Modification of elastic stable intramedullary nailing with a 3rd nail in a femoral spiral fracture model - results of biomechanical testing and a prospective clinical study

Abstract

Background: Elastic stable intramedullary nailing (ESIN) is the standard treatment for displaced diaphyseal femoral fractures in children. However, high complication rates (10-50%) are reported in complex fractures. This biomechanical study compares the stiffness with a 3rd nail implanted to that in the classical 2C-shaped configuration and presents the application into clinical practice.

Methods: For each of the 3 configurations of ESIN-osteosynthesis with titanium nails eight composite femoral grafts (Sawbones®) with an identical spiral fracture were used: 2C configuration (2C-shaped nails, 2 × 3.5 mm), 3CM configuration (3rd nail from medial) and 3CL configuration (3rd nail from lateral). Each group underwent biomechanical testing in 4-point bending, internal/external rotation and axial compression.

Results: 2C and 3CM configurations showed no significant differences in this spiroid type fracture model. 3CL had a significantly higher stiffness during anterior-posterior bending, internal rotation and 9° compression than 2C, and was stiffer in the lateral-medial direction than 3CM. The 3CL was less stable during p-a bending and external rotation than both the others. As biomechanical testing showed a higher stability for the 3CL configuration in two (a-p corresponding to recurvation and 9° compression to shortening) of three directions associated with the most important clinical problems, we added a 3rd nail in ESIN-osteosynthesis for femoral fractures. 11 boys and 6 girls (2.5-15 years) were treated with modified ESIN of whom 12 were '3CL'; due to the individual character of the fractures 4 patients were treated with '3CM' (third nail from medial) and as an exception 1 adolescent with 4 nails and one boy with plate osteosynthesis. No additional stabilizations or re-operations were necessary. All patients achieved full points in the Harris-Score at follow-up; no limb length discrepancy occurred.

Conclusion: The 3CL configuration provided a significantly higher stiffness than 2C and 3CM configurations in this biomechanical model. These results were successfully transmitted into clinical practice. All children, treated by 3CL or 3CM according to the individual character of each fracture, needed no additional stabilization and had no Re-Do operations. As a consequence, at our hospital all children with femoral diaphyseal fractures with open physis are treated with this modified ESIN-technique.

Trial registration: ClinicalTrials.gov NCT01673048.

Figure 1

Radiograph (anterior-posterior view) of a 3CL femoral model with retrograde intramedullary nailing, showing two 3.5 mm titanium nails implanted in 2C shaped configuration and one additional 2.5 mm titanium nail implanted antero-lateral.

Figure 2

Radiograph (lateral view) of a 3CL femoral model with retrograde intramedullary nailing, showing two 3.5 mm titanium nails implanted in 2C shaped configuration and one additional 2.5 mm titanium nail implanted antero-lateral.

Figure 3

Torsional testing of a Sawbone® with a spiral fracture. The torsion tests were undertaken with two angular encoders at an angular speed of 20°/min; torsion was limited to 10°.

Figure 4

Radiographs of a left femur with a complex proximal spiroid fracture of the shaft. a: Fracture; b: X-Rays a-p and lateral after 1 month, c: X-Rays a-p and lateral after 4 months.

Figure 5

Radiograph (anterior-posterior view) of a 3CM configuration, 4 months postoperativly, diameter of the nails: 3 × 3.5 mm.

Figure 6

Radiograph (lateral view) of a 3CM configuration, 4 months postoperativly, diameter of the nails: 3 × 3.5 mm.