DYNAMIZATION OF LOCKING PLATE SYSTEMS TO OPTIMIZE INTERFRAGMENTARY MOTION FOR FRACTURE HEALING

The locking compression plate (LCP) supports bridge plating in complex fractures or osteoporotic bones. However, the high stiffness of traditional LCP constructs may lead to stress shielding and inhibit interfragmentary motion. This potentially leads to suboptimal callus formation and fracture healing, thus, increasing the risk of atrophic non-union. Increasing the working length and optimizing screw density are established means to mitigate for excessive bone-plate construct stiffness in a long bone model. However, there are limitations for an ideal construct due to fracture locality, patient anatomy, and peri-articular fractures. To address this issue, devices and strategies to enable controlled axial micro-motion have been developed, but engineering complexities have led to less mechanical predictability and device failures. Instead of modifications in plate or screw designs, the Singapore General Hospital (SGH) developed a novel dynamization technique involving modifications in drilling of the bone. Modified drilling of the near cortex to create an elongated figure-of-8 hole could theoretically allow for controlled movement of the fractured bony ends toward each other. This has similarities to the oblong holes for dynamic locking in intra-medullary devices. Standard drilling as for an insertion of a locking screw was performed. This was followed by drilling only the near cortex of the adjacent hole to the LCP hole with the same drill bit before screw insertion. Single tapping of the far cortex by the LCP screw preserved strength, preventing loss of screw purchase of the far cortex and pull-out of the plate-screw construct. This modified drilling technique was applied to near cortices adjacent to the fracture site, in the direction facing the fracture. Bone healing is a biological process and this lecture hopes to re-emphasise the importance of controlled interfragmentary motion in fracture healing. Clinical case examples illustrate paradoxical delays in bony union inadvertently observed when increased rigidity was introduced by strong locking plate systems to withstand various loading conditions. Solutions in plate or screws often require complex design and engineering modifications with potentially increased costs. Instead, innovation targeted toward minor screw hole modifications in established plating systems and development of jigs to guide precise modified drilling of the near-cortex could represent a cost effective means to optimize interfragmentary motion in modern anatomical LCP systems.