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Nerve injury following popliteal nerve and adductor canal blocks: A case series

Open AccessPublished:August 05, 2022DOI:https://doi.org/10.1016/j.fastrc.2022.100231

      Abstract

      Popliteal nerve blocks are a common form of operative and postoperative regional analgesia for procedures involving the knee, ankle, and foot. This widely used analgesic technique comes with possible neuropathic complications, which remain unknown. In this paper, we review 7 consecutive patients that presented with popliteal/saphenous nerve block complications after foot and ankle surgery. One of the patients developed foot drop, requiring an AFO followed by tendoachilles lengthening and posterior ankle capsular release. The remaining patients reported dysesthesia and painful symptoms. Only 2 out of the 7 patients resulted in symptoms that resolved at the time of publication. The authors hope to provide insight into the potential risks and complications associated with this form of regional anesthesia. It is essential for surgeons to inform patients of the potential risks and propose alternative methods for postoperative pain management as deemed necessary. Further prospective studies are necessary to determine the impact of multiple factors, including ultrasound-guidance versus nerve stimulation, repetitive ipsilateral nerve blocks, adjunct adductor canal blocks, and tourniquet use.

      Keywords

      Abbreviations:

      EMG (electromyography), NCV (nerve conduction velocity), US (ultrasound)

      Introduction

      Popliteal fossa nerve blocks are a common form of operative and post-operative regional analgesia for surgical procedures involving the knee, ankle and foot. This procedure was first performed by Gaston Labat in 1922 as a form of regional anesthesia at the level of the knee.
      • Côté A.V.
      • Vachon C.A.
      • Horlocker T.T.
      • Bacon D.R.
      From Victor pauchet to gaston labat: the transformation of regional anesthesia from a surgeon's practice to the physician anesthesiologist.
      Widespread use of popliteal fossa nerve blocks is increasing, and it is currently a well-established method of regional anesthesia in foot and ankle surgery.
      • Hansen E.
      • Eshelman M.R.
      • Cracchiolo A.
      Popliteal fossa neural blockade as the sole anesthetic technique for outpatient foot and ankle surgery.
      ,
      • Rongstad K.
      • Mann R.A.
      • Prieskorn D.
      • Nichelson S.
      • Horton G.
      Popliteal sciatic nerve block for postoperative analgesia.
      This procedure involves infiltration of a local anesthetic around the sciatic nerve and subsequent branches (tibial nerve and common peroneal or fibular nerve) depending on anatomic variation. Popliteal nerve blocks are typically performed under ultrasound (US) guidance, either with or without a nerve stimulator. Current studies show increased success rates of popliteal nerve blocks when a combination of US guidance and nerve stimulation is utilized.
      • Dufour E.
      • Quennesson P.
      • Van Robais A.L.
      • et al.
      Combined ultrasound and neurostimulation guidance for popliteal sciatic nerve block: a prospective, randomized comparison with neurostimulation alone.
      The goal of the popliteal block is to provide complete analgesia below the knee in the distribution of the sciatic nerve, both intra-operatively and post-operatively.
      • Hansen E.
      • Eshelman M.R.
      • Cracchiolo A.
      Popliteal fossa neural blockade as the sole anesthetic technique for outpatient foot and ankle surgery.
      ,
      • Anderson J.G.
      • Bohay D.R.
      • Maskill J.D.
      • et al.
      Complications after popliteal block for foot and ankle surgery.
      The reported rate of neurological injury after administration of popliteal blocks ranges from 0% to 10%.
      • Provenzano D.A.
      • Viscusi E.R.
      • Adams S.B.
      • et al.
      Safety and efficacy of the popliteal fossa nerve block when utilized for foot and ankle surgery.
      ,
      • Lauf J.A.
      • Huggins P.
      • Long J.
      • et al.
      Regional nerve block complication analysis following peripheral nerve block during foot and ankle surgical procedures.
      The majority of neurological injuries related to peripheral nerve blocks are described as prolonged paresthesia distal to the knee or infiltration site.
      • Anderson J.G.
      • Bohay D.R.
      • Maskill J.D.
      • et al.
      Complications after popliteal block for foot and ankle surgery.
      The exact mechanism of neurologic injury following popliteal blocks is often unclear. Nerves can be injured by three main mechanisms: mechanical injury, chemical injury, and/or ischemic injury. Residual nerve damage may be related to prolonged action potentials at the cellular level, or mechanical injury to the nerve from needle trauma or pressure created by the fluid bolus. It is thought that this mechanism may also induce ischemic injury to the nerve when capillary perfusion is mechanically compromised. Some studies show that nerve trauma may not result in direct nerve damage, but rather a neurotoxicity component resulting from intrafascicular placement of local anesthetic during the injection.
      • Anderson J.G.
      • Bohay D.R.
      • Maskill J.D.
      • et al.
      Complications after popliteal block for foot and ankle surgery.
      ,
      • Weyker P.D.
      • Webb C.A.
      • Pham T.M.
      Workup and management of persistent neuralgia following nerve block.
      ,
      • Hogan Q.H.
      Pathophysiology of peripheral nerve injury during regional anesthesia.
      Spontaneous resolution of symptoms will often occur within 6 weeks after injury. The timeline of recovery is likely related to patient comorbidities, and extent of neurologic injury. Nonetheless, early recognition is important because some cases may be associated with prolonged or permanent disability.
      • Borgeat A.
      • Ekatodramis G.
      • Kalberer F.
      • Benz C.
      Acute and nonacute complications associated with interscalene block and shoulder surgery: a prospective study.
      Currently, there is limited long-term data regarding post-procedure complications of popliteal nerve blocks. The purpose of this article is to provide insight into the possible side effects of this widely used and highly applicable procedure for lower extremity/ foot and ankle surgery. We present a series of cases that have suffered nerve injury following pre-operative popliteal nerve blocks with or without saphenous nerve blocks.

      Case series

      We present 7 consecutive patients with reported postoperative complications related to pre-operative popliteal/saphenous nerve blocks from December 2018 to September 2020. These patients were retrospectively reviewed by two foot and ankle surgeons (A.B., D.L.). There were six females and one male with a mean age of 48 years and a mean follow-up of 24 months. There were 4 left lower extremities and 3 right lower extremities. General anesthesia was employed for all surgeries. 4/7 patients received popliteal and saphenous nerve blocks, while the remainder underwent a single nerve block (popliteal). 1 patient with a history of prior ipsilateral nerve block developed drop foot. All included patients reported nerve paresthesia. 2/7 patients reported complete resolution, while 5/7 demonstrated lack of resolution at the time of this publication. All patients underwent US-guided injections, and two patients underwent nerve stimulation in addition to US guidance.

      Results

      Case 1

      A 56-year-old female with type II diabetes mellitus, hyperlipidemia, gastric reflux, skin cancer, prior hysterectomy, and history of sciatica underwent left foot second and third tarsometatarsal joint fusions with harvesting of calcaneal bone graft. A popliteal nerve block was administered using 30cc of 0.5% Ropivacaine. The nerve was localized under US guidance and nerve stimulation (<1.0mA and >0.5 mA). No complications were reported. A pneumatic tourniquet was applied at the thigh and inflated to 300 mmHg.
      At the first postoperative appointment, the patient reported persistent, global numbness and tingling of the operative foot with increased postoperative edema and muscle paralysis. The patient became hypersensitive to touch over the medial dorsal cutaneous nerve distribution with diminished sensation throughout the foot in a non-dermatomal distribution. She was prescribed 300 milligrams of Gabapentin every night at bedtime, which was increased to 600 mg, with compression therapy. Over the next month, the patient reported worsening pain with knee extension that resolved with knee flexion, radiating from the distal thigh into the leg and foot with persistent global paresthesia. By late January, the symptoms seemed to slightly improve, and the Gabapentin seemed to alleviate some of the pain. On exam, the patient exhibited 5/5 left ankle dorsiflexion with reduced toe strength and weak hindfoot eversion. There was no sensory loss at her left foot via Semmes-Weinstein monofilament testing. Reflexes were symmetric in the lower extremities (2/4) with allodynia at the left foot below the ankle in a non-dermatomal pattern.
      Motor conduction testing demonstrated abnormal results in all tested nerves. The left peroneal nerve revealed a reduced amplitude and slowed nerve conduction velocity between the ankle and fibular head segment. The superficial peroneal nerve revealed reduced peak amplitude and the tibial nerve showed reduced conduction velocity between the ankle and popliteal fossa segment. The sensory conduction testing demonstrated absent responses of the left sural nerve, medial plantar nerve and superficial peroneal nerve. Electromyography (EMG) demonstrated abnormal spontaneous activity in the left tibialis anterior, gastrocnemius, extensor digitorum brevis, adductor hallucis, and L5 paraspinal. These findings were consistent with proximal neurogenic injury to the left L5-S1 nerve distributions. MRI of the lumbar spine demonstrated multilevel degenerative disc disease.
      Reflex sympathetic dystrophy was included in the differential diagnosis however it was less likely due to focal medial nerve dysesthesias. Ultrasound demonstrated that all nerve structures appeared unremarkable throughout their course. There were no signs of enlargement at the popliteal fossa or fibular head. The superficial peroneal nerve, tibial nerve and sural nerve appeared intact with normal muscle echotexture. Repeat nerve conduction velocity (NCV) and EMG testing was performed about one year later, which revealed sciatic nerve injury with improvement from the previous study. There was no severe neuropathy related to diabetes mellitus. Multiple low left-sided responses correlated with sciatic injury. Previously, the tibialis anterior and gastrocnemius showed nerve injury but, at the time of this exam, the abnormalities were limited only to distal areas in the foot, suggesting partial recovery of the neuropathy. She continued to exhibit pain and decreased sensation over the medial aspect of foot, great toe and posteromedial ankle. Patient had persistent subjective numbness in all nerve distributions except the saphenous nerve at twenty four months after onset.

      Case 2

      A 42-year-old female with no significant past medical history underwent a left Achilles tendon detachment/reattachment with calcaneal exostectomy. A popliteal and saphenous nerve block was administered with 50cc of a 1:1 mixture of 0.5% Ropivacaine and 0.5% Bupivacaine, and 10cc of the aforementioned mixture used for the adductor canal block. The nerve was localized under US guidance and nerve stimulation (<1.0 mA and >0.5 mA). No complications were noted. A pneumatic tourniquet was applied at the thigh and inflated at 300 mmHg.
      Approximately one year later, she underwent a revisional insertional Achilles tendon repair with debridement, calcaneal resection, and a flexor hallucis longus tendon transfer with another provider. Patient underwent a second popliteal nerve block. The nerve was localized using ultrasound guidance and nerve stimulation (<1.0 mA and >0.5 mA). No complications noted. Patient had sustained an incidental fall within one week postoperatively without any notable complications.
      At 10–12 weeks postoperatively, the patient noted sensory disturbances with burning and numbness across the plantar and dorsal aspect of the foot. Patient demonstrated foot drop, notably an Achilles contracture with weakness of the anterior and lateral leg muscle groups. There was decreased sensation along the deep peroneal nerve, saphenous nerve and superficial peroneal nerve distributions. The motor deficiency was appreciated when the patient was instructed to ambulate in tennis shoes. This might explain the delayed diagnosis of sensory disturbance and motor dysfunction.
      Based on EMG studies, there was evidence of peripheral neuropathic injury to the left tibial and peroneal nerves. Based on NCV exam findings, there was injury to the peroneal and tibial innervated muscles below the knee indicative of an injury most likely prior to their branching of the sciatic. For the motor conduction test, results were abnormal for the left peroneal nerve where the peak amplitude was reduced. Based on the sensory conduction test, the left superficial peroneal response was considered absent. There was abnormal spontaneous/insertional activity in the left extensor digitorum brevis, tibialis anterior, gastrocnemius (medial head), and peroneus longus and biceps femoris (short head). The left extensor digitorum brevis demonstrated motor unit actional potential abnormalities and decreased recruitment.
      The patient was placed in a non-articulating ankle foot orthosis and instructed to utilize a night splint and continue with physical therapy. A magnetic resonance imaging exam failed to demonstrate any lesion that could be surgically decompressed around the nerve, but did reveal a peroneal brevis tendon tear, which was symptomatic. Patient then proceeded with a third surgery, which included a left Achilles tendon lengthening, left posterior ankle capsular release, and peroneus brevis tendon repair to surgically address the posterior ankle contracture and painful peroneal tendon tear. Patient was able to develop functional ankle motion, however she persisted to have mild eversion weakness with residual numbness in the deep peroneal nerve and superficial peroneal nerve distributions at twenty-six months post-operatively.

      Case 3

      A 38-year-old female with no past medical history underwent left ankle arthroscopy with debridement, lateral ankle stabilization, and peroneus brevis tendon repair. A popliteal nerve block was administered with 50cc of a 1:1 mixture of 0.5% Ropivacaine and 0.5% Bupivacaine. 10cc of the aforementioned mixture was used for the adductor canal block. The nerve was localized under US guidance. No complications were reported. A pneumatic thigh tourniquet was applied and inflated at 300 mmHg. Approximately two weeks later, the patient presented with subjective sensory disturbances. Sensation was grossly intact to light touch in the SPN, DPN, sural, and saphenous distributions. Sensation was diminished in the tibial nerve distribution along the entire plantar aspect of the foot, including the medial and lateral plantar nerve distributions. This is likely secondary to the regional nerve block and not procedure-related, considering the nerves at risk with the procedures performed as mentioned above. Popliteal nerve blocks can cause paresthesia, paralysis and chronic pain. In this case, there is no obvious culprit for the paresthesia and, a result, we ruled in the popliteal nerve block as the etiology for the complication. Perhaps the block affected the sensory fibers within the tibial nerve that are responsible for the sensory function of the tibial nerve distribution. Motor nerve function was intact with inversion, eversion, dorsiflexion and plantarflexion. After seven months, her symptoms improved significantly and she returned to previous activity level.

      Case 4

      A 35-year-old male with a past medical history significant for Crohn's disease and Asthma underwent left ankle syndesmosis open reduction internal fixation. The popliteal nerve block was administered using 25cc of 0.5% Ropivacaine. The saphenous nerve block was administered using 10cc of 0.5% Ropivacaine. The nerve was localized under ultrasound guidance. No complications were reported. A pneumatic tourniquet was applied at the thigh at 300 mmHg. One week postoperatively, the patient reported numbness and tingling throughout the foot, including the entire plantar foot, all five digits, and the anterior aspect of the leg. The patient presented with global dysesthesias and hypersensitivity noted with light touch over the saphenous, sural, deep peroneal and tibial nerve distributions. In addition, the patient demonstrated dysesthesias over the proximal anterior leg approximately 10cm distal to the tibial tubercle. Patient was prescribed Gabapentin and physical therapy. Patient was briefly lost to follow up and returned with improvement in sensory disturbances at thirty months follow up.

      Case 5

      A 31-year-old male with past medical history significant for asthma, hyperlipidemia, gastroparesis, anxiety, depression, obesity, migraines and degenerative disc disease underwent right ankle arthroscopy with extensive debridement, peroneal brevis repair, os trigonum excision lateral ankle stabilization, and a plantar fasciotomy. A popliteal nerve block was administered using 30cc of 0.5% Ropivacaine. The nerve was localized under US guidance. No complications were reported. A pneumatic tourniquet was applied at the thigh and inflated at 300 mmHg. A few months following the surgery, the patient reported dysesthesias and pain of the lateral foot and ankle with worsening edema. Patient demonstrated persistent Tinel sign at the common peroneal, sural and intermediate dorsal cutaneous nerve regions at the right lateral ankle. Patient was prescribed 75 mg QD Lyrica. Needle EMG examination revealed fibrillation potentials, polyphasic motor units and motor unit loss in several of the peroneal nerve innervated muscles. Decreased right peroneal nerve compound muscle action potential was noted compared to the contralateral side. These findings revealed right peroneal neuropathy likely secondary to the popliteal nerve block. The patient had not fully recovered clinically at eighteen months follow up.

      Case 6

      A 36-year-old female with past medical history significant for asthma, anxiety, depression and pancreatic cancer underwent a right foot distal first metatarsal osteotomy with tibial sesamoid excision for hallux valgus deformity with tibial sesamoiditis. The popliteal nerve block was administered under US-guidance using 25cc of a 1:1 mixture of 0.5% Ropivacaine and 0.25% Bupivacaine plain. No complications were reported. A calf tourniquet was applied and inflated to 250 mmHg. Patient presents at the first postoperative visit with a chief complaint of pain, numbness and tingling of the operative extremity. There was no motor impairment noted. Patient was prescribed 75 mg QD Lyrica. This patient demonstrated abnormal nerve studies with evidence of tibial neurapraxia at the level of the medial malleolus. There was evidence of mild denervation in the right extensor digitorum brevis muscle, which in isolation likely represents local injury since the peroneal motor nerve responses were normal. There was no electrophysiologic evidence of a large fiber neuropathy, myopathy or radiculopathy in the segments studied. The right tibial distal latency was prolonged, the compound muscle action potential amplitudes were mildly decreased, and the conduction velocity was normal. All other conduction studies were normal. EMG studies demonstrated mild abnormal spontaneous activity within the right extensor digitorum brevis muscle, where there was also an increased number of large and polyphasic motor unit action potentials and decreased motor unit recruitment. All other muscle studies appeared normal. At twenty months follow up, the patient continued to exhibit symptoms of numbness and tingling

      Case 7

      A 64-year-old female with past medical history significant for degenerative arthritis underwent a right lateral calcaneal displacement osteotomy, lateral ankle stabilization and peroneal brevis tendon repair. An US-guided popliteal nerve block was employed using 35cc of 0.5% Bupivacaine. An US-guided saphenous nerve block was performed using 10cc of 0.5% Bupivacaine. No complications were reported. A thigh tourniquet was applied and inflated to 300 mmHg. At the first postoperative visit, the patient presented with numbness and painful paresthesia in the right medial leg, in the distribution of the saphenous nerve without restricted range of motion. The saphenous sensory nerve action potentials could not be reliably obtained on the symptomatic or asymptomatic side, which is relatively non-diagnostic due to the frequent technical challenge of recording those small responses. EMG/NCV studies of the right lower extremity were otherwise relatively unremarkable. There remained a concern for neuropathy of the right saphenous nerve due to sensory disturbance. Ultrasound imaging revealed a focal enlargement of the saphenous nerve (greater than 15mm^2) roughly 8-10cm proximal to the superior pole of the patella near the area of discomfort. The contralateral, asymptomatic side measured 5mm^2. These findings were consistent with focal neuropathy of the saphenous nerve at the distal thigh secondary to the nerve block. Patient was placed on Gabapentin 300 milligrams every night at bedtime. Patient continued to experience sensory disturbances at thirty six months post-operatively.

      Discussion

      Popliteal nerve blocks are a common form of operative and postoperative analgesia for procedures involving the knee, ankle, and foot. Popliteal and adductor canal nerve blocks are beneficial and widely used to reduce postoperative pain, decrease narcotic use, and decrease time to discharge from the surgery center or hospital facility. Potential risks associated with the procedure include paresthesia, paralysis and chronic pain. We present seven patients that experienced postoperative complications following the popliteal/saphenous nerve block.
      The senior author (DL) has personally undergone two popliteal blocks and three interscalene blocks, and in none of those five blocks were these risks discussed with him. At most institutions, the risks of regional blocks are encompassed within the anesthesia consent form. However, we are concerned as to whether patients receiving regional blocks are undergoing proper informed consent. Is the patient given a proper informed consent regarding regional anesthesia by their podiatric or orthopedic surgeon? Is the patient undergoing a proper informed consent with the anesthesiologist? This concern is heightened by the fact that when the senior author DL discusses these risks with patients prior to surgery, most patients decline the block. However, more regional blocks are being performed today with surgery than ever before. Because of the documented risks described in this study, the authors recommend thoroughly educating patients about the possibility of both lower extremity sensory and motor complications as a result of popliteal blocks. These sensory complications include but are not limited to dysesthesias, paresthesias, hypersensitivity and residual numbness. Motor complications including lower extremity weakness and foot drop are less common, but may lead to functional impairment, if functionality is unable to be regained. The authors feel it is the obligation of both the surgeon and physician performing the nerve block to formally educate the patient on the possibility of both transient and permanent nerve complications, and ultimately let the patient decide if they wish to proceed with a popliteal block or pursue a more localized form of regional anesthesia.
      Past literature reports minimal risk and low complication rates of peripheral nerve blocks in studies with large sample sizes.
      • Borgeat A.
      • Ekatodramis G.
      • Kalberer F.
      • Benz C.
      Acute and nonacute complications associated with interscalene block and shoulder surgery: a prospective study.
      ,
      • Lollo L.
      • Bhananker S.
      • Stogicza A.
      Postoperative sciatic and femoral or saphenous nerve blockade for lower extremity surgery in anesthetized adults.
      Provenzano et al. did not report any complications affiliated with peripheral nerve blocks in a group of 467 patients that underwent foot and ankle surgery.
      • Provenzano D.A.
      • Viscusi E.R.
      • Adams S.B.
      • et al.
      Safety and efficacy of the popliteal fossa nerve block when utilized for foot and ankle surgery.
      Similarly, Lolo et al. did not report any major nerve injury or deficit after the administration of 357 nerve blocks in the lower extremity.
      • Lollo L.
      • Bhananker S.
      • Stogicza A.
      Postoperative sciatic and femoral or saphenous nerve blockade for lower extremity surgery in anesthetized adults.
      Meanwhile, Anderson et al. reported a cohort of 1014 patients where 52 patients (5%) had neuropathic symptoms postoperatively likely related to popliteal block, excluding patients with complex regional pain syndrome and neurologic-symptoms related to procedure.
      • Anderson J.G.
      • Bohay D.R.
      • Maskill J.D.
      • et al.
      Complications after popliteal block for foot and ankle surgery.
      Lauf et al. discovered a short-term complication rate of 10.1% and the long-term complication rate of 4.3%, with a total of 855 blocks given.
      • Lauf J.A.
      • Huggins P.
      • Long J.
      • et al.
      Regional nerve block complication analysis following peripheral nerve block during foot and ankle surgical procedures.
      One study shows the reported rate of neurological injury after administration of peripheral nerve blocks is 3%.
      • Brull R.
      • McCartney C.J.
      • Chan V.W.
      • El-Beheiry H.
      Neurological complications after regional anesthesia: contemporary estimates of risk.
      The majority of neurological injuries resolve within 4-6 weeks.
      • Borgeat A.
      • Blumenthal S.
      • Lambert M.
      • Theodorou P.
      • Vienne P.
      The feasibility and complications of the continuous popliteal nerve block: a 1001-case survey.
      Based on our group of patients, we observed a longer recovery period with symptoms lasting beyond 6 weeks. 5/7 patients in this study did not fully recover and continue to experience clinical symptoms of nerve injury.
      Patients reported dysesthesia in the nerve distributions associated with the popliteal block, the saphenous distribution, or both. It is interesting to note that the patient from case 4 experienced hypersensitivity noted with light touch over the saphenous, sural, deep peroneal and tibial nerve distributions after receiving a popliteal-saphenous nerve block. As a result, the patient manifested symptoms originating from both blocks simultaneously. Case 7, on the other hand, presents a patient that was given a popliteal-saphenous nerve block, resulting in saphenous neuropathy alone. EMG/NCV studies were relatively unremarkable but isolated saphenous neuropathy can be challenging to reliably identify with routine electrophysiologic techniques in many individuals. There remained a concern for focal neuropathy of the right saphenous nerve due to the patient's specific clinical disturbance and focal enlargement of the nerve on US imaging. 5/7 patients underwent nerve study testing. Physicians and surgeons should practice a low threshold to order nerve studies when their patients exhibit side effects from nerve blocks to further investigate the association between nerve blocks and potential complications.
      There are additional factors to consider that may lead to nerve injury following surgery; patient age and tourniquet use.
      • Anderson J.G.
      • Bohay D.R.
      • Maskill J.D.
      • et al.
      Complications after popliteal block for foot and ankle surgery.
      Tourniquet use can result in temporary or permanent injury to nerves, muscles, vasculature and soft tissues.
      • Masari B.A.
      • Eisen A.
      • Duncan C.P.
      • McEwen J.A.
      Tourniquet-induced nerve compression injuries are caused by high pressure levels and gradients - a review of the evidence to guide safe surgical, pre-hospital and blood flow restriction usage.
      Damage to the femoral, common peroneal, saphenous nerves have been observed after thigh tourniquet use.
      • Kornbluth I.D.
      • Freedman M.K.
      • Sher L.
      • Frederick R.W.
      Femoral, saphenous nerve palsy after tourniquet use: a case report.
      • Saw K.M.
      • Hee H.I.
      Tourniquet-induced common peroneal nerve injury in a pediatric patient after knee arthroscopy - raising the red flag.
      • Olivecrona C.
      • Blomfeldt R.
      • Ponzer S.
      • Stanford B.R.
      • Nilsson B.Y.
      Tourniquet cuff pressure and nerve injury in knee arthroplasty in a bloodless field: a neurophysiological study.
      Another risk factor to consider is history of prior popliteal nerve block on the ipsilateral extremity. Case 2 presents a patient that developed a foot drop with history of a popliteal nerve block. In fact, the patient had a repetitive popliteal nerve block within one year from the first occurrence. To the authors’ knowledge, there is no substantial literature evaluating risk of performing nerve blocks with previous or recent administration of the same nerve block. Anderson et al. found that specifically age and tourniquet pressure were statistically significant in terms of associated postoperative neuropathic symptoms, and there were no associations found with tobacco use, diabetes mellitus, tourniquet location or time, or block procedure techniques (steroid and/or epinephrine, single or continuous block, US or nerve stimulator).
      • Anderson J.G.
      • Bohay D.R.
      • Maskill J.D.
      • et al.
      Complications after popliteal block for foot and ankle surgery.
      It is not clearly understood what specific physiologic mechanism causes persistent neurological complications. Jeng et al. described how intrafascicular injections along with high injection pressures can result in neuronal injury. Additionally, a long-beveled needle can cause mechanical injury to the nerves when compared to a short-beveled needle.
      • Jeng C.L.
      • Torrillo T.M.
      • Rosenblatt M.A.
      Complications of peripheral nerve blocks.
      It is also highlighted in the literature that there is a technique variation among providers which may influence efficacy of popliteal blocks, in addition to factors such as US or nerve stimulation guidance.
      • Lauf J.A.
      • Huggins P.
      • Long J.
      • et al.
      Regional nerve block complication analysis following peripheral nerve block during foot and ankle surgical procedures.
      Reliable and accurate needle placement with ultrasound guidance requires sufficient training and experience. Inadequate ultrasound guidance skill can lead to unintended complications. This is particularly true with ultrasound-guided peripheral nerve procedures due to the relative vulnerability of the target.
      • Strakowski J.A.
      Ultrasound-guided peripheral nerve procedures.
      In-plane visualization with the needle parallel to the transducer is preferred with most anesthetic blocks. Inadequate visualization of the needle and needle tip relative to the nerve during the procedure can lead to undesired compressive effects or intraneural injections. This is particularly problematic during larger volume anesthetic injections. Various procedural errors could lead to unintended injectate placement. This includes obliquity of the needle to the transducer during the injection, which can create the false appearance that a portion of the shaft of the needle is the tip. Other factors that can complicate the visualization is poor alignment of the ultrasound screen to the directions of the injection and patient factors such as obesity, edema, or anatomic alteration such as congenital variation or prior trauma. Rushing the procedure due to time demands for a rapid anesthetic block also has the potential for complications.
      There is a paucity of literature regarding the advantages of an ultrasound guided popliteal block versus the traditional nerve stimulation technique. Advocates of ultrasound guided popliteal block report faster time of block performance and higher success rates compared to nerve stimulation alone.
      • Danelli G.
      • Fanelli A.
      • Ghisi D.
      • et al.
      Ultrasound vs nerve stimulation multiple injection technique for posterior popliteal sciatic nerve block.
      ,
      • Sala-Blanch X.
      • de Riva N.
      • Carrera A.
      • López A.M.
      • Prats A.
      • Hadzic A.
      Ultrasound-guided popliteal sciatic block with a single injection at the sciatic division results in faster block onset than the classical nerve stimulator technique.
      Conversely, Sagherian et al. performed a prospective randomized controlled trial comparing ultrasound guided popliteal blocks prior to induction of anesthesia to nerve stimulation guided blocks after induction of general anesthesia. They observed similar block characteristics and patient satisfaction, with a significantly faster performance time when utilizing nerve stimulation compared to the ultrasound guided technique. It was concluded that popliteal blocks performed using nerve stimulation are safe and reproducible, with emphasis on the importance of utilizing proper anatomical landmarks and current intensity.
      • Sagherian B.H.
      • Kile T.A.
      • Seamans D.P.
      • Misra L.
      • Claridge R.J.
      Lateral popliteal block in foot and ankle surgery: comparing ultrasound guidance to nerve stimulation. A prospective randomized trial.
      In the current study, we recorded the use of US guidance and nerve stimulation. The majority of the nerve blocks in this study (5/7) were performed under US guidance alone. The patient that exhibited muscle paralysis received a popliteal and saphenous nerve block under US guidance and nerve stimulation for the initial Achilles surgery as well as the revisional procedure. According to the literature, however, previous studies have demonstrated increased success rates of popliteal sciatic nerve blocks when a combination of ultrasound guidance and nerve stimulation is utilized.
      • Dufour E.
      • Quennesson P.
      • Van Robais A.L.
      • et al.
      Combined ultrasound and neurostimulation guidance for popliteal sciatic nerve block: a prospective, randomized comparison with neurostimulation alone.
      Dufour et al. performed a prospective randomized study comparing outcomes of popliteal sciatic nerve blocks using conventional anatomical landmarks and neurostimulation vs. combined ultrasound and neurostimulation guidance. They observed enhanced sensorimotor block success at 30 minutes using the combined ultrasound and neurostimulation guidance technique.
      • Dufour E.
      • Quennesson P.
      • Van Robais A.L.
      • et al.
      Combined ultrasound and neurostimulation guidance for popliteal sciatic nerve block: a prospective, randomized comparison with neurostimulation alone.
      The incidence of peripheral nerve injury is difficult to understand due to the methodological heterogeneity and quality of studies available. The methodology of reporting the occurrence of nerve block injuries, the duration of patient follow-up, and the definition of nerve injury varies among studies. Majority of these studies are retrospective chart reviews.
      • Anderson J.G.
      • Bohay D.R.
      • Maskill J.D.
      • et al.
      Complications after popliteal block for foot and ankle surgery.
      • Provenzano D.A.
      • Viscusi E.R.
      • Adams S.B.
      • et al.
      Safety and efficacy of the popliteal fossa nerve block when utilized for foot and ankle surgery.
      • Lauf J.A.
      • Huggins P.
      • Long J.
      • et al.
      Regional nerve block complication analysis following peripheral nerve block during foot and ankle surgical procedures.
      Lollo et al., on the other hand, was a prospective study that found zero complications of nerve injury when evaluating a total of 357 nerve blocks.
      • Lollo L.
      • Bhananker S.
      • Stogicza A.
      Postoperative sciatic and femoral or saphenous nerve blockade for lower extremity surgery in anesthetized adults.
      Complication rates as low as 1.6% or less have been reported.
      • Provenzano D.A.
      • Viscusi E.R.
      • Adams S.B.
      • et al.
      Safety and efficacy of the popliteal fossa nerve block when utilized for foot and ankle surgery.
      ,
      • Nielsen K.C.
      • Guller U.
      • Steele S.M.
      • Klein S.M.
      • Greengrass R.A.
      • Pietrobon R.
      Influence of obesity on surgical regional anesthesia in the ambulatory setting: an analysis of 9,038 blocks.
      Short term complication rates range from 7.2% to 11% has been reported.
      • Lauf J.A.
      • Huggins P.
      • Long J.
      • et al.
      Regional nerve block complication analysis following peripheral nerve block during foot and ankle surgical procedures.
      ,
      • Kahn R.L.
      • Ellis S.J.
      • Cheng J.
      • et al.
      The incidence of complications is low following foot and ankle surgery for which peripheral nerve blocks are used for postoperative pain management.
      ,
      • Park Y.U.
      • Cho J.H.
      • Lee D.H.
      • Choi W.S.
      • Lee H.D.
      • Kim K.S.
      Complications after multiple-site peripheral nerve blocks for foot and ankle surgery compared with popliteal sciatic nerve block alone.
      Lauf et al. reported a long term complication rate of 4.3% and patients at greater risk involve 40-65 years of age, normal or underweight BMI, surgery performed at an outpatient surgery center, and current smokers.
      • Lauf J.A.
      • Huggins P.
      • Long J.
      • et al.
      Regional nerve block complication analysis following peripheral nerve block during foot and ankle surgical procedures.
      Lauf et al. suggest that their multicenter study design with a myriad of anesthesiologists and a wide range of procedures, permitted generalizability of available data compared to previous literature.
      • Lauf J.A.
      • Huggins P.
      • Long J.
      • et al.
      Regional nerve block complication analysis following peripheral nerve block during foot and ankle surgical procedures.
      Due to the small sample size presented in this study, the authors are unable to conclude the significance of US-guidance versus nerve stimulation, repetitive ipsilateral nerve blocks, adjunct adductor canal blocks, and tourniquet use. In addition, the available data provided in the study was provider-dependent and relied heavily on level of documentation, clinical assessment, and use of imaging and nerve studies. Multiple surgeons were involved with a large span of surgery types. Due to the retrospective nature of the study, there was selection bias involved. Larger retrospective and prospective studies are necessary to determine the significance of the aforementioned factors.

      Conclusions

      Popliteal nerve blocks are a widely practiced technique for administration of regional anesthesia in the setting of foot and ankle surgery. The goal of this case series is to provide insight into the potential risks and complications associated with regional anesthesia. It is essential for surgeons to inform patients of the potential risks and propose alternative methods for postoperative pain management as deemed necessary, including longer-lasting local anesthesia, local anesthesia delivery device systems, and other multimodal pain regimens. Further prospective studies are necessary to evaluate the impact of multiple factors, including ultrasound-guidance versus nerve stimulation, repetitive ipsilateral nerve blocks, adjunct adductor canal blocks, and tourniquet use. The complication rate following peripheral nerve blocks remains inconsistent and unclear. It is important to note that the anesthesia care team, involved in administering the block pre-operatively, is not participating in the postoperative management of these patients and not managing the short- and long-term complications. We hope to raise awareness and encourage further high-level evidence research that investigates the potential complications of popliteal and adductor canal nerve blocks. It is essential that an informed decision is cautiously made between a surgeon, anesthesiologist, and the patient regarding the safety and necessity of delivering a preoperative peripheral nerve block based on patient risk factors Tables 1 and 2.
      Table 1Overview of patients including follow-up period, surgical intervention and laterality.
      PatientAgeFollow Up (mos)ProcedureLaterality
      15624Tarsometatarsal joint fusionsL
      245261. Achilles detachment/reattachment with calcaneal exostectomy (Block)

      2. Revisional Achilles debridement with flexor hallucis longus transfer (Block)

      3. Achilles tendon lengthening, posterior ankle capsular release, peroneal brevis tendon repair (No Block)
      L
      34215Ankle arthroscopy, lateral ankle stabilization, peroneal repairL
      43530Ankle open reduction internal fixationL
      54818Ankle arthroscopy, lateral ankle stabilization, peroneal repair, os trigonum excisionR
      63920Austin bunionectomy, tibial sesamoid excisionR
      76836Lat ankle stab, peroneal tendon repair, calcaneal osteotomyR
      R = right, L = left.
      Table 2Data pertaining to case series, including nerve block performed, nerve block guidance, history of previous block, treatment following complications with nerve block, the presence of drop foot and whether or not there was resolution of the nerve damage.
      PatientBlockBlock guidanceHistory of prior blockTreatmentPresence of DropfootResolution
      1PoplitealNS + USNGabapentinNImprovement based on repeat NCV/EMG study, but not fully recovered clinically
      21. Popliteal + Saphenous

      2. Popliteal
      NS + USYPT, night splint, non-articulating AFOYImproved; strength in anterior muscle groups returned, however residual numbness in DPN and SPN nerve distribution remained
      3Popliteal + SaphenousUSNPTNImproved
      4Popliteal + SaphenousUSNPT, Gabapentin, Pain MgmtNImproved
      5PoplitealUSNLyricaNN
      6PoplitealUSNLyricaNN
      7Popliteal + SaphenousUSNGabapentinNN
      NS = nerve stimulation, US = ultrasound, Y = yes, N = no, PT - physical therapy, AFO - ankle foot orthosis, NCV = nerve conduction velocity, EMG = electromyography

      Disclosures

      Dr. Brian Steginsky: Arthrex
      Dr. Daniel Logan: Consultant for Flower Orthopedics, Novastep, Acumed

      Funding

      This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

      Informed patient consent

      Complete informed consent was obtained from the patient for the publication of this study and accompanying images.

      Declaration of Competing Interest

      The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

      Acknowledgements

      All authors contributed substantially to the paper. The authors would like to acknowledge Dr. Steven Szames and Dr. Timothy Holmes for providing patients for this study.

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