Dunn 90 view: Definition, Uses, and Clinical Overview

Dunn 90 view Introduction (What it is)

Dunn 90 view is a specialized hip X-ray view taken with the hip flexed to about 90 degrees.
It is designed to better show the shape of the femoral head and neck (the “ball” and the nearby bone).
Clinicians commonly use it when evaluating hip pain, reduced motion, or suspected femoroacetabular impingement (FAI).
It is one of several “lateral” hip projections that complement a standard front-view pelvis X-ray.

Why Dunn 90 view used (Purpose / benefits)

The main purpose of the Dunn 90 view is to improve visualization of the front (anterior) and upper (anterosuperior) portion of the femoral head–neck junction. That region is a common location for subtle bony shape changes that may contribute to hip pain and restricted movement.

In many patients, a standard AP (front-view) pelvis X-ray does not fully show the contour of the femoral head–neck junction. The Dunn 90 view changes the hip position so that this contour is more clearly profiled on the radiograph. This helps clinicians:

• Detect or better characterize cam morphology (a loss of the normal “waist” at the head–neck junction), often discussed in the context of FAI.
• Evaluate anatomy relevant to labral and cartilage stress (soft tissues are not directly visible on X-ray, but bony shape can suggest risk patterns).
• Compare sides for asymmetry and assist in preoperative planning when surgery is being considered (varies by clinician and case).
• Standardize imaging so measurements (such as certain angle-based assessments) are more reproducible when performed consistently.

Overall, the Dunn 90 view is a diagnostic tool that supports clinical decision-making by clarifying bone shape and alignment in a position that can reveal abnormalities not obvious on routine views.

Indications (When orthopedic clinicians use it)

Orthopedic, sports medicine, and radiology teams may request a Dunn 90 view in scenarios such as:

• Hip or groin pain with concern for femoroacetabular impingement (FAI)
• Suspected cam-type femoral head–neck abnormality
• Limited hip flexion or internal rotation on exam, prompting evaluation of bony contributors
• Preoperative or pre-procedural imaging workup for hip preservation evaluation (varies by clinician and case)
• Follow-up imaging to compare known femoral head–neck morphology over time (when clinically justified)
• Assessment of hip shape in patients with prior hip conditions or childhood hip disorders where residual deformity is a concern (case dependent)
• Clarifying findings seen on an AP pelvis view when a lateral profile is needed

Contraindications / when it’s NOT ideal

Because Dunn 90 view requires positioning the hip in significant flexion (and often mild abduction), it is not ideal in certain situations. Clinicians may choose a different view or imaging method when:

• Severe pain prevents safe positioning or tolerating hip flexion
• Acute trauma is present and moving the hip could worsen injury (decision varies by clinician and setting)
• Concern exists for an unstable fracture, dislocation, or immediately post-operative restrictions where flexion is limited
• Marked stiffness or contracture prevents achieving the intended position, reducing image quality
• Patient factors limit positioning (e.g., body habitus, inability to lie flat, severe back pain affecting positioning)
• Pregnancy or other situations where minimizing radiation exposure is a priority; alternative imaging may be considered depending on clinical necessity and local protocols (varies by clinician and case)
• Another projection is more appropriate for the clinical question (for example, a cross-table lateral for certain trauma evaluations)

In these cases, the “best” alternative depends on the suspected diagnosis, urgency, and what the patient can safely tolerate.

How it works (Mechanism / physiology)

Dunn 90 view is not a treatment and does not have a physiologic “mechanism of action” like a medication would. Instead, its value comes from biomechanics and geometry: changing hip position changes what parts of the bone are most visible and how contours overlap on a 2D X-ray image.

At a high level:

• Principle: By flexing the hip to about 90 degrees (and commonly adding slight abduction), the X-ray beam and hip orientation better profile the anterosuperior femoral head–neck junction.
• Relevant anatomy:
• Femoral head: the ball of the hip joint
• Femoral neck: the narrowed segment below the head
• Head–neck junction: where cam-type contour changes are often assessed
• Acetabulum: the socket; acetabular overcoverage patterns are typically assessed with other views too, but the Dunn 90 view can contribute to overall interpretation
• Clinical rationale: Cam morphology can create abnormal contact between the femur and acetabulum in certain hip positions. While the X-ray cannot show cartilage or the labrum directly, it can show bony contours that may be associated with impingement patterns.

Onset/duration/reversibility: These concepts do not apply in the usual way because Dunn 90 view is an imaging projection. The “effect” is immediate—an X-ray image is produced—and there is no lasting change to the body from the positioning itself. The only exposure is a small amount of ionizing radiation typical of diagnostic radiography, managed using standard safety protocols.

Dunn 90 view Procedure overview (How it’s applied)

Dunn 90 view is an imaging step within a broader clinical evaluation. Exact techniques vary by facility, radiology department protocol, and patient factors, but the general workflow is:

1. Evaluation/exam
   A clinician evaluates symptoms, hip range of motion, and medical history and decides whether specialized hip radiographs are needed (often alongside an AP pelvis view).

2. Preparation
   – The technologist confirms patient identity and the requested views.
   – The patient changes as needed to remove objects that may obscure the image (e.g., metal).
   – Radiation safety steps are followed per local policy.

3. Positioning and image acquisition (testing)
   – The patient is positioned on the X-ray table.
   – The hip is flexed to approximately 90 degrees for the Dunn 90 view.
   – The technologist aligns the leg and pelvis according to protocol so the femoral head–neck contour is well profiled.
   – The X-ray is taken; sometimes repeat images are needed if motion or positioning limits clarity.

4. Immediate checks
   The technologist checks image quality (coverage, rotation, visibility of landmarks). If needed, an additional image may be obtained.

5. Follow-up
   A radiologist or clinician interprets the study, often in combination with other hip views. Findings are then integrated with symptoms, exam results, and—when appropriate—additional imaging such as MRI.

Types / variations

“Dunn view” is a family of lateral hip projections, and the name is sometimes used loosely. Variations typically differ by degree of hip flexion and amount of abduction, which changes what part of the femoral head–neck junction is emphasized.

Commonly referenced variations include:

• Dunn 90 view
  Hip flexed to about 90 degrees; used to profile the anterior/anterosuperior head–neck junction.

• Dunn 45 view (or modified Dunn)
  Hip flexed to about 45 degrees (details vary by protocol). Some clinicians prefer it for certain measurement consistency or patient tolerance (varies by clinician and case).

• Frog-leg lateral
  Another lateral projection with hip flexion and abduction, often easier for some patients but not identical in what it shows.

• Cross-table lateral (horizontal beam lateral)
  Frequently used in trauma or when moving the hip is not advisable; emphasizes different geometry and may be preferred when stability is a concern.

• AP pelvis and specialized acetabular views
  The Dunn 90 view is rarely used alone. It is often paired with AP pelvis and other projections that evaluate acetabular coverage and pelvic alignment.

Different facilities may use slightly different naming and positioning conventions, so interpretation typically considers the protocol used.

Pros and cons

Pros:

• Improves visualization of the femoral head–neck junction compared with AP-only imaging
• Helpful for assessing cam-type morphology in a standardized lateral projection
• Generally quick to obtain as part of routine hip radiograph series
• Widely available in settings that perform diagnostic X-rays
• Can support measurement-based assessments when positioning is consistent (varies by clinician and case)
• Noninvasive and does not require injections or contrast

Cons:

• Requires hip flexion; may be difficult with pain, stiffness, or acute injury
• Image quality is sensitive to positioning and pelvic rotation, which can affect interpretation
• Shows bones well but does not directly visualize cartilage or the labrum
• Uses ionizing radiation (though typically low-dose for diagnostic X-rays)
• May not answer the full clinical question by itself; additional views or imaging may still be needed
• Naming and technique can vary between facilities, which can complicate comparison across studies (varies by protocol)

Aftercare & longevity

Because Dunn 90 view is an X-ray projection rather than a treatment, there is usually no aftercare in the way there would be after an injection or surgery. Most people can resume typical activities immediately, unless their underlying condition limits them.

Practical factors that influence the “usefulness over time” include:

• Clinical context: The value of the image depends on symptoms, physical exam, and the differential diagnosis.
• Image quality: Proper positioning and minimal motion improve interpretability.
• Progression of the underlying condition: Bone morphology is generally stable in adults, but symptoms and related soft-tissue injury patterns can change; clinicians may or may not repeat radiographs depending on the case.
• Follow-up plan: Some patients proceed to additional imaging (e.g., MRI to evaluate labrum/cartilage) or nonoperative vs operative pathways; imaging is one input among many (varies by clinician and case).
• Comparability: Using consistent protocols over time helps when comparing prior and current images.

Alternatives / comparisons

The Dunn 90 view is one option among several ways to evaluate hip pain and hip structure. Alternatives are chosen based on the question being asked—bone shape, joint space, soft tissue injury, or acute injury assessment.

Common comparisons include:

• AP pelvis vs Dunn 90 view
• AP pelvis provides a front-on overview of pelvis alignment, joint space, and acetabular coverage patterns.

• Dunn 90 view adds a lateral profile that can better show anterior head–neck contour.

• Frog-leg lateral vs Dunn 90 view
  Both are lateral-style hip views, but they are not interchangeable. Some clinicians use one or both depending on the suspected abnormality, patient tolerance, and local protocol (varies by clinician and case).

• Cross-table lateral vs Dunn 90 view
  Cross-table lateral is often favored in trauma or when hip motion should be minimized. Dunn 90 view may be less suitable if flexion is unsafe or too painful.

• MRI vs Dunn 90 view

• MRI is commonly used to assess soft tissues like the labrum, cartilage, and surrounding tendons.

• Dunn 90 view assesses bony morphology. Many workups use both when indicated, since they answer different questions.

• CT vs Dunn 90 view
  CT can provide detailed 3D assessment of bone anatomy and version/rotation measurements, but involves more radiation than standard radiographs and is not always needed. Dunn 90 view is often a first-line bony assessment because it is simpler and more accessible.

• Ultrasound vs Dunn 90 view
  Ultrasound can evaluate certain soft-tissue structures and fluid collections and can guide injections, but it does not profile bony head–neck shape the same way as radiographs.

In practice, clinicians select imaging based on suspected diagnosis, exam findings, safety, availability, and what information would change management (varies by clinician and case).

Dunn 90 view Common questions (FAQ)

Q: Is the Dunn 90 view the same as a regular hip X-ray?
It is a type of hip X-ray, but it is not the standard front-view image. Dunn 90 view is a specialized lateral projection designed to better show the femoral head–neck contour. It is usually taken alongside other views rather than by itself.

Q: Why would my clinician order a Dunn 90 view for hip pain?
It is commonly used when the clinician wants a clearer look at the femoral head–neck junction, especially if femoroacetabular impingement (FAI) is being considered. The view can highlight bony shape features that may be less obvious on an AP pelvis image. Interpretation is typically combined with your symptoms and exam.

Q: Does the Dunn 90 view hurt?
The X-ray itself is painless, but the positioning can be uncomfortable if hip flexion is limited or painful. Technologists typically try to position you as comfortably and safely as possible while obtaining a diagnostic image. If pain limits positioning, a different view may be chosen (varies by clinician and case).

Q: How long does it take to get the Dunn 90 view done?
The imaging portion is usually brief and often completed within a standard radiograph appointment. Time can vary depending on how easily you can be positioned and whether repeat images are needed for clarity. Reporting turnaround varies by facility.

Q: What does the Dunn 90 view show that an MRI would not?
Dunn 90 view is particularly focused on bony contour and can be useful for assessing femoral head–neck shape. MRI is better for soft tissues like cartilage and the labrum. Many evaluations use radiographs for bone structure and MRI when soft-tissue detail is needed (varies by clinician and case).

Q: Is there radiation exposure with a Dunn 90 view?
Yes. It is a diagnostic X-ray and uses ionizing radiation. Facilities use standard protocols to keep exposure as low as reasonably achievable while still obtaining a useful image.

Q: Can I drive or go back to work after the Dunn 90 view?
In most cases, yes, because it is an imaging test and does not involve sedation. Any limitations are more likely related to your underlying hip condition rather than the X-ray itself. Individual circumstances vary.

Q: Does the Dunn 90 view require contrast dye or an injection?
No. It is a plain radiograph and does not require contrast. If contrast is involved in hip evaluation, it is typically related to specific MRI techniques or injection-based procedures, not the Dunn 90 view.

Q: How much does a Dunn 90 view cost?
Costs vary widely by country, healthcare system, facility type, insurance coverage, and whether it is bundled into a multi-view hip series. The most accurate estimate comes from the imaging center or your insurer. Clinicians generally order it based on diagnostic value rather than price alone.

Q: How long do the “results” last?
The image is a snapshot of bone anatomy at the time it is taken. In adults, bone shape often changes slowly, but symptoms can change even if the X-ray looks similar. Whether repeat imaging is needed depends on clinical changes and the care plan (varies by clinician and case).