Study Design. A retrospective matched cohort study. Objective. To comprehensively compare the 2-year postoperative results of posterior correction and fusion with segmental pedicie screw instrumentation versus those with hook constructs in adolescent idiopathic scoliosis (AIS) treated at a singie institution. Summary of Background Data, Despite the reports of satiefactory correction and maintenance of Scoliotic curves by pedicle screw instrumentation compared to hook constructs, few reports on the comprehensive comparison of segmental pedicle screw instrumentation versus hook instrumentation exist Materials and Methods. A total of 52 patients with AIS at a single institution who underwent a posterior spinal fusion with segmental pedicie screw (26) or hook (26) instrumentation were sorted and matched accoridng to four criteria similar age at surgery (14.8 years in pedicie screw group and 14.2 years in hook group), identical Lenke curve types, same number of fused vertebres (11.7 in each group), and identical operative methods (18 posterior spinal fusions with thoracoplasty, 4 posterior spinal fusions with iliac crest bone graft, and 4 anterior and posterior spinal fusions in each group). Petients were eveluated before surgery, immediate after surgery, and at the 2-year follow-up according to radiographic changes in curve correction, pulmonary function tests, operative time, intraoperative blood loss, implant costs, and SRS-24 scores. Results. After surgery, the average major curve correction was 76% in the scraw group and 60% in the hook group (P < 0.001). At the 2-year follow-up, loss of the mejar curve correction was less in the screw group (6.4%) compared with the hook group (8.0%) (P = 0.35), Postoparative globel coronal and sagittal balance was similar in both groups. An everage of 0.8 leveis from the distal end vertebre was saved using pedicie screws compared with hook constructs (P = 0.002). Postoperative 2-year proximal junctional change in the sagittal plane (angie between uppermost instrumented vertebra and two verte bral bodies above the uppermost-instrumented vertebra) was 9° in the screw group and 6° in the hook group (P = 0.19). Postoparative 2-year distal junctional change in the sagittal plane was similar in both groups. Operative time averaged 341 minutes in the screw group and 338 minutes in the hook group (P = 0.86), and intraoperative blood loss was similar in both groups (879 mL in screw group vs. 896 mL in hook group) (P = 0.12). Average implant cost in the hook group (11.8 fixation points, 5,818 U.S. dollars) was significantly lower than that of the screw group (17.1 fixation points; 11,508 U.S. dollars) (P < 0.001). Two years following surgery, the screw group demonstrated improved percent predicted pulmonary function values compared with that of the hook group (FVC. 80%→ 79% in screw group vs. 92%→ 74% in trock group, P = 0.0068; FEV-1, 73%→ 76% in screw group vs. 80%→ 79% in hook group, P = 0.017). Postoperative 2-year SRS-24 scores ware similar in both groups iscrew group [97] vs. hook group (101)(P = 0.15). There were no neurologic or visceral complications related to hook or pedicle screw instrumentation. Conclusion. Pedicle screw instrumentation, although more expensive, offers a significantly battey major and minor curve correction without neurologic problems and improved pulmonary function values in the operative treatment of AIS and enabias a slightly sharter fusion length then segmental hook intrumentation.

Comparative Analysis of Pedicle Screw Versus Hook Instrumentation in Posterior Spinal Fusion of Adolescent Idiopathic Scoliosis

Two hundred and nineteen patients with untreated adolescent idiopathic scoliosis who were seen at the University of Iowa between 1932 and 1948 were studied, and recent information was available on 194 of the patients. The mortality rate was 15 per cent. Backache was somewhat more common in these pa- tients than in the general population, although it was never disabling. The backache was unrelated to the presence of osteoarthritic changes on roentgenograms. Many curves continued to progress slightly in adult life, particularly thoracic curves that had reached be- tween 50 and 80 degrees at skeletal maturity. The lum- bar components of combined curves between 50 and 74 degrees also tended to progress. Pulmonary function was affected only in patients with thoracic curves.

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Long-term follow-up and prognosis in untreated patients*

Study design Retrospective radiographic review. Objectives To analyze how the Lenke classification of adolescent idiopathic scoliosis provides a template of specific curve patterns that may be appropriate to perform selective fusion of the spine. Methods A new triad classification system of adolescent idiopathic scoliosis has been developed. It consists of a curve type, a lumbar spine modifier (A, B, C), and a sagittal thoracic modifier (-, N, +). A selective fusion is termed when both the thoracic and thoracolumbar/lumbar curves deviate completely from the midline, but only the major curve (largest Cobb measurement) is fused, leaving the minor curve unfused and mobile. In this manner, selective thoracic fusions of the spine are potentially indicated for major main thoracic/minor lumbar curves (Types 1C and potentially 2C and 3C patterns) when the lumbar apex deviates off the center sacral vertical line. Conversely, selective thoracolumbar/lumbar fusions may be indicated for major thoracolumbar/lumbar-minor main thoracic curves, when the thoracic apex lies off the C7 plumbline (Type 5C and potentially 6C patterns). Importantly, additional analysis of ratios of structural characteristics between the main thoracic and thoracolumbar/lumbar curves are necessary to predict when a successful selective main thoracic or thoracolumbar/lumbar fusion will be feasible. Lastly, the clinical appearance of the patient's truncal alignment is essential to confirm the aspirations of performing a selective spinal fusion. Results Successful selective thoracic fusion of 1C (n = 36) and 2C (n = 8) curves have been performed in 44 consecutive patients with adolescent idiopathic scoliosis. The average thoracic curve was 61 degrees before surgery and 39 degrees at final follow-up. The average preoperative lumbar curve was 48 degrees, decreasing to 32 degrees postoperatively. A group of 21 consecutive patients with Type 5C or 6C major thoracolumbar/lumbar-minor main thoracic curves underwent a selective thoracolumbar/lumbar fusion. The average preoperative thoracolumbar/lumbar curve was 56 degrees corrected to 22 degrees at the 2-year follow-up. The average minor main thoracic curve preoperative was 38 degrees, with spontaneous correction to 28 degrees at 2 years postoperative. Discussion Selective thoracic or thoracolumbar/lumbar fusion can be successfully performed in a variety of adolescent idiopathic scoliosis curve patterns. Careful attention to the preoperative Lenke curve classification, analysis of structural characteristics between the planned instrumented and noninstrumented regions of the spine, as well as a documented clinical examination that confirms the planned instrumented and fused regions of the spine to be the most clinically prominent are essential features to determine before surgery. No patients undergoing selective thoracic fusion have required extension of the fusion to the lumbar spine, whereas one patient with a selective thoracolumbar fusion required extension of the fusion up to include the thoracic spine due to continued thoracic progression with growth. Conclusions Selective thoracic or thoracolumbar/lumbar fusions of the major curve can be successfully performed even when the minor curve completely deviates from the midline, based on the Lenke classification system, the analysis of structural criteria between the planned fused and unfused regions of the spine, and the clinical examination of the patient. Selective fusions, when successfully performed, will optimize mobile segments of the spine in patients with adolescent idiopathic scoliosis.

The Lenke classification of adolescent idiopathic scoliosis: how it organizes curve patterns as a template to perform selective fusions of the spine.

Posterior correction and fusion with segmental hook instrumentation represent the gold standard in the surgical treatment of progressive idiopathic thoracic scoliosis. However, there is a debate over whether pedicle screws are safe in scoliosis surgery and whether their usage might enable a better curve correction and a shorter fusion length. The details of curve correction, fusion length and complication rate of 99 patients with idiopathic thoracic scoliosis treated with either hook or pedicle screw instrumentation were analyzed. Forty-nine patients had been operated with the Cotrel-Dubousset system using hooks exclusively ("hook group"). Fifty patients had been operated with either a combination of pedicle screws in the lumbar and lower thoracic and hooks in the upper thoracic spine or exclusive pedicle screw instrumentation using the Munster Posterior Double Rod System ("screw group"). The preoperative Cobb angle averaged 61.3° (range 40°–84°) in the hook group and 62.5° (range 43°–94°) in the screw group. Average primary curve correction was 51.7% in the hook group and 55.8% in the screw group (P>0.05). However, at follow-up (2–12 years later) primary curve correction was significantly greater (P=0.001) in the screw group (at 50.1%) compared to the hook group (at 41.1%). Secondary lumbar curve correction was significantly greater (P=0.04) in the screw group (54.9%) compared to the hook group (46.9%). Correction of the apical vertebral rotation according to Perdriolle was minimal in both groups. Apical vertebral translation was corrected by 42.0% in the hook group and 55.6% in the screw group (P=0.008). Correction of the tilt of the lowest instrumented vertebra averaged 48.1% in the hook group and 66.2% in the screw group (P=0.0004). There were no differences concerning correction of the sagittal plane deformity between the two groups. Fusion length was, on average, 0.6 segments shorter in the screw group compared to the hook group (P=0.03). With pedicle screws, the lowest instrumented vertebra was usually one below the lower end vertebra, whereas in the hook group it was between one and two vertebrae below the lower end vertebra. Both operative time and intraoperative blood loss were significantly higher in the hook group (P<0.0001). One pedicle screw at T5 was exchanged due to the direct proximity to the aorta. There were no neurologic complications related to pedicle screw instrumentation. Pedicle screw instrumentation alone or in combination with proximal hook instrumentation offers a significantly better primary and secondary curve correction in idiopathic thoracic scoliosis and enables a significantly shorter fusion length.

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Comparative analysis of pedicle screw and hook instrumentation in posterior correction and fusion of idiopathic thoracic scoliosis.

Spinal fusion surgery is currently recommended when curve magnitude exceeds 40–45 degrees. Early attempts at spinal fusion surgery which were aimed to leave the patients with a mild residual deformity, failed to meet such expectations. These aims have since been revised to the more modest goals of preventing progression, restoring 'acceptability' of the clinical deformity and reducing curvature. In view of the fact that there is no evidence that health related signs and symptoms of scoliosis can be altered by spinal fusion in the long-term, a clear medical indication for this treatment cannot be derived. Knowledge concerning the rate of complications of scoliosis surgery may enable us to establish a cost/benefit relation of this intervention and to improve the standard of the information and advice given to patients. It is also hoped that this study will help to answer questions in relation to the limiting choice between the risks of surgery and the "wait and see – observation only until surgery might be recommended", strategy widely used. The purpose of this review is to present the actual data available on the rate of complications in scoliosis surgery. Search strategy for identification of studies; Pub Med and the SOSORT scoliosis library, limited to English language and bibliographies of all reviewed articles. The search strategy included the terms; 'scoliosis'; 'rate of complications'; 'spine surgery'; 'scoliosis surgery'; 'spondylodesis'; 'spinal instrumentation' and 'spine fusion'. The electronic search carried out on the 1st February 2008 with the key words "scoliosis", "surgery", "complications" revealed 2590 titles, which not necessarily attributed to our quest for the term "rate of complications". 287 titles were found when the term "rate of complications" was used as a key word. Rates of complication varied between 0 and 89% depending on the aetiology of the entity investigated. Long-term rates of complications have not yet been reported upon. Scoliosis surgery has a varying but high rate of complications. A medical indication for this treatment cannot be established in view of the lack of evidence. The rate of complications may even be higher than reported. Long-term risks of scoliosis surgery have not yet been reported upon in research. Mandatory reporting for all spinal implants in a standardized way using a spreadsheet list of all recognised complications to reveal a 2-year, 5-year, 10-year and 20-year rate of complications should be established. Trials with untreated control groups in the field of scoliosis raise ethical issues, as the control group could be exposed to the risks of undergoing such surgery.

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Howard H. Ginsburg

Papers

Back Pain in Postoperative Idiopathic Scoliosis: Long-Term Follow-Up Study (Abstract)