Radial Head Fracture

Radial head fracture is a fracture of the head of the radius bone, the proximal end of the radius which articulates with the capitellum of the distal humerus and the proximal ulna at the radioulnar joint. It is one of the most common fractures around the elbow in adults, accounting for 5-10 percent of all elbow fractures and 33 percent of upper extremity fractures. The radial head plays an important role in elbow stability (resisting valgus stress as a secondary stabilizer), forearm rotation (pronation-supination), and load transmission across the elbow joint.

Mechanism of injury and pathophysiology: 1) Most common mechanism — fall onto outstretched hand (FOOSH) with the elbow in extension and forearm slightly pronated; the axial force is transmitted through the wrist, radius, and radial head against the capitellum producing the characteristic fracture pattern; 2) Less common mechanisms include direct trauma to lateral elbow, sports injury, motor vehicle accident; 3) Approximately 50-75 percent of radial head fractures are associated with other elbow injuries — collateral ligament injury (medial collateral ligament MCL most clinically important), coronoid fracture (terrible triad), capitellum fracture (with posterolateral rotatory instability), elbow dislocation (Mason Type IV), distal radioulnar joint injury with interosseous membrane disruption (Essex-Lopresti lesion); 4) Pathophysiologic significance — radial head provides 30 percent of valgus stability of elbow with intact MCL, more important when MCL injured; loss of radial head support after radial head excision (without arthroplasty) leads to valgus instability, lateral elbow pain, posterior interosseous nerve injury, distal radioulnar joint instability and arthritis.

Mason classification and modified Hotchkiss classification: 1) Type I — non-displaced or minimally displaced (<2 mm); typically managed conservatively with excellent outcomes; 2) Type II — partial articular fracture with displacement 2-5 mm; controversial management with conservative versus surgical (ORIF) based on mechanical block of motion (positive — surgical, negative — may be conservative); 3) Type III — severely displaced or comminuted complete articular fracture with mechanical block; surgical management standard with ORIF when reconstructible (≥3 reconstructible fragments) or radial head replacement (arthroplasty) when not reconstructible; 4) Type IV — fracture-dislocation; requires stable reduction and surgical management of fracture; modified Hotchkiss classification adds emphasis on elbow stability and number of fragments — Type II with mechanical block managed surgically, Type III considered for radial head replacement based on number of fragments and reconstructability.

Associated injuries and complications: 1) Medial collateral ligament (MCL) injury — most clinically important, present in up to 50 percent of Type III/IV fractures; valgus instability if combined with radial head loss without replacement; 2) Lateral ulnar collateral ligament (LUCL) injury — posterolateral rotatory instability if radial head is excised without LUCL repair; 3) Coronoid fracture — terrible triad of elbow (radial head fracture + coronoid fracture + posterolateral dislocation); particularly unstable; 4) Capitellum fracture — capitellar shear fractures associated with radial head displacement; 5) Essex-Lopresti lesion — radial head fracture + interosseous membrane injury + distal radioulnar joint disruption; presents with wrist pain on initial assessment; recognition important for treatment to prevent radial impaction syndrome from radial head excision; 6) Posterior interosseous nerve (PIN) injury — radial nerve branch passing through supinator near radial head; rare but may occur with extensive surgical exposure; 7) Heterotopic ossification — particularly with terrible triad; prophylactic indomethacin or radiation in high-risk; 8) Stiffness — most common complication; early ROM essential; 9) Post-traumatic osteoarthritis — particularly with intra-articular incongruity; 10) Loss of grip strength; 11) Persistent lateral elbow pain (lateral epicondylitis-like).