Orthopedic X Ray Interpretation Basics Explained with Examples

Orthopedic X ray is the first line imaging technique to look for fractures and joint injuries

Different tissues of human body have different densities, the higher the density, the more radiopaque (white) appears on x ray film, and lesser the density the more radiolucent (black) appears

What to look for in an Orthopedic X ray radiograph

Bones
Joints
Soft tissue

1. Bones

look at the anatomy of the bone, is it normal? , and follow the cortex of the bone looking for cracks. E.g. shoulder radiograph, look at the anatomy, are the humerus, scapula and clavicle bones in their normal positions?, then follow the cortex of these bones looking for cracks If you see the fracture then start by evaluating the fracture then look elsewhere

General appearance of the bone: Look for the density of the bone, is it low density (osteopenia or osteoporosis) or high density (osteosclerosis), abnormal trabeculation (in Paget’s disease)

Look for any lesions in the bone, and if there is any then evaluate each lesion for:

Location of the lesion: (medullary, endosteal, cortical, periosteal)
Look for margin of the lesion: well defined margin (means non aggressive pathology) vs ill defined margin (aggressive pathology)
also look at the morphology of the lesion which could be circular , ovoid …

Look at the lesion matrix, could be lytic lesion in MM and metastases, could be fibrous lesion which appears as ground glass on x ray and occur in fibrous dysplasia ; could be cumulous cloud in osteoid lesion, popcorn in cartilaginous lesion, could be soap bubbly in cystic lesions

Look for periosteal reaction to the lesion: (reaction of the periosteum to the irritation caused by the lesion) could be smooth/benign periosteal reaction in benign lesions, could be lamellated in moderately growing lesion, could be hair on end in fast growing, and could be codman triangles in rapid rate of growth of a lesion

Look for extra osseous or soft tissue involvement

2. Joint

Articular cartilage is radiolucent on X ray, that is why the joint space is radiolucent (occupied by the articular cartilage), articular cartilage varies in thickness depending on the joint, e.g. knee joint is 6mm

Look for the shape of the joint, and congruity of the bone ends, look for narrowing or asymmetry of the joint space (narrowing occurs in joint infection, inflammatory arthropathies and osteoarthritis), look for erosions of the bone ends (occur in arthropathies)

Look at the subchondral bone, it might be sclerosed, or there might be radiolucent bone cysts (osteoarthritis)

Look at the joint margin looking for osteophytes (bone spurs)

3. Soft tissues

Soft tissues planes are often visible

Look for any changes in the soft tissue, e.g. soft tissue mass, calcification, gas (in gas forming infection), foreign body, swelling of the soft tissue around interphalangeal joints suggest rheumatoid arthritis …

Fracture Description

Important to learn how to describe fractures so you can communicate your findings with the other team members and with your seniors

Start by mentioning the patient name, age and presentation

After that, you mention the shape of the fracture: transverse, spiral, oblique, comminuted, segmental

Then you mention fracture location, you describe it according to the location on the bone (long bone: head, neck, shaft, condyle OR epiphysis, metaphysis, diaphysis)

Examples: fracture in the distal metaphysis of the femur OR fracture in the inferior third of the shaft of the femur

Finally you mention displacement, you describe the displacement of distal fragment in relation with the proximal fragment

We have four patterns of displacement: translation (shift), angulation (tilt), rotation, shortening vs lengthening, depressed

And you mention the direction of the displacement (anterior, posterior, medial, lateral)

If not displaced, you say without displacement

Rule of twos in trauma x rays

Two views: AP and lateral views give you a better definition of the pathology
Two joints: the joints above and below the fracture must be included in the x ray , because the bone that is fractured maybe associated with a dislocated joint or another fracture somewhere else on the bone
Two limbs: x ray of the uninjured limb can be used for comparison used in children because the immature epiphysis make it hard to diagnose fractures
Two injuries: in high energy injuries, there is more than one fracture, e.g. if there is femur fracture, expect pelvic or spine fracture associated with it
Two occasions: take x rays on multiple occasions after the injury time because some fractures difficult to detect immediately after injury but they become clear after a week or two of the injury. E.g. scaphoid fractures, femoral neck and stress fractures