Reverse total shoulder - safe baseplate fixation

Scapula fracture incidence in reverse total shoulder arthroplasty using screws above or below metaglene central cage: clinical and biomechanical outcomes

Scapular spine fractures are serious complications of reverse total shoulder arthroplasty.

These authors reviewed 318 reverse total shoulder arthroplasties (RTSAs) to identify scapular spine fractures.
Of 206 patients in the superior screw group, 9 (4.4%) experienced scapula spine fractures.

Of 112 patients in the inferior screw group, 0 had scapular spine fractures.

They also implanted RTSAs in 17 cadaveric scapula specimens with 2 screw configurations: inferior screws alone (group 1INF) vs. inferior screws with one additional superior screw (group 2SUP). 

Biomechanically, superior screw constructs (group 2SUP) demonstrated significantly (P < .05) lower load to failure (1077 N vs. 1970 N) compared with constructs with no superior screws (group 1INF). 

They concluded that the risk of scapular fractures was significantly (P < .05) for patients with no screws placed above the central cage compared with patients with superior metaglene screws.

The superior screw may not add substantially to the quality of the fixation. In an article entitled, Factors affecting fixation of the glenoid component of a reverse total shoulder prothesis, the relatively greater importance of the inferior screw in contrast to the relatively lower importance of the superior screw was emphasized.

In this type of design,  superiorly directed loads applied to the glenosphere by the humeral component are resisted primarily by the inferior screw.

Our approach to reverse total shoulder arthroplasty is to use a fixation system that uses a large central compression screw, avoiding the risks of a superiorly directed screw.

Here are some related posts.

Scapular fracture in reverse total shoulder arthroplasty

Scapular fractures after reverse total shoulder

Scapular spine fractures after reverse total shoulder 2

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You may be interested in some of our most visited web pages including:shoulder arthritis, total shoulder, ream and run, reverse total shoulder, CTA arthroplasty, and rotator cuff surgery as well as the 'ream and run essentials'

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Latarjet - a cautionary tale

A coracoid transfer (Latarjet) is preferred by some surgeons to manage recurrent anterior instability. This procedure is not without its risks as demonstrated by the x-rays below taken of the right shoulder of a young man who presented with pain and crepitant after his coracoid transfer. They show loosening and an intrarticular location of two cannulated screws associated with erosion of the inferior humeral head and loss of glenoid bone stock.

Comment: As pointed out in a prior post (see this link), the Latarjet procedure for shoulder instability carries some risk to the  axillary and musculocutaneous nerves, has had a 16% incidence of complications needing reoperation, has had a recurrence rate of 6%, and has had a 20% rate of subsequent arthritis.

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Consultation for those who live a distance away from Seattle.

Click here to see the new Shoulder Arthritis Book.

Click here to see the new Rotator Cuff Book

Information about shoulder exercises can be found at this link.

Use the "Search" box to the right to find other topics of interest to you.

You may be interested in some of our most visited web pages including:shoulder arthritis, total shoulder, ream and run, reverse total shoulder, CTA arthroplasty, and rotator cuff surgery as well as the 'ream and run essentials'

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Reverse total shoulder - baseplate screw dangers

Glenoid screw position in the Encore Reverse Shoulder Prosthesis: an anatomic dissection study of screw relationship to surrounding structures.

These authors inserted reverse total shoulder prostheses in cadaver shoulders using a 6.5-mm central screw and four 5.0-mm peripheral locking screws placed 90° to the baseplate. They set the screw length at 30 mm for the superior screw holes, 28 mm for the inferior screw holes, 13 mm for the anterior screw holes, and 15 mm for the posterior screw holes [NB that in the recommended technique a set screw length is not recommended, instead the length of the screws is determined by a calibrated drill and a depth gauge]. 

They found that the central screw trajectory was through the anterior cortex. The anterior screw trajectory violated the subscapularis belly in all specimens. The posterior screw touched the suprascapular nerve or artery in 3 of 10 specimens.

Comment: It is difficult to know the degree to which screw penetration affects the outcome of reverse total shoulder. Obviously, the big risk is to the axillary nerve from dissection and to the plexus overall from traction or excess lengthening of the arm. In that many shoulders requiring reverse total shoulders have massive cuff defects, the suprascapular nerve is of less functional concern. In any event, however, drill plunges and excessively long screws need to be carefully avoided by good surgical technique and by customizing the length of the screws used. This is especially important because the rotational position of the baseplate may vary, so that the thickness of scapular bone to be traversed by the peripheral screws will vary from case to case.

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Use the "Search" box to the right to find other topics of interest to you.

You may be interested in some of our most visited web pages including:shoulder arthritis, total shoulder, ream and run, reverse total shoulder, CTA arthroplasty, and rotator cuff surgery as well as the 'ream and run essentials'


See from which cities our patients come.


See the countries from which our readers come on this post.