The primary working hypothesis was that motion preservation would reveal beneficial effects with regard to adjacent leve
问题描述：
The primary working hypothesis was that motion preservation would reveal beneficial effects with regard to adjacent level preservation but that it might be disadvantageous with regard to the progression of the index-segment's facet joint degeneration.
答
句型应该不复杂,是这样：
The primary working hypothesis was that ( ) but that ( ).
主要工作假设是（带来的好处）但同时（其不利后果是……）.
好处是对近邻节段维持有好处,不利是引起脊椎关节退化.