Introduction
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| Tensor Fasciae Latae Muscle |
The muscle of the proximal anterolateral thigh located between the superficial and deep fibers of the iliotibial (IT) band is called the tensor fasciae latae (TFL). Although there is a lot of variation in the length of the muscle belly, the TFL muscle belly stops before the greater trochanter of the femur in the majority of patients.
For flexion, abduction, and internal rotation of the hip, the TFL collaborates with the gluteus maximus, gluteus medius, and gluteus minimus. This muscle helps in knee flexion and lateral rotation by acting through the tibia's connection to the iliotibial (IT) band. Clinically speaking, the TFL is particularly crucial for supporting pelvic stability during standing and walking.
Tensor fasciae latae muscle Anatomy
Origin and insertion
The muscle arises from the anterior iliac crest’s outer lip and the anterior superior iliac spine. Its fibres connect proximally to the fascia lata, a deep tissue that surrounds the whole thigh muscles.
The iliotibial tract is a horizontal reinforcement formed by the tensor fasciae latae, gluteus maximus fibres, and gluteus medius aponeurosis. This connective tissue band travels laterally across the knee joint, inserting at the lateral condyle of the tibia and the lateral patellar retinaculum.
Nerve Supply
The superior gluteal nerve, L4, L5, and S1 innervate the Tensor fasciae latae muscle (TFL). Originating from the anterior rami of L4-S1, the superior gluteal nerve goes parallel to the superior gluteal artery and vein. It passes superior to the piriformis and emerges from the pelvis via the larger sciatic foramen. The gluteus minimus and TFL muscles are where this nerve ends after running anterior to the gluteus maximus muscle.
Blood Supply and Lymphatics
The superior gluteal artery's deep branch supplies blood to the Tensor fasciae latae muscle (TFL). The greatest branch of the internal iliac artery’s posterior division, the superior gluteal artery passes between the first sacral nerve root and the lumbosacral trunk posteriorly. The greater sciatic foramen serves as the superior gluteal artery’s egress from the pelvis, where it splits into superficial and deep branches. To nourish the gluteus medius and minimus as well as the TFL, the deep branch passes between them.
Structure and Function
The TFL descends between and is linked to the deep fascia and the superficial fascia of the IT band. It starts at the anterior superior iliac spine (ASIS) and the anterior side of the iliac crest. The TFL runs superficially to the greater trochanter of the femur as it descends on the anterolateral side of the thigh. The fascial aponeurosis of the gluteus maximus and the tensor fascia latae make up the IT track/band, where the TFL inserts distally. After there, the IT band continues down the lateral part of the thigh to the Gerdy tubercle, which is the lateral condyle of the tibia.
Despite its little size, the TFL collaborates with other muscle groups to support hip and knee mobility and stabilisation.
This muscle works in tandem with the gluteus medius and minimus as well as the gluteus maximus via the IT band to abduct and internally rotate the hip.
Through the IT band’s connection to the lateral tibia’s Gerdy tubercle, the TFL performs its effect on the tibia. Although it is only visible when the knee is flexed over 30 degrees, the TFL is a supporting knee flexor. Moreover, the TFL and IT band collaborate to stabilize the knee during full extension. The lateral rotation of the tibia is also influenced by the TFL through the IT band. As is evident when kicking a football, this lateral rotation may be executed with the hip in the abduction and medial rotation positions.
In terms of clinical use, the TFL’s main purpose is to facilitate walking. The contralateral hip rises as a result of the TFL pulling the ilium inferiorly on the weight-bearing side. During the swing phase of the stride, the leg can swing through without touching the ground thanks to the elevation in the non-weight-bearing hip.
Embryology
One skeletal muscle is the TFL. Skeletal muscle is formed by the paraxial mesoderm, which also forms somitomeres in the head and somites from the occipital to the sacral regions. The progenitor cells known as myoblasts fuse together to form long multinucleated muscle fibres during embryonic development. Myofibrils are seen in the cytoplasm, and by the third month’s end, cross-striations are seen. Tendon is produced by sclerotome cells that are positioned next to myotomes at the boundaries of somites (both anterior and posterior), and it will eventually connect the TFL to the Gerdy tubercle of the tibia.
One kind of transcription factor that controls tendon growth is SCLERAXIS. Together with WNT proteins from nearby ectoderm, lateral plate mesodermal fibroblast growth factors and bone morphogenetic protein 4 (BMP4) instruct the dermomyotome VLL cells to produce the muscle-specific gene MyoD. WNT protein synthesis is stimulated by BMP4 through the dorsal neural tube. In the meanwhile, the dermomyotome DML cells are exposed to the low osmolarity of sonic hedgehog (SHH) proteins, which are released by the neural tube’s floor plate and the notochord. The induction of MYF5 and MyoD endocytosically is caused by these expressions. Myogenic regulatory factors (MRFs) are transcription factors that activate TFL and other pathways involved in muscle development. MyoD and MYF5 belong to this family.
Clinical Significance
When there is tension, friction across or between bony prominences, or when the TFL is attached to the IT band, it can become clinically relevant. Particularly when there is a protracted shortening, such while sitting, the TFL may get constricted. An anterior pelvic tilt and/or medial femur rotation might result from a shortened TFL.
Patients with external snapping hip syndrome describe a perceptible snap that happens with different motions on the lateral part of their hip. Although there are several possible causes of this illness, the IT band shifting across the greater trochanter is the most frequent cause. The posterior band of the IT fascia is assumed to have thickened as a result of this. Even while people with this illness frequently do not complain of discomfort, it might eventually become uncomfortable. Physical therapy along with oral NSAIDs is the usual conservative treatment approach.
A frequent overuse ailment seen in cyclists and runners is IT band syndrome. Patients complain of knee discomfort on the lateral side. Although the exact cause of IT band syndrome is unknown, most experts concur that it falls into one of three primary categories:
Deep to the ITB, compression of the fat and connective tissue
Prolonged inflammation of the bursa in the IT band
Physiologic Variants
While the TFL usually ends before the greater trochanter, it can continue distally to the trochanter in around one-third of cases. This is important from a clinical standpoint since in certain cases, a lateral approach to the proximal femur requires splitting the TFL fibres.
Surgical Considerations
The anterior, anterolateral, posterior, and medial surgical methods are the four fundamental hip joint surgical techniques used in orthopaedics. Surgical landmarks such as the TFL are employed in anterior and anterolateral approaches. The internervous plane between the sartorius (femoral nerve) and the TFL (superior gluteal nerve) is used for the anterior approach to the hip. The intermuscular plane between the TFL and gluteus medius is used in the anterolateral approach to the hip. This method lacks a real internervous plane since the superior gluteal nerve innervates both the gluteus medius and the TFL. But very near to its origin at the iliac crest, the superior gluteal nerve enters the TFL.
The TFL can be utilised to cover soft tissue in reconstructive surgery. There have been documented cases of the TFL being used for free, regional, and local flaps. The TFL is not usually the first option for free flaps because of its modest size, although there have been case reports of TFL free flaps being used in the absence of latissimus dorsi and rectus abdominis flaps. By using the lateral circumflex system of the femoral vasculature, the TFL can be utilised in combination with an anterolateral thigh flap when a significant region has to be covered.
