When Is Hip Replacement Needed? AVN, DDH and Perthes

Hip replacement is needed when the joint has been destroyed beyond repair, and the patients who reach that point fall into four broad groups: a congenital deformity such as developmental dysplasia of the hip (DDH); a childhood problem such as Perthes disease, infection or a displaced growth plate; avascular necrosis that has progressed to arthritis; or a fracture around the hip that has not healed properly.

That classification comes from Dr. Rohit Lamba, an orthopaedic and joint replacement surgeon, in answer to a question on which patients need hip replacement. It matters because many of the patients he presented were not elderly. They were teenagers and young adults whose hips were damaged in childhood or early adult life, and whose operations demanded special techniques, special implants and, in sickle cell disease, careful preparation before surgery is even safe. This article takes each group in turn. The wider spectrum of disorders in the session, from knee arthritis to trauma reconstruction, is in the complete guide to orthopaedic disorders.

When is hip replacement needed? The four patient groups

Dr. Lamba sorts candidates for hip replacement into four categories:

1. Congenital deformity. Developmental dysplasia of the hip, in which the socket is shallow and the hip may sit partly or completely out of it.
2. Childhood damage that changes the shape of the hip. Infection of the hip in early childhood, Perthes disease, or a condition in which the growth plate at the top of the thigh bone slips out of place. Each leaves an abnormally shaped hip that can develop arthritis later and finally need replacement.
3. Avascular necrosis in early adulthood that has reached an advanced stage with arthritis.
4. Fractures around the hip that have not united, or have united in the wrong position, causing arthritis and pain.

The sections below cover each, with sickle cell disease treated separately because it changes how the operation must be prepared.

Avascular necrosis of the hip: diagnosis and treatment

Avascular necrosis (AVN) is the death of bone tissue when its blood supply fails. In the hip, the ball at the top of the thigh bone, the femoral head, loses its blood supply, the dead bone collapses, and arthritis follows. Dr. Lamba described it as very common in Africa as well.

Causes

He named two major causes. The first is steroid use, which, he noted, happened a lot during COVID. The second is sickle cell disease, covered in its own section below. Heavy alcohol use is the other leading cause of non-traumatic avascular necrosis.

Diagnosis: why the X-ray misleads

Patients with avascular necrosis start with pain, and at that stage the X-ray is normal. Only an MRI scan shows the disease. For a referring doctor the practical lesson is clear: a young adult with hip pain, a history of steroid use or sickle cell disease and a normal X-ray needs an MRI, not reassurance.

Treatment by stage

• Early disease (stages 1 and 2). Before the femoral head has collapsed, the hip can sometimes be managed with medication or with a small procedure called core decompression and stem cell grafting. Core decompression involves drilling into the dead area of the femoral head to relieve pressure inside the bone and encourage new blood vessels to grow; stem cell grafting adds cells, usually concentrated from the patient's own bone marrow, to support repair.
• Late disease with advanced arthritis. Once the head has collapsed and the joint is arthritic, the patient needs a total hip replacement.

Dr. Lamba showed how one such patient walked before surgery, and how he walked after hip replacement on both sides performed at the same time. The change in his walking, he said, shows how good the results can be.

Hip replacement in sickle cell disease

Sickle cell disease causes avascular necrosis because the abnormal, sickle-shaped red cells block the small blood vessels of the hip. Dr. Lamba presented a patient with arthritis in both hips from sickle cell disease, a condition he noted clinicians in Africa will recognise.

These patients need special evaluation, and in his words it is not safe to operate "just like that". The first step is to reduce the amount of sickle haemoglobin in the blood by exchange blood transfusion, in which the patient's blood is gradually replaced with donor blood. Only then can surgery proceed safely, and in this patient he operated on one side at a time.

The reason is well established. Surgery, anaesthesia, cold, dehydration and low oxygen can all trigger sickling, and patients with sickle cell disease face higher risks of complications such as acute chest syndrome and painful crises after major operations. Reducing the proportion of sickle haemoglobin before surgery lowers that risk. After his operations, Dr. Lamba's patient was able to stand and walk, and went home very happy.

Hip replacement for developmental dysplasia of the hip (DDH)

Developmental dysplasia of the hip is a condition in which the hip socket is shallow from birth, and the hip may be partly or completely out of it. The child walks with a limp, and pain starts later in life as the abnormal joint wears.

What the patient experiences

In one of Dr. Lamba's patients the hip on one side sat completely outside the socket. The result was a short leg and a limp.

Why the operation is different

A standard hip replacement places the new socket in the patient's existing socket. In a hip that has been dislocated since birth, the thigh bone sits far above the true socket, and the muscles around it have adapted to that position. Dr. Lamba described the solution: a special technique in which a cut is made in the bone so that it comes down to the level of the normal hip socket, followed by a special implant. In practice this means shortening the thigh bone with an osteotomy (a surgical cut through the bone) so that the hip can be reduced into the true socket without overstretching the nerves and soft tissues.

His patient was walking one week after surgery, and a second video, three months after the operation, showed her walking again. He presented a second patient with the same condition on both sides, treated with the same technique, who also returned to walking.

Partial dislocation

Not every dysplastic hip is fully out of the socket. In another case the hip sat at the edge of the socket without dislocating completely, and over time that unstable position caused arthritis. This patient needed a hip replacement and did very well after surgery.

Hip replacement after Perthes disease

Perthes disease is a childhood condition that usually begins between 4 and 8 years of age, caused by damage to the blood supply of the hip bone. Dr. Lamba noted that doctors in general bone practice will have seen many such patients. The femoral head softens and can heal in a flattened shape, and the abnormal joint can develop arthritis years later.

His patient was very young, in his late teens, but had lived with the problem for eight years and was unable to walk. After a well performed hip replacement he could sit cross-legged, squat, and sit down on the floor to pray. Whether deep squatting and floor sitting are advisable after a hip replacement depends on the implant and surgical approach, and is a decision for the operating surgeon.

Hip replacement after a hip fracture that has not united

The fourth group is patients with a fracture around the hip that has not united well, either failing to heal or healing in the wrong position. The distorted joint then develops arthritis and pain, and hip replacement becomes the treatment. The principles of managing fractures that fail to heal elsewhere in the body are set out in the trauma section of the complete guide.

How long does a hip replacement last?

With the implants Dr. Lamba uses, he said, patients can be pain-free, active and doing almost all of their activities for many years. Registry data show that almost 90% of hip replacements last 15 years and nearly 60% last 25 years. For patients whose cartilage is already damaged, he considers hip replacement the definitive treatment. In any one patient the life of an implant depends on age, activity level and bone quality.

Timing of hip replacement

The thread through all four groups is timing. Avascular necrosis caught on MRI at stage 1 or 2 may avoid replacement altogether. Sickle cell patients must be prepared with transfusion before hip replacement. Hips damaged in childhood, by DDH or Perthes disease, can be replaced successfully even in young patients, restoring walking and, in the cases he showed, floor-level sitting.

Costs are on the total hip replacement cost page and, for both hips, the bilateral hip replacement cost page. Knee conditions from the same session are covered in the article on knee arthritis causes, evaluation and complex replacement. For the surgical detail of reconstructing a deficient socket, see Dr. Rakesh Mahajan's guide to complex total hip arthroplasty. Questions from the session are on the Live Discussion page.