Filum terminale fusion and dural sac termination: study in 27 cadavers.

The standard approach for sectioning of the filum terminale for a tethered spinal cord can be achieved via a limited S(1) exposure. This is performed with the commonly believed idea that the filum fuses with the dura at S(2). We dissected 27 cadavers to exclusively look at the level at which the filum pierces/fuses with the dura and also the level at which the dural sac ends. Most of the fila fused at S(2) with a range from L(5) to S(3). The majority of dural sacs ended at S(2) with a range from S(1) to S(3). However, 15% of the fila (4 of 27) fused above the S(1) level. In addition, 11% of the fila (3 of 27) fused off the midline. We hope that this anatomical information may be useful for neurosurgeons when standard approaches fail to identify the filum at its usual level and location.