There are situations that call for necessary lumbar surgery, circumstances when surgery depends upon specific situations and times when surgery is not indicated. Identification of these temporal states is not that difficult when certain rules are applied.
What are the general indications for surgery?
- Nerve compression that leads to motor weakness.
- Nerve pain that is not tolerated or necessitates unacceptable reduction of activities due to pain.
- Degenerative disc disease that causes intolerable back pain.
- Deformity that is progressive.
- Cord compression (remember that the L1 canal contains the conus medularis- the end of the cord.)
Nerve compression that leads to motor weakness
Nerve compression that leads to motor weakness is generally a surgical condition. Compression of a nerve can lead to dynamic pain (pain with walking that is relieved by sitting) or sitting pain but does not always have to be accompanied by weakness. This pain and numbness is not necessarily a surgical indication by itself (see next section below for further information).
If there is weakness of a major motor group (specific group of muscles) from nerve compression, more often than not surgery is indicated. The reason has to do with the integrity or relative “toughness” of the motor nerves.
Pain, numbness and paresthesias (pins and needles) involve the sensory, nociceptive and proprioceptive (location sense) components of the nerve. These portions of the complete nerve root are very sensitive to compression. That is, even slight compression or irritation will lead to symptoms. Conversely, being so sensitive they also have good ability to recover with therapy and injections without surgery. In addition, even some permanent minor deficits in these nerves (remaining skin numbness or pins and needles) are typically easily tolerated.
The motor nerves have a much greater capacity to resist compression than the sensory nerves. It therefore takes significant compression of the motor nerves to block function. Unfortunately, this also means that motor nerves have a poorer capacity to recover or regenerate than the sensory nerves.
If weakness only occurs in a small muscle group (L5 compression causing weakness in the extensor hallicus longus or big toe extensors), rushed surgery is probably not indicated unless the patient is a martial arts instructor, NFL place kicker or rock climber. However, if the weakness is in a major muscle group leading to foot drop or gastroc-soleus weakness, lack of recovery leads to gait disturbances and a limp.
The best chance for motor strength recovery is with surgery to decompress the nerve (microdiscectomy or foraminotomy). There still is a small chance that with surgery, the muscle strength will not recover but with surgical decompression, the chance of recovery is much greater than without surgery.
Nerve Pain that is not tolerated or necessitates unacceptable reduction of activities due to pain
This category is the most common reason patients choose to undergo surgery in the lumbar spine. Disc herniations or nerve compression from bone spur can cause leg pain. Compression of the sensory nerves leads to numbness. Compression of the nociceptive nerves leads to pain. Compression of the proprioceptive nerves leads to paresthesias (pins and needles).
These nerves are highly sensitive and even a small amount of compression will aggravate them. Pain can be substantial and paresthesias can drive some patients absolutely crazy. Nonetheless, without motor weakness, there is generally no need to immediately rush to surgery unless the pain is intolerable.
The reason is that these nerves being so sensitive also have good capacity to recover. Many times, patients in moderate pain can improve with epidural steroid injections, oral medications, therapy and time.
I use the three month rule for surgical indications for these types of patients. If the individual has made at least 50% improvement within three months (or has no desire to undergo surgery), then continuing conservative care is the path to take.
If the pain has not substantially improved in three months or pain relapses occur commonly during this period of time, surgery becomes the treatment of choice. Patients seem to do better if surgery is performed in the first three to four months than if surgery is put off until after six months of symptoms.
There are patients who at rest have little pain but with certain activities, develop incapacitating pain. This is dynamic pain caused by gravity’s effect on an unstable vertebral segment. Without load on the spine, the nerve root can tolerate the narrowed lateral recess or foramen. With loading however, the increased compression causes further compression and significant increase in pain precluding the desired activities.
If the inciting activities can be avoided to the satisfaction of the patient, surgery will not be necessary. For example, if the patient can switch from jogging to cycling and the leg pain is alleviated, surgery is not necessary. If however, the pain is associated with a non-negotiable activity restriction (a professional ball player who cannot field the ball or an auto mechanic who cannot turn a wrench), surgery will be indicated.
There is a subset of patients that show up on my doorstep with severe pain from an acute disc herniation. They lie moaning, curled up in the fetal position on my exam table or are seen in the emergency department on a stretcher after taking substantial amounts of pain medications. These patients need surgery to relieve the unrelenting nerve pain.
There is a subset of patients that have permanent injury to the sensory and pain nerves from prolonged exposure to compression. Surgery will decompress the nerve but not relieve the damage already incurred (see chronic radiculopathy).
Degenerative Disc Disease That Causes Intolerable Back Pain
Back pain from degenerative disc disease can be an indication for surgery. Back pain may be incapacitating but it is not generally life threatening. Back pain tends to wax and wane in many patients. When then is back pain an indication for surgery?
Patients with incapacitating back pain may be surgical candidates. Back pain must have been proven to be non-manageable (failed therapy and medication programs) and affect the patient’s lifestyle. If a patient can acceptably modify his or her lifestyle to reduce the pain to a tolerable level, surgery would not be indicated.
If however, the lifestyle change is not modifiable (a professional baseball player that cannot field a ball or a mechanic that cannot turn a wrench) or the modification is not acceptable (a patient cannot participate in recreational activities without substantial pain), surgery might be indicated.
First, prior to surgical consideration, back pain patients have to complete a thorough rehabilitation program associated with ergonomics (modifications in lifting and loading the spine). If the modification of activities is ineffective, other therapies may be instituted including epidurals and medications. If these treatments fail to relieve symptoms, surgery can be contemplated.
Back pain has to be present for more than three months and most patients considering surgery will have had at least six months of back pain. A surgical workup then can ensue. This workup might consist of imaging (MRI, CT and X-rays), diagnostic nerve blocks and discograms. If the pain generators can be identified, a surgical plan is formulated. Normally, the surgery is a fusion of the painful segment or segments. Artificial discs at this point in my opinion are not an option (see section on lumbar artificial discs for more information).
Certain disorders may cause back pain that do not specifically involve degenerative disc disease. Examples are isthmic spondylolisthesis and degenerative spondylolisthesis. These disorders also respond to fusion.
After a one level successful fusion, the patient can return to almost all sports and activities. If two levels are fused, the post-operative restrictions are somewhat greater. If three or more levels are fused, the patient has to understand that fusion and pain relief is being traded for spine stiffness and the post-operative restrictions are more stringent.
Deformity that is progressive
A spinal malalignment can be stable or progressive. Scoliotic curves and even individual segmental collapses can progressively deform over time. If the angulation can be predicted to continue or is observed over time with serial X-rays to progress, surgery is indicated. This is to prevent problems with correction in a curve that will progressively become larger over time.
A degenerative or isthmic (fracture) slip may progress and be predicted to continue to slip. This is an indication for surgery.
Pars fractures (isthmic spondylolysis) in a younger individual may have a surgical indication if the disc is still normal at the time of diagnosis (no annular tears) to prevent future annular tears.
Most individuals do not think of spinal cord disorders when the lumbar spine is discussed but the spinal cord (conus medularis) terminates behind the body of L1. A disc herniation or a large spur causing stenosis (narrowing of the canal) can cause dysfunction of the cord.
This compression may lead to bowel and bladder malfunction as well as possible motor deficits. At this level, this is a central nervous system injury and surgery is required in a timely basis.