Chronic+Non-Specific+Low+Back+Pain+Prognosis

Ron Drummer, Stephanie Mylin, Abbi Oelschlager, and Taylor Zordel

The purpose of this wiki was to review the literature regarding the likelihood of chronic low back pain leading to disability and the prognostic factors which put patients more at risk to have an outcome of disability.
 * Purpose of Wiki **

What prognostic factor best predicts the likelihood of Chronic Non-Specific Low Back Pain (CNSLBP) leading to an outcome of disability?
 * Clinical Question **

Databases: Pubmed/Google Scholar Search terms: Chronic low back pain, prognosis, disability Boolean terms: AND Levels of Evidence: Systematic review, prospective cohort study, cohort study with 1-year follow-up., retrospective study Inclusion Criteria: Recent evidence (established timeline), studies not involving surgery, chronic cases, age ≥ 18 years, primary complaint was NSLBP Exclusion Criteria: Studies that did not establish timeline of symptoms, acute low back pain cases, surgery was the intervention of choice, studies where you could attribute LBP to a specific reason (i.e. radiculopathy, disc herniation, recent fracture, neoplasm or recent surgery involving the lower back and lower extremity, ankylosing spondylitis, being pregnant or post-pregnancy related issues).
 * Evidence **

Back pain can range from a dull, constant ache to sudden sharp pain. Pain can result abruptly due to a specific injury, such as lifting something heavy, or can occur over time and can be attributed to age-related changes in the spine. Most low back pain is acute, resolving on its own within a few days. Chronic low back pain remains for 12 weeks or longer, even after the initial symptoms have been treated. Treatment can be successful in some cases, but in others, pain persists despite medical efforts.
 * What is Chronic Low Back Pain? ** (7)

For more information, please visit: []




 * ** So What? **
 * LBP causes more global disability than any other condition - there is an urgent need for further research to better understand LBP across settings (1)
 * At any given time 12-33% of the adult population has low back pain (10)
 * Most common of the musculo-skeletal disorders presented in general practice, but clinical management is a significant problem (12)
 * Most CLBP is resistant to diagnosis, and has been estimated that up to 80% of such cases may present with no identifiable pathology (12)
 * Contemporary medicine has little to offer a patient presenting with NSCLBP because it is not a disease defined through the medical model; but rather a symptom located within a biopsychosocial model of illness behavior (12)
 * A complex array of symptoms that do not easily fit within a specific medical model or diagnosis
 * “From the accounts given by our responders, it seems that non-specific chronic low back pain is a problem due to a mismatch of explanatory models.” (12)


 * ** Costs **
 * United States (US) indirect costs of low back pain (LBP) are estimated to be more than US $50 billion per year, in the United Kingdom (UK) US $11 billion, and in the Netherlands almost US $5 billion (1)
 * US Government spending on HIV (AIDS) is $27 billion per year; the cost to treat LBP is nearly double the cost treat HIV (AIDS)
 * The lifetime prevalence for acute LBP exceeds 80% - although the overall prognosis is benign, 10% to 15% of these patients develop chronic LBP. This small percentage accounts for three-quarters of the total direct and indirect costs of medical care and lost productivity associated with LBP (13)


 * ** Factors **
 * ** Predictive **
 * ** Work Participation at Baseline **
 * Explained variance of 30% and AUC of 0.78 at 5 month follow-up (9)
 * Explained variance of 17% and AUC of 0.70 at 12 month follow-up (9)
 * May be because people who are working are generally healthier, have social support, and are more physically active. All of these factors are related to greater well-being and increased possibility of recovery (9)
 * ** High Return to Work (RTW) Expectancy **
 * “Recovery expectations have been identified as one of the most consistent predictors for RTW across several statistical models” (6)
 * An international study found that there was a positive association between high patient expectations to RTW and actual RTW (1)
 * This same study found that there was a negative association between low expectations and RTW as well
 * Regardless of gender, high expectancies were a strong and significant predictor of RTW at 12 months. There was no differences in the levels of expectancies between men and women (6)
 * When looking at subjects with CLBP, multiple studies have shown that those with high RTW expectations were more likely to successfully return to work
 * “After adjusting for sociodemographic factors and other covariates, men and women with high expectancies for RTW had **3-5 times higher** odds of returning to work compared to their respective counterparts with low or moderate expectancies of RTW” (6)
 * Even though this correlation was strong and significant, they are unsure on what factors directly influence individual expectancies on returning to work
 * “Screening expectancies and giving individuals with low expectancies of returning to work interventions with a goal to change expectancies of RTW may contribute to an increase in actual RTW” (6)
 * Examples of expectancy interventions:
 * Cognitive behavioral therapy
 * Self-management interventions
 * Education on CLBP
 * Coping strategies
 * Cognitive Activation Theory of Stress (CATS)
 * Theory on importance of expectancies that gives an explanation of why those with high RTW expectancies do actually RTW
 * Whenever someone has a new task, challenge, demand, or threat, activation occurs
 * The outcome of this activation depends on a person’s response outcome expectancies
 * Response outcome expectancies depend on previous learning
 * Example: coping - positive response
 * “Establishing positive response outcome expectancies may increase the individual’s efforts to solve the task or challenge and reduce the threat” (6)
 * Positive response can lead to temporary activation, which can positively influence someone’s health
 * [[image:http://www.elsevier.es/ficheros/publicaciones/21735077/0000008900000009/v1_201305021735/S2173507711000512/v1_201305021735/en/main.assets/gr1.jpeg width="449" height="548"]]
 * http://www.elsevier.es/ficheros/publicaciones/21735077/0000008900000009/v1_201305021735/S2173507711000512/v1_201305021735/en/main.assets/gr1.jpeg
 * ** Previous Rehabilitation **
 * Previous rehabilitation found to have explained variance of 30% and AUC of 0.78 at 5 month follow - up (9)
 * “Intensive multidisciplinary bio-psychosocial rehabilitation with a functional restoration approach improves pain and function in patients with CNSLBP” (9)
 * Therapy aimed at physical/functional recovery may partly explain a positive course of work-participation. (9)
 * ** Socioeconomic Status **
 * In a systemic review over prognostic factors for RTW in workers with subacute and chronic LBP, socioeconomic status (SES), physical demands, and modified duties were all grouped together in the work related psycho-social factors because they were all considered to be related
 * “Workers classified as having lower SES, often have more physically demanding jobs” (1)
 * In the workplace, modified duties are used to temporarily reduce negative associations of physically demanding work
 * This study found that lower physical demands were positively associated with RTW, but unfortunately those with lower SES feared losing their jobs by adhering to the prescribed modified duties (1)

>
 * What if doing your job just isn’t as efficient using modified duties? Let’s put us PT's in the same scenario!
 * **Marital Status**
 * Explained variance of 30% and AUC of 0.78 (9)
 * “Being married or living with another adult can provide social support for patients during their rehabilitation process, especially when they are involved in a multidisciplinary therapy” (9)
 * “Beneficial effects are reported of spousal support and social interaction with other patients on low back pain coping and function for the outcome back pain and disability” (9)
 * **Lower Quality of Life (QoL)** [both EQ-index and EQ-VAS]
 * [[image:http://apersu.ca/wp-content/uploads/2016/02/How-to-use-the-EQ-5D-EQ-5D-5L_EQ-VAS-1-1.jpg width="410" height="670"]]
 * http://www.euroqol.org/typo3temp/pics/5a1941662b.jpg
 * [[image:https://chiro-trust.org/wp-content/uploads/2015/05/Functional-Outcomes-Big-6.F_Page_2-791x1024.jpg width="436" height="642"]]
 * https://www.google.com/search?q=roland+morris+low+back+pain+questionnaire&espv=2&source=lnms&tbm=isch&sa=X&ved=0ahUKEwi2sbD_jp7TAhUY6GMKHeseDJkQ_AUICCgB&biw=1707&bih=827#imgrc=EDH1SimAC5fGbM:
 * Use different types of outcome measures for patients with NSCLP.


 * ** Non-Predictive **
 * ** Imaging findings **
 * “Imaging findings like MCs (Modic Changes) and HIZs (High Intensity Zones) did not predict future disability, nor did aging, pain medication use, fear avoidance related to physical activity and work, sex, smoking, education…” (4)
 * ** Pain Medication Use **




 * ** Questionable **
 * ** Fear Avoidance **
 * Predictive
 * Retrospective cohort found the FABQ prognostic for RTW but had several limitations (fewer patients, shorter follow-up duration, fewer prognostic factors investigated) (13)
 * Only assessed five domains, the non-prognostic studies looked at an average of more than 9 domains (13)
 * One high-quality prospective cohort study found the FABQ and FABQ-W scores to be prognostic for sick days over 1 year (more than half the patients experienced less than 3 months of LBP, almost ⅓ in subacute) (13)
 * Studied patients with both chronic and acute LBP - did not look at additional psychological factors - all non-prognostic studies looked at additional psychological domains (13)
 * High fear avoidance beliefs in pain persisting longer than 4 weeks are associated with a worse outcome, independent of LBP recurrence (13)
 * “Low levels of fear avoidance was one of the most useful items for predicting recovery at 1 year” (3)
 * Non-Predictive
 * No explanation, except P-value above 5%. (4)
 * Secondary analysis of RCT found avoidance beliefs not to be prognostic for time to RTW (13)
 * TSK (Tampa Scale of Kinesiophobia)found to be non-prognostic in 2 high-quality studies that investigated non work-related perceived measurements (13)
 * Other psychological constructs including the self-regulatory model and self-efficacy model found to be more prognostic than fear avoidance beliefs (13)
 * Low personal control over the pain or poor self-efficacy and inevitability of a future with pain could lead to passive coping and avoidance (13)
 * FABQ and TSK found to be prognostic for work-related outcomes in SUBACUTE LBP (13)
 * ** Sex **
 * Predictive
 * Being male showed an explained variance of 30% and AUC of 0.78 at 5 month follow-up and an explained variance of 17% and AUC of 0.70 at 12 month follow-up (9)
 * May be because in Dutch society where study took place, it is common for men to earn most of the wages for a family and it is less acceptable for men to work fewer hours. (9)
 * Non-Predictive
 * No explanation, except P-value above 5%. (4)
 * “Our systematic review on prognostic factors in chronic NSLBP patients showed no association between age and sex at ≤6 months of follow-up and smoking at ≥12 months of follow-up.” (2)
 * Specifically in chronic and subacute phases of LBP, this systematic review did not find an association between sex and RTW (1)
 * ** Age **
 * Predictive
 * “Recovery at 5- and 12-month follow-up was associated with younger age, back pain intensity at baseline and higher baseline scores on the SF-36 PCS/MCS.” (2)
 * During the chronic phase of LBP, it was found that there was a negative association between older age and RTW (1)
 * One of the identified prognostic factors for CLBP recovery at both 5 and 12 months was younger age (3)
 * Non-Predictive
 * No explanation, except P-value above 5%. (4)
 * ** Education **
 * Predictive
 * “Patients with high disability levels or high intensity of pain at presentation for CLBP, previous sick leave due to low back pain, a lower level of education, and higher perceived risk of persistent pain were more likely to have delayed recovery from their pain” (10)
 * Non-Predictive
 * “Imaging findings like MCs and HIZs did not predict future disability, nor did aging, pain medication use, fear avoidance related to physical activity and work, sex, smoking, education…” (4)
 * **Smoking**
 * Predictive
 * “A dose-response relationship was found between the daily cigarette consumption and the prevalence of chronic low back pain. Smoking is associated not only with low back pain but also with chronic widespread musculoskeletal pain. No conclusive decrease in pain prevalence was found after quitting smoking.” (11)
 * Non-Predictive
 * No explanation, except P-value above 5%. (4)
 * “Our systematic review on prognostic factors in chronic NSLBP patients showed no association between age and sex at ≤6 months of follow-up and smoking at ≥12 months of follow-up.” (2)
 * During the chronic phase of LBP, there was no association found between lifestyle (smoking) and RTW (1)
 * **LBP Intensity**
 * Predictive
 * “Recovery at 5- and 12-month follow-up was associated with younger age, back pain intensity at baseline and higher baseline scores on the SF-36 PCS/MCS.” (2) also in (3)
 * “Patients with high disability levels or high intensity of pain at presentation for CLBP, previous sick leave due to low back pain, a lower level of education, and higher perceived risk of persistent pain were more likely to have delayed recovery from their pain” (10)
 * High score on disability at baseline found to have explained variance of 30% and AUC of 0.78 at 5 month follow-up (9)
 * Non-Predictive
 * No explanation, except P-value above 5%. (4)
 * **Radiological variables like MC and HIZ**
 * Predictive
 * MC and HIZ have been reported to cause stimulation to lumbar nociceptive system (4)
 * Non-predictive
 * MC and HIZ have be found in pain-free people. (4)
 * No explanation, except P-value above 5%. (4)

OR = odds ratio If OR > 1: it means there was a higher probability of 30% recovery for back pain disability outcome If OR < 1: it means there is a lower probability of 30% recovery for back pain disability outcome
 * Multivariable Models of Prognostic Factors for 30% Improvement in CNLBP Disability at 5- and 12-Month Follow-ups Table**
 * Variable ||||||  5-Month Follow-up  ||||||  12-Month Follow-up  ||
 * ^  ||  OR  ||  95% CI  ||  P  ||  OR  ||  95% CI  ||  P  ||
 * Married/living with 1 adult (yes/no) || 1.32 || 0.93–1.87 || .12 || 1.54 || 0.88–2.68 || .12 ||
 * Age || 0.97 || 0.96–0.98 || <.001 || 0.98 || 0.97–0.99 || ≤.01 ||
 * <span style="background-color: #ffffff; color: #2a2a2a; font-family: Arial; font-size: 10pt; vertical-align: baseline;">Work participation || <span style="background-color: #ffffff; color: #2a2a2a; font-family: Arial; font-size: 10pt; vertical-align: baseline;">1.42 || <span style="background-color: #ffffff; color: #2a2a2a; font-family: Arial; font-size: 10pt; vertical-align: baseline;">1.02–1.96 || <span style="background-color: #ffffff; color: #2a2a2a; font-family: Arial; font-size: 10pt; vertical-align: baseline;">.04 ||  ||   ||   ||
 * <span style="background-color: #ffffff; color: #2a2a2a; font-family: Arial; font-size: 10pt; vertical-align: baseline;">Course of pain intensity due to CNLBP in the previous 3 mo (1=increase of pain) || <span style="background-color: #ffffff; color: #2a2a2a; font-family: Arial; font-size: 10pt; vertical-align: baseline;">1.05 || <span style="background-color: #ffffff; color: #2a2a2a; font-family: Arial; font-size: 10pt; vertical-align: baseline;">0.84–1.32 || <span style="background-color: #ffffff; color: #2a2a2a; font-family: Arial; font-size: 10pt; vertical-align: baseline;">.65 ||  ||   ||   ||
 * <span style="background-color: #ffffff; color: #2a2a2a; font-family: Arial; font-size: 10pt; vertical-align: baseline;">Course of pain intensity due to CNLBP in the previous 3 mo (2=decrease of pain) || <span style="background-color: #ffffff; color: #2a2a2a; font-family: Arial; font-size: 10pt; vertical-align: baseline;">1.66 || <span style="background-color: #ffffff; color: #2a2a2a; font-family: Arial; font-size: 10pt; vertical-align: baseline;">1.05–2.62 || <span style="background-color: #ffffff; color: #2a2a2a; font-family: Arial; font-size: 10pt; vertical-align: baseline;">.03 ||  ||   ||   ||
 * <span style="background-color: #ffffff; color: #2a2a2a; font-family: Arial; font-size: 10pt; vertical-align: baseline;">Education level ||  ||   ||   || <span style="background-color: #ffffff; color: #2a2a2a; font-family: Arial; font-size: 10pt; vertical-align: baseline;">1.45 || <span style="background-color: #ffffff; color: #2a2a2a; font-family: Arial; font-size: 10pt; vertical-align: baseline;">1.01–2.07 || <span style="background-color: #ffffff; color: #2a2a2a; font-family: Arial; font-size: 10pt; vertical-align: baseline;">.04 ||

First looking at 5 month follow-up, the prognostic factors with an OR > 1 were: “AUC of this model was 0.68 AUC and the explained variance was 12.8%” (3) When looking at the 12 month follow-up, the prognostic factors with an OR > 1 were: “AUC of this model was 0.66 AUC and the explained variance was 10.7%” (3) “AUC of 0.5 to 0.7 is considered moderate discrimination” (3) “Explained variance ranged between 2.7% and 12.8%, which indicates that other potential prognostic factors (eg, physical parameters) should be considered to predict recovery of a patient” (3)
 * Being married or living with one adult
 * Younger age
 * Decreased course of pain in 3 months prior to baseline
 * More work participation at baseline
 * Being married or living with one adult
 * Younger age
 * Higher education level


 * ** How prognostic factors (predictive or non-predictive) affect PT? **
 * ** Patient-Therapist Relationship **
 * “One of the features of this study is the uniformly low expectations that both patients and professionals had of one another, and the great sense of pessimism that pervaded their accounts of medical encounters.” (12)
 * **Patient Education (13)**
 * Attempt to categorize patients according to the Fear Avoidance Beliefs model by misinformed avoiders, learned pain avoiders, affective avoiders and use different treatment strategies to target these beliefs
 * If treating a patient who is still in the subacute phase of injury, provide education regarding fears and beliefs to avoid poor outcomes.
 * “A chronic population has already solidified their beliefs and there may be less variation in beliefs about the effect of activity on pain in this group. Therefore, it makes sense that these beliefs are more important in guiding the course of LBP during the subacute phase, when individuals are at risk of becoming chronic and beliefs may be more disparate”
 * “Our findings emphasize the importance of fear avoidance beliefs as a potentially modifiable belief in subacute LBP”
 * “The most promising variable over the 12 months appears to be staying at work at baseline. This variable may be relevant for clinicians and occupational health physicians in advising their patients with respect to treatment strategy and optimal chance to improve over time” (9)
 * **Return to Work Consultation** (8) (13)
 * A return to work consultation can be used to evaluate a patient’s ability to return to their former job and brainstorm accommodations that may need to take place at patient’s workstation.
 * Low back pain is a pathological model where individual fears and beliefs play an important role in the progression of the disease. A return to work consultation can provide a time for the clinician to address these false fears and beliefs and provide information regarding diagnosis, care, and prognosis.
 * Patients with higher anxiety and more fears and beliefs will most likely require additional education.
 * It is important to remember that a clinician's attitude towards low back pain can have an effect on the message delivered.
 * Avoid using over-medicalized terminology and support oral messages with written information when possible.
 * Limit information to 3 to 5 messages that remind patients that low back pain is due to multiple factors and occupational factors are one of the modifiable factors that can affect low back pain.
 * Poor quality communication between patient and practitioner has been shown to have a negative impact on patient outcomes.
 * Need to take into account “yellow flags” including emotional issues, inappropriate attitudes, behavior towards pain, and inappropriate pain-coping behaviors.
 * Negative representations patients have about their pain and “fears and beliefs” regarding consequences on continuing working are major determining factors of LBP incapacity.
 * If a patient has cases of repeated or long term sick leave >4 weeks it is recommended to explicitly explain to the patient the link between “fears and beliefs”, low back pain, and return to work.
 * Assess psychological risk factors when pain lasts longer than 4 weeks. Use targeted interventions to address high fear avoidance beliefs to lead to better outcomes.
 * Recommended to evaluate a patient early on and repeatedly looking at pain, functional incapacity and its impact, and the main factors relating to work-related long-term disability
 * Use physical tests to evaluate functional capacity and make recommendations to provide advice regarding safe return to work and safe activities to perform.
 * Perform functional capacity tests each time a significant absenteeism or decrease in activity is noted.
 * Periodically assess the patient’s progress and provide them with feedback - ENCOURAGE AND SUPPORT THEM.
 * “The pre-RTW consultation is also the perfect time to remind workers that it is not necessary to wait for the complete disappearance of the symptoms to RTW and that an early RTW does actually improve the prognosis, given that job accommodations are made when necessary (Grade A) and to evaluate, in partnership with the employee the eventual need to implement a job retention approach (Grade AE)”
 * “It is also recommended to encourage worker to continue or resume physical activities, and if possible, returning to work taking into account the characteristics of the job context and the possibilities of job accommodations (Grade A)”. In fact, it is important to underline that long-term rest can promote chronicity and slow down the rehabilitation and that conversely, staying active, continuing normal activities, decreases chronic impairments and the risk of recurrence while promoting an earlier RTW”

media type="youtube" key="BOjTegn9RuY" width="560" height="315"


 * ** Considerations/Questions **
 * ** Obesity **
 * Interesting we found stuff on glucose, BP, triglyceride, and cholesterol but not about weight or obesity being a factor
 * ** Posture **
 * ** Work History **
 * ** Ulterior Motive **
 * Secondary factor (i.e. depression)
 * Not willing to work because low QOL, low job satisfaction
 * Legal Involvement
 * During the chronic phase of LBP, there was strong evidence for a negative association reported between attorney involvement and RTW (1)\


 * ** Closing Statement **[[image:https://lh6.googleusercontent.com/b0PfgVFJbkw_o-kfb02R_3wyuyK92gJ8pg-1kLXkDlFGLV4Mb6UeRWrRZ94OkIFy-27JbcYmwrzJCNhyt9c_H8zR1Wbn7IsEX55ZYlm3mAXeC1q3VzGY7gHIxF-zhWg5Eh9BZ5hA width="215" height="215" align="right"]]
 * Prognosis is “**moderately optimistic**” for patients with chronic low back pain (10)
 * Patient outlook is key
 * Prognosis is best made on a patient-to-patient basis

**References**:
 * 1) Steenstra, I.A., Munhall, C., Irvin, E. et al. J Occup Rehabil (2016). doi:10.1007/s10926-016-9666-x
 * 2) Verkerk, K., Luijsterburg, P.A.J., Heymans, M.W., Ronchetti, I., Pool-Goudzwaard, A.L., Miedema, H.S. and Koes, B.W. (2015), Prognosis and course of pain in patients with chronic non-specific low back pain: A 1-year follow-up cohort study. EJP, 19: 1101–1110. doi:10.1002/ejp.633
 * 3) Karin Verkerk, Pim A.J. Luijsterburg, Martijn W. Heymans, Inge Ronchetti, Annelies L. Pool-Goudzwaard, Harald S. Miedema, Bart W. Koes; Prognosis and Course of Disability in Patients With Chronic Nonspecific Low Back Pain: A 5- and 12-Month Follow-up Cohort Study. Phys Ther 2013; 93 (12): 1603-1614. doi: 10.2522/ptj.20130076
 * 4) Karin Verkerk, Pim A.J. Luijsterburg, Harard S. Miedema, Annelies Pool-Goudzwaard, Bart W. Koes; Prognostic Factors for Recovery in Chronic Nonspecific Low Back Pain: A Systematic Review. Phys Ther 2012; 92 (9): 1093-1108. doi: 10.2522/ptj.20110388
 * 5) Chapman JR, Norvell DC, Hermsmeyer JT, et al. Evaluating common outcomes for measuring treatment success for chronic low back pain. Spine. 2011;36(21 Suppl):S54–68. http://dx.doi.org.proxy.kumc.edu:2048/10.1097/BRS.0b013e31822ef74d. Medline:21952190 [PubMed]
 * 6) Opsahl, J., Eriksen, H. R., & Tveito, T. H. (2016). Do expectancies of return to work and Job satisfaction predict actual return to work in workers with long lasting LBP? BMC Musculoskeletal Disorders, 17, 481. [|__http://doi.org/10.1186/s12891-016-1314-2__]
 * 7) "Back Pain Fact Sheet", NINDS, Publication date December 2014. NIH Publication No. 15-5161
 * 8) A. Petit, S. Rozenberg, J.B. Fassier, S. Rousseau, P. Mairiaux and Y. Roquelaure Annals of Physical and Rehabilitation Medicine, 2015-10-01, Volume 58, Issue 5, Pages 298-304, Copyright © 2015 Elsevier Masson SAS
 * 9) Verkerk K, Luijsterburg PA, Pool-Goudzwaard A, et al. Prognosis and course of work-participation in patients with chronic non-specific low back pain: a 12-month follow-up cohort study. J Rehabil Med 2015; 47:854–859. [PubMed]
 * 10) Costa Luciola da C Menezes, MaherChristopher G, McAuley James H, Hancock Mark J, Herbert Robert D, Refshauge Kathryn M et al. Prognosis for patients with chronic low back pain: inception cohort study BMJ 2009; 339 :b3829
 * 11) Carolyn Chew-Graham, Carl May; Chronic low back pain in general practice: the challenge of the consultation. Fam Pract 1999; 16 (1): 46-49. doi: 10.1093/fampra/16.1.46
 * 12) Andersson H, Ejlertsson G, Leden I. Widespread musculoskeletal chronic pain associated with smoking. An epidemiological study in a general rural population. Scand J Rehabil Med. 1998 Sep;30(3) 185-191. PMID: 9782546.
 * 13) Wertli MM, Rasmussen-Barr E, Weiser S et al. The role of fear avoidance beliefs as a prognostic factor for outcome in patients with nonspecific low back pain: a systematic review. Spine J 2014;14:816–36.e4. doi:10.1016/j.spinee.2013.09.036 [PubMed]
 * 14) Evans, M. (Producer). (2014, January 24). Low Back Pain [Video file]. Retrieved April 3, 2017, from https://www.youtube.com/watch?v=BOjTegn9RuY&t=177s