Forearm shaft fractures

The radius and ulna work as one joint: the radius rotates around the ulna through the proximal and distal radioulnar joints, and its lateral bow is needed for full rotation. That is why shaft fractures in adults are treated like articular fractures, with anatomical reduction of length, rotation and the radial bow. An isolated ulnar shaft fracture from a direct blow (nightstick fracture) is the stable exception.

Mechanism

Both-bone: high-energy trauma or a fall on the outstretched hand. Isolated ulna: a direct blow on the subcutaneous border, typically raising the forearm to ward off a blow.

Clinical findings

• Deformity and instability of the forearm; check the skin (open fractures are common) and the radial, ulnar and median nerves.
• High risk of compartment syndrome (pain on passive finger extension): measure pressures if in doubt.
• Examine the elbow and the wrist: a dislocated joint changes the diagnosis (Monteggia, Galeazzi).

Imaging

• AP and lateral of the whole forearm, including the elbow and the wrist joints.
• Radiocapitellar line on every view (Monteggia) and the DRUJ on the lateral (Galeazzi).
• Compartment pressure measurement when clinical signs are equivocal.

• AP and lateral of the whole forearm with elbow and wrist on the films.
• Check the radiocapitellar line and the distal radioulnar joint on every set of films, before and after treatment.

Classification

2R2 / 2U2 A

Simple: A1 spiral, A2 oblique, A3 transverse. Both-bone fractures are coded for each bone (e.g. 2R2A3 + 2U2A3).

2R2 / 2U2 B

Wedge (intact or fragmented wedge).

2R2 / 2U2 C

Multifragmentary (segmental or comminuted).

Types shown in 3D

2R2A3 + 2U2A3

Both-bone, simple transverse, midshaft: the distal forearm and hand angulate and shorten; the rotational position of each fragment depends on the level relative to the pronator teres insertion. Plate both bones.

2R2B + 2U2A

Both-bone with a wedge (butterfly) fragment of the radius and a simple ulnar fracture at a different level: bridge or compress the wedge with lag screws and a plate.

Nightstick, undisplaced

Isolated ulnar shaft fracture from a direct blow (2U2A3), angulation < 10° and displacement < 50%: the radius and the interosseous membrane keep it stable. Functional brace, early motion.

Nightstick, displaced

Isolated ulnar fracture displaced more than half the shaft width or angulated more than 10°: the interosseous membrane is torn and the fracture is unstable. Plate fixation; check that the radial head is located (Monteggia).

Treatment

Both-bone fracture, adult

Open reduction and internal fixation of both bones with 3.5 mm compression plates (at least 6 cortices, ideally three bicortical screws, on each side): radius through the volar (Henry) or dorsal (Thompson) approach, ulna through a direct approach along the subcutaneous border, two separate incisions to limit synostosis. Restore the radial bow. Bone graft is rarely needed.

Isolated ulnar shaft (nightstick)

Stable when angulated less than about 10° and displaced less than half the shaft width: functional brace or short cast and early motion. Displaced or proximal-third fractures: plate fixation (and exclude a Monteggia lesion).

Children

Closed reduction and an above-elbow cast; marked remodelling potential in the young. Unstable or irreducible fractures: elastic stable intramedullary nails.

Open fractures

Antibiotics within an hour, debridement; immediate plating is usually safe after thorough debridement, otherwise temporary external fixation.

Aftercare

Early active motion of the elbow, wrist and fingers after plating; no lifting or contact sport until union (often 3–4 months). Plate removal only if symptomatic (refracture risk after removal).

Complications

• Loss of rotation (malreduction of the radial bow, rotational malalignment)
• Compartment syndrome
• Radioulnar synostosis
• Non-union (nightstick and comminuted fractures)
• Posterior interosseous nerve injury (dorsal approach to the proximal radius)
• Refracture after plate removal