Spinal Column Shortening Research Articles

Peripubertal Caffeine Exposure Impairs Longitudinal Bone Growth in Immature Male Rats in a Dose- and Time-Dependent Manner.

This study investigated the dose- and time-dependent effects of caffeine consumption throughout puberty in peripubertal rats. A total of 85 male SD rats were randomly divided into four groups: control and caffeine-fed groups with 20, 60, or 120 mg/kg/day through oral gavage for 10, 20, 30, or 40 days. Caffeine decreased body weight gain and food consumption in a dose- and time-dependent manner, accompanied by a reduction in muscle and body fat. In addition, it caused a shortening and lightening of leg bones and spinal column. The total height of the growth plate decreased sharply at 40 days in the controls, but not in the caffeine-fed groups, and the height of hypertrophic zone in the caffeine-fed groups was lower than in the control. Caffeine increased the height of the secondary spongiosa, whereas parameters related to bone formation, such as bone area ratio, thickness and number of trabeculae, and bone perimeter, were significantly reduced. Furthermore, serum levels of IGF-1, estradiol, and testosterone were also reduced by the dose of caffeine exposure. Our results demonstrate that caffeine consumption can dose- and time-dependently inhibit longitudinal bone growth in immature male rats, possibly by blocking the physiologic changes in body composition and hormones relevant to bone growth.

Homogeneous spinal-shortening axial decompression procedure for tethered cord syndrome

Surgical detethering is a traditional treatment for symptomatic tethered cord syndrome. However, such complications as cerebrospinal fluid leakage and neurologic deterioration are common. Homogeneous spinal-shortening axial decompression (HSAD) is a modified procedure of monosegmental spinal-shortening osteotomy and it is a novel surgical alternative of reducing neural tension indirectly. The objective was to evaluate the surgical outcomes of HSAD for tethered cord syndrome. The surgical outcomes were examined for 15 consecutive patients with tethered cord syndrome undergoing HSAD from April 2010 to July 2014. Improvements of neurological symptoms including urinary dysfunction, lower-extremity motor and sensory disturbances and/or gait abnormalities, low-back and/or lower-extremity pain, bowel incontinence and sexual dysfunction were evaluated. Their average follow-up period was 21.5 months. The length of spinal column shortening was 17.2 ± 2.9 mm. Urinary dysfunction (n = 9) was the most common residual deficit. All 9 patients with urological symptoms reported improvements, although deficits persisted at the last follow-up. All patients with lower-extremity motor dysfunction improved and 4 (50.0%) noted complete resolution of preoperative lower-extremity sensory symptoms. All patients reported immediate low-back or lower-extremity pain relief after HSAD. One patient reported improved sexual functioning and regained complete erectile capabilities. Two patients (11%) experienced less satisfactory symptomatic or functional benefit from HSAD. However, the main objective of surgery was to prevent further worsening of neurological status. Complete bone union at osteotomy site was noted in all cases at the last follow-up. As a novel surgical option for tethered cord syndrome, HSAD may avoid such complications as cerebrospinal fluid leakage or neurologic deterioration commonly encountered during traditional detethering surgery. All patients gain satisfactory functional outcomes without complications compared to their preoperative symptoms.

Posterolateral Debridement and Anterior Reconstruction by Limited Spinal Shortening in Thoracic and Lumbosacral Spinal Infections

Introduction Anterior debridement and fusion using bone graft or cage is an accepted way of treatment of spinal infections. This can be achieved either through anterior or posterior or two-stage (anterior then posterior) surgery. In last few years, several research works reported good results with use of single posterior surgical approach for treatment of spinal infections. Spinal column shortening may be used in spinal fractures, deformities, and tumors. Since 2004, posterolateral exposure for debridement of thoracic and lumbosacral spinal infections and limited spinal shortening for anterior spinal reconstruction have been used. Patients and Methods A total of 32 patients with spinal infections (10 patients with infection of the thoracic spine and 22 patients with infections of the lumbar spine) were treated by this technique. Patients included 20 males and 12 females with a mean age of 56.3 (range, 20–72) years. Overall, 10 patients had neurological compromise (two Frankel grade A, three Frankel grade B, three Frankel grade C, and two Frankel grade D). Patients are operated under general anesthesia in the prone position through a single posterior exposure. Posterior stabilization by transpedicular screw fixation is performed. A rod is inserted in one side (usually the right side) while the rod in the other side is not inserted to give space sufficient for laminectomy and debridement. For full exposure of the anterior aspect of the vertebral bodies in the thoracic spine, excision of the medial 5 cm of one or two ribs may be performed. In the lumbar spine, dissection around the vertebral body is not needed as retraction of the cauda equine usually gives good space sufficient for curettage of the disc and debridement of the infected tissues and the technique is posterior lumbar interbody fusion (PLIF). Infected material is curetted and the second rod is inserted. Reconstruction of the anterior column is achieved by limited spinal shortening while carefully observing the dura for kinking. Then, posterior fusion is performed using local bone graft obtained from the laminae and ribs. Results Patients were followed up for a mean of 33 (range, 6–80) months. Causative organisms were TB in 20 patients, Staph aureus in 4 patients, salmonella typhi, 1 patient, brucella in 1 patient, and bacteriologic testing of intraoperative samples did not find germs in 6 patients. Operative time ranged between 100 and 190 (mean 135) minutes. Successful fusion was achieved in all patients 3 to 6 months postoperatively. Neurological recovery to Frankel grade E was obtained in all but four patients (three Frankel grade D and one Frankel grade B). Five complications were encountered; malpositioned pedicle screw, deep venous thrombosis (DVT), delayed wound healing, kyphosis progression, and temporary neurological deterioration. No active infection occurred till the end of follow-up. Conclusion Posterolateral debridement and anterior reconstruction by limited spinal shortening is an alternative method for surgical treatment of spinal infections. Advantages of this technique include a wide cancellous surface for bone healing, good stability, avoid the morbidity of bone graft harvesting, short operative time, and less morbidity.

Predicting Kyphosis Correction During Posterior-Only Vertebral Column Resection by the Amount of Spinal Column Shortening

Study DesignRetrospective. ObjectiveTo investigate the relationship between the amount of correction achieved (K°) and extent of vertebral column shortening (mm) with posterior vertebral column resection (PVCR). Summary of background dataThere is no scientific reference to the correlation between K° and column shortening (mm) with PVCR. MethodsBased on simple geometry, we tested the hypothesis that we could predict the amount of actual kyphosis correction (K°) by calculation on 26 kyphotic PVCR patients. Using multiple linear measurements (mm), two angular approximations (°) were calculated: the geometric approximation (G°) using the geometric calculation (G-cal), and the rough approximation (R°) by more simplistic calculation (R-cal). Both G° and R° were compared against K° as measured on the pre- and postoperative radiographs. If calculated G° and R° is close to measured K°, we can use the calculations (G-cal and R-cal) in the clinical situation. ResultsThe mean correction of K° was 38°. K°−G° and K°−R° were not significantly greater than 3° and 6°, respectively. As K° was very close to G° and R°, K° can replace G° and R°. Therefore, we can use G-cal and R-cal in the clinical setting and we can determine how much posterior shortening and what cage size is required to obtain a certain amount of K°. ConclusionsWith two calculations (G-cal & R-cal), we can determine how much vertebral column shortening (mm) we need during PVCR to obtain the amount of kyphosis correction desired (K°). In order to obtain K°, using the formula deduced from G-cal and R-cal, we can determine the shortening between the upper and lower pedicle screws and cage size.

Multisegmental Spinal-Shortening Osteotomy for the Treatment of Tethered Cord Syndrome: A Retrospective Study of Six Consecutive Cases

Introduction Tethered cord syndrome often presents as low back pain in the early stage and progresses to sensory, motor, bowel, and bladder control dysfunctions. The pathogenesis of tethered cord syndrome is thought to be abnormal longitudinal traction on the caudal end of the spinal cord. Surgical detethering has been considered the gold standard for symptomatic tethered cord syndrome and consistently shown to be effective. However, complications such as cerebrospinal fluid leakage, infection, and neurologic deterioration including motor and bladder function are common. To minimize these complications, vertebral column subtraction osteotomy and pedicle subtraction osteotomy were reported as alternative procedures for the treatment of adult tethered cord syndrome. The concept of the procedures is to reduce neural tension indirectly. We present six consecutive cases with tethered cord syndrome that underwent a modified spinal-shortening osteotomy, which is multisegmental. Materials and Methods We retrospectively reviewed the surgical and radiological data of patients with tethered cord syndrome who underwent multisegmental spinal-shortening osteotomy (MSSO) by one doctor in one of the surgery groups at Changzheng Hospital from July 2009 to July 2013. The average follow-up period was 32 ± 7.5 months. Three patients were male and three were female and the average age at operation was 33 years (range, 16-57 years). MSSO were performed in patients, which required multilevel discectomy and facetectomy. The certain length gap created by the discectomy and facetectomy were then closed with serial compression through the domino connectors. Temporary rods were replaced with permanent rods once final spinal column alignment was achieved. The shortening of the spine was measured at the anterior and posterior borders and the midpoint of the vertebral end plate on the lateral fluoroscopy. Preoperative and postoperative VAS pain scores were evaluated. Results Six patients were followed up for 32 months in average and were included in the analysis. The length of spinal column shortening was 17 ± 1.7 mm. Urinary and sensory dysfunctions (two cases for each) were the most common residual deficits. Two (100%) patients with urological symptoms reported improvements, although deficits remained at the time of last follow-up. Six patients with lower-extremity motor dysfunction improved and six noted complete resolution of preoperative lower-extremity sensory symptoms. Five (100%) reported immediate low back or lower extremity pain relief following MSSO. VAS pain scores of all six patients were greatly improved after surgery. Complete bone union at the osteotomy site was noted in all cases at the time of last follow-up. Conclusion Most of the patients who have undergone MSSO in our study exhibited improvement of urological symptoms, complete recovery of motor functioning, and relief of debilitating back or lower extremity pain. Although many factors preclude a direct comparison of the symptomatic and functional outcomes following traditional surgical detethering compared with MSSO for TCS treatment, the outcomes are grossly similar regarding current literature. We believe that the principal benefits of MSSO over detethering operations will be in preserving the symptomatic and functional neurological improvements with lasting results and potentially obviating the need for future reoperations. However, longer follow-up results are needed from the MSSO series to support this belief. Disclosure of Interest None declared References Agarwalla PK, Dunn IF, Scott RM, Smith ER. Tethered cord syndrome. Neurosurg Clin N Am 2007;18(3):531–547 Alemdaroğlu KB, Atlihan D, Cimen O, Kilinç CY, Iltar S. Morphometric effects of acute shortening of the spine: the kinking and the sliding of the cord, response of the spinal nerves. Eur Spine J 2007;16(9):1451–1457 Hsieh PC, Stapleton CJ, Moldavskiy P, et al. Posterior vertebral column subtraction osteotomy for the treatment of tethered cord syndrome: review of the literature and clinical outcomes of all cases reported to date. Neurosurg Focus 2010;29(1):E6 Kanno H, Aizawa T, Ozawa H, Hoshikawa T, Itoi E, Kokubun S. Spine-shortening vertebral osteotomy in a patient with tethered cord syndrome and a vertebral fracture. Case report. J Neurosurg Spine 2008;9(1):62–66 Kawahara N, Tomita K, Kobayashi T, Abdel-Wanis ME, Murakami H, Akamaru T. Influence of acute shortening on the spinal cord: an experimental study. Spine 2005;30(6):613–620 Kokubun S, Ozawa H, Aizawa T, Ly NM, Tanaka Y. Spine-shortening osteotomy for patients with tethered cord syndrome caused by lipomyelomeningocele. J Neurosurg Spine 2011;15(1):21–27 Miyakoshi N, Abe E, Suzuki T, Kido T, Chiba M, Shimada Y. Spine-shortening vertebral osteotomy for tethered cord syndrome: report of three cases. Spine 2009;34(22):E823-E825 Traynelis VC. Spine shortening of tethered cord. J Neurosurg Spine 2011;15(1):19-20, author reply 20

Simultaneous Posterior and Anterior Approaches With Posterior Vertebral Wall Preserved for Rigid Post-Traumatic Kyphosis in Thoracolumbar Spine

A retrospective study. 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. 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. 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. 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. 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.

Posterior vertebral column subtraction osteotomy for the treatment of tethered cord syndrome: review of the literature and clinical outcomes of all cases reported to date

Tethered cord syndrome (TCS) is a debilitating condition of progressive neurological decline caused by pathological, longitudinal traction on the spinal cord. Surgical detethering of the involved neural structures is the classic method of treatment for lumbosacral TCS, although symptomatic retethering has been reported in 5%-50% of patients following initial release. Subsequent operations in patients with complex lumbosacral dysraphic lesions are fraught with difficulty, and improvements in neurological function are modest while the risk of complications is high. In 1995, Kokubun described an alternative spine-shortening procedure for the management of TCS. Conducted via a single posterior approach, the operation relies on spinal column shortening to relieve indirectly the tension placed on the tethered neural elements. In a cadaveric model of TCS, Grande and colleagues further demonstrated that a 15-25-mm thoracolumbar subtraction osteotomy effectively reduces spinal cord, lumbosacral nerve root, and filum terminale tension. Despite its theoretical appeal, only 18 reports of the use of posterior vertebral column subtraction osteotomy for TCS treatment have been published since its original description. In this review, the authors analyze the relevant clinical characteristics, operative data, and postoperative outcomes of all 18 reported cases and review the role of posterior vertebral column subtraction osteotomy in the surgical management of primary and recurrent TCS.

Erweiterter posteriorer zirkulärer Zugang zur Brust- und oberen Lendenwirbelsäule

Posterior spinal surgical approach to achieve a retropleural/ retroperitoneal corpectomy with circumferential spinal cord decompression following subtotal vertebrectomy, posterior instrumentation and interbody spacer placement under compression as well as kyphosis correction with spinal column shortening. Infective, traumatic or neoplastic lesions of the vertebral body that lead to vertebral body destruction, instability and neurologic deficit. Need for immediate postoperative loading stability to permit ambulation and rehabilitation. Multiple contiguous vertebral disease. Instances where the graft bed preparation and stable interbody spacer placement may be suboptimal due to the limited access offered by this approach. Posterior midline exposure two to three levels above and below lesion, dissection at level of lesion extended bilaterally exposing transverse processes, costotransverse articulations and medial 5-8 cm of ribs. Placement of pedicle screws at proximal and distal levels; in case of osteoporotic bone augment screws with cement. Bilateral costotransversectomy at one or more levels to drain prevertebral abscess and expose diseased vertebral bodies. After temporary stabilization, laminectomy and corpectomy are carried out from both sides to permit circumferential decompression. A temporary rod is placed on the contralateral side in the position of deformity to prevent any inadvertent translatory movements during the subsequent surgical step. After completion of the procedure an appropriately contoured rod is placed. The interbody spacer is positioned. Kyphosis correction by spinal column shortening and compression along the posterior implant is performed. By day 3 ambulation and rehabilitation are initiated. 22 patients were operated in the last 8 years with tuberculosis (18 patients - twelve paraplegics), osteoporotic fractures (two patients), congenital kyphosis and Ewing's sarcoma (one patient each). All patients were followed up at 3, 6, 9, and 12 months and then annually. At each followup, clinical, hematologic and radiologic parameters were assessed. All interbody grafts and cages incorporated without significant loss of correction. Ten of twelve tuberculous paraplegics recovered. No patient had postoperative infection, interbody spacer- or implant-related complications.

The safety range of acute shortening of spinal column after total vertebrectomy

Objective To investigate the change of morphologic and neurological function of spinal cord after acute spinal column shortening, to enlighten the safety range of acute shortening on the spinal column following total spondylectomy. Methods One-hundred and twenty New Zealand white rabbits were used as experimental animals. The animals were randomly divided into three groups: single-level laminectomy group(A), double-level iaminectomy group (B), and three-level laminectomy group(C). Each group was divided into four subgroups according to the percent of spinal column shortening: 25%, 50%, 75% and 100% subgroups. After total vertebrectomy of L3, we performed spinal column shortening and measured the diameter and length of spinal cord, angle between spinal cord and L3 nerve root, the latency and amplitude of somatosensory evoked potential (SEP) accordingly. Tarlov scales were recorded 72 h after surgery, and HE stain was used to observe the histopathological changes of the spinal cord. Results The morphology and neurological function of spinal cord had no significant change when spinal column shortening was less than 50% in all groups (P>0.05). The morphology and neurological function were significantly changed when spinal column shortening was 75% in group A (P<0.05), and massive hemorrhages and shrinkage of neurons were observed in the pathological sections. The morphology and neurological function of spinal cord had no significant change until spinal column shortening was more than 75% in group B and C. There was no significant difference between group B and C. Conclusion The safety range of spinal column shortening after vertebrectomy and single laminectomy was no more than 50% of vertebral height. However, it can be extended to 75% by performing double or three levels laminectomy to avoid spinal cord injury caused by spinal cord kinking. The range of laminectomy has obvious effect on the morphologic change and neurological function of spinal cord after spinal column shortening. Key words: Osteotomy; Spine; Laminectomy; Spinal cord injuries

Posterior vertebral column subtraction osteotomy: a novel surgical approach for the treatment of multiple recurrences of tethered cord syndrome

Recurrent tethered cord syndrome (TCS) has been reported to develop in 5-50% of patients following initial spinal cord detethering operations. Surgery for multiple recurrences of TCS can be difficult and is associated with significant complications. Using a cadaveric tethered spinal cord model, Grande and colleagues demonstrated that shortening of the vertebral column by performing a 15-25-mm thoracolumbar osteotomy significantly reduced spinal cord, lumbosacral nerve root, and terminal filum tension. Based on this cadaveric study, spinal column shortening by a thoracolumbar subtraction osteotomy may be a viable alternative treatment to traditional surgical detethering for multiple recurrences of TCS. In this article, the authors describe the use of posterior vertebral column subtraction osteotomy (PVCSO) for the treatment of 2 patients with multiple recurrences of TCS. Vertebral column resection osteotomy has been widely used in the surgical correction of fixed spinal deformity. The PVCSO is a novel surgical treatment for multiple recurrences of TCS. In such cases, PVCSO may allow surgeons to avoid neural injury by obviating the need for dissection through previously operated sites and may reduce complications related to CSF leakage. The novel use of PVCSO for recurrent TCS is discussed in this report, including surgical considerations and techniques in performing PVCSO.

Reversal of Neurologic Deterioration After Vertebral Column Resection by Spinal Cord Untethering and Duraplasty

Case report. To describe a novel surgical approach for the treatment of a patient who developed neurologic deterioration after vertebral column resection (VCR). VCR is a valuable osteotomy technique for the treatment of fixed spinal deformity. Despite an evolving compendium of information about this procedure, little has been described regarding the management of neurologic complications after VCR. A 58-year-old woman underwent a T12 VCR for the treatment of fixed sagittal post-traumatic deformity. The patient was monitored intraoperatively with SSEPs and TcMEPs, both of which revealed no changes at any point during the operation. She awoke with normal motor function; however, her strength and sensory modalities deteriorated in a gradual progressive pattern over the first several postoperative days. She was then taken back to the operating room and intradural exploration was performed at the osteotomy site. The patient was found to have dense arachnoid adhesions that tethered the spinal cord to the dura at the level of the osteotomy. With spinal column shortening during osteotomy closure, tension was placed on the spinal cord, which was bound by the adhesions. Spinal cord untethering and duraplasty proved to be successful in reversing her neurologic deterioration. Moreover, kyphosis correction was maintained. In patients with neurologic deterioration after VCR and no clear evidence of epidural neural compression, intradural exploration should be considered.

External fixation for dynamic correction of severe scoliosis

Background context The ideal treatment for scoliosis may be the correction of the factors that cause the disease. An external fixation device was used in 12 patients to achieve a correction by dynamic distraction, compression and derotation of the curve. Follow-up was done over a 7-year period. Purpose To describe the treatment of inflexible and severe scoliosis by special correction with external fixation. Study design/setting This was a prospective, longitudinal and descriptive study, with a follow-up period of 7 years. Patient sample Twelve patients (9 female, 3 male) from the National Orthopaedic Institute Spine Service in external consultation. Outcome measures Radiographic measurements with the scoliosis angulation of Cobb's method were used before surgery, after surgery and in the final follow-up period. Methods The surgical procedure consisted of two stages, anterior and posterior approach, dissectomies, vertebrectomy at the apex, spinal column shortening and the placement of an external stabilization device. Progressive correction of the curve was done by a daily increase in distraction (3 mm/day). When the correction was finished, a different internal fixation device was used to maintain the correction. The time between initial treatment and final correction was 50 days. Ten thoracic curves, one thoracolumbar curve and one lumbar curve were treated, with an average of 93 degrees. All patients had kyphosis with an average of 89 degrees. Vertebral rotation was not found in two patients. Results Average correction of scoliosis was 52.9% and of kyphosis, 29%. Vertebral rotation in eight cases was corrected. There were no neurological irreversible lesions in any patient. There was one infection. Using an evaluation result scale, there were 2 excellent, 6 good and 4 fair outcomes. The average loss of correction was 5 degrees. Conclusion The results suggest that the use of an external stabilization device with controlled compression on the convexity and distraction on the concavity of the curve can achieve a correction of up to 50% in scoliosis, 30% in kyphosis and 1 degree in the rotation of the spine.

Influence of Acute Shortening on the Spinal Cord: An Experimental Study

Morphometric changes of the spinal cord and influence on spinal cord-evoked potentials and spinal cord blood flow and postoperative function of hind limbs were studied in various degrees of acute spinal column shortening in dogs. To study the morphometric and physiologic effects of acute spinal column shortening on the spinal cord. The technique of acute spinal column shortening is sometimes applied for correction of spinal deformity, total en bloc spondylectomy operation, or other diseases. However, safe limits and physiologic effects of acute spinal column shortening have not yet been described. Total spondylectomy of T13 was performed in dogs after spinal instrumentation placed 2 levels above and 2 levels below the spondylectomy level. Spinal column was gradually shortened until the lower endplate of T12 contacted the L1 upper endplate (maximum of 20 mm). When any morphologic change of the dural sac or the spinal cord was observed, the length of shortening was measured. Spinal cord-evoked potentials were recorded on the exposed dura mater following epidural stimulation at the C7 level in 8 dogs. Spinal cord blood flow was measured during shortening in 6 dogs. Hindlimb function was evaluated 2 weeks after operation in 10 dogs. No morphometric changes occurred in the dural sac and the spinal cord until shortening of 7.2 +/- 1.7 mm (n = 6). From 7.2 +/- 1.7 to 12.5 +/- 1.1 mm shortening, the dural sac was deformed, whereas the spinal cord maintained its shape. Shortening more than 12.5 +/- 1.1 mm buckled the dural sac, and the spinal cord kinked itself and was compressed by the buckled dura in its concave side (n = 6). No changes could be detected in spinal cord-evoked potentials in 5 or 10 mm of shortening. Spinal cord-evoked potential changes were recorded in the 2 of 6 dogs with 15 mm of shortening. At 20 mm of shortening, spinal cord-evoked potential abnormality was observed in 4 of 6 dogs. At shortening of 5, 10, 15, and 20 mm, spinal cord blood flow was 146 +/- 10%, 160 +/- 21%, 102 +/- 17%, and 93 +/- 7% of the control (29.2 +/- 7.9 mL/100 g/min, n = 6), respectively. All 3 dogs with 10 mm ofshortening had normal hindlimb function 2 weeks after operation. One of the 3 dogs with 15 mm of shortening had paraparesis. Three of the 4 dogs with 20 mm of shortening had also paraparesis after operation. Acute spinal column shortening can be characterized into 3 phases. Phase 1, safe range: occurred during shortening within one-third of the vertebral segment and is characterized by no deformity of the dural sac or the spinal cord. Phase 2, warning range: occurred during spinal shortening between one-third and two-thirds of the vertebral segment and is characterized by shrinking and buckling of the dural sac and no deformity of the spinal cord. Phase 3, dangerous range: occurred after shortening in excess of two-thirds of the vertebral segment and is characterized by spinal cord deformity and compression by the buckled dura. Spinal shortening within the safe range increases spinal cord blood flow.

P43. Influence of acute shortening on the spinal cord: an experimental study

BACKGROUND CONTEXT: The technique of acute spinal column shortening is sometimes applied for correction of spinal deformity, total en bloc spondylectomy operation or other diseases. However, safe limits and physiological effects of acute spinal column shortening have not yet been described.

Reviewer point of view on the treatment of fixed thoracolumbar kyphosis in immature achondroplastic patient

Sir, In achondroplastic patients the natural history and surgical treatment of spinal stenosis and thoracolumbar kyphosis are notorious for their high rate of neurologic complication [4, 5, 6, 8]. The authors have chosen with success a modern way of correcting this very challenging spinal deformity by a way of posterior spinal column shortening. Classically, some authors would recommend a simple decompression with posterior instrumentation for fear of neurologic complication [8, 9]; however, if the stenosis is associated with kyphosis, simple laminectomy may expose to further instability and kyphosis [10]. This is the reason why other authors would perform an anterior disc excision, followed by a posterior decompression and instrumentation [7]. One of the major disadvantages of this latter approach is that by doing the disc excision first in the presence of a very narrow canal, the anterior spinal manipulation along with the edema induced by the surgery may be harmful to the already compromised spinal cord. By doing an anterior spinal release first, followed by posterior surgery, the cord may even end up being lengthened and further compromised. Bradford and Tribus reported initially in 1997 the concept of spinal column resection for complex and rigid spinal deformities. By doing a two-stage front and back spinal resection they could address rigid coronal decompensation [1]. More recently Suk et al. has popularized the concept of posterior spinal resection for all kinds of spinal deformities [11]. In the meantime pedicle subtraction osteotomies have become popular for the treatment of flat-back deformities and associated syndromes [2, 3]. In the paper published the authors report on a two-level posterior column resection done according to the Thomasen technique; however it is not clear in their description if they removed also the disc of this two-level resection or if they performed a two-adjacent-segments pedicle subtraction osteotomy. It is not possible to judge on the post-operative X-rays that were provided the type of posterior osteotomy that was achieved. Nevertheless, the correction is very impressive and we congratulate the authors for that. I agree that the use of pedicle screws is the safest fixation in these spinal deformities with narrow canal. I would like to emphasize a few concerns relevant to this case. The issue of spinal stenosis must always be considered in these patients. In this specific case, looking at the MRI the stenosis seems to originate at T10 down to L2. In these patients a myelo-CT scan is often more appropriate to judge the extent of the stenosis rather than a sole MRI that may overestimate some stenotic levels. In the case presented the decompressive laminectomy necessary to perform the posterior column resection was carried out only at the level of T12 and L1. This is in my mind insufficient to carry out a safe two-level posterior column resection and did not address the stenoses at T10–T11 and T11–T12. Finally, the other issue of concern is the lack of anterior support or fusion as there is a persisting small angular kyphosis even though the follow-up is 2 years. Even with segmental pedicle instrumentation we have observed failure of constructs well after 2 years. A complementary anterior fusion would have been necessary, in my mind. Overall, we congratulate the author for this very nice result and their innovative way of treatment. Posterior column resection may effectively prove to be safer than the anterior and posterior sequence. I would, however, recommend that posterior decompression extend to all the stenotic levels as seen on a CT myelogram. Should the posterior spinal resection involve two contiguous vertebrae or be staggered with one or two segments left intact will need to be determined. A complementary anterior fusion for stability and longevity purposes may be necessary for the long term.

Neurological and pathological effects of second lumbar spondylectomy and spinal column shortening in the dog.

The second lumbar vertebra was surgically removed from 10 dogs, and the shortened vertebral column was stabilized by internal fixation with two types of plastic plates. Shortening of the spinal column was usually not associated with detectable loss of function or neurological deficit. Histological lesions, however, included widely disseminated axonal degeneration, gliosis, and atrophy of spinal nerve roots in the surgical area. The spinal cord adapted to shortening of the vertebral column by becoming intrinsically shorter, rather than be being displaced within the spinal canal.