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 an uneventful surgery and 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, they will initiate some investigations which will determine if your pain is due to an infection, loosening, and malposition of the implants or leg length inequality. Inevitably these tests will be normal, confirming that an infection, loosening or malposition are not the cause of the persistent pain. Your surgeon may say to you that your hip looks good and they will be correct. There is nothing wrong with your hip prosthesis.
Total hip replacements are done these days through many different surgical approaches. The current approaches used today are the direct lateral approach (DAA), the posterior approach (PA), the direct anterior approach (DLA) or an approach which is called SuperPath (SP) a variation of the posterior approach. The arthroplasty society of the Australian Orthopaedic Association does no 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 in the legs.
The cause of the pain
When the hip is exposed to implant a new hip prosthesis, the soft tissues around your hip, of necessity, are disturbed. This means the tendons and hip capsule must be divided. Considerable time is spent in reconstructing these tissues and tendons as your wound is being closed. These tendons are attached to some enormously powerful muscles, several of which can generate a pull which is stronger than the repair. When you get up on your new hip and take full weight on your operated leg, the hip muscles contract strongly and in some fit patients, so strongly that the repair may pull 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 muscle pulling on the wrong spot or perhaps applying traction 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 of the gluteal tendonsresulting from wear and tear at the hip tendon attachmentat the side of your hip (the gluteal muscles). Occasionally 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. If this problem is not addressed at the time of replacement, the component of your pain from the disordered tendons at their trochanteric attachment will persist.
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 procedures can be done at the same time and there is no need at all to disturb the hip prosthesis in any way.
The reconstruction of the hip tendons and the sciatic release can be done through the original surgical incisions if the PA or SP approachhave been used. A new incision will need to be made if the DAA has been used. As it is a soft tissue operation, there is very little blood loss and most patients bounce back from this surgery very rapidly.
All operation can have complications and this is no exception. The most common complication is that which is common to all hip operations and that is a blood clot in the vein (DVT). Other complications are infection, worsening of pre-existing medical problems such as diabetes and failure of the repaired tendon to stay attached to the bone. Although this seem a lot, it also means that you have better than 97% chance of having no problems at all and losing all your pain.
After leaving hospital, arrangements can be made for you to go to a specialist rehabilitation centre. Most patients are well enough to go straight home. While weight-bearing on the leg is not advised, it is desirable that you move around as much as possible on your walking aid of choice to maintain good muscle tone. It is prudent and essential to protect your tendon repair from normal weight-bearing stresses. After five weeks, weight-bearing commences by graduating to 25% weight and then at six weeks to one crutch on the opposite side of the operation, then onto a stick and finally full weight-bearing as soon as this is tolerated. The best exercise by far to train your hip muscles is walking on flat ground. However, physiotherapy, hydrotherapy and a dedicated home exercise programme will help to restore your normal tendon and muscle function more quickly. Initially the muscles become quite sore because they are weak and unfit but this improves with regular exercises.
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.