Testing for Shoulder Infection: IL-6, α-defensin Look Promising
While surgeons can readily identify a periprosthetic joint infection (PJI) following hip or knee surgery, it’s not always so easy when it comes to the shoulder. In the first study of its kind, Eric Ricchetti, M.D., an orthopedic surgeon with the Cleveland Clinic, worked with colleagues and dug deeper into the use of α-defensin and Interleukin 6 (IL-6) to diagnose such infections. He tells OTW, “We are accustomed to seeing draining wounds and obvious signs of infection commonly accompany PJI in large joints, but this type of infection after shoulder replacement surgery typically occurs with a weaker clinical presentation. The most common bacteria seen in the shoulder—Propionibacterium acnes (P. acnes)—is challenging because its presence doesn’t show up like a typical infection. The only symptom commonly seen is pain after the shoulder replacement surgery, which can be due to causes unrelated to infection. The surgeon is left asking, ‘Is there a problem with the implant, or the rotator cuff…or is there an infection?’ And the typical tests used to diagnose infection often come up negative because it’s such a weak bacteria. Often the bacteria is not identified until after the patient has undergone a revision surgery.”
“We conducted two studies in which we evaluated the synovial fluid of shoulder replacement patients: one looking at IL-6 and another examining α-defensin. We found that IL-6 is more sensitive and specific than standard preoperative testing for predicting positive cultures in revision shoulder replacement surgery—even with P. acnes. The sensitivity of IL-6 was 87% and the specificity was 90%. The tests we typically use have a sensitivity and specificity that is often below 50%. As for α-defensin, it had a sensitivity of 63% and a specificity of 95%.”
“We are now looking at a larger group of biomarkers in synovial fluid to see if together, they can provide even better insight into diagnosing infection. The work we have done to this point seems to indicate that several markers together does make for a more predictive test.”
“Synovial fluid α-defensin is more sensitive and specific than current preoperative testing for predicting positive cultures in revision shoulder replacement surgery. Increasing diagnostic accuracy of shoulder PJI will lead to improved decision-making regarding treatment, which will ultimately optimize clinical outcomes. These findings suggest that synovial fluid α-defensin may be an appropriate alternative, or an adjuvant, in identifying infection in the preoperative work-up of patients with a painful shoulder replacement.”
“The better job we can do of diagnosing an infection, the better job we can do at determining what the best surgical treatment should be. There is the fundamental decision, for example, of whether to do a one-stage or two-stage revision surgery.”
Anterior Osteotomy: Less Blood and Fewer Minutes in the OR
Less bleeding and everyone is in the OR for a shorter amount of time…what’s not to like? In what amounts to an advancement for patients suffering from cervical deformities, Dan Riew, M.D., an orthopedic surgeon with Washington University in St. Louis, soon to join the faculty at Columbia University in New York City, has developed a new technique for anterior osteotomy. He tells OTW, “Because of this new technique, I almost never do posterior osteotomies anymore for kyphotic or kyphoscoliotic deformities. Even when the patient’s chin is on his or her chest, it is surprising, but we can usually get in from the anterior aspect to do the osteotomy. Then, we stabilize from the back. Occasionally, we may have to finish the correction with further posterior osteotomies. But usually, that is not necessary. We’ve even had success in patients who have posterior instrumented fusions. This allows us to do a two stage—instead of a three stage—operation.”
Han Jo Kim, M.D., an orthopedic surgeon with Hospital for Special Surgery in New York, analyzed the results of all of Dr. Riew’s cases. He notes, “Osteotomy options for the cervical spine have to date included Ponte, Pedicle Subtraction, Smith-Petersen and Simmons. We describe a new technique that allowed Dr. Riew to achieve similar corrections in alignment compared to pedicle subtraction osteotomies, with less blood loss and similar operative times. For the Riew anterior osteotomy, thorough knowledge of the vertebral artery anatomy is critical for executing a safe and successful operation. In our paper, we describe methods for protecting the vertebral artery and the importance of pre-operative imaging of the vertebral arteries to recognize their precise location.”
Asked what kind of underlying conditions might make this an unwise approach for a given patient, Dr. Kim told OTW, “This approach may not be the best for someone who has vertebral artery anomalies that make this approach more difficult and if a patient is so deformed with a rigid chin on chest deformity that makes it impossible to access the anterior cervical spine. In addition, patients who have a history of extensive retropharyngeal surgery with significant scar formation may make this approach less favorable.”
“Special” Kind of RA for Diabetics
What’s worse than rheumatoid arthritis (RA)? A horrific type of arthritis that occurs with diabetes, called neuroarthropathy, says Lew Schon, M.D., director of foot and ankle services at MedStar Union Memorial Hospital in Baltimore. Dr. Schon, past president of the American Orthopaedic Foot and Ankle Society, tells OTW, “My colleague and chief scientist Dr. Zijun Zhang and I are looking into a particularly destructive type of arthritis that affects patients with diabetic neuropathy. Worse than RA, with this condition the results are structural and functional disintegration of the bones, joints, ligaments and tendons. Because it’s unclear what exactly is driving this problem, we have undertaken a series of studies and have thus found that the fibroblast-like synovial cells (FSC) in diabetic patients are aggressively making chemicals that break down the bone, cartilage and soft tissues. There are an especially high number of these FSCs in the joints of diabetics, and most impressively they are aggressive due to the absence of nerve ending produced neurotransmitters. This makes sense since we have stained the nerve endings of the diabetic joints and found out that they are depleted of nerves.”
“Interestingly, when we introduce the chemical produced by the nerve cells, the FSC are controlled and they become more passive. So, when you have these FSC cultured in the presence of normal cartilage and you add a neurotransmitter, instead [of] chewing up cartilage, it remains intact.
“When I do a reconstruction on one of these patients I remove the damaged joint and send tissues to the lab; there we have the chance to look into all the joint elements involved in this pathology and identified these FSC and seen their aggressive functioning. The big picture is that half of the 29 million diabetics in the U.S. have neuropathy and probably up to 0.8-7.5% of those diabetics with neuropathy of have this bad arthritis. Now we want to see if we can develop biologic ways to stop the disease from progressing. To that end we will look into the development of this disease and dissect the complex interplays of diabetes, neuropathy and arthritic pathology.”
