RSNA 2003 

Abstract Archives of the RSNA, 2003


M23-1191

Alterations in Volume, Strength, and Contraction Velocities of the Triceps Surae Complex after Four Weeks of Lower Limb Suspension and Subsequent Rehabilitation

Scientific Papers

Presented on December 3, 2003
Presented as part of M23: Musculoskeletal (Muscle and Soft-Tissue Disorders)

Participants

Shantanu Sinha PhD, PRESENTER: Nothing to Disclose

Abstract: HTML Purpose: To determine using MRI techniques in vivo, the extent of changes in the contraction velocities, muscle volume and strength of the MG and Soleus muscles, between normal, following 28 days of unloading, and after standard rehabilitation. Methods and Materials: Atrophy from unloading of the lower leg for 28 days was achieved by suspension (ULLS) of the left leg by a Velcro strap going under the foot at one end and the waist at the other, aided by a 5 cm raised heel in the right leg shoe, in 10 subjects. This was followed by physical therapy for 6 weeks. MRI was performed with both legs in the head coil of a 1.5T GE LX scanner, with the left leg immobilized within a lower half cast. The subject exerted isometric contraction against the sole of the cast, synchronized with a computer generated audio cue. Strength measures of plantar flexor force levels at 100% MVC was measured by an optical force transducer imbedded in the sole of the cast. Its output was also used to gate the acquisition and to provide a feedback via an LED bar-graph, for consistent level of force exerted. Velocity of muscles at different points in saggital slices was measured using velocity-encoded phase contrast MRI, with 4 views/segment, VENC =10cm/s in S/I direction, 32 cm FOV, 2 avg., 5 mm thick, TE/TR/Flip angle of 5.3/11.3/30o, with 20 (shared) views/cycle of ~40 bpm. An axial stack of slices was acquired across the entire length and volume rendered on a Vitrea workstation to estimate muscle volume. Strength measures, contraction velocities and muscle volumes were determined prior to, and on the last day of suspension and after 6 weeks of recovery. Results: Decrease from atrophy following suspension of the MG volume was 11.1%+-3.9 and for the Sol plus the deep plantar flexors was 7.6%+-8.4. Force of MVC declined by 47.5%+-18. Both returned to presuspension levels after therapy. The contraction velocity of the MG (presuspension peak -0.41 cm/s+-0.54) did not change following suspension or after recovery. That for the Sol changed from 0.83 cm/s+-0.48 to -0.24 cm/s+-0.53 following suspension, and normalized after 6 weeks of recovery (0.68 cm/s+-0.48). Presuspension, the Sol lengthened during the force development, after suspension it shortened but returned to lengthening after recovery. Conclusion: This methodology has the clinical potential to determine quantitatively the functional aspects including muscle atrophy, strength and contracting velocities of the muscuoskeletal system, allowing us to investigate the individual muscle compartments, in normal, atrophied and recovering muscles.       Questions about this event email: ssinha@mednet.ucla.edu

Cite This Abstract

Sinha PhD, S, Alterations in Volume, Strength, and Contraction Velocities of the Triceps Surae Complex after Four Weeks of Lower Limb Suspension and Subsequent Rehabilitation.  Radiological Society of North America 2003 Scientific Assembly and Annual Meeting, November 30 - December 5, 2003 ,Chicago IL. http://archive.rsna.org/2003/3107812.html