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Improving stability of elastic stable intramedullary nailing in a transverse midshaft femur fracture model: biomechanical analysis of using end caps or a third nail.

Rapp M, Gros N, Zachert G, Schulze-Hessing M, Stratmann C, Wendlandt R, Kaiser MM - J Orthop Surg Res (2015)

Bottom Line: The modification with end caps did not improve the stiffness in any direction.The configuration with a third nail provided a significantly higher stiffness than the classical 2C configuration as well as the modification with end caps in this biomechanical model.This supports the ongoing transfer of the additional third nail into clinical practice to reduce the axial deviation occurring in clinical practice.

View Article: PubMed Central - PubMed

Affiliation: Department of Paediatric Surgery, Hospital of Kassel, Mönchebergstr. 41-43, 34125, Kassel, Germany.

ABSTRACT

Background: Elastic stable intramedullary nailing (ESIN) is accepted widely for treatment of diaphyseal femur fractures in children. However, complication rates of 10 to 50 % are described due to shortening or axial deviation, especially in older or heavier children. Biomechanical in vitro testing was performed to determine whether two modified osteosyntheses with end caps or a third nail could significantly improve the stability in comparison to classical elastic stable intramedullary nailing in a transverse femur fracture model.

Methods: We performed biomechanical testing in 24 synthetic adolescent femoral bone models (Sawbones®) with a transverse midshaft (diaphyseal) fracture. First, in all models, two nails were inserted in a C-shaped manner (2 × 3.5 mm steel nails, prebent), then eight osteosyntheses were modified by using end caps and another eight by adding a third nail from the antero-lateral (2.5-mm steel, not prebent). Testing was performed in four-point bending, torsion, and shifting under physiological 9° compression.

Results: The third nail from the lateral showed a significant positive influence on the stiffness in all four-point bendings as well as in internal rotation comparing to the classical 2C configuration: mean values were significantly higher anterior-posterior (1.04 vs. 0.52 Nm/mm, p < 0.001), posterior-anterior (0.85 vs. 0.43 Nm/mm, p < 0.001), lateral-medial (1.26 vs. 0.70 Nm/mm, p < 0.001), and medial-lateral (1.16 vs. 0.76 Nm/mm, p < 0.001) and during internal rotation (0.16 vs. 0.11 Nm/°, p < 0.001). The modification with end caps did not improve the stiffness in any direction.

Conclusions: The configuration with a third nail provided a significantly higher stiffness than the classical 2C configuration as well as the modification with end caps in this biomechanical model. This supports the ongoing transfer of the additional third nail into clinical practice to reduce the axial deviation occurring in clinical practice.

No MeSH data available.


Related in: MedlinePlus

Sawing of a standard midshaft transverse fracture exactly in the middle of the distance between the condyles and trochanter minor (AO paediatric comprehensive classification of long bone fractures: 32D41 [25]; LiLa classification for paediatric long bone fractures: 3.2.s.3.2. [26])
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Fig1: Sawing of a standard midshaft transverse fracture exactly in the middle of the distance between the condyles and trochanter minor (AO paediatric comprehensive classification of long bone fractures: 32D41 [25]; LiLa classification for paediatric long bone fractures: 3.2.s.3.2. [26])

Mentions: Biomechanical testing was performed using 24 synthetic adolescent-sized composite femoral models (fourth generation, Sawbones®, Malmö, Sweden). The whole setting followed in principle the standardised protocol of previous studies [18]. The femoral model measured 45 cm in length, with a central canal diameter of 10 mm. Each standard midshaft transverse fracture was sawed exactly in the middle of the distance between condyles and trochanter minor (AO paediatric comprehensive classification of long bone fractures: 32D41 [25]; LiLa classification for paediatric long bone fractures: 3.2.s.3.2. [26]) (Fig. 1). The fracture parameters were measured before use in the biomechanical model. The distal femoral entry portals (medial/lateral) were created by a 5-mm drill 2 cm proximal to the virtual physis (Fig. 2). In eight specimens, a further entry point for a third nail was drilled 2 cm cranial anterior of the lateral entry point (Fig. 3). All 24 specimens underwent retrograde elastic stable intramedullary nailing with two 3.5-mm steel nails (Santech Nord, Schneverdingen, Germany), equally prebent to 40°, by the same paediatric surgeon specialised in paediatric traumatology (MMK), with special emphasis on broad contact of the fragments of the transverse fracture. Due to the conception of the composite femur, the ends of the nails were just inferior to the greater trochanter (Fig. 4); fluoroscopic imaging confirmed the correct configuration and position.Fig. 1


Improving stability of elastic stable intramedullary nailing in a transverse midshaft femur fracture model: biomechanical analysis of using end caps or a third nail.

Rapp M, Gros N, Zachert G, Schulze-Hessing M, Stratmann C, Wendlandt R, Kaiser MM - J Orthop Surg Res (2015)

Sawing of a standard midshaft transverse fracture exactly in the middle of the distance between the condyles and trochanter minor (AO paediatric comprehensive classification of long bone fractures: 32D41 [25]; LiLa classification for paediatric long bone fractures: 3.2.s.3.2. [26])
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4528722&req=5

Fig1: Sawing of a standard midshaft transverse fracture exactly in the middle of the distance between the condyles and trochanter minor (AO paediatric comprehensive classification of long bone fractures: 32D41 [25]; LiLa classification for paediatric long bone fractures: 3.2.s.3.2. [26])
Mentions: Biomechanical testing was performed using 24 synthetic adolescent-sized composite femoral models (fourth generation, Sawbones®, Malmö, Sweden). The whole setting followed in principle the standardised protocol of previous studies [18]. The femoral model measured 45 cm in length, with a central canal diameter of 10 mm. Each standard midshaft transverse fracture was sawed exactly in the middle of the distance between condyles and trochanter minor (AO paediatric comprehensive classification of long bone fractures: 32D41 [25]; LiLa classification for paediatric long bone fractures: 3.2.s.3.2. [26]) (Fig. 1). The fracture parameters were measured before use in the biomechanical model. The distal femoral entry portals (medial/lateral) were created by a 5-mm drill 2 cm proximal to the virtual physis (Fig. 2). In eight specimens, a further entry point for a third nail was drilled 2 cm cranial anterior of the lateral entry point (Fig. 3). All 24 specimens underwent retrograde elastic stable intramedullary nailing with two 3.5-mm steel nails (Santech Nord, Schneverdingen, Germany), equally prebent to 40°, by the same paediatric surgeon specialised in paediatric traumatology (MMK), with special emphasis on broad contact of the fragments of the transverse fracture. Due to the conception of the composite femur, the ends of the nails were just inferior to the greater trochanter (Fig. 4); fluoroscopic imaging confirmed the correct configuration and position.Fig. 1

Bottom Line: The modification with end caps did not improve the stiffness in any direction.The configuration with a third nail provided a significantly higher stiffness than the classical 2C configuration as well as the modification with end caps in this biomechanical model.This supports the ongoing transfer of the additional third nail into clinical practice to reduce the axial deviation occurring in clinical practice.

View Article: PubMed Central - PubMed

Affiliation: Department of Paediatric Surgery, Hospital of Kassel, Mönchebergstr. 41-43, 34125, Kassel, Germany.

ABSTRACT

Background: Elastic stable intramedullary nailing (ESIN) is accepted widely for treatment of diaphyseal femur fractures in children. However, complication rates of 10 to 50 % are described due to shortening or axial deviation, especially in older or heavier children. Biomechanical in vitro testing was performed to determine whether two modified osteosyntheses with end caps or a third nail could significantly improve the stability in comparison to classical elastic stable intramedullary nailing in a transverse femur fracture model.

Methods: We performed biomechanical testing in 24 synthetic adolescent femoral bone models (Sawbones®) with a transverse midshaft (diaphyseal) fracture. First, in all models, two nails were inserted in a C-shaped manner (2 × 3.5 mm steel nails, prebent), then eight osteosyntheses were modified by using end caps and another eight by adding a third nail from the antero-lateral (2.5-mm steel, not prebent). Testing was performed in four-point bending, torsion, and shifting under physiological 9° compression.

Results: The third nail from the lateral showed a significant positive influence on the stiffness in all four-point bendings as well as in internal rotation comparing to the classical 2C configuration: mean values were significantly higher anterior-posterior (1.04 vs. 0.52 Nm/mm, p < 0.001), posterior-anterior (0.85 vs. 0.43 Nm/mm, p < 0.001), lateral-medial (1.26 vs. 0.70 Nm/mm, p < 0.001), and medial-lateral (1.16 vs. 0.76 Nm/mm, p < 0.001) and during internal rotation (0.16 vs. 0.11 Nm/°, p < 0.001). The modification with end caps did not improve the stiffness in any direction.

Conclusions: The configuration with a third nail provided a significantly higher stiffness than the classical 2C configuration as well as the modification with end caps in this biomechanical model. This supports the ongoing transfer of the additional third nail into clinical practice to reduce the axial deviation occurring in clinical practice.

No MeSH data available.


Related in: MedlinePlus