Spinal cord compression in Scheuermann's kyphosis: case report

Spinal cord intramedullary pressure in thoracic scoliotic deformity: a cadaveric study

STUDY DESIGN

In vitro cadaveric study of thoracic spinal cord intramedullary pressure (IMP) in scoliotic deformity.

OBJECTIVE

To define the relationship between thoracic scoliotic deformity and spinal cord IMP.

SUMMARY OF BACKGROUND DATA

Clinical studies of patients with thoracic scoliosis without other spinal pathology (spinal stenosis, etc.) have rarely reported an associated thoracic myelopathy. Previous clinical and cadaveric studies of kyphosis have reported associated myelopathy and increased spinal cord IMP. We sought to determine if IMP changes in response to main thoracic scoliotic deformity.

METHODS

In 6 fresh-frozen cadavers, a progressive main thoracic scoliotic deformity was created. Cadavers were positioned sitting with physiological spinal alignment, head stabilized using a skull clamp and spine segmentally instrumented from occiput to L3. The T3-T4 ligamentum flavum was removed, dura opened, and 3 pressure sensors were advanced caudally to T4-T5, T7-T8, and T10-T11 within the cord parenchyma. A step-wise main thoracic scoliotic deformity was then induced by sequentially releasing and retightening the skull clamp while coronally bending, concavity compressing, and convexity distracting posterior segmental instrumentation, allowing closure of lateral segmental osteotomies. After each step, fluoroscopic images and pressure measurements were obtained; the T4-T11 coronal Cobb angle was measured.

RESULTS

Induction of main thoracic scoliosis did not significantly increase IMP. The mean main thoracic maximal scoliotic deformity created was 77° ± 2° (range: 71°-84°). At maximal deformity, the mean ΔIMP at T4-T5, T7-T8, T10-T11 was 2.2 ± 1.9 mm Hg, 1.0 ± 0.7 mm Hg, and 1.0 ± 0.8 mm Hg, respectively.

CONCLUSION

In this cadaveric study, main thoracic scoliotic deformity did not significantly increase thoracic IMP. This correlates with clinical presentation such that clinical studies of patients with thoracic scoliosis without other spinal pathology have rarely reported an associated thoracic myelopathy with the thoracic scoliosis. This study helps explain the relative absence of myelopathy in isolated main thoracic coronal plane deformity.

LEVEL OF EVIDENCE

5.

Spinal cord intramedullary pressure in thoracic kyphotic deformity: a cadaveric study

STUDY DESIGN

In vitro cadaveric study of thoracic spinal cord intramedullary pressure (IMP) in kyphotic deformity.

OBJECTIVE

To define the relationship between thoracic spinal kyphotic deformity and spinal cord IMP.

SUMMARY OF BACKGROUND DATA

Previous studies of asymptomatic volunteers have revealed that there is wide variation in regional sagittal neutral upright thoracic spinal alignment with "normal" thoracic T4-T12 kyphosis ranging up to approximately +69° for 98.5% of the asymptomatic adult population. We sought to determine whether IMP changes in response to increasing thoracic kyphosis.

METHODS

In 8 fresh-frozen cadavers, a progressive kyphotic deformity was created. Cadavers were positioned sitting with physiological thoracic kyphosis, head stabilized using a skull clamp, and spine segmentally instrumented from occiput to L2. The T3-T4 ligamentum flavum was removed, dura opened, and 3 pressure sensors were advanced caudally to T4-T5, T7-T8, and T11-T12 within the cord parenchyma. A stepwise thoracic kyphotic deformity was then induced by sequentially releasing and retightening the skull clamp while distracting posterior short segment rods and closing anterior segmental osteotomies. After each step, fluoroscopic images and pressure measurements were obtained; the T4-T12 Cobb angle was measured.

RESULTS

Minor IMP increases of 2 to 5 mm Hg were observed at 1 or more spinal cord levels in 1 of 8 cadavers when the Cobb angle was less than +51° and in 4 of 8 cadavers when the angle was more than +51° and less than +63°. For Cobb angles more than +51° and less than +63°, a statistically significant, minor increase in IMP was detected at the T7-T8 level only (P = 0.02). At Cobb angles exceeding +63°, ΔIMP progressively increased at 1 or more spinal cord levels in 8 of 8 cadavers. Cobb angles ranging from +63° to +149° resulted in statistically significant increases in IMP ranging to more than 50 mm Hg. ΔIMP did not correlate with segmental spinal canal diameter (stenosis).

CONCLUSION

Thoracic kyphosis less than +51° resulted in no meaningful increase in IMP, whereas kyphosis measuring +51° to +63° resulted in minor increases in IMP. After the thoracic kyphosis exceeded +63°, IMP increased significantly. ΔIMP with spinal alignment may help explain the wide range of "normal" thoracic neutral upright sagittal alignment in studies of asymptomatic adult individuals and may help further define thoracic kyphotic deformity.

Acutely progressing paraplegia caused by traumatic disc herniation through posterior Schmorl's node opening into the spinal canal in lumbar Scheuermann's disease

STUDY DESIGN

A case report.

OBJECTIVE

To report an unusual neurologic complication caused by traumatic disc herniation through atypical posterior Schmorl's node (SN) opening into the spinal canal in lumbar Scheuermann's disease.

SUMMARY OF BACKGROUND DATA

Neurologic complications in Scheuermann's disease are rare and disc hernia has been reported as one of the causes of neural compression. However, there has been no report on acutely progressing paraplegia caused by traumatic disc herniation through an atypical posterior SN opening into the spinal canal in lumbar Scheuermann's disease.

METHODS

A clinical and radiologic review of such a case of traumatic disc herniation through an atypical posterior SN that resulted in acutely progressing paraplegia in Scheuermann's disease was performed.

RESULTS

The patient presented with severe back pain after a fall, without any neurologic abnormalities. Computed tomographic scan revealed lumbar Scheuermann's disease, acute compression fracture of T12, and a large posterior SN with "trough-like" indentation of the lower endplate of T12 opening into the spinal canal. Abruptly progressing paraplegia occurred in less than 24 hours after the first visit and the magnetic resonance imaging revealed severe spinal cord compression by large disc extrusion with superior migration at T12-L1 through the atypical posterior SN at the lower endplate of T12. The patient underwent posterior decompression and discectomy at T12-L1 through transfacet pedicle-sparing approach. Postoperatively, the patient showed immediate improvement in the sensory deficit on L1 dermatome and the perianal area and motor function of the hip flexors to grade 2 without further neurologic improvement, at 2-year follow-up.

CONCLUSION

The case report highlights the clinical significance of the atypical posterior SN that could be a channel for large disc extrusion after a traumatic event in Scheuermann's disease and the clinical importance of surgeon's close attention to the possibility of abruptly progressing neurologic compromise in this situation.

Thoracic cord compression caused by disk herniation in Scheuermann's disease: a case report and review of the literature

We present the case of a 14-year-old male with Scheuermann's disease and significant neurological deficit due to thoracic disk herniation at the apex of kyphosis. He was treated with an anterior decompression, anterior and posterior fusion in the same setting using plate, cage and a segmental instrumentation system. The patient had an excellent outcome with complete neurological recovery.

Scheuermann’s kyphosis: surgical management

Indications for surgery in Scheuermann disease are not well codified and remain rare, as the natural history of the disease is in most cases benign. In the immature adolescent, conservative treatment, such as bracing or casting, can be tried for moderate curves. For larger curves, or in the adult, conservative treatment is usually not effective, and surgery can be considered. Such indications are mostly cosmetic for large curves above 75 degrees. Pain over the deformity or in the low back may represent another surgical indication, especially in the adult group. The question of anterior release or straight posterior fusion has become more of an actuality with the advent of powerful, third-generation stiff segmental instrumentation. However, the long-term results of a modern, posterior-only instrumentation fusion are not known. Concern about loss of correction, late pseudarthrosis or the need to remove instrumentation for infected hardware or due to late pain at the operative site must make us careful about choosing this method. Very rigid and large curves still require an anterior release, either done in a conventional or mini-open fashion, or through video-assisted thoracoscopic surgery. The extent of the posterior instrumentation has now been better defined. One must fuse the whole Cobb angle without hypercorrection and stop distally, above the first lordotic disc, to avoid sagittal decompensation. New approaches such as short anterior fusion with bone-on-bone techniques and pedicle substraction osteotomies have not yet been reported in the literature as having been used for treating Scheuermann's kyphosis. These should be considered experimental.