Dislocation, loosening and infection after arthroplasty — Rapid

Synopsis

Triage a painful hip or knee replacement into immediate mechanical emergency, infection and gradual failure pathways; use comparison imaging and disciplined sampling, and avoid revision without a specific diagnosis.

For sudden deformity or loss of function, record neurovascular status and obtain AP and orthogonal radiographs before and after reduction; do not repeatedly manipulate a possible fracture.
A first hip dislocation is reduced promptly with adequate sedation or anaesthesia, then assessed for fracture, component position, cause and stability; recurrent episodes need revision expertise.
A painful replacement is not automatically loose or infected. Build a timeline of surgery, wound, pain-free interval, trauma, bacteraemia, antibiotics, mechanical symptoms and systemic features.
Initial problematic-knee assessment includes consultant review, examination, infection screening and full weight-bearing AP and lateral, long-leg alignment and skyline radiographs.
A sinus communicating with the prosthesis confirms infection. Stable suspected infection stays off antibiotics until aspiration or deep samples; septic infection receives blood cultures, immediate intravenous therapy and drainage.
Loosening is assessed first on comparison radiographs; CT clarifies rotation, bone loss or occult fracture, while more complex tests should be targeted through the revision arthroplasty MDT.
Do not perform revision for unexplained pain. Identify a specific correctable cause such as infection, loosening, instability, malposition, stiffness, fracture, wear or extensor failure.
After reduction, DAIR or revision, monitor wound, infection markers, component stability, thrombosis, neurovascular status and rehabilitation and provide explicit recurrence and emergency instructions.

Key red flags

A shortened deformed limb, sudden inability to move after hip replacement or an abnormal radiograph indicates dislocation or fracture and requires urgent orthopaedic management.

Fever, wound drainage, sinus, acute severe implant pain or systemic illness requires prosthetic-joint infection assessment; sepsis treatment must not wait for elective aspiration.

New foot weakness, numbness, absent pulses or severe swelling before or after reduction requires immediate neurovascular reassessment and escalation.

Rapidly increasing pain with trauma, deformity or inability to bear weight raises peri-prosthetic fracture or component migration and requires protected transfer and full-length imaging.

Investigation priorities

Immediate orthogonal radiographsFirst step

Confirm dislocation, fracture and component position.

Management branches

Acute mechanicalProtect, image and restore anatomy

Dislocation, fracture or abrupt component failure produces deformity or inability to load.

Document distal neurovascular status, provide analgesia, protect the limb and obtain urgent full implant radiographs.
Reduce a confirmed dislocation promptly with adequate relaxation and orthopaedic support; avoid force when fracture is possible.
Repeat examination and imaging and use CT for fracture, component or non-concentric reduction uncertainty.
Escalate irreducible, recurrent, malpositioned or fractured constructs to revision expertise.

InfectionSeparate stable sampling from septic treatment

Pain, drainage, sinus, effusion or systemic illness makes prosthetic infection plausible.

If septic, take blood cultures, start intravenous treatment and drain urgently; if stable, withhold antibiotics before aspiration.
Apply validated criteria and obtain five deep cultures and histology at surgery.
Select DAIR, exchange or salvage from timing, fixation, tissue, organism and host.
Link organism-directed therapy, interaction monitoring and recurrence surveillance to the exact operation.

Key medicines

Analgesia and procedural sedation for dislocationGive titrated intravenous analgesia and procedural sedation or general anaesthesia under the emergency department and anaesthetic protocol, with continuous monitoring and personnel able to manage airway and fracture complications; no fixed drug combination replaces patient-specific assessment.Older adults are vulnerable to hypotension, respiratory depression and delirium; account for fasting, frailty, cardiopulmonary disease and opioids already given, and never attempt forceful repeated reduction without adequate conditions.

Empirical parenteral therapy for septic prosthetic-joint infectionAfter urgent blood cultures, give the full adult sepsis and prosthetic-joint-infection protocol regimen immediately; obtain deep samples at emergency drainage and narrow to organism, renal function and the selected implant operation.Stable patients should remain off empirical therapy until aspiration or deep samples; document allergy, renal injury, prior resistance and all interactions, and do not use antibiotics alone for a loose infected implant or mature biofilm.

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