近年来，随着人寿的延长和体重的增加，关节置换手术特别是膝关节和髋关节置换者逐年增多，仅在美国每年就有近40万人接受人工髋关节置换术（In the United States alone, almost 400,000 people each year have hip replacement surgery）。目前，在临床上常用的人工髋关节主要有四种类型。它们分别是：金属配金属（metal-on-metal），陶瓷配陶瓷（ceramic-on-ceramic），和金属配聚乙烯（metal-on-polyethylene），陶瓷配聚乙烯（ceramic-on-polyethylene），其中又以“金属配金属”之人工髋关节为最新型号产品。

那么，如此多类别的人工髋关节在质量上是否有好坏之分呢？根据最近研究的结果，上述4种类别的人工髋关节之临床应用效果（疗效与副作用）相似或相当。因此，大家在选择人工髋关节时，主要考虑的问题就是价格与来源了。

当下，各类人工髋关节的“寿命”约为十年左右，大多数病友在接受人工髋关节置换后十年左右常常因感染、脱臼、磨损、不稳定或松动等（infection, dislocation, wear, instability, loosening or other mechanical failures）而需要再次接受手术。通常在美国一副人工髋关节的价格约为35,000～40,000美元，价格不菲啊。

New Hip Implants No Better Than Older Ones, Study Finds

Not enough data to tell which device is best, researchers say

TUESDAY, Nov. 29 (HealthDay News) -- No matter the material, all types of hip replacement devices appear to work the same, a new analysis finds.

Specifically, the newer, metal-on-metal implants seem to be no more effective than older implants and may sometimes even be more problematic, the researchers said.

　　"Metal-on-metal and ceramic-on-ceramic hip implants might not be associated with any advantage, compared with traditional bearings such as metal-on-polyethylene or ceramic-on-polyethylene," said lead researcher Dr. Art Sedrakyan, director of the Patient-Centered Comparative Effectiveness Program at Weill Cornell Medical College in New York City.

There is some evidence from three large national registries that higher rates of replacement surgery are associated with metal-on-metal implants, compared with metal-on-polyethylene implants, Sedrakyan noted.

However, the bottom line for Sedrakyan is that there is not enough information about these devices to really tell if one type is better or safer than another.

"There are very successful implants on the market today for hip replacement," Sedrakyan said. "We need to have stronger data on improvement in clinical outcomes for new hip implants," he said.

Even for newer implants such as metal-on-metal or ceramic-on-ceramic bearings, their advantage over traditional implants is not clear, Sedrakyan added.

The report was published in the Nov. 29 online edition of the BMJ.

In the United States alone, almost 400,000 people each year have hip replacement surgery, Sedrakyan noted. A small percentage have surgery to fix problems with previous hip replacements. Often these operations occur within 10 years after initial surgery and are needed because of infection, dislocation, wear, instability, loosening or other mechanical failures.

Although the cost of a hip replacement varies by location and insurance, the average cost in the United States ranges between $35,000 and $40,000, with the newer devices costing on the high end of the spectrum, according to a 2006 report from the nonprofit Integrated Healthcare Association.

Older hip implants made with metal-on-polyethylene or ceramic-on-polyethylene surfaces are associated with low failure rates. However, newer metal-on-metal hip implants have been linked with severe cases of accumulation of metal ions in patients' tissues.

In 2009, the U.S. Food and Drug Administration began a review of the evidence for the safety and effectiveness of approved hip implants.

Working with the FDA, Sedrakyan's team looked at the safety and effectiveness of various types of hip implants in 18 studies including more than 3,000 patients and 800,000 operations.

The investigators found no difference between the various types of implants in terms of the patients' quality of life or ability to function normally.

Commenting on the study, Dr. Peter Cram, an associate professor of medicine in the division of internal medicine at the University of Iowa Carver College of Medicine, said that "the study highlights a critical issue in joint replacement surgery, which is there is not a lot of good data."

Cram noted that it is "shocking" that there are so many hip replacements done with so little data about which implants are best.

For patients, the best way of ensuring they are getting the best hip replacement they can get has really nothing to do with the device, Cram added. "You probably want an experienced surgeon, who does lots of these procedures, in a hospital that does lots of these procedures," he said.

Dr. Joseph Zuckerman, professor of orthopedic surgery and chair of the orthopaedic surgery department at NYU Langone Medical Center in New York City, said that "this study confirms what many surgeons already practice -- that in the pursuit of providing the best outcome, a surgeon must base his or her treatment recommendation on important factors that include each individual patient's health status and lifestyle, their own clinical experience, the documented evidence about outcomes and the available technology."

SOURCES: Art Sedrakyan, M.D., Ph.D., associate professor and director, Patient-Centered Comparative Effectiveness Program, Weill Cornell Medical College, New York City; Joseph D. Zuckerman, M.D., the Walter A.L. Thompson professor of orthopedic surgery and chair, department of orthopaedic surgery, NYU Langone Medical Center, New York City; Peter Cram, M.D., M.B.A., associate professor, medicine, department of internal medicine, University of Iowa Carver College of Medicine, Iowa City; Nov. 29, 2011, BMJ, online