Effects of High Intensity Laser Therapy Compared With Ultrasound Therapy on Hemiplegic Shoulder Pain; Randomized Control Trial

Hemiplegic shoulder pain is a common clinical consequence of stroke and can result in significant disability. Shoulder pain can negatively affect rehabilitation outcomes as good shoulder function is a prerequisite for successful transfers, maintaining balance, effective hand function, and performing activities of daily living. The reported prevalence of shoulder pain varies between 5% and 84%, depending on timing and definition of shoulder pain used. An incidence of hemiplegic shoulder pain during the first year range from 1% to 22%. Causes of hemiplegic shoulder pain are multifactorial. Pain is associated with shoulder tissue injury, abnormal joint mechanics, and central nociceptive hypersensitivity. About one third of patients with acute stroke have abnormal ultrasound findings in the hemiplegic shoulder when studied at the time of admission to acute inpatient rehabilitation, including effusion in biceps tendon or subacromial bursa; tendinopathy of biceps, supraspinatus, or subscapularis; and rotator cuff tear There are several treatments for Hemiplegic shoulder pain. Patient and family education (ie, range of motion and positioning) is recommended for shoulder pain and shoulder care after stroke, particularly before discharge or transitions in care. Well- known interventions for Hemiplegic shoulder pain includes botulinum toxin injection, intraarticular steroid injection and transcutaneous electrical nerve stimulation. Nowadays, there are high technology modalities which are less invasive such as ultrasound therapy, extracorporeal shockwave therapy, repetitive transcranial magnetic stimulation and laser therapy.

Ultrasound therapy is frequently used to relieve pain in hemiplegic shoulder; although there were limited evidences of benefit of ultrasound in hemiplegic shoulder. Randomized control trials in 2010 showed that ultrasound therapy significantly reduce pain and increase pain free ROM of post stroke shoulder pain.

However from previous study in1972 showed that ultrasound dose not significantly increases pain free range of motion in the involved shoulders of patients with hemiplegia.

Laser therapy has become increasing use in hemiplegic shoulder pain. Previous study shows that low level laser therapy significantly reduced pain and improved range of motion in hemiplegic shoulder compared with electrotherapy. High intensity laser therapy (HILT) has been known to reduce pain through multiple pathways including central nervous system pathway, peripheral nervous system pathway and tissues pathway. In the central nervous system, laser therapy centrally inhibits pain sensation by increasing the secretion of endogenous opioids such as b-endorphins. In the peripheral nervous system, laser therapy has been reported to decrease the secretion of substance P by peripheral receptors. Laser therapy might increase the latency and decrease the conduction velocity of sensory nerves by inhibiting Aδ- and C-fiber transmission; these in turn may decrease the transmission of pain signals. In tissues, laser therapy may also reduce the release of histamine and bradykinin in injured tissues and increase the pain threshold. HILT increases cell metabolism, vascular permeability, and blood flow in deep tissue structures. Compared to low level laser therapy, HILT have a shorter laser emission time and a longer laser emission interval. Therefore, a large amount of laser irradiation can be delivered to deep tissues.

According to Latest systematic review and meta-analysis, HILT significantly improved pain and disability scores compared with control in musculoskeletal disease especially with neck and back pain. From this study there was insufficient evidence to conclude the efficacy of HILT on shoulder pain. However, in randomized controlled trial which studied the efficacy of HILT in patients with subacromial impingement syndrome showed greater reduction in pain, improvement in articular movement and muscle strength of the affected shoulder after 10 treatment sessions of HILT than did participants receiving Ultrasound therapy over a period of 2 consecutive weeks. In management of frozen shoulder, HILT (3 times per week for 3 weeks) provided significant pain relief at 3 and 8 weeks, but not at the final follow-up time point ( 12 weeks).