From AAOS: 2015 Meeting is Hip-Deep in Research

The American Academy of Orthopaedic Surgeons (AAOS) presented some rather hip research during its Annual Meeting this week.
 
Literally speaking, of course.
 
While every meeting is rich in clinical data, this year’s installment, held March 24-28 in Las Vegas, Nev., seemed awash in hip joint analyses. The following studies represent only a small portion of all hip research presented at the show:
 
Hip Fractures and Delirium
University of Toronto (Canada) researchers found that 48 percent of hip fracture patients age 65 and older experienced delirium, or acute confusion, before, during and after surgery (perioperative), increasing both hospitalization stays and costs of care.
 
The researchers determined the economic implications of perioperative delirium in older orthopedic patients by reviewing hip fracture records between January 2011 and December 2012. A total of 242 hip fracture patients with a mean age of 82 (ages 65 to 103) were studied. Demographic, clinical, surgical and adverse events data were analyzed. Perioperative delirium was assessed using the Confusion Assessment Method (CAM).  

The study found that 116 patients (48 percent) experienced delirium during hospital admission. The patients with delirium were significantly older (mean age 85), and more likely to have a higher American Society of Anesthesiologists (ASA) score (“one” represents a “completely healthy fit patient,” and “five,” a patient not expected to live beyond 24 hours without surgery). After controlling for these differences, perioperative delirium was associated with 7.4 additional hospital days and $8,282 ($8,649 in U.S. dollars) in additional hospital costs (1.5 times the cost of patients who did not experience delirium).
 
There were no differences in mean time between triage or admission and surgery, length of surgery, or anesthesia type between groups. A significantly greater proportion of patients who experienced perioperative delirium required long-term and/or skilled care facility admission follow their hospital stay (8 percent versus 0 percent).
 
“Older patients are at high risk of developing delirium during hospitalization for a hip fracture, which is associated with worse outcomes,” said orthopedic surgeon and lead study author Michael G. Zywiel, M.D. “Our work demonstrates that delirium also markedly increases the cost of elderly patient care while in the hospital. Given the high number of patients hospitalized every year with a hip fracture, there is a real need to develop and fund improved interventions to prevent in-hospital delirium in these patients. Our research suggests that reducing the rate of delirium would simultaneously increase the quality of care while decreasing costs, presenting hospitals, surgeons and other stakeholders with promising opportunities to improve the value of hip fracture care.”
 
Approximately 300,000 Americans are hospitalized annually with hip fractures. The risk particularly is high in post-menopausal women who face an increased risk for osteoporosis, a disease that diminishes bone mass and increases fracture risk. Delirium is common among older hip fracture patients, and multiple studies have found that patients with postoperative delirium are more likely to have complications, including infections, and less likely to return to their pre-injury level of function. Delirium patients also are more frequently placed in nursing homes following surgery, and have an increased rate of mortality.
 
New Hips and Driving
Aging baby boomers now have reason to rejoice, with proof that hip replacement recipients might safely be able to drive as soon as two weeks after the procedure.
 
A study conducted by doctors in southern New Jersey contradicts research conducted more than a decade ago that recommends hip replacement patients wait between six and eight weeks before getting back behind the wheel of a car. The new study, appearing online in the Journal of Arthroplasty, included 38 people who underwent total hip replacement (THR) between 2013 and 2014. Researchers tested their brake reaction time both before and after the procedure.
 
The results showed that 87 percent of the patients regained the pre-surgery brake reaction times within two weeks after surgery; the other 13 percent reached that point within four weeks. Of the 33 patients who tested ready to drive at two weeks, 24 (73 percent) felt ready to drive and five (15 percent) were unsure. Four patients (12 percent) felt uncomfortable driving so soon.
 
Of the five patients who were ready to drive at four weeks, three agreed they were not ready at the two-week mark. Two, however, thought they were able to drive after two weeks.
 
There was no difference in terms of age, gender or use of assistance devices, according to the data.
 
“We found that brake reaction time returned to baseline or better in the vast majority of patients undergoing contemporary THR by two weeks following surgery, and all patients achieved a safe brake reaction time according to nationally recognized guidelines,” lead study author and orthopedic surgeon Victor Hugo Hernandez, M.D., said.   
 
The findings allowed the study team to “encourage patients to re-evaluate their driving ability as soon as two weeks after THR,” he noted. But since the data is based on a particular group of patients, physicians should be careful in translating the results to the general population, Hugo Hernandez said. Also, patients should never drive if they are still taking narcotic pain medication, he warned.
 
Middle Age: Prime Time for Hip Replacements
New York City researchers have found the number of THRs nearly doubled among middle-aged patients between 2002-2011, primarily due to expansion of the middle-aged population in the United States.
 
Researchers used the Nationwide Inpatient Sample to identify primary THRs performed between 2002 and 2011 in patients age 45 to 64, as well as related hospital charges. Population data and projections were obtained from the U.S. Census Bureau, and surgeon workforce estimates from the AAOS.
 
In 2011, 42.3 percent of THRs were performed in patients age 45 to 64 compared with 33.9 percent in 2002. Use of THR in this age group increased 89.2 percent from 2002 to 2011, from approximately 68,000 THRs in 2002 to 128,000 THRs in 2011. The overall population increased 21.3 percent. In addition, the authors discovered that:

• Growth of THR in the 45- to 64-year-old age group grew 2.4 times faster than it did in the Medicare-aged population (age > 65).
• A rise in the prevalence of obesity, a known risk factor for hip osteoarthritis, among middle-aged Americans was not significantly associated with increased THRs.
• Mean hospital charges in the THR 45- to 64-year-old age group declined 5.7 percent from 2002 to 2011, and declined 2.5 percent in the Medicare population (age > 65).
• Mean physician reimbursement per THR, in 2011 U.S. dollars, declined 26.2 percent over the same period.
• Concurrently, the number of physicians reporting that they performed THR surgeries declined 28.2 percent.

 
“The purpose of this study was to identify potential drivers of THR utilization in the middle-aged patient segment,” said lead study author Alexander S. McLawhorn, M.D., an orthopedic surgery resident at the Hospital for Special Surgery in New York City. “Our multivariable statistical model suggested that the observed growth was best explained by an expansion of the middle-aged population in the U.S. This particular age group is projected to continue expanding, and as such the demand for THR in this active group of patients will likely continue to rise as well.  Our results underscore concerns about consumption of premium-priced implants in younger patients and the future revision burden this trend implies in the face of a dwindling number of physicians who specialize in hip arthroplasty surgery.” 
 
The Female Advantage
Women may not be the weaker sex, after all. Though they generally undergo their first total joint replacement (TJR) at an older age, they are less likely to experience 
complications related to their procedure or require revision surgery, according to a new study initiated by Canadian researchers.
 
The findings contradict a long-held theory that TJR is underutilized in female patients because they experience worse outcomes than men.

Clinicians reviewed patient databases from an Ontario hospital for first-time primary total hip replacement (THR) and total knee replacement (TKR) patients between 2002 and 2009. A total of 37,881 THR surgeries (53.8 percent female) and 59,564 TKR surgeries (60.5 percent female) took place. Women who underwent THR were significantly older than males (70 years vs. 65 years); however, there was no difference in age between male and female patients undergoing TKR (median age 68 for both). A greater proportion of female patients undergoing TJR were defined as frail (6.6 percent vs. 3.5 percent for THR; and, 6.7 percent vs. 4 percent for TKR).   
 
Following surgery, men were:

• 15 percent more likely to return to the emergency department within 30 days of being discharged after a THR or TKR procedure.
• 60 percent and 70 percent more likely to have an acute myocardial infarction (heart attack) within three months after THR and TKR, respectively.
• 50 percent more likely to require a revision arthroplasty within two years of TKR.
• 25 percent more likely to be readmitted to the hospital and 70 percent more likely to experience an infection or revision surgery within two years of TKR, compared to women.

“Despite the fact that women have a higher prevalence of advanced hip and knee arthritis, prior research indicates that North American women with arthritis are less likely to receive joint replacement than men,” said lead study author Bheeshma Ravi, M.D., Ph.D., an orthopedic surgery resident at the University of Toronto. “One possible explanation is that women are less often offered or accept surgery because their risk of serious complications following surgery is greater than that of men.
 
“In this study, we found that while overall rates of serious complications were low for both groups, they were lower for women than for men for both hip and knee replacement, particularly the latter” Ravi continued. “Thus, the previously documented sex difference utilization of TJR cannot be explained by differential risks of complications following surgery.”