Introduction

This e-Anatomy anatomical module is dedicated to the anatomy of the hip, showing the normal MRI appearance of the acetabular labrum, cartilage of the femoral head and acetabulum, capsule and capsular ligaments, bone structures, muscles, and tendon insertions on a high-resolution 3T MRI (multiplanar PD-FS and T1 images).

Magnetic resonance imaging (MRI) of the hip is indicated for a variety of clinical scenarios due to its high sensitivity and specificity in detecting both osseous and soft tissue abnormalities that may cause hip pain. The primary indications for a hip MRI include:

1. Detection of occult fractures: MRI is highly sensitive for identifying radiographically occult fractures, particularly in cases of acute hip pain with negative radiographs.
2. Evaluation of femoroacetabular impingement: MRI is useful in diagnosing FAI, which can lead to labral tears and cartilage abnormalities. This is particularly relevant in younger patients and athletes.
3. Assessment of labral and chondral lesions: MRI of the hip provides detailed visualization of the hip cartilage and labrum, aiding in the diagnosis of labral tears and chondral lesions.
4. Identification of soft tissue injuries: MRI is effective in evaluating musculotendinous injuries, ligament tears, and conditions like greater trochanteric pain syndrome and athletic pubalgia.
5. Detection of osteonecrosis: MRI is the most sensitive imaging modality for detecting early osteonecrosis of the femoral head, which is crucial for timely intervention.
6. Evaluation of neoplasms and infections: MRI is valuable in assessing primary and secondary neoplasms, as well as musculoskeletal infections such as septic arthritis and osteomyelitis.
    

Material and methods

This MRI of the hip was performed on a healthy female patient using a Siemens 3T MRI. (Images were provided by Pr. Catherine Cyteval-Montpellier, France).

Magnetic resonance imaging (MRI) of the hip employs various sequences and planes to provide comprehensive evaluation of joint structures. The primary sequences used include:

1. Proton Density with fat suppression (PD-FS): for evaluating acetabular labral tears, ligament injuries, and cartilage abnormalities and providing high contrast between different tissues.
2. T1 turbo spin echo (TSE): offers better delineation of certain anatomical structures such as muscles and tendons.

The primary imaging planes used in hip MRI are:

1. Axial Plane: provides cross-sectional images of the hip joint. It is useful for evaluating the femoral head, acetabulum, and surrounding soft tissues.
2. Coronal Plane: particularly useful for assessing the acetabular labrum, femoral head, and the relationship between the femoral head and acetabulum.
3. Sagittal Plane: beneficial for evaluating the anterior and posterior aspects of the hip joint, including the labrum and cartilage.

Labeled structures on this normal hip MRI are grouped in different categories:

• General anatomy: the different anatomical areas of the gluteal region (groin, inguinal region and the anterior and posterior regions of the hip and thigh).
• Bones: the femur and hip bone (subdivided into ilium, ischium, and pubis), as well as the sacrum, were labelled separately using different colours.
• Joints: identified in this MRI are the hip joint and the sacroiliac joint, as well as various foramina (obturator canal, small and large ischial foramina).
• Ligaments: the main ligaments of the hip and surrounding area (iliofemoral, ischiofemoral and pubofemoral ligaments, as well as the ligament of the head of the femur, also known as the round ligament).
• Muscles: muscle and tendon anatomy of the hip (adductors, gluteal muscles (or buttocks), hamstring muscles, femoral muscle quadriceps).
• Fascia: fascia lata and iliotibial tract.
• Bursae of the lower limb: the bursae of the hip region (trochanteric, ischial and iliopectineal bursae).
• Arteries: the arrangement of external and internal iliac arteries, as well as the common and deep branches of the femoral artery in the gluteal and hip regions.
• Veins: superficial (saphenous) and deep venous circulation (branches of the femoral veins).
  Lymph nodes: mainly the iliac and inguinal lymph nodes.
• Nerves: branches of the lumbosacral plexus, including the sciatic and femoral nerves.

The anatomical structures were labeled by Antoine Micheau M.D. (Radiologist, Montpellier – France), following the Terminologia Anatomica 2.