April 2010

In the moment: knee OA

Photo courtesy of Össur Americas

by Jordana Bieze Foster

Bracing casts a wider net

Lateral, severe cases respond positively

Two studies presented in March suggest that bracing for knee osteoarthritis may be effective in two patient populations that are not well represented in the OA bracing literature: those with lateral tibiofemoral compartment OA and those with severe disease.

Both studies were presented at the annual meeting of the American Academy of Orthopaedic Surgeons. Researchers from the Steadman Philippon Research Foundation in Vail, CO, found that improvements in pain and function associated with six months of bracing in patients with lateral knee OA were similar to the outcomes seen in patients with medial knee OA. Meanwhile, investigators from Iceland reported significant functional improvement with three weeks of bracing in patients with moderate to severe knee OA, which were maintained for six months.

Neither patient population has been well represented in bracing studies to date. In the case of lateral knee OA, it’s about numbers; the majority of unicompartmental tibiofemoral osteoarthritis cases involve the medial compartment. When it comes to those with severe disease, it’s about triage; few patients with severe knee OA are available for study because most have undergone total knee arthroplasty. In fact, eight of the 11 patients in the Iceland study who had severe knee OA completed the bracing protocol while waiting for a total knee procedure.

The Vail study involved 34 patients with medial knee OA and 15 patients with lateral OA. Average baseline scores on the WOMAC (Western Ontario and McMaster Universities) assessment scale, which measures pain and function, were significantly higher in the medial OA group than in the lateral OA group (34 vs 26 points; higher scores indicate higher levels of disability).

At six weeks, WOMAC scores in both groups had improved to 18 points; this improvement was maintained at six month follow up. However, functional scores were correlated with different anatomical variables in each of the two groups. In the medial OA group, medial joint space was correlated wtih WOMAC score at baseline, six weeks and six months. But in the lateral OA group, six-month WOMAC score was strongly correlated with deviation from neutral alignment.

The Vail researchers also found that bracing was associated with increased mean activity levels, as measured by Tegner score, in the group overall. Tegner score improved in 18 patients, while 29 patients had unchanged Tegner scores but still saw decreases in disability. This may be related to the fact that patient expectations included a desire to return to recreational sports, said Karen K. Briggs, MPH, MBA, the foundation’s director of clinical research, who presented the findings at the AAOS meeting.

The Iceland study included 82 patients with knee OA, 75 of whom had medial compartment disease. In terms of  radiographic severity, 11 patients were Kellgren-Lawrence grade IV, 35 were grade III, and 29 were grade II. Mean baseline WOMAC score was 50, which is considerably higher than a previous study’s suggested threshold for TKA of 39.

After three weeks of brace wear, total WOMAC score improved to a mean of 34, with significant improvements from baseline in all three components of the assessment (pain, stiffness, and function). Those improvements were maintained at six month follow up.

“Future research is needed to see if unloading is underestimated in severe knee OA,” said Thorvaldur Ingvarsson, MD, an orthopedic surgeon and medical director at Central Hospital iin Akureyri, Iceland, who presented the results at the AAOS meeting.

Functional improvement was not significantly associated with age, body mass index, medial vs lateral compartment, or K-L score. WOMAC score was correlated with gender, with female patients having higher scores throughout the study, but the amount of improvement was similar for both genders.

Gait analysis (finally) favors flip-flops over high heels, stability running shoes

Heel height and flexibility may influence the effects of footwear on knee adduction moment in patients with knee osteoarthritis, according to research from Rush Medical College in Chicago.

Investigators used an optoelectronic camera system and force plate to analyze gait in 31 subjects (21 female) with knee osteoarthritis while barefoot and while wearing four different types of footwear: clogs, stability running shoes, flat walking shoes, and flip-flops.

Though recent studies have focused on the biomechanical shortcomings of flip-flops (see “Data suggest preschool children run differently in flip-flops than sneakers”), peak knee adduction moment for the flip-flops and the flat walking shoes did not differ significantly from barefoot walking in the Rush study. Peak KAM was about 15% higher, however, for the clog and stability shoe conditions. The findings were e-published on Feb. 26 by Arthritis Care & Research.

Previous studies have linked heel height to risk factors for knee OA (see “Balancing Act: A real-world approach to high heels”). A December study in PM&R also found increased joint torques associated with stability shoes in runners.

Triple-dose platelet rich plasma bests viscosupplementation for pain relief

Platelet-rich plasma injections may be more effective than viscosupplementation for improving symptoms in patients with early knee osteoarthritis, according to research from Italy presented in March at the AAOS meeting.

Investigators from the Rizzoli Orthopaedic Institute in Bologna used PRP to treat 50 patients with symptomatic knee OA, in three 5-ml doses, each administered two weeks apart. Their outcomes were compared to those of 50 patients treated with high molecular weight hyaluronan and 50 treated with low molecular weight hyaluronan.

At the end of therapy and at six months follow up, all groups had improved in terms of the IKDC (International Knee Documentation Committee) and the EQ-VAS (EuroQol Visual Analog Scale) outcomes measures, but the PRP group demonstrated significantly more improvement than the other two groups at all time points.

“Platelet rich plasma is very popular, but we don’t know what is the mechanism,” said Elizaveta Kon, MD, an orthopedic surgeon in the Biomechanics Laboratory at the institute, who presented the results at the AAOS meeting. “For sure, it’s not a holy water.”

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