Last Updated on October 27, 2023
Periosteal reaction is the formation of new bone after trauma or some other pathology from the periosteum as visualized on the radiographs. The periosteum is a membrane that covers bones except in the cartilage part. Periosteal reaction is also known as periostitis.
When an insult occurs, vascular proliferation and thickening of the normal periosteum occur as a response. The morphology of periosteal reaction suggests the intensity, duration, and aggression of the trigger.
On radiographs, it usually takes between 10-21 days for the periosteal reaction to become visible as visualization occurs after a certain degree of mineralization.
The periosteal reaction can be termed as benign or aggressive, or a more specific classification system can be used.
Benign and Aggressive Periosteal Reaction
It occurs in cases of low-grade persistent irritation to the periosteum and periosteum has enough time to form normal or near normal cortex. The cortex will be thick and dense and have a wavy or uniform appearance. Benign periosteal reactions can be seen in callus formation in a fracture or with slowly growing tumors.
If the process is rapid, it does not allow the periosteum time to lay down and consolidate new bone to form normal cortex. The cortex may appear lamellated, amorphous, or sunburst-like. [see below]
Morphological Classification of Periosteal Reaction
More specific classification of periosteal reactions is
- Single layer
- Multilayered
- Solid
- Spiculated – perpendicular (hair-on-end), divergent (sunburst), sloping (velvet)
- Disorganized/complex
- Codman triangle
Single Layer Periosteal Reaction
In this type of periosteal reaction, a uniformly dense, single thin layer of new bone about 1-2 mm from the cortical surface is formed. Increase in blood supply causes increased osteoblastic activity and production of new bone. It is seen in
- Premature infants for up to 6 months
- Early fracture healing
- Osteosarcoma
- Osteomyelitis
- Langerhans cell histiocytosis
- Metastasis
- Osteoid osteoma
- Aneurysmal bone cyst
- Ewing sarcoma
- Giant cell tumor
- chronic venous insufficiency
Multilayered Periosteal reaction
It is also known as a lamellated or lamellar or onion skin periosteal reaction because of multiple concentric parallel layers of new bone like the layers on an onion. This occurs with fast-growing processes as the periosteum cannot produce new bone as fast as the lesion is growing leading to intermittent bouts of bone formation, unlike solid continuous bone formation.
The pattern of interrupted periosteal reaction varies depending upon the growth of the lesion.
With malignant tumors, the spaces between the layers may become secondarily infiltrated by malignant cells.
Found in
- Osteosarcoma
- Acute osteomyelitis
- Ewing sarcoma
- Langerhans cell histiocytosis (LCH)
Solid Periosteal Reaction
This occurs with slow-growing processes, as the periosteum in such cases the periosteum has plenty of time to respond to the process and can produce new bone just as fast as the lesion is growing leading to solid, uninterrupted periosteal new bone formation.
The cortex will be thick and dense and have a wavy or uniform appearance.
It can be seen in-
- Osteoid osteoma
- Osteomyelitis, Brodie abscess
- Fibrous dysplasia, Non-ossifying fibroma
- Chondrosarcoma, Osteosarcoma
- Osteoblastoma, Chondroblastoma
- Osteofibrous dysplasia, Giant cell tumor
- Metastasis
- Ewing sarcoma
- Simple bone cyst
Spiculated Periosteal Reaction
In a spiculated pattern, the periosteal reaction is perpendicular to the bone cortex. Spicules are not neoplastic and originate from the ossification along periosteal vascular channels and fibrous bands. A spiculated periosteal reaction signifies a rapid underlying process that prevents the formation of new bone under the raised periosteum.
The orientation of the spicules reflects the direction of tumor growth. Spiculated periosteal reactions can be divided into subtypes based on the orientation of the spicules.
- Perpendicular (hair-on-end pattern) – Ewing sarcoma, osteosarcoma, metastasis
- Divergent (sunburst pattern) – Osteosarcoma, hemangioma, Osteoblastic metastasis, osteoblastoma
- Focal slopping (velvet) – Chondrosarcoma
Disorganized Periosteal Reaction
This has spicules with random orientation and appearance. It can be seen in highly aggressive processes like osteosarcoma, metastasis, osteomyelitis, chondrosarcoma, malignant fibrous histiocytoma, spindle cell sarcoma, Ewing’s sarcoma
Codman Triangle
With aggressive lesions, the periosteum does not have time to ossify with shells of new bone (e.g. as seen in a single layer and multilayered periosteal reaction), so only the edge of the raised periosteum will ossify at an angle with cortex.
The Codman triangle may be seen with
- Osteosarcoma
- Ewing sarcoma
- Osteomyelitis
- Active aneurysmal bone cyst
- Giant cell tumor
- Metastasis
- Chondrosarcoma
- Malignant fibrous histiocytoma
