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

Tethered spinal cord tension assessed via ultrasound elastography in computational and intraoperative human studies

BACKGROUND

Tension in the spinal cord is a trademark of tethered cord syndrome. Unfortunately, existing tests cannot quantify tension across the bulk of the cord, making the diagnostic evaluation of stretch ambiguous. A potential non-destructive metric for spinal cord tension is ultrasound-derived shear wave velocity (SWV). The velocity is sensitive to tissue elasticity and boundary conditions including strain. We use the term Ultrasound Tensography to describe the acoustic evaluation of tension with SWV.

METHODS

Our solution Tethered cord Assessment with Ultrasound Tensography (TAUT) was utilized in three sub-studies: finite element simulations, a cadaveric benchtop validation, and a neurosurgical case series. The simulation computed SWV for given tensile forces. The cadaveric model with induced tension validated the SWV-tension relationship. Lastly, SWV was measured intraoperatively in patients diagnosed with tethered cords who underwent treatment (spinal column shortening). The surgery alleviates tension by decreasing the vertebral column length.

RESULTS

Here we observe a strong linear relationship between tension and squared SWV across the preclinical sub-studies. Higher tension induces faster shear waves in the simulation (R2 = 0.984) and cadaveric (R2 = 0.951) models. The SWV decreases in all neurosurgical procedures (p < 0.001). Moreover, TAUT has a c-statistic of 0.962 (0.92-1.00), detecting all tethered cords.

CONCLUSIONS

This study presents a physical, clinical metric of spinal cord tension. Strong agreement among computational, cadaveric, and clinical studies demonstrates the utility of ultrasound-induced SWV for quantitative intraoperative feedback. This technology is positioned to enhance tethered cord diagnosis, treatment, and postoperative monitoring as it differentiates stretched from healthy cords.

Development of a sacral fracture model to demonstrate effects on sagittal alignment

PURPOSE

To develop a modeling framework to predict the secondary consequences on spinal alignment following correction and to demonstrate the impact of pedicle subtraction osteotomy (PSO) location on sagittal alignment.

METHODS

Six patients were included, and pelvic incidence (PI) was measured. Full-length standing radiographs were uploaded into PowerPoint and manipulated to model S1-S2 joint line sacral fractures at 15°, 20°, 25°, and 30°. PSO corrections with hinge points at the anterior superior corner and vertical midpoint of the L3-5 vertebral bodies were modeled. Anterior translation (AT) and vertical shortening (VS) were calculated for the six PSO locations in the four fracture angle (FA) models.

RESULTS

PI had a strong effect in the mixed AT and VS models (P < 0.001). Both AT and VS were significantly different from zero at all FA (p < 0.001), and pairwise comparisons revealed all FA were different from each other with respect to both AT and VS after adjusting for PSO location (p < 0.001), increasing as FA increased. Varying PSO location resulted in significant differences in AT when comparing all locations (p < 0.001). AT was greatest for all FA in all patients when the PSO correction was performed at the L3-AS (p < 0.001). There were significant differences in VS when comparing the L5-Mid PSO location to the L3-AS, L3-Mid, L4-AS, and L4-Mid PSO locations (p < 0.034).

CONCLUSION

PSO correction superior to a sacral fracture resulted in AT and VS of the spine. It is crucial that these changes in spinal measures be predicted and accounted for to optimize patient sagittal alignment and outcomes.

Modified Bone-Disc-Bone Osteotomy for Spinal Kyphosis: A Retrospective Clinical Study with 2-Year Follow-Up

OBJECTIVE

To determine the efficacy of modified bone-disc-bone osteotomy to treat spinal kyphosis.

METHODS

Between January 2018 and December 2022, 20 patients underwent modified bone-disc-bone osteotomy surgery for spinal kyphosis. Radiologic parameters pelvic incidence, pelvic tilt, sagittal vertical axis, and kyphotic Cobb angle were measured and compared. Oswestry Disability Index, visual analog scale, and general complications were recorded to evaluate clinical outcomes.

RESULTS

All 20 patients completed 24 months of postoperative follow-up. Mean kyphotic Cobb angle correction was from 40.2 ± 6.8° to 8.9 ± 4.1° immediately after surgery to 9.8 ± 4.8° at 24 months postoperatively. Average surgical time was 277 minutes (range, 180-490 minutes). Mean intraoperative blood loss was 1215 mL (range, 800-2500 mL). Sagittal vertical axis was improved from 4.2 cm (range, 1-5.8 cm) preoperatively to 1.1 cm (range, 0-2 cm) at final follow-up (P < 0.05). Pelvic tilt was reduced from 27.6 ± 4.1 preoperatively to 14.9 ± 4.4 postoperatively (P < 0.05). Visual analog scale decreased from 5.8 ± 1.1 preoperatively to 1 ± 0.6 at final follow-up (P < 0.05). Oswestry Disability Index changed from 28.7 ± 2.7% preoperatively to 9.4 ± 1.8% at final follow-up. Bony fusion was achieved at 12 months postoperatively in all patients. All patients experienced significant improvement in clinical symptoms and neurological function at final follow-up.

CONCLUSIONS

Modified bone-disc-bone osteotomy surgery is an effective and safe method for treatment of spinal kyphosis.

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.

Spinal column shortening for tethered cord syndrome: a systematic review and individual patient data meta-analysis

OBJECTIVE

Tethered cord release (TCR) is the gold standard treatment for tethered cord syndrome (TCS); however, there are significant shortcomings including high rates of retethering, especially in complex and recurrent cases. Spinal column shortening (SCS) is an alternative treatment for TCS intended to avoid these shortcomings. Early studies were limited to case reports and smaller case series; however, in recent years, larger case series and small cohort studies have been conducted. Given the increase in available data, a repeat systematic review and meta-analysis is warranted to assess the safety and efficacy of SCS for TCS.

METHODS

The authors conducted a systematic review using MEDLINE (OVID), Embase (Elsevier), and Web of Science records dating from 1944 to July 2021 to identify all articles investigating SCS for TCS. They performed standard and individual patient data (IPD) meta-analyses, with 2 independent reviewers using PRISMA-IPD guidelines. Primary outcomes were improvement of preoperative clinical symptoms of pain, motor weakness, and bladder and bowel dysfunction, and also surgical complication rate. Secondary outcomes included urodynamic improvement and health-related quality-of-life outcomes determined using patient-reported outcome tools. Individual study quality assessment was performed using a standardized assessment tool for case reports/series, and publication bias was assessed using funnel plot analyses.

RESULTS

The review yielded 15 studies with 191 cases of TCS treated with SCS. IPD were available in 11 studies with 89 cases. The average age at time of surgery was 28.0 years (range 5-76 years). The average follow-up time was 33.2 months (range 7-132 months). Improvement was observed at last follow-up in 60 of 70 (85.7%) patients with preoperative pain, in 38 of 60 (60.3%) patients with preoperative weakness, and in 36 of 76 (47.4%) patients with preoperative bladder or bowel dysfunction. Complications of CSF leak, new neurological deficit, wound infection, or reoperation occurred in 4 of 89 (4.5%) patients.

CONCLUSIONS

SCS may be considered a safe and efficacious treatment option for TCS in children and adults (level C evidence; class IIb recommendation), especially for recurrent and complex cases. Current evidence is likely to be affected by selection and publication bias. Prospective comparative studies of SCS and TCR for TCS are recommended to determine long-term duration of outcomes, long-term safety in skeletally immature children, and exact indications of SCS versus traditional TCR.

Intradural view of the spinal cord and dura after three-column osteotomy: illustrative case

BACKGROUND

A three-column osteotomy results in dural buckling, which may appear concerning upon intraoperative visualization because it may appear that the neural elements may also be buckled. The authors presented an intraoperative view after intentional durotomy of the neural elements and the relaxed state of the dura after three-column osteotomy.

OBSERVATIONS

A 52-year-old woman with adult tethered cord syndrome and previous untethering presented with worsening leg pain and stiffness, urinary incontinence, and unbalanced gait. Magnetic resonance imaging demonstrated an arachnoid web at T6 and spinal cord tethering. Spinal column shortening via three-column osteotomy was performed with concomitant intradural excision of the arachnoid web. Dural buckling was observed intraoperatively after spinal column shortening. After the durotomy, the spinal cord was visualized without kinking or buckling.

LESSONS

Dural buckling after spinal column shortening of 15 mm via three-column osteotomy at T6 did not result in concomitant buckling of the underlying neural elements.

Posterior Vertebral Column Subtraction Osteotomy for Recurrent Tethered Cord Syndrome: A Multicenter, Retrospective Analysis

BACKGROUND

Few have explored the safety and efficacy of posterior vertebral column subtraction osteotomy (PVCSO) to treat tethered cord syndrome (TCS).

OBJECTIVE

To evaluate surgical outcomes after PVCSO in adults with TCS caused by lipomyelomeningocele, who had undergone a previous detethering procedure(s) that ultimately failed.

METHODS

This is a multicenter, retrospective analysis of a prospectively collected cohort. Patients were prospectively enrolled and treated with PVCSO at 2 institutions between January 1, 2011 and December 31, 2018. Inclusion criteria were age ≥18 yr, TCS caused by lipomyelomeningocele, previous detethering surgery, and recurrent symptom progression of less than 2-yr duration. All patients undergoing surgery with a 1-yr minimum follow-up were evaluated.

RESULTS

A total of 20 patients (mean age: 36 yr; sex: 15F/5M) met inclusion criteria and were evaluated. At follow-up (mean: 23.3 ± 7.4 mo), symptomatic improvement/resolution was seen in 93% of patients with leg pain, 84% in back pain, 80% in sensory abnormalities, 80% in motor deficits, 55% in bowel incontinence, and 50% in urinary incontinence. Oswestry Disability Index improved from a preoperative mean of 57.7 to 36.6 at last follow-up (P < .01). Mean spinal column height reduction was 23.4 ± 2.7 mm. Four complications occurred: intraoperative durotomy (no reoperation), wound infection, instrumentation failure requiring revision, and new sensory abnormality.

CONCLUSION

This is the largest study to date assessing the safety and efficacy of PVCSO in adults with TCS caused by lipomyelomeningocele and prior failed detethering. We found PVCSO to be an excellent extradural approach that may afford definitive treatment in this particularly challenging population.

In vivo deformation of the spine canal before and after surgical corrections of severe and rigid kyphoscoliosis

Background

Ponte osteotomy and posterior vertebral column resection (PVCR) are two popular surgical techniques in treatment of severe and rigid kyphoscoliosis. However, quantitative effects of the two surgeries on spinal cord deformation are unclear. This information is critical for improvement of the treatment methods that can maximally correct the spinal deformity and prevent neurological complications.

Methods

Ten patients with severe kyphoscoliosis were investigated. X-ray and CT images of full spine of all patients were acquired before and 6–24 months after surgical treatment using either Ponte osteotomy or PVCR. A 3D model of the spine was constructed for each patient using the CT images that included the spinal canal between T2 and L2 vertebrae. The spinal canal length (SCL) was determined at 5 locations on the cross section of the canal: anterior, posterior, left, right (concave or convex side) and centre positions. The perpendicular distances between the T2 and L2 vertebrae, COBB angles and patient reported outcome measures before and after operations were determined.

Results

For patients treated with Ponte osteotomy, the SCLs were elongated by 12.7 ± 9.5 mm (5.4 ± 3.9%) at the concave side and 3.2 ± 6.8 mm (1.3 ± 2.8%) at the convex side. The COBB angle was corrected by 55.8% and the T2-L2 distance was increased by 66.1 ± 12.0 mm (68.4 ± 15.9%). For patients treated using PVCR, the SCLs were shortened by −5.5 ± 5.3 mm (−2.3 ± 2.2%) at the concave side and −14.0 ± 6.6 mm (−5.2 ± 2.6%) at the convex side. The COBB angle was corrected by 60.0% and the T2-L2 distance was increased by 41.5 ± 12.4 mm (32.1 ± 23.0%). The patient reported outcome scores were improved using both surgeries (p < 0.05).

Conclusion

Ponte and PVCR surgeries caused significant changes of the SCL in scoliosis patients in different ways. The Ponte osteotomy mainly caused elongation of the SCL at concave side and the PVCR caused compression of the SCL at the convex side. Both surgeries partially improved the spinal deformity. The data provide insights for development of new surgical techniques that integrates the advantages of both Ponte and PVCR osteotomies to maximally correct the spine deformity and prevent neurological complications.

The translational potential of this article

The methodology and the data presented in this paper could be instrumental for development of computer assisted surgical techniques that can maximally correct the spinal deformity and minimize the effect on the spinal cord in scoliosis patients.

Retethering : A Neurosurgical Viewpoint

During the follow-up period after surgery for spinal dysraphism, a certain portion of patients show neurological deterioration and its secondary phenomena, such as motor, sensory or sphincter changes, foot and spinal deformities, pain, and spasticity. These clinical manifestations are caused by tethering effects on the neural structures at the site of previous operation. The widespread recognition of retethering drew the attention of medical professionals of various specialties because of its incidence, which is not low when surveillance is adequate, and its progressive nature. This article reviews the literature on the incidence and timing of deterioration, predisposing factors for retethering, clinical manifestations, diagnosis, surgical treatment and its complications, clinical outcomes, prognostic factors after retethering surgery and preventive measures of retethering. Current practice and opinions of Seoul National University Children’s Hospital team were added in some parts. The literature shows a wide range of data regarding the incidence, rate and degree of surgical complications and long-term outcomes. The method of prevention is still one of the main topics of this entity. Although alternatives such as spinal column shortening were introduced, re-untethering by conventional surgical methods remains the current main management tool. Re-untethering surgery is a much more difficult task than primary untethering surgery. Updated publications include strong skepticism on re-untethering surgery in a certain group of patients, though it is from a minority of research groups. For all of the abovementioned reasons, new information and ideas on the early diagnosis, treatment and prevention of retethering are critically necessary in this era.

Homogeneous Spinal-Shortening Axial Decompression for Tethered Cord Syndrome: Modified Spinal Column Shortening

OBJECTIVE

Tethered cord syndrome is a rare and intractable disease. The aim of this study was to investigate surgical outcome of homogeneous spinal-shortening axial decompression (HSAD) for tethered cord syndrome through a minimum 3-year follow-up.

METHODS

Patients who underwent HSAD for tethered cord syndrome in our institution between May 2011 and July 2015 were included in this study. After a minimum 3-year follow-up, radiologic and clinical data were collected. Surgical outcome was evaluated with Japanese Orthopaedic Association, visual analog scale, International Consultation on Incontinence Questionnaire-Short Form, and Rintala scores and urodynamics.

RESULTS

The study included 64 patients (28 men and 36 women) with a mean age of 35.7 ± 18.1 years. Significant improvement of visual analog scale and Japanese Orthopaedic Association scores was noted postoperatively and at a minimum 3-year follow-up. At the final follow-up, Japanese Orthopaedic Association and visual analog scale scores in all patients were improved compared with preoperatively. The International Consultation on Incontinence Questionnaire-Short Form score was decreased from 14.94 ± 4.15 preoperatively to 7.63 ± 4.40 at final follow-up (P < 0.01). Rintala score was improved from 5.26 ± 3.45 preoperatively to 12.32 ± 3.43 at final follow-up (P < 0.01). All urodynamic parameters improved compared with preoperatively.

CONCLUSIONS

HSAD was effective and safe. The results were satisfactory with a minimum 3-year follow-up. HSAD could be an alternative surgical treatment of TCS.

Homogeneous Spinal-Shortening Axial Decompression as a Revision Surgery After Untethering Surgery in Pediatric Patients with Tethered Cord Syndrome

OBJECTIVE

To evaluate surgical outcomes of homogeneous spinal-shortening axial decompression (HSAD) for reoperation in pediatric patients with tethered cord syndrome.

METHODS

Twenty consecutive pediatric patients (≤18 years old, 7 boys, 13 girls) who underwent HSAD after untethering surgery between June 2012 and May 2015 were included. The Japanese Orthopaedic Association score and visual analog scale were used to evaluate preoperative and postoperative neurologic function and pain. The International Consultation on Incontinence Questionnaire-Short Form and urodynamics were used to evaluate urinary function. The Rintala score was used to evaluate stool function.

RESULTS

Mean age of patients was 13.4 ± 3.6 years (range, 7-18 years). The mean duration of follow-up was 31.2 ± 12.7 months (range, 12-48 months). The Japanese Orthopaedic Association score was increased from 13.31 ± 4.03 preoperatively to 19.15 ± 4.17 at final follow-up (P < 0.01). The visual analog scale score was decreased from 5.25 ± 1.78 preoperatively to 2.21 ± 1.63 at final follow-up (P < 0.01). The International Consultation on Incontinence Questionnaire-Short Form score was decreased from 14.94 ± 4.15 preoperatively to 7.63 ± 4.40 at final follow-up (P < 0.01). All urodynamics parameters improved compared with before the operation. The Rintala score improved from 5.26 ± 3.45 preoperatively to 12.32 ± 3.43 at final follow-up (P < 0.01).

CONCLUSIONS

Outcomes of HSAD for revision surgery of tethered cord syndrome were satisfactory. HSAD improved neurologic function of patients significantly. HSAD could become an alternative surgical treatment of reoperation for tethered cord syndrome.

Osteotomies in ankylosing spondylitis: where, how many, and how much?

INTRODUCTION

This article presents the current concepts of correction of spinal deformity in ankylosing spondylitis (AS) patients. Untreated AS can be a debilitating disease. In a few patients, disease progression results in severe spinal deformity affecting not only the thoracolumbar, but also the cervical spine. Surgery for correction in AS patients has a long history. With the advent of modern instrumentation, standardization of surgical and anesthesiologic techniques, surgical safety and corrective results could be improved and experiences from lumbar osteotomies could be transferred to the cervical spine.

METHODS

This article presents the current concepts of correction of spinal deformity in AS patients. In particular, questions regarding the localization and number of osteotomies, the optimal surgical target angle as well as planning and prediction of postoperative alignment are discussed.

RESULTS

Insight into recent technical developments, current challenges with correction and geometric analysis of center of rotation (COR) in cervical 3-column osteotomies (3CO) will be presented.

CONCLUSION

The article should encourage readers to improve surgical correction efficacy and provide a better understanding of correction geometry in 3CO for thoracolumbar and cervical spinal deformities.

Posterior Vertebral Column Resection With Intraoperative Manual Retraction for the Treatment of Posttubercular Kyphosis in Upper Thoracic Spine or Cervicothoracic Junction

STUDY DESIGN

This is a case-series.

OBJECTIVE

To evaluate the clinical and radiologic outcomes of posterior vertebral column resection (PVCR) for treatment of posttubercular kyphosis in upper thoracic spine and cervicothoracic junction (CTJ).

SUMMARY OF BACKGROUND DATA

Surgical management of severe posttubercular kyphosis in upper thoracic spine or CTJ is challenging. A new technique that combines PVCR and intraoperative manual traction in a single procedure, was developed to maximize the correction rate and minimize the risk of dural buckling and spinal cord injury. However, the safety and effectiveness of the procedure is yet to be established.

MATERIALS AND METHODS

Ten patients with upper thoracic or CTJ posttubercular kyphosis, who underwent PVCR with intraoperative manual traction between December 2008 and 2013, were studied retrospectively. Data pertaining to operation time, blood loss, and perioperative complications were collected. Outcomes were evaluated using the visual analog scale; the 12-Item Short Form Health Survey (SF-12), Mental Component Summary, and SF-12 Physical Component Summary. Neurological status was assessed using American Spinal Injury Association (ASIA) impairment scale. Radiologic outcomes including fusion and deformity correction were assessed using plain radiography and computed tomography.

RESULTS

The average duration of follow-up was 53.6±7.2 months. Average operating time and blood loss were 263±35.3 minutes and 2490±569 mL, respectively. Visual analog scale score for back pain, SF-12 Mental Component Summary, and Physical Component Summary showed significant improvement postoperatively. Kyphosis improved from a preoperative average of 73.6±13.1 degrees to an average of 37.9±8.7 degrees at final follow-up (correction rate: 48.5%). No postoperative neurological deterioration was observed based on the ASIA score. As of the last follow-up, solid fusion was not achieved only in 1 patient.

CONCLUSIONS

PVCR with intraoperative manual traction is a safe and effective procedure for treatment of upper thoracic or CTJ posttubercular kyphosis.

LEVEL OF EVIDENCE

Level 4.

Spinal Shortening for Recurrent Tethered Cord Syndrome via a Lateral Retropleural Approach: A Novel Operative Technique

Spine shortening via vertebral osteotomy (SSVO) for recurrent tethered cord syndrome (TCS) is a novel surgical technique that avoids the complication profile associated with revision detethering. While SSVO has previously been described via a posterior approach, we describe a lateral retropleural approach for SSVO in recurrent TCS in a 21-year-old female.

Our patient presented with progressive lower extremity weakness, bowel and bladder incontinence, and back pain in the setting of childhood repair of myelomeningocele and two previous detethering procedures. SSVO was offered to the patient as further detethering was deemed to have significant risk. A discectomy at T11-T12 via the lateral retropleural approach was performed, followed by a T12 partial corpectomy removing the vertebral body down to the inferior aspect of the T12 pedicle, followed by the removal of the ipsilateral pedicle. The T10, T11, L1, and L2 pedicle screws were then placed in the prone position and temporary rods were placed for temporary stability, followed by a laminectomy at T12 and a facetectomy for posterior element release. The remaining pedicle was removed, permanent rods were sequentially placed, and spinal column shortening was achieved by compression against the rods. Standing lateral radiographs demonstrated 19 millimeters (mm) of shortening after the intervention. The patient remained at her neurologic baseline postoperatively. At the six-month follow-up, the patient reported decreased lower extremity radicular pain and improved bowel and bladder function.

This operative report demonstrates that SSVO via a lateral retropleural approach is a viable treatment for the recurrence of TCS. The advantages of this minimally invasive approach compared to the posterior approach are direct access to the vertebral body and disc space, avoiding the need to operate around the spinal cord. Further studies are necessary to assess this minimally invasive approach to spinal shortening and to see if a complete minimally invasive approach is possible.

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.

Spinal column shortening for tethered cord syndrome associated with myelomeningocele, lumbosacral lipoma, and lipomyelomeningocele in children and young adults

OBJECTIVE Tethered cord syndrome is the clinical manifestation of an abnormal stretch on the spinal cord, presumably causing mechanical injury, a compromised blood supply, and altered spinal cord metabolism. Tethered cord release is the standard treatment for tethered cord syndrome. However, direct untethering of the spinal cord carries potential risks, such as new neurological deficits from spinal cord injury, a CSF leak from opening the dura, and retethering of the spinal cord from normal scar formation after surgery. To avoid these risks, the authors applied spinal column shortening to children and transitional adults with primary and secondary tethered cord syndrome and report treatment outcomes. The authors' aim with this study was to determine the safety and efficacy of spinal column shortening for tethered cord syndrome by analyzing their experience with this surgical technique. METHODS The authors retrospectively reviewed the demographic and procedural data of children and young adults who had undergone spinal column shortening for primary or secondary tethered cord syndrome. RESULTS Seven patients with tethered cord syndrome caused by myelomeningocele, lipomyelomeningocele, and transitional spinal lipoma were treated with spinal column shortening. One patient with less than 24 months of follow-up was excluded from further analysis. There were 3 males and 4 females; the average age at the time was surgery was 16 years (range 8-30 years). Clinical presentations for our patients included pain (in 5 patients), weakness (in 4 patients), and bowel/bladder dysfunction (in 4 patients). Spinal column osteotomy was most commonly performed at the L-1 level, with fusion between T-12 and L-2 using a pedicle screw-rod construct. Pedicle subtraction osteotomy was performed in 6 patients, and vertebral column resection was performed in 1 patient. The average follow-up period was 31 months (range 26-37 months). Computed tomography-based radiographic outcomes showed solid fusion and no instrumentation failure in all cases by the most recent follow-up. Five of 7 patients (71%) reported improvement in preoperative symptoms during the follow-up period. The mean differences in initial and most recent Scoliosis Research Society Outcomes Questionnaire and Oswestry Disability Index scores were 0.26 and -13%, respectively; minimum clinically important difference in SRS-22 and ODI were assumed to be 0.4% and -12.8%, respectively. CONCLUSIONS Spinal column shortening seems to represent a safe and efficacious alternative to traditional untethering of the spinal cord for tethered cord syndrome.

A proposed classification system for guiding surgical strategy in cases of severe spinal deformity based on spinal cord function

PURPOSE

Spinal cord function classification systems are not useful for guiding surgery in patients with severe spinal deformities. The aim of this study is to propose a classification system for determining a surgical strategy that minimizes the risk of neurological dysfunction in patients with severe spinal deformities.

METHODS

The records of 89 patients with severe spinal deformities treated with vertebral column reconstruction from 2008 to 2013 were retrospectively analyzed. Based on neurophysiological monitoring, magnetic resonance imaging, and neurological symptoms patients were categorized into three groups: group A, normal spinal cord, normal evoked potentials and no neurological symptoms; group B, spinal cord abnormalities and/or abnormal evoked potentials but no neurological symptoms; group C, neurological symptoms with or without spinal cord abnormalities/abnormal evoked potentials. Outcomes and complications were compared between the groups.

RESULTS

A total of 89 patients (51 male, 38 female) were included with 47 (52.8 %), 16 (18.0 %), and 26 (29.2 %) patients in groups A, B and C, respectively, and a mean follow-up 34.5 months. There were no differences in age, gender, average preoperative scoliosis, and kyphosis among three groups, but there were differences with respect to the causes of severe spinal deformity and the corrective rate of scoliosis and kyphosis. Changes in intraoperative evoked potentials were different in these three types according to this new classification, and the recovery rates of changes in the three groups were 71.1, 50.0, and 14.1 %, respectively. Postoperative spinal cord injury was positively related to intraoperative changes of evoked potentials.

CONCLUSION

The classification system may be useful for guiding surgical decisions in patients with severe spinal deformities to minimize the risk of neurological complications.