What is a herniated disc and why does it occur?
A disc connects 2 vertebral bodies with each other and is placed like a cushion between them. It consists of a strong fibrous shell surrounding an elastic core, both made of fibrous tissue. It is a natural degeneration process that makes the strong fibrous ring weaker with time, and it can happen that a tear occurs within this fibrous ring and then, when too much load is put on the disc as during lifting heavy weights, for instance, parts of the elastic core, the so-called nucleus pulposus, can slip through this tear out of the disc into the spinal canal. So it comes into contact with the nerves traveling down inside the spinal canal.
How does the condition manifest itself?
The spinal canal is quite narrow, approx 15mm in diameter. So once disc tissue went out of the disc into the spinal canal, it compresses the nerves traveling down inside the spinal canal, depending on how big the part of the disc is that slipped out through the tear. Therefore we speak about a „slipped disc”. This disc herniation of course irritates the nerves then, either by compression, or even because of an inflammatory reaction that occurs around the herniated disc. Once nerves are irritated, one feels pain not so much in the back, but especially in those areas the affected nerves are responsible for, in lumbar disc herniations this is a typical sciatic pain starting from the back and traveling down the entire leg to the foot. Back pain without radiation to the leg hardly ever is caused by a disc herniation, but it can be caused by a degenerated disc that lost its elasticity and cannot sufficiently absorb high loads anymore.
In which vertebrae does a herniated disc occur most often
Disc herniations can occur in any part of the spine; however, mostly the lower part of the lumbar spine is affected. The reason for this is that the lumbar spine is considerably curved, and the discs at L4/5 and L5/S1, for instance, not only must bear high vertical loads, but because or their oblique orientation also high shear forces. This accelerates the natural degeneration process and makes disc herniations more common at the lower lumbar spine.
How common is lumbar herniation?
This is a common disease; approx 150 out of 100.000 people suffer from disc herniations per year.
Treatment of a herniated disc
It must be kept in mind that „disc herniation” is just the headline of a disease that occurs in many different severities. Many disc herniations are very small and heal within 6 weeks without any specific treatment. During this period some amount of pain killers will be necessary and high loads upon the lumbar spine must be avoided, but it is nature itself that „treats” the herniation. Even bigger herniations sometimes can shrink and pain is gone after 6 weeks. Surgery is a very reasonable treatment option when significant pain lasts longer than approx 6 weeks despite of conservative treatment like physical treatments, mild massages and pain killers; it is known in the scientific literature that most cases with pain longer than 6 weeks finally receive disc surgery. In case a disc herniation occurs and causes motor weakness or even functional loss of the urinary bladder, then surgery should be considered right away. But it is not more than about one third of all disc herniation that are finally treated by surgery.
What does herniated disc surgery involve and how long does recovery take?
Disc surgery nowadays is micro-surgery using either the surgical microscope or endoscopes. The golden standard is disc removal under the microscope. This still requires a small skin incision of approx 3 to 5cm (depending on the weight of the patient), but such a small incision does not do any harm to the patient. The microscope then is necessary for perfect visualization of the nerves in the depth of the operating field; once the surgeon can see these delicate nerves, the risk for nerve injury during surgery is significantly lower (approx. 0.1%). Especially when big disc herniations cause severe motor deficit, then the risks associated with disc surgery are significantly lower than the risk that motor deficit persists when surgery is refused. Finally the herniated part of the disc is removed and the nerves are relieved from compression. Because this is a microsurgical procedure, recovery is usually very quick, in most cases the patients can leave bed on the very next day, and after discharge from hospital after another 2 or 3 days – provided no complications occur – the necessary daily activities can be well mastered at home. Patients are then allowed to walk, carry light shopping bags, drive a car and sit as long as they feel comfortable. Complete healing of the disc takes approx 6 weeks, during this period heavy lifting, for instance, must be avoided.
Does the pain disappear completely after surgery?
The pain caused by disc herniations comes from a compressed nerve. After surgical removal of the herniated disc the nerve has free course again, but it is still the same nerve, not a new one. Sometimes it may take some time till the nerves shows complete recovery, and pain killers are necessary for several days after surgery. But most patients report that pain was relieved approx 90% immediately after surgery. Recovery of neurological deficits like numbness or motor weakness may take a longer time and require additional post-op treatement, like physical treatments. But the chance of recovery from neurological deficits caused by a disc herniation is much higher once the herniation is removed, of course.
Is there a risk of the herniation recurring after surgery?
During disc surgery, only the herniated parts of the disc are removed and eventually loose fragments if such are found inside the disc. Especially the strong fibrous ring – which accounts for approx 30% of the entire volume of the disc – is left in place, because removal of this fibrous ring would cause instability and fusion with screws and rods would become necessary. Therefore, even after disc surgery there is still plenty of disc tissue in place and and a recurring disc herniation can occur. The risk is approx. 5% and is very similar to the risk of a recurrent disc herniation when conservative treatment is chosen instead of surgery.
What can we do to keep our spine healthy and prevent disc herniation if possible?
Every spine shows natural degeneration with time. And even when surgery can do amazing things nowadays, we still cannot implant a new spine. The entire spine is surrounded by strong muscles, not only the back muscles, but especially the deep stomach- and trunk muscles. These muscles can protect the spine by taking over high loads that otherwise must be fully carried by the spine. Training these muscles life-long is the best thing in order to protect your spine. It cannot completely avoid the occurence of a disc herniation, but it can definitely lower the risk for it.