Table 2 Descriptions of 20 studies included in a systematic review of anatomical mechanisms of spinal manipulation
First author year of publication | Mechanism(s) of spinal manipulation investigated | Study design | Study setting | Study cohort | Sample size: – N cases – N controls (or control interventions) | Control group description | Spinal region(s) | Outcome variable(s) | Instrument(s) used for measurement | Time interval between spinal manipulation and measurement |
|---|---|---|---|---|---|---|---|---|---|---|
Jirout 1972 | Change in vertebral position | Uncontrolled intervention | – | Humans with palpatory finding of a “blocade” on lateral flexion of neck | 250: − 250 − 0 | N/A | Cervical | Vertebral segment position change | Plain radiography | – |
Cramer 2000 | Increase in facet joint space | RCT | Chiropractic school, USA | Healthy adults, 22–29 yrs | 16: − 8 (2 groups of 4) − 8 (2 groups of 4) | (i) Neutral position (ii) Side posture position | Lumbar | Facet joint space change | MRI | “Immediately” |
Cramer 2002 | Increase in facet joint space | RCT | Chiropractic school, USA | Healthy adults, 22–30 yrs | 64: − 32 (2 groups of 16) − 32 (2 groups of 16) | (i) Neutral position (ii) Side posture position | Lumbar | Facet joint space change | MRI | “Immediately” |
Cascioli 2003 | (i) Increase in facet joint space (ii) Formation of intra-articular gas bubbles | Uncontrolled intervention | Medical teaching hospital, South Africa | Chiropractic students, 23–24 yrs, without cervical complaints | 2: − 2 − 0 | N/A | Cervical | (i) Facet joint space change (ii) Intra-articular gas bubble formation | Plain radiography | “Immediately” |
Lisi 2006 | Change in intervertebral disc pressure | Feasibility | - | Healthy adults, 41–42 yrs | 1: − 1 − 0 | N/A | Lumbar | Intervertebral disc pressure | Pressure sensor probe | Immediately and for 15 s after spinal manipulation |
Brenner 2007 | Change in multifidous muscle thickness | Case report | Army facility, USA | Male, 33 yrs, chronic LBP | 1: − 1 − 0 | N/A | Lumbo-pelvic | Thickness of multifidus at rest | Diagnostic ultrasound | “Immediately” |
Haussler 2007 | Change in spinal stiffness | Crossover | Equine research park at a university, USA | Healthy adult horses with 2 pins in spinous processes to simulate acute back pain | 10: − 10 − 10 | 7-day washout before crossover; Control was no intervent | Thoracic Lumbar | Spinal stiffness | Cable extensometer Pressure sensor mat | – |
Raney 2007 | Change in lateral abdominal muscle thickness | Prospective case series | Army facility, USA | Adults, 18–53 yrs, acute/subacute LBP, SMT responders | 9: − 9 − 0 | N/A | Lumbo-pelvic | Thickness of lateral abdominal muscles at rest | Diagnostic ultrasound | “Immediately” |
Wynd 2008 | Further damage to already damaged arteries | Uncontrolled intervention | University lab, Canada | Dogs | 10: − 0 − 0 | N/A | Cervical | Increase in dimensions of vascular lesion | Intravenous diagnostic ultrasound Fluoroscopy | - |
Palmer 2009 | Change in vertebral position | Retrospective case series | Private chiropractic clinic, USA | Chiropractic patients, 18–65 yrs, non-migraine headache | 35: − 35 − 0 | N/A | Cervical | Vertebral segment position change (“atlas laterality”) | Plain radiography | “Immediately” |
Cramer 2011 | Increase in lumbar facet joint space | Feasibility | Chiropractic school, USA | Healthy adults, 25–27 yrs | 5: − 5 − 0 | None, but cavitated joints were compared with non-cavitated | Lumbar | Facet joint space change | MRI for gapping; Accelerometer for cavitation | “Immediately” |
Fritz 2011 | Change in spinal stiffness | Prospective case series | – | Physiotherapy patients, 19–60 yrs, LBP with or without leg symptoms | 51: − 50 − 0 | N/A | Lumbo-pelvic | Spinal stiffness | Mechanical indentation device | “Immediate” |
Konitzer 2011 | Change in thickness of transverse and internal oblique abdominal muscles | Prospective case series | Army facility, USA | 11F, 8M, 21–46 yrs, chronic LBP who met a clinical prediction rule for lumbar stabilization | 19: − 19 − 0 | N/A | Lumbo-pelvic | Thickness of transverse and internal oblique abdominal muscles at rest | Diagnostic ultrasound | “Immediately” |
Puentedura 2011 | Change in thickness of transverse abdominal muscles | Crossover, randomised | University, USA | 19F, 16M, 21–34 yrs, asymptomatic university staff and students | 35: − 35 − 35 | 19F, 16M, 21–34 yrs, asymptomatic university staff and students | Lumbar | Thickness of transverse abdominal muscle at rest | Diagnostic ultrasound | “Immediately” |
Cramer 2012 | Increase in facet joint space | RCT | Chiropractic school, USA | Healthy adults, 18–30 yrs | 40: − 30 − 10 | No SMT; Also cavitated joints were compared with non-cavitated | Lumbar | Facet joint space change | MRI for measuring facet joint space; accelerometer for cavitation | “Immediately” |
Barnes 2013 | Change in myofascial hysteresis | RCT | Private osteopathic college lab, USA | NR | 80: − 40 − 40 | NR | Cervical | Change in tissue texture characteristics | Durometer | “Approx 10 min” |
Wong 2015 | Change in spinal stiffness | Non-randomised controlled study | – | 18–60 yrs, LBP, SMT responders | 107: − 32 (15 previously identified SMT responders, 17 non-responders) − 75 | (i) 59 asympto-matic (to session 1); 57 for sessions 2 and 3 who did not receive SMT − 16 w/LBP that did not receive SMT | Lumbo-pelvic | Spinal stiffness | Mechanical indentation device | “Immediate” |
Haavik 2016 | Change in pelvic floor muscle thickness | Crossover, unrando-mised | Chiropractic school, New Zealand | Healthy pregnant, 18–38 yrs | 26: (i) 11 pregnant (ii) 15 non-pregnant (i) 15 non-pregnant (ii) 11 pregnant | Non-pregnant chiro-practic students, 19–32 yrs | Unspeci-fied spine and/or pelvis | Thickness of levator hiatus muscles at rest | Transperineal diagnostic ultrasound | (i) Same day for pregnant participants (ii) Not reported for nonpregnant |
Flaum 2017 | Change in vertebral position | RCT | Medical school, USA | Asymptomatic medical students, 22–40 yrs | 51: − 25 − 26 | Asympto-matic medical students, 22–40 yrs | Cervical | Tissue depth to articular pillar compared bilaterally (proxy for vertebral rotation) | Diagnostic ultrasound | “Immediately” |
Fosberg 2019 | Change in transverse abdominal muscle thickness | RCT | University and private clinic, USA | 18–70 yrs, LBP, SMT responders | 67: − 33 − 34 | 18–70 yrs, LBP, SMT responders | Lumbar | Thickness of transverse abdominal muscles at rest | Diagnostic ultrasound | “Immediately” |