Fasciae of the Hip and Thigh
Fascia is a band of connective tissue located beneath the skin, which encloses and separates muscles. There are two main types of fascia: superficial and deep. The superficial fascia is attached to the dermis and aids in movement of the skin. The deep fascia is denser than its superficial counterpart and forms intermuscular septa, which are involved in the formation of muscular compartments. This article will talk about the structure and function of the fasciae of the hip and thigh, followed by any related clinical pathology.
Superficial Fascia of the Hip and Thigh
The superficial fascia of the hip and thigh is continuous with the fascia of the lower back posteriorly and the fascia of the abdominal region anteriorly. This fascia consists of loose areolar and adipose tissue. In the inguinal region, this fascia splits into two layers to enclose the long saphenous vein and superficial inguinal lymph nodes. The superficial fascia is referred to as the cribriform fascia as it is perforated by the long saphenous vein, lymphatic vessels and by superficial branches of the femoral vein.
Deep Fascia of the Hip
The deep fascia of the hip is thin over the gluteus maximus muscle but thickens over the anterior two-thirds of the gluteus medius muscle to form a strong aponeurosis. This aponeurosis is attached to the lateral aspect of the iliac crest and splits into two parts to enclose the tensor fascia latae and gluteus maximus muscles. The deep fascia is attached anteriorly to the inguinal ligament and the superior ramus of the pubis and posteriorly to the sacrum and coccyx bones. Medially, it is attached to the inferior pubic ramus and to the lower aspect of the sacrotuberous ligament as well as to the ramus and tuberosity of the ischium.
The fascia lata, the deep fascia of the thigh, varies in thickness and is continuous with the deep fascia of the hip. It is thicker in the proximal and lateral aspects of the thigh where it attaches to the gluteus maximus and tensor fasciae latae muscles. It is also thick around the knee joint. Over the adductor muscles and posterior aspect of the thigh, the fascia lata is thinner. The fascia lata is split into two layers, which are referred to as the superficial stratum and the deep stratum. The superficial stratum reflects inferolaterally from the pubic tubercle to form the arched falciform margin. Distally, the fascia lata attaches to the head of the fibula as well as to the tibial and femoral condyles. There are three modifications of the fascia lata, which are known as the:
- Iliotibial tract
- Intermuscular septa
- Saphenous opening
On the lateral aspect of the thigh, the fascia lata thickens to form the iliotibial tract. Superiorly, the iliotibial tract splits into a superficial and a deep layer. The superficial layer is attached to the iliac crest and descends lateral to the tensor fasciae latae muscle. The deep layer is medial to this muscle and blends with the capsule of the hip joint. Distally, the iliotibial tract blends with the aponeurosis of the vastus lateralis muscle before it attaches to Gerdy’s tubercle, which is located on the anterolateral surface of the lateral tibial condyle.
There are two intermuscular septa formed by the fascia lata and these septa form the anterior, posterior and medial compartments of the thigh. These septa are referred to as:
- The medial septum
- The lateral septum.
The medial septum is thinner and weaker than the lateral one and lies between the vastus medialis anteriorly and the adductor and pectineus muscles posteriorly.
The lateral septum descends from the gluteus maximus muscle to the lateral condyle of the femur and lies between the vastus lateralis and the short head of the biceps femoris muscle. Both of these septa are attached to the linea aspera of the femur.
In the deep fascia, there is an opening 3 cm lateral to the pubic tubercle, which allows the passage of the long saphenous vein. This aperture, referred to as the saphenous opening, is covered by the superficial fascia and is located inferomedial to the superficial stratum of the fascia lata. It is located lateral to the deep stratum and its superior, inferior and lateral borders are formed by the arched falciform margin.
The iliac fascia covers the psoas major and iliacus muscles and thickens as it descends towards the inguinal ligament. Superiorly, the part covering the psoas major muscle thickens as the medial arcuate ligament. Medially, fibrous arches attach the fascia to the upper part of the sacrum and to the lower lumbar intervertebral discs and vertebral bodies. The fascia blends with the quadratus lumborum fascia superior to the iliac crest and with the fascia covering the iliacus posterior to the crest.
The part of the fascia that covers the iliacus muscle is connected to the iliac crest laterally and the pelvic brim medially. The fascia, located between the external iliac vessels and the branches of the lumbar plexus, is separated from the peritoneum by loose extraperitoneal tissue. Medially, the fascia descends posterior to the femoral vessels to become the pectineal fascia. The iliac part forms a septum between the hip-bone and the inguinal ligament, forming a vascular space medially and a muscular space laterally. The psoas major, iliacus and femoral nerve are located within the muscular space whereas the vascular space contains the femoral vessels.
The femoral sheath is a funnel-shaped continuation of the transversalis fascia and the iliac fascia and consists of three compartments. The lateral compartment contains the femoral artery whilst the femoral vein is located in the intermediate compartment. The medial compartment, the femoral canal, consists of lymphatic vessels, is 2.5 cm long and allows distension of the femoral vein. The proximal end of the canal, the femoral ring, consists of extraperitoneal tissue and is larger in women. This is because females have a wider pelvis and have smaller femoral vessels.