Resources/Protocols
Hip (FAI & labrum)
A deep, curved joint where the labrum wraps a full circle and the femoral head is prone to avascular necrosis. The radial 'clock-face' sequence, spun around the femoral head, is what profiles the entire labrum.
When this study is used
- Femoroacetabular impingement (FAI) or labral tear.
- Groin or hip pain, clicking or catching.
- Suspected avascular necrosis of the femoral head.
Patient & coil positioning
- Head-first supine; feet gently internally rotated and strapped to profile the femoral neck.
- Torso/cardiac array for large-FOV survey, or a dedicated surface coil for high-resolution hip imaging.
- Centre on the femoral head; pad for comfort — hip patients struggle to stay still in pain.
Localizer
Three-plane localizer showing the whole femoral head, neck and acetabulum.
Sequence planning
Each sequence below lists how the slice group is positioned — the reference line it follows, its coverage, and why it earns its place in the protocol. Plan against the localizer, not by eye.
Coronal T1 + PD/T2 fat-sat
CoronalPlanning — Parallel to the femoral-neck axis on the axial.
Why — Bone anatomy and marrow (T1); bone-marrow oedema of impingement (fat-sat).
Radial PD fat-sat ('clock face')
RadialPlanning — 6–12 slices radiating from the centre of the femoral head like spokes on a wheel, on the axial.
Why — True perpendicular views of the entire acetabular labrum — the key to catching subtle tears anywhere around the rim.
Sagittal / axial-oblique fat-sat
Sagittal / axial obliquePlanning — Perpendicular to the femoral neck (sagittal); axial oblique for the anterosuperior labrum.
Why — The anterosuperior labrum — the commonest impingement and tear site.
Coronal STIR
CoronalPlanning — Matched coverage.
Why — Early AVN oedema before subchondral collapse.
Representative parameters
Ranges, not commandments — field strength, coil and vendor move the numbers. What must not move is understanding why each sits where it does.
| Sequence | Field | Notes |
|---|---|---|
| Coronal T1 | 1.5–3 T | Anatomy, marrow, AVN line |
| Radial PD FS | 1.5–3 T | 6–12 spokes; whole labrum |
| STIR | 1.5–3 T | Early AVN oedema |
| MR arthrogram T1 FS | 1.5–3 T | If intra-articular contrast given |
Artifacts & how to fix them
| Artifact | Typical cause | Mitigation |
|---|---|---|
| Bowel / vessel motion | Nearby pelvic structures | Saturation bands; adequate coverage |
| Poor labral detail | Curved labrum not cut perpendicular | Radial sequence for true cross-sections |
| Metal blooming | Hip prosthesis | High bandwidth; TSE over GRE; MARS if available |
| Motion (pain) | Uncomfortable patient | Padding; shorten with parallel imaging |
What am I looking at?
You are not reporting the study, but recognising pathology helps you keep it in the field of view and know when to add a sequence or contrast. How the common findings read on the console:
| Finding | Sequence to check | How it reads |
|---|---|---|
| Labral tear | Radial / coronal PD FS | Bright signal into the labral substance or detaching it from the rim |
| Avascular necrosis | Coronal T1 + STIR | Serpiginous dark line on T1; bright marrow oedema early on STIR |
| FAI (cam/pincer) | Radial / axial oblique | Bony bump at the head–neck junction; marrow oedema |
Review checklist
- Coronal aligned to the femoral-neck axis.
- Radial sequence covers the labrum around the whole clock face.
- Anterosuperior labrum profiled on the oblique.
- STIR reviewed for early AVN.
Mistakes that cost repeats
- Relying on orthogonal planes that cut the curved labrum obliquely.
- Missing early AVN by skipping a fat-sensitive sequence.
- Femoral neck not profiled because of external rotation.
- Motion from an uncomfortable, painful hip.
Common questions
- Why use a radial sequence for the hip labrum?
- The acetabular labrum wraps around the joint as a curve. A radial acquisition takes slices that spoke out from the centre of the femoral head, giving true perpendicular cross-sections of the labrum at every 'clock position' — so a tear anywhere around the rim is seen properly.
- How does avascular necrosis appear on hip MRI?
- As a serpiginous (snake-like) low-signal line beneath the articular surface on T1, often with bright bone-marrow oedema on STIR early on — before the subchondral bone collapses, which is when treatment still helps most.
- Why internally rotate the feet for a hip MRI?
- Gentle internal rotation profiles the femoral neck, so coronal and sagittal slices aligned to the neck axis show the head–neck junction and the weight-bearing surfaces in a standard, comparable way.
Try it in ScanFlo: Plan a radial stack spoking out from the femoral head, then a standard coronal, and compare how the labrum is cut. The radial views show it in true cross-section all the way round — which is why subtle tears hide from orthogonal planes.