Anatomical structures that exit the pelvis deep to the inguinal ligament are, from lateral to medial, the femoral nerve, the external iliac to the femoral artery, and the external iliac to femoral vein. Distal portions of all three major structures enter what is known as the femoral triangle, found within the anterior proximal portion of the femoral region. Known more commonly as the “thigh,” this area serves as a confluence of all major vasculature, lymphatic and nerve supply to the lower extremity; along with the origin and/or insertion of significant musculature which mediates the full range of motion of the hip. The region’s clinical significance stems from both the anatomical structures that consist of it and the related procedural/surgical implications involved within this area of the body.
The main structure of the femoral region relates to the femur and its proximal articulation with the pelvis to form the coxa (hip) joint and its distal articulation with the tibia and patella, and by extension the fibula, to form the knee joint. The femur, considered a long bone in development, from proximal to distal consists of the head, anatomical neck, greater and lesser trochanters, shaft with linea aspera along its posterior surface, and the medial and lateral femoral condyles. Within the hip joint, the femoral head articulates with the acetabular fossa. This articulation has support from the lunate surface (cartilage) lining the acetabular fossa, and the joint is supported by the ligament of the head of the femur (ligamentum teres of the acetabulum). Through this runs the foveal artery to the acetabular labrum and surrounding joint capsule (synovial membrane, iliofemoral ligament, ischiofemoral ligament, pubofemoral ligament). Within the knee joint the medial/lateral femoral condyles articulate with the medial/lateral tibial plateaus. The knee articulation is supported by the medial/lateral menisci and the joint supported by the anterior/posterior cruciate ligaments, tibial (medial)/fibular (lateral) collateral ligaments, and patellar ligament in which sits the patella
The function relates to the multiple muscle groups contained within this region which support and induce a range of motion in the hip and the knee. The main muscle groups found within this region can be categorized by the relative anatomical locations of each group, which normally correlates with a specific range of motion of the hip that they facilitate when stimulated. The anterior thigh muscles tend to induce flexion and some adduction of the hip and extension of the knee, medial thigh muscles primarily induce adduction with some flexion and internal rotation of the hip, posterior thigh muscles tend to produce extension and some abduction and internal/external rotation of the hip and flexion of the knee. The specific muscles of these compartments are covered below in a later section.
During week four of embryologic development, limb buds begin to develop - the upper limbs appear before the lower limbs. On the distally growing end, each limb tip contains apical ectodermal ridge tissue which mediates the proper development of each limb to full differentiation at week 8. Within the base of the lower limb buds, layers of mesoderm organize into what is known as the zone of polarizing activity (ZPA) which produces sonic hedgehog gene product. The function of this protein involves activation of the bone morphogenetic protein (BMP) gene and Hoxd-9 through Hoxd-13 genes; both serving roles which modulate the proper growth and lengthening of the limb. Initially, the lower limb buds, as they begin to develop around week four, grow along a coronal plane. However, by week 6 to 8, the buds start to move and grow in first a horizontal movement growing along a sagittal plane and then rotating internally so that the knee faces anteriorly.
While the limb structure is developing, other tissues within the limb follow suit:
From the external iliac artery that exits the pelvis immediately deep to the inguinal ligament, the segment known as the femoral artery runs through the femoral triangle in parallel with the femoral vein and the deep inguinal lymphatic chain via the femoral canal. Each vessel serves as the proximal origin of the structures supporting the tissues of the femoral region; except for the sciatic nerve (L4 to S3) in the posterior compartment, that comes off the lumbosacral plexus.
The femoral artery, as it exits the femoral triangle, branches into the three major arteries of this region:
The femoral vein and its branches within the femoral region follow very similar courses to the related arteries; the femoral vein follows the femoral artery, the profunda femoris vein follows the profunda femoris artery, and the lateral circumflex veins follow the lateral circumflex arteries. The only exception is the course of the great saphenous vein, a major superficial branch off the femoral vein as it moves distally through the femoral canal and extends superficial to the fascia lata surrounding the structures of the thigh via the saphenous opening and takes a subcutaneous course along the medial thigh and extended distally past the knee.
From this saphenous opening also extends the major lymphatic chains of the region originating from the deep inguinal lymph nodes that move alongside the femoral vessels through the femoral canal. From the deep inguinal chain follows the superficial inguinal lymph chains that extend subcutaneously in a superior directed course towards the landmark of the anterior superior iliac spine of the ilium, as well as extending an inferior division along the medial portion of the proximal thigh.
Motor innervation of these nerves is covered below. Sensory innervation includes both the dermatomal and cutaneous nerve distributions. For dermatomal, the anterior thigh includes coverage by L2-L4, with the margin of L2 indicated just inferior to the inguinal ligament and L4 over most of the anterior/medial knee. Posterior thigh dermatomes include L5 covering the lateral thigh and moving medially by S1-S4, the latter covering a small portion immediately inferior to the medial margin of the gluteal cleft. For cutaneous nerve distribution, the femoral nerve covers most of the anterior medial thigh sharing the most proximal medial portions with the ilioinguinal and genitofemoral nerves and a medial portion just superior to the medial femoral condyle with the obturator nerve. The posterior thigh medial to mid receives coverage from the posterior cutaneous nerve of the thigh and the lateral most portion covered by the lateral cutaneous nerve of the thigh.
As stated above, the compartment of the muscles found in the femoral region are generally intrinsic to the function of the compartment The anterior thigh muscles generally induce flexion and adduction of the hip and extension of the knee. Medial thigh muscles as a rule produce adduction, flexion, and internal rotation of the hip. Posterior thigh muscles generally induce extension, abduction, and internal/external rotation of the hip and flexion of the knee. The specific muscles of each compartment and their motor innervation include:
*Ssome exceptions to the general rules: sartorius flexes/abducts/externally rotates hip, tensor fasciae lata flexes/abducts hip, obturator externus externally rotates the hip.
Significant variants that can be present within the femoral region involve angle of inclination of the femoral head and neck, the origin of the profunda femoris and its lateral circumflex branches of the femoral artery, and the locations of vessels within the femoral canal. For the angle of inclination, an average measurement for an adult male is between 115 -140 degrees, adult females tending to run more acutely in comparison. Pathologically, whether due to a genetic defect in ossification or process that weakens the femoral neck (i.e., osteomalacia), a decreased angle is known as coxa vara, and an increased angle is termed coxa valga. As for the origin of the profunda femoris and circumflex branches, there are discrepancies on distance from the inguinal ligament as reported by various cadaveric studies; the most common origin pattern from the femoral artery has been found to be posterolateral, then followed by the next common being the posterior, and then the posteromedial. Not an extremely common variation though an important one due to its clinical implications in central femoral venous access, ultrasound-guided evaluations of several cases have reported a transposition of the femoral artery and vein in the femoral canal. The normal orientation being the femoral artery lateral and the femoral vein medial, several cases warn that without ultrasound guidance complications can arise due to this anatomical variation.
Surgical interventions commonly indicated in the femoral region involve the repair and fixation of femur fractures. Performed by orthopedic surgeons, several important notes merit consideration within the perioperative setting which involves the complex neuro-vasculature present around the proximal femur as outlined above. Interventions for repair and modes of fixation are dependent on the type of fracture; which in turn determines the specific anatomical considerations when performing these procedures:
Within the femoral region, two clinically significant anatomical associations are noted, which are heavily utilized by anesthesiologists for perioperative pain management in lower extremity procedures and intensivists and ED physicians in accessing central venous circulation via the femoral vein. Known as the femoral triangle and adductor canal, these anatomic associations serve as landmarks for important neuro-vasculature connected to tissues of the femoral region - providing motor/sensory innervation and blood supply. The femoral triangle is bordered superiorly by the inguinal ligament, medially by the adductor longus, and laterally by the sartorius. Running through this location, the femoral vein is the most medial and the femoral artery immediately lateral as they course through the femoral canal as formed by the fascia lata – both separated from the femoral nerve which runs immediately lateral to the canal The two blood vessels and a branch of the femoral nerve known as the saphenous nerve then dive deep to the sartorius muscle and enter the adductor canal. This association is bordered superficial medially by the sartorius muscle, deeply by the adductor longus muscle, and superficial laterally by the vastus medialis muscle. Contained within this canal are the structures mentioned above, the saphenous nerve being the most superficial, and the femoral vein medial and femoral artery lateral.
For perioperative pain management of the lower extremity, a nerve block can be administered to the femoral triangle, or in many cases both the femoral and adductor canals. Using ultrasound-guided needle insertion, space around the femoral and saphenous nerves within these neuro-vascular bundles can be infiltrated with analgesic agents. Common agents used in these blocks include lidocaine or bupivacaine, among other up and coming agents; the choice of agent used in the block based on the provider’s judgment and the reason for use.
Due to the typical location of the femoral vein within the femoral triangle and canal, ease of access allows providers to insert central IV lines if indicated. Though not the primary site for central catheter placement, this being the internal jugular vein, central venous access via femoral vein has been proven as an efficient alternative.
|||Ishiguro S,Yokochi A,Yoshioka K,Asano N,Deguchi A,Iwasaki Y,Sudo A,Maruyama K, Technical communication: anatomy and clinical implications of ultrasound-guided selective femoral nerve block. Anesthesia and analgesia. 2012 Dec; [PubMed PMID: 22886842]|
|||Runge C,Jensen JM,Clemmesen L,Knudsen HB,Holm C,Børglum J,Bendtsen TF, Analgesia of Combined Femoral Triangle and Obturator Nerve Blockade Is Superior to Local Infiltration Analgesia After Total Knee Arthroplasty With High-Dose Intravenous Dexamethasone. Regional anesthesia and pain medicine. 2018 May; [PubMed PMID: 29346228]|
|||Watanabe T,Ogihara H,Soeta T,Fujiwara T,Yoshida H, Comparison of range of motion during movement from supine to sitting position in healthy young and elderly participants. Journal of physical therapy science. 2019 Jan; [PubMed PMID: 30774215]|
|||Cowan PT,Kahai P, Anatomy, Bones 2018 Jan; [PubMed PMID: 30725884]|
|||Gold M,Varacallo M, Anatomy, Bony Pelvis and Lower Limb, Hip Joint 2018 Jan; [PubMed PMID: 29262200]|
|||Gupton M,Terreberry RR, Anatomy, Bony Pelvis and Lower Limb, Knee 2018 Jan; [PubMed PMID: 29763193]|
|||Yamauchi K,Kato C,Kato T, Characteristics of individual thigh muscles including cross-sectional area and adipose tissue content measured by magnetic resonance imaging in knee osteoarthritis: a cross-sectional study. Rheumatology international. 2019 Jan 28; [PubMed PMID: 30689015]|
|||Sheeba CJ,Andrade RP,Palmeirim I, Getting a handle on embryo limb development: Molecular interactions driving limb outgrowth and patterning. Seminars in cell [PubMed PMID: 25617599]|
|||Stainton H,Towers M, Polarizing Region Tissue Grafting in the Chick Embryo Limb Bud. Methods in molecular biology (Clifton, N.J.). 2018; [PubMed PMID: 30324596]|
|||Mróz I,Kielczewski S,Pawlicki D,Kurzydło W,Bachul P,Konarska M,Bereza T,Walocha K,Kaythampillai LN,Depukat P,Pasternak A,Bonczar T,Chmielewski P,Mizia E,Skrzat J,Mazur M,Warchoł Ł,Tomaszewski K, Blood vessels of the shin - anterior tibial artery - anatomy and embryology - own studies and review of the literature. Folia medica Cracoviensia. 2016; [PubMed PMID: 27513837]|
|||Rivera RE,Hootnick DR,Gingold AR,Levinsohn EM,Kruger LM,Packard DS Jr, Anatomy of a duplicated human foot from a limb with fibular dimelia. Teratology. 1999 Nov; [PubMed PMID: 10525205]|
|||Dennis SC,Berkland CJ,Bonewald LF,Detamore MS, Endochondral ossification for enhancing bone regeneration: converging native extracellular matrix biomaterials and developmental engineering in vivo. Tissue engineering. Part B, Reviews. 2015 Jun; [PubMed PMID: 25336144]|
|||Sun Q,Fan G,Li X,Gong J,Ge W,Cai M, Relationship Between Femur and Femoral Arteries for Identifying Risk Factors for Vascular Injury. Medical science monitor : international medical journal of experimental and clinical research. 2017 Apr 10; [PubMed PMID: 28392552]|
|||Mednick RE,Alvi HM,Morgan CE,Stover MD,Manning DW, Femoral vein blood flow during a total hip arthroplasty using a modified Heuter approach. The Journal of arthroplasty. 2015 May; [PubMed PMID: 25660612]|
|||Portugal IB,Ribeiro Ide L,Sousa-Rodrigues CF,Monte-Bispo RF,Rocha AC, Distribution of saphenous vein valves and its practical importance. Revista brasileira de cirurgia cardiovascular : orgao oficial da Sociedade Brasileira de Cirurgia Cardiovascular. 2014 Oct-Dec; [PubMed PMID: 25714210]|
|||Rao AS,Rajmanickam K,Narayanan GS, Study of distribution of inguinal nodes around the femoral vessels and contouring of inguinal nodes. Journal of cancer research and therapeutics. 2015 Jul-Sep; [PubMed PMID: 26458584]|
|||Fracol ME,Janes LE,Ko JH,Dumanian GA, Targeted Muscle Reinnervation in the Lower Leg: An Anatomical Study. Plastic and reconstructive surgery. 2018 Oct; [PubMed PMID: 30020229]|
|||Swezey E,Bordoni B, Anatomy, Head and Neck, Lateral Femoral Cutaneous Nerve 2018 Jan; [PubMed PMID: 30335334]|
|||Kendir S,Torun Bİ,Akkaya T,Comert A,Tuccar E,Tekdemir I, Re-defining the anatomical structures for blocking the nerves in adductor canal and sciatic nerve through the same injection site: an anatomical study. Surgical and radiologic anatomy : SRA. 2018 Nov; [PubMed PMID: 30167824]|
|||Üçeyler N,Vollert J,Broll B,Riediger N,Langjahr M,Saffer N,Schubert AL,Siedler G,Sommer C, Sensory profiles and skin innervation of patients with painful and painless neuropathies. Pain. 2018 Sep; [PubMed PMID: 29863528]|
|||Ransom AL,Nallamothu SV, Anatomy, Bony Pelvis and Lower Limb, Femoral Muscles 2018 Jan; [PubMed PMID: 29763184]|
|||Chang A,Hubbard JB, Anatomy, Bony Pelvis and Lower Limb, Femur 2018 Jan; [PubMed PMID: 30422577]|
|||Hartel MJ,Petersik A,Schmidt A,Kendoff D,Nüchtern J,Rueger JM,Lehmann W,Grossterlinden LG, Determination of Femoral Neck Angle and Torsion Angle Utilizing a Novel Three-Dimensional Modeling and Analytical Technology Based on CT Datasets. PloS one. 2016; [PubMed PMID: 26933877]|
|||Seto AH,Tyler J,Suh WM,Harrison AT,Vera JA,Zacharias SJ,Daly TS,Sparling JM,Patel PM,Kern MJ,Abu-Fadel M, Defining the common femoral artery: Insights from the femoral arterial access with ultrasound trial. Catheterization and cardiovascular interventions : official journal of the Society for Cardiac Angiography [PubMed PMID: 27566991]|
|||Nasr AY,Badawoud MH,Al-Hayani AA,Hussein AM, Origin of profunda femoris artery and its circumflex femoral branches: anatomical variations and clinical significance. Folia morphologica. 2014 Feb; [PubMed PMID: 24590524]|
|||Yu SK,Chung TT,Yeh CC,Cherng CH,Lin SL, A patient with femoral triangle anatomy transposition challenges NAVY rule. Journal of clinical anesthesia. 2018 Feb; [PubMed PMID: 29161543]|
|||Radowsky JS,Rodriguez CJ,Wind GG,Elster EA, A Surgeon's Guide to Obtaining Hemorrhage Control in Combat-Related Dismounted Lower Extremity Blast Injuries. Military medicine. 2016 Oct; [PubMed PMID: 27753567]|
|||Waewsawangwong W,Ruchiwit P,Huddleston JI,Goodman SB, Hip arthroplasty for treatment of advanced osteonecrosis: comprehensive review of implant options, outcomes and complications. Orthopedic research and reviews. 2016; [PubMed PMID: 30774467]|
|||Liu C,Von Keudell A,McTague M,Rodriguez EK,Weaver MJ, Ideal length of thread forms for screws used in screw fixation of nondisplaced femoral neck fractures. Injury. 2019 Jan 31; [PubMed PMID: 30772052]|
|||Gao YS,Guo YJ,Yu XG,Chen Y,Chen C,Lu NJ, A novel cerclage wiring technique in intertrochanteric femoral fractures treated by intramedullary nails in young adults. BMC musculoskeletal disorders. 2018 Oct 6; [PubMed PMID: 30292231]|
|||Streubel PN,Gardner MJ,Ricci WM, Management of femur shaft fractures in obese patients. The Orthopedic clinics of North America. 2011 Jan; [PubMed PMID: 21095432]|
|||Christ AB,Chawla H,Gausden EB,Villa JC,Wellman DS,Lorich DG,Helfet DL, Radiographic and Clinical Outcomes of Periprosthetic Distal Femur Fractures Treated With Open Reduction Internal Fixation. Journal of orthopaedic trauma. 2018 Oct; [PubMed PMID: 30247279]|
|||Lew V,Kang M, Anatomy, Abdomen and Pelvis, Femoral Sheath 2018 Jan; [PubMed PMID: 29494010]|
|||Wong WY,Bjørn S,Strid JM,Børglum J,Bendtsen TF, Defining the Location of the Adductor Canal Using Ultrasound. Regional anesthesia and pain medicine. 2017 Mar/Apr; [PubMed PMID: 28002228]|
|||Aso K,Izumi M,Sugimura N,Okanoue Y,Kamimoto Y,Yokoyama M,Ikeuchi M, Additional benefit of local infiltration of analgesia to femoral nerve block in total knee arthroplasty: double-blind randomized control study. Knee surgery, sports traumatology, arthroscopy : official journal of the ESSKA. 2018 Dec 8; [PubMed PMID: 30536047]|
|||Saugel B,Scheeren TWL,Teboul JL, Ultrasound-guided central venous catheter placement: a structured review and recommendations for clinical practice. Critical care (London, England). 2017 Aug 28; [PubMed PMID: 28844205]|