Analysis of an unexplored group of sagittal deformity patients: low pelvic tilt despite positive sagittal malalignment.

PURPOSE: In adult spinal deformity (ASD), patients increase pelvic tilt (PT) to maintain standing alignment. Previously, ASD patients with low PT and high disability were described. This study investigates this unusual population in terms of demographic, radiographic, and clinical features after three-column osteotomy (3CO). METHODS: In this multicenter retrospective study, ASD patients underwent single lumbar 3CO. Since PT is proportional to pelvic incidence (PI), the low PT group (LowPT) was defined as having a baseline (BL) PT/PI <25th percentile. HRQOL and full spine x-rays were analyzed at BL and 1 year. LowPT patients were compared to those with high PT/PI (HighPT) in a matched range of T1 pelvic angle. RESULTS: LowPT group had PT/PI <0.4 (n = 31). High disability was reported at baseline for both groups with significant improvement postoperatively, but without difference between groups. LowPT had significantly smaller lack lumbar lordosis but larger SVA, T1 spinopelvic inclination. Postoperatively, there were improvements in all sagittal modifiers except PT in LowPT. 33 % of LowPT had an increase in PT (>5°) postoperatively. This subset had more deformity at baseline, achieving good T1SPi postoperative correction but without achieving the SRS-Schwab target SVA at 1 year. CONCLUSION: LowPT group had high levels of disability. After 3CO surgery, low PT patients experience only partial improvements in sagittal vertical axis (SVA) and 33 % of the group increased their PT. Further work is necessary to determine optimal realignment approaches for this unusual set of patients. It is unclear if neuromuscular pathology plays a role in the setting of high SVA without pelvic retroversion.

Spondylolysis outcomes in adolescents after direct screw repair of the pars interarticularis.

OBJECT: Isthmic spondylolysis can significantly decrease functional abilities, especially in adolescent athletes. Although treatment can range from observation to surgery, direct screw placement through the fractured pars, or Buck's procedure, may be a more minimally invasive procedure than the more common pedicle screw-hook construct. METHODS: Review of surgical databases identified 16 consecutive patients treated with Buck's procedure from 2004 to 2010. Twelve patients were treated at Miami Children's Hospital and 4 at Barrow Neurological Institute. Demographics and clinical and radiographic outcomes were recorded and analyzed retrospectively. RESULTS: The 16 patients had a median age of 16 years, and 14 were 20 years or younger at the time of treatment. Symptoms included axial back pain in 100% of patients with concomitant radiculopathy in 38%. Pars defects were bilateral in 81% and unilateral in 19% for a total of 29 pars defects treated using Buck's procedure. Autograft or allograft augmented with recombinant human bone morphogenetic protein as well as postoperative bracing was used in all cases. Postoperatively, symptoms resolved completely or partially in 15 patients (94%). Of 29 pars defects, healing was observed in 26 (89.6%) prior to 1 revision surgery, and an overall fusion rate of 97% was observed at last radiological follow-up. There were no implant failures. All 8 athletes in this group had returned to play at last follow-up. CONCLUSIONS: Direct screw repair of the pars interarticularis defect as described in this series may provide a more minimally invasive treatment of adolescent patients with satisfactory clinical and radiological outcomes, including return to play of adolescent athletes.

Analysis of the direct cost of surgery for four diagnostic categories of adult spinal deformity.

BACKGROUND CONTEXT: Existing literature on adult spinal deformity (ASD) offers little guidance regarding an evidence-based approach to care. To optimize the value of medical treatment, a thorough understanding of the cost of surgical treatment for ASD is required. PURPOSE: To evaluate four clinically and radiographically distinct groups of ASD and identify and compare the cost of surgical treatment among the groups. STUDY DESIGN/SETTING: Multicenter retrospective study of consecutive surgeries for ASD. PATIENT SAMPLE: Three hundred twenty-five consecutive ASD patients treated between 2008 and 2010. OUTCOME MEASURES: Cost data were collected from hospital administrative records on the direct costs (DCs) incurred for the episode of surgical care, excluding overhead. METHODS: Based on preoperative radiographs and history, patients were categorized into one of four diagnostic categories of deformity: primary idiopathic scoliosis (PIS), primary degenerative scoliosis (PDS), primary sagittal plane deformity (PSPD), and revision (R). Analysis of variance and generalized linear model regressions were used to analyze the DCs of surgery and to assess differences in costs across the four diagnostic categories considered. RESULTS: Significant differences were observed in DC of surgery for different categories of ASD, with surgical treatment for PDS the most expensive followed in decreasing order by PSPD, PIS, and R (p<.01). Results further revealed a significant positive relationship between age and DC (p<.01) and a significant positive relationship between length of stay and DC (p<.01). Among PIS patients, for every incremental increase in levels fused, the expected DC increased by $3,997 (p=.00). Fusion to pelvis also significantly increased the DC of surgery for patients aged 18 to 29 years (p<.01) and 30 to 59 years (p<.01) but not for 60 years or more (p=.86). CONCLUSIONS: There is an increasing DC of surgery with increasing age, length of hospital stay, length of fusion, and fusions to the pelvis. Revision surgery is the least expensive surgery on average and should therefore not preclude its consideration from a pure cost perspective.

Reoperation rates and impact on outcome in a large, prospective, multicenter, adult spinal deformity database: clinical article.

OBJECT: Complications and reoperation for surgery to correct adult spinal deformity are not infrequent, and many studies have analyzed the rates and factors that influence the likelihood of reoperation. However, there is a need for more comprehensive analyses of reoperation in adult spinal deformity surgery from a global standpoint, particularly focusing on the 1st year following operation and considering radiographic parameters and the effects of reoperation on health-related quality of life (HRQOL). This study attempts to determine the prevalence of reoperation following surgery for adult spinal deformity, assess the indications for these reoperations, evaluate for a relation between specific radiographic parameters and the need for reoperation, and determine the potential impact of reoperation on HRQOL measures. METHODS: A retrospective review was conducted of a prospective, multicenter, adult spinal deformity database collected through the International Spine Study Group. Data collected included age, body mass index, sex, date of surgery, information regarding complications, reoperation dates, length of stay, and operation time. The radiographic parameters assessed were total number of levels instrumented, total number of interbody fusions, C-7 sagittal vertical axis, uppermost instrumented vertebra (UIV) location, and presence of 3-column osteotomies. The HRQOL assessment included Oswestry Disability Index (ODI), 36-Item Short Form Health Survey physical component and mental component summary, and SRS-22 scores. Smoking history, Charlson Comorbidity Index scores, and American Society of Anesthesiologists Physical Status classification grades were also collected and assessed for correlation with risk of early reoperation. Various statistical tests were performed for evaluation of specific factors listed above, and the level of significance was set at p < 0.05. RESULTS: Fifty-nine (17%) of a total of 352 patients required reoperation. Forty-four (12.5%) of the reoperations occurred within 1 year after the initial surgery, including 17 reoperations (5%) within 30 days. Two hundred sixty-eight patients had a minimum of 1 year of follow-up. Fifty-three (20%) of these patients had a 3-column osteotomy, and 10 (19%) of these 53 required reoperation within 1 year of the initial procedure. However, 3-column osteotomy was not predictive of reoperation within 1 year, p = 0.5476). There were no significant differences between groups with regard to the distribution of UIV, and UIV did not have a significant effect on reoperation rates. Patients needing reoperation within 1 year had worse ODI and SRS-22 scores measured at 1-year follow-up than patients not requiring operation. CONCLUSIONS: Analysis of data from a large multicenter adult spinal deformity database shows an overall 17% reoperation rate, with a 19% reoperation rate for patients treated with 3-column osteotomy and a 16% reoperation rate for patients not treated with 3-column osteotomy. The most common indications for reoperation included instrumentation complications and radiographic failure. Reoperation significantly affected HRQOL outcomes at 1-year follow-up. The need for reoperation may be minimized by carefully considering spinal alignment, termination of fixation, and type of surgical procedure (presence of osteotomy). Precautions should be taken to avoid malposition or instrumentation (rod) failure.

Adolescent idiopathic scoliosis treated with open instrumented anterior spinal fusion: five-year follow-up.

STUDY DESIGN: 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). OBJECTIVES: To present the intermediate radiographic and pulmonary function testing (PFT) data from patients who underwent OASF using modern, rigid instrumentation. SUMMARY OF BACKGROUND DATA: 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. METHODS: 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. RESULTS: 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. CONCLUSION: 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.

Radiographic classification of complications of instrumentation in adolescent idiopathic scoliosis.

UNLABELLED: In spinal deformity surgery, techniques and implants must be assessed for their safety and efficacy. Regulatory bodies, third-party payors, and patients will increasingly scrutinize treatment methods based on the frequency of adverse events. We therefore developed a classification of adverse hardware-related events using plain radiographic criteria. We analyzed the adverse events in 466 patients surgically treated for adolescent idiopathic scoliosis for a Type 1 (Lenke et al.) curve. We used plain radiographic films to define complications as either serious radiographic adverse events or radiographic adverse events in four technique groups: posterior spinal fusion with hooks and/or hybrid systems, posterior spinal fusion using mostly pedicle screws, open anterior spinal fusion, and thoracoscopic anterior spinal fusion. We defined serious radiographic adverse events as those requiring subsequent surgery. The minimum followup was 2 years. We found a reoperation rate ranging from 4.5% (open anterior spinal fusion) to 8.8% (posterior spinal fusion with hooks); we found no difference in the incidence of serious radiographic adverse events between surgical techniques. Among serious radiographic adverse events, the most common problems were revision for lumbar progression, rod breakage, and proximal screw pullout in the anterior spinal fusions and instrumentation removal for pain and infection in the posterior spinal fusions. We propose a new radiographic system of adverse hardware-related events for patients with Type 1 adolescent idiopathic scoliosis. LEVEL OF EVIDENCE: Level III, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.

Restoration of thoracic kyphosis after operative treatment of adolescent idiopathic scoliosis: a multicenter comparison of three surgical approaches.

STUDY DESIGN: Multicenter analysis of 3 groups of patients who underwent surgical treatment for adolescent idiopathic scoliosis (AIS). OBJECTIVE.: To evaluate 3 surgical approaches to determine the modality that has the greatest influence on improving thoracic kyphosis. SUMMARY OF BACKGROUND DATA: AIS is characterized by thoracic hypokyphosis which may be restored to normal to varying degrees with surgery. METHODS: A multicenter retrospective AIS surgical database was reviewed. Patients with only a structural main thoracic curve (Lenke 1, 2, or 3), and instrumentation of only the main thoracic curve were included. Lateral radiographs were analyzed to determine sagittal plane measurements before surgery, after surgery at 6 to 8 weeks, 1 year, and 2 years. The 3 groups were compared and statistical significance was defined as P < 0.05. RESULTS: Three groups were analyzed: (1) ASF group (n = 135), Anterior spinal fusion and instrumentation, (2) PSF-Hybrid group (n = 86), PSF with proximal hooks, +/- apical wires and distal pedicle screws, and 3) PSF-Hooks group (n = 132), PSF with only hooks. All groups had similar preoperative coronal main thoracic curve magnitudes (ASF: 50.6 degrees , PSF-Hybrid: 49.1 degrees , PSF-Hooks: 52.0 degrees ) and thoracic kyphosis (ASF: 23.7 degrees , PSF-Hybrid: 19.3 degrees , PSF-Hooks: 21.9 degrees ). After surgery, the T5-T12 kyphosis was greater in the ASF group (25.1 degrees ) compared with PSF-Hooks (19.0 degrees ) and PSF-Hybrid (18.5 degrees (P < 0.05). At 1 year, thoracic kyphosis (T5-T12) remained greater in the ASF group (28.8 degrees ) compared with PSF-Hooks (22.6 degrees ) and PSF-Hybrid (20.2 degrees ) (P < 0.05), and was also greater at 2 years (29.9 degrees vs. 23.8.8 degrees and 19.7 degrees ) (P < 0.05). Kyphosis at the thoracolumbar junction was not seen in the PSF-Hybrid group. Lumbar lordosis increased only in the ASF group in response to the increase in thoracic kyphosis. CONCLUSION: ASFI is the best method to restore thoracic kyphosis when compared with posterior approaches using only hooks or a hybrid construct in the treatment of thoracic adolescent idiopathic scoliosis.

Thoracic and thoracolumbar kyphosis in adults.

STUDY DESIGN: Author experience and literature review. OBJECTIVES: To investigate the spectrum of adult kyphosis and to discuss the various surgical and nonsurgical treatment options. SUMMARY OF BACKGROUND DATA: Kyphosis with its various etiologies and associated pathophysiologies has been discussed in the literature for many decades. The nonsurgical treatment primarily consists of symptom reduction via physical therapy and has not changed significantly for decades. The surgical treatment, however, has changed dramatically. A decade ago, most large kyphotic deformities required anterior and posterior procedures. With the advent of numerous posterior osteotomy techniques and pedicle fixation, most of these deformities are now treated via posterior methods only. METHODS: Using literature review and the author's experience, kyphosis and its characteristics will be discussed. Important details pertinent to presurgical planning and execution of surgical will be discussed. Three cases will be presented to illustrate the surgical treatment options for three qualitatively different kyphotic deformities. RESULTS: Flexible kyphotic deformities may respond well to aggressive facetectomies and cantilever corrections. Multisegmental osteotomies may be most appropriate for long sweeping deformities. Fixed, sharply, angulated deformities may respond best to pedicle subtraction osteotomies or vertebral column resections. CONCLUSION: Segmental pedicle screw fixation coupled with one of four posterior osteotomy/resection techniques can be used to address most sagittal plain deformities. Careful application of these techniques is important. Smith-Petersen and Ponte osteotomies are most appropriate for long sweeping deformities with mobile anterior columns. Pedicle subtraction osteotomies and vertebral column resections are most appropriate for fixed, sharply angulated spinal deformities. The successful application of these techniques is dependent on accurate preoperative evaluation of the structural properties of the kyphosis and meticulous execution of the surgical technique.

Comparison of the lowest instrumented, stable, and lower end vertebrae in "single overhang" thoracic adolescent idiopathic scoliosis: anterior versus posterior spinal fusion.

STUDY DESIGN: A retrospective multicenter study. OBJECTIVE: To investigate the relationship between the lowest instrumented, stable, and lower end vertebrae in patients with "single overhang" thoracic (main thoracic) curves treated with anterior or posterior spinal fusion. SUMMARY OF BACKGROUND DATA: Previous studies have shown "saving" fusion levels with anterior spinal fusion, as opposed to posterior spinal fusion; however, to our knowledge, none of these studies evaluated the relative position to the lower end vertebra to compare study groups accurately. For clarification, "single overhang" includes Lenke 1A and 1B curves. For these thoracic curves, the lumbar curve does not cross the midline. MATERIALS AND METHODS: A retrospective multicenter study of adolescent idiopathic scoliosis was performed to identify specifically patients with "single overhang" thoracic (Lenke 1A and 1B) curves with more than a 2-year follow-up. To analyze relative fusion levels, the differences were computed as follows: (1) the difference between the vertebra position for the stable vertebra of the main thoracic (MT) curve and the lowest instrumented vertebra, as noted on postoperative radiographs, or [equation: see text] (2) the difference between the vertebra position for the lower end vertebra of the main thoracic (MT) curve and the lowest instrumented vertebra, as noted on postoperative radiographs, or [equation: see text]. RESULTS: A total of 298 "single overhang" thoracic curves (148 Lenke 1A, 150 Lenke 1B) were identified, of which 293 had either an anterior spinal fusion or posterior spinal fusion; 5 patients underwent a combined anterior-posterior spinal fusion. Anterior spinal fusion was performed in 70 patients (23.9%) and posterior spinal fusion in 223 (76.1%). While comparing the lowest instrumented vertebra to the stable vertebra with anterior spinal fusion, the lowest instrumented vertebra was identified either at the level of the stable vertebra or above in 97% of 1A/B curves (P < 0.001). Using posterior spinal fusion techniques, the lowest instrumented vertebra was identified either at the stable vertebra or above in 65% of the 1A/B curves (P < 0.05). CONCLUSIONS: These data confirm that anterior spinal fusion techniques result in a mean shorter fusion of 1.5 vertebral segments/patient when compared to posterior spinal fusion techniques with respect to the position of the lowest instrumented and stable vertebrae for "single overhang" thoracic (Lenke 1A/B) curves. However, because this is a retrospective multicenter study over 10 years, it represents various posterior spinal fusion techniques that do not include all pedicle screw constructs.

Comparison of manual and digital measurements in adolescent idiopathic scoliosis.

STUDY DESIGN: Comparison of manual and digital measurement of radiographic parameters in patients with adolescent idiopathic scoliosis (AIS). OBJECTIVE: To assess the reliability of digital measures as compared to manual measures in the evaluation of AIS. SUMMARY OF BACKGROUND DATA: Radiographic parameters are critical to the evaluation of patients with AIS, and are frequently used to monitor curve progression and guide treatment decisions. The reliability of many of the more common radiographic measures has only recently been elucidated for both manual and digital measures. However, a comparative analysis of manual versus digital measures has been performed only for coronal Cobb angles. The inter-technique reliability of these parameters will have increasing importance as digital radiographic viewing and analysis become commonplace. METHODS: There were 2 independent, blinded observers that measured 30 complete sets of preoperative (posterior-anterior, lateral, and both side-bending) and postoperative (posterior-anterior and lateral) radiographs on 4 different occasions. For the first 2 iterations, manual measurements were taken using the same pencil and protractor. For the last 2 iterations, measurements of digitized radiographs were taken on a software measurement program (PhDx, Albuquerque, NM). Coronal measures included the main thoracic and thoracolumbar/lumbar standing and side-bending Cobb angles, apical vertebral translation, coronal balance, T1 tilt angle, lowest instrumented vertebrae angle, angulation of the disc inferior to the lowest instrumented vertebrae, apical Nash-Moe vertebral rotation, and Risser grade. Sagittal parameters included T2-T5 and T5-T12 regional thoracic kyphosis, T2-T12 thoracic kyphosis, T10-L2 thoracolumbar junction sagittal curvature, T12-S1 lumbar lordosis, and global sagittal balance. The technique-dependent measurement variability and the inter-technique (manual vs. digital), intraobserver reliability were evaluated for each radiographic parameter (within 3 degrees ). RESULTS: Digital measurement showed decreased intraobserver variability for many (9 of 15) of the radiographic parameters assessed. Likewise, digital measures indicated good or excellent correlation with the absolute values obtained with manual measurement for many (10 of 15) parameters. All but 1 of those parameters having moderate-to-poor correlation had been previously shown to have poor reliability, regardless of measurement technique. Statistically significant differences between measurement variability were noted for 6 measures, including 2 favoring digital and 4, manual. Significant differences in the absolute values were noted for 5 measures, determined at a difference of 3 degrees . However, the differences in both parameter variability and absolute values tended to be small and of little clinical significance for manual versus digital measurement. CONCLUSIONS: Digital measurement showed improved measurement precision and good correlation with manual measurements for the majority of AIS parameters. Absolute differences between manual and digital measurements were generally small. Therefore, digital measures are acceptable as a valid technique for scoliosis evaluation. The importance of digital versus manual measurement reliability will increase as digital radiographic viewing becomes more prevalent.

Reliability analysis for digital adolescent idiopathic scoliosis measurements.

OBJECTIVE: Analysis of adolescent idiopathic scoliosis (AIS) requires a thorough clinical and radiographic evaluation to completely assess the three-dimensional deformity. Recently, these radiographic parameters have been analyzed for reliability and reproducibility following manual measurements; however, most of these parameters have not been analyzed with regard to digital measurements. The purpose of this study is to determine the intra- and interobserver reliability of common scoliosis radiographic parameters using a digital software measurement program. METHODS: Thirty sets of preoperative (posteroanterior [PA], lateral, and side-bending [SB]) and postoperative (PA and lateral) radiographs were analyzed by three independent observers on two separate occasions using a software measurement program (PhDx, Albuquerque, NM). Coronal measures included main thoracic (MT) and thoracolumbar-lumbar (TL/L) Cobb, SB MT Cobb, MT and TL/L apical vertical translation (AVT), C7 to center sacral vertical line (CSVL), T1 tilt, LIV tilt, disk below lowest instrumented vertebra (LIV), coronal balance, and Risser, whereas sagittal measures included T2-T5, T5-T12, T2-T12, T10-L2, T12-S1, and sagittal balance. Analysis of variance for repeated measures or Cohen three-way kappa correlation coefficient analysis was performed as appropriate to calculate the intra- and interobserver reliability for each parameter. RESULTS: The majority of the radiographic parameters assessed demonstrated good or excellent intra- and interobserver reliability. The relationship of the LIV to the CSVL (intraobserver kappaa = 0.48-0.78, fair to excellent; interobserver kappaa = 0.34-0.41, fair to poor), interobserver measurement of AVT (rho = 0.49-0.73, low to good), Risser grade (intraobserver rho = 0.41-0.97, low to excellent; interobserver rho = 0.60-0.70, fair to good), intraobserver measurement of the angulation of the disk inferior to the LIV (rho = 0.53-0.88, fair to good), apical Nash-Moe vertebral rotation (intraobserver rho = 0.50-0.85, fair to good; interobserver rho = 0.53-0.59, fair), and especially regional thoracic kyphosis from T2 to T5 (intraobserver rho = 0.22-0.65, poor to fair; interobserver rho = 0.33-0.47, low) demonstrated lesser reliability. In general, preoperative measures demonstrated greater reliability than postoperative measures, and coronal angular measures were more reliable than sagittal measures. CONCLUSIONS: Most common radiographic parameters for AIS assessment demonstrated good or excellent reliability for digital measurement and can be recommended for routine clinical and academic use. Preoperative assessments and coronal measures may be more reliable than postoperative and sagittal measurements. The reliability of digital measurements will be increasingly important as digital radiographic viewing becomes commonplace.

Single-rod versus dual-rod anterior instrumentation for idiopathic scoliosis: a biomechanical study.

STUDY DESIGN: Anterior single- and dual-rod instrumented human and ovine thoracolumbar spines, with and without structural interbody support (SIS), were biomechanically tested and compared in flexion, lateral bending, and torsion. OBJECTIVE: To determine significant differences in global stiffness of the constructs in an attempt to clarify specific indications for each in the treatment of spinal deformities. SUMMARY OF BACKGROUND DATA: Single- and dual-rod anterior systems have been used without any consensus as to indications for one versus the other. The potential added benefit of incorporating SIS and transverse connectors (dual-rod) with these constructs has also not been fully explored. METHODS: Four human cadaveric and six ovine spines were instrumented in single- and dual-rod constructs and biomechanically tested intact, postdiscectomy with and without SIS, with single- and dual-rod constructs, and with and without transverse connectors (ovine only). Biomechanical testing modes were flexion, lateral bending, and torsion. RESULTS: In the human cadaveric specimens, testing in flexion revealed that SIS was the major contributing factor for construct stiffness. In lateral bending, stiffness of single- and dual-rod constructs with and without SIS was equivalent. In torsion, both single- and dual-rod instrumentation and SIS appeared to contribute to global stiffness. In ovine specimens, dual rods were stiffer than single-rod constructs and SIS played only a minor role. Transverse connectors appeared to significantly stiffen dual-rod constructs in torsion only. CONCLUSIONS: Dual-rod constructs with SIS appear to be the best combination for providing stiffness in anterior instrumentation. The addition of cross-links to anterior constructs does not appear to increase stiffness except in torsion.

Reliability analysis for manual adolescent idiopathic scoliosis measurements.

STUDY DESIGN: Manual radiographic measurement analysis. OBJECTIVES: To determine the intraobserver and interobserver reliability of numerous radiographic process measures used in the assessment of adolescent idiopathic scoliosis. SUMMARY OF BACKGROUND DATA: Analysis of scoliosis requires a thorough radiographic evaluation to completely assess the deformity. Numerous radiographic process measures have been studied extensively and used for outcomes assessment and thus become the de facto standard of care. However, many of these measures have not been evaluated to determine the reliability and reproducibility. Validation of radiographic process measures is necessary to compare these measures with patient-focused outcome measures, as well as to permit valid comparison of different surgical techniques. METHODS: Thirty complete sets of long-cassette scoliosis radiographs (anteroposterior [AP], lateral and side-bending preoperative and AP, and lateral postoperative) were analyzed by three independent experienced observers on two separate occasions. Coronal image measures included the coronal Cobb angles, side-bending Cobb, apical vertebral translation, coronal balance, T1 tilt, lowest instrumented vertebrae (LIV) tilt, angulation of the disc below the LIV, apical vertebral rotation (Nash-Moe),and Risser sign; sagittal measures included T2-T5, T5-T12, T2-T12, T10-L2, T12-S1, and sagittal balance. Intraobserver and interobserver reliability for each measure was then assessed. RESULTS: The vast majority of the radiographic process measures assessed demonstrated good to excellent or excellent intraobserver and interobserver reliability. However, the angulation of the disc below the LIV demonstrated only fair interobserver reliability for postoperative measurements (rho = 0.59). Likewise, Risser grade measurements reflected good intraobserver (0.81-0.99) but only fair interobserver reliability (0.60-0.70). Apical vertebral rotation assessed by the technique of Nash and Moe produced good intraobserver reliability before surgery (0.74-0.85) but only fair reliability after surgery (0.50-0.85). The interobserver reliability for apical Nash-Moe rotation was fair to poor (0.53-0.59). For T2-T5 regional kyphosis, intraobserver (0.22-0.83) and interobserver (0.33-0.47) reliability was generally poor. Overall, the reliability of postoperative measurements tended to be decreased relative to preoperative values, likely due to instrumentation overlying radiographic landmarks. CONCLUSIONS: Most of the radiographic process measures evaluated in this study demonstrated good or excellent reliability. The reliability of measuring the angulation of the disc below the LIV, the apical Nash-Moe rotation, and Risser grading was decreased relative to other measures. The reliability of measuring T2-T5 regional kyphosis was disappointing and poor. With regards to the other 13 measures assessed, our findings support the use of these process measures obtained by experienced deformity surgeons via manual measurement for routine clinical and academic purposes.

Accuracy and efficacy of thoracic pedicle screws in curves more than 90 degrees.

STUDY DESIGN: Retrospective study of large-magnitude thoracic curves (> or =90 degrees ) treated with pedicle screw constructs. OBJECTIVE: To evaluate the results of pedicle screw constructs for thoracic curves > or = 90 degrees in terms of sagittal and coronal correction/efficacy, as well as accuracy and safety of thoracic pedicle screw placement. SUMMARY OF BACKGROUND DATA: Thoracic pedicle screw constructs continue to become increasingly more common; however, the debate continues about the safety and efficacy of these constructs because of their perceived increased risk of neurologic injury and the increased cost of spinal instrumentation. METHODS: Since 1998, all patients with adolescent idiopathic scoliosis, or adult progression of adolescent idiopathic scoliosis, a thoracic curve > or = 90 degrees and a minimum 2-year follow-up who were treated with pedicle screw constructs were included in this study. Standing anteroposterior (or posteroanterior), lateral and bending preoperative radiographs, and anteroposterior (or posteroanterior) and lateral postoperative radiographs were evaluated for curve magnitude, flexibility, and postoperative correction to assess the efficacy of these constructs in the immediate postoperative period and at latest follow-up. Postoperative CT scans were evaluated for screw accuracy using established 2-mm increments (intrapedicular, 0-2 mm breach, 2-4 mm breach, > 4 mm breach). Preoperative plans were also reviewed to evaluate the ability to place a pedicle screw at each planned level in these large-magnitude curves. RESULTS: Twenty patients with thoracic curves > or = 90 degrees and an average follow-up of 3.3 years (range, 2.0-5.2 years) were included in the study. All patients underwent a posterior spinal fusion with a pedicle screw only construct. The average preoperative main thoracic curve measured 100.2 degrees (range, 90 degrees -133 degrees ), with an average side-bender of 71.6 degrees (29% flexibility). The average postoperative main thoracic curve was 32.3 degrees (68% correction). A total of 352 thoracic screws were placed in the 20 cases (17.6 screws/case). Screw accuracy (either intrapedicular or <2 mm breach) was 96.3% (339 of 352 screws) by postoperative CT scanning. Ten screws were considered to have a breach between 2 and 4 mm (3 medial, 7 lateral), while three screws were > 4 mm (2 medial, 1 lateral). The two medial screws were the only placed screws that were removed (0.57%). Overall, 94% of planned screws (352 of 374 screws) were placed according to the preoperative plan. There were no incidences of screw or instrumentation failure. Of note, there was a temporary decrease in motor-evoked potentials during curve correction in 2 cases; however, there were no identifiable neurologic complications. CONCLUSIONS: Thoracic pedicle screw constructs can be safely used for large-magnitude curves. Curve correction (68%) is powerful for these curves, which are stiff and difficult to manage. Correction should be performed carefully with consideration given to convex compression for cases with concomitant hyperkyphosis for these "at risk" spinal cords. Screw accuracy (96.3%) was excellent in this review. The authors found that screws can consistently be placed according to the preoperative plan even in these large-magnitude curves.

A biomechanical study of regional endplate strength and cage morphology as it relates to structural interbody support.

STUDY DESIGN: An in vitro biomechanical investigation to quantify the endplates resistance to compressive loads, in the thoracic and lumbar spine. Comparisons were made to determine the regional strength of the endplate, the optimal size and geometry of interbody support, and the effects of endplate removal on structural strength. OBJECTIVES: To biomechanically assess the regional variation of endplate strength in the thoracic and lumbar spine, the optimal geometry and cross-sectional area for structural interbody support, and endplate preparation techniques with respect to endplate failure or subsidence. SUMMARY OF BACKGROUND DATA: Anterior column interbody support plays an important role in spinal reconstruction. Subsidence of interbody structural support is a common problem and may be related to regional weakness of the endplate, the size and/or geometry of structural support, and the preparation of the endplate. Biomechanical data related to these issues should be of importance to spine surgeons and reduce the risk of subsidence and its inherent complications. METHODS: The indentation tests were performed in three subgroups, each with a different set of test variables. The first test consisted of 65 vertebrae at six different endplate test positions using a 9.53-mm diameter indenter. The second test was performed on 48 vertebrae at a central endplate test site using three hollow and two solid cylindrical indenters of varying diameter. The third test was done using 24 vertebrae with the endplate intact, partially removed, or fully removed. All tests were run using human cadaveric specimen using both the superior and inferior endplates. The maximum load to failure (MLF) was determined for each test performed. RESULTS: For all levels tested, the highest MLF occurred in the posterolateral region of the endplate. The lowest value occurred in the central and anterocentral regions for levels T7-L5 and T1-T6, respectively. Hollow indenters with a small diameter had the lowest MLF, whereas solid large-diameter indenters had the highest MLF. The ultimate compressive strength for all hollow indenters was significantly higher than all solid indenters. There was a significant reduction in the endplate strength with the complete removal of the endplate. CONCLUSIONS: The posterolateral region of the endplate provides the greatest resistance to subsidence while the central region provides the least resistance. A larger-diameter solid support has the greater MLF and the lower the risk of subsidence, suggesting a more efficient transfer of force to the endplate with the hollow indenters. Parameters such as the geometry of structural support and the position and preparation of the endplate can influence the resistance of an interbody support to subside. Partial removal of the endplate may provide both, for adequate mechanical advantage and a highly vascular site for fusion.

Anterior single rod instrumentation for thoracolumbar adolescent idiopathic scoliosis with and without the use of structural interbody support.

STUDY DESIGN: A radiographic and clinical outcomes analysis of 41 patients treated for thoracolumbar adolescent idiopathic scoliosis utilizing a single anterior rigid rod construct. OBJECTIVES: To evaluate the necessity of structural interbody support to improve primary curve correction and preserve or augment lordosis when used in conjunction with a single anterior rigid rod construct, to identify parameters that predict horizontalization of the lowest instrumented vertebra, adjacent disc angulation, and distal uninstrumented vertebrae, and to assess patient satisfaction following surgery. BACKGROUND DATA: Instrumentation-induced kyphosis has been a concern with nonrigid anterior systems used in the past for the treatment of scoliosis. Interbody structural support has been recommended to maintain appropriate sagittal profile when anterior systems are utilized. It has also been suggested that the use of structural interbody support creates a fulcrum to increase curve correction when compression is applied to the convexity of the deformity. However, the necessity of interbody structural support when used in conjunction with a rigid anterior system has not been previously evaluated in patients with adolescent idiopathic scoliosis. MATERIALS AND METHODS: Forty-one patients mean age 15.9 years (range 12.1-18.6 years) with thoracolumbar adolescent idiopathic scoliosis underwent anterior spinal fusion using a single 6.0 to 6.5 mm solid rod construct between June 1995 and August 1999 performed by the senior author (T.G.L.). Four additional patients with thoracolumbar curves with similar anterior instrumentation over the same time period were lost to follow-up or had incomplete records and were not included in the study. Structural interbody support was used in 21 patients and packed morselized autograft alone was used in 20 patients. The patients in the group with packed morselized bone alone generally underwent surgery earlier in the series before the author began using structural interbody support on a regular basis. Each patient had a minimum follow-up of 3 years. Preoperative, initial, and most recent (>3 years) follow-up radiographs were reviewed to determine in each group Cobb angle measurements, flexibility of primary, secondary, and fractional curves, apical and end vertebral translation, lowest instrumented vertebral and caudal disc angulation, global coronal and sagittal balance, and sagittal Cobb measurements in both instrumented levels as well as lumbar lordosis (T12-S1). In addition, the SRS outcomes instrument was completed by 38 of 41 patients. RESULTS: The mean preoperative primary curve in patients with structural support was 47 degrees (Group II) and 45 degrees in patients without structural support (Group I). Mean curve correction was to 13 degrees in Groups I and II. One patient in Group II became slightly more unbalanced at final follow-up; otherwise all were improved after surgery. Sagittal measurements over instrumented segments as well as total lumbar lordosis (T12-S1) was maintained between preoperative and final postoperative values in both groups. Similarly, in both groups, when horizontalization of the distal end instrumented vertebra was achieved on the preoperative reverse side-bending radiograph, more normal relationships were achieved between instrumented and distal noninstrumented segments (adjacent disc angulation and fractional lumbar curve) at final follow-up (P

Analysis of patient and parent assessment of deformity in idiopathic scoliosis using the Walter Reed Visual Assessment Scale.

OBJECTIVES: This study evaluates the Walter Reed Visual Assessment Scale (WRVAS) compared with clinical parameters and written descriptions of the deformity from idiopathic scoliosis patients and their parents. SUMMARY OF BACKGROUND DATA: The WRVAS demonstrates seven visible aspects of spinal deformity in an analogue scale. Higher scores reflect worsening deformity. MATERIALS AND METHODS: The WRVAS was administered to 182 idiopathic scoliosis patients at four centers in conjunction with open-ended questions about patients' and their parents' perceptions of their spinal deformity. The open-ended responses were categorized as either "deformity noted" or "no deformity noted." RESULTS: WRVAS scores strongly correlate with curve magnitude (P = 0.01) and clearly differentiates curves of 30 degrees or more from lesser curves. Among treatment groups, patients with surgery recommended had significantly higher scores than that of other patients. The instrument differentiated those noting no deformity from those noting a deformity. The correlation between patients' and parents' scores was high (Spearman's rho = 0.8). When a deformity was noted, parents gave higher scores than did their children for rib prominence, shoulder level, scapular rotation, and the total score, but not for the other dimensions. CONCLUSIONS: Increasing scores of the WRVAS are strongly correlated with curve magnitude lending construct validity to this type of assessment tool. Patients with "surgery recommended" report more visible deformity on the scale than observed, braced, and postoperative patients, supporting the hypothesis that surgery improves the perceived appearance. Parents perceive more deformity of the ribs and shoulders more than did the patients, but other aspects of the deformity are identified equally. WRVAS scores correlate significantly with curve magnitude and treatment. Parents and patients have similar scores, but with parents perceiving more deformity of the ribs and shoulders than patients.

Low-grade isthmic/lytic spondylolisthesis in adults.

Three basic classification schemes have been developed to categorize spondylolisthesis, the slippage or forward displacement of one vertebra over another. Two rely on radiographic appearance, and the third stresses the developmental aspect of the pathology. The pathology is relatively rare in individuals younger than 18 years, appears to be influenced by race, and is found more frequently in males than females and in patients with symptomatic low back pain. Lytic spondylolisthesis occurs more frequently at certain spinal levels, and certain sports activities have been implicated in its development. The etiology remains unclear, but hereditary factors are unlikely with no evidence of the lytic defect in newborns. Recent research indicates that the architecture of the pelvis may be an important parameter. Some have postulated that the underlying pathomechanical event is a fracture, either acute or secondary to fatigue. Once the pars defect has been created, anatomic and biomechanical forces conspire to prevent healing of the fracture and create a spondylolisthesis. Although mechanical considerations are likely most significant, genetic considerations have also been discussed. All the imaging modalities play useful roles in defining the pathoanatomy, including diskography. Patients typically report symptoms as back pain and/or neurologic symptoms; however, these symptoms can have other causes even though a spondylolisthesis is present. A thorough history and physical examination, along with the radiographic investigations, are essential to determining proper treatment. Nonsurgical options are activity modification, bracing, physical therapy, and intervention in the form of medications or injections. Use of muscle relaxers and narcotics may be appropriate for managing initial acute pain. Surgical options are direct repair of the pars defect, decompression, fusion, or a combination of these procedures. The various techniques of pars repair are recommended only for patients younger than 30 years. Although decompression alone may be suitable in some situations, decompression with fusion is more standard, certainly when instability and low back pain exist.

Histology of the craniocervical junction in chronic rheumatoid arthritis: a clinicopathologic analysis of 33 operative cases.

STUDY DESIGN: A histologic review of surgical specimens with clinical and radiographic correlations. OBJECTIVE: To analyze the histopathology at the craniocervical junction in chronic rheumatoid arthritis (RA). SUMMARY OF BACKGROUND DATA: It has been assumed that the tissue identified on radiography at the craniocervical junction causing anterior spinal cord compression in patients with chronic RA is hypertrophic rheumatoid synovium. To date, no study has positively identified the histology of this tissue. METHODS: Transoral resection of the dens and spinal cord decompression were performed in 33 myelopathic rheumatoid patients with craniocervical instability. The resected specimens were examined histologically. RESULTS: Two unique histologic patterns were identified. Type I synovium has a recognizable synovial structure but without a hyperplastic synovial layer, significant inflammatory cell population, or lymphocytic infiltration typical of early active rheumatoid synovium. Type II synovium is a bland, fibrous, hypercellular tissue that is hypovascular, with little synovium and few inflammatory cells. Clinically and radiologically the two groups are distinct. Patients with Type II synovium are older ( = 0.008) and present with more advanced neurologic involvement caused by spinal cord compression ( = 0.0001). The mean difference in the spinal cord area between the two groups was 20.6 mm (95% confidence interval, 10.0-31.2 mm; = 0.004). CONCLUSIONS: The histologic specimens suggest that ligamentous destruction is followed by replacement of the rheumatoid synovium with fibrous tissue, whereas the osseous structures reveal severe destruction secondary to mechanical instability, rather than to an acute inflammatory process. Early, preemptive surgical intervention may prevent the development of spinal cord injury caused by instability.

Rheumatoid arthritis of the cervical spine: current techniques for management.

The incidence of rheumatoid arthritis in the European and North American population is significant. Rheumatoid arthritis can result in serious damage to the cervical spine and the central neuraxis, ranging from mild instability to myelopathy and death. Aggressive conservative care should be established early. The treating physician should not be lulled into a false sense of security by reports suggesting that cervical subluxations are typically asymptomatic [76-78]. Gradual spinal cord compression can result in severe neurologic deficits that may be irreversible despite appropriate surgical intervention when applied too late. [figure: see text] The treatment of rheumatoid disease in the cervical spine is challenging. Many details must be considered when diagnosing and attempting to institute a treatment plan, particularly surgical treatment. The pathomechanics may result in either instability or ankylosis. The superimposed deformities may be either fixed or mobile. The algorithm suggested by the authors can be used to navigate through the numerous details that must be considered to formulate a reasonable surgical plan. Although these patients are [figure: see text] frail, an "aggressive" surgical solution applied in a timely fashion yields better results than an incomplete or inappropriate surgical solution applied too late. When surgical intervention is anticipated, it should be performed before the development of severe myelopathy. Patients who progress to a Ranawat III-B status have a much higher morbidity and mortality rate associated with surgical intervention than do patients who ambulate. Although considered aggressive by some, "prophylactic" stabilization and fusion of a [figure: see text] relatively flexible, moderately deformed spine before the onset of severe neurologic symptoms may be reasonable. This approach ultimately may serve the patient better than "observation" if the patient is slowly drifting into a severe spinal deformity or shows signs of early myelopathy or paraparesis.