Impact of tip–apex distance and femoral head lag screw position on treatment outcomes of unstable intertrochanteric fractures using cephalomedullary nails

Abstract

BackgroundCephalomedullary nails are frequently used in unstable intertrochanteric fractures. The implant position is an important factor for surgical success. Thus, in the present study, finite element analysis methods were used to investigate the biomechanical behavior of five different cephalomedullary nail positions in unstable intertrochanteric fractures.MethodsFive different cephalomedullary nail implant positions were investigated. The observed indicators were the maximum displacement of the lag screw, the stress on the intertrochanteric fracture with involvement of the posteromedial cortex, and the tip–apex distance.ResultsThe smallest lag screw displacement was achieved when the implant was closer to the inferior femoral head. Lower stress was placed on the posteromedial cortex when the implant was positioned closer to the inferior femoral head. However, the tip–apex distance increased when the lag screw was positioned more inferiorly.ConclusionsThe results of this study suggest that positioning the lag screw closer to the inferior aspect of the femoral head can reduce stress on the posteromedial cortex and deformation of the implant in unstable intertrochanteric fractures. These findings provide a biomechanical basis for selection of the cephalomedullary nail implantation site.Level of evidenceIII.

Finite element analysis of two cephalomedullary nails in treatment of elderly reverse obliquity intertrochanteric fractures: zimmer natural nail and proximal femoral nail antirotation-ΙΙ

“…The boundary condition was set as a fixation at the distal end of the femur, and the displacement along the x -, y - and z -axes at that site was set to zero [16]. Our study simulated the forces acting on the hip during the stance phase of walking [17].…”

Assessment of the Bone Mineral Density and Microstructure of the Human Femoral Head according to Different Tip-apex Distances Can Guide the Treatment of Intertrochanteric Hip Fractures

“…Reports involving radiographic surveys have found that the cut-out rate of lag screws is higher in the superior region than in other regions 2) . Some reports have suggested that the central-inferior region is the ideal position for the lag screw 9 10 11 12) . One explanation for this difference is that when the screw is placed in the inferior region, it does not damage the area where the bone is the strongest.…”

“…According to the most widely used guidelines at present, some studies report that TAD less than 25 mm is recommended 6 7 8) . The results of many retrospective studies have not been in uniform agreement on the optimal position of screws, and there is no persuasive basis to explain the correlation between these specific screw positions and a good prognosis 9 10 11 12) . In addition, some studies have reported a positive correlation between bone microarchitecture around screws and the pullout resistance of screws 13) .…”

A Finite Element Analysis and Cyclic Load Experiment on an Additional Transcortical-Type Hole Formed Around The Proximal Femoral Nail System’s Distal Locking Screw

“…The individual differences revealed that the FE model was satisfactorily validated. The boundary condition was set by xing the distal end of the femur, and the displacement along the x-, y-, and z-axes at that site was set to zero [7]. This study simulated the forces acting on the hip during the stance phase of walking [8].…”