Symptoms

Radicular symptoms correlate with the level and laterality of lumbar disc herniations. Central, paracentral, and posterolateral disc herniations cause mass effect and irritation on the traversing nerve root. Foraminal and extraforaminal disc herniations compress the exiting nerve root and are considered to be more painful if compression on the dorsal root ganglion exists.

Patients often present after an acute onset of lower extremity radiculopathy and less commonly have a temporal correlation to an inciting event. Pain, paresthesia, and/or numbness often occurs in the respective nerve root dermatomes with or without correlative myotomal deficits.

Physical Examination

A complete neurological exam should be performed paying particular attention to lower extremity individual motor group testing, dermatomal sensory changes, nerve root tension signs, and reflexes.

Imaging

Magnetic resonance imaging (MRI) is the diagnostic imaging study of choice for herniated discs. For patients who cannot obtain an MRI, non-contrasted computed tomography (CT) can be obtained. CT imaging can be the first-line imaging for those with the inability to lay supine, claustrophobia, or implanted metallic hardware. However, a CT myelogram study is typically necessary for those unable to undergo MRI.

Non-operative Management

Initial management of lumbar disc herniation typically entails a spectrum of medications and non-surgical interventions. Radiculopathy of short duration is frequently managed initially by NSAIDs, muscle relaxants, short course corticosteroids, and if necessary, opioids. Activity modification is typically required. Mechanical interventions including physical therapy, core stabilization, and other exercises may be beneficial if pain levels are not too high [3, 6, 7]. For persistent pain, epidural steroid injections can be offered. Interventions such as chiropractic manipulations, acupuncture, and trigger point injections have also been used with variable success [8]. Non-operative treatment strategies are aimed at reducing disability and pain and returning patients to activities of daily living since the majority of lumbar disc herniation cases will resolve without surgery.

Surgical Indications

Most data support a trial of non-operative management for at least 4 weeks, if not longer [3, 6, 7]. While early surgery may lead to earlier resolution of symptoms, long-term outcomes have been shown to be similar in both surgical and non-surgical groups [6, 7]. Persistent and/or worsening pain is the primary non-urgent indication for surgical intervention, and some patients undergo early decompression as they are unable to tolerate the severity of pain. More urgent surgical intervention is indicated in those with cauda equina syndrome or acute and disabling motor weakness [7].

Positioning

Most commonly patients are positioned prone using gel rolls or the Wilson frame on a radiolucent table. The patient’s arms are externally rotated and abducted to less than or equal to 90 degrees at the shoulder, raised above the head, and padded at the pressure points to avoid a brachial plexus injury. The head rests on foam padding, making sure the eyes are free of compression. Other positioning techniques including knee-chest and lateral decubitus are available but much less commonly used.

Central and Posterolateral Disc Herniation

Following standard, sterile skin preparation and draping, a conventional open microdiscectomy begins by localizing the correct level on fluoroscopy, and a midline skin incision is made. Monopolar cautery is used to dissect the subcutaneous tissue and fascia and perform a subperiosteal dissection along the spinous process to expose the facet capsule laterally, the laminar edge inferiorly, and the lamina and pars interarticularis superiorly.

Alternatively, MIS tubular approach may be performed. The entry site is planned as previously described, but the incision is made approximately 1.5 cm off midline to the affected side. A guide wire is used to pierce the fascia and, using fluoroscopy, is docked on the laminofacet junction. Sequential tubular dilation is then used with intermittent fluoroscopy to dock the tube at the level of the index disc space. For MIS microdiscectomy, we prefer to use tubes 18 mm in diameter. A microscope is then brought in for visualization.

For conventional open as well as MIS discectomies, a laminotomy is performed using a high-speed drill. The lamintomy begins inferiorly and medially and is carried superiorly to the insertion of the ligametum flavum and laterally to the medial facet. A medial facetectomy is often necessary for visualization taking care to maintain 50% of the facet if possible. The ligamentum flavum is dissected away from and resected using a combination of curettes and Kerrison rongeurs. The dura and traversing nerve root are identified and retracted medially. The disc is localized, its capsule incised and the herniation removed using a combination of rongeurs, nerve hooks and ball-tipped probes.

Decompression of the neural structures is confirmed with angled dissectors. Hemostasis is achieved and the retractor is removed slowly, obtaining hemostasis through the various soft tissue layers. The fascia and subcutaneous layer are closed with absorbable suture and the skin sealed with topical adhesive.

Foraminal/Extraforaminal Disc Herniations

True foraminal disc herniations can be approached by a “cross-canal” technique that involves either a full laminectomy or a unilateral approach (from the contralateral side) for bilateral decompression. The former can be performed open, the latter, MIS. Either will allow observation of the foramen from the contralateral side, and the disc herniation can be removed easily. True extraforaminal disc herniations often require the far lateral approach. The target for a tubular or open conventional dissection is the lateral facet-transverse process junction. The inferolateral facet and pars interarticularis are identified and the intertransverse membrane dissected off the bone. The pedicle of the level below is palpated and the disc herniation encountered in Kambin’s triangle. The inferolateral facet can be shaved back if necessary to visualize the exiting nerve root. The disc fragment is removed and the nerve root inspected to ensure adequate decompression.