Thomas N. Scioscia and Jeffrey C. Wang

Description

Recent advances in plating systems have made anterior fixation possible after anterior lumbar interbody placement. Following a supine retroperitoneal or transperitoneal approach, diskectomy is performed and end plates are prepared to bleeding bone. The anterior lumbar interbody fusion (ALIF) graft of choice is then press-fit into the interspace, and fixation is achieved with a low-profile conventional or locking plate. After meticulous hemostasis, abdominal closure is performed. Anterolateral plating is performed through a lateral retroperitoneal approach. After exposure and corpectomy, a structural graft or cage is placed to re-create lordosis. A low-profile conventional or locking contoured plate is then applied laterally with two screws in the superior and inferior vertebral bodies.

Expectations

Supplemental fixation after ALIF for discogenic back pain with positive diskogram, instability or grade one spondylolisthesis, and pseudarthrosis after failed posterior surgery. The Pyramid plate is indicated only at the L5-S1 disk level. The plate is indicated from L1 to S1, though it should be placed anterolaterally above L5-S1 and used with extreme caution at these higher levels.

Relative Indications

Supplemental fixation after ALIF for revision of failed spine arthroplasty.

Contraindications

Instability with greater than 25% listhesis in any direction. Low-lying bifurcation of the great vessels.

Relative Contraindications

• Prior retroperitoneal surgery with adhesions
  
• Calcification of the aorta and iliac arteries
  
• Osteoporosis

Special Considerations

Great vessel anatomy must be visualized on magnetic resonance imaging (MRI). The bifurcation should be located superior to the L5 vertebral body when plating the L5-S1 interspace. If this is not the case, consent for posterior instrumentation should be obtained. Calcified great vessels visualized on preoperative radiographs should be retracted carefully to minimize the risk of a thrombotic event with catastrophic consequence. Pulse oximetry placed on the left second toe can alert the surgeon to the need for emergent thrombectomy of the left lower extremity vessels. A retroperitoneal approach is favored over a transperi-toneal approach. The transperitoneal approach is associated with a five- to 10-fold increase in retrograde ejaculation as a complication. Placement of the conventional Pyramid plate needs to be flush on both vertebral bodies because it relies on friction with the screw/plate/bone interface for fixation. This implies that all osteophytes must be removed and the plate may not be ideal with spondylolisthesis. The locking plate is a fixed angle device and it still affords stability even if the plate is not fully seated on bone. When placing the ATB plate at all levels above L5-S1, careful attention must be paid to the great vessels.

Tips, Pearls, and Lessons Learned

An experienced vascular surgeon minimizes the risk of vascular injury during the approach. The placement of the interbody graft should be recessed a few millimeters in the disk space. Lateral fluoroscopy is helpful in identifying the disk space margins as the implant is seated and is useful to guide plate and screw placement. The osteophytes should be rongeured before plate placement to ensure maximum bony contact. The smallest plate possible should be used to minimize the risk of vascular erosion. Placement of the plate should be away from the vessels, avoiding direct placement under venous structures.

Key Procedural Steps

Direct Anterior Approach with the ATB Plate