SHOULDER INSTABILITY SHOULDER INSTABILITY – PART I WHAT’S NEW? By Jo Gibson, MCSP
Shoulder instability continues to provide a challenge to the physical therapist. The use of arthroscopy and more sophisticated imaging techniques have increased our understanding of the structural anatomy of the glenohumeral joint and the interrelationship of the static and dynamic stabilisers. Identification of reflex loops exist- ing between the capsule and rotator cuff demonstrates the importance of normal afferent input in optimal motor control of the shoulder complex (1). However, much of this research, while answering some questions, succeeds in raising many more! Shoulder instability classification systems are also often confusing and misdiagnosis can lead to inap- propriate management. The aim of this article is to update the reader regarding a new classification sys- tem and introduce the concept of muscle patterning instability together with key factors in assess- ment and treatment of this complex problem.
TRADITIONAL CLASSIFICATION SYSTEMS Matsen’s classification system using the pseudonyms TUBS and AMBRIL has been well reported. TUBS (‘Torn Loose’) describes the typical Traumatic, Unidirectional dislo- cation, often resulting in a Bankart lesion (anterior-inferior labral tear) which com- monly necessitates Surgical repair. The other extreme (‘Born loose’) is the Atraumatic, Multidirectional instability which commonly has Bilateral symptomol- ogy and in which Rehabilitation should be the primary treatment option. In those patients who fail to respond to rehabilita- tion surgical options include an Inferior Capsular Shift or Laser Capsulography. Systems such as Matsen’s essentially differ- entiate between structural damage such as
that incurred in a traumatic dislocation and ‘atraumatic’ instability which results from unbalanced muscle recruitment around the shoulder on a background of a lax capsule. However the reality is a spec- trum of instability including those patients with deficient capsule-labral structures and
those with acquired structural deficiency.
THE STANMORE TRIANGLE The main limitation of traditional classifi- cation systems is that they fail to acknowledge an increasingly recognised group of patients with instability as a