Biomechanical evaluation of femoral neck fracture osteosynthesis

Bone geometry, density, and thickness of the cortical layer of the femoral neck (FN) contribute to the mechanical strength in osteosythesis of femoral neck fractures (FNF) in young adults. The available techniques for fracture fixation of the FN are reviewed with respect to the biomechanical stability.

A biomechanical study of the osteosynthesis stability of the FNF with three cannulated screws was carried out using synthetic models of the proximal part of the femoral bone (FB). The experimental models were divided into 4 groups. Each group related to the configuration of screws in the FN. The vertical and horizontal FNF stability was assessed using two series of load. In series I, models were loaded with forces in the longitudinal axis to the FB and in series II, forces acted in the perpendicular direction to the FB axis. The loading forces were evaluated when the displacement of 2 mm fragments was achieved. The highest stability strengths were obtained in group I in the both series ‒ 1898 N with a vertical load and 1046 N with a horizontal load. Further, in decreasing order, the results of stability were obtained in groups II, III and IV.

In this study, it was found that the consideration of the position of screws according to architectonics of the FN is crucial for fragment stability. The triangular position of screws with three points of contact with the compact bone ensures the maximum stability of the construct in osteosynthesis of the FN fractures, which is comparable to the normal walking load conditions.

We hypothesize that osteosynthesis of FN fractures with three screws in a triangular manner could provide a better stability when inserted into the dense tissues of the proximal FB with relation to bone architectonics. To ensure a maximum stability, each screw should have three points of contact with the compact bone – the lateral cortical wall of the subtrochanteric region of the FB, the inner wall of the FN, and the compact part of the FB head. New triangular configuration of screws’ placement could have a better neutralization of share forces in FN fractures.

1. Loskutov A. E., Oleinik A. E., Bredikhin A. V. Total hip arthroplasty for medial fractures of the femoral neck. Zbіrnik naukovikh prats’ spіvrobіtnikіv NMAPO іmenі P. L. Shupika. Tom 9, kniga 1 [Collection of scientific works of NMAPE named after P. L. Shupik. Vol. 9, book 1]. Kiev, 2000, pp. 51–54 (in Russian).

2. Klimovitskii V. G., Kanzyuba M. A., Kanzyuba A. I. Analysis of changes in the stress-strain state of the femoral neck during its osteosynthesis with screws. Ukraїns’kii medichnii al’manakh [Ukrainian medical almanac], 2005, suppl. 2, pp. 77–80 (in Russian).

3. Parker M. J., Blundell C. Choice of implant for internal fixation of femoral neck fractures. Meta-analysis of 25 randomised trials including 4,925 patients. Acta Orthopaedica Scandinavica, 1998, vol. 69, no. 2, pp. 138–143. https://doi.org/10.3109/17453679809117614

4. Spangler L., Cummings P., Tencer A. F., Mueller B. A., Mock C. Biomechanical factors and failure of transcervical hip fracture repair. Injury, 2001, vol. 32, no. 3, pp. 223–228 https://doi.org/10.1016/s0020-1383(00)00186-8

5. Lindequist S., Wredmark T., Eriksson S. A., Samnegård E. Screw positions in femoral neck fractures. Comparison of two different screw positions in cadavers. Acta Orthopaedica Scandinavica, 1993, vol. 64, no. 1, pp. 67–70. https://doi.org/10.3109/17453679308994532

6. Parker M. J., Dynan Y. Is Pauwels classification still valid? Injury, 1998, vol. 29, no. 7, pp. 521–523. https://doi.org/10.1016/s0020-1383(98)00118-1

7. Augat P., Bliven E., Hackl S. Biomechanics of femoral neck fractures and implications for fixation. Journal of Orthopaedic Trauma, 2019, vol. 33, suppl. 1, pp. S27–S32. https://doi.org/10.1097/BOT.0000000000001365

8. Bonnaire F. A., Weber A. T. Analysis of fracture gap changes, dynamic and static stability of different osteosynthetic procedures in the femoral neck. Injury, 2002, vol. 33, suppl. 3, pp. 24–32. https://doi.org/10.1016/s0020-1383(02)00328-5

9. Mayhew P. M., Thomas C. D., Clement J. G., Loveridge N., Beck T. J., Bonfield W., Burgoyne Ch. J., Reeve J. Relation between age, femoral neck cortical stability, and hip fracture risk. Lancet, 2005, vol. 366, no. 9480, pp. 129–135. https://doi.org/10.1016/S0140-6736(05)66870-5

10. Samsami S., Augat P., Rouhi G. Stability of femoral neck fracture fixation: a finite element analysis. Proceedings of the Institution of Mechanical Engineers, Part H: Journal of Engineering in Medicine, 2019, vol. 233, no. 9, pp. 892–900. https://doi.org/10.1177/0954411919856138

11. Popov V. A., Vadzyuk N. S., Ivanchenko O. O. X-ray anthropometric examination of the femoral neck in minimally invasive osteosynesis planning. Ukraїns’kii zhurnal telemeditsini ta medichnoї telematiki [Ukrainian journal of telemedicine and medical telematics], 2009, vol. 7, no. 2, pp. 219–223 (in Ukrainian).

12. Popov V. A., Vadzyuk N. S. Structural features of the femoral neck according to computed tomography. Lіtopis travmatologії ta ortopedії [Chronicle of traumatologу and orthopedics], 2010, no. 1–2, pp. 65–69 (in Ukrainian).

13. Popov V. A., Vadzyuk N. S., Krishchuk N. G., Eshchenko V. O. Analysis of stressedly-deformed condition in modelling of nailing оf femoral neck fracture fragments. Vіsnik ortopedії, travmatologії ta protezuvannya [Journal of orthopedics, traumatology and prosthetics], 2011, no. 1, pp. 59–64 (in Ukrainian).

14. Glants S. Medical-biological statistics. Moscow, Praktika Publ., 1998. 459 p.