Fig. 3A–B.

(A) On a universal testing machine, cyclic loadings were applied through the sacrum that was allowed to pivot in all planes while the left hip socket articulated with a fixed femoral head substitute. Hip abductor muscles were simulated by cable pulleys attached to the iliac crest. (B) Displacement under loading was measured using an optoelectronic camera system. Markers were placed on the iliac crest, the sacrum, and the S1 screw (*).