Research Review By Demetry Assimakopoulos©

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Date Posted:

December 2011

Study Title:

Additive effects of low-level laser therapy with exercise in subacromial impingement syndrome: A randomized, double-blind, controlled trial

Authors:

Mohammad S, Abrisham Jalil, Kermani-Alghoaishi M et al

Author's Affiliations:

Shahid Sadoughi University of Medical Sciences, Yazd, Iran

Publication Information:

Clinical Rheumatology 2011; 30 1341-1346.

Background Information:

The majority of pathologies causing shoulder pain are articular or peri-articular in nature. One such injury is the subacromial syndrome (commonly referred to as ‘impingement’). There are many forms of conservative treatment for this common injury including NSAIDs, corticosteroids and physical therapy; however, very little evidence supports their effectiveness. One facet of physical therapy includes the use of electromodalities such as ultrasound, interferential current, TENS and low-level laser therapy (LLLT).

LLLT is theorized to accelerate the repair of connective tissue and effect fibroblast function. Additionally, it is hypothesized to improve local microcirculation and oxygen supply to cells that are lacking oxygen delivery and remove collected waste products (1). There is also research suggesting that LLLT has an anti-inflammatory effect (2). One of the standard interventions for subacromial syndrome is the use of corrective exercise. It was the goal of this study to identify if there is any additive effect of LLLT and corrective exercise in the treatment of subacromial syndrome (loosely operationally defined as rotator cuff and biceps tendonitis, as these three injuries are often related).

Pertinent Results:

Statistically significant improvements in pain severity and ROM were found in both groups, subsequent to treatment. There was a statistically significant difference between groups in VAS scores; group I (intervention group) improved to a greater degree than group II (control group). Group I improved their active and passive ranges of motion to a greater degree than group II as well. The authors draw no conclusion as to the mechanism of the greater improvement in Group I.

The results of this study only add to the plethora of articles in the ether which, in their entirety, come to very inconsistent conclusions. A systematic review published in 2009 by Kromer et al (3) found 2 studies that investigated the clinical efficacy of LLLT in the treatment of impingement syndrome. They concluded that there is conflicting evidence and no specific recommendation can be offered. However, Michener et al.’s systematic review on the effectiveness of rehabilitation on patients with shoulder impingement syndrome (4) came to a much different conclusion.

They noted that, while overall the evidence is conflicting, LLLT is actually more beneficial than placebo when applied as a lone intervention for subacromial impingement syndrome. However, they also concluded that there is no additive benefit when LLLT is combined with rehabilitation, which contradicts the results of the study reviewed above.

However, this evidence does not preclude any clinician from using LLLT as a form of treatment for overall pain relief. Fulop et al., in their 2010 meta-analysis (5) concluded that LLLT has the capacity to effectively relieve pain regardless of the etiology. This study did not make the effort to compare the effect of LLLT with any other treatment modality or therapy – just simply analyzed the pertinent data that related to their research question asking what the effect of LLLT is on overall pain.

Clinical Application & Conclusions:

This double-blind, randomized control trial showed that LLLT and exercise therapy is more effective than exercise therapy alone for the purposes of improving pain and active/passive range of motion in patients with subacromial syndrome.

What is the science behind laser therapy?
The theory is that the infrared radiation (specifically, within a spectrum of wavelengths between 630-1300 nm) is converted into heat by the body, which then increases the vibrational energy of biomolecules. This spectral range of wavelengths is thought to improve microcirculation, stimulate metabolism, facilitate cell recovery and activate the immune system. Additionally, this therapy is said to reduce pain, relax muscles, improve tissue healing, repair ligaments, promote fibroblast proliferation and decrease inflammation.

Writer’s notes: This study is important for clinicians who are thinking about using modalities in their practice. Most of the research on tissue repair, fibroblast proliferation and anti-inflammatory effects of laser therapy is not definitive, thus researchers can only suggest that its usage results in the biochemical and physiological effects described in this article. However, one cannot pass over clinical studies that prove, even mildly, the efficacy of a treatment – especially when the use of a modality is outside of the offered recommendations for use (listed below in the strengths/weaknesses section).

Study Methods:

The researchers recruited 80 patients, diagnosed with subacromial syndrome via positive results on Neer’s sign, Hawkins-Kennedy, Jobe test (empty can) and Speed’s test (for biceps tendinopathy). Subjects who had a history of trauma, systemic inflammatory conditions, structural or neurological abnormality, pregnancy and/or breastfeeding, anticoagulation therapy, diabetes mellitus, chest pain, smoking, septic arthritis of the shoulder or trauma were excluded from the study; as were any individuals in whom LLLT is contraindicated.

Once recruited, the subjects were assessed for ranges of motion about the shoulder and pain severity. Subsequent to this, the subjects were randomized into two groups and were either given LLLT and exercise therapy for 10 sessions over 2 weeks (group I; n = 40) or given a placebo laser and the same exercise therapy as the other group (group II; n = 40). The same physical therapist administered treatment for all subjects included.

Shoulder physical therapy included strengthening, stretching and mobilization exercises (at home and at the clinic). The exercise program started in the clinic setting, and included pulley and shoulder wheel exercises. Later on, the subjects were allowed to perform the exercises at home, unsupervised. In the first two sessions at home the subjects performed pendulum exercises. Once they reached the third visit, they started performing isometric exercises and active assisted exercises.

After the exercise therapy sessions, each subject in group I received infrared laser therapy, set to a wavelength of 890 nm in a pulsed mode for 2 minutes. The sites targeted were the coracoid process (anterior), glenohumeral joint (posteriorly) and the rotator cuff tendon(s) (laterally) – 2 minutes at each area for a total of 6 minutes. The individuals diagnosed with biceps tendonitis had their biceps tendon treated as well. Group II received the same laser treatment, only the LLLT machine was not turned on.

The researchers utilized shoulder ranges of motion (active and passive flexion, abduction and external rotation using goniometry in a supine position) and the visual analogue scale (VAS) as outcome measures.

Study Strengths / Weaknesses:

Weaknesses:
  • It is not clear why the researchers lumped rotator cuff pathology and biceps tendonitis into the same category as subacromial syndrome.
  • Some of the tests the researchers used to diagnose subacromial syndrome are weak. It is unclear whether or not they used only a single test to diagnose the condition or a number of them together, so as to exclude false positives. Additionally, some of the research on the diagnosis of subacromial syndrome/impingement advocates attempting to relieve the symptoms in addition to provoking them using orthopedic tests (ie. scapula relocation test, glenohumeral repositioning, etc.). I am unsure as to why, given that this is a recent article, this was not done to come to a final diagnosis of subacromial impingement syndrome. As stated above, there is literature which recommends the use of LLLT for generalized pain. It is unclear as to whether or not the researchers were actually treating subacromial syndrome or some other shoulder injury that was missed. Despite this, the additive effect the researchers found cannot be ignored.
  • What were the researchers treating? Impingement (if so, which kind of impingement; anterior or posterior), rotator cuff tendinopathy or biceps tendinopathy? In order for this to be clinically relevant, clinicians need to know what they are treating. It is unclear in this study whether the groups were entirely homogeneous.
  • The researchers administered LLLT after the exercise session. The standard protocol for LLLT is to administer treatment before exercise/manipulation/soft tissue therapy.
  • No functional scales were used as an outcome measure (such as the DASH).
  • The researchers only used ROM and pain as their outcome measures. They did not indicate whether they redid the positive orthopedic tests.
  • There was no long-term follow-up.
  • While the authors utilized a standard rehabilitation protocol, they failed to go further than active assisted exercises. Why did they not go on to perform resistance exercises against gravity and with weight?
Strengths:
  • The study included a large number of subjects.
  • The authors administered a different protocol than utilized the current literature. This creates the new research question of which intensity, wavelength and settings are ideal any given tissue or therapy?

Additional References:

  1. Kreisler M et al.Low level 809 nm diode laser induced in vitro stimulation of the proliferation of human gingival fibroblasts. Lasers Surg Med 2002; 30:365–369.
  2. Sakurai Y, Yamaguchi M, Abiko Y. Inhibitory effect of low-level laser irradiation on LPS-stimulated prostaglandin E2 production and cyclooxygenase-2 in human gingival fibroblasts. Eur J Oral Sci 2000; 108: 29–34.
  3. Kromer TO, Tautenhahn UG, de Bie RA et al. Effects of physiotherapy in patients with shoulder impingement syndrome: A systematic review of the literature. Journal of Rehabilitation Medicine 2009; 41: 870-880.
  4. Michener LA, Walsworth MK & Bumet EN. Effectiveness of rehabilitation for patients with subacromial syndrome: A systematic review. Journal of Hand Therapy 2004; 4(17): 152-164.
  5. Furlop AM, Dhimmer S, Deluca JR et al. A Meta-analysis of the efficacy of laser phototherapy on pain relief. Clinical Journal of Pain 2010; 26: 729-736.