Primary callus
- Exuberant cartilage and disorderly membranous bone may resemble osteosarcoma
- Increased callus is present in unstable areas
Bone & joints
Other nonneoplastic
Fracture
Author: Dariusz Borys, M.D.
Last author update: 1 June 2012
Last staff update: 10 May 2023 (update in progress)
Copyright: 2003-2023, PathologyOutlines.com, Inc.
PubMed Search: Bone Fracture[title]
Table of Contents
Definition / general | Congenital pseudoarthrosis | Fracture callus | Healing process | Osgood-Schlatter disease | Primary callus | Pseudoarthrosis | Stress fractures | Subchondral insufficiency fractures | Case reports | Microscopic (histologic) description | Microscopic (histologic) imagesCite this page: Borys D. Fracture. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/bonefracture.html. Accessed June 6th, 2023.
Definition / general
- Break in continuity of bone, often with severance of blood vessels, periosteum or muscle
- Complete (bone broken completely) versus incomplete
- Closed (intact overlying tissue, also called simple) versus compound (fracture site communicates with skin surface)
- Displaced (ends of bone not aligned)
- Comminuted (many fragments)
- Pathologic (due to diseased bone) or traumatic
- Fractures often due to weakened bone (osteoporosis, tumor, infection) or falls in elderly and children
Types of fractures
- Spiral configuration through cortex is typical
- Transverse fractures (like breaking chalk) are associated with Paget disease, osteopetrosis or other severe bone disturbances
- Stress or insufficiency fractures - see below
- Avulsion fractures are associated with trauma at ligamentous and tendinous insertions, often in pelvis or distal thigh
Congenital pseudoarthrosis
- Rare; equally in girls and boys
- Almost always unilateral
- Fractures occur during first 2 yrs of life, usually shortly after birth
- Associated with anterolateral bowing and neurofibromatosis (Orthop Traumatol Surg Res 2011;97:750)
Fracture callus
Radiology description
Microscopic (histologic) description
- Stress fractures may resemble tumors with extensive periosteal new bone formation
- Postmenopausal women may have insufficiency fractures in pelvis resembling metastatic carcinoma
Microscopic (histologic) description
- Spindle cell proliferation with cartilage and bone
- May be hypercellular but orderly maturation present
Healing process
- Hematoma forms between two ends of bone, creates fibrin mesh which seals fracture site
- Young capillaries enter hematoma
- Dead bone reabsorption begins at 3 days
- Periosteal inner layer promotes intramembranous bone growth on each side of fracture, which meets at fracture site to form a primary callus, which anchors ends but doesn’t support weight bearing
- This is resorbed and replaced by secondary callus, composed of mature lamellar bone
- New bone is laid down along lines of stress
- In children, marked bone remodeling occurs, even with gross deformities or shortening of a long bone
- Open reduction and internal fixation of fractures is usually not needed
- Movement along fracture line creates lining of synovial cells and pseudoarthritis
- Soft tissue must be removed and bone stabilized to promote healing
- Fractures may not heal due to improper immobilization, devascularization of bone fragments, persistent infection or interposition of soft tissue between ends of bone
- Noncorrosive nails are isolated from bone substance by fibrous tissue; do not elicit foreign body giant cell reaction
Osgood-Schlatter disease
- Avulsion fractures of tibial tubercle causing fragmentation, in children
- Most common causes of knee pain in adolescents, pain in children and young athletes usually between the ages of 10 and 15
- Occurs due to rapid bone growth plus high level of sporting activity; associated with overuse injury
- Can be quite painful, but usually resolves itself within 12 to 24 months (SportsInjuryClinic.net-Osgood Schlatter Disease)
Pseudoarthrosis
- False joint developing after chronic nonunion of a fracture
Stress fractures
Definition / general
Gross description
Microscopic (histologic) description
Differential diagnosis
- Also called fatigue or insufficiency fractures
- Due to physical activity (ballet dancing, long distance running, military training) or metabolic bone disease
- Usually lower limbs, especially femoral neck in those with metabolic disease, tibial shaft in joggers or dancers, second or third metatarsal bones in military trainees
- May require serial parallel cuts to find evidence of stress fractures
Gross description
- White-gray with linear notched zone paralleling subchondral bone end plate
Microscopic (histologic) description
- Zonal with necrotic, reparative (fracture callus, granulation tissue) and viable tissue
Differential diagnosis
- Aseptic bone necrosis: younger patients, wedge shaped infarct, total necrosis of bone trabeculae and bone marrow
Subchondral insufficiency fractures
Definition / general
Radiology description
Treatment
Microscopic (histologic) description
- Relatively common in elderly osteoporotic women or renal transplant recipients (Joint Bone Spine 2004;71:131, Am J Surg Pathol 2000;24:464)
- Usually resolves after conservative therapy, without surgery
- May cause acute onset of hip pain
Radiology description
- Bone marrow edema by MRI
Treatment
- Immobilization, no NSAIDs
Microscopic (histologic) description
- Fracture callus and granulation tissue growing along both edges of fracture line
Case reports
- 52 year old man with sarcoma developing 35 years after uncomplicated fracture (Arch Pathol Lab Med 2003;127:e186)
Microscopic (histologic) description
- Varies with type of injury
- A few days - acute tissue damage and hemorrhage, necrotic bone [empty lacunae, poorly staining bone matrix] at fracture, may be more extensive in patella, femoral neck, carpal scaphoid
- 1 - 2 weeks - hypercellular, hypervascular tissue, often with brisk mitotic activity, resembles sarcoma but without atypia or atypical mitotic figures; reduced callus in midshaft of tibia or other poorly vascularized areas
- Callus reduced if rigid internal or external surgical fixation
Microscopic (histologic) images
Contributed by Mark R. Wick, M.D.
Fracture callus:
Atypical cartilage component
Healing
