Staged Correction of Severe Thoracic Kyphosis in Patients with Multilevel Osteoporotic Vertebral Compression Fractures

Paraspinal myopathy-induced intervertebral disc degeneration and thoracolumbar kyphosis in TSC1mKO mice model-a preliminary study

BACKGROUND

Increasing kyphosis of the spine in a human is a well-recognized clinical phenomenon that has been associated with back pain, poor physical performance and disability. The pathophysiology of age-related kyphosis is complex and has been associated with physiological changes in vertebrae, intervertebral disc (IVD) and paraspinal musculature, which current cross-sectional studies are unable to demonstrate. Creating an in vivo, paraspinal myopathic animal model for longitudinal study of these changes under controlled conditions is thus warranted.

PURPOSE

To confirm the TSC1 gene knockout effect on paraspinal muscle musculature; to analyze the development of spinal kyphosis, IVD degeneration and vertebra structural changes in a longitudinal manner to gain insights into the relationship between these processes.

STUDY DESIGN

A prospective cohort study of 28 female mice, divided into 4 groups-9-month-old TSC1mKO (n=7), 9-month-old control (n=4), 12-month-old TSC1mKO (n=8), and 12-month-old controls (n=9).

METHODS

High resolution micro-computed tomography was used to measure sagittal spinal alignment (Cobb's angle), vertebral height, vertebral body wedging, disc height index (DHI), disc wedge index (DWI), histomorphometry of trabecular bone and erector spinae muscle cross-sectional area. Paraspinal muscle specimens were harvested to assess for myopathic features with H&E stain, muscle fiber size, density of triangular fiber and central nucleus with WGA/DAPI stain, and percentage of fibers with PGC-1α stain. Intervertebral discs were evaluated for disc score using FAST stain.

RESULTS

Compared to controls, paraspinal muscle sections revealed features of myopathy in TSC1mKO mice similar to human sarcopenic paraspinal muscle. While there was significantly greater presence of small triangular fiber and density of central nucleus in 9-and 12-month-old TSC1mKO mice, significantly larger muscle fibers and decreased erector spinae muscle cross-sectional area were only found in 12-month-old TSC1mKO mice compared to controls. TSC1mKO mice developed accelerated thoracolumbar kyphosis, with significantly larger Cobb angles found only at 12 months old. Structural changes to the trabecular bone in terms of higher bone volume fraction and quality, as well as vertebral body wedging were observed only in 12-month-old TSC1mKO mice when compared to controls. Disc degeneration was observed as early as 9 months in TSC1mKO mice and corresponded with disc wedging. However, significant disc height loss was only observed when comparing 12-month-old TSC1mKO mice with controls.

CONCLUSIONS

This study successfully shows the TSC1 gene knockout effect on the development of paraspinal muscle myopathy in a mouse which is characteristic of sarcopenia. The TSC1mKO mice is by far the best model available to study the pathological consequence of sarcopenia on mice spine. With paraspinal muscle myopathy established as early as 9 months, TSC1mKO mice developed disc degeneration and disc wedging. This is followed by kyphosis of the spine at 12 months with concomitant disc height loss and vertebral body wedging due to bone remodeling. Age-related bone loss was not found in our study, suggesting osteoporosis and myopathy-induced vertebral body wedging are likely two independent processes.

CLINICAL SIGNIFICANCE

This is the first study to provide key insights on the early and late consequences of paraspinal myopathy on intervertebral disc degeneration, spinal kyphosis, and vertebral body changes. With this new understanding, future studies evaluating therapies for spinal degeneration may be performed to develop time-sensitive interventions.

Osteoporotic Thoracolumbar Vertebral Fractures With Neurological Deficit Treated by Balloon Kyphoplasty Augmented with Newly Developed Minimally Invasive Posterior Hook Stabilization

Most osteoporotic vertebral fractures (OVFs) are treated conservatively, but surgery is often indicated for residual pain, neuropathy, or severe deformity. OVFs tend to develop in elderly patients, so less invasive surgery is desirable. Surgery is mainly performed to stabilize the fractured vertebral body. Percutaneous cement augmentation, such as via balloon kyphoplasty (BKP), has produced satisfactory results as a surgical method for managing OVFs. Posterior fixation with implants is often performed with or without cement augmentation when stronger fixation is considered necessary for OVFs with local kyphosis and angular instability. Pedicle screws (PSs) are widely used as an implant for posterior fixation, but given the risk of backing out in bones with severe osteoporosis, several measures have been taken to increase the strength such as by adding hooks. In cases of osteoporosis, hooks that can use cortical bone as an anchor are considered more useful than PS but are rarely used in minimally invasive surgery. We developed a minimally invasive posterior hook stabilization approach to directly stabilize the posterior spinal components as a new augmentation method for BKP and applied it to four cases of thoracolumbar OVF with neurological symptoms. The operation time was about 60 minutes, including BKP, and the estimated blood loss was about 10 ml. No postoperative implant problems occurred, and in all cases, neurological symptoms, such as buttocks and leg pain, were alleviated at an early stage after surgery. One patient had a postoperative adjacent vertebral body fracture that was conservatively treatable. Minimally invasive posterior hook stabilization, which we developed as a way of augmenting BKP, was considered useful for managing vertebral body fractures of the thoracolumbar spine with local kyphosis and angular instability.

Planned two-stage surgery using lateral lumbar interbody fusion and posterior corrective fusion: a retrospective study of perioperative complications

PURPOSE

To determine the effect of planned two-stage surgery using lateral lumbar interbody fusion (LLIF) on the perioperative complication rate following corrective fusion surgery in patients with kyphoscoliosis.

METHODS

Consecutive patients with degenerative scoliosis who underwent corrective fusion were divided into a control group that underwent single-stage posterior-only surgery and a group that underwent planned two-staged surgery with LLIF and posterior corrective fusion. We collected the patient background and surgical data and assessed the perioperative complication rates. We also investigated spinopelvic parameters and patient-reported outcome measurements (PROMs).

RESULTS

One hundred and thirty-eight patients of mean age 69.8 (range, 50-84) years who met the study inclusion criteria were included. The two-stage group (n = 75) underwent a staged anterior-posterior surgical procedure, and the control group (n = 63) underwent single-stage surgery. There was no significant between-group difference in the incidence of perioperative complications, except for deep wound infection (reoperation is necessary for surgical site infection). Revision surgery within 3 months of the initial surgery was more common in the control group (n = 8, 12.7%) than in the two-stage group (n = 3, 4.0%). Spinopelvic parameters and PROMs were significantly better in the two-stage group at 2 years postoperatively.

CONCLUSION

The complication rate for planned two-stage surgery was similar to that of previous posterior-only single-stage surgery. However, early reoperation was less common, and the degree of spinal correction and clinical results were significantly better after two-stage surgery.

The Morphology and Clinical Significance of the Extraforaminal Ligaments at the T1-T12 Levels

STUDY DESIGN

A dissection-based study of 10 embalmed human cadavers.

OBJECTIVE

The purpose of this study was to describe the extraforaminal ligaments in the exit regions of the T1-T12 intervertebral foramina and to discuss their possible clinical significance.

SUMMARY OF BACKGROUND DATA

The ligaments at the lumbar intervertebral foramina have been well studied. However, detailed descriptions of the extraforaminal ligaments at the T1-T12 levels are lacking.

METHODS

Two hundred forty T1-T12 intervertebral foramina from 10 embalmed cadavers were studied. The presence of the ligament was noted. The quantity, morphology, distributions, proximal attachments, distal attachments, and spatial orientations of the extraforaminal ligaments in the exit regions of the T1-T12 intervertebral foramina were examined. The length, width, diameter, and thickness of the ligaments were measured with digital calipers by three independent investigators.

RESULTS

A total of 564 extraforaminal ligaments were identified in the 229 intervertebral foramina; no ligaments were found in the other 11 intervertebral foramina, resulting in an occurrence rate of extraforaminal ligaments of 95.42%. One hundred thirty-six (24.11%) of the extraforaminal ligaments were radiating ligaments, and 428 (75.89%) were transforaminal ligaments. Radiating ligaments had a tendency to be abundant at T1 and T9-T12 and sparse at T2-T8. There were 245 (43.44%) ligaments at the anterior aspect of the exit regions of the intervertebral foramina, 225 (39.89%) ligaments at the posterior aspect, 64 (11.35%) ligaments at the inferior aspect, and 30 (5.32%) ligaments at the superior aspect.

CONCLUSION

In the exit region of thoracic intervertebral foramina, there are two types of extraforaminal ligaments. They may serve as a protective mechanism against traction and play a role in the positioning of the nerves in the intervertebral foramen. Transforaminal ligaments may be an underlying cause of rib or chest pain after thoracic fracture and may be of clinical importance to surgeons.

LEVEL OF EVIDENCE

N/A.