Postoperative posterior lumbar muscle changes and their relationship to segmental motion preservation or restriction: a randomized prospective study

50 adult patients with chronic low-back pain and single-level degenerative disc disease (L4-L5 or L5-S1) were randomized to either motion restricted treatment through stand-alone anterior lumbar interbody fusion (ALIF), or motion preservation through total disc replacement (TDR). The purpose of this study was to compare muscle atrophy and fatty degeneration of the the posterior paravertebral muscles at the index and adjacent segments, as well as clinical outcomes, between groups over 1 year follow-up. The results at 1 year displayed a small decrease in paravertebral muscle volume and a small increase in the relative fat content within both groups at both the index and adjacent segments. At the index segment, there were no significant differences between groups. At the adjacent segments, the muscle volume after 1 year was maintained, relative to 1 week measures, to a significantly greater degree in the ALIF group compared to the TDR group, and that increase in fat content after 1 year, relative to 1 week measures, was significantly lower in the ALIF group compared to the TDR group. No significant differences were noted between groups in clinical outcomes at 1 year postoperatively.