Do spinal mobilization / manipulation techniques have a role in treatment of patients with LBP?
When I first trained to graduate as a physiotherapist, I learned techniques to mobilize joints of the back. At this point of my life I had absolutely no idea of any form of critical thinking. When I began my MSc, I discovered that physiotherapy existed in social media. I started to witness a debate opposing those for and those against manual therapy. I could not know who was right, so I probably decided to believe the group that created the less “dissonance” with what I learned, and the postgraduate courses I paid for. Then during my MSc postgraduate training, I have been asked to explain why I was using such techniques. This question made me stop and realize that I did not know why I used them. I just did it because I was taught to and because I read experts physios on social media that seemed to encourage it. With some step back and information about cognitive bias, I then reached the following conclusion. I did not know why I used these techniques, and my relationship with manual therapy belonged more to faith than science. Now that I learned to think, research and critique information, I will attempt to give some insights on the effects of spinal mobilizations and manipulations techniques in the field of manual therapy, hoping that it will encourage readers to reflect on their own practice too. The techniques discussed in my blog will be the passive accessory intervertebral movements (PAIVMS), passive physiological intervertebral vertebral movements (PPIVMS), the mobilization with movement (MWM) called sustained natural apophyseal glide (SNAG) when applied to the spine and grade 5 manipulation techniques. I will use the “spinal mobilization and manipulation therapy” SMMT acronym to encompass the aforementioned techniques.
Why do spinal mobilization and manipulation techniques work? What are the current hypotheses regarding their effects?
When I reviewed literature, I found that the mechanisms underlying SMMT are not yet fully understood. However, three main mechanisms are used to discuss their effects. The mechanical effects, the neurophysiological effects and the non-specific effects. Each of these will be discussed in a separate paragraph through the blog.
The mechanical effects are all effects that can be produced only by mechanical and biomechanical properties of tissues affected by the technique. One of the first hypothesis regarding the manual therapy’s techniques was that they could “detect and correct biomechanical faults” (Joel E. Bialosky, George, & Bishop, 2008). It also was first hypothesis of Brian Mulligan to explain the good outcomes he had with his MWM as he proposed the “positional fault hypothesis” (PFH) in 1989. These similar hypotheses seem not supported by evidence for several reasons. First because the existence of the “faults” has not yet been demonstrated. Measuring them validly and reliably remains difficult even when using powerful imagery techniques, although it was studied in peripheral superficial joints (Vicenzino, Hing, Rivett, & Hall, 2011). This is all the more complicated for clinicians and regarding the lumbar spine’s joints that are not directly accessible to visual inspection and manual palpation. Secondly, in lumbar spine, clinicians seem unable to agree on the location of the “fault” (Seffinger et al., 2004). In this systematic review the research team noticed that the majority of spinal palpatory diagnostic procedures are not reliable and regarding lumbar spine, that regional is superior to segmental range of motion assessment. In other words, we could say that it is not possible to identify reliably a segmental “fault” in the lumbar spine through manual palpation. Another interesting element that is discussed by (Seffinger et al., 2004) is: what is the clinical relevance of the “fault” ? Only 26% of included studies recruited only symptomatic subjects and 17% had recruited both symptomatic and asymptomatic persons. This information leads to a major questioning of the relevance of what clinicians may find during these types of palpatory procedures. Furthermore, it is not yet understood how positional faults could impact pain and range of motion. Some authors proposed models in which the positional faults could contribute to repetitive stress potentially leading to pain and / or tissue failure (Comerford & Mottram, 2001; Dye, 2005). Even though the theory is conceptually attracting, it remains experts’ opinion and low-level evidence. The third point that tends to be conflicting regarding the biomechanical fault hypothesis is about the specificity of the intervention itself. Indeed, the application of a passive physiological or accessory movement to a precise segmental joint in the lumbar spine may not be supported by literature (Lee & Evans, 1997). For example, during a prone posteroanterior mobilization, the force spreads through a large area moving several joints and all surrounding soft tissues. The movement affects every joint of the lumbar spine. The whole extension movement is a three-point bending between the ribcage and the pelvis. A posterior translation of vertebras superior to the point of applied force occurs while the inferior joints translate anteriorly (Lee & Evans, 1997). It is then difficult to admit that a technique that cannot aim a specific area could correct a “positional fault” which is barely identifiable with extremely developed imagery. All this again shows that the hypothesis of a biomechanical fault that would be corrected through manual therapy by the clinician cannot currently be identified as a fully or partly responsible for SMMT’s effects.
The lack of support of this theory does not imply that SMM techniques do not have any mechanical effect. Indeed, human tissues demonstrate viscous and elastic characteristics and hence react to viscoelastic properties like “creep” and “preconditioning”. The creep phenomenon is the elongation of a viscoelastic structure subject to a constant force which is lesser than its rupture point (Twomey & Taylor, 1982). In other words, while applying a constant strain on a tissue, it will elongate through time. This phenomenon is probably due to the modification of water distribution and collagen fibers’ position within the structure (Carlstedt & Nordin, 1989). Creep increases with load, progresses with time and is age dependent (Twomey & Taylor, 1982).In lumbar spine, sustained loading of a posteroanterior force at L4 level during 30 seconds showed the greatest amount of creep and then decreased with time (Evans, 1992). The preconditioning phenomenon occurs when applying a cyclic loading to a vertebra leading to an increase of displacement with each loading cycle. The effect of preconditioning decreases with each cycle (Evans, 1992; Lee & Evans, 1994). Nevertheless, the effects of creep and preconditioning are reversible, and unloaded structures tend to return to their original size (Lee & Evans, 1994). Recovery time has been shown to be longer than creep to occur, but half of the creep effects disappears within two minutes in lumbar spine of young subjects after twenty minutes of seated full flexion. (McGill & Brown, 1992). In study by (Solomonow et al., 2000) after 50 minutes of cyclic loading of cats’ supra-spinal ligament 17% of creep had recovered after 10 minutes and 92% after 7 hours. In the study by (Lu, Solomonow, Zhou, Baratta, & Li, 2004), after 7 hours rest, 64,4% of creep effect was still present. The duration of creep or preconditioning cannot be precisely estimated clinically because the studies mentioned above are laboratory studies, some studied animals’ tissues, and the holding duration is not representative of the clinical encounter. The point I am trying to raise is simply that some (temporary) mechanical effect is produced during mobilization and cannot be denied, however it does not seem responsible for the efficacy of the techniques alone either.
To summarize this paragraph, it can be said that transient mechanical effects are likely to happen during mobilization and may be sufficient to produce immediate increase in range of motion but there is insufficient evidence to support the positional-fault hypothesis and their correction with SMMT.
With the increasing knowledge in neuroscience and the difficulties faced when trying to prove the biomechanical effects of manual therapy; new hypothesis emerged. The neurophysiological effects are the other main category of effects that could be responsible for the efficacy of manual therapy techniques. They are mainly subdivided in three areas. The local analgesic mechanisms, the spinal cord mediated mechanisms and the supra-spinal mechanisms.
Regarding the local analgesia, evidence is lacking. The theory is that mobilizations and manipulations could have an anti-inflammatory effect. This explanation was developed because some studies showed concurrent to local hypoalgesia measured through pressure pain threshold : an increase in blood’s substance P level following cervical and dorsal manipulation (Molina-Ortega et al., 2014); or a raise in blood’s production of inflammatory cytokines unrelated to substance P levels following upper thoracic manipulation (Teodorczyk-Injeyan, Ruegg, & Injeyan, 2006) or sympathoexcitation after MWM. The primary hypoalgesia does not appear linked with endogenous opioid system (Vicenzino, Paungmali, & Teys, 2007). However, this theory implies that an inflammatory response is the origin of low back pain which has not been demonstrated. In addition, the aforementioned studies were done on asymptomatic subjects and the measures were at a global scale (blood level) and not locally. It is then difficult to link these observations with the local hypoalgesic effect. Moreover, we don’t know to what extent this increase in substance P in the participants’ blood can affect pain or range of motion in patients. More research is needed to ascertain the involvement of these local analgesic mechanisms, but literature tends to show their existence without explaining their impact. In conclusion, local analgesia measured with pressure pain thresholds exists after mobilizations and manipulations, but we are unable to understand the mechanisms explaining it at a local level.
The spinal cord-mediated mechanisms are another area studied that is thought to be involved in effects of SMMT. According to (Pickar & Bolton 2012) manipulations could stimulate joint’s mechanosensitive paraspinal primary afferent neurons. They then hypothesized that this primary afferent discharge could inhibit joint’s nociceptors’ activity. Their reasoning relies on the “Pain Gate Theory” of (Melzack & Wall 1965) in which mechanoreceptors could, in dorsal horn of spinal cord, inhibit the afferent activity of nociceptors. Other studies showed that SMMT could impact temporal summation. Temporal summation is a phenomenon of increase in pain when a constant nociceptive stimulus is applied with a precise frequency. It is a phenomenon known to be occurring in central sensitization and this wind-up phenomenon is happening at level of spinal horn (J. E. Bialosky, Bishop, Robinson, Zeppieri, & George, 2009; Bishop, Beneciuk, & George, 2011). In studies on healthy participants, decrease in temporal summation has been showed after manipulation at lumbar and thoracic levels (Bishop et al., 2011; George, Bishop, Bialosky, Zeppieri, & Robinson, 2006). It was also shown to be reduced after SMMT in low back pain participants (J. E. Bialosky et al., 2009). The effect is thought to be local, as the measures taken above the manipulated area had no change in temporal summation. However, it is yet unknown how a short stimulus could modify efferent pathways for a longer duration lasting after the end of the mobilization or manipulation. (Boal & Gillette, 2004) studied the neuronal plasticity of spinal cord’s neurons. They suggested that manual therapy could provoke long term depression of neurons in dorsal horn leading to reduced central sensitization. In the other hand, an animal study (Skyba, Radhakrishnan, Rohlwing, Wright, & Sluka, 2003) in which they blocked specific neurotransmitters showed that the analgesia obtained after mobilization does not seem affected by dorsal horn mechanisms. So, it is currently still unclear how this hypothesis of spinal cord mediation of pain could be responsible for SMMT’s efficacy.
The third theory that has been studied is involving the supraspinal mechanisms. It is thought that SMMT can stimulate descending pain inhibitory pathways from periaqueductal grey matter (PAG). The study of (Hosobuchi, Adams, & Linchitz, 1978) showed that electric stimulation of periventricular and periaqueductal gray matter can create hypoalgesia in human. This reduction in pain can be inhibited by naloxone which implies that brain can produce analgesia through morphine-like substances. (Skyba et al., 2003) showed that SMMT is likely to stimulate the PAG increasing release of spinal serotonin and noradrenalin hence hypoalgesia, but they showed that this pathway was non-opioid mediated. Systematic reviews seems to agree on the fact that SMMT creates immediate hypoalgesia effect (Lascurain-Aguirrebena, Newham, & Critchley, 2016; Millan, Leboeuf-Yde, Budgell, & Amorim, 2012; Voogt et al., 2015) at least on some nociceptive stimuli like pressure pain threshold but not thermal pain threshold. In contrast, research is conflicting regarding the location of effects as some authors claim that the effect is global with increased PPT at remote location (Coronado et al., 2012; Lascurain-Aguirrebena et al., 2016; Vicenzino, Collins, & Wright, 1996) while other systematic reviews are less conclusive saying that evidence is conflicting (Millan et al., 2012; Voogt et al., 2015). When using SMMT, in addition to hypoalgesia, concurrent sympathoexcitation has been demonstrated (Kingston, Claydon, & Tumilty, 2014) and seem correlated with it. Indeed, increase in skin conductance and decreased skin temperature has been measured in a RCT following cervical mobilization on 30 patients (Sterling, Jull, & Wright, 2001). They also measured decreased motor activity of neck flexor leading to hypothesize that the effects of manual therapy could be partly due to changes in muscles’ motor activity. This could be another element that might be a factor in reduction in pain and increase in patient’s ability to move following SMMT (Zusman, 1986). The model proposed is that muscle inhibition could concurrently to changes in nociception, reduce periarticular pressure hence reduction in pain.
To conclude, I would say that currently, precise supraspinal mechanisms responsible for effects of SMMT are unknown, but some evidence of its role has clearly been demonstrated and it is currently the most plausible hypothesis that has been investigated. However, a combination of all the previous hypothesis cannot be excluded either. The final effect might also be reached by a combination of many mechanisms from local, spinal-cord and supraspinal mechanisms.
The last point I would like to raise is about the nonspecific effects. As any type of treatment, it generates non-specific effects, so it is important to mention it. Placebo effect and other effects as patient-clinician relationship, expectations etc. are present in all type of treatment and cannot be avoided; so, we should always keep them in mind. In addition, non-specific effects are the reason why RCT that does not include control group and placebo like intervention group should be interpreted with caution. Manual contact has been proven to induce sympathoexcitation measured with increased skin conductance (Moulson & Watson, 2006; Petersen, Vicenzino, & Wright, 1993); but also increased activity of superficial neck flexors when hand contact with neck (Sterling et al., 2001). The patient’s beliefs about the benefits of the intervention seems linked with its results. In patients with neck pain, differences were found when comparing results of an intervention with patient’s expectation about it, showing better results when the patient had good expectations of relief from the technique (Bishop, Mintken, Bialosky, & Cleland, 2013). Another study was performed on patients with chronic low back pain and also showed better outcomes when the patient had good expectations of outcome. It also showed that the patient’s preference may influence the outcome. Patients expecting one type of treatment and receiving another one were less likely to improve than the one receiving the treatment they expected (Kalauokalani, Cherkin, Sherman, Koepsell, & Deyo, 2001). This is why it is an important part of evidence based practice to assess patients’ expectations and preferences and discuss treatment options with them (Sackett, Rosenberg, Gray, Haynes, & Richardson, 1996). The famous, well documented placebo effect also takes part into the global effect of SSMT. Its precise psychological mechanism of action is not fully understood but there is evidence of a lot of elements involved (Benedetti, 2005) that cannot be developed in this blog, as it is not its primary aim. Clinical outcomes are influenced by all kind of contextual elements ranging from the patient-physiotherapist’s relationship, the care settings, or personal features (of patient or therapist) (Testa & Rossettini, 2016). It has been shown that clinicians can positively or negatively influence outcomes with verbal suggestions (Van Laarhoven et al., 2011). All this illustrates well that SMMT’s efficacy can also be influenced positively or negatively with non-specific effects. So, there is no reason they would not be a part of SMMT’s efficacy and be reminded in their mechanisms of action.
Now that I have written this blog, I can eventually explain what science has proven regarding the effects of spinal mobilization and manipulation techniques. It has been proven that mechanical effects exist following SMMT. That neurophysiological effects like hypoalgesia (measured with increased pressure pain threshold, reduction in VAS scores and functional scores); sympathoexcitation (measured through skin temperature changes, skin conductance), and muscles motor activity changes are happening following SMMT. However, it is not precisely known yet how these parameters are modified at local, spinal-cord and supraspinal levels although some hypotheses have been formulated. From now on, every time I will use manual therapy techniques, I will be able to explain what I expect from it and be aware of current evidence regarding effects of spinal mobilization and manipulation techniques. This makes me less of a believer and more of an evidence based driven clinician.
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An interesting read. I just have a couple of questions and I will try to keep them short! You start talking about the accuracy of using palpation as a diagnostic tool to identify the structure at fault. You ask “How can I know that the ‘restriction’ noticed during my assessment is related to the patient’s presentation if it can be found in asymptomatic persons?” I would like to ask you isn’t this a similar issue to a lot of diagnostic testing in the physiotherapy world? Therefore, do you think you can still use this along with other subjective/objective information to support your hypothesis? If so, could you expand on how you would do this and what other information you could use to support your clinical rationale? Finally, I would ask how relevant is knowing the exact structure at fault in relation to getting the patient better and do you know of any evidence looking at this?
There are a few questions there which roll into one and hopefully you get my point.
Thank you for your questions Melissa.
Regarding the first part of your first question about the use of palpation: I completely agree with the fact that this issue is common in our practice. But knowing this does not give any justification for or against the use of palpation as a diagnostic tool. I would like to specify that I do not condemn the use of palpation for diagnostic purpose. My aim was to inform that alone, palpation of a hypothetical “positional fault” is not enough to link it with the patient’s issue, as these “faults” can be found in asymptomatic population. Therefore, it cannot be used to validate the hypothesis of positional faults to explain the efficacy of SMMT.
However, as you mentioned in the second part of your question, if these findings are linked with subjective assessment or symptom reproduction; then they might be useful for the clinician. (Rabey et al., 2017) Not that they would indicate a positional fault, but they could indicate a local tenderness to mobilisation or pressure that could be linked with other elements of the assessment. They could be used as an asterisk marker for the clinician and reassessed after SSMT treatment for example. So, I could use palpation in combination with symptom reproduction, limited range of motion, elements from the subjective assessment to get a global picture of the patient. But it would still not provide any information to support a positional misalignment of a vertebral segment. Indeed, there is no evidence of this theory as I explained it in the paragraph. To conclude, my point was not to blame the use of palpation in clinical practice as it provides information; it simply was to illustrate that it cannot explain in itself the theory proposed to explain the “positional fault hypothesis” which still has not been demonstrated.
Then to answer your second question about knowing the exact structure at fault, it is a really interesting topic even though it is more related to diagnosis of LBP and efficacy of SSMT than their effects. However, the assumption according to which knowing which structure is responsible for the patient’s issue is attractive. Especially when trying to figure out what is happening during the technique we perform. However, we saw in the blog that we cannot reliably identify the restricted level with palpation nor with imagery. Let’s imagine we could, would it be more efficient than applying SMMT randomly on the spine? Some articles seem to lead in this direction. (Aquino et al., 2009) showed in the cervical spine that improvement in pain is achieved irrespective of the location of the mobilisation in one session in a chronic cervical pain sample of patient. Regarding this study, several elements should be considered. The sample is relatively small. The random location is not developed and could be close enough to the most restricted segment to mobilise it too, especially in such a small area as cervical spine. As it has been shown in lumbar spine, mobilisation do not affect a precise joint but multiple joints around the point of application (Lee & Evans, 1997). Aquino’s study measured only pain response and did not evaluate mobility, and it was measured in chronic patients on the results of only one session of treatment without developing how long and how many repetitions were used. Then, it is difficult to draw firm conclusions against the use of targeted mobilisation. Another study also seems to suggest that directing a manipulation technique towards a precise or random location has the same effects. This study should also be interpreted carefully as the specific treatment used is not specific. Indeed, manipulations have been showed to occur in the whole thoracolumbar spine but that they could not be aimed at a segmental level (Bialosky, George, & Bishop, 2008). So, this study compares two non-specific techniques. Then it cannot be concluded that all SMMT can randomly be applied to produce effects. The third study is the most interesting and best conducted one. A study by (Donaldson, Petersen, Cook, & Learman, 2016), showed that lumbar segmental mobilisation in chronic low back pain patients do not differ whether it is performed on the most provocative level or on L4-5. One issue here is that the most painful level has not been assessed in patients receiving L4-5 mobilisation and a part of this group could have their tender spot on this location. The study showed no difference between groups. But it can be due to the absence of selection of patients that might be better responders to this type of treatment. Maybe if correctly identifying responders to SSMT, targeting the mobilisation on this subgroup of patient would be more beneficial; but this is still an under-studied area (Rabey et al., 2017) and it does not refute the study’s results in anyway. However, interestingly even though the study showed no difference in outcomes between groups, it still revealed a significantly better global rate of change (GROC) in the targeted mobilisation group at the 4th session and six-month follow-up. This result indicate that a difference might be achieved in some way. The GROC might be a tool which is global, it is still interesting. Indeed, as will be developed in part two and three and already mentioned in the previous part, SMMT needs to be viewed as a tool to improve the patient as a whole. Within a new framework in which through SMMT we can modify the patient’s symptom, and in combination with explanation about pain, bringing confidence in movement and empowering the patient to move; SMMT may still have an important role to play in rehabilitation.
To conclude I would say that these techniques have effects on the person for sure, but its mechanisms of action are more global than explained by “positional fault” theory initially introduced in 1989. However, even though SMMT cannot affect a precise vertebra, it is worth considering the location of maximal stiffness and symptoms while applying them. First because it is more likely to fit with the patient’s expectation or belief and hence increase non-specific effects (see part 3). Secondly, because we are not sure yet whether it can improve outcomes or not. If targeting a spinal level may or not improve outcome for some patients, it surely does not worsen results either. So, it is worth applying them on the most provocative location rather assuming that it does not make a difference. It does not require much more effort from the clinician to apply pressure on a spot or another, but it might lead to better outcomes. Then, I would definitely go for the most provocative one.
Aquino, R., Caires, P., Furtado, F., Loureiro, A., Ferreira, P., & Ferreira, M. (2009). Applying Joint mobilization at Different Cervical vertebral Levels does not Influence Immediate Pain Reduction in Patients with Chronic Neck Pain: A Randomized Clinical Trial. The Journal of Manual & Manipulative Therapy, 17(2), 95–100. https://doi.org/DOI: 10.1179/106698109790824686
Bialosky, J. E., George, S. Z., & Bishop, M. D.
(2008). How Spinal Manipulative Therapy Works: Why Ask Why? Journal of
Orthopaedic & Sports Physical Therapy, 38(6), 293–295.
Donaldson, M., Petersen, S., Cook, C., &
Learman, K. (2016). A Prescriptively Selected Nonthrust Manipulation Versus a
Therapist-Selected Nonthrust Manipulation for Treatment of Individuals With Low
Back Pain: A Randomized Clinical Trial. Journal of Orthopaedic & Sports
Physical Therapy, 46(4), 243–250. https://doi.org/10.2519/jospt.2016.6318
Lee, R., & Evans, J. (1997). An in vivo study
of the intervertebral movements produced by posteroanterior mobilization.
Clinical Biomechanics, 12(6), 400–408.
Rabey, M., Hall, T., Hebron, C., Palsson, T. S., Christensen, S. W., & Moloney, N. (2017). Reconceptualising manual therapy skills in contemporary practice. Musculoskeletal Science and Practice, 29, 28–32. https://doi.org/10.1016/j.msksp.2017.02.010