Topography of the lumbar part of the erector spinae muscle

Summary The topography of different muscles in the erector spinae muscle at different lumbar levels was studied by serial cutting as well as by dissections in 21 subjects. The lumbar part of the erector spinae muscle is subdivided into a medial muscle compartment, the transversospinalis compartment, and a lateral muscle compartment, the sacrospinalis compartment. The former contains mainly the multifidi muscles, the latter chiefly being made up of the longissimus and the iliocostalis muscles. The different muscles and parts of muscles within the transversospinalis compartment are interwoven in such a way that it is difficult to separate them from each other. The longissimus and the iliocostalis muscles are posteriorly but usually not anteriorly separated from each other in the lumbar spine.It is assumed that it is possible to study the multifidi, the longissimus and the iliocostalis muscles at different lumbar levels with present electromyographic methods. Two techniques for insertion of EMG electrodes into these muscles at different lumbar levels are suggested. The techniques are based on the assumption that the insertion can be guided either by fluoroscopy or by palpation only.