What is Hip Replacement Surgery?

Hip replacement surgery is also referred to as total hip arthroplasty. Replacement is performed on a damaged hip joint, usually due to osteoarthritis. Other causes include rheumatoid arthritis and injury to the hip caused by trauma such as fracture.

Hip replacement surgery is performed when the patient suffers incessant pain that restricts the daily activities and compromises the quality of life. The medication in such situations provides only limited relief from the pain.

Hip replacement surgery involves replacing the hip joint with new artificial joint parts. These artificial parts are called “prosthesis”.

The aims of hip replacement surgery is to:

Increase patient’s mobility,
Improve function of the hip joint,
Offer relief from pain.

The surgery should in short improve the quality of the patient’s life.

Understanding the Normal Hip Joint

To understand what happens in a hip replacement surgery, one needs to know the components of a normal hip joint.

The hip joint is a ball and socket type of joint. It has 2 components, one component acting as the ball which fits into the hollow socket.

The hollowed out acetabulum of the pelvic bone forms the socket into which the head of the femur (thigh bone) fits into perfectly as the ball component.

For normal hip joint function, both components have to be healthy and articulate with each other smoothly and freely.

In a hip joint that is damaged by disease or trauma, the smooth and free articulation is disrupted leading to pain and restricted mobility. Initially the pain may be alleviated by medications. However, with progression of disease and further weakening of joint components, the pain disrupts the patient’s daily life and forces him to seek surgical relief.

What are the Types of Hip Replacement Surgery?

Artificial hip joint consists of a ball and a socket to hold it. The material for the ball is made of metal or ceramic and the socket can be made of plastic, ceramic, or metal.

The ball as in a normal joint attaches to the top of the thigh bone called the femur and the new socket attaches to the hip bone or pelvis.

There are two main types of hip replacement surgery – Cemented or un-cemented.

Uncemented replacement is used in younger people who are active and where there is no bone loss or osteoporosis. The cemented joint is used where the bones are weak as in older people.

1. Total Hip Replacement (THR) – Cemented

In total hip replacement, part of the thigh bone (femur) including the ball (head of femur) is removed and a new, smaller artificial metal head is fixed into the rest of the thigh bone. Next the surface of the existing socket in the pelvis (the acetabulum) is reshaped and roughened for cement to hold the metal cup. Once the two components have been fixed firmly, the components are made to join up or get articulated. The cement is made of acrylic to hold these components into the bone.

2. Total Hip Replacement (THR) – Un-cemented

In this procedure a metal cap, which is hollow and shaped like a mushroom is placed over the head of the femur while a matching metal cup (similar to what is used with a THR) is placed in the acetabulum (socket in the pelvic bone). Thus the articulating surfaces of the patient's hip joint are replaced while removing very little bone when compared to the total hip Arthroplasty and no cement is used.

Benefits of Hip Replacement Surgery

Increased mobility
Improved activities of daily living
Better quality of life
Reduced pain

What are the Types of Hip Implants Available?

Currently, in the West, five types of total hip replacement devices (prostheses) are available with different bearing surfaces. These include:

Metal-on-Plastic: The ball is composed of metal while the socket is made out of plastic (polyethylene) or has a plastic lining.
Ceramic-on-Polyethylene: The ball is composed of ceramic while the socket is made out of plastic (polyethylene) or has a plastic lining.
Metal-on-Metal: Both the ball and socket are composed of metal
Ceramic-on-Ceramic: The ball is composed of ceramic while the socket has a ceramic lining.
Ceramic-on-Metal: The ball is composed of ceramic while the socket has a metal lining.

An orthopedic surgeon will determine which type of hip implant will offer the most benefit and least risk for each patient. While making the decision, orthopaedic surgeons need to consider several factors such as the patient’s age, weight and height, activity level, and the cause of hip pain and other medical conditions.

For example, metal-on-metal resurfacing isn’t suitable for people with low bone density or osteoporosis, where the bones are already weakened.

Indications for Hip Replacement Surgery

Rheumatoid Arthritis: An auto-immune disease that results in inflammation and thickening of the joint capsule leading to joint damage.
Avascular Necrosis: Death of bone tissue and collapse of the hip joint due to interruption of blood supply.
Certain Hip Fractures
Benign and Malignant Bone Tumors
Arthritis Caused by Paget’s Disease of Bone: Disease causing weakened and misshapen
bones that are prone to fractures and arthritis.
Ankylosing Spondylitis: An auto-immune disease that leads to restricted movement of the joint.
Osteoarthritis: Joint disease that occurs due to degeneration of the articular cartilages.

Hip Replacement Surgery Procedure

Hip replacement requires stay in a hospital. Procedures vary depending on the patient’s condition and the surgeon’s practices.
The surgery is performed under general or spinal or epidural anesthesia.
- The surgical incision can be placed in front, side or behind depending on the preference of the orthopedic surgeon. These are called anterior, lateral or posterior approach. Some surgeons use a smaller incision and call it a minimally invasive approach. There are no clinical long term studies to show which approach is superior; however the posterior approach is most commonly used approach for total hip replacement.
During the procedure, the damaged parts of the hip joint will be removed and replaced with the artificial ball and socket parts or prosthesis.
The ‘ball’ portion of the prosthetic joint is attached to the femur or thighbone using a cement or a special material which permits the remaining bone to attach to the new joint. More recently ‘uncemented’ prostheses are also being used, especially in younger and active persons. Both have comparable success rates.
Next, the damaged socket part in the hip bone is replaced by the prosthetic socket.
The new ball part of the thighbone is then inserted into the socket part of the hip.
Traditional hip replacement surgery involved making an 8 – 10 inch incision along the side of the hip.

Currently however ‘minimally invasive’ procedures are being performed with much smaller incisions. This is thought to reduce the blood loss and also minimise scar tissue formation. However, the minimally invasive technique requires skill and experience and has to be performed by an experienced surgeon.

Hip Replacement Surgery - Recovery and Rehabilitation

Normally, people do not spend more than 3 to 5 days in the hospital after a hip replacement surgery. Full recovery from the surgery takes about 3 to 6 months, depending on the type of surgery, overall health of patient, and the success of the rehabilitation program.

It is essential to get instructions from the surgeon before discharge and to follow them carefully at home. Doing so will offer the greatest chance of a successful recovery.

General Precautions

Take the recommended pain medications
Keep the surgical area clean and dry.
Doing physiotherapy and exercising the joint muscles regularly to hasten recovery
Occupational therapy to overcome the physical disability following surgery. Some examples include using a raised toilet seat to avoid bending low and gadgets to help with daily activities.
Avoid squatting, sitting on low chairs or crossing legs till the recovery is complete
Use walking aids such as crutches for about 6 weeks

Avoiding falls and watching one’s step
Avoid driving for at least 6 weeks

Complications of Hip Replacement Surgery

Deep Vein Thrombosis and Pulmonary Embolism: Prevented by anticoagulant therapy following surgery for a few weeks.
Dislocation: Occurs rarely and needs correction under anesthesia. Can be reduced by following muscle strengthening exercises to improve hip stability and function.
Infection: Incidence is minimised by following sterile precautions during the operating procedure and giving antibiotic cover to the patient.
Wear and Tear of the Artificial Sockets: Mostly seen with plastic implants. Less common with metal or ceramic implants. New, harder-wearing plastics are also being developed.
Loosening of the Artificial Hip: Occurs due to thinning of the bone around the implant, making the bone more prone to fracture. This complication usually needs to be fixed through surgery and/or revision of the implant.
Bleeding and Wound Hematoma: May occur rarely necessitating surgical drainage.
Allergic Reaction to the metal or plastic implants.
Unequal Length of Legs: If the legs are equal, the sense of inequality resolves within 4 – 6 weeks of surgery. If the leg is actually unequal, it will not. A shoe lift for the short leg, or in rare cases, a corrective surgery may be needed.
Chronic Pain: Due to nerve injury.

Alternatives to Hip Replacement Surgery

Before deciding on surgery, the surgeon may try several non-surgical, conservative measures to relieve the pain and inflammation in the hip joint. These include:

Lifestyle Modifications: Such as weight reduction, avoiding activities such as prolonged standing or walking, use of a cane or similar walking aid to reduce stress on the injured hip.
Exercise and Physical Therapy: To improve the strength and flexibility of hip and other lower extremity muscles. An aquatic therapy regimen is especially effective in the treatment of arthritis as it allows mild resistance while removing weight bearing stresses.

Anti-inflammatory Medications: Reducing the inflammation of the hip joint and provide temporary relief from pain and may delay surgery. Non-steroidal anti-inflammatory drugs, the newer COX-2 inhibitors and in certain cases steroids provide the much needed pain relief.Sometimes, corticosteroids may be injected into the hip joint.
Glucosamine /Chondroitin are dietary supplements, (commonly available in a combined tablet), and may decrease the symptoms of hip arthritis.
Viscosupplementation: Is the intra-articular administration of preparations containing hyaluronic acid (a lubricant), to help restore the lubrication lost from degenerative joint disease.
It may be useful in persons with early stage hip osteoarthritis. It might help those who cannot take NSAID’s long term and those who wish to delay surgery.
Osteotomy: Involves cutting and realigning bone, to shift the stress from a damaged and painful bone surface to a healthier one.