Instability and impending instability of the thoracolumbar spine in patients with spinal metastases: a systematic review

Abstract

Abstract. Metastatic disease commonly occurs in the spine and incidence is likely to increase secondary to improved survival rates in many cancer patients. Despite published research on instability in patients with metastatic disease of the thoracolumbar spine, controversy exists regarding risk factors for instability and indications for surgical stabilization. The objective of this systematic review was to determine what defines instability and impending instability in patients with metastatic disease of the thoracic and lumbar spine. We systematically reviewed the medical literature in order to identify all the relevant studies concerning patients with metastatic involvement of T1-L5, in the domains of biomechanics, epidemiology, clinical issues, and radiographic parameters. Two independent observers performed study selection, methodological quality assessment, and data extraction in a blinded and objective manner for all the identified studies. We were then able to define the criteria to identify instability of the spine with metastases. A literature search and review identified 14 relevant, good quality studies for inclusion. The predictors of instability included increased tumor size, a larger cross-sectional area of bone defect, increased force of spinal loading, decreased bone density, posterior location of the tumor within the vertebrae, destruction of the costovertebral joint, pedicle destruction in the thoracolumbar spine, increased axial rigidity, and sagittal spinal deformity. Definitive conclusions cannot be reached due to lack of evidence. However, variables such as tumor size, magnitude of spinal loading, bone density, tumor location within the vertebrae and spine, and tumor type are risk factors for instability in spinal metastases. Improved clinical research methodology for this patient population is required.

Large Lytic Defects Produce Kinematic Instability and Loss of Compressive Strength in Human Spines

“…In patients with osteolytic spinal lesions, movement-related bone pain 44,45 , assumed to be caused by spinal instability 10,11 , is a risk factor for PVF. Our findings of greater kinematic abnormality in spine segments that have lower strength may explain these clinical observations 12,30 . Although direct radiographic assessment of kinematics is not clinically feasible at present, elucidating the role of aberrant kinematics in PVF pathophysiology will help to guide treatment decisions and optimize management strategies for this important patient population.…”

“…In patients with spinal metastases, mechanical instability directly affects the risk of PVF 12 . Derived from retrospective patient data 25 and cadaver spines 6,22,25 , computational models of spine segments with lytic anterior column disruption predicted that higher axial deformation of the vertebral body would increase spinal fracture risk under compression 6,22,25 and bending moments 24 .…”

“…Currently, the treatment of these fractures is primarily reactive, after a fracture has occurred. Enhancing the ability to predict PVFs before they occur is a critical but, as of yet, imprecise 10,11 element in the management of these patients 12 .…”

Changes in Spinal Instability After Conventional Radiotherapy for Painful Vertebral Bone Metastases

“…They have been shown to decrease and delay the occurrence of skeletal-related events in metastatic solid tumors and are approved in many countries. 9 , 10 These options are selected as the multidisciplinary approach in consideration of the prognosis and performance status of the patients.…”

Stereotactic Body radiotherapy and pedicLE screw fixatioN During one hospital visit for patients with symptomatic unstable spinal metastases: a randomized trial (BLEND RCT) using the Trials within Cohorts (TwiCs) design

“…Radiotherapy is the standard of care for symptomatic spinal metastases and aims to relieve pain and to obtain local control of the tumor. In addition, in case of metastatic spinal cord compression or unstable spinal metastases, surgical stabilization with or without decompression may be required [ 4 , 5 ]. Currently, radiotherapy is delivered after surgery as soon as the surgical wound is healed sufficiently, which is usually after a minimum time interval of one week.…”