Joint Replacement

Definition & Aims

Arthroplasty is the surgical reconstruction or replacement of a joint to relieve pain and restore movement and function. Total joint replacement (arthroplasty) replaces both articulating surfaces with prosthetic components; the hip and knee are the commonest and most successful. The principal aim is relief of pain, with improvement of function and correction of deformity.

Indications

The main indication is severe joint pain and disability from end-stage arthritis (osteoarthritis, rheumatoid arthritis, post-traumatic arthritis, AVN) that has failed adequate conservative treatment. Other indications include certain fractures (e.g. Displaced femoral neck fracture in the elderly) and tumours requiring joint resection.

Types & Fixation

Components may be fixed to bone with cement (PMMA) or by cementless (press-fit, bone-ingrowth) fixation; hybrid constructs combine both. Bearing surfaces pair a metal or ceramic head with a polyethylene, ceramic or metal counterface. Replacement may be total (both surfaces) or partial (e.g. Hemiarthroplasty of the hip, unicompartmental knee replacement).

Complications

Early: infection, venous thromboembolism (DVT/PE), dislocation (especially the hip), neurovascular injury, and peri-prosthetic fracture. Late: aseptic loosening (the commonest cause of long-term failure, driven by wear-particle osteolysis), polyethylene wear, late infection, peri-prosthetic fracture and implant failure. Revision surgery is more complex and less durable than primary replacement.

Post-operative Care

Multimodal analgesia, thromboprophylaxis, early mobilisation and physiotherapy, and measures to prevent dislocation (hip precautions) optimise outcome. Patients are counselled that a modern hip or knee replacement typically lasts many years but is not permanent and may eventually need revision.

Pre-operative Assessment

Careful patient selection and preparation underpin success. This includes optimising medical comorbidities (anaemia, diabetes, cardiac and respiratory disease), assessing and eradicating sources of sepsis (dental, urinary, skin), templating the radiographs to plan implant size and restore limb length and offset, and counselling the patient on the risks, the rehabilitation required and the finite lifespan of the implant. Body weight, activity level and bone quality all influence the choice of implant and fixation.

Revision Arthroplasty

When a replacement fails — through infection, aseptic loosening, wear, instability or peri-prosthetic fracture — revision surgery is required. Revision is technically more demanding than the primary operation: bone stock is often deficient, exposure is harder, and specialised implants (augments, longer stems, constrained bearings) may be needed. Outcomes are generally less good and complication rates higher than primary replacement, which is why preserving bone and avoiding infection at the first operation matters so much.

Aseptic loosening is the commonest long-term cause of failure.

• Arthroplasty replaces joint surfaces; hip/knee commonest; main aim is pain relief.
• Indication: end-stage arthritis failing conservative care (also some fractures/tumours).
• Fixation cemented (elderly/soft bone) vs cementless (younger/good bone) vs hybrid.
• Feared complication: deep prosthetic infection; also VTE and dislocation early.
• Aseptic loosening (wear-particle osteolysis) is the main long-term cause of failure.