Instrumentation For Scoliosis Research Articles

Postoperative pulmonary complications following posterior spinal instrumentation and fusion for congenital scoliosis.

BackgroundCongenital scoliosis (CS) may lead to more serious pulmonary complications compared with idiopathic scoliosis after spinal fusion surgery. However, little has been reported about postoperative pulmonary complication events in patients with CS after spinal fusion surgery.ObjectiveTo investigate the incidence of and predictive factors of postoperative pulmonary complications following posterior spinal instrumentation and fusion surgery for the treatment of CS.MethodsWe retrospectively reviewed the records of 174 patients with CS (128 females and 46 males, mean age 16.4 years) treated with posterior spinal instrumentation and fusion surgery between January 2012 and April 2017. We extracted demographic, medical history, and clinical data, and investigated the major predictive factors for postoperative pulmonary complications by logistic regression and receiver-operating characteristic curves analyses.ResultsA total of 26 (14.9%) patients developed postoperative pulmonary complications, consisting of pleural effusion (10.9%), pneumonia (6.9%), pneumothorax (1.1%), atelectasis (2.3%), hypoxemia (6.3%), and respiratory failure (1.1%). Logistic regression analysis revealed that the predictive factors for postoperative pulmonary complications were age > 18.1 years (P = 0.039), a Cobb angle of > 77° (P = 0.011), operation time of > 430 min (P = 0.032), and blood transfusion volume > 1500 ml (P = 0.015).ConclusionsPostoperative pulmonary complications are among the main complications following posterior spinal instrumentation and fusion surgery in patients with CS. Such patients aged >18.1 years, with Cobb angles > 77°, operation times > 430 min, and/or blood transfusion volume of > 1500 ml may be more likely to develop postoperative pulmonary complications.

Vancomycin Concentrations in Paraspinal Muscles During Posterior Spinal Fusions for Neuromuscular Scoliosis

Study DesignProspective consecutively enrolled cohort. ObjectivesTo evaluate paraspinal muscle concentration of intravenously administered vancomycin, at predetermined time points, during posterior spinal fusion (PSF) with instrumentation in neuromuscular scoliosis (NMS). SummarySurgical site infection (SSI) after PSF for NMS can be a devastating complication, which may lead to prolonged antibiotic use, multiple additional surgical procedures, pseudarthroses, and sepsis. Because of significant morbidity of SSIs in NMS, the prophylactic use of vancomycin has been adopted at our institution as standard wound prophylaxis, despite any high-level evidence of its efficacy. MethodsA prospective study of 20 patients who underwent definitive PSF for NMS and received vancomycin infusion preoperatively per institutional protocol. Serum levels were obtained immediately after infusion, at surgical incision, and then at 1, 2, and 4 hours post incision. Muscle tissue samples were simultaneously obtained at incision and at 1, 2, and 4 hours post incision. Samples were analyzed by a validated liquid chromatography–tandem mass spectrometry method. Results10 males and 10 females with a mean age of 14+11 years (9–20 years) received a mean infusion of 15.0 mg/kg vancomycin. Mean serum levels were 26.7 μg/mL after infusion, 18.1 at incision, 13.2 at 1 hour, 11.8 at 2 hours, and 7.6 at 4 hours post infusion. Mean muscle levels were 0.5 μg/mL at incision, 0.6 at 1 hour, 0.5 at 2 hours, and 0.7 at 4 hours post infusion. Mean serum levels reached minimum inhibitory concentration (MIC) for Staphylococcus aureus at incision and at all timepoints during surgery. Mean muscle vancomycin levels never reached MIC. No patients had any cardiac or kidney disease, and all patients had normal kidney function according to their preoperative laboratory values. ConclusionsUsing accepted guidelines for the administration of intravenous vancomycin preoperatively, serum levels reached MIC at incision and at all timepoints tested during PSF for neuromuscular scoliosis. At no timepoint tested did muscle levels reach MIC. Level of EvidenceLevel II.

Intra-operative computed tomography guided navigation for pediatric pelvic instrumentation: A technique guide.

Pelvic instrumentation for neuromuscular scoliosis has been part of neuromuscular scoliosis surgery since the era of the Luque Galveston construct. Unit Rod (Medtronic Sofamor-Danek, Nashville, TN) instrumentation brought with it the concept of cantilever correction by placing the implants in the pelvis and then gradually bringing the rod to the spine by sequentially tightening the sublaminar wires, with the goal of creating a level pelvis over a straight spine. More recently surgeons have utilized pedicle screw constructs in which the corrective strategies have varied. Challenges with pelvic fixation using iliac screws linked to the spinal rod have led to the development of the S2-alar-iliac technique (S2AI) in which the spinal rod connects to the pelvic screw. The screw is placed in the S2 ala, crosses the sacro-iliac joint and into the ilium through a large column of supra-acetabular bone. This column is the same area used for anterior inferior iliac spine external fixation frames used in trauma surgery. S2AI screw placement can be technically difficult and can require experienced radiology technologists to provide the appropriate views. Additionally, although the technique was originally described being placed via freehand technique with intra-operative flouroscopy, the freehand technique suffers from the anatomic anomalies present in the pelvis in neuromuscular scoliosis. As such, we prefer to place them using intra-operative navigation for all pediatric spinal deformity cases. Below in detail we report our intra-operative technique and an illustrative case example.

Skull-femoral traction after posterior release for correction of adult severe scoliosis: efficacy and complications

BackgroundIt is a great challenge for spine surgeons to correct severe rigid scoliosis. We developed a three- staged correction (one stage posterior release and screw placement, two stage skull-femoral traction and three stage posterior instrumentation) for adult severe scoliosis. The objective of this study is to investigate safety and efficacy of a three- staged correction for adult severe scoliosis.MethodsA retrospective review was performed for patients with severe scoliosis receiving three- staged correction (one stage posterior release and screw placement, two stage skull-femoral traction and three stage posterior instrumentation) from June 2001 to October 2014. The inclusion criteria were as follows: [1] age more than 18 years; [2] main curve larger than 90°; [3] a minimum 2-year follow-up. Patients were excluded if they had a history of surgery or anterior release or receiving three column osteotomies.ResultsA total of 63 patients were included (37 female and 26 male), with a mean age of 22.7 years (range: 18–30 years) and follow-up of 42.6 months (range: 24–108 months). The aetiology was congenital in 27 patients, neuromuscular in 18, idiopathic in 11, neurofibromatosis-1 in 4 and Marfan syndrome in 3. The mean traction weight was 28.4 kg (range: 18–32 kg), equal to 57.2% of patients’ body weight (range: 42.7–72.3%). The mean traction time was 22.7 days (range: 12–44 days). Postoperative correction rate was 55% (range: 38–78%) for scoliosis and 51% (range: 32–75%) for kyphosis. Contribution of traction to correction was 51% (range: 36–70%) for scoliosis and was 43% (range: 34–55%) for kyphosis.ConclusionsThree- staged correction (one stage posterior release and screw placement, two stage skull-femoral traction and three stage posterior instrumentation) could effectively correct adult severe scoliosis. The incidence of complications of skull-femoral traction was not low, but transient and could be successfully managed.

Fifteen Years and 2530 Patients: The Evolution of Instrumentation, Surgical Strategies, and Outcomes in Adolescent Idiopathic Scoliosis in a Single Institution

Over the past decade, the surgical treatment of adolescent idiopathic scoliosis (AIS) has established new techniques to reduce curve severity and shifted to include the regular use of pedicle screws. Few studies have focused on this evolving trend in AIS correction surgery. In this study, we investigated how the operative approach, instrumentation, and surgical techniques have changed over the past 15 years and to quantify the related improvements in AIS surgical treatment. This is a retrospective review of a prospective AIS registry in a single center. Patient data were reviewed from January 2001 to December 2015. The age and surgical case distribution were recorded for each year. Trends in classification use, instrumentation types, levels of fusion, and surgical approaches were analyzed by year. The major Cobb angles and correction rates were compared between different instrumentations and surgical approaches. A total of 2530 patients with AIS (83.0% female) were included, with a mean age of 15.14 years. Most patients underwent surgery at 14 years of age (473 patients, 18.7%), followed by 15 years of age (468 patients, 18.5%). In our center, the classification of patients with AIS shifted from the King classification to the Lenke classification in 2005. The major baseline Cobb angle of the entire cohort averaged 50.99° and this mean Cobb angle decreased to 14.41° after surgery. The correction rates for the first 3 years (2001-2003) were less than 70%, whereas the correction rates for the rest of the years were all greater than 70%. In addition, significantly higher correction rates were observed in patients with Cobb angles <90° (72.93% vs. 55.61%, P < 0.001). A total of 218 anterior-only surgeries and 109 combined anteroposterior surgeries were performed; the remaining 2205 surgeries were performed with a posterior-only approach. The use of anterior-only and anteroposterior approaches trended to decrease after 2005. The correction rate of anterior-only approaches was significantly greater than posterior-only and anteroposterior approaches (77.86%, 72.51%, and 59.37%, respectively). In patients corrected with a posterior-only approach, the screw-hook hybrid construct was used in 342 patients, whereas the all-pedicle-screw construct was used in 1835 patients. The shift from hybrid to all-screw construct occurred in 2006. In patients with thoracic AIS, the correction rate was significantly higher in the all-screw group (73.26% vs. 67.76%; P < 0.001). Consistent improvement of major curve correction has been achieved by the spine community over 15 years. After stabilized coronal correction and fewer fusion levels, the next steps in this evolution are the restoration of sagittal profiles, especially the hypokyphosis seen in patients with Lenke 1, the posterior minimally invasive approach, and a fast-track return to activity.

Repeat Surgical Interventions Following “Definitive” Instrumentation and Fusion for Idiopathic Scoliosis: 25-Year Update*

Study DesignSingle-institution, retrospective review of prospectively collected data on pediatric patients with adolescent idiopathic scoliosis (AIS) undergoing spinal fusion with a minimum two-year follow-up. ObjectiveTo determine the rate of reoperation in AIS patients undergoing spine fusion from 2008 to 2012. Summary of Background DataRecent trends in the surgical treatment of AIS have included increased use of all–pedicle screw constructs, smaller implants, more posterior-only approaches, and improved correction techniques. MethodsA retrospective review of 467 patients undergoing spinal fusion from 2008 to 2012 was performed. Demographic, clinical, radiographic, and surgical data were collected prospectively on all patients for the index procedure and any reoperations. Data were compared to previously published cohorts of patients from the authors' institution who underwent spinal fusion for AIS between 1988 and 2007. ResultsThe rate of reoperation in this five-year cohort of patients was 9.9%. The most common indications for reoperation were infection (4.5%: 2.4% delayed infections and 2.1% acute infections), symptomatic implants (2.1%), and misplaced pedicle screws (1.7%). When compared to the 2003-2007 cohort, the rate of reoperation for acute infection and malpositioned pedicle screws increased significantly (p = .01 and p = .04), whereas the rate of reoperation for curve progression decreased (p = .01). Reoperations for acute infections and malpositioned pedicle screws also increased significantly (p = .047 and p = .042) compared with the 1988-2002 cohort, whereas the rate of reoperation for pseudarthrosis decreased (p = .002). ConclusionReoperation rates for AIS have not improved with more sophisticated implants and techniques, predominantly because of increased acute infections and malpositioned pedicle screws despite decreasing pseudarthrosis rates and curve progression. Level of EvidenceLevel II.

Thoracoscopic Anterior Instrumentation and Fusion as a Treatment for Adolescent Idiopathic Scoliosis: A Systematic Review of the Literature

Study DesignA systematic review and meta-analysis on thoracoscopic anterior instrumentation and fusion as a treatment for adolescent idiopathic scoliosis (AIS). ObjectiveThe goal of this study is to determine the current status of thoracoscopic instrumentation and fusion as a treatment for AIS. Summary of Background DataTraditional surgical techniques for AIS have been open anterior thoracotomy with instrumentation and posterior spinal fusion and instrumentation. With the growing clinical interest in growth modulation surgeries, such as vertebral body tethering, there is a resurgence of interest in a thoracoscopic technique. MethodsThe most commonly used medical databases (PubMed, Medline, EMBASE, CINAHL, and the Cochrane library) were searched up to November 2016 using the search terms VATS, thoracoscopic scoliosis, and thoracoscopic scoliosis instrumentation. ResultsThirteen studies met the strict inclusion criteria. Five hundred thirty patients were reported: 81.7% females, with the majority diagnosed as AIS. The mean operative time was 371.5 minutes, mean blood loss of 502.85 mL, and mean hospital stay of 5.9 days. Mean preoperative curve magnitude was 52.9°; postoperative curve magnitude was 17.9°, with a correction of 62.7%. Number of levels instrumented was 6.3, pulmonary function tests returned to preoperative values by 2 years postoperation, and the complication rate was 21.3%. Compared to thoracotomy, VATS had similar complication rates, blood loss, operation theater time, curve correction, and number of fused levels. Compared to posterior fusion, VATS has higher complication rates and operation theater time. Blood loss and percentage correction were similar. VATS had a smaller number of fused segments. ConclusionsAdvantages include less invasive, excellent curve correction, few levels fused, good satisfaction, and no long-term effect on pulmonary function. Drawbacks are increased operative time and incidence of pulmonary complications. With appropriate surgeon training and careful patient selection, this technique offers an acceptable alternative to the more traditional procedures. Level of EvidenceLevel II.

Implant Density at the Apex Is More Important Than Overall Implant Density for 3D Correction in Thoracic Adolescent Idiopathic Scoliosis Using Rod Derotation and En Bloc Vertebral Derotation Technique.

Biomechanical analysis of 3D correction and bone-screw forces through numerical simulations of scoliosis instrumentation with different pedicle screw patterns. To analyze the effect of different screw densities and distributions on 3D correction and bone-screw forces in adolescent idiopathic scoliosis (AIS) instrumentation. Instrumentation constructs with various numbers of pedicle screws and patterns have been proposed for thoracic AIS instrumentation. However, systematic biomechanical studies have not yet been completed on the appropriate screw patterns for optimal 3D correction. Patient-specific biomechanical models of the spine were created for 10 AIS cases (Lenke 1). For each case, surgical instrumentation patterns were computationally simulated using respectively a reference screw pattern (two screws per level fused) and six alternative screw patterns with fewer screws. Simulated surgical maneuvers and model definition were unchanged between simulations except the number and distribution of screws. 3D correction and bone-screw forces were compared. A total of 140 posterior instrumentations were computationally simulated. Mean corrections in the coronal and sagittal planes with alternative screw patterns were within 4° to the reference pattern. Increasing screw density in the apical region from one to two screws per level improved percent apical vertebral rotation (AVR) correction (r = 0.887, P < 0.05). Average bone-screw force associated with the reference screw pattern was 243N ± 54N and those with the alternative screw patterns were 11% to 48% lower. Compared with the reference maximal screw density pattern, alternative screw patterns allowed similar corrections in the coronal and sagittal planes. AVR correction was strongly correlated with screw density in the apical region; AVR correction varied significantly with screw patterns of the same overall screw density when an en bloc vertebral derotation technique was simulated. High screw density tended to overconstrain the instrumented spine and resulted in higher forces at the bone-screw interface. N/A.

Segmental Pedicle Screw Instrumentation and Fusion Only to L5 in the Surgical Treatment of Flaccid Neuromuscular Scoliosis.

A retrospective cohort study was performed. The purpose of this study was to determine the efficacy and safety of stopping segmental pedicle screw instrumentation constructs at L5 in the treatment of neuromuscular scoliosis. Duchenne muscular dystrophy and spinal muscular atrophy are flaccid neuromuscular disorders in which gradual deterioration is the hallmark and have a lot of characteristics in common despite differences in etiology. Instrumentation and fusion to the sacrum/pelvis has been a mainstay in the surgical treatment of flaccid neuromuscular scoliosis and recommended to correct pelvic obliquity. However, the caudal extent of instrumentation and fusion in the surgical treatment of flaccid neuromuscular scoliosis has remained a matter of considerable debate and there have been few studies on the use of segmental pedicle screw instrumentation for flaccid neuromuscular scoliosis. From 2005 to 2007, a total of 27 consecutive patients with neuromuscular disorders (20 Duchenne muscular dystrophy and 7 spinal muscular atrophy), aged 11 to 17 years, underwent segmental pedicle screw instrumentation and fusion only to L5. Assessment was performed clinically and with radiologic measurements. Minimum 2-year follow-up was required for inclusion in this study. Twenty patients were enrolled in this study. No patient was lost to follow-up. All patients had L5 tilt of less than 15° and a coronal curve with apex L2 or higher preoperatively. Preoperative coronal curve averaged 70° (range: 51°-88°), with a postoperative mean of 15° (range: 5°-25°) and 17° (range: 6°-27°) at the last follow-up. The pelvic obliquity improved from 15° (range: 9°-25°) preoperatively to 5° (range: 3°-8°) postoperatively and 6° (range: 3°-8°) at the last follow-up. The L5 tilt improved from 9° (range: 2°-14°) preoperatively to 2° (range: 0°-4°) postoperatively and 2° (range: 0°-5°) at the last follow-up. Physiologic sagittal plane alignment was recreated after surgery and maintained long-term. There was no significant loss of correction of coronal curve and pelvic obliquity. There was no major complication. Segmental pedicle screw instrumentation and fusion to L5 was safe and effective in patients with flaccid neuromuscular scoliosis with apex L2 or higher and minimal L5 tilt of less than 15°. Segmental pedicle screw instrumentation ending at L5 offered the ability to correct spinal deformity and pelvic obliquity initially, intermediate and even long-term, with no major complications. This method in appropriate patients can be a viable alternative to instrumentation and fusion to the sacrum/pelvis in the surgical treatment of flaccid neuromuscular scoliosis. N/A.

Surgical outcome of scoliosis in Marfan syndrome: a case series report

Scoliosis in marfan syndrome (MFS) manifests on 60% patients. Moreover, the scoliosis noticeable in earlier age is more progressive, refracted, and rigid compared to idiopathic adult scoliosis. The surgical correction provides notorious higher perioperative risk, whereas conservative treatment using brace is not effective to prevent progressivity of the scoliosis. In this a case report, we reported the surgical outcome of MFS scoliais patients with MFS who operated using posterior fusion instrumentation by mean of the quality of life SF-36 questioner. This was a retrospective case series involving five MFS scoliosis patients who underwent posterior fusion instrumentation with initial Cobb angle of 87.417.57o and initial kyphotic angle of 32.8 ± 14.52o. Clinical, radiological and quality of life of the patients based on SF-36 questionnaire were evaluated within 6-36 months follow up. Post-operative showed the Cobb angle become 46.2 ± 16.3o and the kyphotic angle become 21.6 ± 9.94o. No intraoperative or post-operative complications were observed. After 6-36 months follow up, the Cobb angle became 45.2 ± 17.48o and the kyphotic angle became 21.6 ± 9.94o. In addition, all patients had physical and mental health scored similar to 2 years post-surgery scoliosis scoring according to SF- 36 orthopedic scoring guidelines. I conclusion, the surgical outcome of posterior fusion instrumentation in MFS scoliosis showed good correction of Cobb angle and Kyphotic angle. The quality of life of the patients based on physical and mental health questionnaire is satisfactory.

Comparison of Low versus Medium Dose Naloxone Infusion Combined with Patient Controlled Analgesia After Posterior Spinal Fusion and Instrumentation for Adolosecent Idiopathic Scoliosis: A Randomized Controlled Trial

Comparison of Low versus Medium Dose Naloxone Infusion Combined with Patient Controlled Analgesia After Posterior Spinal Fusion and Instrumentation for Adolosecent Idiopathic Scoliosis: A Randomized Controlled Trial

Metal Ion Release During Growth-Friendly Instrumentation for Early-Onset Scoliosis: A Preliminary Study

BackgroundMetal ions released from spinal instruments can cause localized debris and distribute systemically to settle on distant organs. Children with early-onset deformities live with metallic implants for a substantial amount of time. No research focused on metal distribution in growth-friendly instrumentations. The aim of this study was to compare age-matched growing rod (GR) and magnetically controlled growing rod (MCGR) groups to noninstrumented controls. MethodsThe study was designed as a multicenter, prospective, cross-sectional case series. GR and MCGR applications of three institutions were included. A total of 52 children were enrolled. Blood samples were collected between December 2014 and February 2015. Biochemical serum analyses were performed to trace and quantify titanium, vanadium, aluminum, and boron. The GR group included 15 children. Mean age was 10.7 (range 6-15). MCGR group included 22 children. Mean age was 8.5 (range 2-13). Fifteen age-matched nonoperated children formed the control group. The mean age was 10.4 (range 5-15). One-way analysis of variance, Kruskal-Wallis, and Mann-Whitney U tests were used for comparisons. ResultsThe mean serum titanium level in control, GR, and MCGR groups were 2.8 ± 1.4, 7.3 ± 4.3, and 10.2 ± 6.8 μg/L, respectively. GR and MCGR group titanium levels were higher than controls' (p = .008 and p < .001). The mean serum vanadium level in control, GR, and MCGR groups were 0.2 ± 0.0, 0.2 ± 0.0, and 0.5 ± 0.5 μg/L, respectively. MCGR group vanadium level was higher than control (p < .001) and GR groups (p = .004). Mean serum levels in control, GR, and MCGR groups were, respectively, 5.4 ± 4.1, 8.1 ± 7.4, and 7.8 ± 5.1 μg/L for aluminum and 86.7 ± 2.7, 86.9 ± 2.5, and 85.0 ± 6.6 μg/L for boron. The distribution of aluminum and boron were similar across groups (p = .675 and p = .396). ConclusionsBoth GR and MCGR applications significantly release titanium and possibly aluminum. MCGR further releases vanadium. MCGR possibly releases more titanium than traditional GR. Time-dependent alterations of serum ion levels, structural properties of the MCGR device, and exposure caused by magnetic distraction processes warrant investigation.

Short Segment Spinal Instrumentation in Early-onset Scoliosis Patients Treated With Magnetically Controlled Growing Rods: Surgical Technique and Mid - Short-term Outcomes.

A prospective, a single-institution, nonrandomized study. The aim of this study was to evaluate the safety and effectivity of short-segment instrumentation in early-onset scoliosis (EOS) patients treated by magnetic-controlled growing rods (MCGRs). Despite the common use of conventional growing rods and the recent popularity of MCGR in the treatment of progressive EOS, distal instrumented vertebra and number of the spanned levels are not standardized. Patients with progressive EOS, characterized by the major thoracic curve and nonstructural compensatory curve, were a candidate to be treated by dual MCGR short segment spinal instrumentation spanning the major thoracic curve; such patients are followed up for a minimum period of 30 months. Radiological data were collected and analyzed in terms of Cobb angle of both primary and secondary curve, kyphosis angle, T1-T12, and T1-S1 distances, and T1-T12/T1-S1 ratio in preoperative, postoperative, and last follow-up. Sixteen patients with different diagnoses of EOS, mean age at the operation was 7 years and 10 months (5 years and 6 months-9 years and 10 months), and mean period of follow-up was 37 (30-54) months. The Cobb angle of both major and compensatory curve are corrected by the mean value of 62° (44-85), 35° (22-45) preoperatively to 29° (12-49), 14° (9-24) postoperatively, and maintained at 28° (10-47), 10° (2-20) in the last follow-up, respectively. The T1-T12/T1-S1 ratio was 0.58 preoperatively, 0.6 postoperatively, and 0.62 at the last follow-up. The average yearly T1-T12 and T1-S1 length increase were calculated as 7 and 9 mm/year, respectively. Selective fusion principals are applicable to EOS, in that short segment instrumentation with MGCR in thoracic curve EOS patients is an effective technique in correction of both structural and compensatory curve, and in maintaining the correction during subsequent nonsurgical spinal distraction. 4.

0049 - Growing Rod Instrumentation in Early Onset Scoliosis

0049 - Growing Rod Instrumentation in Early Onset Scoliosis

P143 - Fifteen Years and 2530 Patients: The Evolution of Instrumentation, Surgical Strategies, and Outcomes in Adolescent Idiopathic Scoliosis in a Single Institution

P143 - Fifteen Years and 2530 Patients: The Evolution of Instrumentation, Surgical Strategies, and Outcomes in Adolescent Idiopathic Scoliosis in a Single Institution

Temporary occipital fixation in young children with severe cervical-thoracic spinal deformity

OBJECTIVE The long-term effects of instrumentation and fusion of the occipital-cervical-thoracic spine on spinal growth in young children are poorly understood. To mitigate the effects of this surgery on the growing pediatric spine, the authors report a novel technique used in 4 children with severe cervical-thoracic instability. These patients underwent instrumentation from the occiput to the upper thoracic region for stabilization, but without bone graft at the craniovertebral junction (CVJ). Subsequent surgery was then performed to remove the occipital instrumentation, thereby allowing further growth and increased motion across the CVJ. METHODS Three very young children (15, 30, and 30 months old) underwent occipital to thoracic posterior segmental instrumentation due to cervical or upper thoracic dislocation, progressive kyphosis, and myelopathy. The fourth child (10 years old) underwent similar instrumentation for progressive cervical-thoracic scoliosis. Bone graft was placed at and distal to C-2 only. After follow-up CT scans demonstrated posterior arthrodesis without unintended fusion from the occiput to C-2, 3 patients underwent removal of the occipital instrumentation. RESULTS Follow-up cervical spine flexion/extension radiographs demonstrated partial restoration of motion at the CVJ. One patient has not had the occipital instrumentation removed yet, because only 4 months have elapsed since her operation. CONCLUSIONS Temporary fixation to the occiput provides increased biomechanical stability for spinal stabilization in young children, without permanently eliminating motion and growth at the CVJ. This technique can be considered in children who require longer instrumentation constructs for temporary stabilization, but who only need fusion in more limited areas where spinal instability exists.

Radiological Outcome of Cotrel-Dubousset Instrumentation in Nineteen Patients with Adolescent Idiopathic Scoliosis

Objective: Adolescent idiopathic scoliosis is a progressive type of scoliosis that may lead to permanent deformity unless prevented and treated effectively. To present radiological outcome of patients with adolescent idiopathic scoliosis treated with the Cotrel-Dubousset (CD) instrumentation in our clinic. Methods: This was a prospective follow-up study of 19 patients (8 males, 11 females; mean age 18.5 years; age range 12-43 years) who underwent CD instrumentation for late onset idiopathic scoliosis. The CD instrumentation and posterior spinal fusion was performed using the standard technique through either anterior or posterior approach. On average, 13.52 vertebrae (range, 8-16) were included in the spinal fusion. The mean postoperative follow-up duration was 18 months (2-32 months). Results: Cobb angle on frontal plane was corrected 47.74%±21.73% at thoracic region and 34.52%±15.96% at lumbar region. On sagittal plane, the percentage of correction was 28.61%±20.91% on thoracic kyphosis angle and 38.96%±29.73% lumbar lordosis angle. In general, physiological sagittal contour of spine was obtained in 49.2% of patients after CD instrumentation. The most common postoperative complications were hook dislocation (n=8), bending and dislocation of screw (n=7), broken lamina and pedicule (n=5), and infection (n=3), all of which were effectively treated. Conclusio n: CD instrumentation effectively corrects the late onset idiopathic scoliosis if it is performed after a proper preoperative planning.

Are There 3D Changes in Spine and Rod Shape in the 2 Years After Adolescent Idiopathic Scoliosis Instrumentation?

Retrospective analysis of spine and rods 3D shape in the 2 years after adolescent idiopathic scoliosis (AIS) posterior surgical instrumentation. To evaluate spine and rod shape 3D changes in the 2 years after AIS instrumentation with different rod materials. Postoperative loss of correction has been reported with modern segmental instrumentation. The postoperative 3D rod shape changes of different rod materials and their implication in postoperative loss of correction have never been studied. A total of 42 Lenke 1 AIS cases who underwent surgery all with pedicle screws and 5.5 mm rods of three different materials were retrospectively reviewed (14 cases for each of the three rod material subgroups: titanium, cobalt-chromium, stainless steel). 3D reconstructions of the spine were performed using biplanar radiographs preoperatively, 1-week postoperatively (1WPO), and 2 years follow-up (2YFU). Rods 3D shape also was reconstructed at 1WPO and 2YFU. The spine and rods shapes were analyzed and compared between time points. An average of 1.93 implant per vertebra was used. The main thoracic curve (61° ± 9°) was corrected on average by 75% (15° ± 6°, P < 0.01) with no change at 2YFU (17° ± 7°, P = 0.14). The apical vertebral rotation (23° ± 7°) was corrected by 44% (13° ± 9°, P < 0.01) with no change at 2YFU (14° ± 9°, P = 0.64). The thoracic kyphosis (24° ± 12°) remained unchanged (P = 0.78). The orientation of the planes of maximal curvature with respect to the sagittal plane of the main thoracic curve (39° ± 15°) and of the rods (concave: 28° ± 23°, convex: 12° ± 10°) at 1WPO was unchanged at 2YFU (all P > 0.05). Rod curvature and deflection also remained unchanged (all P > 0.05). 3D curve correction was maintained in the 2YFU for all rod materials subgroups (all P > 0.05). The lumbar lordosis changed from 1WPO (47° ± 8°) to 2YFU (56° ± 9°, P < 0.01). At preoperatively, 57% of the cases had a balanced posture (sacral vertical axis/sacral femoral distance ≤0.5 and sacral vertical axis ≤0), 33% at 1WPO and 79% at 2YFU. There was no significant 3D shape change of the instrumented thoracic spine or of the rods postoperatively for any of the segmental pedicle screw constructs with titanium, stainless steel, and cobalt-chromium rods. Patients overall unbalanced sagittal posture documented immediately after surgery came back to balanced 2 years after surgery. 3.

Correction Capability in the 3 Anatomic Planes of Different Pedicle Screw Designs in Scoliosis Instrumentation.

Computer simulations to compare the correction capabilities of different pedicle screws in adolescent idiopathic scoliosis (AIS) instrumentations. To compare the correction and resulting bone-screw forces associated with different pedicle screws in scoliosis instrumentations. Pedicle screw fixation is widely used in surgical instrumentation for spinal deformity treatment. Screw design, correction philosophies, and surgical techniques are constantly evolving to achieve better control of the vertebrae and correction of the spinal deformity. Yet, there remains a lack of biomechanical studies that quantify the effects and advantages of different screw designs in terms of correction kinematics. The correction capabilities of fixed-angle, multiaxial, uniaxial, and saddle axial screws were kinematically analyzed, simulated, and compared. These simulations were based on the screw patterns and correction techniques proposed by 2 experienced surgeons for 2 AIS cases. Additional instrumentations were assessed to compare the correction and resulting bone-screw forces associated with each type of screw. The fixed-angle, uniaxial and saddle axial screws had similar kinematic behavior and performed better than multiaxial screws in the coronal and transverse planes (8% and 30% greater simulated corrections, respectively). Uniaxial and multiaxial screws were less effective than fixed-angle and saddle axial screws in transmitting compression/distraction to the anterior spine because of their sagittal plane mobility between the screw head and shank. Only the saddle axial screws allow vertebra angle in the sagittal plane to be independently adjusted. Pedicle screws of different designs performed differently for deformity corrections or for compensating screw placement variations in different anatomic planes. For a given AIS case, screw types should be determined based on the particular instrumentation objectives, the deformity's stiffness and characteristics so as to make the best of the screw designs.

Biomechanical effect of pedicle screw distribution in AIS instrumentation using a segmental translation technique: computer modeling and simulation

BackgroundEfforts to select the appropriate number of implants in adolescent idiopathic scoliosis (AIS) instrumentation are hampered by a lack of biomechanical studies. The objective was to biomechanically evaluate screw density at different regions in the curve for AIS correction to test the hypothesis that alternative screw patterns do not compromise anticipated correction in AIS when using a segmental translation technique.MethodsInstrumentation simulations were computationally performed for 10 AIS cases. We simulated simultaneous concave and convex segmental translation for a reference screw pattern (bilateral polyaxial pedicle screws with dorsal height adjustability at every level fused) and four alternative patterns; screws were dropped respectively on convex or concave side at alternate levels or at the periapical levels (21 to 25% fewer screws). Predicted deformity correction and screw forces were compared.ResultsFinal simulated Cobb angle differences with the alternative screw patterns varied between 1° to 5° (39 simulations) and 8° (1 simulation) compared to the reference maximal density screw pattern. Thoracic kyphosis and apical vertebral rotation were within 2° of the reference screw pattern. Screw forces were 76 ± 43 N, 96 ± 58 N, 90 ± 54 N, 82 ± 33 N, and 79 ± 42 N, respectively, for the reference screw pattern and screw dropouts at convex alternate levels, concave alternate levels, convex periapical levels, and concave periapical levels. Bone-screw forces for the alternative patterns were higher than the reference pattern (p < 0.0003). There was no statistical bone-screw force difference between convex and concave alternate dropouts and between convex and concave periapical dropouts (p > 0.28). Alternate dropout screw forces were higher than periapical dropouts (p < 0.05).ConclusionsUsing a simultaneous segmental translation technique, deformity correction can be achieved with 23% fewer screws than maximal density screw pattern, but resulted in 25% higher bone-screw forces. Screw dropouts could be either on the convex side or on the concave side at alternate levels or at periapical levels. Periapical screw dropouts may more likely result in lower bone-screw force increase than alternate level screw dropouts.