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Shoulder Multidirectional Instability

January 4th, 2010

Instability of the shoulder in multiple directions is moderately often encountered, occurring normally on both sides of the body and is not related to accident or injury. The underlying difficulty is the laxity of the capsule of the shoulder and the deficiencies of these stabilising ligamentous structures. This ligament laxity shows itself in excessive joint mobility in all anatomical directions. Patients may describe joint instability as the shoulder may sublux (partial dislocation) or wholly dislocate from time to time. However, the patient may not suffer such obvious symptoms and complain only of pain.

The mainstay of treatment is conservative management, with physiotherapists working on increasing the strength of the stabilising muscular systems such as the rotator cuff muscles and the scapular stability muscles. If conservative rehabilitation is not successful then surgical intervention can be undertaken to stabilise the more static stabilisers such as the shoulder capsule, tightening up so that stability is increased. Open surgery is the typical technique but arthroscopic techniques are developing rapidly.

The incidence of this instability problem in the general public is not obvious and shoulder instability from accidents is much more common as a secondary effect from shoulder dislocation. The shoulder instability types are classified in various ways and TUBS stands for:

* Trauma involved in the cause

* Unidirectional instability – only in a single direction

* Bankart lesion (damage to the rim around the shoulder socket)

* Surgery – which is often required

TUBS summarises the typical shoulder picture which results from single or multiple episodes of shoulder dislocation.

The multidirectional type of shoulder dislocation is summarised by AMBRI, standing for:

* Atraumatic onset (no injury or accident to explain the onset)

* Multidirectional – the shoulder is lax in all directions

* Bilateral – both shoulders are always involved due to general laxity

* Rehabilitation is the first line of treatment with a physiotherapist

* I stands for the techniques of surgery and where this is performed.

The shoulder is designed for maximum mobility to allow the hands to be placed in a myriad of useful positions, usually in front of the eyes so we can see what we are doing. This mobility is extreme and at the expense of the stability of the joint, leading to instability problems under certain physical stresses.

In considering what stability of the shoulder means it is useful to think about various concepts. Balance is the concept that the head of the humerus should be centred on the centre of the glenoid socket. The rotator cuff muscles are the main controllers of this positional requirement, allowing the shoulder to be moved around by the large nearby muscles. If the rotator cuff muscles or the muscles stabilising the scapula weaken this can alter the ability to maintain balance. The muscles compress the head into the socket which is made deeper by the labrum, the cartilage rim around the socket.

The upper half of the shoulder socket adds to the resistance against upwardly movement of the head of the humerus which the rotator cuff also provides by its compressive function. Synovial fluid makes the joint surfaces wet and so they adhere to each other to a degree, the convex ball and the concave deepness of the socket combining to push any air out and create an amount of suction force holding the joint in place. A tight joint typically has a degree of negative pressure and this helps it hold together too. These methods of enhancing stability work in the mid ranges of the joint, the parts of the joint range where the ligaments are least effective.

The main passive constraints to excessive movement of the shoulder joint are the capsule and ligaments. The ligaments are thickened parts of the capsule designed to contain shoulder movements within sensible and safe limits, the most important ligament being the inferior glenohumeral ligament. The importance of the dynamic parts of the stability picture must not be ignored and physiotherapists concentrate on these muscles, attempting to re-educate and strengthen the scapular stabilisers and rotator cuff muscles.

Jonathan Blood Smyth, editor of the Physiotherapy Site, writes articles about physiotherapy, physiotherapy, physiotherapists in London, back pain, orthopaedic conditions, neck pain and injury management. Jonathan is a superintendant physiotherapist at an NHS hospital in the South-West of the UK.

Tags: alternative medicine, back injury, back pain, back pain relief, fitness tips, Frozen Shoulder, health, injury management, pain management, physical fitness, physiotherapists, physiotherapy, Piriformis Syndrome, sciatica

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