The hip is one of the largest joints in the body and is referred to as a ball-and-socket joint.
The upper end of the thigh bone (femur) or femoral head forms the ball, which fits into the acetabulum, which forms a socket in the pelvis. A layer of articular cartilage covers this bone and socket, cushioning them to allow ease of movement. A liquid called the synovial fluid surrounds the hip joint, lubricating the cartilage so that friction does not occur as the structures move against each other. The main purpose of the hip joint is to support the weight of the upper body and maintain balance during standing, walking, and running.
Hips also help when certain movements are carried out such as bending or stretching. A hip replacement may be necessary in cases where one or both of the hip joints have become damaged and painful, making it difficult to carry out day-today activities such as driving, walking or dressing. Many of the conditions that lead to a hip replacement being needed are age-related, such as osteoporosis, rheumatoid arthritis and hip fracture.
In a hip replacement procedure, a patient’s damaged hip is removed and replaced with a prosthetic implant. There are two forms of hip replacement –total hip arthroplasty, where both the femoral head and acetabulum are replaced and hemiarthroplasty, where usually only the femoral head is replaced.
Hip replacement is one of the most successful and reliable orthopaedic operations currently performed, with replaced hips still functioning in around 85% of patients 20 years following the procedure.
One of the most common reasons for performing a hip replacement is to treat hip joint failure caused by osteoarthritis. Some further examples of reasons why hip replacements are performed include:
- Rheumatoid arthritis
- Traumatic arthritis
- Injury to the hips
- Protrusio acetabuli
- Avascular necrosis
- Hip fracture
- Arthritis associated with Paget's disease
- Juvenile rheumatoid arthritis
- Arthritis due to ankylosing spondylitis
- Benign and malignant bone tumors
Some of the benefits that are seen after a hip replacement is performed include pain relief, improved hip function, improved mobility and improved quality of life.
Reviewed by Sally Robertson, BSc