Lateral femur X-ray positioning (trauma)
An extra femur view, used when a routine one is not enough. The patient lies on their back, the beam passes from side to side, straight on to the receptor with the tube horizontal, and the centring point is the mid-shaft.
By the ScanFlo Editorial Team · Updated
In this section · X-ray positioning
- X-ray positioning guides
- Skull positioning
- Face & sinuses positioning
- Soft tissue neck positioning
- C-spine positioning
- Chest positioning
- Shoulder positioning
- Humerus positioning
- Elbow positioning
- Forearm positioning
- Wrist positioning
- Hand positioning
- T-spine positioning
- Abdomen positioning
- L-spine positioning
- Sacrum & SI joints positioning
- Pelvis positioning
- Hip positioning
- Femur positioning
- Knee positioning
- Tibia & fibula positioning
- Ankle positioning
- Foot positioning
Still being checked: a radiographer is reviewing this guide. If your department does it differently, follow your department.
Patient position
Supine. Do not move the injured leg. Detector vertical against it on a foam pad; raise and support the other leg.
Centring & collimation
Central ray
lateralCentre: the mid-shaft.
Beam: lateral, perpendicular to the receptor, horizontal beam.
Collimate: the knee and the shaft
Distance, receptor & grid
| Setting | Value | Notes |
|---|---|---|
| SID | 100 cm | Horizontal beam |
| Receptor | 18 × 43 cm | portrait |
| Placement | Erect (wall) bucky | Grid in |
| Angulation | None | Perpendicular to the receptor |
Marker & breathing
- Marker: R or L marker on the side nearest the detector
- Breathing: Suspend respiration.
Exposure by patient size
Treat these as a starting point. Your detector, your generator and the patient in front of you will all move the numbers.
| Patient size | kV | mAs (chart) | mAs (DR default) |
|---|---|---|---|
| XS | 70 | 6.3 | 2.5 |
| S | 70 | 10 | 4 |
| M | 70 | 12.5 | 5 |
| L | 70 | 20 | 8 |
These start from a classic film-screen chart (70 kV, 25 mAs at 140 cm) and are adjusted for a digital detector at 100 cm. The DR column is what ScanFlo's console suggests; each step up or down changes the mAs by about a quarter.
Image quality checklist
- The knee joint is shown.
- The anatomical side marker is visible, correct and clear of the anatomy.
- Collimation borders are visible on all sides, no wider than the area requested.
Faults & how to fix them
| Fault | Cause | Fix |
|---|---|---|
| Knee missed | Centring high | Make sure the knee is on the film. |
Common questions
- Where do you centre for a femur lateral (after injury) X-ray?
- The centring point is the mid-shaft.
- What distance and beam angle does a femur lateral (after injury) need?
- 100 cm from the tube to the receptor. The beam passes from side to side, straight on to the receptor with the tube horizontal.
- What size receptor, and do you need a grid?
- Use an 18 × 43 cm receptor, portrait, in the wall bucky. A grid is needed.
- What should the patient do with their breathing?
- Ask them to stop breathing for the moment of the exposure.
- What goes wrong most often on a femur lateral (after injury)?
- Knee missed. Usual cause: centring high. The fix: make sure the knee is on the film.
Try it in ScanFlo: the ScanFlo XR X-ray Room, coming soon, lets you set up a femur lateral (after injury) in a 3D room and score your positioning. See ScanFlo XR →
Written by the ScanFlo team from everyday radiographic practice.