Browsing by Author "Ronsky, Janet Lenore"
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- ItemOpen AccessCharacterization of OA Severity in Knee Articular Cartilage in-Vivo Using MR Imaging and Loading Techniques(2017) Dai, Xu; Ronsky, Janet Lenore; Frayne, Richard; Schmidt, Tannin; Boyd, Steven Kyle; Nowicki, Edwin Peter; Holdsworth, David W.Early osteoarthritis (OA) is primarily associated with proteoglycan (PG) loss and changes in collagen structure. MR T2 imaging of knee under in-vivo loading may help to further reveal the differences between healthy and OA cartilage. This study investigated the in-vivo loading effect on MR T2 values of human knee patellar cartilage. The results demonstrated T2 value distributions in patellar cartilage were inhomogeneous. In-vivo loading had a site-specific influence on participants’ T2 values. The in-vivo loading produced a significant difference on T2 values in the middle region of interest (ROI) of patellar cartilage (p=0.004<0.025), but not at the superior or inferior ROIs. The T2 value variation for the OA group during loading was lower than that of the healthy group (p=0.016<0.025). The T2 recovery ratio was presented in this study as a new variable. The findings indicated the T2 recovery ratio of the OA group was significantly lower than the healthy group (p=0.042<0.05) in the patellar cartilage middle ROI. It suggests that the OA cartilage had weaker ability to restore its original status after off-loading than healthy cartilage. This study examined the glycosaminoglycan (GAG) mass% concentration (relating PG) in human cadaveric patellar cartilages using biochemical assay. Results showed that the GAG mass% concentrations in OA lesion positions were lower than that in comparative healthy positions (p<0.001). MR T2 imaging of healthy and OA cadaver knee joints were performed. Correlations between T2 values and the GAG mass(%) of cadaver patellar cartilage specimens were established. As PG concentration of in-vivo human articular cartilage cannot be directly measured non-invasively, the correlation of cadaveric patellar cartilage may serve as an important bridge between the T2 value and GAG mass% for living human assessment. The findings provide an indirect approach to estimate PG concentration of in-vivo patellar cartilage based on an individual’s cartilage T2 values to evaluate the extent of degradation within cartilage. This subject specific method is especially suitable for longitudinal evaluation of OA. By position-matched comparison of previous and current T2 images, the GAG mass% variation may be estimated to assess OA progression non-invasively.
- ItemOpen AccessDevelopment of a Real-time Performance Measurement System for Sprint Starts(2017) Iyer, Parth; Brennan, Robert; Goldsmith, Peter; Ronsky, Janet Lenore; Herzog, WalterThis thesis is an expansion of a Capstone Project where a set of portable sprint starting blocks that can be used for training was developed. For this thesis, two piezo-electric sensors were implemented in the blocks that transmitted data from each of the sprinter’s feet to a micro-controller. The sensors, after a series of impact hammer tests, offered a cost-efficient means of collecting valuable telemetric data during a sprint start, and crucially, were non-intrusive. Majority of the athletes demonstrated a consistent three-peak-force pattern in the data collected which was statistically correlated to qualitative performance scores given by a coach evaluating the start. The correlation helped develop a fuzzy method that estimated a performance score for sprint starts and detected false starts. The need to validate this method also helped produce a definitive coach’s sprint start evaluation checklist from the National Coaching Certification Program.
- ItemOpen AccessIn-vivo quantification of patellofemoral joint contact characteristics(1994) Ronsky, Janet Lenore; Nigg, Benno M.
- ItemOpen AccessQuantifying Temporal Changes in Knee Joint Laxity and Dynamic Knee Stability for Healthy and Acute ACL Injured Individuals(2015-02-02) Bishop, Emily Lynn; Ronsky, Janet LenoreACL rupture causes altered joint dynamics and leads to greater risk of joint degeneration and development of knee OA. The current study investigated relations amongst passive knee laxity and dynamic knee stability in healthy and ACLD individuals over time to understand adaptations following ACL rupture during a sub-acute stage post-injury. An in vivo MR based measure of passive knee laxity was obtained using a novel knee loading apparatus to image the knee joint under various loading conditions. Dynamic knee stability was evaluated during two dynamic tasks using the finite helical axis (FHA) approach to quantify kinematics, combined with wavelet analysis of muscle activity. The healthy group demonstrated side-to-side differences in FHA measures not present in the ACLD group. This revealed asymmetrical movement in the healthy group and enabled appropriate interpretation of side-to-side differences due to ACL rupture. Passive knee laxity was larger in the ACLD injured limb compared to the healthy dominant limb at six weeks post-injury, and did not significantly change in the injured limb between six and twelve weeks post-injury. FHA measures in the ACLD injured limb were not significantly different from healthy at six weeks post-injury. However, the ACLD group demonstrated changes in both limbs in FHA measures and muscle power between six and twelve weeks post-injury suggesting bilateral adaptations to ACL rupture. These changes resulted in increased limb symmetry during the swing task, and decreased limb symmetry during the squat task. At twelve weeks post-injury, ACLD individuals revealed significant correlations between passive knee laxity and FHA measures not present in the contralateral limb or the healthy group. ACLD individuals with increased passive knee laxity demonstrated more constrained movement during the swing, and less constrained movement during the squat. Relationships amongst passive knee laxity and dynamic knee stability in the ACLD group provided an understanding of the influence of structural joint laxity on dynamic movement patterns. Early adaptations in the ACLD knee joint are speculated to contribute to the initiation of degenerative changes in the knee joint, which may be modifiable with targeted rehabilitation protocols aimed at minimizing or slowing the progression of OA.