The total hip replacement operation is performed to deal with the severe pain associated with osteoarthrosis of the hip joint. It is one of the most successful surgical procedures we perform today. On very rare occasions, despite uneventful surgery and post-operative recovery, troublesome pain persists in the replaced hip. This is always of great concern to both you and your surgeon.
When you inform your surgeon that your hip remains painful, your surgeon will initiate some investigations which will determine if your pain is due to an infection, loosening of the prosthesis, malposition of the implants or perhaps a leg length inequality. Usually all of these tests will be completely normal, confirming that infection, loosening and malposition are not the cause of your persistent pain. Your surgeon may say to you that your hip looks good and they will be absolutely correct. There is nothing wrong with your hip prosthesis.
Total hip replacements are done these days through a number of different surgical approaches. The current approaches used today are the direct lateral approach (DLA), the posterior approach (PA), the direct anterior approach (DAA) or an approach which is called SuperPath (SP) a variation of the posterior approach. The arthroplasty society of the Australian Orthopaedic Association does not advocate any particular approach, each one being equally good for different reasons. By three months post-operative, most hips will be functioning very well whatever approach has been used. Each approach is managed slightly differently in the post-operative period. The most common protocol for rehabilitation has you up and full weight-bearing in the immediate post-operative days to accelerate your rehabilitation and reduce the risk of blood clots forming in your legs.
When the hip is exposed to implant the new hip prosthesis, the soft tissues around your hip, of necessity, are disturbed. This means the tendons and hip capsule have to be divided. Considerable time and care is spent in reconstructing these tissues and tendons as your wound is being closed. These tendons are attached to some enormously powerful muscles, a number of which can generate a pull which is actually stronger than the repair. When you first stand up on your new hip and take full weight on you operated leg, the hip muscles contract strongly and in some fit patients, so strongly that the repair may actually be pulled apart. This does not happen all the time but it is well known to happen and has been shown on follow-up MRI scans. If this does happen, there may be pressure on the surrounding normal tissue from the retracted muscles pulling in a wrong manner or perhaps after a PA, applying traction on the sciatic nerve which is close by. If this happens, it will result in buttock pain making it uncomfortable even to sit on that side.
Another cause is unrecognised degeneration causing wear and tear of the major hip tendons attached to the side of your hip (the gluteal muscles). On occasion these tendons become worn for all the same reasons that the hip wears out. Particular attention is paid not to disturb these tendons in the PA, SP and the DAA. However, if this problem is present and is not addressed at the time of your hip replacement, the component of your pain from the disordered tendons at their trochanteric attachment will persist despite the hip replacement.
This problem is normally diagnosed by most of the tests being normal but some changes can be noted on an MRI scan which can be done on some machines even in the presence of a hip replacement.
When the gluteal tendons have separated from their bony attachment they need to be reconstructed to relieve the pain. If the tendons at the back of your hip have pulled apart, the pain associated with that can be improved by releasing the sciatic nerve where it becomes trapped in scar. Both of these can be done at the same time and there is no need at all to disturb the hip prosthesis in any way.
This is very likely to settle the pain in your replaced hip. Once the secondary problem of your soft tissue repair has been rectified, you will be able to return to all normal activity and enjoy the huge benefits of your replaced hip.