Both-Bone Forearm Fractures

Both-bone forearm fractures in adults are typically high-energy injuries requiring operative fixation. The forearm is unique because it functions as a paired bone articulated joint - both bones rotate around each other, and any disruption of anatomy impairs this function.

Mechanism of injury:

• Direct trauma - blow to forearm
  • Often comminuted at impact site
  • Industrial injuries, assault
• Indirect trauma - fall on outstretched hand
  • Rotational component common
  • Motor vehicle accidents
• High-energy mechanisms predominate - MVA, falls from height, sport

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Associated injuries:

• Compartment syndrome (high risk)
• Neurovascular injury
• Ipsilateral elbow injury (floating elbow)
• Ipsilateral wrist injury (floating wrist)
• Associated hand injuries

Deforming Muscle Forces:

• Proximal Radius (Supinator/Biceps): Supinated and flexed
• Middle Radius (Pronator Teres): Pronated (if distal to insertion)
• Distal Radius (Pronator Quadratus): Pronated

Radial anatomy:

• Radial head - articulates with capitellum and PRUJ
• Radial tuberosity - biceps insertion
• Radial bow - maximum curvature at junction proximal/middle thirds
• Lateral surface - covered by wrist extensors
• Volar surface - FPL origin, plate placement area

Ulnar anatomy:

• Olecranon - triceps insertion
• Coronoid - anterior buttress
• Shaft - relatively straight, triangular cross-section
• Subcutaneous border - medial, palpable throughout
• Dorsal surface - ECU groove, plate placement area

Key relationships:

• Interosseous membrane (IOM) - connects radius to ulna
• PRUJ - proximal radioulnar joint
• DRUJ - distal radioulnar joint
• Interosseous space - maintained for rotation

Biomechanics of rotation:

• Normal supination/pronation: 75°/75° approximately
• Radius rotates around relatively fixed ulna
• Rotation occurs at PRUJ, DRUJ, and through IOM
• Loss of 10° rotation malalignment = significant functional loss

Surgical anatomy - approaches:

• Thompson (dorsolateral radius) - between ECRB and EPL
• Henry (volar radius) - between BR and PT/FCR
• Ulnar approach - along subcutaneous border

History:

• Mechanism (high vs low energy)
• Time of injury
• Open wound (assume open until proven otherwise)
• Associated injuries
• Hand dominance, occupation

Physical examination:

Compartment syndrome assessment:

Key examination points:

1. Compartment assessment - volar and dorsal
2. Neurovascular status - PIN, median, ulnar nerves; radial and ulnar pulses
3. Skin integrity - open wound assessment
4. Associated injuries - elbow, wrist, hand
5. Soft tissue swelling - predictor of complications

Radiographic assessment:

Standard views:

• AP forearm - entire forearm including elbow and wrist
• Lateral forearm - true lateral
• Dedicated elbow views - AP and lateral if proximal injury
• Dedicated wrist views - AP and lateral if distal injury

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Radiographic assessment checklist:

1. Fracture location and pattern (both bones)
2. Degree of comminution
3. Angulation and displacement
4. Radial head congruent with capitellum?
5. DRUJ congruent?
6. Shortening present?

CT imaging:

• Rarely indicated for shaft fractures
• May help for complex articular extension
• 3D reconstruction for difficult patterns

Compartment pressure monitoring:

• If clinical suspicion
• Absolute pressure greater than 30mmHg concerning
• Delta pressure (Diastolic - Compartment) less than 30mmHg = fasciotomy

Compartment syndrome:

• Most critical early complication
• High-energy injuries at highest risk
• Pain with passive finger extension is early sign
• Emergency fasciotomy - both volar and dorsal compartments

Malunion:

• Loss of rotation most functionally limiting
• Greater than 10° angulation or rotation = significant deficit
• Corrective osteotomy with bone graft if symptomatic

Synostosis:

• Abnormal bone bridge between radius and ulna
• Risk factors: high energy, single incision, head injury
• Prevention: orthogonal plating (90° apart), avoid IOM damage
• Treatment: excision when mature (greater than 1 year), interposition material

Postoperative protocol:

Key rehabilitation principles:

• Early motion critical - prevents stiffness
• Stable fixation allows early motion
• Focus on rotation (supination/pronation)
• Progressive loading after union confirmed
• Final ROM assessment at 6 months

Expected outcomes:

Prognostic factors:

• Open vs closed (open = worse outcomes)
• Energy of injury
• Quality of reduction
• Bone quality
• Patient compliance
• Smoking status

A "both-bone forearm fracture" on a single film can be a fracture-dislocation in disguise. Distinguishing these patterns changes the operation.

• Locking vs conventional plates: Locking plates have not shown superior union or function over conventional 3.5mm DCP/LC-DCP in standard diaphyseal bone (Iacobellis & Biz; Hertel). Their clearest role is osteoporotic bone and bridge plating of comminution, not routine use.
• Plate vs intramedullary nailing: Modern locked forearm nails achieve good union, but restoring the radial bow and rotation is harder than with plates. Nailing is most attractive in segmental fractures, poor soft tissues, or limited-resource settings; plating remains the default where anatomic reduction is the priority.
• Routine implant removal: Removing plates exposes the patient to refracture (around 4% in long-term cohorts) and a second operation. Most surgeons leave asymptomatic plates in situ; if removal is undertaken, delay it (commonly 18-24 months) and protect the limb afterwards.
• Acceptable malalignment: "Anatomic" is the goal, but the precise threshold beyond which rotation is meaningfully lost is debated; radial bow restoration matters more than absolute angular numbers.
• Compartment pressure thresholds: The diagnosis remains clinical. Absolute and delta-pressure cut-offs (delta less than 30mmHg) guide equivocal cases but should never delay fasciotomy when the clinical picture is clear.
• Single vs separate incisions: A single incision for both bones increases synostosis risk; orthogonal plating through separate approaches is preferred, though high-energy injury itself is the dominant non-modifiable risk factor.

Global epidemiology:

• Forearm shaft fractures account for roughly 1-2% of all adult fractures; both-bone patterns are the high-energy subset.
• Bimodal distribution: young men from high-energy trauma (road traffic, especially motorcycles, industrial machinery, falls from height, contact and wheeled sport) and older adults from lower-energy falls.
• Male predominance in the high-energy group; rising motorcycle use makes these injuries disproportionately common in low- and middle-income countries.

Guideline and society positions (areas of genuine agreement and difference):

Registry and evidence notes:

• Unlike arthroplasty, forearm shaft fractures are not tracked by a dedicated implant registry; the evidence base is institutional cohorts and trauma databases rather than national joint registries.
• Across cohorts, plate fixation delivers union rates of roughly 90-98%, with locking and conventional 3.5mm constructs performing comparably.

High- vs limited-resource practice variation:

• Well-resourced settings: routine ORIF with 3.5mm plates, intra-operative imaging, on-site plastic surgery for Gustilo IIIB/C, and compartment-pressure monitoring where the diagnosis is equivocal.
• Limited-resource settings: square or Hackethal intramedullary nailing and external fixation are used more often when plating implants or image intensifiers are unavailable; transfer pathways may be limited, so compartment syndrome is frequently managed at the presenting hospital.