Morphometric effects of acute shortening of the spine: the kinking and the sliding of the cord, response of the spinal nerves

Could extended laminectomy effectively prevent spinal cord injury due to spinal shortening after 3-column osteotomy?

OBJECTIVE

To explore whether the laminectomy extension can effectively prevent spinal cord injury (SCI) due to spinal shortening after 3-column osteotomy in goat models.

METHODS

A total of twenty healthy goats were included and done with 3-column osteotomy of T13 and L1 under the somatosensory evoked potential (SSEP) monitoring. The samples were divided into two groups. The first group underwent regular laminectomy while the second group underwent an extended laminectomy with an extra 10 mm-lamina cranial to L2. The SSEP measured after 3-column osteotomy was set as the baseline, and the SSEP decreased by 50% from the baseline amplitude and/or delayed by 10% relative to the baseline peak latency was set as positive results, which indicated spinal cord injury. The vertebral column was gradually shortened until the SSEP monitoring just did not show a positive result. The height of the initial osteotomy gap (the distance from the lower endplate of T12 to the upper endplate of L2), the shortened distance (△H), the number of spinal cord angulated and the changed angle of the spinal cord (△α) were measured and recorded in each group. Neurological function was evaluated by the Tarlov scores on day 2 postoperatively.

RESULTS

All the goats except one of the first group due to changes in the SSEP during the osteotomy were included and analyzed. In the first group, the height of the initial osteotomy segment and the safe shortening distances were 61.6 ± 2.6 mm and 35.2 ± 2.6 mm, respectively; the spinal cord of 5 goats was angulated (46.4 ± 6.6°), the other four goats were kinked and not angulated. In the second group, the height of the initial osteotomy segment and the safe shortening distances were 59.8 ± 1.5 mm and 43.3 ± 1.2 mm, respectively, and the spinal cord of ten goats were angulated (97.6 ± 7.2°). There was no significant difference in the height of the initial osteotomy segment between the two groups by using Independent-Samples T-Test, P = 0.095 (P > 0.05); there were significant difference in the safe shortening distance and the changed angle of the spinal cord between the two groups by using Independent-Samples T-Test (both [Formula: see text]H and [Formula: see text]α of P < 0.001), the difference between their mean were 8.1 mm and 51.2°. Significant difference was found in the number of spinal cord angulation between the two groups through Fisher's exact test (5/9 vs. 10/10, P = 0.033).

CONCLUSIONS

An additional resection of 10 mm-lamina cranial to L2 showed the satisfactory effect in alleviating SCI after 3-column osteotomy. Timely and appropriate extend laminectomy could be a promising therapeutic strategy for SCI attributable to facilitating spinal cord angulation rather than spinal cord kinking and increasing the safe shortening distance.

One-stage Spine-shortening Osteotomy Treated Severe Spinal Deformity Associated With Spinal Cord Malformations

STUDY DESIGN

Retrospective case series.

OBJECTIVE

To evaluate the safety and efficacy of spine-shortening using 1-stage 3-column osteotomy for a severe rigid spinal deformity with a spinal cord malformation (SCM).

SUMMARY OF BACKGROUND DATA

One-stage spine-shortening osteotomy has been suggested for the treatment of a tethered spinal cord. However, the safety and efficacy of 1-stage spine-shortening osteotomy for the treatment of a severe spinal deformity with an SCM is not known.

METHODS

The records of 32 patients with a severe spinal deformity and SCM treated with spine-shortening using 3-column osteotomy from January 2010 to December 2016 were analyzed retrospectively. Intraoperative neurophysiological monitoring was used in all cases. Imaging parameters and neurological complications were analyzed to evaluate clinical safety and efficacy.

RESULTS

Spine-shortening using a 3-column osteotomy was conducted successfully in all 32 patients. The mean main coronal curve and maximum kyphotic angle were corrected from 119.8 and 119.1 degrees to 58.6 and 53.9 degrees, respectively, with the corrective rate of 51.4% and 54.3%. The mean correction loss of the major coronal curve and maximum kyphosis was 2.3 and 2.6 degrees, respectively, at a mean follow-up of 73.6 months. Intraoperative monitoring events occurred in 9 patients; of these 9 patients, 3 suffered transient SC injury, and all recovered within 1 year without suffering permanent paralysis.

CONCLUSIONS

Spine-shortening using a 3-column osteotomy seems to be safe and efficacious for treating a severe spinal deformity with an SCM. A deep understanding of the method and intensive intraoperative neuromonitoring improved the safety of this challenging and complex surgical procedure.

Treatment of rigid post-traumatic thoracolumbar kyphosis by a novel technique of spinal joints release

OBJECTIVE

The purpose of this study was to evaluate the feasibility of a novel technique named spinal joints release (SJR) and observe its efficacy in treating rigid post-traumatic thoracolumbar kyphosis (RPTK).

METHODS

RPTK patients who were treated by SJR with facet resection, limited laminotomy, clearance of the intervertebral space, and release of the anterior longitudinal ligament through the intervertebral foramen and disc of injury segment from August 2015 to August 2021 were reviewed. Intervertebral space release, internal fixation segment, operation time, and intraoperative blood loss were recorded. The intraoperative, postoperative, and final follow-up complications were observed. An improvement in the VAS score and ODI index was observed. Spinal cord functional recovery was evaluated by American Spinal Injury Association Impairment Scale (AIS). Improvement of local kyphosis (Cobb angle) was evaluated by radiography.

RESULTS

Forty-three patients were successfully treated by the SJR surgical technique. Open-wedge anterior intervertebral disc space was performed in 31 cases, and repeated release and dissection of the anterior longitudinal ligament and callus were performed in 12 cases. There was no lateral annulus fibrosis release in 11 cases, the anterior half release of lateral annulus fibrosis in 27 cases, and complete release in five cases. There were five cases of screw placement failure in one or two side pedicles of the injured vertebrae due to excessive resection of the facets and improper pre-bending of the rod. Sagittal displacement occurred in four cases at the released segment due to the complete release of bilateral lateral annulus fibrosus. Autologous granular bone + Cage was implanted in 32 cases, and autologous granular bone was implanted in 11 cases. There were no serious complications. The average operation time was 224 ± 31 min, and intraoperative blood loss was 450 ± 225 mL. All the patients were followed up with an average of 26 ± 8.5 months. The VAS scores and ODI index improved significantly at the final follow-up. All of the 17 patients with incomplete spinal cord injury achieved more than one grade of neurological recovery at the final follow-up. An 87% correction rate of kyphosis was achieved and maintained, with the Cobb angle decreasing from 27.7° preoperatively to 5.4° at the final follow-up.

CONCLUSION

Posterior SJR surgery for patients with RPTK has the advantages of less trauma and less blood loss, and kyphosis correction is satisfactory.

Biomechanical comparison of spinal column shortening - a finite element study

BACKGROUND

At present, research on spinal shortening is mainly focused on the safe distance of spinal shortening and the mechanism of spinal cord injury, but there is no research on the biomechanical characteristics of different shortening distances. The purpose of this study was to study the biomechanical characteristics of spine and internal fixation instruments at different shortening distances by the finite element (FE) method.

METHODS

An FE model of lumbar L1-S was established and referred to the previous in vitro experiments to verify the rationality of the model by verifying the Intradiscal pressure (IDP) and the range of motion (ROM) of the motion segment. Five element models of spinal shortening were designed under the safe distance of spinal shortening, and the entire L3 vertebra and both the upper and lower intervertebral discs were resected. Model A was not shortened, while models B-E were shortened by 10%, 20%, 30% and 50% of the vertebral body, respectively. Constraining the ROM of the sacrum in all directions, a 7.5 N ·m moment and 280 N follower load were applied on the L1 vertebra to simulate the motion of the lumbar vertebrae in three planes. The ROM of the operated segments, the Von Mises stress (VMS) of the screw-rod system, the VMS of the upper endplate at the interface between the titanium cage and the L4 vertebral body, and the ROM and the IDP of the adjacent segment (L5/S) were recorded and analysed.

RESULTS

All surgical models showed good stability at the operated segments (L1-5), with the greatest constraint in posterior extension (99.3-99.7%), followed by left-right bending (97.9-98.7%), and the least constraint in left-right rotation (84.9-86.3%) compared with the intact model. The VMS of the screw-rod system and the ROM and IDP of the distal adjacent segments of models A-E showed an increasing trend, in which the VMS of the screw-rod system of model E was the highest under flexion (172.5 MPa). The VMS of the endplate at the interface between the cage and L4 upper endplate of models A-E decreased gradually, and these trend were the most obvious in flexion, which were 3.03, 2.95, 2.83, 2.78, and 2.61 times that of the intact model, respectively.

CONCLUSION

When performing total vertebrae resection and correcting the spinal deformity, if the corrected spine has met our needs, the distance of spinal shortening should be minimized to prevent spinal cord injury, fracture of internal fixations and adjacent segment disease (ASD).

Protective effect of extended laminectomy on spinal cord injury induced by spinal shortening

This study aims to investigate the effect of extended laminectomy (EL) on spinal cord injury (SCI) caused by spinal shortening and further the best time for performing this operation and the optimal length of the additional lamina to remove. Dogs were allocated to 6 groups and all received spinal column shortening at T13 segment. Animals in the control group received non-extended laminectomy following shortening. Those in the "1-lamina EL 6h" group underwent laminectomy with an additional 1-lamina length removed 6h post shortening. For the "1.5-lamina EL 6h" and "1.5-lamina EL 12h" groups, the animals had an extra 1.5-lamina length of lamina resected at 6h and 12h, respectively, post shortening. In the "2-lamina EL 6h" and "2-lamina EL 12h" groups, an extra 2-lamina length was removed at 6h and 12h post shortening, respectively. Somatosensory evoked potential (SSEP) and neurological function were recorded periodically; spinal cord blood flow (SCBF) and nerve cell apoptosis were detected. We have discovered that resection of an additional 1-lamina length appeared not adequate to relieve the sharp kinking of the spinal cord, whereas the kinking disappeared when the laminectomy extended to an additional 2-lamina length. The "1-lamina EL 6h" and "1.5-lamina EL 12h" groups showed no significant difference, as compared with the control, in latency of SSEP, SCBF, hind-limb function and apoptosis. By contrast, significant recovery of SSEP, SCBF and hind-limb function as well as reduction of apoptosis presented in other three experimental groups. The "2-lamina EL 6h" group, in particular, showed the most prominent recovery. In conclusion, in the case of shortening of 2/3 vertebral body length with 2 laminae resected, an additional resection of two laminae at 6 h post shortening showed the best performance in alleviating SCI. Timely and adequately extended laminectomy could be a potential therapeutic strategy for SCI due to spinal shortening.

Relationship between the laminectomy extension and spinal cord injury caused by acute spinal shortening: goat in vivo experiment

OBJECTIVE

To investigate the relationship between different types of laminectomy extension and spinal cord injury subsequent to acute spinal shorting after 3-column osteotomy in living goat model.

METHODS

A total of 18 healthy goats were selected, and a procedure of bivertebral column resections and total laminectomy of T13 and L1 was completed followed by different laminectomy extensions under the somatosensory evoked potential (SSEP) monitoring. The samples were divided into three groups according to types of subsequent laminectomy extension. In the first group (enlarged resection of upper lamina group), laminectomy extension was performed on 10 mm caudal to T12; in the second group (equidistant enlarged resection of upper and lower lamina group), laminectomy extension was performed on 5 mm caudal to T12 and 5 mm cranial to L2 simultaneously; and in the third group (enlarged resection of lower lamina group), laminectomy extension was performed on 10 mm cranial to L2. The SSEP measured after vertebral resection was set as the baseline, and the SSEP decreased by 50% from the baseline amplitude and/or delayed by 10% relative to the baseline peak latency was set as positive results, which indicated spinal cord injury. Spinal column was gradually shortened until the SSEP monitoring just did not show a positive result. The shortened distance (ΔH) and the changed angle of the spinal cord buckling (Δα) were measured in each group. Neurologic function was recorded by the Tarlov scores at 2 days after the surgery.

RESULTS

The safe shortening distances of three groups were 38.6 ± 1.2 mm, 41.5 ± 0.7 mm, 43.7 ± 0.8 mm, respectively; the corresponding changed angles of the spinal cord buckling were 62.8 ± 6.9°, 82.8 ± 7.5°, and 98.5 ± 7.0°. Significant differences of ΔH and Δα were found among the three groups by LSD multiple comparison test (P < 0.05). Strong correlation between ΔH and Δα was shown in each group by Pearson's correlation test.

CONCLUSIONS

Different laminectomy extensions after 3-column osteotomy have different effects on the prevention of SCI caused by acute spinal shortening. The enlarged resection of lower lamina is superior to equidistant enlarged resection of upper and lower laminas which is superior to enlarged resection of upper lamina in preventing SCI. These slides can be retrieved under Electronic Supplementary Material.

Effect of Spinal Shortening for Protection of Spinal Cord Function in Canines with Spinal Cord Angulation

Background

Posterior vertebral column resection (PVCR) has been widely used as a treatment for severe spinal deformity. By using the canine model of vertebral column resection, this study explored the effect of spinal shortening on blood flow and function of the spinal cord during spinal cord angulation.

Material/Methods

The canine model of L1 vertebral column resection was constructed with the PVCR technique. The canines were divided into 5 groups according to the degree of shortening: the 0/4 group, the 1/4 group, the 2/4 group, the 3/4 group, and the control group. Spinal cord blood flow, neuroelectrophysiology, HE staining, nitric oxide, and endothelin-1 were measured during the procedure of vertebral column resection and spinal cord angulation.

Results

The results showed that, in the 1/4 group and the 2/4 group, the blood flow of the spinal cord decreased by 16.5% and 10.6%, respectively, with no obvious damage in the spinal cord; in the 0/4 group and the 3/4 group, the blood flow decreased by 23.5% and 23.1%, respectively, with significant damage in the spinal cord.

Conclusions

When the spinal cord is shortened by 1/4 to 2/4, the tolerance of the spinal cord can increase and spinal cord injury resulting from angulation can be avoided. However, when the shortening reaches 3/4, it is harmful to the spinal cord. Proper shortening of the spinal cord by 1/4 to 2/4 may increase the tolerance of the spinal cord to the damage caused by angulation during PVCR.

Surgical Outcome Comparison of Posterior Vertebral Column Resection with or without Anterior Column Support in Treatment of Yang's Type A Severe Thoracic Spinal Deformity

BACKGROUND

The use of posterior vertebral column resection (PVCR) has extended the treatment of severe spinal deformity. However, the practice guidelines for anterior column support in patients treated by PVCR remain ill defined. The objective of the present study was to compare the clinical and radiographic outcomes of severe thoracic spinal deformity treated by PVCR with and without anterior column support (ACS).

METHODS

We performed a prospective study of 57 patients with severe thoracic deformity (classified as Yang's A type) treated by PVCR with or without anterior column support from January 2010 to April 2015. The patient characteristics, radiographic parameters, intraoperative data, and complications were analyzed to clarify these 2 clinical series.

RESULTS

The sex, age, diagnosis, curve magnitude, and curve type were similar between the PVCR with ACS group (n = 21) and non-ACS group (n = 36) preoperatively. Evaluation of the radiographic parameters, intraoperative data, and complications found no statistically significant intergroup differences, except for the osteotomy distance (non-ACS group, 4.0 cm; ACS group, 5.3 cm; P < 0.001) and shortening distance of the osteotomy gap (non-ACS group, 4.0 cm; ACS group, 3.5 cm; P = 0.005).

CONCLUSIONS

The results of the present study have shown that PVCR without ACS seems to be a safe and effective technique for Yang's A type severe thoracic spinal deformity correction compared with PVCR with ACS. PVCR without ACS requires a relatively smaller osteotomy range and could potentially decrease the risk of implant failure due to bone to bone fusion.

Computed Tomography Based Three-dimensional Measurements of Spine Shortening Distance After Posterior Three-column Osteotomies for the Treatment of Severe and Stiff Scoliosis

STUDY DESIGN

Retrospective study.

OBJECTIVES

This study is to measure and analyze the changes of three-dimensional (3D) distances of spinal column and spinal canal at the three-column osteotomy sites and address their clinical and neurologic significance.

SUMMARY OF BACKGROUND DATA

Three-column osteotomies were developed to treat severe and stiff spine deformities with insufficient understanding on the safe limit of spine shortening and the relationship between the shortening distance of the spinal column and that of the spinal canal.

METHODS

Records of 52 continuous patients with severe and stiff scoliosis treated with three-column spine osteotomies at our institution from July 2013 to June 2015 were reviewed. The preoperative spinal cord function classification were type A in 31 cases, type B in 10 cases, and type C in 11 cases. The types of osteotomies carried out were extended pedicle subtraction osteotomy in nine patients and posterior vertebral column resection in 43 patients. Multimodality neuromonitoring strategies were adopted intraoperatively. 3D pre- and postoperative spine models were reconstructed from the computed tomography (CT) scans. The distances of convex and concave spinal column and the spinal canal shortening were measured and analyzed.

RESULTS

The spinal column shortening distance (SCSD) measured on the 3D models (27.8 mm) were statistically shorter than those measured intraoperatively (32.8 mm) (P < 0.05); however, they were strongly correlated statistically (r = 0.82). The central spinal canal shortening distance (CCSD) was significantly shorter than the convex SCSD (P < 0.05). The convex SCSD and CCSD were significantly shorter in cases with anterior column strut graft than in those with bone-on-bone fusion (P < 0.05).

CONCLUSION

The shortening distance of the convex spinal column cannot represent that of the central spinal canal in patients with severe scoliosis. The spinal column shortening procedure in appropriately selected patient groups with bone-on-bone fusion is a viable option with the CCSD being significantly shorter than the convex SCSD.

LEVEL OF EVIDENCE

4.

Instrumentation Failure After Posterior Vertebral Column Resection in Adult Spinal Deformity

STUDY DESIGN

Retrospective study of instrumentation failure after posterior vertebral column resection (pVCR) in adult spinal deformity (ASD) patients.

OBJECTIVE

The morbidity and related risk factors of the instrumentation failure.

SUMMARY OF BACKGROUND DATA

Instrumentation failure is another common complication after pVCR. But no report about it has been published before. The safety of titanium mesh cages (TMCs) for this failure is still unknown so far.

METHODS

A total of 35 consecutive ASD patients (18 females and 17 males), who underwent pVCR between May 2005 and December 2014 in our hospital, were retrospectively reviewed. The mean age and follow-up period were 37.8 ± 12.8 years and 45.5 ± 27.3 months. Proportion was used to describe the morbidity of instrumentation failure. Potential risk factors were compared between patients with and without instrumentation failures by using Student t test or χ tests (Fisher exact tests). Risk factors related to TMCs were analyzed in TMC group.

RESULTS

There were 70 vertebra resected in total, with the mean of 10.3 segments instrumented. The mean correction rates of main curve (n = 25) and segmental kyphosis (n = 35) were 68.8% and 67.9%, respectively. Five patients (14.3%) suffered rod breakage. The failure was noted an average of 6.8 months after surgery. The risk factors included BMI (>27, P = 0.026), comorbidity (Achondroplasia, P = 0.047), and anterior column defect (ACD>20 mm, P = 0.045). TMC subsidence of ≥5 mm was the risk factor related to TMC in TMC group (P = 0.041).

CONCLUSION

It is safe to reconstruct with a TMC after pVCR in ASD, but the height should be as low as possible to reduce ACD. For those patients with risk factors, autologous bone graft and a satellite rod should be considered. If TMC subsidence ≥5 mm, a frequent follow-up should be performed.

LEVEL OF EVIDENCE

4.

Surgical Treatment of Congenital Scoliosis Associated With Tethered Cord by Thoracic Spine-shortening Osteotomy Without Cord Detethering

STUDY DESIGN

Retrospective case series.

OBJECTIVE

To investigate the safety and efficacy of spine-shortening osteotomy for congenital scoliosis with tethered cord.

SUMMARY OF BACKGROUND DATA

Conventional surgery for congenital scoliosis associated with tethered cord risks the complications of detethering. Spine-shortening osteotomy holds the potential to correct scoliosis and decrease spinal cord tension simultaneously without an extra detethering procedure, but no data on this issue is available.

METHODS

21 patients (14 females and 7 males, average age 15.4 yr) underwent spine-shortening osteotomy without detethering. All of the patients had tethered cord. Patients with main curve more than 90° underwent vertebral column resection (VCR), whereas the others had pedicle subtraction osteotomy (PSO) performed. The average postoperative follow-up period was 45.2 months.

RESULTS

The mean operation time was 544.5 min with average blood loss of 2769.1 ml. The deformity correction was 61.3% in the coronal plane and 43.9° in the sagittal plane. 10 patients had neurological deficits preoperatively. At the final follow-up, the deficits in 8 (80%) patients were significantly improved, whereas 2 (20%) remained unchanged. At final follow-up, 71.4% (5/7) patients reported improvement in motor function, 100% (3/3) had improved pain scores, and 75% (3/4) reported better sensory function after the spine-shortening osteotomy. Urinary dysfunction and bowel incontinence present preoperatively in 3 patients all recovered by final follow-up. 5 (23.8%) patients incurred complications including temporary neurological deterioration in 1 patient, urinary tract infection in 2 patients, cerebrospinal fluid leakage in 1 patient, and blood loss more than 5000 ml in 1 patient.

CONCLUSION

Spine-shortening osteotomy is a safe and effective procedure for congenital scoliosis associated with tethered cord. Spine-shortening osteotomy at the thoracic apical vertebrae level not only corrects the spine deformity but also simultaneously releases the tension of the tethered cord, resulting in improved neurologic function.

Spinal Cord Kinking in Thoracic Myelopathy Caused by Ossification of the Ligamentum Flavum

Background:

Ossification of the ligamentum flavum (OLF) is being increasingly recognized as a cause of thoracic myelopathy. This study was to describe a rare clinical entity of spinal cord kinking (SK) in thoracic myelopathy secondary to OLF.

Methods:

The data of 95 patients with thoracic myelopathy secondary to OLF were analyzed retrospectively. The incidence and location of SK were determined using preoperative magnetic resonance imaging (MRI). The clinical presentation and radiological characteristics in patients with SK were analyzed. Posterior en bloc laminectomy with OLF was performed, and the surgical results were evaluated.

Results:

SK was found in seven patients (7.4%) based on preoperative MRI. The patients included one male and six females with an average age of 55.6 years (range, 48–64 years). Five patients presented with radiculomyelopathy and two presented with typical thoracic myelopathy of spastic paraparesis. In all cases, the kinking was located just above the end of the spinal cord where the conus medullaris (CM) was compressed by the OLF. The degree of SK varied from mild to severe. The tip of the CM was located between the upper third of T11 to the lower third of L1, above the lower edge of L1. With an average follow-up of 30.4 months, the modified Japanese Orthopedic Association score significantly improved from 5.7 ± 1.8 preoperatively to 8.9 ± 1.4 postoperatively (t = 12.05; P < 0.0001) with an improvement rate of 63.1 ± 12.3%.

Conclusions:

SK is a rare radiological phenomenon. It is typically located at the thoracolumbar junction, where the CM is compressed by the OLF. Our findings indicate that these patients may benefit from a posterior decompressive procedure.

Relationship between Spinal Cord Volume and Spinal Cord Injury due to Spinal Shortening

Vertebral column resection is associated with a risk of spinal cord injury. In the present study, using a goat model, we aimed to investigate the relationship between changes in spinal cord volume and spinal cord injury due to spinal shortening, and to quantify the spinal cord volume per 1-mm height in order to clarify a safe limit for shortening. Vertebral column resection was performed at T10 in 10 goats. The spinal cord was shortened until the somatosensory-evoked potential was decreased by 50% from the baseline amplitude or delayed by 10% relative to the baseline peak latency. A wake-up test was performed, and the goats were observed for two days postoperatively. Magnetic resonance imaging was used to measure the spinal cord volume, T10 height, disc height, osteotomy segment height, and spinal segment height pre- and postoperatively. Two of the 10 goats were excluded, and hence, only data from eight goats were analyzed. The somatosensory-evoked potential of these eight goats demonstrated meaningful changes. With regard to neurologic function, five and three goats were classified as Tarlov grades 5 and 4 at two days postoperatively. The mean shortening distance was 23.6 ± 1.51 mm, which correlated with the d-value (post-pre) of the spinal cord volume per 1-mm height of the osteotomy segment (r = 0.95, p < 0.001) and with the height of the T10 body (r = 0.79, p = 0.02). The mean d-value (post-pre) of the spinal cord volume per 1-mm height of the osteotomy segment was 142.87 ± 0.59 mm³ (range, 142.19–143.67 mm³). The limit for shortening was approximately 106% of the vertebral height. The mean volumes of the osteotomy and spinal segments did not significantly change after surgery (t = 0.310, p = 0.765 and t = 1.241, p = 0.255, respectively). Thus, our results indicate that the safe limit for shortening can be calculated using the change in spinal cord volume per 1-mm height.

The effect of spinal osteotomies on spinal cord tension and dural buckling: a cadaveric study

OBJECT

The standard surgical release of a tethered cord may result in recurrent scar formation and occasionally be associated with retethering. The application of spinal shortening procedures to this challenging problem potentially can reduce tension on the retethered spinal cord while minimizing the difficulties inherent in traditional lumbosacral detethering revision. Although spinal shortening procedures have proven clinical benefit in patients with a recurrent tethered cord, it is unclear how much shortening is required to achieve adequate reduction in spinal cord tension or what impact these osteotomies have on dural buckling.

METHODS

The authors calculated mean values from 4 human cadavers to evaluate the effect of 3 different spinal shortening procedures--Smith-Petersen osteotomy (SPO), pedicle subtraction osteotomy (PSO), and vertebral column resection (VCR)--on spinal cord tension and dural buckling. Three cadavers were dedicated to the measurement of spinal cord tension, and 3 other cadavers were devoted to myelography to measure dural buckling parameters.

RESULTS

The SPO was associated with a maximal decrease in spinal cord tension of 16.1% from baseline and no dural buckling with any degree of closure. The PSO led to a mean maximal decrease in spinal cord tension of 63.1% from baseline at 12 mm of closure and demonstrated a direct linear relationship between dural buckling and increasing osteotomy closure. Finally, VCR closure correlated with a mean maximal decrease in spinal cord tension of 87.2% from baseline at 10 mm of closure and also showed a direct linear relationship between dural buckling and increases in osteotomy closure.

CONCLUSIONS

In this cadaveric experiment, the SPO did not lead to appreciable tension reduction, while a substantial response was seen with both the PSO and VCR. The rate of tension reduction may be steeper for the VCR than the PSO. Adequate tension relief while minimizing dural buckling may be optimal with 12-16 mm of posterior osteotomy closure based on this cadaveric experiment.

Symptomatic spinal cord kinking due to focal adhesive arachnoiditis, with ossification of the ligamentum flavum: a case report

STUDY DESIGN

A case report.

OBJECTIVE

To describe a rare case of symptomatic spinal cord kinking due to focal adhesive arachnoiditis, with ossification of the ligamentum flavum (OLF).

SUMMARY OF BACKGROUND DATA

Spinal cord kinking without spinal surgery is rare, and symptomatic spinal cord kinking due to focal adhesive arachnoiditis, with OLF is even rarer.

METHODS

A 66-year-old female presented with numbness of the lower extremities and subsequently experienced gait disturbance due to motor weakness. Magnetic resonance imaging of the thoracic spine showed anterior displacement and kinking of the spinal cord from T11 to T12. Laminectomy and OLF resection were performed. The arachnoid membrane at the affected part was markedly thick and seemed cloudy. Adhesiolysis for arachnoid adhesion and release of spinal kinking were performed.

RESULTS

She could walk with a cane 6 months postoperatively. One year postoperatively, thoracic computed tomography-myelography showed that the cord was repositioned in the dural sac, and that release of the spinal cord kink was maintained.

CONCLUSION

Symptomatic spinal cord kinking due to focal adhesive arachnoiditis, with OLF is a rare clinical condition. It was difficult to diagnose the precise pathology of the spinal cord before surgery. Microsurgical arachnoidolysis resolved the spinal cord kinking, and no recurrence was noted within the follow-up period.

LEVEL OF EVIDENCE

N/A.

The risk factors of neurologic deficits of one-stage posterior vertebral column resection for patients with severe and rigid spinal deformities

PURPOSE

To determine the risk factors of neurologic deficits during PVCR correction, so as to help improve safety during and after surgery.

METHODS

A consecutive series of 76 patients with severe and rigid spinal deformities who were treated with PVCR at a single institution between October 2004 and July 2011 were included in our study. Of the 76 patients, 37 were male and 39 female, with an average age of 17.5 years (range 10-48 years). There were 52 adolescent patients (with an age <18 years) and 24 adult patients (with an age ≥18 years). Preoperatively, postoperatively and 6 months after surgery, we performed systemically neurologic function evaluations of each patients through meticulous physical examination. Any new abnormality or deterioration in evaluation of neurologic function than preoperative is reckoned postoperative neurologic deficits. Ten variables that might affect the safety of neurologic deficits during PVCR procedures, including imaging factors, clinical factors and operational factors, were analyzed using univariate analysis. Then the variables with statistical difference were analyzed by using multi-factor unconditional logistic regression analysis.

RESULTS

No patient in this series had permanent paraplegia and nerve root injury due to operation. Change of neurologic status was found in six patients after surgery. Results of single-factor comparison demonstrated that the following seven variables were statistically different (P < 0.05): location of apex at main curve (X 3), Cobb angle at the main curve at the coronal plane (X 4), scoliosis associated with thoracic hyperkyphosis (X 5), level of vertebral column resected (X 6), number of segmental vessels ligated (X 7), preexisting neurologic dysfunction (X 8), and associated with intraspinal and brain stem anomalies (X 9). The multi-factor unconditional logistic regression analysis revealed that X 8 (OR = 49.322), X 9 (OR = 18.423), X 5 (OR = 11.883), and X 6 (OR = 8.769) were independent and positively correlated with the neurologic deficit.

CONCLUSIONS

Preexisting neurologic dysfunction, associated with intraspinal and brain stem anomalies, scoliosis associated with thoracic hyperkyphosis and level of vertebral column resected are independent risk factors for neurologic deficits during PVCR procedure.

Simultaneous posterior and anterior approaches with posterior vertebral wall preserved for rigid post-traumatic kyphosis in thoracolumbar spine

STUDY DESIGN

A retrospective study.

OBJECTIVE

To evaluate the radiological and clinical results of simultaneous surgery with preservation of the posterior vertebral wall for rigid post-traumatic kyphosis in the thoracolumbar spine.

SUMMARY OF BACKGROUND DATA

Management of rigid post-traumatic kyphosis has been a challenge for surgeons. Current widely used posterior osteotomy procedures have the disadvantages of significant invasiveness, spinal column shortening, and instrumentation-related complications.

METHODS

From 2004 to 2009, 21 patients with rigid post-traumatic kyphosis in the thoracolumbar spine (T11-L2) were managed in our hospital. Average kyphotic angle was 45.2° ± 11.2° (range, 31°-67°). The surgical technique used was posterior and anterior circumferential release and anterior corpectomy with posterior vertebral wall preservation and short segmental instrumentation. Preoperative and postoperative kyphotic angle was measured to assess the degree of kyphosis correction and maintenance. Changes in low back pain were assessed by Japanese Orthopaedic Association scores.

RESULTS

All patients were successfully managed with this procedure without major complications. Most patients (19 of 21) were instrumented with anterior-only fixation, while posterior interspinal wire was added in 2 patients with osteoporosis. The mean blood loss was 470 mL (range, 300-700 mL). Patients were followed for an average of 32 months (range, 6-70 mo) postoperatively. Back pain was relieved to some degree in all patients and the improvement in Japanese Orthopaedic Association scores was 76.9% ± 7.9. Average kyphotic angle was 6.0° ± 5.7° (range, -2 to 17) immediately after surgery and 7.2° ± 5.8° (range, -3 to 17) at final follow-up. Average of 1° of correction loss was documented and all patients obtained solid fusion uneventfully.

CONCLUSION

This technique is indicated for most patients with rigid post-traumatic kyphosis in the thoracolumbar spine and can yield satisfactory clinical results not only in terms of pain relief, kyphosis correction, vertebral height restoration, and spinal canal integrity preservation, but also in reducing the risk of excessive bleeding and spinal cord injury.

Treatment of acute tuberculous spondylitis by the spinal shortening osteotomy: a technical notes and case illustrations

Surgical treatment for spinal tuberculosis is necessary in particular cases that a large amount of necrotic tissue is encountered and there is spinal cord compression. A spinal shortening osteotomy procedure has previously been described for the correction of the sagittal balance in a late kyphotic deformity, but there have been no reports on this as a surgical treatment in the acute stage. Thus, the aim of this report is to present the surgical techniques and clinical results of 3 patients who were treated with this procedure. Three patients with tuberculous spondylitis at the thoracic spine were surgically treated with this procedure. All the patients presented with severe progressive back pain, kyphotic deformity and neurological deficit. The patients recovered uneventfully from surgery without further neurological deterioration. Their pain was improved and the patients remained free of pain during the follow-up period. In conclusion, posterior spinal shortening osteotomy is an alternative method for the management of tuberculous spondylitis.

Progressive kyphoscoliosis associated with tethered cord treated by posterior vertebral column resection: a case report

STUDY DESIGN.: A case report. OBJECTIVES.: To report a case of progressive kyphoscoliosis associated with a tethered cord that was corrected by posterior vertebral column resection after complicated untethering surgery. SUMMARY OF BACKGROUND DATA.: There have been few clinical reports on posterior vertebral column resection conducted for severe deformity associated with a tethered cord. METHODS.: A patient with progressive kyphoscoliosis associated with a tethered cord first underwent untethering surgery, resulting in neurologic deterioration. Posterior vertebral column resection was performed to correct the kyphoscoliosis while shortening the spinal column to prevent the spinal cord from stretch injury. RESULTS.: Good correction of kyphoscoliosis was obtained without further neurologic deterioration. The Cobb angles of scoliosis was 103 degrees before surgery and 25 degrees after surgery (correction rate; 75.7%), and that of kyphosis was 90 degrees and 36 degrees , respectively (correction rate; 60.0%). CONCLUSION.: Correction of progressive kyphoscoliosis associated with a tethered cord can be achieved successfully by posterior vertebral column resection even after complicated untethering surgery.