The Effects of Extramedullary Reduction in Unstable Intertrochanteric Fracture: A Biomechanical Study Using Cadaver Bone

Abstract

To prevent excessive sliding and subsequent fixation failures in unstable intertrochanteric fractures with posteromedial comminution, extramedullary reduction through overlapping of the anteromedial cortices of both proximal and distal fragments as a buttress has been introduced. The purpose of this study was to compare the biomechanical properties between two reduction methodsintramedullary reduction and extramedullary reduction-in treating unstable intertrochanteric fractures with posteromedial comminution (AO/OTA classification 31-A2.2). Materials and Methods: Eight pairs of frozen human cadaveric femora were used. The femora of each pair were randomly assigned to one of two groups: the intramedullary reduction group or the extramedullary reduction group. A single axial load-destruction test was conducted after cephalomedullary nailing. Axial stiffness, maximum load to failure, and energy absorbed to failure were compared between the two groups. Moreover, the pattern of mechanical failure was identified. Results: The mean axial stiffness in the extramedullary reduction group was 27.3% higher than that in the intramedullary reduction group (422.7 N/mm vs. 332.0 N/mm, p=0.017). Additionally, compared with the intramedullary reduction group, the mean maximum load to failure and mean energy absorbed to failure in the extramedullary group were 44.9% and 89.6% higher, respectively (2,848.7 N vs. 1,966.5 N, p=0.012 and 27,969.9 N•mm vs. 14,751.0 N•mm, p=0.012, respectively). In the intramedullary reduction group, the mechanical failure patterns were all sliding and varus deformities. In the extramedullary reduction group, sliding and varus deformities after external rotation were noted in 3 specimens, sliding and varus deformities after internal rotation were noted in 3 specimens, and medial slippage was noted in 2 specimens. Conclusion: In unstable intertrochanteric fractures with posteromedial comminution, the biomechanical properties of extramedullary reduction are superior to those of intramedullary reduction. Anteromedial cortex could be the proper buttress, despite a comminuted posteromedial cortex. It could help enhance the stability of the bone-nail construct.

Factors Associated with Mechanical Complications in Intertrochanteric Fracture Treated with Proximal Femoral Nail Antirotation

“…However, blade sliding was not blocked by cortical apposition in the intramedullary reduction group, and after that, cut-out occurred following varus malposition and rotation of proximal fragment. A previous biomechanical study demonstrated results similar to those in the extamedullary reduction group which had better resistance against axial loading compared with the intramedullary reduction group 17) .…”

“…For the prevention of mechanical complications, appropriate fracture reduction and blade position are essential 15 16) . Anatomical reduction or extramedullary reduction with medial cortical overlap known as the Wayne-County technique are associated with biomechanical stability compared with intramedullary reduction 17) . Intramedullary reduction in comminuted intertrochanteric fractures without posteromedial cortical support is prone to excessive sliding and varus malposition of proximal fragment leading to mechanical failures.…”

Utility of the 30° oblique tangential view for evaluation of anteromedial cortical reduction in reconstruction of intertrochanteric fractures

“…The authors believed that the Chang's criteria which emphasized anteromedial cortical contact was more reliable and effective than the Baumgaertner's criteria in predicting postoperative mechanical complications and worthy of clinical applications. Biomechanical [14] and clinical [15] researches have confirmed that the anteromedial cortical contact can not only share stress load from the internal fixation device (mechanical role), but also can promote close contact and fracture healing at the fracture sites (biological role), both of which are benefit for maintaining the normal femoral neck length and the neck-shaft angle.…”

Additional Reduction Screw Fixation Technique for Pertrochanteric Hip Fractures: A Novel Method to Prevent Excessive Sliding in Cephalomedullary Nail Surgery

“…The advantages of EM reduction have been recently reported in several clinical and biomechanical studies 1 2 4 5) . Additionally, several reduction techniques were noted to remove the head-neck fragment from the intramedullary (IM) space of the distal femoral shaft fragment 2 4 6) to achieve fracture reduction in the EM position.…”

“…One of the major reasons for treatment failure in pertrochanteric hip fracture surgeries is excessive sliding of the lag screw 1) . Extramedullary (EM) reduction, defined as the medial cortex of the head-neck fragment located outside of the medullary canal of the distal shaft fragment, has been introduced to prevent excessive postoperative sliding or failure of the lag screw in pertrochanteric fracture surgeries 1 2 3 4 5) . In EM reduction, the anteromedial cortical bone of the proximal fragment has bony contact with the distal fragment during sliding and theoretically plays the role of a buttress from the beginning, preventing excessive sliding and varus deformity of the proximal fragment 5) .…”