Total Hip Replacement for Hip Arthritis
What is Hip Arthritis?
Arthritis of the hip is a condition in which the cartilage of the hip joint thins or wears away with time. The hip joint is made up of a ball (femoral head) and socket (acetabulum). The cartilage is a protective surface which allows the bones of the hip joint to move smoothly against each other. When the cartilage wears away, the bone rubs against the bone, which can be an extremely painful condition.
Hip arthritis presents with pain in the groin approximately 90% of the time. In 10% of patients, pain may be isolated to the side of the hip, buttock or knee. Arthritis of the hip is unfortunately a progressive problem, although the rate of progression is variable.
How is Hip Arthritis Diagnosed?
The diagnosis of hip arthritis is made in combination with a history of pain localized to the hip area, a clinical examination which reproduces pain with movement of the hip, and x-ray findings showing narrowing of the joint space between the ball and socket Figure 1: Osteoarthritis of the left hip
On occasion where there is doubt regarding the source of one’s pain, a “diagnostic” injection of local anaesthetic into the hip joint may be performed. If this injection alleviates the patient’s pain, then it is highly likely that the hip is the cause of the symptoms.
Options for Treatment
All patients should attempt non-surgical treatments initially. These consist of medications, exercises (in the form of physiotherapy), weight loss (if applicable), activity modification, and hip injections.
Medications may be helpful in managing degenerative arthritis, although no medications currently exists that can reverse the process of osteoarthritis. For degenerative arthritis, anti-inflammatory medications (NSAIDS) may be helpful for the management of symptoms.
Injections into the hip of steroid (cortisone) or lubricants (hyaluronic acid) are typically performed using X-ray guidance under local anaesthetic. Whilst useful as a short-term option for pain control, they seldom provide long-term benefit and therefore are not commonly a long-term solution.
Those patients who still have significant pain, (e.g., pain that inhibits them in their daily activities or keeps them awake at night) following attempts at non-surgical treatment, would be recommended for total hip replacement surgery.
Traditional hip replacement surgery involves making an incision on the side of the hip (lateral approach) or the back of the hip (posterior approach). Both techniques involve detachment of muscles and tendons from the hip in order to replace the joint. Detachment of these muscles may result in increased pain after surgery, and may prolong the time to fully recover. Failure of these muscles to heal after surgery may increase the risk of hip dislocation (the ball and socket separating), which is one of the leading causes of hip replacement failure. Hip precautions after surgery (no bending greater than 90 degrees, no crossing legs, no excessive rotation) are generally required for this reason.
Direct anterior approach (DAA) hip replacement is a minimally invasive surgical technique. This approach involves a 3 to 4 inch incision on the front of the hip that allowsthe joint to be replaced by moving muscles aside along their natural tissue planes, without cutting or detaching any tendons. This approach has been shown in several high quality studies to result in quicker recovery and less post-operative pain. Because the tendons are not detached from the hip during direct anterior hip replacement, hip precautions are not necessary. This allows patients to return to normal daily activities shortly after surgery with a reduced risk of dislocation. This is particularly important for young patients who would like an early return to work or sport.
Potential Benefits of Direct Anterior Approach (Minimally Invasive) Total Hip Replacement
Regardless of the surgical approach, hip replacement surgery has a success rate approaching 95%. The longevity of a hip replacement has been reported as approximately 90% at 20 year follow-up. The most important factor in terms of technical success involves placing the hip replacement components in the best position. The use of X-ray and the fact that the patient is lying on their back during DAA hip replacement aids the surgeon in getting the implants in the correct positions.
The major advantages of direct anterior hip replacement in comparison to traditional approaches include:
- a more rapid recovery, particularly in the first 3 months following surgery.
- less pain in the immediate post-operative period – with more likelihood that you will be discharged within 24 hours of your surgery.
- more normal gait mechanics quicker.
- a more stable artificial hip without the need for hip precautions.
- achieving the correct leg-lengths (ie, have both legs the same length after surgery). This is largely due to two reasons, (1) the patient is lying on their back during surgery, so the surgeon is able to accurately compare the lengths of both legs during surgery. Traditional hip replacement surgery requires the patient to be lying on their side, which makes it harder to accurately assess the leg lengths, (2) the use of X-ray during the surgery aids the surgeon in ensuring the components are placed in the correct positions.
DAA hip replacement is an option for most patients with severe arthritis of the hip. Patients may not be suitable candidates for the DAA if they have abnormal anatomy (i.e. dysplasia, post-traumatic arthritis) or in cases of morbid obesity (i.e. body mass index greater than 35).
Direct anterior total hip replacement typically takes between 1 and 2 hours. An incision is made in the front of the thigh over the hip joint, typically 3 cm from the thigh crease (Figure 2). The typical length of an incision is 3 to 4 inches, although this may vary depending on the size of the patient. Figure 2: Red line indicates the position of the skin incision.
Once the hip joint has been fully exposed, the arthritic femoral head is removed using surgical instruments. The socket (acetabulum) of the hip joint is then exposed, which involves removing bone spurs and excess tissue within the socket. Hemispherical reamers are then used to remove the damaged cartilage and reshape the arthritic acetabulum to accept the metal acetabulum. A metal artificial acetabulum is then impacted in to the prepared socket. Bone screws may be placed through the metal acetabulum to increase fixation depending a patient’s bone quality. A plastic bearing (highly cross-linked polyethylene) is then impacted and locked into the metal socket.
The femur is then prepared. This involves placing a series of progressively larger broaches into the canal of the femur until a tight fit is achieved. A trial head is placed on the final broach, and the hip is reduced. The stability of the hip is assessed at this time throughout a range of motion and leg lengths are measured. If this is felt to be satisfactory the real femoral stem (cemented or uncemented) is implanted into the femur, and a ceramic head is impacted on the neck of the component. X-ray is used throughout, to ensure that the components are placed in the correct position.
The wound is then thoroughly washed, and the incision closed with absorbable sutures.
The typical length of stay in hospital after direct anterior total hip replacement is at most one night, with some patients able to go home on the day of surgery.
There are typically no “hip precautions” (i.e. no bending greater than 90 degrees, no crossing legs, pillow between legs while sleeping) after direct anterior total hip replacement. Because of this, no significant home modifications are typically necessary (e.g., raised toilet seat, bath tub rails, etc.)
Patients can return to work when they feel comfortable, although this typically takes 2 weeks or more. Patients can drive when they feel comfortable, but should typically be off opiate medication prior to this. Return to higher level activity (e.g., skiing, tennis, gym activities) is usually restricted for 3 months after surgery.
A 44 year old male works as a manual labourer, with a 1 year history of worsening right groin pain. He has tried non-surgical treatment (physiotherapy and pain-control medication). His X-rays show moderate-severe right hip osteoarthritis.
Figure 3: Right hip Osteoarthritis
Following a clinic consultation, and discussion regarding the benefits and risks of surgery, he was listed to undergo a right total hip replacement.
He successfully underwent a right “hybrid” total hip replacement via a Direct anterior approach. A hybrid hip replacement describes an uncemented metal cup/socket, and a cemented femoral stem.
Prior to surgery his hip was “templated” by the surgeon, in order to help plan what sizes and in which position the implants needed to be placed. He was able to walk 2 hours after surgery and was discharged later that day. X-rays of the hip after the surgery show satisfactory implant positioning. He was off crutches at 7 days post-surgery and back to driving at 2 weeks.
Figure 4: Hip replacement after surgery
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