The importance of preserving the coracoacromial ligament in reverse total shoulder.

Does Preservation of Coracoacromial Ligament Reduce the Acromial Stress Pathology Following Reverse Total Shoulder Arthroplasty?

These authors point out that acromial pathologies (AP), such as acromial stress reaction (ASR), acromial stress occult fracture (ASOF), and acromial stress fracture (ASF), are known as complications that compromise the outcome for patients having reverse total shoulder arthroplasty (RSA). 

They point out that the coracoacromial ligament (CAL) distributes the stress on the acromion.

In 265 patients, they investigated the incidence of AP according to the preservation (68) or sectioning (197) of the CAL.

ASR and ASOF were identified through symptoms and ultrasound, and ASF identified through simple radiograph or computed tomography. 

In the 197 patients with CAL sectioning 

there were 21 cases of ASR(10.7%), 28 cases of ASOF (14.2%),10 cases of ASF (5.1%), and 59 cases of total AP (29.4%). 

In the 68 cases with preservation of the CAL 

there were 2 cases of ASR (2.9%) , 6 cases of ASOF (8.8%), 1 case of ASF (1.5%), and 9 cases of total AP (13.2%). 

Comment: These clinical results are consistent with the results of a recent cadaver study:

Scapular Ring Preservation: Coracoacromial Ligament Transection Increases Scapular Spine Strains Following Reverse Total Shoulder Arthroplasty

Stating that the coracoacromial ligament (CAL) is often transacted during surgical exposure for reverse total shoulder arthroplasty (RSA), these authors hypothesized that the CAL contributes to the structural integrity of the “scapular ring” and that the transection of this ligament during RSA alters the scapular strain patterns in a way that may contribute to scapular fractures following this procedure.

They performed RSA on 8 cadaveric specimens and measured strains at the acromion and scapular spine before and after CAL section while a shoulder simulator positioned the joint in 0, 30, and 60 of glenohumeral abduction.

With the CAL intact, there was no significant difference between strain experienced by the acromion and scapular spine at 0, 30, and 60 of glenohumeral abduction. 

CAL transection generated significantly increased strain in the scapular spine at all abduction angles compared with an intact CAL. 

They concluded that the  CAL is an important structure that completes the “scapular ring” and therefore serves to help distribute strain in a more normalized fashion. 

Comment: In his 1934 book, E. A. Codman wrote prophetically, "The coracoacromial ligament has an important duty and should not be thoughtlessly divided at any operation."

We have not found it necessary to divide the CAL "at any operation." Not only is it a halyard stabilizing the scapular spine and acromion to the robust coracoid process, as suggest by this study, but it is also an essential element of the stabilizing coracoacromial arch.

which, when sacrificed, risks anterosuperior escape

which, in turn, is one of the reasons for performing a reverse total shoulder. 

So, we agree with Codman, "The coracoacromial ligament has an important duty and should not be thoughtlessly divided at any operation."

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How you can support research in shoulder surgery Click on this link.

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 total shoulder arthroplasty (see this link).

The ream and run technique is shown in 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).

The world is not flat and neither is the acromion.

Our former fellow Mike Moskal sent a concise set of his personal dissections that reinforce Codman's 1930 observations that the coracoacromial arch is a stabilizing concavity for the proximal humerus and "should not be sacrificed at any procedure". 

Here are some great photographs of his dissections that make the point.

 

He also included a couple of related articles, see this link and this link.

Comment: In his 1934 book, E. A. Codman wrote prophetically, "The coracoacromial ligament has an important duty and should not be thoughtlessly divided at any operation."

We have not found it necessary to divide the CAL "at any operation." Not only is it a halyard stabilizing the scapular spine and acromion to the robust coracoid process, as suggest by this study, but it is also an essential element of the stabilizing coracoacromial arch.

which, when sacrificed, risks anterosuperior escape

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How you can support research in shoulder surgery Click on this link.

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.

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'

 

Acromioplasty - is it benign?

The effect of coracoacromial ligament excision and acromioplasty on the amount of rotator cuff force production necessary to restore intact glenohumeral biomechanics.


These authors point out that coracoacromial ligament (CAL) excision and acromioplasty increase superior and anterosuperior glenohumeral translation. They used a cadaver model to estimate how much of an increase in rotator cuff force is required to re-establish intact glenohumeral biomechanics after acromioplasty.

Nine cadaveric shoulders were subjected to loading in the superior and anterosuperior directions in the intact state after CAL excision, acromioplasty, and recording of the translations. The rotator cuff force was then increased to normalize glenohumeral biomechanics.

At 150 and 200 N of superior and anterosuperior loading, an increase in the rotator cuff force of 25% was required to eliminate the increased translation resulting from CAL excision.

At 150 and 200 N of superior and anterosuperior loading, an increase in the rotator cuff force of 25% and 30%, respectively, was required to eliminate the increased translation resulting from acromioplasty and CAL excision.

The authors concluded that after subacromial decompression, the rotator cuff has to increase  its force production to maintain baseline glenohumeral mechanics. Under many circumstances, in vivo force requirements may be even greater after surgical attenuation of the coracoacromial arch.

Comment: As Codman pointed out in 1934 "The coracoacromial ligament has an important duty and should not be thoughtlessly divided at any operation." 

He recognized then, as we should today, that the coracoacromial arch provides an important stabilizing function resisting the superiorly directed force applied by the deltoid or when pushing up from a chair, bed, floor or bar. He pointed to the normal articulation between the superior aspect of the cuff and the undersurface of the coracoacromial arch. 

The center of curvature of the arch is the same as the center of curvature of the humeral head.

The stabilizing effect of the arch remains the same if there is ossification of part of the coracoacromial ligament.

We have previously demonstrated that the acromion is loaded when superiorly directed force is applied through the humeral head (whether or not the cuff is intact).

 When the superior cuff tissue is absent, superiorly directed loads applied to the humeral head produce superior translation of the head until it is stopped by the coracoacromial arch.

Sacrifice of the coracoacromial arch in the cuff deficient shoulder is a common cause of anterosuperior escape and pseudoparalysis.

Where does that leave the concept of 'impingement'? See this link.

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Consultation for those who live a distance away from Seattle.

Click here to see the new Shoulder Arthritis Book

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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'

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Rotator Cuff 2 - Clinical Considerations Relating to Shoulder Strength

Neurogenic and Muscular Causes

The most devastating injury to a muscle is the loss of its nerve supply. Losses of the innervation of the deltoid, supraspinatus, and infraspinatus can be congenital (Erb’s Palsy), inflammatory (brachial neuritis), degenerative (cervical radiculopathy), traumatic (penetrating or stretch), compressive (a ganglion in the spinoglenoid notch), or iatrogenic (dissection or screw placement). These conditions along with myopathies, such as facioscapular muscular dystrophy, must be considered when the shoulder is weak.

The day this paragraph was written, we saw a patient sent in for a cuff repair. He had been in a water-skiing accident and landed on the water in a way that pressed his head to the left and his right shoulder down. At the moment of impact he experienced a shock down his right arm and noted severe weakness of his right shoulder. His physician sent him for an MRI that showed a partial tear of his supraspinatus. On exam in our office he had, six weeks after injury, atrophy and weakness of his spinati, deltoid, and biceps – a classic Erb’s type injury.

Electromyography, nerve conduction velocities, and muscle biopsies may be needed to sort out these diagnoses.

Loss of the Humeral Fulcrum

If the humeral head does not remain centered during muscle contraction, the forces intended to cause rotation will cause translation. As an example, the shoulder with posterior instability: when the arm is elevated forward, the humeral head slips out the back, losing its fulcrum. In this situation, valuable muscle excursion is consumed by displacement of the head and the strength of elevation is lost. The effects of loss of centering are also seen with the cuff and superior labral deficient shoulder in which contraction of the deltoid produces ascension of the humeral head rather than abduction

However, if the glenoid concavity is intact, the humeral head may remain stabilized in the glenoid in spite of superior cuff deficiency. This is why many shoulders with cuff tears remain functional.

Alternatively, if the coracoacromial arch remains intact, the humeral head of the cuff deficient shoulder may be secondarily stabilized in a new position, superiorly displaced against the arch.

Thus in the presence of cuff deficiency, it is vitally important to protect and maintain the coracoacromial arch. Without it, the humeral head will escape anterosuperiorly when the deltoid contracts – a complication that can result from acromioplasty and resection of the coracoacromial ligament.

This phenomenon is nicely demonstrated in this short video clip of a patient before surgery.

The treatment of anterosuperior instability may require a reverse total shoulder.

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How you can support research in shoulder surgery Click on this link.

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).

Revision surgery for failed shoulder replacement arthroplasty due to superior instability, Part 12

Loss of the integrity of the coracoacromial arch can be a major problem following shoulder arthroplasty allowing anterosuperior escape of the proximal humerus from the glenoid.  This problem is often caused by prior surgery attempting to repair a large rotator cuff tear. It most commonly seen when an acromioplasty has been performed, compromising the stabilizing effect of the coracoacromial arch.

In this situation a reverse total shoulder arthroplasty may be considered.

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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.