Dynamic Wedging: A Novel Treatment for Knee Osteoarthritis

The Biomechanical System The biomechanical system is a biomechanical device (US Patent No. 6,979,287) combined with a treatment methodology (US Patent No. 7,101,330). The device is calibrated for the individual patient according to pathology and motion characteristics. Appropriate calibration is defined as bringing the damaged joint to a biomechanical alignment that minimizes/eliminates pain by shifting and/or changing the applied forces and, consequently, altering pressure distribution within the joint. Together with the biomechanical perturbation applied through all phases of the step-cycle (i.e. initial contact, mid-stance and toe-off), this enables home-based, dynamic, functional and repetitive training to strengthen dynamic stabilizers and improve neuromuscular control.

The device consists of two half spherical-shaped biomechanical elements attached to each of the patient's feet. One is located under the hindfoot region and the other is located under the forefoot region. The elements are available in different degrees of resilience and convexity, and are attached to the patient's foot using a platform in the form of a shoe. The platform is equipped with a specially designed sole, which consists of two mounting rails to enable flexible positioning of each element under each region.

A specific level of "unloading" under a specific level of perturbation is required for controlling pain in the affected compartment while reducing excessive loads of soft tissue structures. Primary guidelines for calibration dictate the choice of resilience, convexity and the position of each element. For example, in a genu-varus deformity the elements are positioned under the neutral axis of the patient's leg. The element under the hindfoot is further translated laterally to the longitudinal axis of the patient's leg in order to apply wedging, while the element under the forefoot is further translated medially to reduce the tension applied by soft tissue in the medial compartment, and to decrease adduction moment. When required, further soft tissue tension and/or pressure can be decreased by adding plantar flexion and/or forward translation of the hindfoot element.

Pain and motion instability are periodically evaluated to determine whether recalibration is required.

Treatment (Active) Protocol The device was calibrated for each patient after baseline assessment. Then, treatment was initiated and continued daily for a period of 8 weeks, during which the device was again calibrated, as necessary, after the first, third and sixth week. Patients were instructed to follow a treatment protocol which was based on walking during activities of daily living and started with 10 minutes of indoor walking each day during the first week and gradually increased to 30 minutes of daily outdoor walking in the last week. Other than that, they were told to continue their daily activities wearing their regular footwear. They were also instructed not to ingest any pain relief medication, non-steroidal anti-inflammatory drugs or food supplements except for the acetaminophen tablets (unmarked) that had been given to them at study entry to be taken when needed. The consumption of acetaminophen or any other medication was monitored during each assessment.