We reported the first single surgeon series comparing outcome of microscopic and open primary single level unilateral lumbar decompression or discectomy. We aimed to determine any difference in outcomes between the two techniques.

Forty-six decompressions were performed with use of an operating microscope (microscopic), and forty without (open) at two different hospitals. All procedures were performed by the senior author. Information was obtained by analysis of the patients' notes. The average age of the patients in both groups was comparable. Operating time was shorter in the microscopic group (68min, range 30-130) compared to the open group (83 mins, range 30-180). Dural tear rate was 4.3% with use of a microscope (0% symptomatic dural tear rate) and 7.5% without (2.5% symptomatic dural tear rate). Nerve damage incidence was 0% with use of a microscope and 5% (two patients) without. One of these was a neurapraxia and the patient made a full recovery. Wound infection rates, diagnosed on grounds of clinical suspicion, were 4.3% and 2.5% for microscopic and open respectively. There were no incidences of deep infection or post-operative discitis. Average inpatient stay was under 48 hours in both groups.

Using the modified Macnab criteria, results using the microscope were 0% poor, 14% fair, 32% good, and 55% excellent. The results for the open group were 0% poor, 10% fair, 37% good and 53% excellent. Average follow-up was six months (1-19) for the microscope group, and seven months (2-16) for the open group.

We conclude that primary single level unilateral lumbar decompressive surgery, performed without the use of a microscope, has a higher dural tear rate than the same surgery performed with the benefit of an operating microscope. Surgical time and incidence of nerve damage are also reduced by use of the microscope.