The most common joints replaced electively are the hip, knee and shoulder. The most common indication is osteoarthritis. Most patients that have joint replacements are over 60.
The artificial joints are built to last more than 10-15 years. However, they may be affected by loosening, wear and dislocation. Some patients may require further surgery and replacement of the artificial joint at some point.
Joint replacement is major surgery. Patients need to have the alternatives discussed before deciding to undergo surgery. The other options usually include analgesia, steroid injections and physiotherapy.
Indications
Osteoarthritis is the most common indication for an elective joint replacement. It is not usually performed until symptoms are severe and not manageable with conservative treatments.
Joints may also require replacement for:
- Fractures
- Septic arthritis
- Osteonecrosis
- Bone tumours
- Rheumatoid arthritis
Options
There are several options for elective joint replacement surgery:
- Total joint replacement – replacing both articular surfaces of the joint
- Hemiarthroplasty – replacing half of the joint (e.g., the head of the femur in the hip joint)
- Partial joint resurfacing – replacing part of the joint surfaces (e.g., only the medial joint surfaces of the knee)
Total Hip Replacement
Usually, a lateral incision over the outer aspect of the hip is used. The hip joint is dislocated (separated) to give access to both articular surfaces.
The head of the femur is removed. A metal or ceramic replacement head of femur, on a metal stem, is used to replace it. The stem can either be cemented into the shaft of the femur or carefully pushed into the shaft to make a tight enough fit to hold it securely in place. Uncemented stems have a rough surface that holds them tightly in place.
The acetabulum (socket) of the pelvis is hollowed out and replaced by a metal socket, which is cemented or screwed into place. A spacer is used between the new head and socket to complete the new artificial joint.
Total Knee Replacement
Usually, a vertical, anterior incision is made down the front of the knee. The patella is rotated out of the way to allow access to the knee joint.
The articular surfaces (the cartilage and some of the bone) of the femur and tibia are removed. A new metal surface replaces these. They can be either cemented or pushed tightly into place.
A spacer is added between the new articular surfaces of the femur and tibia to complete the new artificial joint.
Total Shoulder Replacement
Usually, an anterior incision is made down the front of the shoulder, along the deltoid. The shoulder joint is dislocated (separated) to give access to both articular surfaces.
The head of the humerus is removed and replaced with a metal or ceramic ball. This replacement head is attached to the humerus either by a metal stem or screws (stemless).
The glenoid (socket) is hollowed out and replaced by a metal socket. This completes the artificial shoulder joint.
Reverse Total Shoulder Replacement
A reverse total shoulder replacement involves adding a sphere in place of the glenoid (socket) and a spacer with a cup to replace the head of the humerus. This reverses the normal ball-in-cup structure of the shoulder joint, but the joint function remains the same.
Before Surgery
Planning for joint replacement surgery will involve:
- X-rays
- CT or MRI scans may be required for a more detailed assessment
- Pre-operative assessment (pre-op)
- Consent for surgery
- Bloods (including group and save and crossmatching of blood)
- Medication changes if needed (e.g., temporarily stopping anticoagulation)
- Venous thromboembolism assessment
- Fasting immediately before surgery
- The limb will be marked with the patient awake to ensure the operation is performed on the correct joint
During Surgery
Joint replacement surgery requires a general anaesthetic. Alternatively, a spinal anaesthetic may be used for lower limb surgery.
Prophylactic antibiotics are given before the procedure to reduce the risk of infection.
Tranexamic acid may be used to minimise blood loss during the procedure.
After Surgery
Post-operative management after joint replacement surgery involves:
- Analgesia
- Physiotherapy to guide when and how to mobilise
- VTE prophylaxis
- Post-operative x-rays
- Post-operative full blood count (to check for anaemia)
- Monitoring for complications (e.g., deep vein thrombosis or infection)
VTE prophylaxis usually involves low molecular weight heparin (LMWH). The 2018 NICE guidelines on VTE prophylaxis have specific recommendations on potential regimes that can be used after joint replacement surgery (see full national and local guidelines when treating patients). This involves the option of LMWH for:
- 28 days post elective hip replacement
- 14 days post elective knee replacement
Other measures that may be used for VTE prophylaxis after joint replacement surgery are:
- Aspirin
- DOACs (e.g., rivaroxaban)
- Anti-embolism stockings
Risks
The generic risks of joint replacement surgery are:
- Risks of the anaesthetic
- Pain
- Bleeding
- Infection – infection of the prosthesis can be highly problematic (see below)
- Damage to nearby structures (e.g., nerves or arteries)
- Stiffness or restricted range of motion in the joint
- Joint dislocation
- Loosening
- Fracture during the procedure
- Venous thromboembolism (DVT or PE)
Prosthetic Joint Infections
Infection in a prosthetic joint is a big problem. This occurs in around 1% of joint replacements and extensive measures are taken to prevent it, such as perioperative prophylactic antibiotics. It is more likely to occur in revision surgery rather than during the initial joint replacement. The most common organism is Staphylococcus aureus (a common skin organism).
Risk factors for prosthetic joint infection are:
- Prolonged operative time
- Obesity
- Diabetes
Symptoms include:
- Fever
- Pain
- Swelling
- Erythema
- Increased warmth
Diagnosis involves a combination of clinical findings, x-rays, blood tests (raised inflammatory markers), cultures (e.g., blood or synovial fluid) and findings during further operations.
Management involves repeat surgery and prolonged antibiotics (over months). Surgery may involve joint irrigation, debridement or complete replacement.
Last updated August 2021