1. Overview / High-Yield Summary
Forearm fractures involve the diaphysis of the radius and/or ulna. In adults, these injuries are functionally considered intra-articular fractures because the forearm operates as a complex joint allowing pronation and supination.
* The "Two-Bone" Concept: The radius and ulna are mechanically linked by the proximal radioulnar joint, the interosseous membrane (IOM), and the distal radioulnar joint (DRUJ).
* * The Ring Principle: Disruption of this ring at one point (fracture) often leads to injury at another point (dislocation or second fracture).
* Primary Goal: Anatomic restoration of the "radial bow" is the single most important factor for regaining rotational function.
2. Etiology and Pathophysiology
2.1 Mechanism of Injury
* High-Energy Trauma: Motor vehicle accidents (MVA) or falls from significant heights are common causes of both-bone fractures.
* Direct Blow: Typically results in an isolated ulnar shaft fracture, termed a "Nightstick Fracture" (classic defensive injury warding off a blow).
* Low-Energy Falls: Fall onto an outstretched hand (FOOSH), common in sporting collisions or elderly patients.
2.2 Deforming Forces (Muscle Imbalance)
* The forearm muscles are contained within separate fascial envelopes, which influences displacement.
* Proximal Radius: The biceps and supinator muscles exert forces that supinate the proximal fragment.
* Distal Radius: The pronator teres and pronator quadratus pull the radius into pronation.
* Key Concept: Failure to restore the anatomical relationship and radial bow leads to permanent loss of pronation/supination.
3. Clinical Presentation
3.1 History
* Patients typically present with pain, deformity, and an inability to rotate the forearm.
* A history of high-energy trauma should prompt an assessment for other associated injuries.
3.2 Physical Examination
Inspection
* Gross Deformity: Angulation and shortening are often obvious.
* Soft Tissue: The subcutaneous position of the ulna leads to a relatively high incidence of open fractures; careful inspection of lacerations is mandatory.
* Swelling: Tense swelling may indicate developing compartment syndrome.
Neurologic Screening (Critical)
* Radial Nerve (PIN): Must be assessed, especially in proximal radius fractures or Monteggia injuries.
* Median & Ulnar Nerves: Sensory and motor function of the hand must be documented.
Compartment Syndrome Check
* Pain with passive stretch of the fingers is a critical early sign.
* The forearm has indispensible fascial envelopes making it prone to compartment syndrome.
4. Imaging
4.1 Standard Radiographs
* Views: Full-length AP and Lateral views of the forearm.
* "Rule of Twos": Imaging must include the Elbow and the Wrist to rule out associated dislocations.
* Rationale: To diagnose Monteggia (proximal) or Galeazzi (distal) fracture-dislocations.
4.2 Specific Fracture Patterns (Eponyms)
* Nightstick Fracture: Isolated ulnar shaft fracture.
* * Monteggia Fracture: Fracture of the proximal ulna with dislocation of the radial head.
* Galeazzi Fracture: Fracture of the distal/middle radius with disruption of the DRUJ.
5. Treatment Principles
Key Concept
* Adults: Operative treatment (ORIF) is the standard of care for almost all both-bone fractures. Closed treatment is rarely successful due to muscle forces.
* Goal: To reestablish the anatomic relationship between the radius and ulna with rigid fixation to restore the functional joint.
* Stability: Stability of the DRUJ and PRUJ depends on anatomic reduction of the shafts.
6. Nonoperative Treatment
Indicated primarily for:
* Isolated "Nightstick" Fractures: Specifically those in the distal two-thirds with <50% displacement and <10° angulation.
* Patients medically unfit for anesthesia.
Options:
* Long-Arm Cast: Used initially to control rotation.
* Functional Bracing (Sarmiento): Can be used for isolated ulna fractures after acute pain subsides.
Limitations:
* Nondisplaced fractures must be monitored closely for displacement.
* Historically, nonoperative treatment of both-bone fractures leads to poor outcomes and loss of motion.
7. Operative Treatment
Indicated for:
* Displaced Both-Bone fractures.
* Galeazzi and Monteggia fracture-dislocations.
* Open fractures.
* Isolated radial shaft fractures (almost always require surgery).
7.1 Surgical Approaches
* Volar Approach (Henry):
* Interval: Between Brachioradialis and Flexor Carpi Radialis (distally) or Pronator Teres (proximally).
* Usage: Standard for middle and distal radius fractures.
* Dorsal Approach (Thompson):
* Interval: Between ECRB and EDC.
* Usage: Proximal radius fractures.
* Risk: Requires protecting the Posterior Interosseous Nerve (PIN) within the supinator.
* Subcutaneous Approach: Direct access to the subcutaneous border of the ulna between ECU and FCU.
7.2 Fixation Technique
* Plating: 3.5mm dynamic compression plates (DCP) or limited-contact plates (LC-DCP) are routinely used.
* Technique: Fractures are reduced anatomically, and the radial bow must be restored.
* Intramedullary Nailing: Reserved for cases with severe soft-tissue trauma where plating is unsafe, or for pathologic fractures.
8. Complications
* Malunion: Inadequate reduction, typically loss of radial bow, results in a reduction in pronation/supination.
* Nonunion: Relatively rare with modern fixation, but more common in the ulna than the radius.
* Synostosis: A bony bridge between radius and ulna preventing all rotation. Risk factors include crush injuries, single-incision approaches (historical), or head injury.
* Compartment Syndrome: Can accompany high-energy fractures; requires emergency fasciotomy.
* Refracture: Can occur after plate removal; plates are generally left in place unless symptomatic.
9. Prognosis
* Union Rates: Excellent/satisfactory results are reported in ~86% of patients with union rates of 96-98% using compression plating.
* Functional Outcome: Directly related to the restoration of the radial bow.
* Recovery: Heavy lifting is typically avoided until fracture union is evident.