Abstract
Progressive high-grade spondylolisthesis can lead to spinal imbalance. High-grade spondylolisthesis is often reduced and fused in unbalanced pelvises, whereas in-situ fusion is used more often in balanced patients. The surgical goal is to recreate or maintain sagittal balance but if anatomical reduction is necessary, the risk of nerval damage with nerve root disruption in worst cases is increased. Spinal dysraphism like spina bifida or tethered cord syndrome make it very difficult to achieve reduction and posterior fusion due to altered anatomy putting the focus on anterior column support. Intensive neural structure manipulation should be avoided to reduce neurological complications and re-tethering in these cases. A 26-year-old patient with a history of diastematomyelia, occult spina bifida and tethered cord syndrome presented with new onset of severe low back pain, and bilateral L5/S1 sciatica after a fall. The X-ray demonstrated a grade III spondylolisthesis with spina bifida and the MRI scan revealed bilateral severely narrowed exit foramina L5 due to the listhesis. Because she was well balanced sagittally, the decision for in-situ fusion was made to minimise the risk of neurological disturbance through reduction. Anterior fusion was favoured to minimise manipulation of the dysraphic neural structures. Fusion was achieved via isolated access to the L4/L5 disc space. A L5 transvertebral hollow modular anchorage (HMA) screw was passed into the sacrum from the L4/L5 disc space and interbody fusion of L4/L5 was performed with a cage. The construct was augmented with pedicle screw fixation L4-S1 via a less invasive bilateral muscle split for better anterior biomechanical support. The postoperative course was uneventful and fusion was CT confirmed at the 6-month follow-up. At the last follow-up, she worked full time, was completely pain free and not limited in her free-time activities. The simultaneous presence of high-grade spondylolisthesis and spinal dysraphism make it very difficult to find a decisive treatment plan because both posterior and anterior treatment strategies have advantages and disadvantages in these challenging cases. The described technique combines several surgical options to achieve 360° fusion with limited access, reducing the risk of neurological sequelae.