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AAOS Now

Published 4/1/2009

Second Look – Clinical News and Views

If you missed these Headline News Now items the first time around, AAOS Now gives you a second chance to review them. Headline News Now—the AAOS thrice-weekly, online update of news of interest to orthopaedic surgeons—brings you the latest on clinical, socioeconomic, and political issues, as well as important announcements from AAOS.

Older fracture patients have increased mortality risk
Among older women and men, low-trauma fractures may be associated with an increased mortality risk, according to an Australian
study published in the Feb. 4 issue of the Journal of the American Medical Association (JAMA). A prospective study of community-dwelling women and men aged 60 years and older who sustained a fracture between April 1989 and May 2007 found 952 low-trauma fractures followed by 461 deaths among women and 343 fractures followed by 197 deaths among men. All age groups had an increased mortality risk following hip, vertebral, and major fractures when compared to the general population. The mortality risk for men was higher than for women in all categories except for minor fractures.

Imaging for lower back pain only not recommended
Lumbar imaging for low-back pain without indications of serious underlying conditions may not improve clinical outcomes, according to a
study published in the Feb. 7 issue of The Lancet. In six randomized controlled trials covering 1,804 patients that compared immediate lumbar imaging (radiography, magnetic resonance imaging, or computed tomography) to usual clinical care without immediate imaging for low-back pain, no significant differences were found for primary outcomes at either short-term (3 months) or long-term (6 to 12 months) follow-up.

Reinnervated muscles can control advanced artificial arms
A
study (5 patients) in the Feb. 11 issue of JAMA suggests that reinnervated muscles can produce sufficient electromyogram (EMG) information for real-time control of advanced artificial arms. Patients with shoulder-disarticulation or transhumeral amputations who underwent targeted muscle reinnervation (TMR) surgery between February 2002 and October 2006 were able to repeatedly perform 10 different elbow, wrist, and hand motions with the virtual prosthetic arm, although mean motion selection and completion times were slightly longer than the times for control (no amputation) patients. Three of the TMR patients were able to demonstrate the use of this control system in advanced prostheses, including motorized shoulders, elbows, wrists, and hands.

Early oral therapy not harmful to children with acute osteomyelitis
Early transition to oral therapy is not associated with a higher risk of treatment failures among young patients with acute osteomyelitis and can avoid certain risks of prolonged intravenous therapy, according to a
study published in the Feb. 1 issue of Pediatrics. A retrospective cohort study of 1,969 children aged 2 months to 17 years diagnosed with acute osteomyelitis between 2000 and 2005 in the United States found a 5 percent treatment failure rate in the prolonged intravenous therapy group and 4 percent treatment failure rate in the oral therapy group; 35 (3.4 percent) children in the prolonged intravenous therapy group were readmitted for a catheter-associated complication. No significant association was found between treatment failure and the mode of antimicrobial therapy.

Immobilization helpful for ankle sprain patients
Patients who sustain a sprained ankle may recover faster if they have a short period of immobilization compared to tubular compression bandaging, according to a randomized trial
study published in the Feb. 14 issue of The Lancet. Of 584 patients with severe ankle sprain treated in emergency departments between April 2003 and July 2005, those who received a below-knee cast had a more rapid recovery than those treated with a tubular compression bandage. At 3 months, clinically important benefits in quality of ankle function were noted among patients in the cast group. At 9 months, no significant differences between tubular compression bandaging and the other treatments were found, and side-effects were rare with no discernible differences between treatments.

Knee OA associated with mechanical strain
A Dutch
study in the Feb. 15 issue of Arthritis Care & Research finds that older adults who engage in “low muscle strength” activities or activities causing high mechanical strain may be at increased risk for clinical knee osteoarthritis (OA). Based on longitudinal data from 1,678 men and women aged 55–58 years old, researchers found that, during a 12-year follow-up, clinical knee OA developed in 463 respondents (28 percent). A high mechanical strain score and a low muscle strength score were associated with an increased risk of knee OA. Results were similar for men and women, and for obese and nonobese respondents.

HTO and return to sports
High tibial osteotomy (HTO) for the treatment of medial compartment knee OA in active people may allow patients to return to recreational activities at a level similar to preoperative levels, according to the results of a
study published in the February American Journal of Sports Medicine. At an average follow-up of 36 months (range, 14–84 months), researchers surveyed 65 HTO patients and found that 90.9 percent of respondents were engaged in sports and recreational activities after surgery, compared to 87.9 percent who had been so engaged prior to the surgery (P =0.182). The number of different sporting activities had declined from 3.5 preoperatively to 3.0 postoperatively (P =0.178). Sports frequency per week and the activity duration per week did not significantly change; no patient returned to competitive sports after surgery.

MRSA central line–associated BSI incidence on the decrease?
The incidence of methicillin-resistant Staphylococcus aureus (MRSA) central line–associated bloodstream infection (BSI) decreased from 1997 to 2007 across most intensive care unit (ICU) types, according to
data published in the Feb. 18 JAMA. Of 33,587 central line–associated BSIs reported, 2,498 (7.4 percent) were MRSA and 1,590 (4.7 percent) were methicillin-susceptible S. aureus (MSSA). Across all ICU types, MSSA central line–associated BSI incidence declined from 1997 through 2007, with changes in incidence ranging from –60.1 percent in surgical ICUs to –77.7 percent in medical ICUs.

Protein interaction and cartilage breakdown
According to
research published in the Feb. 27 Journal of Biological Chemistry, blocking interaction between the proteins responsible for inducing inflammation may prevent cartilage breakdown in arthritis patients. Examining the interaction between proteins AP-1 and SAF-1, researchers found that the two can partner to induce activation of the MMP-1 gene, causing a breakdown of collagen. By competitively inhibiting an active site on the SAF-1 protein, they were able to limit expression of the MMP-1 gene.

High impact activities and BMD
A
study published in the February Journal of Strength and Conditioning Research finds that high impact activities such as running may positively affect bone mineral density (BMD) more than resistance training. In a cross-sectional study of cyclists, runners, and resistance-training participants, researchers found significantly greater body weight, lean body mass (LBM), and fat mass in the resistance-training group than in the other groups. However, after adjusting for LBM, runners had significantly greater spine BMD than cyclists. An individual’s LBM was a significant predictor of BMD in the resistance training and cycling groups, but not in the running group, suggesting that high-impact activity may override the benefits of LBM on BMD.

Proximal humeral fractures and hip fractures
Among white women 65 years of age or older, a fracture of the proximal humerus may be associated with increased risk of subsequent hip fracture, according to a
study published in the March 1 Journal of Bone and Joint Surgery—American (JBJS). Among a cohort of 8,049 older white women followed for a mean of 9.8 years, 321 women sustained a proximal humeral fracture. After adjusting for age and bone mineral density, researchers found the hazard ratio for hip fracture for subjects with a proximal humeral fracture relative to those without a proximal humeral fracture to be 1.83 (95 percent confidence interval = 1.32 to 2.53). The risk of a subsequent hip fracture after a proximal humeral fracture was highest within 1 year after the proximal humeral fracture and was not significant after the first year.

Progenitor cells and heterotopic ossification
Another
study in the March 1 JBJS finds that Tie2-expressing progenitor cells form heterotopic bone in response to overactive bone morphogenetic protein signaling in animal models of fibrodysplasia ossificans progressiva. Thus, the ectopic skeleton is not only supplied by a rich vasculature, but appears to be constructed in part by cells of vascular origin. Cells that expressed the vascular endothelial marker Tie2/Tek at some time in their developmental history contributed robustly to the fibroproliferative, chondrogenic, and osteogenic stages of the evolving heterotopic endochondral anlagen, and expressed endothelial markers at all stages of heterotopic ossification.

Immune response linked to implant loosening
Researchers have identified a key immunologic defense reaction to certain metals that may lead to loosening and early failure of joint replacement devices, according to a
study published online in the Journal of Orthopaedic Research. The authors tested soluble cobalt (Co), chromium (Cr), molybdenum (Mo), and nickel ions and Co-Cr-Mo alloy particles to determine if those agents can induce inflammasome-mediated macrophage reactivity. They found that those materials can stimulate inflammasome-mediated IL-1 secretion in human macrophages. The metal ion- and particle-induced activation of the inflammasome in human macrophages provides evidence of a pathway for implant debris-induced inflammation.

CDA: An alternative to fusion?
A prospective, randomized, multicenter
study published in the Jan. 15 issue of Spine finds that, at 24-month follow-up, cervical disk arthroplasty (CDA) may be a viable alternative to anterior cervical diskectomy and fusion (ACD/F) in patients with persistently symptomatic, single-level cervical disk disease. An analysis of 12- and 24-month postoperative data on 463 patients (242 CDA and 221 single-level ACD/F) showed improvement in all clinical outcome measures for both groups. However, at 24 months postoperative, the CDA patients had a statistically greater improvement in the primary outcome variables: neck disability index score (P = 0.025) and overall success (P = 0.010) compared to ACD/F patients. The rate of implant- or implant/surgical-procedure–associated serious adverse events was 1.7 percent for the CDA patients and 3.2 percent for the ACD/F patients.

Physicians override medication safety alerts
Physicians often override electronic medication safety alerts and rely on their own judgment when prescribing drugs, says a
study in the Feb. 9 Archives of Internal Medicine. A retrospective analysis of 233,537 medication safety alerts generated by 2,872 clinicians in Massachusetts, New Jersey, and Pennsylvania from Jan. 1, 2006, through Sept. 30, 2006, found that 6.6 percent of electronic prescription attempts generated alerts. Of those, physicians accepted 9.2 percent of drug interaction alerts and 23.0 percent of allergy alerts. The physicians accepted high-severity alerts slightly more often than moderate- or low-severity interaction alerts and were less likely to accept a drug interaction alert if the patient had previously received the medication.