This was a quote from a school-age friend decades ago, which I considered senseless at the time, but now appreciate in a different context as a spine surgeon.
Low back paraspinal muscles play an important role in the stability and functional movements of the lumbar spine. The condition of the muscle, such as density, cross-sectional area, and fatty infiltration can be seen on spine imaging.
Evidence suggests that these muscles may be smaller in patients with chronic low back pain when compared to healthy people of a similar age. With therapy and strengthening this can be improved, but overall is only a modestly modifiable risk factor for pain.
Lumbar surgery is a treatment option for lumbar spine problems, however paraspinal muscle changes after surgery may result in spinal stiffness, adjacent segment degeneration, and chronic low back pain. This includes loss of muscle thickness, edematous and fatty changes, and may be very modifiable by the surgical approach used.
The multifidus muscles may be the most important muscle for lumbar spine stability. It is the largest of the paraspinal muscles and the closest to the spine. The multifidus muscle was uniquely designed to stabilize and produce large forces. It unfortunately is most directly affected by retraction and dissection from the lumbar spine.
During “open” midline lumbar spine procedures, a large amount of the multifidus muscle is retracted, incorporating some of the spinal levels above and below the surgical site. The muscle is detached from the bone, disrupting its blood supply. To limit multifidus muscle injury during “open” surgical procedures, the intermittent release of the retractor has been recommended.
However, tubular minimally invasive surgery provides much less damage to the muscle. Using a tubular retractor off the midline, the multifidus muscle is not ripped off the bone. The circular shape of the access tube provides concentric forces, which may distribute the retraction evenly. The tube allows a stealth-like mission directly to the site of surgery, confining any muscle irritation focally.
Overall, the literature indicates that the multifidus muscles is less injured by minimally invasive tubular retractors compared to open approaches. This may lead to less pain or adjacent level disease postoperatively. This most often has been discussed regarding fusion procedures. Detractors to minimally invasive approaches cite similar pain and functional outcomes between “open” and “minimally invasive” lumbar decompressions. However, it appears multifidus damage is even observed in “open” lumbar decompressions, compared to minimally invasive tubular techniques.
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