A donor model assessing the effect of errant drill passes during placement of femoral nail interlock screws

Abstract

Current orthopaedic practice to fix femoral shaft and intertrochanteric fractures is intramedullary (IM) nailing. Technical errors in nailing often result in errant drill passes (EDP) during placement of distal interlock screws. This study determined if EDP create stress risers that significantly alter the biomechanical strength of the bone. Ten mm IM femoral nails were placed in 16 paired adult cadaveric distal femur specimens. Matched specimen pairs were randomized into two groups (n=16/group). Nails were statically locked distally with two 4.5 mm bicortical screws in both groups, with specimens in Group 2 being exposed to a 4.2 mm drill hole placed anterior and inferior to the nail, representing an EDP. Using the Instron 8874 Axial‐Torsion Testing System, torsional load to failure and rotational angle at failure were recorded. Student t‐tests revealed no significant decrease in load to failure for the distally locked group with an errant drill pass (p=0.435) or any differences in rotational angle at failure between groups (p=0.581). Introducing an errant drill hole while distally locking a femoral nail did not significantly decrease the specimens’ load to failure indicating that bone strength may remain uncompromised. This suggests that although these technical errors may occur intraoperatively, post‐operative outcomes may remain unaffected.Grant Funding Source : Not Applicable