While there is no study in the literature specific to the natural history of spondyloptosis, Di Martino et al. reported a case of spondyloptosis at L5/S1 diagnosed at the age of 9 with occasional low back pain treated conservatively. Spontaneous fusion was noted at the age of 36 and confirmed with CT scan. They concluded that conservative treatment may be a viable option in treatment for patients with mild symptoms, also it supports in situ fusion as a viable option for treatment of spondyloptosis [18].

Instrumentation is highly advised in posterior fusion of spondyloptosis, to stabilize the spine as it provides higher fusion rates and can maintain reduction in case correction of deformity is attempted. Particularly if laminectomy and destabilization of the spine is done to decompress neural elements which is often needed given the neurological symptoms associated with the deformity. In high-grade spondylolisthesis and spondyloptosis, there is no role for decompressive surgery alone unless spontaneous and complete autofusion has been confirmed by CT scan and the patient complains only of neurological symptoms without back pain.

Although excellent results from in situ fusion for high-grade slips have been reported by some authors, the outcomes are not very predictable. High rates of pseudarthrosis and bending of the fusion mass have also been reported. Fusion rates are higher with addition of anterior column support. Reduction may help restoring the overall sagittal balance of the spine and indirect decompression of spinal and foraminal stenosis. However it is associated with higher complication rates secondary to stretching of nerve roots if more than 50 % correction is attempted [19]. If there is sufficient disc height, interbody fusion is advised as it provides better spinal alignment, fusion surface, and indirect foraminal decompression as well as anterior biomechanical support, thus relieving the stress on posterior implants.

Anterior surgery poses certain risks related to the approach, major vessel manipulation or injury, retrograde ejaculation in males along with increased operative time, bowel complications, deep venous thrombosis, pulmonary complications, and hospitalization. Posterior partial reduction correcting the lumbosacral kyphosis may avoid the complications of full reduction as well as a second anterior approach. It also helps in correction of the sagittal balance. The sacral dome can cause significant anterior impingement of the dural sac in which case, partial sacral dome resection can be performed to further decompress the neural elements through a posterior approach.

Bohman et al. described placement of fibular graft through a posterior approach from S1 body across the disc space into the L5 body. This technique obviates the need for an anterior approach but involves manipulation of the thecal sac. As described by Bohlman during surgery the surgeon can protect the neural elements under fluoroscopic control with guidewire advancement through the body of S1, across the L5-S1 disc space, and up to the anterior cortex of L5. Over reaming of the guidewire can be performed under fluoroscopic guidance, beginning at 6 mm, increasing by 2 mm increments, up to 12 mm. Thereafter, a single fibula allograft can be impacted into position. A modification of the above technique can include addition of pedicle screw fixation in L4 and trans-sacral pedicle screws capturing L5 to supplement the trans-sacral fibula fixation [20].

The mainstay of operative treatment of spondylolisthesis is posterior in situ lumbosacral arthrodesis, with extension to the fourth lumbar vertebra if the slippage is more than 50 %. With this approach, symptomatic relief has been reported in 75 % or more of patients. However, it has been reported that additional slippage may occur after a posterolateral or posterior arthrodesis even if the patient is kept supine, and that progression is even more likely in patients who have had decompression combined with a posterior lateral arthrodesis. Boxall et al. reported that 46 % of their patients who had a slippage of more than 50 % and a solid posterior fusion had progression of the deformity. In these patients, the average lumbosacral kyphosis preoperatively was 50°. Continued progression also has been noted by Newman, Bosworth et al., and Laurent and Osterman and has ranged from 10 to 37 % [21, 22].

Bradford et al. reported on 22 consecutive who had severe spondylolisthesis (Grade IV and V) who were treated by a first-stage posterior decompression (Gill procedure) and a posterolateral arthrodesis, followed by halo-skeletal traction (femoral or pelvic) for 7–10 days, and then by a second-stage anterior interbody arthrodesis, followed by immobilization in a cast. They reported an average follow-up of 5 years. The slip angle averaged 71° preoperatively, was corrected to an average of 31° by reduction, and averaged 28° at follow-up. The average preoperative percentage of slippage (98 %) did not change substantially. Radicular pain improved in all 12 patients who had the complaint preoperatively. Ten patients had postoperative neurological deficits that completely resolved in all but one at follow-up. They also reported 21 % (four patients) pseudoarthrosis [12–14].

The operative treatment of severe, symptomatic spondylolisthesis (more than 50 % slippage) continues to pose a therapeutic challenge. Options for patients who have this deformity include posterior arthrodesis in situ, with or without decompression, posterior interbody arthrodes, anterior arthrodesis in situ, and reduction of the spondylolisthesis, with associated arthrodesis.

In major lumbosacral kyphosis, the fusion mass is subjected to abnormal bending forces. Progression of the deformity is less likely to occur if the kyphosis can be partially corrected and the fusion mass can be placed under compression, or less tension thus allowing a better biomechanical environment for fusion to occur.

Lumbosacral kyphosis leads to loss of sagittal balance. Thus for the patient to look forward, they have to compensate by hyperextending the upper lumbar levels, tilt the pelvis forward and flex the hips and knees with possible associated hypokyphosis of the thoracic spine. This posture places much more stresses on all the muscles and joints leading to easy fatigability.

While in situ fusion has been a mainstay in treatment of high-grade slips, reduction can aid in the outcomes of surgery as it allows decompression of the neural elements which are usually impinged by the posterior elements. It allows correction of the lumbosacral kyphosis, which results in less hyperlordosis at the upper lumbar and thoracic spine as well as less hamstring tightness or hip and knee flexion, thus giving the patient a more balanced posture with less muscular fatigue. Reduction can also restore the paraspinal and abdominal muscles to more physiologic alignment with a normal length-tension relationship, thus providing a more efficient function of those muscles with less fatigability.

Various techniques for reduction of high-grade spondylolisthesis have been described by including corrective casts by Scaglietti, which required extensive periods of bed rest, Harrington rods, wires attached to an external corrective system by Snijder, and through a two-stage procedure utilizing posterior decompression and posterolateral fusion followed by anterior reduction with fusion by Bradford [20–26].

Gaines described a technique of anterior excision of the vertebral body of L5 and the L4-5 and LS-S I discs were resected at the first stage, through a low midline transverse abdominal incision and a retroperitoneal approach. Major vessels need to be mobilized to allow access to the spine. Once exposed, the L4-5 disc is removed followed by resection of the L5 body all the way to the base of the pedicles. At this point the L5-S1 disc can be visualized and removed down to bone. All bone and intervening disc between lower endplate of L4 and upper endplate of S1 were removed with complete exposure of the dura. No correction was attempted at this stage. They waited 2 weeks until the second stage was done. During the second stage, a posterior exposure was done to excise the remaining posterior elements of L5 and compress L4 over S1 with posterolateral bone grafting [15].