An Acta Orthopaedica educational article: Treatment of pediatric spondylolysis and spondylolisthesis

Abstract

Spondylolysis is defined as a defect or elongation in the pars interarticularis of the lumbar spine, either unilateral or bilateral. Growing children with bilateral spondylolysis may develop spondylolisthesis, i.e., forward slipping of the affected vertebra. The etiology of spondylolysis is regarded as a stress fracture due to repetitive loading associated with a genetic predisposition. Lumbar magnetic resonance imaging (MRI) shows an increased signal intensity before an actual fracture line develops. In low grade spondylolisthesis, two-thirds of children with acute pediatric spondylolysis will undergo bony union with early activity restriction. Health-related quality of life is improved in patients achieving bony union as compared with patients having non-union, of which one-fourth will additionally develop spondylolisthesis. In patients with high-grade spondylolisthesis, defined as a more than 50% forward slippage of the affected vertebra, spinal fusion is recommended to prevent further progression.

Figure 1

Stress fracture of the pars interarticularis.

Figure 2

Progressive unilateral spondylolysis in the pars interarticularis of the L5. (A) axial CT, (B) sagittal reformatting.

Figure 3

(A) Isthmic and (B) dysplastic spondylolisthesis in T2 weighted MR images. Central spinal canal remains wide in the isthmic lesion, while in the dysplastic lesion it has narrowed. The sacrum has developed a ridge necessitating sacral osteotomy (ridge resection) to facilitate reduction of the forward slip and bony healing.

Figure 4

Radiographic healing of the progressive unilateral spondylolysis on CT after 4 months’ activity restriction. (A) Axial and (B) sagittal reformatting demonstrate bony bridging of the stress fracture, although trabeculation is not complete.

Figure 5

Low-grade spondylolisthesis at 2-year follow-up radiograph after non-union of bilateral L5 spondylolysis.

Figure 6

(A) Bilateral L5 spondylolysis. (B, C) Revision of the pseudoarthrosis with bilateral pedicle screw and hook instrumentation.

Figure 7

High-grade spondylolisthesis in a 9-year-old girl. (A) Standing lateral radiograph shows pelvic retroversion (increased pelvic tilt) and lower thoracic lordosis as a sign of compensatory mechanisms for sagittal imbalance. (B) Axial T2 weighted MR image shows central canal stenosis typical of dysplastic high-grade spondylolisthesis. (C) Instrumented spinal fusion from L4 to S1 was supplemented by iliac screws to prevent bending of sacrum between S1 and S2 disc space. Reduction was facilitated by sacral dome osteotomy and interbody fusion was carried out to increase the possibilities for circumferential spinal fusion.

Figure 8

Spondyloptosis in a 12-year-old girl with bilateral L5 radicular symptoms. (A) Standing radiograph shows pelvic retroversion. (B) Sagittal T2 weighted MR image shows spondyloptosis with narrowing central spinal canal. (C) Sagittal reformatting of lumbar CT shows remodeling of the S1 endplate with residual apophyseal growth plate. (D) Axial CT image with trans-sacral screw fixation with a non-vascular fibular strut. (E) Standing lateral and (F) posteroanterior radiograph at 2-year follow-up shows bridging bone formation posterolaterally and reduced pelvic retroversion.