Influence of cervical spine sagittal alignment on range of motion after corpectomy: a finite element study
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ORIGINAL ARTICLE - SPINE - OTHER
Influence of cervical spine sagittal alignment on range of motion after corpectomy: a finite element study Jobin D. John 1,2
&
Gurunathan Saravana Kumar 1
&
Narayan Yoganandan 2
&
Vedantam Rajshekhar 3
Received: 18 September 2020 / Accepted: 12 October 2020 # Springer-Verlag GmbH Austria, part of Springer Nature 2020
Abstract Background Sagittal alignment of the cervical spine might influence the development of radiological adjacent segment pathology (RASP) after central corpectomy (CC). Range of motion (ROM) of the adjacent segments is closely linked to the development of RASP. Methods To investigate the ROM of the adjacent segments after CC, we developed a C2-T1 finite element (FE) model. The model with a lordotic sagittal alignment served as the baseline model. Models with straight and kyphotic alignment were generated using mesh morphing methods. Single-level corpectomy at C5 was done on these models. Segmental ROMs of intact and corpectomized spines were compared for physiologic flexion-extension loads. Results The flexion ROM decreased by an average of 13% with the change in sagittal alignment from lordosis to kyphosis; however, a consistent decrease was not observed in extension. After CC, the ROM increased by an average of 95% and 31% in the superior and inferior adjacent segments. With kyphotic change in the sagittal alignment, the postoperative increase in flexion ROM exhibited a decreasing trend, while this was not seen in extension. Conclusions Kyphotic changes of the intact spine resulted in segmental stiffening, and after corpectomy, it resulted in inconsistent variations of segmental extension ROMs. Keywords Adjacent segment pathology . Cervical spine . Sagittal alignment . Finite element model . Mesh morphing
Introduction Central corpectomy is an effective intervention for treatment of cervical spondylotic myelopathy (CSM) and ossified posterior longitudinal ligament (OPLL) [1, 32]. The procedure involves the removal of the central part of vertebral body/ bodies for decompression, and in its place, a graft is used to achieve fusion between the adjacent vertebrae for stability. Instrumented corpectomy uses plates to secure the graft, while in an uninstrumented corpectomy the graft is anchored in This article is part of the Topical Collection on Spine - Other * Vedantam Rajshekhar [email protected] 1
Department of Engineering Design, Indian Institute of Technology Madras, Chennai, India
2
Center for Neurotrauma Research, Department of Neurosurgery, Medical College of Wisconsin, Milwaukee, WI, USA
3
Department of Neurological Sciences, Christian Medical College Hospital, Vellore 632004, India
mortises made in the adjacent vertebrae and relies on external orthoses to maintain graft position initially [20]. Although early and long-term functional outcomes for uninstrumented corpectomy are reported to have good outcomes with low rates of acute graft extrusion [20, 32, 33, 35], radiologically evident accelerated adjacent segment pathology (RASP, ra
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