Anatomy and potential clinical significance of the vastoadductor membrane

Adductor canal block techniques do not lead to involvement of sciatic nerve branches: a radiological cadaveric study

INTRODUCTION

Low and high volume mid-thigh (ie, distal femoral triangle) and distal adductor canal block approaches are frequently applied for knee surgical procedures. Although these techniques aim to contain the injectate within the adductor canal, spillage into the popliteal fossa has been reported. While in theory this could improve analgesia, it might also result in motor blockade due to coverage of motor branches of the sciatic nerve. This radiological cadaveric study, therefore, investigated the incidence of coverage of sciatic nerve divisions after various adductor canal block techniques.

METHODS

Eighteen fresh, unfrozen and unembalmed human cadavers were randomized to receive ultrasound-guided distal femoral triangle or distal adductor canal injections, with 2 mL or 30 mL injectate volume, on both sides (36 blocks in total). The injectate was a 1:10 dilution of contrast medium in local anesthetic. Injectate spread was assessed using whole-body CT with reconstructions in axial, sagittal and coronal planes.

RESULTS

No coverage of the sciatic nerve or its main divisions was found. The contrast mixture spread to the popliteal fossa in three of 36 nerve blocks. Contrast reached the saphenous nerve after all injections, whereas the femoral nerve was always spared.

CONCLUSIONS

Adductor canal block techniques are unlikely, even when using larger volumes, to block the sciatic nerve, or its main branches. Furthermore, injectate reached the popliteal fossa in a small minority of cases, yet if a clinical analgesic effect is achieved by this mechanism is still unknown.

Ultrasound-guided adductor canal block is superior to femoral nerve block for early postoperative pain relief after single-bundle anterior cruciate ligament reconstruction with hamstring autograft

PURPOSE

This study aimed to compare the combination of a lateral femoral cutaneous nerve (LFCN) block with a femoral nerve block (FNB) and an adductor canal block (ACB) for postoperative pain control in patients undergoing anterior cruciate ligament (ACL) reconstruction with hamstring autograft.

METHODS

A non-randomized, prospective, controlled clinical trial was conducted. The FNB and ACB groups consisted of 41 and 40 patients, respectively. Thirty minutes prior to surgery, the patients received an ultrasound-guided LFCN block either with FNB or ACB. The following values were recorded and compared between the two groups: duration of surgery, pain management during surgery (including total amount of fentanyl administered), and numerical rating scale (NRS) scores at 30 min and 4, 8, 12, 24, 48, and 72 h after surgery. Factors affecting pain relief (NRS < 2) were evaluated, including block type, total amount of fentanyl administered, duration of surgery, age, sex, body mass index, and postoperative suppository use. Significant factors predicting pain relief were determined using the Cox proportional hazard regression model.

RESULTS

There were no significant differences in pain management during the surgery. Pain scores were significantly lower in the ACB group at 30 min, 4 h, 24 h, and 48 h after surgery. The Cox proportional hazard regression model identified ACB as a significant factor for pain relief (hazard ratio: 1.88; 95% confidence interval: 1.12-3.13; p = 0.018).

CONCLUSION

The combination of ACB with LFCN block during ACL reconstruction significantly reduced pain in the early postoperative period compared to FNB with LFCN block.

Surgeon-placed peripheral nerve block and continuous non-opioid analgesia in total knee arthroplasty is accessible intraoperatively: A cadaveric study

BACKGROUND

Pain management in TKA patients is challenged by a postoperative requirement for early ambulation along with the concurrent goal of reducing opioid consumption while simultaneously reducing the length of hospital stay. Peripheral nerve blocks (PNB) address these concerns to some degree, with femoral nerve and adductor canal blocks being the most-used regional nerve blocks for surgeries performed around the knee joint.

PURPOSE

The authors hypothesized that placing a catheter between the muscles that make up the adductor canal during a standard surgical approach for a Total Knee Arthroplasty would provide equitable or superior access for a peripheral nerve block in the adductor canal. The nerves that are located between the muscles that make up the adductor canal transmit the majority of the pain after TKA.

METHODS

This cadaveric study was conducted in 12 fresh-frozen human cadaveric lower limbs, comparing the standard technique of adductor canal block, placed under ultrasound guidance, to this experimental technique. Using colored indicator dyes to locate the site of surrogate peripheral nerves, the techniques were compared.

RESULTS

Through a standard anterior surgical approach to the knee, an intraoperative catheter placement technique can be performed to provide a peripheral nerve block to the saphenous nerve for patients undergoing TKA that is comparable to standard ultrasound guided anesthesia block techniques.

CONCLUSIONS

This cadaveric study demonstrates the availability for the surgeon to place a catheter between the muscles that form the adductor canal during a standard surgical approach for TKA. This novel technique can provide equivalent coverage of the nerves for an ACB when compared to a standard ultrasound guided ACB.

Anatomical study of the adductor canal: three-dimensional micro-computed tomography, histological, and immunofluorescence findings relevant to neural blockade

BACKGROUND

A precise anatomical understanding of the adductor canal (AC) and its neural components is essential for discerning the action mechanism of the AC block. We therefore aimed to clarify the detailed anatomy of the AC using micro-computed tomography (micro-CT), histological evaluation, and immunofluorescence (IF) assays.

METHODS

Gross dissections of 39 thighs provided morphometric data relevant to injection landmarks. Serial sectional images of the AC were defined using micro-CT and ultrasonography. The fascial and neural structures of the AC proper were histologically evaluated using Masson's trichrome and Verhoeff-Van Gieson staining, and double IF staining using choline acetyltransferase (ChAT) and neurofilament 200 antibodies.

RESULTS

The posteromedial branch insertion of the nerve to vastus medialis (NVM) into the lateral border of the AC proper was lower (14.5 ± 2.4 cm [mean ± SD] above the base of the patella) than the origin of the proximal AC. The AC consists of a thin subsartorial fascia in the proximal region and a thick aponeurosis-like vastoadductor membrane in the distal region. In the proximal AC, the posteromedial branch of the NVM (pmNVM) consistently contained both sensory and motor fibers, and more ChAT-positive fibers were observed than in the saphenous nerve (27.5 ± 11.2 / 104 vs. 4.2 ± 2.6 / 104 [counts/µm2], P < 0.001).

CONCLUSIONS

Anatomical differences in fascial structures between the proximal and distal AC and a mixed neural component of the neighboring pmNVM have been visualized using micro-CT images, histological evaluation, and IF assays.

Reevaluation of the topographical anatomy of the mid-thigh: A magnetic resonance and ultrasound imaging study

Adductor canal (AC) and sciatic nerve (SN) blockades are commonly used during total knee arthroplasties for postoperative pain control. Medical professionals have begun to utilize single injection combined regional anesthesia methods due to increased patient comfort. In this study, we examined the topographical anatomy of the mid-thigh, which is recommended as the appropriate intervention level for combined AC and SN blockades, in order to provide a safe approach for clinicians. We examined 184 thigh magnetic resonance images (MRI) from 98 patients. We measured the diameter of the mid-thigh, anterior thigh muscle thickness, subcutaneous adipose tissue thickness, and SN depth on the MRIs. We obtained ultrasound (US) images of the vastoadductor membranes (VAM) of 26 volunteers, and measured the vertical distances between the greater trochanter and the adductor tubercle (A) and the greater trochanter and the upper edge of the VAM (B). We then proportioned B to A in order to determine in which part of the thigh the AC was located. The AC was in the distal third of the thigh, and the SN's depth was located in the third quarter of the thigh's diameter. Only the adductor magnus, and no neurovascular structure, was at risk of injury between the AC and the SN. The upper edge of the VAM was 6.5 cm below the mid-thigh, therefore it is not appropriate to suggest performing an AC blockade at mid-thigh. We think that it is safe to perform a combined AC and SN blockade in a single injection in selected patients.

Pro and Con: How Important Is the Exact Location of Adductor Canal and Femoral Triangle Blocks?

In this Pro-Con commentary article, we debate the importance of anterior thigh block locations for analgesia following total knee arthroplasty. The debate is based on the current literature, our understanding of the relevant anatomy, and a clinical perspective. We review the anatomy of the different fascial compartments, the course of different nerves with respect to the fascia, and the anatomy of the nerve supply to the knee joint. The Pro side of the debate supports the view that more distal block locations in the anterior thigh increase the risk of excluding the medial and intermediate cutaneous nerves of the thigh and the nerve to the vastus medialis, while increasing the risk of spread to the popliteal fossa, making distal femoral triangle block the preferred location. The Con side of the debate adopts the view that while the exact location of local anesthetic injection appears anatomically important, it has not been proven to be clinically relevant.

Motor-Sparing Effect of Adductor Canal Block for Knee Analgesia: An Updated Review and a Subgroup Analysis of Randomized Controlled Trials Based on a Corrected Classification System

OBJECTIVE

Discrepancies in the definition of adductor canal block (ACB) lead to inconsistent results. To investigate the actual analgesic and motor-sparing effects of ACB by anatomically defining femoral triangle block (FTB), proximal ACB (p-ACB), and distal ACB (d-ACB), we re-classified the previously claimed ACB approaches according to the ultrasound findings or descriptions in the corresponding published articles. A meta-analysis with subsequent subgroup analyses based on these corrected results was performed to examine the true impact of ACB on its analgesic effect and motor function (quadriceps muscle strength or mobilization ability). An optimal ACB technique was also suggested based on an updated review of evidence and ultrasound anatomy.

MATERIALS AND METHODS

We systematically searched studies describing the use of ACB for knee surgery. Cochrane Library, PubMed, Web of Science, and Embase were searched with the exclusion of non-English articles from inception to 28 February 2022. The motor-sparing and analgesic aspects in true ACB were evaluated using meta-analyses with subsequent subgroup analyses according to the corrected classification system.

RESULTS

The meta-analysis includes 19 randomized controlled trials. Compared with the femoral nerve block group, the quadriceps muscle strength (standardized mean difference (SMD) = 0.33, 95%-CI [0.01; 0.65]) and mobilization ability (SMD = -22.44, 95%-CI [-35.37; -9.51]) are more preserved in the mixed ACB group at 24 h after knee surgery. Compared with the true ACB group, the FTB group (SMD = 5.59, 95%-CI [3.44; 8.46]) has a significantly decreased mobilization ability at 24 h after knee surgery.

CONCLUSION

By using the corrected classification system, we proved the motor-sparing effect of true ACB compared to FTB. According to the updated ultrasound anatomy, we suggested proximal ACB to be the analgesic technique of choice for knee surgery. Although a single-shot ACB is limited in duration, it remains the candidate of the analgesic standard for knee surgery on postoperative day 1 or 2 because it induces analgesia with less motor involvement in the era of multimodal analgesia. Furthermore, data from the corrected classification system may provide the basis for future research.

Anatomical basis for ultrasound-guided infiltration of the saphenous nerve in the subsartorial canal

The present work is aimed studying the visibility and position of the vasto-adductor membrane with ultrasonography and demonstrating that injection performed under this membrane allows to infiltrate the saphenous nerve. It was analyzed with ultrasonography in four cadaveric subjects and in 13 volunteers. This membrane was clearly visible and methylene blue was located underneath it after injection in all cadaveric subjects. This study demonstrates that it can be used as a reliable anatomic landmark when performing an injection for both regional anesthesia and in the treatment of saphenous nerve tunnel syndrome.

Unusual case of the saphenous plexus in the thigh and why we should have borne this variation in mind

Detailed knowledge of the anatomy and different variations of the saphenous nerve could be of great importance not only to anatomists but also to clinicians. There are very few studies of saphenous nerve morphology in thigh. Most of the reported variations of this nerve concern the infrapatellar branch. In contrast, a saphenous plexus has been described in only one case. Herein, we present an unusual case of unilateral saphenous plexus formation in the right thigh found during routine anatomical dissection of a 69-year-old male Caucasian cadaver. We also present a brief discussion of the saphenous plexus and emphasize its potential clinical implications.

Continuous block at the proximal end of the adductor canal provides better analgesia compared to that at the middle of the canal after total knee arthroplasty: a randomized, double-blind, controlled trial

Background

The optimal position for continuous adductor canal block (ACB) for analgesia after total knee anthroplasty (TKA) remians controversial, mainly due to high variability in the localization of the the adductor canal (AC). Latest neuroanatomy studies show that the nerve to vastus medialis plays an important role in innervating the anteromedial aspect of the knee and dives outside of the exact AC at the proximal end of the AC. Therefore, we hypothesized that continuous ACB at the proximal end of the exact AC could provide a better analgesic effect after TKA compared with that at the middle of the AC (which appeared to only block the saphenous nerve).

Methods

Sixty-two adult patients who were scheduled for a unilateral TKA were randomized to receive continuous ACB at the proximal end or middle of the AC. All patients received patient-controlled intravenous analgesia with sufentanil postoperatively. The primary outcome measure was cumulative sufentanil consumption within 24 h after the surgery, which was analyzed using Mann-Whitney U tests. P-values < 0.05 (two-sided) were considered statistically significant. The secondary outcomes included postoperative sufentanil consumption at other time points, pain at rest and during passive knee flexion, quadriceps motor strength, and other recovery related paramaters.

Results

Sixty patients eventually completed the study (30/group). The 24-h sufentanil consumption was 0.22 μg/kg (interquartile range [IQR]: 0.15–0.40 μg/kg) and 0.39 μg/kg (IQR: 0.23–0.52 μg/kg) in the proximal end and middle groups (P = 0.026), respectively. There were no significant inter-group differences in sufentanil consumption at other time points, pain at rest and during passive knee flexion, quadriceps motor strength, and other recovery related paramaters.

Conclusions

Continuous ACB at the proximal end of the AC has a better opioid-sparing effect without a significant influence on quadriceps motor strength compared to that at the middle of the AC after TKA. These findings indicates that a true ACB may not produce the effective analgesia, instead, the proximal end AC might be a more suitable block to alleviate pain after TKA.

Trial registration

This study was registered at ClinicalTrials.gov (NCT03942133; registration date: May 06, 2019; enrollment date: May 11, 2019).

Adductor canal blocks for postoperative pain treatment in adults undergoing knee surgery

BACKGROUND

Peripheral regional anaesthesia techniques are well established for postoperative pain treatment following knee surgery. The adductor canal block (ACB) is a new technique, which can be applied as a single shot or by catheter for continuous regional analgesia.

OBJECTIVES

To compare the analgesic efficacy and adverse events of ACB versus other regional analgesic techniques or systemic analgesic treatment for adults undergoing knee surgery.

SEARCH METHODS

We searched CENTRAL, MEDLINE, and Embase, five other databases, and one trial register on 19 September 2018; we checked references, searched citations, and contacted study authors to identify additional studies.

SELECTION CRITERIA

We included all randomized controlled trials (RCTs) comparing single or continuous ACB versus other regional analgesic techniques or systemic analgesic treatment. Inclusion was independent of the technique used (landmarks, peripheral nerve stimulator, or ultrasound) and the level of training of providers.

DATA COLLECTION AND ANALYSIS

We used Cochrane's standard methodological procedures. Our primary outcomes were pain intensity at rest and during movement; rate of accidental falls; and rates of opioid-related adverse events. We used GRADE to assess the quality of evidence for primary outcomes.

MAIN RESULTS

We included 25 RCTs (1688 participants) in this review (23 trials combined within meta-analyses). In 18 studies, participants underwent total knee arthroplasty (TKA), whereas seven trials investigated patients undergoing arthroscopic knee surgery. We identified 11 studies awaiting classification and 11 ongoing studies. We investigated the following comparisons. ACB versus sham treatment We included eight trials for this comparison. We found no significant differences in postoperative pain intensity at rest (2 hours: standardized mean difference (SMD) -0.56, 95% confidence interval (CI) -1.20 to 0.07, 4 trials, 208 participants, low-quality evidence; 24 hours: SMD -0.49, 95% CI -1.05 to 0.07, 6 trials, 272 participants, low-quality evidence) or during movement (2 hours: SMD -0.59, 95% CI -1.5 to 0.33; 3 trials, 160 participants, very low-quality evidence; 24 hours: SMD 0.03, 95% CI -0.26 to 0.32, 4 trials, 184 participants, low-quality evidence). Furthermore, they noted no evidence of a difference in postoperative nausea between groups (24 hours: risk ratio (RR) 1.91, 95% CI 0.48 to 7.58, 3 trials, 121 participants, low-quality evidence). One trial reported that no accidental falls occurred 24 hours postoperatively (low-quality evidence). ACB versus femoral nerve block We included 15 RCTs for this comparison. We found no evidence of a difference in postoperative pain intensity at rest (2 hours: SMD -0.74, 95% CI -1.76 to 0.28, 5 trials, 298 participants, low-quality evidence; 24 hours: SMD 0.04, 95% CI -0.09 to 0.18, 12 trials, 868 participants, high-quality evidence) or during movement (2 hours: SMD -0.47, 95% CI -1.86 to 0.93, 2 trials, 88 participants, very low-quality evidence; 24 hours: SMD 0.56, 95% CI -0.00 to 1.12, 9 trials, 576 participants, very low-quality evidence). They noted no evidence of a difference in postoperative nausea (24 hours: RR 1.22, 95% CI 0.42 to 3.54, 2 trials, 138 participants, low-quality evidence) and no evidence that the rate of accidental falls during postoperative care was significantly different between groups (24 hours: RR 0.20, 95% CI 0.04 to 1.15, 3 trials, 172 participants, low-quality evidence).

AUTHORS' CONCLUSIONS

We are currently uncertain whether patients treated with ACB suffer from lower pain intensity at rest and during movement, fewer opioid-related adverse events, and fewer accidental falls during postoperative care compared to patients receiving sham treatment. The same holds true for the comparison of ACB versus femoral nerve block focusing on postoperative pain intensity. The overall evidence level was mostly low or very low, so further research might change the conclusion. The 11 studies awaiting classification and the 11 ongoing studies, once assessed, may alter the conclusions of this review.

Hybrid Blocks for Total Knee Arthroplasty: A Technical Description

INTRODUCTION

This narrative review article aims to examine current evidence of knee innervation in order to develop a technique of targeting pure sensory innervation of the knee joint without compromising motor function.

METHODS

A literature review of knee innervation was performed to gain an anatomic understanding of terminal sensory branches of the relevant target nerves (femoral, obturator, sciatic, and lateral femoral cutaneous).

RESULTS

Pure sensory block of the knee joint is challenging due to important contributions from themuscular innervation close to the joint and the variability of nerves afferents contained within and around the adductor canal.

CONCLUSION

On the basis of this anatomic knowledge we describe an ultrasound-guided 3-injection hybrid technique that represents a balance between preserving adequate motor power while still providing analgesia in a simple method.

Lower extremity regional anesthesia: essentials of our current understanding

The advent of ultrasound guidance has led to a renewed interest in regional anesthesia of the lower limb. In keeping with the American Society of Regional Anesthesia and Pain Medicine's ongoing commitment to provide intensive evidence-based education, this article presents a complete update of the 2005 comprehensive review on lower extremity peripheral nerve blocks. The current review article strives to (1) summarize the pertinent anatomy of the lumbar and sacral plexuses, (2) discuss the optimal approaches and techniques for lower limb regional anesthesia, (3) present evidence to guide the selection of pharmacological agents and adjuvants, (4) describe potential complications associated with lower extremity nerve blocks, and (5) identify informational gaps pertaining to outcomes, which warrant further investigation.

Spread of dye injectate in the distal femoral triangle versus the distal adductor canal: a cadaveric study

Background and objectives

The nerve to vastus medialis (NVM) supplies sensation to important structures relevant to total knee arthroplasty via a medial parapatellar approach. There are opposing findings in the literature about the presence of the NVM within the adductor canal (AC). The objective of this cadaveric study is to compare the effect of injection site (distal femoral triangle (FT) vs distal AC) on injectate spread to the saphenous nerve (SN) and the NVM.

Methods

Four unembalmed fresh-frozen cadavers acted as their own control with one thigh receiving 20 mL of dye injected via an ultrasound-guided injection in the distal FT while the other thigh received an ultrasound-guided injection in the distal AC. A standardized dissection took place 1 hour later to observe the extent of staining to the NVM and SN in all cadaver thigh specimens.

Results

In all specimens where the injectate was introduced into the distal FT, both the SN and NVM were stained. In contrast, when the dye was administered in the distal AC only the SN was stained.

Conclusions

Our findings suggest that an injection in the distal AC may be suboptimal for knee analgesia as it may spare the NVM, while an injection in the distal FT could provide greater analgesia to the knee but may result in undesirable motor blockade from spread to the nerve to vastus intermedius.

An Exact Localization of Adductor Canal and Its Clinical Significance: A Cadaveric Study

Background and Objectives:

Adductor canal block is a regional anesthetic block procedure commonly employed for knee surgeries. This study aims at locating the adductor canal precisely which will be of great use for the surgeons operating on knee.

Materials and Methods:

Forty cadaveric lower limbs fixed with formalin were utilized for the study. The length of the lower limb from anterior superior iliac spine to the base of patella is measured, and the midpoint between the two is marked. Adductor canal is dissected and the distance between proximal foramen and the midpoint of thigh, the length of the adductor canal, and the distance between the distal foramen and the base of the patella are measured.

Results:

The mean value of the adductor canal is about 10.5 cm. The average distance from anterior superior iliac spine to proximal foramen is 25 cm. The average distance from base of patella to distal foramen is 8.5 cm. In 36 (90%) lower limbs, the proximal foramen is 3 cm distal to the midpoint of the thigh.

Interpretation and Conclusion:

This study suggests that a point more than 3 cm below the midpoint of thigh will be the ideal location for the approach of adductor canal block.

Defining the Location of the Adductor Canal Using Ultrasound

Background and Objectives

The precise location of the adductor canal remains controversial among anesthesiologists. In numerous studies of the analgesic effect of the so-called adductor canal block for total knee arthroplasty, the needle insertion point has been the midpoint of the thigh, determined as the midpoint between the anterior superior iliac spine and base of patella. “Adductor canal block” may be a misnomer for an approach that is actually an injection into the femoral triangle, a “femoral triangle block.” This block probably has a different analgesic effect compared with an injection into the adductor canal. We sought to determine the exact location of the adductor canal using ultrasound and relate it to the midpoint of the thigh.

Methods

Twenty-two volunteers were examined using ultrasound. The proximal end of the adductor canal was identified where the medial border of the sartorius muscle intersects the medial border of the adductor longus muscle. The distal end of the adductor canal is the adductor hiatus, which was also visualized ultrasonographically.

Results

The mean distance from the anterior superior iliac spine to the midpoint of the thigh was 22.9 cm (range, 20.3–24.9 cm). The mean distance from the anterior superior iliac spine to the proximal end of the adductor canal was 27.4 cm (range, 24.0–31.4 cm). Consequently, the mean distance from the midpoint of the thigh to the proximal end of the adductor canal was 4.6 cm (range, 2.3–7.0 cm).

Conclusions

In all volunteers, the midpoint of the thigh was proximal to the beginning of the adductor canal, suggesting that an injection performed at this level is in fact a femoral triangle block.

A review of main anatomical and sonographic features of subcutaneous nerve injuries related to orthopedic surgery

Lesion to subcutaneous nerves is a well-known risk of orthopedic surgery and a significant cause of postoperative pain and dissatisfaction in patients. High-resolution ultrasound can be used to visualize the vast majority of small subcutaneous nerves of the upper and lower limbs. Ultrasound detects nerve abnormalities such as focal hypoechoic thickening, stump neuroma, and scar encasement, and provides information not only about the peripheral nerve itself but also about its relationship to adjacent anatomical structures. The purpose of this review is to provide an overview of the anatomy of the main subcutaneous nerves damaged during orthopedic surgery, recall at-risk procedures, and offer useful anatomic landmarks to help the sonographer identify and follow the nerves when an iatrogenic lesion is suspected.

Ultrasound-guided adductor canal block: a cadaver study investigating the effect of a thigh tourniquet

BACKGROUND

Placement of local anaesthetic within the adductor canal using ultrasonography is an alternative to femoral nerve blocks for postoperative pain relief after knee joint replacement surgery. However, the effect of an inflated thigh tourniquet on the distribution of local anaesthetic within the adductor canal is unknown. The aim of this cadaveric study was to compare the distribution of radio-opaque dye within the adductor canal in the presence or absence of an inflated thigh tourniquet.

METHODS

Bilateral ultrasound-guided adductor canal blocks were performed on the thawed lower limbs of five fresh frozen human cadavers. The left and right lower cadaver limbs were randomised to receive or not receive a thigh tourniquet inflated to 300 mm Hg for 1 h. X-rays with iohexol radio-opaque dye were obtained in four views, and fiducial markers inserted as reference points. Virtual editing technology was used to recreate outlines representing the distribution of the radio-opaque dye and superimpose these on anatomical images.

RESULTS

Radio-opaque dye was distributed on the medial aspect of the thighs with entire and well circumscribed margins. The majority of the radio-opaque dye was confined within the adductor canal. Superior-inferior dye distribution was 315 mm [95% confidence intervals (CI) 289-342] and 264 mm (95% CI 239-289) in the presence and absence of an inflated thigh tourniquet, respectively (diff 95% CI -80.46 to -22.22, P=0.0081). Image analysis using the recreated radio-opaque outlines suggested that the most proximal point of the radio-opaque dye was 100 mm (95% CI 82-117) or 117 mm (95% CI 62-171) below the inguinal ligament in the presence and absence of an inflated thigh tourniquet, respectively (diff 95% CI -38 to 72, P=0.456).

CONCLUSIONS

Application and inflation of thigh tourniquets significantly increased the combined superior-inferior dye distribution within the adductor canal of cadaveric limbs. There was insufficient evidence to suggest significant proximal spread of 25 ml of local anaesthetic to involve the motor branches of the femoral nerve. In some patients, the local anaesthetic may reach the popliteal fossa in close approximation to the sciatic nerve.

Successful Continuous Adductor Canal Block Placement in a Patient With Absent Sartorius Muscle: A Case Report

We report a novel case of a patient who presented for elective total knee arthroplasty and had distorted adductor canal anatomy due to previous sartorius rotational flap surgery. Despite the lack of a sartorius muscle on the intended operative limb, we describe the successful placement of a continuous adductor canal block. This case is a clinically relevant example that highlights the importance of the vastoadductor membrane as the anatomical anteromedial boundary for the adductor canal, and that it remains intact even after sartorius muscle flap surgery.

Morphological study and relations of the fascia vasto-adductoria

The precise description of the fascia vasto-adductoria (FVA) has become an issue of great surgical and clinical importance. Neurovascular entrapment within the adductor canal (AC) may simulate many clinical conditions for cases presented with medial knee or leg pain and ischemic manifestations of the leg. The aim of the present work is to describe the morphological features of the FVA and to elucidate its neurovascular relations. Forty thigh specimens, pertaining to 15 embalmed and five fresh adult human cadavers, were dissected in pursuit of this aim. The FVA was a continuous subsartorial fascia, roofing the whole length of AC and extended between two points lying at a mean distance of 25.6 and 7 cm proximal to the base of patella. It was subdivided into two parts; proximal thin quadrangular (proximal part of FVA) and distal thick pentagonal (vastoadductor membrane; VAM) and the subsartorial space was observed superficial to it. The mean length of its proximal and distal parts was 7.8 and 7.9 cm, respectively. The proximal part of FVA, while stretched across the vastus medialis (VM) and the adductor longus (AL) muscles, became attached to the wall of the femoral artery and overlaid the femoral vessels, the saphenous nerve (SN), and an arterial pedicle for VM muscle. It was constantly pierced by two arterial pedicles arising from the femoral artery to the sartorius muscle and occasionally (50%) by a communicating nerve branch arising from the SN to join the medial femoral cutaneous nerve. The VAM stretched across the VM muscle and both the AL and adductor magnus (AM) muscles and overlaid the SN, its subsartorial and lower medial femoral cutaneous branches, femoral vessels, 1-3 arterial pedicles for the sartorius and descending genicular vessels. The VAM originated from the tendinous fibres of the AM tendon and constantly spread anterolaterally. It was constantly pierced by 1-3 arterial pedicles to sartorius muscle and both the lower medial femoral cutaneous branch and the subsartorial branches of the SN. An arterial pedicle to the VM muscle and perforating veins between the superficial veins and the femoral vein proved to pierce it in 8/40 specimens. Entrapment of the SN at the distal narrow aperture of the AC, or one of its cutaneous branches at the piercing sites of the FVA, should be remembered when diagnosing cases presented with medial knee or leg pain. The attachment of the proximal part of the FVA to the wall of the femoral artery could add to the mechanism of its potential compression. True AC block should be done deep to the FVA to ensure effective SN analgesia. Its site is recommended to be at the distal one cm of the proximal part of the AC which is at a distance of 16-17 cm proximal to the base of patella. The VAM, being an anatomical connection between the VM and AM muscles, is theorized to increase the mechanical efficiency of the VM oblique muscle to maintain the knee extensor mechanism.

Saphenous and Infrapatellar Nerves at the Adductor Canal: Anatomy and Implications in Regional Anesthesia

Conflicting data exist regarding the anatomical relationship of the saphenous and infrapatellar nerves at the adductor canal and the location of the superior foramen of the canal. Therefore, the authors performed a cadaveric study to detail the relationship and course of the saphenous and infrapatellar nerves and the level of the superior foramen of the canal. The adductor canal and subsartorial compartment were dissected in 17 human cadavers. The distance between the superior foramen of the canal and the mid-distance (MD) between the base of the patella and the anterior superior iliac crest were measured; the course of the saphenous and infrapatellar nerves and the level of origin of the infrapatellar branch were detailed. In 13 of 17 specimens, the superior foramen of the adductor canal was distal to the MD (mean, 6.5 cm); in the remaining specimens, it was proximal to the MD. In 12 of 17 specimens, the infrapatellar branch exited the canal separately from the saphenous nerve; in the remaining specimens, it originated caudally to the canal. In all dissections, the infrapatellar branch had a constant course in close proximity to the saphenous nerve within the canal and between the sartorious muscle and femoral artery caudally to the canal. Most commonly, the superior foramen of the adductor canal is located caudally to the MD; the infrapatellar branch originates from the saphenous nerve within the canal and has a constant course in close proximity to the saphenous nerve. These observations should be considered for regional anesthesia techniques at the adductor canal.

The spread of injectate during saphenous nerve block at the adductor canal: a cadaver study

BACKGROUND

The spread of injectate during a saphenous nerve block at the adductor canal has not been clearly described.

METHODS

We examined the spread of 15 ml dyed injectate during ultrasound-guided saphenous nerve blocks at the adductor canal in 15 unembalmed cadavers' lower limbs followed by comparative dissections of the same limbs.

RESULTS

The spread of the injectates was determined by the fascial limits and the muscles surrounding the adductor canal. The anteromedial limit of the adductor canal (the roof) was found to be a continuous fascia, with a thin proximal part and a thicker distal part (the vastoadductor membrane) covering the canal from the apex of the femoral triangle to the adductor hiatus. The fascial limits of the adductor canal formed a conduit around the femoral neurovascular bundle. The dyed aqueous injectate spread throughout the entire adductor canal to the femoral triangle and reached 1-2 cm into the popliteal fossa. Injections superficial to the adductor canal spread over the femoral artery within the subsartorial fat compartment resembling the injections within the canal but with ultrasonographic distinct features. These injections spread only half the length of the adductor canal. The only nerve observed within the adductor canal was the saphenous nerve.

CONCLUSIONS

Injection of 15 ml dye was sufficient to spread throughout the adductor canal and beyond both proximally and distally. Distinct ultrasonographic features could be identified separating a subsartorial injection from an injection within the adductor canal with consequent differences in the spread.

Anatomy of the Hunter's canal and its role in the venous outlet syndrome of the lower limb

BACKGROUND

The "Adductor canal syndrome" has been described as an unusual cause of acute arterial occlusion inside the Hunter's canal in young sportsmen. It may also produce a compressive neuropathy of the saphenous nerve. To our knowledge, femoral vein compression in the canal has never been reported.

OBJECTIVE

To describe the anatomy, to propose a physiology of this canal, and to show that the femoral vein is much more exposed than the artery to compression inside this adductor hiatus, particularly at the outlet.

MATERIAL AND METHODS

The whole adductor canal was exposed in 100 limbs for anatomical study following latex injection. A series of 200 phlebographies and 100 CT venograms were also analyzed.

RESULTS

Anatomically, we found a musculotendinous band called the "vastoadductor membrane," which jointed the adductor tendon to the vastus medialis in all the cases. The femoral vein, located more posteriorly, was frequently narrowed at this level. This band can create a notch with a venous stenosis at the outlet of the Hunter's canal, usually located 12-14 cm above the femoral condyle. Two femoral valves constitute the landmark of the canal on the venograms: the lower is just below the outlet, 9 cm above the condyle. The second valve is 3 cm higher inside the canal.Functionally, the cadaveric simulations showed that the contraction of the adductor longus closes the hiatus, while the adductor magnus opens it. Our hypothesis is that Hunter's canal prevents femoropopliteal axis reflux by synchronizing with calf pump ejection during ambulation.

CONCLUSION

Compression of the femoral vein inside the adductor's canal is an underestimated and misdiagnosed cause of postural stenosis of the femoral vein. Ultrasound investigation of both limbs in patients with chronic venous disease (CVD) should be systematically carried out at this precise level in order to prevent future occlusion and onset of acute deep vein thrombosis.

Human obturator nerve: Gross anatomy

AIM: To study the anatomy (formation, course, relationships and branching pattern) of the obturator nerve in detail.

METHODS: The study was based on 500 adult human formalin-embalmed cadavers, 342 males and 158 females. We studied the anatomical formation, course and relationships of the obturator nerve within the lesser pelvis before the obturator canal. Finally, the whole course of the obturator nerve was examined.

RESULTS: We found numerous anatomical variations about the formation of the obturator nerve, its division into two main branches, its articular branches, its intrapelvic branches for the periosteum of the pubic bone, and also the number of its muscular divisions and its anatomical relationship to the obturator externus muscle and obturator artery. We found that fibers from the L3 and L4 spinal nerves are standard components of the obturator nerve. The main trunk of the obturator nerve divides into anterior and posterior branches, within the pelvis in 23.30%, within the obturator canal in 52.30% and extrapelvic in 24.35% of cases. The anterior branch of the obturator nerve supplies three muscular branches in 67.10%, two muscular branches in 28.94% and four muscular branches in 3.94% of the cases. The posterior branch of the obturator nerve supplies two muscular branches in 60.52%, three muscular branches in 19.07%, one muscular branch in 14.47% and four muscular branches in 5.92% of cases.

CONCLUSION: We present a gross anatomical study of the human obturator nerve based on a remarkably large number of cases as well as potential clinical applications of our findings.

Conservative management of a saphenous nerve entrapment in a female ultra-marathon runner

Entrapment of the saphenous nerve is a frequently overlooked cause of medial knee pain. Delayed or misdiagnosis is a result of a lack of detailed reporting of the vastoadductor membrane, and by direct visualization of the entrapment only being accomplished at the time of surgical decompression. To date there are no documented conservative interventions discussed in the literature. This is a case of diagnosis and conservative resolution of a spontaneous saphenous nerve entrapment in a competitive female ultra-marathon runner. In-office Active Release Technique(®) combined with an at-home rehabilitative exercise program relieved the patient's subjective pain and paresthesia with two treatments provided over a one week period of time.

Classification and localization of the adductor hiatus: a cadaver study

OBJECTIVE

To determine not only the vertical but also horizontal localization of the adductor hiatus (AH) and classify its shape and structure macroscopically.

MATERIAL AND METHODS

Forty lower extremities were dissected to expose the AH. Its shape and structure were macroscopically noted, and the AH was classified into four types. For determining the localization, measurements were made with digital calipers.

RESULTS

Twenty-four oval fibrous types, 12 oval muscular types, 2 bridging fibrous types and 2 bridging muscular types of AH were determined. For the horizontal localization of AH, the apex of the AH was determined to be located medial to the vertical line between the midpoint of the interepicondylar distance and the line which was drawn transversely from the apex of the AH, in all of the cadavers. For the vertical one, the apex of the AH was located in the middle third of the femur length in 14 thighs, and in the remaining 26 ones, the apex of the AH was located in the distal third of the femur length.

CONCLUSION

Adductor hiatus was classified according to its shape and structure for the first time. Moreover, the localization of the AH was practically defined, in order not to harm the popliteal artery and vein.

The corticoperiosteal medial femoral supracondylar flap: anatomical study for clinical evaluation in mandibular osteoradionecrosis

PURPOSE

An ideal way to treat osteoradionecrosis of the jaws is to transfer an osteogenic, appropriately vascularized flap to the affected site. The corticoperiosteal femoral medial supracondylar flap is being used increasingly in the treatment of complex pseudarthrosis of long bones, but is yet to find robust indications for use in the treatment of osteoradionecrosis of the jaw, the reasons being a lack of anatomical data concerning its vascular supply and the local constraints of its routine harvest. This study presents an anatomical study and literature review to explore its potentials in clinical practice.

MATERIALS AND METHODS

A total of 25 legs were dissected following vascular injection of colored neopren. The descending genicular artery (DGA) and veins were studied with particular attention paid to anatomical variations found in their branches. Calibers and length of the vessels were recorded.

RESULTS

Many anatomical variations of the DGA were found and a classification proposed. The mean caliber of the DGA at the origin was 1.9 mm, and for the vein, 1.8 mm. The mean useful length of the pedicle was 7.9 cm. A case is reported.

CONCLUSION

A clear anatomical knowledge (and, therefore, a sound classification system to grade flap harvesting potential) is the key first step prior to extensive clinical use of this flap. Various anatomical patterns of the pedicle are frequently encountered; branches can be elusive when raising the flap. Vascular imaging is therefore a critical step in identifying types and subtypes before surgery.

The connective tissue of the adductor canal--a morphological study in fetal and adult specimens

The adductor canal is a conical or pyramid-shaped pathway that contains the femoral vessels, saphenous nerve and a varying amount of fibrous tissue. It is involved in adductor canal syndrome, a claudication syndrome involving young individuals. Our objective was to study modifications induced by aging on the connective tissue and to correlate them to the proposed pathophysiological mechanism. The bilateral adductor canals and femoral vessels of four adult and five fetal specimens were removed en bloc and analyzed. Sections 12 microm thick were obtained and the connective tissue studied with Sirius Red, Verhoeff, Weigert and Azo stains. Scanning electron microscopy (SEM) photomicrographs of the surfaces of each adductor canal were also analyzed. Findings were homogeneous inside each group. The connective tissue of the canal was continuous with the outer layer of the vessels in both groups. The pattern of concentric, thick collagen type I bundles in fetal specimens was replaced by a diffuse network of compact collagen bundles with several transversal fibers and an impressive content of collagen III fibers. Elastic fibers in adults were not concentrated in the thick bundles but dispersed in line with the transversal fiber system. A dynamic compression mechanism with or without an evident constricting fibrous band has been proposed previously for adductor canal syndrome, possibly involving the connective tissue inside the canal. The vessels may not slide freely during movement. These age-related modifications in normal individuals may represent necessary conditions for this syndrome to develop.

The effect of aging on deformations of the superficial femoral artery resulting from hip and knee flexion: potential clinical implications

PURPOSE

Vessel deformations have been implicated in endoluminal device fractures, and therefore better understanding of these deformations could be valuable for device regulation, evaluation, and design. The purpose of this study is to describe geometric changes of the superficial femoral artery (SFA) resulting from hip and knee flexion in older subjects.

MATERIALS AND METHODS

The SFAs of seven healthy subjects aged 50-70 years were imaged with magnetic resonance angiography with the legs straight and with hip and knee flexion. From geometric models constructed from these images, axial, twisting, and bending deformations were quantified.

RESULTS

There was greater shortening in the bottom third of the SFA than in the top two thirds (top, 5.9% +/- 3.0%; middle, 6.7% +/- 2.1%; bottom, 8.1% +/- 2.0% [mean +/- SD]; P < .05), significant twist in all sections (top, 1.3 degrees /cm +/- 0.8; middle, 1.8 degrees /cm +/- 1.1; bottom, 2.1 degrees /cm +/- 1.3), and greater curvature increase in the bottom third than in the top two thirds (top, 0.15 cm(-1) +/- 0.06; middle, 0.09 cm(-1) +/- 0.07; bottom, 0.41 cm(-1) +/- 0.22; P < .001).

CONCLUSIONS

The SFA tends to deform more in the bottom third than in the other sections, likely because of less musculoskeletal constraint distal to the adductor canal and vicinity of knee flexion. The SFAs of these older subjects curve off axis with normal joint flexion, probably resulting from known loss of arterial elasticity with age. This slackening of the vessel enables a method for noninvasive quantification of in vivo SFA strain, which may be valuable for treatment planning and device design. In addition, the spatially resolved arterial deformations quantified in this study may be useful for commercial and regulatory device evaluation.