Medial helical versus straight lateral plating of distal femoral fractures-a biomechanical comparative study

Torsten Pastor; Ivan Zderic; Firas Souleiman; Ludmil Drenchev; Hristo Kostov Skulev; Till Berk; Boyko Gueorguiev; Matthias Knobe

doi:10.1016/j.clinbiomech.2023.106119

Medial helical versus straight lateral plating of distal femoral fractures-a biomechanical comparative study

Clin Biomech (Bristol, Avon). 2023 Dec:110:106119. doi: 10.1016/j.clinbiomech.2023.106119. Epub 2023 Oct 5.

Authors

Torsten Pastor¹, Ivan Zderic², Firas Souleiman³, Ludmil Drenchev⁴, Hristo Kostov Skulev⁴, Till Berk⁵, Boyko Gueorguiev², Matthias Knobe⁶

Affiliations

¹ AO Research Institute Davos, Davos, Switzerland; Department of Orthopaedic and Trauma Surgery, Lucerne Cantonal Hospital, Lucerne, Switzerland. Electronic address: Torsten.pastor@luks.ch.
² AO Research Institute Davos, Davos, Switzerland.
³ AO Research Institute Davos, Davos, Switzerland; Department of Orthopaedics, Trauma and Plastic Surgery, University Hospital Leipzig, Leipzig, Germany.
⁴ Bulgarian Academy of Sciences, Institute of Metal Science "Acad. A. Balevski", Sofia, Bulgaria.
⁵ AO Research Institute Davos, Davos, Switzerland; Department of Trauma, University Hospital Zurich, Zurich, Switzerland.
⁶ Department of Orthopaedic and Trauma Surgery, Lucerne Cantonal Hospital, Lucerne, Switzerland; Medical Faculty, RWTH Aachen University Hospital, Aachen, Germany.

PMID: 37832469
DOI: 10.1016/j.clinbiomech.2023.106119

Abstract

Background: Distal femoral fractures are commonly treated with lateral straight plates. However, the lateral approach may not always be desirable, and 180°-helical plates may be an alternative.

Aim: To investigate the biomechanical competence of 180°-helical plating versus standard straight lateral plating of unstable fractures at the distal femur.

Methods: Twelve left artificial femora were instrumented with a 15-hole Locking Compression Plate-Distal Femur, using either 180°-helical plates (group 1) or conventional straight lateral plates (group 2). An unstable distal femoral fracture AO/OTA 33-A3.3 was simulated. All specimens were biomechanically tested under quasi-static and progressively increasing combined cyclic axial and torsional loading in internal rotation until failure.

Findings: Initial axial stiffness (N/mm) was significantly higher in group 1 (185.6 ± 50.1) compared to group 2 (56.0 ± 14.4), p < 0.001. Group 1 demonstrated significantly higher initial interfragmentary flexion (°) and significantly lower initial varus/valgus deformation (°) under 500 N static axial compression versus group 2 (2.76 ± 1.02 versus 0.87 ± 0.77 and 4.08 ± 1.49 versus 6.60 ± 0.47), p ≤ 0.005. Shear displacement (mm) under 6 Nm static torsion was significantly higher in group 1 versus group 2 in both internal (1.23 ± 0.28 versus 0.40 ± 0.42) and external (1.21 ± 0.40 versus 0.57 ± 0.33) rotation, p ≤ 0.013. Cycles to failure and failure load (N) (clinical/catastrophic) were significantly higher in group 1 (12,484 ± 2116/13,752 ± 1518 and 1748.4 ± 211.6/1875.2 ± 151.8) compared to group 2 (7853 ± 1262/9727 ± 836 and 1285.3 ± 126.2/1472.7 ± 83.6), p ≤ 0.001.

Interpretation: Although 180°-helical plating using a pre-contoured standard straight lateral plate was associated with higher shear and flexion movements, it demonstrated improved initial axial stability and resistance against varus/valgus deformation compared to straight lateral plating. Moreover, the helical plates were associated with significantly higher endurance to failure. From a biomechanical perspective, 180°-helical plating may be considered as a valuable alternative to standard straight lateral plating of unstable distal femoral fractures.

Keywords: Biomechanics; Distal femur fracture; Helical plating; Lateral plating; Medial approach.

MeSH terms

Biomechanical Phenomena
Bone Plates
Femoral Fractures* / surgery
Femoral Fractures, Distal*
Fracture Fixation, Internal
Humans