Search

Background: Adolescent idiopathic scoliosis (AIS) patients typically undergo surgical treatment as teenagers, follow-ups of >5 years are necessary to evaluate effects on peak pulmonary reserves. However, limited data is available regarding the long-term (>10 years) effects of surgical intervention on pulmonary function (PF) in patients with thoracic AIS., Objective: To provide long-term (>10 years) information on the PF after posterior spinal fusion for treating main thoracic AIS. We especially investigated whether surgical correction for AIS led to impairment of the PF., Methods: A total of 35 patients with main thoracic AIS treated with posterior spinal fusion were included. Radiographs and PF tests, which included measurements of absolute and percent-predicted values of forced vital capacity (FVC) and forced expiratory volume in 1 second (FEV1), were evaluated., Results: Mean age at surgery was 14.9 years (12-19 years). Mean follow-up period was 15.1 years (10-24 years). Although the final postoperative FVC and FEV1 absolute values were higher than the preoperative values, the differences were not statistically significant (p = 0.22 and p = 0.08, respectively). Percent-predicted FVC and FEV1 values between preoperative and final postoperative measurements were not statistically different (p = 0.63 and p = 0.29, respectively). However, for the patients who presented with pulmonary impairment preoperatively, both the FVC and FEV1 significantly increased at the final follow-up (p = 0.01 and p = 0.01, respectively)., Conclusions: Long-term results of AIS patients who underwent posterior spinal fusion in main thoracic curves demonstrated absolute and percent-predicted PF test values similar to preoperative measurements; thus, indicating that posterior spinal fusion did not decrease PF 15 years after the initial surgery. Instead, patients with severe preoperative pulmonary impairment might show some degree of improvement after surgery., Competing Interests: The authors have declared that no competing interests exist.

Purpose: There is limited consensus on the optimal surgical strategy for double thoracic adolescent idiopathic scoliosis (AIS). Recent studies have reported that pedicle screw constructs to maximize scoliosis correction cause further thoracic spine lordosis. The objective of this study was to apply a new surgical technique for double thoracic AIS with rigid proximal thoracic (PT) curves and assess its clinical outcomes., Methods: Twenty one consecutive patients with Lenke 2 AIS and a rigid PT curve (Cobb angle ≥30º on side-bending radiographs, flexibility ≤30 %) treated with the simultaneous double-rod rotation technique (SDRRT) were included. In this technique, a temporary rod is placed at the concave side of the PT curve. Then, distraction force is applied to correct the PT curve, which reforms a sigmoid double thoracic curve into an approximate single thoracic curve. As a result, the PT curve is typically converted from an apex left to an apex right curve before applying the correction rod for PT and main thoracic curve., Results: All patients were followed for at least 2 years (average 2.7 years). The average main thoracic and PT Cobb angle correction rate at the final follow-up was 74.7 and 58.0 %, respectively. The average preoperative T5-T12 thoracic kyphosis was 9.3°, which improved significantly to 19.0° (p < 0.0001) at the final follow-up. Although 71 % patients had preoperative level shoulders or a positive radiographic shoulder height, all patients had mildly imbalanced or balanced shoulders at the final follow-up. The average preoperative main thoracic apical vertebral rotation angle of 20.7° improved significantly after surgery to 16.4° (p = 0.0046), while the average preoperative total SRS questionnaire score of 3.7 improved significantly to 4.4 (p = 0.0012) at the final follow-up., Conclusions: Radiographic findings and patient outcomes were satisfactory. Thoracic kyphosis can be maintained or improved, while coronal and axial deformities can be corrected using SDRRT for Lenke 2 AIS with a rigid PT curve.

Study Design: Retrospective analysis of a prospectively collected, consecutive, nonrandomized series of patients., Objective: To assess the surgical outcomes of the simultaneous double-rod rotation technique for treating Lenke 1 thoracic adolescent idiopathic scoliosis (AIS)., Summary of Background Data: With the increasing popularity of segmental pedicle screw spinal reconstruction for treating AIS, concerns regarding the limited ability to correct hypokyphosis have also increased., Methods: A consecutive series of 32 patients with Lenke 1 main thoracic AIS treated with the simultaneous double-rod rotation technique at our institution was included. Outcome measures included patient demographics, radiographical measurements, and Scoliosis Research Society questionnaire scores., Results: All 32 patients were followed up for a minimum of 2 years (average, 3.6 yr). The average main thoracic Cobb angle correction rate and the correction loss at the final follow-up were 67.8% and 3.3°, respectively. The average preoperative thoracic kyphosis (T5-T12) was 11.9°, which improved significantly to 20.5° (P < 0.0001) at the final follow-up. An increase in thoracic kyphosis was significantly correlated with an increase in lumbar lordosis at the final follow-up (r = 0.42). The average preoperative vertebral rotation angle was 19.7°, which improved significantly after surgery to 14.9° (P = 0.0001). There was no correlation between change in thoracic kyphosis and change in apical vertebral rotation (r =-0.123). The average preoperative total Scoliosis Research Society questionnaire score was 3.0, which significantly improved to 4.4 (P < 0.0001) at the final follow-up. Throughout surgery and even after, there were no instrumentation failures, pseudarthrosis, infection of the surgical site, or clinically relevant neurovascular complications., Conclusion: The simultaneous double-rod rotation technique for treating Lenke 1 AIS provides significant sagittal correction of the main thoracic curve while maintaining sagittal profiles and correcting coronal and axial deformities., Level of Evidence: 4.

Study Design: Retrospective review., Objective: To assess the long-term outcomes of anterior spinal fusion (ASF) for treating thoracic adolescent idiopathic scoliosis (AIS)., Summary of Background Data: Although ASF is reported to provide good coronal and sagittal correction of the main thoracic (MT) AIS curves, the long-term outcomes of ASF is unknown., Methods: A consecutive series of 25 patients with Lenke 1 MT AIS were included. Outcome measures comprised radiographical measurements, pulmonary function, and Scoliosis Research Society outcome instrument (SRS-30) scores (preoperative SRS-30 scores were not documented). Postoperative surgical revisions and complications were recorded., Results: Twenty-five patients were followed-up for 12 to 18 years (average, 15.2 yr). The average MT Cobb angle correction rate and the correction loss at the final follow-up were 56.7% and 9.2°, respectively. The average preoperative instrumented level of kyphosis was 8.3°, which significantly improved to 18.6° (P = 0.0003) at the final follow-up. The average percent-predicted forced vital capacity and forced expiratory volume in 1 second were significantly decreased during long-term follow-up measurements (73% and 69%; P = 0.0004 and 0.0016, respectively). However, no patient had complaints related to pulmonary function. The average total SRS-30 score was 4.0. Implant breakage was not observed. All patients, except 1 who required revision surgery, demonstrated solid fusion. Late instrumentation-related bronchial problems were observed in 1 patient who required implant removal and bronchial tube repair, 13 years after the initial surgery., Conclusion: Overall radiographical findings and patient outcome measures of ASF for Lenke 1 MT AIS were satisfactory at an average follow-up of 15 years. ASF provides significant sagittal correction of the main thoracic curve with long-term maintenance of sagittal profiles. Percent-predicted values of forced vital capacity and forced expiratory volume in 1 second were decreased in this cohort; however, no patient had complaints related to pulmonary function.

Background: Anterior spinal fusion with instrumentation is used for the treatment of thoracolumbar/lumbar scoliosis. The aim of this long-term, retrospective, hospital-based cohort study was to determine the outcomes of anterior dual-rod instrumentation in a consecutive series of patients with thoracolumbar/lumbar adolescent idiopathic scoliosis managed by a single surgeon at a single institution., Methods: A consecutive series of thirty-two patients with Lenke type-5C thoracolumbar/lumbar adolescent idiopathic scoliosis were included. Outcome measures included patient demographics, radiographic measurements, adjacent-segment degeneration, pulmonary function, and Scoliosis Research Society outcome instrument (SRS-30) scores. Perioperative and postoperative complications were recorded., Results: Thirty patients were followed for a mean of 17.2 years (range, twelve to twenty-three years). The mean thoracolumbar/lumbar Cobb angle correction rate and correction loss at the time of the latest follow-up were 79.8% and 3.4°, respectively. The average percent-predicted forced vital capacity and forced expiratory volume in one second were 91.8% and 81.8%, respectively. The average total SRS-30 score was 4.2. Mild degeneration below the fusion mass was observed in 23% of the patients. No instrumentation failure, pseudarthrosis, surgical site infection, or clinically relevant neurovascular complications were observed. Two patients required surgical revision with posterior spinal instrumentation, one because of subjacent disc wedging and the other because of progression of the thoracic curve deformity., Conclusions: Radiographic findings, pulmonary function, and clinical measures were satisfactory at the time of follow-up, at a minimum of twelve years. Anterior dual-rod instrumentation remains a useful surgical treatment for Lenke type-5C thoracolumbar/lumbar adolescent idiopathic scoliosis.

Object: Use of computer-assisted spine surgery (CASS) technologies, such as navigation systems, to improve the accuracy of pedicle screw (PS) placement is increasingly popular. Despite of their benefits, previous CASS systems are too expensive to be ubiquitously employed, and more affordable and portable systems are desirable. The aim of this study was to introduce a novel and affordable computer-assisted technique that 3-dimensionally visualizes anatomical features of the pedicles and assists in PS insertion. The authors have termed this the 3D-visual guidance technique for inserting pedicle screws (3D-VG TIPS)., Methods: The 3D-VG technique for placing PSs requires only a consumer-class computer with an inexpensive 3D DICOM viewer; other special equipment is unnecessary. Preoperative CT data of the spine were collected for each patient using the 3D-VG TIPS. In this technique, the anatomical axis of each pedicle can be analyzed by volume-rendered 3D models, as with existing navigation systems, and both the ideal entry point and the trajectory of each PS can be visualized on the surface of 3D-rendered images. Intraoperative guidance slides are made from these images and displayed on a TV monitor in the operating room. The surgeon can insert PSs according to these guidance slides. The authors enrolled 30 patients with adolescent idiopathic scoliosis (AIS) who underwent posterior fusion with segmental screw fixation for validation of this technique., Results: The novel technique allowed surgeons, from office or home, to evaluate the precise anatomy of each pedicle and the risks of screw misplacement, and to perform 3D preoperative planning for screw placement on their own computer. Looking at both 3D guidance images on a TV monitor and the bony structures of the posterior elements in each patient in the operating theater, surgeons were able to determine the best entry point for each PS with ease and confidence. Using the current technique, the screw malposition rate was 4.5% in the thoracic region in corrective surgery for AIS., Conclusions: The authors found that 3D-VG TIPS worked on a consumer-class computer and easily visualized the ideal entry point and trajectory of PSs in any operating theater without costly special equipment. This new technique is suitable for preoperative planning and intraoperative guidance when performing reconstructive surgery with PSs.

Object: The aim of this study was to evaluate the outcomes of fusion surgery in patients with ossification of the posterior longitudinal ligament in the thoracic spine (T-OPLL) and to identify factors significantly related to surgical outcomes., Methods: The study included 76 patients (34 men and 42 women with a mean age of 56.3 years) who underwent fusion surgery for T-OPLL at 7 spine centers during the 5-year period from 2003 to 2007. The authors evaluated the patient demographic data, underlying disease, preoperative comorbidities, history of spinal surgery, radiological findings, surgical methods, surgical outcomes, and complications. Surgical outcomes were assessed using the Japanese Orthopaedic Association (JOA) scale score for thoracic myelopathy (11 points) and the recovery rate., Results: The mean JOA scale score was 4.6 ± 2.1 points preoperatively and 7.7 ± 2.5 points at the time of the final follow-up examination, yielding a mean recovery rate of 45.4% ± 39.1%. The recovery rates by surgical method were 38.5% ± 37.8% for posterior decompression and fusion, 65.0% ± 35.6% for anterior decompression and fusion via an anterior approach, 28.8% ± 41.2% for anterior decompression via a posterior approach, and 57.5% ± 41.1% for circumferential decompression and fusion. The recovery rate was significantly higher in patients without diabetes mellitus (DM) than in those with DM. One or more complications were experienced by 31 patients (40.8%), including 20 patients with postoperative neurological deterioration, 7 with dural tears, 5 with epidural hematomas, 4 with respiratory complications, and 10 with other complications., Conclusions: The outcomes of fusion surgery for T-OPLL were favorable. The absence of DM correlated with better outcomes. However, a high rate of complications was associated with the fusion surgery.

Study Design: Case report., Objective: To report an extremely rare case of hematoma derived from the ligamentum flavum within the thoracic spine., Summary of Background Data: Only one previous case has been reported of a hematoma derived from the ligamentum flavum in the thoracic spine. METHODS.: A 61-year-old man presented with gait disturbance and numbness below the navel. Magnetic resonance imaging on the 16th day after the onset of the symptoms showed spinal cord compression at the T10-T11 level caused by a round mass. This intraspinal, extradural space occupying lesion, continuous with ligamentum flavum was centrally hypointense and marginal hyperintense on a T1-weighted image and central heterogeneous and marginal hypointense on a T2-weighted image. The wall of the lesion was slightly enhanced after use of a contrast medium., Results: The patient underwent a T10 laminectomy and the mass was carefully resected from the dura mater. Histologic examination showed that the wall of the mass comprised fibrous connective tissue that contained elastic fibers derived from a degenerative ligamentum flavum tear. It also revealed that evidence of previous hemorrhagic events within the mass. There was no evidence of neoplastic nor synovial tissue. After surgery, the patient's numbness and gait disturbance disappeared., Conclusion: This report identifies an extremely rare case of spinal cord compression by a hematoma from the ligamentum flavum within the thoracic spine.

Study Design: A retrospective review., Objective: This study examined the clinical outcomes of circumferential spinal cord decompression through a posterior approach for thoracic ossification of posterior longitudinal ligament (OPLL), to determine the efficacy of this procedure and the incidence of complications., Summary of Background Data: Since posterior decompressive laminectomy is not always effective in the treatment of thoracic myelopathy caused by OPLL, circumferential spinal cord decompression through a single posterior approach seems to offer an effective treatment option. However, this procedure is technically demanding and has a high risk of postoperative neurologic deterioration. Long-term clinical outcome data and complication rates of this procedure are not well covered in the literature., Methods: Medical records of sequentially treated 30 patients, who had undergone circumferential spinal cord decompression through a single posterior approach, were reviewed to determine demographic data, neurologic examination, imaging findings, surgical procedure, and follow-up data. The Japanese Orthopedic Association (JOA) score was used to assess physical dysfunction and neurologic impairment., Results: The mean follow-up period was 8 years; the average operative time was 389 minutes; the mean blood loss was 1883 mL. An average of 4-level spinal cord decompression was performed on all 30 patients. Posterior spinal fusion was performed on 26 of the 30 patients. The mean preoperative JOA score was 3.4/11, and it improved to an average of 7.1/11 at final evaluation. Clinical symptoms and the JOA score improved in 24 patients, but were unchanged or worsened in the other 6 patients compared to the preoperative conditions. Surgical complications included dural tear in 12 patients (40%), deep infection in 3 (10%), and postoperative neurologic deterioration in 10 (33%). Statistical analysis showed that a risk factor associated with the unfavorable surgical outcomes was multiple level circumferential spinal cord decompression of 5 or more vertebral levels., Conclusion: Despite circumferential spinal cord decompression through posterior approach for thoracic OPLL providing effective neurologic recovery, there was a high rate of complications such as postoperative neurologic deterioration. Risk factor analysis shows that multiple level circumferential decompression of 5 or more vertebral levels to be associated with unfavorable surgical outcome.

Study Design: Clinical results of posterolateral endoscopic debridement and irrigation followed by percutaneous drainage for pyogenic spondylodiscitis were analyzed., Objectives: To report clinical results of transforaminal endoscopic surgery for pyogenic spondylodiscitis and to evaluate the effectiveness of this procedure in treatment of pyogenic spinal infections., Summary of Background Data: Pyogenic spinal infections have been increasing due to the development of medical treatment for patients with comorbid medical problems. Common treatments for spinal infections are administration of antibiotics or surgical debridement with bone grafts. There have been no reports, however, regarding the clinical outcome of posterolateral endoscopic treatment for pyogenic spinal infections., Methods: Fifteen consecutive patients with pyogenic spondylodiscitis in the thoracic or lumbar spine were enrolled. Preoperative antibiotic treatment had failed in all the patients. The procedures consisted of posterolateral endoscopic debridement and irrigation followed by percutaneous drainage through single portal under the combination of local and intravenous anesthesia. Pain response using visual analog scale (VAS, 0-100 mm), inflammation parameters, and duration of antibiotic therapy were investigated. Radiologic evaluation focused on bony fusion, local kyphosis, disc height reduction, and abscess formation., Results: All patients showed immediate pain reduction after surgery. Averaged VAS for pain was 86 before surgery and 25 at postoperative 1 week. Average of CRP was 4.00 mg/dL before surgery and 1.88 mg/dL at postoperative 1 week. Averaged duration of antibiotics therapy was 3.7 weeks. Spinal fusion was obtained in 13 patients. Two patients with neurologic deficits due to epidural abscess returned to normal. Preoperative psoas abscess in 6 patients disappeared after surgery on MRI., Conclusions: Posterolateral spinal endoscopic debridement and irrigation brought immediate pain reduction and good clinical results to patients who had comorbid medical problems and had pyogenic spondylodiscitis.

Study Design: This is a biomechanical study using sheep thoracic spine to investigate the probability of mechanical failure of the thoracic spine with various sizes or locations of tumor metastasis., Objective: The objectives of this study were to investigate biomechanical effects of not only tumor sizes within the thoracic vertebral body but also its involvement of other spinal components on the probability of mechanical failures of the thoracic spine., Summary of Background Data: There have been no experimental studies concerning mechanical influences of destruction of costovertebral joint or posterior elements as well as vertebral body on the load-bearing capacity of the thoracic spine., Methods: Ninety-nine fresh sheep thoracic spine specimens with ribs were used (T7-T9, T10-T12). Within vertebral bodies of 39 specimens, only trabecular defects were created in different sizes. In other 48 specimens, not only vertebral body defects that were 40% to the cross-sectional area of the vertebral body but also additional destruction of costovertebral joint, pedicle, and facet joint were created. All specimens were subjected to destructive biomechanical testing., Results: The failure load decreased as the defect size in the vertebral body increased. A negative linear correlation was observed between the failure load and the size of vertebral body defect (r = 0.782). With 40% cross-sectional defect in the vertebral body, additional costovertebral joint destruction brought 25% reduction of the failure load, which was statistically significant., Conclusion: The load-bearing capacity of metastasized vertebrae in the thoracic spine was proportionally decreased when the defect size in the vertebral body increased. Destruction of costovertebral joint significantly increased the probability of vertebral collapse.

Study Design: A nondestructive biomechanical investigation among five anterior spinal instrumentation systems for scoliosis., Objectives: The purpose of this study is to analyze the static and dynamic biomechanical stability of five different systems., Summary of Background Data: Although a variety of anterior spinal instrumentation systems for scoliosis are available, very few attempts have been made at comparative biomechanical studies., Methods: Thirty calf spines were underwent static biomechanical tests, including flexion-extension, axial rotation, and lateral bending loading modes in the multisegmental spinal model. Five anterior instrumentation systems included: 1) Texas Scottish Rite Hospital system; 2) Bad Wildungen Metz; 3) anterior ISOLA; 4) Cotrel-Dubousset Hoph; and 5) Kaneda Anterior Scoliosis System. The initial and postfatigue stability after a cyclic loading test were analyzed by measuring the range of motion at instrumented segments compared to the intact within the same specimen (% to intact)., Results: Two-rod systems showed a significant decrease in range of motion compared to one-rod systems in flexion-extension (P < 0.001) and axial rotation (P < 0.05). In lateral bending, all systems demonstrated a significant decrease in range of motion of less than 40% to the intact (P < 0.001). After cyclical loading test, all systems increased in range of motion. In flexion-extension, one-rod systems depicted a significant increase in range of motion, compared to two-rod systems (P < 0.05)., Conclusions: In the initial stability analysis, two-rod systems are superior to one-rod systems. For one-rod systems, repeated physiologic loading may result in reduced stability in flexion-extension.

Study Design: After total spondylectomy, five types of spinal reconstruction techniques were compared biomechanically., Objectives: To evaluate the stability provided by five reconstruction methods after total spondylectomy., Summary of Background Data: Total spondylectomy presents a worst-case scenario for spinal reconstruction. However, few investigators have biomechanically investigated spinal reconstruction stability after total spondylectomy., Methods: Eight human cadaveric spines (T11-L5) were used. After intact analysis, a total spondylectomy was performed at L2 and reconstructed using Harms titanium mesh (Depuy-Motech, Warsaw, IN) as an anterior strut. Anterior, posterior, or circumferential instrumentation techniques were then performed using the Kaneda SR and ISOLA pedicle screw systems (AcroMed Corp., Cleveland, OH) as follows: 1) anterior instrumentation at L1-L3 with multisegmental posterior instrumentation at T12-L4 (AMP), 2) anterior instrumentation at L1-L3 with short posterior instrumentation at L1-L3 (ASP), 3) anterior instrumentation at L1-L3 (A), 4) multilevel posterior instrumentation at T12-L4 (MP), and 5) short posterior instrumentation at L1-L3 (SP). Nondestructive biomechanical testing was performed under axial compression, flexion-extension, and lateral bending loading modes., Results: Only circumferential instrumentation techniques (AMP, ASP) exhibited higher stiffness than the intact spine in all loading modes (P < 0.05). Short circumferential fixation provided more stability than did multilevel posterior instrumentation (P < 0.05). Multilevel posterior fixation provided more stiffness than did short posterior and anterior instrumentation alone (P < 0.05)., Conclusions: Only circumferential fixation techniques provide more stability than the intact spine in all testing modes. Short circumferential instrumentation provides more stability than multilevel posterior instrumentation alone and requires fewer levels of spinal fusion.

Study Design: Biomechanical evaluation was performed to investigate the stability of the thoracic spine. Unilateral resection of the intervertebral disc, the rib head joint, and the costotransverse joint were sequentially performed, and nondestructive cyclic loading tests were conducted at each injury stage to examine the roles of the intervertebral disc and the costovertebral joint of the thoracic spine. The effects of each resection were three-dimensionally analyzed as the main motion and the associated coupled motions., Objective: To examine the role of the intervertebral disc and the costovertebral joint in stability of the thoracic spine., Summary of Background Data: The effects of unilateral resection of the intervertebral disc and the costovertebral joints in the thoracic spine with the rib cage have not been documented three-dimensionally in a biomechanical study., Materials and Methods: Ten canine rib cage-thoracic spine complexes, consisting of the sixth to eighth ribs, the sternum and T5-T8 vertebrae, were used. Six pure moments along three axes, flexion-extension, lateral bending, and axial rotation, were applied to the specimen, and the angular deformation between T6-T7 was recorded by a stereophotogrammetric method. After the intact specimens were tested, staged resections were conducted in the following manner: partial resection of the T6-T7 intervertebral disc, performed as a resection of the anterior longitudinal ligament, the nucleus pulposus, and the annulus fibrosus on the approach side, leaving the posterior longitudinal ligament intact; resection of the right seventh rib head with the joint capsule; and resection of the right seventh costotransverse joint. At each stage, the main motion and associated coupled motions were determined three dimensionally., Results: The ranges of motion (ROM) in flexion-extension, lateral bending, and axial rotation were significantly increased after partial discectomy (P < 0.01). Moreover, along with large increases in the ROM of the main motions in left axial rotation and right lateral bending, coupled motions, expressed by right lateral bending and left axial rotation, showed marked increases after resection of the rib head joint (P < 0.05). The neutral zones also increased in lateral bending, axial rotation, and flexion-extension after partial discectomy (P < 0.01). A further increase in the neutral zone was observed in lateral bending after resection of the right seventh rib head (P < 0.01)., Conclusions: In this canine spine model, the intervertebral disc regulates the stability of the thoracic spine in flexion-extension, lateral bending, and axial rotation. Moreover, the articulation of the rib head with the vertebral bodies provides stability to the thoracic spine in lateral bending and axial rotation. Unilateral resection of the rib head joint after partial discectomy on the same side produces significant coupled motions in lateral bending and axial rotation, resulting in a significant decrease in thoracic spinal stability, and integrity.

Study Design: Spinal reconstruction procedures for metastasis evaluated biomechanically using human cadaver specimens., Objective: To investigate the stiffness of anterior versus circumferential spinal reconstructions for different anatomic stages of tumor lesions., Summary of Background Data: Metastatic tumors predominantly involve the vertebral bodies. Although anterior instrumentation and strut grafts provide excellent stability, it remains unclear to what extent vertebral destruction requires anterior reconstructions alone versus combined anterior and posterior procedures., Methods: Ten human cadaveric thoracolumbar spines were used. The L1 vertebral body and posterior elements were resected sequentially based on Weinstein's anatomic zone classification for tumor lesions. Anterior reconstruction was performed between T12 and L2 using an iliac strut graft and the Kaneda SR system (AcroMed, Cleveland, OH). For circumferential reconstruction, the Cotrel-Dubousset hook and rod system was combined with the anterior reconstruction procedure. Experimental groups included the intact condition and five reconstruction stages: anterior reconstructions for corpectomy, subtotal and total spondylectomies, and circumferential reconstructions for subtotal and total spondylectomies. Nondestructive biomechanical testing was performed under four different loading modes., Results: All the reconstruction groups except anterior instrumentation alone for total spondylectomy returned stiffness to a level equivalent or higher to that of the intact spine. There were no statistical differences observed between anterior and circumferential reconstruction for subtotal spondylectomy. Anterior instrumentation alone for total spondylectomy did not restore stiffness to the intact level, and demonstrated significantly lower stiffness than that of circumferential reconstruction., Conclusions: For corpectomy or subtotal spondylectomy, anterior reconstruction alone can provide stiffness equivalent to circumferential reconstruction. However, total spondylectomy significantly reduces the anterior reconstruction stiffness, suggesting the need for combined anterior and posterior procedures.

Study Design: Analysis of the clinical results of 20 patients with thoracic scoliosis treated by anterior procedure with Kaneda anterior spinal system., Objectives: To evaluate the efficacy of the anterior surgical correction procedure with a new anterior instrumentation in thoracic scoliosis., Summary of Background Data: Posterior correction and fusion with posterior instrumentation has been a main component of the surgical management of thoracic scoliosis. However, to the best of the authors' knowledge, no clinical results of anterior instrumentation surgery for thoracic scoliosis have been published in the English literature., Methods: Anterior correction and fusion using Kaneda anterior spinal system was performed in 20 patients with thoracic scoliosis (3 patients with King Type II curve, 13 with Type III, and 4 with Type IV). The average follow-up was 3 years, with a range of 2 years, 3 months to 4 years, 1 month. There were 1B patients with idiopathic scoliosis (13 adolescents and 5 adults) and 2 patients with a single thoracic curve caused by other etiologies. All patients had correction of scoliosis by fusion within the major thoracic curve. Radiographic evaluations were performed to analyze frontal, sagittal, and rotational deformities of the spine., Results: The average correction rate of scoliosis was 71%. Above the instrumented levels, the correction rate was 75%. Preoperative kyphosis of the instrumented levels of 7 degrees was corrected to 14 degrees of kyphosis. The trunk shift was improved from 17 mm before surgery to 9 mm at final follow-up evaluation. The average improvement of the tilt-angle in the lower and vertebra of fusion was 81%, and was 83% in the stable vertebra. Apical vertebral rotation showed correction rate of 15% in patients without performing resection of the rib head joints and rod rotation maneuver (n = 6). However, the correction rate was improved to 58% after introduction of the technique discussed (n = 14). The angle of tangential rib deformity (rib hump) showed a correction rate of 50%. There was 1.2 degrees of frontal plane and 1.0 degree of sagittal plane correction loss within the instrumented area at final follow-up evaluation. At final follow-up, nonunion at the uppermost segment of the fusion range developed in one patient, and decompensation in the lumbar spine was observed in one patient with Type II curve., Conclusions: Anterior correction with Kaneda anterior spinal system provides excellent correction of the frontal curvature and sagittal alignment by fusing within the range of the major curve, without a significant loss of correction and implant failure. Rigid rotational deformity of the thoracic scoliosis is effectively corrected by resection of the rib head joints and rod rotation maneuver. However, too much correction of the thoracic curve should be avoided, to prevent decompensation of the lumbar curve, especially in Type II curves.

Study Design: The associations between vertebral body collapse and the size or location of the metastatic lesions were analyzed statistically to estimate the critical point of collapse., Objectives: To determine risk factors for collapse, to estimate the predicted probability of collapse under various states of metastatic vertebral involvement, and to establish the criteria of impending collapse., Summary of Background Data: Pathologic vertebral collapse brings about severe pain and paralysis in patients with cancer. Prevention of collapse plays a significant role in maintaining or improving their quality of life. Because no previous study has clarified the critical point of vertebral collapse, however, the optimum timing for prophylactic treatment has been unclear., Methods: The size and location of metastatic tumor from Th1 to L5 were evaluated radiologically for 100 thoracic and lumbar vertebrae with osteolytic lesions. The correlations between collapse and the following risk factors (x1-x4) were determined by means of a multivariate logistic regression model: x1, tumor size (the percentage of tumor occupancy in the vertebral body [% TO]); x2, pedicle destruction, x3, posterior element destruction; and x4, costovertebral joint destruction., Results: Significant risk factors were costovertebral joint destruction (odds ratio, 10.17; P = 0.021) and tumor size (odds ratio of every 10% increment in %TO, 2.44; P = 0.032) in the thoracic region (Th1-Th10), whereas, tumor size (odds ratio of every 10% increment in %TO, 4.35; P = 0.002) and pedicle destruction (odds ratio, 297.08; P = 0.009) were main factors in the thoracolumbar and lumbar spine (Th10-L5). The criteria of impending collapse were: 50-60% involvement of the vertebral body with no destruction of other structures, or 25-30% involvement with costovertebral joint destruction in the thoracic spine; and 35-40% involvement of vertebral body, or 20-25% involvement with posterior elements destruction in thoracolumbar and lumbar spine., Conclusions: With respect to the timing and occurrence of vertebral collapse, there is a distinct discrepancy between the thoracic and thoracolumbar or lumbar spine. When a prophylactic treatment is required, the optimum timing and method of treatment should be selected according to the level and extent of the metastatic vertebral involvement.

One hundred and fifty consecutive patients who had a burst fracture of the thoracolumbar spine and associated neurological deficits were managed with a single-stage anterior spinal decompression, strut-grafting, and Kaneda spinal instrumentation. At a mean of eight years (range, five years to twelve years and eleven months) after the operation, radiographs showed successful fusion of the injured spinal segment in 140 patients (93 per cent). Ten patients had a pseudarthrosis, and all were managed successfully with posterior spinal instrumentation and a posterolateral arthrodesis. The percentage of the canal that was obstructed, as measured on computed tomography, improved from a preoperative mean of 47 per cent (range, 24 to 92 per cent) to a postoperative mean of 2 per cent (range, 0 to 8 per cent). Despite breakage of the Kaneda device in nine patients, removal of the implant was not necessary in any patient. None of the patients had iatrogenic neurological deficits. After the anterior decompression, the neurological function of 142 (95 per cent) of the 150 patients improved by at least one grade, as measured with a modification of the grading scale of Frankel et al. Fifty-six (72 per cent) of the seventy-eight patients who had preoperative paralysis or dysfunction of the bladder recovered completely. One hundred and twenty-five (96 per cent) of the 130 patients who were employed before the injury returned to work after the operation, and 112 (86 per cent) of them returned to their previous job without restrictions. We concluded that anterior decompression, strut-grafting, and fixation with the Kaneda device in patients who had a burst fracture of the thoracolumbar spine and associated neurological deficits yielded good radiographic and functional results.

Study Design: This is a biomechanical study of the thoracic spine. Various ligaments and joints were resected sequentially and nondestructive cyclic loading tests were performed. Effects of each resection were analyzed biomechanically., Objectives: To investigate the role of the posterior elements, costovertebral joints, and rib cage in the stability of the thoracic spine., Summary of Background Data: There have been no experimental studies concerning the mechanical interaction between the thoracic spine and rib cage., Methods: Eight canine rib cage-thoracic spine complexes, consisting of the sixth to eighth ribs, sternum, and T5-T9 vertebrae, were used. Six pure moments along three axes were applied to the specimens, and angular deformation of T6-T7 was recorded. After testing the intact specimen, resection of the stabilizers was conducted incrementally in the following manner: 1) removal of the posterior elements at T6-T7, 2) resection of the bilateral seventh costovertebral joints, and finally, 3) destruction of the rib cage. The same loading tests were repeated at each stage. The ranges of motion and neutral zones were calculated by digitization., Results: A large increase in the range of motion in flexion-extension was observed after resection of the posterior elements and in lateral bending and axial rotation after resection of the costovertebral joints. A significant increase in the neutral zone in lateral bending and axial rotation was observed after bilateral resection of the costovertebral joints and destruction of the rib cage., Conclusions: The costovertebral joints and rib cage play an important role in providing stability to the thoracic spine. The state of the costovertebral joints and rib cage should be assessed to evaluate the stability of the thoracic spine.

Twenty-seven burst fractures with neurologic deficits of the thoracolumbar-lumbar spine were treated with an one-stage anterior operation consisting of anterior decompression through vertebrectomy, realignment and stabilization with Zielke instrumentation (12 patients), and our new anterior instrumentation (15 patients). Only two disc spaces directly related to the injury were fused. No patient showed neurologic deterioration after surgery. All 26 patients with incomplete lesions improved postoperatively, with 19 of them entering the next Frankel subgroup. The newly designed anterior instrumentation afforded enough stability to enable early ambulation with alignment and solid fusion.

The purpose of this study was to evaluate the stabilizing effect of various types of spinal instrumentation now used for reconstruction of injured spine. Six types of moments were applied on fixed human thoracolumbar cadaveric spines with posterior and middle column injury. Stereophotogrammetry was used to evaluate the spinal movements three-dimensionally. Achievement of stabilization against axial rotation was most difficult in all kinds of instrumentations, though transpedicular external fixator and the Kaneda device with transverse fixators provided relatively good stability for this load mode. These two devices were also stable enough for other load modes. From the view point that sufficient stability should be obtained by short instrumentation area, these two forms of spinal instrumentation are optimal among those tested in this study. Regarding transpedicular external fixator and the Kaneda device with transverse fixators, the stability was reinforced with interbody bone grafting and application of compressive force on it.

Using CT scans of 112 consecutive patients with thoracolumbar burst fractures, we investigated the relationship between traumatic spinal canal stenosis and neurologic deficits. We calculated the stenotic ratios of the area occupied by the retropulsed bony fragments to the estimated area of the original spinal canal. We also examined the shape of the narrowed canal and the disruption of spinal elements. Burst fractures having the following ratios are at significant risk of neurologic involvement: at T11 to T12 with 35% more, at L1 with 45% or more, and at L2 and below with 55% or more.