Dislocation, loosening and infection after arthroplasty

Start with timing. Immediate postoperative pain, acute pain after a previously well interval and gradual progressive pain carry different probabilities. Ask about original indication and implant, wound healing, drainage, later infections or bacteraemia, antibiotic exposure, falls, clicks, instability, start-up pain, night pain and systemic symptoms. Establish whether the hip or knee ever functioned well. Obtain operative and implant records and compare serial radiographs; revision planning without knowing components and previous exposures is unsafe.

For acute suspected dislocation or fracture, assess limb length, rotation, swelling, wounds and distal pulses, capillary refill, motor and sensory function. Obtain orthogonal radiographs including the whole relevant implant and adjacent bone. Keep nil by mouth, provide analgesia and avoid unsupported weight bearing. Closed reduction needs adequate relaxation, appropriate personnel and readiness for fracture or irreducibility. Repeat neurovascular examination and radiographs afterwards. CT is indicated when fracture, component failure or uncertain concentric reduction persists.

A problematic replacement needs structured consultant-led assessment. BOASt for knee replacement recommends clinical examination, radiographs and infection serology as initial tests. Full weight-bearing AP and lateral, long-leg alignment and patellar skyline views are standard for knee; partial replacements need appropriate flexion views. For hips obtain AP pelvis and lateral views and assess migration, lucency, osteolysis, wear, fracture, leg length and component orientation. Serial change is more convincing than a single subtle line.

Always exclude infection before labelling loosening aseptic or revising for another reason. Examine the wound and any sinus without probing, take FBC and CRP or ESR, and obtain blood cultures in systemic illness. A communicating sinus or visible prosthesis is confirmatory. A stable patient should not receive antibiotics before image-guided aspiration or planned deep sampling. Send synovial count, differential, cultures and crystals and apply validated infection criteria. At surgery use five deep microbiology specimens and appropriate histology with separate instruments.

Aseptic loosening typically causes load or start-up pain with progressive radiolucency, migration, subsidence or osteolysis. CT maps bone loss, component rotation and occult fracture. SPECT-CT may help selected uncertain cases but complex testing belongs in the revision MDT. Bone scanning and minor exploratory operations have no routine role in a problematic knee under BOASt. Investigate metal-related adverse tissue reaction only for relevant bearing and clinical context using the current implant-safety pathway.

After first hip dislocation, identify precipitating movement, component orientation, impingement, abductor function, neurological disease and spinopelvic stiffness. A brace is selective rather than automatic. Recurrent dislocation, irreducibility, component malposition, fracture, liner failure or major soft-tissue deficiency may require revision. Educate on safe movement according to surgical approach and individual cause without imposing indefinite generic restrictions that delay mobility.

Prosthetic-joint infection management depends on sepsis, symptom duration, implant stability, soft tissue and organism. A septic patient receives urgent cultures, immediate parenteral treatment and drainage. Carefully selected early postoperative or short-duration haematogenous infection may undergo open debridement, modular-component exchange and implant retention. Chronic biofilm, loosening, sinus or unsuitable organisms usually requires component exchange. Antimicrobial choice and duration are tied to surgery through the infection MDT.

Revision should correct a defined mechanism. BOASt warns that surgery without a firm diagnosis is less likely to benefit; unexplained cases need MDT discussion and may need pain, physiotherapy or other specialist pathways. Explain that further surgery can worsen pain, stiffness, bone loss and infection. After intervention, follow wound, cultures, radiographs, stability and personal functional goals. Urgent return signs include fever, drainage, recurrent deformity, inability to bear weight, new neurological symptoms and calf or chest symptoms.