Hip replacements usually last at least 20 years. Carrying excess body weight or doing high-impact activities and exercise can put excess strain on the artificial joint and cause it to wear out early. An accident, fall, or another impact injury can also cause the hip replacement to come loose.
This article discusses hip replacement loosening and its causes. It also explains why hip replacements may fail and require joint revision surgery.
Hip Replacement Overview
Hip replacement surgery is among the most common orthopedic procedures and is performed more than 300,000 times in the United States every year. It has a proven track record for safety and for improving the quality of life and life expectancy in those with the functional loss of mobility.
One of the key concerns about hip replacement surgery is the loosening of the hip prosthetic. It is a normal consequence of implant surgery, sometimes requiring revision surgery to correct the problem.
Unfortunately, the revision process is often less successful than the first surgery. Of equal concern is the risk of infection or breakage of the implant when joint loosening occurs, both of which can lead to potentially severe and, in some cases, life-threatening complications.
Life Span of Hip Prosthetics
Most hip replacements last an average of 20 to 25 years. Some implants last longer, while others fail much sooner. Occasionally, the implant will fail immediately after surgery, but, in other cases, an implanted joint may last for 30 or more years with no problems whatsoever.
Decades ago, when joint replacement surgery was considered new, there were different factors that determined how long a hip implant would last. Some of the earliest implants failed because the metals were susceptible to breakage or the plastics quickly shattered.
Due to improvements in the strength of hip prosthetics and fixation techniques, current implants tend to hold up well once implanted. Furthermore, with improvements in sterile surgical protocols and infection control, serious complications of joint prosthesis infection have also been reduced.
Why Hip Replacements Loosen
When a hip replacement is placed in the body, it is either pressed or cemented into place so that it fits tightly into the pelvis and the bone of the thigh (femur). Although the implant may be stable at first, it can sometimes loosen over time. This is typically a gradual process that increasingly impedes the normal function of the prosthesis.
There are several factors that may contribute to hip replacement loosening, including a person’s age, sex, weight, and activity levels. A study published in the Journal of Orthopedic Surgery concluded that hip replacements are less likely to loosen in the following groups:
Women: A women’s anatomical differences, including the angle of the hip bones, tend to place less stress on an artificial joint. Differences in physical activity between the sexes may influence failure rates. People over 60: The risk of a loosening hip implant decreases with each advancing year, most likely due to decreased activity levels. People with obesity: Persons with a body mass index (BMI) under 25 are more likely to maintain joint implant integrity. With each BMI unit over 25, the risk of loosening increases by 3%.
Beyond these risk factors, the most common cause of joint replacement loosening is the wearing of the implant surfaces and the subsequent weakening of the surrounding bone. This is known as osteolysis.
Osteolysis
Osteolysis is a problem that causes the bone surrounding the implant to seemingly “melt away.” When viewed on an X-ray, it will look as though there are holes in the bone around the implant. Because of the weakened bone, the hip replacement can become loose and begin to wobble over time. Pain and limitations in the motion of the hip are also common.
After years of use, microscopic fragments of the hip replacement cause irritation to the tissues around the implant and begin to weaken the bone. Even though modern hip implants are made of materials that can withstand wear, even small amounts of these particles can damage the bone and cause the implant to loosen.
Joint Revision Surgery
Hip implant loosening is an issue of particular concern because revision surgery is a much more difficult operation than the initial procedure. If and when revision surgery is needed, the hip joint is more likely to be worn and the femur and pelvis are more likely to be unstable or brittle.
Generally speaking, people tend to recover less range of motion (ROM) of the joint following revision surgery. The longevity of the implant will also decrease, increasing the risk of a second revision surgery.
Therefore, healthcare providers tend to avoid joint replacement surgery until absolutely necessary and try to get as much mileage out of each replacement as possible.
Urgent Cases
Hip replacements can fail for reasons other than loosening. For example, the ball of the joint may slip out of the socket in the weeks following surgery, leading to dislocation.
An infection can also occur, either due to the loosening of the joint or a complication from the initial surgery itself. An infection can be detrimental to surrounding muscles, ligaments, cartilage, and bones and in rare cases become systemic. In such cases, prompt revision surgery is needed to maintain the structural integrity of the joint and prevent the cataclysmic loss of mobility.
Prevention
In recent years, researchers have begun to investigate whether or not traditional metal-on-polyethylene implants are ideal choices for hip replacement.
Newer implants made of ceramic-on-polyethylene, ceramic-on-ceramic, and metal-on-metal are largely believed to have improved longevity compared to these traditional implants. They tend to have much smaller wear particles and debris accumulating around the joint. The overall volume of wear in these implants is also less than that of traditional metal-on-polyethylene implants.
However, it is not yet known if these newer models will actually lower the rate of loosening over time. Furthermore, there may be other complications associated with different types of hip implants that may not occur with metal-on-polyethylene models.
A Word From Verywell
There is no definitive answer as to which type of hip implant is “best.” Although it may be reasonable to assume that newer models are better, long-term studies have yet to firmly establish this as fact.
Many orthopedic surgeons have a strong preference for one type of implant or another based on personal experience. If you have questions about which type of implant is being used for your surgery, do not hesitate to discuss this with your healthcare provider or to seek a second option if needed.
