Hip resurfacing - AbsoluteAstronomy.com

Hip resurfacing has been developed as a surgical alternative to total hip replacement

Hip replacement

Hip replacement is a surgical procedure in which the hip joint is replaced by a prosthetic implant. Hip replacement surgery can be performed as a total replacement or a hemi replacement. Such joint replacement orthopaedic surgery generally is conducted to relieve arthritis pain or fix severe...

(THR). The procedure consists of placing a cobalt-chrome

Cobalt-chrome

Cobalt-chrome is a metal alloy of cobalt and chromium. Cobalt-chrome has a very high specific strength and is commonly used in gas turbines, dental implants, and orthopaedic implants....

metal cap, which is hollow and shaped like a mushroom, over the head of the femur

Femur

The femur , or thigh bone, is the most proximal bone of the leg in tetrapod vertebrates capable of walking or jumping, such as most land mammals, birds, many reptiles such as lizards, and amphibians such as frogs. In vertebrates with four legs such as dogs and horses, the femur is found only in...

while a matching metal cup (similar to what is used with a THR) is placed in the acetabulum

Acetabulum

The acetabulum is a concave surface of the pelvis. The head of the femur meets with the pelvis at the acetabulum, forming the hip joint.-Structure:...

(pelvis socket), replacing the articulating surfaces of the patient's hip joint and removing very little bone compared to a THR. When the patient moves the hip, the movement of the joint induces synovial fluid

Synovial fluid

Synovial fluid is a viscous, non-Newtonian fluid found in the cavities of synovial joints. With its yolk-like consistency , the principal role of synovial fluid is to reduce friction between the articular cartilage of synovial joints during movement.-Overview:The inner membrane of synovial joints...

to flow between the hard metal bearing surfaces lubricating them when the components are placed in the correct position. The surgeon's level of experience with hip resurfacing is most important; therefore, the selection of the right surgeon is crucial for a successful outcome.

Advantages and disadvantages

The potential advantages of hip resurfacing compared to THR include less bone removal (bone preservation), a reduced chance of hip dislocation due to a relatively larger femoral head size (giving the patient an anatomically correct femoral head size), and easier revision surgery for any subsequent revision to a THR device because a surgeon will have more original bone stock available The potential disadvantages of hip resurfacing are femoral neck fractures (rate of 0-4%), aseptic loosening, and metal wear.
Due to the retention of the patient's complete femoral neck other advantages exist: Surgeon induced discrepancies in leg length (as could happen with THR) are now minimized. Also, the toe-in or toe-out faults that could occur interoperatively with THR are now over because the femoral neck that determines foot direction is left undisturbed with hip resurfacing.

Patient selection

Patient suitability for hip resurfacing is decided by the patient's anatomy and the patient's surgeon. Hip resurfacing is intended for younger patients who are not morbidly obese, are clinically qualified for a hip replacement (determined by the doctor), have been diagnosed with noninflammatory degenerative joint disease, do not have an infection, and are not allergic to the metals used in the implant. Hip resurfacing should not be used on patients who have severe bone loss in their femoral head, those with large femoral neck cysts present (typically found at surgery) or cysts that are close to the head neck junction, or patients who have poor bone stock or osteoporosis. Caution should be used for patients who have rheumatoid arthritis, are tall, thin, or small boned, those with osteonecrosis (poor blood supply) to the femoral head, or those with femoral head cysts > 1 cm on an x-ray taken before surgery. Patients with any of these conditions MAY not be suitable candidates for hip resurfacing.

Devices

In 2006, the United States

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

FDA

Food and Drug Administration

The Food and Drug Administration is an agency of the United States Department of Health and Human Services, one of the United States federal executive departments...

approved hip resurfacing using the Birmingham Hip Resurfacing (BHR) system, designed by British orthopaedic surgeon Derek McMinn

Derek McMinn

Derek McMinn is a British orthopaedic surgeon and inventor who practises in Birmingham, United Kingdom at the BMI Edgbaston Hospital. Mr. McMinn developed the first successful modern metal-on-metal hip resurfacing and the instrumentation and surgical technique to implant it...

. On July 3, 2007, the FDA approved the Cormet hip resurfacing system made in the UK by Corin Group and marketed in the U.S. by Stryker Corporation. On November 9, 2009 the FDA also approved the Conserve-Plus hip resurfacing system made by Wright Medical Technology. There are several other manufacturers of hip resurfacing systems, mainly in Europe. Another THR and hip resurfacing system, the DePuy

DePuy

DePuy is a franchise of orthopaedic and neuroscience companies. Acquired by Johnson & Johnson in 1998, its companies form part of the Johnson & Johnson Medical Devices & Diagnostics group...

ASR, which had been undergoing clinical trials for hip resurfacing in the United States and marketed overseas, has been recalled as a result of having been proven to have abnormally high revision rates. A prospective patient, therefore, needs to be cautious to confirm the type of device being used has an acceptable track record. Subtle differences among the devices in terms of design, manufacturing and surgical technique can prove to be detrimental to clinical success.

Procedure

The hip resurfacing devices are metal-on-metal articulating devices which differ from total hip replacement devices because they are more bone conserving and retain the natural geometry (so-called large ball THR devices share this trait). A THR requires that the upper portion of the femur bone be cut off to accept the stem portion of a THR device. The femur cap of the hip resurfacing devices does not require the femur bone be cut off; instead the top of the femoral head is shaped to closely fit the underside of the cap. Both hip resurfacing and hip replacement require that a cup is placed in the acetabulum of the hip socket. The main advantage of the hip resurfacing surgery is that when a revision is required, there is still an intact femur bone left for a THR stem. When a THR stem requires a revision, the metal stem in the femur has to be removed and often more bone is lost in the process of removal and replacement with a larger diameter stem. Having a hip resurfacing at a younger age means that a revision will likely be easier to perform when required.

Recent studies have shown that the outcome of a hip resurfacing is dependent on surgeon experience and that proper positioning of hip resurfacing components is crucial. Therefore, in addition to ensuring that a proven device is used, patients should take care in selecting a surgeon with experience and a good track record.

Although formal labeling restrictions exist in some countries, including the United States, hip resurfacing may allow younger, active people to return to many activities they enjoyed prior to their hip problems, which is an advantage over a traditional hip arthroplasty. The large size cap and cup of the hip resurfacing devices are the same size as a person's original ball and socket and thus are less prone to dislocation.

An often forgotten but very important advantage of hip resurfacing and thereby the retention of the femoral neck is the fact that hip resurfacing has the least measurable amount of "stress shielding" when compared to any type of THR. This means that with hip resurfacing the femur's upper portion fully retains its natural mechanical characteristics under load, also ensuring less disturbance of the processes that place inside bone that is alive.

Notable Athletes

There are many athletes with resurfaced hips that continue to compete at the personal and the professional level in a myriad of activities. They include:

Ron Noreman, who on July 24, 2010 won the Masters Division of the NPC Empire States Bodybuilding Championships only 5 months after hip resurfacing surgery.
Cory Foulk, who finished a marathon three months after his surgery, and finished 11th in the Ultraman world championship eleven months later
Ian MacLaren, of the Torashin Karate Club, who is believed to be the first 5th dan Karate-ka in the world to have had both hips resurfaced
Floyd Landis
Floyd Landis
Floyd Landis is an American retired cyclist who after initially being awarded victory in the 2006 Tour de France was stripped of his title for a doping offense. He was an all-around rider, with special skills in climbing and time-trialing, and is also known to be a very fast descender.Landis...

, the 2006 Tour de France
Tour de France
The Tour de France is an annual bicycle race held in France and nearby countries. First staged in 1903, the race covers more than and lasts three weeks. As the best known and most prestigious of cycling's three "Grand Tours", the Tour de France attracts riders and teams from around the world. The...

winner (until disqualified). His procedure was performed after the Tour win.

Recall

In August 2010, DePuy Orthopaedics, Inc., issued a voluntary recall of the ASR™ XL Acetabular System and DePuy ASR™ Hip Resurfacing System after new information from the UK National Joint Registry indicated that the number of patients who required a second hip replacement procedure, called a revision surgery, was higher than previously reported data.

Potential complications include pseudotumors, metallosis, ALVAL (Aseptic Lymphocytic Vasculitis Associated Lesions), and femoral neck fracture. Surgeon selection can greatly reduce the risk of some of these complications.

External links

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