Current status of adult spinal deformity.

Purpose To review the current literature for the nonoperative and operative treatment for adult spinal deformity. Recent Findings With more than 11 million baby boomers joining the population of over 60 years of age in the United States, the incidence of lumbar deformity is greatly increasing. Recent literature suggests that a lack of evidence exists to support the effectiveness of nonoperative treatment for adult scoliosis. In regards to operative treatment, current literature reports a varying range of improved clinical outcomes, curve correction, and complication rates. The extension of fusion to S1 compared with L5 and lower thoracic levels compared with L1 remains a highly controversial topic among literature. Summary Most adult deformity patients never seek nonoperative or operative treatment. Of the few that seek treatment, many can benefit from nonoperative treatment. However, in selected patients who have failed nonoperative treatment and who are candidates for surgical intervention, the literature reflects positive outcomes related to surgical intervention as compared with nonoperative treatment despite varying associated ranges in morbidity and mortality rates. If nonoperative therapy fails in addressing a patient's complaints, then an appropriate surgical procedure that relieves neural compression, corrects excessive sagittal or coronal imbalance, and results in a solidly fused, pain-free spine is warranted.

The fatigue life of contoured cobalt chrome posterior spinal fusion rods.

Intraoperative contouring of posterior rods in lumbar arthrodesis constructs introduces stress concentrations that can substantially reduce fatigue life. The sensitivity of titanium (Ti) and stainless steel (SS) to intraoperative contouring has been established in the literature; however, notch sensitivity has yet to be quantified for cobalt chrome (CoCr), which is now being advocated for use in posterior arthrodesis constructs. The goal of this study is to evaluate the sensitivity of CoCr rods to intraoperative contouring for posterior lumbar screwrod arthrodesis constructs. In this paper lumbar bilateral vertebrectomy models are constructed based on ASTM F1717-01 with curved rods (26-30 degrees total curvature) and poly-axial pedicle screws. Three types of constructs are assembled: first, 5.5 mm SS rods with SS screws (6.5 x 35 mm), second, 6.0 mm Ti rods with Ti screws (7.5 x 35 mm), and third, 6.0 mm CoCr rods with Ti screws (7.5 x 35 mm). All specimens are tested at 4 Hz in dynamic axial compression-bending with a load ratio of ten and maximum load levels of 250, 400, and 700 N until run-out at 2 000 000 cycles. Results are presented that show that the fatigue life of CoCr constructs tend to be greater than Ti constructs at all levels. At the 400 N maximum loading, CoCr lasts an average of 350 000 cycles longer than the Ti constructs. The CoCr constructs are able to sustain the 250 N load until run-out at 2 000 000 cycles but they fail at high load levels (maximum 700 N). The CoCr constructs fail at the neck of the Ti screw at high loads whereas Ti screws fail at the notch induced by contouring. Since CoCr is compatible with magnetic resonance imaging and has high static strength characteristics, the results of this study suggest that it may be an appropriate substitute for Ti.

An improved metric for quantifying the stiffnesses of intact human vertebrae.

Accurately quantifying the compressive stiffnesses of whole human vertebrae is important in the development of new treatment regimes for fractures due to osteoporosis or metastatic involvement. Two methods are commonly used to quantify compressive stiffnesses of whole vertebrae: first, the maximum slope of the force-deformation curve over a 0.2 per cent strain window; second, the slope of the best-fit line to the load-deflection curve over a specified loading range. Because the whole bone load-displacement response is non-linear, these two measurement systems yield different stiffness values for the same set of experimental data. Thus, the goal of this study was to develop and validate a standard method for deriving the whole bone stiffnesses of human vertebrae. Data from uniaxial compression tests on isolated human thoracic vertebrae (N=30 from 24 donors; T7-T10; age, 84 +/- 10, seven male, and 17 female) were analysed using the two aforementioned stiffness measurement techniques. A sensitivity analysis was also conducted whereby stiffness values were calculated for strain windows ranging from 0.05 per cent to 10 per cent. The results showed that the whole vertebra stiffness was sensitive to the calculation method. Using strain window approaches, the calculated stiffness was erratic at small strain ranges (less than 0.75 per cent), but it began to stabilize at 1 per cent strain. Comparing the historical measurement techniques versus the new standard, it was found that the 1 per cent and 0.2 per cent strain window techniques were well correlated (R2 = 0.91; p < 0.01); however, compared with the 1 per cent strain window method, the 0.2 per cent technique consistently overestimated stiffness and had five times the sensitivity to small changes in strain window magnitude. In conclusion, it is recommended that the 1 per cent strain window technique is adopted as a new standard for measuring the whole bone compressive stiffnesses of human vertebrae based on this method's superior level of accuracy and repeatability when compared with current techniques. The adoption of such a standard in the biomechanics field is important because it allows for inter-study comparisons of new orthopaedic treatments, such as vertebroplasty products.

Clinical outcome of trans-sacral interbody fusion after partial reduction for high-grade l5-s1 spondylolisthesis.

STUDY DESIGN: A clinical retrospective study was conducted. OBJECTIVE: To evaluate the clinical and radiographic outcome of reduction followed by trans-sacral interbody fusion for high-grade spondylolisthesis. SUMMARY OF BACKGROUND DATA: In situ posterior interbody fusion with fibula allograft has improved the fusion rates for patients with high-grade spondylolisthesis. The use of this technique in conjunction with partial reduction has not been reported. METHODS: Nine consecutive patients underwent treatment of high-grade (Grade 3 or 4) spondylolisthesis with partial reduction followed by posterior interbody fusion using cortical allograft. The average age at the time of surgery was 27 years (range, 8-51 years), and the average follow-up period was 43 months (range, 24-72 months). Before surgery, eight patients had low back pain, seven patients had radiating leg pain, and five patients had hamstring tightness. The average grade of spondylolisthesis by Meyerding grading was 3.9 (range, 3-5). Charts and radiographs were evaluated, and outcomes were collected by use of the modified SRS outcomes instrument. RESULTS: Radiographic indexes demonstrated significant improvement with partial reduction and fusion. The slip angle, as measured from the inferior endplate of L5, improved from 41.2 degrees (range, 24-82 degrees ) before surgery to 21 degrees (range, 5-40 degrees ) after surgery. All the patients were extremely or somewhat satisfied with surgery. The two patients who underwent this operation without initial instrumentation experienced fractures of their interbody grafts. Both of these patients underwent repair of the pseudarthrosis with placement of trans-sacral pedicle screw instrumentation and subsequent fusion. CONCLUSIONS: Partial reduction followed by posterior interbody fusion is an effective technique for the management of high-grade spondylolisthesis in pediatric and adult patient populations, as assessed by radiographic and clinical criteria. Pedicle screw instrumentation with the sacral screws capturing L5 is recommended when this technique is used for the treatment of high-grade spondylolisthesis. According to the clinical and radiographic results from this study, partial reduction and posterior fibula interbody fusion supplemented with pedicle screw instrumentation is an effective technique for select patients with high-grade spondylolisthesis at L5-S1.

Management of fixed sagittal plane deformity: results of the transpedicular wedge resection osteotomy.

STUDY DESIGN: Retrospective review of a consecutive clinical series. OBJECTIVES: To evaluate the efficacy of the transpedicular wedge resection osteotomy as a technique for correction of sagittal and coronal deformity and to assess the clinical value of the procedure as assessed by patient satisfaction. SUMMARY OF BACKGROUND DATA: The transpedicular wedge resection osteotomy is a well-established procedure for management of fixed sagittal deformity in ankylosing spondylitis. The utility of the procedure for applications in fixed deformity other than ankylosing spondylitis has not been demonstrated, and the efficacy of the procedure in the correction of coronal deformity has not been reported. METHODS: A total of 13 consecutive cases undergoing transpedicular wedge resection osteotomy for the management of sagittal deformity of any etiology were reviewed. Radiographic studies, complications, and satisfaction assessment using the modified Scoliosis Research Society instrument were the outcome parameters measured. RESULTS: Etiologies of deformity included postsurgical, ankylosing spondylitis, idiopathic, and infectious. Measurement of C7 sagittal plumb line to sacrum improved 63% at the most recent follow-up. Lumbar lordosis increased from -15.5 degrees to -45.4 degrees. Coronal balance was improved in all patients who had preoperative imbalance, with an average improvement of 60% maintained at follow-up. Patient satisfaction was high in all patients and not dependent on the etiology of deformity. CONCLUSIONS: The transpedicular wedge resection osteotomy is an effective procedure for the management of fixed sagittal deformity and is generalizable for multiple etiologies. Simultaneous correction of coronal deformity is possible. The clinical value of the procedure is demonstrated in high rates of patient satisfaction.

Does transverse apex coincide with coronal apex levels (regional or global) in adolescent idiopathic scoliosis?

STUDY DESIGN: Cross-sectional. OBJECTIVES: To identify the regional and global apexes of curves in adolescent idiopathic scoliosis and to compare the levels of those with the most rotated vertebral levels on computed tomography scans. SUMMARY OF BACKGROUND DATA: The terminology regarding the terms and definitions had been arbitrary until being refined and standardized by the Scoliosis Research Society Working Group on Three-Dimensional Terminology of Spinal Deformity. Apical vertebra or disc is defined as the most laterally deviated vertebra or disc in a scoliosis curve, but the most rotated vertebra (or disc) has not been included in this terminology. One study suggested that the most rotated vertebral level was always located at the apex. METHODS: Thirty-three structural curves of 25 consecutive patients scheduled for surgery for thoracic or thoracolumbar scoliosis were analyzed with standing anteroposterior radiographs and computed tomography scans covering the curve apexes and pelvis. Thoracic and lumbar curves were evaluated separately for all Type II curves. Vertebral rotations were normalized by the rotation of the pelvis. The most rotated vertebral (or disc) levels (transverse apex) were compared with the regional and global apex levels (vertebra or disc) (coronal apexes) of the corresponding curves separately. RESULTS: Regional and global apexes were at the same level in 18 (54.5%) curves, and within half a level in another 15 (45.4%), and the regional apex was one level higher in two curves (95% confidence levels: -0.82, +0.88). Comparison of the most rotated levels with regional and global apex levels revealed a higher variability, extending up to two levels for the global apex (95% confidence levels: -1.19, +1.54 levels for the global and -1.0, +1.41 levels for the regional apexes). CONCLUSION: This study demonstrated that the regional or global apex of a given curve is the most rotated level in only a minority of the curves. The most rotated level may be as far as two levels from the global apex and one level from the regional apex.

Excision of hemivertebrae in the management of congenital scoliosis involving the thoracic and thoracolumbar spine.

We present a study of ten consecutive patients who underwent excision of thoracic or thoracolumbar hemivertebrae for either angular deformity in the coronal plane, or both coronal and sagittal deformity. Vertebral excision was carried out anteriorly alone in two patients. Seven patients had undergone previous posterior spinal fusion. Their mean age at surgery was 13.4 years (6 to 19). The mean follow-up was 78.5 months (20 to 180). The results were evaluated by radiological review of the preoperative, postoperative and most recent follow-up films. The mean preoperative coronal curve was 78.2 degrees (30 to 115) and was corrected to 33.9 degrees (7 to 58) postoperatively, a mean correction of 59%. Preoperative coronal decompensation of 35 mm was improved to 11 mm postoperatively. Seven patients had significant coronal decompensation preoperatively, which was corrected to a physiological range postoperatively. There were no major complications and no neurological damage. We have shown that resection of thoracic and thoracolumbar hemivertebrae can be performed safely, without undue risk of neurological compromise, in experienced hands.

Measurement of vertebral rotation in standing versus supine position in adolescent idiopathic scoliosis.

Thirty-three structural curves of 25 patients with adolescent idiopathic scoliosis were evaluated using computed tomography (CT) scans and plain radiography. The average Cobb angle on standing radiographs was 55.72 degrees and was observed to be corrected spontaneously to 39.42 degrees while the patients were in supine position (29.78% correction). Average apical rotation according to Perdriolle was 22.75 degrees on standing radiographs and 16.78 degrees on supine scanograms. The average rotation according to Aaro and Dahlborn on CT scans was 16.48 degrees. Radiographic measurements were significantly different from axial CT slice or scanogram measurements (p = 0.000), but the two latter measurements, both obtained in the supine position, did not appear to be different (p = 0.495). Deformities on the transverse plane as well as on the coronal plane are influenced by patient positioning. If the patient lies supine, the scoliosis curve corrects spontaneously to some degree on both planes. Measurements obtained from the scanograms by the Perdriolle method in the supine position are very similar to those obtained by CT. Perdriolle's is a simple, convenient, and reliable method to measure rotation on standing radiograms.