Review Question - QID 219591

For the treatment of adult isthmic spondylolisthesis, ALIF has demonstrated improved segmental lordosis and disc height compared to TLIF (Answer 1). This improvement is purportedly due to the anterior longitudinal ligament's direct release during the ALIF approach.

Adult isthmic spondylolisthesis is characterized by pars interarticularis defects that result in subluxation of one vertebral body anterior to the adjacent inferior vertebral body. It most commonly occurs at the L5/S1 junction and may lead to worsening pain and radiculopathy. In a healthy spine, lumbar lordosis is primarily generated by the lower lumbar segments, and the segmental alignment at the lumbosacral junction can have a significant impact on global spinal alignment. Therefore, the central goal of surgically treating isthmic spondylolisthesis is maintaining or improving sagittal balance. ALIF has been shown to significantly increase the resultant post-operative disc height and segmental lordosis compared to TLIF. These findings result in greater indirect neural decompression and could (1) substantially affect global sagittal balance over time and (2) reduce the progression of adjacent segment degeneration. While prospective randomized control trials are lacking, contemporary findings suggest ALIF (+/- posterior percutaneous pedicle screws) provides better radiographic and patient-reported outcomes for the treatment of L5-S1 isthmic spondylolisthesis compared to TLIF.

Tye and colleagues retrospectively reviewed their institutional results, comparing the clinical, radiographic, and financial differences between TLIF and ALIF for L5-S1 adult isthmic spondylolisthesis. They reported no difference in the total cost between both procedures. Further, they found that ALIF significantly improved segmental lordosis, disc height, and outcome scores at one year. The authors concluded that the superior radiographic outcomes achieved with ALIF may have contributed to improved clinical outcomes.

Lightsey and colleagues performed a similar retrospective review comparing the outcomes of ALIF to TLIF for treating L5-S1 adult isthmic spondylolisthesis. They reported that ALIF generated greater segmental and L4-S1 lordosis, greater disc height, and more improved patient-reported outcome scores at final follow-up. The authors concluded that ALIF generates multiple improved radiographic outcomes and patient-reported outcomes relative to TLIF patients.

Figure A demonstrates a lateral radiographic lumbar spine image where bilateral pars defects resulted in anterolisthesis of the L5 vertebral body relative to S1.

Incorrect Answers:
Answer 2: ALIF’s direct approach carries a HIGHER risk of injury of the superior hypogastric plexus, resulting in sexual dysfunction (i.e., retrograde ejaculation). The TLIF’s approach does not place patients at risk for sexual dysfunction.
Answer 3: ALIF and TLIF have similar, high rates of successful fusion.
Answer 4: The TLIF approach involves direct visualization and decompression of nerve roots. Since the ALIF approach does not allow visualization, neural decompression is achieved indirectly by restoring disc height space and/or correcting anterolisthesis.
Answer 5: Given that its approach requires dissection through the abdomen, ALIF has the added risk of post-operative retroperitoneal hematomas. However, given that its dissection is away from the spinal cord and nerve roots, ALIF imparts a lower risk of injury to the dura and neural structures than posterior-based approaches.