Stiffness Modulation of Locking Plate Constructs Using Near Cortical Slotted Holes: A Preliminary Study

Abstract

Purposeful stiffness modulation in fracture fixation is critical to facilitate uneventful fracture healing. Converting near cortical holes to slots allowed selective axial stiffness adjustment without sacrificing fixation stability under cyclic loading. With further refinement, this simple modification of standard implant application may allow the surgeon to decrease the modulus mismatch between plating constructs and bone to decrease the risk of fixation failure.

Plating of Metacarpal Fractures with Locked or Nonlocked Screws, a Biomechanical Study: How Many Cortices are Really Necessary?

“…A more recent view of locking plate technology shows an environment that is too stiff to reliably promote bone healing if there is not sufficient compression and bony contact at the time of plate application. Recent studies suggest that locked plate constructs suppress interfragmentary motion to a level that is insufficient to promote healing, especially at the cortex adjacent to the plate [3,12].…”

“…This model has been used previously to simulate comminuted metacarpal fractures [12]. The specimens were then fixed with a seven-hole 2.0-mm LCP stainless steel straight plate (Synthes, West Chester, PA, USA) and either six bicortical nonlocking screws or four bicortical locking screws.…”

Effects of Construct Stiffness on Healing of Fractures Stabilized with Locking Plates

“…Far Cortical Locking Reduces Construct Stiffness While Maintaining Construct Strength S everal strategies to reduce the stiffness of locked-plate constructs have been proposed, including the use of thinner plates, increasing the plate elevation from the bone surface, using slotted holes in the near cortex, and increasing the plate span 14,[42][43][44] . However, either a reduction in stiffness is gained at the cost of construct strength or stiffness remains insufficient to promote bone-healing by callus formation.…”

“…Biomechanical studies have suggested that locked-plate constructs are stiff and suppress interfragmentary motion to a level that may be insufficient to reliably promote secondary fracture-healing 1,[13][14][15] . Recent clinical studies substantiate the concern that the inherently high stiffness of locked-plate constructs suppresses callus formation, contributing to a nonunion rate of up to 19% seen with periarticular locking plates 16,17 .…”

Clinical and radiologic outcomes associated with the use of dynamic locking screws (DLS) in distal tibia fractures

“…Several innovations have sought to reduce axial stiffness on the plate side [3,9]. In the context of these concerns, a completely new screw concept and design was developed.…”