The shoulder joint is particularly vulnerable to trauma, being the most mobile joint of the body in terms of its anatomical structure. It is dependent upon muscular activity for stability and therefore, when abnormal tone prevails, the mechanics of the joint are compromised (Lippitt & Matsen 1993).
Movements of the upper limb must be carried out with great care and with a detailed know- ledge of the shoulder mechanism. The therapist must appreciate the holistic nature of functional activity. Movements of the upper limb cannot be viewed in isolation. Attention must be paid to the position in which the movements are performed, the stability afforded by the supporting surface, the patients' ability to maintain themselves or move against gravity and the ability of the trunk to respond effectively to the imposition of distal movement.
Potential problems affecting the shoulder girdle and upper limb function
The patient with low tone. In sitting or stand- ing, the scapula rotates medially as there is little or no muscular activity to maintain its position of lateral rotation around the chest wall. The inferior angle of the scapula lies closer to the vertebral column than normal, as illustrated in Figure 6.15. This produces abnormal align- ment of the glenoid fossa, leading to a degree of abduction at the shoulder joint.
In the adducted position, the capsule becomes taut, preventing downward displacement of the humerus (Cailliet 1980). The shoulder is vul- nerable in a position of abduction, as the superior
Figure 6.15 Relationship of the shoulder girdle and
vertebral column: (A) normal; (B) abnormal (reproduced from Bromley 1998 with permission).
portion of the capsule is slack. In the patient with hypotonus the 'locking mechanism' is no longer effective, resulting in a subluxation of the glenohumeral joint, as shown in Figure 6.16. Preventive measures offering support to the
upper limb should be employed before irrepara- ble damage occurs.
The scapulohumeral rhythm is impaired and therefore movement performed by the therapist at the glenohumeral joint must include adequate excursion of the scapula.
Specific problems which may arise as a result of hypotonus include:
• hyperactivity of the upper fibres of trapezius in an attempt to support the flail arm
• loss of shoulder girdle stability due to weak- ness of the lower fibres of trapezius
• shortening of the pectorals leading to reduced range of horizontal abduction
• shortening of latissimus dorsi • immobility of the scapula or
• hypermobility of the scapula should the medial rotators, namely latissimus dorsi, teres major and subscapularis, become short- ened.
The patient with increased tone. In patients with hypertonia, the most commonly observed posturing of the upper limb is that of retraction of the scapula, adduction and medial rotation of the glenohumeral joint, flexion of the elbow, pronation of the forearm, flexion and ulnar devi- ation of the wrist, and flexion of the fingers with adduction of the thumb (Bobath 1990, Rothwell 1994).
Increased tone produces a degree of immobil- ity; the dynamic co-contraction and stability afforded by the scapula as described in Chapter 3 is impaired. Reciprocal innervation is compro- mised; the grading of movement is lost with the static co-contraction of the dominant hyperactive muscle groups. Selective movement of the upper limb becomes difficult if not impossible due to impaired proximal stability. Shortening of the muscle groups, producing the stereotyped posturing, may result.
The scapula is pulled closer to the vertebral column by hypertonus of the rhomboids. This may be either in a vertical position or with a degree of medial rotation. The angle of the glenoid fossa becomes vertical or possibly even downward facing. This malalignment of the glenohumeral joint produces a degree of relative
abduction at the shoulder joint, as seen in hypo- tonia. Increased tone of pectorals and medial rota- tors produces an anterior, rotational movement of the humerus, further distorting its position in relation to the glenoid fossa (Irwin-Carruthers & Runnalls 1980).
Movements undertaken by the physiotherapist to maintain range of movement must incorporate techniques of tone reduction. There is both mal- alignment of the joint surfaces and resistance from hypertonic muscle groups. Hypertonia invariably affects all muscle groups in spite of the predominance of flexion, adduction and medial rotation. Attention must be paid to the position in which the movements are performed. For example, movement of the arm into elevation will be more successful with adequate thoracic spine extension (Crawford & Jull 1993).
The scapulohumeral rhythm is altered, the extent to which this is disrupted being depend- ent upon the severity and distribution of hyper- tonia. For example:
• The excursion of the scapula may be limited by the increased tone of its extensive mus- culature. In this situation, attempted move- ment of the arm away from the body may traumatise the glenohumeral joint and the surrounding tissues.
• Hypertonia of the medial rotators may reduce the range of movement at the glenohumeral joint through shortening of latissimus dorsi, teres major and subscapularis in particular. In this instance, attempted movement of the arm away from the body produces hypermobility of the scapula to compensate for the immobil- ity at the glenohumeral joint (Fig. 6.17). Pain may be an additional complication which may develop as a result of the stereotyped pos- turing and/or forcing range without appro- priate tone reduction, thereby traumatising the shoulder.
Prehension is dependent upon the proximal musculature of the shoulder for placing the hand in the correct spatial location to effect function. Neurological impairment affecting the shoulder mechanism will therefore affect the selective use of the hands for function.
Prophylactic or corrective splinting by means of a drop-out cast (see Ch. 10) is the preferred option where there is excessive hypertonus and subsequent inability to maintain extension of the elbow.
Figure 6.17 Reduced glenohumeral movement resulting in
increased excursion of the scapula.