A hip fusion is a procedure where the ball of the femur and socket are brought together to form a single bone. The purpose of the fusion is to relieve pain and to sta-bilize the hip joint.
In a hip fusion, the articular cartilage on the two joint surfaces is removed. This exposes raw cancellous bone with good surfaces for healing. When the cartilage is removed and the bones are put together, the two bone surfaces will heal to one another and form a single unit. The bones are thus fused together. The technical name for this procedure is hip arthrodesis.
Fusing the bones together relieves the pain of an arthritic hip. It also stabilizes the joint. When the hip has been fused, the results are permanent. The down side is that even though a fusion relieves pain, it elimi-nates all motion at the hip joint. A person with a hip fusion will never again be able to move the joint or to have a normal gait.
Hip fusion was first performed in the early part of the 20th century. For many years it was a standard treat-ment for painful osteoarthritis of the hip. With the advent of cup arthroplasty in the 1940s and total hip arthroplasty in the late 1960s, hip fusion has become less popular. Originally, it was felt that the best patient for a hip fusion was an active individual younger than forty years of age with arthritis in a single hip.
A hip fusion puts additional stress on the opposite hip, the lumbar spine, and the knee on the same side. It was not appropriate for patients with problems in these areas. Most hip fusion patients were young and had arthritis due to previous fracture or an old infection.
The success of total hip arthroplasty has made hip fusion less desirable, even for patients in their twenties and thirties. Younger active patients who have total hip arthroplasty know that they may need a revision proce-dure when they get older. Despite this, most will not accept the loss of mobility, abnormal gait, and pro-longed recovery time that come with a hip fusion.
Hip fusion is done through a long incision on the front or anterior aspect of the hip joint. The joint capsule is incised and the hip joint is exposed. All of the articular cartilage is removed from both sides of the joint. The bones are then shaped to fit together. Internal fixation with screws or a metal plate and screws is used to hold the fusion together. Bone graft material may be placed around the fusion to add additional bony surface and to speed the healing.
The hip is fused in a slightly bent or flexed position and a position of slight external rotation. Care is taken to allow enough flexion for sitting but not to flex the hip too much so that the leg is very shortened. This will allow the best position for daily function and activities. Years ago patients were placed in spica cast from the waist to the toes of the surgical leg after the procedure.
Modern methods of internal fixation, however, are much stronger and most patients do not need a cast. A period of nonweight bearing or partial weight bearing on crutches is required until healing is complete. The progress of the fusion and the degree of healing can be assessed with periodic x-rays.
A patient may be full weight bearing once the fusion has completely healed. This may take 3 to 6 months. Nonunion or failure of the fusion to heal is the major complication of the procedure. With modern tech-niques, this occurs in about 10–15% of patients. If nonunion occurs, a repeat fusion needs to be done. As with any surgical procedure, infection can also be a complication.
Hip fusion puts additional strain on the joints surround-ing the hip. It may put pressure on the lumbar spine or cause pain in the knee joint below the hip. Beyond this, it may affect the opposite hip. This is because patients must compensate for the loss of motion in the fused hip joint. Individuals with pain in these areas or a disease such as rheumatoid arthritis that involves multiple joints are not candidates for hip fusion.
In some circumstances, hip fusion is still used as a sal-vage procedure following an infected total hip arthro-plasty. The popularity of total hip arthroplasty has led many patients who have had hip fusion to seek conversion to a total hip. They would like to regain the mobility that was lost when their hip was fused.
Conversion of a fusion to a total hip can be a technically demanding procedure. Since the joint surfaces are fused together, they must first be separated at the appropriate level and the bones reshaped to accept the prosthetic components. The anatomy is distorted and accurate component placement is more difficult. While the results of a fusion takedown and conversion to arthroplasty may be gratifying, the overall incidence of complications is higher than that for primary total hip arthroplasty.
Even though hip fusion provides a durable long-term solution for painful hip, most younger patients will not accept the limitations of function and motion that come with fusion. Since total hip arthroplasty has become so popular, hip fusions are now relatively rare.