Supracondylar Humerus Fracture

Supracondylar humerus fracture is the most common elbow fracture in children. Peak age 5-7 years.

Mechanism

Extension Type (97%): FOOSH (fall on outstretched hand) with elbow hyperextension. Distal fragment displaces posteriorly.

Flexion Type (3%): Direct blow to posterior elbow. Distal fragment displaces anteriorly.

Gartland Classification (Extension Type)

Type I: Undisplaced or minimally displaced. Posterior cortex intact. Fat pad sign may be only clue.

Type II: Displaced with posterior cortex intact (hinged). May be angulated.

Type IIa: Extension angulation only. Type IIb: Rotation or translation (more unstable).

Type III: Completely displaced, no cortical contact.

Type IIIa: Posteromedial displacement (the more common direction, approximately three-quarters; radial nerve at risk). Type IIIb: Posterolateral displacement (less common; median/AIN and brachial artery at risk).

The supracondylar region is the thinnest, weakest part of the distal humerus — a flat segment of bone between the medial and lateral columns, bounded by the coronoid and olecranon fossae. In the 5-7 year age group this region is undergoing remodelling and is mechanically vulnerable, which is why it fails before the ligaments rupture (the reverse of the adult elbow, where dislocation predominates).

Mechanism and fragment behaviour:

• Extension type (~97%): a fall on the outstretched hand transmits a hyperextension force through a locked olecranon, levering the distal fragment posteriorly. The proximal (shaft) fragment is driven anteriorly into the brachialis and the overlying neurovascular bundle.
• The anteriorly migrating proximal spike is the source of the classic complications: it tents or buttonholes the brachialis (pucker sign), and stretches/kinks the brachial artery and the closely applied median nerve / AIN.
• Displacement direction predicts the injured nerve: posterolateral displacement tethers the anteromedial structures (median/AIN), while posteromedial displacement threatens the laterally placed radial nerve.
• Flexion type (~3%): a direct blow to the flexed elbow displaces the distal fragment anteriorly, drawing the ulnar nerve taut behind the medial epicondyle.

Why cubitus varus occurs: malunion is driven chiefly by uncorrected internal rotation and medial column collapse at reduction, not by simple varus angulation — hence rotation control intra-operatively is critical.

Neurovascular Examination

CRITICAL: Assess before any manipulation.

Vascular:

• Brachial pulse, radial pulse
• Capillary refill
• Hand color (pink or white)

Nerve Function:

• AIN: OK sign (FPL, FDP to index)
• Median: Thenar power, sensation
• Radial: Wrist/finger extension, sensation
• Ulnar: Interossei, little finger sensation

Pulseless Hand Algorithm

Pink pulseless hand: Reduce fracture urgently. If perfusion improves → observe. Remain pink without pulse → may observe with close monitoring.

White pulseless hand: True ischemia. Reduce urgently. If still white → explore brachial artery (may be trapped, kinked, or injured).

The displaced supracondylar fracture is rarely subtle, but the undisplaced fracture and the swollen, painful paediatric elbow have several mimics. Distinguishing these changes management entirely.

Early

• Vascular injury (brachial artery)
• Nerve injury (AIN most common in extension type)
• Compartment syndrome
• Volkmann's ischemic contracture (missed ischemia)

Late

• Cubitus varus (gunstock deformity): Most common complication. Malunion with varus tilt. Cosmetic deformity. May need late supracondylar osteotomy.
• Stiffness: Usually temporary. Avoid aggressive physiotherapy.
• Myositis ossificans: Rare in children.

The topic names cubitus varus as "the most common complication" and mentions a "late supracondylar osteotomy" and "dome or closing wedge" options, but never develops the deformity or its correction - a classic viva progression.

• It is a triplanar malunion, not simple varus. Although called cubitus "varus", the deformity is a combination of varus angulation, extension and (crucially) internal rotation of the distal fragment - the same rotational malreduction that also causes it. The "gunstock" appearance is what the child and family notice; the carrying angle is lost or reversed.
• Mostly cosmetic - but not entirely benign. It usually does not limit function, but recognised sequelae include posterolateral rotatory instability, tardy (late) posterolateral rotatory or ulnar/PIN nerve palsy, an increased risk of a later lateral condyle fracture, and snapping triceps/medial elbow pain - which is why a symptomatic or severe deformity is corrected rather than simply observed.
• When to correct. Indications are a cosmetically unacceptable or progressive deformity, functional limitation, or symptomatic instability/nerve compromise, usually deferred until the deformity is established and remodelling has plateaued (typically at least a year, and with adequate remaining bone stock).
• How to correct. A distal humeral (supracondylar) osteotomy re-aligns all three planes. Options include a lateral closing-wedge osteotomy (simplest and commonest, but can leave a prominent lateral condyle / "bump"), a dome osteotomy (better cosmetic contour, technically harder), step-cut and complex multiplanar/oblique osteotomies, and increasingly CT-planned patient-specific guides for the rotational component. Fixation is typically K-wires, a plate or a lateral external fixator; the radial and ulnar nerves are at risk and the rotational and lateral-prominence components must be addressed, not just the varus angle.

The topic repeatedly flags the flexion type (~3%) - ulnar nerve at risk, often needs open reduction - but never develops it, and it behaves as the mirror image of the extension fracture.

• Reversed mechanism and displacement. A direct blow to the flexed elbow (or a fall onto the point of the elbow) drives the distal fragment anteriorly, the opposite of the FOOSH extension injury. On the lateral radiograph the anterior humeral line therefore passes posterior to the capitellum (the reverse of the extension malalignment).
• The ulnar nerve, not the AIN. Because the distal fragment displaces anteriorly and often into valgus, the ulnar nerve is the nerve most at risk in flexion-type fractures (whereas the AIN/median dominates in extension type). Assess ulnar motor (interossei, froment) and sensation specifically.
• Reduce in the opposite direction. The reduction manoeuvre is essentially reversed: after traction and correction of translation/rotation, the fragment is controlled and the elbow is often held/pinned in relative extension rather than the deep flexion used for extension-type fractures - so the closed reduction can be awkward and the fracture is prone to losing reduction in flexion.
• Higher open-reduction rate. Flexion-type fractures are more often irreducible closed (soft-tissue interposition, an unstable pattern, or ulnar nerve tethering) and thus have a higher rate of open reduction than extension types; fixation is still K-wires, with the same medial-pin ulnar-nerve caution.

Supracondylar humerus fractures are the most common elbow fracture in children (peak age 5-7 years). Extension type (97%) results from FOOSH with hyperextension; flexion type (3%) from direct blow. The Gartland classification guides management: Type I (undisplaced - cast), Type II (hinged on posterior cortex - K-wires), Type III (complete displacement - surgical emergency). Critical assessment: the 3Ps - Pulse, Perfusion, Paralysis. Brachial artery is at risk; pink pulseless hand indicates artery kinked but collaterals perfusing - reduce urgently and reassess. AIN is the most commonly injured nerve (test OK sign). Fixation with crossed or lateral-only K-wires; medial wire placement risks ulnar nerve.

Landmark Evidence