Dual Rod System Research Articles

Influence of posterior instrumented correction with pedicle screw dual rod systems on thoracic kyphosis in Lenke 1 and 2 curves: minimum 2years follow-up.

Adolescent idiopathic scoliosis (AIS) often correspond with hypo thoracic kyphosis (TK) or even lordosis. The aim of this study was to analyze the influence of posterior instrumentation in thoracic AIS. Analysis of prospectively collected AIS-data with structural thoracic curves (Lenke type 1 & 2), operated 2010-2019 with pedicle screw dual rod systems in one scoliosis center. Follow-up (FU) minimum 24months. Coronal and sagittal angles measured based on standing long-cassette-X-rays: thoracic major (MC), proximal thoracic (PC) and lumbar curve (LC), TK, lumbar lordosis (LL). values as mean ± SD, differences by student's t-test (significancy a = 0.05), Pearson's correlation, sub-analysis with sagittal modifier (-, N, +). A total of 127 AIS could be identified (63% type 1, 37% type 2). Mean FU 32.2 ± 16.6months, mean age 14 ± 1.5years. Mean Correction of MC 73 ± 12%, PC 51 ± 17%, LC 69 ± 21% with a significantly better correction of PC in Lenke 2 curves(p < 0.05). On average, TK (FU-preop) decreased by -2.1 ± 12.1°(p < 0.05) in all AIS. Whereas TK in type 1 was unchanged (p = 0.9), TK significantly decreased by - 6.0 ± 12.7°(p < 0.05) in type 2. No significant difference in LL. TK in hypokyphotic cases increased by 9.5 ± 5.5°(p < 0.05), stayed almost unchanged (- 1.4 ± 9.1°,p = 0.2) in normokyphotic, decreased by - 17.2 ± 14.2°(p < 0.05) in hyperkyphotic cases. Only hypokyphotic cases had a moderately strong correlation between correction of LC (r = 0.6) and PC (r = - 0.4) (frontal plane) and change from pre- to postoperative TK (sagittal plane) (r = 0.6). No relevant correlations for normo- and hyperkyphotic AIS. Postoperative hypokyphosis was significantly more often in Lenke 2 (16.3% vs. 2.6%, p < 0.05). Rod diameter (5,5mm versus 6mm) had no significant influence. Significant correction of hypo- and hyperkyphosis can be achieved with posterior spinal fusion (pedicle screw dual rod systems), whereas normokyphotic spines stay unchanged. However, Lenke 2 curves have a significantly higher risk for a postoperative thoracic hypokyphosis.

Increased risk of thoracic hypokyphosis after posterior spinal correction and fusion in adolescent idiopathic scoliosis with thoracic double curve

Adolescent idiopathic scoliosis (AIS) is often associated with thoracic hypokyphosis or even lordosis. To analyze the influence of posterior correction and fusion in thoracic, structurally double-curved AIS. Out of 127 thoracic AIS (Lenke types1 and2) recorded prospectively, idiopathic double thoracic curve AIS were analyzed retrospectively. Surgery 2010-2019 with pedicle screw double rod systems in ascoliosis center. Follow-up (FU) at least 2years. Frontal and sagittal angles (whole-spine radiographs, 2planes): thoracic curve (MK), proximal-thoracic curve (PK) and lumbar curve (LK), thoracic kyphosis (TK), lumbar lordosis (LL). values as MW ± SD, students t‑test (significance a = 0.05), Pearson's correlation, sub-analysis with sagittal modifiers (-, N, +). Atotal of 47AIS-double thoracic curve were identified, mean FU 29.3 ± 12.2months, mean age 14 ± 1.5years. The mean correction (FU-preop) of MK was 67%, PK 53%, LK 73%, each significant, (p < 0.05). On average, TK (FU-preop) decreased by -6.5 ± 11.6° (p < 0.05), no significant change from FU (p = 0.6). TK (FU-preop) increased by 8.6 ± 5.0° (p < 0.05) in hypokyphotic cases, significantly decreased by -4.8 ± 9.6° in normokyphotic AIS and -25.3 ± 11.1° in hyperkyphotic cases, respectively (p < 0.05). In hypokyphosis: moderately strong correlation between correction PK (r = -0.5) and spontaneous correction LK (r = 0.8) (frontal plane) and change from pre- to postop TK (sagittal plane) (p < 0.05). Moderate correlation for hyperkyphosis: correction PK (r = -0.5) and postop TK (p < 0.05). No relevant correlations for normokyphosis. 17% had postop hypokyphosis, of which 0% had preop hypokyphosis. Rod diameter (5.5 mm vs. 6 mm) had no significant effect on TC. Posterior instrumented correction and fusion (pedicle screw dual rod systems) can significantly correct both lateral curves in idiopathic double thoracic curves, although it is associated with an increased risk of postop thoracic hypokyphosis, especially in preoperatively normokyphotic patients.

Intraoperative radiation exposure to patients in idiopathic scoliosis surgery with freehand insertion technique of pedicle screws and comparison to navigation techniques.

In surgical correction of scoliosis with pedicle screw dual-rod systems, frequently used freehand technique of screw positioning is challenging due to 3D deformity. Screw malposition can be associated with serious complications. Image-guided technologies are already available to improve accuracy of screw positioning and decrease radiation to surgeon. This study was conducted to measure intraoperative radiation to patients in freehand technique, evaluate screw-related complications and compare radiation values to published studies using navigation techniques. Retrospective analysis of prospectively collected data of 73 patients with idiopathic scoliosis, who underwent surgical correction with pedicle screw dual-rod system. Evaluated parameters were age, effective radiation dose (ED), fluoroscopy time, number of fused segments, correction and complications. Parameters were compared with regarding single thoracic curve (SC) and double thoracic and lumbar curves (DC), adolescent (10-18years) or adult (> 18years) idiopathic scoliosis, length of instrumentation. ED was compared with values for navigation from online database. Average age was 21.0 ± 9.7years, ED was 0.17 ± 0.1mSv, time of fluoroscopy was 24.1 ± 18.6s, 9.5 ± 1.9 fused segments. Average correction for SC was 75.7%, for DC 69.9% (thoracic) and 76.2% (lumbar). No screw-related complications. ED was significantly lower for SC versus DC (p < 0.01), short versus long fusions (p < 0.01), no significant difference for age (p = 0.1). Published navigation data showed 6.5- to 8.8-times higher radiation exposure for patients compared to our results. Compared to navigation procedures, freehanded positioning of pedicle screws in experienced hands is a safe and effective method for surgical correction of idiopathic scoliosis with a significant decrease in radiation exposure to patients.

The dual rod system of amphibians supports colour discrimination at the absolute visual threshold.

The presence of two spectrally different kinds of rod photoreceptors in amphibians has been hypothesized to enable purely rod-based colour vision at very low light levels. The hypothesis has never been properly tested, so we performed three behavioural experiments at different light intensities with toads (Bufo) and frogs (Rana) to determine the thresholds for colour discrimination. The thresholds of toads were different in mate choice and prey-catching tasks, suggesting that the differential sensitivities of different spectral cone types as well as task-specific factors set limits for the use of colour in these behavioural contexts. In neither task was there any indication of rod-based colour discrimination. By contrast, frogs performing phototactic jumping were able to distinguish blue from green light down to the absolute visual threshold, where vision relies only on rod signals. The remarkable sensitivity of this mechanism comparing signals from the two spectrally different rod types approaches theoretical limits set by photon fluctuations and intrinsic noise. Together, the results indicate that different pathways are involved in processing colour cues depending on the ecological relevance of this information for each task.This article is part of the themed issue ‘Vision in dim light’.

Clinical utility of ultrasound to prospectively monitor distraction of magnetically controlled growing rods

Background ContextGrowing rods are commonly used for surgical treatment of skeletally immature patients with scoliosis, but require repeated surgeries for distractions and are fraught with complications. As an alternative, the use of magnetically controlled growing rods (MCGR) allows for more frequent non-invasive distractions to mimic normal growth. However, more plain radiographs are needed to monitor increased distraction frequency, thereby increasing ionizing radiation exposure to the developing child. The use of ultrasound, which emits no radiation, has been found in a cross-sectional study to be reliable in measuring MCGR distractions. PurposeThe study aims to address the prospective clinical utility of ultrasound compared with plain radiographs for assessing MCGR distractions. Study DesignThis is a prospective study. Patient SampleThe study includes patients with early-onset scoliosis undergoing distractions after MCGR implant. Outcome MeasuresThe distraction length on plain radiographs and ultrasound was measured. MethodsThis is a prospective study of patients treated with MCGR. Patients with both single- and dual-rod systems were included. Outpatient distractions were performed at monthly intervals, targeting 2 mm of distraction on each occasion. Assessment of distraction length was monitored by ultrasound at each visit; plain radiographs were taken every 6 months and were compared with ultrasound measurements. ResultsNine patients (5 female, 4 male), with a mean of 29 distractions (standard deviation [SD] ±14.3), were recruited. The mean distracted length per 6 months was 5.7 mm (SD ±3.6 mm) on plain radiographs and 5.2 mm (SD ±3.9 mm) on ultrasound for the concave rod, and 6.1 mm (SD ±3.6 mm) on plain radiographs and 5.9 mm (SD ±3.8 mm) on ultrasound for the convex rod. Excellent inter- and intra-rater reliabilities were observed for radiographic and ultrasound measurements. An excellent correlation was noted between the two imaging modalities (r=0.93; p<.0001). ConclusionsThis is the first prospective study to validate that ultrasound assessment of MCGR distraction lengths was highly comparable with that of plain radiographs. The present study has verified that ultrasound can be used to document length changes by distraction over time and that it had high clinical utility. Ultrasound can be a reliable alternative to plain radiographs, thereby avoiding radiation exposure and its potential detrimental sequelae in the developing child.

Range of motion after thoracolumbar corpectomy: evaluation of analogous constructs with a novel low-profile anterior dual-rod system and a traditional dual-rod system

An in vitro biomechanical study. To compare the biomechanical stability of traditional and low-profile thorocolumbar anterior instrumentation after a corpectomy with cross-connectors. Dual-rod anterior thoracolumbar lateral plates (ATLP) have been used clinically to stabilize the thorocolumbar spine. The stability of a low-profile dual-rod system (LP DRS) and a traditional dual-rod system (DRS) was compared using a calf spine model. Two groups of seven specimens were tested intact and then in the following order: (1) ATLP with two cross-connectors and spacer; (2) ATLP with one cross-connector and spacer; (3) ATLP with spacer. Data were normalized to intact (100%) and statistical analysis was used to determine between-group significances. Both constructs reduced motion compared to intact in flexion-extension and lateral bending. Axial rotation motion became unstable after the corpectomy and motion was greater than intact, even with two cross-connectors with both systems. Relative to their respective intact groups, LP DRS significantly reduced motion compared to analogous DRS in flexion-extension. The addition of cross-connectors reduced motion in all loading modes. The LP DRS provides 7.5mm of reduced height with similar biomechanical performance. The reduced height may be beneficiary by reduced irritation and impingement on adjacent structures.

Biomechanical Study Comparing a New Combined Rod-plate System With Conventional Dual-rod and Plate Systems

Most anterior spinal instrumentation systems are designed as either a plate or dual-rod system and have corresponding limitations. Dual-rod designs may offer greater adjustability; however, this system also maintains a high profile and lacks a locking design. Plate systems are designed to be stiffer, but the fixed configuration is not adaptable to the variety of vertebral body shapes. The authors designed a new combined rod-plate system (D-rod) to overcome these limitations and compared its biomechanical performance with the conventional dual-rod and plate system. Eighteen pig spinal specimens were divided into 3 groups (6 per group). An L1 corpectomy was performed and fixed with the D-rod (group A; n=6), Z-plate (Sofamor Danek, Memphis, Tennessee) (group B; n=6), or Ventrofix (Synthes, Paoli, Pennsylvania) (group C; n=6) system. T13-L2 range of motion was measured with a 6 degrees of freedom (ie, flexion-extension, lateral bending, and axial rotation) spine simulator under pure moments of 6.0 Nm. The D-rod and Ventrofix specimens were significantly stiffer than the Z-plate specimens (P<.05) based on results obtained from lateral bending and flexion-extension tests. The D-rod and Z-plate specimens were significantly stiffer than the Ventrofix specimens (P<.05) in axial rotation. The D-rod combines the advantages of the plate and dual-rod systems, where the anterior rod exhibits the design of a low-profile locking plate, enhanced stability, and decreased interference of the surrounding vasculature. The posterior rods function in compression and distraction, and the dual-rod system offers greater adjustability and control over screw placement. The results indicate that it may provide adequate stability for anterior thoracolumbar reconstruction.

Anterior surgery for adolescent idiopathic scoliosis

Anterior open scoliosis surgery using the dual rod system is a safe and rather effective procedure for the correction of scoliosis (50-60%). Thoracic hypokyphosis and rib hump correction with open anterior rather than posterior instrumentation appear to be the better approaches, although the latter is somewhat controversial with current posterior vertebral column derotation devices. In patients with Risser grade 0, hyperkyphosis and adding-on may occur with anterior thoracic spine instrumentation. Anterior thoracoscopic instrumentation provides a similar correction (65%) with good cosmetic outcomes, but it is associated with a rather high risk of instrumentation (pull-out, pseudoarthrosis) and pulmonary complications. Approximately 80% of patients with adolescent idiopathic scoliosis (AIS) curves of >70° have restrictive lung disease or smaller than normal lung volumes. AIS patients undergoing anterior thoracotomy or anteroposterior surgery will demonstrate a significant decrease in percentage of predicted lung volumes during follow-up. The thoracoabdominal approach and thoracoscopic approach without thoracoplasty do not produce similar changes in detrimental lung volume. In patients with severe AIS (>90°), posterior-only surgery with TPS provides similar radiographic correction of the deformity (44%) with better pulmonary function outcomes than anteroposterior surgery. Vascular spinal cord malfunction after segmental vessel ligation during anterior scoliosis surgery has been reported. Based on the current literature, the main indication for open anterior scoliosis instrumentation is Lenke 5C thoracolumbar or lumbar AIS curve with anterior instrumentation typically between T11 and L3.

Distraction Phenomenon After Lengthening of Spinal Growing Rods: A Case Report.

The treatment of early-onset scoliosis remains challenging, and growing-rod instrumentation has been shown to be an option for allowing trunk and lung development while partially straightening and controlling spine deformity1-4. Initial treatment with single rods had an unacceptable risk-benefit ratio3-6, and dual rods are currently preferred, achieving corrections from 30% to 64% at the time of the final spinal fusion3,7. Unfortunately, dual-rod systems retain complication rates ranging from 19% to 58%2,3,8,9 in instrumented patients. The most common complications include wound infections, skin breakdown, proximal and distal junctional kyphosis, and implant-related complications (e.g., rod breakage, implant prominence, and hook and/or screw pullout)8,10. Spontaneous fusion rates of 89% were also reported as a potential complication associated with submuscular rod placement and surgical procedures at early ages7,11, sometimes requiring osteotomies during the final posterior fusion7. To the best of our knowledge, there is no prior report of distraction phenomenon related to the growing-rod lengthening procedure. The patient’s parents were informed that data concerning the case would be submitted for publication, and they provided consent. A two-day-old girl was urgently transferred to our hospital because of a thoracic mass that grossly resembled arachnoid tissue. Radiographs showed a right thoracic curve measuring 15° from T1 to T10, a localized kyphosis of 57° from T5 to T7, and a global kyphosis of 18° from T2 to T12. Additional image investigation revealed a congenital malformation with butterfly vertebrae from T5 to T7 and a posterior vertebral defect with incomplete laminae extending from T3 to T6. Magnetic resonance imaging showed that the mass had grown out from the spinal cord. The patient underwent neurosurgery, and the final histologic characteristics …

Pulmonary function after anterior double thoracotomy approach versus posterior surgery with costectomies in idiopathic thoracic scoliosis

The surgical approach in the treatment of idiopathic thoracic scoliosis depends on the type of curve involved. In anterior correction, the rib hump is corrected by derotating the thoracic spine. In posterior scoliosis surgery, additional rib hump resection is sometimes necessary to achieve an optimal cosmetic result. The aim of this study was to compare pulmonary function in these two patient groups. Forty patients in the anterior group (A) were treated with standard double thoracotomy, with an anterior derotation spondylodesis and a primary stable dual-rod system. The posterior group (P) included 29 patients who were treated with a pedicle screw-based posterior instrumentation spondylodesis, with additional rib hump resection. Pulmonary function was evaluated preoperatively, on the 12th postoperative day, and at 3, 6, 12 and 24 months during the follow-up. The patients' mean age was 15 years in group A and 19 in group P with a standard deviation 8.7 years and a significant difference. With regard to body height or weight there were no significant differences between the two groups. In group A, the deterioration in pulmonary function immediately after the operation (from [Formula: see text] 75.3 %/71.3 % preoperatively to 38.5 %/36.1 % postoperatively) was clearer than in group P ([Formula: see text] 71.6 %/65.7 % preoperatively to 47.7 %/48.4 % postoperatively). During a follow-up period of 3 months, the values improved in both groups in comparison with the values immediately after the operation. Up to the 2 year follow-up, pulmonary function in the posterior and anterior groups corresponded to the preoperative values, with no significant differences. There was a trend toward moderately increased values in the posterior group and moderately decreased values in the anterior group at the 2-year follow-up examination, in comparison with the preoperative baseline, but without a statistically significant difference. Two major complications occurred in the anterior group, with reintubation and several bronchoscopy examinations due to atelectasis. The severe deterioration in group A is caused by the substantial trauma with double thoracotomy in contrast to rib hump resection. For patients with severe restrictive pulmonary distress, posterior instrumentation in combination with rib hump resection would be preferable to an anterior procedure involving double thoracotomy. Respiratory physiotherapy exercise should be administered in order to minimise postoperative pulmonary distress. In conclusion opening of the chest wall leads to deterioration of pulmonary function with improvement to the preoperative values after 6 months in the posterior and after 24 months in the anterior group.

Spontaneous lumbar curve correction in selective anterior instrumentation and fusion of idiopathic thoracic scoliosis of Lenke type C

Posterior pedicle screw instrumented correction and fusion have become the gold standard in the surgical treatment of thoracic scoliosis. However, in thoracic Lenke type C curves selective posterior fusion of the thoracic curve may lead to spinal imbalance. The aim of the study was to analyse the radiological results of selective anterior thoracic fusion using a standard open dual rod technique with special respect to spontaneous lumbar curve correction (SLCC). Twenty-eight patients (26 patients with Lenke 1C and 2 patients with Lenke 2C curves) with an average age of 15 years were surgically treated with an anterior dual rod system through a standard open double thoracotomy approach. Average clinical and radiological follow-up was 4 years (24-84 months). Fusion was carried out mostly from end-to-end vertebra. The primary curve was corrected from 61.6° (average correction on reverse bending films 42.9 %) to 27.1° (56.0 % correction) with an average loss of correction of 2.2°. The secondary lumbar curve measured 47.7° preoperatively (40-56°, average correction on reverse bending films 66.2 %) and corrected spontaneously to 30.1° (36 % SLCC) and remained stable without any cases of deterioration or decompensation during follow-up. Lumbar apical vertebral translation increased minimally by an average of 4 mm directly, postoperatively, and returned to an average of preoperative values during follow-up. All but two curves remained as type C lumbar modifier at follow-up. Preoperatively, three patients showed a marked coronal imbalance of more than 3 cm (all left, average 4.0 cm); at follow-up, two patients were still out of balance by more than 3 cm (all to the left, average 3.4 cm). Preoperatively, a marked shoulder imbalance of more than 1.0 cm was found in 11 patients; this was corrected in all patients to <1.0 cm at follow-up. The apical vertebral rotation measured according to Perdriolle was corrected from 23.5° to 15.0° in the thoracic spine (36.2 % correction) with an average clinical reduction of the rib hump of 63.2 %. In the lumbar spine, there was no relevant radiological derotation; however, clinically, the lumbar hump corrected spontaneously by 44.3 %. Thoracic kyphosis measured 28.5° preoperatively and 32.3° at follow-up. All six patients with a preoperative hypokyphosis (<20°) of an average of 9.5° were successfully corrected to an average thoracic kyphosis of 23.8° at follow-up. There were no cases of junctional thoracolumbar kyphosis. There were neither reoperations nor implant failures with pseudarthrosis. Selective anterior correction and fusion in primary thoracic curves with lumbar modifier type Lenke C resulted in a reliable and satisfactory SLCC. Advantages of anterior versus posterior techniques are the true segmental derotation with excellent rib hump correction and a superior restoration of thoracic kyphosis.

Short Segment Bone-On-Bone Instrumentation for Adolescent Idiopathic Scoliosis

Prospective case series. To evaluate the clinical and radiologic outcomes of short segment anterior scoliosis surgery with bone-on-bone apposition using a dual screw, dual rod system. Posterior segmental fixation for correction of AIS involves instrumentation of all the vertebrae included in the major curve. Our short segment anterior technique produces similar results by fusion of fewer levels. Forty-five patients operated between 1996 and 2004. Twenty-eight thoracic (Lenke 1) and 17 thoracolumbar (Lenke 5). The mean age was 19 years, 87% were females, and the mean follow-up was 72 months (range 28-121 months). We operated on curves less than 85° with "total discectomy," bone-on-bone apposition, and dual-screw, dual-rod fixation. A mean of five vertebrae (four discs) were instrumented, with a mean operative time of 360 minutes, blood loss of 877 mL and a hospital stay of 9.1 day. Lenke 1. The main preop thoracic curve was 52.5°, final postop curve 27.9°, by fusing five vertebrae, four discs. A spontaneous improvement of 47.5% of the lumbar compensatory curve was seen. The lower tilt angle corrected from 20.9° to 11°. Lenke 5. The preoperative thoracolumbar major curve corrected from 50.5° to 18.3° (final) with fusion of four vertebrae, three discs. A spontaneous improvement of 37.4% occurred in the thoracic compensatory curve. The preop tilt angle improved from 27.7° to 8.3°.The sagittal and coronal balance was restored in all the patients. There were no neurologic, vascular, pulmonary, or implant-related complications. Union occurred within 3 months. All the patients returned to an unrestricted lifestyle within 4 months. We report good results after surgical correction using our short segment bone-on-bone technique. Improvements were noted and maintained, over a 6-year period.

Approach-related lesions of the sympathetic chain in anterior correction and instrumentation of idiopathic scoliosis

During anterior scoliosis instrumentation with a dual-rod system, the vertebrae are dissected anterolaterally. After surgery, some patients report a change in temperature perception and perspiration in the lower extremities. Sympathetic lesions might be an explanation for this. The aim of this clinical study was to investigate sympathetic function after anterior scoliosis instrumentation. A total of 24 female patients with idiopathic scoliosis (mean age at follow-up, 23.8 years) who had undergone anterior instrumentation on average 6.6 years earlier were included. Due to the suspected relevance of the sympathetic L2 ganglion, two groups were created: a T12 group, in which instrumentation down to T12 was carried out (n = 12), and an L3 group, in which instrumentation down to L3 was done (n = 12). Sympathetic function was assessed by measuring skin temperature at the back of the foot, a plantar ninhydrin sweat test and sympathetic skin responses (SSRs) following electrical stimulation. The side on which the surgical approach was carried out was compared with the contralateral, control side. Health-related quality of life was investigated using the Scoliosis Research Society SRS-22 patient questionnaire. In the T12 group, mean temperatures of 29.6 degrees C on the side of the approach versus 29.5 degrees C on the control side were measured (P > 0.05); in the L3 group, the mean temperatures were 33.2 degrees C on the approach side versus 30.5 degrees C on the control side (P = 0.001). A significant difference between the T12 group and the L3 group (P < 0.001) was observed on the approach side, but not on the control side (P = 0.15). The ninhydrin sweat test showed reduced perspiration in 11 of 12 patients in the L3 group on the approach side in comparison with the control side (P = 0.002). In the T12 group, no significant differences were noted between the left and right feet. SSRs differed significantly between the two groups (P = 0.005). They were detected in all nine analyzable patients in the T12 group on both sides. In the L3 group, they were found on the approach side only in 4 of 11 analyzable patients versus 11 patients on the control side. The results of the SRS-22 questionnaire did not show any significant differences between the two groups. In conclusion, anterior scoliosis instrumentation with a dual-rod system including vertebrae down to L3 regularly leads to lesions in the sympathetic trunk. These are detectable with an increase in temperature, reduced perspiration and reduced SSRs. The caudal level of instrumentation (T12 vs. L3) has an impact on the extent of impairment, supporting the suspected importance of the L2 ganglion. The clinical outcome does not seem to be significantly limited by sympathetic trunk lesions.

Adolescent Idiopathic Scoliosis Treated With Open Instrumented Anterior Spinal Fusion

A multicenter prospective database was queried for patients who underwent open instrumented anterior spinal fusion (OASF) for treatment of primary thoracic (Lenke 1) adolescent idiopathic scoliosis (AIS). To present the intermediate radiographic and pulmonary function testing (PFT) data from patients who underwent OASF using modern, rigid instrumentation. Anterior spinal fusion is an excellent method to correct the 3-dimensional deformity produced by AIS. Modern instrumentation consisting of stronger metals, unthreaded rods, and dual rod systems should theoretically decrease the incidence of rod breakage, pseudarthrosis, and loss of correction seen in earlier OASF studies. The paucity of intermediate and long-term data prevents surgeons and patients from making an informed decision regarding the true incidence of these complications. Of 101 potential patients who underwent OASF with a minimum 5-year follow-up, 85 (85%) were studied. Standing radiographs were analyzed before surgery and at first standing erect, 2-year, and 5-year follow-up. PFT data were collected before surgery and at 5 years after surgery. Complete 5-year follow-up was obtained in 85 patients. Five years after surgery, the mean coronal correction was 26 degrees (51%; P < 0.05) and the thoracolumbar/lumbar curve improved 16 degrees (51%). There was a 9-degree (P < 0.001) increase in kyphosis, and there were 9 patients (11%) in whom the C7 plumb line translated >2 cm. There was a 6.7% decrease in predicted FEV1 over the 5-year period, from 75.5% +/- 13% before surgery to 68.8% +/- 2% at 5-year follow-up (P = 0.007); however, there was no significant change in FVC. There were 3 significant adverse events: 1 implant breakage requiring reoperation and 2 cases of progression of the main thoracic curve requiring reoperation. OASF is a reproducible and safe method to treat thoracic AIS. It provides good coronal and sagittal correction of the main thoracic and compensatory thoracolumbar/lumbar curves that is maintained with intermediate term follow-up. In skeletally immature children, this technique can cause an increase in kyphosis beyond normal values, and less correction of kyphosis should be considered during instrumentation. As with any procedure that employs a thoracotomy, pulmonary function is mildly decreased at final follow-up.

Shilla Growing Rods in a Caprine Animal Model: A Pilot Study

There are few good surgical options that allow for continued spinal growth in patients with early-onset scoliosis. The "Shilla" is a growth guidance system that does not require repeated surgical lengthenings. The Shilla system guides growth at the ends of dual rods with the apex of the curve corrected, fused, and fixed to the rods. The growth occurs through the extraperiosteally implanted pedicle screws that slide along the rods at either end of the construct. We implanted 11 2-month-old immature goats with the dual rod system and euthanized all 11 goats 6 months postoperatively. We evaluated plain radiographs, regular computed tomography, microcomputed tomography, physical and histologic examinations, and a microscopic wear analysis. All of the goat spines grew with the implants in place; growth occurred in both the thoracic and lumbar ends of the rods for a total average of 48 mm. None of the implants failed, although we observed minor wear at the rod/screw interface. Growth guidance with the Shilla rod system allowed for continued growth in this goat model.

Ventrale Skolioseoperationen

For more than 2 decades ventral derotation spondylodesis (Zielke VDS) as a major improvement over Dwyer instrumentation (DI) was the gold standard of instrumented curve correction and stabilization from the anterior approach. As the first available system it enables a true three-dimensional curve correction. A disadvantage is the low internal stabilization capability with a need for long-term external stabilization by means of cast and brace treatment postoperatively. Meanwhile with the development of modern single and dual solid rod systems these disadvantages can be avoided completely. Video-assisted (thoracoscopic) anterior scoliosis surgery accounts for less than 2% of anteriorly treated scoliosis cases, mainly due to a long operating time and significant learning curve.From the posterior approach the Cotrel-Dubousset instrumentation (CDI) as a polysegmentally attached posterior hook threaded dual rod system used to be state of the art for a long time, since it eliminated the disadvantages of Harrington instrumentation (HI) in terms of only one-dimensional correction and low stabilization capabilities. However even with CDI effective derotation was impossible. In posterior scoliosis surgery there is a strong trend away from hook systems towards transpedicular segmentally fixed dual rod systems not only in the lumbar spine but also in the thoracic area. Advantages of these newer techniques are shorter fusion, improved correction, and less loss of correction over time.Advantages of modern anterior instrumentation systems in comparison to posterior transpedicular instrumented dual rod systems are less blood loss, better derotation, slightly shorter fusion levels, and a better influence on sagittal plane control or improvement especially for hypokyphotic thoracic scoliosis cases. Our data also document a superior spontaneous correction of the lumbar curve after selective anterior instrumented correction (Lenke 1B+C), although other studies could not find significant differences. In our experience the neurological risk of anterior instrumented correction is also lower than that of posterior scoliosis surgery, although the morbidity and mortality data of the Scoliosis Research Society could not prove that anymore in recent years. A negative effect of anterior transthoracic scoliosis surgery in comparison to posterior surgery is a more negative effect on lung function, which improves slower after surgery and does not quite reach the levels of posterior surgery at follow-up. But new data on posterior segmental transpedicular correction and fusion also prove a lordosating effect with negative effect on lung function.

Stabilization and fusion of the cervicothoracic junction

Purpose of review A review of the biomechanical and clinical studies of instrumentation at the cervicothoracic junction is presented. A number of studies have presented conflicting recommendations on fixation for instability due to trauma, tumor, and decompression. Focus on the cervicothoracic junction as a challenging area is appropriate because anterior fixation is limited due to the sternum, posterior fixation must successfully avoid the vertebral artery and spinal cord, and fixation must be strong enough to withstand the force concentration resulting from the transition from flexible to rigid. Recent findings Prior studies have suggested that anterior‐posterior treatment is necessary for three-column destabilization at the cervicothoracic junction. Recent clinical and in-vitro biomechanical studies have shown that posterior-only treatment may be adequate in the absence of a total vertebrectomy. Notably, the combined use of C7 pedicle screwfixation, monoaxial screws in the thoracic spine, and a dual diameter rod system by posterior-only approach has now been shown to provide sufficient stability in cervicothoracic junction injuries. A review of relevant studies is presented. Summary

En-bloc spondylectomy and reconstruction for primary tumors and solitary metastasis of the spine

In primary tumors of the spine and, with limitations, solitary metastasis, the surgical approach should aim for curative treatment of the disease. Because the prognosis of malignant bone tumors is extremely limited, if an intralesional approach is performed, an extralesional en bloc resection is the treatment of choice. Therefore, it is mandatory to use an appropriate staging system. For the spine, the WBB staging system has been approved, which transfers the principles of the Enneking classification for treating primary malignant tumors of the limb to the spine. After en bloc spondylectomy, rigid and primary stable instrumented dorsoventral reconstruction must be performed - posteriorly with a dual-rod system using pedicle screws, and anteriorly in the ideal case by means of a vertebral body replacement cage. The possibility of extralesional (wide or marginal) resection of spinal tumors depends on tumor size and location. Extralesional resection and, if indicated, other neoadjuvant, adjuvant, or local therapeutic modalities have a strong positive influence on long-term survival rates. A good prognosis for primary tumors is associated with a good response to chemotherapy and extralesional resection. Solitary metastases have a much worse quod vitam prognosis. Therefore, local control of the disease in en bloc resections of solitary metastasis is a second relevant goal, although curative treatment is the primary aim.

The Use of Multiple Anchors for the Treatment of Idiopathic Scoliosis

Retrospective study. The purpose of this study was to determine the effectiveness of concave collar-button wires used as anchors to correct and maintain spinal alignment in adolescent idiopathic scoliosis (AIS). Correction of idiopathic scoliotic deformity has been reported with various systems. We have added concave collar-button wires to a multihook, dual-rod system as an adjunct to translation and stabilization of the spine during correction of AIS. Sixty-seven patients failing brace treatment or with curve patterns >45 degrees underwent spinal correction. Evaluation was obtained with preoperative standing posteroanterior, lateral, and recumbent right and left bending radiographs using the Cobb method. The initial postoperative films and latest radiographs were measured also. A dual-rod multihook construct with a derotation maneuver was used in all cases. Collar-button wire implants were placed from the convex side of the deformity toward the concave rod through the base of the spinous processes within the construct to achieve and augment correction and stability. Twenty-four patients underwent prior anterior release and fusion by video assisted thoracoscopic surgery. Sixty-seven patients in total underwent this procedure. We achieved a 72.2% mean correction of thoracic curves and 63.2% mean correction of lumbar curves. There was a mean loss of correction of 2 degrees in the thoracic area and 2.2 degrees in the lumbar area after 2 years. Sagittal curve was unchanged after surgery. All patients demonstrated a solid fusion with no evidence of pseudarthrosis or junctional deformities. There were no cases of clinically significant wire breakage or hook pullout. Three delayed infections were noted. The use of multiple concave collar-button wires as anchors is a safe, easy, and reliable method of spinal stabilization in the coronal and sagittal planes. There is minimal loss of correction at long-term follow-up.

NS10 ANTERIOR APPROACHES FOR THORACOLUMBAR FRACTURES

The anterior approach for surgery in thoracolumbar injuries allows decompression of anterior neural compression, reconstruction of the anterior and middle columns of the thoracolumbar spine, and osteototomy through the vertebral body if there is a need for late correction of deformity. In acute injuries the burst fracture with neurological injury is the ideal indication for anterior surgery and reconstruction. Because of the neural anatomy in the spinal canal at the throracolumbar junction, the injury can involve cord, conus, nerve root and peripheral nerve in either a pure or mixed lesion, with variable prognosis for recovery. The decompression optimises neurological recovery on the basis of animal models and clinical series of late decompression cases. In the last few years there has been a dramatic increase in the reconstruction options that have improved post surgical spinal stability and reduced morbidity from major bone grafting techniques. Anterior vertebral plates, dual rod and screw systems, titanium mesh cages, and now expanding cages facilitate reconstruction and improve stability, however this procedure remains technically demanding with significant morbidity for the patient.