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Mr. Michael Solomon, Sydney Australian Surgeon Gives Advice on Hip Replacement

Source – Mr. Michael Solomon, Sydney Australia Surgeon – his practices’ website

The hip is one of the largest weight-bearing joints in the body. When it’s working properly, it lets you walk, sit, bend, and turn without pain. Unlike the shoulder, the hip sacrifices degree of movement for additional stability. To keep it moving smoothly, a complex network of bones, cartilage, muscles, ligaments, and tendons must all work in harmony.

The hip is a ball-and-socket joint where the head of the femur articulates with the cuplike acetabulum of the pelvic bone. The acetabulum fits tightly around the head of the femur. The ball is normally held in the socket by very powerful ligaments that form a complete sleeve around the joint (the joint capsule). The capsule has a delicate lining (the synovium).

The head of the femur is covered with a layer of smooth cartilage which is a fairly soft, white substance. The socket is also lined with cartilage. This cartilage cushions the joint, and allows the bones to move on each other with very little friction.

An x-ray of the hip joint usually shows a “space” between the ball and the socket because the cartilage does not show up on x-rays. In the normal hip this “joint space” is approximately 1/4 inch wide and fairly even in outline.

Information for patients needing a Total Hip Replacement or Hip Resurfacing Replacement

Timing of Surgery

The timing of hip replacement surgery is a decision that you as the patient must make. The need for surgery is a quality of life decision and the aim of the surgery is to eliminate your hip pain. As an added bonus you will likely get a better range of motion, your limp may reduce or disappear and your quality of life should improve significantly.

If you feel that you can manage with your current pain levels then there is no urgency to have your arthritic hip replaced. Simple analgesics (eg.Panadol) or anti-inflammatories (eg.voltaren, celbrex etc) may be sufficient to provide you with a relatively painfree hip. These drugs will not improve stiffness and the arthritis will continue to progress and at some point the drugs will no longer have their pain relief affect.

Alternative medicines (eg. Glucosamine and chondroitin, fish oil etc) may have a role in helping with pain but scientific studies have proven that the claim that they “prevent arthritis or progression of the disease” is false. These medicines whilst not doing you major harm will not stop your hip continuing to wear out.

If you are overweight, weight loss may help in reducing your hip pain. Low impact exercises (walking, cycling and swimming) help maintain muscle tone and thereby control the arthritis pain.

Physiotherapy is often useful in helping strengthen surrounding muscles and maintaining good muscle tone and pelvic balance. Try to avoid overstretching the joint as this will only cause discomfort.

Things you need to know about Hip Replacements and Hip Resurfacing Replacements

Total Hip Replacement, Hip Resurfacing Replacement or “mini stem” Hip Replacement are simply different designs of prosthesis. They all replace your hip and therefore are collectively termed Hip Replacements. Some prosthesis (Birmingham Hip Resurfacing) are more bone conserving but these prosthesis still replace the acetabulum (socket) and either resurface the femoral head (ball) or replace the head but preserve more bone lower down.

What Replacement should you have ?

This can be a most complex topic particularly in discussing the options and correct choice in a young patient.

It is important to get an understanding of what’s available and in which patient group you are best placed.

The key to a successful hip replacement is the surgical skill of the surgeon implanting the prosthesis and the type of bearing used in the ball and socket joint.

Modern day hip prosthesis may well last a patient a lifetime. It is most likely that a well recognized, tried and tested implant will not wear out in patients over the age of 70 provided the surgery is performed correctly. The key to implant longevity apart from good surgical technique is the materials used in the bearing (the actual parts that move).

Facts about bearings

The traditional hip bearing is a metal head (chrome cobalt ball) that moves on a polyethelene liner (“plastic” liner). Modern day plastic liners have very low wear rates unlike the material used 30 years ago. Studies show that modern day liners will probably take about 30 years to wear out. It is for this reason that it is likely that an artificial hip joint implanted in a patient over the age of 70 will last them a lifetime. Off course should the lining wear out sooner a new plastic lining can be inserted.

In an effort to develop bearings that last longer than the traditional “plastic” lining, a number of other alternatives are available. These include the following:

1. Ceramic on Ceramic

2. Metal on Metal

3. Ceramic on Metal

These bearings were developed to allow younger patients to have hip replacements as they may last longer than traditional metal on plastic bearings and hopefully last a “lifetime”

Ceramic on Ceramic

The ceramic – ceramic bearings have been around for over 20 years. They have extremely low wear rates (1000 times less than plastic) and if implanted correctly may last 40 years or more.

Unfortunately ceramics are not perfect in that there is a 1 in 20 000 incidence of breakage / fracture (ceramic is more brittle than metal) and a very rare chance that the hip can develop a squeak.

In general however ceramic on ceramic bearings are an excellent choice to use in the young patient (under the age of 60). Surgical technique is critical.

Metal on Metal Bearings

These bearings have been around for over 30 years but have regained popularity with the introduction of modern designed hip resurfacing replacements.

The wear rate of metal on metal bearings is only slightly higher than ceramic on ceramic but like ceramics is significantly lower than metal on plastic bearings. Metal on metal bearings are very tough and are not susceptible to breakage (fracture).

The disadvantage of metal on metal bearings is that they produce metal ion particles and if the implant is not functioning properly these metal ions can invoke a significant inflammatory response in and around the hip joint which can cause hip pain and swelling.

Some patients are allergic to metal on metal implants but this is extremely rare. Some metal on metal bearings squeak but this is usually a temporary phenomenon.

Approaches

Minimally Invasive Hip Surgery and Anterior Approach

Is this a marketing ploy or are the results better ??

There has been a lot of recent advertising press about the mini incision hip, anterior approach technique etc etc.

There are many approaches to implant a hip replacement. Over the last decade surgeons have become more skilled in making smaller incisions using refined techniques with better instrumentation.

Some approaches are more muscle sparing than others and recovery may be a little quicker HOWEVER the most important aspect of any hip surgery is to ensure that the prosthesis is implanted accurately and correctly, that the surgery is carried out in an efficient manner minimizing blood loss and reducing anaesthetic time and the risk of complications is kept to a minimum.

ANY approach will produce a good functional pain free outcome provided the surgeon is skilled at what he is doing.

The Anterior Approach (from the front) is more muscle sparing and allows a slightly quicker recovery. Patient selection is important and not all patients are suitable for this approach. This approach has a higher complication rate related to the technique and it is important that you choose a surgeon who is skilled in this technique. Whilst patients may recover quicker there is NO evidence to show that at 6 months post surgery there is any difference in functional outcome. Studies are on going to evaluate the long term benefit of this approach.

Total Hip Replacement surgery has now been in existence for almost 50 years. There are various surgical approaches that enable the surgeon to enter the hip joint and replace the arthritic hip.

Most surgical approaches involve splitting or dividing muscles / tendons and then repairing them at the end of the procedure.

The anterior approach to the hip joint was initially developed in 1949 / 1950 by Smith Peterson (USA) and Judet (France). The approach was developed to allow access to the hip joint by not dividing muscles or tendons and allowing exposure of the hip by going between muscles.

For 40 years the French used a traction table to perform hip replacement surgery however most of the orthopaedic world preferred to perform the surgery with the patient on their side allowing entry into the hip joint either through the side (transgluteal) or the back (posterior) approach. The posterior approach is the most popular approach used by surgeons all over the world as it is a very straight forward approach allowing good visualization of the hip joint.

The literature shows no evidence at 1 year post op that any approach is better than another with excellent clinical outcomes shown in all approaches.

In the last 7 years advances in technology in the design of equipment and instrumentation has allowed the surgeon to implant a hip through the anterior muscle sparing approach using a versatile traction table. The AMIS (Anterior Minimally Invasive Surgery) is a technique that uses a traction table to assist in implantation of the hip joint.

Published results have shown that a patient who undergoes a successful direct anterior approach hip replacement will recover quicker than conventional approaches. At this stage however there is no evidence that there is any long term advantage between approaches although should that patient require revision surgery in the future, there is a theoretical benefit as the anterior approach results in less internal scarring than other approaches.

Not all patients are suitable for the AMIS technique. Patients who are significantly overweight are at risk of having intraoperative complications due to limited visibility. Patients with abnormal hip joint anatomy are not suitable for the AMIS approach as this approach does not allow the correction of severe hip deformities. Some patients with very soft bone may not be suitable for the AMIS approach as there is a risk of fracture. Most revision hip surgery needs to be performed through conventional approaches.

The most important part of hip replacement surgery is that the surgeon implants the replacement safely and in excellent alignment to ensure optimum hip function, full pain relief and long term success of the implant.

Remember that ALL approaches if performed correctly will result in a successful pain free outcome that should last at least 20-30 years using modern day implants.

All patients would prefer a quicker recovery and therefore my approach is to use the AMIS procedure provided there are no contraindications.

Advantages of the AMIS approach include:

1. Less muscle damage

2. Surgery between muscle groups supplied by different nerves (internervous)

3. Earlier recovery with quicker return to function

4. Reduced incidence of hip dislocation

5. Ability to return to activities such as driving earlier

6. Reduced post operative precautions whilst the wound heals compared to other approaches.

7. Smaller scar

8. Post operative rehabilitation is easier and quicker

Hip Resurfacing:

Hip Resurfacing Replacements were designed to preserve bone so that should a patient require a revision in the future there was adequate bone left to revise the hip. This type of replacement is reserved for patients with good quality bone ie: no osteoporosis. It is therefore not suitable for elderly patients as there is a high risk of fracture of the bone that the implant is attached to.

THERE IS NO ADVANTAGE FOR A PATIENT OVER THE AGE OF 65 TO HAVE A HIP RESURFACING

Modern day resurfacings have been around for the past 12 years. The Birmingham Hip Resurfacing Replacement (Smith & Nephew Inc: http://www.smith-nephew.com) is the most successful of the Resurfacings on the market and has the longest track record (over 12 years) We have learned a great deal about resurfacings and the literature (including the Australian Joint Registry http://www.dmac.adelaide.edu.au/aoanjrr/) has outlined the best patients that are suited for this procedure.

Resurfacings do best in the young (less than 55 yr old) male or female with a large femoral head and who have primary osteoarthritis (ie primary osteoarthritis is wear and tear not due to underlying issues such as rheumatoid disease, shallow hip disease, avascular necrosis).

Most females however have smaller bones than males and therefore are not ideally suited to resurfacing replacement using available data.

In my practice I recommend hip resurfacing in the young active male with strong bone and a large femoral head.

Important facts to know about hip resurfacing:

Hip resurfacing patients take LONGER to recover than conventional total hip surgery patients. The reason for this is that in order to preserve the femoral head for resurfacing, more muscle and ligaments need to be released internally to allow the socket to be prepared. Patients are also advised to partial weight bear for 4 weeks post operatively to allow the bone to adapt to the new implant and not fracture. Conventional hip replacement patients are allowed to full weight bear immediately.

Hip Range of Motion in Resurfacing replacements is LESS than conventional total hip replacements using the same size ball and socket. The reason for this is that the resurfacing sits on the patient’s femoral head and neck and as such in maximal motion the femoral neck may impinge on bone preventing maximum movement compared to a ball that sits on a stemmed hip because the stemmed hip has a narrow neck allowing more impingement free motion (see drawing)

Activity Level:

A good functioning hip resurfacing is very durable and whilst it is not recommended, there have been many reports of patients running and doing triathlons with resurfacings.

ALL hip replacements, resurfacing or conventional, allow the patient to partake in sporting activities including

  • Tennis
  • Skiing
  • Golf
  • Bowls
  • Backyard running with the kids
  • Cycling
  • swimming

As a general rule orthopaedic surgeons do not recommend high contact sports with ANY type of replacement (resurfacing or conventional) including rugby, competition soccer, competition basketball etc)

So what’s the advantage in having a resurfacing ??

Resurfacings preserve the femoral shaft and there are reports that some patients feel that the resurfaced hip “feels more natural”

It allows the possibility of a future revision to be done without to much difficulty HOWEVER it is likely that a well done standard total hip replacement with a modern day bearing will not need revising anyhow.

The BIGGEST issue with metal on metal resurfacings is accuracy in surgical technique. This fact has only recently come to our attention as it was thought that metal on metal implants are as “forgiving” as metal on plastic implants. Recent literature has shown that the metal on metal implants (and ceramic on ceramic bearings) are very susceptible to mal-alignment and if this occurs then these implants may fail.

Cemented or Uncemented prosthesis:

There is NO difference in the revision rates of either a cemented or uncemented femoral component (the hip stem that sits on the thigh bone). A well implanted cemented stem works just as well as a well implanted uncemented stem. As outlined above the key to longevity is in the bearing and NOT whether the stem is cemented or uncemented. A surgeon will choose what stem fits best into your bone quality. In general softer osteoporotic bone with thin cortices do better when cement is used to fixate the implant.

Most acetabular components (sockets) are uncemented and the bone will grow into the component. The lining is then placed in the metal shell and this lining is either plastic, ceramic or metal. Occasionally the bone is so soft that a plastic liner is cemented onto the bone instead of using and uncemented shell..

The Final word

I hope I have enlightened you on the basic facts about hip replacement surgery. I would summarize as follows:

1. Choose a surgeon who is well experienced in Hip Replacement Surgery

2. Be guided by the information presented above as to the types of hip replacements available, bearing options and operative approaches.

3. Do not be fooled by advertising and marketing hype.

My approach and recommendations to patients requiring a hip replacement. This is a GUIDE ONLY and each patient’s individual needs are taken into account before a final implant decision is made

1. Patients over the age of 75 usually have an uncemented stem (if bone quality good) or cemented stem (if bone quality poor) with an uncemented socket and polyethelene (plastic) liner. A metal head is used. This hip should last a lifetime

2. Patients between 65-75 usually have an uncemented stem and socket with either a ceramic on ceramic liner or ceramic on polyethelene liner. This hip should last a lifetime

3. Males under the age of 60 who are active and have excellent bone quality are candidates for a resurfacing HOWEVER we discuss the pros and cons of resurfacing vs total hip replacement with a ceramic bearing according to the patients individual circumstances.

4. Females under age 65 usually have an uncemented stem and socket with a ceramic on ceramic bearing

5. Males between 55-75 usually have an uncemented stem and socket with the bearing appropriate for their age.

6. Males under 55 have a resurfacing if they satisfy various criteria or an uncemented implant with a ceramic on ceramic bearing.

Michael Solomon

(Revised May 2011)

 

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