Floating Elbow

The injury. A floating elbow is the combination of ipsilateral fractures on both sides of the elbow, one above it in the humerus and one below it in the forearm. The elbow joint is left flail, "floating" between the two. Whatever the exact bones, the injury reflects substantial energy transmitted through the limb.

Children and adults. The classic paediatric pattern is a completely displaced supracondylar humerus fracture with an ipsilateral forearm fracture, either of the distal radius or of both bones. In adults the analogous injury is an ipsilateral humeral fracture, of the shaft or the distal humerus, with a forearm fracture.

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A marker of energy. Compared with isolated fractures, the floating elbow carries higher rates of open fractures, neurovascular injury and the need for open reduction. The brachial artery and the median, anterior interosseous, radial and ulnar nerves are at risk, especially with a displaced supracondylar fracture. The high-energy mechanism, the swelling, the two fractures and possible vascular injury together put the forearm at risk of compartment syndrome, and the limb is often one of several injuries in a polytrauma patient.

Assessment. The aim is to find everything the energy has done:

• A full neurovascular examination before and after any reduction: pulses, perfusion and every nerve
• Inspection for open wounds, and assessment of the soft-tissue swelling and the compartments
• Radiographs of the whole limb (humerus, elbow, forearm and wrist), so that the second fracture is not missed
• Treatment as a high-energy, potential polytrauma patient, on ATLS principles where relevant

Compartment syndrome: what "a high index of suspicion" means

Maintain a high index of suspicion and monitor closely, but telling a candidate to be vigilant is not an answer. The examinable content is how the diagnosis is made and what is done about it.

In the child, the five Ps are useless. Pain, pallor, paraesthesia, paralysis and pulselessness are late signs, and pulselessness is often absent altogether. Compartment pressure rises well above capillary filling pressure long before it occludes a major artery, so a palpable pulse never excludes the diagnosis.

The early signs. In a child these are the three A's, with the local signs alongside them:

• Increasing analgesia requirement, the most useful single sign: a child needing escalating opioid after fixation is declaring itself
• Anxiety
• Agitation
• Pain on passive extension of the fingers
• A tense, swollen forearm
• Pain disproportionate to the injury

Measure when the clinical picture is unreliable. In the obtunded, intubated, very young or regionally blocked patient the clinical signs cannot be trusted, so keep a low threshold for measuring pressures and measure if in doubt. The threshold is a delta P of less than 30 mmHg: the diastolic blood pressure minus the measured compartment pressure. An absolute pressure alone is misleading in a hypotensive patient, which is why the differential is used.

Where to measure. Measure in the compartment nearest the fracture and in the deep volar compartment, which is where the pressure is highest and where flexor digitorum profundus dies.

Fasciotomy is the treatment, and it is time-critical. For the forearm:

1. A volar release through an extended Henry-type or curved ulnar-based incision, decompressing the superficial and, crucially, the deep flexor compartment
2. A carpal tunnel release with it
3. A separate dorsal incision for the extensor and mobile wad compartments if they remain tight after the volar release
4. Wounds left open, a re-look at 48 hours, and closure or grafting when the swelling permits

Beware the regional block. A regional block can mask the developing syndrome, which is a real argument against dense regional anaesthesia in exactly this injury.

The pulseless hand: pink is not the same as white

A pulseless hand comes in two forms, and they are managed differently.

The white (or dusky) pulseless hand is an unperfused hand: cool, pale, with sluggish or absent capillary refill. This is limb-threatening ischaemia. Reduce and stabilise the fracture immediately and, if perfusion does not return at once, explore the brachial artery with vascular surgical support. Do not observe it.

The pink pulseless hand is perfused but has no palpable radial pulse. It is warm and pink, with capillary refill, presumably supported by collateral flow, and it is the genuinely contested one. After reduction and fixation the reasonable position is admission and close serial observation by an experienced team, with documented perfusion checks. Persistent pulselessness, any deterioration or an inability to observe reliably should prompt vascular assessment and exploration rather than indefinite watching.

Why pink is not reassuring. The concern is not the missing pulse itself but the occult ischaemia and the developing compartment syndrome behind it, and there is a well-recognised subgroup whose collateral flow proves inadequate. A pink pulseless hand with a rising analgesia requirement or a tense forearm is a compartment syndrome until proven otherwise.

The conventional rule. The teaching is operative stabilisation of both fractures, because a flail elbow between two fractures cannot be controlled in a cast. Rigid fixation of both converts the flail elbow into a stable segment, reduces complications and allows early motion, which is the single best protection against the elbow stiffness this injury otherwise causes.

How firm the rule is. "Fix both" is a safe default, but say it honestly in a viva. The CORTICES systematic review (Baghdadi, J Pediatr Orthop 2020; 11 studies, 433 children) found compartment syndrome in only 2%, a pulseless limb in 4% (every one regained a pulse after reduction), and good-to-excellent outcomes in 83-100%. It concluded that mandatory fixation of both fractures is not supported by evidence.

The real hazard is the cast. The documented historical hazard is the tight circumferential cast over a swelling limb (Ring 2001: the compartment events clustered in the casted forearms), not the un-pinned forearm fracture. The defensible position is therefore to pin the displaced supracondylar fracture urgently, stabilise the forearm when it is unstable, and never trap a swelling limb in a tight cast.

Which fracture first. There is no absolute rule. A common strategy is to stabilise the more proximal (humeral or supracondylar) fracture first, which restores a stable proximal segment, a lever against which the forearm can then be reduced and fixed. Some surgeons instead fix whichever fracture is simpler or more unstable first.

For every patient. Whatever the age:

• Treat open wounds with debridement, antibiotics and tetanus cover
• Monitor the compartments, and repeat the neurovascular assessment
• Have a plan for fasciotomy and for vascular repair if needed

Damage control. In a grossly contaminated open injury or a physiologically unstable polytrauma patient, temporary spanning external fixation or K-wires buy time, with definitive fixation once the soft tissues and the patient allow. The principles are developed in Damage Control Orthopaedics.

Implants, and one position that must be avoided

In the child. The supracondylar fracture is treated by emergency closed (or open) reduction and percutaneous K-wire stabilisation: two or three lateral-entry wires, or crossed wires accepting the ulnar nerve risk of the medial pin. The forearm fracture is conventionally stabilised too, rather than cast as it might be in isolation, because a cast fails to abolish the flail segment and needs a circumferential dressing over a maximally swelling limb. It is fixed with flexible intramedullary nails, K-wires or a plate, depending on level and age.

In the adult: the humerus. Both fractures are usually plated. For the humerus, plate fixation is generally preferred to intramedullary nailing in this setting: it gives rotational control, permits direct reduction and, where the fracture is distal or intra-articular, is the only option. An antegrade nail adds shoulder morbidity and controls rotation less well in a limb where the forearm is also unstable.

When a nail is reasonable. Nailing remains reasonable for a segmental or pathological midshaft fracture, or in the polytrauma patient where speed and soft-tissue preservation dominate. With a distal-third humeral fracture the radial nerve must be identified or deliberately protected, and again at plate removal.

In the adult: the forearm. Restore radial bow, length, alignment and rotation with plate fixation of both bones, to allow early rehabilitation. Malunion here costs pronation and supination, which is the function the patient will actually notice.

Then move it. Once both fractures are fixed, begin early supervised motion to protect against stiffness and loss of forearm rotation.

Outcomes

Generally good, less predictable. With prompt, aggressive operative management outcomes are generally good: in the paediatric series cited below, 10 of 12 children achieved good or excellent results after emergency reduction and K-wire stabilisation of both fractures. Read that as a small single-centre series rather than a reliable rate. The injury is rare enough that the literature is case series and reports, with no comparative trials.

What drives the result. Because of the associated injuries (open fractures, nerve injury, compartment syndrome), results are less predictable than for isolated fractures, and early recognition and treatment of those complications drives the outcome. Children generally do better than adults, whose stiffness, articular involvement and higher rate of open injury make a full functional recovery less likely.

The feared complication: Volkmann's ischaemic contracture. This is the devastating end-stage of an unrecognised forearm compartment syndrome, with a fixed flexion contracture of the wrist and fingers and intrinsic loss. It is the reason for the relentless compartment vigilance, and the syndrome is covered in detail in Forearm Compartment Syndrome.

The commonest functional problem: stiffness. The flail joint, extensive surgery and any immobilisation predispose to elbow stiffness and lost forearm rotation. Rigid fixation of both fractures with early motion is the main preventive, developed in Elbow Stiffness & Contracture.

Nerve injury and recovery. Most nerve injuries are traction neurapraxias that recover over weeks to months. A nerve that is interposed in the fracture or lacerated, especially in an open injury, needs exploration; document the injury and follow it.

Malunion and nonunion. Paediatric supracondylar malunion can give cubitus varus, forearm malunion costs the rotation described above, and adults risk nonunion of the humeral or forearm fracture.

Other complications include heterotopic ossification around the high-energy elbow, re-displacement or loss of fixation, and vascular sequelae.

Guidance and the Evidence Reality

No society publishes a dedicated floating-elbow guideline; the injury is rare enough that the literature is case series plus two systematic reviews, and practice is extrapolated from supracondylar and forearm fracture principles. The honest viva summary:

• Paediatric: the displaced supracondylar component drives the urgency (standard CRPP teaching). The CORTICES review (433 children) found compartment syndrome in only 2% and does not support mandatory dual fixation - but a tight circumferential cast over a swelling limb is the documented hazard (Ring 2001).
• Adult: the Ditsios systematic review (32 studies) quantifies the associated-injury burden - 51.2% open fractures, 34.9% neural injury, 76.3% multiple-system injury - which is why adults fare worse and dual operative stabilisation is the norm.
• Polytrauma frameworks (ATLS, damage-control orthopaedics) govern sequencing when the limb is one of several injuries.

Registry and Resource Notes

• No registry captures floating elbow as an entity; outcomes come from single-centre series pooled in the reviews above.
• High-resource settings: percutaneous pinning, flexible nails, plating and compartment-pressure monitoring are routine. Limited-resource settings rely on K-wire fixation and clinical compartment assessment - the non-negotiables are the same everywhere: never a tight cast over a swelling forearm, and repeated neurovascular checks.