Incomplete Recovery of Lumbar Intervertebral Discs 2 Years After 60-Day Bed Rest

Study Design. Prospective longitudinal study. Objective. To evaluate the recovery of the lumbar intervertebral discs after bed rest. Summary of Background Data. Prolonged bed rest is a useful model to understand the modeling and remodeling of tissues due to disuse and reloading, yet this process in the lumbar intervertebral discs has not been examined in detail. Methods. A total of 24 male subjects completed 60 days of head-down tilt bed rest as part of the 2nd Berlin BedRest Study and returned for magnetic resonance scanning 180 days (n = 22) and 2 years (n = 21) after bed rest. Lumbar disc volume, anterior and posterior disc height, disc signal intensity, intervertebral length, and lordosis were measured on sagittal plane magnetic resonance images. Results. Compared with prior to bed rest, increases in disc volume, disc height, and intervertebral length persisted 180 days (P <= 0.0004) and 720 days (P <= 0.024) after bed rest. Disc signal intensity remained increased 180 days (P = 0.034) after bed rest but was then decreased (P = 0.018) compared with baseline at the next measurement date. Conclusion. The recovery of the lumbar intervertebral discs after 60-day bed rest is a prolonged process and incomplete within 2 years.