Hormuzdiyar Dasenbrock, Department of Neurosurgery, Brigham and Women’s/Children’s Hospital of Boston/Harvard Medical School, Boston, USA, and co-authors reported that minimally invasive discectomy has been proposed as an alternative to open discectomy because, potentially, it may cause less muscle damage, decreased pain, and improved recovery time after surgery.
However, they added that while several small randomised controlled trials have shown the technique to have equivalent outcomes regarding leg pain to open discectomy, the largest trial to date found that open discectomy was associated with significantly greater improvements in leg pain. Dasenbrock et al wrote: “Thus, the authors concluded that patients undergoing minimally invasive discectomy have less favourable outcomes.”
Dasenbrock et al added that as the results of the randomised controlled trials on the technique differed, a meta-analysis of the evidence was “merited”.
After searching for relevant studies using the Medline and Embase databases, Dasenbrock et al identified six randomised control trials for review (837 patients in total; 388 randomised to minimally invasive discectomy and 449 randomised to open discectomy). They did not find a significant difference in the relief of leg pain between the two techniques at either short-term or long-term follow-up. They wrote: “The pooled mean Visual Analogue Scale (VAS) leg pain score was preoperatively was 6.9 and 7.2 in the minimally invasive discectomy and open discectomy groups, respectively. Postoperatively, in both groups, there was a substantial decrease in the VAS score with long-term follow-up—to 1.6 points in the minimally invasive discectomy and the open discectomy cohorts.” Additionally although recurrent disc herniation was more common in patients randomised to minimally invasive discectomy, the pooled risk of recurrent disc herniation was not significantly different in this group compared with the discectomy group.
Incidental durotomies were significantly more frequent in patients randomised to the minimally invasive technique than patients randomised to the open technique (5.67 vs. 2.9%, respectively, relatively risk 2.05, 95% confidence interval 1.05–3.98). Dasenbrock et al suggested that this difference may be because of the limited visualisation and poor depth perception that are known potential limitations of minimally invasive open discectomy. They added: “But, it may also be due to the learning curve associated tubular retraction.” However, despite this finding, there was no significant difference in the number of total complications between the two techniques.
Dasenbrock et al concluded: “The current evidence suggests that both open and minimally invasive discectomy lead to a substantial and equivalent degree of short- and long-term improvement in leg pain, the primary symptom of many patients with lumbar radiculopathy.”
Ali Bydon, associate professor of neurosurgery and clinical director of spinal surgery at Johns Hopkins University, told Spinal News International that although both procedures, open or minimally invasive, are equally efficacious, he favours open discectomy because of the higher incidence of spinal fluid leakage and dural injury with minimally invasive discectomy. He added: "We found that open discectomy remains the most viable and least risky surgical option for patients with lumbar disk herniation."