Innovations In Lower Extremity Blockade

Innovations in Lower Extremity Blockade Gary E Morris, MD, FRCPC, and Scott A. Lang, MD, FRCPC

Nerve blocks of the lower extremity are undertaken less often than blocks of the upper limb. Spinal and epidural techniques are more common approaches to regional anesthesia of the lower extremity. Contrary to neuraxial techniques, isolated nerve blocks do not cause hypotension, retain the ability to void, and allow earlier unassisted ambulation despite a longer duration of action. However, the ideal block for every clinical scenario is not known. A knowledge of anatomy and some imagination may add some new approaches to our armamentarium. This article describes several new approaches to lower extremity blockade developed at the University of Saskatchewan. Many have proven successful, whereas others will have more limited applications. In this review we wish to outline the parasacral sciatic nerve block, the nerve stimulator approach to the lateral femoral cutaneous nerve of the thigh, the transsartorial saphenous nerve block, and the intraoperative transcruciate injection for total knee arthroplasty. The strengths and limitations are discussed together with a discussion of the relevant clinical anatomy of each approach. Copyright 9 1999 by W.B. Saunders Company

'erve blocks for anesthesia and/or analgesia are performed

less frequently for the lower extremity than for the upper N extremity. With an upper extremity block, anesthesia of the

entire limb may be accomplished with a single injection near the elements of the brachial plexus. Surgical anesthesia of the entire lower limb would require, at a minimum, anesthesia in the distribution of the femoral, lateral femoral cutaneous, obturator, posterior femoral cutaneous, and sciatic nerves (Fig 1). Therefore, procedures of the lower extremity usually require at least two injections. It is interesting that analgesia for surgical procedures on the lower extremity may not require conduction block of all nerves carrying sensory information from the operative site. For example, arthroscopy of the knee may be performed with a femoral block alone, although we know that the knee receives sensory supply from the sciatic and obturator nerves. 1Similarly, postoperative analgesia following anterior cruciate ligament repair of the knee is improved with the performance of a femoral nerve block. 2 Alternatively, analgesia following total knee arthroplasty may be inadequate with a femoral block alone, 3 requiring additional sciatic anesthesia to manage posterior knee pain. 4 Unfortunately, precisely which nerves should be blocked for any given surgical procedure is not clear from the literature, nor is it intuitive. From the Departments of Anesthesia, University of Saskatchewan, Royal University Hospital, Saskatoon, Saskatchewan and University of Calgary, Foothills Hospital, Calgary,Alberta Canada. Address reprint requests to Gary F. Morris, MD, FRCPC, Clinical Assistant Professor, Department of Anesthesia, University of Saskatchewan, 103 Hospital Drive, Saskatoon, Saskatchewan, Canada S7N 0W8. Copyright 9 1999 by W.B. Saunders Company 1084-208X/99/0301-0002510.00/0

Postoperative pain is a complex topic. Although it may be possible to demonstrate improved analgesia with a particular nerve block using patients as their own controls, it may not be possible to duplicate those results in a well-designed clinical trial. For example, femoral nerve blocks can be shown to improve analgesia if performed in the recovery room in a patient suffering pain from a total knee arthroplasty (TKA). 3,5 However, when femoral nerve blocks are performed in a double-blind fashion for the same procedure, patients have not appreciated improved analgesia. 3 Therefore, we cannot recommend the routine use of femoral nerve blocks as an analgesic adjunct after TKA even though the block does provide improved analgesia. Our sole focus should not be whether a particular block provides analgesia. The relative efficacy of the technique, its simplicity, safety, cost, limitations, and mechanisms of action should also be investigated and outlined. We first outline some principles that have enhanced our overall success and enabled us to "develop" new techniques. Although many factors contribute to success in regional techniques, we believe that the single most important element of any nerve block is the deposition of local anesthetic near the targeted nerve. 6 Therefore, we used rigid end points to facilitate the success of our blocks. We have demonstrated that it is easier to anesthetize a nerve when accessing it centrally (ie, as a single nerve trunk as opposed to the more proximal "roots" or distal "branches"). 79 The same concept is used when performing a supraclavicular brachial plexus block as opposed to an axillary brachial plexus block. Furthermore, the deposition of local anesthetic in a well-defined tissue plane or compartment, as opposed to injection at a point at which components of a nerve or plexus travel in different tissue planes or within muscle, is another concept that our research supports. 7,1~ Finally, we often use a grid approach (ie, 2-dimensional seek and block) to nerve localization that allows the operator to methodically locate the target nerve and both shortens the time to completion of the block and improves overall success. 9

Parasacral Sciatic Nerve Block 9 9 9 9 9 9

Simple anatomic landmarks Technique readily mastered Blocks the entire sacral plexus Proximal approach within a fascial compartment Frequently blocks obturator nerve Suitable for catheter techniques for continuous infusions

Sciatic nerve blocks are useful but may be technically demanding. Many approaches have been described, with success rates varying between 33% and 95%. The parasacral approach to the sciatic nerve represents a proximal approach at the level of the sacral plexus and is easy to perform. Not only is sacral plexus anesthesia achieved, but spread of local anesthetic often results in anesthesia of the obturator nerve as well.

Techniques in Regional Anesthesia and Pain Management, Vol 3, No 1 (January), 1999: pp 9-18

9

[ ] Femoral 9

Obturator

the sciatic nerve may result in an effective block of the entire nerve. This observation is supported by recent work by other investigators. 11 However, there is insufficient experience with the technique to be sure that success or latency or both will not be affected by the choice of alternative endpoints. The 22-G, 100-mm needle was adequate to reach the sacral plexus in all of our patients. Our largest patient weighed 122 kg. Even in obese patients, the landmarks are usually palpable, and anecdotal success at reaching an acceptable motor response was similar to that in patients of average build. The sacral plexus (Fig 3) consists of nerve fibers originating from L4 to $3 nerve roots. These nerve roots travel within the pelvis anterior to the ischial bone and the piriformis muscle. They then coalesce to form the common peroneal, tibial, posterior femoral cutaneous, inferior gluteal, and superior gluteal nerves just before exiting the pelvis via the greater sciatic notch immediately caudad to the piriformis muscle. In addition to the components of the sciatic nerve, the sacral plexus also gives rise to the pudendal nerve. The pelvic splanchnic nerves ($2-$4), the terminal portion of the sympathetic trunk, and the inferior hypogastric plexus all lie in close proximity to the elements of the sacral plexus. Almost all patients experience unilateral anesthesia of the perineum. Therefore, the parasacral approach represents a sacral plexus block rather than an isolated sciatic nerve block. Despite sacral plexus anesthesia and the close proximity of the

[ ] Saphenous [ ] Sciatic [ ] Lateralfemoral cutaneous [ ] Posteriorfemoral cutaneous [ ] Sacral Fig 1. Sensory innervation of the lower extremity. (Reprinted with permission from Morris et aM ~

Single Injection Technique 1~ Monitored with pulse oximetry, the patient is positioned laterally with the operative limb uppermost. Oxygen is administered via nasal prongs. Small incremental boluses of an opioid (eg, alfentanil or remifentanil) are administered to facilitate positioning and block placement. The posterior superior iliac spine (PSIS) is identified, and a line is constructed between that point and the ischial tuberosity (Fig 2). At a point approximately 3 finger-breadths (6 cm) from the PSIS, a 22-G, 100-mm insulated needle is inserted and advanced in a sagittal plane. The needle is "walked" off the contour of the greater sciatic notch into the pelvis. The sacral plexus is usually reached at a depth of 5 to 7 cm from the skin. A brisk motor response at the ankle is sought with the aid of a peripheral nerve stimulator. Once a motor response is elicited at 0.2 mamp (Digistim II, Neurotechnology, Houston, TX), 30 mL of lido caine 1.5% with 1:200,000 epinephrine is injected. Onset of sensory anesthesia is brisk and followed shortly by motor anesthesia in the distributions of the sciatic and obturator nerves. There is little difference in rate of onset in any of the distributions regardless of whether the response at the ankle was plantar flexion (tibial) or dorsiflexion (peroneal). Though not formally tested, the injection of local anesthetic at any 0.2 mA motor response in the distribution of

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Fig 2, Parasacral sciatic nerve block (landmarks and technique), Six centimeters along a line from the posterior superior iliac spine (A) and the ischial tuberosity (C) a 22-gauge insulated needle is inserted at (B) and advanced in a parasagittal plane seeking a motor response, (Reprinted with permission from Morris et al, 1~

MORRISAND LANG

nately, lie in a different plane more anteriorly than the neural structures. No episodes of local anesthetic toxicity or vascular puncture have been identified. The bladder, uterus, and rectum all lie within the pelvis. No infectious complications have been seen, and there are no clinical findings in any patient compatible with visceral puncture (eg, hematuria, melena, infection). Some questions remain. Although dissection in the anatomy laboratory suggests that the sacral plexus is contained within a distinct fascial plane, we have not been able to demonstrate this using radiography with contrast or magnetic resonance imaging. Caution must be exercised with new techniques. Observations from small studies need to be confirmed to evaluate the limitations of the block, its success rate, and associated complications. Because complications are expected to be rare, the actual incidence and nature of complications associated with a new technique will not be known until several hundred or thousands of blocks have been performed.

Continuous Parasacral Technique 14

Fig 3. Pelvic view of the sacral plexus (anatomy). (A) Sacral plexus. (B) Sciatic nerve. (C) Pudendal nerve. (D) Obturator nerve. (E) Sympathetic chain. (F) Internal iliac artery. (G) Internal iliac vein. (Reprinted with permission from Morris et al. 1~ sympathetic nerve supply to the bladder, no patient has experienced difficulty with voiding, and none has required postoperative bladder catheterization. We demonstrated anesthesia of the obturator nerve in most patients. As illustrated in Fig 3, the obturator nerve courses along the pelvic brim close to and in the same plane as the lumbosacral trunk. Spread of local anesthetic to the obturator nerve along a common fascial plane likely accounts for this adductor weakness. There is a paucity of sensory changes in the upper leg despite marked motor weakness in the distribution of the obturator nerve. At best, a few patients described patchy sensory changes, although in no patient could a discrete area of cutaneous analgesia to pin prick be mapped. This obturator nerve sensory-motor dichotomy questions the classic description of the sensory distribution of the obturator nerve. 12 We believe that either the obturator nerve has no significant sensory innervation of cutaneous structures or that the sensory and motor fibers within the nerve follow very divergent courses from their inception to their termination. However, we are convinced that the obturator nerve does provide a consistent sensory component to the knee joint. Obturator anesthesia is reported to be a necessary component of regional anesthesia for major surgery on the knee. Total joint replacement may be impossible despite excellent sciatic and femoral nerve blocks if the obturator nerve is spared. 13 Traditional approaches to the obturator nerve can be painful and may be technically difficult for the anesthesiologist to perform. In view of the controversy surrounding the ability of the femoral 3-in-1 nerve block to achieve conduction blockade of the obturator nerve, 13 the parasacral sciatic nerve block may offer a more reliable method of producing obturator nerve anesthesia. The pelvis is also rich in vascular structures, which fortuINNOVATIONS IN LOWER EXTREMITY BLOCKAGE

The parasacral approach to the sciatic nerve allows a catheter to be threaded into a "fascial" plane for continuous infusion of local anesthetic. By using the landmarks described previously, an insulated 18-gauge, 6-inch Tuohy needle (Contiplex; B. Braun/McGraw, Bethlehem, PA) is "walked" off of the bony contour of the greater sciatic notch into the pelvis. With the aid of a nerve stimulator, a brisk ankle motor response is elicited near 0.2 mA. An epidural catheter can then be threaded through the Tuohy needle to a depth of 15 cm. The parasacral sciatic block may then be established with 30 mL of lidocaine 1% with 1:200,000 epinephrine for surgical anesthesia. Postoperative analgesia is maintained with a continuous infusion of bupivacaine 0.125% with 1:200,000 epinephrine at 8 mL/hr. We recommend the injection of local anesthetic through the catheter in 5 mL aliquots much as you would perform an injection via a catheter placed in the epidural space. If resistance to catheter advancement through the needle is encountered, 5 to 10 mL of saline injected via the needle may expand the fascial compartment enough to facilitate catheter advancement. Rapid administration of large volumes of local anesthetic through the Tuohy needle is not recommended because of the risk of intravascular injection. Insertion of a continuous catheter near the elements of the sacral plexus in the pelvis is easily accomplished (ie, little resistance to catheter advancement). This approach avoids the dense connective tissue and poorly defined tissue planes that surround the sciatic nerve more distally. The catheter resists migration and dislodgement and has remained effective for the entire duration of the infusion (48 hr) despite ambulation. In summary, we have found that the parasacral approach to sciatic nerve blockade provides excellent surgical anesthesia for surgical procedures below the knee when combined with either a femoral or a transsartorial saphenous n e r v e b l o c k . 10,14 The parasacral sciatic nerve block has a high success rate, is easily mastered, and is associated with excellent patient satisfaction. Coincidentally, it frequently provides anesthesia in the distribution of the obturator and pudendal nerves. The addition of this approach to the sciatic nerve and the sacral plexus represents a welcome addition to regional anesthetic techniques for the lower limb and may also allow reliable anesthesia of the obturator nerve. Continuous parasacral techniques may provide excellent analgesia, allowing ambula11

tion yet avoiding problems such as urinary retention, hypotension, and bilateral limb weakness.

Nerve Stimulator Assisted Block of the Lateral Femoral C u t a n e o u s Nerve of the Thigh 9 9

9 9 9 9

Can be used to locate and block a pure sensory nerve High success rate Rapid onset of anesthesia Small local anesthetic volume Reduced incidence of coincident femoral nerve block

Mixed sensory and motor nerves may be localized with the stimulation of sensory fibers via a paresthesia technique or with stimulation of motor units using a peripheral nerve stimulator. Localization of motor fibers can be readily achieved using a peripheral nerve stimulator at a high current (2 mA). Refinement of delivered amperage can then be used to determine the minimum effective stimulating current thus guiding the needle to the nerve. At a current of 0.2 to 0.3 mA (Digistim II, Neurotechnology, Houston, TX) an insulated probing needle should be within a few millimeters of a motor nerve. Until recently, identification of purely sensory nerves using a nerve stimulator was thought to be impractical because of the known differences in electrical conductance between sensory and motor nerve fibers is and because electrical stimulation of sensory nerves was expected to be too painful for patients to tolerate. 16 Success eliciting a mechanical paresthesia by direct contact with the nerve is improved when the course of the nerve bears a consistent relationship to anatomic landmarks and when the nerve is of a sufficient size to increase the likelihood of stimulation by a probing needle. However, when the position of the targeted nerve is not precisely known, achieving direct contact with a needle may be frustrating. Finally, direct needle contact may injure the nerve. 17 The lateral femoral cutaneous nerve (LFCN) of the thigh is a purely sensory nerve that is formed from the second, third, and fourth lumbar roots and is "classically" described as entering the thigh below the inguinal ligament medial to the anterior superior iliac spine (ASIS). 12 However, the location of the LFCN has been shown to range from 1.5 cm lateral to 3 cm medial to the ASIS. 9 Shannon et al. 9 describe the use of a hand-held peripheral nerve stimulator to facilitate identification of the approximate location of this nerve because it has such a variation in anatomic location. A relatively large current (26 mA) is applied to the skin surface using a pulsed nerve stimulator. Fig 4 illustrates how a cutaneous electrical stimulus is applied in the region of the ASIS seeking a paresthesia in the lateral thigh typical of the distribution of the LFCN (Fig 1). A mark at the skin is made at the point of the maximal intensity of the paresthesia, and this provides the point to begin percutaneous stimulation. A 2 cm grid is constructed (Fig 5) perpendicular to the long axis of the LFCN and 3 m m markings provide a structure for a systematic search for a paresthesia. A 27-G uninsulated needle is inserted at point A (Fig 5), and a paresthesia response in the distribution of the LFCN is sought that is synchronous with the beep of the nerve stimulator. A paresthesia at 0.6 mA referred to the distal lateral thigh should be sought (Digistim II, Neurotechnology, Houston, TX). A total of 6 mL of 1.5% lidocaine with 1:200,000 epinephrine is then injected. With this end-point the onset of

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Fig 4. Cutaneous electrical stimulation of the lateral femoral cutaneous nerve (LFCN). A hand-held peripheral nerve stimulator is applied to the surface of the skin surrounding the anterior superior iliac spine (ASIS) searching for a paresthesia radiating to the lateral thigh. The point of maximum intensity is marked on the surface of the skin.

anesthesia occurs within seconds. Total time from landmarking to anesthesia averages 10 minutes. The proximity of the femoral nerve may be problematic if an isolated LFCN block is desired. Shannon et al. 9 demonstrated that 35% of patients blocked with the traditional fan technique and 5% of those with the nerve stimulator technique experienced a femoral block as demonstrated by quadriceps weakness. Finally, although the classic description of the cutaneous distribution of the LFCN extends proximal to the greater trochanter and frequently as far proximal as the anterior superior iliac spine (Fig 1), we have found that most patients did not achieve anesthesia as far as the greater trochanter (Fig 6).

Transsartorial S a p h e n o u s Nerve Block 7 High success rate 9 Complete anesthesia of the saphenous nerve to the ankle 9 No loss of motor power

9

Fig5. Percutaneous electrical stimulation of the lateral femoral cutaneous nerve (LFCN). A grid is constructed perpendicular to the line of the LFCN and a paresthesia referred to the knee is sought at 0.6 mA using a 27-G uninsulated needle. MORRIS AND LANG

~

greater trochanter

The overall success rate is 80%, and the onset of the block occurs within 5 minutes. In successful blocks, complete anesthesia of the medial malleolus occurs significantly more often than with saphenous nerve blocks performed at or below the knee joint (ie, 94% vs 39%). This demonstrates that blocking the saphenous nerve while still a single trunk is more likely to provide anesthesia for of all components of the nerve when compared with attempting anesthesia of its individual branches more distally. This will prove useful if surgical procedures on the ankle are attempted with a saphenous block. We would expect complications to be rare with this site of injection, as the superficial femoral vessels and the saphenous nerve part company more proximally at the adductor canal. There have been no serious complications, although some patients have complained of bruising and tenderness at the injection site. The clinical use of this block has been demonstrated when it is used in conjunction with a parasacral sciatic nerve block for lower extremity surgery. 10

Transcruciate Block for Total Knee Arthroplasty is 9 9 9 9 9 9 Fig 6. Cutaneous distribution of the lateral femoral cutaneous nerve (LFCN). The classic anatomy and sensory distribution of the lateral femoral cutaneous nerve of the thigh (LFCN) are illustrated. The actual distribution of the LFCN does not extend as far as the greater trochanter In most patients. (Reprinted with permission from Shannon et al. 9)

9 Compartment block of a single nerve 9 Well tolerated Successful anesthesia of the saphenous nerve is important for surgery of the lower extremity. The cutaneous innervation of the saphenous nerve is extensive. The transsartorial saphenous nerve block demonstrates the concept that a conduction block of the parent trunk provides more reliable anesthesia of all terminal branches than a field block performed more distally. The saphenous nerve travels with the femoral artery and vein, within the neurovascular sheath from the femoral triangle as far as the adductor hiatus. At this point, the superficial femoral artery and vein pass through the adductor hiatus into the popliteal fossa, and the saphenous nerve continues on its original course just beneath the sartorius muscle. From the adductor hiatus, the saphenous nerve consistently travels within this subsartorial fat pad before arborizing into its terminal branches at or below the knee.

Technique The sartorius muscle belly is identified as the patient actively elevates an extended leg. At a point one fingerbreadth above the upper border of the patella, a skin wheal of local anesthetic is raised and a 20-G Tuohy pediatric needle is advanced through the muscle belly until a loss of resistance identifies the subsartorial fat pad (Fig 7). Following aspiration, 10 mL of local anesthetic is injected. INNOVATIONS IN LOWER EXTREMITY BLOCKAGE

Simple to perform Anatomy visible intraoperatively Profound postoperative analgesia Decreased need for urinary catheterization Patients can ambulate Remarkable range of motion for postoperative physiotherapy 9 Can be discharged from hospital several days earlier than with traditional analgesia Patients may experience severe pain after TKA. An ideal postoperative analgesia technique remains elusive. Intravenous patient-controlled analgesia minimizes motor weakness, although the intensity of the pain frequently leaves patients afraid to move and resistant to suggestions of postoperative physiotherapy. The "gold standard" postoperative analgesic regimen is often considered to be epidural analgesia with a combination of local anesthetic and narcotic. 19 Although effective, the epidural use of local anesthetic and narcotic is associated with significant limitations and has not been shown to be superior to other analgesic regimens after TKA. 2~ The administration of local anesthetic via lumbar epidural catheters is associated with a significant incidence of bilateral lower extremity weakness and sensory disturbances that may interfere with the ability of the patient to ambulate. 21 In addition, the use of local anesthetic in the lumbar epidural space is associated with a significant incidence of hypotension 19 that mandates strict observation protocols and may interfere with patient management. Finally, the use of femoral 3-in-1 nerve blocks for postoperative analgesia after TKA has been shown to be of little value when studied in a double-blind manner. 3 The exact explanation for this observation is unclear but may be related to the fact that an isolated femoral nerve block will not provide analgesia for the articular structures of the knee supplied by the sciatic nerve.

Technique A femoral block is established in an awake patient using 20 mL of 0.5% bupivacaine with 1:200,000 epinephrine. The patient 13

Fig 7. Transsartorial saphenous nerve block. A blunt, 20-gauge, Tuohy needle was advanced through the sartorius muscle by using a loss of resistance technique (similar to that used for identification of the epidural space with saline). The saphenous nerve and relevant anatomy (anteromedial view of the leg) are (A) sartorius muscle; (B) fascial envelope containing the saphenous nerve (black), superficial femoral artery (white), and femoral vein (black-white stripes); (C) saphenous nerve; (D) fat pad beneath sartorius muscle, within which lies the saphenous nerve; (E) vastus medialus. The adductor hiatus is the point at which the saphenous nerve diverges from the superficial femoral artery and vein. (Reprinted with permission from Morris et al. 10)

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MORRIS AND LANG

receives a "transcruciate" injection through the posterior cruciate ligament once the surgical team has completed the femoral and tibial osteotomies (Fig 8). The surgeon performs the transcruciate block using a loss of resistance technique with an 18-G Tuohy needle in a fashion similar to that used for identification of the epidural space. All of our attempts at passage of the transcruciate needle by the surgeon were accomplished easily on the first attempt. A total of 20 mL of

bupivacaine 0.5% with 1:200,000 epinephrine is injected to ensure that at least 10 mk reaches the posterior fat pad (Fig 9). To assess the transcruciate block in the postanesthesia care unit during our initial study, all procedures were performed with the patient under general anesthesia although not studied, the transcruciate block performed in conjunction with spinal or epidural anesthesia should yield similar results. We found that visual analogue scores (VAS) with movement

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Fig 8. Anterior view of the knee intraoperatively seen during transcruciate injection of the right knee. The knee has been opened anteriorly. The Tuohy needle with attached syringe is shown penetrating the posterior cruciate ligament (PC) between the tibial and fibular heads. INNOVATIONS IN LOWER EXTREMITY BLOCKAGE

15

GON SMGN SMGA

TA TV TN 3PN LGN LGA

Fat Pad Tip of Needle, MGN MGA IMG IMG

,GN .GA IGN

Fig9. Posterior view of the right knee demonstrating needle placement in relation to associated anatomic structures. The knee has been dissected posteriorly and the neurovascular bundle retracted at the joint line. The tip of the Tuohy needle is shown emerging from the posterior cruciate ligament into the fat pad behind the knee joint. GON, geniculate obturator nerve; SMGN, superior medial geniculate nerve; SMGA, superior medial geniculate artery; MGN, medial geniculate nerve; MGA, medial geniculate artery; IMGN, inferior medial geniculate nerve; IMGA, inferior medial geniculate artery; TA, tibial artery; TV, tibial vein; TN, tibiai nerve; CPN, common peroneal nerve; SLGN, superior lateral geniculate nerve; SLGA, superior lateral geniculate artery; ILGN, inferior lateral geniculate nerve; ILGA, inferior lateral geniculate artery; RGN, recurrent geniculate nerve. demonstrated a remarkable improvement in the study patients who received a combination of femoral nerve and transcruciate blocks compared with control patients who received only intravenous patient-controlled morphine for postoperative analgesia (Fig 10). In fact, patients who received a combination of femoral and transcruciate blocks were able to flex the operative knee to greater than 90 ~ in the recovery room. This degree of mobility was not obtained until 48 hours postoperatively in control patients dependent on intravenous morphine for analgesia. However, the analgesic efficacy of the nerve blocks faded after 18 to 24 hours as demonstrated by a rebound in the severity of VAS scores and an increase in the use of rescue analgesia (intravenous morphine) in the study patients. 16

The average time to first ambulation was shorter, fewer patients required catheterization, and the average time to discharge from the hospital was significantly shorter in the transcruciate group compared with the control group. Although our initial numbers are small, on average the transcruciate patients were discharged more than 3 days earlier than control patients. These are interesting observations in light of the fact that the analgesic efficacy of the combined femoral nerve and transcruciate blocks diminished significantly after 18 to 24 hours. No neurological or vascular complications have been reported with this technique. There was no difference in patient satisfaction between the transcruciate and control groups MORRIS AND LANG

Although our results are encouraging, more patients must be studied to confirm the significance of our results and to further ensure the safety of the technique while following patients through the rehabilitation period.

10 VAS

5

Conclusions and Challenges ~

R hours post-op [3 t r a n s c r u c i a t e 9 control Fig 10. VAS scores with flexion comparing patients with no nerve blocks to patients with femoral nerve blocks and transcruciate analgesia. VAS pain scores with attempted flexion of the operative knee to 90 ~ VAS scores were statistlcally different with P < .05 at the assessment times indicated with an asterisk (*).

despite marked improvement in analgesia in the transcruciate group. All patients expressed satisfaction with their perioperative course on telephone follow-up interview. Other investigators 22,23 have confirmed this dichotomy between adequacy of analgesia and patient satisfaction. The lack of such an association needs explanation. The sensory nerve supply to the knee includes contributions from the femoral, lateral femoral cutaneous, obturator, and sciatic nerves. 18 With the failure of isolated femoral nerve blocks to significantly improve analgesia after TKA,3 femoral nerve blocks have been combined with sciatic nerve blocks in a successful attempt to overcome this shortfall. 4 However, it takes additional time, effort, and expense to perform a separate sciatic nerve block; and it leaves the patient with a totally anesthetic limb for hours postoperatively. In comparison, the intraoperative transcruciate injection is performed by the surgeon and is completed easily and quickly with a loss of resistance technique that requires the use of only a Tuohy needle and a syringe of local anaesthetic. The femoral nerve block provides analgesia in the territory of the primary surgical incision that provides exposure for the intra-articular part of the operative procedure. We believe that intraoperative transcruciate injection by the surgeon provides additional analgesia by blocking the terminal articular sensory fibers of the sciatic and obturator nerves. This approach differs from both traditional and popliteal sciatic blocks z4 in that after a transcruciate injection of local anesthetic, these patients do not experience sensory or motor anesthesia in the distribution of the sciatic nerve. This leaves patients with the ability to move the operative limb and allows them to ambulate immediately with the use of a knee brace (eg, Zimmer splint) and the assistance of a nurse or walker. In summary, a combination of femoral and transcruciate blocks is a promising new approach for controlling pain after TKA. However, as this combination provides excellent analgesia for only 18 to 24 hours (Fig 10), solutions must be found to help extend the duration of improved analgesia further into the postoperative period. The major advantage of the technique is improved analgesia with movement (Fig 10). We need to change postoperative management of these patients to take advantage of this improved analgesia with early and aggressive physiotherapy. There may be potential for improved long-term outcomes to complement a less eventful recovery and an earlier discharge. INNOVATIONS IN LOWER EXTREMITY BLOCKAGE

Anatomic dissection has been used for hundreds of years, and local anesthetics have been applied to block painful sensation for more than a century. Many questions remain unanswered. What is the relative importance of cutaneous sensation compared with the innervation of deeper structures in postoperative analgesia? Can we improve outcome with regional techniques and, if so, in which patients? We are now entering the era of evidence-based medicine. We need well-designed investigations to provide the evidence by which we can improve our practice of regional anesthesia. Many results of our studies are subjective. There is a great variation in pain perception among patients. Patients who may exhibit a very different outward pain appearance may record very similar VAS scores. Patients with vastly different VAS pain scores may be equally very satisfied with their care and pain management. It is possible to design double-blind studies for the evaluation of regional techniques. ],3,1s In fact, we have been surprised by our results. We would not have expected that surgeons could not recognize which of their patients presenting for knee arthroscopy had received a femoral nerve block. 1 With each piece of the puzzle we uncover, we discover more questions. Let us learn from our patients. The observations from "failed" blocks and unexpected occurrences may lead us on a fascinating journey of discovery.

Acknowledgments We wish to thank the Departments of Anesthesia and Orthopedic Surgery within the Saskatoon District Health Board for their support during the development of novel approaches to regional anesthesia. We thank our illustrator, Beth Lozanoff for her creative efforts in illustrating the concepts that we have developed.

References 1. Goranson BD, Lang SA, Cassidy JD, et al: A comparison of three regional anaesthesia techniquesfor outpatient knee arthroscopy. Can J Anaesth 44:371-376, 1997 2. Urmey WF, Stanton J, Portnoy R, et al: Femoral nerve block for postoperative analgesia in outpatient anterior cruciate ligament (ACL) reconstruction.Reg Anesth 23:$88, 1998 (abstr) 3. Hirst GC, Lang SA, Dust WN, et al: Femoral nerve block: Single injection versus continuous infusion for total knee arthroplasty. Reg Anesth 21:292-297, 1996 4. Mansour NY, Bennetts FE: An observational study of combined continuous lumbar plexus and single-shot sciatic nerve blocks for post-knee surgery analgesia. Reg Anesth 21:287-291, 1996 5. Capdevila X, Biboulet P, Bouregba M, et al: Comparison of the femoral three-in-one and fascia iliaca compartment blocks in adults: Clinical and radiographic analysis. Anesth Analg 86:1039-1044, 1998 6. Albert DB: Use of the nerve stimulator, in Altman RA, Bernstein RL, Broadman LM, et al. (eds): Regional Blocks: How To Do Them. 67th Congress of the International Anesthesia Research Society, San Diego, CA, 1993 7. Van der Wal M, Lang SA, Yip RW: The trans-sartorial approach to the saphenous nerve block. Can J Anaesth 40:542-546, 1993 17

8. Comfort VK, Lang SA, Yip RW: Saphenous nerve anaesthesia--A nerve stimulator technique. Can J Anaesth 43:852-857, 1996 9. Shannon J, Lang SA, Yip RW: Lateral femoral nerve block revisited: A nerve stimulator technique. Reg Anesth 20:100-104, 1995 10. Morris GF, Lang SA, Dust WN, Van der Wal M: The parasacral sciatic nerve block. Reg Anesth 22:223-228, 1997 11. Bruelle P, Cuvillon P, Ripart J, Eledjam MD: Sciatic nerve block: Parasacral approach. Reg Anesth 23:$78, 1998 12. Bridenbaugh PO: The lower extremity: Somatic blocade, in Cousins MJ, Bridenbaugh PO (eds): Neural Blockade in Clinical Anesthesia and Pain Management (ed 2). Philadelphia, PA, Lippincott Raven, 1988, pp 417-441 13. Lang SA, Yip RW, Chang PC, et al: The femoral 3-in-1 block revisited. J Clin Anesth 5:292-296, 1993 14, Morris GF, Lang SA: Continuous parasacral sciatic nerve block: Two case reports. Reg Anesth 22:469-472, 1997 15. Pither CE, Raj PP, Ford DJ: The use of peripheral nerve stimulators for regional anesthesia. A review of experimental characteristics, technique, and clinical applications. Reg Anesth 10:49-58, 1985 16. Hopkins PM, Ellis FR, Halsall PJ: Evaluation of local anesthetic blockade of the lateral femoral cutaneous nerve. Anesthesia 46:9596, 1991

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17. Rice ASC, McMahon SB: Peripheral nerve injury caused by injection needles used in regional anaesthesia: The influence of bevel configuration, studied in a rat model. Br J Anaesth 69:433-438, 1992 18. Rooney ME, Lang SA, Klassen L, et al: Intraoperative transcruciate injection: A new approach to postoperative analgesia following total knee arthroplasty. Reg Anesth 23:$34, 1998 (abstr) 19. Liu S, Carpenter RL, Neal JM: Epidural anesthesia and analgesia. Anesthesiology 82:1474-1506, 1995 20. MarchianoAE, Cwik J, Dontelli L, et al: Epidural versus femoral nerve sheath catheter for postoperative analgesia following total knee arthroplasty. Reg Anesth 21 :$10, 1996 (abstr) 21. Wiebalck A, Brodner G, Van Aken H: The effects of adding sufentanil to bupivacaine for postoperative patient-controlled epidural analgesia. Anesth Analg 85:124-129, 1997 22. Sandier AN, Katz J: Perioperative analgesia and patient satisfaction. Can J Anaesth 41:1-5, 1994 (editorial) 23. Egan KJ, Ready B: Patient satisfaction with intravenous PCA or epidural morphine. Can J Anaesth 41:6-11, 1994 24. Ohkawa S, VIoka J, Hadzic A, et al: Combination of femoral and popliteal nerve blocks in patients following total knee replacement: A study of analgesic efficacy. Reg Anesth 23:A43, 1998 (abstr)

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