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Shoulder Instability in Multiple Directions
This condition is moderately common, occurs typically on both sides and is a non-traumatic condition which interferes with the function of the shoulder. The laxity of the shoulder capsule and thereby the lack of its inherent ligamentous restrictions is the underlying problem causing these difficulties. With this laxity there is an excess of mobility in the shoulder joints in every joint direction. Patients may complain of instability, with the feelings that the shoulder will partly or wholly come out of joint at times. If this instability is not obvious to the patient they may complain only of pain when they present.
Conservative treatment is the first line of management for this condition, with physiotherapy treatment consisting of strengthening of the muscular parts of the scapular stability and rotator cuff systems. Once conservative treatment has been attempted and not been successful then consideration can be given to surgery. Surgery can tighten up the shoulder capsule, increasing the strength of the static stabilisers. Typically surgery has been done in open technique but arthroscopic technique is become more prevalent.
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:
* Traumatic cause
* Unidirectional – the instability is only in one joint movement direction
* Bankart lesion is found – where the cartilage rim of the shoulder socket becomes detached
* Surgery – is a common requirement
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 instability – laxness in all joint movements
* Bilateral – both shoulders are typically affected
* Rehabilitation used as the initial management
* I refers to the technical types of surgery and where they are performed.
The shoulder joint has a very high degree of mobility and is designed to allow us to place our hands where we want to within our visual fields, enabling us to perform actions while we watch. We have sacrificed stability of this joint for its mobility, leading to consequent problems when the shoulder is stresses in various ways.
Thinking about the stability of the shoulder it is helpful to concentrate on a few concepts. The idea of balance is related to the way the head of the humerus centres itself on the socket accurately. The main muscles responsible for maintaining this anatomical alignment are those of the rotator cuff, keeping the joint in line as the larger movement muscles do their actions. If an imbalance or weakness develops in the muscles of the scapula or the rotator cuff then the balance can be disturbed. A cartilage rim around the socket, the glenoid labrum, deepens the socket and the muscles compress the two parts together, enhancing stability.
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 is the Superintendent of Physiotherapy at an NHS hospital in the South-West of the UK. He writes articles about back pain, neck pain, and injury management. If you are looking for physiotherapists in Sheffield visit his website.
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Filed under back pain by on Jan 10th, 2010. 
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