Introduction Always look to see if physis is open Unique principals in pediatric bone elasticity more elastic which leads to unique fracture patterns buckle fractures greenstick fractures remodeling potential open physes (growth plates) can allow extensive bone deformity remodeling potential occurs more rapidly in plane of joint motion sagittal plane in wrist, due to primarily extension/flexion occurs more at the most active physes, due to most growth and potential for remodeling most active physes in upper extremity proximal humerus distal radius most active physes in lower extremity distal femur proximal tibia distal tibia lateral ligament sprains are more common than Salter-Harris 1 fractures in pediatric ankle inversion injuries Same principles as adult bone intra-articular fractures must be reduced Physeal Anatomy Physeal Growth Plate Reserve zone (B) Cells store lipids, glycogen, and proteoglycan aggregates for later growth and matrix production Low oxygen tension Gaucher's Diastrophic dysplasia Kneist Pseudoachondroplasia Proliferative zone (C) Proliferation of chondrocytes with longitudinal growth and stacking of chondrocytes. Highest rate of extracellular matrix production Increased oxygen tension in surroundings inhibits calcification Achondroplasia Gigantism MHE Hypertrophic zone (D) Zone of chondrocyte maturation, chondrocyte hypertrophy, and chondrocyte calcification. Three phases occur in the hypertrophic zone Maturation zone: preparation of matrix for calcification, chondrocyte growth Degenerative zone: further preparation of matrix for calcification, further chondrocyte growth in size (5x) Provisional calcification zone: chondrocyte death allows calcium release, allowing calcification of matrix Chondrocyte maturation regulated by local growth factors (parathyroid related peptides, expression regulated by Indian hedgehog gene) Type X collagen produced by hypertrophic chondrocytes important for mineralization SCFE (not renal) Rickets (provisional calcification zone) Enchondromas Mucopolysacharide disease Schmids Fractures most commonly occur through zone of provisional calcification Primary spongiosa (E) (metaphysis) Vascular invasion and resorption of transverse septa. Osteoblasts align on cartilage bars produced by physeal expansion. Primary spongiosa mineralized to form woven bone and then remodels to become secondary spongiosa (below) Metaphyseal "corner fracture" in child abuse Scurvy Secondary spongiosa (metaphysis) Internal remodeling (removal of cartilage bars, replacement of fiber bone with lamellar bone) External remodeling (funnelization) Renal SCFE Physis Periphery Groove of Ranvier During the first year of life, the zone spreads over the adjacent metaphysis to form a fibrous circumferential ring bridging from the epiphysis to the diaphysis. This ring increases the mechanical strength of the physis and is responsible for appositional bone growths Supplies chondrocytes to the periphery Osteochondroma Perichondrial fibrous ring of La Croix Dense fibrous tissue that is the primary limiting membrane that anchors and supports the physis through peripheral stability Perichondrial artery Major source of nutrition to physis Injury Classification Salter-Harris classification Type 1: physeal separation Type 2: fracture traverses physis and exits metaphysis most common type Thurston Holland fragment Type 3: fracture traverses physis and exits epiphysis Type 4: fracture passes through epiphysis, physis, metaphysis Thurston Holland fragment Type 5: crush injury to physis Treatment Closed reduction vs. CRPP vs. ORIF depends on injury pattern intra-articular fractures must be reduced Complications Growth arrests overview complete arrest leads to shortening see Leg Length Discrepancy partial arrest leads to angulation treatment bar resection with interposition indications < 50% physeal involvement > 2 years or 2cm growth remaining ipsilateral completion of arrest indications > 50% physeal involvement can combine with contralateral epiphysiodesis and/or ipsilateral lengthening