Hip Revision Surgery

A hip revision procedure involves removing and replacing a worn, loosened or misaligned implant in order to relieve pain and improve the function of the implanted hip system. In the majority of cases, hip revision surgery is more complex and time consuming than the original hip replacement.1

With over 332,000 hip replacements performed in the United States and 70,000 in the UK in 2011, more than 85% of patients experience a favorable outcome and can expect their replaced hip to function well for at least 20 years and potentially much longer.2 However up to 15% of patients may experience some condition which may require further surgery, known as revision surgery.

Reasons implants may fail

The decision to perform a revision surgery is based on several issues. The implant may have become loose, worn or infected. As the replacement fails you may experience a limp, stiffness and pain, or instability. X-rays or scans may show a change in the position or condition of the implants. Assessment of these indicators will help determine when hip revision surgery is needed.2

Loosening: Cemented implants can become loose because the cement-bone interface has failed. This is usually due to bone die back, meaning the honeycomb-like bone the cement is initially attached to has either broken off during weight bearing, deteriorated due to infection, as a result of wear related particles destroying the surrounding bone or due to weak bone (osteoporosis). Uncemented implants can loosen for much the same reason except it is the implant-bone interface that fails.

Wear: In hip replacements utilizing metal on polyethylene (plastic) cups, the plastic is obviously softer than the metal and therefore more prone towards wear during use. This usually happens after a long period of time as modern plastics (ultra high molecular weight polyethylene or UHMWPE for short and highly crossed linked polyethylene) are very durable and can withstand a considerable amount of wear and impact. Generally speaking, plastic parts are more likely to wear if the accompanying metal parts are not properly aligned, the plastic itself is misaligned, infection has occurred, or because the implant components have been in the patient for a long time.

Low Wear Rate Ceramic-on-Ceramic Hip Implant
(CeramTec)

It is recognized that wear begins from day one after surgery and early stages of wear are minimal, usually measured in microns. Implant manufacturers have worked to significantly decrease the amount of wear particles that are created by improving the bearing surfaces of implants with fortifying substances such as vitamin E.3 However, after several years there may be a build-up of worn off particles which can cause problems in nearby tissues as microscopic fragments get absorbed into the cells and create inflammatory conditions causing pain.

Infection: With modern surgical techniques the risk of infection from total hip replacement is very low at about 0.5%.2 If infection does occur, it usually arises due to a substance on the devices called bio-film. This organic material is a microscopic layer of fungal material containing microbes living in a state of hibernation. All implanted devices have this phenomenon including items such as stents and pacemakers. Infection arises when the microbes become active and multiply. It is not yet known what provokes this sudden change, but it is known that a series of changes occur allowing the microbes to reach a state of maturity and become more susceptible to eradication with antibiotic treatment. Patients with deep infection can be cured in over 90 percent of cases.3

Dislocation: If you dislocate your hip at some point after your initial total hip replacement, hip revision surgery may be indicated, most likely because of misalignment of the cup, the stem, or both.1 Replacing the hip implants should reduce the risk of further dislocation.1

Fractures: Trauma to the hip, such as in a serious road accident or fall, could result in a fracture of the upper end of the femur that may disrupt the stability of the hip and will require surgery to repair.

Implant related fractures: Component fractures occur very rarely. Fracture of the femoral stem is usually due to insufficient support from the surrounding bone. A similar situation can occur in the case of plastic components which are not loaded correctly usually due to misalignment. One of the rarest types of fractures is that of ceramic articulating components and is usually the result of trauma or improper assembly.

Patient-related factors: Most patients today expect a total hip replacement to allow them to resume the activities they enjoy. As is the case with any mechanical device, younger patients engaged in very active sports and activities are more likely to require a future revision. On the other hand, hip replacement patients in their 70′s and above generally place fewer demands on their new hips and are less likely to require a revision.

Revision surgery is more complicated

In the majority of cases a revision procedure is more complex than the initial replacement surgery because your surgeon must remove the original implant and replace it with new components. This is made more complicated where there is infection, lack of adequate bone stock, or difficulty encountered in separating the implants from the bone. The surgery can also take considerably longer to perform when specialized techniques and equipment are required.3

Revision hip replacement surgery further complicates recovery as surgical trauma, scar tissue, and mechanical weakening of bone can reduce performance of the joint and hip area in general.

Recovery and outcomes

Care after hip revision surgery is similar to the care you’d receive after total hip replacement. This includes a combination of light physical therapy and pain medications as needed. Blood thinning medication will also be given to prevent blood clots. A walker or crutches will be used early in your recovery period, then you’ll progress to a cane and eventually walking without any assistance as your condition improves.

More than 90% of patients who undergo revision procedures can expect good to excellent results. Although pain relief and increased stability are expected outcomes, occasionally complete pain relief and restoration of function is not always possible. However strength and mobility may continue to improve over the next one to two years after hip revision surgery.2

Sources

  1. McBrair, Wendy MS, BSN, CHES “Hip or Knee Replacement: The Second Time Around” http://www.arthritisselfmanagement.com/health/surgery/hip-or-knee-replacement-the-second-time-around/?page=all
  2. American Academy of Orthopaedic Surgeons “Joint Revision Surgery – When Do I Need It?” http://orthoinfo.aaos.org/topic.cfm?topic=A00510
  3. Sood, Manoj MD “The challenge of revision hip replacement surgery” http://www.arthritisresearchuk.org/arthritis-information/arthritis-today-magazine/159-winter-2013/the-challenge-of-revision-hip-replacement-surgery.aspx

image credit: flickr.com/mscsealift

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