A pilot study of patient-led identification of the midline of the lumbar spine

The midline of the lumbar spine is usually identified by palpation of the spinous processes. Placement of an epidural or spinal needle is more difficult when these bony landmarks are impalpable. This pilot study investigated the ability of 50 healthy volunteers to identify the midline of their own backs, using light touch or proprioception. The midline as identified in this manner was compared with the 'gold standard' as defined by the interspinous line. Sensation to light touch was the most accurate, with 90% of the volunteers able to identify the midline to within 6.5 mm. Proprioception using a finger to touch the midline was less accurate. This study was carried out on volunteers with palpable spinous processes but suggests that, in certain circumstances, a patient-led identification of the midline may be of value.