Biomechanical Evaluation of Extramedullary Versus Intramedullary Reduction in Unstable Femoral Trochanteric Fractures

Abstract

Introduction: The failure rate of operations involving the cephalomedullary nail technique for unstable femoral trochanteric fractures is 3-12%. Changing the reduction strategy may improve the stability. This study aimed to confirm whether reducing the proximal fragment with the medial calcar contact, as opposed to utilizing an intramedullary reduction, would improve the stability of such fractures. Materials and Methods: The unstable femoral trochanteric fracture model was created with fixation by cephalomedullary nails in 22 imitation bones. The 2 reduction patterns were as follows: one was with the proximal head-neck fragment external to the distal bone in the frontal plane and anterior in the sagittal plane as “Extramedullary,” while the other was the opposite reduction position, that is, bone in the frontal plane and sagittal plane as “Intramedullary.” We evaluated the tip-apex distance, compression stiffness, change in femoral neck-shaft angle, amount of blade telescoping, and diameter of the distal screw hole after the compression test. Statistical analysis was conducted using the Mann-Whitney U test. Results: No significant differences were seen in compression stiffness ( p = 0.804) and femoral neck-shaft angle change ( p = 0.644). Although the “Extramedullary” tip-apex distance was larger than the “Intramedullary” distance ( p = 0.001), it indicated clinically acceptable lengths. The amount of blade telescoping and the distal screw hole diameter were significantly larger in “Intramedullary” than in “Extramedullary” ( p < 0.001, p = 0.019, respectively). Our results showed that “Intramedullary” had significantly larger blade telescoping and distal screw hole diameters than “Extramedullary,” and contrary to our hypothesis, no significant differences were seen in compression stiffness and femoral neck-shaft angle change. Conclusions: As opposed to the “Intramedullary” reduction pattern, the biomechanical properties of the “Extramedullary” reduction pattern improved stability during testing and decreased sliding.

AP3×ML3 reduction quality classification for femoral trochanteric fractures: validation for reliability focusing on positive medial cortical support

“…Fukuda et al [ 11 ] stressed the importance of PMCS when they first described the AP3 × ML3 classification. Kawamura et al [ 10 ] confirmed the stability of the extramedullary reduction pattern when mimicking the concept of PMCS in their biomechanical study. Effective bone-on-bone contact is desirable, and the intramedullary type in the lateral view was reported to be a reduction that should be avoided due to the larger sliding distance of the proximal fragments [ 16 , 17 ].…”

“…Recently, the concept of positive medial cortical support (PMCS) has been proposed [ 2 ]. PMCS is defined as slight medial displacement of the cortical bone on the side of the proximal fragment and could provide cortical support between the proximal and distal fragments, thereby resisting further sliding of the proximal fragment [ 9 , 10 ]. A new reduction quality classification for trochanteric fractures, which applies the concept of PMCS, was proposed by Fukuda et al [ 11 , 12 ] (Fig.…”

Anterior Malreduction is Associated With Lag Screw Cutout After Internal Fixation of Intertrochanteric Fractures

“…2). Because anatomic reduction and posterior malreduction have positive contact with the anteromedial cortex [19,40], they were combined. In this study, these three classifications were divided into two groups according to the anteromedial cortex contact (anterior malreduction or other reduction) as the main exposure.…”

“…An observational study among Japanese women suggested that TAD was the most influential factor in cutout [11]. On the other hand, recent studies have reported that anteromedial cortex contact between the neck and diaphyseal fragment affects postoperative instability [6,19,22]. In the past decade, a method for evaluating anteromedial cortex contact using radiographs in the sagittal plane has been reported in East Asia [7,17,19,21,28,38,40].…”

“…In anatomic reduction and posterior malreduction, during weightbearing, the distal edge of the anterolateral cortex of the neck fragment contacts the proximal anteromedial cortex of the diaphyseal fragment, thus causing load sharing between the fragments. In contrast, in anterior malreduction, Anterior Malreduction-associated Cutout the distal edge of the anterolateral cortex of the neck fragment slides into the canal of the diaphyseal fragment without load sharing [19,40]. Consequently, anterior reduction results in greater postoperative sliding and instability than anatomic reduction or posterior malreduction [17,28,36,38].…”