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Copyright: © Vladimir Lera 2018 et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Received: 01 January 1970 | Accepted: 02 June 2018 | Published: 10 June 2018
Keywords: low back pain, CLBP, back spine
Chronic low back pain (CLBP) is a chronic pain syndrome in the lower back region, lasting for at least 3 months. CLBP represents the second leading cause of disability worldwide being a major welfare and economic problem. The prevalence of CLBP in adults has increased more than 100% in the last decade and continues to increase dramatically in the aging population, affecting both men and women in all ethnic groups, with a significant impact on functional capacity and occupational activities. It can also be influenced by psychological factors, such as stress, depression and/or anxiety. Given this complexity, the diagnostic evaluation of patients with CLBP can be very challenging and requires complex clinical decision-making. Answering the question “what is the pain generator” among the several structures potentially involved in CLBP is a key factor in the management of these patients, since a mis-diagnosis can generate therapeutical mistakes. Traditionally, the notion that the etiology of 80% to 90% of LBP cases is unknown has been mistaken perpetuated across decades. In most cases, low back pain can be attributed to specific pain generator, with its own characteristics and with different therapeutical opportunity. Here we discuss about radicular pain, facet Joint pain, sacro-iliac pain, pain related to lumbar stenosis, discogenic pain. Our article aims to offer to the clinicians a simple guidance to identify pain generators in a safer and faster way, relying a correct diagnosis and further therapeutical approach.
Low back pain (LBP) is the most common musculoskeletal condition affecting the adult population, with a prevalence of up to 84% 1. Chronic LBP (CLBP) is a chronic pain syndrome in the lower back region, lasting for at least 12 weeks 2. Many authors suggest defining chronic pain as pain that lasts beyond the expected period of healing, avoiding this close time criterion. This definition is very important, as it underlines the concept that CLBP has well-defined underlying pathological causes and that it is a disease, not a symptom. CLBP represents the leading cause of disability worldwide and is a major welfare and economic problem 1. Given this complexity, the diagnostic evaluation of patients with LBP can be very challenging and requires complex clinical decision-making. Answering the question, “what is the pain generator?” among the several structures potentially involved in CLBP is a key factor in the management of these patients, since a diagnosis not based on specific pain generator can lead to therapeutic mistakes.
Low back pain epidemiology
LBP represents a major social and economic problem. The prevalence of CLBP is estimated to range from 15 to 45% in French healthcare workers 3; the point prevalence of CLBP in US adults aged 20–69 years old was 13.1% 4. The general population prevalence of CLBP is estimated to be 5.91% in Italy 5. The prevalence of acute and CLBP in adults doubled in the last decade and continues to increase dramatically in the aging population, affecting both men and women in all ethnic groups 6. LBP has a significant impact on functional capacity, as pain restricts occupational activities and is a major cause of absenteeism 7– 9. Its economic burden is represented directly by the high costs of health care spending and indirectly by decreased productivity 7, 9. These costs are expected to rise even more in the next few years. According to a 2006 review, the total costs associated with LBP in the United States exceed $100 billion per year, two-thirds of which are a result of lost wages and reduced productivity 10.
Anatomy of the low back
The lumbar spine consists of five vertebrae (L1–L5). The complex anatomy of the lumbar spine is a combination of these strong vertebrae, linked by joint capsules, ligaments, tendons, and muscles, with extensive innervation. The spine is designed to be strong, since it has to protect the spinal cord and spinal nerve roots. At the same time, it is highly flexible, providing for mobility in many different planes.
The mobility of the vertebral column is provided by the symphyseal joints between the vertebral bodies, with an IVD in between. The facet joints are located between and behind adjacent vertebrae, contributing to spine stability. They are found at every spinal level and provide about 20% of the torsional (twisting) stability in the neck and low back segments 26. Ligaments aid in joint stability during rest and movement, preventing injury from hyperextension and hyperflexion. The three main ligaments are the anterior longitudinal ligament (ALL), posterior longitudinal ligament (PLL), and ligamentum flavum (LF). The canal is bordered by vertebral bodies and discs anteriorly and by laminae and LF posteriorly. Both the ALL and PLL run the entire length of the spine, anteriorly and posteriorly, respectively. Laterally, spinal nerves and vessels come out from the intervertebral foramen. Beneath each lumbar vertebra, there is the corresponding foramen, from which spinal nerve roots exit. For example, the L1 neural foramina are located just below the L1 vertebra, from where the L1 nerve root exits.
Pathophysiology of spinal pain
Pain is mediated by nociceptors, specialized peripheral sensory neurons that alert us to potentially damaging stimuli at the skin by transducing these stimuli into electrical signals that are relayed to higher brain centers 35. Nociceptors are pseudo-unipolar primary somatosensory neurons with their neuronal body located in the DRG. They are bifurcate axons: the peripheral branch innervates the skin and the central branches synapse on second-order neurons in the dorsal horn of the spinal cord 36. The second-order neurons project to the mesencephalon and thalamus, which in turn connect to somatosensory and anterior cingulate cortices in order to guide sensory-discriminative and affective-cognitive features of pain, respectively 37. The spinal dorsal horn is a major site of integration of somatosensory information and is composed of several interneuron populations forming descending inhibitory and facilitatory pathways, able to modulate the transmission of nociceptive signals 38.
Type of spinal pain according to pain generator
In spite of the hard work done by the International Association for the Study of Pain 41, there remains a degree of confusion in the medical community regarding the definitions of back pain, referred pain, radicular pain, and radiculopathy. Nevertheless, a precise diagnostic assessment is necessary to indicate the right treatment. An incorrect diagnosis and use of a therapy that is not appropriate could also be related to insufficient diagnostic skills of a non-physician specialized in this syndrome, attributed to a clinical and/or instrumental analysis of insufficient depth, or a therapeuthic approach geared towards controlling the symptom (pain) rather than the pain generator mechanisms 25.
Sacroiliac joint pain
Sacroiliac joints (SIJs) are dedicated to providing stable but flexible support for the upper body 62, 63. SIJs are involved in sacral movement, which additionally directly influences the discs and almost certainly the higher lumbar joints. Its innervation is still not well known but has been reported to be by branches from the ventral lumbopelvic rami 64; however, this has not yet been confirmed. On the other hand, several authors have reported innervation of the SIJ by small branches from the posterior rami 65, 66. In a 2012 study by Patel et al. 66, the authors demonstrated that SIJ pain was successfully attenuated using neurotomy of the L5 dorsal primary ramus and lateral branches of the dorsal sacral rami from S1 to S3 63. Hence, there is sufficient evidence that this procedure has an important value for establishing diagnosis and prognosis. The SIJ is well recognized as a source of pain in many patients who present with CLBP 67, 68. It is thought that pain could be generated by ligamentous or capsular tension, extraneous compression or shear forces, hypermobility orhypomobility, altered joint mechanics, and myofascial or kinetic chain dysfunction causing inflammation 69. Intra-articular sources of SIJ pain include osteoarthritis; extra-articular sources include enthesis/ligamentous sprain and primary enthesopathy. In addition, ligamentous, tendinous, or fascial attachment and other cumulative soft tissue injuries that may occur posterior to the dorsal aspect of the SIJ may be a source of discomfort. In physical examination, it is important to examine the movement of the joint, for example with a stress test, consisting of pressing down on the iliac crest (pelvis) or upper thigh, which may reproduce the patient’s pain.
LBP is one of the most common symptoms and conditions motivating individuals to seek medical consultation. The effects of back pain on society are significant, both epidemiologically and economically, and this is likely to only further increase owing to a combination of shifting attitudes and expectations, medical management techniques, and social provision.
Hence, LBP must always be addressed as a complex disease in which it is mandatory that an accurate diagnosis of pain generators is determined before starting any treatment. All the guidelines currently avalaible stress the importance of a multimodal and multidisciplinary approach in order to determine a strategy to solve the problem and not simply alleviate symptomatic pain. Finally, a careful follow up is important to adapt our therapeuthic strategies to dynamic clinical manifestations of CLBP.