Combined Popliteal and Saphenous Nerve Blocks at the Knee An Underused Alternative to General or Spinal Anesthesia for Foot and Ankle Surgery

Transcription

1 Combined Popliteal and Saphenous Nerve Blocks at the Knee An Underused Alternative to General or Spinal Anesthesia for Foot and Ankle Surgery Cornelius M. Donohue, DPM* Larry R. Goss, DPM Samuel Metz, MD Michael S. Weingarten, MD, MBA Larry B. Dyal, Jr., DPM, MS Peripheral blocks at the ankle have long been used for foot surgery. However, when local foot and ankle blocks are inappropriate or contraindicated, general and spinal anesthesia are the common alternatives. Both have disadvantages and require added equipment and monitors. Combined popliteal and saphenous blocks at the knee can offer a desirable alternative to general and spinal anesthesia for foot and ankle surgery. In addition, popliteal and saphenous blocks provide anesthesia of the entire lower leg, thus permitting a greater variety of procedures to be performed. This article reviews the anatomical considerations, various block techniques, and surgical applications of this useful approach to lower-leg anesthesia. (J Am Podiatr Med Assoc 94(4): , 2004) Regional blocks at the ankle produce sufficient anesthesia to permit most operative procedures on the foot. However, conditions such as anatomical disturbance from previous operations or infection at the operative site may render the application of ankle blocks difficult or inappropriate, respectively. Common alternatives to local foot and ankle blocks include general and spinal anesthesia. *Department of Podiatric Surgery, Hahnemann University Hospital, Philadelphia, PA. Surgical Residency Program, Tenet Parkview Hospital and Medical College of Pennsylvania Hospital, Philadelphia; Temple University School of Podiatric Medicine, Philadelphia, PA; private practice, Philadelphia Foot & Ankle, Philadelphia, PA. Department of Anesthesiology, Drexel University College of Medicine, Philadelphia, PA. Wound Healing Program, Medical College of Pennsylvania Hospital, Philadelphia. Tenet Parkview Hospital and Medical College of Pennsylvania Hospital, Philadelphia. Corresponding author: Cornelius M. Donohue, DPM, 748 Camp Woods Rd, Villanova, PA General and spinal anesthesia have substantial disadvantages. Skill in airway management, including anti-aspiration maneuvers and airway patency preservation, is required for general anesthesia. Spinal anesthesia demands meticulous sterile technique. Both types require specialized equipment, facilities, and monitors for hemodynamic and respiratory management during the anesthesia, and both increase the risk of postoperative complications, including nausea and vomiting, postdural puncture headache, and prolonged recovery. 1, 2 Incorporation of a combined popliteal fossa block and saphenous block at the knee has certain advantages over general and spinal anesthesia for foot and ankle surgery. This combined block provides an attractive alternative that avoids some of the disadvantages of general and spinal anesthesia. The combined block is performed with a clean, rather than a sterile, technique; requires similar equipment, drugs, and monitoring as an ankle block; and extends surgical anesthesia to include the entire distal lower 368 July/August 2004 Vol 94 No 4 Journal of the American Podiatric Medical Association

2 leg. 3-5 In addition, the combined block does not interfere with whole-body physiology and so can be used in high-risk patients who might not be ideal candidates for general anesthesia because of comorbidities. 4 Similar to local blocks at the ankle, the combined block at the knee spares the hamstring s, promotes immediate postoperative ambulation, provides unilateral anesthesia as necessary, is safe in anticoagulated patients, and can prolong the postoperative analgesia effect, and it has resulted in high patient satisfaction in several studies. 3, 5-8 Rorie et al, 9 in 1980, reported an 88.2% overall satisfaction rate in a study of 119 patients. Despite these advantages, the combined block at the knee remains underused in the United States. Reasons for its infrequent use may be related to lack of resident training, concerns over operating room efficiency, and an unpredictable success rate of the block Anatomical Considerations The sciatic courses down the posterior aspect of the thigh and enters the popliteal fossa deep to the adductors of the knee. Its position is slightly lateral to the midline, adjacent to the more medial popliteal vein and artery as they exit the adductor hiatus. 3 Formed from spinal roots L4-S2 and occasionally S3, the sciatic bifurcates at a variable distance above the popliteal fossa into the tibial and the common peroneal (Fig. 1). These s share a common epineural sheath from their division in the popliteal fossa. 13 Injection of local anesthetic into the sheath, a popliteal fossa block, constitutes a terminal block of the sciatic at the knee. 14 The tibial is the larger of the two sciatic branches, and it runs parallel and slightly lateral to the midline, between the femoral condyles, and into the deep posterior compartment of the leg. Inferiorly, it passes between the heads of the gastrocnemius. 14 The common peroneal follows the of the biceps femoris laterally and travels around the fibular head as it leaves the popliteal fossa and enters the anterior compartment of the leg. Both s innervate the entire leg below the knee, except for the anteromedial aspects of the leg and foot, which are innervated by the saphenous (L2-4). The saphenous, a terminal branch of the femoral, becomes subcutaneous as it arises from the adductor canal between the s of the sartorius and gracilis s at the anteromedial aspect of the knee. 15 A combined block at the knee requires blockade of two s at two sites: the terminal sciatic in the popliteal fossa and the saphenous on the medial aspect of the knee. Although popliteal and saphenous blocks may be performed with the patient supine and with the use of surface landmarks, success with the popliteal block can be improved with the patient prone and with the use of a peripheral stimulator. Onset of both blocks is typically rapid, with surgical anesthesia achieved within a few minutes. 16 As motor blockade is usually not essential, use of a diluted solution of local anesthetic allows administration of a greater volume without increasing toxicity risk. A larger volume of local anesthetic distributed over a larger area increases success at both sites. Including both blocks, we routinely combine 20 ml of 1% lidocaine hydrochloride with 20 ml of 0.5% bupivacaine hydrochloride to create 40 ml of 0.5% lidocaine hydrochloride and 0.25% bupivacaine hydrochloride without added vasoconstrictor. The total dose of lidocaine hydrochloride (200 mg) and bupivacaine hydrochloride (100 mg) is well below reported toxic doses in average-sized adults. 17 Additional solution can be reserved for supplemental injections if necessary. Patient discomfort with these blocks is usually minimal and can be decreased by appropriate preoperative discussion and intervention. Should the patient be unusually anxious, small doses of short-act- Semimembranosus Semitendinosus Tibial Medial Figure 1. Anatomical landmarks of the popliteal fossa. General Principles Sural Common peroneal Biceps femoris Lateral Journal of the American Podiatric Medical Association Vol 94 No 4 July/August

3 ing narcotics (eg, fentanyl citrate) or intravenous sedative hypnotics (eg, propofol) may be given provided appropriate monitors and resuscitation equipment are available. 18 Whereas the saphenous block involves only subcutaneous infiltration without precise localization of the needle, the popliteal block requires placement of the needle as close as possible to each of the two tributary s at the sciatic bifurcation. Imprecise placement of the needle may produce inadequate anesthesia. We recommend use of a peripheral stimulator to identify s in the popliteal fossa whenever available. This stimulator is an excellent teaching device, allows more accurate needle placement in obese and other patients with poor surface landmarks, may reduce the risk of damage, and maximizes success rates. 8, Popliteal Fossa Nerve Block Technique A popliteal fossa block may be performed with the patient either prone or supine. 22 In the prone position, either a classic or an intertendinous approach is commonly used based on anatomical surface landmarks Classic Approach Landmarks for the classic approach constitute a triangle in the posterior aspect of the knee. 26 The triangle is formed using the popliteal crease as the inferior border, the biceps femoris and as the lateral border, and the semimembranosus as the medial border. A line is drawn from the intersection of the medial and lateral borders inferiorly to meet the popliteal crease at a right angle. The needle insertion site is 1 cm lateral to this line and 5 cm above the popliteal crease (Fig. 2). Intertendinous Approach Recently, results with the popliteal fossa block have improved by using the semimembranosus and biceps femoris s as landmarks rather than their respective s. Hadzic and Vloka 18 contend that the boundaries of the popliteal triangle are often difficult to detect accurately; consequently, the classic approach frequently directs needle placement lateral to the sciatic. Subsequent medial redirection of the needle for sciatic contact may carry an increased risk of puncturing the popliteal vessels, especially when needles longer than 40 mm are used. Using magnetic resonance imaging, Vloka et al, 27 in 1997, reported 75% accuracy in contacting the sciatic compared with 25% accuracy using the classic approach. Furthermore, needles inserted using the classic approach are more prone to transect the body of the biceps femoris, resulting in increased pain during the procedure. 28 The intertendinous approach calls for needle insertion midway between the semimembranosus and biceps femoris s (rather than s) and 5 cm above the popliteal crease (Fig. 3). The needle is directed 45 to 60 cephalad to a depth of 3 to 5 cm (Fig. 4). To maximize the chances of success, we recommend use of a peripheral stimulator and the intertendinous approach. Intertendinous Popliteal Fossa Nerve Block Technique 1. With the patient prone, identify the landmarks as described in Intertendinous Approach. Attach a peripheral stimulator and set the output at 3.0 ma. 2. Advance the needle until plantarflexion of the foot occurs (or until paresthesia of the foot is reported if not using the stimulator). 3. Holding the needle still, decrease the output of the stimulator until it reaches 0.5 ma. Persistent plantarflexion confirms close proximity of the tibial. 4. Inject 1 ml of local anesthetic solution. Elimination of paresthesia or motor response further suggests close proximity to the. An alternative approach is to use 1 ml of plain lidocaine for the test block to increase the onset of anesthesia. 5. While intermittently aspirating for blood, follow with 9 ml of additional solution to a total of 10 ml of the lidocaine-bupivacaine mixture, as described in the General Principles section. 6. Without withdrawing the needle from skin, redirect the needle slightly laterally. 7. Eversion of the foot using a stimulator or paresthesia confirms proximity to the common peroneal. 8. Repeat the divided injection of 1 ml and add an additional 9 ml while intermittently aspirating for blood. Supine (Lateral) Position The prone position may be contraindicated in conditions such as advanced pregnancy, morbid obesity, spinal and hemodynamic instability, and mechanical ventilation. 29 However, difficulty in positioning patients prone for the popliteal fossa block often precludes its use in patients who are potentially the 370 July/August 2004 Vol 94 No 4 Journal of the American Podiatric Medical Association

4 Semitendinosus Popliteal artery and vein 5 6 cm Popliteal skin crease Semimembranosus Biceps femoris Common peroneal Tibial A Peripheral stimulator B Medial Gastrocnemius Lateral Figure 2. A, Needle insertion with a peripheral stimulator for the classic approach to the popliteal fossa block. B, Clinical landmarks demonstrating the classic approach to the popliteal fossa block. greatest beneficiaries. 22 In these circumstances, the lateral approach to the popliteal s, with the patient supine, is an alternative technique, although it may require more attempts at localization. 28 In 1988, Hadzic and Vloka 26 compared a lateral approach with the classic posterior approach and found no significant differences in anesthesia results. Supine (Lateral) Popliteal Technique 1. With the patient supine, identify the biceps femoris and the popliteal crease. 2. Insert the needle along the anterior border of the biceps femoris and 5 cm proximal to the popliteal crease in a slightly cephalad direction. A B Semimembranosus Popliteal artery and vein Popliteal fascia Semitendinosus X i X c Tibial Common peroneal Sciatic Biceps femoris Femur Medial Lateral Figure 3. A, Intertendinous approach on the left leg and classic approach on the right leg. Note the more lateral position of the injection point with the classic approach (X c ) and the more midline position with the intertendinous approach (X i ). There is increased risk of neurovascular and damage with the classic approach, including laceration of the biceps femoris. The anatomical bisection of the popliteal fossa (abpf) is represented by the dashed lines. Bft, biceps femoris ; smt, semimembranosus ; smm, semimembranosus ; bfm, biceps femoris. B, Transverse plane of popliteal level showing the differences in tissue contact between the intertendinous approach (X i ) and the classic approach (X c ). Note the risk of biceps femoris laceration with the classic approach. Journal of the American Podiatric Medical Association Vol 94 No 4 July/August

5 Tibial Angle of injection 60 Figure 4. Sagittal plane view of popliteal fossa block showing 60 angle of needle to the popliteal (tibial and common peroneal). Sartorius Gracilis Saphenous 3. The needle will usually encounter the common peroneal first, identified by paresthesia or a foot eversion motor response. 4. Decrease the stimulator output as described in Intertendinous Popliteal Fossa Nerve Block Technique to confirm proximity. 5. Repeat the sequence of divided injection of solution described in Intertendinous Popliteal Fossa Nerve Block Technique to a total of 10 ml while intermittently aspirating for blood. 6. Continue inserting the needle until tibial paresthesia or a plantarflexion motor response is elicited. 7. Repeat the sequence of divided injection of solution to a total of 10 ml. Saphenous Nerve Block Technique Regardless of the technique or the position used for popliteal fossa block, the saphenous must be anesthetized. This is usually performed with the patient supine. 15, 30 At the knee, the saphenous is relatively superficial. 1. Identify the tuberosity of the tibia and the intersection of the anterior and medial borders of the gastrocnemius (Fig. 5). 2. Draw a line from the tuberosity distal and medial at a 45 angle to the intersection. 3. Infiltrate 10 ml of local anesthetic along the length of this line into the subcutaneous tissues while intermittently aspirating for blood. Complications As with any local anesthetic technique, the combined block has risks. All blocks have the potential for toxic or allergic reactions to the local anesthetic agent. Attention to the patient s history of drug reactions, limitation of the total dose of local anesthetic, and consideration of vasoconstrictors in the Figure 5. Saphenous block technique. anesthetic solution decrease but do not eliminate these risks. Therefore, clinicians must be able to recognize and treat these reactions. Because the injection site for popliteal block brings the needle close to the popliteal artery and vein, there is the additional risk of vascular damage. 31 Also, the proximity of blood vessels to the injection site increases the risk of intravascular injection, hematoma, and toxic reactions. Using small needles, carefully moving the needle during injection, and intermittently aspirating for blood reduces these risks. All blocks risk mechanical damage to the by the injecting needle, resulting in transient or permanent deficits. 32, 33 Again, use of small needles and cautious manipulation of the needle during injection reduces this risk. Similar to local blocks at the ankle, the combined block at the knee can be performed with a clean, rather than a sterile, technique with little risk of infection. 17 Generally, the combined block is performed with only alcohol swabbing at the injection site. However, clinicians who want further reduction of infection risk may use a sterile technique. Discussion The combined block at the knee offers significant advantages over spinal and general anesthesia when a foot or ankle block is not possible. The combined block at the knee requires no more equipment than an ankle block and adds little or no risk. Because of the positioning and technique challenges of the combined block, appropriate resident training 372 July/August 2004 Vol 94 No 4 Journal of the American Podiatric Medical Association

6 and planning are indicated to make this block more economically and surgically attractive. We recommend use of a peripheral stimulator for all popliteal blocks. It is an excellent training aid, assisting clinicians in estimating where the popliteal s lie and reinforcing proper block technique. With appropriate training, the stimulator increases the chances of success even for experienced clinicians. 20 In addition, the stimulator can produce motor activity in patients with diminished or absent paresthesia from diabetic or other peripheral neuropathies or central nervous system disease. Compared with the equipment needed for general or spinal anesthesia, stimulators are inexpensive, portable, reusable, easy to maintain, and easy to use. Our experience with the combined block at the knee using a stimulator suggests that this block can be easily integrated into even the busiest operating room suites. As motor neuropathy and significant atrophy may eliminate any visible motor activity even with use of a stimulator, we encourage more empirical research to determine reliable techniques using surface landmarks only for unassisted popliteal block. Combined block at the knee offers significant advantages over ankle block. It offers an alternative to injection into an ankle that may be edematous, infected, or ulcerated. The combined technique provides surgical anesthesia not only for incision and drainage and debridement, but also for reconstruction of the foot, ankle, and leg threatened by trauma, infection, ischemia, arthritis, primary ulcerative disease, neoplasia, neuropathy, and congenital and neuromuscular deformity. 2, 3, 8, 17, 34 In addition, this technique can be used to provide anesthesia for application of external fixators to the foot and leg for procedures involving reconstruction of the diabetic Charcot foot and ankle with or without additional components of foot and ankle internal fixation such as screws, plates, and staples. 7 Postoperative pain management is an inherent benefit of this technique, particularly when long-acting anesthetic agents are used. 35 The value of prolonged analgesia in the chronically ill postoperative patient in preventing complications is obvious, particularly in patients with hypertension, diabetes mellitus, and cardiac disease. 5, 6 The relative ease of applying the combined block at the knee makes it especially attractive in developing regions of the world. In many rural, medically underserved areas around the world, early intervention in lower-extremity wounds caused by infection, trauma, ischemia, neuropathy, and primary ulcerative disease can mean the difference between reconstruction and restored function and the alternative of amputation or even death from sepsis. Where general and spinal anesthesia are not available, combined block at the knee could be used routinely as the preferred technique for anesthesia of the foot and lower leg in modestly equipped medical facilities with limited resources. In our experience with more than 60 cases during the past 3 years, no patient required conversion to general anesthesia because of failed block. The technique is a viable and valuable alternative to general and spinal anesthesia when ankle blocks are not possible. We advocate incorporating resident teaching of this combined block into anesthesia, podiatric, orthopedic, plastic, vascular, and general surgery training programs and consideration of the combined block as a primary anesthetic technique in cases in which general or spinal anesthesia is contraindicated. Conclusion We advocate increased use of the combined block at the knee, particularly in chronically ill patients who might not be ideal candidates for general or spinal anesthesia because of comorbidities. This block technique is a valuable alternative to general and spinal anesthesia for surgical procedures below the knee. Techniques with and without the assistance of a peripheral stimulator can be employed. Its many benefits include good postoperative pain management. During the past 3 years, we have had good results in more than 60 cases using this form of anesthesia, with minimal adverse effects. More resident training initiatives in hospital settings are needed. References 1. BROWN DL: Popliteal Block, in Atlas of Regional Anesthesia, ed by DL Brown, p 109, WB Saunders, Philadelphia, BESKIN JL, BAXTER DE: Regional anesthesia for ambulatory foot and ankle surgery. Orthopedics 10: 109, HANSEN E, ESHELMAN MR, CRACCHIOLO A III: Popliteal fossa neural blockade as the sole anesthetic technique for outpatient foot and ankle surgery. Foot Ankle 21: 39, PROVENZANO DA, VISCUSI ER, ADAMS SB JR, ET AL: The safety and efficacy of the popliteal fossa block for foot and ankle surgery. Paper presented at the American Orthopaedic Foot and Ankle Society 31st Annual Meeting, March 2001, San Francisco. 5. RONGSTAD KM, MANN RA, PRIESKORN D, ET AL: Popliteal sciatic block for postoperative analgesia. Foot Journal of the American Podiatric Medical Association Vol 94 No 4 July/August

7 Ankle 17: 378, MCLEOD DH, WONG DH, CLARIDGE RJ, ET AL: Lateral popliteal sciatic block compared with subcutaneous infiltration for analgesia following foot surgery. Can J Anaesth 41: 673, MYERSON MS, RULAND CM, ALLON SM: Regional anesthesia for foot and ankle surgery. Foot Ankle 13: 284, NUSBAUM LM, HAMELBERG W: Intravenous regional anesthesia for surgery on the foot and ankle. Anesthesiology 64: 91, RORIE DK, BYER DE, NELSON DO, ET AL: Assessment of block of the sciatic in the popliteal fossa. Anesth Analg 59: 371, HADZIC A, VLOKA JD, KURODA MM, ET AL: The practice of peripheral blocks in the United States: a national survey. Reg Anesth Pain Med 23: 241, HADZIC A, VLOKA JD, KURODA MM, ET AL: The use of peripheral blockade in anesthesia practice: a national survey. Anesth Analg 84: 300, KOPACZ DJ, BRIDENBAUGH LD: Are anesthesia residency programs failing regional anesthesia? the past, present, and future. Reg Anesth 18: 84, VLOKA JD, HADZIC A, LESSER JB, ET AL: A common epineural sheath for the s in the popliteal fossa and its possible implications for sciatic block. Anesth Analg 84: 387, SUNDERLAND S: The Sciatic Nerve and Its Tibial and Common Peroneal Divisions: Anatomical Features, in Nerves and Nerve Injuries, p 95, E & S Livingstone, Edinburgh, VAN DER WAL M, LANG SA, YIP RW: Transsartorial approach for saphenous block. Can J Anaesth 40: 543, BENZON HT, KIM C, BENZON HP, ET AL: Correlation between evoked motor response of the sciatic and sensory blockade. Anesthesiology 87: 547, LEE TH, WAPNER KL, HECHT PJ, ET AL: Regional anesthesia in foot and ankle surgery. Orthopedics 19: 578, HADZIC A, VLOKA JD: Peripheral stimulator for unassisted blockade. Anesthesiology 84: 1528, GOUVERNEUR JM: Sciatic block in the popliteal fossa with atraumatic needles and stimulation. Acta Anaesthesiol Belg 4: 391, SINGELYN FJ, GOUVERNEUR JM, GRIBOMONT BF: Popliteal sciatic block aided by a stimulator: a reliable technique for foot and ankle surgery. Reg Anesth 16: 278, SMITH BE, ALLISON A: The use of a low-power stimulator during sciatic block. Anaesthesia 42: 296, VLOKA JD, HADZIC A, KOORN R, ET AL: Supine approach to the sciatic in the popliteal fossa. Can J Anaesth 43: 964, BECK GP: Anterior approach to sciatic block. Anesthesiology 24: 222, KILPATRICK AA, COVENTY DM, TODD JG: A comparison of two approaches to sciatic block. Anaesthesia 47: 155, SINGELYN FJ, AYE F, GOVERNEUR JM: Continuous popliteal sciatic block: an original technique to provide postoperative analgesia after foot surgery. Anesth Analg 84: 384, HADZIC A, VLOKA JD: A comparison of the posterior versus lateral approaches to the block of the sciatic in the popliteal fossa. Anesthesiology 88: 1480, VLOKA JD, HADZIC A, SINGSON R, ET AL: The popliteal block revisited: results of an MRI study. Anesth Analg 84: 344, ZETLAOUI PJ, BOUAZIZ H: Lateral approach to the sciatic in the popliteal fossa. Anesth Anal 87: 79, VLOKA JD, HADZIC A, KITAIN E, ET AL: Anatomic considerations for sciatic block in the popliteal fossa through the lateral approach. Reg Anesth 21: 414, BOUAZIZ H, BENHAMOU D, NARCHI P: A new approach for saphenous block. Reg Anesth 21: 490, SELANDER D: Paresthesias or no paresthesias? complications after neural blockades. Acta Anaesthesiol Belg 39: 173, SELANDER D, DHUNER KG, LUNDBORG G: Peripheral injury due to injection needles used for regional anesthesia: an experimental study of the acute effects of needle point trauma. Acta Anaesthesiol Scand 21: 182, BONNER SM, PRIDIE AK: Sciatic palsy following uneventful sciatic block. Anaesthesia 52: 1205, SARRAFIAN SK, IBRAHIM IN, BREIHAN JH: Ankle-foot peripheral block for mid and forefoot surgery. Foot Ankle 4: 87, MCLEOD DH, WONG DH, VAGHADIA H, ET AL: Lateral popliteal sciatic block compared with ankle block for analgesia following foot surgery. Can J Anaesth 42: 765, July/August 2004 Vol 94 No 4 Journal of the American Podiatric Medical Association