The patient described in the clinical scenario has a high-grade L5/S1 spondylolisthesis. Surgical reduction of this condition places the L5 nerve root at risk. Injury to the L5 nerve root can manifest as weakness to hip abduction, EHL, and tibialis anterior (dual innervation with L4). Sensory manifestations would include pain or paresthesia over the lateral calf and dorsal foot.
Cheung et al reviewed spondylolysis and spondylolisthesis in adolescents. They recommended in-situ L5 to S1 posterolateral fusion for low-grade (<50%) slips that have failed non-surgical management. Although still controversial, they recommend in-situ L4-S1 fusion for high-grade slips.
Lonner et al addressed the pros and cons of surgical reduction for high-grade pediatric spondylolisthesis. In their review of five patients who underwent decompression and reduction, two had L5 nerve root deficits which resolved within three months. Benefits of reductions included decrease in slip progression, restoration of sagittal balance, regional balance and improved clinical outcomes.
Petraco et al performed a cadaveric stidu to quantify the change in length of the L5 nerve root associated with reduction of spondylolisthesis. They found that the risk of stretch injury to the L5 nerve with reduction of a high-grade spondylolisthesis is not linear; with 71% of the total L5 nerve strain occurring during the second half of reduction. They infer that partial reduction may be a significantly safer treatment approach for high-grade spondylolisthesis than complete reduction.
1. Decreased patellar reflexes would be caused by an L4 nerve injury.
2. Weakness to hip flexion would be caused by injury to L1-3.
4. Weakness to knee extension would be caused by an L4 nerve injury.
5. Weakness to ankle plantar flexion would be caused by an S1 nerve injury.
Cheung EV, Herman MJ, Cavalier R, Pizzutillo PD. Spondylolysis and spondylolisthesis in children and adolescents: II. Surgical management. J Am Acad Orthop Surg. 2006 Aug;14(8):488-98.
PMID:16885480 (Link to Abstract)
Lonner BS, Song EW, Scharf CL, Yao J. Reduction of high-grade isthmic and dysplastic spondylolisthesis in 5 adolescents. Am J Orthop (Belle Mead NJ). 2007 Jul;36(7):367-73.
PMID:17694184 (Link to Abstract)
Petraco DM, Spivak JM, Cappadona JG, Kummer FJ, Neuwirth MG. An anatomic evaluation of L5 nerve stretch in spondylolisthesis reduction. Spine (Phila Pa 1976). 1996 May 15;21(10):1133-8; discussion 1139.
PMID: 8727186 (Link to Abstract)