We have studied, prospectively, 116 patients with motor deficits associated with herniation of a lumbar disc who underwent microdiscectomy. They were studied during the first six months and at a mean of 6.4 years after surgery. Before operation, muscle weakness was mild (grade 4) in 67% of patients, severe (grade 3) in 21% and very severe (grade 2 or 1) in 12%. The muscle which most frequently had severe or very severe weakness was extensor hallucis longus, followed in order by triceps surae, extensor digitorum communis, tibialis anterior, and others.

At the latest follow-up examination, 76% of patients had complete recovery of strength. Persistent weakness was found in 16% of patients who had had a mild preoperative deficit and in 39% of those with severe or very severe weakness. Muscle strength was graded 4 in all patients with persistent weakness, except for four with a very severe preoperative deficit affecting the L5 or S1 nerve root. They showed no significant recovery. Excluding this last group, the degree of recovery of motor function was inversely related to the preoperative severity and duration of muscle weakness. The patients’ subjective functional capacity was not directly related to the degree of recovery except in those with persistent severe or very severe deficit.

We analysed prospectively 26 patients who had revision operations for ipsilateral recurrent radicular pain after a period of pain relief of more than six months following primary discectomy. They were assessed before the initial operation, between the two procedures and at a minimum of two years after reoperation. MRI was performed before primary discectomy and reoperation. Fifty consecutive patients who had a disc excision during the study period but did not have recurrent radicular pain, were analysed as a control group.

Of the study group 42% related the onset of recurrent radicular pain to an isolated injury or a precipitating event, but none of the control group did so (p < 0.001). T2-weighted MRI performed before primary discectomy showed that patients in the study group had significantly more severe disc degeneration compared with the control group (p = 0.02). Intraoperative findings revealed recurrent disc herniation in 24 patients and bulging of the disc in two, one of whom also had lateral stenosis. Epidural scarring was found to be abundant, intraoperatively and on MRI, in eight and in nine patients, respectively.

At the last follow-up, the clinical outcome was satisfactory in 85% of patients in the study group and in 88% of the control group (p > 0.05). Work or daily activities had been resumed at the same level as before the onset of symptoms by 81% of the patients in the study group and 84% of the control group. No correlation was found between the amount of epidural fibrosis, as seen intraoperatively and on MRI, and the result of surgery. The recurrence of radicular pain caused no significant changes in the psychological profile compared with the assessment before the primary discectomy.

We made a prospective study of 43 consecutive patients treated for intraforaminal (34) or extraforaminal (9) herniations of a lumbar disc by excision through an interlaminar approach, using an operating microscope. The intraforaminal herniations were contained or extruded in 52% and sequestrated in 47%; for extraforaminal herniation the proportions were 66% and 33%, respectively. There was additional posterolateral protrusion or spinal stenosis at the level of the lateral herniation in seven and four cases, respectively. The patients were reviewed at three months and two years after surgery. Radiographs showed three grades of facetectomy: grade I, removal of 50% or less, grade II, excision of 51% to 75%, and grade III, subtotal or total facetectomy.

For intraforaminal herniations the results were excellent or good in 88% of patients when reviewed at three months and in 91% at two years. For extraforaminal herniations, there was an excellent or good outcome in 89% of patients in the short term and in all in the long term. The facetectomy had been grade I in 14 and grade II in 25; it had been grade III in four, but only one had had total facetectomy. No patient had developed vertebral hypermobility as a result of the operation.

An intralaminar approach using an operating microscope can provide adequate access to a lateral protrusion. It has the advantage of allowing the treatment of posterolateral protrusion or posterior annular bulge and of spinal stenosis at the same level.