MasterclassDynamic evaluation and early management of altered motor control around the shoulder complex
Introduction
The focus of this paper is assessment and management of dynamic control of the shoulder complex. The shoulder is a mobile joint that relies heavily for mid-range stability on muscle control (Schenkman M, Rugo de Cartaya V (1987), Schenkman M, Rugo de Cartaya V (1994); Lippitt & Matsen 1993; Lippitt et al. 1993; Souza 2000; Ciullo 1996; Kibler 1998a; David et al. 2000). Therefore, evaluation of such control and treatment directed at its improvement should form an integral part of management of all shoulder disorders. The programmes suggested are yet to be subjected to the rigours of scientific evaluation but follow principles demonstrated to be effective in other areas of the body (Richardson & Jull 1995; O’Sullivan PB (2000), O’Sullivan PB, Twomey LT, Allison GT (1997a), O’Sullivan PB, Twomey LT, Allison GT, Taylor J (1997b); Richardson et al. 1999). They are based on research on muscle function and control (Hodges PW, Richardson CA (1996), Hodges PW, Richardson CA, Jull GA (1996); O’Sullivan PB (2000), O’Sullivan PB, Twomey LT, Allison GT (1997a), O’Sullivan PB, Twomey LT, Allison GT, Taylor J (1997b); Richardson et al. 1999; Cowan SM, Bennell KL, Hodges PW (2000), Cowan SM, Bennell KL, Hodges PW, Crossley KM, McConnell J (2001); Shumway-Cook & Woollacott 2001), reports from other experienced clinicians (for example, Wilk & Arrigo 1992; Kibler & Chandler 1994; Wilk 1994; Kibler B (1998a), Kibler B (1998b); Chmielewski & Snyder-Mackler 2001; McConnell 2001) coupled with extensive clinical experience within a framework of sound reflective reasoning (Jones et al. 2000) and knowledge of patterns of presentation of shoulder disorders (Magarey 1999).
Panjabi's (1992) now familiar concept of a “neutral zone” for the lumbar spine as a zone in which translatory movements are available can equally be applied to the glenohumeral joint (Hess 2000). The capsulolabral structures (passive restraints) are responsible for setting the limits of passive movement (Jobe 1990; O’Brien et al. 1990; O’Driscoll 1993; Pagnani & Warren 1994) with the muscles, influenced in their activity by their neural control, responsible for maintaining the humeral head centred in the glenoid fossa during mid-range movements, thus stiffening the joint (Schenkman M, Rugo de Cartaya V (1987), Schenkman M, Rugo de Cartaya V (1994); Lippitt & Matsen 1993; Lippitt et al. 1993; Wilk 1994; Burkhart 1996; Ciullo 1996; David G, Jones MA, Magarey ME, Sharpe MH, Dvir Z (1997), David G, Magarey M, Jones M, Türker K, Sharpe M, Dvir Z (2000); Kibler 1998a). Any disruption to those mechanisms can lead to abnormal translation of the humeral head during active movement. In relation to the scapula, muscle and neural influences are very important to its stability as its ligamentous attachments are limited to those of the acromioclavicular joint (Kibler 1998b).
The balance of muscle activity within force couples is often more important to normal function than isolated strength of individual muscles (Kibler B (1998a), Kibler B (1998b); Kibler & Chandler 1994). Such balance is determined by the length of muscle and associated fascial tissue and the pattern of recruitment. When tested in isolation in a classic isometric manual muscle test, a muscle may test strongly, but perform poorly during functional activity.
Kibler (1998a) used the term, the ‘length-dependent pattern’ of muscle activity to describe co-contraction force couples which operate locally around a joint, controlled by feedback from muscle spindle receptors and responding to perturbations of joint position. The primary function of such force couples is maintenance of joint stability.
One key force couple relevant to stability of the glenohumeral joint is that between the lower elements of the rotator cuff – subscapularis anteriorly and infraspinatus/teres minor posteriorly (Saha 1971; Poppen & Walker 1978; Kapandji 1982; Soderberg 1986; Schenkman M, Rugo de Cartaya V (1987), Schenkman M, Rugo de Cartaya V (1994); Norkin & Levangie 1988; Burkhart SS (1994), Burkhart SS (1996); Wilk 1994) (Fig. 1). These muscles are ideally placed to draw the humeral head into the glenoid and maintain its axis of rotation, so that they can perform their role of concavity compression (Saha 1971; Lippitt & Matsen 1993; Lippitt et al. 1993; Sharkey & Marder 1995; Wuelker et al (1998), Wuelker et al (1995)). Failure of function of these muscles in their stabilizing role will lead to creation of an abnormal axis of rotation (Poppen & Walker 1978; Howell & Galinat 1987; Schenkman M, Rugo de Cartaya V (1987), Schenkman M, Rugo de Cartaya V (1994); Howell et al. 1988; Souza 2000) and abnormal translation of the head of humerus (Burkhart SS (1994), Burkhart SS (1996)).
In the scapulothoracic area, the force couples associated with movement overhead alter through range, as the axis of rotation changes with increasing elevation and plane of movement (Inman et al. 1944; Poppen & Walker 1978; Dvir & Berme 1978; Schenkman M, Rugo de Cartaya V (1987), Schenkman M, Rugo de Cartaya V (1994); Bagg & Forrest 1988; Culham & Laprade 2000; Abelew 2001), but the primary contributors are serratus anterior and trapezius (Inman et al. 1944; Basmajian 1963; Kapandji 1982; Bagg SD, Forrest WJ (1986), Bagg SD, Forrest WJ (1988); Schenkman M, Rugo de Cartaya V (1987), Schenkman M, Rugo de Cartaya V (1994); Norkin & Levangie 1988; Souza 2000). In the early part of range, when the axis of rotation is at the root of the scapular spine, the principal rotators are the upper fibres of both serratus anterior and trapezius (Basmajian 1963), whereas when the axis of rotation moves towards the acromioclavicular joint, the relative contribution of upper trapezius lessens while that of lower trapezius increases, together with the lower fibres of serratus anterior (Basmajian 1963; Schenkman M, Rugo de Cartaya V (1987), Schenkman M, Rugo de Cartaya V (1994)) (Fig. 2A, B). Serratus anterior is, therefore, a significant component of the force couple throughout range (Bagg & Forrest 1986).
David et al. (2000) demonstrated consistent activation of the rotator cuff prior to the more superficial delto-pectoral muscles during isokinetic rotation in normal shoulders, confirming their role as dynamic stabilizers for the glenohumeral joint. Similarly, analysis of activation during rotation in the normal shoulder revealed that at least one component of the antagonist rotator cuff was always active (David et al. 2000), providing evidence of their stabilizing role.
Strong evidence is available that pain alters the timing of contraction in stabilizing muscles – transversus abdominis and multifidus in relation to the lumbar spine (Hides JA, Richardson CA, Jull GA (1996), Hides JA, Stokes MJ, Saide M, Jull GA, Cooper DH (1994); Richardson C, Jull G (1994), Richardson CA, Jull GA (1995); Hodges PW, Richardson CA (1996), Hodges PW, Richardson CA (1998), Hodges PW, Richardson CA, Jull GA (1996); Hodges PW, Richardson CA (1996), Hodges PW, Richardson CA, Jull GA (1996); O’Sullivan PB (2000), O’Sullivan PB, Twomey LT, Allison GT (1997a), O’Sullivan PB, Twomey LT, Allison GT, Taylor J (1997b)), vastus medialis obliquus in relation to the knee (Cowan et al. 2001). Preliminary continuation of our shoulder stabilization research (David et al. 2000) with unstable shoulders has shown widely differing patterns of onset of muscle activity, with failure of the rotator cuff and biceps to be activated prior to the delto-pectoral group and, in some instances, failure to fire until after the onset of movement – thus demonstrating a similar disruption to stabilizing function as found in the knee and lumbar spine.
Kibler (1998b) considered that serratus anterior and lower trapezius are susceptible to inhibition in painful shoulders. This inhibition is seen early as a non-specific response to any painful condition in the shoulder, presenting as a disorganization of the normal firing pattern and a decreased ability to produce torque and to stabilize the scapula, a phenomenon Kibler (1998b) described as ‘scapular dyskinesis’.
Alteration in activity of serratus anterior in the painful shoulders of swimmers and throwers has been found when compared to that of non-painful athletes (Glousman et al. 1988; Scovazzo et al. 1991; Pink et al. 1993). Wadsworth and Bullock-Saxton (1997) found significant delay in activation of serratus anterior in the painful shoulders of swimmers compared with non-painful shoulders, with little change in timing of activation of trapezius. All these studies highlight serratus anterior as the primary stabilizer of the scapulothoracic region, functioning in a manner similar to other deep stabilizers.
The movement of elevation has been used as an example of the need to consider force couples. Clearly, different considerations must be made if the disorder involves other movements and loads. Adduction against resistance needs to be considered in conjunction with elevation in the throwing or swimming athlete, for example. This function is well described in Schenkman and Rugo de Cartaya (1994) and Souza 2000.
Section snippets
Principles of a dynamic assessment
Patients move in a variety of ways, with a wide range of what can be called ‘normal’ (Shumway-Cook & Woollacott 2001). Influences on movement patterns include avoidance of pain, general health and mood, relative length of tissues, strength and level of activity of muscles and timing of contraction of those muscles. Functional demands and habitual activities also contribute to development of particular movement patterns (Shumway-Cook & Woollacott 2001). All these factors must be considered
Dynamic examination
Knowledge of, and the indications for, inclusion of specific muscle length (Evjenth & Hamberg 1980) and isolated strength tests (Kendall et al. 1993) is assumed by the reader. In this paper, those components and techniques that we have found particularly useful during dynamic examination will be discussed.
Management of muscle control dysfunction of the shoulder complex
From the examination findings, a management plan can be made, addressing those aspects of each part of the examination found to be impaired and ensuring maintenance of an appropriate balance between function of the scapulothoracic and scapulohumeral muscles. Training for control of one region must not occur at the expense of the other. Similarly, training for either the glenohumeral joint or scapulothoracic region must be implemented in positions of total body control and stability. In this
Conclusion
In this paper, we have presented an approach to dynamic evaluation and management of the shoulder complex that we use in conjunction with detailed passive examination and management as indicated for each patient. The ideas presented here represent one set of strategies that we have found to improve shoulder function. A deliberate setting in neutral rather than specific pre-activation can also be effective with different patients. Interestingly, a number of researchers have demonstrated that
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