Risks and complications associated with lumbar laminectomy include: dural tear (with or without pseudomeningocele), adhesive arachnoiditis (with or without epidural scarring), residual stenosis, instability, and failure to improve.
Many of the complications of lumbar laminectomy are common to all posterior spinal procedures:
Table: Neurosurgical Risks & Complications
Complications particular to lumbar laminectomy include:
dural tear (with or without pseudomeningocele), adhesive arachnoiditis (with or without epidural scarring), residual stenosis, instability, and failure to improve.
Incision of the yellow ligament following removal of a lumbar lamina
The dura mater is the thick membrane that makes up the thecal sac containing, in the lumbar segment of the vertebral canal, cerebrospinal fluid and the cauda equina. A hole in the dura allows leakage of cerebrospinal fluid (CSF) from the thecal sac into the surrounding tissue possibly leading to formation of a pseudomeningocele.
Intraoperative:
A dural tear is recognized usually at the moment it occurs with the sudden appearance at the site of the last bite with the ronguer or cut with the knife of clear, apparently cerebrospinal, fluid.
Immediate post operative, delayed post operative:
A dural tear that is too small to release enough CSF to be grossly apparent may nevertheless over several days or weeks postoperatively allow enough to accumulate a volume sufficient push open the suture line and fill separated deeper tissues of the wound with fluid sufficient to cause a visible bulge of the soft tissues of the lower back most prominently below the surgical incision.
Surgeon -- technique:
If the dura has not been separated from the overlying yellow ligament (ligamentum flavum) to which it is frequently attached in lumbar stenosis it is liable to be traumatized during cutting and grabbing of the ligamentum.
Patient -- disease:
Lumbar laminectomy is frequently done for decompression in patients with lumbar stenosis. Lumbar stenosis is associated with inflammation of the ligamentum flavum with formation of adhesions between this structure and the underlying dura. Grabbing or cutting the ligamentum flavum can inadvertently injure the underlying adherent dura.
Neurologic deficit:
The nerves of the cauda equina lie within the thecal sac and can herniate (extrude) through a hole created by a tear. If suction is applied near the tear to drain collecting cerebrospinal fluid, a nerve root can be inadvertently sucked up into the tip with injury of possible destruction of the root leading, depending on the root, to a neurologic deficit such as weakness or numbness of an extremity, or impairment of the function of the urinary bladder and or anal sphincter.
A pseudomeningocele is an extension of the subarachnoid space into the soft tissue surrounding the central nervous system. Unlike meningocele, pseudomeningocele is cerebrospinal fluid not bounded or confined by a biological membrane.
Reoperation:
No consequence:
Intraoperative:
When the dural tear is recognized intraoperatively every effort should be made to identify and securely close the defect.
Acute post operative:
In the acute post operative period the goal is to keep the dural repair intact (with the dural edges approximated) long enough for the body's normal healing mechanisms (especially scar formation) to seal the defect. Some neurosurgeons keep patients flat or even tilted with the head down (Trendelenberg position) to decrease CSF pressure against the suture line in the lower lumbar thecal sac for 24 to 48 hours post operatively.
A lumbar drain can be placed to decrease the pressure of CSF at the site of the tear. Once there is no flow across the dural defect the dura can repair itself.
Long term:
Closure of the dura in the presence of a pseudomeningocele can be very complicated and difficult.
Dural tear is a frequent, usually inconsequential, complication of lumbar laminectomy. Perhaps as many as 1 in 20 lumbar stenosis decompression operations are complicated by a dural tear. Only a very small number of these require intervention. A tear that fails all less invasive interventions and ultimately requiring re-operation for closure is rare.
Judgment:
Any tissues adherent to the dura must be completely separated from it along and line along which they are to be pulled, bitten, or cut.
Technique:
A patty placed over the dura will protect it from a significant amount of ronguer and sucker trauma.
Pain:
adhesive arachnoiditis with epidural fibrosis is the most common anatomic diagnosis associated with the syndrome called "failed back".
Neurophysiologic compromise:
adhesive arachnoiditis following lumbar laminectomy probably causes some pain through compromise of blood supply to the nerve roots -- the blood vessels that supply the nerve roots are tiny and vulnerable to compression by even small amounts of scarring in the subarachnoid space. Decreased blood supply over the long term (months, years) can lead to permanent injury (stroke) of the nerves beyond rescue by surgical intervention.
Reoperation:
adhesive arachnoiditis and epidural fibrosis following lumbar laminectomy are difficult to treat surgically. The planes between the nerve roots and the thecal sac and the epidural space and the ligamentum flavum may be indistinguishable within the scar. Dissecting through this scar with even the most deliberate caution is risky for inadvertent violation across a tissue plane (such as the dura) resulting in injury to an unanticipated neural structure (such as the nerve) with possibly devastating functional consequences (such as a foot drop) for the patient.
No consequence:
adhesive arachnoiditis (and/or epidural fibrosis) are frequently seen on post operative imaging of the lumbosacral spine in patients who have undergone lumbar laminectomy and are then scanned for some reason other than leg pain (i.e. the patients is asymptomatic in terms of the adhesions and fibrosis).
Irreversible:
unfortunately it seems that epidural fibrosis and arachnoid scarring are not reversible -- there is no medication or chemical that can be reliably applied to scar to make it dissolve or get smaller without injury to nervous and its surrounding tissues.
Reoperation:
in cases of less extensive, less dense scar only minimally displacing the roots and thecal sac, re-operation for removal of residual or recurrent fragments of disc, or for pieces of bone accessible without undo manipulation around nervous structures, can be attempted.
The frequency of symptomatic epidural and/or arachnoid scarring following lumbar laminectomy ("failed back syndrome") is high -- affecting probably as many as 15% of patients.
Planning:
the surgeon should always plan to do an exposure large enough to perform the manipulations at the target necessary for accomplishment of the surgical goal, but always with the least possible disturbance to nervous and contiguous tissues within and without the lumbar vertebral canal.
Technique:
placement of a piece of fat (usually obtained from the subcutaneous tissues during opening or closure) in the subarachnoid space in the area of surgical manipulation around a nerve root is believed by some to prevent formation of scar in this space.
Incomplete removal of all areas of stenosis is sometimes deliberate and sometimes inadvertent.
Delayed:
Residual stenosis following lumbar laminectomy is a complication usually delayed in its discovery for weeks or months post-operatively.
the most common cause of residual stenosis following lumbar laminectomy is failure of the surgeon to extend the decompression to include the actual site of origin of the patient's complaints. Often the patient gives sufficient consistent historical information and on physical exam is found to have findings consistent with a single site of pathology on a lumbosacral MR scan. More difficult (and demanding of judgment) are pain complaints that do not correlate or are inconsistent with imaging findings or whose origin could be due to any one or combination of several MR abnormalities.
The surgeon must weigh the increased risk of spinal instability associated with removal of bone to decompress each vertebral level. Only as many levels should be decompressed as are sites of symptomatic nerve root compression. If the surgeon does too few levels the patient is likely to need a repeat procedure (to get the residual stenosis). If the surgeon does too many, he or she may be subjecting the patient to significant risk of spinal instability (with possible complicating fracture, dislocation, and neurologic injury).
Patient -- disease:
patients with severe multilevel acquired or congenital stenosis are more apt to have residual stenosis following lumbar laminectomy.
Neurologic deficit:
residual stenosis following lumbar laminectomy can be associated with continued nerve root compromise due to compression with persistence (or worsening) of neurologic deficit.
Pain:
residual stenosis can be the cause persistent pain following lumbar laminectomy. In patients with neurogenic claudication (cramping pain in the calves worsened by exercise, relieved by rest), claudication may return or persist due to incomplete removal of a stenotic site of thecal sac and/or nerve root compression. If epidural and/or arachnoid scar form in the vicinity of the residual stenosis they may exacerbate its clinical consequences -- i.e. worsening of neurologic deficit or, more commonly, of back and leg pain).
Neurophysiologic compromise:
residual stenosis following lumbar laminectomy
Prolongation of surgery: residual stenosis following lumbar laminectomy
Reoperation: residual stenosis following lumbar laminectomy
No consequence: residual stenosis following lumbar laminectomy
Judgment:
residual stenosis that is due to mistaken judgment as to the localization of the patient's symptomatic level and insufficient bony decompression
Technique:
unintentional residual stenosis due to inadequate bony removal can be avoided by repeatedly probing the space between the dorsal dura mater of the thecal sac and nerve root and overlying ligaments and bone. These structures should be removed at any site where the space between them and the dura is abnormally small and especially when the dura can be seen to be displaced downwards by them.
Neurologic deficit:
instability complicating lumbar laminectomy will result in neurologic deficit if movement of vertebral bodies, facet joints, and other ligamentous or bony structures causes neural compression at the level of the cauda equina or nerve roots.
Pain:
lumbosacral instability complicating lumbar laminectomy can cause considerable pain.
Neurophysiologic compromise:
instability can result in subluxation (movement of a bone with respect to another disrupting their normal relationship). If the abnormal spatial relationship is achieved at the cost of spaces through which a nerve root of the cauda equina travels in its course from the spinal cord to and through the neural foramen injury to the nerve can result.
Prolongation of surgery:
instability discovered intraoperatively may require prolongation of the surgical procedure -- an eventuality that should be discussed pre-operatively with the patient and those who will be in the waiting room -- in order to do a fusion (with or without instrumentation).
Reoperation:
instability complicating lumbar laminectomy may require re-operation if non-surgical measures such as bracing fail to control pain
No consequence:
instability complicating lumbar laminectomy may be a radiographic finding (movement by flexion/extension views) without accompanying symptoms of pain or signs of neurologic deficit.
Intraoperative:
when spinal instability is recognized intraoperatively consideration should be given to doing a fusion with or without instrumentation at the termination of the laminectomy. If instability is a possibility, the surgeon should obtain consent for any conceivable stabilizing measure that may be determined necessary intraoperatively.
Post operative:
some spinal instability can be managed non-operatively with external corsets and braces. Many patients who come to operation do so because they are unable to tolerate the rigid braces that are sometimes required to adequately stabilize the unstable lumbosacral spine.
Long term:
bracing that succeeds in relieving patient pain during the acute and immediate post-operative periods can be continued as a long term means to control instability-related pain.
In patients who fail bracing (or as noted above, who cannot tolerate it) surgical stabilization is a more drastic, but in appropriate patients very effective, means of achieving partial or total pain relief.
The frequency of instability complicating lumbar laminectomy is higher in patients with pre-existing pas defect (spondylolisthesis)
Planning:
instability complicating lumbar laminectomy can be avoided if the surgeon plans to do an in-situ or other fusion in the event that gross instability is encountered intraoperatively.
Technique:
Removal of as little of surrounding bone and soft tissue is essential in the prevention of instability following lumbar laminectomy.
Removal of the ligamentous and bony structures of the posterior lumbar spine can de-stabilize the lumbosacral spine.
Pathological movement between components of the lumbar vertebral column (lumbar instability) can result from lumbar laminectomy and can threaten the integrity of the lumbar and sacral nerve roots that travel through this region.
Intraoperative:
instability can be demonstrated intraoperatively by grabbing a bone of the lumbar spine
Immediate post operative:
Patients suspected of having spinal instability at whatever level should be externally braced pending workup.
Delayed post operative:
instability of the lumbar spine following decompressive lumbar laminectomy is usually seen as movement on a lumbosacral flexion-extension plain X-ray film, or as a spondylolisthesis (dislocation of one vertebral body with the respect to the one above or below) on MR of the lumbosacral spine in a patient with unresolved or recurrent low back back following decompressive lumbar laminectomy.
Surgeon -- planning:
instability can complicating lumbar laminectomy that is planned without adequate attention to the implications for spinal stability.
Surgeon -- judgment:
instability complicating lumbar laminectomy can result from bad intraoperative judgments
Patient -- anatomy:
patients who present with a small degree of subluxation (displacement, spondylolisthesis) are at increased risk for developing worse instability following lumbar laminectomy.
Patient -- disease:
instability is more likely after lumbar laminectomy in patients with preoperative evidence of spondylolisthesis on plain x-ray or MR images.
The frequency of symptomatic instability following decompressive lumbar laminectomy is highest among women with osteoporotic bone and pre-surgical spondylolisthesis (subluxation, dislocation).
Planning:
instability is usually an avoidable complication of lumbar laminectomy: by a combination of limited bone and ligament resection, and stabilization as needed and when required.
Technique:
instability can also result from excessive removal of bone due to technical inexperience or deficient knowledge of the bony anatomy. The best prevention of iatrogenic instability is familiarity with the anatomy of the bone, ligament, and dura, with restraint in disturbing and removing these vertebral column support tissues.
Post operative:
failure to improve in the first few days to weeks following decompressive laminectomy can be managed with oral analgesics and physical therapy hoping that clinical improvement will follow healing of the surgical site.
Long term:
failure to improve if chronic after several months post op should be evaluated for correctable causes (recurrent disc herniation, piece of bone in vertebral canal or neural foramen pushing against nerve). If no surgically correctable cause is found non-surgical modalities such as physical therapy, epidural injections, and oral analgesics are still the mainstays of chronic spinal pain management.
Many patients who have decompressive laminectomy for treatment of neurogenic claudication and other symptoms and signs of lumbar stenosis are disappointed with the outcome - the so-called "failed back" syndrome. Sometimes this is due to scarring or is the consequence of a technical mishap but sometimes it results from unrealistic expectations going into surgery.
Immediate post operative:
although not a good prognostic sign, failure to improve within the first few days after a decompressive laminectomy does not necessarily mean inevitable progression to "failed back".
The reasons why patient's fail to improve follow decompressive laminectomy for degenerative (arthritic) spinal stenosis are many:
1. poor surgical candidate - the patient should never have had the operation in the first place.
2. unrealistic expectations - most lumbar laminectomy patients go into surgery with a positive attitude, hoping for a good outcome, realizing that no matter how good his or her outcome statistics no neurosurgeon can "guarantee" a "good" outcome from palliative ( treating symptoms only) surgery for a relentless degenerative disease (aging).
Many patients are not satisfied with a 30 or 60% improvement that is really a "good" outcome from decompressive laminectomy for many patients with lumbar stenosis
Failure to improve can result in a number of counterproductive patterns of emotion and behavior. Anger, frustration, and depression are the most common emotional reactions to surgery that seems to have been useless and, therefore, unnecessary. Patients cope better with the disappointment of residual symptoms following decompressive lumbar laminectomy when they have been fully warned of the possibility during preoperative counseling and have accepted this as a significant risk.