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. 2022 Aug 3:10:868299.
doi: 10.3389/fped.2022.868299. eCollection 2022.

Intercalary reconstruction of long bones by massive allograft: Comparison of construct stability ensured by three different host-graft junctions and two types of fixations in a synthetic femur model

Massimiliano Baleani  1 , Paolo Erani  1 , Manon Blaise  1 , Roberta Fognani  1 , Marco Palmas  2 , Marco Manfrini  2
Affiliations

Intercalary reconstruction of long bones by massive allograft: Comparison of construct stability ensured by three different host-graft junctions and two types of fixations in a synthetic femur model

Massimiliano Baleani et al. Front Pediatr. .

Abstract

An intercalary segmental allograft is an option for limb salvage in bone tumours. Stable and congruent intercalary reconstructions are a prerequisite for achieving host-graft union. However, a too rigid fixation could increase the risk of late complications correlated with negative bone remodelling. This study compared the reconstruction stiffness achieved by three different host-graft junctions, namely, end-to-end, modified step-cut, and taper. A low-stiffness bone plate was used as the fixation method, except for the taper junction where a low-stiffness intramedullary nail was also used to investigate the effects of different types of fixation on construct stiffness. Composite femora were tested under four loading conditions to determine coronal and sagittal bending stiffness, as well as torsional stiffness in opposite directions. Stiffness values were expressed as a percentage of intact host bone stiffness (%IBS). While a reduction of coronal bending stiffness was found with taper junctions (76%IBS) compared with the high values ensured by end-to-end (96%IBS) and modified step-cut junctions (92%IBS), taper junctions significantly increased stiffness under sagittal bending and torsion in intra- and extra-direction: end-to-end 29%IBS, 7%IBS, 7%IBS, modified step-cut 38%IBS, 20%IBS, 21%IBS, and taper junction 52%IBS, 55%IBS, 56%IBS, respectively. Construct stiffness with taper junctions was decreased by 11-41%IBS by replacing the bone plate with an intramedullary nail. Taper junctions can be an alternative to achieve intercalary reconstructions with more homogeneous and, in three out of four loading conditions, significantly higher construct stability without increasing bone plate stiffness. The risk of instability under high torsional loads increases when taper junctions are associated with a low-stiffness intramedullary nail.

Keywords: biomechanical behaviour; bone tumours; host-graft interface; intercalary allograft reconstruction; reconstruction stability.

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Conflict of interest statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Figures

FIGURE 1
FIGURE 1
Scheme of the experimental setup. (A) Four-point bending test (showing bending in the coronal plane). The two support rollers (span 300 mm) are adjustable in the vertical direction to place the femoral axis in the horizontal position. The two loading rollers (span 200 mm) rotate around a horizontal hinge to ensure equal force between the roller and diaphysis surface during testing. An extensometer measures the vertical deflection of the mid cross-section. (B) Torsion test. The femoral axis is aligned with the testing machine axis. The two epiphyses are constrained by acrylic resin in metal holders leaving a free length of 300 mm. The upper holder is free to move in the transversal plane. The biaxial testing machine avoids undesired axial load during testing.
FIGURE 2
FIGURE 2
(A) End-to-end junction reconstruction with bone plate fixation. Two additional cortex screws were added to fix the massive graft. (B) Modified step-cut junction reconstruction with bone plate fixation. (C) Taper junction reconstructions with bone plate fixation; (D) taper junction reconstructions with intramedullary nail fixation.
FIGURE 3
FIGURE 3
(A) Example of force-displacement curve collected during construct bending in the coronal plane generating tension on the lateral side. (B) Example of a force-displacement curve collected during construct bending in the sagittal plane, generating tension on the anterior side. (C) Example of a torque-rotation curve collected during construct torsion, causing intra-rotation of the proximal femur. (D) Example of a torque-rotation curve collected during construct torsion, causing extra-rotation of the proximal femur.
FIGURE 4
FIGURE 4
Bending and torsional stiffness, expressed as a percentage of intact host bone stiffness (%IBS) determined for the intercalary reconstruction with bone plate fixation differing in junction geometry. (A) Bending stiffness in the coronal plane. (B) Bending stiffness in the sagittal plane. (C) Torsional stiffness in intra-rotation direction. (D) Torsional stiffness in extra-rotation direction (S = statistically significant difference; * = test limited to 14 Nm).
FIGURE 5
FIGURE 5
Bending and torsional stiffness, expressed as a percentage of intact host bone stiffness (%IBS) determined for the intercalary reconstruction with the taper junctions differing in the type of fixation. (A) Bending stiffness in the coronal plane. (B) Bending stiffness in the sagittal plane. (C) Torsional stiffness in intra-rotation direction. (D) Torsional stiffness in extra-rotation direction (S, statistically significant difference).
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