Do lateralization and distalization after reverse total shoulder have a clinically significant relationship with patient outcome?

There are a host of variables that may affect the clinical outcome of reverse total shoulder arthroplasty. A number of authors have attempted to relate distalization and lateralization to outcome scores. For example in Managing rotator cuff tear arthropathy: a role for cuff tear arthropathy hemiarthroplasty as well as reverse total shoulder arthroplasty, the authors found that the postoperative position of the center of rotation and greater tuberosity on anteroposterior radiographs did not correlate with the clinical outcomes for either procedure.

The authors of How To Choose The Best Lateralization And Distalization Of The Reverse Shoulder Arthroplasty To Optimize The Clinical Outcome In Cuff Tear Arthropathy investigated the effect on the 1 year ASES score of combinations of lateralization and distalization of 62 patients having reverse total shoulder arthroplasty performed for cuff tear arthropathy. They measured lateralization by the LSA as shown below





and distalization by the DSA as shown below.







They found the correlation between ASES score and LSA to be = -0.43 and the correlation between ASES score and DSA to be 0.39; both values lying in the "moderate" range.


The accepted value for minimal clinically important difference for the ASES score in total shoulder arthroplasty is 20.9


The DSA of patients with ASES scores > 76 was 48.55 while the DSA of patients with ASES scores < 76. was 37.82, a difference of 10.7.


The LSA of patients with ASES > 76 was 86.43 while the LSA of patients with ASES scores <76 was 100.09, a difference of 13.7.


Thus neither measurement exceeded the threshold for clinical significance.


The authors suggest that optimal LSA should be no more than 90.5° yet of the 24 patients with LSA > 90.5 degrees 75% had ASES scores >76. Furthermore, what should be the lower limit of the LSA?







The authors also suggest that the optimal DSA should be no less than 37.5°, yet of the 17 with DSA less than 37.5, 65% had ASES scores >76. Furthermore, what should be the upper limit of the DSA?




Comment: This is a well done study that effectively uses scatter plots to show all their data. This type of presentation lends itself to an understanding of the variability in the studied relationships.


As the authors point out in their discussion, prior authors have come to varying conclusion about the clinical (rather than statistical) significance of the relationships between distalization angles and lateralization angles.


It seems curious that distalization (a linear dimension) is being measured as an angle, rather than as a linear dimension (see yellow line) and






that laterialization (a linear dimension) is being measured as an angle, rather than as a linear dimension (see yellow line).




Both lateralization and distalization affect deltoid tension, moment arms, center of rotation, stretch on the brachial plexus, the stabilizing compressive force across the articulation, the function of the remaining cuff muscles, the ability to repair the subscapularis and more. We need to know what is the "sweet spot" when the effects of these two variables are considered together?

Finally, distalization and lateralization do not reflect other clinically important variables, such as glenoid tilt, baseplate seating, baseplate fixation, as well as baseplate-bone contact. To determine the relationship of ASES score to the geometry of the reverse total shoulder arthroplasty, a multivariable analysis would be required.

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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).

How do we know when patients are SIGNIFICANTLY better

A Primer on Clinically Important Outcome Values Going Beyond Relying on P Values Alone

These authors tackle in depth the question "how do we evaluate the effectiveness of treatment"?

Their bullet points are below:

➤ Clinically important outcome values allow physicians to provide patients with more realistic expectations regarding their treatment that are based on their specific demographics.
➤ Clinically important outcome values can vary for the same procedure or population depending on the method of calculation used, which raises the need for uniform ways to calculate and compare these values across populations and procedures.
➤ A shift in approach from focusing solely on significant outcomes, or p values, to considering both clinically important and significant outcomes will allow clinicians to provide more efficient care, in line with recent trends toward a value-based health-care system.

Comment: It is important to recognize that a study can show that one treatment is statistically significantly better than another without it being clinically significantly better. Consider a hypothetical study of a traditional treatment (A) and a novel treatment (B) with 25 patients each evaluated by the Simple Shoulder Test (SST). The increased benefit (difference between the pre and the post op SST) for the new treatment B is significantly better than the traditional treatment (p=0.003).

However the difference between the average outcomes is only 0.76, a value well below the published values for the minimal clinically important difference (MCID) for the Simple Shoulder Test (1.5 to 3.6). So the benefit of the new treatment is statistically significant, but not clinically significant.

This article points out that there are many different ways for measuring the clinical benefit and, furthermore, that the value of a measure such as the MCID may be different for different treatments or different populations of patients.

Another issue relates to studies showing significant "geometric" improvement with respect to the positioning of arthroplasty components, without evidence that there is associated clinical improvement.

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How you can support progress in shoulder surgery

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

Today's shoulder fellowship interviews: clinical significance vs. significantly greater value to the patient

Today we completed our interviews of a second group of outstanding candidates for the fellowship at the University of Washington (after gathering 'round for the traditional home-cooked salmon dinner last night).

This, like our previous interview day in January, was a most stimulating session. Among many other topics, we got into a discussion of two important goals of the fellowship year.

The first is to assure that the fellows become competent and confident in the evaluation and management of the 'big four': shoulder instability, rotator cuff disease, shoulder arthritis, and failed prior surgery (as well as of sternoclavicular, acromioclavicular, clavicular, scapular, biceps and other clinically important shoulder and elbow problems).

The second is for us to learn together to be cautious consumers of new technology. Among many other things, this means that we need to distinguish a new procedure that results in 'clinically significant improvement' from one that provides 'significantly greater' value to the patient than what is in current use. For example, every type of shoulder arthroplasty is likely to result in 'clinically significant improvement' for the patient with arthritis. However, the test for new implant systems should be whether or not they yield better results than those we now use. It is a question of differentiating the value of a new system from its increased value.

This question is critical to our informed consumption of precious health care resources. As this graph shows, there is an ever increasing number of shoulder arthroplasties approved cleared by the FDA each. Each new system carries with it costs of research and development, marketing, and potential unexpected complications.

However, as shown in a recent article (see link) it is unclear that the costs associated with the introduction of these new technologies is offset by increased benefit to the patient. Before adopting a new system, we need to look for this evidence.

We thoroughly enjoyed our day with the applicants. We look forward to the opportunity to partner with them as they master the currently accepted means of treatment on one hand and seek to increase the value of what our field has to offer patients disabled by shoulder and elbow disorders on the other.