Dear Editor, High dysplastic developmental spondylolisthesis (HDDS) is a rare spinal disorder characterized by pronounced lumbosacral kyphosis and potential disruption of sagittal spinal-pelvic alignment1. Surgical management of this condition remains a subject of considerable debate due to its anatomical complexity and associated neurological risks. Traditional posterior in situ fusion, although capable of providing symptomatic relief, is limited by high rates of pseudarthrosis, risk of progressive slippage, and inability to address sagittal imbalance or cosmetic deformity2. Current controversies in the surgical treatment of HDDS center on the optimal reduction strategy, the extent of vertebral realignment, and the appropriate level of instrumentation and fusion3. A 15-year-old female adolescent presented with a 1-year history of progressive low back pain. Plain radiography demonstrated grade IV spondylolisthesis of L5–S1 according to the Meyerding classification, corresponding to type 5 in the Spinal Deformity Study Group (SDSG) system. Severe lumbosacral kyphosis and pelvic retroversion were evident. Sagittal spino-pelvic parameters were as follows: pelvic incidence (PI) 67°, pelvic tilt (PT) 37°, sacral slope (SS) 30°, Dubousset lumbosacral angle (Dub-LSA) 63°, lumbar lordosis (LL) 72°, and sagittal vertical axis (SVA) 45 mm anterior to the femoral heads (Fig. 1). Computed tomography (CT) disclosed elongation and attenuation of the L5 pars interarticularis, wedge-shaped morphology of the L5 vertebral body, and a dome-shaped configuration of the S1 superior endplate. Bilateral osseous narrowing of the L5–S1 neural foramina was present, without evidence of an anterior ossification bridge. Magnetic resonance imaging (MRI) revealed preserved signal intensity of all discs cranial to L5. Severe central and bilateral foraminal stenosis at L5–S1 resulted in compression of the cauda equina against the postero-superior margin of S1. The L5 nerve root within the thecal sac was displaced ventro-cranially toward the disc space margin. Figure 1.: Preoperative radiographs of L5-S1 dysplastic spondylolisthesis. (A) Lateral radiography showing Meyerding Grade IV spondylolisthesis, SDSG type 5, and lumbosacral kyphosis with Dub-LSA of 63°; (B) Spinopelvic parameters: PI 67°, PT 37°, SS 30°; (C) LL of 72°; (D) SVA of 45 mm anterior to the femoral heads. The surgery proceeded in three steps with the patient prone. A midline approach exposed L5–S1. Complete L5 laminectomy and bilateral foraminal decompression were performed, with release and protection of the L5 nerve roots. The S1 superior endplate was resected. A unilateral spreader distracted the disc space from the L5 antero-inferior corner. Contralateral disc material was excised, trial inserts restored height, and a lordotic cage packed with autograft was placed. The sequence was repeated on the other side. Fluoroscopy confirmed restored disc height and partial reduction of slip and kyphosis. This interbody placement elevated L5, facilitating pedicle screw insertion into L5 and S1. A pre-contoured rod was engaged, and final reduction was achieved via cantilever and compression maneuvers under continuous nerve monitoring. Axial compression locked the construct. After hemostasis and irrigation, a drain was placed and the incision closed. Operative time was 120 minutes with 200 ml blood loss. At 3 months, imaging showed complete reduction of spondylolisthesis, with L5–S1 disc height 11 mm, Dub-LSA 110°, PI 62°, PT 23°, SS 39°, LL 48°, and SVA 26 mm, indicating corrected lumbosacral kyphosis and restored sagittal balance. At 18 months, correction remained well maintained with solid fusion at L5–S1, no implant failure, and no adjacent segment degeneration at L4–5. Clinical outcomes included JOA 24, lumbar VAS 1, and ODI 15.6%. A notable intraoperative observation was that partial reduction of the L5 vertebral slip could be attained immediately upon distraction of the L5–S1 intervertebral space. This effect was particularly evident in patients with severe preoperative narrowing of the disc space. Based on this finding, we developed a distinct “indirect reduction technique”: a pedicle spreader was inserted unilaterally to gently open the intervertebral space, followed by sequential placement of a trial inserter and a fusion device on the contralateral side. This approach offers two principal advantages. First, it achieves partial reduction of the slip and partial correction of lumbosacral kyphosis, contributing to early restoration of spinopelvic sagittal alignment. Second, and importantly, elevation of the L5 vertebral body raises the entry point for the L5 pedicle screw, rendering screw insertion technically less demanding and facilitating subsequent formal reduction using a rod-screw construct. Thus, this indirect distraction method establishes a stable environment for interbody fusion while simultaneously improving spinal alignment, representing a practical and effective preliminary reduction strategy prior to direct instrumented reduction. In summary, indirect reduction via intervertebral distraction with short-segment fusion represents a safe and effective option for adolescent HDDS. This approach achieves satisfactory sagittal alignment restoration while preserving lumbar mobility and minimizing neurological complications.
Yang et al. (Mon,) studied this question.