So yet again I am pleased to give you another fantastic guest article, this time from Chris Littlewood a physio and a research fellow at the University of Sheffield. He is currently undertaking a PhD in relation to rehabilitation of rotator cuff tendinopathy and has recently published a book entitled Understanding Physiotherapy Research (here). His full biography can be found here
Chris has kindly done an excellent article for us fitting in with the critical thinking theme of this site by questioning the role the scapula does or doesn't have in shoulder pains and problems, and if we are doing the right thing in giving scapula stability exercises, take it away Chris…
Scapula stabilisation exercises are commonly prescribed as a core component of rehabilitation programmes for many types of shoulder pain syndromes, particularly subacromial impingement syndrome or rotator cuff tendinopathy (Littlewood et al. 2012). There appears to have been an unquestioned proliferation of such prescription despite doubts raised in the literature about the relevance of scapula dyskinesia and the role of scapula stabilisation exercises in these painful shoulder syndromes.
This paper will consider some of the relevant evidence with the aim of stimulating the reader to question the rationale which appears to currently underpin the prescription of scapula stabilisation exercises across the spectrum of patients complaining of shoulder pain without significant movement restriction.
Normal or ideal positions and movement patterns of the scapula, in association with the glenohumeral joint, have previously been described (Kibler and McMullen 2003). Aberrations from this ideal, broadly referred to as scapula dyskinesis, are thought to contribute to the development and maintenance of various painful shoulder syndromes, including subacromial pain syndrome (Struyf et al. 2013). Broadly, scapula stabilisation exercises are prescribed to address and correct these aberrations with the intention of reducing the associated pain and disability. Such a “cause and effect” model appears plausible and logical, i.e. joint/ tissue movement deviates from normal which results in dysfunction and possible overload which subsequently results in a pain syndrome. If the movement aberration is addressed then the dysfunction and possible overload should be minimised or removed and the pain syndrome should abate. Despite the clarity and plausibility of such a pathway, messages have appeared in the literature that serve to question this reasoning process and these will now be considered in turn.
Relevance of scapula dyskinesia
It seems logical to suggest that if scapula dyskinesis contributes to painful shoulder syndromes then such movement aberrations would present more in those complaining of shoulder pain and less so in those who do not complain of shoulder pain. Previous studies have investigated whether there is such an association between dyskinesia, measured in various ways, and shoulder pain and have concluded that the evidence does not support such a theory (Catlin et al. 1995; Lucasiewicz et al. 1999). This evidence highlights that scapula dyskinesis is present in those with and without painful shoulder syndromes.
Further to this, a recent study evaluated movement of the scapula in healthy subjects (Morais and Pascoal 2013). In comparison to the scapula of the non-dominant shoulder, this study found that the scapula of the dominant shoulder showed greater retraction and upward rotation at all points during elevation of the arm. This is an interesting finding because the presence, absence or relevance of scapula dyskinesis in a painful shoulder syndrome is often identified in comparison to the asymptomatic shoulder. This study questions the validity of such an assessment process and also further highlights the presence of relative movement differences in the scapulae of asymptomatic or healthy individuals.
However, such evidence, in isolation, should not be used to discount the relevance of scapula dyskinesis entirely, at least not at this stage. It is theoretically plausible that shoulder pain presents at the end of a continuum which begins with dyskinesia and, secondary to a gradual build-up of overload, over time ends with pain. Subsequent evidence however might add weight to the argument that scapula dyskinesis is less relevant to shoulder pain than we think.
Assessment of dyskinesia
There are many different approaches to the assessment of scapula dyskinesis including static, dynamic, low-tech and high-tech approaches. If scapula dyskinesis is to be regarded as a credible basis upon which treatment is prescribed then it seems fair to suggest that practitioners should be able to agree upon its presence or absence and relevance when assessing their patients. Many researchers have investigated whether therapists can reliably detect what is considered clinically significant dyskinesis over recent years and generally they report poor levels of reliability (Ellenbecker et al. 2012). This means that whereas one practitioner might suggest that there is a deviation from normal, it is highly likely that another practitioner would disagree. Therefore even if scapula dyskinesis is related to the shoulder pain syndrome, is this a credible basis upon which to prescribe a treatment? Although such poor levels of reliability are not unique to the assessment of scapula dyskinesis, it still serves to question the credibility of such an approach.
Mechanism of action
Thus far it has been suggested that scapula dyskinesis is present in those with and without shoulder pain and that practitioners struggle to agree whether such aberrations are present, absent or relevant. Notwithstanding these concerns, scapula stabilisation rehabilitation protocols have evolved with the explicit aim of addressing such dyskinetic movement patterns (Kibler et al. 2013). Hence it seems reasonable to suggest that if these rehabilitation protocols are implemented and shoulder pain is diminished, then the dyskinetic movement patterns should also improve. A recent study evaluated this and found that despite significant improvements in shoulder pain and disability at the end of treatment and after three months, the measurements of scapula dyskinesis did not change (Struyf et al. 2013).
In contradiction to the evidence from Struyf et al (2013), Baskurt et al (2011) found that following a six-week programme of exercise which included scapula stabilisation exercises, scapula dyskinesis did improve compared to the control group who received a programme of stretching and strengthening exercises but not specifically scapula stabilisation exercises. A closer look at the study tells us that scapula dyskinesis was evaluated using the Lateral Scapula Slide Test (LSST). This test measures the distance between the thoracic spine and the inferior angle of the scapula but the reliability of this test has been questioned (Shadmehr et al. 2010). This means that any reported differences could be attributable to measurement error rather than being representative of a true difference. More importantly the LSST could have been subject to outcome assessor bias. The LSST relies on a person to take the measurements and if this person, the outcome assessor, is aware that the person they are measuring received the programme including scapula stabilisation exercises then they are more likely to assess the LSST in a favourable way, i.e. one that suggests a change has occurred. This is a common flaw in much research and is addressed by ‘blinding’ the outcome assessor. This means that the person undertaking any measurements is not aware of which treatment has been received and hence the potential for bias is minimised. However, this was not reported to have been undertaken in this study
Therefore although conclusions from Baskurt et al (2011) might be seen to question the conclusions of the Struyf et al (2013), it is possible that methodological flaws explain the reported differences.
Looking more broadly it is apparent that the finding, that stabilisation exercises do not improve stability or reduce dyskinesis, is not unique to the shoulder. A recent systematic review of studies (Laird et al. 2012) found that movement-based interventions for low back pain, e.g. stabilisation exercises, were rarely found to be effective for changing observable movement patterns, e.g. dyskinesia. These researchers were also unable to identify a relationship between changes in movement patterns and improvement in pain or disability, which fits with the studies referred to here in relation to the shoulder. These studies, and others, contribute to the increasing body of evidence which is now questioning those who approach the rehabilitation of pain syndromes from a purely biomechanical perspective.
In the context of what has been suggested so far, it is questionable whether the clinical effectiveness of scapula stabilisation exercises needs to be considered. However, for completeness, clinical effectiveness will be reviewed although there is a paucity of such evidence due to the emerging nature of the field. Struyf et al. (2013) investigated whether exercises focused upon the scapula were superior to a control intervention that included exercise, manual therapy, including glenohumeral mobilisation and friction massage, and electrotherapy directed at the rotator cuff. After three months there were no significant differences between the groups in terms of self-reported shoulder pain and disability as measured by the Shoulder Disability Questionnaire. There are methodological limitations associated with this study including a small sample size (n = 22) and the fact that only one therapist delivered both the control and intervention treatments which introduces the potential for therapist preference bias, i.e. the therapist has a preference for one treatment and delivers this in a different (superior) way to the non-preferred treatment. This is important in therapy-based research because if a therapist or practitioner has a strong preference for one treatment or another, which many of us do, then the process and subsequent outcomes are likely to be affected by this. Despite this potential for bias, no significant differences were reported after three months.
Buskart et al (2011) reported no significant difference when comparing one group that received stretching, strengthening and scapula stabilisation exercises and a second group that received stretching and strengthening exercises only. Both groups reported a favourable outcome at the end of the six-week treatment period. This was measured, amongst other tests, by the Western Ontario Rotator Cuff Index (WORC). The WORC is a condition-specific self-reported outcome measure that is used to evaluate the quality of life of people with problems relating to the rotator cuff (de Witte et al. 2012). As with the study by Struyf et al (2012), methodological limitations did exist. Most notable was the low number of participants recruited (n=40), which means that the study might not have adequate statistical power to detect a true difference between groups if one actually did exist.
On balance of the evidence presented so far, it is unclear whether scapula dyskinesis is relevant to shoulder pain and it is questionable whether practitioners can identify such aberrations. Furthermore, it is questionable whether scapula stabilisation exercises do “what they say on the tin” because the studies reviewed here do not convincingly show that dyskinesia changes following a scapula stabilisation rehabilitation programme. Finally, although there is a paucity of evidence and concern about the quality of the research that has been conducted to date, approaches that focus upon scapula stabilisation do not appear to confer superior clinical outcomes to other, more generalised, exercise approaches.
Implications for practice
These issues, relating to the relevance and assessment of scapula dyskinesis and the value of scapula stabilisation exercises, raise a number of implications for practice. Firstly, if the relevance of scapula dyskinesis is questionable and practitioners are unable to identify its presence reliably then it seems reasonable to suggest that time spent assessing patients in this manner is an inefficient use of resources. Secondly, if scapula stabilisation exercises do not significantly correct movement aberrations or confer superior outcomes over other existing approaches, then it also seems reasonable to suggest that prescribing treatment with the explicit aim of correcting movement aberrations is mis-guided and not evidence-based. Although there is a strong theoretical argument underpinning such an approach, this is generally not borne out by the research that has been undertaken to date.
This paper has questioned the relevance of scapula dyskinesis and the value of scapula stabilisation exercises as core components of rehabilitation strategies for shoulder pain syndromes. Currently, despite a proliferation of such assessment and prescription strategies, there is a lack of evidence to support such narrow biomechanical approaches. The time has come to pause and reflect upon the relevance of scapula dyskinesis and the rationale underpinning scapula stabilisation exercises.
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