Chronic back pain from a medicolegal perspective

Back pain is extremely common; only the common cold occurs more frequently (1, 2). The annual incidence of back pain is around 15–20%, and up to 85% of people will be affected at some point during their lifetime (1, 3-7). It has an enormous physical and financial cost, as it restricts function, participation in daily activities and the ability to work (1, 6, 7) and it is the most frequent reason for disability in patients aged under 45 years (1). Back pain is considered acute when it lasts for less than 6 weeks, subacute between 6 weeks and 3 months, and chronic when it lasts for longer than 3 months (1, 2, 4).

The usual course of a new episode of back pain is for symptoms to abate substantially, but not fully resolve, during the first few weeks. Although many patients report that residual symptoms persist for months, only a small minority become significantly disabled. However, in all patients, recurrence of symptoms is common, particularly in the first year (2, 4-7). Furthermore, recovery is often based on measures, such as a return to work or cessation of medical treatment, which do not necessarily correlate with a complete resolution of symptoms (4).

It is not entirely clear how or why some cases of acute back pain become chronic but evidence is emerging that the brains of patients with chronic back pain (CBP) are different from those without the condition, with corresponding changes in brain function. These patients exhibit greater reactivity in the primary somatosensory cortex, as well as biochemical changes and reduced activity in other areas of the brain. Furthermore, these changes appear to be proportional to the duration and severity of the patient’s condition. Reactivation of pain memories characteristic of fear avoidance behaviour may also explain the persistence of pain in the absence of significant ongoing pathology, and it is likely that these mechanisms coexist (6-8).

It is now widely recognised that there is an emotional, as well as a physical, aspect of pain and the biopsychosocial model of pain attempts to encapsulate the interaction between the diverse risk, protective and prognostic factors that influence the experience and presentation of CBP (6, 8). Psychological factors can significantly affect both pain and functionality in patients with CBP, and probably account for much of the variance in symptoms and treatment response between individual patients (7, 8). Patients with CBP have higher rates of anxiety and depression than healthy individuals, which increase with the chronicity of the condition (3, 4). However, this relationship is bi-directional and it is difficult to establish whether the psychological symptoms are a cause or effect of the patient’s chronic pain.

Psychological factors may also contribute to the maintenance of CBP. Avoidance of pain, driven by catastrophising and pain-related fear, is a maladaptive behaviour that plays an important role in the development of chronic pain, while patients who have active coping strategies and try to function in spite of their pain are more likely to experience a resolution of their symptoms (3, 6-8). Thus, the presence or absence of psychological distress may be a better predictor of treatment outcome than physical factors (1, 2, 7).

Underlying systemic disease is rare in CBP, and probably accounts for no more than 10% of cases. However, some cases are the result of conditions such as cancer, compression fractures, infection or cauda equina syndrome. A history of significant trauma, unexplained weight loss, widespread neurologic changes or other symptoms specific to each condition may indicate their presence, and should immediately raise suspicion in the examining doctor (1, 2). As patients with these conditions almost always require referral to a specialist, it is important that they are quickly identified and a thorough physical examination and history are vital in diagnosing systemic disease (1).

The remaining 90% of CBP cases have no obvious cause and are often termed mechanical, musculoskeletal or non-specific (1, 4, 5, 7). These cases may arise due to overuse of one part of the back, or because of trauma, deformity or degeneration of one of the structures of the spine (1, 5, 8). Conditions of this nature that result in CBP include osteoarthritis of the spine, spinal stenosis and facet joint arthropathy (1, 5). Typically, symptoms are worsened by certain activities, such as lifting or standing for prolonged periods of time, and relieved by others, such as lying down. The presence of sciatica, a sharp pain that radiates down the leg as far as the foot, indicates compression of a nerve root, which is most commonly associated with herniation of the lumbar disks and spinal stenosis. However, it can also be a symptom of cauda equina, a condition that requires urgent treatment (1).

Spinal stenosis often occurs when arthritic changes narrow the canal through which the spinal cord passes (1, 5). It is typically indicated by pain in the back, buttocks or thighs which is exacerbated by walking or prolonged standing and relieved by stooping, bending forwards or sitting down. This is due to changes in the size of the spinal canal, which impinges on the roots of the spinal nerves, caused by the extension and flexion of the spine during these activities. Around 50% of patients also demonstrate deficits in sensory functioning and muscle strength, and their balance may also be altered, particularly as the condition progresses. Depending on where the stenosis is determines whether a single or multiple nerve roots are involved.  Classically, radiculopathy is defined as sciatica where clinical signs of nerve dysfunction such as reduced sensory or altered motor function exist. Spinal stenosis can be distinguished from bilateral hip osteoarthritis, which is often indicated by a similar pattern of pain symptoms, by the absence of pain during rotation of the hip joint (1).

Given the lack of an obvious cause in most cases of CBP, diagnosis can be extremely difficult. One notable feature is that there is often little correlation between reported symptoms and visible pathology (1, 5, 7, 8). For example, around 20% of people aged over 60 years show evidence of stenosis of the lumbar spinal canal, even in the absence of other symptoms (1). Therefore, diagnosis should be based on physical examination and history, with imaging being reserved for cases where there is a strong suspicion of a serious underlying disease. A thorough examination should include visual inspection and palpation of the patient’s back, as well as assessments of spinal movement, muscle tone and strength, sensory perception and reflexes. Leg-raising tests should also be carried out (1, 2). In addition, the examination should include the hip, facet and sacroiliac joints, as back pain may actually be a referred symptom from a condition affecting one of these joints (1).

Successful management of CBP requires good listening and communication with the patient (1), and it is important to reassure patients that the presence of serious disease is unlikely (2). This can be therapeutic in itself. The main goals of treatment are to decrease the pain and to preserve or restore mobility, thus allowing the patient to resume normal daily activities (1). However, most treatments offer only small, short-term benefits and while there is generally little evidence to recommend one treatment option over another (1, 4, 7), doing something is almost always better than doing nothing (4, 7).

Whilst previously recommended, there is now a consensus that prolonged bed rest is not beneficial. Instead, the patient should be encouraged to remain as active as possible, while avoiding activities, such as prolonged sitting or standing, that may aggravate their symptoms. Low-stress aerobic activities, including walking, are particularly beneficial (1, 2, 5).

Although painkillers, such as nonsteroidal anti-inflammatory drugs, acetaminophen, muscle relaxants and opioids, are frequently offered, these are more appropriate for short-term use in acute cases, and adverse side-effects may also be an issue (1, 2). Epidural corticosteroids may be useful for the short-term relief of sciatica but offer no significant long-term benefits (1). The usefulness of spinal manipulation remains controversial, but may result in improvements in patients who have not responded to first-line treatments. However, there is no evidence to show which form of manual therapy is most effective (2, 7). Similarly, electrical stimulation of the spine via TENS machine can reduce pain, but not resolve it completely (7) and is not recommended in NICE guidance. Surgery is usually reserved for cases of identified underlying disease, such as cauda equina and fractures or tumours that are compressing the spinal cord, severe or progressive neurological conditions and cases of intractable pain that have shown no response to conservative therapy options (1).

Interventions that target the psychological aspects of CBP are within NICE guidance and they may help patients to cope with their condition more effectively, thus increasing quality of life. Patients who underwent a course of cognitive behavioural therapy (CBT) reported lower levels of long-term sick leave from work and a significant decrease in doctor consultations but no overall reduction in pain intensity when compared to control subjects (6). CBT is an important component in many multimodal and multidisciplinary programs aimed at the management of CBP, which integrate therapeutic and psychological interventions with manual therapies to provide a treatment program tailored to the individual patient. This combined approach has achieved considerably more success than the component therapies used in isolation, with patients reporting significant reductions in pain intensity and an increase in functionality, which appear to persist for some time after treatment (9).

CBP presents a significant healthcare challenge, due to its widespread occurrence and the lack of obvious causality in the majority of cases. Effective treatment solutions remain an unmet clinical need, but interventions that focus on cortical processing or the psychological aspects of pain may offer novel therapies. Although grouped together under one heading, patients with CBP probably represent a very diverse population, with a wide variation in aetiology, symptoms and response to treatment. An understanding of this fact is vital in developing personalised treatment programs, with the aim of achieving better outcomes for patients.