Fracture general principles
Description of Fractures
Fracture: interruption of the continuity of part of the skeletal system (=broken bone)
Luxation: dislocation, interruption of the normal interrelation between the components of a joint.
When asked to confirm a fracture, the area in question is always imaged in (at least) 2 different directions. A fracture is generally visible in one direction only. Therefore, never settle for an image in only one direction.
If bone fragments are displaced as a result of a fracture, the X-ray beam will not be absorbed by the bone at the fracture site (= the gap) (fig. 1a). This is visible as a lucent line (= black line). Bone fragments may also be compressed (= impacted fracture), causing overlap of bone structures (fig. 1b). In this case there will be increased X-ray absorption at the fracture site, resulting in increased density (= whiter).
Figure 1. Fracture gap in a proximal humerus fracture (a) and impacted distal radius fracture (b).
- Uncomplicated fracture: fracture where the adjacent skin is intact.
- Complicated/open fracture: fracture with skin penetration of a fracture fragment.
- Comminuted fracture: fracture with > 2 bone fragments.
- Intra-articular fracture: fracture line continues up to the joint surface (fig. 2).
Figure 2. Left elbow. Open intra-articular comminuted fracture of the proximal radius and ulna, with air in the soft tissues.
- Stress fracture: fracture resulting from excessive stress on the bone. Can be seen e.g. in the metatarsal bones of fanatical sportsmen (fig. 3a).
- Pathological fracture: fracture line at the level of abnormal bone, as in a bone metastasis or bone cyst (fig. 3b).
Figure 3. A (cloudy) periostal reaction around the mid shaft of metatarsal III, image of a stress fracture (a). Pathological humeral shaft fracture in a child with a bone cyst (b) Normal epiphyseal plates (= growth plates).
- Insufficiency fracture: fracture secondary to reduced bone strength, e.g. osteoporotic vertebral collapse.
- Avulsion fracture: fracture at the site of a tendon insertion. The bone is ripped loose from the insertion site by the tendon/muscle (excessive traction on the bone).
- Greenstick fracture: incomplete fracture where the bone is bent (one-sided cortical interruption). These fractures are seen in the distal radius and ulna in particular (fig. 4).
- Torus fracture (= buckle fracture): incomplete fracture creating a 'buckle’ of the cortex. The picture resembles the bottom of a Greek pillar. Torus fractures heal quicker than greenstick fractures.
Figure 4. Lateral image (a) and anteroposterior image (b) of a radial greenstick fracture and ulnar torus fracture.
- Epiphysiolysis: fractures of the epiphyseal plate (=growth plate)
Classification according to Salter & Harris (fig. 5)
Type I: fracture through the epiphyseal plate.
Type II: fracture through the epiphyseal plate and the metaphysis (most common)
Type III: fracture through the epiphyseal plate and the epiphysis.
Type IV: fracture through the epiphyseal plate, metaphysis and epiphysis.
Type V: crush injury of the epiphysis.
Memory aid based on the epiphyseal plate: SALTeR Same level (I),Above (II), Lower (III), Through (IV), Ruined (V).
Figure 5. Epiphysiolysis as per Salter & Harris classification.
- Is everything imaged correctly and suitable for evaluation? (image in multiple directions!).
- Is there soft tissue swelling?
- General impression of the bone (including osteoporosis, intra-ossal lesions).
- Check each cortex. Are there sharp or rounded cortex interruptions?
- Secondary signs of a fracture? (asymmetry, abnormal position, periostal response, changes versus old images).
Description of Fractures:
Descriptions based on typical fracture types (fig. 6/7).
Figure 6. Various fracture types.
Figure 7. Spiral fracture of distal fibula (a) Avulsion fracture of the quadriceps tendon with retraction of the muscle (b).
Note: the above fracture types are less applicable in non-tubular bones (e.g. fractures of the calcaneus and carpal bones). In this case the terms ‘horizontal, vertical, coronal, sagittal or axial’ fracture lines are more appropriate.
- Location: proximal, middle, distal
- Type of fracture line (see fig. 6)
• extent of dislocation (= displacement); medial, lateral, anterior, posterior, volar/dorsal, radial/ulnar.
• shortening (particularly in oblique fractures)
Practical information to add to a fracture description:
- To avoid confusion, the following terms are used for the hands: volar (= palmar side) & dorsal (= back of hand). Use radial and ulnar for lateral and medial respectively.
- Dislocation and angulation are usually described from the perspective of the distal fracture fragment. See figure 8 as an example.
Figure 8. AP image (a) and lateral image (b) of the right lower leg/ankle. Extra-articular transversal fracture of distal tibia with dorsolateral dislocation over a half shaft width.
- Unfused epiphyseal plate (= growth plate), e.g. in the elbow and shoulder (see fig. 3b, section General).
- Unfused apophysis (= ossification center where tendon inserts). The apophysis at the base of metatarsal V is a notorious fracture mimic.
- Accessory ossification centers, particularly in the feet (fig. 9).
In all the above-described mimics, it is crucial to evaluate older images.
Additionally, when in doubt, it is useful to consult a book of reference describing the normal variations of the skeletal system (e.g. Keats, T.E.; Atlas of Normal Roentgen Variants That May Simulate Disease). Each Emergency Assistance department should have such a (thick!) reference book.
Figure 9. Lateral ankle image with an accessory ossification center dorsal from the talus; the os trigonum.
- Radiologic reporting of skeletal trauma.M J MJ Pitt and D P DP Speer Radiol Clin North Am 28(2):247-56 (1990)
- B.J. Manaster et al. The Requisites – Musculoskeletal Imaging. 2007
- N. Raby et al. Accident & Emergency Radiology – A Survival Guide. 2005.
- Annelies van der Plas, MSK radiologist Maastricht UMC+
24/01/2014 (translated 23/08/2016)
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