Hello, and welcome to the third instalment of the IPRS Health Clinical Blog Series.
Following on from our introductory blog about the ‘Industrial Athlete’ and second instalment ‘Working Through Back Pain’; this month we are looking at the impact work can have on the shoulders. This blog aims to discuss the common problems for the shoulder when lifting and what to do in the management of the shoulder if things do go wrong, with the ultimate goal of reducing sickness absence for the employer and employee.
Before I start I must of course tip my hat to those who have influenced this post. We of course all stand on the shoulders of giants (no pun intended) and this writing is a reflection of those. Jeremy Lewis, Neer, Cook and Purdam have lead much of my thought process in this area, as they have I am sure for many clinicians!
Now, down to business! I just wanted to first have a quick run through of the anatomy at the shoulder. This is not, I admit surgeon level anatomy but will just serve as a platform for the rest of the blog.
So, the shoulder is a little less stable than our other joints due to its shallow nature and requires a number of passive and dynamic structures to compensate for this fact. The shoulder complex is made up of 3 joints, the glenohumeral, sterno- clavicular and acromioclavicular (4 if you include the scapulo- thoracic). The dynamic structures include the rotator cuff muscles (supraspinatus, infraspinatus, subscapularis and teres minor) which create rotation torque whilst maintaining stability of the gleno-humeral joint.
There are also the muscles that stabilise and move the scapula, for example serratus anterior, trapezius and the muscles that attach from the thorax to the humerus for example the deltoids, lats, pecs. There is also a number of bursa and passive constraints such as the ligaments (superior, middle and inferior glenohumeral) and the glenoid labrum which improve the surface area of the joint as a whole, thus increasing stability.
Now with the brief anatomy done, let’s move onto how prevalent shoulder pain is and what are the common pathologies associated with this joint.
The prevalence of shoulder pain in the general population is as high as 27%, with up to 14% of the 27% being classed under Sub acromial impingement syndrome or rotator cuff tendinopathy. Mechanical exposures such as heavy lifting, working above shoulder height and pushing and pulling increases the risk of onset of shoulder symptoms. These are known to occur in the workplace for example a manual worker repetitively carrying heavy blocks to a sedentary office worker repetitively reaching for their phone. Although there is a strong link between mechanical factors and onset of shoulder pain, links between psychosocial factors and shoulder pain have been inconsistent.
So what is sub- acromial impingement syndrome/ rotator cuff tendinopathy and why does it affect the shoulder in the working population?
Sub-acromial impingement syndrome was first defined by Neer back in the 1970s, it is the most commonly diagnosed condition of the shoulder and it was believed that the pathology was caused by impingement or bony irritation by the inferior aspect of the anterior part of the acromion whilst the shoulder was in elevation. Postural deviations or scapula dyskinesia are proposed mechanisms of this and are said to cause the acromion to change location reducing the sub-acromial space creating impingement of the underlying structures. However, current research has challenged this concept, suggesting that the pathology is more likely due to intrinsic failure of the actual rotator cuff tendons, following the normal continuum of tendon pathology, or from bursal irritation, with the possible contribution from extrinsic factors.
Excessive tissue loading remains the most substantial causative mechanical factor in the development of rotator cuff tendinopathy, occurring more regularly in the dominant upper limb. In recent years our understanding of the pathology of a tendinopathy has grown thanks to the research of Jill Cook and Craig Purdam on their continuum model of tendon pathology (see image below).
Ref: Cook & Purdam 2009
This model outlines a continuum of 3 stages of tendinopathy process, reactive, tendon disrepair and degeneration. Reactive tendinopathy typically involves the tendons response to acute overload, or compression. You could easily get a reactive tendon swelling which if happening at the rotator cuff, can reverse the paradigm, and rather than the acromion pushing down it could be the tendon pushing up. It was previously thought that this reaction was due to an inflammatory process however this is not the case; swelling of the tendon is due to movement of water into the tendon matrix and not inflammatory products. At this stage the tendon thickens but remains relatively intact, but if the tendon is subject to further excessive load it may lead to the next stage of tendon disrepair characterised by greater tissue matrix breakdown, collagen separation, proliferation and possibly changes in neovascularity. With appropriate management it is possible that these changes are mostly reversible. The third stage known as the degenerative phase usually occurs in the older population with a history of chronic overloading, and changes in the tendon structure are more advanced making it less efficient at coping with load and at risk of rupture.
Studies on the effect of fatigue of the rotator cuff have also been shown to lead to short term decrease in sub acromial space and swelling of the tendon in rotator cuff tendinopathy. The enlarged tendon occupies more subacromial space, increasing the potential for compression. This swelling combined with loss of humeral head control (superior migration) may lead to symptoms clinically associated with subacromial impingement. Function of the shoulder in the lifting activity will often require energy transfer from the lower limb, through the trunk and into the shoulder. Deficits further down the kinetic chain could detrimentally impact shoulder function, leading to reduced energy transfer to the shoulder which could result in higher requirements locally, potentially leading to early fatigue of the rotator cuff muscles and a lower threshold at which tissue failure and or shoulder symptoms may occur.
It is well documented that extension of the thoracic spine is required for full elevation of the shoulder however links between posture and shoulder impingement type pain are unclear. Changes in posture have been found to increase range of movement (ROM) of shoulder before a pain response is reported, but no decrease in severity of pain. The correlation between scapula kinematics and impingement type pain also remains very unclear, however it is still argued that some patients may benefit from a scapular focused rehabilitation programme. Recommendations for the clinicians is to attempt to idealise the position of the scapula, however this must be done with caution as no definitive abnormal position has been identified.
Organisational factors and social factors of the working environment such as working Individuals that have little control at work, high work place demands and low social support from colleagues or supervisors may possibly lead to an increase stress levels and are found to be at a higher risk of developing a variety of adverse health outcomes. Stress has been found to be significantly associated with shoulder pain, however the relationship between these factors is unclear as it can be difficult to determine whether shoulder pain is a consequence of stressful work, or work is more stressful due to shoulder pain. In terms of psychosocial risk factors, the strongest predictor in the onset of new shoulder pain is found to be the worker’s perception of a boring, monotonous workload.
Much is known about the central sensitisation mechanisms, although limited in relation to the role it plays in chronic tendon pain. Lowered mechanical pain thresholds which may be an indicator of central sensitisation have been demonstrated in shoulder tendinopathy.
So how do we approach the management of the manual worker with a shoulder complaint?
Diagnosing rotator cuff tendinopathy or subacromial impingement currently involves performing a structured assessment that includes taking the patients history in conjunction with performing clinical assessment procedures.
History taking of the shoulder should try to determine the exact site of the pain which may prove difficult as the majority of time it can be quite diffuse. Severity of pain, aggravating/easing factors should also be taken in to account and also night pain which is common in rotator cuff dysfunctions or frozen shoulder. Onset can either be acute or insidious and mechanism of injury can help to narrow down a diagnosis. If the patient is unclear of mechanism surrounding onset it may help to discuss any possible risk factors such as an occupational or sporting activity, sudden increase in activity, or unaccustomed activity. Neural type symptoms should be noted as this may suggest cervical or thoracic involvement or even a labral injury. It may prove useful to inquire about past or present problems elsewhere in the kinetic chain. Discussing a medical history may uncover factors such as medications, or metabolic disorders which could have an effect on tendon healing. Along with increasing age those factors are can affect the prognosis, with poorer outcomes likely. It is also important to consider life style factors for example smoking, nutrition, stress and sleep as considering these may enhance outcomes. For example, the patient who has had 6 months of shoulder pain who is not sleeping due to the pain and/or job security worries due prolonged sickness is likely to present as more of a challenge.
Objective examination should generally involve observation, AROM, PROM, resisted movements and palpation. It is important to consider posture and biomechanical factors, or local anatomic factors. A combination of special tests is generally carried out in attempt to isolate a structure such as the tendon, however evidence shows that although test findings demonstrate high sensitivity, the specificity is low therefore should only be used as a pain provocative procedure.
It has been suggested that any weakness assessed during strength testing is likely due to pain inhibition rather than structural failure, which is supported by studies involving imaging uncovering structural failure does not always correlate with functional loss, nor symptoms. A study revealed that 96% of asymptomatic shoulders over the age of 40 had some sort of structural changes on imaging, and similar results have been found in a study in asymptomatic baseball players that the shoulders can remain highly functional in the presence of significant structural changes.
Jeremy Lewis developed the ‘Shoulder Symptom Modification Procedure’ (SSMP) approach for assessment for the shoulder which guides treatment to the patient’s clinical presentation rather than taking a one size fits all approach. This approach requires a series of four different manual techniques that is applied whilst the patient performs an activity that reproduces symptoms. The four techniques are directed at influencing the humeral head, scapular positioning, cervical/thoracic techniques or thoracic kyphosis techniques whilst the patient performs a number of provocative actions. If the technique applied reduces the patient’s symptoms or increases ROM, similar techniques would be used to guide the treatment process. For example, if adding an external rotation resistance to forward flexion (as seen below) eases their symptoms, treatment will be directed towards correcting this.
Ref: J. Lewis 2012
However, If the SSMP process does not produce any change to the patient’s symptoms other treatment options shoulder be explored such as pain relieving techniques, other modalities or onwards specialist referral.
Despite an optimum intervention not being clear in terms of tendon pathology, it may be important to consider the stage of the tendon continuum model at which the patient presents, as if the patient presents in the reactive stage, this may require reduced loading, whereas the disrepair or degenerative tendon presentation may benefit from a loading programme.
As with most rehabilitation, making the exercise specific for the patients functional goals will likely create better compliance and is likely to achieve improved treatment outcomes.
Clinically a kinetic chain approach involving functional movement patterns and closed kinetic chain exercises have been shown to have positive outcomes in the patient that does not respond to a traditional shoulder programme. Principles of shoulder rehabilitation should include early pain reduction, such as avoiding provocative activity, or relative rest along with combined physiotherapy modalities or pharmaceuticals. Early aims to restore scapular stability and ROM, alongside kinetic chain exercises may be beneficial. When pain subsides, ROM and strength becomes sufficient, rehab should progress using a variety of closed chain exercise initially, then open chain exercises including functional movement patterns throughout rehab with the ultimate goal of returning the patient to their previous function.
Furthermore, advice and education can be vital to prognosis, combined with addressing psychosocial factors considering not only the contribution of local pain mechanisms, but central pain mechanisms also. It may be unrealistic to expect patients to totally avoid mechanical loading in the workplace without taking time-off, whereas interventions aimed at altering psychosocial factors may be more realistic. For example, building communication between employee and employer, alongside recommendations of a varied workload or more breaks may change the perception of a monotonous workload.
As an overview, shoulder pain may not always be avoidable in the working population. When things go wrong, significant pain and loss of function may be experienced by the employee which can lead to long term sick absence which may create consequential worry. With early access to physiotherapy services, the right management can significantly improve outlook for the employee and a healthier workforce for the employer. For the clinician there are many factors to be considered when the patient presents in clinic with shoulder pain, including a combination of mechanical and psychosocial factors and when these are confidently addressed outcomes will be notably enhanced.
Furthermore, by implementing the SSMP into your normal examination process, directing the rehabilitation process should no longer be difficult and will only lead to improved success when managing the patient with shoulder pain. In doing this a variety of treatment options should be offered, but crucially it should be remembered that the patient should be at the heart of deciding which goals are most valuable to them and you are there to help them achieve it.
Thanks for taking the time to read this post. I hope you have found it useful and interesting.
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IPRS Health Physiotherapist