Transcutaneous Lumbar Diskectomy for Internal Disk Derangement: A New Indication

Richard A. Marks, MD, Baylor/Richardson Medical Center, Richardson, Tex

South Med J. 2000;93(9) 

In This Article

Materials and Methods

Under the care of one physician (R.A.M.), 103 patients had lumbar diskectomy using either Onik's original technique of automated percutaneous lumbar diskectomy[10] or a refinement thereof, transcutaneous lumbar diskectomy with microrongeur decompression (Blackstone Diskectomy System, Blackstone Medical Inc, Springfield, Mass). All patients had a diagnosis of internal disk derangement, defined for the purposes of this study as either diskographic fissuring of the annulus with pain reproduction and/or dessication on magnetic resonance imaging (MRI) study with or without disk bulge, protrusion, or herniation; this in combination with intractable back or leg pain or both.

All patients treated had low back pain, with or without radiation to one or both lower extremities, and they had had an unsuccessful rigorous trial of conservative care. Such care varied only slightly with the situation or individual. In all cases, pain had been present a minimum of 4 months and was deemed no longer tolerable to the patient. Preoperative care routinely included physical therapy and use of heat, massage, ultrasound, possible electrical stimulation, or application of a transcutaneous electrical nerve stimulation unit on an acute basis. If the patient preferred, chiropractic care was occasionally substituted for this phase of care.

Either subsequent to or concurrent with this modality phase of treatment, back care education was given, and the patient was taught and supervised in learning an exercise program to both stretch and strengthen all the soft tissues responsible for the support of the back. Pool therapy was also considered when believed potentially useful. If not contraindicated, nonsteroidal anti-inflammatory drugs were used preferentially, but when appropriate, muscle spasm agents were prescribed as well as narcotic or nonnarcotic analgesics.

Besides these mainstays of care, other forms of treatment were more patient-specific. Job or recreational demands often indicated lumbosacral corsetry. Injections were performed at the joint discretion of myself, a dolorologist, and the patient. These variably included facet, sacroiliac, trigger point, or epidural steroid injections. Psychologic consultations were obtained for patients in whom it was thought to be important to patient care.

Conservative treatment was considered to have failed when the patient's pain and subsequent dysfunction had reached a plateau at an unacceptable level, the time ranging from 4 months to several years. At that time, if there was treatable disease as confirmed radiographically (as defined in this study), the patient was offered options of still further time and conservative care, traditional surgery, or a transcutaneous disk resection. For such radiographic consideration, each patient must have had MRI and/or diskography showing frank disk dessication with or without bulge, protrusion, or herniation. If the MRI was not definitive for internal disk derangement, diskograms were necessary for confirmation of the diagnosis. Positive diskogram criteria included fissuring or extravasation of dye, and reproduction of symptoms with dye injection.

Physical findings for inclusion were not absolute; therefore, the subjective complaint of pain with its subsequent limitations, coupled with radiographic findings and failure of conservative care, were used as criteria, rather than mandatory objective physical signs. Although most patients had painful and limited range of motion, lumbar tenderness or spasm was not uniform. Positive findings on straight leg raising examination, sensory deficit, weakness, or reflex asymmetry were carefully noted, but they were considered incidental for inclusion in this series.

The operation was done in a sterile operating room environment on a fluoroscopic table with the patient in the lateral decubitus position. After reviewing the preoperative radiographic studies, the operative entry site was selected. The entry point was between 8 and 12 cm from the midline and approximately midway between the end plates of the involved disk. Once the entry point on the patient's skin had been determined, a skin wheel was raised, using a 25 gauge needle to deliver 0.25% plain Marcaine. Marcaine was further disseminated intramuscularly as a 22 gauge spinal needle was advanced toward the disk space. When the needle tip appeared to be within 1 to 2 cm of the disk space on both anteroposterior (AP) and lateral radiographs, a 3 to 4 mm skin incision was made, using a No. 11 blade, immediately lateral to the entry point of the needle.

Leaving the needle in place to act as a positional guide, a sharpened, 1 mm diameter trocar was introduced via the small incision and advanced through the muscular tissue. The progress of the trocar was checked frequently on AP and lateral radiographs using the image intensifier to ascertain its proper positioning. When the trocar tip was clearly seen to be located within approximately 1 cm of the posterolateral margin of the annulus on both views, the spinal needle was removed. The patient, under intravenous sedation with local anesthetic supplement, was asked whether any pain was felt with further trocar advancement toward the annulus and exactly where the pain was located. If further trocar advancement resulted in the patient admitting to a radicular type of pain, the trocar was redirected. When the annulus was encountered by the leading edge of the trocar, as confirmed by radiology and by palpation, and if the patient then admitted to back pain alone with no radiation to the leg, the trocar tip was advanced through the annulus to the nucleus of the disk. Next, a cannula with a dissecting tapered dilator was threaded over the trocar. When the cannula was seen radiographically to be approaching the depth of the nerve root, the patient was again carefully questioned regarding the location of pain, if any. If radicular pain was felt at this stage, the trocar was removed and repositioned. If no such radicular pain was reported, the dilator and cannula were advanced until felt by palpation to be firmly seated against the annular margin. The position was confirmed radiographically. The tapered dilator was then removed, as the surrounding cannula was advanced to the annulus. At this stage, the trocar was still centrally located in the disk and was used as a direct guide in threading. A trephine was then placed surrounding the trocar and within the cannula and was advanced to the annulus. The patient was once again asked about any pain, before an annulotomy was done using the sharp trephine. As the cannula remained tightly abutted against the annular margin, the trephine and trocar were removed, and the transcutaneous disk resection instrument was threaded through the cannula into the disk. With AP and lateral radiographic images, the instrument's position was confirmed as being identical to the earlier placement of the probing trocar guide.

Assuming a position either exactly central to the nucleus or one believed to be well within the nuclear confines, the disk resection instrument was then activated by beginning the flow of saline and vacuum suction. A retractable blade, mounted internally in the instrument adjacent to the fenestration portal, was repeatedly advanced and retracted through the full length of the fenestration, either by automation or manually, to sever the nuclear material as it was drawn by vacuum into the shaft. The severed nuclear material was then trapped in a filter for later gross and microscopic identification as well as quantification. The resection device was then itself advanced, retracted, and rotated, always remaining within nuclear margins. The fenestration device was positioned in all directions to physically explore the nuclear confines.

If the nuclear return appeared to be minimal or decreasing, and it was thought that further material should be removed, the suction and saline flow were deactivated, and the instrument was removed. With the cannula still firmly in place against the annulus, the microrongeur or grasping device was guided into the nuclear space. Intradiskal position was again confirmed radiographically. Once position had been verified, the dissecting instrument was used to remove additional nuclear material. The micrograsper or microrongeur was also useful to loosen possibly adherent or coherent nuclear material before replacement of the suction instrument.

When total nuclear return was believed to be adequate, or after no more disk material could be removed, the instrument last used was withdrawn into the cannula, and the two were simultaneously removed from the patient. A single stitch was placed across the incision and a sterile bandage dressing was applied. The patient was discharged when awake, alert, and stable postoperatively.

The patients in this study were assessed retrospectively. Medical records were examined and data were extracted regarding patient diagnosis, age, sex, number of disk levels, and workers' compensation versus privately insured patients. Patients were contacted and asked questions regarding pain symptoms, return to employment and activities, and medications. The patients were rated on a scale ranging from excellent to poor based on the overall subjective satisfaction and functional improvement as defined in Table 1. If the patient did not meet every criterion at a rating level, the lower rating was assigned.

The Wilcoxon rank sum test was used to determine whether the individual factors of sex, levels of disk surgery, and workers' compensation status affected the subjective outcome rating. Spearman correlation coefficient was used to determine whether a correlation existed between age and the subjective outcome rating. Logistic regression analysis was used to determine the collective effect of each factor upon the subjective outcome rating. Statistical significance was set at P < .05.

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