Reherniation of Intervertebral Disc after Microdiscectomy
The prolapsed intervertebral disc may either be a protrusion or an extrusion. In disc protrusion, the inner soft nucleus pulposus herniates through the annulus ring without an actual breach of the ring. The protrusion of the nucleus leads to thinning of the outer ring as the ring is stretched. Microdiscectomy for protrusion may increase the risk of re-herniation through a thinned-out part of the annulus.
In cases of disc extrusion, the nucleus pulposus herniates out through a defect in the annulus. The extruded disc material is removed during microdiscectomy and re-herniation may occur through the same defect if the defect in the annulus during primary herniation was large.
During a microdiscectomy surgery, the surgeon utilizes a small incision (1-1.5 inches) at the back to access the diseased intervertebral disc. The surgeon uses a magnifying operating microscope to better visualize the disc. During microdiscectomy, the surgeon proceeds to remove only a small part of the nucleus as compared to an aggressive complete discectomy during the open technique.
In the case of protrusion, the surgeon uses a blunt incision to enter the disc space and remove the free lying fragments. The surgeon removes the free lying fragments outside the disc space in the case of disc extrusion. The defect in the annulus is often closed to prevent re-herniation.
The type of surgical technique used during microdiscectomy and the type of herniation may correlate with the re-herniation risk after the surgery. The removal of insufficient disc material and inadequate closure of a large gap in the annulus may lead to re-herniation. Similarly, the thinned and stretched-out annulus is at risk of re-herniation. Wide incisions of the annulus during surgery also increase the risk of re-herniation.
Other factors such as uncontrolled diabetes mellitus, smoking, obesity, may contribute to re-herniation after microdiscectomy surgery. Patients are motivated to continue normal day-to-day activities after the surgery, however, inadequate precautions and poor posture after microdiscectomy may lead to re-herniation.
The re-herniation may occur in the immediate postoperative period, few weeks to few months after the surgery, or after years following the surgery. The symptoms of re-herniation may however not be as clear as the initial symptoms for surgery. The re-herniation symptoms may be easily mistaken with continued symptoms of initial disc herniation. A long pain-free interval after microdiscectomy and subsequent development of symptoms may more clearly point towards a possible re-herniation.
The patients may complain of symptoms similar to the original complaints of disc herniation. The symptoms of disc herniation include radicular pain radiating in the thighs and the legs. The patients may also report numbness and tingling in the lower extremities.
There may be a weakness in the lower extremity muscles. However, during re-herniation, the patients may report pain different in location, intensity, and its relation with any physical activity. The difference may be due to compression at a different site or a tethering of the nerve root to epidural fibrosis.
Diagnosis is made by physical examination findings which are correlated with imaging studies. During the physical examination, the surgeon may look for pain during specific maneuvers and power/sensory examination of the lower extremities. The physician may also perform a diagnostic nerve root injection in cases when the clinical diagnosis is not evident.
An imaging study in the form of an MRI is used to diagnose re-herniation. MRI studies with gadolinium may be used to differentiate between scar tissue and re-herniation. Other imaging studies such as an X-ray and a CT scan are more commonly used to visualize the bony anatomy of the patient. The evaluation of the bony anatomy helps in the planning of a subsequent surgery if needed.
The management of re-herniation is similar to the primary disc prolapse. The mainstay treatment is conservative in the form of pain medications, physical therapy, and activity modification. An epidural steroid injection may also be used for the management of the symptoms.
Surgical management in the form of repeat microdiscectomy is done for re-herniation. The indications for repeat surgery are more strict as compared to primary surgery due to a high number of false-positive cases. Further, the repeat surgery may be complicated due to the presence of fibrous tissue and tethering of the nerves. Depending upon the underlying condition the surgeon may access the spine through the same incision or a different incision.
In some patients who require surgery, lumbar interbody fusion surgery may be indicated. Patients with multiple re-herniations and instability of the spinal segment are better managed with lumbar fusion surgery. During a lumbar fusion surgery, the surgeon completely removes the intervertebral disc material and uses a bone graft to weld/fuse the two adjoining vertebrae together to create stability.