Role of an additional third screw in the fixation of transverse patellar fracture with two parallel cannulated screw and anterior wire

Abstract

Background Two parallel cannulated screws along with an anterior wire to construct a tension band is a popular approach in transverse patellar fractures. However, the optimal screw proximity, either deep or superficial screw placements, remains controversial. Hence, a new concept of the addition of a third screw to form a triangular configuration along with the original two parallel screws was proposed in this study. Therefore, the biomechanical effect of the additional third screw on the stability of the fractured patella was investigated with finite element (FE) simulation. Methods An FE knee model including the distal femur, proximal tibia, and fractured patella (type AT/OTA 34-C) was developed in this study. Four different screw configurations, including two parallel cannulated screws with superficial (5-mm proximity) and deep (10-mm proximity) placements and two parallel superficial screws plus a third deep screw, and two parallel deep screws plus a third superficial screw, with or without the anterior wire, were considered for the simulation. Results Results indicated that the addition of a third screw increased stability by reducing the dorsal gap opening when two parallel screws were deeply placed, particularly on the fractured patella without an anterior wire. However, the third screw was of little value when two parallel screws were superficially placed. In the existence of two deep parallel screws and the anterior wire, the third screw reduced the gap opening by 23.5% (from 1.15 mm to 0.88 mm) and 53.6% (from 1.21 mm to 0.61 mm) in knee flexion 45° and full extension, respectively. Furthermore, in the absence of the anterior wire, the third screw reduced the gap opening by 73.5% (from 2 mm to 0.53 mm) and 72.2% (from 1.33 mm to 0.37 mm) in knee flexion 45° and full extension, respectively. Conclusion Based on the results, a third cannulated screw superficially placed (5-mm proximity) is recommended to increase stability and maintain contact of the fractured patella, fixed with two parallel cannulated screws deeply placed (10-mm proximity), particularly when an anterior wire was not used. Furthermore, the third screw deeply placed is not recommended in a fractured patella with two parallel superficial screws.

Comparative study of locking neutralization plate construct versus tension band wiring with a cannulated screw for patella fractures: experimental and finite element analysis

“…A key part of this analysis involved conducting a sensitivity analysis, wherein we carefully adjusted and examined the impact of various parameters, including material properties and boundary conditions. Furthermore, we aligned our model's predictions with clinical observations and existing biomechanical literature [ 17 , 35 , 36 ].…”

Biomechanical comparison of different screw-included angles in crossing screw fixation for transverse patellar fracture in level walking: a quasi-dynamic finite element study

“…Some specific systems with minimally invasive techniques, such as the cable-pin system, have been proposed to reduce post-surgery pain compared with conventional approaches [ 18 ]. In addition, many approaches with percutaneous screw fixation without the anterior wire, such as two parallel headless compression screws, two parallel full-thread screws, crossing screws, and triangular screw configurations, have been proposed recently [ 12 , 13 , 20 , 35 ]. All approaches satisfy the criteria of a minimally invasive technique.…”

“…According to the literature, more than half of those cases with patellar fracture accepted tension band wiring from 2003 to 2015, while the combined approach has increased recently [ 11 ]. The major advantage of the combined approach, such as cannulated screws along with an anterior wire, is its excellent stability [ 12 , 13 ]. Cannulated screws along with an anterior wire were also reported to be superior to tension band wiring in the literature [ 14 ].…”

“…However, the major disadvantage of cannulated screws with an anterior wire is delayed healing and pain after surgery due to damage to the soft tissue because of open surgery [ 15 – 17 ]. Hence, several studies have focused on minimally invasive surgery without the anterior wire and with a specific cable-pin system, two and three parallel headless compression screws, and full-thread screws to enhance the healing process and reduce pain [ 12 , 13 , 18 , 19 ].…”

Comparison of The Two Different Patella Fracture Fixation Technique: Finite Element Analysis

“…In addition, in the analysis, a contact definiton was made between the two materials at the fracture line and on the contact surfaces. A friction coefficient of 0.45 for bone-bone contact, 0.3 for bone to metal, and 0.3 for metal to metal contact has been defined [15,16]. Under all these loads, the amount of displacement at the fracture line, the average amount of pressure and the Von Miss stress on the implants were calculated.…”