Forearm Fractures – General Principles

Modern Study Review (AI-Generated)

High-Yield Summary

Forearm fractures, involving the radius and ulna, are common injuries requiring precise management to restore pain-free function and forearm rotation. Understanding the unique anatomy, deforming muscular forces, and remodeling potential in pediatric patients is critical for treatment decisions. Modern care balances non-operative management in children with acceptable angulation and alignment against operative fixation in adults or unstable fractures to optimize outcomes. Preservation of rotational alignment and interosseous space is paramount to maintain forearm pronation and supination.

Key Diagnostic Findings

Anatomy

• Distal radial physis closure: ~17 years in girls, 18 years in boys.
• Proximal radial physis closure: ~17-18 years.
• Radius and ulna shape: Non-cylindrical bones; malrotation can be detected by changes in fragment width at the fracture site.
• Proximal radioulnar joint stability: Maintained primarily by the annular ligament, most stable in supination.
• Distal radioulnar joint (DRUJ): Stability depends on the triangular fibrocartilage complex (TFC) and associated ligaments.

Clinical Presentation

• Pain, swelling, deformity, and limited forearm rotation (pronation/supination).
• Malrotation leads to functional deficits even if angulation is minimal.

Imaging

• Standard AP and lateral radiographs of forearm including wrist and elbow.
• Evaluate for angulation, displacement, malrotation (assessed by cortical width mismatch), and interosseous space preservation.
• Ulnar variance should be assessed in neutral forearm position due to positional changes with pronation/supination.

Classification Systems

• No single universal classification; fractures are described by location (proximal, midshaft, distal), pattern (transverse, oblique, comminuted), and displacement.
• Pediatric fractures consider remodeling potential and physeal involvement.

Current Gold Standard Treatment

Non-operative Indications and Treatment

• Pediatric patients <10 years with angulation ?10° (up to 20° in children <8 years) and no malrotation.
• Bayonet apposition acceptable in children <10 years if interosseous space and rotation are preserved.
• Immobilization typically with long arm cast in position optimizing stability (often supination for proximal radius fractures).
• Close radiographic follow-up to monitor alignment and remodeling.

Operative Indications and Treatment

• Adults and adolescents with displaced, unstable fractures or malrotation.
• Pediatric fractures with unacceptable angulation, malrotation, or unstable bayonet apposition beyond remodeling potential.
• Surgical options:
• Open reduction and internal fixation (ORIF) with plates and screws is gold standard in adults.
• Intramedullary nailing or flexible nails may be used in select pediatric cases.
• Goal: Restore length, alignment, rotation, and interosseous space to preserve forearm rotation.

Modern Complications & Outcomes

Complications

Outcomes

• Pediatric fractures have excellent remodeling potential if criteria are met, with restoration of function and minimal deformity.
• Adults require anatomic reduction for optimal functional outcomes.
• Early restoration of rotation correlates with improved pain and function.
• Long-term outcomes depend on maintaining forearm rotation and preventing DRUJ dysfunction.

Classic Clinical Notes

Forearm Fractures – General Principles

Anatomy

• Distal radial physis closes about age 17 in girls, 18 in boys
• Proximal radial physis closes about age 17-18
• Because the radius and ulna are not completely cylindrical, you can tell malrotation by the width of the proximal and distal fragments at the fracture site.
• The annular ligament is most responsible for maintaining the proximal radioulnar joint – most stable in supination
• The TFC complex and ligaments is responsible for maintaining the DRUJ

Rotational Considerations

• Supination tends to shorten the ulna on the radius (ulnar minus) while pronation tends to lengthen the ulna relative to the radius (hence, if looking for ulnar variance, must do it in neutral)
• Interosseous membrane and space is narrowest in pronation, widest in neutral to 30 of supination
• 10 degrees of angulation in the midshaft limits rotation 20-27 degrees
• Bayonet apposition does not limit rotation as long as the interosseous space is maintained

Deforming Forces

• Biceps and supinator flex and supinate the proximal radius fragment
• Pronator teres pronates the mid-radius fragment
• Pronator quadratus pronates distally
• It is hard to predict how to immobilize the arm based on these deforming forces and the level of the fracture. Just be aware of them!

Remodeling Potential

• The amount of spontaneous correction is dependent on age, amount of residual angulation, the fracture to epiphyseal plate proximity, and relationship of deformity with plane of motion
• Don’t depend on remodeling after age 11; best remodeling is seen in kids less than 8
• Average rate of remodeling at the distal radius is 0.9 degrees per month, or 10 degrees per year
• Volar and ulnar angulation result in a higher rate of correction than do dorsal angulation
• Increased correction takes place when there is greater deformity
• Bayonet apposition is acceptable and will remodel in a child less than 8-10 if rotation is correct, if interosseous space is preserved, and there is no angulation!

In general:

• Accept no more than 10 degrees of angulation (maybe 20 in a child less than 8)
• Accept no malrotation
• Accept bayonet apposition only in a child less than 10.

Last Updated on January 25, 2026 by orthonet