Avascular Necrosis of the Hip

By Ehren Allen, Certified Manual Therapist/Physical Therapist

Avascular Necrosis of  the Hip

 By: Ehren Allen PT/Certified Manual Therapist 

JOI Image of the Hip

Medical illustration of the hip

What is AVN of the hip?

AVN (Avascular Necrosis) of the hip is a rare condition which can occur in the hip joint.  The hip joint is where the thigh bone (femur) connects to the pelvis.  It is a ball and socket joint.  AVN occurs when the blood supply to the end of the thigh bone (the ball of the joint) is compromised.  This causes tissue death (necrosis) in the the bone.

There are several reasons that the blood supply may become compromised in 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 conditions such as Sickle Cell Disease 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 to 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 with treating AVN.  This may include cholesterol meds to control lipid levels.

There are invasive procedures to manage AVN if medication management does no work.  The last line of treatment is a complete total hip replacement.

 

Can AVN heal itself?

AVN typically does not heal itself, but with treatment of the cause, improvements can be made.  Blood flow can be improved 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 AVN of the hip?

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

 

Dr. Philip Hardy

Dr. Philip Hardy states that 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). 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, and the new joint is thus formed of the metal ball fitting into the plastic socket. This operation is very effective at alleviating pain due to arthritis of the hip joint, and is a very successful surgery in elderly patients. However, physicians have always had more concern about performing total hip replacements in younger patients

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 cause the body’s defense mechanisms to produce those cells whose job it 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 redo operation is always more technically difficult than doing the operation the first time and 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. This most recent development in total hip arthroplasty is a potential answer to the problem of plastic wear debris. There is no plastic socket in this replacement. Instead, the socket is made of
metal where the ball fits against it. The promise here is that with today’s engineering capabilities and quality control, the weight bearing surfaces can be made with such accuracy that only the most minute amount of wear particles are generated. Thus, the problem of subsequent loosening of the implants can be avoided or, at the very least, substantially delayed. 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 lifetime of the patient, even in the especially demanding circumstances of the young patient. Not all metal on metal replacements are created equally, however. There is currently only one manufacturer in the U. S. whose metal on metal replacement does not include any plastic parts at
all. The concern as to the future of these implants is the fact that even though they appear from the laboratory tests to possibly last 40 years or more, the only way to prove that they last that long in patients is to wait that long after they have been implanted. At least, however, as of this time, that hope now exists.

 

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 JOI-2000.

 


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