Premature babies with ROP were randomly assigned to an ACTH treatment group or a no‑treatment control group within the same hospital. Both groups were treated identically, apart from the use or not of ACTH. Within a few months the results emerged. An impressive 70 per cent of the infants treated with ACTH completely recovered their sight. Remarkably, the results in the control group were even more impressive, with an 80 per cent recovery rate. Babies in the untreated group had fared slightly better in terms of avoiding blindness, and moreover they suffered fewer fatalities compared to babies in the group treated with ACTH. It seemed that ACTH offered no benefit to babies and also had side‑effects. A follow‑up study confirmed the results of Silverman’s rigorous clinical trial.
The initial results from the Lincoln Hospital were abnormally poor, which had fooled Silverman into believing that he had discovered a powerful new treatment, but he had been wise enough not to be complacent and rest on his laurels. Instead, he re‑tested his own hypothesis and disproved it. Had he had not been so critical of his own work, subsequent generations of paediatricians might have followed his example and administered ACTH, a useless, expensive and potentially harmful treatment.
Silverman was a passionate believer in the randomized clinical trial as the tool for questioning and improving the care of babies, which made him an unusual figure among doctors in the 1950s. Although researchers were convinced of the importance of evidence in determining best practice, the doctors on the ground still tended to be overconfident about their gut instincts. They had faith in their own sense of what the ideal conditions should be for helping premature babies, but according to Silverman this was a primitive way of deciding serious health issues:
Like the approach taken by farmers caring for newborn piglets, conditions considered ideal for survival were provided, and it was assumed that those who were ‘meant’ to survive would do so. But none of these purportedly ‘ideal conditions’ had ever been subjected to formal parallel‑treatment trials…almost everything we were doing to care for premature infants was untested.
Doctors in the 1950s preferred to rely on what they had seen with their own eyes, and would typically respond to patients with the mantra ‘in my experience’. It did not seem to matter to doctors that their personal experience might be limited or misremembered, as opposed to the evidence from research trials, which would be extensive and meticulously documented. That is why Silverman was determined to instil a more systematic approach among his colleagues, and he was supported in his mission by his former tutor Richard Day:
Like Dick, I was completely sold on the numerical approach; soon we were making nuisances of ourselves by criticizing the subjective ‘in‑my‑experience’ reasoning of our co‑workers…I was increasingly aware that the statistical approach was anathema to free‑wheeling doctors who resented any doubts being expressed about the effectiveness of their untested treatments.
Half a century later, today’s doctors are much more accustomed to the concept of evidence‑based medicine, and most accept that a well‑designed randomized clinical trial is crucial for deciding what works and what does not. The purpose of this book has simply been to apply these same principles to alternative medicine. So what does evidence‑based medicine say about chiropractic therapy?
Manipulating patients
When patients visit a chiropractor, they are usually suffering from back or neck pain. After taking a medical history, the chiropractor will embark on a thorough examination of the back, particularly the bones of the spine, called vertebrae. This will include looking at the patient’s posture and overall mobility, as well as feeling along the spine to assess the symmetry and mobility of each spinal joint. Often X‑ray images or MRI scans are also used to give a detailed view of the vertebrae. Any misalignment in the spine is then corrected in order to restore the patient’s health. Chiropractors see the spinal column as a complex entity, such that each vertebra affects all the others. Hence, a chiropractor might work on a patient’s upper spine or neck in order to treat pain in the lower back.
The hallmark treatment of the chiropractor is a range of techniques known as spinal manipulation, which is intended to realign the spine in order to restore the mobility of joints. Chiropractors also call this an adjustment. It can be a fairly aggressive technique, which pushes the joint slightly beyond what it is ordinarily capable of achieving. One way to think about spinal manipulation is as the third of three levels of flexibility that can be achieved by a joint. The first level of flexibility is that which is possible with only voluntary movement. A second and higher level of flexibility can be achieved by exerting an external force, which pushes the joint until there is resistance. The third level of flexibility, which corresponds to spinal manipulation, involves a thrusting force that pushes the joint even further. The chiropractor will submit the vertebrae of the spine to this third level of motion by using a technique called high‑velocity, low‑amplitude thrust. This means that the chiropractor exerts a relatively strong force in order to move the joint at speed, but the extent of the motion needs to be limited, because otherwise there would be damage to the joint and its surrounding structures. Although spinal manipulation is often associated with a cracking sound, this is not a result of the bones crunching against each other or a sign that bones are being put back in their right place. Instead, the noise is caused by the release and popping of gas bubbles, which are generated when the fluid in the joint space is put under severe stress.
If you have never visited a chiropractor, then the easiest way to imagine spinal manipulation is by analogy to an experiment you can do with your hand. Position your right forearm vertically upwards and hold your right hand flat, with the palm facing up–as if you are carrying a tray of drinks. Your wrist should be able to bend backwards so far that your flat hand begins to dip slightly below the horizontal–this is what we have called level‑one flexibility. If you use your left hand to press steadily and firmly downwards on your right palm, then the wrist can be bent a little further down by a few degrees, which is level‑two flexibility. Imagine–and please do not do this–that your left hand applied an additional short rapid thrust on your right hand, thus bending it down even further by a small amount. This would be level‑three flexibility, akin to the sort of action involved in spinal manipulation via a high‑velocity, low‑amplitude thrust.
Because spinal manipulation is the technique that generally distinguishes chiropractors from other health professionals, it has been at the centre of efforts to establish the medical value of chiropractic therapy. Researchers have conducted dozens of clinical trials in order to evaluate spinal manipulation, but they have tended to generate conflicting results and have often been poorly designed. Fortunately, as with acupuncture and homeopathy, there have been several systematic reviews of these trials, in which experts have attempted to set aside the poor trials, focus on the best‑quality trials and establish an overall conclusion that is reliable.
In fact, there have been so many systematic reviews that in 2006 Edzard Ernst and Peter Canter at Exeter University decided to take all of the current ones into account in order to arrive at the most up‑to‑date and accurate evaluation of chiropractic therapy. Published in the Journal of the Royal Society of Medicine, their paper was entitled ‘A systematic review of systematic reviews of spinal manipulation’. Ernst and Canter’s review of recent reviews covered spinal manipulation in the context of a large range of conditions, but for the time being we will concentrate on the most common problems dealt with by chiropractors, namely back and neck pain. In this context they took into account three reviews looking at back pain alone, two reviews looking at neck pain alone and one review that covered both neck and back pain.