Topographic differences of 1H-NMR relaxation times (T1, T2) in the normal intervertebral disc and its relationship to water content.

1H-nuclear magnetic resonance studies, in vitro, on normal intervertebral discs dissected from adult bovine (3- or 4-year-old) coccygeal vertebrae were performed to clarify topographic differences in relaxation times (T1, T2) and relationships between the relaxation times and water content. Immediately after death, intervertebral discs were dissected from 1st/2nd and 2nd/3rd coccygeal vertebrae and divided into three specimens: the nucleus pulposus, inner anulus fibrosus, and outer anulus fibrosus. T1, T2, and water content were measured for the specimens collected from 15 intervertebral discs (untreated group). Secondly, specimens were similarly collected from 12 intervertebral discs and were treated to changed water contents (dehydrated group and hydrated group). For each treated specimen, T1, T2, and water content were measured. The results showed highly significant differences (P < 0.01) in T1 values among the nucleus pulposus, inner anulus fibrosus, and outer anulus fibrosus, and also in T2 values between the nucleus pulposus and anulus fibrosus. In each of the nucleus pulposus and anulus fibrosus, a positive linear relationship (r = 0.97, P < 0.01) was found between T1 and water content. The respective regression lines for the nucleus pulposus and anulus fibrosus had different slopes, and the slope of the nucleus pulposus was significantly greater than that of the anulus fibrosus. Thus, the decrease in water content shortens the T1 in intervertebral discs, and changes in water content have a greater influence on T1 in the nucleus pulposus than in the anulus fibrosus.(ABSTRACT TRUNCATED AT 250 WORDS)