Hip arthritis in India affects young and middle aged persons unlike the west where Primary hip osteoarthritis predominantly affects the elderly. Surgery in this group of relatively younger patients requires newer techniques and implants. This article will shed light on the disease and the current modalities of treatment available.
Types of Hip arthritis
Hip arthritis is classified as Primary and secondary Osteoarthritis. Primary osteoarthritis is age related wear and tear arthritis. It is rare in India. Secondary osteoarthritis occurs at a younger age and is more common. Rheumatoid arthritis, avascular necrosis, traumatic arthritis and other connective tissue disorders like SLE, Psoriasis etc. all lead to secondary osteoarthritis.
Rheumatoid arthritis is an auto immune disorder, affects all joints particularly the small joints but also does not spare the hip and knees.
Avascular necrosis is a condition that reduces the blood supply to the end of the bone. It affects patients with excess alcohol intake, consuming steroids, connective tissue disorders like SLE. Systemic lupus erythematosus (SLE) is a connective tissue disorder affecting mainly young women A photo sensitive rash on the cheeks, renal involvement and arthritis are some notable features. Avascular necrosis affects a proportion of the patients with SLE.
Gaucher’s disease is a genetic storage disorder. Post traumatic arthritis occurs after a severe injury to the hip. Fractures of the ball (top of the femur) or socket (acetabulum) can lead to arthritis after inadequate treatment.
Hip arthritis is very disabling as it is a small ball and socket joint unlike the Knee joint which is a large one. In advanced disease a total hip replacement was recommended by Orthopaedic surgeons until recently. Advances in orthopaedic surgery now cater to the specific requirements of these younger patients.
These are the mainstay of treatment as conservative measures fail to relieve pain. Total Hip replacement (THR) is a time tested operation and has a success rate of 93 % survivorship at 10 years.
The hip joint may need to be replaced with an artificial joint when it is irreversibly damaged and cannot be salvaged by alternate surgery. The patient complains of pain and restriction of movement. The pain may often be referred to the knee or felt in the knee and no hip symptoms. Occasionally the pain may be felt more in the buttock area rather than in front of the groin.
Who needs a hip replacement?
In India, many young patients with ankylosing spondylitis, avascular necrosis, post septic arthritis, post injury suffer from hip arthritis and are advised a hip replacement for disabling pain. Thus many hip replacement operations are performed in younger patients. The surgery should cater to the enhanced demands on an artificial joint by younger and more active patients. Naturally an operation designed for Western elderly patients is not suitable for younger patients.
What is a total hip replacement?
In this operation the ball shaped upper end of the thigh bone (femur) and the socket (acetabulum) are replaced. The ball is replaced with a long metal stem that is fixed into the upper end if the thigh bone. Its upper spherical end articulates with a cup shaped polyethylene socket that is cemented into the pelvis.
Conventional hip replacements sacrifice a great deal of normal bone as the head, neck, and upper part of the thigh bone is removed for implantation of the prosthesis. Moreover wear debris from the poly-etheylene liner lead to osteolysis and bone loss. When this first hip is to be changed or revised after its lifespan more bone loss occurs. Conventional hips have a small ball to reduce friction and wear, but the ill effect of this is an increased risk of dislocation. An average dislocation rate of 3- 4 % has been reported. These implants do not last very longer than 20 years and revision rates of 50% at 20 years have been reported. Survival rates are less satisfactory for the relatively younger active patients. Thus a total hip replacement is not an ideal implant for younger patients less than fifty years old who need a new hip.
Problems with conventional total hip replacement:
o Excessive bone sacrifice and loss
o Increased risk of dislocation
o Patients cannot squat or sit cross legged on the floor with out the risk of dislocation
o Range of movement is less
o Patients cannot involve in sports
o Poor survival in young and active patients they require earlier revision
o Revision surgery is difficult
o The hip feels less like a normal hip
o The cup wears with time and plastic from it harms bone
o Change in length of the leg after surgery leading to leg length discrepancy
Why remove normal bone when only the surface of the ball is bad?
This is the logic behind hip resurfacings. This bone preserving hip resurfacing involves replacing only the diseased bony surfaces of the head of femur and acetabulum. This involves sculpting the head of the femur and covering it with a metal cap and fixing an uncemented socket into the acetabulum to receive the head.
Hip Resurfacing- A bone preserving hip replacement!
Preservation of bone and less stress shielding makes it easy to revise this hip if needed. The large head size provides a very stable joint and recreates the sensation of a normal hip joint. Patients have gone back to playing Judo and Squash after this operation. Advances metallurgy makes the metal on metal articulation likely to survive longer in the young and active patient. With less metal inside the bone and less invasion of the medullary cavity of the femur, the risk of infection is reduced. Rehabilitation is faster and better.
Advantages of hip resurfacing:
o Allows the patient to squat and sit cross legged on the floor safely
o Allows a normal range of movement
o Sacrifices only the surface diseased bone and preserves normal bone
o Imparts a more normal sensation
o The joint is likely to last longer even in younger and active patients
o Earlier and faster rehabilitation
o Less risk of dislocation
o Easier to revise if needed
o No leg length discrepancy
Proxima hip replacement – A perfect bone preserving hip replacement?
This is the latest addition to the armamentarium of the hip surgeon in India. It is a bone preserving hip replacement. In this operation, the entire diseased head of the femur is removed. The lining of the hip socket is resurfaced with a metal cup. A tiny uncemented hip with a short stem called the Proxima hip is impacted into the upper end of the femur or thigh bone.
The size of the implant matches the natural one and hence the risk of dislocation is almost eliminated. It is recommended when the bony destruction is advanced and hence unsuitable for resurfacing and a total hip replacement would be overkill.
The advantages of the Proxima are:
o suited for minimally invasive surgery
o No thigh pain
o Metal on metal – confers longevity
o Conformity to normal size eliminates risk of dislocation
o Ability to correct biomechanical abnormalities makes this superior to resurfacing
o Imparts a more normal sensation
o Allows a normal range of movement and normal activities