10.3 Femur & Hip
Key Takeaways
- Femur AP and lateral require inclusion of both hip and knee joints when possible, often as two overlapping fields on adults; true AP shows the femoral neck without excessive foreshortening when the leg is slightly internally rotated.
- Routine non-trauma hip AP uses ~15–20° internal rotation of the feet to place the femoral necks parallel to the IR; bilateral hips may be included on a pelvis-centered AP when indicated.
- Frog-leg lateral (modified Cleaves) abducts and flexes the hips for a lateral neck/proximal femur view but is contraindicated when femoral neck or intertrochanteric fracture is suspected.
- Trauma proximal femur/hip laterals use cross-table axiolateral inferosuperior methods (Danelius-Miller concept) with the unaffected leg elevated and the IR vertical against the affected hip.
- Neck of femur (NOF) and intertrochanteric fractures are common in older adults; never frog-leg a suspected hip fracture—obtain AP pelvis/hip and horizontal-beam lateral per trauma protocol.
10.3 Femur & Hip
Quick Answer: Image the entire femur with AP and lateral that include hip and knee (two fields if needed). For the hip in non-trauma patients, AP with 15–20° internal rotation and a frog-leg (modified Cleaves) lateral are common. If fracture of the femoral neck or intertrochanteric region is possible, do not frog-leg—use AP pelvis/hip and a cross-table axiolateral (Danelius-Miller / inferosuperior) lateral. CAMRT items punish unsafe positioning of hip fractures as hard as they punish rotated anatomy.
General radiography — skeletal (femur and hip) is high-stakes skeletal content: missed NOF fractures and displaced fragments from improper movement are patient-safety failures as well as image-quality failures. RTR.4 procedure skill and Care Provider competencies meet at the stretcher side.
Femur
| Projection | Setup | CR | Evaluation |
|---|---|---|---|
| AP | Supine; leg extended; internally rotate foot ~5–15° (neck parallel principles for proximal; epicondyles parallel for distal) | Mid-femur; include both joints via one or two images | Entire femoral shaft; hip and knee included with overlap on dual fields; no rotation (epicondyles symmetric distally; lesser trochanter partially hidden proximally with proper IR) |
| Lateral | True lateral of the segment imaged; for distal femur, lateral recumbent with epicondyles perpendicular; for proximal, often use hip lateral methods | Mid-femur of the segment | Superimposed condyles distally; true lateral shaft; joints included |
Two-image rule: Adult femurs rarely fit one 35×43 cm field with both joints. Acquire proximal and distal AP (and lateral) with generous overlap so mid-shaft fractures are not cropped at field edges. Collimate to the segment but never exclude a joint when the clinical question is trauma to the whole bone.
Proximal femoral laterals in trauma are not standard mediolateral tabletop rolls when hip fracture is suspected—use axiolateral hip techniques described below.
Hip — AP
| Projection | Setup | CR | Evaluation |
|---|---|---|---|
| AP unilateral hip | Supine; internally rotate affected foot 15–20° unless fracture suspected and rotation impossible | Perpendicular to femoral neck (approx. 2.5–4 cm distal to mid-inguinal point / localized by ASIS–symphysis localization methods taught in lab) | Greater trochanter in profile; lesser trochanter minimally visible or superimposed; neck without severe foreshortening; acetabulum and proximal third of femur included |
| AP pelvis (for bilateral hips / trauma survey) | Supine; both feet inverted 15–20° if safe | Midway between ASIS and pubic symphysis, MSP | See pelvis section (10.4); both hips comparable |
Why internal rotation? In anatomic neutral, the femoral neck is anteverted and rises anteriorly; without internal rotation the neck is foreshortened and the lesser trochanter projects prominently. Internal rotation places the neck parallel to the IR, elongates the neck, and hides the lesser trochanter—evaluation criteria used constantly in critique questions.
Trauma exception: If the leg is already shortened and externally rotated (classic NOF presentation), do not force internal rotation. Image as found for the initial AP, then obtain the horizontal-beam lateral. Forcing rotation can displace an unstable neck fracture.
Frog-Leg Lateral — Modified Cleaves
| Aspect | Detail |
|---|---|
| Purpose | Lateral projection of the femoral head, neck, and proximal third in non-trauma (e.g., pediatric DDH follow-up concepts, outpatient proximal femur) |
| Position | From supine, flex knee and hip; abduct thigh ~45° (bilateral modified Cleaves for comparison); plantar surfaces may approximate; pelvis remains as flat as possible |
| CR | Perpendicular to femoral neck / mid-way between ASIS and pubic symphysis for bilateral; to affected neck for unilateral |
| Evaluation | Femoral neck superimposed by greater trochanter appropriately for method; lesser trochanter in profile anteriorly; no pelvic rotation on bilateral |
Trauma precautions (critical)
Do not perform frog-leg (modified Cleaves) when femoral neck, intertrochanteric, or subtrochanteric fracture is suspected. Abduction and external rotation stresses the fracture line and can convert a non-displaced neck fracture into a displaced one—raising avascular necrosis risk and surgical complexity. CAMRT application stems frequently test this safety rule.
Also avoid frog-leg after acute hip dislocation until the referring team has directed post-reduction imaging protocols.
Cross-Table Lateral Hip — Danelius-Miller (Axiolateral Inferosuperior)
This is the trauma lateral of choice for suspected proximal femoral fracture.
| Step | Action |
|---|---|
| 1 | Patient supine; do not forcibly rotate the affected limb |
| 2 | Flex and elevate the unaffected hip and knee; support so the thigh is out of the beam |
| 3 | Place IR vertical against the affected lateral hip/iliac wing, parallel to the femoral neck as much as possible |
| 4 | Internally rotate the affected foot only if already known safe / ordered—otherwise leave as found |
| 5 | Direct CR horizontal, perpendicular to the IR, through the femoral neck |
| 6 | Use grid cassette oriented correctly for horizontal beam; collimate tightly; shield gonads when not obscuring anatomy per policy |
Evaluation criteria: Femoral head, neck, trochanters, and acetabulum demonstrated; ischial tuberosity and soft tissue of elevated thigh not superimposing the neck; neck elongated without extreme distortion; marker visible.
Related axiolateral concepts
- Clements-Nakayama (modified axiolateral): used when both hips are limited (e.g., bilateral arthroplasty or bilateral trauma) and the unaffected leg cannot be elevated for classic Danelius-Miller—IR tilted and CR angled posteriorly ~15–20° to match. Know that alternatives exist when the “good leg up” position is impossible.
- Inferosuperior geometry: beam travels from medial to lateral through the neck onto a vertical IR—this is not a standard table Bucky lateral roll.
High-Yield Fracture Patterns
| Pattern | Typical context | Imaging implications |
|---|---|---|
| Intracapsular neck of femur (NOF) | Older adult fall; shortened, externally rotated leg; AVN risk | AP pelvis + AP hip as found; cross-table lateral; no frog-leg |
| Intertrochanteric | Extracapsular; between greater and lesser trochanters; older adults | Same trauma series; lesser/greater trochanter involvement affects classification |
| Subtrochanteric | Below lesser trochanter; high-energy or pathologic in some cases | Include enough shaft distal to the lesser trochanter; full femur may be needed |
| Femoral shaft | High energy; check hip and knee joints for associated injury | Overlapping AP/lateral femur fields; both joints |
| Posterior hip dislocation | High energy; femoral head superior/lateral on AP | AP pelvis; lateral/oblique per trauma protocol; reduction imaging after orthopedic management |
Avascular necrosis context (NOF): The femoral head’s blood supply (retinacular vessels along the neck) is vulnerable after displaced intracapsular fractures. Your job is not surgical staging—it is safe, complete radiographic demonstration without adding displacement.
Technique & Image Quality
Hips and proximal femurs usually require grid technique, higher kVp than distal extremities, and careful AEC chamber selection (center chamber over neck/head region per protocol—not over radiopaque hardware alone). For prosthesis follow-up, include the entire length of the femoral stem and cement mantle when that is the clinical question—cropping the tip of a stem is a common reject.
Radiation protection: collimate; use gonadal shielding when it does not cover required pelvic bony anatomy and aligns with current departmental guidance; minimize repeats through correct centering the first time. Pregnancy status must be checked per facility protocol for any pelvic-region exam (see also 10.4).
Care Provider Notes at the Hip Stretcher
- Verify identity, consent, and correct side (wrong-site imaging of hips is a never-event risk).
- Log-roll and transfer with enough staff; support the injured limb.
- Pain control and explanation reduce motion unsharpness.
- Document “imaged as found—external rotation” when internal rotation is unsafe.
- Communicate with the referring team if the patient cannot tolerate elevation of the opposite leg for Danelius-Miller so an alternate axiolateral can be planned.
CAMRT Application Focus
When a stem describes an elderly patient with a shortened, externally rotated lower limb after a fall, select AP pelvis/hip without forced internal rotation and Danelius-Miller (or equivalent) cross-table lateral, and explicitly reject frog-leg. When a young outpatient needs non-trauma proximal femoral laterals, modified Cleaves is appropriate. When a femur trauma series is ordered, guarantee both joints across overlapping fields. Safety plus geometry—neck parallel on AP when safe, horizontal-beam lateral when not—is the competency package for hip imaging under RTR.4.
Why is the affected foot usually internally rotated 15–20° for a non-trauma AP hip projection?
A stretcher patient has a suspected femoral neck fracture. Which lateral projection strategy is most appropriate?
Which statement best reflects safe practice when a hip fracture is clinically likely and the leg is already externally rotated?
For AP and lateral radiography of the adult femoral shaft after trauma, which inclusion rule is correct?