New Concept in Rotator Cuff Retraining

New Paradigms in Rotator Cuff Retraining Bahram Jam, MPhty, BScPT, FCAMT (E-mail: [email protected]) Abstract: Rotator cuff strengthening exercises are frequently prescribed to address various shoulder dysfunctions and pain syndromes. The primary function of the rotator cuff muscles is to compress, stabilize and provide fine tune control at the glenohumeral joint. Most exercise programs focus on general strengthening and not on the fine tune control function of these muscles. The purpose of this article is to introduce clinicians to new concepts in rotator cuff retraining that focus on therapeutic exercises to assist these muscles in regaining their functional role as dynamic stabilizers of the glenohumeral (GH) joint. Key Words: Rotator cuff, Shoulder, Instability, Impingement syndrome. Rotator cuff (RC) retraining / to produce medial rotation (MR) torque resulting in relatively poor moment arm strengthening is a routine treatment at the GH joint (Fig 1). to produce an abduction torque at the GH option for many Physical Therapists. joint (Fig. 2). It can however be Many papers and reviews hypothesize appreciated that the primary function of Fig 1: the value of RC retraining for individuals the supraspinatus is not to abduct the Force vector for Subscapularis. presenting with various shoulder shoulder, but to compress the humeral dysfunctions, including impingement head into the glenoid fossa and prevent syndromes, glenohumeral (GH) excessive superior translation of the instability and post surgical humeral head during functional activities. interventions1-2. The infraspinatus and the teres minor are The purpose of this paper is two-fold. both described as lateral rotators of the 1) To introduce and discuss four shoulder, however it can be appreciated paradigm shifts in RC retraining that the primary function of the 2) To review the techniques for infraspinatus and the teres minor is not retraining of the RC muscles only to laterally rotate the shoulder, but considering the new paradigm shifts to compress the humeral head into the glenoid fossa and prevent excessive Although clinicians are well aware of the superior and posterior translations of the value of RC retraining, it is the author’s It can however be appreciated that the humeral head during functional activities belief that most prescribed RC exercise primary function of the subscapularis (Fig. 2). regimes are not specific enough, in that muscle is not to medially rotate the they do not address the functional role of shoulder, but to compress the humeral this group of muscles as stabilizers of the head into the glenoid fossa and prevent Fig 2: GH joint. excessive anterior and superior I: Force vector for Supraspinatus translations of the humeral head during II: Force vector for Infraspinatus & The RC muscles include the functional activities (Fig. 1). Both Teres minor subscapularis, supraspinatus, anterior and superior translations of the III: Resultant vector producing infraspinatus and the teres minor humeral head are leading compression force at the GH joint muscles. The subscapularis is described biomechanical causes of RC as a medial rotator of the shoulder, impingement syndromes3. however looking at it logically it would seem that it is a relatively “insignificant” The supraspinatus muscle is most medial rotator, compared to the powerful commonly described as an abductor of pectoralis major, teres major, latissimus the shoulder. Considering its size and dorsi and the anterior deltoid muscles. If position, it is a relatively we appreciate the force-vector angle of “insignificant” abductor compared to the subscapularis muscle we can see that the powerful deltoid muscle. If we it is extremely close to the GH joint line appreciate the force-vector angle of the resulting in relatively poor moment arm supraspinatus muscle we can see that it is extremely close to the GH joint line 1 Many of the concepts outlined in this based on the findings from the studies gentle isometric supraspinatus paper are based on a single research on the lumbar multifidus following contractions held for 10 seconds. It may study by David et al “Rotator cuff muscle lumbar injury. It has been demonstrated take a few minutes to a few weeks to performances during gleno-humeral joint that patients with low back pain have achieve this goal. rotations: An Isokinetic, selective neural inhibition with Electromyographic and Ultrasonographic significant reductions in the CSA of Study”, which was presented at the their lumbar multifidus muscles5. It has Manipulative Physiotherapists also been demonstrated that specific Association of Australia Conference in multifidus retraining in isolation of the Melbourne Australia in 1997. superficial muscles can increase the The remainder of this clinical multifidus CSA6 and may dramatically commentary will focus on four paradigm reduce the risk of low back pain shifts, supportive evidence, clinical recurrences in the long term7. relevance and the clinical application for each of the new paradigms. Clinical relevance: It is hypothesized that the more effective supraspinatus is Paradigm shift #1: as a stabilizer of the GH joint, the Old paradigm: Supraspinatus muscle stronger the shoulder is during LR, Fig. 3: Supraspinatus activation facilitated weakness and loss in size is due to disuse which would also increase the LR/MR by self-palpation and mental imagery. atrophy and therefore requires strength ratio. The loss of supraspinatus strengthening. Strengthening the CSA may decrease its effectiveness at supraspinatus using general resisted producing compressive forces at the Several studies have used functional MRI pulley and dumbbell exercises will GH joint, which in turn may reduce GH to compare the effects of mental imagery increase the cross sectional area (CSA) joint stiffness. Specific neural control with actual execution of simple motor and the stabilizing function of the retraining of the supraspinatus (similar tasks. These studies have demonstrated muscle. to that suggested for the deep fibers of dramatic overlapping of the motor and the lumbar multifidus6) may help pre-motor cortex activity during visualization and actual physical New paradigm: Supraspinatus muscle increase its tonic activation, neural 9-10 weakness and loss in size is due to control and eventually its CSA. This performance of an activity . The selective neural inhibition and therefore may be essential for some individuals cortical activity that occurs at the thought requires specific retraining. To restore presenting with persistent shoulder pain of a movement is very similar to the cortical activity when the movement the primary function of the supraspinatus syndromes. 11 muscle, the focus of rehabilitation must actually occurs . be on specific neural control retraining, Clinical application: To specifically and not on a generic strengthening retrain the supraspinatus in isolation of Many scientific papers have program. the superficial muscles, instruct the demonstrated that overuse, lack of use or patient to self-palpate and with open or injuries to specific musculoskeletal structures can alter cortical Evidence to support the paradigm shut eyes visualize their own 12-14 shift: Using ultrasonography, David et al supraspinatus muscle. They are then representation . It may be measured the supraspinatus muscle CSA instructed to “think about” and pull hypothesized that mentally focusing on at rest. They found a strong positive their humeral head into its socket and specific and isolated supraspinatus correlation between supraspinatus CSA simultaneously “swell up” / contract contraction, may help increase the and isokinetic lateral rotation (LR) torque the supraspinatus muscle (Fig.3). This patients’ awareness of the “existence” of productions and LR/MR strength ratios. may be performed in sitting with the the muscle and enhance its cortical In other words, the bigger the shoulder abducted 60-80 degrees in the representation. Repeated tonic supraspinatus muscle, the greater the scapular plane while the ulnar border of contractions of the supraspinatus may torque production into LR and the greater the hand rests on a table or desk. It rejuvenate the neural pathways required the LR/MR strength ratio. Other studies must be appreciated that only a subtle for its activation and fine tune control. have found the LR/MR strength ratio to contraction of the supraspinatus is This clinical hypothesis is similar to what has been demonstrated with the deep be significantly less in subjects with expected and that no scapular or GH 6- 8 fibers of the lumbar multifidus muscles shoulder pain and dysfunction . joint movement is to take place. Strong 7 contractions palpated over the . It may be hypothesized that the suprascapular region during this supraspinatus muscle may undergo exercise is most likely to be due to Paradigm shift #2: selective neural inhibition following a unwanted over activity of the upper Old paradigm: The supraspinatus shoulder injury or pain episode, which fibers of trapezius. This mental muscle should primarily be strengthened may reduce its CSA. The hypothesis of imagery exercise is performed until the by resisted GH abduction with the supraspinatus neural inhibition following therapist and the patient are able to shoulder maintained in medial rotation. shoulder pain syndromes is indirectly consistently palpate five repetitions of 2 New paradigm: The supraspinatus clinically focus on retraining the GH These findings support the hypothesis muscle may also be effectively retrained

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