Monday, March 7, 2016

B2 glenoids and retroversion - which is the chicken and which is the egg?

Premorbid retroversion is significantly greater in type B2 glenoids.

These authors hypothesized that patients with posterior erosion may exhibit premorbid glenoid morphology that is inherently retroverted compared with age-matched normal glenoids. They examined 80 scapulae, evenly distributed between 2 groups: osteoarthritic with type B2 glenoids and age-matched normal glenoids. From 3-dimensional computed tomography reconstructions, version and inclination were measured from the anterior apparently unaffected region of the B2 glenoids - below right - which they suggest is representative of the pre-arthritic glenoid anatomy, and compared with measurements obtained from similar regions in the normal scapulae - below left.

They found that anterior half of B2 glenoids was significantly (P < .001) more retroverted (-14° ± 6°) compared with similar regions in nonarthritic normal glenoids (-5° ± 5°). 

Comment: These findings are interesting in that they may help understand why some patients' shoulders are predisposed to osteoarthritis. We tend to use our arms out in front of us, in which position the deltoid pushes the humerus backward on the glenoid socket. If there is insufficient support from the posterior part of the glenoid, subluxation can begin. Subluxation leads to posterior glenoid erosion which results in a biconcave glenoid.

It would be very interesting to know the retroversion and glenoid shape of the shoulders contralateral to those reported in this article. As pointed out previously, a CT scan is not necessary to make these determinations, as shown here, a standardized axillary is preferable.

This phenomenon is demonstrated by a memorable case. 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).

His axillary view shows that the anterior half of his glenoid (the 'normal' part) is indeed retroverted with respect to the plane of the scapula while the posterior half is eroded forming the biconcave glenoid.
 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 conservatively reamed to a single concavity with a diameter of 58 mm without attempting to 'normalize' glenoid version. The stem was fixed with impaction grafting. A rotator interval plication was used to augment his posterior stability. This approach 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 in the concentrically reamed glenoid.
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.


PS—my first “honest” pull-up in roughly seven years. That was a pretty sweet victory!


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