The importance of scapulo-thoracic motion.

 The motion of the arm in relation to the body takes place at two articulations, the glenohumeral joint and the scapulothoracic joint.

When we measure the motion of the shoulder, we usually measure the overall motion of the humerus in relation to the thorax (chest)

If we look carefully, however, we can see that while much of this motion takes place between the humerus and the scapula

a substantial portion takes place between the scapula and the thorax.

Thus, overall humero-thoracic motion is the result of the combination of humero-scapular motion (also known as glenohumeral motion) and scapulo-thoracic motion.

When patients and surgeons think of "shoulder problems", they commonly focus on the glenohumeral joint - the articulation between the shoulder blade's socket (glenoid) and the humeral head. These areas are easy to assess on physical exam, plain x-rays and MRIs.

However - as shown above - a substantial component of shoulder function is determined by the articulation of the shoulder blade on the chest wall: the scapulothoracic joint. This area is hidden with the patient's shirt on and is difficult to evaluate with x-ray or other types of imaging. On one hand, impaired scapulothoracic function can compromise the overall workings of the shoulder. On the other hand, enhanced scapulothoracic function can compensate for poor motion at the glenohujmeral joint. Because female patients typically have more lax joints than men, a stiff glenohumeral joint can be overlooked because of compensatory motion at the scapulothoracic joint.

The components of shoulder motion are wonderfully demonstrated in two videos produced by our late partner, Doug Harryman, including the now famous "pin brother" studies (video 1 and video 2).

While there are many ways to assess the relative contributions of glenohumeral and scapulothoracic motion to overall humerothoracic motion (including the Kinect and fluoroscopy), a clinically useful method is for the examiner to hold the scapula in its resting position while attempting to elevate the arm.

This reveals the amount of motion at the glenohumeral joint which can then be compared to the amount of arm elevation achievable when the scapula is not stabilized. The difference between these two measurements is the scapulothoracic contribution to shoulder motion.

The authors of The contribution of the scapula to active shoulder motion and self-assessed function in three hundred and fifty two patients prior to elective shoulder surgery found that scapulothoracic motion is an important component of active shoulder motion and function in both healthy shoulders and in those compromised by common pathologies. They concluded that rehabilitation directed at improving active scapulothoracic motion may improve the function of shoulders with loss of active glenohumeral motion. Three papers illustrate this principle: (1) Harryman's paper Residual motion and function after glenohumeral or scapulothoracic arthrodesis, (2) Scapulohumeral rhythm in shoulders with reverse shoulder arthroplasty measured with a new portable three-dimensional scapular kinematics assessment system, and (3) Scapulohumeral rhythm relative to active range of motion in patients with symptomatic rotator cuff tears

Scapulo-thoracic motion can be restricted because of muscle weakness (serratus anterior, trapezius, latissimus dorsi, rhomboids), abnormalities of the sternoclavicular and acromioclavicular joint, prior scapular or rib fractures, snapping scapula, tumors, and disuse (see link). Using four clinically palpable landmarks (1 inferior pole of scapula, 2 medial edge of the scapular spine, 3 the posterior corner of the acromion, and 4 the coracoid process), the position and motion of the scapula can be assessed and compared to the opposite side.

Comment: It can be concluded that active scapulothoracic motion can be a major contributor to the function of normal and pathologic shoulders. In shoulders with glenohumeral pathology (e.g. arthritis, rotator cuff tears) and in patients with anatomic and reverse total shoulder arthroplasties, simple exercises such as the "press plus" (see this link) can help activate the scapulothoracic musculature than may be in suboptimal condition and thereby substantially improve overall shoulder function.

Great thanks to our shoulder fellow, Mihir Sheth, who proposed this post and did much of the "spade work" on it.

You can support cutting edge shoulder research and education that are leading to better care for patients with shoulder problems, click on this link.

Follow on twitter: https://twitter.com/RickMatsen or https://twitter.com/shoulderarth
Follow on facebook: click on this link
Follow on facebook: https://www.facebook.com/frederick.matsen
Follow on LinkedIn: https://www.linkedin.com/in/rick-matsen-88b1a8133/

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 is the motion of the scapula on the chest wall affected in common shoulder conditions?

The contribution of the scapula to active shoulder motion and self-assessed function in three hundred and fifty two patients prior to elective shoulder surgery

These authors determined the contribution of the scapula to active shoulder motion in control subjects and patients with loss of shoulder function.

They used the Kinect motion capture system to assess active scapulothoracic (ST) and humerothoracic (HT) abduction in 12 controls and in 352 patients before elective shoulder surgery.

For the controls, ST abduction averaged 26 ± 7° or 19% of the active HT abduction (135 ± 5°). 

For the 352 patients prior to elective surgery, active ST abduction averaged 12 ± 10°, or 17% of the active HT abduction (72 ± 38). 

For 10 of the 12 Simple Shoulder Test functions, patients unable to perform the function had significantly less scapulothoracic abduction, e.g., shoulders unable to lift one pound to shoulder level had 9 ± 8° of ST abduction in contrast to 17 ± 10 for those able to perform this function (p < .001). 

They concluded that scapulothoracic motion is an important component of active shoulder motion and function in both healthy shoulders and in those compromised by common pathologies. 

They suggested that rehabilitation directed at improving active scapulothoracic motion may improve the function of shoulders with loss of glenohumeral motion.

Comment: This study shows that in common conditions that involve the glenohumeral joint, such as osteoarthritis, rotator cuff tear, and cuff tear arthropathy, motion at both the glenohumeral and the scapular articulations are compromised. After surgery to address the glenohumeral pathology, rehabilitation directed at the scapulothoracic joint may enhance the outcome.

===

We have a new set of shoulder youtubes about the shoulder, check them out at this link.

Be sure to visit "Ream and Run - the state of the art"  regarding this radically conservative approach to shoulder arthritis at this link and this link

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

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'

Reverse total shoulder - scapular motion

How does scapula motion change after reverse total shoulder arthroplasty? - a preliminary report

This report examines changes in scapular position after reverse total shoulder arthroplasty in seven patients having reverse total shoulder arthroplasty for cuff tear arthropathy from July 2007 to October 2008. The distance between the long axis of the thoracic spine and the inferior pole of the scapula (lateralization of the scapula) was measured on shoulder A-P radiographs at 0 degrees (the neutral position) and at 30, 60, 90, and 120 degrees of shoulder abduction. In addition, the angle between the long axis of the thoracic spine and medial border of the scapula was measured and compared with the patients' contralateral shoulder.

Of interest is that the authors tracked the change in position and orientation of the scapula without the use of elaborate sensors attached to the bone, but rather with plain radiographs. While the authors concluded "The pattern of scapular position after RTSA, was found to differ from that of the contralateral shoulder, and showed a more scapular upward rotation," when I replotted their data from their Table II, I was impressed at how similar the motion patterns were, with somewhat greater ST motion in the reverse than in the contralateral shoulder:

It is always of interest to view radiographs of reverse total shoulders.

Here's one showing notching and some heterotopic bone formation. We're fortunate that shoulders forgive these happenings.

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.

See from which cities our patients come.

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

Kinematic analysis of dynamic shoulder motion in patients with reverse total shoulder arthroplasty JSES

JSES has published Kinematic analysis of dynamic shoulder motion in patients with reverse total shoulder arthroplasty.


This important article reminds us that apparent shoulder motion, i.e. the motion of the arm relative to the thorax, is comprised of two components, humeroscapular and scapulothoracic. These to combine to yield the humerothoracic motion we discussed in yesterday's post. The article on reverse total shoulders referenced above uses an electromagnetic tracking system to differentiate humeroscapular (glenohumeral) motion from scapulothoracic motion. In 17 patients with reverse total shoulders, they found that, although humeroscapular motion exceeded scapulothoracic motion, the percent contribution of scapulothoracic motion to total humerothoracic motion was greater in patients with reverse total shoulders than in normal subjects. Since they found that humeroscapular motion in reverse total shoulders was 1.6 to 2 times the scapulothoracic motion, we can conclude that scapulothoracic motion provides about 1/3 of the total humerothoracic motion. The authors make a important recommendation: "scapulothoracic joint function...should be carefully assessed before proceeding with the operation [reverse total shoulder]."

So, how does one do this? As pointed out yesterday, one way is to use sensors connected to pins drilled into the humerus and scapula of volunteers to make sure that the movement of soft tissues on the bones did not affect the position of surface mounted sensors. To seen an example, look at minute 6:31 of this video

Another way as suggested in Practical Evaluation and Management of the Shoulder. Chapter 2. is to recognize that the position and motion of the scapula can be observed clinically through the use of four easily palpable landmarks:

By observing the patient's ability to actively move the scapula and comparing this ability to their unaffected shoulder, the surgeon can assess the scapulothoracic function necessary for a functioning reverse total shoulder.

The recognition that we can, using our fingers, define the position of the scapula while examining the shoulder gives us the ability to more precisely define humerothoracic (or glenohumeral) motion using scapular landmarks:

These data, whether obtained by our fingers or by electromagnetic tracking, can be recorded on a humeroscapular global diagram:

----


If you have suggestions for topics you'd like us to address in this blog, please send an email to
shoulderarthritis@uw.edu

Use the "Search the Blog" 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.

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