Contouring Plates in Fracture Surgery

Indications and Pitfalls

Julius A. Bishop, MD; Sean T. Campbell, MD; Matthew L. Graves, MD; Michael J. Gardner, MD

Disclosures

J Am Acad Orthop Surg. 2020;28(14):585-595. 

In This Article

Plate Function and Contouring

Adjustments to plate shape are often made to optimize the implant's ability to perform a certain function. Therefore, the type of contouring needed in a specific situation will depend on the fixation strategy. There are situations in which perfectly contoured or undercontoured implants are desired. An overcontoured implant (ie, a plate that touches the bone centrally, but not at the proximal or distal end) will rarely be beneficial to the surgeon or the patient.

When compression plating, the plate is applied to a surface of the bone that does not correspond to the bone's central anatomic axis. As compression is generated through a straight plate, it will be eccentric and a torque will be generated, resulting in maximum compression at the near cortex and gapping at the far cortex[6,15] (Figure 2). To avoid this, the plate must initially be prebent so that it rests against the bone proximally and distally, but not along its entire length.[5,6,8,15–17] This is sometimes also referred to as pretensioning of the plate. When compression is applied in this situation, first the far cortex compresses, whereas the plate straightens (or bends back). Because the only contact initially between the fracture fragments is at the far cortex, the lever arm for back bending is long. Eventually, the plate straightens and the entire fracture plane comes into contact; the center of compression is located in the center of the bone, and the lever arm for back bending decreases.[15] The amount of force required to achieve this depends on the thickness of the bone and the angle of prebend, and can be calculated.[15] The amount of prebending required depends on the shape and thickness of the bone, as well as the length of the implant.[15] This is most commonly clinically relevant during compression plating of the humeral diaphysis.

Figure 2.

Radiograph demonstrating the results of inadequate undercontouring when compression plating. A, Single plane injury radiograph demonstrating a simple, transverse diaphyseal humerus fracture. B, The fracture was reduced and a compression plate selected for fixation. After the plate was fixed to the proximal segment and compression applied using the articulated tension device, an eccentric gap (*) was produced opposite the plate due to inadequate undercontouring. C, Final fluoroscopic image of the final construct demonstrating a small, but persistent fracture gap (#). One option to correct this is to remove the fixation and recontour the implant. In this case, the gap was accepted and the fracture went on to heal uneventfully.

A plate applied in buttress mode is meant to resist shear at the apex of a partial articular fracture and to generate compression, which requires the plate be undercontoured.[18] A nonlocking screw is placed at the axilla of the fracture to autocontour the implant, creating intimate fit with the metaphyseal segment, resulting in an absolute stability construct[6] (Figure 3). Antiglide plating follows similar principles, but instead of resisting shear at a partial articular fracture, it resists shortening under axial load.[19] A perfectly contoured or overcontoured implant will not be efficacious in this application. This technique requires a relatively flexible plate that will deform with the insertional torque of the screw. If the plate is too rigid and cannot be deformed, (ie, there is excessive undercontouring) it can generate shear at the fracture site, leading to malreduction. This can be prevented by increasing the amount of provisional fixation before inserting the apex screw, altering the contour of the implant, or using a more flexible implant (Figure 4). Common anatomic locations for buttress and antiglide plating include the posterior malleolus, the posterior wall of the acetabulum, and the tibial plateau.[6,16,20–23]

Figure 3.

Intraoperative fluoroscopic images (A-C) and six week follow-up radiograph (D) of a patient showing a low energy lateral tibial plateau fracture. A, The articular surface has been reduced and provisionally stabilized; the partial articular fracture apex is clearly visible. B, The partial articular fracture is reduced under direct visualization and stabilized with a second wire. A relatively flexible plate is positioned to buttress the fracture apex and is left undercontoured. C, A nonlocking screw is placed into the intact segment, autocontouring the implant, stabilizing the fracture, and generating compression. D, The final construct six weeks postoperatively. A second distal nonlocking screw was used for rotational stability. The articular surface was rafted using a second implant and nonlocking screws.

Figure 4.

Intraoperative fluoroscopic images demonstrating how an excessively undercontoured plate applied in buttress mode can lead to an articular malreduction. A, A stout precontoured plate was chosen to buttress this partial articular tibial plateau fracture. The initial plate and fracture fragment positions are shown on the left panel. On the right, a nonlocking screw was placed into the intact segment to create a buttress effect. However in this case, the plate was excessively undercontoured and lacked the flexibility to autocontour appropriately, resulting in shear forces across the fracture, proximal displacement of the articular fragment, and a malreduction (*). B, To address this, additional provisional fixation in the form of k-wires were placed proximally near the joint before placing the nonlocking screw at the fracture apex. This prevented proximal displacement of the articular fragment while compression was generated.

In neutralization or bridge plating, it is advantageous if the plate is contoured perfectly to the bone. This is important for several reasons. Stability in nonlocked plating requires adequate plate-bone friction which is facilitated by a good fit. Poor plate contour can also result in loss of reduction if the nonlocking screws pull the fracture fragments to a relatively rigid and nonanatomically contoured plate.[5,6,24] Poorly contoured implants can also be prominent and symptomatic. This is particularly relevant in subcutaneous locations, such as the clavicle, proximal ulna, distal fibula, and in locations where the implant will be adjacent to sensitive soft-tissue structures as in the volar or dorsal distal radius.[25–29] Finally, a poorly contoured neutralization plate can "overpower" the lag screw(s), resulting in the loss of reduction because the bone is pulled to the plate.

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