Mansueto Gomes-Neto, Jordana Moura Lopes, Cristiano Sena Conceição, Anderson Araujo, Alécio Brasileiro e, Camila Sousa, Vitor Oliveira Carvalho e Fabio Luciano Arcanjo.
1. Background: Low back pain (LBP) is a multifactorial disorder with a high prevalence; most people experience back pain at some point in their life and it has a significant impact on individuals, their families, and the healthcare systems. This disorder causes disability, participation restriction, a career burden, the use of health-care resources, and a financial burden. In addition to medical treatment, musculoskeletal physiotherapy (exercise therapy and manual therapy) is the most common method of conservative intervention for LBP (Amit, Manish, & Taruna, 2013; Hoy, Brooks, Blyth, & Buchbinder, 2010; Smith et al., 2014). The European Guidelines for Management of Chronic Non-Specific Low Back Pain (Airaksinen et al., 2006) recommend supervised exercise therapy as the first-line treatment. Stabilization exercise programs have become widely used for low back rehabilitation because of its effectiveness in some aspects related to pain and disability (Ferreira, Ferreira, Maher, Herbert, & Refshauge, 2006; Liddle, David Baxter, & Gracey, 2009). Stabilization exercise are exercise interventions that aim to improve function of specific trunk muscles thought to control inter-segmental movement of the spine and enable the patient to regain control and coordination of the spine and pelvis using principles of motor learning such as segmentation and simplification (Hodges and Richardson, 1996; Richardson, Jull, Hides, & Hodges, 1999). Although stabilization exercises have become the major focus in spinal rehabilitation, as well as in prophylactic care, the therapeutic evidence using pain and disability control variables as outcomes remains controversial. Most therapeutic studies have compared stabilization exercise, general exercise, and manual therapy. Systematic reviews to date that have evaluated the effectiveness of exercise therapies have concluded that there is no evidence to support the superiority of one form of exercise over another (Ferreira et al., 2006; Macedo et al., 2010). In a recent review, Wang et al. (Wang et al., 2012) showed that stability exercise is more effective for decreasing pain than general exercise, and it may improve physical function in patients with chronic LBP. However, the efficacy of stability exercise was not compared with manual therapy. After reviews on this topic were published (Ferreira et al., 2006; Macedo et al., 2010; Wang et al., 2012), new randomized controlled trials (RCTs) have been released (Amit et al., 2013; Inani and Selkar, 2013; Macedo et al., 2012; Sung, 2013). The Cochrane Collaboration recommends that systematic reviews be updated biannually (Higgins and Green, 2006). Moreover, as far as we know, no meta-analysis has been performed on studies comparing segmental stabilization exercise with manual therapy. The meta-analysis technique minimizes subjectivity by standardizing treatment effects of relevant studies into effect sizes (ESs), pooling, and analyzing data to draw conclusions. The aim of this systematic review with meta-analysis was to analyze published RCTs that investigated the efficacy of stabilization exercises versus general exercises or manual therapy in patients with LBP.
2. Methods: This review was planned and performed in accordance with PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines (Moher et al., 2009).
2.1. Eligibility criteria: This systematic review included all RCTs that investigated the efficacy of stabilization exercises in patients with non-specific LBP. Studies that compared a stabilization exercises group with a general exercises group or a stabilization exercises group with a manual therapy group were included. Studies were considered for inclusion regardless of publication status, language, or size. Trials that enrolled patients with chronic non-specific LBP were included in this meta-analysis. For this study was considered the chronic nonspecific LBP as low back pain (>3 months’ duration) without leg pain. The studies that enrolled patients with acute LBP in association with neurologic diseases were excluded from this systematic review. The main outcomes of interest were pain (assessed using visual analog scale, numerical rating scale, or any other instrument or scale) with scores ranging from 0 to 10, disability, and function assessed by any questionnaire. To be eligible, the RCTs should have randomized patients with chronic LBP to at least one group of stabilization exercises. For this review, stabilization exercises was considered as prescribed exercises aimed at improving function of specific trunk muscles that control inter-segmental movement of the spine, including the transversus abdominis, multifidus, diaphragm, and pelvic floor muscles (Hodges and Richardson, 1996; Richardson et al., 1999). General exercise were prescribed exercises that included strengthening and/or stretching exercises for the main muscle groups of the body as well as exercises for cardiovascular fitness. Manual therapy comprised physiotherapy based on manual techniques (joint mobilization or manipulation techniques).
2.2. Search methods for identification of studies: We searched for studies on MEDLINE, LILACS, EMBASE, SciELO, Cumulative Index to Nursing and Allied Health (CINAHL), PEDro, and the Cochrane Library, up to November 2014, without language restrictions. A standard protocol for this search was developed and whenever possible, a controlled vocabulary was used (Mesh terms for MEDLINE and Cochrane; EMTREE for EMBASE). Keywords and their synonyms were used to sensitize the search. For identification of RCTs in PUBMED, the optimally sensitive strategy developed for the Cochrane Collaboration was used (Higgins and Green, 2006). For identification of RCTs in EMBASE, a search strategy using similar terms was adopted. In the search strategy, there were four groups of keywords: study design, participants, interventions, and outcome measures. We analyzed the reference lists of all eligible articles in order to detect other potentially eligible studies. For ongoing studies or when any data was to be confirmed or additional information was needed, the authors were contacted by e-mail. The previously described search strategy was used to obtain titles and abstracts of studies that were relevant for this review. Each identified abstract was independently evaluated by two authors. If at least one of the authors considered one reference eligible, the full text was obtained for complete assessment. Two reviewers independently assessed the full text of selected articles to verify if they met the criteria for inclusion or exclusion. In case of any disagreement, the authors discussed the reasons for their decisions and a consensus was reached. Two authors, independently blinded, extracted descriptive and outcome data from the included studies using a standardized form developed by the authors and adapted from the Cochrane Collaboration’s (Higgins and Green, 2006) model for data extraction. We considered: 1) aspects of the study population, such as the average age and sex; 2) aspects of the intervention performed (sample size, type of stabilization exercise performed, presence of supervision, frequency, and duration of each session); 3) follow-up (if the patients included were analyzed); 4) loss to follow-up (if there was a loss in the sample); 5) outcome measures; and 6) presented results. Another author resolved disagreements. Any additional information required from the original author was requested by e-mail. The risk of bias of included studies was assessed independently by two authors using The Cochrane Collaboration’s “Risk of bias” tool (Higgins and Green, 2006). The following criteria were assessed: Random sequence generation, allocation concealment, blinding of participants and personnel, blinding of outcome assessment, incomplete outcome data, selective reporting, intention-to-treat analysis, and completeness of follow-up. The quality of evidence was independently scored by two researchers based on the PEDro scale (Olivo et al., 2008) that consisted of 11 items based on a Delphi list (Verhagen et al., 1998). The PEDro scale is a useful tool for assessing the quality of physical therapy and rehabilitation trials (Olivo et al., 2008). One item on the PEDro scale (eligibility criteria) is related to external validity and is generally not used to calculate the method score, leaving a score range of 0e10 (Maher, Sherrington, Herbert, Moseley, & Elkins, 2003).
2.3. Statistical assessment: Pooled-effect estimates were obtained by comparing the least square mean percentage change from the baseline to the study end for each group, and were expressed as the weighted mean difference between groups. Calculations were performed using a random-effects model. Two comparisons were made: stabilization exercises group versus general exercises group and stabilization exercises group versus manual therapy group. An a value of 0.05 was considered significant. Statistical heterogeneity of the treatment effect among studies was assessed using Cochran’s Q-test and the inconsistency I (Hoy et al., 2010) test, in which values between 25% and 50% were considered indicative of moderate heterogeneity, and values > 50% were considered indicative of high heterogeneity (Higgins, Thompson, Deeks, & Altman, 2003). All analyses were conducted using Review Manager Version 5.0 (Cochrane Collaboration). (CollaborationAvailab).
3. Results: The initial search led to the identification of 653 abstracts, from which 24 studies were considered as potentially relevant and were retrieved for detailed analysis. After complete reading of 24 articles, 13 were excluded. Finally, 11 papers (Akbari, Khorashadizadeh, & Abdi, 2008; Amit et al., 2013; Ferreira et al., 2007; França, Burke, Hanada, & Marques, 2010, 2012; Goldby, Moore, & Doust, 2006; Inani and Selkar, 2013; Macedo et al., 2012; Rasmussen-Barr, Nilsson-Wikmar, & Arvidsson, 2003; Sung, 2013; Unsgaard-Tøndel, Fladmark, Salvesen, & Vasseljen, 2010) met the eligibility criteria. Fig. 1 shows the PRISMA flow diagram of studies for this review. Each of the papers was scored using the PEDro scale. Table 1 presents the results of individual assessment by the PEDro scale. The final sample ranged from 30 to 172 participants, and the mean age ranged from 59 to 67 years. All studies analyzed in this review included outpatients with documented LBP. The parameters used in the application of stabilization exercises have been reported, and all studies described the progressive nature of the programs. The duration of stabilization exercises programs ranged from 4 to 12 weeks. The duration of sessions varied from 20 to 60 min in the studies. The frequency of sessions ranged from one to three times per week. Table 2 summarizes the characteristics of included studies.
3.1. Pain intensity: In total, eight trials assessed pain intensity (Akbari et al., 2008; Amit et al., 2013; Ferreira et al., 2007; França et al., 2010; Goldby et al., 2006; Macedo et al., 2012; Rasmussen-Barr et al., 2003; Sung, 2013). The meta-analyses showed (Fig. 2) a significant improvement in pain of 1.03 (95% CI: 1.79 to 0.27, N ¼ 603) for participants in the stabilization exercises group compared to the general exercises group. Three studies compared stabilization exercise to manual therapy (Ferreira et al., 2007; Goldby et al., 2006; Rasmussen-Barr et al., 2003). A non-significant difference in pain of 0.38 (95% CI: 0.98 to 0.22, N ¼ 358; Fig. 3) was noted for participants in the stabilization exercises group compared to the manual therapy group. Age mean.
3.2. Disability: Seven trials assessed disability (Ferreira et al., 2007; França et al., 2010, 2012; Inani and Selkar, 2013; Macedo et al., 2012; Sung, 2013; Unsgaard-Tøndel et al., 2010). Five of these studies measured disability using the Oswestry Disability Index (França et al., 2010, 2012; Inani and Selkar, 2013; Sung, 2013; Unsgaard- Tøndel et al., 2010), and two assessed disability using the Roland-Morris Disability Questionnaire (Ferreira et al., 2007; Macedo et al., 2012). In four individual trials, significant improvements were found in the stabilization exercises group compared to the general exercises group as measured by the Oswestry Disability Index. The meta-analyses showed a significant improvement in disability of 5.41 (95% CI: 8.34 to 2.49, N ¼ 209; Fig. 4) for participants in the stabilization exercises group compared to the general exercises group. As assessed using the Roland-Morris Disability Questionnaire, the non-significant difference in disability of 0.75 (95% CI: 2.26 to 0.75, N ¼ 310; Fig. 5) was noted for participants in the stabilization exercises group compared to the general exercises group. Three studies compared stabilization exercise to manual therapy (Ferreira et al., 2007; Goldby et al., 2006; Rasmussen-Barr et al., 2003). A non-significant difference in disability of 0.17 (95% CI: 0.38 to 0.03, N ¼ 358) was found for participants in the stabilization exercises group compared with manual therapy (Ferreira et al., 2007; Goldby et al., 2006; Rasmussen-Barr et al., 2003). (Fig. 6) Owing to the differences between instruments used to measure disability (stabilization exercises group versus manual therapy group), a meta-analysis was performed using the standardized mean difference. All studies included patients of both genders, but there was an overall predominance of female. The mean age ranged from 38 (Rasmussen-Barr et al., 2003) to 53 (Ferreira et al., 2007) years. All studies analyzed in this review included outpatients with documented chronic nonspecific LBP (pain duration > 12 weeks). The parameters used in the application of manual therapy have been reported. The duration of manual therapy programs ranged from 8 (Ferreira et al., 2007) to 12 (Goldby et al., 2006; Rasmussen-Barr et al., 2003) weeks. The duration of sessions varied from 45 (Rasmussen-Barr et al., 2003) to 60 (Ferreira et al., 2007; Goldby et al., 2006) min in the studies. The frequency of sessions ranged from one (Rasmussen-Barr et al., 2003) to two (Ferreira et al., 2007) times per week. Table 2 summarizes the other characteristics of included studies.
3.3. Function: Two trials assessed function using the Patient-Specific Functional Scale (Macedo et al., 2012; Verhagen et al., 1998). The nonsignificant difference in function of 0.01 (95% CI: 1.18 to 1.21, N ¼ 310) (Fig. 7); was noted for participants in the stabilization exercises group compared with the general exercises group.
3.4. Risk of bias in the included studies: The studies did not have enough detail for assessing the potential risk of bias. Details regarding the generation and concealment of the random allocation sequence were poorly reported. Six studies presented objective evidence of the random allocation characteristics. The studies presented objective evidence of balance in baseline characteristics. Only three studies stated that the measurements were blinded.
4. Discussion: In the present systematic review, a meta-analysis of 8 studies indicated that stabilization exercises were more effective than general exercises in reducing pain. Five studies demonstrated a significant improvement in disability between patients treated with stabilization exercises compared with those treated with general exercises. Moreover, the meta-analysis of three studies demonstrated that stabilization exercises were as efficacious as manual therapy in decreasing pain and disability. In our meta-analysis the mean of pain in the analyzed studies was 6.01 at baseline, being 2.1 at the end of the stabilization exercises on a 0e10 pain scale. Specifically, the WMD in pain was 1.03 favoring stabilization exercises, what represents an improvement of 39% in pain. Considering pain, for patients with subacute or chronic LBP, the minimally clinically important change for pain on a visual analog scale (0e10) should at least be 20%. If a numerical rating scale (0e10) is used it seems reasonable to suggest that the minimally clinically important change should at least be 25% for patients with chronic LBP (Ostelo and de Vet, 2005). The results of this review are consistent with the findings of a previous systematic review (Ferreira et al., 2006; Macedo et al., 2010) on the effects of stabilization exercise on nonspecific LBP. Our meta-analysis indicated that stabilization exercise can be more effective than general exercise in improving pain and disability in the short term, but it was not superior to manual therapy. In another systematic review by Pereira et al. (Pereira et al., 2012), stabilization exercise and Pilates offered no significant improvement in functionality. Previously, two other meta-analyses (Rackwitz et al., 2006; Wang et al., 2012) reported that specific stabilization exercises was better than ordinary medical care provided by a general practitioner to reduce pain over the short and intermediate terms. However, in a recent meta-analysis, Macedo et al. (Macedo, Maher, Latimer, & McAuley, 2009) demonstrated that stabilization exercises were superior to minimal intervention, but not more effective than manual therapy. Macedo and coworkers’ results are in agreement with those of our meta-analysis (Macedo et al., 2009). Contrary to our results, the meta-analysis by Macedo et al. (Macedo et al., 2009) also demonstrated that stabilization exercises were not more effective than other forms of exercise.
This disagreement can be explained by several different approaches currently in use for stabilization exercise to treat LBP. A standard protocol and definition for stabilization exercises is yet to be established. Therefore, there is a wide variation among studies in how the exercises were named and implemented (Lewis et al., 2005). Nevertheless, multiple studies have shown that not all subjects with LBP benefit equally from stabilization exercise (Hicks, Fritz, Delitto, & McGill, 2005). A recent review of studies has shown that therapy that is specifically directed at well-defined subgroups leads to improved effectiveness of interventions (Karayannis, Jull, & Hodges, 2012). The identification of predictive factors in patients with LBP should allow the prescription of the most appropriate treatment intervention, maximizing the likelihood of a favorable clinical outcome (Brennan et al., 2006; Fersum et al., 2010). In the present review, the included studies did not report concealment allocation or randomization in an appropriate manner. Thus, the effectiveness of stabilization exercises may be even lower in studies with proper randomization and concealment allocation. Our meta-analysis showed that stabilization exercise was as efficient as manual therapy for improving in pain and disability. However, the total number of patients involved in the meta-analysis was too small to identify relatively small disparities between the effects of stabilization exercise and manual therapy. It is difficult to make a definitive and pragmatic recommendation regarding stabilization exercise for patients with LBP. There was a variation in the duration of exercise programs, progression criteria, muscle activation, and type of feedback used during the interventions. However, with the exception of the study of Ferreira et al. (Ferreira et al., 2007) did not inform which protocol was used for stabilization, the protocol used in the studies were based on the protocol proposed by Richardson & Hodges (Hodges and Richardson, 1996; Richardson et al., 1999). Caution is warranted when interpreting the present results given the significant heterogeneity found in primary analyses. The use of different instruments for assessment and intervention programs (session time and duration of intervention) can compromise the comparisons. The studies used different scales and time periods to measure pain intensity (e.g., pain in last 24 h, pain in the last months) and disability (e.g. the Roland Morris Disability Index and the Oswestry Disability Index) and the duration of intervention and the time points of follow-up were different. Despite the differences in frequency and duration, stabilization exercise using the principles proposed by Richardson & Hodges (Hodges and Richardson, 1996; Richardson et al., 1999). were superior to general exercise that prioritizes exercise of superficial muscles. One of the limitations of this review was that the findings were based on relatively low quality data that led to a high risk of bias. Additional research is required to ascertain the positive effects of stabilization exercise over time and to determine their essential attributes, such as mode, intensity, frequency, duration, and timing. New RCTs testing different stabilization exercise for LBP should be conducted to determine the optimal treatment approach. Additionally, it will be important to match exercise prescription to clinical/treatment characteristics of a patient subgroup or individual patient.
5. Conclusion: Stabilization exercises and/or manual therapy can be encouraged as part of musculoskeletal rehabilitation for patients with LBP. However, the best prescription program, needs to be determined by new RCTs.