The one-third tubular plate comes only in the 3.5 mm size. Its complements the 4.5 mm system in the semi-tubular plate. The one-third tubular plate can be accessible in either stainless steel or titanium. As the thickness of the plate is only 1.0 mm, its ability is slightly limited. However, it can be beneficial in parts with minimal soft-tissue covering, like the lateral malleolus, the olecranon and the distal end of the ulna. Each hole is surrounded by a small collar to prevent the spherical screw heads from penetrating the plate and making cracks in the near cortex. The oval shape of each hole enables a certain degree of eccentric screw placement to produce fracture compression.
One-third tubular plate
The collar around the hole of the one-third tubular plate avoids the screw head from protruding and safeguards contact of plate-bone. Without a collar, the bone screw head protrudes from the plate, preventing good fixation. Because of the collar, the plate-screw bone coupling is improved. The oval shape of each hole enables a certain degree of eccentric placement of screw to create fracture compression, which may be augmented by pulling at one end of the plate.
Reconstruction plates have deep notches on the edge of the plate. These notches are positioned between the holes and allow accurate contouring of the plate in all planes. There are 2 plate sizes available for use with 3.5 mm Cortical screws and another which has 4.5 mm cortex screws. The plate is not as strong as the LC-DCP as well as can be further weakened by heavy contouring, so sharp bends in any direction should be prevented. The holes are oval to enable dynamic compression. These orthopedic plates are particularly beneficial in fractures of bone with complex 3-D geometry, like the clavicle, acetabulum, pelvis, distal humerus, and distal tibia. Special instruments should be utilized for the contouring of these plates.
There are special bending pliers for the reconstruction plates. Bending irons are accessible to twist the plate.
Design and biomechanics
The most recent progress in plate technology is the locking plate. The main change is the coupling between the plate and the screw head, which leads to some unique biomechanical properties. The locking compression plate (LCP) may be applied to function like any other plate, such as it offers protection, bridging, compression, and so on. whereas other plates, like the less invasive stabilization system (LISS), act as internal fixators and may only offer a function of bridging. Schematic demonstration of the LCP combination hole, enabling conventional and locking head screws to be positioned in the same orthopedic implant.
Conically threaded undersurfaces of the screw heads fit matching threads in the bone plate, enabling the screws to effectively bolt into the plate and bone. This has important biomechanical implications. Because of angular-stable screws, the construction does not need the plate to be compressed to the bone for stability.
Locking plates may be utilized as internal fixators or orthopedic implants: Ideally, there is no contact with the periosteum. This offers relative stability and maximizes the possible blood supply to enable indirect, rapid healing by callus formation.
Angular stable screws also enable the load to be evenly distributed along the whole construction, rather than being concentrated at a single bone-screw interface, that is a difference to traditional plates. Fixation failure with traditional plates mostly initiates at one screw, which can then propagate to other screws. As a similar phenomenon does not occur with locked plates, they can be specifically useful in osteoporotic bone. Furthermore, the screw-plate locking mechanism functions as a surrogate cortex, occasionally precluding the need for bi-cortical screws. This enables the insertion of mono-cortical locking screws by percutaneous aiming arms without precise measurement of screw length.
As a conventional screw head may toggle during loading, energy is degenerate at the bone-screw interface farthest from the fracture. Energy is focused at this level, shielding additional bone screws from load initially. In locking bone plates, the angular-stable screws (LHS) avoid load concentration at a single bone-screw interface, by distributing the load more evenly.
Orthopedic devices like the LISS and other special plates have round threaded holes to accommodate a single threaded screw. Though, the LCP, as well as specific regions of some specialty plates, comprise of combination holes, which enable insertion of either locking head screws or conventional screws into the same hole. The combination hole comprises of a dynamic compression unit for the insertion of conventional screws as well as a threaded part for the insertion of locking head screws.
The LCP is versatile and may be utilized as an internal fixator to offer any of the biochemical functions of a plate as well as can also be utilized as a reduction tool.