A New Spondylolisthesis Reduction Technique

Abraham Rogozinski

Chaim Rogozinski

Open reduction of high-grade spondylolisthesis in combination with posterior instrumentation and fusion is intended to restore sagittal balance, reduce the slip angle, and provide anatomical restoration of the spine. This allows reduced tension of the lumbar nerves (1,2,3,4). Clinical benefits to the patient include decreased postoperative pain, immediate mobilization of the patient without bracing, a halt to the progression of the deformity, the ability for the surgeon to perform complete neural decompression, the promotion of successful arthrodesis, and the restoration of body posturing mechanisms with corresponding improvement in appearance and self-image (2,3,4,5,6).

Decompression of spondylolisthesis alone has been associated with instability and in some cases can increase the deformity (7,8,9,10,11,12,13). Pedicle screw fixation has been utilized to stabilize the spine in these instances; however, the use of fixation without other attempts at postural reduction has had limited success in restoring the anatomical lumbosacral angle (6,14,15). This chapter is not an argument for justifying reduction of spondylolisthesis, but rather a description of a unique technique for spondylolisthesis reduction when indicated.

A new spinal fixation system (SpineLink, EBI, Parsippany, NJ, USA) with polydirectional screws and modular links was recently introduced. The independent linking of multiple vertebral fixation points has been termed “intrasegmental” fixation. The intrasegmental nature of the fixation eliminates the need for intraoperative contouring and cutting of the rods and plates. The addition of extended polydirectional screws and StepLinks, along with the development of an attachable spondylolisthesis reduction jack, affords the surgeon the ability to internally fix the spine and reduce the spondylolisthesis by manipulating two unconnected instrumented segments. The corrective forces that can be applied to the spine with this system are (a) extension, (b) distraction-compression, and (c) translation, to achieve the desired reduction.

SURGICAL TECHNIQUE

The reduction technique for spondylolisthesis can be performed regardless of the number of vertebral levels fused. Described here is the surgical technique for a two-level posterior fusion of L4 to the sacrum with reduction of an L5-S1 spondylolytic spondylolisthesis.

After a complete decompression of L5, soft tissue and intervertebral disc space release, and any bone resection needed, the segmental instrumentation is applied to the spine using the standard technique for the polydirectional pedicle screw insertion and link placement. To facilitate application of the links and the subsequent reduction, the
machine-threaded portion of the polydirectional screws at L4 and L5 is oriented perpendicular to the floor. The machine-threaded portion of S1 screw is angled caudally in the sagittal plane to match the slip angle determined by preoperative radiographic measurements (Fig. 20.1). This angle can be reproduced using a goniometer, which is included with the instrumentation. With the S1 pedicle screws in position, the caliper is used to measure the interscrew distance and an appropriately sized standard link is used to transversely connect the S1 screws. This link is provisionally maintained in position with end caps and lock nuts. The caliper is used to measure the distance between the L4 and L5 pedicle screws on both sides, and an appropriately chosen standard link is then used to affix the L4 and L5 screws ipsilaterally. This is done bilaterally. The interscrew distance between L4 is then measured with the caliper, and a standard link is used to link the L4 screws transversely. The transverse link is locked into position with lock nuts. Temporary end caps and lock nuts are applied to provisionally lock the construct to the L5 pedicle screws. To allow reduction to proceed, no link is applied at this point to connect L5 to the sacrum.

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