Views: 1 Author: Site Editor Publish Time: 2023-01-15 Origin: Site
Patellar fractures account for 1% of all trauma cases, and the current guideline recommended surgical procedure for the treatment of simple transverse patellar fractures with articular surface displacement is the tension band wire (TBW), which acts as an antitension device when the patellar (stretched) surface is subjected to bending forces.
However, complications of this procedure include wire internal fixation failure, infection, and wound dehiscence. In addition, the application of longitudinal wires can be very challenging, especially when clipping and burying the end of the wire in the patellar tendon and quadriceps tendon.
We designed 3 new techniques for fixation of transverse patella fractures using the same materials as standard TBW.
application of a figure-of-eight wire tension band after cross-driving the kerf pins.
longitudinal Kirschner pins and tension bands on both sides of the patella.
crossed Kirschner pins and lateral tension straps.
Therefore, the purpose of this biomechanical study was to compare 3 new fixation methods with the AO gold standard of wire tension banding.
Our first hypothesis was that the biomechanical integrity of the structures using crossed kerf pins should not deteriorate. Our second hypothesis was that lateral TBW would have similar results to standard TBW.
The simple transverse patellar fracture was truncated with a pendulum saw, and the 3 new techniques were then applied sequentially to separate knees to ensure that they could be constructed in a manner that represented a safe and reproducible procedure based on human anatomy (as shown in Figures 2 and 3). All were successfully achieved. A biomechanical device was used to test the biomechanical integrity of the 3 new techniques.
The results of all tests are shown in Figures 4 and 5.
The results showed that The configuration with the smallest total fracture gap displacement was the crossed kerf pins combined with lateral TBW (technique 3), with a mean fracture gap displacement of 0.43 mm (range 0.10-0.80 mm) after 100 cycles, well below the significant displacement of 2 mm.
The standard TBW combined with crossed kerf pins (technique 1) was the next best, with a mean fracture gap displacement of 0.61 mm (0.06 to 2.06 mm).
The mean applied load was 69.2 N. The AO standard was the worst, with a mean final fracture gap displacement of 1.72 mm (0.47 to 2.24 mm) and a mean applied load of 79.6 N. The AO standard was the worst, with a mean final fracture gap displacement of 1.72 mm (0.47 to 2.24 mm).
In terms of incremental displacements per cycle, both crossed kerf (techniques 1 and 3) structures show smaller displacements: 0.27 mm for both crossed kerf structures in the last cycle, compared to 0.41 mm and 0.60 mm for the standard AO and the longitudinal kerf structure with lateral TBW, respectively. this is evidence that the crossed kerf structure gives greater stiffness to the fracture under load This is evidence of the greater stiffness of the fracture gap under load given by the crossed Clinch pin structure.
The results suggest that reorienting the Kirschner pin into a cross-shaped structure away from the surrounding soft tissues, but keeping it in the same plane (i.e., 5 mm behind the anterior convex surface of the patella), does not negatively affect the biomechanical integrity, but rather positively affects the stability of the internal fracture fixation. Compared to longitudinal kerf pins, the cruciform structure appears to better stabilize the fracture block against anterior tension and may increase the compressive stress at the articular surface.
These data support our first hypothesis that crossed kyphotic pins are not a worse surgical procedure compared to longitudinal kyphotic pins, and in fact, both structures perform better than longitudinal kyphotic pins using crossed kyphotic pins. Our second hypothesis remains balanced, as it remains unclear from this study whether the results of lateral TBW are comparable to standard TBW.
This is the first biomechanical study to show superiority over the AO technique by simply reevaluating the surgical approach to TBW. There is no additional cost and the procedure may be faster because less exposure is required. The use of crossed kyphotic pins reduces damage to the surrounding soft tissues (mainly the quadriceps and patellar tendons). In addition, if surgeons are concerned about the quality of the covered soft tissues and the risk of irritation or protrusion of the anterior metal internal fixation, this study should reassure them that placing the TBW on either side of the patella avoids this and does improve overall fixation.
This study demonstrates that two new crossed kerf pin techniques are superior to the gold standard currently described by the AO in the treatment of simple transverse patella fractures.
