=====High grade spondylolisthesis=====
Lumbosacral [[spondyloptosis]], by definition, is more than 100% anterior displacement of the [[L5]] [[vertebra]] with regard to the [[sacrum]]. It is also known as grade 5 [[spondylolisthesis]]
((Boos N, Marchesi D, Zuber K, Aebi M. Treatment of severe spondylolisthesis by reduction and pedicular fixation. A 4-6-year follow-up study. Spine. 1993;18(12):1655–1661.))
((Jo D J, Seo E M, Kim K T, Kim S M, Lee S H. Lumbosacral spondyloptosis treated using partial reduction and pedicular transvertebral screw fixation in an osteoporotic elderly patient. J Neurosurg Spine. 2012;16(2):206–209.))
((Chandrashekhara S H, Kumar A, Gamanagatti S. et al. Unusual traumatic spondyloptosis causing complete transaction of spinal cord. Int Orthop. 2011;35(11):1671–1675)).


Hresko et al. proposed a classification system dividing high grade [[spondylolisthesis]] cases into unbalanced and balanced pelvic groups based on the orientation, i.e. radiographic parameters, of the [[pelvis]]. Balanced pelvises had higher SS and lower pelvic tilt, whereas unbalanced pelvises incompletely compensate with lower SS and pelvic retroversion, resulting in a higher pelvic tilt (PT)
((Hresko MT, Labelle H, Roussouly P, Berthonnaud E. Classification of high-grade spondylolistheses based on pelvic version and spine balance: possible rationale for reduction. Spine 2007;32:2208-13.))

====Treatment====
Surgical stabilization of high-grade spondylolisthesis remains controversial.

High-grade [[spondylolisthesis]] can be a debilitating condition for the patient and present a significant challenge for the surgeon
((Boxall D, Bradford DS, Winter RB, Moe JH (1979) Management of severe spondylolisthesis in children and adolescents. J Bone Joint Surg Am 61:479–495)).

====Surgical techniques====
Several surgical techniques have been advocated to deal with symptomatic [[L5 S1 spondylolisthesis]]. 

[[Posterolateral fusion]] with [[pedicle screw fixation]] has become increasingly popular 
((Lee GW, Lee SM, Ahn MW, Kim HJ, Yeom JS (2014) Com- parison of posterolateral lumbar fusion and posterior lumbar interbody fusion for patients younger than 60 years with isthmic spondylolisthesis. Spine 39:1475–1480)).

====Complications====
It has been associated with a relatively high rate of pseudoarthrosis and progressive slippage
((Boxall D, Bradford DS, Winter RB, Moe JH (1979) Management of severe spondylolisthesis in children and adolescents. J Bone Joint Surg Am 61:479–495)).