Interbody Device Shape and Size Are Important to Strengthen the Vertebra–Implant Interface

Abstract

The cloverleaf-shaped indentor displayed an improved strength and stiffness profile when compared to oval or kidney-shaped indentors of similar surface areas.

Biomechanical evaluation of interbody devices by using mechanical compressive test: PEEK spacers versus PMMA cement spacers

“…The average failure loads of 2017 N and 2207 N for PMMA and PEEK cages in this study ( Table 2) were comparable to the values reported in previous literature, 5,[8][9][10] however, there are considerable differences in the failure loads obtained by different embedding methods of the specimens. The average segmental stiffness of 557 N/mm of group of PEEK spacers and the higher stiffness of 1373 N/mm in group of novel PMMA cement spacers compared well with the values reported in.…”

“…The average segmental stiffness of 557 N/mm of group of PEEK spacers and the higher stiffness of 1373 N/mm in group of novel PMMA cement spacers compared well with the values reported in. 5,8,10 The average failure displacements of 5,56 mm of PEEK group and 2.80 mm of PMMA group are in the ranges reported in. 1,10 Surprisingly, the load bearing capacity of segments is inversely proportional with the bone quality of vertebrae in the case of PMMA cages, mainly centrally, while the load bearing of PEEK spacers is strongly related to the bone quality, mainly subcortically ( Figure 3 and Table 3).…”

“…5 The goal of this work is to compare the mechanical characteristics: strength, stiffness and deformability of lumbar motion segments stabilized by traditional PEEK and PMMA cement spacers (without posterior instrumentation), by using uniaxial compression tests. Parallel, we have developed the quantitative computed tomography QCT-based patientspecific nonlinear finite element models of each test specimen to analyze the vertebra-implant interface and the elastic-plastic damage process of the vertebral internal cancellous bone, local and global failure of the motion segment.…”

“…In this case inserting the interbody devices, the traditional spacers into the intervertebral space is very difficult due to the irregularly deformed, weakened osteoporotic endplates of vertebrae, moreover, implant subsidence reduces the strength of the joint and yield further complications. [1][2][3][4][5] To avoid implant subsidence, the strength of the vertebra-device interface must be increased. According to a new method developed in the National Center for Spinal Disorders in Budapest, instead of traditional spacers, bone cement is applied as interbody device at a certain part of the removed disc, while the other part of the removed disc is filled up by bone graft.…”

Biomechanical evaluation of two different vertebral interbody devices by using QCT-based case-specific nonlinear finite element models

“…in osteoporosis, application of the standard fixation approaches using interbody implants can be inadequate due to the reduced bone quality and the degeneration of the vertebral endplates and may lead to damage of the bone tissue at the interface via excessive subsidence of the spacer, yielding to further complications, pain, instability and potentially to the collapse of the motion segment. [1][2][3][4] A novel method aims at circumventing the drawbacks of the conventional techniques by using cement spacers. In the frame of this approach bone cement is injected into the gap of the removed parts of the degenerated intervertebral disc and the remaining space is filled with graft material to foster fusion of the adjacent vertebrae.…”