Rationale of Intramedullary Nailing

Recent developments on intramedullary nailing: a biomechanical perspective

“…The friction and an elastic union between the implant and the inner medullary cavity were responsible for limiting bone motion in relation to the nail. The resistance to rotation and axial motion at the fracture site was guaranteed by interdigitating of the fracture fragments and endosteal contact with the nail above and below the fracture site . Its relative simplicity—no need for external fixation, high joint mobility, early ambulation (patients were out of bed in a matter of days rather than months)—and the overall good results achieved comparatively to the frequent intervention of traction (or “extension” as it was often called) followed by casting guaranteed the worldwide success of Küntcher's nails …”

“…In the early 1980s, there was an awareness of the benefits of replacing slotted nail designs with nonslotted ones. This important decision was made on the basis of the limitations identified in the slotted design, such as the low torsional strength of the implant and the fragility of the stress concentration zone (i.e., the transition zone between the nonslotted and slotted portions, which is characterized by material thickness variation) …”

“…Such effect was perceived as a potential problem and was assumed to cause delayed recovery and nonunion cases . In an attempt to reduce the stress‐shielding effect and promote healing, Grosse and Kempf emphasized nail dynamization , where a fixed end is responsible for ensuring fracture rotational stability, while the opposite extremity is free to slide slightly inside the bone . In the materials field, a strong novelty was also introduced in the 1990s with the adoption of titanium, a new material competing with the until then commonly used AISI 136 LVM ASTM F138 stainless steel (generally known as medical‐grade stainless steel) .…”

“…In the materials field, a strong novelty was also introduced in the 1990s with the adoption of titanium, a new material competing with the until then commonly used AISI 136 LVM ASTM F138 stainless steel (generally known as medical‐grade stainless steel) . Today, both materials are widely accepted; however, there is a preferential tendency for titanium alloy owing to its attractive mechanical properties (see Table ), such as Young's modulus closer to the intact diaphyseal cortical bone, higher fatigue strength and yield strength, and the fact that it is biocompatible and shows less magnetic resonance imaging interference than that observed for stainless steel implants . Today, the increased preference for limited reaming or “ream‐to‐fit” techniques allowed the adoption of anatomically smaller diameter nails, which in static locked mode provide a sufficiently large interfragmentary motion that favors callus development .…”

“…The resistance to rotation and axial motion at the fracture site was guaranteed by interdigitating of the fracture fragments and endosteal contact with the nail above and below the fracture site. 3,[12][13][14][15] Its relative simplicity-no need for external fixation, high joint mobility, early ambulation (patients were out of bed in a matter of days rather than months)-and the overall good results achieved comparatively to the frequent intervention of traction (or "extension" as it was often called) followed by casting guaranteed the worldwide success of Küntcher's nails. 3,16,17 Another turning point in the history of intramedullary nail emerged in the 1950s with the introduction of flexible intramedullary reamers, again through Küntscher progressive thinking.…”