AAOS Now

Published 8/1/2012

Second Look- Clinical News and Views

MoM surveillance studies flawed
The postmarket surveillance studies that the Food and Drug Administration (FDA) ordered manufacturers of metal-on-metal (MoM) hip prostheses to undertake have several shortcomings that should be remedied, according to an opinion piece in the New England Journal of Medicine (NEJM) (June 20). Although it has been a year since the order, it is unclear whether any of the studies have even begun and manufacturers have no incentive to initiate studies that may yield adverse information on their products. Furthermore, each manufacturer is allowed to conduct its own study, possibly leading to difficult-to-compare results, and current law prevents FDA from requiring studies to last more than 3 years.

Viscosupplementation for knee OA
Information from a meta-analysis published online in Annals of Internal Medicine suggests that viscosupplementation for symptomatic knee osteoarthritis (OA) is associated with a clinically irrelevant benefit and an increased risk of serious adverse events. The review of data from 89 trials involving 12,667 adult patients found that 71 trials (9,617 patients) showed that viscosupplementation moderately reduced pain. However, 18 large trials with blinded outcome assessment (5,094 patients) demonstrated a clinically irrelevant effect size, while six trials (811 patients) showed that viscosupplementation increased—although not statistically significantly—the risk for flare-ups, and 14 trials (3,667 patients) showed that viscosupplementation increased the risk for serious adverse events.

Single-leg or double-leg spica cast
Treatment of pediatric femoral fractures with a single-leg spica cast is effective and safe, according to findings from a study in the Journal of Bone & Joint Surgery—American (June 13). In the prospective, randomized controlled study of 52 patients, aged 2 to 6 years, with a diaphyseal femoral fracture, 24 patients were treated with a single-leg cast and 28 were treated with a double-leg cast. All limbs healed in satisfactory alignment. Children treated with a single-leg cast were more likely to fit into car seats and fit more comfortably into chairs than those with double-leg casts, and their caregivers took less time off work than caregivers of patients with double-leg casts.

Oral anticoagulants for VTE prophylaxis
According to data from a study published online in BMJ, there is no significant difference between four anticoagulants as prophylaxis against venous thromboembolism (VTE) after total hip or knee replacement. The systematic review of 16 trials covering 38,747 patients found that, compared with enoxaparin, the risk of symptomatic VTE was lower with rivaroxaban, and similar with dabigatran and apixaban. However, compared with enoxaparin, the relative risk of clinically relevant bleeding was higher with rivaroxaban, similar with dabigatran, and lower with apixaban. The treatments did not differ on the net clinical endpoint in direct or indirect comparisons.

Study: Cemented hips, revision, and mortality
A British study published online in BMJ compares outcome data for various hip arthroplasty procedures. Data on approximately 275,000 hip arthroplasty patients from the U.K. National Joint Registry showed a small but significant increased risk of revision with uncemented total hip devices and Birmingham hip resurfacings compared to cemented total hips. Conversely, cemented procedures had a small but significant increased mortality risk, and patients who underwent Birmingham hip resurfacing had a significantly decreased mortality risk.

Study: PRP in patellar tendon harvest
A study published online in the American Journal of Sports Medicine (AJSM) finds that platelet-rich plasma (PRP) had a positive effect on patellar tendon harvest site healing after 6 months and also reduced pain in the immediate postoperative period. The randomized controlled trial involved 27 patients who either received (n = 12) or did not receive (n = 15) PRP in the patellar tendon harvest site during anterior cruciate ligament (ACL) reconstruction. At 6-month follow-up, magnetic resonance imaging found that the patellar tendon gap area was significantly smaller in the PRP group compared to the control group.

Study: Autografts in younger ACL patients
According to information in AJSM (June), young, active patients may be less likely to experience clinical failure of autologous graft ACL reconstruction, compared to allograft ACL reconstruction. The prospective cohort study of 120 cadets (122 knees) at the United States Military Academy who had undergone prior ACL reconstruction used three types of grafts: autologous bone–patellar tendon–bone (BTB), autologous hamstring, and allograft. Of 20 failures requiring revision, seven were BTB, seven were allograft, and six were hamstring. No significant difference in graft failure between BTB and hamstring autograft groups was found, but cadets with an allograft were 7.7 times more likely to experience a subsequent graft failure during the follow-up period, compared with the BTB autograft group.

Endocrine Society CPG on bone density testing
Men at high risk for developing osteoporosis—including men aged 70 years or older and men between the ages of 50 years and 69 years who have risk factors—should undergo dual-energy X-ray absorptiometry (DXA) testing, according to a recently released clinical practice guideline (CPG) from the Endocrine Society. The CPG, which was published in the Journal of Clinical Endocrinology and Metabolism (June), also states that men with low Vitamin D levels (< 30 ng/mL) should receive Vitamin D supplementation to achieve levels of at least 30 ng/mL.

Vitamin D and fracture risk
According to findings by the United States Preventive Services Task Force, daily supplementation with low levels of Vitamin D (up to 400 international units) combined with 1,000 milligrams of calcium does not reduce fracture risk in healthy postmenopausal women. In addition, this amount of Vitamin D supplementation, with or without calcium, is associated with a small but significantly increased risk of developing kidney stones.

A study in the NEJM (July 5) found that high-dose Vitamin D supplementation (at least 800 IU daily) is “somewhat favorable” in the prevention of hip fracture and any nonvertebral fracture in persons 65 years of age or older, based on data from 11 double-blind, randomized, controlled trials of oral vitamin D supplementation, with or without calcium, as compared with placebo or calcium alone in persons 65 years of age or older. Participants who received vitamin D had a 10 percent reduction in risk of hip fracture and a 7 percent reduction in risk of nonvertebral fracture, compared to controls.

Study: Polished tray and knee insert wear
Data from a study in Clinical Orthopaedics and Related Research suggest that knee devices with polished cobalt-chrome (CoCr) tibial tray surfaces may have a reduced wear rate compared to those with inserts mated with rough titanium (Ti) trays. The comparison of wear in two series of retrieved knee devices—94 rotating platform (RP) mobile bearing devices with polished CoCr trays (median implantation time, 36 months; range, 0.4–124 months), and 218 fixed bearing devices with either rough Ti or polished CoCr trays (median implantation time, 72 months; range, 2–179 months)—found a lower wear rate for RP inserts than for fixed bearing inserts, and a lower backside wear rate for fixed bearing inserts mated to polished CoCr trays than for inserts mated to rough Ti trays.

These items originally appeared in AAOS Headline News Now, a thrice-weekly enewsletter that keeps AAOS members up to date on clinical, socioeconomic, and political issues, with links to more detailed information. Subscribe at www.aaos.org/news/news.asp (member login required)