A Biomechanical Analysis on the Sensitivity of Bone Graft and Osteotomy Orientation in Relation to Post-Operative Stability in Open Wedge High Tibial Osteotomy

Abstract

Potential complications after open wedge high tibial osteotomy (HTO) still remain unanswered as they are known to be primarily dependent on the surgical technique or the fixation strength. In this study, we evaluated the sensitivity of surgical variations (presence of bone graft, osteotomy line orientation and loading pattern) affecting post-operative stability using finite element analysis. Changes in stress distribution were also assessed at the lateral cortex bone and bone plate. A total six types of post-operative FE model were constructed to accommodate surgical variations based on the validated intact tibia model; Case 1 (lower level osteotomy, with no bone graft or with auto-tri-cortical bone), Case 2 (safe level osteotomy, with no bone graft or with auto-tri-cortical bone), Case 3 (upper level osteotomy, with no bone graft or with auto-tri-cortical bone). Two types of loading condition (axial compression_2450N with bending_240N and torsion_15Nm) were imparted. The use of bone graft material at the osteotomy site decreased the stress distribution at the lateral cortex bone and bone screw. And the lower level provided more post-operative stability than other osteotomy level (safe, upper). However, the ‘safe’ zone offered relatively similar results to those of the ‘lower’ zone. The osteotomy line near the lower end of the ‘safe’ zone was indeed the safest and most practical surgical approach as suggested in previous clinical studies. Therefore, our results suggested the use of bone graft with safe level osteotomy to assure the greatest post-operative stability and to reduce the likelihood of correction loss.

Keywords

• open wedge high tibia osteotomy
• finite element analysis
• surgical variations
• bone graft
• osteotomy level