Position of the popliteal artery in revision total knee arthroplasty

Background

Injury to the popliteal artery during total knee arthroplasty is a devastating complication. This topic was studied previously prior to primary total knee arthroplasty. This study aims to demonstrate the position of the popliteal artery in patients prior to revision total knee replacement.

Methods

The ultrasound scan results of the position of the popliteal artery in 23 patients were reviewed. The implant/artery distance at different levels was measured with the knee in extension and 70°–90° of flexion.

Results

There was no significant difference in the artery position at the level of the tibial metal base plate (the most critical site) on moving the knee from extension to flexion (P?=?0.26). However, the implant/artery distance was found to increase on moving from extension to flexion in relation to the femoral component at the joint line (69%), as well as 15?mm below the level of the tibial base plate representing 69.3%. There was a significant difference at 15?mm above the joint line, where the distance was found to be increased in 84.6% of cases (P?=?0.019).

Conclusion

This study has shown that in a revision knee situation, there is no reliable fall back of the popliteal artery in knee flexion; in fact, implant/artery distance may be decreased and caution must be exercised throughout the procedure. It may be worth considering either ultrasound or arteriography in selected cases.     

The division of the sciatic nerve in the popliteal fossa: anatomical implications for popliteal nerve blockade

The sciatic nerve (SN) originates from the L4-S3 roots in the form of two nerve trunks: the tibial nerve (TN) and the common peroneal nerve (CPN). The TN and CPN are encompassed by a single epineural sheath and eventually separate (divide) in the popliteal fossa. This division of the SN occurs at a variable level above the knee and may account for frequent failures reported with the popliteal block. We studied the level of division of the SN in the popliteal fossa and its relationship to the common epineural sheath of the SN. The level of division of the SN sheath into TN and CPN above the knee was measured in 28 cadaver leg specimens. The SN was invariably formed of independent trunks (TN and CPN) encompassed in one common epineural sheath. The SN divided at a mean distance of 60.5 +/- 27.0 mm (range 0 to 115 mm) above the popliteal fossa crease. We conclude that the TN and CPN leave the common SN sheath at variable distances from the popliteal crease. This finding and the relationship of the TN and CPN sheaths may have significant implications for popliteal block. Implications: When performing popliteal block, insertion of the needle at 100 mm above the popliteal crease is more likely to result in placement of the needle proximal to the division of the sciatic nerve than placement at 50 or 70 mm, according to the classical teaching.     

胫骨上段骨折并腘动脉分叉部闭合性损伤的临床观察

目的：探讨手术治疗胫骨上段骨折合并腘动脉特殊部位损伤的疗效,为临床提供可选择的显微手术方法。方法：2002年2月至2007年10月,胫骨上端骨折并腘动脉分叉处损伤患者19例,男15例,女4例;年龄21～48岁,平均35岁。合并胫骨平台骨折6例;合并神经损伤3例。采用外固定支架固定胫骨骨折,结合小腿近端后侧及前外侧切口对骨间膜开窗引洞,利用移植的大隐静脉（或＂Y＂形）桥接同时修复胫前及胫后动静脉。疗效评价依照Rasmussen评分法。结果：19例均恢复血运,骨折均愈合,愈合时间3～14个月,平均5.5个月。19例获得随访,随访时间8～23个月,平均13个月。疗效评价依照Rasmussen评分法,术后总评分达（27.0±2.9）分;疗效分级：优11例,良7例,可1例。结论：诊断明确后或高度怀疑有血管损伤者应该尽早手术探查。同时重建胫前、胫后动静脉血循环能够降低伤残并且有利于肢体功能恢复。     

Response of the popliteal artery to treadmill exercise and stress positioning in patients with and without exertional lower extremity symptoms

ObjectiveFunctionally limiting exertional lower extremity pain and neurologic symptoms are commonly encountered in military and civilian settings. Exertional muscle compression of the popliteal artery (PA) and tibial nerve in the proximal calf (the “popliteal outlet”) can be associated with these symptoms but is rarely investigated as a cause. Exertional ankle-brachial index (EABI) and dynamic PA ultrasound imaging may be suitable to screen for this syndrome of “functional” popliteal entrapment, but neither has been rigorously studied. Our objective was to characterize the response of the PA to lower extremity exertion and dynamic ankle positioning in symptomatic and asymptomatic limbs.MethodsLimbs characterized as symptomatic (n = 29) or asymptomatic (n = 61) had duplex ultrasound PA diameter and peak systolic velocity measurements with the ankle neutral and maximally plantar flexed. EABIs were obtained at rest and 1 minute and 5 minutes after walking (5 minutes, 3 mph, 10-degree incline) and running (5 minutes, 6 mph, 0-degree incline). Significance was set at P ≤ .05. Data are expressed as mean ± standard error of the mean.ResultsPlantar flexion resulted in PA occlusion and changes in diameter and peak systolic velocity in symptomatic (three occluded, ?2.4 ± 0.34 mm, +49 cm/s) and asymptomatic (six occluded, ?1.6 ± 0.21 mm, +65 cm/s) limbs. The difference in percentage change was significant between groups only for diameter change. EABIs in both groups were similar at rest, decreased with running and walking at 1 minute, and were not fully recovered by 5 minutes. Symptomatic limbs had a greater decrease in ABI than did asymptomatic limbs with both running and walking. The decrease was greatest at 1 minute after running and significantly more pronounced in symptomatic (?0.18) than in asymptomatic (?0.02) limbs.ConclusionsEABI decrease at 1 minute after running and PA diameter decrease with dynamic ankle plantar flexion are significantly greater in limbs with than without exertional lower extremity symptoms. These noninvasive measurements may be valuable in the workup of such symptoms. PA and tibial nerve compression at the popliteal outlet may be a more frequent cause of functionally limiting exertional lower extremity pain and neurologic symptoms than previously recognized.     

Proximity of the posterior cruciate ligament insertion to the popliteal artery as a function of the knee flexion angle: Implications for posterior cruciate ligament reconstruction

Purpose: The purpose of this study was to determine if an optimal knee flexion angle existed that would minimize the risk of neurovascular injury from the passage of transtibial hardware during posterior cruciate ligament (PCL) reconstruction. Type of Study: Cadaveric. Materials and Methods: Fourteen fresh-frozen cadaveric knees were mounted in a Plexiglas apparatus that could be set at 5 different knee flexion angles (0°, 45°, 60°, 90°, and 100°) while joint distention was maintained. Each knee underwent magnetic resonance imaging in the axial and sagittal planes at each of the 5 flexion angles to determine the distance between the PCL tibial insertion and popliteal artery. Results: The mean distance, over all 5 flexion angles, between the PCL insertion and the popliteal artery in the axial plane was 7.6 mm, whereas the mean distance in the sagittal plane was 7.2 mm. There was a significant increase in distance with progressive flexion in both planes. Maximum mean distances were noted at 100° of flexion in both the axial (9.9 mm) and sagittal (9.3 mm) planes. An artificial line mimicking the path of a transtibial drill passed through the popliteal artery in 10 of 10 cases at the 0°, 45°, 60°, and 90° angles, and in 6 of 10 cases at the 100° angle. Conclusions: The results of this study suggest that increasing knee flexion reduces, but does not completely eliminate, the risk of arterial injury during arthroscopic PCL reconstruction.Arthroscopy: The Journal of Arthroscopic and Related surgery, Vol 16, No 8 (November-December), 2000: pp 796–804     

Ultrasound imaging for popliteal sciatic nerve block

BACKGROUND AND OBJECTIVES: Ultrasound is a novel method of nerve localization but its use for lower extremity blocks appears limited with only reports for femoral 3-in-1 blocks. We report a case series of popliteal sciatic nerve blocks using ultrasound guidance to illustrate the clinical usefulness of this technology. CASE REPORT: The sciatic nerve was localized in the popliteal fossa by ultrasound imaging in 10 patients using a 4- to 7-MHz probe and the Philips ATL HDI 5000 unit. Ultrasound imaging showed the sciatic nerve anatomy, the point at which it divides, and the spatial relationship between the peroneal and tibial nerves distally. Needle contact with the nerve(s) was further confirmed with nerve stimulation. Circumferential local anesthetic spread within the fascial sheath after injection appears to correlate with rapid onset and completeness of sciatic nerve block. CONCLUSIONS: Our preliminary experience suggests that ultrasound localization of the sciatic nerve in the popliteal fossa is a simple and reliable procedure. It helps guide block needle placement and assess local anesthetic spread pattern at the time of injection.     

Lateral popliteal sciatic nerve block: a single injection targeting the tibial branch of the sciatic nerve is as effective as a double-injection technique

BACKGROUND: Evidence indicating that single- and double-injection techniques for inducing a sciatic nerve block via a posterior subgluteal approach yield a similar success rate prompted us to investigate whether the two anesthetic techniques yield a similar success rate via a lateral approach. We also hypothesized that, owing to the peculiar anatomic features of the sciatic nerve at the popliteal level, a single injection via the lateral approach might induce effective anesthesia by targeting the tibial nerve only. METHODS: Ninety-six patients undergoing popliteal sciatic nerve block via a lateral popliteal approach for foot surgery were randomized to receive a single 30-ml injection of ropivacaine 7.5 mg/ml to block the tibial nerve (TN group, n= 32) or the common peroneal nerve (CPN group, n= 32), or two separate 15-ml injections (TN + CPN group, n= 32), after stimulation to evoke motor responses from the target nerves. RESULTS: The mean time to obtain a complete sensory blockade (surgical anesthesia) was shorter in the TN group than in the CPN and TN + CPN groups (14 +/- 7 min vs. 23 +/- 17 and 21 +/- 14 min, respectively; P < 0.05). The success rate was similar in the TN and TN + CPN groups (94%) and, 25 min after the initial injection, was already better in these groups than in the CPN group (94% vs. 75%; P < 0.05). CONCLUSIONS: A lateral popliteal sciatic nerve block obtained with a single 30-ml injection of ropivacaine 7.5 mg/ml after electrostimulation to locate the tibial nerve is as effective as multiple TN + CPN stimulation and injection, and local anesthesia has a significantly shorter onset time.     

Open endarterectomy in short atherosclerotic occlusion of the popliteal artery

Background

The purpose of the study is to evaluate the results of open endarterectomy in short atherosclerotic occlusion of the popliteal artery.

Methods

47 patients (25 male and 22 female) underwent endarterectomy of the popliteal artery or popliteal artery and adjoining Superficial Femoral Artery (SFA) and tibio-peroneal bifurcation between January 2008 and December 2011. All patients underwent routine follow up at 1, 3, 6, and 12 months and yearly thereafter. Routine clinical examination, colour Doppler scan and if necessary, arteriogram were done to assess the outcome.

Results

The patients had a median age of 58 +/? 10.3 years. There was no difference in results between the limb side affected (left, n?=?25, right, n?=?22). The length of the lesion varied from 2 to 12 cm, and the largest endarterectomy done was 14 cm. The segments involved were popliteal artery alone in 32 (68.08 %) cases, popliteal artery with adjoining SFA in 5 (10.64 %) cases, popliteal artery with tibioperoneal bifurcation in 6 (12.76 %) cases, and popliteal artery with both SFA and tibioperoneal bifurcation in 4 (8.52 %) cases. The patency of the endarterectomy was determined as primary patency and primary assisted patency. The primary patency rates were 97.87 % at discharge and at 1 month and 95.74 %, 93.61 % and 89.36 at 6 months, 1 year and at 3 years respectively. 3 patients required balloon dilation of the endarterectomy site at 1 and 3 year and the primary assisted patency rates were 95.74 % at 1 year and at 3 years. Major amputation was done in one patient along with lumbar sympathectomy. In 1 patient, femoro-popliteal vein bypass was done on 12th post-operative day because of the haemorrhage from the arteriotomy site.

Conclusion

The present study illustrates that endarterectomy of the popliteal artery should be considered a viable option to bypass techniques in selected patients with localized disease. Endarterectomy provides for revascularization without use of the long sephenous vein. It also spares the long sephenous vein for its use if a future bypass, either coronary or femoro-popliteal or tibial, is required. Furthermore, amputation may be avoided in a vast majority of patients with threatened limbs.     

Proximity of the Common Peroneal Nerve to the Tibial Nerve Entering the Gastrocnemius Muscle: The Implications for Calf Reduction

This article describes the precise anatomic relation and close proximity of the common peroneal nerve (PN) to the tibial nerve branch entering the gastrocnemius muscle (NLG) in the popliteal region. For the study, 22 legs from 13 Korean fresh cadavers (5 men and 8 women ranging in age from 50 to 80 years) were dissected. An x-axis was set as a transverse line crossing the lateral and medial epicondyle of the femur. A longitudinal y-axis accorded with a perpendicular midline between the medial malleoulus of the tibia and the lateral malleolus of the fibula. The PN diverged from the sciatic nerve above the interepicondylar line (−0.4 cm, +10.3 cm) and ran inferolaterally at 20.2° ± 2.4°. The PN crossed the midpoint of the x-axis (+3.4 cm, 0 cm). The NLG diverged from the tibial nerve above the interepicondylar (transverse) line (0 cm, 2.3 cm) and ran inferiorly and laterally at 17.7° ± 4.3°. The distance from the diverging point of the NLG from the tibial nerve to the nearest point of the PN was 2.5 ± 0.5 cm. The distance from the point at which the PN crossed the x-axis to the nearest point of the NLG was 2.7 ± 0.3 cm. In procedures that involve handling of the lateral gastrocnemius muscle itself or the nerves to the lateral gastrocnemius, surgeons should be aware of the close proximity of the PN to the NLG in the popliteal region.     

A surgical case of aneurysm of the persistent sciatic artery

Seventy two-year-old woman was admitted in September, 1985 to our hospital with complaints of painful mass in the right buttock and ischias. Aorto-peripheral arteriogram showed that enlarged right internal iliac and inferior gluteal arteries passed posteriorly to cross the right hip and down the posterior aspect of the femur to supply the popliteal artery. A saccular aneurysm was seen immediately posterior to the right femoral head. The femoral artery was small in size, but connecting to the popliteal artery. Delayed flow to the popliteal artery through the sciatic artery was noted in contrast to the femoral system. With Osborne's right buttock approach, the gluteus maximus muscle was divided in the direction of its fibers, exposing a 3.5 by 5 cm aneurysm which was located above, the sciatic nerve and adherent to it. The proximal sciatic artery and the trunk of the sciatic nerve passed beneath the piriformis muscle. The pressure of the dorsalis pedis artery decreased from 156/77 to 117/72 mmHg after ligation of the proximal sciatic artery. The aneurysm was dissected free from the sciatic nerve. Postoperatively she had no more gluteal discomfort, nor did she have any ischemic symptoms by walking.     

Flexion of the knee increases the distance between the popliteal artery and the proximal tibia: MRI measurements in 15 volunteers

We determined which angle of flexion best prevents popliteal artery injury during knee surgery. We took MRIs of the knee in the lateral position with the knee in 0°, 45°, 90°, and 120° of flexion in 15 volunteers. The shortest distance between the posterior cortex of the tibia and the popliteal artery was measured at various levels from the knee joint to 60 mm distally. At the level of the joint and 15 mm distally, the distance between the tibia and artery increased with increasing knee flexion. More distally, no significant difference was noted with increasing flexion. Flexion of the knee may minimize injury to the popliteal artery in procedures between the level of the joint and 15 mm distal to the joint.     

Study of the anatomical position of the femoral nerve by magnetic resonance imaging in patients with fractured neck of femur: relevance to femoral nerve block

Study ObjectiveTo determine the anatomical location of the femoral nerve in patients who have sustained fracture of the neck of femur, and its relevance to femoral nerve block technique.DesignProspective, observational clinical study.SettingOrthopedic and Radiology departments of a regional hospital.Subjects10 consecutive adult ASA physical status II and III patients (mean age, 78.5 yrs) and 4 adult healthy volunteers.InterventionsA T1 magnetic resonance imaging scan was performed of both upper thighs in patients and healthy volunteers successfully.MeasurementsThe distance (mm) between the midpoint of the femoral artery and the midpoint of the femoral nerve, and the distance of the femoral nerve from the skin was measured at the mid-inguinal ligament, the pubic tubercle, and at the mid-inguinal crease. Data are shown as means (SD). Differences between both sides were compared using paired Student's t-tests. P < 0.05 was significant.Main ResultsIn patients the mean distance (mm) between the midpoint of the femoral nerve from the midpoint of femoral artery at the mid-inguinal crease on the fractured and non-fractured sides was 10.7 and 11.0, respectively (P = 0.87). The mean distance (mm) between the midpoint of the femoral nerve from the midpoint of the femoral artery at the mid-inguinal ligament on the fractured and non-fractured sides was 9.64 and 12.5, respectively (P = 0.03). The mean distance (mm) between the midpoint of the femoral nerve from the midpoint of the femoral artery at the pubic tubercle on the fractured and non-fractured sides was 8.74 and 10.49, respectively (P = 0.18).ConclusionsBlockade of the femoral nerve may be easier to perform at the mid-inguinal crease in patients with fractured neck of femur.     

Ultrasound-guided posterior approach to block the sciatic nerve at the popliteal fossa

The recent introduction of ultrasound guidance for locating peripheral nerves and nerve plexi has allowed injection of anesthetic agents to block the sciatic nerve at the popliteal fossa proximal to division, thus preventing damage to adjacent structures, repeated punctures, and multiple nerve stimulations to verify anesthetic diffusion around the nerve. We report the case of a 23-year-old man, ASA I, who underwent reduction and osteosynthesis of a fractured right fibula. Ultrasound was used to guide the needle after identification of the sciatic nerve 10 cm from the knee fold and 3.5 cm deep. When the point of the needle was near the nerve, the nerve stimulator was switched on to 0.5 mA, and when no response was obtained the current was increased to 1.5 mA. The needle was moved slightly (1-2 mm) to produce a plantar flexion (tibial component) that persisted until stimulation had been reduced to 0.4 mA, at which time 30 mL of 1.5% mepivacaine was injected. The sonographic image during injection showed that the anesthetic had surrounded the nerve (donut sign). The motor and sensory block of the sciatic nerve was complete and no adverse events occurred during or after surgery. We conclude that the combination of ultrasound guidance and nerve stimulation allows the sciatic nerve to be located easily. The approach to the point before division of the sciatic nerve can be guaranteed so that puncture of neighboring vessels can be avoided and optimal anesthesia provided.     

Ultrasound guided injection inside the common sheath of the sciatic nerve at division level has a higher success rate than an injection outside the sheath

Background and objectiveThe recommendations for the level of injection and ideal placement of the needle tip required for successful ultrasound-guided sciatic popliteal block vary among authors. A hypothesis was made that, when the local anesthetic is injected at the division of the sciatic nerve within the common connective tissue sheath, the block has a higher success rate than an injection outside the sheath.MethodsThirty-four patients scheduled for hallux valgus repair surgery were randomized to receive either a sub-sheath block (n = 16) or a peri-sheath block (n = 18) at the level of the division of the sciatic nerve at the popliteal fossa. For the sub-sheath block, the needle was advanced out of plane until the tip was positioned between the tibial and peroneal nerves, and local anesthetic was then injected without moving the needle. For the peri-sheath block, the needle was advanced out of plane both sides of the sciatic nerve, to surround the sheath. Mepivacaine 1.5% and levobupivacaine 0.5% 30 mL were used in both groups. The progression of motor and sensory block was assessed at 5 min intervals. Duration of block was recorded.ResultsAdequate surgical block was achieved in all patients in the subsheath group (100%) compared to 12 patients (67%) in the peri-sheath group at 30 min. Sensory block was achieved faster in the subsheath than peri-sheath (9.1 ± 7.4 min vs. 19.0 ± 4.0; p < .001).ConclusionsOur study suggests that for successful sciatic popliteal block in less than 30 min, local anesthetic should be injected within the sheath.     

Sciatic nerve block in the popliteal fossa: description of a new medial approach

PURPOSE: Sciatic nerve blocks through lateral approaches in the popliteal fossa have been proposed. We describe a new medial approach to the sciatic nerve at this level. METHODS: After an anatomical study on six cadavers, we performed sciatic nerve blocks on 20 patients. A 100-mm insulated needle and a nerve stimulator were used; 20 mL of lidocaine 1.5% with epinephrine were injected. RESULTS: Patients lied in the supine position, the thigh flexed, abducted and rotated externally (30 degrees in all directions). The leg was flexed at 130 degrees . In this position, above the adductor tubercle, a depression known as Jobert's fossa is palpated. Through this groove, a medial approach to the sciatic nerve at the level of the popliteal fossa is possible. The mean distance between the adductor tubercle and the puncture site is 6.18 cm (range 4-8 cm) and the mean distance between the skin and the sciatic nerve is 6.62 cm (range 4-9 cm). Mean time to perform the block was 100 sec (range 55-165 sec). Complete motor blockade was obtained after a mean time of 30 min (range 5-60 min) inside the common peroneal nerve area and 43 min (range 15-75 min) inside the tibial nerve area. Motor block was complete in 17 patients and sensory block in 18 patients. No vessel puncture was observed. CONCLUSION: We describe a new medial approach to the sciatic nerve in the popliteal fossa. More studies will be required to demonstrate the technique is effective and safe.     

0.5%罗哌卡因用于超声引导侧入路腘窝坐骨神经阻滞的半数有效剂量

目的 确定0.5%罗哌卡因用于超声引导侧入路腘窝坐骨神经阻滞时的半数有效剂量.方法 拟在脊椎-硬膜外联合麻醉下行足踝手术患者23例,性别不限,年龄l9～20岁,体重2～90 kg,ASA分级Ⅰ或Ⅱ级,在超声引导下行侧入路腘窝坐骨神经阻滞,定位成功后注入0.5%罗哌卡因.采用Dixon序贯法进行试验,5%罗哌卡因起始容量为18 ml,若阻滞效果完全,则下一例减少2 ml;若阻滞效果不完全,则下一例增加量2 ml.采用Probit概率单位回归法计算0.5%罗哌卡因超声引导侧入路腘窝坐骨神经阻滞时的半数有效剂量及其95%可信区间(95%CI).结果 0.5%罗哌卡因超声引导侧入路腘窝坐骨神经阻滞的半数有效剂量及其95%CI为13.0(11.3～14.9)ml.结论 0.5%罗哌卡因超声引导侧入路腘窝坐骨神经阻滞的半数有效剂量为13.0ml.     

Lateral approach to the sciatic nerve block in the popliteal fossa: correlation between evoked motor response and sensory block

BACKGROUND AND OBJECTIVES: The purpose of this study was to identify which of two motor responses of the foot (plantar flexion versus dorsiflexion) best predicts complete sensory blockade of the sciatic nerve when is used for lateral popliteal sciatic nerve block. METHODS: Thirty American Society of Anesthesiologist physical status I or II patients scheduled for foot and ankle surgery under lateral popliteal sciatic nerve block were enrolled in the study. During each block, the needle was placed to evoke one of the following motor responses of the foot: plantar flexion or dorsiflexion. Thirty milliliters of 0.75% ropivacaine was injected after the motor response was elicited at <0.5 mA. The sequence of elicited motor response was randomized. Sensory blockade of the areas of the foot innervated by the deep peroneal, superficial peroneal, posterior tibial, and sural nerves was checked in a blinded manner. Time required for onset of sensory and motor block of the foot was recorded. RESULTS: The 2 groups were similar with regard to demographic variables and type of surgery. The total of nerves blocked (deep and superficial peroneal, posterior tibial, and sural nerves) after elicited plantar flexion was greater (complete sensory block in 58 of 60 nerve distributions) than after elicited dorsiflexion (34 of 60 nerve distributions) (P <.05). Onset of complete sensory and motor blockade of the foot was faster after elicited plantar flexion (16.6 +/- 5.1 minutes, 20.1 +/- 5.1 minutes, respectively) than after elicited dorsiflexion (24.3 +/- 5.1 minutes, 28.1 +/- 5.0 min, P <.05). CONCLUSIONS: After stimulation of the sciatic nerve, plantar flexion better predicts complete sensory blockade of the foot than dorsiflexion when using the lateral approach to the popliteal fossa. The findings of the present study apply to a single injection of 30 mL of ropivacaine 0.75%.     

Posterior approach to the sciatic nerve in the popliteal fossa for lower limb surgery

Background and objectives: To evaluate success rate, acceptance and complications of sciatic nerve (SN) block at the popliteal fossa (popliteal block, PB) for ambulatory or inpatient orthopedic and vascular surgical procedures. Methods: A retrospective study was carried out in 312 patients who received a PB for vascular and orthopedic lower leg surgery. A single injection, posterior approach technique with 40 ml of either 0.5% ropivacaine or 1% mepivacaine was used. Data collected included demographic and clinical variables. Results: Observed success rate was 95.5%. Acceptance of anesthetic procedure among outpatients was high (94.1%). There were no intraoperative or postoperative complications. For ambulatory surgery patients, the postoperative stay was 130±25 min. Conclusions: PB was a useful anesthetic technique for minor foot and ankle surgery. The single-injection, posterior approach obtained a high success rate without untoward events. It was well accepted by patients and proved to be suitable for ambulatory surgery.     

Surgical anatomy of the sciatic nerve: A meta‐analysis

The sciatic nerve has varying anatomy with respect to the piriformis muscle. Understanding this variant anatomy is vital to avoiding iatrogenic nerve injuries. A comprehensive electronic database search was performed to identify articles reporting the prevalence of anatomical variations or morphometric data of the sciatic nerve. The data found was extracted and pooled into a meta‐analysis. A total of 45 studies (n = 7068 lower limbs) were included in the meta‐analysis on the sciatic nerve variations with respect to the piriformis muscle. The normal Type A variation, where the sciatic nerve exits the pelvis as a single entity below the piriformis muscle, was most common with a pooled prevalence of 85.2% (95%CI: 78.4–87.0). This was followed by Type B with a pooled prevalence of 9.8% (95%CI: 6.5–13.2), where the sciatic nerve bifurcated in the pelvis with the exiting common peroneal nerve piercing, and the tibial nerve coursing below the piriformis muscle. In morphometric analysis, we found that the pooled mean width of the sciatic nerve at the lower margin of the piriformis muscle was 15.55 mm. The pooled mean distance of sciatic nerve bifurcation from the popliteal fossa was 65.43 mm. The sciatic nerve deviates from its normal course of pelvic exit in almost 15% of cases. As such we recommend that a thorough assessment of sciatic nerve variants needs to be considered when performing procedures in the pelvic and gluteal regions in order to reduce the risk of iatrogenic injury. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:1820–1827, 2016.