Lumbar spine degeneration is on the rise in Singapore, with back pain and sciatica as the two most common presentations. While most cases can be successfully managed in primary care with rest, analgesia and physical therapy, find out more about the red flags to look out for that may warrant referral.
LUMBAR SPINE DEGENERATION
Spinal degeneration is the result of changes in the mechanical and biochemical properties of the three-joint complex that form the lumbar spine, consisting of the intervertebral disc anteriorly and the facet joints posteriorly.
Beyond ageing, other factors have been identified to be associated with accelerated lumbar degeneration – genetic predisposition, mechanical loading and smoking.
The spinal degenerative cascade was first proposed by Kirkaldy-Willis in the 1970s, and is based on the notion that degeneration begins anteriorly in the intervertebral disc, and subsequently leads to corresponding adaptive changes affecting the facet joints posteriorly.
This article looks at two of the most common clinical presentations of lumbar spine degeneration and how they can be managed:
1. Low back pain
2. Sciatica
1. Low back pain
OVERVIEW
Axial low back pain is the most common clinical manifestation of lumbar spine degeneration with an estimated lifetime prevalence of up to 80%.
It is often multifactorial and in the setting of spinal degeneration, may arise from the intervertebral discs as well as the other mobile structures of the motion segment, namely the facet joints. It is typically subacute (symptom duration between 1 to 3 months) or chronic (symptom duration of more than 3 months) at the time of presentation and can be broadly categorised by origin of the pain into two groups – discogenic low back pain and facetogenic low back pain.
CLASSIFICATION
1. Discogenic low back pain
Mechanism
Discogenic back pain is nociceptive pain that arises as a result of stimulation of the nociceptive nerve receptors located in the annulus fibrosus.
Degenerative changes of the intervertebral discs lead to mechanical stimulation of these nociceptors due to abnormal micromotion when the spine is subjected to mechanical load.
In addition, for cases with an annular fissure, it is believed that an inflammatory component is present as well, further exacerbating the perception of pain.
Presentation
Discogenic back pain is characterised by axial back pain that is aggravated by spinal flexion, such as when sitting, bending forwards as well as axial loading.
2. Facetogenic low back pain
Mechanism
Each lumbar facet is a synovial joint that is richly innervated by the medial branch of the dorsal ramus of the corresponding lumbar spinal nerve.
While the exact mechanism of facetogenic back pain is still the subject of study, it is believed that inflammatory cytokines play a key role in the pathogenesis.
Presentation
Facetogenic back pain is characterised by axial back pain that is aggravated by back extension and trunk rotation.
The pain is often worse in the mornings and after periods of inactivity.
It may also be referred distally into the lower limb in a ‘pseudo-radicular’ pattern, extending to the buttocks, groin and thighs but not beyond the knee and without motor or sensory deficits.
THE GP’S ROLE IN CARE
Evaluation in primary care
Given that the vast majority of cases encountered are likely degenerative or non-specific in nature, the goal of clinical evaluation in the primary healthcare setting is to:
Efficiently exclude potentially serious causes (red flags)
Identify patients with neurological compromise
Flag those who are at risk of delayed improvement due to psychosocial issues, so that appropriate referrals can be made
To this end, the importance of a thorough history and physical examination cannot be overemphasised.
The vast majority of cases can be managed effectively at the primary care setting with appropriate analgesia, rest and in some cases, physiotherapy as will be discussed later.
Red flags to take note of
Figure 1 indicates potential red flags to look out for. It is meant as a guide and the conditions listed are non-exhaustive; it remains at the discretion of the primary care physician to decide which patients to refer to the hospital early for further evaluation and treatment.
ROLE OF RADIOGRAPHIC IMAGING STUDIES
The use of routine radiographic imaging as a diagnostic tool for patients with chronic low back pain is generally not indicated.
This is because the imaging findings are often poorly associated with symptoms (i.e., not specific) and important causes are often not picked up (i.e., not sensitive). The yield from routine radiographic studies for this group of patients is low and may not be cost-effective.
However, they are still of value for patients with red flags, neurological deficits, or symptoms that do not improve after a course of conservative treatment.
MULTIMODAL CONSERVATIVE APPROACH
Conservative management remains the first line of treatment for the vast majority of cases, with a multimodal approach involving physical therapy, medications and cognitive behaviour therapy (CBT).
There is little evidence to support the use of bracing, traction or bed rest for chronic low back pain.
Many of these interventions are available in the primary healthcare setting, with services offered at polyclinics as well as in the private sector.
In the hospital setting, the SingHealth Rehabilitation Medicine Service under the SingHealth Duke-NUS Disease Centre framework adopts a multidisciplinary approach in the management of such patients to ensure optimal outcomes.
Physical therapy
Options may include:
The McKenzie method which involves repeated movements or sustained positions accompanied by mobilisation with a trained physiotherapist
Aerobic exercises
Stabilisation exercises which are aimed at improving core body strength
Cognitive behaviour therapy
CBT, on the other hand, addresses the psychosocial contributors to chronic low back pain and when combined with an appropriate physical therapy programme, has been shown to reduce pain and disability in such patients.
INTERVENTIONAL PROCEDURES BY SPECIALISTS
1. Lumbar facet interventions
Lumbar facet interventions are minimally invasive procedures sometimes offered in cases of chronic facetogenic low back pain where conservative methods have failed. Yet, there remains considerable controversy with regard to their effectiveness.
Such interventions include intra- or periarticular facet blocks, radiofrequency ablation (RFA) and medial branch facet blocks.
Indications
Although no clear guideline exists, they are generally reserved for cases that have undergone at least three months of conservative therapy consisting of pharmacological intervention, physical therapy and behavioural modifications.
The challenge in many cases lies in the difficulty to reliably diagnose facetogenic back pain and the subsequent identification of the symptomatic level(s).
Together with a suggestive clinical presentation and signs such as paraspinal tenderness, imaging modalities such as MRI or CT scans may be helpful in localising the pathological level for intervention.
Intra- or periarticular facet injections
Intra- or periarticular facet injections are short-term therapeutic, non-surgical radiological procedures performed in an outpatient setting under fluoroscopic or CT guidance with contrast media, a local anaesthetic agent and a corticosteroid.
They often demonstrate excellent immediate effectiveness, and a good proportion of patients continue to report significant relief of chronic low back pain at two months post-intervention.
Radiofrequency ablation
RFA, on the other hand, is regarded as a long-term therapeutic option that is sometimes employed in cases of intractable facetogenic chronic low back pain that have failed conservative therapy.
It involves the delivery of radiofrequency pulses to produce heat so as to destroy the nociceptive pain fibres innervating the facet joints.
Medial branch facet blocks
Prior to RFA, medial branch facet blocks under image guidance are usually performed for their role in predicting the effectiveness of subsequent RFA.
These blocks can be performed with a local anaesthetic alone if the intent is purely for its diagnostic value, or coupled with a corticosteroid if longer-term pain relief is desired, with or without subsequent RFA.
2. Intradiscal electrothermal annuloplasty (IDA)
Indications
IDA may be a therapeutic option for a subset of patients with significant discogenic low back pain and who have failed to respond to conservative treatment.
Procedure
Performed under local anaesthesia, the procedure is performed percutaneously and involves the positioning of a catheter via an introducer needle at the posterior annulus of the disc under fluoroscopic guidance. The catheter is gradually heated with the
aim of thermal destruction of the intradiscal nociceptive nerve fibres in the annulus, thereby disrupting the pain pathway believed to be responsible for the perception of discogenic low back pain.
Provocative discography
Although clinical assessment remains important, the gold standard for diagnosing lumbar discogenic pain is provocative discography which is sometimes performed prior to IDA.
This involves injection of a contrast medium into the nucleus pulposus of the intervertebral disc. If the pain that is provoked during the injection of the contrast medium is relieved by a subsequent injection of local anaesthetic into the disc, one can infer that the disc is likely
the source of the pain.
Outcomes
The results of IDA as a means to relieve discogenic low back pain are mixed. It is currently offered by the pain management services at SingHealth institutions.
3. Surgery
Surgical intervention is sometimes offered to patients with chronic low back pain refractory to conservative management.
Lumbar fusion
Lumbar fusion is often regarded as the standard of care for such cases, based on the premise that the back pain is the result of abnormal motion in the degenerate disc segment. Hence, elimination of such movement by fusion of the affected spinal segment will conceivably bring about significant pain relief.
While there may be a clear benefit for cases with demonstrable segmental instability, the evidence for lumbar fusion as a means of treatment for axial low back pain secondary to degenerative changes as a whole is weak.
Some studies report that the outcomes of lumbar fusion are no better than intensive rehabilitation and CBT.
Simply put, radiologically successful lumbar fusion does not always correlate with a clinically significant improvement in axial low back pain.
Lumbar disc arthroplasty
In recent years, lumbar disc arthroplasty has emerged as an alternative surgical option to fusion for a selected subset of patients with chronic discogenic low back pain.
The theoretical advantages are:
Faster postoperative recovery and return to work
Maintenance of motion of the affected lumbar segment, hence reducing the risk of adjacent segment degeneration
However, there is presently no evidence to show that lumbar disc arthroplasty produces superior clinical outcomes to lumbar fusion.
For both surgical options, careful patient selection on the part of the spine surgeon remains key to successful outcomes.
2. Sciatica
OVERVIEW
After low back pain, sciatica is the second most common clinical manifestation amongst patients with degenerative disease of the lumbar spine, having an estimated prevalence of 3% to 5% of the population.
The most common cause is structural with a compressive lesion leading to functional impairment of one or more lumbosacral nerve roots, although an inflammatory component may be present as well.
The natural history of sciatica generally remains favourable, with most cases reporting significant improvement of symptoms typically over weeks to months. In those with acute disc herniations, clinical improvement is often accompanied by spontaneous radiological resolution of such herniation.
Most cases can thus be managed effectively in the primary healthcare setting with a multimodal approach comprising of a period of rest, analgesia and physiotherapy.
THE GP’S ROLE IN CARE
Evaluation in primary care
The goal of clinical assessment is to identify patients who are at high risk of progressive or permanent neurological impairment, so that referral to a specialist spine centre for further management can be instituted in a timely fashion.
When to refer a patient
Suggested guidelines for referral are indicated in Table 2. These guidelines are not exhaustive, and it remains at the discretion of the attending physician to decide with regard to the urgency for referral to specialist care.
Consider urgent referral to A&E
| 1. Clinical suspicion of cauda equina syndrome (CES) (sphincter disturbance or perianal anaesthesia) 2. Gross motor deficit in the lower limbs
3. Rapidly progressive neurological symptoms or deficits
|
Fast-track referral to a spine clinic
| 1. Presence of constitutional symptoms such as unexplained fever or weight loss
2. Intravenous drug abuser
3. Immunocompromised 4. Acute motor deficits in the lower limbs
|
Normal referral to a spine clinic
| 1. Sensory neurological deficits in the lower limbs 2. Neurogenic claudication or sciatica
|
Table 2
INTERVENTIONAL PROCEDURES BY SPECIALISTS
1. Lumbar nerve blocks
Lumbar nerve blocks are percutaneous procedures performed under local anaesthesia and may be an option for patients with sciatica who have failed to respond to at least six weeks of conservative management.
Lumbar epidural nerve blocks can be performed via either a transforaminal or interlaminar approach using local anaesthetics and corticosteroids, often under fluoroscopic guidance in the hospital setting.
As a therapeutic procedure, it has the potential to provide good relief of radicular pain for a period of time whilst the natural history of the underlying condition takes its course.
2. Selective spinal nerve root block
Selective spinal nerve root block is another option that is sometimes used as a diagnostic tool to determine whether a particular nerve root is mediating a patient’s leg pain.
This may be especially useful in cases where the clinical presentation may not correlate exactly with the level of radiological compression. However, this does not replace surgical intervention; in these cases, the value of the selective spinal nerve root block lies in its ability to guide subsequent surgical decompression to the pathological level responsible for the patient’s symptoms.
3. Surgical intervention
Indications
Although most cases respond well to conservative management, surgery may be indicated for sciatica in the following situations:
When multimodal conservative management fails to bring about significant symptom relief after a period of at least six weeks; or
When the neuropathic pain is intractable and so debilitating that an initial six-week period of conservative management is not a viable option; or
When there is severe acute or progressive motor deficit in the lower limbs (e.g., acute footdrop); or
When there is concomitant presence of CES
Lumbar decompression surgery
Lumbar decompression surgery remains the cornerstone of surgical management of sciatica and is aimed at addressing the compressive pathology – oftentimes a herniated disc, hypertrophic facet joints or buckled and hypertrophic ligamentum flavum.
Outcomes are generally favourable, with most patients reporting significant relief of radicular symptoms.
Surgical approaches have evolved over time and minimally invasive techniques such as tubular and endoscopic decompression have demonstrated equivalent clinical outcomes compared to traditional open decompression, with the added advantage of smaller incisions and less pain in the early postoperative period.
In cases whereby neural compression is contributed by segmental instability such as dynamic spondylolisthesis, instrumentation and fusion may be required.
Careful assessment and patient selection on the part of the spine surgeon remains key to successful clinical outcomes.
CONCLUSION
Back pain and sciatica remain the two most common clinical presentations for lumbar spine degeneration, a condition which is growing in prevalence alongside an ageing population. The majority of cases can be managed successfully in the primary healthcare setting, although clinicians should be cognisant of the red flags that warrant early referral to the hospital for further assessment and management.
REFERENCES
Kengo Fujii, Masashi Yamazaki, et al. Discogenic back pain: Literature review of definition, diagnosis and treatment. JBMR Plus. 2019 May; 3(5): e10180
Ruihuan Du, Gang Xu, et al. Facet Joint Syndrome: Pathophysiology, Diagnosis, and Treatment. J Pain Res. 2022; 15: 3689–3710.
Dawood Sayed, Jay Grider, et al. The American Society of Pain and Neuroscience (ASPN) Evidence-Based Clinical Guideline of Interventional Treatments for Low Back Pain. J Pain Res. 2022; 15: 3729–3832.
Steven J Atlas, Richard A Deyo. Evaluating and Managing Acute Low Back Pain in the Primary Care Setting. J Gen Intern Med. 2001 Feb; 16(2): 120–131
Steven D Waldman. Atlas of Interventional Pain Management (Fourth Edition), Elsevier
Dr Chen Haobin is a Consultant Orthopaedic Surgeon practising at Sengkang General Hospital (SKH) and is also the Spine Service Chief at SKH under the SingHealth Duke-NUS Spine Centre framework. He has a keen interest in mentoring young doctors in spine surgery, and believes in a multidisciplinary approach to the management of spinal conditions.
GPs who would like more information about this procedure, please contact Dr Chen at [email protected].
GPs can call the SingHealth Duke-NUS Spine Centre for appointments at the following hotlines or click here to visit the website:
Singapore General Hospital: 6326 6060
Changi General Hospital: 6788 3003
Sengkang General Hospital: 6930 6000
KK Women's and Children's Hospital: 6692 2984
National Neuroscience Institute: 6330 6363
