Abstract: We identified 11 studies (1172 participants). We assessed seven out of 11 studies as having high overall risk of bias. There was low-quality evidence that MID was associated with worse leg pain than MD/OD at follow-up ranging from six months to two years (e.g. at one year: MD 0.13, 95% CI 0.09 to 0.16), but differences were small (less than 0.5 points on a 0 to 10 scale) and did not meet standard thresholds for clinically meaningful differences. There was low-quality evidence that MID was associated with worse LBP than MD/OD at six-month follow-up (MD 0.35, 95% CI 0.19 to 0.51) and at two years (MD 0.54, 95% CI 0.29 to 0.79). There was no significant difference at one year (0 to 10 scale: MD 0.19, 95% CI -0.22 to 0.59). Statistical heterogeneity was small to high (I2 statistic = 35% at six months, 90% at one year and 65% at two years). There were no clear differences between MID techniques and MD/OD on other primary outcomes related to functional disability (Oswestry Disability Index greater than six months postoperatively) and persistence of motor and sensory neurological deficits, though evidence on neurological deficits was limited by the small numbers of participants in the trials with neurological deficits at baseline. There was just one study for each of the sciatica-specific outcomes including the Sciatica Bothersomeness Index and the Sciatica Frequency Index, which did not need further analysis. For secondary outcomes, MID was associated with lower risk of surgical site and other infections, but higher risk of re-hospitalisation due to recurrent disc herniation. In addition, MID was associated with slightly lower quality of life (less than 5 points on a 100-point scale) on some measures of quality of life, such as some physical subclasses of the 36-item Short Form. Some trials found MID to be associated with shorter duration of hospitalisation than MD/OD, but results were inconsistent. MID may be inferior in terms of relief of leg pain, LBP and re-hospitalisation; however, differences in pain relief appeared to be small and may not be clinically important. Potential advantages of MID are lower risk of surgical site and other infections. MID may be associated with shorter hospital stay but the evidence was inconsistent. Given these potential advantages, more research is needed to define appropriate indications for MID as an alternative to standard MD/OD.

Plain-language summary: We found 11 studies up to November 2013, examining 1172 people, with studies ranging from 22 to 325 participants, and people aged from 12 to 70 years. All had tried non-surgical treatments and all had leg pain that was worse than their back pain. The follow-up period after surgery ranged from five days to 56 months. People who had a MD/OD had less pain in their legs, and less low back pain, but the difference was small. They were less likely to need a second operation because the first had been unsuccessful. They felt slightly better in some physical aspects of their quality of life, but again the difference was too small to be meaningful. In terms of complications, the two operations were similar, though people who had a MD/OD were more likely to have wound infections. Many of the studies were carried out on a small number of people and had a high risk of bias, so the overall quality of the evidence for leg and low back pain was low.