Do Gender Knee Implants Provide Better Outcomes?

- Study finds gender-specific total knee prostheses provide no clinical benefits compared to standard prostheses in women

- For information about knee replacement surgery in Argentina please don’t hesitate to contact Sublimis.

Rosemont, IL – A gender-specific total knee prosthesis was developed to more closely match the anatomy of the female knee, aiming to be a better fit resulting in better outcomes for women. However, a recent study in the Journal of Bone and Joint Surgery (JBJS) found that 85 women who received a gender-specific implant in one knee and a standard prosthesis in the other knee found no clinical benefits of the gender-specific knee.

“We conducted this study to investigate whether women derive less benefit, or perhaps less predictable benefit, from total knee replacement using a standard conventional total knee implant,” said Young-Hoo Kim, M.D., orthopaedic surgeon and lead author of the study.

After receiving knee implants – one gender-specific and one standard prosthesis – the women were assessed for at least two years after surgery. The knees with the gender-specific implant and the knees with the standard implant had similar knee scores and similar range of motion while lying down (125° for the knees with standard implants and 126° for the knees with gender-specific implants). All patients except three were able to bend their knees at least 90°.

Additionally, patient satisfaction with the implants was similar (8.3 points for the standard implants and 8.1 points for the gender-specific implants). A rating of 6 to 8 meant “satisfied,” and a rating of 9 to 10 meant “fully satisfied.”

Important findings included:

* The majority of women in the study (71 females or 84 percent) had no preference between the two implants,
* eight women (9 percent) preferred the standard prosthesis, and
* six (7 percent) preferred the gender-specific prosthesis.

Knee Implant. Source: AAOS.org

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Timing of surgery for knee injuries may not affect outcomes

Rosemont, Ill – Multiple-ligament knee injuries resulting from traumatic knee dislocations – such as high impact car accidents or certain sports are uncommon, and the optimal timing of surgical repair or reconstruction has not been definitively established.

According to a new study published in the December 2009 issue of The Journal of Bone and Joint Surgery (JBJS), patients who undergo surgery more than three weeks after a multiple ligament knee injury (called chronic intervention treatment) may have comparable outcomes to those who undergo surgery within three weeks of injury (called acute intervention treatment) with regard to knee stability. Additionally, researchers found that early mobility is associated with better outcomes than immobilization in those patients who are treated within that three week time period.

“After a review of the available literature, we found that chronic intervention provides results that are at least as good as acute intervention, despite some recent studies showing that acute intervention may be better,” said lead author of the study William R. Mook, MD, who conducted the study with colleagues from the Department of Orthopaedic Surgery at the University of Virginia in Charlottesville.

Dr. Mook and his colleagues surveyed 24 retrospective studies that included 396 knees treated surgically for the most severe multiple-ligament knee injuries. Patients were managed either acutely, chronically, or with a combination of both interventions, which is called staged treatment. The researchers also studied whether the patient’s leg should or should not be mobile or immobilized after surgery.

The study found that:

* patients receiving acute intervention had less stable knees and were not able to bend their knees as far as those who were treated with chronic intervention; and
* patients who underwent staged procedures (treatment from both the acute and chronic intervention stages) reported better outcomes than those treated just early or late.

“The reasons for this are not clear. The patient population is heterogeneous, and surgery can be delayed for a variety of reasons. It is difficult to tell which procedures were delayed intentionally and which were delayed due to other medical reasons occurring as a result of their initial injury,” Dr. Mook said.

This literature review suggests the following:

* Surgical reconstructions within three weeks of the injury and those performed later provide comparable knee stability.
* In patients treated within three weeks of injury, early mobility (compared with immobilization) is associated with better outcomes. However, early surgery is highly associated with range-of-motion limitations.
* Patients reported better outcomes and fewer range-of-motion limitations with a combination of acute and chronic procedures. However, additional treatment for joint stiffness may be required in these patients.
* In patients treated within three weeks of their injury, more aggressive rehabilitation may prevent the need for additional treatment for joint stiffness.

Previous studies have indicated that early treatment provides better outcomes, but that may not be the case. “Although recent evidence suggests that acute intervention is superior to chronic interventions in all outcomes, we found that chronic intervention may provide knees with equal stability as those managed acutely,” Dr. Mook concluded.

Source: American Academy of Orthopaedic Surgeons

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Laser processes promise better artificial joints, arterial stents

West Lafayette, Ind. – Researchers are developing technologies that use lasers to create arterial stents and longer-lasting medical implants that could be manufactured 10 times faster and also less expensively than is now possible.

New technologies will be needed to meet the huge global market for artificial hips and knees, said Yung Shin, a professor of mechanical engineering and director of Purdue’s Center for Laser-Based Manufacturing.

The worldwide population of people younger than 40 who receive hip implants is expected to be 40 million annually by 2010 and double to 80 million by 2030. In addition to speeding production to meet the anticipated demand, Shin said another goal is to create implants that last longer than today’s.

“We have 200,000 total hip replacements in the United States,” he said. “They last about 10 years on average. That means if you receive an implant at 40, you may need to have it replaced three or four times in your lifetime.”

One of the researchers’ techniques works by depositing layers of a powdered mixture of metal and ceramic materials, melting the powder with a laser and then immediately solidifying each layer to form parts. Because the technique enables parts to be formed one layer at a time, it is ideal for coating titanium implants with ceramic materials that mimic the characteristics of natural bone, Shin said.

Findings will be detailed in a presentation this week during the International Medical Device Expo’s Advanced Laser Applications Conference in San Jose, Calif.

“Titanium and other metals do not match either the stiffness or the nature of bones, so you have to coat it with something that does,” Shin said. “However, if you deposit ceramic on metal, you don’t want there to be an abrupt change of materials because that causes differences in thermal expansion and chemical composition, which results in cracks. One way to correct this is to change the composition gradually so you don’t have a sharp boundary.”

The gradual layering approach is called a “functionally gradient coating.”

Researchers used their laser deposition processes to create a porous titanium-based surface and also a calcium phosphate outer surface, both designed to better match the stiffness of bone than conventional implants.

The laser deposition process enables researchers to make parts with complex shapes that are customized for the patient.

“Medical imaging scans could just be sent to the laboratory, where the laser deposition would create the part from the images,” Shin said. “Instead of taking 30 days like it does now because you have to make a mold first, we could do it in three days. You reduce both the cost and production time.”

The laser deposition technique lends itself to the requirement that each implant be designed specifically for each patient.

“These are not like automotive parts,” Shin said. “You can’t make a million that are all the same.”

The process creates a strong bond between the material being deposited and the underlying titanium, steel or chromium. Tests showed the bond was at least seven times as strong as industry standards require, he said.

The researchers use computational modeling to simulate, study and optimize the processes.

Additional research is needed before the techniques are ready for commercialization. Future work will involve studying “shape-memory” materials that are similar to bone and also have a self-healing capability for longer-lasting implants.

The researchers also are developing a technique that uses an “ultra short pulse laser” to create arterial stents, which are metal scaffolds inserted into arteries to keep them open after surgeries to treat clogs. The laser pulses last only a matter of picoseconds, or quadrillionths of a second.

Because the pulses are so fleeting, the laser does not cause heat damage to the foil-thin stainless steel and titanium material used to make the stents. The laser removes material in precise patterns in a process called “cold ablation,” which turns solids into a plasma. The patterns enable the stents to expand properly after being inserted into a blood vessel.

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