RESUMEN
PURPOSE: Modifying foot progression angle (FPA), the angle between the line from the heel to the second metatarsal head and the line of progression, can reduce peak knee adduction moment (pKAM). However, determining the optimal FPA that minimizes pKAM without inducing unnatural walking patterns can be challenging. This study investigated the FPA-pKAM relationship using a robotic stepping trainer to assess the feasibility of determining the optimal FPA based on this relationship. Additionally, it examined knee moments during stepping with three different FPAs, as stepping is a recommended exercise for knee osteoarthritis (KOA) rehabilitation. METHODS: Twenty-six asymptomatic individuals stepped on a robotic stepping trainer, which measured 6-axis footplate-reaction forces/torques and three-dimensional (3-D) ankle kinematics to determine external knee moments. The robot rotated the footplates slowly (~0.5 deg/sec) between 10°-toe-out and 10°-toe-in while participants stepped continuously, unaware of the footplate rotations. The slope of pKAM-FPA relationship during continuous stepping was determined. Peak 3-D knee moments were compared between the 10°-toe-in, 0°-FPA, and 10°-toe-out FPAs with repeated-measure ANOVA. Multiple linear regression determined the covariates that predicted pKAM during stepping. RESULTS: Eighteen participants had lower pKAM and KAM impulse with 10°-toe-in than 10°-toe-out (p < 0.001) and 0°-FPA (p < 0.001 and p = 0.008, respectively) (called toe-in responders). Conversely, eight participants reduced pKAM and KAM impulse with 10°-toe-out compared to 0°-FPA (p < 0.001, p = 0.017) and 10°-toe-in (p = 0.026, p = 0.004) (called toe-out responders). A linear pKAM-FPA relationship was determined for each individual, and its slope (the pKAM rate with FPA) was positive for toe-in responders (p < 0.01) and negative for toe-out responders (p = 0.02). Regression analysis revealed that smaller pKAM with toe-in in toe-in responders was explained by increased tibia medial tilt, tibia internal rotation, footplate-reaction lateral force, footplate-reaction anterior force, and decreased footplate-reaction internal rotation torque. CONCLUSIONS: Individuals may exhibit different responses to FPA modification during stepping. The slope and intercept of the linear pKAM-FPA relationship can be determined for individual subjects. This allows for a targeted pKAM reduction through guided FPA positioning and potentially offers subject-specific precision KOA rehabilitation.
RESUMEN
MRI is an essential diagnostic imaging modality for many knee conditions; however, it is not indicated in the setting of advanced knee arthritis. Inappropriate MRI imaging adds to health care costs and may delay definitive management for many patients. The primary purpose of this study was to ascertain the frequency of inappropriate MRI scans performed at one Veterans' Administration Medical Center (VAMC). We performed a retrospective chart review of all knee MRIs ordered over a 6-month period. Inappropriate MRI was defined as MRI performed prior to radiographs (XRs), or in the presence of XRs demonstrating severe osteoarthritis, without leading to a nonarthroplasty procedure of the knee. Of the 304 cases reviewed, 36.8% (112) of the MRIs were deemed inappropriate, 33 were ordered by orthopedists, and 79 were ordered by other health care providers. Of the 33 ordered by orthopedists, 25 were ordered by retired/nonsurgical orthopedists. Obtaining an MRI delayed care by an average of 29.2 days. Of the 252 cases that had XR prior to MRI, none included all four views in the standard knee XR series and only four had weightbearing images. Over a third of knee MRIs performed at this VAMC were inappropriate and delayed care. Additionally, no XRs in our study contained all the necessary views to properly assess knee arthritis. These concerning findings signify a potential opportunity for education in diagnostic strategies, to better patient care and resource utilization in the VAMC.
