Femoral and lateral femoral cutaneous nerve symptoms are a common presentation in osteopathic practise.
These symptoms are not always caused by an entrapment neuropathy. However cases that are and amenable to osteopathic treatment can be greater understood by appreciating the relation of the femoral nerve and lateral femoral cutaneous nerve to the psoas, iliacus, fascia iliaca and inguinal ligament.
The key clinical points in this article are:
- The relationship of the psoas major with the femoral and lateral femoral cutaneous nerves.
- The relationship of the psoas minor with the fascia iliaca.
- The relationship of the fascia iliaca and iliacus muscle sandwiching the femoral nerve.
- Entrapment of the lateral femoral cutaneous nerve in the fascia iliaca-internal oblique septum.
- Entrapment of the lateral femoral cutaneous nerve in the fascia between the tensor fascia lata and sartorius (including the iliolata ligaments).
- Treatment options for the fascia iliaca in relation to its anatomical connections to the iliacus, psoas major, psoas minor, inguinal ligament and fascia lata.
This article outlines:
- Anatomy of the femoral nerve.
- Anatomy of the lateral femoral cutaneous nerve.
- Anatomy of the fascia iliaca.
- Anatomy of the inguinal ligament (& mechanical movement of the inguinal ligament).
- Anatomy of the lacunar ligament.
- Function of the inguinal and lacunar ligaments.
Anatomy of the femoral nerve
The femoral nerve is the largest branch of the lumbar plexus originating from the dorsal divisions of the ventral rami of L2-4.
It descends through the posterior third of the psoas major muscle and emerges from its postero-lateral border at the junction of the muscles upper two thirds and lower one third.
Desouki et al (2016) found the psoas major composed of two sections. The whole of the lumbar plexus, including the femoral and lateral femoral cuatneous nerves, runs between these two sections:
- Anterior section: comprises of fleshy slips that arise from the anterolateral part of the vertebral bodies of T12-L5 and their corresponding intervertebral discs. This makes the main part of the psoas major.
- Posterior section: comprises of strips that originate from the front and lower border of the transverse processes of T12-L5. This makes the accessory part of the psoas major.
After exiting the psoas major the femoral nerve then travels caudally in the gutter between the bulk of the psoas major and the iliacus deep to the fascia iliaca.
It enters the thigh behind the inguinal ligament in the potential space of the fascia iliaca compartment (lacuna musculorum). The nerve travels in this compartment tightly sandwiched between the floor, (formed by the iliacus and psoas major) and the roof, (formed from the fascia iliacus).
This compartment is lateral to the femoral artery and vein being separated from the femoral artery by the fascia iliaca (iliopectineal ligament, refer anatomy of the fascia iliaca).
Motor innervation: quadriceps femoris and sartorius muscles.
Sensory innervation: anteromedial surface of the thigh. Via the femoral nerves terminal branch, the saphenous nerve, the medial aspect of the lower leg, ankle and foot.
Lateral Femoral Cutaneous Nerve
The lateral femoral cutaneous nerve arises from the dorsal divisions of L2 and L3.
It emerges from the lateral border of the psoas major and runs on the anterior surface of the iliacus muscle being covered by the fascia iliaca. The relation of all the nerves of the lumbar plexus to the psoas major is described by Desouki et al (2016) in the section above ‘femoral nerve’.
Passing behind the inguinal ligament close to its lateral insertion at the ASIS, the lateral femoral cutaneous nerve perforates the fascia iliaca.
The lateral femoral cutaneous nerve exits the pelvis via a tendinous canal within the internal oblique-iliac fascia septum. This canal may make the lateral femoral cutaneous nerve susceptible to mechanical entrapment near the ASIS.
The nerve then runs in an adipose compartment between the sartorius and iliolata ligaments inferior to the ASIS.
Xu et al (2018) found the iliolata ligaments are 2-3 curtain strip-like structures which attached to the ASIS superiorly and are interwoven with the fascia lata inferomedially, and continued laterally as skin ligaments anchoring to the skin.
Between the sartorius and tensor fasciae latae, the lateral femoral cutaneous nerves runs in a longitudinal ligamental canal bordered by the iliolata ligaments.
Putzer et al (2017) noted dense fascial fibers after dissecting the interval between the tensor fascia lata, sartorius, and rectus femoris. They described a strong band of fibers extending from a proximal-lateral to distal-medial direction.
Henry (1957) possibly described these same fascial webs that are found in the layers that occupy “the space between the origins of the rectus femoris and tensor fasciae [lata] muscles, uniting the deep aspects of their sheaths”.
Xu et al (2018) identified possible sites of entrapment of the lateral femoral cutaneous nerve in the internal oblique-iliac fascia septum and the iliolata ligaments. Could the dense fascia between the tensor fascia lata and sartorius with the iliolata ligaments also be a site of entrapment for the lateral femoral cutaneous nerve?
Once in the thigh the lateral femoral cutaneous nerve splits into its terminal cutaneous branches, which usually cross over the sartorius muscle and are covered by the fascia lata.
Innervation: sensory supply to the lateral aspect of the thigh as far distal as the knee.
Anatomy of the fascia iliaca
The fascia iliaca covers the iliacus and psoas muscle. Whilst a single structure the fascia of the iliacus and psoas major are decribed separately.
The iliacus fascia lines the pelvis (inner lip of the iliac crest and pelvic brim), covering the iliacus muscle and extending down to the anterior thigh. Meyer (1927) found the iliac fascia to merge very intimately with the periosteum around the pelvic brim and the innominate bone where no muscles seperated the fascia from the underlying bone.
Around the pelvic brim at the iliopubic ramus, the iliacus fascia receives a slip, when present, from the psoas minor. It also blends superiorly at this point with the transversalis fascia.
Inferiorly the iliacus fascia blends with the transversalis fascia at:
- Femoral sheath: the iliacus fascia forms the posterior wall of the femoral sheath. The transversalis fascia, scarpa's fascia and fascia lata form the anterior wall (Lytle 1956).
- Beneath the lateral part of the inguinal ligament: McWhinne (1835) decsribed the fusion of the iliacus and transversalis fascia as forming a fibrous cul-de-sac preventing the viscera prolapsing beneath the lateral part of the inguinal ligament. Teale (1846) found by "destroying" this aponeurotic cul-de-sac the peritoeum could be pushed "very easily" by the finger between the inguinal ligament and iliacus muscle.
The transversalis fascia is the fascia anterior to the transverse abdominis and quadratus lumborum extending medially to cover the anterior aspect of the psoas major where it gets renamed the psoas fascia. The fascia seperates these muscles from the retroperitoneal abdominal contents. Superiorly it forms the subdiaphragmatic fascia travelling through the medial and lateral arcuate ligaments and aortic hiatus to become the endothoracic fascia. Inferiorly it blends with the iliacus fascia (Elsharkawy et al 2019) and forms the endopelvic fascia, that lines the walls and floor of the pelvis covering the obturator internus, piriformis, levator ani and coccygeus (Raychaudhuri & Cahill 2008).
Lateral to the femoral vessels the iliac fascia is continuous with the posterior margin of the inguinal ligament.
Posterior to the inguinal ligament the iliacus fascia relations are:
- Iliopectineal ligament (or arch): the iliacus fascia forms the iliopectineal ligament. This ligament extends from the lateral part of the inguinal ligament to the iliopectineal eminence. It can receive attachments from the psoas minor.
The iliacus fascia then extends from the iliopectineal eminence to the hip joint capsule.
The iliopectineal ligament acts as a septum dividing the space under the inguinal ligament into a lateral compartment (psoas major, iliacus and femoral nerve) and medial compartment (femoral artery laterally and femoral vein medially).
The lateral compartment contains the fascia iliaca compartment (lacuna musculorum). The floor of this compartment is formed by the iliacus and psoas major, the roof by the fascia iliacus. Sandwiched between the floor and the roof is a potential space containing the femoral nerve.
The medial compartment contains the femoral sheath. The posterior wall of the femoral sheath is formed from the iliacus fascia (lacuna vasorum). The anterior wall of the femoral sheath is formed from the transversalis fascia, fascia lata and fascia of Scarpa (Lytle 1956). The femoral sheath contains the femoral artery and vein.
- Pectineal ligament: the iliacus fascia passes behind the femoral vessels to become the pectineal ligament (lacunar ligament --> pectineal line of the pubic bone).
- Muscular attachment: the iliacus fascia, in its own right and as a continuation of the transversalis fascia, gives attachment to the internal oblique and transverse abdominis muscles (Lytle, 1974). Xu et al (2018) identified the internal oblique-iliac fascia septum as a potential site of entrapment for the lateral femoral cutaneous nerve.
- Iliopubic tract: the iliopubic tract is a thickening of the transversalis fascia. The iliacus fascia provides a lateral attachment to the iliopubic tract as it extends from the transversalis fascia to the fascia iliacus (Teoh et al 1998).
- The iliacus fascia descends into the thigh as the fascia lata and is also continuous with the sartorius and pectineal fascia (a condensation of the transversalis fascia overlying the pectineal ligament).
The iliacus fascia covers the:
- Femoral nerve.
- Obturator nerve.
- Lateral femoral cutaneous nerve.
The Psoas fascia attachments are:
- Superior: the psoas fascia blends with the diaphragm (medial arcuate ligament, Van Dyke et al 1987 and right and left crus, Sajko & Stuber 2009) and lumbar spine via the diaphragmatic attachments (including anterior longitudinal ligament, Sajko and Stuber 2009). Van Dyke et al (1987) found the psoas fascia continuous superiorly with the endothoracic fascia. The transversalis fascia extends around the inner surface of the transverse abdominis, quadratus lumborum and the psoas major, where it gets renamed the psoas fascia. It thus forms one continuous fascial sheet. Extending superiorly, to form the subdiaphragmatic fascia, the transversalis fascia passes through the medial and lateral arcuate ligaments and aortic hiatus to be renamed the endothoracic fascia (Elsharkawy et al 2019).
- Inferior: the psoas fascia merges with the endopelvic fascia of the pelvic floor (this forms a link with the conjoint tendon, transverse abdominus, and the internal oblique, Sajko & Stuber 2009), pelvic brim (as the psoas major courses over the pelvic brim the fascia of the posterior fascicles attach firmly to it Sajko & Stuber 2009) and the fascia lata (Van Dyke et al 1987). Again the transversalis fascia extends over the psoas major where it gets renamed the psoas fascia making them “both” one continuous sheet of fascia. As well as blending with the iliacus fascia Raychaudhuri & Cahill (2008) found the transversalis fascia descends as the endopelvic fascia lining the walls and floor of the pelvis covering the obturator internus, piriformis, levator ani and coccygeus.
- Anteriorly: the psoas fascia merges with the fascia that covers the kidneys, the pancreas, the descending aorta, the inferior vena cava, the colon (ascending and descending), the duodenum and the cecum (Bordoni and Varacallo 2019)
- Posteriorly: the psoas fascia merges with the transversalis fascia covering the quadratus lumborum.
Contiguous structures include (Van Dyke et al 1987):
- Vertebral bodies.
- Intervertebral discs.
- Posterior paraspinal muscles.
- Innominate bone.
- Lumbar vessels.
- Branches of the sympathetic trunk that pass beneath the tendinous arches of the psoas major.
- Nerves of the lumbar plexus pass through the psoas major.
Anatomy of the inguinal ligament
The inguinal ligament extends from the ASIS to the pubic tubercle and pectin pubis. Some fibres near the ASIS may end in the fascia lata.
The inferior surface of the narrow lateral half of the inguinal ligament is fixed to the fascia lata. This part of the fascia lata is an extension of the fascia iliaca. The fascia iliaca descends over the iliacus, under the inguinal ligament attaching to its underside and into the thigh as the fascia lata.
The under surface of the medial part of the inguinal ligament, before it reaches its attachment to the pubic tubercle and pecten pubis, is fixed to the pectineus muscle and fascia (a condensation of the transversalis fascia overlying the pectineal ligament).
The superior aspect of the inguinal ligament gives attachment to the internal oblique and transverse abdominis. Lytle (1974) found the fascia iliaca, posterior to the inguinal ligament, also gave attachment to muscle fibres of the internal oblique and transverse abdominis muscles. Xu et al (2018) found the internal oblique-iliac fascia septum as a potential site of entrapment for the lateral femoral cutaneous nerve.
Fascia lata arises from the posterior border of the inguinal ligament.
- Femoral sheath: the fascia lata passes down to cover and blend with the anterior wall of the femoral sheath. Here it blends with Scarpa’s fascia and the transversalis fascia as it descends from the anterior abdominal wall over the inguinal ligament (Lytle 1956). The posterior wall of the femoral sheath is formed from the fascia iliaca.
- Lacunar ligament: medial to the femoral sheath the fascia lata attaches to the posterior border of the inguinal ligament to form the lacunar ligament.
The myofascial attachments of the inguinal ligament are:
- Cremaster muscle (Lunn 1948).
- Deep fascia of pectineus (Lunn 1948)
- External oblique aponeurosis: forms the medial half of the inguinal ligament (Lunn 1948).
- Fascia iliaca: a thickened strip of the fascia iliaca forms the superolateral part of the iliopectineal arch (Acland 2008).
- Fascia lata (Lytle 1974).
- Transversalis fascia.
- The iliopubic tract or deep femoral arch (Lytle 1974).
Mechanical movement of the inguinal ligament
Lunn (1948) found the medial half of the inguinal ligament is more mobile than the lateral. (No author, 1835) found when the thigh is extended and rotated outwards this produced a stretch on the crural arch (inguinal ligament) drawing it downwards without producing much effect upon the lacunar ligament. This was produced by stretching the part of the fascia lata attaching on to [and forming] part of the lacunar ligament and anterior part of the femoral canal. The author found flexing and rotating the thigh inwards had the opposite effect.
Anatomy of the lacunar ligament
The lacunar ligament is attached in front to the posterior border of the inguinal ligament and behind the pecten pubis being fused, along with the inguinal ligament, to the pectineus muscle and its fascia (a condensation of the transversalis fascia overlying the pectineal ligament).
The lacunar ligament, with the pectineus muscle and its fascia, passes upwards and backwards to reach the pectineal ligament on the pecten pubis
The lacunar ligament is derived from the fascia lata of the thigh. It is reinforced by the transversalis fascia. It gives rise to the anterior part of the femoral canal and supports the femoral vein.
The fascia lata attaches to the lacunar ligament and continues down to blend with the medial aspect of the femoral sheath. As it descends in the thigh it is known as the cribiform fascia.
Function of the inguinal and lacunar ligaments
The inguinal and lacunar ligaments:
- Forms a strong protective diaphragm between the abdomen and the thigh.
- Forms a broad aponeurotic floor for the inguinal canal which keeps its anterior and posterior walls apart to give roomy passage for the spermatic cord.
- Supports the femoral sheath and holds open the lumen of the large thin-walled femoral vein, fixed within the walls of the femoral sheath, amid the stresses and strains of thigh movement and variations of intra-abdominal pressure and body posture.
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