Anterior Spinal Arthrodesis Research Articles

Combined spinal arthrodesis with instrumentation for the management of progressive thoracolumbar kyphosis in children with mucopolysaccharidosis

To evaluate the outcome and complications of a novel technique for the treatment of progressive thoracolumbar kyphosis in children with mucopolysaccharidosis (MPS). The medical records and spinal imaging of four consecutive paediatric patients who underwent a single stage anteroposterior spinal fusion with segmental pedicle screw instrumentation were reviewed. Patients underwent spinal deformity correction at the mean age of 3 years (2.4-3.7) with mean clinical follow-up of 3.2 years (2.1-4.5) and mean postoperative radiographic follow-up was 2.4 years (0.8-3). Preoperative kyphosis was corrected from a mean angle of 65º (63º-70º) to 6.5º (-12º-13º). Vertebral subluxation at the apex of the deformity was corrected from an average 64% (56-83%) to 12% (0-24%). Spinal cord monitoring with somatosensory evoked potentials (SSEP) was successfully obtained and stable throughout surgery. No instrumentation failure, loss of correction or junctional problems occurred at final follow-up. Anterior and posterior spinal arthrodesis with segmental pedicle screw instrumentation is a safety and reliable technique for the treatment of severe thoracolumbar kyphosis in children with MPS. This technique achieves excellent correction of the deformity with adequate decompression of the spinal canal. The fusion is limited to the thoracolumbar junction and interferes minimally with the longitudinal growth of the thorax. No neurological complications or intraoperative spinal cord monitoring events occurred. No loss of correction or junctional kyphosis was observed.

Cancer Risk After Use of Recombinant Bone Morphogenetic Protein-2 for Spinal Arthrodesis

Recombinant human bone morphogenetic protein-2 (rhBMP-2) is a growth factor known to have in vitro effects on the growth and invasiveness of cancer. It has been approved by the U.S. Food and Drug Administration in limited doses for single-level anterior spinal arthrodesis, but it is commonly used off-label and at high doses. The effect of rhBMP-2 on the risk of cancer has been a concern. We sought to evaluate the risk of new cancers in patients receiving high-dose rhBMP-2. We used publicly available data from a pivotal, multicenter, randomized controlled trial of patients with degenerative lumbar spine conditions who underwent a single-level instrumented posterolateral arthrodesis with either high-dose rhBMP-2 in a compression-resistant matrix (CRM) (rhBMP-2/CRM; n = 239) or autogenous bone graft (control group; n = 224). We compared the risks of new cancers in the rhBMP-2/CRM and control groups at two and five years after surgery. At two years, with 86% follow-up, there were fifteen new cancer events in eleven patients in the rhBMP-2/CRM group compared with two new cancer events in two patients in the control group treated with autogenous bone graft. The incidence rate of new cancer events per 100 person-years was 3.37 (95% confidence interval [CI], 1.89 to 5.56) in the rhBMP-2/CRM group at two years compared with 0.50 (95% CI, 0.06 to 1.80) in the control group. The incidence rate ratio was 6.75 (95% CI, 1.57 to 60.83; p = 0.0026) at two years. Calculated in terms of the number of patients with one or more cancer events two years after the surgery, the incidence rate per 100 person-years was 2.54 (95% CI, 1.27 to 4.54) in the rhBMP-2/CRM group compared with 0.50 (95% CI, 0.06 to 1.82) in the control group at two years; the incidence rate ratio was 5.04 (95% CI, 1.10 to 46.82; p = 0.0194). At five years, there was a 37% loss of follow-up, but a significantly greater incidence of cancer events was still observed in the rhBMP-2/CRM group. A high dose of 40 mg of rhBMP-2/CRM in lumbar spinal arthrodesis was associated with an increased risk of new cancer.

Neurofibromatosis: Etiology, Commonly Encountered Spinal Deformities, Common Complications and Pitfalls of Surgical Treatment

Neurofibromatosis 1 (NF-1) is a multisystemic, autosomal dominant genetic disorder. Skeletal complications usually present early in life and can be attributed to abnormalities of bone growth, remodeling, and repair, or can be secondary to nearby soft-tissue abnormalities complicating NF-1. Skeletal complications can be categorized as generalized or focal manifestations. The incidence of spinal deformities in association with NF-1 varies from 2% to 36%, with scoliosis being the most common. Both heritable and nonheritable factors contribute to the pathogenesis of spinal deformities in NF-1 patients. Traditionally, the spinal deformities are classified into dystrophic or nondystrophic. The pathophysiology of dystrophic curves is still uncertain, but may require a nonhereditary event, such as an adjacent tumor or a second hit event in local bone cells, leading to the underlying dysplasia. Dystrophic curves may result in scoliosis, kyphosis, or frequently, kyphoscoliosis. The goal of surgical management is to arrest the progression of deformity instead of achieving complete correction. The current state-of-the-art treatment for significant deformity is combined anterior and posterior spinal arthrodesis. Postoperative orthotic immobilization is almost always recommended in an effort to prevent pseudoarthrosis. The orthosis should be maintained until a fusion mass is obtained. Assessment of the fusion mass by computed tomography (CT) or magnetic resonance imaging (MRI) should be performed. Major complications, such as paraplegia, pseudoarthrosis, intraoperative hemorrhage, and postoperative progression of the deformity may occur. In an attempt to eliminate complications and achieve the best results, a multidisciplinary treatment strategy is needed. The intent of this article is to present the spinal deformities that are most commonly associated with NF-1, to identify the underlying biology of spinal deformities based on the most recent literature, and to address the common complications and pitfalls of their surgical management.

Spinal Deformity in Patients With DiGeorge Syndrome

Retrospective review of a case series. To present the clinical characteristics and treatment of spinal deformity in DiGeorge syndrome. There are no data on the development of spinal deformity in this condition. A high rate of wound infection could be expected after spinal surgery due to congenital thymic hypoplasia. The medical records and spinal radiographs of 4 consecutive patients were reviewed. All patients were followed for a minimum of 2.5 years after spinal surgery. The mean age at diagnosis of spinal deformity was 9.9 years. The type of deformity was not uniform but the curves progressed in all patients requiring a spinal arthrodesis at a mean age of 16.1 years. Two patients developed a thoracolumbar scoliosis and underwent an anterior spinal arthrodesis with instrumentation, which produced a good outcome. The remaining 2 patients developed a double thoracic and lumbar scoliosis with increased thoracic kyphosis. Brace treatment was unsuccessful to control the deformity in one of these patients. Both patients underwent a posterior spinal arthrodesis with segmental instrumentation, which achieved satisfactory correction of the scoliosis with no loss of correction or detected pseudarthrosis at follow-up. However, both patients developed junctional kyphosis above the proximal end of the instrumentation. This was asymptomatic and nonprogressive; therefore, cephalad extension of the fusion was not required. Irradiated blood products were administered in all patients to prevent graft-versus-host disease. The postoperative course was uncomplicated and none of the patients developed wound healing problems or infections. The development of spinal deformity in patients with DiGeorge syndrome may be associated to the presence of marked ligamentous laxity and congenital cardiac disease. There is significant variability on the pattern of spinal deformity, which in our series was progressive in all patients and required surgical correction with no perioperative complications.

The Effect of Anterior Spinal Fusion on Spinal Canal Development in an Immature Porcine Model

Experimental study. To investigate whether anterior spine fusion in the immature porcine spine has an adverse effect on the development of spinal canal. Neurocentral cartilage (NCC) is located in the posterior vertebral body and responsible for the development of posterior aspect of the spinal canal. Injury to the NCC interferes with the development of the spinal canal. Twelve 8-week-old domestic pigs were used to develop an anterior fusion model. A standard procedure as L3-L4, L4-L5 discectomy, and L3-L5 anterior instrumented spine fusion was performed. To evaluate the development of the spinal canal, all subjects had computed tomography scans before the procedure and at the final follow-up. The spinal canal area was measured at the control level (CL) (L2), arthrodesis level (AL) (L4), superior (L3), and inferior (L5) instrumented level (SIL and IIL). Percent change in spinal canal area from before surgery to final follow-up was also calculated. RESULTS.: Eleven subjects were available for the study. All subjects developed local kyphosis over the fused segments. The average area of L2 (CL) was 0.56 +/- 0.06 cm before surgery. The average areas of the L3 (SIL), L4 (AL), and L5 (IIL) were 0.62, 0.70, and 0.77 cm, respectively. At the final follow-up the average area of L2 was 1.20 cm. The average areas of the SIL, AL, and IIL were 1.16, 1.19, and 1.33 cm, respectively. The percent increase in spinal canal area at the CL was 116.6% whereas it was 85.8%, 71.0%, and 71.2% at SIL, AL, and IIL, respectively. Anterior spinal arthrodesis in the immature porcine spine results in iatrogenic retardation on spinal canal growth. This effect is most likely related to the tethering effect of the interbody fusion over the NCC. Although, it is difficult to directly extrapolate these findings to clinical practice, the spine surgeons operating on pediatric patients should be aware of this possibility.

Influence of Lumbar Lordosis Restoration on Thoracic Curve and Sagittal Position in Lumbar Degenerative Kyphosis Patients

A retrospective study. To determine postsurgical correlations between thoracic and lumbar sagittal curves in lumbar degenerative kyphosis (LDK) and to determine predictability of spontaneous correction of thoracic curve and sacral angle after surgical restoration of lumbar lordosis and fusion. To our knowledge, there are only a limited number of articles about the relationship between thoracic and lumbar curve in sagittal thoracic compensated LDK. Retrospective review of 53 consecutive patients treated with combined anterior and posterior spinal arthrodesis. We included patients with sagittal thoracic compensated LDK caused by sagittal imbalance in this study. Total lumbar lordosis, thoracic kyphosis, sacral slope, and C7 plumb line were measured on the pre- and postoperative whole spine lateral views. Postoperative changes in thoracic kyphosis, sacral slope, and C7 plumb line according to the surgical lumbar lordosis restoration were measured and evaluated. The mean preoperative sagittal imbalance by plumb line was 78.3 mm (+/-76.5); this improved to 13.6 mm (+/-25) after surgery (P < 0.0001). Mean lumbar lordosis was 9.4 degrees (+/-19.2) before surgery and increased to 38.4 degrees (+/-13.1) at follow-up (P < 0.0001). Mean thoracic kyphosis was 1.1 degrees (+/-12.7) before surgery and increased to 17.6 degrees (+/-12.2) at follow-up (P < 0.0001). Significant preoperative correlations existed between kyphosis and lordosis (r = 0.772, P < 0.0001) and between lordosis and sacral slope (r = 0.785, P < 0.0001). Postoperative lumbar lordosis is correlated to thoracic kyphosis increase (r = 0.620, P < 0.0001). Postoperative lumbar lordosis is correlated to sacral slope increase (r = 0.722, P < 0.0001). Reciprocal relationship exists between lumbar lordosis and thoracic kyphosis in sagittal thoracic compensated LDK. Surgical restoration of lumbar lordosis for LDK brings about high level of statistical correlation to thoracic kyphosis improvement. At the same time, the reciprocal relationship is maintained.

CAN PATIENTS WITH SAGITTALLY WELL-COMPENSATED LUMBAR DEGENERATIVE KYPHOSIS BENEFIT FROM SURGICAL TREATMENT FOR INTRACTABLE BACK PAIN?

To analyze pre- and postoperative x-rays of sagittal spines and to review the surgical results of 21 patients with lumbar degenerative kyphosis whose spines were sagittally well compensated by compensatory mechanisms but who continued to suffer from intractable back pain We performed a retrospective review of 21 patients treated with combined anterior and posterior spinal arthrodesis. Inclusion criteria were: lumbar degenerative kyphosis patients with intractable back pain and whose spines were sagittally well compensated by a compensatory mechanism, defined as a C7 plumb line to the posterior aspect of the L5-S1 disc of less than 5 cm. Outcome variables included: radiographic measures of preoperative, postoperative, and follow-up films; clinical assessment using the mean Numeric Rating Scale, Oswestry Disability Index, and Patient Satisfaction Index; and a review of postoperative complications. All patients were female (mean age, 64.5 years; age range, 50-74 years). The mean preoperative sagittal imbalance was 19.5 (+/- 17.6) mm, which improved to -15.8 (+/- 22.2) mm after surgery. Mean lumbar lordosis was 13.2 degrees (+/- 15.3) before surgery and increased to 38.1 degrees (+/- 14.4) at follow-up (P < 0.0001). Mean thoracic kyphosis was 5.5 degrees (+/- 10.2) before surgery and increased to 18.9 degrees (+/- 12.4) at follow-up (P < 0.0001). Mean sacral slopes were 12.9 degrees (+/- 11.1) before surgery and increased to 26.3 degrees (+/- 9.6) at follow-up (P < 0.0001). The mean Numeric Rating Scale score improved from 7.8 (back pain) and 8.1 (leg pain) before surgery to 3.0 (back pain) and 2.6 (leg pain) after surgery (P < 0.0001). The mean Oswestry Disability Index scores improved from 56.2% before surgery to 36.7% after surgery (P < 0.0001). In 18 (85.5%) of 21 patients, satisfactory outcomes were demonstrated by the time of the last follow-up assessment. This study shows that even lumbar degenerative kyphosis patients with spines that are sagittally well compensated by compensatory mechanisms may suffer from intractable back pain and that these patients can be treated effectively by the restoration of lumbar lordosis.

Late post-operative paraparesis after rib penetration of the spinal canal in a patient with neurofibromatous scoliosis

Rib displacement into the spinal canal is a rare cause of paraplegia or paraparesis in patients affected by neurofibromatous scoliosis. We describe a case of paraparesis in a 14-year-old child affected by neurofibromatous dystrophic kyphoscoliosis, treated with combined posterior and anterior spinal arthrodesis. Seventeen days after the surgical treatment the patient developed clinical signs and symptoms of paraparesis. A CT scan showed the head of the fifth rib protruding into the spinal canal with cord compression. Rib resection and posterior cord decompression were carried out following complete neurological recovery.

Late presentation of superior mesenteric artery syndrome following scoliosis surgery: a case report

IntroductionObstruction of the third part of the duodenum by the superior mesenteric artery (SMA) can occur following surgical correction of scoliosis. The condition most commonly occurs in significantly underweight patients with severe deformities during the first few days to a week following spinal surgery.Case presentationWe present the atypical case of a patient with normal body habitus and a 50° adolescent idiopathic thoracolumbar scoliosis who underwent anterior spinal arthrodesis with instrumentation and developed SMA syndrome due to progressive weight loss several weeks postoperatively. The condition manifested with recurrent vomiting, abdominal distension, marked dehydration, and severe electrolyte disorder. Prolonged nasogastric decompression and nasojejunal feeding resulted in resolution of the symptoms with no recurrence at follow-up. The spinal instrumentation was retained and a solid spinal fusion was achieved with good spinal balance in both the coronal and sagittal planes.ConclusionSMA syndrome can occur much later than previously reported and with potentially life-threatening symptoms following scoliosis correction. Early recognition of the condition and institution of appropriate conservative measures is critical to prevent the development of severe complications including the risk of death.

Surgical Treatment of Failed Back Surgery Syndrome due to Sagittal Imbalance

Retrospective study of consecutive patient series. To review the etiology of failed back surgery syndrome due to sagittal imbalance and radiographic and clinical results of surgical treatment of these patients who were treated with combined anterior and posterior arthrodesis. Sagittal imbalance after spinal fusion surgery may be a major source of pain and disability. Preventing iatrogenic sagittal imbalance should be a key objective during spinal fusion surgery. Retrospective review of revision spine surgery due to sagittal imbalance treated with combined anterior and posterior spinal arthrodesis in the 19 patients. Outcome variables included radiographic measures of preoperative, postoperative, and follow-up films, and a clinical assessment using the Verbal Analogue Scale (VAS), Oswestry Disability Index, Macnab criteria, Satisfactory Index Instrument, and a review of postoperative complications. Mean age was 62 years (range, 49-74 years), and mean follow-up was 31 months (range, 24-37 months) for clinical and radiographic outcome variables. The mean preoperative sagittal imbalance was 116 (+/-65) mm, which improved to 32 mm (+/-29) after surgery. Mean lumbar lordosis was 15 degrees (+/-20 degrees) before surgery, and increased to 38 degrees (+/-13 degrees) at follow-up, an increase of 23 degrees. The mean VAS improved from 7.2 (back pain), 6.8 (leg pain) before the surgery to 3 (back pain), 3.2 (leg pain) after the surgery (P < 0.0001). The mean Oswestry Disability Index scores improved from 62 (+/-11) before the surgery to 36 (+/-12) after the surgery (P < 0.0001). Excellent or good outcome was demonstrated in 16 patients (84.2%). Most common causes of revision spine surgery due to sagittal imbalance were failure to enhance lumbar lordosis and adjacent disc degeneration after lumbar fusion surgery. These patients were effectively treated with a combined anterior and posterior arthrodesis. Following these surgical treatment, sagittal balance was generally improved with fair-to-good clinical outcomes, high patient satisfaction, and low perioperative complication rates.

Changes in sagittal alignment after restoration of lower lumbar lordosis in patients with degenerative flat back syndrome

Object The authors investigate the correlation between thoracic and lumbar curves in patients with degenerative flat back syndrome, and demonstrate the predictability of spontaneous correction of the thoracic curve and sacral angle after surgical restoration of lower lumbar lordosis. Methods The cases of 28 patients treated with combined anterior and posterior spinal arthrodesis were retrospectively reviewed. Inclusion criteria included loss of lower lumbar lordosis resulting in sagittal imbalance. Total lumbar lordosis, thoracic kyphosis, sacral slope, and C-7 plumb line length were measured on pre- and postoperative lateral views of the whole spine. Postoperative changes in thoracic kyphosis, sacral slope, and length of the C-7 plumb line were measured and evaluated according to extent of lumbar lordosis restoration. Results The mean (± standard deviation) preoperative sagittal imbalance was 64.6 ± 63.2 mm, which improved to 15.8 ± 20.7 mm after surgery (p < 0.0001). The preoperative mean lumbar lordosis was 15.6 ± 14.1°, which increased to 40.3 ± 14.5° at follow-up (p < 0.0001). The preoperative mean thoracic kyphosis was 1.6 ± 10.5° and increased to 17.2 ± 12.5° at follow-up (p < 0.0001). Significant preoperative correlations existed between kyphosis and lordosis (r = 0.628, p = 0.0003), and between lordosis and sacral slope (r = 0.647, p = 0.0002). Postoperative correlations also existed between kyphosis and lordosis (r = 0.718, p < 0.0001 and r = 0.690, p < 0.0001, respectively). Conclusions Lower lumbar lordosis plays an important role in sagittal alignment and balance. Surgical restoration of lumbar lordosis results in predictable spontaneous correction of the thoracic curve and sacral slope in patients with degenerative flat back syndrome.

Changes in sagittal alignment after restoration of lower lumbar lordosis in patients with degenerative flat back syndrome

The authors investigate the correlation between thoracic and lumbar curves in patients with degenerative flat back syndrome, and demonstrate the predictability of spontaneous correction of the thoracic curve and sacral angle after surgical restoration of lower lumbar lordosis. The cases of 28 patients treated with combined anterior and posterior spinal arthrodesis were retrospectively reviewed. Inclusion criteria included loss of lower lumbar lordosis resulting in sagittal imbalance. Total lumbar lordosis, thoracic kyphosis, sacral slope, and C-7 plumb line length were measured on pre- and postoperative lateral views of the whole spine. Postoperative changes in thoracic kyphosis, sacral slope, and length of the C-7 plumb line were measured and evaluated according to extent of lumbar lordosis restoration. The mean (+/- standard deviation) preoperative sagittal imbalance was 64.6 +/- 63.2 mm, which improved to 15.8 +/- 20.7 mm after surgery (p < 0.0001). The preoperative mean lumbar lordosis was 15.6 +/- 14.1 degrees, which increased to 40.3 +/- 14.5 degrees at follow-up (p < 0.0001). The preoperative mean thoracic kyphosis was 1.6 +/- 10.5 degrees and increased to 17.2 +/- 12.5 degrees at follow-up (p < 0.0001). Significant preoperative correlations existed between kyphosis and lordosis (r = 0.628, p = 0.0003), and between lordosis and sacral slope (r = 0.647, p = 0.0002). Postoperative correlations also existed between kyphosis and lordosis (r = 0.718, p < 0.0001 and r = 0.690, p < 0.0001, respectively). Lower lumbar lordosis plays an important role in sagittal alignment and balance. Surgical restoration of lumbar lordosis results in predictable spontaneous correction of the thoracic curve and sacral slope in patients with degenerative flat back syndrome.

Surgical Correction of Developmental Scoliosis Following Cardiac Transplantation

Case report. To present a pediatric patient who underwent successful 2-stage anterior and posterior scoliosis surgery 20 months after cardiac transplantation. Cardiac transplantation has increased the life expectancy in children with end-stage cardiac failure caused by congenital heart disease or cardiomyopathy. Scoliosis is commonly associated with congenital cardiac disease. Previous reports have suggested that anterior scoliosis surgery is contraindicated after heart transplantation. We describe the case of a 13-year-old patient who underwent staged anterior and posterior spinal arthrodesis to correct a severe thoracic developmental scoliosis. The 2 procedures were performed 1 week apart. Following the first stage, pulmonary edema had developed, which required reintubation and administration of diuretics. Significant blood loss occurred during the posterior spinal fusion. The patient had a satisfactory correction of her scoliosis and made a good recovery. Three years after surgery, she had no complaints of her back and had a solid spinal fusion. Elective anterior and posterior spinal arthrodesis can be safely performed in cardiac transplant recipients with severe developmental scoliosis. This procedure can achieve optimum correction of the curvature and a successful outcome without long-term medical or technical complications.

Use of rhBMP-2 in Combination with Structural Cortical Allografts: Clinical and Radiographic Outcomes in Anterior Lumbar Spinal Surgery

Recombinant human bone morphogenetic protein-2 soaked into an absorbable collagen sponge (rhBMP-2/ACS) has been shown in a nonhuman primate study and in a pilot study in humans to promote new bone formation and incorporation of an allograft device when implanted in patients undergoing anterior lumbar interbody arthrodesis. However, a larger series with longer follow-up is needed to demonstrate its superiority to autogenous iliac crest bone graft. Between 1998 and 2001, a two-part, prospective, randomized, multicenter study of 131 patients was conducted to determine the safety and efficacy of the use of rhBMP-2/ACS as a replacement for autogenous iliac crest bone graft in anterior lumbar spinal arthrodesis with threaded cortical allograft dowels. Patients were randomly assigned to a study group that received rhBMP-2/ACS or to a control group that received autograft. The clinical and radiographic outcomes were determined with use of well-established instruments and radiographic assessments. The patients in the study group had significantly better outcomes than the control group with regard to the average length of surgery (p < 0.001), blood loss (p < 0.001), and hospital stay (p = 0.020). Fusion rates were significantly better in the study group (p < 0.001). The average Oswestry Disability Index scores, Short-Form-36 physical component summary scores, and low-back and leg-pain scores were significantly better in the study group (p < 0.05). In patients undergoing anterior lumbar interbody arthrodesis with threaded allograft cortical bone dowels, rhBMP-2/ACS was an effective replacement for autogenous bone graft and eliminated the morbidity associated with graft harvesting.

An Investigational Study on the Healing Process of Anterior Spinal Arthrodesis Using a Bioactive Ceramic Spacer and the Change in Load-Sharing of Spinal Instrumentation

Ceramic anterior lumbar interbody arthrodesis was performed using an in vivo sheep model. Observations of fusion status and the load-sharing of spinal instrumentation were studied at sequential intervals for 1 year after surgery. To elucidate the healing process of spinal arthrodesis performed with a bioactive ceramic spacer and the change in load-sharing of anterior spinal instrumentation. With the improved development of spinal instrumentation, anterior spinal arthrodesis has become a standard spinal reconstruction technique; however, the mechanistic basis underlying the healing process is not well documented. Moreover, it remains unclear how load-distribution through the fusion mass and spinal instrumentation change throughout the healing process. Using 24 sheep, a two-level anterior lumbar interbody fusion (L2-L3, L4-L5) was performed using a smooth surface and a porous surface-modified bioactive ceramic, with each segment instrumented using a one-rod anterior spinal instrumentation system. Four animals each were killed at 2, 4, 8, 12, 24, and 52 weeks after surgery. Postmortem analysis included quantification of anterior rod strain under multidirectional flexibility testing and radiographic and histologic analyses of the arthrodesed segments. From 0 to 8 weeks after surgery, the bending strain of the rod gradually decreased despite no obvious bone formation. From 8 to 24 weeks after surgery, the rod strain markedly decreased with the development of bridging trabeculated bone formation between vertebral bodies. After 24 weeks after surgery, minimal changes were observed in rod strain; however, the fusion mass volumetrically increased with corresponding facet joint atrophy. The porous surface-modification of ceramic did not influence the histologic healing process, despite the improvement of interface osseous union rate. In anterior spinal arthrodesis, spinal instrumentation is mainly exposed to bending stress, with decreased load-sharing with corresponding development of the spinal fusion. Continuous bone remodeling of the anterior fusion mass results in concurrent decreases in spinal instrumentation and posterior spinal element load-transmission. The principal healing mechanism of ceramic anterior interbody spinal fusion is not an osseous union between the ceramic and vertebral body, but bridging bone formation around the ceramic, which directly connects the vertebral bodies above and below the disc.

THE POSITION OF THE AORTA RELATIVE TO THE SPINE

There is little information documenting the relationship of the aorta to the thoracic scoliotic spine. Recent studies have suggested that the ends of screws placed during an anterior spinal arthrodesis, and pedicle screws used for the treatment of right thoracic scoliosis, may be in proximity to the aorta. The purpose of this study was to analyze the anatomical relationship between the aorta and the spine in a comparison of patients with idiopathic right thoracic scoliosis and patients with a normal spine. Thirty-six patients with adolescent idiopathic scoliosis with a right thoracic curve and forty-three with a normal straight spine were studied. Radiographs were analyzed to determine the Cobb angle, the apex of the curve, and the apical vertebral rotation for the patients with scoliosis. Axial magnetic resonance images from the fourth thoracic vertebra to the third lumbar vertebra at the midvertebral body level were used to measure the distance from the aorta to the closest point of the vertebral body cortex, the distance from the posterior edge of the aorta to the spinal canal, and the aorta-vertebral angle. No differences were found between the groups with respect to age or sex distribution. For the scoliosis and normal groups, boys had greater average vertebral body width and depth for all levels than did girls (p < 0.05). For the scoliosis group, the most common apical vertebra was the eighth thoracic vertebra, the average coronal curve measurement was 55.2 degrees, and the average apical rotation was 17.3 degrees. The average distance from the aortic wall to the vertebral body cortex at the apex of the curve was greater in the patients with scoliosis (4.0 mm) than at similar levels in the normal group (2.5 mm) (p < 0.05). The distance from the posterior aspect of the aorta to the anterior aspect of the spinal canal was less in the scoliosis group (11.1 mm) than in the normal group (19.2 mm) for the fifth to the twelfth thoracic level (p < 0.05). The aorta was positioned more laterally and posteriorly adjacent to the vertebral body at the fifth to the twelfth thoracic level in patients with scoliosis compared with that in normal patients as reflected in a smaller aorta-vertebral angle (p < 0.05). With an increasing coronal Cobb angle in the thoracic curve and apical vertebral rotation, the aorta was positioned more laterally and posteriorly (p < 0.05). In patients with right thoracic idiopathic scoliosis, the aorta is positioned more laterally and posteriorly relative to the vertebral body compared with that in patients without spinal deformity.

Management of fixed sagittal plane deformity: outcome of combined anterior and posterior surgery.

Retrospective study of consecutive patient series. To review the radiographic and clinical results of patients with preoperative fixed sagittal imbalance treated with combined anterior and posterior arthrodesis, and to determine factors that predict clinical outcome. Combined anterior and posterior arthrodesis of the spine is useful in the management of fixed deformity involving the coronal and sagittal planes. The specific indications for combined surgery in the patient with regional and global imbalance have not been well defined. Retrospective review of 25 consecutive patients treated with combined anterior and posterior spinal arthrodesis. Inclusion criteria included a preoperative global sagittal imbalance of at least 5 cm. Outcome variables included radiographic measures of preoperative, postoperative, and follow-up films, and a clinical assessment using the Modified SRS Outcomes Instrument and a review of postoperative complications. Twenty-five consecutive cases were reviewed. Mean age was 58 years (range 38-77), and mean follow-up was 55 months (range 24-81) for clinical and 44.5 (range 24-81) months for radiographic outcome variables. The mean preoperative sagittal imbalance was 10.5 cm (range 5.2-23.3), which improved to 2.9 cm (range 0-12.6) after surgery, and was maintained as 3.3 cm (range 0-13.5) at follow-up. Mean lumbar lordosis was -23 degrees (range +40 to -47) before surgery, and increased to -42 degrees at follow-up (range -20 degrees to -60 degrees ), an increase of 19 degrees. Patients with preoperative regional hypolordosis in the lumbar spine that was corrected surgically had the highest postoperative scores. The mean score for patient satisfaction with surgical management was 4.45 (range 2.5-5). Correlation analysis of clinical outcome domains demonstrated that patient satisfaction correlated poorly with domains of pain (r = 0.37, P = 0.1) and function (r = 0.4, P = 0.09). Within the domains, self-image showed highest correlation with patient satisfaction (r = 0.65, P = 0.006) and total score (r = 0.89, P = 0.0001). Patients with global sagittal imbalance of the spine were effectively treated with a combined anterior and posterior arthrodesis as measured by radiographic parameters. Patient satisfaction with surgery, and overall clinical outcomes were best in cases that resulted in an increase in lumbar lordosis. The subset of patients with preoperative regional hypolordosis of the lumbar spine has better outcomes than those with preoperative lumbar lordosis in the physiologic range.

Gene transfer approaches to the healing of bone and cartilage.

Gene transfer approaches to the healing of bone and cartilage.

Scoliosis in Arthrogryposis Multiplex Congenita: Results After Nonsurgical and Surgical Treatment

Forty-six patients (25 male and 21 female) with arthrogryposis multiplex congenita who were seen at the Alfred I. duPont Hospital for Children between the years 1940 and 1997 were evaluated to assess the prevalence and patterns of scoliosis and the long-term results after both nonsurgical and surgical treatment methods. We found the prevalence of scoliosis to be 65.9% (32 of 46 patients). A single thoracolumbar curve was the predominant curve pattern. No congenital curve types or vertebral anomalies were seen in our group of patients. In the nonsurgical group, the mean curve was <30° at follow-up. In the surgical group, the mean primary curve before spinal arthrodesis was 78.5°. Three patients in the surgical group who were nonambulators have become household ambulators at the most recent follow-up. We recommend bracing in patients who are ambulators and have a curve of <30°. Combined anterior and posterior spinal arthrodesis gave the best results.

Posterolateral and anterior interbody spinal fusion models in the sheep.

Posterolateral and anterior interbody spinal arthrodesis is a frequent procedure, but high nonunion rates are reported and harvesting autologous bone graft from the iliac crest significantly increases morbidity. Bone graft substitutes are an alternative, but to date clinical results are not conclusive. Bone substitutes can be organic or inorganic, biologic or synthetic. They can have osteoconductive properties, inductive properties or both. Animal experiments are essential to investigating bone substitutes using biomechanical and histologic methods not available in clinical studies. Few authors reported on instrumented anterior fusion models, but none used the sheep model. In the current study posterolateral and anterior interbody fusion models in sheep are described. Both models used instrumented fusions, applying porous mineral scaffolds, alone or mixed with bone. The surgical techniques are described step-by-step and potential difficulties are highlighted. Preliminary results are reported for the posterolateral fusion model using coralline graft substitutes. The coral granules mixed with locally harvested bone had fusion outcomes similar to pure autologous bone. The graft substitute showed marked resorption between 12 and 20 weeks. All fusions had bone cortex and good trabecular connectivity. Histologic evaluation suggests after 20 weeks nearly the entire surface of the substitute is covered with new bone. Porous mineral bone substitutes mixed with locally harvested autologous bone are thought to be a valid alternative for posterolateral fusions.