Effect of Running on Cartilage T2 Profile
M. Jason Hancey, Class of 2004
Timothy J. Mosher, M.D.
Department of Radiology
June - July, 2001
Determine the effect of running on the T2 profile of human patellar/femorotibial cartilage.
Articular cartilage consists mostly of water (roughly 75 %), the other 25 % being a complex arrangement of solid matrix. This matrix consists almost entirely of proteoglycans and collagen fibers (generally type II) 1,2. Cartilage at the knee joint acts to absorb shock during exercise. Upon impact force is applied to the articular cartilage as the femur and tibia converge. At the same time as the knee is flexed and under load, force is placed indirectly on the patellar cartilage through the quadriceps and patellar tendons (Archimedes forces). As these forces are applied to the joint and the accompanying cartilage there is a flux of water through the solid matrix of the cartilage and a concurrent exudation of water out of the matrix and onto the surface of the articular cartilage 3. This flowing water is subject to huge frictional drag forces within the solid matrix due to osmolarity, interstitial pressure, and fixed charge density 4. The abilities of the articular cartilage to restrict the movement of this water is key to withstanding repetitive compressions. As a result, energy is dissipated, and up to 90 % of the load on the joint is carried by the water 4,5. It has been shown that with increased water movement, more of the operating load is absorbed by the solid phase matrix leading to stress, fatigue, and ultimately structural fragmentation 6. We suspect that repetitive vigorous compression and flexion of the knee(as seen in running) will cause a measurable decrease in water content of the femorotibial cartilage as well as patellar cartilage. This would demand that the solid matrix support more of the total load. The aim of this study is to use T2 values to confirm and quantify any decrease in cartilage water content following running.
MRI imaging and analysis is noninvasive, and provides the best measure of articular cartilage water content available. This technique involves the input of radio frequency energy while monitoring the resultant signals produced as this energy effects moving protons in the tissue7. Transverse relaxation time, also know as T2, is a time constant measurement which can be used to describe the mobility of water 8,9. Lusse and co-workers have demonstrated a linear relationship between T2 and water content10,11. T2 values rise with increasing water content. Thus we expect to see a decreased T2 in the same knee immediately after the volunteer runs. T2 values are not static throughout the thickness of the cartilage. The Penn State, Hershey NMR laboratory was the first to show a gradient-like increase in T2 values from the deep to the outer layers of articular cartilage12. This can be explained by looking at the arrangement of collagen fibers and proteoglycans within the matrix. These fibers and proteoglycans are highly organized deep within the cartilage but become more random and disorganized as they near the surface13. It is expected that following repeated compression the greatest change in T2 will be seen in the most superficial layers of articular cartilage.
Seven male volunteers will be recruited for this study. Each male will meet the following guidelines:
- Between the ages of 18-30.
- No knee pain or discomfort (quantified by use of the WOMAC questionnaire).
- Not currently engaged in extensive running activities
- No surgical corrections to knee or the like.
Subjects will begin study in the morning to avoid diurnal variation in cartilage water content. An initial Quantitative T2 map of the right femorotibial cartilage will be captured using the Bruker Medspec S300 3.0 MR imaging-spectrometer located at the NMR laboratory on the Penn State Hershey COM campus. Following this initial imaging study subjects will commence a 30 minute timed run. The entire run will occur on asphalt, along a predetermined course. Immediately after the run, participants will return to the spectrometer for a repeat imaging study of the same limb.
Quantitative analysis of the seven pre-run, and seven post-run images will be performed using CCHIPs/IDL software. Results of pre and post-run patellar, as well as femoral/tibial weight bearing cartilage T2 values will be pooled. The 95% confidence Interval(CI) for those T2 values will be calculated with respect to distance from the subchondral bone to determine if a difference in the cartilage T2 appears post-run. Any points along the pre and post-run CI's which do not overlap will be considered statistically different.
- Develop knowledge of MRI theory and data interpretation using CCHIPS software
- Review current literature pertaining to degenerative cartilage changes, their prevalence, and detection methods
- Recruit participants
- Coordinate / Direct participant use (MRI timing, exercise protocol)
- Perform data analysis
- Prepare final project report
- Confer MRI, Physiology, and Study design knowledge
- Oversee project flow
- Aid in data interpretation
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