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. 2020 Dec 10:27:17-24.
doi: 10.1016/j.jot.2020.10.003. eCollection 2021 Mar.

Comminuted patellar fractures: The role of biplanar fixed angle plate constructs

Mauricio Kfuri  1 , Igor Escalante  2 , Clemens Schopper  2   3 , Ivan Zderic  2 , Karl Stoffel  4 , Christoph Sommer  5 , Feras Qawasmi  2   6 , Matthias Knobe  7 , Geoff Richards  2 , Boyko Gueorguiev  2
Affiliations

Comminuted patellar fractures: The role of biplanar fixed angle plate constructs

Mauricio Kfuri et al. J Orthop Translat. .

Abstract

Background: Comminuted patellar fractures represent a challenging clinical problem. Treatment aims to restore the integrity of the extensor mechanism and the congruity of patellofemoral joint. Controversy exists regarding the ideal fixation method. Metallic constructs aiming to convert pulling forces on the anterior aspect of the patella into compression forces across the fracture site are the standard of care. More recently, low profile plates have been described in the management of comminuted patellar fractures. The aims of this study were to (1) develop a novel unstable patellar fracture model and (2) to compare biomechanically three different constructs for fixation comminuted patellar fractures. We hypothesized that an orthogonal biplanar disposition of the screws within an anteriorly placed locking plate provides the best biomechanical properties in the management of comminuted fractures.

Methods: Six-part complex AO 34-C3 patella fractures were simulated in 18 human cadaveric knees by means of osteotomies including comminution around the distal patellar pole. The specimens were randomly assigned to 3 fixation techniques (n ​= ​6) for either anterior plating, antero-lateral plating, or tension band wiring (TBW). Biomechanical testing was performed over 5000 cycles in active extension and passive flexion, followed by ultimate destructive quasi-static testing. Interfragmentary movements were captured by means of optical motion tracking.

Results: Displacement between the proximal and distal medial patella fragments was lower after anterior plating compared to both antero-lateral plating (P ​= ​0.084) and TBW (P ​< ​0.001). Moreover, displacement between the proximal and distal lateral fragments was significantly lower after anterior plating compared to both other techniques (P ​≤ ​0.032). In addition, it was significantly lower for antero-lateral plating versus TBW (P ​< ​0.001). Rotation around the medio-lateral axis between the proximal and distal medial fragments was significantly lower after anterior plating compared to TBW (P ​= ​0.017).

Conclusions: Anterior mesh plating with biplanar placement of locking screws provides superior stability for fixation of comminuted patellar fractures when compared to both antero-lateral mesh plating and TBW. The latter is associated with considerably inferior performance.

Keywords: Biomechanics; Comminuted fracture; Mesh plate; Patella; Tension band wiring.

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Conflict of interest statement

The authors have no conflicts of interest to disclose in relation to this article.

Figures

Figure 1
Figure 1
Cutting jig for a standardized patellar anterior wedge resection. The cutting guide was obtained by 3D printing and fits the anterior surface of the patella. It is fixed to the bone with four Kirschner wires. It has slots that allow for a reproducible 15-degree anterior wedge resection.
Figure 2
Figure 2
Development of a comminuted patellar fracture. A: Resection of the anterior wedge and creation of a transverse fracture; B: Sagittal fracture of the superior pole; C: Sagittal and coronal fractures of the inferior pole; D: Axial view of the six main patellar fragments.
Figure 3
Figure 3
Visualization of tension band wiring (TBW); a) photograph of an instrumented specimen; b) anteroposterior and c) lateral radiograph projections of the instrumented specimen.
Figure 4
Figure 4
Visualization of anterolateral plating; a) photograph of an instrumented specimen; b) anteroposterior and c) lateral radiograph projections of the instrumented specimen.
Figure 5
Figure 5
Visualization of the anterior plating; a) photograph of an instrumented specimen; b) anteroposterior and c) lateral radiograph projections of the instrumented specimen.
Figure 6
Figure 6
Specimen preparation and set up for biomechanical testing.
Figure 7
Figure 7
Modes of catastrophic failure after cyclic testing for the three fixation constructs a) anterior plating and b) anterolateral plating, and c) TBW.
Figure 8
Figure 8
Interfragmentary rotation around the medio–lateral axis between the superior and inferior a) lateral and b) medial fragments in terms of mean and SD over the seven investigated time points for each fixation technique separately.
Figure 9
Figure 9
Interfragmentary longitudinal displacement between the superior and inferior a) lateral and b) medial fragments in terms of mean and SD over the seven investigated time points for each fixation technique separately.
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