DR Topic 6: Tibia & Fibula imaging

Question 1

Exposure factors and rationale

Answer 1

55kVp

• High image contrast
• Low beam penetration (small/thin anatomical area)

100mA

• Fine focus required
• Low chance of movement artefact so exposure time doesn’t need to be really short

0.05s

• 5 mAs provides appropriate image density

No grid

• Small anatomical area = minimal scatter radiation

Question 2

Tibia & Fibula projections

Answer 2

• AP Tibia/Fibula
• Lateral Tibia/Fibula

Question 3

AP Tibia/Fibula imaging technique

Answer 3

• Leg placed with posterior aspect in contact with IR, foot dorsiflexed as possible
• Centre midway between ankle and knee joint
• Collimate tibia, fibula, ankle joint, knee joint, soft tissue

Question 4

Lateral Tibia/Fibula imaging technique

Answer 4

• From AP, leg externally rotated onto side under examination, lateral aspect in contact with IR, ankle dorsiflexed
• Centre midway between ankle and knee joint
• Collimate tibia, fibula, ankle joint, knee joint, soft tissue

Question 5

Tibia & Fibula pathologies

Answer 5

• Shaft fracture
• Post-operative (ORIF)
• External fixation
• Rickets
• Non-accidental injury

Question 6

Shaft fracture

Answer 6

A break in the mid-section (diaphysis) of the tibia and/or fibula

Can be…

• Comminuted fracture = bone in more than two fragments
• Open (compound) fracture = part of bone going through skin

Question 7

Projections and rationale for shaft fracture

Answer 7

AP Tibia/Fibula

• Assess alignment, displacement, angulation of shaft

HB Lateral Tibia/Fibula

• Assess anterior/posterior displacement
• Horizontal beam due to significant trauma

Question 8

Radiographic appearance of shaft fracture

Answer 8

• Fracture in midshaft of tibia/fibula
• Medial/lateral or posterior/anterior displacement
• Fragmentation (comminution)
• Soft tissue swelling

Question 9

Post-operative (ORIF)

Answer 9

Post surgery imaging

Question 10

Projections and rationale for post-operative/ORIF imaging

Answer 10

AP Tibia/Fibula

• Visualise alignment and hardware placement

Lateral Tibia/Fibula

• Further assess alignment and hardware positioning

Question 11

Radiographic appearance of post-operative/ORIF imaging

Answer 11

Nails, screws, plates holding tibia and fibula in place

Question 12

External fixation

Answer 12

Rigid frame is externally attached to bone using pins or screws to keep fractured bones stabilised and in alignment

Question 13

Projections and rationale for external fixation

Answer 13

AP Tibia/Fibula

• Visualise alignment of tib/fib, pin/bone interfaces

Lateral Tibia/Fibula

• Visualise posterior/anterior alignment, depth and angle of fixator pins

Question 14

Radiographic appearance of external fixation

Answer 14

Fixator pins/wires inserted into bone, connected to external rods outside of soft tissue

Question 15

Rickets

Answer 15

Bone disease in children

• Due to lack of vitamin D
• Results in soft and weakened bone
• Leads to bowing (outward curving) of legs
• Can lead to fractures due to stress placed on bone

Question 16

Projections and rationale for rickets

Answer 16

AP Tibia/Fibula

• Assess structure of tibia and fibula, including metaphyses, diaphyses and epiphyses

Lateral Tibia/Fibula

• Assess bone shape and structure from side

Question 17

Radiographic appearance of rickets

Answer 17

• Bowing of legs
• Changes at growth plates (cupping, fraying, widening)

Question 18

Non-accidental injury

Answer 18

Injuries inflicted on a child, often by parent or caregiver

Question 19

Projections and rationale for non-accidental injury

Answer 19

AP Tibia/Fibula

• Assess bone alignment and length

Lateral Tibia/Fibula

• Side perspective of tibia and fibula, assess positioning, potential fractures

Question 20

Radiographic appearance of non-accidental injuries

Answer 20

• Fractures if present
• Tissue swelling if present
• Damage to growth plates