Rotator Cuff Disease - all you need to know. Part1
My name is Gavin Jennings. I am a consultant orthopaedic surgeon specialising in the shoulder.
This presentation gives an in-depth overview of rotator cuff disease.
The presentation is divided into three parts.
Part 1 will focus on the anatomy, epidemiology and pathophysiology of problems of the rotator cuff.
Firstly I would like to briefly run over the anatomy of the rotator cuff.
The muscles of the shoulder girdle are numerous, but the focus here is on the top four i.e. the supra and infra -spintatus, the teres minor and the subscapularis.
The subscapularis arises from the front (or undersurface of the scapula if looking from behind), then passes in front of the shoulder to attach to the lesser tuberosity of the humerus. It is supplied by the subscapular nerves and is both an internal rotator of the humerus and stabiliser of the glenohumeral joint.
The teres minor arises from the lateral side of the scapula and inserts on the lowest part of the greater tuberosity. It’s nerve supply is from the axillary nerve. It’s action is to externally rotate the humerus (particularly in abduction) and again to stabilise the glenohumeral joint.
The supraspinatus originates from the back of the scapula, above the spine and it inserts on the greater tuberosity. It’s nerve supply, like the infraspinatus, is the suprascapular nerve. It acts as an abductor of the shoulder and once more is a stabiliser of the glenohumeral joint.
The infraspinatus arises below the spine, inserts just below and shares a nerve supply with the supraspinatus. It is an external rotator, particularly in the adducted arm, and yet again also acts to stabilise the humeral head.
Considering the suprascapular nerve in a little more detail. The nerve originates from the superior trunk of the brachial plexus and passes backwards through the suprascapular notch under the transverse scapular ligament. After supplying the supraspinatus, it passes around the spinoglenoid notch and supplies the infraspinatus. Compression of the nerve, which can result in posterior shoulder pain and cuff weakness, can occur at two points. The first is under the transverse scapular ligament in the notch. Compression here will result in weakness and wasting of both supra- and infraspinatus.
Compression at the spinoglenoid notch (usually from a cyst arising from under the labrum) will affect the infraspinatus alone as the supraspinatus will already have received its nerve supply.
Really, the key message to take from the previous slides is that that the humeral head stabilising function of the rotator cuff is vital and key when considering cuff disease and its treatment. When the cuff is functioning well and effectively stabilising the joint, it helps prevent further injury to itself, for example, by ensuring good clearance of the tendons as they pass under the coracoacromial arch during movements. I thus often think of the cuff as “autoprotective”
Rotator cuff disease is often considered as a spectrum. With degenerative type problems, the initial issue is often one of impingement. Repetitive microtrauma, perhaps with altered blood supply may eventually outstrip the tendons’ power of recovery and eventually macroscopic damage can occur. This can result in tearing of the tendons. As the tendon tears, the forces that the remaining tendon insertion is subjected to will naturally increase, which explains why tears often progress over time. If the tear becomes large, the balance of the opposing forces acting on the shoulder can be lost. The depressor effect of the cuff is lost and unopposed deltoid activity can lead to an upward shearing force on the humeral head which can culminate in the development of rotator cuff arthropathy. This is a type of arthritis associated with chronic cuff deficiency and is characterised by a high riding humeral head.
Considering the epidemiology of rotator cuff disease now, problems are rarely seen in the under 40 age group, however about a quarter of over 60 years olds will have had some symptoms. We know that the incidence of cuff tears in the older age group is quite high, but by no means all of these people have symptomatic shoulders. For some people tears seem to be part of the normal ageing process. They are often compensated for very well, particularly if the tear progresses slowly over time. Such people may have no symptoms at all. We should not consider, therefore that a cuff tear= a need for repair.
However, 4% of people with any kind of full thickness tear will develop symptomatic rotator cuff arthropathy and in those with a large chronic tear, the incidence may well be significantly higher.
Rotator cuff dysfunction and pain in younger patients is more likely to be due to overuse, subtle instability and muscle imbalance. Thus factors such as these need be considered and assessed when planning the treatment of the younger individual.
In the older age group, however, degenerative factors are more prevalent and important.
Th theories of pathophysiology of cuff disease can be divided into extrinsic and intrinsic factors
The extrinsic theory suggests that cuff pathology is caused by trauma to the tendons from abnormal contact with the surrounding structures i.e. the tendon is impinged upon by something external. Three types of impingement are recognised. The first is anterosuperior, the second is posterosuperior (or internal) impingement and the third anterointernal (or subcoracoid).
Anterosuperior or external impingement as described by Neer in 1972 is the type of which there is probably greatest awareness i.e. impingement of the cuff below the coracoacromial arch, occurring particularly in mid-abduction.
Posterosuperior or internal impingement described by Walch, occurs between the undersurface of the supraspinatus and the posterosuperior labrum and glenoid rim. This occurs in abduction and extreme external rotation and is a common pathology in overhead athletes. The “pathological cascade” is one theory as to how this situation arises particularly in overhead athletes with a glenohumeral internal rotation deficit or GIRD. More details on this can be found on the website.
Finally, subcoracoid impingement, as described by Gerber in 1985, occurs when the subscapularis becomes pinched between the posterior tip of the coracoid and the lesser tuberosity. Anterior shoulder pain is felt in a position of flexion, adduction and internal rotation.
An intrinsic theory was first described by Von Meyer. This theory suggests that cuff disease occurs as a result of age related degeneration of the tendon. In other words the tendon fails internally, not as a result of cuff damage from an external cause. It seems likely that in many cases of rotator cuff disease, there may be a combination of both intrinsic and extrinsic factors implicated as causative factors.
Thanks for listening to part 1 of an overview of rotator cuff disease. Part 2 will deal with symptoms, examination and non-operative treatment.