Table 1. Characteristics of the clinical effectiveness studies included into the quantitative synthesis of Chiropractic care for non-specific low back pain.

First Author, Year, Country and Setting	Participants and Indication	Comparative Treatments	Follow-up assessment	Relevant outcomes
- Bronfort 2011[50] - USA, University research clinic in Bloomington, MN	18 to 65 years old with mechanical LBP of at least 6-week duration with or without radiating pain. (sub-acute/chronic)	• Chiropractic care once to twice per week for 15 to 30 minutes including: SMT and few minutes of soft-tissue massage, ice, or heat (n = 100). • Supervised exercise therapy provided by exercise therapists (n = 100).	• Total: 1 year • Relevant for this review: 1 month (week 4), 3 months (week 12), 12 months (week 52)	- Functional status (Roland-Morris 0–23) - Health related quality of life (SF-36 physical and mental scales) - Global improvement (1 = complete improvement, 9 = twice as bad) - Adverse events
- Cherkin 1998 [51] - USA, Group Health Cooperative of Puget Sound (HMO), Seattle, WA	Patients 20 to 64 years of age who saw their primary care physician for low back pain and who still had pain seven days later. (mix/not specified)	• Chiropractic care: according to usual clinicians procedures including recommendations about exercise and activity restrictions (n = 122). • Physical therapy care: provided by therapists trained by the McKenzie Institute faculty. Subjects received McKenzie’s Treat Your Own Back book and a lumbar-support cushion. Therapists were instructed to avoid therapies such as heat, ice, transcutaneous electrical nerve stimulation, ultrasonography, and back classes (n = 133).	• Total: 2 years • Relevant for this review: 1 month (week 4), 3 months (week 12)*	- Functional status (Roland-Morris 0–24) - Adverse events
- Herzog 1991 [52] - Canada, Unknown setting in Calgary, Alberta	Ambulatory patient between 18 and 50 years old with a sacroiliac joint problem since at least one month. (sub-acute/chronic)	• Chiropractic care: SMT and the optimal treatment modality to the discretion of the chiropractor** for 10 sessions over 4 week (n = 16). • Physical therapy care: back school therapy for 10 sessions over 4 week (n = 13).	• Total: 1 month (week 4, treatment completion) • Relevant for this review: none	- Actual pain (VAS 0–10) - Functional status (Oswestry 0–100)
- Hurwitz 2002 [45, 46] - USA, 3 Primary Care Centers of a 100 000 member health-care network based in southern California	HMO member of at least 18 years old with a complaint of low back pain with or without leg pain. (mix/not specified)	• Chiropractic Care: SMT, instruction in strengthening and flexibility exercises, and instruction in proper back care (n = 169). • Medical care: One or more of the following: instruction in proper back care and strengthening and flexibility exercises; prescriptions for pain killers, muscle relaxants, anti-inflammatory agents, and other medications used to reduce or eliminate pain or discomfort; and recommendations regarding bed rest, weight loss, and physical activities (n = 170).	• Total: 1.5 year • Relevant for this review: 1 month (week 6), 12 months	- Average pain (VAS 0–10) - Functional status (Roland-Morris 0–24)Adverse events
- Meade 1990 [43, 44] - United-Kingdom, 11 centres with hospital and chiropractic clinics within a reasonable distance	Patients 18 to 65 years of age with low back pain of mechanical origin. (mix/not specified)	• Chiropractic care: at the discretion of the chiropractor for a maximum of 10 treatments over one year. The treatments were intended to be concentrated within the first 3 months (n = 384). • Physiotherapy care: within hospital outpatient clinics (n = 357).	• Total: 3 years • Relevant for this review: 1 month (week 6), 1 year	- Functional status (Oswestry 0–100) - Global improvement (Number of patients partially or complete relieved)
- Petersen 2011[53] - Denmark, Primary care specialist center in Copenhagen	Patients of 18 and 60 years of age suffering from LBP with or without leg pain since more than 6 weeks. (sub-acute/chronic)	• Chiropractic care: all type of manual technique including SMT and myofascial trigger-point massage at the discretion of the chiropractor for a maximum of 15 treatments in a 12 weeks period. Mobilizing exercises, alternating lumbar flexion/extension movements, and stretching, were allowed (n = 175). • Physical therapy care: according to the McKenzie treatment protocols. An educational booklet about self-care or a “lumbar roll” for the seated posture were sometimes provided to the patient (n = 175).	• Total: 12 months (post-treatment completion) • Relevant for this review: 3 months (treatment completion (12 week)), 12 months (post-treatment completion)	- Functional status (Roland-Morris 0–23) - Back and leg pain (0–60 scale from 6 VAS (actual, worst, average)) - Health related quality of life (SF-36 general health perception and mental health scales (0–100)) - Global improvement (Number of patients scoring completely cured_ or much improved on a 6-point Likert scale (much worse, worsened, no change, improved, much improved, completely cured))

HMO: Health Maintenance Organization; SMT: Spinal Manipulative Therapy; VAS: Visual Analog Scale

* Results for the one-year follow-ups were only provided graphically and could not be used for this review

** Precisions regarding the chiropractic care modalities obtained from communication with the study authors