Elbow Dislocation

3-6% of all elbow injuries Peak: 13-14 yrs after closure of physes High association with the following fractures Medial epicondyle Coronoid Radial head and neck

Modified hinge joint Very stable Joint congruity Opposing tension of triceps and flexors Ligaments Most important: Medial Collateral Ligament

Mechanism of Injury Fall on an outstretched hand o elbow Causes unlocking of the olceranon from the trochlea + translation of the articular surfaces 2 types of dislocation Posterior Anterior

Malunion Discussion

Bone Healing Primary Secondary Cortex attempts to heal without callus formation Occurs when fx is anatomically reduced, the blood supply is preserved, and the fracture is rigidly stabilized Secondary Formation of callus Involves participation of the periosteum and external soft tissues

4 Stages of Fracture Healing Hematoma formation (inflammation) and angiogenesis. Cartilage formation with subsequent calcification Cartilage removal and bone formation Bone remodeling

Stage 1 - Hematoma Formation and Angiogenesis < 1 week after a fracture Transforming growth factor beta (TGF-) and platelet derived-growth factor (PDGF) are released from platelets at the fracture site Osteogenic cells and inflammatory cells ensheathe the fracture and differentiate into chondrocytes or osteoblasts. -Transforming growth factor beta (TGF-) and platelet derived-growth factor (PDGF) are released from platelets at the fracture -Low-oxygen tension, low pH, and movement favor the differentiation into chondrocytes; high-oxygen tension, high pH, and stability predispose to osteoblasts

Stage 2 - Cartilage formation with subsequent calcification ~ 1 to 3 weeks after fracture Radiologic evidence of mineral formation signals the onset of this phase. consisting of calcified cartilage, woven bone made from cartilage, and woven bone formed directly. Woven bone replaces cartilage in callus by active transport of minerals and their precipitation from a supersaturated solution

Stage 3 - Cartilage removal and bone formation ~ 1 to 3 months after fracture woven-bone mineralized callus replaced by lamellar bone arranged in osteonal systems 3 characteristics: It forms only under conditions of mechanical stability; It has the ability to replace fibrous or muscle tissue; and It forms within the confines of the bone defect

Stage 4 – Bone Remodelling Can be around several years meticulously coordinated removal of bone from one site and deposition in another. Two lines of cells, osteoclasts and osteoblasts, are responsible for this process Osteoclasts – resorption Osteoblast - accretion

Malunion Described to be a fractured bone that did not heal in an anatomic position Bone may have: Angulated Rotated out of position Overrided another bone Causes shortening of the limb

Shortening is better tolerated in the upper limb >1 inch poorly tolerated in the lower limb Causes: Inadequate immobilization Misalignment Premature removal of an immobilizer

Surgical Indication: Pain Impaired normal function

Non-union Healing by fibroblastic response instead of bone formation Caused by: Overdistraction Excessive motion Inadequate immobilization

Malunion vs. Non-union