In Part 1 of this 2-part post, we went over the form and function of orthopedic screws. However, another common method of internal fixation you’ve surely seen (or will see) on your orthopedic rotations is plating. Plates come in many different varieties, serve many different functions, and are used in many different anatomic locations. In this article, we’ll go over some basic concepts of plates and their various functions in fracture fixation.

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Let’s start with what they’re made of. The most common plate materials are typically stainless steel or titanium. Stainless steel is a stiff, strong, and inexpensive metal that is easy to manufacture, making it the most popular choice by far. Titanium is more rarely used given its high price tag; however, it is arguably a better material due to its improved biocompatibility, greater fatigue resistance, and fewer negative health effects from metal ions released into the body. Because it is less stiff than steel, titanium has been shown to have less stress shielding effects as well. To understand why, recall that stress shielding is a loss of bone density that occurs when typical loading stresses are removed (think of it like “bone deconditioning,” similar to how your muscles lose their strength when you stop working out). Therefore, a super-stiff plate would take away more loading force than a less-stiff plate, leading to greater stress shielding effects.

Regardless of what type of material your plate is made from, it is critical that your screws are made of the same thing—otherwise, corrosion can occur. Furthermore, when applying a plate, it is important that it “fits” correctly. It should be the appropriate length, width, and thickness, and in some cases may need to be “contoured” or bent to fit the shape of the bone more closely, or apply optimal compression force.

So what are the different ways in which plates are used to fix fractures? (A point of clarification here: we’re going over different plate functions, not different types of plates.) One way is simply to act as additional support for a lag screw. We discussed principles of lag screw fixation in Part 1. While the screw itself might be all you need to achieve compression, additional bending and twisting forces on the bone might compromise its function. In these cases, it can be helpful to add a neutralization plate for extra support and protection. It is important to note that the plate does not apply any compression here—it’s just protecting the lag screw. Fibular fractures are often fixed this way.

Compression plates can be used to apply compression forces similar to a lag screw. In this case, the plate is placed across the fracture site, and non-locking screws are applied on either side of the fracture to compress the fragments together. A common type of plate used for this purpose is called the dynamic compression plate, or DCP. It has special holes that are oval-shaped with one end sloping downwards, allowing the screw to slide as it is tightened, applying a greater compressive force to pull the bone fragments together. If a screw is placed eccentrically, or at the side of the screw hole, it will slide downwards along the sloping plane as the screw is tightened; however, if it is placed in the neutral position, or in the center of the hole, it will not slide or provide compressive force. Another important thing to keep in mind when using a compression plate is that it is often necessary to prebend the plate to avoid gapping on the far cortex. If a flat plate is applied directly over the fracture site, it will act like a hinge to compress the fragments together on the near cortex while opening it further on the far cortex. Overbending the plate so there is a gap above the fracture site allows the forces on the near and far cortices to balance out.

Tension band plating can be used on fractures that have resulted from eccentric loading forces, and therefore have a “tension” side (with the fracture gap) and a “compression” side. The plate is applied to the tension side to convert the tension forces into compression forces.

In intra-articular fractures, a buttress plate is often used. Axial loading on the bone results in a shearing force that causes the fragmented piece to slide downwards. The buttress plate resists this shearing force and pushes the fragmented piece up against the bone. This technique is often called antiglide plating when used in diaphyseal fractures (as opposed to metaphyseal/intra-articular fractures).

Finally, a bridge plate is used to span comminuted fractures where it is too challenging to compress fragments together. Unlike the other fixation techniques, which rigidly fix the fracture in place to provide absolute stability, bridge plates provide relative stability; in other words, they allow more motion through the fracture site, and healing is achieved through callus formation.

Hopefully you found this article helpful in understanding some of the basics of orthopedic plates. If you want to learn more, check out the references below.

Written by: Jessa Fogel, MS4

References and further reading:

1. “Basic Principles of Plating.” AO Surgery Reference, https://surgeryreference.aofoundation.org/orthopedic-trauma/adult-trauma/basic-technique/basic-principles-of-plating#bridge-plate.
2. Ebraheim, Nabil. “Principles of Buttress Plating.” OrthopaedicPrinciples.com, https://orthopaedicprinciples.com/2018/02/principles-of-buttress-plating/.
3. Kim, Tiffany, et al. “Orthopedic Implants and Devices for Bone Fractures and Defects: Past, Present and Perspective.” Engineered Regeneration, vol. 1, 2020, pp. 6–18., https://doi.org/10.1016/j.engreg.2020.05.003.
4. “Orthopedic Hardware.” UW Radiology, 18 Apr. 2017, https://rad.washington.edu/about-us/academic-sections/musculoskeletal-radiology/teaching-materials/online-musculoskeletal-radiology-book/orthopedic-hardware/#:~:text=In%20general%2C%20there%20are%20compression,the%20tension%20side%20of%20bone.
5. Singh, Arun Pal. “Bone Plates in Orthopedics – Principle, Types and Uses.” Bone and Spine, 20 Nov. 2019, https://boneandspine.com/plating-and-different-modes-of-plating-in-orthopedics/#indications-for-use-of-bone-plates.
6. Singh, Arun Pal. “Tension Band Principle and Its Applications.” Bone and Spine, 19 Sept. 2018, https://boneandspine.com/tension-band-principle/.