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The objective of this review is to discuss the indications, surgical technique, and potential complications of thoracic hemivertebra excision in the pediatric population. Thoracic hemivertebra produce a congenital scoliosis or kyphoscoliosis that may progress and require surgical intervention. Patients may require either separate anterior and posterior approaches for hemivertebra excision, or more recently, a posterior-only approach has been developed, which is our preferred method. A posterior-only approach is accomplished with a unilateral costotransversectomy, which allows complete hemivertebra excision as well as reconstruction of the anterior as well as posterior column. Preoperative preparation, intraoperative pearls, and pitfalls and postoperative care will be discussed for this surgical procedure.

STUDY DESIGN.: A retrospective clinical study. OBJECTIVE.: To find the corrective capacity of a thoracic pedicle subtraction osteotomy (PSO), determine if segmental correction is dependent on level, and to compute the impact of thoracic PSO on regional and global spinal balance. SUMMARY OF BACKGROUND DATA.: PSO is a technique popularized in the lumbar spine primarily for the correction of fixed sagittal imbalance. Despite several studies describing the clinical and radiographic outcome of lumbar PSO, there is no study in literature reporting its application in the thoracic spine. METHODS.: We retrospectively analyzed patients with fixed thoracic kyphosis who underwent thoracic PSOs for sagittal realignment. Segmental pedicle screw instrumentation and intraoperative neurophysiologic monitoring was used in all patients. Data acquisition was performed by reviewing medical charts and radiographs to determine sagittal correction (segmental/regional/global) and complications. Clinical outcome using the Scoliosis Research Society-22 (SRS-22) instrument was determined by interview. RESULTS.: A total of 25 thoracic PSOs were performed (mean: 1.7 PSOs/patient, range: 1-3) in 15 patients (9 M/6 F). The study population had an average age of 56 years (range, 36-81 years) and was followed up after surgery for a mean of 3.5 years (range, 24-75 months). The osteotomies were carried out in the proximal thoracic spine (T2-T4, n = 6), midthoracic spine (T5-T8, n = 12), and distal thoracic spine (T9-T12, n = 7). Mean correction at the PSO for all 25 levels was 16.3 degrees +/- 9.6 degrees . Stratified by region of the spine, thoracic PSO correction was as follows: T2-T4 = 10.7 degrees +/- 15.8 degrees , T5-T8 = 14.7 degrees +/- 4.6 degrees , and T9-T12 = 23.9 degrees +/- 4.1 degrees . Mean thoracic kyphosis (T2-T12 Cobb angle) was improved from 75.7 degrees +/- 30.9 degrees to 54.3 degrees +/- 21.4 degrees resulting in a significant regional sagittal correction of 21.4 degrees +/- 13.7 degrees (P < 0.005). Global sagittal balance was improved from 106.1 +/- 56.6 to 38.8 +/- 37.0 mm yielding a mean correction of 67.3 +/- 54.7 mm (P < 0.005). One patient, in whom there was segmental translation during osteotomy closure, had a decline in intraoperative somatosensory-evoked potentials. No patient sustained a temporary or permanent neurologic deficit after surgery. The mean SRS-22 Questionnaire score at final follow-up was 82.4 +/- 10.2. CONCLUSION.: Thoracic PSO can be performed safely. Segmental sagittal correction appears to vary based on the region of the thoracic spine the PSO is performed. The distal thoracic segments, which more closely resemble lumbar segments in morphology, rendered the greatest sagittal correction after PSO, approximately 24 degrees . There was no case of neurologic injury associated with thoracic PSO, and clinical outcomes according to the SRS-22 instrument were generally favorable.

Study Design A single large family, in which adolescent idiopathic scoliosis (AIS) and pectus excavatum (PE) segregate as an autosomal dominant condition, was evaluated. Genome-wide linkage analysis and candidate gene sequencing were performed.

Study Design. This is an in vitro biomechanical study. Objective. The current investigation was performed to evaluate adjacent level kinematic change following unilateral and bilateral facet violation and laminectomy following 1-, 2-, and 3-level reconstruction. Summary of Background Data. The incidence of superior-segment facet violation with lumbar transpedicular fixation has been reported as high as 35%; however, its contribution to biomechanical instability at the supradjacent level is unknown. In addition, superior-segment laminectomy has been implicated as a risk factor for the development of adjacent level disease. The authors assess the acute biomechanical effects of proximal facet violation and subsequent laminectomy in an instrumented posterior fusion model in 10 cadaveric specimens. Methods. Biomechanical testing was performed on 10 human cadaveric spines under axial rotation (AR), flexion-extension (FE), and lateral bending (LB) loading. After intact analysis, pedicle screws were inserted from L5-S1 and testing repeated with: (1) preserved L4-L5 facets, (2) unilateral facet breach, (3) bilateral breach, and (4) L5 laminectomy. Following biomechanical analysis, instrumentation was extended to L4, then L3 and biomechanical testing repeated. Full range of motion (ROM) at the proximal adjacent levels were recorded and normalized to intact (100%). Results. Supradjacent level ROM was increased for all groups under all loading methods relative to intact (P < 0.05). However, AR testing revealed progressive instability at the adjacent level in groups 3 and 4, relative to group 1, following 1-, 2- and 3-level fixation (P < 0.05). During FE, supradjacent level ROM was significantly increased for group 4 specimens compared with group 1 after L5-S1 fixation (P < 0.05), and was greater than all other groups for L3-S1 constructs (P< 0.05). Interestingly, under lateral bending, facet joint destabilization did not change adjacent segment ROM. Conclusion. There were significant changes in proximal level ROM immediately after posterior stabilization. However, an additional increase in supradjacent segment ROM was recorded during AR after bilateral facet breach. Subsequent complete laminectomy at the uppermost-fixation level further destabilized the supradjacent segment in FE and AR. Therefore, meticulous preservation of the cephalad-most segment facet joints-is paramount to ensure stability.

Background context Untreated osteoporosis causes decreased bone mineral density, which predisposes to fragility fractures. Low-energy vertebral compression fractures are the most common type of osteoporotic fragility fracture. Prior studies have shown that only one-quarter of patients diagnosed with an osteoporotic fracture are referred or treated for osteoporosis. Purpose To identify the rate of therapeutic interventions for patients aged 50 years and older within a capitated population who sustained low impact vertebral compression fractures over a 6-month period. Study design/setting Retrospective observational study. Patient sample The reports of all imaging studies of the chest, abdomen, and spine taken from July to December 2002 within a large military health-care system were queried on the Composite Health Computer System (CHCS). The sample included patients 50 years or older who had a low-energy vertebral compression fracture. Outcome measures The computerized medical records were examined for osteoporotic medication prescriptions, referrals to endocrinology, and to dual-energy X-ray absorptiometry (DEXA) scans. These results were compared with results obtained from a similar study on osteoporotic distal radius fractures. Results The records of 156 patients (average age: 77.3 y; 78 women, 78 men) meeting the inclusion criteria were analyzed to determine what proportion was followed-up with osteoporosis interventions. Within 1 year after the fracture, 39% (37 females, 24 males) had undergone a DEXA scan, 35% (37 females, 18 males) had been referred to endocrinology, 38% (47 females, 12 males) were receiving active osteoporosis treatment, and 51% (55 females, 25 males) were receiving any form of osteoporosis-directed medication. The rate of medical intervention was similar to the rate of intervention after distal radius fragility fractures (n=111; 30% active medication; 47% any osteoporosis medication) (p>.21). The rate of all interventions was significantly greater for women than men. Conclusions Although the likelihood of intervention is slightly greater after vertebral compression fractures than for distal radius fractures, orthopedic surgeons, emergency room physicians, and primary care providers continue to miss opportunities, especially in males, to diagnose and/or initiate active therapeutic interventions for osteoporosis in patients presenting with osteoporosis-related fragility fractures.

STUDY DESIGN An in vitro biomechanical cadaver study of long segment thoracic pedicle screw constructs with transverse connectors (TC). OBJECTIVE To determine the resultant degree of motion of the instrumented thoracic spine after segmental pedicle screw instrumentation with and without TC. SUMMARY OF BACKGROUND DATA.: TC are generally not thought to be necessary with thoracic pedicle screw constructs, yet to date no study has reported the effect of TCs after all pedicle screw long thoracic fusions. METHODS Eight human cadaveric spines were potted and then instrumented from T4-T10 with bilateral 5.5 mm multiaxial titanium (Ti) pedicle screws and 5.5 mm contoured Ti rods. Specimens were tested with a six-degree-of-freedom spine stimulator in the intact condition, after instrumentation, after placement of 1 TC (3 different locations) and after placement of both TCs. Data were analyzed by loading modality (axial rotation, flexion-extension, and lateral bending) using one-way analysis of variance with an alpha of 0.05. Paired t tests were used for post hoc analysis with correction for multiple comparisons. RESULTS There was no difference with the addition of 1 or 2 TCs in terms of flexion-extension or lateral bending when compared to the instrumented condition (P > 0.05). Biomechanical testing of the long-segment thoracic constructs in axial rotation (torsion) loading modes generated the most significant findings of this study. After instrumentation with thoracic pedicle screws, T4-T10 full ROM was significantly reduced from the intact condition (P < 0.05). On average, TPS alone resulted in a 65% decrease in ROM. However, the addition of a transverse connector at 1 of the 3 positions tested yielded another 20% improvement in axial segmental stability as represented by further ROM reduction. These differences were significant from the TPS only group (no TCs), regardless of the TC position (P < 0.05). Furthermore, 2 TCs placed at the proximal and distal ends of the construct provided the greatest biomechanical axial stability to the instrumented specimens (P < 0.05). This was highlighted by an average of 35% ROM reduction from the stability level achieved with the TPS only constructs (P < 0.05), or an additional 15% improvement in axial stability over a single TC. CONCLUSION For long thoracic pedicle screw constructs, the addition of 1 or 2 TCs significantly decreases construct axial rotation, which is the primary plane of motion for the thoracic spinal region. A single TC contributed to a significant reduction of T4-T10 ROM (an additional 20%) relative to TPS fixation alone (P < 0.05), while the location of the TC within the construct was irrelevant. A second TC had an additive effect (an additional 15% reduction) on axial stability. (P < 0.05) Flexion-extension and lateral bending are not affected. Single TC significantly improves axial rotation stability in long thoracic pedicle screw constructs. Two crosslinks, however, are better than one.

Human cadaveric biomechanical analysis.The purpose of this study is to evaluate the ability of using 1 of the remaining 2 methods of instrumenting C2, should the initial method fail.Although 3 different methods of C2 fixation (pedicle, pars, and laminar screws) are possible, occasionally an attempt at screw insertion fails. In such cases, the surgeon needs a viable alternative to salvage/obtain fixation to obviate the need to instrument an additional motion segment. METHODS.: Eleven fresh-frozen cadaveric specimens (Occ-C4) were DEXA scanned for bone mineral density. On the left side, pedicle screws were first inserted, then pulled out. Then, "salvage" pars screws were inserted, then pulled-out, followed by laminar screws. On the right, a similar sequence was repeated, except that a pars screw was followed by a pedicle screw, then a laminar screw. All screws were placed by experienced cervical spine surgeons. Insertional torque (IT) was measured in Newton-meters (Nm). Tensile loading to failure was performed "in-line"with the screw axis at a rate of 0.25 mm/s using a MTS 858 MiniBionix II System with data recorded as peak pull-out strength (POS) in newtons "N".Pedicle screws generated statistically greater IT and POS than other techniques as the initial fixation type (P0.0001). Similar trends were observed with transpedicular fixation as a salvage procedure (P0.05). Laminar screws yielded consistently higher POS values than pars fixation when applied in a salvage scenario (POS range: LS = 146-707 N; PrS = 8-548 N); however, high standard deviation precluded statistical significance (P0.05). Significant predictive relationship was established between IT and POS for all screws using Pearson correlation coefficient and bivariate linear regression analysis (r = 0.75 and r = 0.511, respectively; P0.01).Our results suggest that pedicle screws provide the strongest fixation for both initial and salvage applications. If they should fail, lamina screws appear to provide stronger and more reproducible fixation than pars screws.

Study design A retrospective clinical study. Objective To evaluate the use of recombinant human bone morphogenetic protein-2 (rhBMP-2) as the primary graft material for the surgical treatment of vertebral osteomyelitis. Summary of background data The clinical and radiographic results using allograft, autograft, and vascularized bone flaps for the surgical treatment of osteomyelitis have been previously reported. Despite an expanding body of literature documenting the value of rhBMP-2 in spinal fusion, its application to the management of spinal infection has never before been analyzed. Methods Twenty patients underwent surgical treatment of vertebral osteomyelitis using rhBMP-2 and were analyzed with a mean follow-up of 40 months (range, 24-53 months). All patients were treated with anterior column debridement and instrumented reconstruction. Four (20%) patients were treated with an anterior approach alone while the remaining 16 (80%) patients underwent circumferential spinal reconstruction. Clinical outcomes were assessed by Frankel grade and Odom criteria. Radiographic fusion was characterized based on thin-section computerized tomography (CT) analysis. Results Pathogens responsible for infection included Staphylococcus aureus (11; 55%), S. epidermidis (6; 30%), Bacteroides (1; 5%), and polymicrobial species (1; 5%). Infected segments of the spinal column based on region were found to be: thoracic (1; 5%), thoracolumbar (5; 25%), lumbar (11; 55%), and lumbosacral (3; 15%). The mean number of anterior and posterior segments fused was 3.3 (range, 2-5) and 6.5 (range 2-16), respectively. Forty-five percent of the subjects underwent multilevel corpectomies and fusion. All patients demonstrated clinical and radiographic evidence of spinal fusion at the time of follow-up. Patients had stable (14 patients) or improved (6 patients) Frankel grades after surgery. Odom criteria at final follow-up were: excellent (3; 15%), good (12; 60%), fair (4; 20%), and poor (1; 5%). There was no case of persistent or recurrent infection requiring revision surgery. Conclusion rhBMP-2 is a valuable graft option for the surgical treatment of vertebral osteomyelitis. When dosed in the manner reported, very high rates of fusion are achievable as is eradication of infection.

STUDY DESIGN Prospective, sequential enrollment. OBJECTIVE We report the development and testing of the Spinal Appearance Questionnaire (SAQ) for reliability, validity, and responsiveness in patients with idiopathic scoliosis. SUMMARY OF BACKGROUND DATA The SAQ was designed to measure patients' and their parents' perception of their spinal deformity's appearance using standardized drawings and questions. This study was designed to test the instrument's psychometric properties. METHODS The SAQ was administered as a test-retest to idiopathic scoliosis patients and parents for reliability and initial validity assessment (Group I). It was then administered to patients before surgery and 1 year after surgery (Group II) for responsiveness and further validity testing. Finally, both the SAQ and SRS instruments were administered to adolescent idiopathic patients before surgery and 1 year after surgery (Group III) for comparison of the 2 instruments. RESULTS Group I: The individual scale items had good to excellent reliability (Spearman's rho, 0.57-0.99) and high internal scale consistency (Cronbach's alpha >0.7). The mean scale scores differentiated between curves greater than 30 degrees and lesser curves (P < 0.01). Surgery improved scores compared with those with "surgery recommended." Group II: The domains correlated with clinical and radiographic aspects of the deformity before surgery. All of the domains showed significant difference after surgery (P < 0.0001) and large effect size for all domains except for the patient chest domain. Group III: Both the SAQ and the SRS instruments had significant improvement in all of their domains except for the SRS Activity scale. The relative efficiency of the SAQ domains to the SRS appearance domain (the most responsive SRS domain) was greater for 5 SAQ domains. CONCLUSION The SAQ is reliable, responsive to curve improvement, and shows strong evidence of validity. It provides more detail than the SRS in the appearance domain, and provides explanation of spinal deformity's concerns and improvements.

STUDY DESIGN A retrospective review. OBJECTIVE The purpose of this study is to document a series of cases of neurologic deficit following percutaneous vertebral stabilization, to identify patterns of neurologic injury, and to describe potential methods for avoiding these injuries. SUMMARY OF BACKGROUND DATA Percutaneous vertebral stabilization procedures, including vertebroplasty and kyphoplasty, have become a widely used for the treatment of osteoporotic vertebral compression fractures, primary and metastatic vertebral tumors, and traumatic burst fractures. Despite an increasing array of indications, there have been few reports of adverse events. Neurologic complications associated with vertebroplasty and kyphoplasty have been described previously as case reports and have generally been considered as infrequent and minor in severity. METHODS The clinical course of 14 patients with documented loss of neurologic function following percutaneous vertebral cement augmentation was retrospectively reviewed. RESULTS The average patient age was 74.9 years (range, 46-88 years) with 3 male and 11 female patients. Four patients underwent a vertebroplasty procedure while 10 were treated with kyphoplasty. Six patients developed neurologic deficits acutely (

Study design Review article. Objectives To identify decision-making principles for selecting fusion levels in adult spinal deformity, with particular attention to lumbar curves and double major curves. Summary of background data Although numerous articles have been published on the selection of fusion levels for adolescent idiopathic scoliosis (AIS) curves, relatively less attention has been paid to the selection of fusion levels for the operative management of adult scoliosis. Methods This is a literature review pertaining to the surgical management of adult scoliosis. Results Selection of fusion levels for adult scoliosis can be difficult; however, certain biomechanical and surgical principles can consistently be applied. Conclusion An appreciation of both the coronal and sagittal plane components of spinal deformity is mandatory to achieve optimal results with surgical stabilization of adult scoliosis.

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. 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 δvertebra MT = lowest instrumented vertebraMT - stable vertebra MT ; (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 Slower end vertebraMT = lowest instrumented vertebra - lower end vertebraMT 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.

Purpose: To assess the intraobserver reliability and prognostic value of magnetic resonance arthrography (MRA) on the basis of postoperative outcome measures following arthroscopic acetabular labral debridement (partial limbectomy). Methods: Between January 1999 and November 2000, 24 patients (13 females, 11 males) with an average age of 37.1 years (range, 21 to 56 years) underwent hip arthroscopy for the treatment of presumed acetabular labral tears. All patients underwent preoperative MRA and/or magnetic resonance imaging (MRI); images were evaluated by a single musculoskeletal radiologist on 2 independent occasions. Hip arthroscopy was performed on all patients. Outcomes were assessed by means of the Modified Harris Hip Score (MHHS) and the Short Form-36 (SF-36) questionnaires, which were completed by patients an average of 24.1 months (range, 12 to 55 months) postoperatively. The accuracy of the initial read, as well as the prognostic value of the Czerny MRA classification system for stage II (intrasubstance tears) and stage III (complete avulsions) acetabular labral tears, was assessed. Results: Twenty-two of 23 tears (96%) were detected on the initial read. On the basis of intraoperative findings, 1 false-positive MRA, 1 false-negative MRA, and 1 incident of MRA overstaging were reported. On repeat interpretation, 23 of 23 (100%) tears were identified, and intraobserver reliability for recording the presence of a tear was excellent (kappa coefficient=0.96). No difference was noted in outcomes between patients with or without arthroscopic evidence of chondromalacia (all P > .29), or between patients older or younger than 30 years (all P > .34). Likewise, no difference in outcome was seen between 15 patients with Czerny stage II tears revealed on MRA versus 9 patients with Czerny stage III tears (all P > .79). Conclusions: MRA is sensitive and accurate for the detection of acetabular labral tears, with excellent intraobserver reliability. Arthroscopic partial limbectomy is successful in two thirds of patients. Patients with Czerny stage II and III tears do not appear to have significantly different outcomes following arthroscopic labral debridement. Level of Evidence: Level IV, prognostic case series.

Single institution retrospective review.To report a series of pyogenic spinal infections treated with single-stage debridement and reconstruction with titanium mesh cages.Various studies have reported surgical results of pyogenic spinal osteomyelitis with anterior debridement, strut grafting and fusion, including delayed posterior spinal instrumentation. Additionally, various authors have recommended against the use of instrumentation because of the concern about glycocalyx formation on the metal and chronic infection. At our institution, we routinely treat chronic vertebral osteomyelitis with single-stage debridement, reconstruction with a titanium mesh cage filled with allograft chips and demineralized bone matrix, and posterior pedicle screw instrumentation. To our knowledge, this is the largest single series reporting single-stage debridement and instrumentation of pyogenic spinal infection with titanium mesh cages and posterior instrumentation.We retrospectively reviewed the patient records and radiographs of 21 consecutive patients (average age 49.3 years, range 23 to 80 years) with pyogenic vertebral osteomyelitis, all treated with titanium mesh cages. Average follow-up was 44 months (range, 25 to 70 months). Spinal levels included 6 thoracic, 4 thoracolumbar, 9 lumbar, and 2 lumbosacral (L5-S1) lesions. All patients had preoperative serum evaluation, which usually included blood cultures, complete blood count, erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP), in addition to plain radiographs and magnetic resonance imaging. A positive needle biopsy was available in only 2/7 patients (29%), and overall, preoperative pathogen identification was available in only 7/21 patients (33%). All patients were treated postoperatively with a minimum of 6 weeks of intravenous antibiotics, with a specific antibiotic regimen directed toward the postoperative pathogen when identified (17/21 cases). Extensive radiographic evaluation was also performed.ESR and CRP were routinely elevated (18/20 and 11/17 cases respectively), whereas the white blood count was elevated in only 8 out of 21 cases (38%). The average duration of symptoms to diagnosis was approximately 13.6 weeks (range 3 weeks to 10 months). The indications for surgery included neurologic compromise, significant vertebral body destruction with loss of sagittal alignment, failure of medical treatment, and/or epidural abscess. All patients had resolution of infection, as noted by normalization of the ESR and CRP. Further, 16 out of 21 patients also had a significant reduction of pain. There were no deaths or new postoperative neurologic compromise. The most common pathogen was Staphylococcus aureus. Two patients required a second surgery (posterior irrigation and debridement) during the same admission for persistent wound drainage. Radiographically, the average segmental kyphosis (or loss of lordosis) was 11.5 degrees (range, 0 to 24 degrees) preoperatively, and +0.8 degrees (range, -3 to +5 degrees) at latest postoperative follow-up. There was an average of 2.2 mm cage settling (range, 0 to 5 mm) on latest follow-up. There were no instrumentation failures, signs of chronic infection, or rejection.Titanium mesh cages present a viable option for single-stage anterior surgical debridement and reconstruction of vertebral osteomyelitis, without evidence of chronic infection or rejection. When used in conjunction with pedicle screw instrumentation, there is minimal cage settling without loss of sagittal alignment.

Background/Objective: Digital imaging tools for linear and angular measurements facilitate measurement requirements compared to conventional techniques. However, the accuracy of these measurements, especially in spinal trauma, has not been assessed. The objective of this study was to validate current onscreen measurement tools available on picture archiving and communication systems (PACS) for distance and angular measurements in cervical spine plain digital radiographs and computed tomographic (CT) images. Method: A cervical spine sawbone was prepared with radio-opaque markers at known distances and angles. This model was then imaged with digital plain radiographs (spine model at a fixed [24 cm] and variable distance from the X-ray receiver) and CT (1-mm slice thickness) at 4 centers. Using 4 different commercially available digital imaging viewing programs, linear and angular measurements were performed by a musculoskeletal radiologist and 5 spinal surgeons. Results: At only 24 cm (distance from the ana...

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.

Study Design. Literature review. Objectives. Members of the Spine Trauma Study Group evaluated various imaging methods and compiled standardized approaches to making radiographic measurements for the assessment of sacral fractures. Summary of Background Data. The diagnosis of sacral fractures is frequently missed or delayed, and the treatment is controversial, with significant variations in recommendations regarding nonoperative treatment, neural decompression, and internal fixation. A paucity of specific radiographic measurements and criteria exist to aid the clinician in making sound treatment decisions. This may obligate surgeons to base clinical decisions on nonstandardized, nonvalidated recommendations and measures and, in some cases, anecdotal evidence. We think that a critical first step toward valid and optimal clinical decision-making requires an accurate and clear definition of imaging measurement parameters used to evaluate sacral injuries and gather data for future studies. Methods. A review of the English-speaking literature was performed to assess cited radiographic measurement techniques of sacral fractures currently in use. This allowed the formulation of detailed radiographic assessments designed to more reliably describe sacral fracture morphometry. Results. These measurements include: anterior-posterior sacral fracture displacement (axial computed tomography [CT] of the pelvis), vertical sacral fracture displacement (coronal CT reconstruction), anterior-posterior translation and kyphotic angulation (sagittal CT reconstructions), and degree of central canal involvement and foraminal encroachment (axial CT with fine cuts and coronal and sagittal reconstructions). Other radiographic factors that should be considered that may impact treatment outcomes include the level and type of sacral fracture, lumbosacral junction and sacroiliac joint involvement, and associated pelvic ring injury. Conclusions. With adoption of these radiographic guidelines, future studies will have a uniform method in which to describe sacral injuries and therefore allow study of the efficacy of various recommended treatment protocols.

STUDY DESIGN Clinical radiographic and outcomes investigation. OBJECTIVE To investigate clinical and radiographic outcomes for lumbosacral fusion (in patients with spinal deformity) using a combination of bilateral sacral and iliac screws with a minimum 5-year follow-up. SUMMARY OF BACKGROUND DATA To our knowledge, long-term results (>5 years of follow-up) of bilateral S1 screw/bilateral iliac screw fixation have never been published or presented. MATERIALS AND METHODS A total of 67 patients (from an initial consecutive cohort of 81) undergoing lumbosacral fusion with bilateral sacral and iliac screws with a minimum follow-up of 5 years (range 5-10 + 5, average 6 + 3) were analyzed for radiographic outcome and clinical course by an outcome questionnaire (administered at ultimate follow-up) analysis. Patients were divided into 2 groups: group 1, 34 patients with mostly high-grade spondylolisthesis; and group 2, 33 with adult scoliosis fused mostly from the thoracic spine to the sacrum. A true anteroposterior pelvis film was obtained in all patients to assess for sacroiliac joint arthritis, as were standard spine radiographs. Patients were administered Oswestry and directed buttock pain questionnaires at latest follow-up. RESULTS There were no cases of sacral screw failure (i.e., screw loosening, partial screw pullout, or fracture of the sacral screw). There were 5 cases of nonunion at L5-S1. Of the 5 cases, 3 did not have anterior column support at L5-S1. Four of the 5 cases were revised, and, subsequently, 3 achieved union. Iliac screws were removed electively on 1 or both sides in 23 of the patients after 2 years postoperatively because of prominence. There were 7 cases of iliac screw breakage. Iliac screw halos were observed in 29 patients. No sacroiliac osteoarthritis was observed on the true anteroposterior pelvis films. At ultimate follow-up, average visual analog painscale (0-10) score to assess buttock pain was 2.4, and average Oswestry score was 20.1. CONCLUSIONS For high-grade spondylolisthesis and long adult deformity fusions to the sacrum, a montage of bilateral S1 screws and iliac screws were effective in protecting the sacral screws from failure. Pseudarthrosis at L5-S1 was manifested by rod breakage at that level. We saw no evidence of a long-term effect of the iliac screws predisposing the sacroiliac joints to degeneration at follow-up ranging from 5 to 10 years.

Study design Retrospective radiographic analysis of patients with adolescent idiopathic scoliosis (AIS) status after instrumentation removal. Objective To evaluate the effect of instrumentation removal in surgically corrected AIS. Summary of background data Spinal instrumentation is occasionally removed for various reasons, most commonly for postoperative pain or infection, in surgically corrected AIS. The fate of instrumentation removal in adults has been previously reported with documented loss of sagittal alignment. However, to our knowledge, the long-term follow-up after instrumentation removal in AIS has not been reported. Methods We retrospectively reviewed the preoperative, pre-instrumentation removal, postoperative following instrumentation removal, and latest follow-up radiographs of all patients with a primary diagnosis of AIS who underwent instrumentation removal after posterior spinal fusion. There were 21 patients (15 females, 6 males) from 2 institutions, at an average age of 14.8 years (range 9-19), who were originally treated between 1988 and 2002. Instrumentation removal occurred at an average of 2.4 years after surgery (range 8 months to 4 years, 2 months), with an average follow-up of 5.2 years (range 2-11). Fifteen patients underwent removal secondary to pain (2 of these with undetected infection) and 6 for known infection. Evaluation included coronal proximal thoracic, main thoracic, thoracolumbar/lumbar (TL/L), and sagittal T2-T5, T5-T12, T2-T12, T10-L2, T12-S1, and sagittal balance before surgery, before instrumentation removal, at immediate post-removal evaluation, and at latest follow-up. Results There were 12 main thoracic curves (Lenke type 1), 6 double thoracic curves (Lenke type 2), and 3 double major curves (Lenke type 3) in the series. Average proximal thoracic curve was 19.7 degrees (range 5 degrees -35 degrees ), the main thoracic curve 63.3 (range 42 degrees -112 degrees ), and the TL-L curve averaged 31.4 degrees (range 17 degrees -53 degrees ). There was an immediate loss of approximately 4 degrees (range 0 degrees -8 degrees ) in the main thoracic curve and 6 degrees (range 1 degrees -15 degrees ) in the TL/L curve after removal, with continued settling of an additional 6 degrees (10 degrees total, P = 0.002) in the main thoracic curve, and 3 degrees in the TL/L curve (9 degrees total, P = 0.01). There was also a significant difference in the group that underwent instrumentation removal 2 years (main thoracic curve 13 degrees vs. 7 degrees , P = 0.017; TL/L 11 degrees vs. 7 degrees , P = 0.036). There were no significant changes in sagittal curvature or sagittal balance in either group (P > 0.39). Conclusions Instrumentation removal in AIS is not always a benign process because the long-term follow-up of this cohort of patients shows a "settling" effect in the coronal plane of the main thoracic and TL/L curves after instrumentation removal. Interestingly, there was no change in the sagittal plane with time. Parents and patients should be counseled for this result when instrumentation removal is contemplated, and limited removal of focally symptomatic implants should be considered.

STUDY DESIGN An in vitro biomechanical study of different pedicle screw configuration usage on the thoracic spine using a cadaveric model. OBJECTIVES To investigate the degree of motion afforded different pedicle screw configurations in the thoracic spine using a cadaveric model with 2 different degrees of intrinsic stability. SUMMARY OF BACKGROUND DATA Recently, thoracic pedicle screws have become an alternative to hook and wire fixation, and have gained popularity. Clinically, pedicle screw use has ranged from application to every segment, to skipping every other level. There exists no clear consensus as to which strategy is most appropriate. METHODS The load-displacement behavior of 6 different constructs was determined on 8 fresh frozen cadaver spine specimens (T4-T12). Each construct was evaluated on 2 destabilization models, including minimum destabilization (bilateral facetectomy) and maximum destabilization (facetectomy and annulotomy). Pure moments were applied, and the resultant range of motion for each scenario was determined. RESULTS Facetectomy did not significantly destabilize the thoracic spine. Annulotomy and facetectomy created gross instability that rendered testing of this destabilization model impossible. All constructs significantly reduced the range of motion compared to intact or facetectomized specimens (P < or = 0.001). When different constructs were compared to each other, a pattern of continuously increasing stability emerged, with the "maximum" construct being the most stable and "minimum" configuration being the least, with varying degrees of statistical significance. CONCLUSIONS Our results suggest that the most important factor for the acute postoperative stability of spinal fixation is the degree of preoperative or iatrogenic destabilization. The minimum amount of pedicle screws provides adequate stability when there is minimal destabilization of the spine. On the other hand, when anterior column release has been performed or instability exists before surgery, segmental pedicle screw fixation may be necessary to achieve adequate stability.

Object.Disc arthroplasty in the lumbar spine is an alternative to fusion when treating discogenic pain. Its theoretical benefits include preservation of the motion segment and the potential prevention of adjacent-segment degeneration. Despite the need to evaluate the benefit of preserving the adjacent segments after disc replacement, no study has been conducted to assess the ability of magnetic resonance (MR) imaging to depict the adjacent segments in patients who have undergone disc replacement surgery.Methods.Postoperative lumbar MR images were obtained in the first 10 patients in whom a metal-on-metal disc arthroplasty system was used to treat the L4–5 or L5—S1 levels. At the superior adjacent level, the superior endplate and disc space were demonstrated on 90% of the images on both T1-weighted fluid-attenuated inversion-recovery (FLAIR) and T2-weighted sequences despite the presence of artifacts. The inferior endplate at this level was documented on 70% of both T1-weighted FLAIR and T2-weighted sequences. At the level below the disc replacement in patients who underwent L4–5 surgery, the superior endplate was demonstrated on 66.7% of the T1-weighted FLAIR sequences but only 33.3% of the T2-weighted images. The disc space and inferior endplate were depicted on 66.7% of both T1-weighted FLAIR and T2-weighted sequences. Axial images revealed an artifact in every adjacent space except at the L5—S1 level.Conclusions.Based on the results of this pilot study, it appears that sagittal MR imaging can be undertaken to evaluate the adjacent motion segment for degenerative changes following total disc arthroplasty in most patients. This imaging modality will provide an additional measure to assess the long-term efficacy of this intervention compared with other treatment modalities and the natural history of lumbar disc degeneration.

Systems of internal spinal fixation for treatment of lumbar pathology have experienced rapid development over the course of the last 25 years. The resulting variety of spinal instrumentation has allowed for a significant expansion of pathologic conditions that are successfully treated through surgical means. Although different in design and surgical indication, most currently available implantable devices serve a common goal of providing immediate postoperative stabilization to the affected segment and maintaining the enhanced mechanical environment while biologic arthrodesis matures into a successful fusion. The widely expanded armamentarium available to a spine specialist has allowed surgeons to address cases with the evermore challenging biomechanical presentations. However, some of the earlier designs of internal fixation systems did not possess the necessary mechanical properties to meet these requirements, and thus, resulted in an increased rate of complications associated with hardware failure. In 1993, McLain and coworkers 1 reported an overall 36% rateofpediclescrewbendingorbreakagewhentreatinglumbar and thoracolumbar fractures with Cotrel‐Dubousset instrumentation. Since the early 1990s a significant effort has been dedicated to improving material properties and hardware design, thus reducing the implant related complication rate to less than 10%. 2,3 Nonetheless, another important factor contributing to the prolonged longevity of spinal constructs and improved fusion success is the amount offixation strength at the bone‐metal interface. This issue becomes highly significant when treating disorders in elderly individuals, who are expected to comprise up to 30% of the U.S. population by the year 2020. 4 Important to this is an understanding that aging of the human spine is a complex process associated with an overall progressive loss of bone mineral content and development of secondary osteoarthritic changes affecting the functional spinal unit kinematic properties and load-bearing capacity 5 (Fig. 1). The eventual onset ofosteoporosis,definedbytheWorldHealthOrganizationas “a systemic skeletal disease characterized by low bone mass and microarchitectural deterioration, with a consequent increaseinbonefragilitywithsusceptibilitytofracture,”playsa significantroleincompromisingthepotentialeffectivenessof internal fixation, and in certain advanced cases, may altogether eliminate the option of surgical intervention. 6,7 However, with the continuously increasing life-expectancy and quality of life in the mature population of the developed world, adequate methods of treating common spinal disorders in these patients have to be explored. The currently acceptedtechniquesofspinalfixationcanbegeneralizedinto

Radiographic outcome analysis following thoracic fusion of Lenke Type I adolescent idiopathic scoliosis (AIS) curves with segmental pedicle screw fixation.To compare the correctional capacity of monaxial versus multiaxial pedicle screws in a matched cohort of AIS patients.Thoracic pedicle screws provide improved curve correction over hook and wire or hybrid constructs for AIS. Further, both monaxial and multiaxial screws are available, with each offering certain advantages over the other. However, different screw types have not been evaluated against each other.We retrospectively reviewed the preoperative and final postoperative follow-up radiographs of an age- and curve-matched cohort of 35 consecutive Lenke Type I AIS patients. Fifteen were treated with monaxial and 20 were treated with multiaxial pedicle screw constructs. All patients had a minimum 2-year follow-up. The average age at surgery was 14 years 4 months (range, 12-17 years) in the monaxial group and 13 years 8 months (12-16 years) in the multiaxial group. Evaluation included coronal proximal thoracic (PT), main thoracic (MT), and thoracolumbar/lumbar (TL/L) Cobb angles and flexibility indexes, regional sagittal curvature, the sagittal apical rib hump (RH) deformity, the apical vertebral body-rib ratio (AVB-R: ratio of linear measures from left and right apical body to lateral rib), and the apical rib spread distance (ARSD, difference of the sums of the intercostal distances at the five periapical segments measured at the lateral transverse process).There was no statistically significant difference with regard to the preoperative PT curves, MT curves, TL/L curves, flexibility indexes, regional sagittal curvature, AVB-R, or ARSD. The preoperative rib humps were significantly greater in the monaxial screw group (42.4 mm vs. 34.7 mm; P = 0.02). Postoperative follow-up averaged 59.9 months (range, 24-98 months) for the monaxial group and 38.0 months (range, 24-55 months) for the multiaxial group (P0.0001). An average of 7.7 vertebral levels were fused in the monaxial group compared with 7.2 levels in the multiaxial group (P = 0.39). After surgery, both constructs provided excellent instrumented correction of the MT curves (64.9% vs. 60.0% for the monaxial and multiaxial groups, respectively; P = 0.33), as well as good spontaneous correction of the PT (41.3% vs. 40.5%; P = 0.92) and TL/L curves (55.4% vs. 51.7%; P = 0.66). Monaxial screws demonstrated significantly greater absolute (13.9 mm vs. 25.2 mm; P0.0001) and relative (66.1% vs. 24.7%; P0.0001) correction of the apical RH. Additionally, AVB-R (77.9% vs. 54.1%; P = 0.0007) and ARSD (82.8% vs. 69.9%; P = 0.04) corrections were significantly greater in the monaxial group. There were no neurologic deficits or major complications in either group.Both monaxial and multiaxial thoracic pedicle screws provide excellent coronal deformity correction for thoracic fusion of main thoracic AIS. Monaxial screws provide superior derotation and restoration of thoracic symmetry as noted by significantly greater correction of the AVB-R, RH, and ARSD.

Aging spine is prone to osteoporotic fractures that can cause considerable morbidity due to pain and deformity. Most osteoporotic vertebral compression fractures will respond to non-operative therapy that includes pain medications and bracing. For those who are resistant to conservative therapy, vertebroplasty or kyphoplasty can be a viable option. Most recent studies show 88%-96% satisfaction in pain reduction with vertebroplasty. Several studies have also shown similar satisfaction with kyphoplasty. Because these procedures are relatively new, however, indications, long-term effects, and intra-operative and peri-operative complications are not yet fully understood. Reported complications from both vertebroplasty and kyphoplasty are low, but can include increased pain, radiculopathy, spinal cord compression, pulmonary embolism, infection, and rib fractures. In this review, we summarize the current understanding of anatomy, biomechanics, indications, complications, techniques, and new technologies of vertebroplasty and kyphoplasty.

Osteoporosis is a prevalent and treatable disease encountered by the spine surgeon on a regular basis. The following review summarizes the pathogenesis, physiological and biomechanical effects, diagnosis, and medical treatment options for osteoporosis with emphasis on how this disease pertains to the spine.

STUDY DESIGN Analysis of radiographic outcomes following surgical correction of scoliosis. OBJECTIVES To compare the curve correction and derotation following anterior spinal fusion (ASF) versus posterior spinal fusion (PSF) with thoracic pedicle screws. SUMMARY OF BACKGROUND DATA The benefits of ASF in adolescent idiopathic scoliosis include saving distal fusion levels and historically greater correction and derotation compared with PSF. However, comparative studies between ASF and PSF have generally consisted only of posterior hook instrumentation or hybrid constructs, with no direct comparisons between anterior fusion and thoracic pedicle screw (TPS) series. METHODS We performed a retrospective review of the radiographic and medical records of 40 patients (two curve-matched groups) with Lenke Type I main thoracic adolescent idiopathic scoliosis. There were 20 patients who underwent open ASF with single-rod instrumentation with a mean age at surgery of 15 years + 6 months (range, 12-20 years) and 20 patients who underwent PSF with TPS constructs with a mean age at surgery of 13 + 6 (range, 12-15). Radiographic follow-up averaged 44.1 month (24-80) for the ASF group and 55.1 month (25-83) for the PSF/TPS group. We evaluated the sagittal alignment, Cobb angles, rib hump deformity (RH), apical rib spread difference (ARSD), and apical vertebral body-rib ratio (AVB-R), measures of rotation and thoracic torsion, between both groups. RESULTS Before surgery, the main thoracic curve was 55.1 degrees (range, 47-66 degrees) for the ASF group and 52.5 degrees (range, 46-68 degrees ) for the PSF/TPS group (P = 0.16). Additionally, there was no difference in the pelvic tilt curves, thoracic kyphosis, lumbar lordosis, RH, or ARSD. However, there was a slightly greater preoperative thoracolumbar-lumbar (TL/L) curve (34.6 degrees versus 29.5 degrees , P = 0.04) and AVB-R (1.75 versus 1.5, P = 0.003) in the ASF group. After surgery, an average of 6.5 levels (range, 6-8) were fused in the ASF group, compared with 7.7 levels (range, 5-12) in the PSF/TPS group (P = 0.001) or 1.2 additional levels for PSF/TPS. At final postoperative follow-up, spontaneous pelvic tilt curve correction was greater in the ASF group (47% versus 35%), although this difference did not reach statistical significance (P = 0.07). For the main thoracic and TL/L curves, there was greater correction in the PSF/TPS group (62% versus 52%, P = 0.009; and 56% versus 41%, P = 0.03), respectively. Additionally, the PSF/TPS group demonstrated significantly greater RH correction (51% versus 26%, P = 0.005) and AVB-R ratio improvement (73% versus 32%, P < 0.0001). We also noted a trend towards increased correction of the ARSD in the PSF/TPS group (58% versus 32%, P = 0.07). Further, the postoperative thoracic kyphosis decreased 4.4 degrees in the PSF/TPS group (postop avg. 25.0 degrees ) and increased 5.7 degrees (average, 30.6 degrees ) in the ASF group (P = 0.04). CONCLUSIONS In this curve-matched cohort of Lenke Type I curves, PSF with TPS provided superior instrumented correction of main thoracic curves and spontaneous correction of TL/L curves. Perhaps more importantly, PSF/TPS demonstrated improved correction of thoracic torsion and rotation as compared with ASF in terms of RH (P = 0.005) and AVB-R ratio (P= 0.0001), with only one additional spinal segment fused on average.

Background: Enchondromas originating in the epiphyses of long bones are rare. The purpose of the present study was to evaluate the prevalence as well as the radiographic and clinical characteristics of epiphyseal enchondromas among patients who had been referred to the Armed Forces Institute of Pathology and Walter Reed Army Medical Center. Methods: We performed a retrospective review of 761 patients who had been referred to our two institutions over an approximately fifty-five-year period and who received a final diagnosis of enchondroma. All lesions had been biopsied, and the pathological diagnosis had been confirmed. Lesions of the hands, feet, or axial skeleton (253 patients) as well as lesions that appeared to originate in the metaphysis or diaphysis (475 patients) were excluded. Only enchondromas of the long bones that originated in the epiphysis were analyzed. The study group included thirty-three patients (twenty male patients and thirteen female patients) with a mean age of 26.7 years, including eleven patients with open physes. We performed additional descriptive analyses with regard to patient age, gender, lesion location, clinical presentation, and treatment as well as an extensive radiographic analysis. Results: The most common locations were the proximal part of the humerus (ten lesions; 30%) and the distal part of the femur (six lesions; 18%). The most common presenting symptom was pain (twenty-three patients). Radiographic analysis demonstrated extensive matrix mineralization in association with twenty-three lesions. Twenty-eight of the thirty-three lesions were geographically well defined; of these, twenty-one had sclerotic borders, and seven did not. Although all lesions were centered and were predominantly located within the epiphysis, twenty of the thirty-three lesions demonstrated radiographic evidence of metaphyseal extension, including four of the eleven lesions in patients with open physes. Twenty-four lesions extended into the subchondral bone. The mean size of the thirty-three enchondromas in greatest radiographic dimension was 2.7 cm (range, 1.1 to 4.9 cm). Twenty-six of the thirty-three lesions were amenable to surgical treatment with curettage with or without bone-grafting, with only one recurrence. With the limited follow-up available, no lesion underwent sarcomatous degeneration. Conclusions: Epiphyseal enchondromas are rare lesions. Although their biologic behavior appears to mirror that of conventional metaphyseal enchondromas, their proximity to the joint space may lead to more frequent painful symptoms, a propensity for physeal involvement, and the need for earlier definitive surgical intervention. Level of Evidence: Prognostic Level IV. See Instructions to Authors for a complete description of levels of evidence.

With the advent of minimally invasive surgical approaches to the spine, the ability to adequately expose the desired anatomic structures while minimizing the disadvantages of excessive soft tissue stripping, dissection, and prolonged retraction has become increasingly popular. A minimally invasive one- or two-level posterior exposure of the spine is now safely attainable with the latest minimal-access systems that exploit the biomechanics of an adjustable blade retractor. As the clinical use of these developing systems escalates, more outcomes data will become available to determine the safety and value of these minimally invasive procedures.

STUDY DESIGN Descriptive. OBJECTIVE To report a case of a recurrent giant cell tumor (GCT) of the lumbar spine during pregnancy. SUMMARY OF BACKGROUND DATA GCT is a locally aggressive tumor that primarily occurs in young female adults. These tumors rarely present in the spine, recur locally, and may be present during pregnancy because of growth promoting receptors. METHODS A 31-year-old pregnant woman presented to us from Europe at 24 weeks' gestation (G1P1) with severe back pain and an enlarging mass. A large, firm, nontender mass was palpable in the right upper quadrant. Radiographs of the lumbar spine were obtained and revealed a 10-cm x 8 cm x 15 cm expansive bony mass at L2 with vertebral body collapse and junctional kyphosis. Following delivery of a healthy 6 lb. 8 oz. baby, MRI, CT, and full-length standing radiographs were obtained. A needle-guided biopsy showed amorphous bone with numerous giant cells consistent with a GCT. At 6 weeks postpartum, the tumor was resected. RESULTS At 1-year follow-up, there is no evidence of local reoccurrence and the patient is without constitutional symptoms. CONCLUSION This is an unusual presentation of an expanding intra-abdominal mass originating from the lumbar spine during pregnancy. It most likely represents rapid growth of a previous unrecognized recurrence of a GCT. Close observation and follow-up CT scanning are imperative to identify and treat GCTs of the spine before rapid growth occurs.

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 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.

Object The purpose of this study was to evaluate the safety and efficacy of prophylactic inferior vena cava (IVC) filter placement in high-risk patients who undergo major spine reconstruction. Methods In the pilot study, 22 patients undergoing major spine reconstruction received prophylactic IVC filters. These patients were prospectively followed to evaluate complications related to the filter, the rate of deep venous thrombosis (DVT) formation, and the rate of pulmonary embolism (PE). These data were compared with those obtained in a retrospective review for PE in a matched cohort treated at the same institution. At a second institution the treatment guidelines were implemented in 17 patients undergoing complex spine surgery with the same follow-up criteria. In the pilot study, no patient experienced PE (0%), whereas two had DVT (9%). Bilateral DVT developed postoperatively in one patient (associated morbidity rate 4.5%), who required thrombolytic therapy. One patient died of unrelated surgical complications. The PE rate in the matched cohort at the same institution was 12%. At the second institution, no patient had PE, and no complications were noted. Conclusions In this patient population, prophylactic IVC filter placement appears to decrease the PE rate substantially, from 12 to 0%. The placement of IVC filters appears to be a safe and efficacious intervention for prevention of PE in high-risk patients.

Background:Previous studies have demonstrated high rates of intraspinal anomalies in patients with congenital scoliosis; however, various authors have not considered the presence of an isolated hemivertebra to be sufficient reason for further evaluation with magnetic resonance imaging. Consequently

C T g k b a he purpose of this final chapter is to present interesting cases requiring creative or demanding solutions for acropelvic unit (SPU) fixation from several busy spinal reonstruction practices. The pathology represented ranges rom infection, trauma, and degenerative disease to complex pinal deformity and tumor reconstruction. Considering the ide spectrum of pathology, the vast array of instrumentaion available, and the number of possible fixation points in he SPU, it is not surprising that many surgical options are vailable. Although the author’s (M.O.B.) predilection is for liac fixation in any situation requiring adjunctive sacropelvic nit fixation beyond S1, it is not always required. Depending n the biomechanics of the reconstruction, the available soft issue coverage, previous surgery, and available bone stock, ones 1, 2, or 3 fixation may be sufficient for a particular case. Inadequate fixation of the SPU can result in nonunion, instruentation failure, and deformity. Therefore, in this biomechanially challenging environment, more instrumentation rather han less may be better as a rule of thumb when considering xation to the SPU. Concerns regarding prominent distal hardare or sacroiliac joint irritation ought not to deter the spinal econstruction surgeon from utilizing this valuable anatomic eal estate to achieve immediate postreconstruction stabilization f the lumbosacral spine. Iliac fixation can always be removed if t is too prominent or if postoperative complaints develop, sugesting sacroiliac joint irritation. In the author’s experience

I H t d h t l d pondylolysis occurs in approximately 6% of the population, and the incidence may be increasing.1,2 Of these atients, fewer than 50% will develop olisthesis, and the vast ajority will remain asymptomatic with only low-grade lips.1,3,4 Further, many patients who become symptomatic ill respond to conservative measures. Currently, the indications for surgical treatment include ocumented progression of spondylolisthesis, back or leg ain unresponsive to conservative treatment, or dysfuncional gait due to neurologic impairment or severe hamstring ightness. Slips greater than 30 to 50% may be considered a elative indication for surgery dependent on patient age, raiographic stability, and symptoms. For patients with lowrade slips and symptoms refractory to conservative meaures, in situ fusion with or without instrumentation has roduced reliably good clinical results, although fusion rates ave varied.5-8 Whether or not the addition of instrumentaion increases fusion rates and improves clinical outcomes ontinues to be the subject of debate. The surgical treatment of patients with “high-grade” pondylolisthesis, traditionally considered as Meyerding rade III or greater ( 50% listhesis), has been considered ontroversial by some authors.9 Herein, we review the urgical results for the treatment of high-grade sponylolisthesis, with particular attention to methods of saral and sacro-iliac fixation.

Background context Intradiscal electrothermal therapy (IDET) is a new treatment option for chronic discogenic low back pain that is minimally invasive and has demonstrated success rates equal to or better than those for spinal fusion at short-term follow-up. Purpose To report our experience with IDET in the management of chronic discogenic low back pain in active-duty soldiers. Study design/setting Consecutive case series at a US Army medical center. Outcome measures The primary outcome measured was a reported 50% or greater reduction in pain at latest follow-up. Additional outcomes measured included analog pain scores, satisfaction, complications, duty status and subsequent spinal surgery. Methods Between 1999 and 2001, 41 active-duty soldiers (34 men, 7 women) underwent IDET for chronic discogenic low back pain unresponsive to nonoperative therapy. Data were collected through clinic chart review and follow-up questionnaires. Success was defined as a stated “50% decrease in pain” from baseline. Results During the study period, 36 of 41 patients underwent a single trial of IDET, and the remaining 5 underwent two trials of IDET. Only the results of the 36 patients who underwent one trial of IDET were used for statistical analysis. All 36 patients were available for follow-up at 6 months, whereas only 31 patients (86%) were reached for final follow-up (average, 29.7 months; range, 24 to 46). The success rate was 47% (17 of 36) at 6 months and 16% (5 of 31 patients) at latest follow-up. Although overall success rates were low, 20 of 31 soldiers (65%) had a persistent decrease in their analog pain score (average decrease of 2.5±1.6 on a 10-point scale), with 52% having 2-point or greater decrease. Nineteen of 31 soldiers (61%) were still on active duty at a minimum of 24 months after IDET. There were five transient complications (16%) from IDET, all reported within the first month. Seven of 31 soldiers (23%), all male, went on to spinal surgery within 24 months of failed IDET. Conclusions IDET is not a substitute for spinal fusion in the treatment of chronic discogenic low back pain in active-duty soldiers. Our reasonable early results diminished with time and up to 20% of patients report worsening of baseline symptoms at final follow-up. IDET will prove its role in the treatment of chronic discogenic low back pain as more outcome data are obtained, but for now we consider it, at best, an antecedent rather than alternative to spinal fusion.

Study design A biomechanical study of cadaver vertebrae to determine the feasibility of obtaining adequate thoracic pedicle screw fixation in a salvage situation. OBJECTIVE To investigate the ability to safely place a thoracic pedicle screw with adequate maximal insertional torque (MIT) using the anatomic trajectory (AT) (directed along the true anatomic axis of the pedicle) after purposeful failure/medial violation of the pedicle using the straight-forward trajectory (ST) (paralleling the vertebral endplate). Summary and background data Failure to place a pedicle screw at an intended segment of the thoracic spine may theoretically render the level uninstrumented, because pedicle hook placement may be unsafe and the transverse process may be fractured. An alternative pedicle screw insertion technique, if biomechanically sound in this situation, may present an excellent alternative for critical instrumentation levels. Materials and methods Fixed-head 5.0 mm stainless steel pedicle screws were placed using the ST and MIT was recorded after determination of bone mineral density (BMD) with dual-energy radiograph absorptiometry (DEXA) scanning. Purposeful screw malposition and critical pedicle wall failure were performed, followed by salvage placement of the screw using the AT. Insertional torque was recorded for each screw revolution with a digital torque wrench and MIT was again recorded to compare the MIT obtainable in the salvage situation. Results BMD for the vertebrae averaged 732 g/cm2 (620-884 g/cm2). The MIT for the straight-forward technique without pedicle violation was 2.61 +/- 0.19 (SE) inches per pound, whereas that of the salvage procedure after medial wall violation (AT) averaged 1.62 +/- 0.12 (SE) inches per pound. Therefore, the AT achieved 62% (P = 0.027) of the fixation strength (in terms of MIT) during salvage after failure/medial violation of the pedicle. MIT for both the ST* and AT trajectories correlated with both global BMD of the vertebrae (*P = 0.008; P = 0.004) and regional BMD of the vertebral body (*P = 0.044; P = 0.023). Conclusions The AT achieved 62% (P = 0.027) of the MIT during salvage of a failed/violated pedicle. BMD correlated with both the initial and salvage techniques. The AT provides adequate fixation in a salvage situation and may be safely used to provide segmental fixation at critical levels.

Study design A biomechanical study on cadaveric thoracic vertebrae using pullout strength, insertional torque, and bone mineral density to determine the optimal sagittal trajectory of thoracic pedicle screws. Objective To perform a biomechanical study on cadaveric thoracic vertebrae using insertional torque, pullout strength, and bone mineral density to determine the optimal biomechanical sagittal trajectory for placement thoracic pedicle screws. We compared the straight-forward (paralleling the vertebral endplate) with anatomic trajectory (directed along the true anatomic axis of the pedicle). Methods Thirty cadaveric thoracic vertebrae were harvested and evaluated with dual-energy x-ray absorptiometry to assess bone mineral density. Matched, fixed-head pedicle screws were then randomly assigned by side and placed using the straight-forward or anatomic technique under fluoroscopic visualization while recording the maximum insertional torque. Pullout strength testing was then performed. Results The maximum insertional torque for the straight-forward technique was 2.58 +/- 0.14 (SE) in pounds, whereas the anatomic technique averaged 1.86 +/- 0.14 (SE) in pounds (P = 0.0005). The maximum insertional torque at the neurocentral junction for the straight-forward technique averaged 1.89 +/- 0.17 (SE) in-lbs. (73% of maximum insertional torque), whereas the anatomic trajectory averaged 1.39 +/- 0.11 (SE) in pounds (75% of maximum insertional torque) (P = 0.007). The average pullout strength using a straight-forward trajectory was 611 +/- 50 (SE) N compared to the anatomic trajectory, which averaged 481 +/- 54 (SE) N (P = 0.034). The pullout strength correlated with mean bone mineral density for both the straight-forward (r = 0.461, P = 0.027) and anatomic (r = 0.598, P = 0.004) techniques. Conclusions The straight-forward technique results in a 39% increase in maximum insertional torque and a 27% increase in pullout strength compared to the anatomic technique. The maximum insertional torque at the neurocentral junction resulted in a 36% increase using the straight-forward technique versus the anatomic trajectory. Bone mineral density directly correlates with pullout strength for both techniques.

Background context: Many studies have reported on the use of anterior instrumentation for thoracolumbar scoliosis and more recently thoracic scoliosis. However, the optimal construct design remains an issue of debate. Purpose: To optimize construct design and enhance implant survival until a successful spinal arthro- desis is achieved. Study design: This study evaluated the effect of rod diameter and intervertebral cages on construct stiffness and rod strain using a long-segment, anterior thoracic scoliosis model with varying levels of intervertebral reconstruction. Methods: Sixteen fresh-frozen calf spine specimens (T1 to L1) were divided into two groups based on rod diameter reconstruction (4 mm and 5 mm). Testing included axial compression, anterior flexion, extension and lateral bending with variations in the number and level of intervertebral cage reconstructions: apical disc (one), end discs (two), apical and end discs (three), all seven levels (seven). Multisegmental construct stiffness and rod strain were determined and normalized to the intact specimen for analysis. Results: The seven-level intervertebral cage construct showed significantly greater stiffness in axial compression for both the 4-mm (366% increased stiffness) and 5-mm (607% increased stiffness) rod groups (p .05). In flexion, similar results were obtained for the 4-mm construct (p Conclusions: Intervertebral cages at every level significantly improved construct stiffness compared with increasing rod diameter alone. Moreover, cages markedly decreased rod strain, and when structural interbody supports were not used, axial compression created the greatest rod strain.

This study describes a new arthroscopic method using a whip-stitch technique for treating a displaced type III tibial eminence fracture. A 12-year-old girl who sustained a displaced type III tibial eminence fracture was treated with arthroscopic fixation using the Arthrosew disposable suture device (Surgical Dynamics, Norwalk, CT) to place a whip stitch into the anterior cruciate ligament (ACL). The Arthrex ACL guide (Arthrex, Naples, FL) was used to reduce the avulsed tibial spine fragment. Sutures were then passed through the tibial tunnel and secured over a bony bridge with the knee in 20 degrees of flexion. At 9 months, the patient has a full range of motion with normal Lachman and anterior drawer testing, and she has returned to competitive basketball. Radiographs show complete fracture healing. KT-1000 and isokinetic testing at 9-month follow-up show only minimal side-to-side differences. The Arthrosew device provides a significant advantage in the treatment of type III and IV fractures of the tibial eminence by obtaining arthroscopic fixation within the substance of the ACL, thus obviating arthrotomy and hardware placement. This technique also restores the proper length and tension to the ACL, and provides a simplified, reproducible method of treatment for this injury.

Techniques to improve segmental fixation have advanced the ability to correct complex spinal deformity. The purpose of instrumentation is to correct spinal deformity or to stabilize the spine to enhance the long-term biological fusion. The ultimate goal of spinal deformity surgery is the creation of a stable, balanced, pain-free spine centered over the pelvis in the coronal and sagittal planes. The minimum number of segments should be fused. These concepts remain challenging in the setting of deformity and instability. Successful results can be obtained if the surgeon understands the technology available, its capabilities, biological limitations, and the desired solution. The authors prefer to use thoracic pedicle screws when treating patients with spinal deformity because they provide greater corrective forces for realignment. This allows shorter-segment constructs and the possibility of true derotation in correction. In this article the authors focus on the use of thoracic transpedicular screw fixation in the management of complex spinal disorders and deformity.

Study design A case series of patients with hemimetameric shift. Objectives To describe the radiographic and physical findings as well as treatment provided to a subset of patients with congenital scoliosis. Summary of background data Hemimetameric segmental displacement, or hemimetameric shift, is a clinical entity defined by two contralateral hemivertebrae separated by at least one normal vertebra. Although the entity is briefly described in textbooks, there are no published series to date. Methods From 1974 to 2000, 186 cases of congenital scoliosis were identified from two referral centers. Of these, 27 cases (15%) of hemimetameric shift were identified. Medical records and radiographs were reviewed, as well as magnetic resonance imaging when available. Results There were an average of 2.9 hemivertebrae per patient (range 2-6) with the following distribution: T1-T6 (29), T7-T11 (28), T12-L1 (10), L2-L4 (11), and L5 (1). The average curve magnitude at presentation was 28 degrees (range 9 degrees -55 degrees). Nine patients required surgery-most commonly with involvement of the thoracolumbar or lumbosacral junction. Eleven patients also had associated anomalies to include Klippel-Feil syndrome (3), Goldenhar syndrome (2), imperforate anus (2), tracheoesophageal fistula (2), and a single kidney (2). There was only one patient who had an abnormal magnetic resonance imaging (1 out of 17; 6%). Conclusions Hemimetameric shift is a common finding in congenital scoliosis. Hemivertebrae are most commonly found in the thoracic spine; however, surgical intervention is most commonly observed when the caudal hemivertebrae is located from the thoracolumbar to lumbosacral junction. The incidence of abnormal magnetic resonance imaging findings is low (6%).

Pigmented villonodular synovitis is a slowly progressive lesion that originates from the synovial membrane of the tendons and joints 1-6. It most frequently occurs in the hip and knee joints as a monoarticular proliferative process but may arise in any joint 1,2,7,8. However, the cervical spine is an uncommon site of involvement, with the cases of only twelve patients previously reported in the English-language literature, to our knowledge 9-15. The lesion was in proximity to the first and second cervical levels in only one of these patients 15 ; the lesions in the remaining patients involved the subaxial cervical spine. We describe a patient who had a unique case of pigmented villonodular synovitis involving not only the facet joint at the first and second cervical level but also the first and second cervical vertebrae. A forty-six-year-old woman was seen because of a nine-month history of neck pain. She reported that she had no history of trauma, paresthesia, loss of motor control, bowel or bladder dysfunction, or constitutional symptoms. The pain was exacerbated with flexion and extension movements of the neck as well as during bouts of sneezing or coughing. Anti-inflammatory medications provided minimal pain relief. On physical examination, she could extend the neck only 20° to 30°. Neurological examination showed normal motor and sensory findings, with reflexes bilaterally symmetrical, and a normal gait. Roentgenograms of the neck showed a lytic lesion that had destroyed the joint between the right lateral masses of the first and second cervical vertebrae and had extended into the second cervical vertebral body (see Appendix). A thin sclerotic margin bordered the lesion. No central stenosis was present. Computerized tomographic scans showed invasion of the lesion into the right lateral masses of both the …