability of correcting glenoid version. Here is a related post. Taken together, these findings also bring into question the advisability of sacrificing some of the dense posterior bone to accommodate glenoid components with a posterior step off.

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Ream and run for the triad of biconcavity, retroversion and posterior humeral subluxation

Can the Ream and Run Procedure Improve Glenohumeral Relationships and Function for Shoulders With the Arthritic Triad?

It is recognized that glenoid biconcavity, glenoid retroversion, and posterior displacement of the humeral head on the glenoid are associated with an increased risk of failure of the glenoid component in total shoulder joint replacement. The combination of these three pathologic elements have come to be known as the "bad arthritic triad" or BAT.

In that the ream and run procedure manages arthritic pathoanatomy without a glenoid component, these authors sought evidence that this procedure can be effective in improving the centering of the humeral head contact on the glenoid and in improving the comfort and function of shoulders with the arthritic triad without subjecting the shoulder to the risk of glenoid component failure.

They reviewed 30 shoulders in 30 patients that had the ream and run procedure for the arthritic triad and had two years of clinical and radiographic follow-up.  The average age of the patients was 56 ± 8 years; all but one were male.

Two of the 30 patients requested revision to total shoulder arthroplasty within the first year after their ream and run procedure because of their dissatisfaction with their rehabilitation progress.

For the 28 unrevised shoulders the mean followup was 3.0 years (range, 2–9.2 years). In these patients, the ream and run procedure resulted in improved centering of the humeral head contact point on the face of the glenoid - from 75% posterior to 59% posterior - notably without a significant change in the glenoid version.

Patient-reported function as assessed by the Simple Shoulder Test was improved from 5 ± 3 to 10 ± 4. Ten of the individual functions of the SST were significantly improved:

Comment: While this report shows that the ream and run can be successful in managing selected shoulders with the arthritic triad, the authors point out that this procedure is not for every patient with an arthritic shoulder and not for every surgeon. Patient selection and surgeon experience are critical to the outcome.

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Ream and Run for a B2 glenoid - the x-rays and the patient's own story

Two years ago a very physically active man in his mid thirties presented with severe pain in his right shoulder that required him to take substantial narcotic and other medication. His Simple Shoulder Test score was only 3 out of 12. His x-rays showed severe degenerative joint disease with a biconcave glenoid (type B2), posterior humeral subluxation on the glenoid, and glenoid retroversion = the bad arthritic triad (BAT).

 He desired a ream and run. At surgery we used a humeral head with a diameter of curvature of 56 mm, a height of 21, and anterior eccentricity. The glenoid was reamed to a diameter of 58 mm. The stem was fixed with impaction grafting. A rotator interval plication was used to augment his posterior stability. This approached is explained in this prior post.

His x-rays at two years are shown here.

 Note on the axillary view his anteriorly eccentric humeral head is centered in the glenoid. In spite of the fact that we did not correct his retroversion, the head is stable.

His recovery was long and difficult, but he hung in there with great resolve. 

Recently, he sent this email:

Greetings—I hope that you are doing well! I have owed you an email for a while, so my apologies for not being in touch sooner, but I just wanted to reach out to you and say that my shoulder if doing GREAT! It has now 100% surpassed my wildest pre-surgery hopes, and I am now back to doing virtually all of the things that I love, including sailing, which was really tough on the bionic shoulder up until two or three months ago (not that it stopped me…but it did hurt a lot). But, in early May, I did a mini-distance race, from Shileshole to Smith Island and back (85 nm), and it got kind of choppy/rough on the way home, out by near Port Townsend. A year ago I would have been in sheer agony, but when I got up the next morning and was pain-free, so I hit my rowing machine for a full workout. Amazing!

All that said, I am still careful to avoid outwards-rotation movements such as grinding winches on sailboats, but otherwise, I’m back to being a normal person, in no small part to your help and surgical magic. I still do my PT religiously, including stretching twice a day (if anything, I think that I’ve gained ROM since you saw me last!), running 3 or 4 times a week and rowing 2 or 3 times per week. It’s a lot of revolving maintenance work, but to be able to sit on a plane for 18.5 hours, pain-free (as I did yesterday, flying home from Barcelona), is truly a gift.

I’m now 2.5 years out from surgery, and based on the progression/recovery charts that I’ve seen you post on your blog, I’m guessing that I am now 100% recovered. If someone had asked me, say three years ago, if I could ever envision a largely pain-free life, I would have laughed in their face. But, this is now my reality most days (and an Aleve takes care of the rough days when I overexert my shoulder), and I just wanted to reach out and say thank you again. You made a massive difference in my life, and I will never forget the second chance that you have given me.

THANK YOU,

PS—this photo was taken in September of 2013…my first “honest” pull-up in roughly seven years. That was a pretty sweet victory!

Comment: An extraordinary result from an extraordinary effort on the part of the patient

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Ream and run for severe shoulder arthritis and Walch B2 glenoid -2.5 year followup

Here are the x-rays of a man in the mid forties with severe arthritis after a prior surgical repair for anterior instability many years ago. We refer to this condition as capsulorrhaphy arthropathy. On presentation to us he had very little shoulder motion and a Simple Shoulder Test of 6 out of 12.

On the AP view, note the complete obliteration of the joint space.

 On the axillary view, not the almost complete posterior subluxation of the deformed humeral head on the deformed glenoid.

He requested a ream and run procedure which we performed over two and a half years ago. He worked very hard at his rehabilitation exercises.

Today we saw him for follow-up. He reported he was back to full activities and had a Simple Shoulder Test score of 12 out of 12.

His x-rays show excellent position of his humeral prosthesis, a nicely concave glenoid, and a stable shoulder. Note the use of the anteriorly eccentric head which can be seen on the axillary view. Note also the absence of a plastic socket and the absence of bone cement. 

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The relationship of glenoid version to stability in shoulder arthritis, the bad arthritic triad

There has been a lot of interest in methods for 'correcting' glenoid version in performing total shoulder arthroplasty using anterior glenoid reaming, stepped or posteriorly augmented glenoid components, or posterior bone grafts. This interest in version correction probably results from the observation that retroverted plastic glenoids are at risk for failure from loosening or wear from the often associated posterior humeral subluxation on the glenoid. However, it has yet to be shown that 'correction' of glenoid version enhances should

er stability. In other words, glenoid retroversion is associated with posterior instability, but correction of retroversion may not correct the instability, which may be related to factors such as posterior soft tissue laxity and muscle imbalance.

Credit where credit is due. Gilles Walch and colleagues made this point in their 1998 articlePrimary glenohumeral osteoarthritis: clinical and radiographic classification. 

We quote from that paper: "…subluxation of the humeral head correlates with glenoid wear, and it is reasonable to suggest that subluxation causes the wear. This presents a problem which must be emphasized: when one corrects the posterior glenoid wear (using a glenoid component with or without a graft) the subluxation is not corrected. This therefore leaves the risk of recurrence and may be responsible for glenoid loosening due to the 'rocking-horse' mechanism described by Franklin et al."

As we have shown with the ream and run procedure, posterior subluxation can be managed by the use of eccentric humeral head components and rotator interval plication without changing glenoid version.

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