BIOMECHANICAL ANALYSIS OF HEMIPELVIC DEFORMATION AFTER CORTICOSPONGIOUS BONE-GRAFT HARVEST FROM THE POSTERIOR ILIAC CREST

Study Design. The stiffness of the hemipelvis during simulated physiol ogic loading and the bone deformation in the remaining posterior ilium after the harvest of sizes of corticospongious bone graft were compar ed with values in intact bone. Objectives. To quantify the biomechanic al effects of the removal of bone grafts from the posterior ilium and to relate the size of graft removed to the stiffness of the hemipelvis and deformation of the remaining bone. Summary of Background Data. Bo ne fractures and pelvic instability have been reported to complicate g raft harvest from the posterior iliac crest. There is no quantitative data relating graft size to the mechanical properties of the remaining ilium. Methods. Seven cadaveric hemipelves were loaded with a materia ls testing machine through the superior sacrum while supported at the acetabulum and stabilized with a cable fixed to the ilium. Force and d isplacement histories and deformation in the greater sciatic notch wer e recorded for the intact bone and after removal of corticospongious b one graft in 1.5-cm increments from the posterior iliac crest. Results . If the length of the removed corticospongious bone graft exceeded 3. 0 cm, the stiffness of the posterior pelvic ring decreased, and deform ation in the remaining bone increased substantially. Conclusions. Remo val of bone graft in excess of 3 cm from the posterior ilium increases the risk of iatrogenic fatigue fracture.