Discectomy

Discectomy is the most common surgery for lower back pain performed for the treatment of disc herniations. It is often combined with other spinal procedures such as laminotomy or foraminotomy or artificial disc replacement and other forms of spinal fusion. Discectomy techniques can be generally subdivided into conventional open discectomy and minimally invasive discectomy ¹.

Indications

The main indication of discectomy is a herniated disc with nerve root compression or spinal canal stenosis related to the following symptoms ^1,3:

• severe radiculopathy and progressive neurological deficits

• no response to adequate conservative non-operative treatment

• lumbar discectomy: cauda equina syndrome

• cervical discectomy: soft disc herniations

Contraindications

Contraindications of discectomy are those of spinal surgery including:

• bony spinal canal stenosis

• overt segmental instability

• malignant tumors with dural involvement

• neurological or vascular pathologies mimicking disc herniations

Procedure

A rough overview and example of different discectomy techniques are listed below ^1,2. There might be variations to the technique especially in certain settings such as extraforaminal discectomy ^1,2.

Conventional open discectomy

• unilateral posterior approach

• incision and interlaminar space exposure

• removal of the ligamentum flavum after laminotomy/hemilaminectomy or without bone removal

• discal hernia exposure

• nerve root confirmation and gentle release

• incision of the posterior longitudinal ligament at the point of maximal disc herniation

• resection  and removal of the disc herniation

• confirmation of complete nerve root decompression and exclusion of residual herniations

An extraforaminal discectomy might require a paraspinal approach between the multifidus and longissimus muscles with additional complete or partial facetectomy with or without spinal instrumentation.

Microendoscopic discectomy

Microendoscopic discectomies are performed with video monitor system ¹.

• insertion of serial dilators at the affected level

• insertion of a tubular retractor on the lamina

• insertion of a rigid endoscope into the retractor and setup of the video monitor

• removal of the ligamentum and laminotomy

• nerve root retraction and discectomy

Percutaneous endoscopic discectomy

Transforaminal lumbar approach ² (suitable for intracanal disc herniation at L1-2 to L4-5 without migration):

• cannula insertion through the intervertebral foramen under fluoroscopic guidance (Hijikata’s percutaneous nucleotomy technique)

• cannula positioning through the safety triangle under the annular outer layer

• removal of disc fragments

Interlaminar lumbar approach ² (suitable for disc herniation  at L5-S1 without migration):

• cannula insertion via interlaminar approach under fluoroscopy

• entry point at the medial edge of the pedicle directing the cannula towards the superior endplate of S1

• incision and splitting of the ligamentum flavum

• epidural fat removal with a radiofrequency coagulator

• insertion of the cannula into the spinal canal

• nerve root protection

• identification and removal of the disc herniation

Anterior cervical approach ³ (cervical soft disc herniations):

• intradiscal cannula insertion through safety zone between the carotid artery and trachea/esophagus

• intraoperative discography with a demonstration of the hernia

• serial dilation serial and insertion of the endoscope

• inspection of annular fissure posterior longitudinal ligament, endplates and herniated disc

• selective discectomy with forceps under preservation of the central nucleus

Posterior cervical approach ³ (foraminal or lateral cervical disk herniations):

• percutaneous endoscope insertion to the ipsilateral laminofacet junction

• foraminal unroofing with foraminotomy

• selective discectomy under endoscopic view

Complications

Complications of discectomy depend on the approach and include complications of spinal surgery in particular the following ^1,4:

• spinal hematoma

• pseudomeningocele/dural tear

• spinal infection

  • epidural abscess

  • spondylodiscitis

• wound complications

• radiculitis/nerve root damage

• failed back or neck surgery syndrome

• epidural fibrosis

• recurrent disc herniation

• adjacent segment disease

• postsurgical synostosis

• abdominal vascular injury

• ureteral injury

• bowel perforation

Radiographic features

CT

A CT scan can visualize the spinal canal and characterize the location of spinal hardware as well as complications. 

MRI

MRI can be used to evaluate the success of decompression and show complications and the amount of epidural fibrosis or recurrent disc herniation.

Radiology report

The postoperative radiological report should include a description of the following features:

• level of spinal surgery

• operative access route (laminotomy/laminectomy)

• epidural fibrosis

• spinal instrumentation hardware

• complications

Outcomes

For sciatica, due to disc herniations, discectomy can provide outcome improvement in a short and medium-term of up to four to five years ¹. Up to 9% of patients experience recurrent disc herniation on the same level and up to two-thirds of them or almost 6% undergo repeat surgery ⁴.

A major drawback of conventional open discectomy is the extensive injury of paraspinal muscles and ligamentous structures inducing surgical scar formation and thus potentially leading to adverse postsurgical clinical outcomes or failed back surgery ¹.

Compared to conventional open surgery minimally invasive techniques are characterized by less postoperative pain and improved postoperative recovery or shortened hospital stay ^1,2. However clinical outcome between an open discectomy and minimally invasive techniques is apparently not significantly different ^1,2. A drawback of the minimally invasive techniques is the high learning curve ¹. Micro endoscopic discectomy can reduce injury to the paraspinal muscles and can preserve facet joints in the setting of extraforaminal disc herniations. Percutaneous endoscopic discectomy leads to a reduction in nuclear volume and thus tension on the annular fibers and the posterior longitudinal ligament ¹.

History and etymology

Conventional open discectomy has been first described by Mixter and Barr in 1934  and later by Love in 1939 ^1,2. A paraspinal approach for extraforaminal disc herniations was described by Wiltse and Spencer in 1988 ².  Microdiscectomy was first described by Caspar and Williams in 1977 ². The endoscopic approach was independently introduced by Kambin and Sampson ² and Hijikata in the 1970s ³. The microendoscopic discectomy being developed and first reported by Foley and Smith in 1997 ^1,2. Yeung and Tsou described the transforaminal approach for percutaneous endoscopic discectomy ². The first anterior percutaneous cervical discectomy was introduced by Tajima and colleagues ³.