Effect of distal interlocking of a cephalomedullary femoral nail on peri-implant fractures: A sawbone biomechanical analysis.

Background: A large proportion of hip fractures involve inter-trochanteric fractures which are managed by cephalomedullary nails. There is ongoing debate about the advantages and disadvantages of locked versus unlocked long cephalomedullary femoral nails in the treatment of intertrochanteric fractures. The objectives of our study are to evaluate the biomechanical effects of a distal interlocking bolt on the type of peri-implant fractures in a healed intertrochanteric fracture with long cephalomedullary nail fixation.
Methods: 20 femoral sawbone specimens were prepared with the TFN-ADVANCED Proximal Femoral Nailing System (TFNA) and divided into 2 groups: locked and unlocked. The specimens were subjected to axial loading force until failure. Compressive forces, strain and fracture patterns were compared between the 2 groups.
Results: There was no significant difference in the mean load to failure of the unlocked specimens compared to locked specimens. However, there was significant difference in the mean compressive stress at the time of failure with the unlocked specimen (1.79±0.17 MPa) compared to the locked group (1.92±0.05 MPa) (p < 0.05). Video review analysis showed unlocked specimens consistently having basi-cervical type peri-implant fractures while locked specimens showed complex, compound fractures of the head-neck region with 2 or more fracture propagation points.
Conclusion: Distal-locked long cephalomedullary nails in a healed intertrochanteric fracture model are able to tolerate higher compressive stress at the point of failure but demonstrate more complex peri-implant fracture patterns in the femoral head-neck region as compared to unlocked specimens.
Competing Interests: Declaration of Competing Interest This manuscript is original research and has not been previously published, nor submitted for publication elsewhere. There are no conflicts of interests between authors related to this paper. SSS and HRBAR obtained the SingHealth Musculoskeletal Sciences ACP Pitch-for-fund grant which contributed funding for the study. All authors contributed to the intellectual development of this paper and approved of the final manuscript. Synthes Singapore Pte Ltd contributed both implants and surgical sets used in the project. No honoraria was granted in support of this project and all authors do not have any employment, consultancy or stock ownership with the company.
(Copyright © 2022. Published by Elsevier Ltd.)