Degenerative Disc Disease
Degenerative disc disease refers to the natural deterioration of the intervertebral disc structure, such that they become progressively weak and begin to collapse. While many patients remain asymptomatic, a proportion will develop pain and further complications.
Degenerative disc disease is often related to aging; the factors which precipitate damage to the intervertebral discs include:
- Progressive dehydration of the nucleus pulposus
- Daily activities causing tears in the annulus fibrosis
- Injuries or pathology resulting in instability
- Including mechanical insults (such as spinal fractures), iatrogenic injuries (such as spinal surgery), or systemic metabolic processes (such as osteoporosis)
The cascade of changes seen degenerative disc disease can be subdivided into three stages, the duration of which can vary significantly:
- Dysfunction – outer annular tears and separation of the endplate, cartilage destruction, and facet synovial reaction
- Instability – disc resorption and loss of disc space height, along with facet capsular laxity, can lead to subluxation and spondylolisthesis
- Restabilisation – degenerative changes lead to osteophyte formation and canal stenosis
The clinical features of degenerative disc disease depend on the region and severity of the disease.
Early stage disease symptoms are often localised and the clinical examination may be unremarkable. Potential signs include local spinal tenderness or contracted paraspinal muscles, hypomobility, or painful extension of the back or neck.
All cases require a complete neurological examination, importantly to assess for evidence of spinal cord compression or cauda equina syndrome.
When the disc degeneration progresses to cause instability, the pain may become more severe and include radicular leg pain or paraesthesia. Pain may be reproduced by passively raising the extended leg (positive Lasegue sign).
Further disease progression may demonstrate signs of worsening muscle tenderness, stiffness, reduced movement (particularly lumbar region), and scoliosis.
Lasègue test, also known as the straight leg raise, is used to assess for disc herniation in patients presenting with lumbago.
With the patient lying down on their back, the examiner lifts the patient’s leg while the knee is straight. The ankle can be dorsiflexed and / or the cervical spine flexed for further assessment.
A positive sign is when pain is elicited during the leg raising +/- ankle dorsiflexion or cervical spine flexion. Sensitivity and specificity have been reported at 91% and 26% respectively.
Important differentials to consider include cauda equina syndrome, infection (such as discitis), or malignancy (inc. metastatic disease)
All patients presenting with back pain should be assessed for the red flag signs, including new onset faecal incontinence or urinary, saddle anaesthesia, immunosuppression or chronic steroid use, intravenous drug abuse, unexplained fever, significant trauma, osteoporosis or metabolic bone disease, new onset after 50 years old, or a history of malignancy.
Recent NICE guidelines suggest imaging should only be warranted in cases of suspected degenerative disc disease if:
- Red flags present
- Radiculopathy with pain for more than 6 weeks
- Evidence of a spinal cord compression
- Imaging would significantly alter management
Spine radiographs are only recommended if the patient has a history of recent significant trauma, known osteoporosis, or aged over 70 years.
A MRI spine is the gold standard investigation for suspected degenerative disc disease warranting imaging, however the majority of cases do not require imaging.
A disc that appears normal on MRI is unlikely to be the cause of any pain. Characteristics that may be present include signs of degeneration, reduction of disc height, the presence of annular tears, and endplate changes.
Management of degenerative disc disease is highly variable and patient-dependent*.
In the acute stage of disc disease, adequate pain relief is the mainstay of treatment. Simple analgesics should be used first-line, with neuropathic analgesics as adjuncts if required.
Encouraging mobility within patient limits is recommended for the treatment of acute low back pain, with physiotherapy for strengthening exercises.
*Emergency intervention is only warranted in cases of cauda equina syndrome, necessitating decompression of the spinal canal within 24-48 hrs of symptom onset, through commonly either laminectomy or discectomy
If pain continues beyond 3 months, despite analgesia, referral to the pain clinic may be required.
Although spinal fusion has previous been suggested for chronic low back pain, there is no evidence to support surgical intervention (indeed, evidence suggests surgery may make back pain worse in the long term).
- Degenerative disc disease refers to the natural deterioration of the intervertebral disc structure
- The clinical features of degenerative disc disease depend on the region and severity of the disease
- Diagnosis is often clinical and the majority of cases do not require imaging
- Analgesia and physiotherapy is the mainstay of management