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.