For nonoperative treatments, when the outcome was measured by the pain score, HYA+EXE and NSAID+EXE showed better treatment effects than the other treatments, whereas HYA and NON exhibited the worst effects. However, with respect to CMS, a contradictory result was found regarding NSAID+EXE, namely, it demonstrated a worse effect than any other treatment. In this analysis, KT+EXE, SE+EXE, and ACU+EXE were found to be the preferred treatments.
Regarding operative treatments, with respect to the pain score and the CMS, ASD together with treatments derived from it, such as ASD+RF and onlyBUR, showed better effects than OSD and OSD+PLG. Additionally, onlyBUR appeared inferior to ASD and ASD+RF.
In network 1, 1 quadrilateral loop (EXE vs ACU+EXE vs COR vs NON) and 2 triangle loops (EXE vs LLLT+EXE vs US+EXE and HYA vs COR vs NON) were found, but the latter triangle loop (HYA vs COR vs NON) was disregarded because it was described by only one 3-arm trial and no inconsistency was detected. In network 2, 1 triangle loop (EXE vs LLLT+EXE vs US+EXE) was found. There was no loop in networks 3 and 4. In these 3 loops, the Z values were 1.60, 0.01, and 0.01, with corresponding P values of 0.11, 0.99, and 0.99, respectively. The P values were all >0.05, which demonstrated that no inconsistency was detected in these loops.
Due to the small number of studies in networks 3 and 4, the meta-regression was only performed for networks 1 and 2. In the meta-regression, no significant difference in the DIC was observed (109.8 and 111.3 for the pain score; 143.6 and 142.1 for CMS), and the 95% CIs of the regression coefficients were −0.04 to 0 for the pain score and −0.08 to 0.32 for CMS, indicating that the covariate (the sample size of the study) was not associated with the treatment effect.
The results of pair-wise meta-analysis and network meta-analysis were in good accordance with each other. In terms of nonoperative treatments, exercise-based therapies demonstrated better treatment effects. Regarding operative treatments, the arthroscopic technique tended toward better efficacy than the open surgical technique. These results were supported by inconsistency test, sensitivity test, and meta-regression.
This is the first network meta-analysis to include all the available treatment strategies for SIS. It was based on a Bayesian framework and summarized a series of treatment options for SIS from related RCTs, and it was conducted to simultaneously compare various treatment options that have never been directly compared previously. This method overcomes the significant shortcoming of conventional meta-analyses, which cannot compare each treatment versus all other treatment options. The outcome is robust because the prospective design of all the included studies may minimize the selection bias and recall bias. Furthermore, all the included studies were RCTs, which provide the most ideal type of evidence for inclusion in meta-analyses. The sensitivity analysis demonstrated no significant change in the rank probability, with meta-regression also showing no positive findings and the inconsistency analysis showing that all the P values were >0.05. Therefore, the outcome of this meta-analysis appears convincing.
With respect to the pain score, the results provide support for the effectiveness of exercise therapy. Additionally, treatment options composed of exercise plus other therapies all exhibited a trend toward better effects than exercise alone. These therapies included some common modalities, such as specific exercises, kinesio taping, low-level laser therapy, radial extracorporeal shockwave therapy, and manual therapy, as well as some therapies that are less frequently used, such as acupuncture, diacutaneous fibrolysis, pulsed electromagnetic field therapy, and microwave diathermy ultrasound therapy. However, for localized drug injection therapy, the results appeared to change according to whether exercise therapy was involved; specifically, localized drug injections that were combined with exercise showed better treatment effects than any other treatment options, whereas the worst effects were obtained when they were used alone. Notably, however, no significant difference was found in this set of results due to a wide CI. Only a trend toward better or worse outcomes could be observed.
With respect to the CMS, fewer treatment options were compared due to the limitations of the published data from the included RCTs. However, similar outcomes to the pain score outcomes were observed. Treatment options that were composed of exercise plus other therapies usually yielded better effects than exercise alone. Regarding kinesio taping, specific exercise, and acupuncture therapies, the combined treatment option superiority was supported by significant differences. Additionally, regarding pulsed electromagnetic field, diacutaneous fibrolysis, and ultrasound therapies, only a trend toward a benefit could be obtained. Low-level laser therapy demonstrated a different result from those of other physiotherapies by showing a relatively worse effect than exercise therapy when it was combined with exercise, although this difference had a 95% CI that covered the null value. For treatment options that combined localized injection of NSAIDs and exercise therapy, the CMS results were quite different from the pain score results; specifically, these treatment options exhibited significant inferiority compared with exercise therapy alone. This difference may have been due to the pharmacological properties of NSAIDs. As commonly used analgesic medication, NSAIDs may effectively relieve the sense of pain. However, the CMS evaluation system contains some items besides the pain score. Thus, different outcomes were obtained.
Recently, other studies that were focused on nonoperative treatment options have also been published. Some studies reproduced the effectiveness of exercise,60 whereas others found that several treatments may provide additional benefits to an exercise-based regimen,53 such as localized injection of corticosteroids54,61 and manual therapy.58 Some authors demonstrated that no significant difference could be found between specific exercises and extracorporeal shock-wave therapy,55 whereas high-level laser therapy demonstrated a better effect than ultrasound therapy.51 Some authors reported that acupuncture56 and motor control training of the scapula49 were more efficacious than ultrasound therapy when applied in addition to exercises.
Compared with nonoperative treatments, fewer options are available for operative treatments. The most commonly used methods were ASD and OSD, which represent arthroscopic and open techniques, respectively. Additionally, certain modified methods were derived from these modalities, such as ASD combined with radiofrequency, ASD without acromioplasty, and localized injection of platelet-leukocyte gel combined with OSD.
In this meta-analysis, no significant difference in the treatment effect was detected with respect to either the pain score or the CMS. However, the arthroscopic technique tended toward better efficacy than the open surgical technique. Furthermore, acromioplasty may play an important role in the arthroscopic technique to some extent because bursectomy without acromioplasty does not appear to be as good as standard ASD and ASD combined with radiofrequency. Another notable finding was that exercise therapy also demonstrated an excellent effect in this subgroup.
Some reviews and other studies regarding these techniques have been published in the past few years. In some published RCTs, the authors reported that the use of radiofrequency59 and laser57 therapy provided no additional benefit to ASD. In 1 study, the authors emphasized that OSD was equivalent to ASD at the 1-year follow-up.33 In other studies, the authors concluded that ASD had a better short-term effect because patients could spend less time in the hospital and could return to their activities of daily living and work more quickly62; however, after 1 year, the OSD group tended to catch up, although ASD still showed significant benefits in some respects.37 Some authors have concluded that the difference between ASD and supervised exercise is not clinically important63 and that supervised exercise should be the basis of treatment for SIS.52 A systematic review, which focused on the comparison between standard ASD and bursectomy only, concluded that there was no significant difference between them.71 Another review concluded that ASD and OSD had equivalent ultimate clinical outcomes.72 According to another systematic review, there was no evidence that a certain surgical treatment option was better than another or better than nonoperative treatment option.73 Moreover, these findings are also supported by our study.
Certain limitations existed in this meta-analysis. First, most included RCTs had brief follow-up periods, most of which lasted <1 year, and further studies with longer follow-up periods may be required to support our conclusions. Second, although no significant inconsistency was found by the Z test, we recognize that the number of loops was only 3 (2 in network 1 and 1 in network 2). This limitation may be resolved if additional head-to-head trials are included in future studies. Third, most comparisons were performed based on only 1 RCT, so the potential for bias should not be neglected. This problem could be solved by replicating the RCTs in the future. Fourth, the insufficient blinding of most studies may have caused potential bias in the assessment of treatment effects.
Exercise and other exercise-based therapies are the most important treatment options for SIS patients. For those patients who seek nonoperative treatment option at an early stage of SIS, exercise combined with other therapies should be recommended. Among these therapies, kinesio taping, specific exercises, and acupuncture therapy should be considered as the first-line choices, whereas pulsed electromagnetic field therapy, localized corticosteroid injection, diacutaneous fibrolysis, and ultrasound therapy may be considered as the second-line treatment choices; however, low-level laser therapy and the localized injection of NSAIDs are not recommended. For patients with chronic SIS, operative treatment options may be considered. In this case, standard arthroscopic subacromial decompression surgery is a relatively superior option to open subacromial decompression and arthroscopic bursectomy. Notably, however, the decision for operative treatment should be made cautiously because similar outcomes may also be achieved by the implementation of exercise therapy.
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