Revision hip arthroplasty involves redoing all or some of an existing hip replacement. Sometimes both the cup and stem need to be changed, sometimes just the stem or just the cup are addressed and occasionally only the plastic liner of the cup needs to be changed. Also the size of the procedure depends on the reason for revision and the fixation of the components e.g whether they are cemented in place and whether or not they are loose already. In general however, revision surgery is considerably bigger, somewhat more unpredictable and has higher risks when compared to the initial operation.
The most common indication for revision is simply loosening of one or both components. Persistent pain is also a reason although it must be stressed that every effort be made beforehand to find the reason for ongoing pain. Revision based purely for pain alone will often yield disappointing results. Other reasons include bone loss. This is often due to a process known as osteolysis whereby bone is resorbed in response to the production of wear debris produced by the plastic (polyethylene) cup. Wear debris can is also produced by metal on metal articulations and this can also create soft tissue reactions. A fracture of the bone around or near the femoral stem will also often require revision. Recurrent dislocations are another reason for revision surgery. Finally although only a reason for a small number of revisions, infection can involve a two stage procedure with removal of all the components, a radical debridement and a temporary spacer until the infection has subsided. The second operation then involves putting back in a new replacement a few weeks later.
Many revision hip replacements are still performed under a spinal anaesthetic, where the legs are numbed from an injection of local anaesthetic into the back. This can be combined with sedation if you prefer not to be aware of the surgery. If a more prolonged procedure is anticipated, then a general anaesthetic may be used but ultimately this is the decision of the Anaesthetist looking after you and can be discussed with them prior to surgery.
Usually the old scar will be used again although depending on the extent of the revision, this may need to be extended. The hip joint is then exposed, with careful attention paid to protecting the sciatic nerve. If the femoral stem is well fixed and needs to be removed, sometimes the bone around it may need to be split open and this is known as an extended trochanteric osteotomy. After the stem is removed, the bone is closed over again and held with special wires around it.
The old components are removed with every attempt to preserve as much bone as possible. Often special revision implants are required that have many more screw options on the cup side or a much longer stem on the femoral side. Once the bone has been prepared for the new components, a trial reduction allows for any small adjustments to be made and ensure that the hip is stable through an arc of motion. The implants are then inserted, the hip reduced and the joint fully washed out and closed in layers.
With revision surgery, the large nerve that runs down behind the back of the femur, the sciatic nerve, is more prone to injury. This is due to the fact that it is often surrounded by scar tissue making it more difficult to identify and less resistant to stretch. This would manifest itself after the surgery as a weakness in bringing your foot up and is known as a foot-drop
The risk of dislocation after revision surgery is substantially higher than after a primary hip replacement. This is true even if you just require a liner exchange where only the worn liner is replaced and the main components are left in place. Following any revision surgery, it is especially important to follow the rules regarding leg movements, bending and lying in order to help minimize this risk.
The above x-ray shows a loose femoral stem
X-ray following revision of both the acetabular and femoral components
With revision surgery, the blood loss is often significantly more than with your initial hip replacement. Thus there is a higher chance that you will need a blood transfusion either during or after your surgery. Please be aware that whilst a blood transfusion carries a risk, the meticulous screening of all blood products prior to use makes this risk extremely small. The quoted risk for acquiring HIV or Hepatitis C from a transfusion is 1 in 4 000 000 and 1 in 250 000 for Hepatitis B. For further information please see https://www.giveblood.ie/.
Prior to revision surgery, there will often be a difference in length between your two legs. Every effort is made to equalize these at the time of surgery. However, sometimes it is necessary to lengthen the leg to tension the tissues and ensure the hip is stable throughout a range of motion. Small differences often go unnoticed but if this is more than 1cm, you may require a small heel raise in the opposite shoe.
Often after a revision you will need to protect the leg by using crutches for the first 6 weeks. Sometimes, you will be allowed to put your full weight through the leg but occasionally you will only be allowed to rest the foot to the ground. Your physiotherapist will instruct you carefully in this regard.
In general the recovery after a revision is slower than after the initial surgery and you can probably double the estimated times for returning to activities. For example, it may take up to 6 months to be able to return to work fully.
Unfortunately revision surgery also carries a higher risk of infection. Whilst the risk of infection following a primary hip replacement is under 1%, in a revision this risk may be 2 or 3 times that. Every effort is made to minimize the risk at every stage during the procedure and you will be given antibiotics both before and afterwards to help reduce it.
Compiled October 2015
Review date: March 2016
Review date: March 2016