Dorsal-ventral (D-V) stiffness study design.
The 3 arms of this repeated measures study were link period without a subsequent unlinked period (arm 1), link period followed by an unlinked period (arm 2), and control (arm 3). The link configurations were neutral (EN), flexed (EF), or rotated (ER). Control rats received SAU implants but were never linked (CSAU configuration). Dorsal-to-ventral stiffness testing for experimental group rats was performed just before linking (U1), immediately after linking (L1), immediately before link removal (L2), immediately after link removal (U2), and at the conclusion of any unlinked period (U3).
Dorsal-to-ventral stiffness tests for control rats (C-U1, C-L1, C-L2, C-U2, C-U3) were at equivalent periods to tests on experimental rats. Seven equivalent periods were examined in arm 3. These were homologous to the 1- to 16-week link periods with a “*to 20 weeks” period for comparison with the 8-week linked plus 12-week unlinked rats in arm 2. The animal counts reported in this figure are explained in the text.