Selection of upper instrumented vertebra for long-segment fixation in adult degenerative scoliosis

Abstract

To review the research progress of upper instrumented vertebra (UIV) selection strategy for long-segment fixation (LSF) in adult degenerative scoliosis (ADS). The relevant domestic and foreign literature in recent years was reviewed, and the selection strategy of sagittal and coronal UIV for LSF in ADS patients, the relationship between UIV selection and proximal junctional kyphosis (PJK) and proximal junctional failure (PJF), the impact of minimally invasive spine surgery on the selection strategy of UIV were summarized. LSF can restore the biomechanical balance of the spine and reconstruct the physiological curve of the spine for ADS patients. LSF should be selected for ADS patients with severe scoliosis, vertebral rotation, and severe sagittal imbalance. For patients with poor general condition, UIV can choose the thoracic and lumbar vertebrae to reduce the operation time and intraoperative bleeding, which is conducive to early mobilization and reduce complications; for patients with good general condition, the upper thoracic vertebrae can be considered if necessary, in order to achieve satisfactory long-term effectiveness. However, the lower thoracic vertebra (T 9、10) should be selected as much as possible to reduce postoperative complications such as PJK and PJF. In recent years, a new reference marker, the first coronal reverse vertebra was proposed, to guide the selection of UIV. But a large-sample multicenter randomized controlled study is needed to further verify its reliability. Studies have shown that different races and different living habits would lead to different parameters of the spine and pelvis, which would affect the selection of UIV. Minimally invasive surgeries have achieved satisfactory results in the treatment of ADS, but the UIV selection strategy in specific applications needs to be further studied. The selection strategy of UIV in LSF has not yet been unified. The selection of UIV in the sagittal plane of the upper thoracic spine, the lower thoracic spine, or the thoracolumbar spine should comprehensively consider the biomechanical balance of the spine and the general condition of the patient, as well as the relationship between the upper horizontal vertebra, the upper neutral vertebra, and the upper end vertebra on the coronal plane.