In with the new, out with the old? Comparison of two approaches for psoas compartment block

We compared the approaches of Winnie and Capdevila for psoas compartment block (PCB) performed by a single operator in terms of contralateral spread, lumbar plexus blockade, and postoperative analgesic efficacy. Sixty patients underwent PCB (0.4 mL/kg levobupivacaine 0.5%) and subsequent spinal anesthesia for primary joint arthroplasty (hip or knee) in a prospective, double-blind study. Patients were randomly allocated to undergo PCB by using the Capdevila (group C; n = 30) or a modified Winnie (group W; n = 30) approach. Contralateral spread and lumbar plexus blockade were assessed 15, 30, and 45 min after PCB. Contralateral spread (bilateral from T4 to S5) and femoral and lateral cutaneous nerve block were evaluated by sensory testing, and obturator motor block was assessed. Bilateral anesthesia occurred in 10 patients in group C and 12 patients in group W (P = 0.8). Blockade of the femoral, lateral cutaneous, and obturator nerves was 90%, 93%, and 80%, respectively, for group C and 93%, 97%, and 90%, respectively, for group W (P > 0.05). No differences were found in PCB procedure time, pain scores, 24-h morphine consumption, or time to first morphine analgesia.     

A radiologic and anatomic assessment of injectate spread following transmuscular quadratus lumborum block in cadavers

We performed bilateral transmuscular quadratus lumborum blocks in six cadavers using iodinated contrast and methylene blue. Computed tomography imaging was performed in four cadavers and anatomical dissection was completed in five. This demonstrated spread to the lumbar paravertebral space in 63% of specimens, laterally to the transversus abdominis muscle in 50% and caudally to the anterior superior iliac spine in 63% of specimens. There was no radiographic evidence of spread to the thoracic paravertebral space. Anatomical dissection revealed dye staining of the upper branches of the lumbar plexus and the psoas major muscle in 70% of specimens. Further clinical studies are required to confirm if the quadratus lumborum block might be a suitable alternative to lumbar plexus block.     

Effects of electrical stimulation of the sciatic nerve on background electromyography and static stretch reflex activity of the trunk muscles in rats: possible implications of neuronal mechanisms in the development of sciatic scoliosis

STUDY DESIGN: The effects of electrical stimulation of the sciatic nerve on background electromyographic and static stretch reflex activity of the trunk muscles were studied. OBJECTIVES: To verify the hypotheses that sciatic scoliosis is induced reflexively by radiculopathic pain, and that scoliosis might be maintained by prolonged asymmetric alteration of the trunk muscle tonus caused by central sensitization of the spinal neurons that constitute the postural reflex pathways. SUMMARY OF BACKGROUND DATA: Sciatic scoliosis usually occurs with convexity to the side of the herniated disc. The neuronal mechanism of sciatic scoliosis has not been well clarified. Recently, prolonged alteration of motor function in the hindlimbs of animals caused by central sensitization has been reported. METHODS: In spinalized rats (transection of the spinal cord), the sciatic nerve was stimulated electrically as a conditioning stimulus. Muscle stretch elicited by bending of the lumbar spine was applied as a test stimulus. Background and stretch reflex activities of the bilateral oblique abdominal, psoas, and quadratus lumborum muscles were recorded. Rats in which MK-801, an N-methyl-d-aspartate antagonist, was preadministered also were used. RESULTS: The conditioning stimulus enhanced background electromyographic activity in bilateral oblique abdominal, contralateral psoas, and quadratus lumborum muscles. Furthermore, the conditioning stimulus induced prolonged facilitation and depression of stretch reflex activity of the contralateral psoas and quadratus lumborum, and ipsilateral psoas and quadratus lumborum muscles, respectively. Preadministration of MK-801 reduced these excitatory and inhibitory effects. CONCLUSION: It was found that the pattern of electromyographic activity of the trunk muscles evoked by sciatic nerve stimulation coincided with the typical direction of sciatic scoliosis in patients with lumbar disc herniation. It was supposed that the prolonged asymmetric alteration of the trunk muscle tonus was caused by central sensitization, and that central sensitization of spinal neurons may underlie the neuronal mechanism of sciatic scoliosis.     

Retroperitoneal laparoscopic lateral approach to the lumbar spine: a new approach, technique, and clinical trial

A retroperitoneal laparoscopic (retroperitoneoscopic) lateral approach to achieve decompression for a far lateral disk lesion in the lumbar spine or to remove a paravertebral neurinoma without disrupting the facet is described. The operating space is maintained using a powered mechanical lift and a flat inflatable retractor mainly to make a longitudinal separation between the psoas major and the quadratus lumborum. This technique has been performed successfully in 22 cases using retroperitoneoscopy. The best indications of this new procedure are lateral disk herniation at the L5-S1 level or around the conus medullaris at the L1-L2 level. The described procedure provides adequate exposure necessary for extraforaminal exploration, discectomy, and nerve root decompression, and it is sufficient for treating extreme lateral lumbar herniation localized to the L1-S1 level and spinal nerve root tumors.     

Ultrasound-guided lateral-medial transmuscular quadratus lumborum block for analgesia following anterior iliac crest bone graft harvesting: a clinical and anatomical study

Background

The anterior iliac crest (AIC) is one of the most common sites for harvesting autologous bone, but the associated postoperative pain can result in significant morbidity. Recently, the transmuscular quadratus lumborum block (TQL) has been described to anesthetize the thoraco-lumbar nerves. This study utilizes a combination of cadaveric models and clinical case studies to evaluate the dermatomal coverage and analgesic utility of TQL for AIC bone graft donor site analgesia.

Methods

Ten ultrasound-guided TQL injections were performed in five cadaver specimens using a lateral-to-medial transmuscular approach. Twenty mL of 0.5% methylcellulose was injected on each side after ultrasound confirmation of the needle tip ventral to the quadratus lumborum muscle (QLM). Cranio-caudal and medial-lateral extent of the dye spread in relation to musculoskeletal anatomy and direct staining of the thoraco-lumbar nerves were recorded. Following the anatomical findings, continuous catheter TQL blocks were performed in four patients undergoing ankle surgery with autologous AIC bone graft. The dermatomal anesthesia and postoperative analgesic consumption were recorded.

Results

In the anatomical component of the study, 9/10 specimens showed a lateral spread anterior to the transversalis fascia and medially between the QLM and psoas major muscle. Direct staining of the branches of the T12, L1, and L2 nerves was noted ventral to the QLM, while variable staining of the T9-T11 nerves was seen laterally in the transversus abdominis plane and the transversalis fascia. The vertical spread of injectate anterior to the QLM was T12 to the iliac crest (n = 5/10) and L1 to the iliac crest (n = 4/10). In the four patients who received TQL, the T9-L2 dermatomal anesthesia correlated with the injectate spread seen in the cadavers and provided effective analgesia at the bone graft donor site.

Conclusion

Ultrasound-guided TQL injections consistently cover the thoraco-lumbar innervation relevant to the AIC graft donor site. The injectate spread seen in anatomical dissections correlated with the dermatomal anesthesia clinically. The TQL has the potential to provide reliable analgesia for patients undergoing AIC bone graft harvesting.

     

Continuous lumbosacral block using a Tuohy needle and catheter technique

Three cases are reported where continuous lumbosacral block was performed using a catheter through an epidural needle technique. Good unilateral lower limb surgical anaesthesia was achieved in all three cases with successful blockade of the lumbar and sacral plexuses. A 17-gauge Tuohy needle was positioned between the transverse processes of L4 and L5 and an epidural catheter inserted into the space between the quadratus lumborum and psoas muscles. Forty to seventy millilitres of local anaesthetic were injected and resulted in good surgical anaesthesia within 12-20 min. Radiographic studies in these patients confirmed placement of the catheter in close proximity to the lumbosacral plexus. Experience in a further 12 cases is also reported. There were no side-effects. The technique is successful and is recommended when unilateral lower limb anaesthetic is required and when spinal and epidural anaesthesia are contraindicated.     

Unexpected motor weakness following quadratus lumborum block for gynaecological laparoscopy

Quadratus lumborum block has recently been described as an effective and long‐lasting analgesic strategy for various abdominal operations, including gynaecological laparoscopy. Despite evidence that the analgesic effect is mediated by indirect paravertebral block and that local anaesthetic spreads to the lumbar paravertebral space, there have been no reports to date of lower limb motor weakness. We present a patient with unilateral hip flexion and knee extension weakness leading to unplanned overnight admission following lateral quadratus lumborum block with 20 ml levobupivacaine 0.25%. The L2 dermatomal sensory loss and hip flexion weakness suggested spread to either the L2 paravertebral space or to the lumbar plexus, causing weakness of the psoas and iliacus muscles and possibly the quadriceps. The duration of motor block was approximately 18 h. This complication should be considered when performing the block, especially in the setting of day‐case surgery.     

Continuous psoas compartment block for postoperative analgesia after total hip arthroplasty: new landmarks,technical guidelines,and clinical evaluation

A computed tomographic scan was obtained in 35 patients to measure the depth and the relationship of the branches of the lumbar plexus to the posterior superior iliac spine projection and the vertebral column. In addition, we prospectively studied 80 patients scheduled for total hip arthroplasty who received a continuous psoas compartment block (CPCB) in the postoperative period. CPCB was performed after surgical procedures by using modified Winnie's landmarks and nerve stimulation. From 5 to 8 cm of catheter was inserted. Radiographs were obtained after injection of 10 mL of contrast medium. An initial loading dose (0.4 mL/kg) of 0.2% ropivacaine was injected, followed by continuous infusion of 0.2% ropivacaine for 48 h. The depth of the lumbar plexus and the distance between the lumbar plexus and the L4 transverse process were measured. Visual analog scale values of pain at 1, 12, 24, and 48 h were obtained at rest and during mobilization. Amounts of rescue analgesia were also recorded. Sensory blockade of the principal branches of the lumbosacral plexus was noted at 1 and 24 h, as were adverse events related to the technique. There was a significant difference between men and women in depth of the lumbar plexus (median values, 85 vs 70 mm for men and women, respectively). There was a positive correlation between the body mass index and skin-lumbar plexus distances. In contrast, there was no difference regarding the distance between the transverse process of L4 and the lumbar plexus. The catheter tip lay within the psoas major muscle in 74% of the patients and between the psoas and quadratus lumborum muscles in 22%. In three patients, the catheter was improperly positioned. At 1 h, sensory blockade of the femoral, obturator, and lateral femoral cutaneous nerves was successful in, respectively, 95%, 90%, and 85% of patients. At 24 h, these rates were 88%, 88%, and 83%, respectively. During the 48-h study period, median visual analog scale values of pain were approximately 10 mm at rest and from 18 to 25 mm during physiotherapy. Five patients received 5 mg of morphine at 1 h. Five cases of unilateral epidural anesthesia were noted after the bolus injection. We conclude that CPCB with 0.2% ropivacaine allows optimal analgesia after hip arthroplasty, with few side effects and a small failure rate. Before lumbar plexus branch stimulation and catheter insertion, anesthesiologists should be aware of the L4 transverse process location and lumbar plexus depth. IMPLICATIONS: Lumbar plexus depth is correlated with the patient's body mass index and differs between men and women, but this is not true of the lumbar plexus-transverse process distance. Considering new landmarks, a continuous psoas compartment block promotes optimal analgesia after hip arthroplasty, with few side effects.     

Anatomy of the posterior approach to the lumbar plexus block

The purpose of this study was to describe the relation of the lumbar plexus with the psoas major and with the superficial and deep landmarks close to it. Four cadavers were dissected and 22 computed tomography files of the lumbosacral region studied. Cadaver dissections demonstrated that the lumbar plexus, at the level of L₅, is within the substance of the psoas major muscle rather than between this muscle and the quadratus lumborum. The femoral nerve lies between the lateral femoral cutaneous and obturator nerves. However, while the lateral femoral cutaneous nerve is in the same fascial plane as the femoral nerve, the obturator nerve can be found in the same plane as the two other nerves or in its own muscular fold. Radiological data provided the following measurements: the femoral nerve is at a depth of 9.01 ± 2.43 cm; the psoas major medial border is at 2.73 ± 0.64 cm from the median sagital plane; and its lateral border is at 6.41 ± 1.61 cm from the same plane. It is concluded that the lumbar plexus is within the psoas major, that the obturator nerve localization within the psoas major varies and that computed tomography data define precisely the relationship of the lumbar plexus with superficial and deep landmarks.     

Retroperitoneoscopic nephropexy for symptomatic nephroptosis

PURPOSE: Recently, laparoscopic nephropexy has been performed using a transperitoneal approach. We evaluated the efficacy of a retroperitoneoscopic technique for symptomatic nephroptosis. PATIENTS AND METHODS: Three men and two women with right nephroptosis underwent retroperitoneal laparoscopic nephropexy. Their symptoms were right flank pain, gross hematuria, or both. The mean body mass index was 18.7. Surgery consisted of complete dissection of the kidney, after which three sutures were placed between the renal capsule at the posterior lateral edge and the psoas or quadratus lumborum muscle. Silk sutures were used in all five patients. RESULTS: Retroperitoneoscopic nephropexy was successful with no intraoperative complications. The mean operative time was 167 minutes, and the mean estimated blood loss was <10 mL in all five patients. The mean convalescence period was 19.6 days. A postoperative urogram with the patients both supine and erect revealed an improvement in renal function, decreased displacement of the kidney (less than one vertebral body), or both. All patients were satisfied with the clinical outcome during an average of 18 months of follow-up. CONCLUSIONS: Retroperitoneoscopic nephropexy is feasible for patients with symptomatic nephroptosis. We recommend nonabsorbable materials such as silk for fixation of the kidney to the psoas or quadratus lumborum muscle.     

Comparison of ultrasound-guided transmuscular quadratus lumborum block catheter technique with surgical pre-peritoneal catheter for postoperative analgesia in abdominal surgery: a randomised controlled trial

Following abdominal surgery, the provision of postoperative analgesia with local anaesthetic infusion through both transmuscular quadratus lumborum block and pre-peritoneal catheter have been described. This study compared these two methods of postoperative analgesia following laparotomy. Eighty-two patients 18–85 years of age scheduled to undergo elective surgery were randomly allocated to receive either transmuscular quadratus lumborum block or pre-peritoneal catheter block. In the transmuscular quadratus lumborum group, an 18-gauge Tuohy needle was passed through the quadratus lumborum muscle under ultrasound guidance to reach its anterior aspect. A 20-ml bolus of ropivacaine 0.375% was administered and catheters placed bilaterally. In the pre-peritoneal catheter group, 20 ml of ropivacaine 0.375% was infiltrated at each of three subcutaneous sub-fascial levels, and pre-peritoneal plane catheters were placed bilaterally. Both groups received an infusion of ropivacaine 0.2% at 5 ml.h⁻¹, continued up to 48 h along with a multimodal analgesic regime that included regular paracetamol and patient-controlled analgesia with fentanyl. The primary end-point was postoperative pain score on coughing, assessed using a numerical rating score (0–10). Secondary outcomes were pain score at rest, fentanyl usage until 48 h post-operation, satisfaction scores and costs. There was no treatment difference between the two groups for pain score on coughing (p = 0.24). In the transmuscular quadratus lumborum group, there was a reduction in numerical rating score at rest (p = 0.036) and satisfaction scores on days 1 and 30 (p = 0.004, p = 0.006, respectively), but fentanyl usage was similar. In the transmuscular quadratus lumborum group, the highest and lowest blocks observed in the recovery area were T4 and L1, respectively. The transmuscular quadratus lumborum technique cost 574.64 Australian dollars more per patient than the pre-peritoneal catheter technique.     

Studies on the spread of local anaesthetic solution in transversus abdominis plane blocks

The extent of analgesia provided by transversus abdominis plane blocks depends upon the site of injection and pattern of spread within the plane. There are currently a number of ultrasound-guided approaches in use, including an anterior oblique-subcostal approach, a mid-axillary approach and a more recently proposed posterior approach. We wished to determine whether the site of injection of local anaesthetic into the transversus abdominis plane affects the spread of the local anaesthetic within that plane, by studying the spread of a local anaesthetic and contrast solution in four groups of volunteers. The first group underwent the classical landmark-based transversus abdominis plane block whereby two different volumes of injectate were studied: 0.3 ml.kg(-1) vs 0.6 ml.kg(-1). The second group underwent transversus abdominis plane block using the anterior subcostal approach. The third group underwent transversus abdominis plane block using the mid-axillary approach. The fourth group underwent transversus abdominis plane block using the posterior approach, in which local anaesthetic was deposited close to the antero-lateral border of the quadratus lumborum. All volunteers subsequently underwent magnetic resonance imaging at 1, 2 and 4 h following each block to determine the spread of local anaesthetic over time. The studies demonstrated that the anterior subcostal and mid-axillary ultrasound approaches resulted in a predominantly anterior spread of the contrast solution within the transversus abdominis plane and relatively little posterior spread. There was no spread to the paravertebral space with the anterior subcostal approach. The mid-axillary transversus abdominis plane block gave faint contrast enhancement in the paravertebral space at T12-L2. In contrast, the posterior approaches, using both landmark and ultrasound identifications, resulted in predominantly posterior spread of contrast around the quadratus lumborum to the paravertebral space from T5 to L1 vertebral levels. We concluded that the pattern of spread of local anaesthetic differs depending on the site of injection into the transversus abdominis plane. This may have important implications for the extent of analgesia produced with each approach.     

Misplacement of a psoas compartment catheter in the subarachnoid space

BACKGROUND AND OBJECTIVES: This case report describes an unusual cause of misplacement of an indwelling catheter in the subarachnoid space after primary psoas compartment block in a patient undergoing total knee arthroplasty. CASE REPORT: A 67-year-old woman presenting for total knee joint replacement received a combination of continuous psoas compartment block and sciatic nerve block. Neurostimulation and additional ultrasound guidance were used for identification of the lumbar plexus. After elicitation of a quadriceps motor response, a negative aspiration test, and an uneventful test dose, 20 mL ropivacaine 0.375% and 20 mL mepivacaine 1% were injected. Despite difficult ultrasound conditions because of intestinal air, local anesthetic spread was observed paravertebrally at the medial border of the psoas muscle as usual. A catheter was then advanced 7 cm through the insulated directional puncture needle. An additional sciatic nerve block was performed by using Labat's approach. Ten minutes after injection unilateral sensory block was noted and surgery was started. After uneventful surgery, bilateral sensory block to the T4 level and complete motor block in both lower limbs was detected. A second aspiration test was negative, and an epidural block was suspected. For verification of the catheter tip location, a computed tomography scan with contrast dye was performed revealing catheter placement in the subarachnoid space. The catheter was removed and showed a kink about 7 cm from the tip. After regression of the neuraxial block, lumbar plexus block persisted for another 2 hours. CONCLUSION: An additional test dose via the catheter is recommended if the indwelling catheter is inserted after injection of the local anesthetics through the puncture needle. If epidural anesthesia occurs, an x-ray of the catheter is advisable because negative aspiration via catheter does not rule out subarachnoid catheter location.     

Extent of blockade with various approaches to the lumbar plexus

The extent of blockade when four different techniques were used for blocking the lumbar plexus was prospectively evaluated in 80 adult patients. The extent of blockade was measured by testing motor function of all nerves except the lateral and posterior femoral cutaneous nerves, which were evaluated by pinprick response. The posterior approaches of Dekrey at L3 (n = 20) and Chayen at L4-5 (n = 20) proved similarly effective in producing blockade of the femoral, obturator, and lateral femoral cutaneous nerves, as well as the nerves to the psoas muscle. The anterior approach of Winnie (femoral sheath or 3-in-1 block) using paresthesia (n = 20) or peripheral nerve stimulation (n = 20) proved effective in producing blockade of the femoral and lateral femoral cutaneous nerves, but ineffective for obturator nerve blockade. None of the four techniques produced blockade of the sacral plexus. Perhaps our means of assessing blockade (motor) is what produced the difference between our findings and those of others.     

Magnetic resonance imaging of the distribution of local anesthetic during the three-in-one block

The three-in-one technique of simultaneously blocking the femoral, the lateral femoral cutaneous (LFC), and the obturator nerves by a single injection of a local anesthetic was first described in 1973, and it was suggested that the underlying mechanism was one of cephalad spread resulting in a blockade of the lumbar plexus. Today, the technique is widely used in surgery and pain management of the lower limb. Many investigators have, however, reported suboptimal analgesia levels, particularly in the obturator nerve. The purpose of this prospective study was to trace the distribution of a local anesthetic during a three-in-one block by means of magnetic resonance imaging (MRI). Seven patients scheduled for surgery of the lower limb were analyzed with the aid of a primary MRI and then received three-in-one blocks using 30 mL of bupivacaine 0.5% under the guidance of a nerve stimulator. A secondary MRI was performed to determine the distribution pattern of the local anesthetic. It emerged that the local anesthetic blocks the femoral nerve directly, the LFC nerve through lateral spread, and the anterior branch of the obturator nerve by slightly spreading in a medial direction. No involvement of the proximal and posterior portions of the obturator nerve was observed, nor was there any cephalad spread that could have resulted in a lumbar plexus blockade. We therefore conclude that the basis of the three-in-one block is confined to lateral, medial, and caudal spread of the local anesthetic, which effectively blocks the femoral and LFC nerves, as well as the distal anterior branch of the obturator nerve. IMPLICATIONS: We demonstrate by using magnetic resonance imaging that the mechanism of a three-in-one block is one of lateral, caudal, and slight medial spread of a local anesthetic with subsequent blockade of the femoral, the lateral femoral cutaneous, and the anterior branch of the obturator nerves. It does not involve cephalad spread of the local anesthetic with blockade of the lumbar plexus.     

腰方肌阻滞临床应用的研究进展

腰方肌阻滞是一种将局麻药物注射至腰方肌周围的躯干神经阻滞技术。近年来,腰方肌阻滞的临床应用已成为研究热点,是广受欢迎的镇痛方式。腰方肌阻滞逐渐被应用于剖宫产手术、胃肠道手术、泌尿手术、下肢手术等围术期多模式镇痛,并且在慢性疼痛治疗中也有报道。全文就腰方肌阻滞的应用解剖、穿刺入路、临床应用及可能的作用机制进行综述,为其临床应用提供参考。     

Schwannoma developing in the psoas major muscle: a case report

Schwannoma can occur wherever peripheral nerve Schwann cells are found. However, retroperitoneal schwannoma is extremely rare in that only 16 cases have been reported, including that of the present patient. A 51-year-old male complained of chronic lower back pain and paresthesia in the lower left region. Lower back pain increased with leftward bending. Magnetic resonance imaging (MRI) revealed a neoplastic lesion about 6 cm in diameter in the left psoas major muscle, and the lesion was in contact with the L4 and L5 vertebral bodies. The tumor did not continue to the lumbar foramen. The symptom had become disabling, therefore tumor removal was performed using Wiltse's approach. From intraoperative findings, the origin of the tumor was suspected to be the L4 nerve root. The ventral surface of the tumor could not be observed with this posterior approach. Lumbar plexus might adhere closely to the ventral surface of the tumor, therefore the capsule of the tumor was left to avoid neurological deterioration. Schwannoma was diagnosed by pathological analysis, and no malignancy was evident. After the operation, symptoms were completely relieved, and the residual capsule of the tumor diminished in size on MRI after 12 months. The posterior Wiltse's approach can be useful to treat mass lesions in the psoas major muscle. The 16 reported cases of retroperitoneal schwannoma, including that of the present patient, are reviewed.     

Conservative management of psoas haematoma following complex lumbar surgery

We report psoas hematoma communicating with extradural hematoma and compressing on lumbar nerve roots during the postoperative period in a patient who underwent L3/4 level dynamic stabilization and L4/5 and L5/S1 posterior lumbar interbody fusion. Persistent radicular symptoms occurring soon after posterior lumbar surgery are not an unknown entity. However, psoas hematoma communicating with the extradural hematoma and compressing on L4 and L5 nerve roots soon after surgery, leading to radicular symptoms has not been reported. In addition to the conservative approach in managing such cases, this case report also emphasizes the importance of clinical evaluation and utilization of necessary imaging techniques such as computed tomography (CT) scan and magnetic resonance imaging (MRI) scan to diagnose the cause of persistent severe radicular pain in the postoperative period.     

Lumbar plexus and psoas major muscle: not always as expected

BACKGROUND AND OBJECTIVES: Conflicting definitions concerning the exact location of the lumbar plexus have been proposed. The present study was carried out to detect anatomical variants regarding the topographical relation between the lumbar plexus and the psoas major muscle as well as lumbar plexus anatomy at the L4-L5 level. METHODS: Sixty-three lumbar plexuses from 32 embalmed cadavers were dissected to determine the topographical relation between lumbar plexus and psoas major muscle. At the L4-L5 levels variability in the course of the femoral as well as obturator nerve were described. RESULTS: The lumbar plexus was situated within the psoas major muscle in 61 of 63 cases. In 2 of 63 cases the entire plexus was localized posterior to the psoas major muscle. In the 61 of 63 cases in which the lumbar plexus was situated within the psoas major muscle, emergence of the individual nerves most often occurred on the posterior or posterolateral surface. CONCLUSIONS: Our results synthesize contrasting assumptions in previous literature, by demonstrating that both locations of the lumbar plexus may be encountered in clinical practice: within and posterior to the psoas major muscle. However, the latter situation represents a minor variant. At the level of L4-L5 the femoral nerve, showing a remarkable degree of branching, as well as the obturator nerve, were found within the psoas major muscle in the vast majority of specimens.     

Ultrasound-guided lumbar facet nerve block: accuracy of a new technique confirmed by computed tomography

BACKGROUND: Lumbar facet nerve (medial branch) blocks are often used to diagnose facet joint-mediated pain. The authors recently described a new ultrasound-guided methodology. The current study determines its accuracy using computed tomography scan controls. METHODS: Fifty bilateral ultrasound-guided approaches to the lumbar facet nerves were performed in five embalmed cadavers. The target point was the groove at the cephalad margin of the transverse (or costal) process L1-L5 (medial branch T12-L4) adjacent to the superior articular process. Axial transverse computed tomography scans, with and without 1 ml contrast dye, followed to evaluate needle positions and spread of contrast medium. RESULTS: Forty-five of 50 needle tips were located at the exact target point. The remaining 5 were within 5 mm of the target. In 47 of 50 cases, the applied contrast dye reached the groove where the nerve is located, corresponding to a simulated block success rate of 94% (95% confidence interval, 84-98%). Seven of 50 cases showed paraforaminal spread, 5 of 50 showed epidural spread, and 2 of 50 showed intravascular spread. Despite the aberrant distribution, all of these approaches were successful, as indicated by contrast dye at the target point. Abnormal contrast spread was equally distributed among all lumbar levels. Contrast traces along the needle channels were frequently observed. CONCLUSIONS:: The computed tomography scans confirm that our ultrasound technique for lumbar facet nerve block is highly accurate for the target at all five lumbar transverse processes (medial branches T12-L4). Aberrant contrast medium spread is comparable to that of the classic fluoroscopy-guided method.