The Effect of Posterior Thoracic Spine Anatomical Structures on Motion Segment Flexion Stiffness

Abstract

Posterior thoracic skeletal structures involved in upper instrumented vertebra exposure andanchor placement were found to contribute to adjacent segment flexion stiffness. Although stiffness loss was small after individual procedures, the effects were additive for routinely used combinations.

Proximal junctional kyphosis and clinical outcomes in adult spinal deformity surgery with fusion from the thoracic spine to the sacrum: a comparison of proximal and distal upper instrumented vertebrae

“…Despite reports on the prevalence, outcomes, possible risk factors, and prevention of PJK in adult spinal deformity surgery, these factors remain controversial and are not fully understood. 2,4,7,21,22 Moreover, there are still questions regarding the role of different UIV levels in preventing PJK. The effect of PJK on clinical outcomes in adults had yet to be clarified prior to the present study.…”

“…5 The complex biomechanics at the cervicothoracic and thoracolumbar junction with the transition from mobile to immobile motion segments certainly may have an effect on the development of PJK. 2,18 Moreover, early-onset PJK due to acute fractures or subluxation may be directly caused by a marked change in sagittal balance and rigid segmental pedicle screw fixation to the sacrum, which produces a high mechanical stress concentration at the UIV. 22 Overall, 11.2% (10 of 89) of the patients required revision surgery for PJK.…”

“…4,7,[9][10][11]21,23 Fixed motion segments after spinal instrumentation and fusion may increase the stress on adjacent unfused spinal segments and cause accelerated degeneration of the adjacent segments. 2,18 The significant stress gradient between the instrumented and noninstrumented spine can result in higher stress concentration at the transition and the development of PJK. 12 The choice of a UIV in construct planning in spinal deformity is characterized by significant variability.…”

Quantification of Increase in Three-dimensional Spine Flexibility Following Sequential Ponte Osteotomies in a Cadaveric Model

“…Oda et al [19] performed a total facetectomy and laminectomy; however the study only evaluated the effects of a single-level surgery on a single functional spinal unit. More recently, Anderson et al [22] studied stiffness in flexion after a posterior procedure similar to the Ponte osteotomy; however, the authors did not evaluate extension, lateral bending, and axial rotation. In short, no studies to date have quantified the increase in 3-dimensional flexibility after sequential Ponte osteotomies in a multi-segment thoracic spine model.…”

“…Previous biomechanical studies have investigated the role of different stabilizing structures in the thoracic spine [13][14][15][16][17][18][19][20][21][22]; however, few have included posterior-only procedures, and none have isolated and quantified Ponte osteotomies. For example, Feiertag et al [21] performed a unilateral facetectomy on a single level in a full thoracic cadaveric spine model and reported no significant increase in range of motion (ROM).…”