Lateral transpsoas approach difficult in lumbarized sacra

(HealthDay) -- In patients with lumbarized sacra, a lateral transpsoas surgical approach to the L5-6 disc space can be managed with appropriate preoperative planning, including axial magnetic resonance imaging (MRI) and advanced neuromonitoring, according to a study published in the July issue of the Journal of Spinal Disorders & Techniques.

William D. Smith, M.D., from the Western Regional Center for Brain and Spine Surgery in Las Vegas, and colleagues conducted a retrospective review involving 351 patients scheduled for lumbar interbody fusion using a mini-open lateral transpsoas approach at L4-5. Neuromonitoring was used to assess accessibility of the L5-6 level (functional L4-5) in patients with six lumbar vertebrae. Qualitative assessments based on MRI were compared with a sample of patients with normal anatomy treated at L4-5.

The researchers identified 10 patients (2.8 percent) with six lumbar vertebrae with the symptomatic level at L5-6. Two of these could be treated using a lateral transpsoas approach and eight were converted to a different approach after neuromonitoring feedback showed no corridor through the psoas muscle. In patients with transitional anatomy unapproachable at L5-6, axial MRI showed a teardrop-shaped psoas detached from the lateral border of the disc space, resembling L5-S1 in normal anatomy. In the two patients who could be treated with the transpsoas approach, the psoas anatomy at L5-6 was similar to that at a normal L4-5 level, with a domed/helmet shape laterally attached to the disc space.

"Treating the L5-6 level using a lateral transpsoas approach in individuals with lumbarized sacra can be challenging due to anatomy more similar to the L5-S1 level in normal patients," the authors write. "Preoperative planning using axial MRI and intraoperative adherence to advanced neuromonitoring can aid in identifying and avoiding injury in these rare patients."