Hip arthritis is a painful condition caused by gradual deterioration of the cartilage in the joint. This cartilage provides padding between the bones, allowing them to move smoothly as you walk. Arthritis can eventually make the bones in the hip rub against each other, causing severe pain and joint deformities. People with severe hip arthritis often undergo hip replacement surgery, in which the damaged bones are replaced by an artificial prosthesis. However, a hip prosthesis sometimes fails in the short or long term.
The hip is a ball-and-socket joint capable of rotation, back-and-forth and side-to-side movement. Hip replacement surgery is most commonly performed to treat pain and disability caused by hip arthritis. The ends of the ball and socket are removed and replaced by artificial implants. The components of a hip replacement prosthesis include a round ball on a stem that sits inside the thigh bone and a smooth, lined socket that is attached to the pelvic bone.
The most common cause of hip prosthesis failure is loosening of one or both of the joint replacement components. According to the 2012 medical text "Recent Advances in Arthroplasty," prosthetic loosening accounts for approximately two-thirds of hip prosthesis revision surgeries. Wear and tear on the hip prosthesis can cause the bond between the bones and the implant to break down over time. This often cause the sensation that the hip will "give out" with pressure on the leg. Other symptoms include pain in the hip or groin, limited hip movement or difficulty walking. Stability of the prosthesis is determined by physical examination and x-rays. Damage to the joint liner in the replacement joint can be caused by normal wear and tear. A worn liner can also cause looseness and failure of a hip prosthesis.
Dislocation of a hip prosthesis causes the ball to move out of position in the socket. This is the most common complication caused by loosening of the prosthetic components. Dislocation usually occurs in the first few months after surgery. According to the American Academy of Orthopaedic Surgeons, the average rate of dislocation after hip replacement is 1 in 50 patients.
Specific movements can increase risk of dislocation: rotating the leg inward; bending over or moving beyond a 90 degree bend at the hip; and crossing the legs. The doctor can often put the hip prosthesis back in place without the need for more surgery. However, if dislocation occurs multiple times, the implant may need to be replaced.
Hip prostheses can fail due to joint infection. This typically occurs soon after surgery, causing severe hip pain, difficulty walking, limited hip motion, abdominal pain and sometimes a fever. This is an emergency situation that requires removal of the hip prosthesis. According to the American Academy of Orthopaedic Surgeons, realistic risk of infection with joint replacement surgery is about 0.5 percent.
Treatment of hip prosthesis failure is based on the underlying cause. Loosening of the hip components may require surgery to replace the implants, a procedure called revision surgery. This is a major procedure with increased risk for infection and future dislocation of the prosthesis. A worn joint liner can sometimes be replaced without removal of the other components of the prosthesis. Joint infection requires immediate removal of the prosthesis followed by 6 weeks of antibiotics. A new prosthesis is later implanted to replace the old one.