Background
When the discs between vertebrae in the spine become damaged (herniated), the soft gel inside them pushes through the wall of the disc and presses against the nerves or the spinal cord, causing a burning pain in legs and pain in the back. When this happens in the lower back, it i s known as lumbar disc herniation.
Review question
The main treatment for this condition is lumbar discectomy, which involves removing the part of the disc pressing on the nerves. There are two main types of this surgery. The first type is standard microdiscectomy, which can be performed with the aid of microscope magnification or headlight loupe, or open discectomy where surgeons do not use a microscope or loupe (MD/OD). However, all steps of the operations are similar. The second type of operation is minimally invasive discectomy (MID) procedures. MID involves a smaller incision and less damage to the surrounding tissue. We reviewed the evidence to see if one type of surgery is more effective than the other type of surgery in terms of the results after surgery including pain in the legs, low back pain, problems with mobility or numbness and disability.
Study characteristics
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.
Key results
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.
Quality of evidence
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.
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.
Microdiscectomy or open discectomy (MD/OD) are the standard procedures for symptomatic lumbar disc herniation and they involve removal of the portion of the intervertebral disc compressing the nerve root or spinal cord (or both) with or without the aid of a headlight loupe or microscope magnification. Potential advantages of newer minimally invasive discectomy (MID) procedures over standard MD/OD include less blood loss, less postoperative pain, shorter hospitalisation and earlier return to work.
To compare the benefits and harms of MID versus MD/OD for management of lumbar intervertebral discopathy.
We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (November 2013), MEDLINE (1946 to November 2013) and EMBASE (1974 to November 2013) and applied no language restrictions. We also contacted experts in the field for additional studies and reviewed reference lists of relevant studies.
We selected randomised controlled trials (RCTs) and quasi-randomised controlled trials (QRCTs) that compared MD/OD with a MID (percutaneous endoscopic interlaminar or transforaminal lumbar discectomy, transmuscular tubular microdiscectomy and automated percutaneous lumbar discectomy) for treatment of adults with lumbar radiculopathy secondary to discopathy. We evaluated the following primary outcomes: pain related to sciatica or low back pain (LBP) as measured by a visual analogue scale, sciatic specific outcomes such as neurological deficit of lower extremity or bowel/urinary incontinence and functional outcomes (including daily activity or return to work). We also evaluated the following secondary outcomes: complications of surgery, duration of hospital stay, postoperative opioid use, quality of life and overall participant satisfaction. Two authors checked data abstractions and articles for inclusion. We resolved discrepancies by consensus.
We used standard methodological procedures expected by The Cochrane Collaboration. We used pre-developed forms to extract data and two authors independently assessed risk of bias. For statistical analysis, we used risk ratio (RR) for dichotomous outcomes and mean difference (MD) for continuous outcomes with 95% confidence intervals (CI) for each outcome.
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.