Hip protocol (MRI)

The MRI hip protocol encompasses a set of different MRI sequences for the routine assessment of the single hip joint.

Note: This article aims to frame a general concept of an MRI protocol for the assessment of a single hip joint. Protocol specifics will vary depending on MRI scanner type, specific hardware and software, radiologist and perhaps referrer preference, patient factors e.g. implants, specific indications and time constraints

Indications

Typical indications include pain in the hip and/or buttock, hip-related groin pain, decreased range of motion, limping and comprise the following:

• osteonecrosis of the hip 
• transient bone marrow edema syndrome
• femoral insufficiency or stress fracture
• different forms of hip impingement
• labral and/or chondral injury
• trochanteric syndrome
• rectus femoris injury

1.5 vs 3 tesla

Musculoskeletal examinations are generally done on both 1.5 and 3 tesla and this is also the case for the hip. They profit from the improved spatial and contrast resolution of 3 tesla. Postoperative examinations in patients with metallic implants, however, should be done on 1.5 tesla with metal artifact reduction sequence.

Patient positioning

An MRI of the hip is conducted with the patient in the supine position.

Technical parameters

Coil

Multi-phased array coils are recommended. The more channels the better.

• one option is a medium flexible coil
• an alternative option is the anterior surface coil

Scan geometry

The hip should be examined with a good spatial resolution.

• in-plane spatial resolution: ≤0.4 x 0.4 mm
• field of view (FOV): ~160 mm
• slice thickness: ≤3 mm
• 3D-GRE with an isotropic spatial resolution of ≤0.7 mm

Planning

A typical MRI of a single hip joint might look like as follows:

• coronal images: in case of suspected extraarticular or acetabular pathology, labral or chondral lesions
  • angulation: strictly coronal      
  • volume: includes everything from the anterior margin of the symphysis to the ischial bone
  • slice thickness: ≤3 mm
• coronal oblique images: in case of proximal femoral pathology e.g. osteonecrosis of the hip, transient bone marrow edema syndrome or assessment of cam morphology
  • angulation: parallel to the femoral neck axis
  • volume: includes whole acetabulum proximal femur and trochanter
  • slice thickness: ≤3 mm
• sagittal images:
  • angulation: strictly sagittal 
  • slice thickness: ≤3 mm
  • volume: includes the greater trochanter and the whole acetabulum
• axial images: in case of suspected extraarticular pathology,
  • angulation: strictly axial to the body axis
  • volume: from the anterior inferior iliac spine to the proximal femur including the lesser trochanter
• axial oblique: in case of articular or proximal femoral pathology
  • angulation: parallel to the femoral neck axis
  • slice thickness: ≤3 mm
• 3D imaging
  • angulation: coronal
  • spatial resolution: isotropic ≤0.7 mm

Sequences

The mainstay in musculoskeletal imaging are water-sensitive sequences, this can be achieved with STIR or fat-saturated images or with intermediate weighted images and is no different for the hip.

At least one T1-weighted sequence should be included to ease the assessment and interpretation of bone marrow and/or soft tissue lesions.

Standard sequences

Most indications for an MRI of the hip joint do not require any contrast media: 

• intermediate weighted (fat-saturated)
  • purpose: bone and/or soft-tissue characterization, detailed anatomy
  • technique: IM fast spin echo
  • planes: coronal, sagittal, axial or coronal oblique* and axial oblique* depending on the pathology
• T1 weighted
  • purpose: bone and/or soft-tissue characterization
  • technique:  T1 fast spin echo
  • planes: coronal, sagittal* (option in osteonecrosis of the hip insufficiency fracture, transient bone marrow edema)
• 3D imaging
  • purpose: for radial reconstructions in femoroacetabular impingement, labral or chondral pathology
  • technique:  3D GRE
  • acquisition plane: coronal or axial, radial MPR along the femoral neck axis

Optional sequences

•  ​T2 weighted*
  • purpose: bone and/or soft-tissue characterization, in particular in tumors or nerve disorders
  • technique: T2 fast spin echo
  • planes: axial* (optional for tumor characterization)

Some indications might benefit from an application of contrast media as e.g. osteonecrosis of the hip, tumors or inflammatory disease   

• T1 weighted C+ (fat-saturated)
  • technique:  T1 fast spin echo
  • purpose: for inflammatory conditions, osteonecrosis of the hip insufficiency fracture, transient bone marrow edema, bursitis or tumors
  • planes: coronal, sagittal, axial depending on the question

(*) indicates optional planes or sequences

MR arthrography of the hip

The most accurate procedure for the assessment of femoroacetabular impingement, labral and chondral lesions including intraarticular loose bodies.

• intermediate weighted (fat-saturated)
  • technique: IM fast spin echo
  • plane: coronal oblique
• T1 weighted
  • technique: T1 fast spin echo
  • planes: sagittal, axial oblique
• T1 weighted (fat-saturated)
  • technique:  T1 fast spin echo
  • plane: coronal oblique
• 3D imaging
  • purpose: for radial reconstructions in femoroacetabular impingement, labral or chondral pathology
  • technique:  3D GRE
  • acquisition plane: coronal or axial, radial MPRs along the femoral neck axis

Practical points

• the protocol can and should be tailored to the specific indication or clinical question
• the examination will benefit if every plane is imaged
• for an overview one of the coronal plains either intermediate weighted or T1 weighted can be performed with an increased field of view covering both hips
• the assessment of the acetabulum for chondral and labral injury really benefits from 3D imaging, which can be radially constructed afterwards
• 3D imaging is also an option if sagittal 2D planes suffer permanently from phase encoding artifacts
• a typical native protocol will contain 4-5 sequences