Long-term effect of high-intensity laser therapy for persistent shoulder pain: A case report

1. Introduction

The prevalence of shoulder injury is over 20% [1], and the shoulder joint is the third cause of musculoskeletal pain [2]. The tendency to chronification implies a high percentage of patients reporting ongoing symptoms three years after the initial episode [3]. Moreover, pain is the main symptom associated with shoulder pathologies [4]. Its treatment turns into a crucial element during the rehabilitation to prevent periarticular soft tissue and capsule stiffness and retraction pattern from installing.

Low-level laser therapy (LLLT) for the treatment of joint and musculoskeletal pain is normally used in rehabilitation. In the past years, high-intensity laser therapy (HILT) is also considered as a therapeutic option. HILT is able to reach and stimulate the large and/or deep joints that are difficult to reach with LLLT [5]. However, there is little evidence about the effectiveness of HILT. In some studies, HILT is used in combination with other therapies and/or short-term follow-up [5, 6, 7, 8]. In the present case report, HILT is used as monotherapy. A nine-months follow-up was performed which is essential in chronic pathologies.

2. Case description

A thirty-one-year-old woman with a trauma background after a bicycle fall in January 2016 was included in the study. The fall caused fracture of the left radius bone without radial cupule displacement.

The patient also reported left shoulder pain. This was diagnosed as subacromial syndrome with supra-spinatus tendinosis and bicipital tendinitis. Twenty sessions of analgesic electrotherapy (TENS: 80 Hz–120 μ s during 20 minutes) were prescribed in February 2016 as a supplement for the provided treatment related to radius fracture. Pain was more intense after two months, reported along the subacromial space. Jobe and Yocum’s maneuvers [9] were positive and a bicipital tendinitis-bursitis was evidenced by echography.

After three months of evolution, 15 sessions of iontophoresis (0.1–0.2 mA/cm 2 during 20 minutes) were taken with dexamethasone (4 mg/ml) and lidocaine (50 mg/ml), and a month later, 15 sessions of LLLT (amount of 68,64 J with sweeping method) combined with pulsatile short wave (110 Hz) showed a slight temporary pain relief.

Five months after the initial injury, echography evidenced subacromial bursitis and bone splinter in the bicipital groove and positive subacromial impingement. An infiltration with corticosteroids (triamcinolone acetonide 40 mg/ml) induced an improvement during a ten-days period.

After 8 months, the patient not only had pain without mobility limitations, but also a sensation of heaviness and a daily continuous pain which increased when performing slight efforts, and pain persistence at night. Furthermore, pain in the interscapular area was also reported.

At this point, ten HILT sessions were applied to the patient. Written informed consent was obtained for publication of this case report (appropriate Ethics Committee approval was also obtained for the research). The evaluation included the validated version of the Spain of Shoulder Pain and Disability Index (SPADI) [10], and the Numeric Pain Rating Scale (0–10) (NPRS) was used for pain and for sensation of heaviness. The evaluation of pressure pain threshold (PPT) was performed by an analogue algometry (algometer Wagner FPN100). This evaluation was made by the same researcher and was performed in five temporal points: before the intervention, at the end of 10 laser sessions, 1 month after the end of the intervention, 3 months after the intervention, after the 5 booster sessions applied 3 months after the intervention and 6 months after the 5 booster sessions (9 months after the initial episode).

The HILT was applied using a Nd-Yag (Neody-mium-doped yttrium aluminum garnet) laser device (“iLux laser”, Mectronic Medicale, Italy), which emits infrared light (wavelength of 1064 nm) and at a maximum power of 15 W. Each treatment session was divided into three phases: i) The laser emission with stochastic function E 2 C, in which the pulse frequency and width are modulated to reduce the thermal effects, was administered with a maximum power of 10 W for 3 minutes in two points, along the sub-acromial and bicipital area. A total of 810 Joules per point were administered. ii) The second phase consisted in a continuous modality 12 W of power and 100 J/cm 2 in the anterior shoulder area. iii) Finally, the third phase included a continuous laser emission in the interscapular area at a power of 15 W and 100 J/cm 2 .

Five booster sessions were applied into three separate phases, after a three-months period without treatment: i) In the anterior shoulder area, 100 J/cm 2 was applied with a power of 15 W (pulsed modality with increasing power) and ii) 100 J/cm 2 in continuous emission of 15 W. iii) The third application was indicated in the interscapular area (continuous – 100 J/cm 2 – 15 W).

3. Results

Results are synthesized in Fig. 1. Values of NPRS pain and NPRS sensation of heaviness, especially the former, significantly decreased clinically (Fig. 1A). Values from the SPADI showed improvement in pain and disability (Fig. 1B). Due to the inability to realize the measurement, basal value was 0 on the PPT graph. The positioning of the algometer was described as “very painful” (Fig. 1C).

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The minimum clinically significant effect has been defined over 2.17 for the NPRS [11] and 8 to 13 points for the SPADI [12]. The results show a clinically significant improvement even in the long-term effect. Paul et al. suggested a central sensitization phenomenon in patients with chronic subacromial syndrome [13]. Our results showed low values in the PPT measurement according to Paul et al. outcomes.

Only a few studies observed the effects of HILT in the subacromial syndrome [14]. Related to SPADI, different HILT phases were applied in the same session to our study. In the short term, our results are in line with those of Karaca [14]. Pekyavas et al. also perceived a greater decrease in the SPADI total values in HILT treated patients, however several treatments were combined [7]. Regarding the visual analogue scale (VAS), a study on the use of HILT in the frozen shoulder syndrome reported a greater decrease in the VAS scale during the intermediate follow-up compared with placebo [8]. However, HILT and placebo groups received anti-inflammatory drugs and a self-exercise programme. Santamato et al. also reported higher efficacy in the decrease of VAS in patients who received HILT compared to ultrasound therapy, but no follow-up was performed [6]. The only evidence on the medium and long-term use of HILT on shoulder pain have been recently published. These studies showed controversial effects compared to sham-device [15, 16].

In this case report, the PPT continued to improve compared to the values observed immediately and one month after the intervention, three months after the intervention without receiving any other treatment. Furthermore, the clinical improvement in SPADI and NPRS slightly decreased but maintained the clinical significance. After five HILT sessions at three months, a further improvement was evidenced again, which was maintained or even increased six months later. Effectiveness of booster sessions is still unclear in manual therapy and exercise therapy [17, 18], but these sessions could be considered for potential beneficial effects of HILT when other therapeutics interventions fail [19]. More studies with booster sessions and long-term follow up are necessary. Booster sessions of HILT are more suitable to applying higher intensity in chronic phase than in the acute phase.

In conclusion, the high-intensity laser therapy could be considered as a therapy for long-term relieving pain in the subacromial syndrome. However, new randomized and controlled clinical trials including a long-term follow-up are needed to confirm our findings. The use of booster sessions could be a new research line in chronic shoulder pathologies.