High-Risk Fractures, Dislocations & Complications
The injuries that threaten a limb, a nerve, or a life
Vascular emergencies: knee and hip dislocations
Knee dislocation. Disruption of multiple knee ligaments follows high-energy trauma or, in patients with severe obesity, a simple fall. The popliteal artery is tethered above at the adductor hiatus and below at the soleus arch, so displacement stretches it, producing intimal tears, thrombosis, or transection. The common peroneal nerve is frequently injured as well. Many dislocations reduce spontaneously before arrival, so a grossly unstable knee after high-energy trauma should be treated as a reduced dislocation. Palpable distal pulses do not exclude an intimal injury that can thrombose hours later.
- Reduce and splintEmergent reduction, then recheck pulses and neurologic function.
- Ankle–brachial indexMeasure in every knee dislocation, even with normal pulses.
- ABI ≥0.9 and normal pulsesAdmit for serial vascular examinations.
- ABI <0.9 or asymmetric pulsesCT angiography.
- Hard signsAbsent pulses, expanding hematoma, pulsatile bleeding, bruit or thrill, or limb ischemia → emergent surgical exploration and revascularization; ischemia beyond about 6–8 hours often ends in amputation.
Posterior hip dislocation. About 90% of hip dislocations are posterior, classically when a flexed knee strikes the dashboard and drives the femoral head backward. The leg is shortened, flexed, adducted, and internally rotated. Associated injuries include posterior acetabular wall and femoral head fractures and injuries of the ipsilateral knee. The sciatic nerve, mainly its peroneal division, may be stretched, causing foot drop. An anterior dislocation leaves the leg abducted and externally rotated, and a femoral neck fracture leaves it shortened and externally rotated.
Management. Closed reduction under procedural sedation should occur as soon as possible, ideally within 6 hours, because the medial femoral circumflex vessels are kinked or torn and delay increases femoral head osteonecrosis. Document sciatic nerve function before and after reduction. A post-reduction CT looks for acetabular or femoral head fragments and confirms a congruent joint; an irreducible or incongruent hip needs open reduction.
Fractures that injure nerves
Humeral shaft and radial nerve. The radial nerve spirals along the posterior humerus in the radial groove, and about 1 in 10 shaft fractures injure it, especially spiral fractures of the distal third. The result is wrist drop, weak finger and thumb extension, and numbness over the dorsal first web space; the triceps is usually spared because its branches arise above the groove. Most palsies with closed fractures are neurapraxias that recover. Treat the fracture with a functional brace, splint the wrist, observe, and obtain EMG if there is no recovery after several months; open fractures are explored.
Fibular neck and common peroneal nerve. The nerve wraps superficially around the fibular neck, where fractures, direct blows, tight casts or braces, prolonged leg crossing, and varus knee injuries damage it. Foot drop with a steppage gait, weak eversion, and numbness of the dorsal foot and lateral leg follow. Inversion (tibial nerve) and hip abduction (superior gluteal nerve) are preserved, which separates it from L5 radiculopathy. Management is padding, removal of compression, and an ankle-foot orthosis during recovery.
| Injury | Nerve | Deficit |
|---|---|---|
| Anterior shoulder dislocation, surgical neck fracture | Axillary | Weak deltoid, numb lateral shoulder |
| Humeral shaft fracture | Radial | Wrist drop, dorsal first web space numbness |
| Supracondylar humerus fracture (extension type) | Anterior interosseous | Cannot make an OK sign; no sensory loss |
| Medial epicondyle fracture, flexion-type supracondylar, medial pin | Ulnar | Weak intrinsics, claw hand |
| Monteggia fracture-dislocation | Posterior interosseous | Finger and thumb drop without wrist drop or sensory loss |
| Posterior hip dislocation | Sciatic (peroneal division) | Foot drop |
| Fibular neck fracture | Common peroneal | Foot drop, weak eversion, inversion spared |
Pediatric supracondylar fracture
Mechanism and anatomy. This is the most common elbow fracture in children, peaking around ages 5–7, after a fall on an outstretched hand with the elbow hyperextended. Nearly all are extension type: the distal fragment displaces posteriorly, and the brachial artery and median nerve are tented over the sharp proximal fragment. The anterior interosseous nerve, a purely motor median branch to flexor pollicis longus, the index flexor digitorum profundus, and pronator quadratus, is the nerve most often injured; the child cannot make an OK sign but has normal sensation.
Management. Displaced fractures are treated with closed reduction and percutaneous pinning, emergently if the hand is pale and pulseless.
Compartment syndrome and Volkmann contracture. Brachial artery injury or massive swelling can cause forearm compartment syndrome, most severe in the deep flexor compartment. In children the warning signs are the 3 A's (anxiety, agitation, and an increasing analgesic requirement) plus pain on passive finger extension; a palpable radial pulse does not exclude it. Treatment is emergent fasciotomy. If missed, necrotic flexor muscle is replaced by fibrous tissue, producing Volkmann ischemic contracture, a fixed claw-like flexion of the wrist and fingers.
Never splint a swollen supracondylar fracture in deep flexion or treat escalating pain with more opioids alone: both hide an evolving compartment syndrome.
Forearm fracture-dislocations
Principle. The radius and ulna form a ring with the proximal and distal radioulnar joints, so a displaced fracture of one bone usually means a dislocation elsewhere. Any apparently isolated forearm shaft fracture needs dedicated elbow and wrist radiographs.
| Feature | Monteggia | Galeazzi |
|---|---|---|
| Fracture | Proximal-third ulnar shaft | Distal-third radial shaft |
| Dislocation | Radial head (proximal radioulnar joint) | Distal radioulnar joint |
| Mechanism | Fall with forced pronation or direct blow | Fall on an outstretched hand |
| Clue | Radiocapitellar line misses the capitellum | Prominent, painful ulnar head at the wrist |
| Nerve | Posterior interosseous | Usually none |
| Adult treatment | ORIF of the ulna, which usually reduces the radial head | ORIF of the radius (fracture of necessity) plus DRUJ stabilization if unstable |
Systemic complications: fat embolism and thromboembolism
Fat embolism syndrome. After long-bone (femur, tibia) or pelvic fractures, or intramedullary reaming, marrow fat enters the circulation and provokes an inflammatory injury, typically 24–72 hours later. Hypoxemia and dyspnea come first and are most common, then confusion, agitation, or seizures, then petechiae over the axillae, conjunctivae, oral mucosa, and upper chest, the most specific sign but often the last to appear. Supporting findings include fever, tachycardia, thrombocytopenia, anemia, fat globules in urine or retinal vessels, bilateral infiltrates, and a starfield pattern of small diffusion lesions on brain MRI.
Management. Care is supportive: oxygen, lung-protective ventilation if needed, and hemodynamic support. Corticosteroids and heparin are not routine therapy. Prevention is early immobilization and early operative fixation of long-bone fractures, ideally within 24 hours. Petechiae and neurologic signs with a negative CT pulmonary angiogram favor fat embolism over thrombotic PE.
Venous thromboembolism. Pelvic, hip, and femoral fractures and major lower-extremity surgery combine every element of the Virchow triad: stasis from immobility, endothelial injury, and post-traumatic hypercoagulability. LMWH is the preferred prophylaxis, started once bleeding risk allows and continued at least 10–14 days, extended up to 35 days after hip fracture surgery. Alternatives include fondaparinux, low-dose unfractionated heparin, warfarin (INR 2–3), or aspirin in selected patients. Intermittent pneumatic compression is used when anticoagulation is contraindicated, and IVC filters are reserved for proven VTE that cannot be anticoagulated.
Late complications: CRPS, malunion, heterotopic ossification
Complex regional pain syndrome. CRPS follows a fracture (classically of the distal radius), surgery, or immobilization. Burning pain is out of proportion to the injury, with allodynia and hyperalgesia, edema, asymmetric color and temperature, altered sweating, and later trophic changes (shiny skin, hair and nail changes, stiffness). Type I (formerly reflex sympathetic dystrophy) has no identifiable nerve lesion; type II (formerly causalgia) follows a nerve injury. Diagnosis is clinical by the Budapest criteria, supported by patchy osteopenia on radiographs and increased periarticular uptake on three-phase bone scan.
CRPS treatment. Early physical and occupational therapy with active motion, desensitization, and graded motor imagery or mirror therapy is the cornerstone. NSAIDs, gabapentinoids or tricyclic antidepressants, a short early course of oral corticosteroids, or bisphosphonates may be added. Sympathetic nerve blocks and spinal cord stimulation are for refractory cases. Prolonged immobilization worsens CRPS, and long-term opioids are not recommended.
Malunion. A fracture that heals with angulation, rotation, or shortening alters joint mechanics and causes deformity, dysfunction, and early arthritis. Classic examples are cubitus varus (gunstock deformity) after a supracondylar fracture and finger scissoring after a rotated metacarpal or phalangeal fracture. Accurate reduction with follow-up radiographs prevents it, and symptomatic malunion is corrected by osteotomy.
Heterotopic ossification. Mature lamellar bone forms in muscle and periarticular soft tissue after hip arthroplasty, acetabular fractures, elbow fracture-dislocations, traumatic brain or spinal cord injury, and burns. It appears weeks to months later as pain, warmth, swelling, and shrinking range of motion that can mimic DVT or infection. Alkaline phosphatase rises and a three-phase bone scan turns positive before radiographs show bone. High-risk patients receive prophylaxis with indomethacin or single-dose radiation, and mature bone is excised only if it limits function. Myositis ossificans is the localized form after a muscle contusion, such as a thigh charley horse.