Discectomy

Article Author:
Alexander Butler
Article Editor:
Chester Donnally III
Updated:
6/17/2019 4:01:27 PM
PubMed Link:
Discectomy

Introduction

Lumbar disc herniations are a relatively common and early manifestation of degeneration of the lumbar spine. Relevant pathophysiology involves extrusion of the central nucleus pulposus through a compromised outer annulus fibrosis. Symptoms are thought to result from a multifactorial mechanism with components of noxious stimuli to the disc material itself, an inflammatory cascade impacting local nerve roots, and direct compression of nerve roots by extruded disc material. Treatment options include conservative treatment, the mainstays of which are oral medication and physical therapy. The potential efficacy of these modalities is well established.[1][2][3][4][5] Rigorous adherence to the objective association between the patient’s symptoms, physical exam findings, and diagnostic imaging is essential to predict the effectiveness of any planned surgery.

Indications

Urgent lumbar discectomy is necessary in cases of cauda equina syndrome and progressive or new motor deficit. Elective lumbar discectomy is indicated in cases of unremitting radicular symptoms that correspond to radiographic evidence of nerve root compression by a herniated disc in patients that have failed conservative treatment methods. A thorough understanding of the expected outcomes is necessary on the part of the patient before proceeding with surgery. Specifically, the relatively higher reliability of improvement in radicular leg pain as compared to back pain must be stressed. Recurrence risk is an important topic, as well. Revision discectomy remains a viable option should recurrent herniation occur, though with the removal or more disc material and especially in the setting of large or repeated annular injury the option to proceed with spinal fusion at the injured level may be a consideration. Prior to surgery, a high level of correspondence between a patient’s symptoms and pathology on MRI must be confirmed to improve the reasonable likelihood of a positive outcome.

Technique

Open Discectomy

After administering general anesthesia, the patient gets positioned prone on a spine frame or dedicated table. Transverse pads at the iliac crest and chest allow for flexion of the hips to increase interlaminar distance while avoiding pressure on the abdomen to reduce central venous pressure.  Palpation of bony landmarks including the sacrum and iliac crests corresponding the to L4-L5 disc level may guide start point and trajectory of the surgical approach. After appropriate sterile skin prep, localization using a spinal needle and fluoroscopic control confirms the target level. A 3 to 4 cm longitudinal incision is marked at the midline centered about the radiographic marker.

The skin incision is made with a sharp scalpel, and subcutaneous dissection with electrocautery reveals the lumbar fascia; this is incised just off of midline, as identified by palpating the spinous processes, ipsilateral to the disc pathology addressed. This fascial should span the interspinous distance at the target level. A radiographic marker may be used to confirm the spinal level and cranially directed trajectory in line with the interspinous space on a lateral fluoroscopic image. Using electrocautery, a subperiosteal elevation of paraspinal musculature from the superior and inferior spinous processes is completed down to the laminar junction. Lateral dissection continues bluntly with a Cobb elevator as far laterally as the facet joint taking care not to violate its capsule. Visualization of the interlaminar space is essential; removal of dissected muscle tissue in the surgical field, proper retraction and diligent hemostasis using electrocautery are crucial. At this point, the surgeon releases the ligamentum flavum from its attachment on the anterior aspect of the lamina of the superior vertebra using a curette. An angled Woodson elevator may then be inserted anterior to the ligamentum, directed caudally, to protect the dura beneath. The ligamentum is then incised sharply to allow for its retraction with a Penfield elevator and visualization of the exiting nerve root and associated epidural fat. The medial aspect of the inferior facet of the superior vertebra may require resection to allow for adequate exposure. A Penfield or blunt probe is then passed into the neuroforamen to mobilize the root, enabling its medial retraction. With adequate visualization of the intervertebral disc space, removal of fragmented or herniated tissue may then be carried out using pituitary rongeurs.  If a portion of the herniation remains beneath the posterior longitudinal ligament, a scalpel may be necessary to incise the annulus for access. Care must be taken to probe the epidural space using a Woodson elevator in all directions for any additional disc or ligamentous tissue.

Additionally, it is advisable to irrigate the disc space with saline via bulb syringe to express any loose disc fragments that may have gone unvisualized.   Meticulous hemostasis via bipolar electrocautery is achieved, and the wound is liberally irrigated with saline. The fascial and subcutaneous layers are closed with absorbable suture, and the skin closure is by surgeon preference.

MIS Tubular Discectomy

The patient is positioned and prepped as described above. A 1.5 to 2.0 cm surgical incision is marked longitudinally, 1.5 cm off of midline on the affected side.  A stab incision with a #15 scalpel allows the introduction of a guide pin or K-wire, which is advanced under lateral fluoroscopy to ensure appropriate depth as well as docking to the lamina cranial to the affected level. Once start point and trajectory are confirmed, the full skin incision is made as well as fascial incision centered over the wire. Sequential dilator retractors are placed to create a working channel which may be anchored to the operating table.  Magnifying surgical loupes or intra-operative microscopic are useful adjuncts to aid in visualization. Utilizing instruments appropriately designed for a tubular approach, the remainder of the procedure takes place as described above.  Meticulous hemostasis is achieved, the tubular retractor system is removed, and closure of subcutaneous tissue and skin completes the case.

MIS Endoscopic Discectomy

The patient is positioned and prepped as described above.  Beginning at a start point 1 to 2 cm off of midline ipsilateral to pathology, the anatomical space bound by traversing nerve root, exiting nerve root, and superior aspect of the caudal vertebra known as a Kambin triangle is approached at the target level using a spinal needle.  A 5 to 10mm skin incision is made, and successive cannulated dilators allow for the introduction of an 8 mm working cannula through which the endoscope, for visualization of the disc space, traversing and exiting nerve roots, and the passing of instruments. A laminotomy of the cranial vertebra may be made, and targeted nerve roots may be decompressed using endoscopic curettes, rongeours, drills, and bipolar electrocautery. Herniated disc material may thus be removed. A single small endoscopic incision is closed with a subcuticular suture.

Post-Operative Care

Typically, patients may be discharged on postoperative day one after an uncomplicated discectomy. An additional postoperative stay may be necessary for physical therapy rehabilitation or oral pain control.  Discectomy on an outpatient basis has been described and practiced at some centers.[6] No external bracing is necessary for spinal stability. Most surgeons advise limiting significant bending, lifting and twisting motions for 3 to 6 weeks after surgery due to concerns for re-herniation, though more expedient or immediate unrestricted activity may yield equivalent outcomes without increased re-herniation rates.[7][8]

Complications

A wound or deep infection occurs at a rate of 2 to 3%, with dehiscence or other wound infections occurring at a rate of 1 to 2%. Direct intra-operative nerve root injury has been described to affect 1 to 2% of cases. The rate of incidental durotomy ranges from 0 to 4% in the literature. Instability following discectomy by the techniques described here is understood to be exceedingly rare, though the difficulty in its definition and metric make objective quantification difficult.

Lumbar disc herniation recurrence rate following discectomy ranges from 1 to 25%, and the rate of intragenic dural tear approaches 9%.[3][9][10] Male gender, smoking status, and heavy labor are risk factors.[11]  Those with concomitant retrolisthesis at L5-S1 appear to have the same long term clinical outcomes as those without retrolisthesis according to an 8 year follow up from the SPORT database.[12] As recurrence has been investigated at widely varying follow-up times and by several outcome measures, including recurrent symptoms and reoperation, patient-specific factors should inform a candid discussion preoperatively regarding the risk of recurrent disease.

Clinical Significance

The gold standard of surgical intervention for lumbar disc herniation is discectomy or removal of disc material contributing to symptoms. Historically completed through an open approach, several more Minimally Invasive Surgery (MIS) options are presently available, giving the surgeon multiple options.  A recent Cochrane Database systematic review comparing open versus minimally invasive discectomy presented low-quality data suggestive of lower infection rates, and shorter hospital stays for minimally invasive techniques, though with possibly inferior improvements in the low back and leg pain.[13] Since the relatively recent adoption of endoscopic techniques, research available thus far appears to indicate a general reduction in immediate post-operative disability and hospital stay with equivalent outcomes when compared to MIS and open techniques. Additional long-term, high-quality studies are warranted before superiority among these methods may be assessed, though each offers unique advantages.[14] The long-term implications of the relatively minimal surgical exposure necessitated by MIS or endoscopic approaches have been topics of debate.[15][16][17]

Enhancing Healthcare Team Outcomes

A high degree of interprofessional coordination and teamwork is necessary for achieving optimal outcomes when performing discectomy. Beginning with the preoperative diagnostic workup, primary care practitioners must be well versed in the signs and symptoms of a painful herniated disc so that they may start the appropriate workup process and initiate the proper referrals, all while effectively managing the patient's pain. Imaging technicians and radiologists contribute critical information to the diagnostic process by way of advanced imaging studies, most commonly MRI. Initial management employs the expertise of pharmacists in determining the safest and most effective anti-inflammatory medication for each individual patient. Physical therapists administer the gold-standard first-line treatment; their understanding of human mechanics and therapeutic modalities allow for successful treatment of many disc herniations without surgery.[5] [Level 1]

If conservative treatment fails, a discectomy is an option. Primary care practitioners again play an essential role in providing recommendations for pre-operative medical optimization and clearance. On the day of surgery, peri-operative and operating room nursing staff ensure the patient remains comfortable and safe. They also facilitate providing that necessary medications, equipment, and supplies allow for completion of the procedure. An anesthesiology team with an attending physician and assistant, maintain safe and effective analgesia during the surgical procedure. Operating room techs assist in the positioning of the patient and placement of necessary equipment. An electrophysiologist carries out neurologic monitoring for the duration of the procedure. An orthopedic or neurosurgical spine surgeon carries out the procedure with an assistant. Postoperative care is agreed upon and executed by the multidisciplinary team as described. Effective alagesia in the immediate postoperative period is critical. Activity recommendations from the surgical team are carried out by the physical therapy staff. Social workers ensure that the patient's hospital stay and discharge, once medically clear, are as seamless as possible. The surgeon's office staff coordinate follow-up care so that all steps towards a maximal recovery are in place. 

Recurrence rates of lumbar disc herniation after discectomy are broadly reported and range from 1 to 25%.[3][9][10] [Level 3] A multitude of factors, including medical comorbidities and specific disc herniation patterns have been shown to play a role in this risk.[18] [Level 2] All involved interprofessional team-members must not only execute their roles properly but also communicate their findings and expertise to the rest of their colleagues to maximize outcomes. Through properly administered conservative treatment modalities, medical optimization, accurately indicated surgical intervention and precise and efficient operations and postoperative care, the interprofessional team caring for patients undergoing discectomy could collectively strive for improved outcomes.

Assessing the need for and performing a discectomy requires an interprofessional team approach, including physicians, specialists, specialty-trained nurses, therapists, and pharmacists, all collaborating across disciplines to achieve optimal patient results. [Level V]


References

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