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The lumbar spine

Introduction

Lumbar spine (low back) pain is defined as pain between the costal margins and the gluteal folds, with or without pain radiating into the leg (Krismer & van Tulder 2007). It is one of the most common complaints presented to healthcare in the western world and, in the United States, it is the fifth commonest reason for any physician visit (Deyo et al 2006). Although most people who suffer with low back pain do not consult a healthcare practitioner – a report from the National Institute for Health and Care Excellence (NICE) found that only around 1 in 15 sufferers in the UK seeks treatment (NICE 2009) – low back pain is still one of the most draining conditions in terms of costs (Dagenais et al 2008, Lambeek et al 2011, Balagué et al 2012). The overall cost for treating patients with low back pain in the UK is estimated to exceed £500 million each year in the private sector and to be over £1000 million in the National Health Service (NHS) (NICE 2009). Moreover, in a recent analysis of the UK General Practice Research Database, it was reported that the annual healthcare costs of those with chronic low back pain were double the costs of those without (£1074 vs. £516) (Hong et al 2013). In the USA, the total spending for low back pain is estimated to be between $100 billion and $200 billion per year (World Health Organization 2013).

Studies have shown that the prevalence of low back pain increased over the second half of the 20th century, possibly linked to an increase in sedentary lifestyles and work (Louw et al 2007, El-Sayed et al 2010). What is interesting is that the incidence of low back pain is lower in countries with low- and middle-income economies than in high-income countries. Proposed reasons for this are that people in lower-income jobs are more active, have higher pain thresholds and have less contact with insurance companies than their higher-income counterparts (Volinn 1997).

Low back pain affects approximately 70–84% of people at some time in their lives (Hong et al 2013). It has been highlighted by the Global Burden of Disease study as the global leader in years lived with disability and the sixth highest with regard to disability-adjusted life years (Murray et al 2013, Vos et al 2013). Globally, the prevalence of low back pain limiting activity has been estimated at 39%. In the UK, it has been estimated that around one-third of the UK population experiences low back pain every year (NICE 2009). Symptoms in most of these patients (80–90%) resolve within a few weeks; the remaining 10–20% have an increased chance of developing chronic low back pain and experiencing disability connected to it (Hong et al 2013).

Both the NICE UK guidelines (NICE 2009) and the Joint Clinical Practice Guideline from the American College of Physicians / American Pain Society (Chou et al 2007) recommend manual therapy for low back pain. A systematic review by Bronfort et al (2004) demonstrated favorable results from articulation in the treatment of acute and chronic low back. Articulation has been shown to significantly decrease localized lower back pain on a short-term basis; it has also been observed to lead to a greater decrease in lower back pain in the long term when compared to no treatment (Hanrahan et al 2005). Studies have demonstrated that the treatment is most effective when directed to a specific joint level rather than a randomly selected vertebral level (Chiradejnant et al 2003).

A meta-analysis by Machado et al (2009) showed that articulation of the lumbar spine had a positive influence on the analgesic effects of treatments for non-specific low back pain, although the results were small for large study groups and larger in smaller groups. Pentelka (2012) also found that articulation of the lumbar spine decreased patients’ pain thresholds but that at least four sets of articulation were needed over either 30 seconds or 60 seconds to achieve a change in threshold. McCollam and Benson (1993) used posterior–anterior articulation of the lower lumbar spine in 130 participants and found a significant increase in range of movement in lumbar extension post treatment. Powers et al (2008) also found increases in range of movement post articulation of the low back, although a later study by Stamos-Papastamos et al (2011) found no significant change in range of movement pre and post treatment.

Evidence suggests that different segments of the lumbar spine respond somewhat differently. For example, when a short-lever anterior–posterior compression is done on L3, L4 and L5, these segments are likely to move into extension; the three segments will move as a response to the anterior–posterior compression on the vertebra. However, with the upper segments, L1 and L2, the lower segments move into flexion (Powers et al 2008). The therapist therefore needs to be aware of the effect anterior–posterior articulation on the neighboring segments of the spine.

Beattie et al (2009) found that articulation of L5/S1 caused an increase in water diffusion of the associated intervertebral disc. Thus it was postulated that an increase in diffusion to the intervertebral disc would cause an elevation in intradiscal cells and activity, and an increase in oxygen levels thus increasing the formation of collagen and proteoglycans within the disc. Although these effects were noted to happen several hours after articulation of the joint, they would still contribute to the health and structural stability of the disc.

When assessing the effectiveness of articulation and the lumbar spine, there is conflicting evidence because some studies have looked at asymptomatic patients and others have looked at symptomatic, with varying numbers of participants and outcomes. There is also the question of what constitutes a good outcome. Is it an increase in range of movement, a decrease in perceived pain, or a decrease in pain threshold? There is clearly much more research to be done into lumbar spine pain and its management and treatment, especially given the extent of the problem.

Anatomy

The lumbar spine, also known as the lower back spine, is the third major segment of the vertebral column. The word ‘lumbar’ has a Latin root and is derived from the word lumbus, which means loin (Arnold & Bryce 1987). The lumbar spine is designed to be incredibly strong, flexible and stable. It protects the spinal cord and spinal nerve roots, allows a wide range of motions, and serves to help support the weight of the body (Kishner et al 2014).

The anatomy of the lumbar spine is complex. It curves inward toward the abdomen, starting just below the thoracic spine and extending downward to the sacral region. It consists of five movable vertebrae, the intervertebral discs, large muscles, flexible ligament or tendons, and highly sensitive nerves (OpenStax 2013).

The lumbar vertebrae, designated L1 to L5, are irregular bones between the ribcage and the pelvis. They are characterized by their large, thick vertebral bodies, short spinous processes and thin transverse processes. They are distinguished from their counterparts by the absence of transverse foramina and costal facets. In addition, they have a horizontal diameter that is greater than their vertical height (Standring 2008).

The vertebral body of a lumbar vertebra is usually a large block of bone that is designed to carry most of the body’s weight. It is wider transversely and is somewhat box-shaped, with essentially flat top and bottom surfaces (Bogduk 2005). It increases in size from L1 to L5. At the posterior end of the body, there is a thin, bony ring attachment called the vertebral arch. The arch encloses the hollow vertebral foramen and serves to protect the neural elements. Each vertebral arch is composed of two pedicles, two laminae and seven bony processes (Kishner et al 2014).

The vertebral foramen at lumbar levels is greater than at thoracic levels but smaller than at cervical levels. The pedicles change in morphology from the superior to the inferior. The laminae are broad and short, but they do not overlap like those of the thoracic vertebrae. The spinous process is more horizontal than in thoracic vertebrae. The transverse processes are typically thin and long; they increase in length from L1 to L3 but then shorten. The articular processes are large, with the superior processes bearing vertical concave articular facets and the inferior having vertical convex articular facets (Standring 2008).

The lumbar spine is normally made up of five vertebrae (L1–L5), but some people have genetic malformations of the lumbar spine that result in abnormalities classed as ‘lumbosacral transitional vertebrae’. These transitional vertebrae can be subdivided into either sacralization or lumbarization. Sacralization is when the L5 is attached to the sacrum; lumbarization is when the first sacral vertebra is not fused (Dharati et al 2012). Research reports that, in most circumstances, the lumbosacral transitional vertebrae are asymptomatic and are most commonly unilateral (Singh et al 2014). Also there is some evidence that lumbosacral transitional vertebrae are racial variations. For example, 18% of Australian aboriginals (Mitchell 1936), 16% of Indians (Sharma et al 2011), 9.2% of Arabs (Hughes & Saifuddin 2006), and 5.8% of Japanese (Toyoda cited in Bergman, Afifi & Miyauchi 2008) have one of the forms of lumbosacral transitional vertebrae.

Intervertebral discs

Each lumbar vertebra is stacked vertically with another vertebra and between them is an intervertebral disc made of tough fibrocartilage. The structure of these discs is very similarly to those in other parts of the vertebral column. However, the discs in the lumbar spine are much thicker than between other vertebrae. Each disc consists of two distinct components: a central nucleus pulposus and a peripheral annulus fibrosus. The annulus fibrosus surrounds the nucleus pulposus by forming a retaining wall, but no clear boundary is observed between them within the disc (McKenzie 1981).

The intervertebral discs hold the vertebrae together, allow movement between them, and prevent them from grinding against each other. They also serve to absorb pressure and distribute stress during movement (Mader 2004).

Ligaments

The lumbar spine has similar ligaments to elsewhere in the vertebral column. These ligaments help to hold the vertebral bodies and the intervertebral discs together (Behrsin & Briggs 1988). The two named ligaments that attach to the lumbar bodies and discs are the anterior and posterior longitudinal ligaments. They cover the anterior and posterior aspects of the bodies and discs, respectively. However, these two ligaments are not restricted to the lumbar region only (Bogduk 2005); they can inferiorly extend into the sacrum and superiorly widen to cover the entire spinal column. The annuli fibrosi of the intervertebral discs are intimately attached to these ligaments (Kishner et al 2014).

The ligaments that join the posterior elements of the lumbar vertebrae are the supraspinous ligaments, the interspinous ligaments and the ligamentum flavum. The supraspinous ligament runs posteriorly to the posterior ends of the spinous processes and bridges the interspinous spaces. It attaches to the tips of the spinous processes of adjacent vertebrae from L1–L3 (Warwick & Williams 1980). The interspinous ligament connects adjacent spinous processes, from root to apex. The ligamentum flavum lies immediately behind the vertebral canal. It joins the laminae of consecutive vertebrae, connecting with the facet capsule laterally and the interspinous ligament medially (Bogduk 2005).

Another important ligament of the lumbar spine is the iliolumbar ligament. It is present bilaterally, and has five bands. It connects the transverse process of the fifth lumbar vertebra to the ilium. Briefly, each ligament arises from the tip of an L5 transverse process to the ilium’s anteromedial surface and the iliac crest’s inner lip (Shellshear & Macintosh 1949, Hughes and Saifuddin 2006).

Joints

All the vertebrae from L1 to L5 articulate by symphyseal joints between their vertebral bodies, synovial joints between their articular processes (zygapophyses), and fibrous joints between their laminae, transverse and spinous processes (Standring 2008). The symphyseal joints (also called the secondary cartilaginous joints) persist throughout the life of an individual and serve to provide mobility for the vertebral column. The articulations between the superior and inferior articular processes of two neighboring vertebrae are known as zygapophyseal joints. These protect the motion segment from anterior shear forces and allow simple gliding movements (Bogduk 2005).

Range of motion

The movements available at the lumbar spine and its individual joints are principally flexion, extension, lateral flexion and axial rotation. Flexion and extension usually occur because of a combination of rotation and translation in the sagittal plane between each vertebra (Hansen et al 2006). Horizontal translation has an involvement in the axial rotation of the spine, but is not available as an isolated or pure movement. Sagittal movement is considerably more available in the lumbar segment than rotation or lateral flexion, especially at the lowest regions (Bogduk 2005). The lumbosacral joint (L5–S1) undergoes the highest sagittal plane motion of the lumbar joints. This joint also offers a relatively small amount of lateral flexion and axial rotation (White & Panjabi 1990).

The range of motion of the lumbar spine is difficult to measure clinically, because it varies considerably from person to person. Moreover, a number of factors may also trigger it, including age, sex, genetics, pathology and ligamentous laxity (McKenzie & May 2003). For example, McGill et al (1999) found a decreased range of motion in full flexion and lateral flexion when comparing elderly participants with younger. In addition, men are reported to have more mobility in flexion–extension, while women have more in lateral flexion (Biering-Sorensen 1984). Ranges of segmental motion are given in Table 8.1, and mean figures for range of motion in males are shown in Table 8.2.

Some research has demonstrated that in the majority of cases of lower back pain, flexion is commonly the first movement to become limited (Sullivan et al 2000, Neumann et al 2001).

Epidemiology

Low back pain is a very common spinal disorder that many people experience at some stage in their lives. It has variable etiologies. It can be due to lumbar arthritis, lumbar instability, spondylolisthesis, spinal deformity, spinal stenosis, disc herniation, disc degeneration, painful scoliosis, injury, arthritis or trapped nerves (Juniper et al 2009). However, the etiology of low back pain is unknown in the vast majority of cases: approximately 90% of cases have no recognizable cause and are defined as nonspecific (Manek & MacGregor 2005). In theory, any structure located in the lumbar spine that receives a neurological supply can be a source of lower back pain. Therefore pain can originate from any of the fascia, muscles, ligaments, joints or discs. Many therapists have postulated that articulation of the lower back has an effect on the nervous system (Knutson 2000, Pickar 2002, Clark et al 2009). Thus nonspecific low back pain may be defined as low back pain that is not connected with a specific pathology such as a tumor, infection, inflammatory disorder, fracture, osteoporosis or cauda equina.

Table 8.3 lists the common disorders of the lumbar spine.

Low back pain has an enormous social and economic impact. It causes difficulty in performing activities of daily living and can lead to activity limitation and work absence (Manchikanti et al 2008). Studies performed in the UK have suggested that low back pain has been the biggest single cause of work absence (Hoy et al 2014, Wynne-Jones et al 2014); it has been estimated that low back pain is responsible for 12.5% of all sick days (Bevan 2012). The financial burden from low back pain is also immense. In 1998, the annual total cost for low back pain in the UK was estimated at £12.3 billion (Maniadakis & Gray 2000).

The exact incidence and prevalence of low back pain in the UK are uncertain. Although a vast raft of literature is available on the subject, most of the epidemiological studies published on it are not only heterogeneous but also contradictory. The varying methodologies used in these studies often limit the ability to compare and pool data, and give rise to problems from clinical and policy perspectives (Friedly et al 2010). According to the systematic reviews carried out by Hoy et al (2010), the unadjusted point prevalence of low back pain in the UK ranges between 18% and 19% (data from Hillman et al 1996 and Harkness et al 2005), with an annual prevalence of 36.1% (data from Walsh et al 1992). The authors also mentioned that the estimated 1-year incidence of a first-ever episode of low back pain was 15.4%, while the estimated 1-year incidence of any or a recurrent episode of low back was 36% (data from Croft et al 1999).

Lumbar spine examination

Medical history

Taking an accurate medical history of the patient is the most important part for the lumbar spine examination, because it helps determine whether the conditions are mechanical or secondary. It also helps identify the red flags and facilitates the physical examination.

The clinician should ask the questions in a logical manner, so that they can draw a conclusion from the answers. The interview should include questions about osteoarthritis, osteoporosis and cancer, and a review of any previous imaging reports (Last & Hulbert 2009). Apart from questioning about pain and other issues related to the lumbar region, the clinician should also inquire about the onset of the problem, behavior since onset, symptom pattern, and exacerbating and relieving factors.

Red flags

While questioning the patient, the clinician should check for the presence of any red flags in their narrative (see Table 8.4). The screening process should begin with a detailed medical history and the use of a medical screening form.

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