MDPT: Fracture & Bone Disorders

Bone Structure and Classification

• Bone is a highly specialized connective tissue with cells calcified in an organic osteoid matrix.
• Salter-Harris Classification categorizes epiphyseal plate fractures into five grades based on which parts of the bone are affected.
  • Grade 1: Incomplete fracture through the epiphyseal plate.
  • Grade 2: Involves the epiphyseal plate and a triangular segment of the metaphysis.
  • Grade 3: Involves the epiphyseal plate and the epiphysis.
  • Grade 4: Involves the epiphyseal plate, the epiphysis, and the metaphysis.
  • Grade 5: Crushed epiphyseal plate.

Embryological Development of Bone

• Membranous ossification involves the gradual transformation of connective tissue into bone via an osteoid matrix, primarily in facial bones and the cranial vault.
• Endochondral ossification occurs when mesenchymal cells transform into cartilage, forming long bones, spine, and ribs.

Bone Cells and Composition

• Osteoblasts are responsible for bone formation, while osteoclasts facilitate bone resorption.
• Normal bone health requires a balance of activities between osteoblasts and osteoclasts.
• Bone consists of approximately 30% organic material (collagen type 1) and 70% inorganic material (hydroxyapatite, phosphate, and carbonate), with water comprising about 10%.

Types of Fractures

• Fractures are classified as incomplete or complete based on the nature of bone breakage.
• Open fractures involve communication with surrounding tissues and may present with a wound, while closed fractures do not.
• Various fracture types include:
  • Transverse: Right angle along the shaft.
  • Oblique: Diagonal angle along the shaft.
  • Comminuted: Bone is crushed into multiple fragments.
  • Spiral: Caused by torsional forces, heals fastest.

Fractures in Different Body Regions

• Common upper extremity fractures include supracondylar fractures near the elbow joint, often leading to Volkmann’s ischemic contracture.
• Lower extremity fractures include femoral neck fractures, which can interrupt blood supply, risking avascular necrosis (AVN), and various others such as intertrochanteric and trimalleolar fractures.

Bone Healing Anomalies

• Delayed union: Failure of fractures to heal within typical timeframes (3-12 weeks for upper extremity, 12-18 weeks for lower extremity).
• Malunion: Fractured bones heal in an unsatisfactory alignment.
• Osteosclerosis: Dense regions in bone, exemplified by conditions like osteopetrosis, characterized by "bone in a bone" appearance due to ineffective osteoclastic activity.

Osteoporosis

• Defined by a bone mass density 2.5 standard deviations below normal; osteopenia is a less severe mid-point.
• Known as a "silent disease" due to lack of symptoms until fracture occurs; assessed using Dual Energy X-ray Absorptiometry (DEXA).

Amputation

• Amputation involves the removal of a body part, either congenital or acquired.
• Types include:
  • Major: Above the MCP and MTP joints.
  • Minor: Below the MCP and MTP joints.
  • Disarticulation: Amputation through a joint.
• Indications for amputation include vascular disease, infections, trauma, tumors, or congenital anomalies.

Terminology Related to Amputation

• Cineplastic: Designed for upper extremity prosthetic use.
• Krukenberg: Separation of the radius and ulna to form a pinching mechanism.