SKELETAL TRAUMA

Bone provides shape and support for the body. As with soft tissue, it can be traumatized during sports participation.

Types of Bone

Bones are classified according to their shapes.

1. Flat bones are in the skull, the ribs, and the scapulae

2. Irregular bones are in the vertebral column and the skull.

3. Short bones are primarily in the wrist and the ankle.

4. Long bones are the most commonly injured bones in sports. They consist of the humerus, ulna, femur, tibia, fibula, and phalanges.
      

Gross Structure of Bones

• The diaphysis is the main shaft of the long bone. It is hollow, cylindrical and covered by compact bone.

• The epiphysis is located at the ends of long bones. It is bulbous in shape, providing space for the muscle attachments.  As discussed previously, the ends of long bones are covered with a layer of hyaline cartilage that covers the joint surfaces of the epiphysis. 

• A dense, white fibrous membrane, the periosteum, covers long bones except at joint surfaces.

• Throughout the periosteum on its inner layer exist countless blood vessels and osteoblasts (bone-forming cells). The blood vessels provide nutrition to the bone, and the osteoblasts provide bone growth and, repair.
• The medullar cavity, a hollow tube in the long bone diaphysis, contains a yellow, fatty marrow in adults.

•  Lining the medullar cavity is the endosteum.

Bone Injuries

• Because of its viscoelastic properties, bone will bend slightly. However, bone is generally brittle and is a poor shock absorber because of its mineral content.

• Anatomical strength or weakness can be affected by a bone's shape and its changes in shape or direction. A hollow cylinder is one of the strongest structures for resisting both bending and twisting, as compared with a solid rod, which has much less resistance to such forces.

• This may be why bones such as the tibia are primarily cylinders.

• Most spiral fractures of the tibia occur at its middle and distal third, where the bone is most solid.

Anatomical Weak Points

• Stress forces become concentrated where a long bone suddenly changes shape and direction.

• Long bones that change shape gradually are less prone to injury than those that change suddenly.

• The clavicle, for example, is prone to fracture because it changes from round to flat at the same time it changes direction.