Patients at risk of knee joint complications when new technology is used

Introducing a new knee replacement model increases the likelihood of early revision surgery


Orthopaedic surgeons face a steep learning curve to get used to new prostheses, and the instruments and methods that go with them, before new total knee replacement procedures are as safe and effective as conventional methods. Patients who undergo the first 15 operations using a new device in a hospital are 48 percent more likely to need early revision surgery, than patients undergoing an operation to fit a prosthesis previously used in the hospital. The work by Mikko Peltola from the National Institute for Health and Welfare in Finland, and colleagues, is published online in Springer's journal, Clinical Orthopaedics and Related Research.

Total knee arthroplasty, or replacement, is an established treatment for patients with severe osteoarthritis of the knee. There are numerous brands and models of endoprostheses (a prosthesis used internally) available and new models continue to emerge as a result of a combination of new technology, marketing efforts and the increasing number of patients requiring the surgery.

Hospital staff makes important decisions when choosing the implants and instruments they use, and these decisions carry consequences for patients' health. According to the research team, however, new equipment and techniques are often used in clinical practice, occasionally without evidence of effectiveness and safety.

Peltola and team looked at the risk of early revision surgery following the introduction of a new endoprosthesis model for total knee arthroplasty. They studied data from the Finnish Arthroplasty Register to identify centers that had performed total knee replacement operations for primary osteoarthritis between 1998 and 2004. Of the 23,707 total number of patients who underwent the surgical procedure, 22,551 were followed up for five years.

The researchers found that the introduction of an endoprosthesis model in a hospital put the first patients at greater risk of revision surgery. The effect was substantial for the first 15 patients operated on with the new model, who were at 48 percent greater risk than patients having undergone an operation to implant a conventional endoprosthesis. Overall, the likelihood of needing revision surgery was greatest during the first two years after the surgery. The learning curve smoothed quickly, however, with no increased risk after the first 15 operations with the new model.
The authors conclude: "Patients should be informed if there is a plan to introduce a new model and offered the option to choose a conventional endoprosthesis instead. Although introducing potentially better endoprosthesis models is important, there is a need for managed uptake of new technology."

Reference

Peltola M et al (2011). Introducing a knee endoprosthesis model increases risk of early revision surgery. Clinical Orthopaedics and Related Research.DOI 10.1007/s11999-011-2171-9

Patients who use narcotics prior to knee replacement experience worse results

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Patients who are dependent on opioids (narcotic pain relievers) for pain management before knee replacement surgery have much more difficulty recovering, a study recently published in the Journal of Bone and Joint Surgery (JBJS) has found. These patients tend to have longer hospital stays, more post-surgical pain, a higher rate of complications, and are more likely to need additional procedures, than patients who are not opioid-dependent.

"We expected to find that the opioid-dependent patients have worse outcomes," says orthopaedic surgeon Michael A. Mont, M.D., the principal investigator and Director of the Center for Joint Preservation and Reconstruction at the Rubin Institute for Advanced Orthopaedics at Sinai Hospital of Baltimore. "But the differences between the two groups of patients were even greater than we thought they would be. The chronic narcotics users did significantly worse in every category."

Study Findings:

Patients included in the study were matched according to age, sex, body-mass index, insurance type, as well as a variety of medical factors. When those factors were accounted for, the study still found that chronic opioid users:

• had to remain in the hospital longer after surgery
• were more likely to need referrals for pain management
• were more likely to suffer unexplained pain or stiffness
• had lower function and less motion in the replaced knee

"This doesn't mean that opioid users shouldn't have the surgery," Mont says. "But those patients and their physicians should know that their results may not be as optimal. It might be possible that we can work with these patients to improve their surgical outcomes."

Dr. Mont and his co-authors outline several strategies to help improve patient outcomes; including:

• weaning patients off strong opioid medications prior to surgery
• prescribing alternate, non-opioid pain medications
• considering non-pharmaceutical pain management strategies

The study's authors acknowledge that some patients who become dependent on opioids before surgery may have lower pain thresholds than those who do not. In addition, those patients may be less compliant with rehabilitation plans and other post-surgical treatments. However, the results of this study are important enough to warrant attention to this issue.

"Previous studies have found that patients who use opioids are more dissatisfied after surgery," Mont says. "But these are more powerful findings since patients require additional surgeries. This is a topic our orthopaedic community and other care providers need to address together."

Glucocorticoid Treatment May Prevent Long Term Damage to Joints,

Joint injury can result in irreversible damage of cartilage which, despite treatment and surgery, often eventually leads to osteoarthritis (OA) in later life. New research published in BioMed Central's open access journal Arthritis Research & Therapy demonstrates that short term treatment of damaged cartilage with glucocorticoids can reduce long term degenerative changes and may provide hope for prevention of OA after injury.

A normal joint is covered by a layer of cartilage containing proteoglycans such as aggrecan and lubricating fluid containing glycosaminoglycans (GAG) such as hyaluronic acid. In a double whammy, after injury proteoglycans and other molecules in cartilage begin to break down and the synthesis of these proteoglycans within cartilage is reduced. Additionally proinflammatory cytokines such as TNFα, IL-1β, and IL-6 are released into the synovial fluid after injury and further increase GAG loss from cartilage.

Using a 'worst-case scenario' system in which cartilage was subjected to mechanical injury and bombarded with immune system-stimulating bio-molecules (TNFα and IL-6) the glucocorticoid dexamethasone (DEX) was able to reduce GAG loss and restore proteoglycan synthesis levels to normal.

Prof Alan Grodzinsky from the MIT Center for Biomedical Engineering said, "Glucocorticoid injections are sometimes used to relieve the pain of established osteoarthritis, but there are concerns about long-term use. Our results suggest that short-term glucocorticoid treatment after joint injury may help restore components of cartilage to preinjury levels and consequently may prevent the long term changes which lead to osteoarthritis."