Avascular Necrosis of the Hip Bone

By Ehren Allen, DPT/Certified Orthopedic Manual Therapist

What is Avascular Necrosis of  the Hip Bone?

AVN (Avascular Necrosis) of the hip is a rare condition in the hip joint.  The hip joint is where the thigh bone (femur) connects to the pelvis.  It is a ball and socket joint.

Avascular necrosis means death due to lack of blood supply. In this context, it refers to the death of the bone that makes up the ball part of the ball and socket hip joint. This may occur in young or old people due to disease or from injuries whereby the hip is dislocated or broken.  Although, in many cases there is no identified cause.

Either way, there is an interruption of the blood supply to the ball end of the thighbone. As a result of this process, the bone of the ball becomes softer and collapses under the person’s own weight. This causes the ball to become out of round, which leads to arthritis. Once this has happened, there is no good way of curing this problem without resorting to a major operation called total hip replacement (arthroplasty).

There are several reasons that the blood supply may become compromised at the end of the femur.

• Trauma: This can be from a fracture or a dislocation of the hip.
• Fat deposits in the vessels: This can occur from high lipid counts in the blood.
• Blood Diseases: This may include Sickle Cell Disease conditions, which may block blood flow to the bone.

Risks for developing AVN vary but may include:

• Trauma.
• Steroid use: This may increase lipids in the blood.
• Radiation therapy from cancer treatment.

How do you know if you have AVN of the hip?

Typically, the symptoms of AVN of the hip start with pain in the hip.  This may be worse with weight-bearing and may alter the way that the hip moves during walking activity.  If pain persists, it is best to see a physician evaluate the cause of the pain.  The physician will likely perform a physical examination to assess the movement and function of the joint.

AVN requires advanced diagnostic imaging to diagnoses it properly.  This may include:

• X-ray.
• CT Scan.
• MRI.
• Bone scan.

What is the best treatment for avascular necrosis of the Hip?

The first line of treatment for AVN of the hip is to manage pain and stiffness.  This may include pain medication or anti-inflammatory medications.  Physical therapy may be helpful to increase strength and ROM in the hip.

Managing any medical causes of AVN is also important in treating AVN.  This may include cholesterol meds to control lipid levels.

There are invasive procedures to manage AVN if medication management does not work.  The last line of treatment is a complete total hip replacement.  In this operation, the dead ball is cut off from the rest of the hip bone and replaced with a metal ball on a stem that fits inside the hollow thigh bone. At the same time, the socket is replaced with a plastic socket.  This is now the formation of the new joint of the metal ball fitting into the plastic socket. This operation is very effective at alleviating pain due to arthritis of the hip joint.  It is a very successful surgery in elderly patients. However, physicians have always had more concern about performing total hip replacements in younger patients.

Can AVN Heal itself?

AVN typically does not heal itself, but improvements can be made with the treatment of the cause.  You can improve blood flow to the bone in some cases, and bone tissue can regenerate.  Usually, though, issues progressively worsen, and medical or surgical intervention is needed.

How painful is Avascular Necrosis of the Hip?

AVN can cause varying levels of pain.  The pain may start mild, and an increase in necrosis (tissue death) progresses.  This may cause an altered walking pattern, which can lead to low back pain or knee pain.

 

Total Hip Replacement

In this operation, the dead ball is cut off from the rest of the hip bone and replaced with a metal ball on a stem that fits inside the hollow thigh bone. Simultaneously, the socket is replaced with a plastic socket, and the new joint is thus formed of the metal ball fitting into the plastic socket. This operation effectively alleviates pain due to the hip joint’s arthritis and is a very successful surgery in elderly patients. However, physicians have always had more concern about performing total hip replacements in younger patients.

Total Hip Revision

The artificial joint does wear over time due to the metal ball rubbing against the plastic socket. This leads to microscopic pieces of ground-up plastic in the surrounding tissue that causes the body’s defense mechanisms to produce those cells whose job is to remove foreign material. In this case, however, the plastic cannot be digested, whereas the tissues around the implant can. This leads to progressive loss of bone and eventually to loosening of the implant. As a result, the operation has to be redone.

The revision operation is always more technically difficult than doing the operation the first time. It has higher risks such as infection, breakage of the bone during the operation, nerve injury, and recurrent dislocation. Additionally, the bone stock is of poorer quality, and the redo total joint replacement typically lasts less time than the previous one. At some point, the situation becomes unsalvageable, and the patient is left with no satisfactory options.

This problem is obviously more serious in younger patients because not only is the patient going to live longer, but they are also going to be more active than the older patients and thus wear the joint at an accelerated rate. This is particularly true in situations where no other joints are involved, such as in avascular necrosis.

Once the painful hip joint is replaced, there is nothing to stop the patient from returning to any activity they want to, except the knowledge that they will eventually wear out their new joint. As a result, they may have to replace the first joint replacement with another, and if that one wears out, they have a long road ahead of them with no long-term solution in sight. That was, however, until the development of the ‘metal on metal’ total hip arthroplasty.

Recent Developments with Hip Replacements

This most recent development in total hip arthroplasty is a potential answer to plastic wear debris. There is no plastic socket in this replacement. Instead, the socket is made of metal, where the ball fits against it. With today’s engineering and quality control, the promise here is that the weight-bearing surfaces can be made with such accuracy that only the most minute amount of wear particles are seen.

Thus, the problem of subsequent loosening of the implants can be avoided.  If the decrease in wear rates does indeed translate into the anticipated increase in longevity by a factor of ten or more, then it is possible for these implants to last the patient’s lifetime.  Even in the especially demanding circumstances of the young patient. Not all metal on metal replacements is created equally, however. For more information on Hip Replacement and Resurfacing watch these videos: Hip Resurfacing Part 1 and Hip Resurfacing Part 2

There is currently only one manufacturer in the U. S. whose metal-on-metal replacement does not include any plastic parts. The concern about these implants is really how long can they last?  The only way to prove that they last that long in patients is to wait that long after surgery. At least, however, as of this time, that hope now exists.

To schedule for physical therapy at a JOI Rehab Center, please call 904-858-7045. 

If You have hip pain, the Jacksonville Orthopaedic Institute can help.  We evaluate and treat issues related to the hip, including AVN, all the time.  Give us a call at 904-JOI-2000.

Related Articles: Types of Hip Surgeries, Hip Anatomy Video and Hip Resurfacing.

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