Lumbosacral Interbody Fibular Strut Placement for High-Grade Spondylolisthesis: Anterior Speed’s Procedure and Posterior Procedure

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Lumbosacral Interbody Fibular Strut Placement for High-Grade Spondylolisthesis: Anterior Speed’s Procedure and Posterior Procedure

Michael E. Janssen and Jason C. Datta

Description

Placement of an interbody fibular strut graft through the sacrum and L5 vertebral body for high-grade lumbosacral spondylolisthesis.

Key Principles

Placement of the strut graft fulfills the following goals in the surgical treatment of high-grade spondylolisthe-sis: immediate structural support and stability, solid bony interface for fusion, and a graft placed under compression. The posterior placement of the graft requires a large decompression of the neural elements, which is advantageous in patients with neurologic complaints. Spinal fusion usually occurs within 3 to 6 months.

Indications

High-grade lumbosacral spondylolisthesis greater than Meyerding grade III that has failed nonoperative treatment for mechanical back pain, lumbosacral neurologic dysfunction, slip progression, or revision of previous failed surgery. This procedure may be ideal for revision surgeries where the posterolateral graft bed is poor, or in the setting of a previously anterior bony strut graft procedure.

Contraindications

Less than 50% spondylolisthesis for the posterior procedure
High-grade lumbosacral kyphosis >80 degrees, which may require L5 vertebral body resection

Special Considerations

The posterior procedure is limited by the cephalad orientation of the graft tract by the patient’s body. This limits the procedure to an in-situ fusion of a slip of greater than 50% or the partial reduction of a higher grade slip to 50%.

Presurgical radiographic evaluation for preoperative planning for both these procedures is essential. This includes preoperative plain films in the upright position to evaluate the posterior element dysplasia and slip angle. This defines lamina and pedicle dysplasia identifying areas at risk during decompression, and the planning of safe segmental posterior stabilization. Dysplasia of the transverse processes of L4 and L5 should be evaluated for the surface area available for posterolateral fusion. Transverse process surface area <2 cm 2 has been correlated with a high pseudarthrosis rate. It is strongly recommended to add the stability and superior graft bed of an interbody strut graft at the lumbosacral junction.

Magnetic resonance imaging (MRI) or computed tomography (CT) myelography should be used to evaluate the geometry and pathology of neural compression. The presence of sacral inlet stenosis should alert the surgeon to the need of a sacral dome resection. Regardless of sacral inlet stenosis, sacral dome resection may ease reduction forces required and the strain placed on the L5 nerve roots by columnar shortening. CT angiography may be a useful adjunct to define the prevertebral vascular anatomy prior to an anterior procedure in a high-grade deformity.

Special Instructions, Position, and Anesthesia

The patient should be placed in the prone position on a radiolucent four-poster frame. Intraoperative fluoroscopy is required.

Tips, Pearls, and Lessons Learned

The graft used, autograft versus allograft, does not appear to affect outcomes in the limited literature available. There may be a role for a vascularized fibular graft in previously radiated tissues. Reduction forces may be decreased by a wide thorough decompression, sacroplasty, and slight distraction. Resection of the iliolumbar ligament and far lateral foraminal decompression may decrease the rate of neurologic complications from the L5 root during reduction maneuvers.

A cannulated reamer from an anterior cruciate ligament reconstruction set is ideal for both the anterior and posterior procedures. An appropriate-size reamer can be chosen using the graft sizing tubes over the strut graft. The reamer sleeves in these sets serve as an excellent soft tissue protector.

The posterior placement of a fibular strut is limited to slips >50% because of limitations present with the pelvis and caudad soft tissues. Anterior graft placement can be performed in partially reduced slips, but it requires some anterior resection of the L4-L5 disk for proper positioning of the guide wire and reamer.

Both the procedures can be used without supplemental posterior segmental instrumentation, but it is felt that higher rates of successful fusion can be achieved with instrumentation. The added instrumentation is needed with dysplastic transverse processes <2 cm 2. This includes L4 pedicle screws, bilateral bicorti-cal S1 fixation, and iliac screws measuring >60 mm in length and 7 mm in diameter to improve fusion rates and decrease interbody strut graft failure.