MUSCULOSKELETAL DIAGNOSIS DIAGNOSIS OF THE SPORTING SHOULDER By Howard Turner, MCSP, SRP

Rehabilitation of the painful and dysfunctional shoulder pre- sents a significant challenge to the practitioner. The paradoxi- cal demands of strength, stability and flexibility, often under intense load, renders the body’s most mobile articulation vul- nerable to injury and the complexities of these disorders reflect its architectural complexity. The therapist’s first and arguably greatest challenge is to correctly interpret the nature of the dis- order so that treatment can be appropriately tailored.

The challenge of diagnosis Disorders of the shoulder are difficult to diagnose. Mary Magarey’s work, which compared the diagnosis reached from a standardised physiotherapy examination with that reached by arthroscopic exam- ination, challenged the accepted effective- ness and sensitivity of our traditional diag- nostic pointers.

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In particular she concluded that: 1. Consistent differentiation between com- plete and partial rotator cuff (RC) tears and tendonitis is not possible 2. Consistent differentiation between mas- sive RC tears and more minor pathology may be possible 3. Consistent isolation of involvement to a single tendon is not possible 4. Consistent detection of increased passive glenohumeral joint translation is not possi- ble

ticular direction, as the tension is transferred widely throughout the cuff. In fact the provocation of pain on a resisted test appears to depend on the orientation of the lesion to the applied force, rather than the proximity of the lesion to the insertion of the muscle being tested.

The site of the tear is the key factor that determines dysfunction

This transfer of tension throughout the cuff is presumably an impor- tant mechanism of glenohumeral stabilisation, as it would help maintain compression at the joint. A thick band of fibres running perpendicular to the cuff’s insertion (the rotator cuff cable) also contributes towards increasing the efficien- cy of this tension transfer. The cable inserts onto the humerus just anterior to the supraspinatus tendon and then arcs around the insertional material of the cuff to re- attach to the humerus posteriorly in the vicinity of teres minor (Fig. 1).

Infraspinatus Teres minor Figure 1: The interdigitation of the rotator cuff muscles

It would appear possible, for example, to have a full thickness tear of the rotator cuff without deterioration in shoulder function being apparent. The degree of dysfunction appears not to be related to the severity of the pathology but rather to its location. This deserves some explanation.

Locating the lesion To explain these findings it must first of all be recognised that the muscles of the rotator cuff cannot be thought of as separate mus- cles with separate insertions onto the humerus. The tendons of the rotator cuff interdigitate and share a sheath of insertion that encapsulates the anterior, posterior and superior aspects of the glenohumeral joint (GHJ).

This sheath is intimately associated with the capsule of the joint and also encloses the tendon of the long head of biceps. This means that tension developed by any one of the rotator cuff muscles will be transferred to the rest of the cuff, and that tension developed in biceps can equally be transferred to the cuff. Hence, we are unable to locate a cuff lesion by its response to a resisted test in a par-

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In his investigations into the presentations of various types of rotator cuff tear, Burkhart noticed a significant difference in presentation of those who had torn through and disrupted the rotator cuff cable versus those who had not. Tears that did not involve the cable could be functionally uncompromised while those in which the

cable was disrupted were guaranteed to have severe functional lim- itations. These tears generally involve a significant detachment of infraspinatus and have been named ‘massive tears’.

The significance of the dysfunction in these types of tear relates to the importance of infraspinatus to the maintenance of gleno- humeral control. Two force couples predominate. The coronal force couple is the balance of force between deltoid and the lower por- tions of the rotator cuff, which controls the cephalo-caudad posi- tion of the humerus. The transverse force couple is formed by sub- scapularis anteriorly and infraspinatus/teres minor posteriorly and controls the humerus antero-posteriorly. A ‘massive tear’ involving infraspinatus leads to an imbalance in both of these force couples leading to abnormal antero-superior translation of the humerus on attempted elevation.

Identifying ‘massive tears’ It would be of obvious benefit to identify this type of dysfunction in the shoulder pain population, as they are unlikely to benefit from rehabilitation without surgical re-attachment of the inferior ele- ments of their rotator cuff.

TIP

Supraspinatus