Total Hip Replacement (THR)

Introduction

Total hip replacement is a surgical procedure in which the damaged cartilage and bone is removed from the hip joint and replaced with artificial components. This is one of the most effective operations known and should give you many years of freedom from pain.

Once you have arthritis that has not responded to conservative treatment, you may well be a candidate for total hip replacement surgery.

Normal hip anatomy

The hip joint is one of the body's largest weight-bearing joints, located between the thigh bone (femur) and the pelvis (acetabulum). It is a ball and socket joint in which the head of the femur is the ball and the pelvic acetabulum forms the socket. The joint surface is covered by a smooth articular cartilage which acts as a cushion and enables smooth movements of the joint.

Arthritis

Arthritis is a general term covering numerous conditions where the joint surface (cartilage) wears out. The joint surface is covered by a smooth articular surface that allows pain free movement in the joint. This surface can wear out for a number of reasons, often the definite cause is not known. When the articular cartilage wears out, the bone ends rub on one another and cause pain. There are numerous conditions that can cause arthritis and often the exact cause is never known. In general, but not always, it affects people as they get older (osteoarthritis).

Other causes include:

• Childhood disorders e.g., dislocated hip, Perthes disease, slipped epiphysis, etc.
• Growth abnormalities of the hip (such as a shallow socket), which may lead to premature arthritis
• Trauma (fracture)
• Increased stress e.g., overuse, overweight, etc.
• Avascular necrosis (loss of blood supply)
• Infection
• Connective tissue disorders
• Inactive lifestyle e.g., obesity, as additional weight puts extra force through your joints, which can lead to arthritis over a period of time
• Inflammation e.g., rheumatoid arthritis

Characteristics of an Arthritic Hip

• The cartilage lining is thinner than normal or completely absent.
• The degree of cartilage damage and inflammation varies with the type and stage of arthritis.
• The capsule of the arthritic hip is swollen.
• The joint space is narrowed and irregular in outline; this can be seen in an X-ray image.
• Bone spurs or excessive bone can also build up around the edges of the joint.
• The combination of these factors makes the arthritic hip stiff and limit activities due to pain or fatigue.

Symptoms

The most common symptom of hip arthritis is joint pain and stiffness resulting in limited range of motion. Vigorous activity can increase the pain and stiffness which may cause limping while walking.

Diagnosis

The diagnosis of osteoarthritis is made on history, physical examination and X-rays. There is no blood test to diagnose osteoarthritis (wear and tear arthritis)

Indications

THR is indicated for arthritis of the hip that has failed to respond to conservative (non-operative) treatment. You should consider a THR when you have:

• Severe arthritis confirmed on X-ray
• Pain that does not respond to analgesics or anti-inflammatories
• Limitation of daily living activities, including your leisure activities, sports or work
• Pain keeping you awake at night
• Stiffness in the hip, making mobility difficult

Prior to surgery, you will need to have tried and failed simple treatments such as simple analgesics, weight loss, anti-inflammatory medications, modification of your activities, walking sticks or physiotherapy.

Benefits

The decision to proceed with THR surgery is a cooperative one between you, your surgeon, family and your local doctor. Benefits of surgery may include:

• Reduced hip pain
• Increased mobility and movement
• Correction of deformity
• Possibly increased leg strength
• Improved quality of life, ability to return to normal activities

Pre-operation

• Your surgeon will send you for routine blood tests and any other investigations required prior to your surgery.
• You will be asked to undertake a general medical check-up with a physician and may require cardiac clearance depending on your history.
• You should have any other medical, surgical or dental problems attended to prior to your surgery.
• Make arrangements for assistance around the house prior to surgery.
• Stop aspirin or anti-inflammatory medications 14 days prior to surgery as they can cause bleeding.
• Stop blood thinners prior to surgery. Length of time will depend on the type of blood thinner and recommendation by your cardiologist.
• Cease any naturopathic or herbal medications 14 days before surgery.
• Stop smoking as long as possible prior to surgery.

Day of your surgery

• You will be admitted to the hospital on the day of your surgery.
• Further tests may be required on admission.
• You will meet the nurses and answer some questions for the hospital records.
• You will meet your anesthesiologist who will ask you a few questions.
• The operation site will be shaved and cleaned.
• Approximately 30 mins prior to surgery, you will be transferred to the operating room.

Surgical Procedure

The surgery is performed under general anesthesia. An incision is made over the hip to expose the hip joint. The femur is dislocated from the acetabulum.

The acetabulum (socket) is prepared using a special instrument called a reamer. The acetabular component is then inserted into the socket. This is sometimes reinforced with screws or occasionally cemented. A liner made of plastic material is then placed inside the acetabular component.

The femur (thighbone) is then prepared. The femoral head that is arthritic is cut off and the bone prepared using special instruments, to exactly fit the new metal femoral component. The femoral component is then inserted into the femur. This will be press fit, relying on bone to grow into it.

The real femoral head component is then placed on the femoral stem, which can be made of metal or ceramic. The hip is then reduced again, for the last time. The muscles and soft tissues are then closed carefully.

Postoperative

You will wake up in the recovery room with a number of monitors to record your vitals: blood pressure, pulse, oxygen saturation, temperature, etc. You will have a dressing on your hip and drain coming out of your wound. Post-operative X-rays will be performed in recovery.

Once you are stable and awake you will be taken up to your room on the orthopaedic floor. You will get up with physical therapy on the day of your surgery. You will have 2 more sessions of therapy the following day.

Pain in the hip is to be expected. Most patients feel this is well controlled with mild narcotics. Most patients will be able to put all their weight on their hip. The physical therapist will help with the post-op hip exercises. Most patients will use a walker in the beginning then progress to a cane. 

Most patients will only stay one night in the hospital and be discharged home the day after surgery. You will then use home health care for 1-2 weeks depending on your medical and physical needs.

Most patients transition to outpatient physical therapy by 2 weeks. This may last 4-8 weeks depending on your progress. Staples are removed in the office 3 weeks after surgery.

Postop precautions

Remember this is an artificial hip and it must be treated with care. You will need to follow several precautions to avoid dislocation of the new hip. Movements to avoid include bending your hip too far, turning your foot inward and crossing your legs. 

Other precautions to be followed after surgery include:

• You should sleep with a pillow or wedge between your legs for at least 6 weeks. 
• Avoid low chairs.
• Avoid bending over to pick things up. Grabbers are helpful as are shoe horns or slip on shoes.
• Elevated toilet seat is helpful.

Risks and complications

As with any major surgery, there are potential risks involved. The decision to proceed with the surgery is made because the advantages of surgery outweigh the potential disadvantages.

It is important that you are informed of these risks before the surgery takes place. Complications can be medical (general) or specific to the hip. Medical complications include those of the anesthetic and your general wellbeing. Almost any medical condition can occur so this list is not complete. Complications may include:

• Allergic reactions to medications
• Blood loss, requiring transfusion with its low risk of disease transmission
• Heart attacks, strokes, kidney failure, pneumonia or bladder infections
• Complications from nerve blocks such as infection or nerve damage
• Serious medical problems can lead to ongoing health concerns, prolonged hospitalization or rarely death

Specific complications include:

• Infection: Infection can occur with any operation. In the hip, this can be superficial or deep. Infection rates are approximately 1%, if it occurs, it can be treated with antibiotics, but may require further surgery. Very rarely, your hip may need to be removed to eradicate infection.
• Dislocation: This means, the hip comes out of its socket. Precautions need to be taken with your new hip forever. If a dislocation occurs, it needs to be put back into place with an anesthetic. Rarely, this becomes a recurrent problem, needing further surgery.
• Blood clots (deep venous thrombosis): These can form in the calf muscles and can travel to the lung (pulmonary embolism). These can occasionally be serious and even life-threatening. If you get calf pain or shortness of breath at any stage, you should notify your surgeon.
• Damage to nerves or blood vessels: Also rare, but can lead to weakness and loss of sensation in parts of the leg. Damage to blood vessels may require further surgery if bleeding is ongoing.
• Wound irritation: Your scar can be sensitive or have a surrounding area of numbness. This normally decreases over time and does not lead to any problems with your new joint.
• Leg length inequality: It is very difficult to make the leg exactly the same length as the other one. Occasionally, the leg is deliberately lengthened to make the hip stable during surgery. There are some occasions when it is simply not possible to match the leg lengths. All leg length inequalities can be treated by a simple shoe raise on the shorter side.
• Wear: All joints eventually wear out. The more active you are, the quicker this will occur. In general, 80-90% of hip replacements survive 15-20 years.
• Failure to relieve pain: Rare, but may occur especially if some pain is coming from other areas such as the spine.
• Unsightly or thickened scar
• Limp due to muscle weakness
• Fractures (break) of the femur (thigh bone) or pelvis (hipbone): This is also rare, but can occur during or after surgery. This may prolong your recovery or require further surgery. Discuss your concerns thoroughly with your orthopaedic surgeon prior to surgery.

Summary

Surgery is not a pleasant prospect for anyone, but for some people with arthritis, it could mean the difference between leading a normal life or putting up with a debilitating condition. Surgery can be regarded as part of your treatment plan. It may help to restore function to your damaged joints as well as relieve pain.