summary Lumbar disc herniation is a very common cause of low back pain and unilateral leg pain (radiculopathy). In rare cases, a large disc herniation can lead to cauda equina syndrome, which requires emergent diagnosis and treatment Diagnosis is made clinically and confirmed with MRI of the lumbar spine Treatment for radicular leg pain is initially nonoperative with oral medications and physical therapy. Surgical microdiscectomy is only indicated for severe pain and/or motor deficits that have failed to respond to nonoperative management. Treatment for cauda equina syndrome is emergent microdiscectomy within 48 hours Epidemiology Incidence peak is in 4th and 5th decades lifetime prevalence of 10% only ~5% become symptomatic Demographics 3:1 male:female ratio Location L5-S1 most common level 95% involve L4-5 or L5-S1 levels Etiology Pathoanatomy recurrent torsional strain leads to tears of the outer annulus, resulting in herniation of the nucleus pulposus lateral edge of posterior longitudinal ligament is the weakest region common site for posterolateral/paracentral disc herniations sinuvertebral nerves provide pain innervation to the posterior annulus mediate vertebrogenic back pain that precedes or accompanies disc herniation Pathophysiology cellular senescence of fibrochondrocytes leads to loss of proteoglycan production and subsequent loss of disc height loss of height causes increased strain on the annulus fibrosus increased strain leads to fissures of the annulus fibrils annular tears compromise hoop stresses that act against the deforming forces of the nucleus pulposus nucleus pulposus herniates through a tear younger, well-hydrated discs are more likely to herniate login to view 1 more bullet older, desiccated discs are less likely to herniate sciatica symptoms result from combined mechanical compression and associated inflammation not all patients with mechanical compression develop symptoms login to view 2 more bullets Anatomy Complete intervertebral disc anatomy and biomechanics Disc composition annulus fibrosus composed of type I collagen, water, and proteoglycans login to view 1 more bullet characterized by extensibility and tensile strength login to view 1 more bullet nucleus pulposus composed of type II collagen, water, and proteoglycans characterized by compressibility login to view 4 more bullets avascular structure login to view 1 more bullet Nerve root anatomy key difference between cervical and lumbar spine is pedicle/nerve root mismatch login to view 3 more bullets horizontal (cervical) vs. vertical (lumbar) anatomy of nerve root login to view 2 more bullets Classification Location classification central prolapse often associated with back pain only may present with cauda equina syndrome, which is a surgical emergency posterolateral (paracentral) most common (90-95%) PLL is weakest posterolaterally affects the traversing/descending/lower nerve root login to view 1 more bullet foraminal (far lateral, extraforaminal) less common (5-10%) affects exiting/upper nerve root login to view 1 more bullet herniated disc material directly compresses the dorsal root ganglion login to view 1 more bullet axillary can affect both exiting and descending nerve roots Morphology classification protrusion eccentric bulging with an intact annulus extrusion disc material herniates through annulus but remains continuous with disc space sequestered fragment (free) disc material herniates through annulus and is no longer continuous with disc space prone to proximal or distal migration Containment classification contained disc material is contained beneath the PLL uncontained disc material passes dorsal to the PLL Timing classification acute herniations present for <3-6 months login to view 1 more bullet chronic herniations present for >6 months Presentation History sudden onset of pain after lifting a heavy object occupational exposure prolonged sitting with lateral bending and rotation in the presence of vibrational energy symptomatic improvement when lying supine with knees and hips flexed especially with lower lumbar disc herniations Symptoms patients may present with symptoms of: axial back pain (low back pain) login to view 2 more bullets radicular pain (buttock and leg pain) login to view 3 more bullets cauda equina syndrome (present in 1-10%) login to view 4 more bullets Physical exam inspection limited lumbar range of motion login to view 1 more bullet patient leaning away from side of radiculopathy login to view 1 more bullet palpation spasms of the paraspinal musculature (nonspecific) associated tenderness in the paraspinal musculature (nonspecific) motor exam & reflexes see lower extremity neuro exam login to view 22 more bullets provocative tests straight leg raise (Laségue's sign) login to view 6 more bullets contralateral SLR login to view 1 more bullet femoral nerve stretch test (Wassermann sign) login to view 4 more bullets Bragard's sign login to view 3 more bullets Bowstring sign login to view 1 more bullet Kernig test login to view 1 more bullet Naffziger test login to view 1 more bullet Milgram test login to view 1 more bullet gait analysis Trendelenburg gait login to view 1 more bullet Imaging Radiographs AP and lateral helpful for surgical localization identify anomalous vertebrae (sacralized L5 or lumbarized S1) optional views flexion-extension login to view 2 more bullets findings most often normal loss of lordosis (spasm) loss of disc height, especially at the involved level lumbar spondylosis (degenerative changes) login to view 3 more bullets sciatic scoliosis login to view 1 more bullet sensitivity poor sensitivity for identifying a disc herniation more often used as a screening tool for other pathology prior to MRI CT myelogram indications patients unable to obtain MRI (pacemaker) views sagittal and coronal reconstructions demonstrate compression of the thecal sac findings myelography filling defect at the level of herniation a calcified disc may be visible sensitivity 93% accurate at detecting associated surgical pathology unable to detect foraminal or extraforaminal herniations MRI without gadolinium indications for obtaining an MRI pain lasting >1 month and not responding to nonoperative management red flags are present login to view 4 more bullets modality of choice for diagnosis of lumbar disc herniations highly sensitive and specific helpful for preoperative planning useful to differentiate from synovial facet cysts high rate of abnormal findings in normal people need to correlate MRI findings with symptoms and physical exam findings views sagittal and coronal T2 reconstructions login to view 2 more bullets MRI with gadolinium indications useful for revision surgery findings distinguish between post-surgical fibrosis (enhances with gadolinium) vs. recurrent herniated disc (does not enhance with gadolinium) Treatment Nonoperative rest and physical therapy, anti-inflammatory medications, and limited narcotics indications login to view 5 more bullets outcomes login to view 3 more bullets selective nerve root corticosteroid injections indications login to view 1 more bullet technique login to view 2 more bullets outcomes login to view 3 more bullets Operative laminotomy and discectomy (microdiscectomy) indications login to view 5 more bullets rehabilitation login to view 1 more bullet outcomes login to view 22 more bullets far lateral microdiscectomy indications login to view 1 more bullet Techniques Rest and physical therapy, anti-inflammatory medications, and limited narcotics historical treatment is bedrest followed by progressive activity as tolerated most modern protocols involve immediate activity with modification to avoid activities that exacerbate pain medications NSAIDs muscle relaxants (more effective than placebo, but have side effects) oral steroid taper login to view 2 more bullets narcotic medications login to view 5 more bullets physical therapy typically initiated 3 weeks after symptom onset extension exercises are extremely beneficial traction chiropractic manipulation login to view 1 more bullet Selective nerve root corticosteroid injections epidural selective nerve block can be therapeutic and diagnostic login to view 1 more bullet Laminotomy and discectomy (microdiscectomy) similar outcomes between all surgical techniques most techniques can be performed in a "minimally invasive" fashion login to view 2 more bullets discectomy performed through microscope or loupe magnification (no difference in outcomes) fragment excision vs. extended disc space curettage (subtotal discectomy) login to view 2 more bullets Far lateral microdiscectomy paraspinal approach of Wiltse can also be done with tubular or crank retractors Complications Dural tear 0-4% of cases treatment if at time of surgery, perform watertight repair login to view 1 more bullet Recurrent HNP defined as recurrent sciatica at the previously operated level pain-free interval of 6 months prior to recurrence of symptoms pathology can be ipsilateral or contralateral to the index presentation recurrence rate 5-15% revision rate at 8-year follow-up is 15% according to the SPORT trial risk factors protective against recurrent herniation login to view 2 more bullets treatment can treat nonoperatively initially revision microdiscectomy in patients with persistent symptoms login to view 1 more bullet Wound infections up to 3% of cases epidural abscess in 0.3% of cases risk factors microscope usage proposed as a source of infection (some refute this claim) treatment superficial infections login to view 1 more bullet deep infections login to view 1 more bullet Epidural fibrosis scarring compresses the dura, leading to radicular symptoms associated with poor outcomes following revision surgery login to view 2 more bullets MRI may demonstrate retraction of the dura on the side of the lesion Pyogenic discitis 2.3% of cases treatment IV antibiotics +/- surgical irrigation and debridement Chronic low back pain not completely understood, but central sensitization may be a factor amplification of neural signaling within the central nervous system (CNS) that elicits pain hypersensitivity Modic changes on MRI are associated with postoperative back pain Pain diagrams may be useful in identifying patients with an increased likelihood of pain sensitization, psychosocial load, and utilizing pain management resources Vascular catastrophe exceedingly rare caused by breaking through anterior annulus and injuring vena cava/aorta treatment immediate recognition of complication followed by coordinated repair by vascular surgery service Instability due to over-resection of lamina and pars interarticularis not all patients are symptomatic treatment instrumentation and fusion of the affected segment Prognosis Natural history 90% of patients will have improvement of symptoms within 3 months without substantial medical treatment patients less likely to improve if still symptomatic after 6 weeks factor associated with good outcomes with nonoperative treatment lack of radiculopathy factors associated with worse outcomes with nonoperative treatment obese patients (BMI >30) symptoms present >6 months prior to starting treatment Size of herniation decreases over time (reabsorbed) sequestered disc herniations show the greatest degree of spontaneous reabsorption macrophage phagocytosis and enzymatic degradation are the mechanisms by which reabsorption occurs Factors associated with favorable surgical outcomes severe preoperative leg pain shorter symptom duration younger age increased preoperative physical activity Surgical treatment is equivalent to nonsurgical treatment in the long-term surgery provides faster pain relief