Abstract ID: A17
Abstract Title: EXAMINATION OF THE LUMBAR PLEXUS AND PSOAS COMPARTMENT IN 95 CADAVERS. AN ANATOMICAL STUDY.
Authors: Wiessner D1, Vicent O2, Heller A3, Litz R4
University Hospital Dresden Dresden Saxony Germany1, University Hospital Dresden Dresden Saxony Germany2, University Hospital Dresden Dresden Saxony Germany3, University Hospital Dresden Dresden Saxony Germany4
Poster Type: Either
ABSTRACT BODY
Background: The psoas compartment block is an established method for postoperative analgesia following total knee joint replacement. The technique consists of a single injection of local anesthetics close to the femoral nerve into a fascial space between the iliac muscle and the psoas muscle. By using this technique the obturator nerve and the cutaneous femoral nerve are also blocked in a higher percentage as compared to femoral nerve block. But even with accurate neurostimulation of the femoral nerve incomplete or even failed blocks may occur. Recently, the existence of the so-called psoas compartment has been questioned. Variable intramuscular location of lumbar plexus branches within separated muscle folds were demonstrated in a small number of dissections and may be the underlying reason for incomplete or failed blocks performance. This study was therefore performed to evaluate the relation between the lumbar plexus and the psoas muscle at the L4 level in a large number of cadavers.
Methods: In 95 formalin-fixed cadavers bilateral dissection of the lumbar region was performed by a ventral approach. The lumbar vertebrae and intervertebral discs of L5 –L2 as well as the cranial border of the sacrum were identified and marked. Likewise, the corresponding sites of the psoas muscles were marked in situ. Measurements were performed in situ for the transversal and sagittal cross section dimension of both psoas muscles. The femoral (FEM), lateral cutaneus femoris (CFL) and obturator nerve (OBT) were marked. Then nerves were cut caudad after they had left the muscles. Muscles were carefully separated from their insertion site at the spine and the fusion site with the iliac muscle. The location of the corresponding nerves within or outside the muscles was studied with special regard to the L4 level.
Results: In 95 cadavers (46 female, 49 male, age 81±10years, height 165±9 cm, weight 58±12 kg) mean cross section diameters at the L4 level were 2.3±0.5 cm (left) and 2.4±0.5 cm (right) for the transversal dimension and accordingly 3.9±0.8 cm (left) and 3.8±0.7 cm (right) for the sagittal dimension. All diameters decreased with age. At the L4 level the FEM was located within the posterior part of the psoas muscle in 71.6% and the CFL in 57.4% of the cadavers.In 19 cases the FEM consisted of 2 branches, whereof 6 had an completely extramuscular course. The CFL was divided in 7 cases, whereof 2 had an completely extramuscular course. The OBT was never located within the muscles and was covered by fat and connective tissue between the vertebral bodies and the psoas muscle.
Conclusion: There was a considerable variation in the course of the main three lumbar plexus nerves at the L4 level which is in contradiction to the idea of the location of the lumbar plexus within a psoas compartment. Division into single nerve branches and varied location either within or outside of the muscle may explain incomplete psoas compartment blocks if neurostimulation of the femoral nerve is considered accurate. Additionally, one may speculate that muscle folds act as anatomical barriers impeding local anaesthetic spread.
ATTACHED FILES
Reg Anesth Pain Med 2005; 30(3):A17