chapter 34 Musculoskeletal medicine

INTRODUCTION AND OVERVIEW

Musculoskeletal medicine (MSM) is that branch of medicine dealing with the conservative management of disorders of the musculoskeletal system, including the muscles, aponeuroses, joints and bones of the axial and appendicular skeletons, and those parts of the nervous system associated with them. These disorders represent the most common cause of disability in most countries across all age groups ¹ and are the third most common reason for presentation to general practice.² The direct and indirect costs of this burden are in the $15 billions per annum.³

Yet, paradoxically, undergraduate and postgraduate education in MSM is at best elementary. The need for MSM training in medical schools and hospitals has been well established.⁴ Currently in Australia there is no public MSM outpatients department (OPD) hospital clinic, which differs from our European and American colleagues, who have vibrant systems in place. For instance, osteopathy and musculoskeletal medicine special-interest doctors are recognised in the United Kingdom, musculoskeletal physicians are recognised in Europe and the United States has osteopathic MDs. Historically in Australia it has been left to the allied healthcare professionals and alternative healthcare practitioners to absorb much of the demand for musculoskeletal (MS) management. The medical profession has been slow to embrace MSM, but has a vital role to play. The optimal management of MSM conditions epitomises the need for an integrated approach from practitioners knowledgeable in the biopsychosocial approach to management. General practitioners with postgraduate MS training can work collaboratively with other healthcare providers to minimise pain and optimise function for patients.

One of the most common MS disorders seen by healthcare practitioners in Australia is spinal pain. Persistent back pain is by far the most common reason for chronic MS patient encounter in Australian general practice, followed by knee, shoulder and neck.⁵

This chapter focuses on the optimal management of spinal pain, although the general principles espoused may be used for all areas of the body.

LOW BACK PAIN

The issue of low back pain (LBP) pervades Western society. Be it through lost work, missed recreation and sporting activities or money spent on prevention or cure, there are few people who have not had dealings with it. Healthcare practitioners have been both blamed for exacerbating its prevalence and given credit for reducing it. It is abundantly covered in the media, and myths circulate swiftly through the populace. This section outlines the evidence on low back pain in a functional fashion.

DEFINITIONS

• Low back pain is pain perceived to be arising from lumbar and/or sacral regions of the spine. It has been defined by the IASP ⁶ as per Figure 34.1. Importantly, low back pain is not perceived to arise from the gluteal, thoracic, loin or groin region, although it may refer into these regions.

• Acute pain is pain that has been present for less than 12 weeks, subacute pain has been present for longer than 5–7 weeks but less than 12 weeks, and chronic (persistent) pain longer than 12 weeks. These terms are common in the research literature and management strategies differ significantly between them.

• Somatic pain is pain arising from noxious stimuli to any of the musculoskeletal components of the body. Studies have shown that the sensitivities of these components are: periosteum > ligament > joint capsule > tendon > fascia > muscle.^7,⁸ Somatic referred pain is pain perceived in a region innervated by nerves other than those that innervate the actual source of pain.⁶ Common examples include buttock and posterior thigh pain referred from the lumbar spine, and knee pain referred from the hip.

• Radicular pain is pain that arises from irritation of a spinal nerve or its roots. Radiculopathy involves conduction block to a spinal nerve or its root, resulting in numbness and/or weakness.⁶ Table 34.1 outlines the differing features of somatic referred pain and radicular pain. Figures 34.2–34.6 show some patterns of referred pain from different vertebral structures. They illustrate the potential of somatic vertebral structures to refer pain to remote areas and thus mimic other pains, such as ‘sciatica’ and visceral pains.

• Hyperalgesia is an increased response to a stimulus that is normally painful. In clinical practice this is commonly seen with persistent pain. It often results in an increase in the referred pain in intensity and area due to central nervous sensitisation.¹⁵ Knowledge of this phenomenon is important in providing patients with a reason for changes in their pain. It is also important for doctors involved in writing reports or assessments, as it invalidates the term ‘non-anatomical’ in describing distribution of pain. This term is often used in medico-legal reports to suggest that an individual’s pain is imaginary or of dubious significance. The use of ‘non-anatomical’ in describing pain should be obsolete in the twenty-first century.

FIGURE 34.1 Pain sites

TABLE 34.1 Somatic versus radicular pain

Somatic referred pain	Radicular pain
Due to spread of pain from deep spinal tissues (including muscles)	Due to chemical or mechanical irritation of nerves
Back pain worse than leg pain, which may be bilateral	Unilateral leg pain worse than back pain
Pain concentrates proximally in buttock and thigh, but may spread below knee	Pain concentrates distally, running into the lower limb, usually extending below the knee
Deep, dull aching, expanding pressure-like quality	Sharp, shooting, electric quality, often deep and superficial
Vague location, varies over time, ill-defined distribution	Pain runs along defined narrow band in dermatome distribution
Poorly defined paraesthesia may be present	Numbness and paraesthesia in dermatomal distribution
Normal reflexes and power (if abnormal, further assessment is needed)	Reflexes may be reduced or absent; motor weakness may be present

FIGURE 34.2 Patterns of referred pain evoked in normal volunteers by noxious stimulation of interspinous ligaments at the segmental levels indicated

(based on Kellgren 1939 ⁹)

FIGURE 34.3 Patterns of referred pain evoked in normal volunteers by noxious stimulation of interspinous ligaments at the segmental levels indicated

(based on Kellgren 1939 ⁹)

FIGURE 34.4 Patterns of referred pain evoked in normal volunteers by noxious stimulation of interspinous ligaments at the segmental levels indicated

(based on Kellgren 1939 ⁹)

FIGURE 34.5 Patterns of referred pain evoked in normal volunteers and in patients by noxious stimulation of the cervical zygapophyseal joints or intervertebral discs at the segments indicated ¹⁰^–¹²

FIGURE 34.6 Various patterns of referred pain produced in normal volunteers or patients by noxious stimulation of lumbar zygapophyseal joints or intervertebral discs ^13,¹⁴

EPIDEMIOLOGY

The lifetime prevalence of acute LBP is about 70%,¹⁶ with the cumulative lifetime prevalence of episodes lasting more than 2 weeks being 14%.¹⁷ In Australia, back complaint is the sixth most common reason for presentation to a general practitioner.²

Data on the natural history of LBP are variable but instructive when closely analysed. A commonly quoted statement is that, with treatment, ‘90% of patients recover within 2 months’.¹⁸ This may be true when follow-up is only for 4 weeks.¹⁸ More-rigorous studies with 12-month follow-up reveal a different picture.^19,²⁰ Around 80% of patients remain disabled to some extent at 12 months, with 10–15% highly disabled. These studies paint a picture of recovery followed by relapse. In general, a patient’s status at 2 months post presentation reflects their status at 12 months.

An Australian study of acute LBP patients without a compensation claim managed with evidence-based guidelines revealed that 70% can expect to recover and stay recovered at 12 months, with a low risk of recurrence.²¹

HISTORY

History-taking primarily allows formulation of a diagnostic framework and assessment of prognosis. It should also be used as a way to gain the patient’s trust and begin the process of education and assurance. A reasonable framework is:

• pain history—use pain chart, VAS, disability, recovergram (see also Ch 38, Pain management)

• red flag check—see Box 34.2

• yellow flag check—see Box 34.3.

BOX 34.3 Yellow flag indicators

Work:

• belief that pain is harmful, resulting in fear-avoidance behaviour

• belief that all pain must be abolished before attempting to return to work or normal activity

• expectation of increased pain with activity or work

• fear of increased pain with activity or work

• belief that work is harmful

• poor work history

• unsupportive work environment

Beliefs:

• catastrophising, thinking the worst

• misinterpreting bodily symptoms

• belief that pain is uncontrollable

• poor compliance with exercise

• expectation of ‘techno-fix’ for pain

• low educational background

Behaviours:

• passive attitude to rehabilitation

• use of extended rest

• reduced activity with significant withdrawal from activities of daily living

• avoidance of normal activity

• impaired sleep because of pain

• increased intake of alcohol or similar substances since the onset of pain

Affective:

• depression

• feeling useless and not needed

• irritability

• anxiety about heightened body sensations

• disinterest in social activity

• over-protective partner/spouse

• socially punitive partner/spouse

• lack of support to talk about problems

(Source: Bogduk 2003 ²²)

EXAMINATION

Although physical examination of LBP patients will rarely allow a patho-anatomic diagnosis to be made, it remains an extremely valuable tool. Its strength lies in the opportunities it opens (Box 34.4). A confidently performed physical examination in association with meaningful dialogue is an important step in the overall management.

Following the orthopaedic model of ‘look, move and feel’ is the standard approach. Initial inspection allows a record of asymmetry, pain behaviour, gait and skin lesions. A knowledge of surface landmarks (Fig 34.7) adds more meaning to the descriptions. The physician should be alert for pain behaviour from the patient and its interpretation. Importantly, pain behaviour needs to be recognised as the patient’s way of communicating distress. Overt or exaggerated pain behaviour is not a sign of malingering but, rather, a signal for the doctor to explore pain management issues in more depth. This would include psychosocial factors as well as biological.

FIGURE 34.7 Surface anatomy landmarks: iliac crests (IC), posterior superior iliac spines (PSIS). Spinous process of L4 lumbar vertebra lies at or just below the level of the iliac crest. Lumbosacral junction (=) lies 10–15° superiorly and towards the midline from the PSISs. T12 can be located by counting spinous processes back from the lumbosacral junction. T10 is at a line drawn along the 12th rib and continued to the midline to meet its contralateral fellow.

The patient can be moved in all six planes—flexion, extension, lateral flexion left and right, and rotation left and right. Rotation is best performed sitting, to stabilise the pelvis. While the patient is seated, straight leg raising (SLR) and slump testing may be performed (Fig 34.8). With the patient in the supine position, SLR can be assessed as well as leg length. Hip range of movement (ROM) can be assessed, noting that if back pain is reproduced, this is most likely to be from the effects on lumbar/pelvic structures than the hip joint (groin/anterolateral thigh pain). In the prone position, hip extension and hip rotation can be assessed.

FIGURE 34.8 Slump test. The patient sits on the edge of the couch, then in a stepwise fashion, increased stretch is introduced as follows: i) the patient slumps forward, ii) then flexes the neck, iii) then straightens the leg, iv) then dorsiflexes the foot. Purportedly, if any back or leg pain reproduced so far is eased when the neck is then extended, and/or the ankle plantar flexed, then neuromeningeal irritation, rather than hamstring pain, is invoked (adopted from Kenna & Murtagh ²³).

Palpation should be performed systematically through the paravertebral tissues, sacroiliac and gluteal area. Attention should be paid to insertional areas such as the posterior greater trochanter, parasacrally and the posterior superior iliac spine (PSIS). To assess the sacrotuberous and sacrospinous ligament, levator ani and other paracoccygeal structures, per rectum examination will be needed. Note should be made of hyperalgesia, allodynia and abnormal tissue texture.

Special tests of spinal dysfunction have been described for the lumbar and pelvic region, including many labelled as sacroiliac tests. A combination of tests shows best utility regarding sacro-iliac joints (SIJ) dysfunction.²⁴

Examination of the visceral, vascular and neurological systems is determined by the presenting symptoms and history. Neurological examination is only necessary if there is radicular leg pain or neurological symptoms. A quick check of the L5 and S1 myotomes can be performed by asking the patient to stand on their heels, then their toes. The L1–S2 dermatomes are easily checked by touching the centre of the respective zones.

INVESTIGATION

Careful thought is needed before investigating a patient. Concern regarding increasing levels of radiological intervention, especially CT scanning, has become topical.^25,²⁶ The risk of exposure to significant ionising radiation, for questionable clinical benefit along with wasting of limited healthcare resources, should be of concern to the healthcare practitioner and consumer alike. By asking: ‘How will this investigation influence my management, what are the chances of a significant finding and will this test detect it?’, unnecessary tests are likely to be avoided.

Red flag conditions and their appropriate investigations are shown in Table 34.2. Plain films have a reasonable pick-up rate (Table 34.3) but will miss early disease. CT scans have no role in the investigation of somatic low back pain, except in confirmation of pathology indicated by other investigations or the history/examination. MRI scan is the investigation of choice for red flag conditions of the spine and gives the best information about the status of the intervertebral disc (i.e. presence or absence of modic lesions and high-intensity zones).

TABLE 34.2 Appropriate investigations for possible serious causes of acute musculoskeletal pain