Is distal locking necessary for proximal femoral nail antirotation
Objective To discuss the necessity of distal locking in the treatment of femoral inter-trochanteric fractures with proximal femoral nail antirotation(PFNA).Methods According to the Evans-Jensen classification,8 pairs of preserved femurs(n=16)were randomly divided into two groups and frac-ture internal fixation models were prepared.A two-part fracture along the trochanter(type Ⅰ/Ⅱ)was made in the stable group(n=8),and an incomplete medial wall fracture(type Ⅳ)was made in the unsta-ble group(n=8).Stiffness values of fracture model under axial,abduction and external rotation load were measured respectively,and the change of stiffness value with or without distal locking was recorded.Paired sample t-test or Wolcoxon test was used for statistical analysis.Results In stable group,the stiffness val-ue with distal locking was lower than that without locking under axial force,and the difference was not sta-tistically significant[(401.13±121.54)N/m vs.(404.75±134.15)N/m,t=-0.596,P＞0.05].The stiffness with distal locking was higher than that without locking under abduction and external rotation,and the difference was not statistically significant[(111.14±52.43)N/m vs.(108.88±48.35)N/m;(30.92±6.93)N/m vs.(29.68±8.09)N/m,t=0.632,1.785,P＞0.05].In unstable group,the stiff-ness with distal locking was higher than that without locking under axial and abduction forces,and the differ-ence was not statistically significant[(438.97±157.86)N/m vs.(420.5947±139.17)N/m,Z=0.700,P＞0.05;(107.25±39.11)N/m vs.(105.44±36.81)N/m,t=0.611,P＞0.05],while in external rota-tion,the difference was statistically significant[(33.76±10.60)N/m vs.(29.98±13.16)N/m,t=3.186,P＜0.05].Conclusion From a biomechanical point of view,PFNA distal locking may not be necessary when the intertrochanteric fracture is stable,but it is necessary when the fracture is unstable.
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