March 2010

Market Mechanics

Stride-Rite taps torsional flexibility

A study of Stride-Rite (Lexington, MA) children’s shoes presented in February at the Combined Sections Meeting of the American Physical Therapy Association suggests that increased torsional flexibility decreases the likelihood of stumbles in children learning to walk.

Researchers from the Hospital for Special Surgery in New York City analyzed gait and plantar pressures in 15 children, aged 9 to 24 months, while walking in four shoe models of differing torsional flexibility. They found that the most flexible shoes were associated with the fewest number of stumbles and the highest plantar pressures under nearly all regions of the foot. The investigators believe the plantar pressure patterns reflect increased proprioception associated with the more flexible shoes, according to Corinne McCarthy, PT, DPT, a pediatric physical therapist at HSS and co-author of the study.

Although the number of study subjects was too small to achieve statistical significance, the findings have prompted the company to develop a new line of baby shoes for first walkers that features added torsional flexibility as well as “sensory pods” on the outsole of the shoe to enhance proprioception. The Sensory Response Technology collection was launched in August.

Sensor Walk results vary for IBM

Findings from the Mayo Clinic in Rochester, MN, were inconclusive regarding the relative benefits of the Sensor Walk stance control orthosis from Minneapolis-based Otto Bock HealthCare in patients with inclusion body myositis.

The study included nine subjects with IBM, a progressive, inflammatory muscle disease characterized by knee weakness, knee buckling and falls. Each subject was braced unilaterally, on his or her weaker leg. Six returned for testing after six months of wearing the device. Of those, four demonstrated knee extensor strength that was 30-40% of normal, while two were much weaker, at less than 15% of normal.

Overall, the brace was associated with a slower walking velocity, slower cadence, wider step width, and less knee flexion during swing, although there were no reports of toe clearance issues. Kinematic and kinetic changes were more apparent in the weakest subjects.

The researchers noted that outcomes were more likely to be positive in those who spent more time wearing the brace during the six-month wear period, regardless of strength. Qualitatively, subjects expressed concern about the bulk and weight of the brace, and some had difficulty with donning and doffing; IBM can also affect finger strength, making it difficult to manipulate straps or make other adjustments.

“Perhaps choosing a device to match each subject might lead to better usage,” said Kathie Bernhardt, a kinesiologist at the Mayo Clinic, who presented the findings in February at the annual meeting of the American Academy of Orthotists & Prosthetists.

Central fab carving lacks consistency

Central fabrication companies are more accurate in carving positive models than in forming prosthetic sockets, but results vary widely from one company to the next, according to research from the University of Washington.

The study, presented in February at the annual meeting of the AAOP, is the second from the same institution to report variable performance from central fab companies with regard to prosthetics. In a 2007 study published in the Journal of Rehabilitation Research & Development, they analyzed prosthetic sockets made by 10 central fab companies and found varying degrees of mismatch in volume between the fabricated sockets and the electronic data files from which they were made.

The current study focused on carving of positive models. Each of the 10 central fab companies were sent electronic shape files for three socket shapes: one tapered with bony landmarks, one cylindrical and bulbous, and one cylindrical with bony prominences.

When the positive models were compared to the shape files, volume differences ranged from -4.2% to +1.0%, and absolute mean radii differences ranged from 0 to 1.2 mm. Most of the variance came from just three companies; for seven companies, the volume difference was less than 1.1%. However, more models (22/30) than sockets (20/30) were within that 1.1% error range, which suggests that in general there is more error in socket forming than in model carving.

To their credit, the central fab companies who participated in both studies expressed interest in how they could improve their accuracy and consistency, said Joan E. Sanders, PhD, associate professor of bioengineering at the university, who presented the results at the AAOP meeting.

Sanders’ advice to practitioners: “If you’re getting CAD-CAM results that seem variable, try a different facility.”

Dr. Scholl’s insole reduces OA pain

A non-wedged foam insole from Dr. Scholl’s was associated with significantly reduced osteoarthritis pain after three weeks of wear, according to in-house research presented in February at the APTA’s Combined Sections Meeting.

The three-quarter length insoles are constructed of three layers, with foam cushioning on the top and bottom layers sandwiching a contoured shell with a cut-out to support the calcaneus.

The study included 227 patients with radiographically confirmed osteoarthritis of the knee, foot, or hip. Subjects wore the Dr. Scholl’s Arthritis Pain Relief Orthotic for eight hours a day, five days a week for three weeks. Pain was assessed using a 10-point visual analog scale.

After three weeks, investigators found a 42.3% decrease in knee and hip OA pain and a 43.6% decrease in foot OA pain.

Dr. Scholl’s is part of Memphis-based Schering-Plough Consumer Health Care, which merged with Whitehouse Station, NJ-based Merck in November.

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