Symposium



Associations between Gait Kinetic Variables and Patellofemoral Cartilage T1ρ and T2 Relaxation Time


Presenting Author Senior Author
Name: Hsiang-Ling Teng Name: Richard Souza
Email: Hsiang-Ling.Teng@ucsf.edu Email: Richard.Souza@ucsf.edu
Presenting Author’s RIG/SRG: Musculoskeletal  
Presenting Author's Lab Location: Mission Bay   

Abstract Information
Imaging Modality: MR
Disease Application: Musculoskeletal
Complete author list: Hsiang-Ling Teng, Nathaniel Calixto, Thomas Link, Sharmila Majumdar , Richard Souza
Abstract highlights: Using quantitative MR methods, we identified biomechanical risk factors associated with patellofemoral cartilage health. Higher knee flexion moment and impulse were found to be related to worst patellofemoral cartilage health (higher T1ρ and T2 relaxation time), especially in the superficial layer and in individuals with existing PFJ cartilage lesions.
 
Introduction
Patellofemoral joint (PFJ) osteoarthritis (OA) is highly prevalent and an important source of pain and dysfunction. Increased knee flexion moment and impulse can result in higher mechanical loading on the PFJ and thus, may be risk factors of PFJ cartilage degeneration. This study aimed to examine whether knee flexion moment and impulse during gait are associated with PFJ cartilage composition quantified by T1ρ and T2 relaxation time.
 
Methods
Ninety-nine subjects with and without PFJ OA participated (62 females, 56 PFJOA, age: 52.0±10.7 years, BMI: 24.6±3.4 kg/m2, walking speed: 1.52±0.23 m/s). 3D gait analysis (VICON, Oxford, UK) was performed while subjects walked at a self-selected speed (Fig 1-A). Knee MR images were acquired using a 3 Tesla MRI scanner (GE Healthcare, Milwaukee, WI, USA) with an 8-channel phased array knee coil (Invivo, Orlando, FL, USA). T1ρ relaxation time sequence (TR/TE = 9/2.6 ms, time of recovery = 1500 ms, field of view = 14 cm, matrix = 256×128, slice thickness = 4 mm, bandwidth = 62.5 kHz, time of spin-lock = 0/2/4/8/12/20/40/80 ms, frequency of spin-lock = 500 Hz, acquisition time = 11 min), and T2 relaxation time sequence (same as the T1ρ sequence except for magnetization preparation TE = 1.8/3.67.3/14.5/ 29.1/43.6/58.2 ms, acquisition time = 11 min) were obtained. Trochlea and patella cartilage compartments were segmented semi-automatically. Laminar analysis was performed automatically by partitioning the cartilage into two equal laminae: the deep layer (closer to the subchondral bone) and superficial layer (closer to articular surface)(Fig 1-B). T1ρ and T2 relaxation times were determined using a pixel-by-pixel, three-parameter exponential fit. T1ρ and T2 values of the entire trochlea and patellar cartilage and each laminae were computed as the mean of all pixels belonging to the ROIs. Linear regression models were built to examine the relationship between knee kinetics (i.e. knee flexion moment and flexion moment impulse) and PFJ cartilage relaxation times (i.e. T1ρ and T2 values) while adjusting for age, gender, BMI, and walking speed.
 
Results
Higher peak knee flexion moment and flexion moment impulse were significantly associated with higher patella and trochlea cartilage T1ρ and T2 values with standardized coefficients (β) ranged from 0.21 to 0.28 (Fig 1-C). Laminar analysis revealed stronger correlations between knee kinetic variables and superficial cartilage T1ρ and T2 values, especially in the patella (β ranged from 0.22 to 0.33, Fig 1-D). Post-hoc analyses showed that the observed associations were stronger in subjects with PFJ OA than those without PFJ OA.
 
Conclusions
Findings support the premise that higher knee flexion moment and impulse during walking are related to degenerative cartilage changes in the PFJ. More specifically, higher knee loading during gait is related to worst PFJ cartilage health in the superficial layer. The observed relationships were stronger in subjects with PFJ cartilage lesions, suggesting that articular cartilage may be more susceptible to mechanical loading with the existence of lesions. Based on the findings, future intervention protocols of PFJ OA may be developed to reduce knee flexion moment and impulse during walking.