Does suprascapular nerve block reduce shoulder pain following stroke: a double-blind randomised controlled trial with masked outcome assessment

In any year, there are approximately 48,000 stroke events amongst Australians. Shoulder pain is a distressing complication of hemiplegia [1] and is reported as one of the 4 most common medical complications of stroke [2]. The prevalence of shoulder pain following stroke has reported to be as high at 70% [3]. A more recent prospective study of 327 consecutive stroke patients concluded that almost a third of this population developed moderate-severe shoulder pain after stroke onset [4]. This more moderate figure reflects the 2006 paper by the same investigators, which focused on patient's perspectives on pain [5]. Each of these studies highlight a correlation between pain and reduced functional ability, as well as a higher incidence of depression. Hemiplegic shoulder pain is associated with reduction in functional use of the arm, interference with rehabilitation and increased length of hospitalisation [6]. A further complication of hemiplegic shoulder pain is identified as a limitation to patient access to developing technological upper-extremity rehabilitation techniques [7].

Investigation into the cause of hemiplegic shoulder pain has revealed a multifactorial aetiology [8]. Note is made of the dependence on musculotendinous integrity to provide stability of the shoulder complex. The most common non-central, musculoskeletal aetiologies of hemiplegic shoulder pain include adhesive capsulitis, subluxation and rotator cuff patholgies, with up to one-third of patients have multiple contributing factors [8]. Biomechanical changes result from a combination of paralysis, fluctuation in muscle tone and prolonged shoulder immobility which lead to postural malalignment [1]. Dromerick et al [7] investigated the characteristics of hemiplegic shoulder pain, demonstrating that approximately 50% of the sample population experienced pain in the vertical stabilisers of the shoulder (biceps and supraspinatus). A 2006 evidence-based medicine review concluded that subluxation may be a cause of shoulder pain [9], though literature is inconsistent regarding this association. It should be noted that not all shoulder pain is associated with the complications of limb flaccidity, and may be attributable to spasticity or central-pain concepts.

There is lack of evidence to support the development of clear clinical guidelines, as identified in an overview of the challenges of managing shoulder pain after stroke [10]. This paper concludes that further efforts are required to examine intervention options. There have been positive research results for the use of Functional Electrical Stimulation [9], though a Cochrane Systematic Review [11] of this topic did not support electrical stimulation as an effective pain treatment. There is a lack of Level 1 evidence for surgical interventions, motor blocks and intra-articular corticosteroid injection.

Suprascapular nerve block is a safe and efficacious treatment of shoulder pain associated with rheumatoid arthritis and degenerative shoulder conditions [12]. The objective of this study is to evaluate the use of Suprascapular nerve block as part of an interdisciplinary approach to the treatment of shoulder pain following stroke. There is anecdotal report of successful use of suprascapular nerve block in treating intractable hemiplegic shoulder pain [1], though to date no clinical trials have been completed to form an evidence base.

The study design is a double blind randomised placebo controlled trial will assess the effect of a suprascapular nerve block compared with placebo in a population of 66 stroke patients (Figure 1). The trial will measure effect of injection on the primary outcome of pain, and secondary outcomes of function and quality of life. Measurements will take place at baseline, and 1, 4 and 12 weeks post intervention. Both groups will continue to receive routine physiotherapy and standard ward care.

The protocol has been carefully designed with the aim of achieving measurable, replicable and important results. The methodological strength of the study focuses around the use of placebo control, though the contributors acknowledge that this may pose a recruitment challenge. Considering that eligible patients have a pain score of > 3, it is anticipated that patients may decline participation on the grounds of not wanting to risk 50/50 chance of randomisation to placebo group. Taking this into account, greater time allowance has been given for recruiting. Careful provision of information prior to consent is vital in ensuring patient's are fully aware of implication of the randomisation. All patients will be informed of their randomisation group at the end of their trial participation and offered active suprascapular nerve block if desired.

Another uncertainty is in establishing methodology to catch probable timing of hemiplegic shoulder pain. Lindgren's 2007 population-based study on hemiplegic shoulder pain found that the majority of the incidence of pain occurred within the first 4 months post stroke [4]. Our inclusion criteria allow for patients to be up to twelve months post stroke, allowing for later incidences of pain occurrence. Difficulty may arise, however, in that ethics approval required injection in inpatient facility only. It is anticipated that many otherwise eligible participants may be unidentified by inpatient recruitment strategies.

Despite the realistic uncertainties outlined above, this study will provide useful information pertaining to an important topic. Shoulder pain is a common and debilitating symptom for a large number of people following a stroke and currently there is poor evidence regarding effective treatments. If the study shows that the suprascapular nerve block is efficacious in management of hemiplegic shoulder pain, it could potentially provide a new treatment option for stroke patients.