AAOS Meeting Rich in Research

Over the course of the last eight decades, the American Academy of Orthopaedic Surgeons (AAOS) annual meeting has become revered for its showcase of new products and technology. In years past, the event has been used as a launching pad for thousands of innovations, including a bioabsorbable suture anchor system; personalized surgical cutting guides for partial knee replacements; an arthritis education app for the iPad; a polyetheretherkeytone (PEEK)-infused soft tissue graft fixation device for ACL reconstruction; and a modular hip stem that is 20 percent shorter than conventional models.

Typically lost amid all the hoopla, however, is the clinical research that eventually could lead to future breakthroughs. Last week, for instance, the academy unveiled a new study showing gender-specific prostheses may not improve overall outcomes for female total knee replacement (TKR) patients. The study was presented during AAOS’ annual meeting March 19-23 in chilly Chicago, Ill.

The study evaluated 1,957 TKRs between 2006 and 2010 in women; 1,515 of those patients received gender-specific knees and 771 were given “unisex” joints. Clinicians reviewed radiographs of the knee for component fit and outcomes in both groups.

While female-specific implants had less overhang, the overall range of motion, knee flexion (bending), lateral release rates (kneecap movement) and pain scores were comparable in both the custom knee and unisex joint, according to the study. “While we certainly use [the female] components frequently [in surgery], we don’t detect any objective improvement in clinical outcomes, including pain scores and range of motion,” noted lead study author and orthopedic surgeon Alexander P. Sah, M.D. “At the same time, there was no detectable disadvantage of using the implant, such as increased blood loss or component migration. Benefits of using the gender-specific component may not be detectable by current measures, or may not exist at all. However, the additional size option definitely provides the surgeon with more flexibility during surgery and that is useful.”

The gender-specific knee research was one of the more noteworthy studies presented at this year’s AAOS meeting. More than a dozen clinical research analyses were discussed during the five-day event, including:

• Two studies that show obesity alone may not diminish outcomes or increase the risk of complications in TKR recipients, though these patients could face longer hospital stays and related costs. The studies found the length of hospital stay and direct medical costs to be lowest among patients with a body mass index (BMI) of 25-30 kg/m2. Those with higher BMIs remained hospitalized for a day longer than their slimmer counterparts (7.77 days vs. 6.29 days) and paid more for their medical care (each five-unit increase beyond 30 kg/m2 cost an additional $250-$300 in primary knee arthroplasty hospitalization and $600-$650 in revision procedure hospitalization). Increasing BMI does not affect complication risk or surgical time, though researchers noticed a higher rate of infections among obese patients.
• A study that associates total hip replacement (THR) with reduced mortality, heart failure, depression and diabetes rates in Medicare patients with osteoarthritis.
• A study indicating sunny climates do not improve vitamin D levels in hip fracture patients. Researchers retrospectively reviewed the vitamin D levels of 1,539 patients (448 with acute hip fractures and 1,091 who received either total hip or total knee replacements) from December 2010 to December 2011 at a major southern California medical center. Overall, investigators found the majority of hip fracture patients over 18 had insufficient vitamin D levels and those aged 71 and older had significantly lower levels than the total hip and total knee replacement control group.
• Research that shows quitting smoking reduces pain in spinal patients. Study authors reviewed the smoking cessation rates and related pain in 6,779 patients undergoing treatment for spinal disorders with severe axial or radicular (leg) pain. Smokers both older and younger than 55 experienced more pain non-smokers; mean improvement in reported pain during treatment significantly was different in smokers and non-smokers in both age groups. Those who quit smoking over the course of their care experienced less pain than patients who continued to smoke. Regardless of their age, smokers who continued their habit during treatment experienced no significant improvement in their pain.
• A study indicating past and current smokers face a greater risk for surgical complications. Researchers reviewed the records of all total hip replacement recipients between 2007 and 2009 to identify patients who used tobacco products at the time of surgery, or who smoked regularly prior to surgery. In general, smokers had a higher overall revision rate and a higher incidence of other complications.
• Research deducing that magnetic resonance imaging (MRI) can detect a failing or potentially failing metal-on-metal (MoM) implant before it can cause considerable damage. After assessing the MRIs of 70 patients who underwent revision surgery for a failed MoM implant, investigators discovered that MRIs effectively can identify tissue damage in MoM total hip replacement patients.
• A study that shows platelet-rich plasma (PRP) can reduce pain and elbow tenderness in patients with a chronic case of the condition. Researchers randomized 230 chronic tennis elbow sufferers and gave them either an injection of PRP made from their own concentrated blood platelets or a placebo. At 12 weeks, 55.1 percent of PRP patients reported improved pain scores compared with 47.4 percent of those given a placebo; 37.4 percent had less elbow tenderness versus 48.4 percent in the placebo group. At six months, 71.5 percent of PRP patients reported improved pain scores compared with 56.1 percent given placebos, and 29 percent experienced less elbow tenderness compared with 54 percent in the control group. At six months, 83.9 percent of PRP patients reported significantly less pain and elbow tenderness compared with 65.9 percent of the placebo group.
• Research indicating that overall sports and recreation musculoskeletal injuries fell 12.4 percent in the United States over the last decade for children ages 5 to 14 but football and soccer injuries rose 22.8 percent and 10.8 percent, respectively. As a group, sports deemed “recreational” (bike, roller sports, trampoline and playground) plummeted 24.9 percent while “ball” or organized sport activity injuries climbed 5.9 percent. Bicycle injuries plunged 38.1 percent; roller sports declined 20.8 percent and trampoline trauma decreased 17.5 percent.