Safe zone for irrigation and debridement of psoas abscess through a dorsal spinal approach.

Abstract

This cadaver study was initiated to identify safe zones for psoas abscess debridement using a dorsal spinal approach. Twenty total specimens were dissected and lumbar transverse process (TP) and psoas muscles were identified. The distance from the lateral psoas muscle to the transverse process tip was measured. The lumbar plexus was dissected from the psoas and the distance from the TP to the lateral border of the lumbar plexus was measured. The area between the lateral edge of the psoas and lumbar plexus at each lumbar level was considered a safe zone of approach for entry into the psoas muscle for abscess debridement. The most lateral portion of the lumbar plexus was 9.3mm medial to the superior tip of the L1 TP and 9.2mm medial to the inferior tip at L1, it was 11.8 and 11.7mm medial at L2, 10.5 and 9.8mm medial at L3, 6.6 and 6.2mm medial at L4, and 1.0 and 0.9mm medial at L5. The distances from the TP tip to the lateral edge of the psoas muscle were 5.7 and 5.5mm medial to the superior and inferior tip of the TP at L1, 5.1 and 4.7mm medial at L2, 2.5 and 1.8mm medial at L3, 0.4 and 0mm medial at L4 and 3.7 and 3.8mm lateral at L5. This study provides landmarks to avoid the critical structures in the lumbar spine.