Near-Perfect Test for Infection in Synovial Fluid // Bracing May Trump Surgery for Scoliosis // and More!

Near-Perfect Test for Infection in Synovial Fluid

“Infection”…the word that keeps orthopedic surgeons up at night. Carl Deirmengian, M.D., a hip and knee replacement surgeon with The Rothman Institute, is helping those surgeons get a better night’s sleep. Dr. Deirmengian tells OTW,

“Through the company I co-founded, CD Diagnostics, we are using joint fluid to detect joint disease—including infection. We have just presented data and submitted a manuscript on testing for joint infection in synovial fluid, and have found excellent results; we obtained a sensitivity and specificity of over 95% among patients with hip and knee replacements. This test, which was developed in partnership with an orthopaedic implant company, is the only one on the market specifically developed to target synovial fluid.

The process is as follows: the surgeon collects the fluid and sends it to our subsidiary laboratory, Citrano, in Maryland. The Synovasure test is then run, which is based on the measurement of alpha-defensin, but also includes a measurement of synovial fluid CRP [C reactive protein] and hemoglobin. Alpha-defensin is an antimicrobial peptide which is secreted into the synovial fluid by the joint in the presence of pathogens. Its concentration in the synovial fluid is dramatically elevated among patients with a periprosthetic joint infection. The surgeon receives a result in 24 hours.

The current laboratory tests that we all use to help diagnose infection were never developed for the purpose of diagnosing periprosthetic infection. Because of widespread confusion and misperceptions regarding the diagnosis of infection, The Musculoskeletal Infection Society (MSIS) recently published their definition of periprosthetic infection, which requires a combination of several clinical, laboratory, and histological tests. The CD Diagnostics’ test very accurately predicts the MSIS diagnosis, potentially providing all surgeons with accuracy in diagnosing infection that was previously unattainable.”

Bracing May Trump Surgery for Scoliosis

Not only is there now proof that bracing works for scoliosis, but it looks like it may make surgery avoidable. Matthew Dobbs, M.D., a pediatric orthopedic at Washington University School of Medicine and Shriners Hospital for Children, St. Louis, and an investigator in this study tells OTW,

“We are just now announcing these results, namely that after seven years, 25 centers, and 383 patients, we know definitively that bracing is effective at preventing curve progression in patients with adolescent scoliosis. It seems odd now, but we have used braces for years and have not been able to tell if they are truly effective. Now we can use braces with confidence, and can prevent unnecessary surgery, and cut down on the potential morbidity that is associated with major spine surgery. This entire study was spear-headed and led by Dr. Stuart Weinstein, principal investigator, at the University of Iowa and funded by the NIH [National Institutes of Health], Shriners Hospital, and the Canadian Institute of Health.

To qualify for bracing, the adolescent must be still growing; otherwise, the brace won’t work. The child must have a mild to moderate curve (25-40 degrees). Now we can tell parents with more confidence that if their child presents like this then he or she is a candidate for bracing. Not only that, but there is a high chance that they will not progress to surgery…in fact there is more than a 90% chance that they will not need surgery if the brace is worn as prescribed.”

Bisphosphonates DECREASE Heterogeneity of Bone?

Heterogenous bone=strong bone. Unfortunately, new research has found that bisphosphonates may decrease the heterogeneity of bone, thus weakening it. Adele Boskey, Ph.D. is the Starr chair in Mineralized Tissue Research and the director of the Musculoskeletal Integrity Program at the Hospital for Special Surgery and a professor at Weill Medical College. She tells OTW,

“I received an NIH grant to examine the changes that occur in the distribution of mineral composition in orthopedic patients treated with different kinds of osteoporosis drugs. In a surprising finding, bisphosphonates decreased the heterogeneity of bone composition; I had expected bisphosphonates to improve heterogeneity.

Given this, I am investigating how to obtain some sort of balance, i.e., even though you lose heterogeneity with bisphosphonates you are gaining bone mass…and since the fracture risk is decreased with bisphosphonates then maybe something off kilter is contributing to atypical fractures. To examine this, we are using biopsies from women treated with different bisphosphonates. Thus far we have a database of 112 women with and without fractures who never took any drug; we will compare these patients with those who have taken bisphosphonates. There has been a tremendous amount of discussion about the effect of heterogeneity in bone; more and more people are aware that it’s important.”

Obese Patients Are Malnourished…May Affect Outcomes

In a landmark study, a team of researchers has found a strong relationship between malnourishment and the risk of infection after joint replacement…and, interestingly, they found that obese patients are protein malnourished. Craig Della Valle, M.D. is an orthopedic surgeon at Midwest Orthopaedics at Rush and Professor at Rush University Medical Center in Chicago. He tells OTW,

“For years we have felt that there was a link between nutrition and the development of periprosthetic joint infection. That being said, there wasn’t a lot of strong data connecting the two. We looked at a cohort of 500 hip and knee revision surgeries that I performed. In the first phase we looked at all joint replacement patients with chronic infection and compared them to those with a noninfectious source of failure such as wear or loosening. We found that malnutrition—measured through common blood tests, total lymphocyte count, transferrin and albumen level—is an independent risk factor for presenting with a chronically infected hip or knee replacement. Overall the prevalence of malnutrition in these patients was about 40%, which is frankly shocking. We also found when we looked at infected patients that being male and having non-private insurance were independent risk factors. So this probably has something to do with patients with lower education and economic status consuming high calorie, protein poor foods.

We next tried to understand the relationship between malnutrition and obesity because we typically think that patients who are obese are not malnourished. We found, however, that about 35% of obese patients were protein malnourished. This type of ‘paradoxical’ malnutrition was again quite surprising. Once again, however, these patients are probably taking in large quantities of calorie rich but nutrient poor food.

Finally, we also looked at malnutrition as a risk factor for acute postoperative infections in the subgroup that were originally aseptic failures. The results were striking; malnourished patients have a six-fold increase in the risk of infection after a revision for an aseptic mode of failure.

This suggests that orthopedic surgeons should consider screening for malnutrition; in all patients whether they are normal weight or obese. It also suggests we might consider correcting malnutrition before we proceed with elective surgery. At the end of the day orthopedic surgeons are being told that infection is a ‘never event, ’ but our work suggests that patient related factors that are out of the surgeon’s control are very important. Screening for malnutrition should begin with the primary care doctors, but, unfortunately, they may not be as in tune with this issue as we would like them to be. The final barrier to addressing these issues is monetary; while we found that both malnutrition and infection are related to insurance status, oftentimes insurance such as Medicaid does not cover nutritional consultations, which is really frustrating.”