Anatomical optimization of skin electrode placement to record electromyographic activity of erector spinae muscles

Fine analysis of body movements is now technologically feasible, together with simultaneous recording of multiple muscle activity. This is especially true for the trunk and back muscles during human walking. However, there have been few anatomic studies of the area where deep back muscle activity is recordable by skin electrodes. We therefore attempted to optimize skin electrode location for recording erector spinae muscle activity at different levels of the back. For this purpose, 20 dissections of the posterior wall of the trunk were performed. The cutaneous plane was reclined on both sides to expose the superficial muscles of the posterior wall of the trunk. We dissected then plane-by-plane until we exposed the erector spinae muscles. The widths of the fascial spinal muscle insertions were measured at spinal levels easily identified clinically, i.e., C7, T3, T7, T12 and L4. Electromyographic assessment of the electrode location at these levels was performed in three subjects. Erector spinae muscle activity proved possible to record on several areas of the posterior wall through a superficial muscle aponeurosis. We propose a protocol for placing skin electrodes to record erector spinae muscle activity based on clinical anatomical references.