Recent developments on intramedullary nailing: a biomechanical perspective

Abstract

Combining contributions from engineering and medicine, we highlight the biomechanical turning points in the historical evolution of the intramedullary nailing stabilization technique and discuss the recent innovations concerning increase in bone-implant system stability. Following the earliest attempts, where stabilization of long bone fractures was purely based on intuition, intramedullary nailing evolved from allowing alignment and translational control through press-fit fixation to current clinical widespread acceptance marked by the mechanical linkage between nail and bone with interlocking screws that allow alignment, translation, rotation, and length control. In an attempt to achieve an optimum interfragmentary mechanical environment, recent improvements considered the impact of different biomaterials on bone-implant stiffness. Another strategy considered the increase in the structural stability through the reduction of the number of movements between the different components that constitute the bone-implant system. Intramedullary nail improvements will most likely benefit from merging mechanics and fracture-healing biology by combining surface engineering with sensor tools associated with the innovative progress in wireless technology and with bone-healing biological active agents. Future research should aim at better understanding the ideal mechanobiological environment for each stage of fracture healing in order to allow for intramedullary nail design that satisfies such requirements.

Healing assessment of fractured femur treated with an intramedullary nail

“…10 Using this device, they were able to obtain strain information to determine the load transfer from the IM Nail to the bone. Rosa et al 11 articulated the potential of an instrumented IM Nail for healing assessment purpose. They stated that the on-going sensor evolution is required to reduce the size of invasive nature of the instrumentation.…”

Management of lower limb fractures in patients with spinal cord injuries

“…However, modern improvements in intramedullary nail design and materials, including the advent of non‐slotted, reamed titanium alloy nails with interlocking screws and retrograde technique have expanded the indications for fixation, allowing for very proximal and distal metaphyseal fractures around the knee to be adequately stabilized . Specific biomechanical properties offered by intramedullary devices such as load sharing, preservation of soft tissue envelopes and greater torsional rigidity are advantageous for fixation in osteoporotic bone, while quicker surgical time and smaller incisions confers benefits of reduced wound complications in SCI patients . Chin et al .…”

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“…An understanding of the importance of stability and mechanical control at the whole bone level has been around for hundreds of years, particularly in the area of fracture healing [13,25,26]. Knothe et al presented a detailed account of the historical evolution of intramedullary fixation devices [25], which will briefly be summarized in part here.…”

“…Therefore, a contact fixated by static compression can lose its stability once the bone resorption takes place in these high-risk patients. Bone resorption can lead to gap formation, resulting in loads being carried by implant hardware and stress shielding of bone, eventually causing hardware fatigue failure [24,26]. As even 3rd generation IM nails with internal compression may lose a high percentage of compression intraoperatively [40], it is possible that much more could be lost during the following weeks and months of the fusion process.…”