Orthopedic Imaging Lecture by Justin C. Willingham PA-C

Orthopedic Imaging

Justin C. Willingham PA-C

OBJECTIVES

• Chapter 22: Recognizing Nontraumatic Abnormalities of the Appendicular Skeleton Including Arthritis

• Chapter 23: Recognizing Nontraumatic Abnormalities of the Spine

• Chapter 24: Recognizing Trauma to the Bony Skeleton

  • Identify common upper/lower extremity fractures, dislocations, and deformities.

  • Identify common radiographic findings of lower extremity pathology.

  • Discuss the types of views obtained with common dislocations.

  • Identify soft tissue pathology and appropriate imaging choice.

  • Describe in detail fractures and dislocations.

  • List a systematic approach to interpreting plain orthopedic images.

Recognizing Trauma to the Bony Skeleton

• Types of fractures:

  • Acute Fractures

  • Dislocations and Subluxations

  • Avulsion Fractures

  • Salter-Harris Fractures

  • Stress Fractures

  • Common Fractures

  • Subtle Fractures and Dislocations

  • Fractures of the Upper and Lower Extremities

  • Spinal Trauma

  • Pathologic Fractures

General Principles

• Studies of bones should include at least two views at 90-degree angles to each other, referred to as orthogonal views.

• Many protocols may also call for two additional oblique views for enhanced visualization of the cortex.

• Computed Tomography (CT) and Magnetic Resonance Imaging (MRI) can demonstrate the entire circumference and internal structure of bone, including surrounding soft tissues that are not visible on conventional radiographs.

Recognizing An Acute Fracture

• Definition of a Fracture: A disruption in the continuity of all or part of the cortex of a bone.

  • Complete Fracture: Cortex is broken completely through.

  • Incomplete Fracture: Part of the cortex is fractured.

• Characteristics of an Acute Fracture:

  • Abrupt disruption of all or part of the cortex.

  • Acute changes in the smooth contour of normal bone.

  • Fracture lines are black and linear.

  • Fracture lines change course at sharply angulated points.

  • Fracture fragments are jagged, lacking a smooth corticated appearance.

Fracture Line Orientations

• Types include:

  • Transverse

  • Oblique

  • Spiral

  • Comminuted

  • Segmental

  • Torus

  • Greenstick: Incomplete fracture characterizing one side of the cortex failing while the other side remains intact.

Pseudofractures: Ossicles and Sesamoids

• Sesamoids: Bones that form in a tendon as it passes over a joint.

• Accessory Ossicles: Accessory epiphyseal or apophyseal ossification centers that fail to fuse with their parent bone.

• Old, unhealed fracture fragments can mimic acute fractures.

Fractures vs Ossicles / Sesamoids Comparison

Recognizing Subluxations and Dislocations

• Subluxation: The bones of a joint are in partial contact with one another.

• Dislocation: The bones of a joint are not in apposition to one another.

Describing Fractures and Dislocations

• Parameters and Terms Used:

  • Number of fracture fragments: Simple (2) or Comminuted (more than 2).

  • Direction of fracture line: Transverse, Oblique, Spiral.

  • Relationship of one fragment to another: Displacement, angulation, shortening, and rotation.

  • Open/Closed: Open or closed (compound).

  • Location, Degree, Articulation involvement.

  • Comminution pattern and intrinsic bone quality.

Displacement and Angulation

• Displacement: Offset from anterior, posterior, or lateral views of the proximal fragment in relation to the distal fragment.

• Angulation: The angle formed between distal and proximal fragments.

• Shortening: Overlap of fracture ends.

• Rotation: Movement along the bone's axis.

Closed vs Open Fractures

• Closed Fracture: No communication between fracture fragments and the outside environment. Common type.

• Open Fracture (Compound Fracture): Communication exists between the fracture and outside atmosphere, such as when a fragment penetrates the skin.

Examples of Fractures

• Transverse Fracture: Proximal left humerus

• Comminuted Fracture: Left humerus with articular extension

• Spiral Fracture: Distal third of left tibia with mild varus angulation

• Buckle Fracture: Left distal radius with no significant displacement.

Avulsion Fractures

• Occur when a fragment of bone is pulled away by a tendon or ligament.

• Commonly seen in young athletes and occur in predictable anatomical locations.

Salter-Harris Fractures

• These are epiphyseal plate fractures in children characterized by:

  • SALT C:

  • S: Straight

  • A: Above

  • L: Below

  • T: Through

  • C: Crush

Stress Fractures

• Result from microfractures due to repeated stretching and compressive forces.

• Initially may appear normal on conventional radiographs (up to 85%).

• Best diagnostic study is technetium 99 bone scan or MRI.

• Common locations include:

  • Shafts of long bones

  • Proximal femur, superolateral proximal tibia

  • Calcaneus

  • Second and third metatarsals (March fractures).

Common Fractures Eponyms

• Colles Fracture: Distal radius fracture with dorsal angulation.

  • Caused by a fall on outstretched hand (FOOSH).

• Smith Fracture: Fracture of distal radius with volar angulation.

  • Caused by a fall on the back of a flexed hand.

• Jones Fracture: Transverse fracture of the fifth metatarsal.

  • Caused by plantar flexion and inversion of the ankle.

• Boxer’s Fracture: Fracture of the neck of the fifth metacarpal, often caused by punching.

• March Fracture: Type of stress fracture from repeated microfractures due to marching, typically affecting the second and third metatarsals.

• Lisfranc Fracture-dislocations: Resulting from foot injuries, involved in athletic injuries or accidents.

Subtle Fractures and Dislocations

• Common Injuries:

  • Scaphoid Fracture: Suspected with tenderness in the anatomic snuff box after FOOSH.

  • Buckle Fracture of Radius/Ulna: Characterized by acute angulation of the cortex near the wrist.

  • Radial Head Fracture: Most common elbow fracture in adults.

  • Supracondylar Fracture of Distal Humerus: Common in children.

  • Posterior Dislocation of the Shoulder: Rare but can occur.

  • Hip Fractures in the Elderly: Often due to osteoporosis.

Spinal Trauma

• Fractures are critical due to implications for spinal cord injury.

• CT has mostly replaced radiography for evaluation of spinal trauma.

• Moreover, CT is effective for detecting bony lesions and soft-tissue abnormalities not visible in conventional methods.

• Compression fractures: Most common type of spinal fracture.

Specific Types of Spinal Fractures

• Jefferson Fracture: C1 fracture from axial loading injuries; usually no neurologic deficits.

• Hangman’s Fracture: Fracture of C2 caused by hyperextension; best evaluated on lateral view of the cervical spine.

• Burst Fracture: High-energy fractures from axial loading, may lead to neurologic deficits;
  assessed best by CT.

• Chance Fracture: Transverse fractures associated with lap belt usage during accidents.

Pathologic Fractures

• Occur in already weakened bone with minimal trauma.

• Common in osteoporotic individuals.

• Typical locations include pelvis, thoracic spine, sacrum, tibia, calcaneus.

Recognizing Non-traumatic Abnormalities of the Skeleton and Spine

• Normal Bone and Joint Anatomy: Clear cortex, medullary cavity, and corticomedullary junction.

• Diseases Influencing Bone Density: Adverse conditions resulting in either increased or decreased bone densities include:

  • Increased Density Conditions: e.g., osteoblastic metastases, Paget disease.

  • Decreased Density Conditions: e.g., osteoporosis, osteomyelitis.

Classification of Arthritis

• Types of Arthritis:

  • Hypertrophic: Bone formation, such as primary osteoarthritis.

  • Erosive: Characterized by erosions seen in conditions like rheumatoid arthritis.

  • Gout: Joint erosions with no osteoporosis; distinct markings.

  • Ankylosing Spondylitis: Causes joint fusion and characterized by certain HLA antigens.

MRI Imaging in the Spine

• Normal MRI: T1 shows bright vertebral bodies while T2 shows CSF is apparent and bright.

• Back pain statistics indicate common causes and imaging follow-ups.

Approach to Interpreting Ortho Imaging

• Begin with plain films and progress based on the patient’s injury, symptoms, and limitations.

How to Order Imaging

• Follow radiology principles ensuring involvement of both proximal and distal joints when ordering long bones imaging.