Across the globe, some 10% of men and 18% of women over the age of sixty suffer from moderate to severe forms of osteoarthritis. Osteoarthritis is a degenerative joint disease in which the cartilage deteriorates, causing injury to the joint and resulting in stiffness, pain and loss of movement as bone rubs against bone. Aside from age, the most common predictors of osteoarthritis appear to be obesity, physical inactivity, smoking, excess alcohol consumption and injury. Rheumatoid arthritis, in which the joint lining becomes inflamed, is responsible for some hip replacement surgeries as well.
A degenerative disease known as avascular necrosis—a condition wherein the head of the femur bone loses blood supply and dies—can also lead to hip surgery and the implantation of an artificial hip. Avascular necrosis can be caused by Gaucher disease, gout, diabetes or a severe trauma such as a break or dislocation. Hip fractures can result in the necessity of hip replacement surgery; between 1990 and 2000 alone, there was a 25% increase in hip fractures across the globe. Nearly three-quarters of hip fractures occur in women, while the highest number of hip fracture occurs in those between the ages of 70 and 79. The lifetime risk of a white woman suffering a hip fracture is 1 in 6, while that same woman’s chance of developing breast cancer is 1 in 9.1 Hip fractures from childhood as well as childhood hip conditions such as developmental dysplasia or Perthes disease can also lead to hip degeneration and the necessity of hip replacement surgery.
Interestingly, the United States and Germany have the highest rates of knee replacements—despite the fact that the overall population of the U.S. is younger than that of Germany. Hip and knee replacements combined are most prevalent in Austria, Germany and Switzerland.2 In any case, the overall number of hip replacements in the United States has increased dramatically over the past decade, nearly doubling in number. Estimates place the number of annual hip replacement operations performed in the U.S. between 285,000 and 300,000 annually, which translates into about 800 hip implant procedures each day. It is believed that the demand for hip replacements will increase by 175% by the year 2030. Although most hip replacement recipients are still over the age of sixty, longer-lasting joints have begun to make such procedures viable for younger, more active patients.
Surgical Techniques for Hip Replacements
The surgical procedure for hip replacement involves removing the damaged bone and cartilage, replacing it with a prosthetic hip joint constructed of metal, polyethylene or ceramic. During hip implantation, the majority of surgeons enter the hip region from the rear, which requires cutting through muscle and cartilage; new procedures allow the surgeon to enter the hip from the front, moving the muscles aside, thus avoiding extensive cutting and significantly minimizing pain and recovery time. This anterior technique is considered minimally invasive and significantly reduces the chances of later hip dislocation. Still, only about 20% of surgeons use the anterior approach, choosing to stick with what is tried and true, (or more likely, what they are familiar with).
As the number of hip replacements increase, so too will the number of repairs to those hip replacements, known as revision surgery. Before the widespread use of metal-on-metal hip implants, there was a 90% chance of an artificial joint (ceramic, polyethylene or metal-on-plastic) lasting a decade.3 This meant that those patients who had their first hip replacement surgery at age 50 or 60 could certainly expect to undergo a revision surgery in their lifetime. Unfortunately, once metal-on-metal hip implants began to be widely used, while the expectation of longevity was high, in reality, patients were forced to undergo revision surgery after two, three or four years.