Even though hip joint replacements are available, doctors sometimes fuse the joint instead. This is often the case with young patients who have severe hip damage on one side. Most of the time, the damage is related to some form of arthritis. Sometimes an accident or injury leads to infection and destruction of the hip joint. Tuberculosis that affects the bones is another cause of hip joint problems.
Doctors try to fuse the joint in a way that still allows the patient to change or convert to a new joint later on. Most hip fusions last at least 25 years before conversion to a new joint. When the patient has back, hip, or knee pain that gets in the way of everyday life, it may be time to convert the fusion.
The conversion from a fused joint to a new hip joint is difficult. An experienced surgeon is needed. Even then, problems after the operation can occur. Complications after conversion include nerve damage, infection, loosening of the implant, and hip dislocation. Rarely, a bone may fracture.
Records kept over the years by doctors who have done this surgery are helpful. Several studies report that converting a fused hip to a total hip replacement has a good outcome. There are some possible problems, but these are limited with a good surgeon.
Atul B. Joshi, FRCS, et al. Conversion of a Fused Hip to Total Hip Arthroplasty. In The Journal of Bone and Joint Surgery. August 2002. Vol. 84-A. No. 8. Pp. 1335-1341.'