Lumbar paraspinal muscle
Lumbar muscles functionally support and maintain the stability of the spine. The weakness of back muscles is the main cause of recurring low back pain 1).
Muscles
It is generally accepted that the major muscles of the lumbar spine can be divided into the anterior and posterior groups 2).
The anterior group is composed of two major muscles: psoas major muscle and quadratus lumborum muscle.
The posterior group comprises the medial multifidus muscle and lateral sacrospinalis muscle 3).
Intermuscular spaces
Recognition of the intermuscular spaces within lumbar paraspinal muscles is critically important for using the paramedian muscle splitting approach to the lumbar spine. As such, it is important to determine the intermuscular spaces within the lumbar paraspinal muscles by utilizing medical imaging such as computed tomography (CT) and magnetic resonance imaging (MRI).
A total of 30 adult cadavers were studied by sectional anatomic dissection, and 60 patients were examined using CT (16 slices, 3-mm thickness, 3-mm intersection gap, n = 30) and MRI (3.0T, T2-WI, 5-mm thickness, 1-mm intersection gap, n = 30). The distances between the midline and the superficial points of the intermuscular spaces at different intervertebral disc levels were measured.
Based on study of our cadavers, the mean distances from the midline to the intermuscular space between multifidus and longissimus, from intervertebral disc levels L1-L2 to L5-S1, were 0.9, 1.1, 1.7, 3.0, and 3.5 cm, respectively. Compared with the upper levels (L1-L3), the superficial location at the lower level (L4-S1) is more laterally to the midline (P<0.05). The intermuscular space between sacrospinalis and quadratus lumborum, and that between longissimus and iliocostalis did not exist at L4-S1. The intermuscular spaces in patients also varied at different levels of the lumbar spine showing a low discontinuous density in CT and a high signal in MRI. There were no significant differences between the observations in cadavers and those made using CT and MRI.
The intermuscular spaces within the paraspinal muscles vary at different intervertebral disc levels. Preoperative CT and MRI can facilitate selection of the muscle-splitting approach to the lumbar spine. This paper demonstrates the efficacy of medical imaging techniques in surgical planning 4).
Perioperative epidural steroids after routine surgery for lumbar degenerative disease may result in a small reduction of post-op pain, length of stay, and the risk of not returning to work at 1 year, but most of the evidence originates from studies not using validated outcome assessment that favor positive results, and further study is recommended (various agents, dosages, co-administered drugs, and delivery methods were reported) 5). However, the combination of systemic steroids at the start of the case (Depo-Medrol® 160 mg IM and methylprednisolone sodium succinate (Solu-Medrol®) 250 mg IV) combined with infiltration of 30 ml of 0.25% bupivacaine (Marcaine®) into the paraspinal muscles at incision and closure, may reduce hospital stay and post-op narcotic requirements 6).