Hip Pain, Fever, and Autonomic Storms After Severe TBI: Sorting Out Heterotopic Ossification, DVT, and Infection
Mr. T is 28, 6 weeks after severe TBI from an assault, with residual left hemiparesis and cognitive impairment, admitted for inpatient rehabilitation. For 5 days he has had worsening right hip and groin pain that limits therapy; the hip is held in 20° of external rotation with limited, painful range of motion. Temperature is 38.1°C, HR 110, and the right thigh is swollen compared with the left. D-dimer is 1,900 ng/mL; lower-extremity duplex ultrasound is negative. Alkaline phosphatase is 210 U/L. He has intermittent autonomic storms with BP 180/100 and tachycardia. He is on enoxaparin prophylaxis.
1. What is your differential and what is the next diagnostic step? Explain why a negative duplex ultrasound is insufficient.
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Differential: heterotopic ossification, proximal or pelvic deep vein thrombosis, occult fracture, septic arthritis or osteomyelitis, hematoma, and groin strain. Autonomic storms can be triggered by pain from any of these.
A negative duplex ultrasound does not exclude DVT because:
- Pelvic and deep femoral veins are often not fully visualized.
- A clot may be distal or nonocclusive.
- Swelling and elevated D-dimer are nonspecific but keep pretest probability moderate to high.
Next step: CT or MRI of the hips and pelvis, which evaluates bone, soft tissue, and marrow and can assess for HO and fracture; CT venography or MR venography if pelvic DVT remains a concern. Obtain CBC, CRP, blood cultures if febrile, and plain films of the hip - early HO may not appear on radiographs. If a joint effusion is present, aspiration for cell count and culture is the definitive way to exclude septic arthritis. Do not anchor on HO simply because the alkaline phosphatase is elevated; that finding is supportive, not diagnostic.
2. If imaging shows early heterotopic ossification, how do you manage it and when do you mobilize?
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Early HO is managed by controlling inflammation and preserving function, not by immobilizing the limb.
- Do not stop therapy. Immobilization accelerates contracture and functional loss. Use gentle, pain-limited active and active-assisted range of motion; avoid aggressive passive stretching and forced end-range, which may worsen inflammation.
- Anti-inflammatory options: NSAIDs are effective for HO prophylaxis and symptom control but are relatively contraindicated with concurrent anticoagulation and recent bleeding risk; discuss with the team. Bisphosphonates (etidronate) are an alternative for prophylaxis in high-risk patients.
- Pain control with acetaminophen and other non-NSAID options; treat the associated autonomic storms, which are often pain-driven.
- Monitor alkaline phosphatase, range of motion, and functional status. Serial imaging is more useful than a single study.
- Surgery is reserved for mature HO causing functional limitation, usually delayed months; early resection is considered in selected cases such as nerve compression or joint ankylosis.
- Prevention for the future: early mobilization, passive range of motion, and consideration of prophylaxis in high-risk patients with spasticity and prolonged immobility.
3. How do you distinguish his autonomic storms from pain, DVT, and other causes, and how do you manage them while the workup proceeds?
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Paroxysmal sympathetic hyperactivity is a diagnosis of exclusion and should not be assumed to be the whole story when a new focal finding appears.
- Look for a trigger: the new hip pain, swelling, and fever are red flags for DVT, infection, or HO. A change in the pattern, duration, or frequency of storms warrants investigation rather than simply escalating sympatholytic therapy.
- Other causes to exclude: nociception (hip, constipation, urinary retention), sepsis, pulmonary embolism, hypoxia, withdrawal, and seizure.
- Management while working up: treat pain, keep the environment calm and minimize handling, ensure bowel and bladder care, and use scheduled rather than reactive analgesia. For PSH itself, options include propranolol, gabapentin, clonidine, and bromocriptine, titrated to frequency and severity with monitoring of blood pressure and heart rate.
- Do not mask deterioration. If storms increase despite trigger control, repeat imaging and cultures.
Document the storm frequency and severity daily so that response to treatment and new triggers are visible to the whole team.