Manipulation - The Level of Evidence

Manipulation has been used for many centuries. The treatment involves the movement of a joint to its full range of movement and then taking it just a little further. This is usually applied to parts of the axial skeleton, most often the lumbar spine, less often the neck and sometimes the thoracic spine. It can be used on peripheral joints too but this article will concentrate on manipulation of the axial skeleton.

There has been considerable interest in "complementary and alternative medicine" with a House of Lords Select Committee Report in November 2000¹ and a subcommittee of the Royal College of Physicians set up to examine certain aspects. The latter reported in Clinical Medicine in 2003,² formerly the Journal of the Royal College of Physicians.
In the UK, 47% of people have used complementary and alternative medicine (CAM) at some time in their lives and 10% use some form of CAM each year.³ Users tend to be older, female and over 90% is purchased outside of the NHS. At least 10% of hospital physicians also use CAM as part of their clinical practice.⁴ A survey, conducted in 2001, estimated that one in two practices in England now offer their patients some access to CAMs.⁵ Of the various forms of CAMS, manipulation is amongst the most popular and is one that has had some effort made to give it an evidence base. The problems of proper trials will be discussed later.

Over the years manipulators have come from many backgrounds, including the very basic bone setters with little or no medical knowledge. Chiropractors and osteopaths are comparatively recent in origin and are unique amongst CAM practitioners in that they are regulated by Act of Parliament. There is a General Chiropractic Council and a General Osteopathy Council to oversee standards and registration. A number of doctors and physiotherapists also manipulate and there is nothing to prevent a totally unregistered practitioner from practising, so long as he does not pretend to be registered.

Techniques are legion, as are the schools of manipulation that are said to number nearly 150. The most important difference is the action of the rotation of manipulation. It may be a small range of movement with high velocity or a larger range of movement with low velocity. There is considerable debate about the relative safety and efficacy of each but very little evidence to support any proposition.

Manipulation should follow a proper history and examination to ascertain the nature and level of the lesion and to identify any contraindication to manipulation that may be present.

In the lumbar spine, flexion tends to fix the lower vertebrae so that a more flexed position will manipulate the higher levels and a more extended position will manipulate the lower levels. In the neck the opposite it true with flexion being used to manipulate lower levels and extension employed to manipulate higher levels.

The mode of action of manipulation in bringing relief, if it does so, is uncertain. The idea that it causes a slight subluxation of the joints that then pop back is not supported by the evidence. The clicking or popping sound that often accompanies manipulation can be most impressive but it is thought to represent gas bubbles in the stretched joint, as with clicking knuckles, and there appears to be no correlation between the presence or impressiveness of the sound and outcome.

The most feasible suggestion for the mode of action of manipulation is that it overstretches the nocioreceptors of the joints and, in doing so, closes the pain pathway as suggested by the gate theory of pain. This is probably similar to the mechanism of action of traction, that does not distract the vertebrae of the lumbar spine to any measurable amount, even with very heavy weights. The gate pathway is also overloaded by rubbing a pain or scratching an itch.

If the mechanism of action is overload of the pain pathways, then presumably manipulation under anaesthetic has no benefit. When orthopaedic surgeons perform MUA, the aim is often to break down adhesions.

Much has been made of the potential dangers of spinal manipulation and whilst they do exist, they have almost invariably been grossly overstated.

Before manipulating it is important to form a working diagnosis. This will involve history and examination but not normally special investigations and routine use of x-rays is to be depreciated. X-ray of the lumbar spine tends to offer little information for the dose of radiation equivalent to 120 chest x-rays. The diagnosis will usually be one of simple back pain. Sinister causes of back pain must be excluded. Manipulating a back that is weakened by Paget's disease, multiple myeloma or metastatic carcinoma may produce vertebral collapse. Cauda equina syndrome does not require manipulation. It requires instant referral to a neurosurgeon. Cauda equina compression resulting from manipulation is extremely rare.⁶ The ability to recognise red flags and to refer on rather than manipulating inappropriate cases is one reason for professional regulation. Despite the very widespread use of manipulation, serious complications as a result of manipulation of the lumbar spine are very few.

Where there have been problems from manipulation, they have far more often been from manipulating the cervical spine. The spinal cord fills far more of the vertebral foramen in the neck than in the lumbar region and so any problem, such as a small haematoma, is far more likely to impinge on the spinal cord. In addition, the shearing stresses of manipulation have been known to tear or cause dissection of the carotid or vertebrobasilar arteries. This can cause a stroke. In rheumatoid arthritis there is weakness of the ligament holding the odontoid peg and manipulation may cause slippage of the atlanto-axial joint with high spinal cord compression. Rheumatoid arthritis is an absolute contraindication to manipulation, especially of the neck.

Sometimes neurologists or neurosurgeons have scoured the neurology wards to find victims of manipulation and these small series can be very poignant. However, they give no indication of the degree of risk involved.⁷ It is difficult to estimate the number of manipulations performed annually as they are performed by so many people of such varied backgrounds. Stroke would seem to be a rare and unpredictable event following manipulation that cannot be blamed on any specific technique.⁸ Where estimates have been made they usually suggest that the risk of serious adverse outcome from manipulating the neck is between 2 per million and 0.5 per million procedures. The risk for the lower back is much lower. To put this into perspective, suppose that a practitioner manipulates 5 necks each morning and 5 each afternoon, 5 days a week, taking 2 weeks holiday a year. He would perform 2,500 manipulations of the neck per year. If his professional lifetime is 40 years, and most people work for less years and have more than 2 weeks holiday a year, he would perform 100,000 manipulations of the neck in his lifetime. If the risk of adverse outcome is 2 per million, then, on average, 1 practitioner in 5 would expect to have one adverse outcome in his entire professional lifetime. This is very much safer than the prescription of NSAIDs. One study concluded that based on the number of practicing chiropractors and neurologists in Canada, 1 of every 48 chiropractors and 1 of every 2 neurologists would have been made aware of a vascular complication from cervical manipulation during their practice lifetime. They estimated the risk of neurological complications as fewer than 1 in 5 million treatments.⁹

Risks have been calculated as per manipulation and not per patient. Patients usually require a course of treatment that involves several manipulations and the same person may return for treatment on a number of occasions. With such small numbers of complications and so many techniques, it is impossible to ascertain which are safer and which are more dangerous. Indeed calculations to determine the incidence of serious adverse effects are beset by the problem of knowing just how much manipulation is done each year.

The following should be seen as contraindications to manipulation at any level:

• Any potential sinister cause of back pain, including a history of malignancy that may involve bone such as breast cancer or haematological malignancy
• Patient on anticoagulants or clotting disorder¹⁰
• Any neurological disease
• Cauda equina syndrome
• Active inflammatory arthritis.

In addition, the following are contraindications to manipulation of the neck:

• Known cerebrovascular disease
• Hypertension not well controlled
• Rheumatoid arthritis.

In view of the increasing risk of sinister causes of back pain with advancing age and the increased incidence of arterial disease, increasing age should be seen as a relative contraindication to manipulation, especially for the neck. There is also increased risk of compression fractures with osteoporosis.¹¹

The gold standard for clinical research is the randomised controlled trial with double blind placebo. This is relatively easy for medicines as has been discussed in the article on homeopathy. For physical treatments, a placebo control is much more difficult,as has been discussed in the articles on acupuncture, reflexology and aromatherapy. For this reason, much of what we do in conventional medicine has a poor evidence base. This includes much physiotherapy and surgical interventions. Sham surgery would neither gain patient consent nor ethics committee approval but it is interesting to see how established treatments such as tonsillectomy and D&C have failed to withstand scrutiny.

For anyone wishing to undertake a RCT of manipulation, there are a number of problems to face.

• Some CAM practitioners complain that their treatment is "tailored" to the individual and as such is not applicable to a trial. This is not true. It is possible to go through all the motions except to give a sham treatment and someone who does not know whether the patient had the sham or the trial treatment makes the assessment.
• Over 90% of people pay for CAM treatment and so are likely to want what they pay for directly and not to risk paying to be in the control group. Trials within the NHS do tend to be easier to arrange.
• Often, manipulation is not the only modality of treatment. There may be analgesia prescribed and massage to reduce muscle spasm. This does not negate a trial so long as manipulation is the only variable.
• It is important to use a validated method to assess outcome. For manipulation this will usually be a validated pain and disability score such as the Oswestry score.
• Sham treatment can be very difficult to achieve. It should seem the same to the patient but it should not have any discernable benefit.
• Recruitment must precede randomization. The practitioner may feel that a certain patient would be a good or a poor candidate for the intervention and this may affect recruitment if the group is already known.
• Analysis must be by intention to treat. This means that if a patient is put in the manipulation group but perhaps pain and muscle spasm prevent the procedure, this must be analysed in the manipulation group and not in the control.

Of these problems, by far the most difficult is the matter of placebo control.

Placebo Control

The ideal placebo is, to the patient, in all ways like the intervention but has no effect. Sham manipulation can take several forms, none of which are satisfactory.

• The practitioners may take the joints through the range of movement but omit the final thrust. The final thrust, with or without the popping or cracking sound from the joints, is impressive and the patient is unlikely to be blind to the placebo state. There may also be some benefit from just taking the joints through to the extreme of movement. This is called mobilization rather than manipulation.
• The most common sham is to manipulate the wrong level. There are two problems with this.
  • One is that the segmental diagnosis is not very accurate. Spinal reflexes can mean that the apparent level of the lesions may be one or two dermatomes higher or lower than suspected.
  • The other is that it is not possible to be precise about exactly which level is manipulated. To say, "I am going to manipulate L2/3 but not L4/5" is fanciful.

These difficulties make placebo control very problematical and it is tempting to make any trial open label, meaning that the patient knows in which group he is. There are a number of problems with this:

• If manipulation has a strong placebo effect, this will be unbalanced without a control. The more we know about the placebo response, the more impressive it becomes.
• If other modalities such as analgesia and massage are involved, it may affect the subjects enthusiasm for these.
• Perhaps one group is sent to a chiropractor or osteopath and the other group is given a prescription and just sent home. A good practitioner will not only manipulate but will discuss such problems as ergonomics at work, in the car and at home as well as exercise and mobility. The fact that someone is also taking a great interest in the patient, talking to him and discussing the problems is also very therapeutic. Interaction with the practitioner is certainly very important in terms of patient satisfaction.¹²

In view of the immense difficulties of placebo control, an open label trial is very attractive. Some people may argue that a placebo response is not important so long as the patient gets better. Such trials are not without merit but they ask a different question. A placebo controlled trial asks, does manipulation produce benefit in its own right? An open label trial asks does manipulation and all that is involved therein, perhaps including a consultation with the practitioner, have benefit over other forms of management. The MRC conducted a trial to compare chiropractic manipulation with standard hospital outpatient treatment for mechanical low back pain.¹³ The result was promising for manipulation.

If controlled trials have a placebo that has a therapeutic effect, the difference between the two groups will be diminished, obscuring any benefit from the investigated intervention.

The volume of papers and the variety of quality make the use of reviews most attractive. A review of reviews from 1995¹⁴ had concluded that the majority of the reviews found that spinal manipulation is an effective treatment for low back pain. The reviews with a relatively high methodological quality had a positive conclusion but strong conclusions were precluded by the overall low quality of the reviews. A review of reviews from the Department of Complementary Medicine in Exeter in 2006 has produced much controversy.¹⁵ Their conclusion was that collectively, there was not enough evidence to recommend manipulation for any condition. Unsurprisingly, there were many responses from practitioners claiming to refute this conclusion.¹⁶ It would be interesting to know if funnel plotting would demonstrate selective publication of positive results as was found with homeopathy.¹⁷ The reviews with the most positive results do tend to have the lowest rigour and to be written by chiropractors of osteopaths.¹⁸

A Cochrane review of 2004¹⁹ concluded that there is no evidence that spinal manipulative therapy is superior to other standard treatments for patients with acute or chronic low-back pain. The UK(BEAM) trial was a "pragmatic randomised trial" based on 181 general practices. BEAM stands for back pain, exercise and manipulation. It concluded that relative to "best care" in general practice, manipulation followed by exercise achieved a moderate benefit at 3 months and a small benefit at 12 months. Spinal manipulation achieved a small to moderate benefit at 3 months and a small benefit at 12 months. Exercise achieved a small benefit at 3 months but not 12 months.²⁰ In terms of value for money it concluded that spinal manipulation is a cost effective addition to "best care" for back pain in general practice. Manipulation alone probably gives better value for money than manipulation followed by exercise.²¹

The volume of evidence for treatment of neck pain by manipulation is rather less than for low back pain.²² A Cochrane review²³ found that mobilization and/or manipulation when used with exercise are beneficial for persistent mechanical neck disorders with or without headache. Done alone, they were not beneficial. Compared to one another, neither was superior. There was insufficient evidence available to draw conclusions for neck disorder with radicular findings. Manipulation of the neck appears to be helpful for headache originating from the cervical spine.²⁴

A Cochrane review found that there was no benefit from the use of manipulation to treat primary of secondary dysmenorrhoea.²⁵ There is no evidence of benefit from manual therapies in asthma.²⁶ RCTs of chiropractic for pathology outside the spinal column include treatment of fibromyalgia, carpal tunnel syndrome, infantile colic, otitis media, dysmenorrhoea and chronic pelvic pain. There is no evidence to support its use in any of these.²⁷ Cranial osteopathy has been advocated for treating infantile colic, glue ear and improving childhood asthma but there are no RCTs to be found and anecdotes of improvement in these conditions may well represent natural history. Neither rationale nor evidence supports the use of manipulation for conditions that are not musculoskeletal in origin.

Manipulation has been used very extensively for a very long time. There is a vast range of techniques and it is impossible to state if any is outstanding (good or bad) in terms of efficacy or safety. The risk of adverse events is extremely low but rather more likely to follow manipulation of the cervical than the lumbar spine.

Despite extensive research of variable quality, it is impossible to be firm about its place, if any, in treatment. It is far more likely to be beneficial for musculoskeletal disorders such as simple back pain or neck pain than for other disorders such as dysmenorrhoea or glue ear.

There does not seem to be a valid method of applying a double blind placebo controlled randomised controlled trial. Pragmatic, open label treatment is assessed. There are many anecdotes of people who walk into a consultation bent in pain and walk out upright but the benefit with time is more dubious. If manipulation simply blocks the pain gate, it can be expected to have just temporary benefit. However, as pain causes muscle spasm that pulls on local structures and causes more pain, breaking this vicious cycle may be beneficial and it may require several treatments. Combined treatment with analgesia, massage and exercise would seem appropriate.

The negative reviews of manipulation have perhaps been too rigorous in their expectations and they have interpreted failure to demonstrate clear and convincing benefit by vigorous methodology as evidence for lack of efficacy. Lack of evidence of effect and evidence of lack of effect are not the same. However, it does seem that if manipulation is beneficial, it is more so in the short than the medium or long term. Individual success stories may also be diluted in the numbers in trials.

Spinal manipulation may well have a part to play in treatment regimens but its precise place is yet to be determined. On the basis of primum non nocere, it must be judged as very, but not totally safe.

Manipulation as a form of treatment is recorded as far back as 2700BC in China and Hippocrates and Galen both used it. Osteopathy was founded in 1874 and chiropractic was founded in 1895. Pretence to be a whole system of healing has caused friction with conventional medicine. Association with unregistered practitioners was one of the cardinal sins of the GMC. AJ Cronin's book The Citadel was first published in 1923 and whilst it is fiction, much is based on his experience as a doctor. He recounts how a colleague had been erased from the medical register for anaesthetising for Jarvis the manipulator.

In Australia in the 1950s, Geoffrey Maitland was a pioneer of manipulation within a setting of physiotherapy. His teachings are much respected.

Many doctors have used manipulation over the years and one of the best known is Dr James Cyriax. He was a controversial character whose books on orthopaedic examination are held in high regard. He is regarded as a luminary by some but others argue that his dogmatic and unscientific stance set back the cause of manipulation. It may be a reflection of his practice or his personality that he spent 30 years as a consultant physician at St Thomas' Hospital in London but was never elected FRCP.

Drs John Patterson and Loic Burn have taught and practised manipulation over many years. They have also made a very good attempt to put a scientific basis to its rationale and practice.