Longitudinal changes in tibial and femoral cartilage thickness are associated with baseline ambulatory kinetics and cartilage oligomeric matrix protein (COMP) measures in an asymptomatic aging population.

OBJECTIVE: To address the need for early knee osteoarthritis (OA) markers by testing if longitudinal cartilage thickness changes are associated with specific biomechanical and biological measures acquired at a baseline test in asymptomatic aging subjects. DESIGN: Thirty-eight asymptomatic subjects over age 45 years were studied at baseline and at an average of 7-9 year follow-up. Gait mechanics and knee MRI were measured at baseline and MRI was obtained at follow-up to assess cartilage thickness changes. A subset of the subjects (n = 12) also had serum cartilage oligomeric matrix protein measured at baseline in response to a mechanical stimulus (30-min walk) (mCOMP). Baseline measures, including the knee extension (KEM), flexion (KFM), adduction (KAM) moments and mCOMP, were tested for associations with cartilage thickness changes in specific regions of the knee. RESULTS: Cartilage change in the full medial femoral condyle (p = 0.005) and external medial femoral region (p = 0.041) was negatively associated with larger early stance peak KEM. Similarly, cartilage change in the full medial femoral region (p = 0.009) and medial femoral external region (p = 0.043) was negatively associated with larger first peak KAM, while cartilage change in the anterior medial tibia was positively associated with larger first peak KAM (p = 0.003). Cartilage change in the anterior medial tibia was also significantly associated (p = 0.011) with mCOMP levels 5.5-h post-activity (percentage of pre-activity levels). CONCLUSIONS: Interactions found between gait, mechanically-stimulated serum biomarkers, and cartilage thickness in an at-risk aging asymptomatic population suggest the opportunity for early detection of OA with new approaches that bridge across disciplines and scales.

Speed, age, sex, and body mass index provide a rigorous basis for comparing the kinematic and kinetic profiles of the lower extremity during walking.

The increased use of gait analysis has raised the need for a better understanding of how walking speed and demographic variations influence asymptomatic gait. Previous analyses mainly reported relationships between subsets of gait features and demographic measures, rendering it difficult to assess whether gait features are affected by walking speed or other demographic measures. The purpose of this study was to conduct a comprehensive analysis of the kinematic and kinetic profiles during ambulation that tests for the effect of walking speed in parallel to the effects of age, sex, and body mass index. This was accomplished by recruiting a population of 121 asymptomatic subjects and analyzing characteristic 3-dimensional kinematic and kinetic features at the ankle, knee, hip, and pelvis during walking trials at slow, normal, and fast speeds. Mixed effects linear regression models were used to identify how each of 78 discrete gait features is affected by variations in walking speed, age, sex, and body mass index. As expected, nearly every feature was associated with variations in walking speed. Several features were also affected by variations in demographic measures, including age affecting sagittal-plane knee kinematics, body mass index affecting sagittal-plane pelvis and hip kinematics, body mass index affecting frontal-plane knee kinematics and kinetics, and sex affecting frontal-plane kinematics at the pelvis, hip, and knee. These results could aid in the design of future studies, as well as clarify how walking speed, age, sex, and body mass index may act as potential confounders in studies with small populations or in populations with insufficient demographic variations for thorough statistical analyses.

An in vitro bacterial surface migration assay underneath sterile barrier material commonly found in a hospital setting.

OBJECTIVE: To determine what barrier material used in hospital neonatal intensive care units most effectively blocks bacterial migration. STUDY DESIGN: Bacterial migration distance was compared across simple and complex solid media using Escherichia coli, an early and common neonatal gut colonizer, and Staphylococcus aureus, a common skin bacterium, across polystyrene, medical-grade silicone, hydrocolloid dressing and transparent film dressing as barrier materials on complex solid media. RESULTS: Bacterial migration was significantly greater on complex versus simple solid media. Bacteria migrated farthest beneath hydrocolloid dressing and transparent film dressing, while migration underneath polystyrene and medical-grade silicone was generally comparable to no barrier. CONCLUSIONS: Commonly used hydrocolloid dressing and transparent film dressing surprisingly increases bacterial migration, possibly by providing a wet capillary surface for bacteria to attach to or inducing biofilm formation. Using polystyrene or silicone to interface with the site of catheter insertion may best avoid a bacterial wicking phenomenon.

Baseline knee adduction and flexion moments during walking are both associated with 5 year cartilage changes in patients with medial knee osteoarthritis.

OBJECTIVE: To test the hypothesis that knee cartilage changes over 5 years are associated with baseline peak knee adduction moment (KAM) and peak knee flexion moment (KFM) during early stance. DESIGN: Baseline KAM and KFM were measured in sixteen subjects with medial knee osteoarthritis (OA). Regional changes in cartilage thickness and changes in medial-to-lateral thickness ratio were quantified using magnetic resonance imaging (MRI) at baseline and again after 5 years. Multiple regression was used to determine whether baseline measures of KAM and KFM were associated with cartilage changes over 5 years. Associations with baseline pain score, Kellgren-Lawrence (KL) grade, walking speed, age, gender, and body mass index (BMI) were tested one-by-one in the presence of KAM and KFM. RESULTS: Changes over 5 years in femoral medial-to-lateral thickness ratio were associated with baseline KAM, KFM, and pain score (R(2) = 0.60, P = 0.010), and most significantly with KAM (R(2) = 0.33, P = 0.019). Changes in tibial medial-to-lateral thickness ratio were associated with baseline KAM, KFM, and walking speed (R(2) = 0.49, P = 0.039), with KFM driving this association (R(2) = 0.40, P = 0.009). Changes in medial tibial thickness were associated with baseline KAM, KFM, and walking speed (R(2) = 0.49, P = 0.041); KFM also drove this association (R(2) = 0.42, P = 0.006). CONCLUSIONS: The findings that the KAM has a greater influence on femoral cartilage change and the KFM has a greater influence on tibial cartilage change provide new insight into the tibiofemoral variations in cartilage changes associated with walking kinetics. These results suggest that both KAM and KFM should be considered when designing disease interventions as well as when assessing the risk for OA progression.