Both-bone forearm fracture refers to combined diaphyseal fractures of the radius and ulna, accounting for ~10% of forearm fractures in adults and a large portion of pediatric forearm fractures. The forearm functions as a complex joint with two articulations between radius and ulna (proximal and distal radioulnar joints) connected by the interosseous membrane, allowing pronation-supination of about 75-85 degrees each direction in healthy adults. Restoration of forearm function depends on restoring normal length, alignment, rotation, and—uniquely—the radial bow (lateral curvature of radius averaging 16 mm at 60% of length from the radial head), as malreduction of these parameters causes loss of forearm rotation. Mechanism is typically high-energy in adults (motor vehicle accidents, falls from height, direct trauma, gunshot wounds) and lower energy in children (falls). Pediatric patterns differ: greenstick (incomplete with cortical disruption on tension side, plastic deformation on compression), torus (impaction near metaphysis), plastic deformation (no visible fracture line, just bowing), complete.
Special variants: Monteggia fracture-dislocation—proximal ulna fracture with radial head dislocation; Bado classification (I anterior dislocation 60%, II posterior dislocation 15%, III lateral dislocation 20%, IV both bone proximal third with anterior radial head dislocation); often missed in children; requires recognition by elbow imaging on every forearm fracture; treatment: in children, closed reduction of ulna typically reduces radial head; in adults, ORIF of ulna with restoration of length and alignment usually reduces radial head, occasionally requires open reduction. Galeazzi fracture-dislocation—radius shaft fracture (typically distal third) with distal radioulnar joint (DRUJ) disruption; called 'fracture of necessity' indicating need for surgical fixation in adults due to poor results with closed treatment; ORIF of radius typically reduces DRUJ; assessment of DRUJ stability after fixation important. Essex-Lopresti—radial head fracture with disruption of interosseous membrane and DRUJ—rare but missed.
Treatment principles: in adults, closed reduction and casting almost universally fails due to inability to restore radial bow and rotation precisely, leading to functional limitation; therefore ORIF is gold standard with 3.5 mm dynamic compression plates (DCP) or limited contact-DCP (LC-DCP) or locking compression plates (LCP) applied through separate radial (Henry anterior or Thompson posterior) and ulna (subcutaneous border) approaches with at least 5-6 cortices of fixation above and below fracture (or 3 bicortical screws on each side per AO principles), interfragmentary lag screw when oblique pattern, and bone grafting if comminuted; postoperative early range of motion if stable. In pediatric patients (under 10-12 years with at least 2 years of skeletal growth remaining), closed reduction and casting acceptable for fractures with adequate reduction (acceptable angulation typically <15 degrees in distal third, <10 degrees in middle, less in proximal; rotation must be near anatomic regardless of age); long-arm cast 6-8 weeks; surgical management (TENS flexible nailing or plate ORIF) for unacceptable closed reduction, refracture, length-unstable, age >10-12. Complications: nonunion (1-5%, higher with smoking, comminution, open injury, inadequate fixation; treatment with revision ORIF and bone grafting); malunion with rotational or angular deficit (>10 degrees angular or >15 degrees rotational impairs function; corrective osteotomy if symptomatic); compartment syndrome (urgent fasciotomy of all compartments); neurovascular injury (median, ulnar, radial, posterior interosseous nerve); posterior interosseous nerve palsy from positioning or surgical approach; radioulnar synostosis (1-3%, more common with high-energy injury, single incision approach, prolonged immobilization, head injury; presents with progressive loss of forearm rotation; treatment: surgical excision after maturation 1 year, occasionally with interposition fat graft or other interposition material, and immediate motion; recurrence common); refracture (1-2% after plate removal, especially first 6 months post-removal; some surgeons leave plates indefinitely).