Real-time ultrasound-guided comparison of adductor canal block and psoas compartment block combined with sciatic nerve block in laparoscopic knee surgeries.

BACKGROUND: Lumbar plexus block, combined with a sciatic nerve block, is an effective locoregional anesthetic technique for analgesia and anesthesia of the lower extremity. The aim of this study was to compare the clinical results outcome of the adductor canal block versus the psoas compartment block combined with sciatic nerve block using real time ultrasound guidance in patients undergoing elective laparoscopic knee surgeries. PATIENTS AND METHODS: Ninety patients who were undergoing elective laparoscopic knee surgeries were randomly allocated to receive a sciatic nerve block in addition to lumbar plexus block using either an adductor canal block (ACB) or a posterior psoas compartment approach (PCB) using 25 ml of bupivacine 0.5% with adrenaline 1:400,000 injection over 2-3 minutes while observing the distribution of the local anesthetic in real time. Successful nerve block was defined as a complete loss of pinprick sensation in the region that is supplied by the three nerves along with adequate motor block, 30 minutes after injection. The degree of motor block was evaluated 30 minutes after the block procedure. The results of the present study showed that the real time ultrasound guidance of PCB is more effective than ACB approach. Although the sensory blockade of the femoral nerve achieved equally by both techniques, the LFC and OBT nerves were faster and more effectively blocked with PCB technique. Also PCB group showed significant complete sensory block without need for general anesthesia, significant decrease in the post-operative VAS and significant increase time of first analgesic requirement as compared to the ACB group. RESULT AND
CONCLUSION: The present study demonstrates that blockade of lumber plexus by psoas compartment block is more effective in complete sensory block without general anesthesia supplementation in addition to decrease post-operative analgesic requirement than adductor canal block.

RCT Entities:   Population Interventions Outcomes

INTRODUCTION

Many regional anesthesia techniques are used for lower limb surgeries, such as central neuraxial blocks (spinal, epidural, or combined spinal epidural) and lumbar plexus nerve block either with anterior approach (inguinal paravascular block or adductor canal block [ACB]) or posterior approach (psoas compartment block [PCB]). Each technique has advantages and disadvantages as regard to postoperative analgesia, patient satisfaction, and rehabilitation, type of surgery, and reduce the incidence of side effects and complications.[1] Regional lower limb block provides high-quality analgesia after lower extremity surgeries, and is superior to systemic morphine administration and has less adverse effects compared to epidural analgesia.[1]

The anterior technique of lumbar plexus block is easier and more popular than the posterior approach.[2] Winnie et al.[3] demonstrated the anterior inguinal paravascular block technique and confirmed that it blocks the femoral, lateral femoral cutaneous (LFC), and obturator (OBT) nerves when used a volume of 20 ml of local anesthetic. Other studies showed that the OBT nerve and the LFC were spared in the majority of the cases underwent this technique.[4] A posterior approach of lumbar plexus block (PCB) results in a complete block of the main three nerves of the lumbar plexus. However, the reported failure rate is around 5% to 7% when using nerve stimulator alone for lumbar plexus localization.[5] Incorporating the use of ultrasound scanning may provide successful block performance in patients with normal and abnormal spinal anatomy.[6] Ultrasound imaging has been used during peripheral nerve blocks, to view either the anatomy before needle puncture or the advancing needle in real time. A preview scan performed before needle puncture improves the success rate of visualizing the transverse process and estimating its depth before needle insertion and reduces the number of puncture attempts.[7] Using real-time ultrasound guidance to direct the needle tip to the lumbar plexus is technically challenging given the limited ultrasound image resolution and quality. Furthermore, visualizing the tip of the needle is difficult when the ultrasound beam and needle are at an acute angle as needed to visualize deep targets.[89]

The aim of this study was to compare the clinical results outcome of the ACB versus the PCB combined with sciatic nerve block using real-time ultrasound guidance in patients undergoing elective laparoscopic knee surgeries.

PATIENTS AND METHODS

Ninety patients aged from 20 to 60 years old were involved in this prospective, randomized, controlled study, American Society of Anesthesiologists physical status I or II from either sex were scheduled for elective laparoscopic knee surgeries (knee arthroscopy, anterior cruciate ligament reconstruction) and subjected to lumbar plexus block either with anterior approach ACB, or posterior approach PCB at Mansoura University Hospitals over a period of 9 months. Patients with body mass index (BMI) more than 35 kg/m2, ischemic heart diseases, hypersensitivity to local anesthetics, infection around the area of injection, bleeding disorders, preexisting peripheral neuropathies, hepatic, and renal failure were excluded from the study.

In the day before surgery, after obtaining informed written consent form; all patients were examined laboratory and radiologically, in the form of complete blood count, liver function tests, and renal function tests, fasting blood glucose, and X-ray. Furthermore, sedation was achieved by giving diazepam 5 mg, 12 h before surgery. In operating room, the patient is premedicated by midazolam 0.02 mg/kg and fentanyl 1 µg/kg through the intravenous (IV) line and basic monitoring in the form of three leads electrocardiogram (ECG), noninvasive blood pressure, and O2 saturation were done. After obtaining written informed consent from all patients before surgery, patients were randomly divided into two equal groups (45 patients in each group) using closed envelopes techniques, first group received ACB with sciatic nerve block, and second group received PCB with the sciatic nerve block. The nerve blocks were performed using a 150-mm insulated needle (22-gauge Stimuplex™, Braun, Melsungen, Germany) connected to a peripheral nerve stimulator (Stimuplex™ DIG, Braun, Melsungen, Germany) and ultrasound (Siemens Acuson X300). The patients were instructed to take the supine position in the first group (ACB) and lateral position with the side to be blocked uppermost, with flexion of the knee and hip in the second group (PCB).

Technique of adductor canal block in the first group

After confirming the operative site, patient in supine position with knee slightly flexed and leg externally rotated (frog-leg position), clean the area with alcohol swap. The ultrasound scan in ACB was performed using a high frequency, 12-5 MHz, linear array transducer. A liberal amount of ultrasound gel were applied to the skin over the anterior aspect of the thigh, mid-point between the inguinal crease and medial condyle after 1–2 ml of 1% lidocaine solution was injected. Identify the femur (usually at a depth of 3–5 cm) and sartorius muscle (trapezoid/boat-shaped) is visualized the femoral artery lies under this muscle in the adductor canal.[10] The aim was to deposit local anesthetic under sartorius and around the femoral artery (i.e., within the adductor canal). The appropriate probe position was positioned perpendicular to the artery. The adductor magnus muscle lays posteromedial, the vastus medialis muscle anterolateral, and the sartorius muscle medial. An insulated nerve block needle connected to nerve stimulator delivering a current of 1 mA at a frequency of 1 MHz was inserted through the anesthetized area via the long axis (in-plane view) of the ultrasound probe from the lateral end. Contraction of ipsilateral quadriceps muscle indicating that the tip of the needle is close to the femoral nerve. After negative aspiration through the needle, 25 ml of bupivacaine 0.5% with adrenaline 1:400,000 was injected over 2–3 min while observing the distribution of the local anesthetic within the adductor canal in real time.[1112]

Technique of psoas compartment block in the second group

The ultrasound scan in PCB was performed using a low frequency, 5-2 MHz curvilinear array transducer. A longitudinal scan of the lumbar paravertebral region was produced by application of the liberal amount of ultrasound gel over the lumbar paravertebral region and positioning of the ultrasound transducer 4 cm lateral and parallel to the lumbar spine, with its orientation marker directed cranially. Moving the transducer caudally until visualization of the sacrum and L5 transverse process. The L5 transverse process is identified by its hyperechoic reflection and an acoustic shadow distal to it, other lumbar transverse processes were identified by counting them from below upward, the transducer finally put over L2, L3, and L4 transverse processes, the acoustic shadow of a longitudinal scan of the transverse processes produce the “trident sign,” The psoas muscle was seen through the acoustic window of the trident as multiple longitudinal hyperechoic striations against a hypo-echoic background, the root of the lumbar plexus can be seen as the hyperechoic structure in the posterior part of the psoas muscle. With the lumbar ultrasound “trident” in view, injection of 1–2 ml of 1% lidocaine solution was done. An insulated nerve block needle connected to nerve stimulator was inserted in the plane of the ultrasound transducer from the caudal end and advanced through the space between the transverse processes of L3 and L4 into the posterior part of the psoas muscle. As the needle was inserted in the plane of the ultrasound beam, it became easy to follow the needle in the real time. Entry of the block needle in the posterior part of the psoas muscle was initially diagnosed by contraction of the psoas muscle on the ultrasound scan followed by ipsilateral contraction of the quadriceps muscle indicating that the tip of the needle is close to the lumbar plexus. After negative aspiration through the needle, 25 ml of bupivacaine 0.5% with adrenaline 1:400,000 was injected over 2–3 min while observation the distribution of the local anesthetic in a real time.[1314]

Technique of sciatic nerve block in both groups

This block was performed while the patients were lying down in the lateral position with the side to be blocked uppermost, with flexion of the hip and knee and ultrasound scan was performed using a low frequency, 5-2 MHz curvilinear array transducers. After identifying the greater trochanter and the ischial tuberosity, a line was drawn between these two landmarks. A liberal amount of ultrasound gel was applied over the skin of this area, and the ultrasound probe was positioned parallel to the line previously drawn with its orientation marker directed laterally.

Preprocedure scan was performed to identify the sciatic nerve in the subgluteal space and to optimize the ultrasound image prior the intervention. The subgluteal space was seen as the hypoechoic area between the hyperechoic of the gluteus maximus and quadratus femoris muscles. At this level, the sciatic nerve was seen as oval hyperechoic nodule within the subgluteal space. At this view, after injection of 2–3 ml lidocaine, the insulated nerve block needle was connected to nerve stimulator then inserted in the plane of the ultrasound beam and advanced toward the sciatic nerve in real-time. When the block needle was in contact with the sciatic nerve (identified by observation nerve movement on the ultrasound scan followed by dorsiflexion or plantar flexion of the foot), after negative aspiration through the needle, 20 ml of bupivacaine 0.5% was injected over 2–3 min while observation the distribution of the local anesthetic in real-time.[15]

Monitoring and assessment

Monitoring included ECG, noninvasive arterial blood pressure, and pulse oximetry. Oxygen was delivered by facemask at flow rate 4–5 L/min. 6–8 ml/kg/h of ringer acetate solution was given to the patients throughout the operation.

The sensory block was evaluated using pinprick response at 10-min intervals throughout the 30-min after injection, then at 30 min intervals until the end of the surgery, and then evaluated every 1 h, postoperative. This was done by testing sensory innervations territories of femoral, LFC, and OBT nerves. The effectiveness of the sensory block was tested, if it is complete or not at 30 min after injection. The onset of sensory block was defined as the time from injection until disappearance of sensation by pinprick test, and duration of sensory block was defined as the duration from onset of the sensory block until the beginning of sensation by pinprick test.

The motor block of lumbar plexus was evaluated 30 min after the block procedure then at 30 min intervals until the end of the surgery and then evaluated every 1 h, postoperative by testing the knee extension (i.e., femoral nerve), thigh adduction (i.e., OBT nerve). The onset of motor block was defined as the time between injection and motor paralysis distal to the injection site. Duration of motor block was defined as the duration from onset of motor block until the complete regression of motor block.

After 30 min, the block was considered complete if anesthesia had spread simultaneously to the femoral, LFC, and OBT nerves. If the nerve block was incomplete, 1 mg/kg ketamine hydrochloride was given IV. If surgical pain still present, general anesthesia was induced.

The postoperative visual analog scale (VAS) score was assessed 1, 6, 12, and 24 h after the end of the operation and if the VAS ≥4, the patient was given opioid analgesia in the form of 0.05 mg/kg morphine. Any adverse effect at the postoperative period was recorded as general anesthesia induced, hematoma, neuropathy, epidural spread, drugs toxicities, and intravascular injection.

Statistical analysis

The primary outcome was the incidence of the complete sensory block at 30 min of injection. The secondary outcomes included the number of the total sensory block of the femoral, LFC, and OBT nerves, noted at 10 min intervals during the first 30 min after injection, the number of general anesthesia requirement, duration of sensory and motor blockade, and VAS among the two groups.

Power of study

In a previous study, incidence of the complete sensory block at 30 min in the anterior approach of lumbar plexus block was about 40%. Assuming alpha (type I error) =0.05 and beta (type II error) =0.2 (power = 80%) 42 patients were required in each group to detect a difference of 30% between the two groups.

Allowing for patients lost to analysis, 45 patients were assigned to each group. Statistical analyses were performed using SPSS version 22 (IBM, SPSS Inc., Chicago, IL, USA). Data were tested for normality using the Kolmogorov–Smirnov test. Continuous data of normal distribution are presented as mean ± standard deviation and were analyzed with the Student's t-test. Non normally distributed data are presented as median (range) and were analyzed with the Mann–Whitney U-test. Nominal data are presented with number (percentage) and were analyzed with the Chi-square test. The value P < 0.05 was considered statistically significant.

RESULTS

Demographic data and operation time showed the nonsignificant difference between either group [Table 1].

Table 1

Patient characteristics, surgery time, and surgical procedures

Sensory block of the LFC nerve (20 min, 30 min after injection) and OBT nerve (10 min, 20 min, 30 min after injection) were significantly increased in the PCB group versus the ACB group. A nonsignificant difference in the sensory block of the femoral nerve was noted in either group [Table 2]. Duration of the sensory block was significantly elongated in PCB group versus the ACB group complete sensory block was significantly noted in all patients with PCB with no need for general anesthesia as compared to the ACB group [Table 3].

Table 2

F, LFC, OBT sensory block at 10, 20, 30 min after injection

Table 3

Durations of sensory and motor block, complete sensory block, and general anesthesia requirement

Motor block of the OBT nerve (30 min after injection) was significantly increased in the PCB group as compared to the ACB group. While a motor block of femoral nerve was nonsignificantly changed in either group [Table 4]. A nonsignificant difference was observed in the duration of the motor blockade [Table 3].

Table 4

F and OBT motor block at 30 min after injection

VAS was significantly decreased in the first postoperative 6 h in PCB group as compared to the ACB group. The time of first analgesic requirement was significantly delayed in PCB group in comparison to the ACB group [Table 5].

Table 5

Time of first analgesic requirement and postoperative assessment of VAS

DISCUSSION

This study showed that the real-time ultrasound guidance of PCB is more effective than the ACB combined with sciatic nerve block in patients undergoing elective laparoscopic knee surgeries. Although the sensory blockade of the femoral nerve achieved equally by both techniques, the LFC, and OBT nerves were faster and more effectively blocked with PCB technique. Furthermore, PCB group showed significant complete sensory block without the need for general anesthesia, significant decrease in the postoperative VAS, and significant increase time of first analgesic requirement as compared to the ACB group.

The present results demonstrated the difficulties in obtaining a complete lumbar plexus block via the ACB. The ACB does not provide adequate analgesia after knee surgery as complete as PCB because the posterior division of the femoral nerve sends branches to the quadriceps muscle at varying levels proximal to the adductor canal (particulary vastus lateralis, intermedius). Each branch gives rise to articular filaments, together with the saphenous termination of the femoral nerve, provides sensory innervation to the knee joint.[13]

Cappelleri et al.[4] proved that patient with PCB required less postoperative analgesic requirements during 1st24 h that passes in parallel with the present results. These finding can be explained by the fact that spread of the local anesthetic through the lumbar plexus is unpredictable.[2] Local anesthetic can pass laterally under the fascia situated between the psoas and iliac muscles to produce blockade of the femoral and LFC nerves, but it does not extend medially in sufficient amount to block the OBT nerve[16] in comparison to the ACB. If the femoral nerve is stimulated in PCB evident by quadriceps femoris muscle contraction, it shows that the tip of the needle is located in the middle of the lumbar plexus nerve roots, so local anesthetic can pass on both sides to OBT and LFC nerves.[16] This explains the high rate of the sensory blockade of the OBT and LFC nerves in PCB.

On the other hand, these findings are in contrast with Winnie et al.[3] who demonstrated that the anterior approach technique of lumbar plexus block is successful to block all the three main branches of the lumbar plexus with a single injection, and proved that if a volume of 20 ml of local anesthetic was injected, anesthesia of the three main branches was done. There has been debate with regard to the efficacy and reliability of this technique.[417]

In spite of more effectiveness of the PCB, the inguinal paravascular and ACB is still commonly performed for fear of side effects of PCB.[18192021] One of the most common and most serious side effects are the epidural/spinal spread of local anesthetic solution, which is mainly due to a proximal movement into the paravertebral space rather than a direct placement of the needle into the epidural space,[19] delayed bilateral spread of local anesthetic,[22] intravascular injections can cause seizure, cardiac arrest, and death,[232425] delayed toxic reactions, unilateral sympathectomy,[5] and renal subcapsular hematoma.[2021] To decrease the incidence of these complications associated with lumbar plexus block, ultrasound guidance has been introduced which allows direct visualization of the needle, anatomy, neural structures, and the spread of local anesthetics.[2627]

All studies have failed to identify the roots of the lumbar plexus until the study that was done by Karmakar et al. in 2008[28] in which he demonstrated that the ability to visualize parts of lumbar plexus in some patient on the longitudinal sonography of the lumbar paravertebral region, needle introduced under real-time ultrasound guidance through the acoustic window of the lumbar ultrasound “trident” places it in the posterior part of the psoas muscle near to the roots of the lumbar plexus and local anesthetics injected under real-time ultrasound guidance is effective in producing PCB.

In this research, the roots of the lumbar plexus could be identified within the posterior part of the psoas muscle. The sonographic appearance of the psoas major muscle is the same as that of other muscles,[29] in the form of hyperechoic striations on a hypoechoic background.[30] The nerve roots appeared hyperechoic with less hyperechoic than peripheral nerves in the extremities. The nerve roots were sonographically thicker than the muscle fibers and took an oblique course through the muscle. They were also more posterior in location than the inter-muscular tendon of the psoas muscle.[2931] The tip of the block needle was usually present in the vicinity or in contact with the nerve root when the motor response was elicited. The nerve roots were also better delineated after injection of the local anesthetic.[28] Karmakar et al.[28] and Koyama et al.[32] were able to see parts of the lumbar plexus within the psoas muscle using low-frequency curved array transducer. However, Kirchmair et al.[33] were unable to distinguish between the nerve roots of lumbar plexus and the inter-muscular tendon fibers within the psoas muscle. Advances of ultrasound technology are improving image processing abilities of ultrasound. Furthermore, the use of tissue harmonic imaging improves the resolution, which is difficult to scan, may have allowed us to see parts of the lumbar plexus in our study. Ability to delineate the lumbar plexus in some of the patients was not available. Possible reasons may have been age because the echo intensity of the muscles is significantly increased with elderly[3334] and the ultrasound images are brighter and whiter in elderly patients. This decrease of the image resolutions makes it difficult to delineate the lumbar plexus.

Sauter et al.[35] reported that the use of ultrasound guided PCB was done through a transverse scan at the flank slightly above the iliac crest “Shamrock method.” The lumbar plexus nerves were identified in the medial and posterior aspects of the psoas muscle. An in-plane needle insertion technique was used to perform the PCB, with the needle inserted posteriorly in the back (4 cm from the midline). However, it was challenging to determine the initial angle for needle insertion as the needle was inserted at a considerable distance from where the ultrasound scan was performed.[3637]

In this study, the opinion which is shared by the others is that real-time ultrasound-guided lumbar plexus nerve block is an extremely challenging and advanced technique that needs to be refined and validated with additional studies.[638] There are very few studies of the real-time ultrasound-guided lumbar plexus nerve block. This may reflect the greater degree of skills to perform the block.[28]

Many limitations of this study were recorded. The exclusion of obese patients led to that the incidence of success in patients with BMI > 35 kg/m2 cannot be determined, as ultrasound visibility of the lumbar paravertebral structures in obese patients was poorer than that observed in patients with low BMI.[39] Other limitation was the wide range of age group and changes in musculoskeletal structures, particularly in the elderly patients (>65 years) that can reduce the contrast between a peripheral nerve and its surrounding muscles and can adversely affect the quality of ultrasound images.[3334] Patients with abnormal spinal anatomy, due to either spinal deformity or history of previous back or spine surgery also showed poor image quality.[39]

CONCLUSION

The present study demonstrates that blockade of lumber plexus by PCB is more effective in the complete sensory block without general anesthesia supplementation in addition to decreasing postoperative analgesic requirement than ACB combined with sciatic nerve block using the real-time ultrasound guide.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest