Classification of coronal imbalance in adult scoliosis and spine deformity: a treatment-oriented guideline.

INTRODUCTION: In adult spinal deformity (ASD), sagittal imbalance and sagittal malalignment have been extensively described in the literature during the past decade, whereas coronal imbalance and coronal malalignment (CM) have been given little attention. CM can cause severe impairment in adult scoliosis and ASD patients, as compensatory mechanisms are limited. The aim of this paper is to develop a comprehensive classification of coronal spinopelvic malalignment and to suggest a treatment algorithm for this condition. METHODS: This is an expert's opinion consensus based on a retrospective review of CM cases where different patterns of CM were identified, in addition to treatment modifiers. After the identification of the subgroups for each category, surgical planning for each subgroup could be specified. RESULTS: Two main CM patterns were defined: concave CM (type 1) and convex CM (type 2), and the following modifiers were identified as potentially influencing the choice of surgical strategy: stiffness of the main coronal curve, coronal mobility of the lumbosacral junction and degeneration of the lumbosacral junction. A surgical algorithm was proposed to deal with each situation combining the different patterns and their modifiers. CONCLUSION: Coronal malalignment is a frequent condition, usually associated to sagittal malalignment, but it is often misunderstood. Its classification should help the spine surgeon to better understand the full spinal alignment of ASD patients. In concave CM, the correction should be obtained at the apex of the main curve. In convex CM, the correction should be obtained at the lumbosacral junction. These slides can be retrieved under Electronic Supplementary Material.

Contribution of Dynamic Surgical Guidance to the Accurate Placement of Pedicle Screws in Deformity Surgery: A Retrospective Case Series.

OBJECTIVE: We assessed the contribution of a dynamic surgical guidance (DSG) probe in the accurate placement of thoracic and lumbar pedicle screws (PSs) in patients with spinal deformity. METHODS: A retrospective review was performed of 98 patients (104 procedures) with various spinal deformities, who had received posterior instrumentation with PSs inserted using either DSG or the conventional free-hand (FH) technique. A total of 882 PSs were inserted using DSG (DSG group) and 603 using the FH technique (FH group). The DSG probe was preferably chosen for large osteosyntheses and severe deformities. Two neurosurgeons, unaware of the surgical groups, reviewed all the intraoperative computed tomography scans and assessed all the PS placements. RESULTS: Of the PSs used, 95.4% in the DSG group and 92.2% in the FH group were correctly placed (P = 0.0136). The difference in screw placement accuracy was greater at the thoracic level (DSG group, 92.5%; vs. FH group, 87.0%; P = 0.0310) than at the lumbar level (DSG group, 98.0%; vs. FH group, 95.4%; P = 0.0385). Severe (>4 mm) lateral breaches occurred in 24 cases (4.0%) in the FH group but in only 5 (0.6%) in the DSG group (P < 0.0001). No severe medial breach was observed in either group. CONCLUSIONS: Despite having more patients with severe deformities in the DSG group, PS insertion was significantly more accurate with DSG. This technique also reduced the severe unacceptable lateral misplacement rate (>4 mm) and, consequently, the incidence of intraoperative screw revisions even in patients with severe deformities.

Complications and risk factors of primary adult scoliosis surgery: a multicenter study of 306 patients.

STUDY DESIGN: A multicentric retrospective study on primary adult scoliosis patients operated on between 2002 and 2007. A 3-step statistical analysis was performed to describe the incidence of complications, the risk factors, and the reoperation risk with survival curves for the entire cohort. OBJECTIVE: To describe complication rate and risk factors as well as survival curves associated with adult primary scoliosis surgery in patients aged 50 years or older. SUMMARY OF BACKGROUND DATA: Adult deformity surgery is classically associated with a high rate of complications. The identification of risk factors for developing such complications is consequently of major interest as well as survival curves that can provide useful information on reoperation risks. Although many reports exist in the literature, the cohorts analyzed are often heterogeneous and the actual prevalence of complications varies widely. This study represents to our knowledge the largest series on adult patients aged 50 years or older operated for the first time for lumbar or thoracolumbar scoliosis and excluding every other possible diagnosis. METHODS: A retrospective review of prospectively collected data from 6 centers in France. A total of 306 primary lumbar adult or degenerative scoliosis patients older than 50 years undergoing surgery between 2002 and 2007 were included. Demographics, comorbidities, x-ray parameters, surgical data, and complications were analyzed. Statistical analysis was performed to obtain correlations and risk factors for developing complications. Reoperation risk was calculated with Kaplan-Meier survival curves. RESULTS: A total of 306 patients aged 63 years (range, 50-83), with 83% women. Mean follow-up was 54 months. Mean Cumulative Illness Rating Scale score was 5 (range, 0-26). Main curve was 50° (range, 4-96) with apex between T12 and L2. Ten percent of patients had anterior surgery only, 18% had double anteroposterior approach, and 72% had posterior surgery only. Seventy-four percent (226 patients) had long fusions of 3 or more levels and 44% (134 patients) were fused to the sacrum. Forty percent (122 patients) had a decompression performed and 18% had an osteotomy. There were 175 complications for 119 patients (39%). No cases of death or blindness were reported. General complication rate was 13.7%, early infection occurred in 4% (12 patients), and late infection occurred in 1.2%. Neurological complications were present in 7% with 2 cases (0.6%) of late cord-level deficits and 12 reoperations (4%). Prevalence of mechanical complications was 24% (73 patients), with 58 patients (19%) needing a reoperation. Risk factors for mechanical or neurological complications were number of instrumented vertebra (P ≤ 0.01) fusion to the sacrum (P ≤ 0.001), pedicle subtraction osteotomy (PSO) (P = 0.01), and a high preoperative pelvic tilt of 26° or more (P ≤ 0.05). Kaplan-Meier survival curves showed reoperation risk of 44% at 70 months. Long fusion risk was 40% at 50 months and fusions to the sacrum reoperation risk was 48% at 49 months. CONCLUSION: Overall complication rate was 39%, and 26% of the patients were reoperated for mechanical or neurological complications. Risk factors include number of instrumented vertebra, fusion to the sacrum, PSO, and preoperative pelvic tilt of 26° or more. There is a 44% risk of a new operation in the 6-year-period after the primary procedure.

Spino-pelvic alignment after surgical correction for developmental spondylolisthesis.

This study is a retrospective multi-centre analysis of changes in spino-pelvic sagittal alignment after surgical correction of L5-S1 developmental spondylolisthesis. The purpose of this study was to determine how sagittal spino-pelvic alignment is affected by surgery, with the hypothesis that surgical correction at the lumbo-sacral level is associated with an improvement in the shape of the spine and in the orientation of the pelvis. Whether L5-S1 high grade spondylolisthesis should or should not be reduced remains a controversial subject. A popular method of treatment has been in situ fusion, but studies have reported a high rate of pseudarthrosis, slip progression and persistent cosmetic deformity. Spinal instrumentation with pedicle screws has generated a renewed interest for reduction, but the indications for this treatment and its effect on spino-pelvic alignment remain poorly defined. Recent evidence indicates that reduction might be indicated for subjects with an unbalanced (retroverted or vertical) pelvis. This is a retrospective multi-centre analysis of 73 subjects (mean age 18 +/- 3 years) with developmental spondylolisthesis and an average follow-up of 1.9 years after reduction and posterior fusion with spinal instrumentation or cast immobilisation. Spinal and pelvic alignment were measured on standing lateral digitised X-rays using a computer software allowing a very high inter and intra observer reliability. Pelvic incidence was unaffected by surgery. The most important changes were noted for grade, L5 Incidence, lumbo-sacral-angle, and lumbar lordosis, which all decreased significantly towards normal adult values. At first evaluation, pelvic tilt, sacral slope and thoracic kyphosis appeared minimally affected by surgery. However, after classifying subjects into balanced and unbalanced pelvis, significant improvements were noted in pelvic alignment in both the sub-groups, with 40% of cases switching groups, the majority from an unbalanced to a balanced pelvis alignment. The direction and magnitude of these changes were significantly different by sub-group: sacral slope decreased in the balanced pelvis group but increased in the unbalanced group, while pelvic tilt values did the opposite. While pelvic shape is unaffected by attempts at surgical reduction, proper repositioning of L5 over S1 significantly improves pelvic balance and lumbar shape by decreasing the abnormally high lumbar lordosis and abnormal pelvic retroversion. These results emphasise the importance of sub-dividing subjects with high grade developmental spondylolisthesis into unbalanced and balanced pelvis groups, and further support the contention that reduction techniques might be considered for the unbalanced retroverted pelvis sub-group.

Lumbar disc degeneration below a long arthrodesis (performed for scoliosis in adults) to L4 or L5.

A retrospective analysis of adults treated with long instrumented fusion for scoliosis from the thoracic spine proximally to L4 or L5. To evaluate the long-term clinical outcomes as well as radiological changes in distal unfused mobile segments and to evaluate factors that may predispose to distal disc degeneration and/or poor outcome. A total of 151 mobile segments in 85 patients (65 female), mean age 43.2 (range 21-68), were studied. Curve type, number of fused levels and pelvic incidence were recorded. Clinical outcome was measured using the Whitecloud function scale and disc degeneration using the UCLA disc degeneration score. Spinal balance, local segmental angulations and lumbar lordosis were measured pre- and post-operatively as well as at the most recent follow up--mean 9.3 years (range 7-19). A total of 62% of patients had a good or excellent outcome. Eleven had a poor outcome of which ten underwent extension of fusion--five for pain alone, three for pain with stenosis and two for pseudarthroses. Pre-operative disc degeneration was often asymmetric and was slightly greater in older patients. Overall, there was a significant deterioration in disc degeneration (P < 0.0001) that did not correlate with clinical outcome. Disc degeneration correlated with the recent sagittal balance (Anova F = 14.285, P < 0.001) and the most recent lordosis (Anova F = 4.057, P = 0.048). The post-operative sagittal balance and local L5-S1 sagittal angulation correlated to L4 and L5 degeneration, respectively. There was no correlation between degeneration and age, pre-operative degenerative score, pelvic incidence, sacral slope, number of fused levels or distal level of fusion. Disc degeneration does occur below an arthrodesis for scoliosis in adults which does not correlate with clinical outcome. The correlation of loss of sagittal balance with disc degeneration may be as a result of degeneration causing the loss of balance or vice versa, i.e. sagittal imbalance causing degeneration. Immediate post-operative imbalance correlates with degeneration of the L4/5 disc, which may imply the latter.

Evaluation of the osteogenesis and biodegradation of porous biphasic ceramic in the human spine.

The histological reports on porous biphasic calcium phosphate ceramic (PBC) in human spine are limited. The osteogenesis and biodegradation of PBC are insufficiently known in human. In present study, the undecalcified histological study was carried out on 20 samples retrieved from posterior spinal fusion in order to reveal the osteogenesis and biodegradation of the PBC in human spine. The quantitative study was performed in 14 samples with sufficient size. Newly formed bone was found in all the samples. More new bone was formed in those samples closely in contact with autogenous bone. The PBC degradation particles were present both in the macrophages and around the tissue. However, those phenomena were highly variable among the samples. New bone formation increased with time and decreased with age. The PBC degradation decreased with age, but it did not differ greatly with time. New bone formation was higher and the residual material was lower in the fusion group than that in non-fusion group. The PBC is a kind of osteoconductive material and do not transform into new bone after a relatively long time. The PBC should be well mixed with the autogenous bone in order to achieve high new bone colonization. The PBC degradation particles and related active phagocytotic activity have been noted.

Clinical, radiological and histological study of the failure of cervical interbody fusions with bone substitutes.

Few histological studies on bone substitutes in human cervical spine are available and the biological processes of bone substitutes are not well documented. The authors studied four failure cases of cervical interbody fusion: two cases with hydroxyapatite (HA), one case with beta-tricalcium phosphate ceramic (beta-TCP) and one case with xenograft (bovine bone). Clinical data showed that all the patients experienced neck pain with or without numbness of upper extremity due to fusion failure. Successful fusions were achieved after the salvage surgeries in which autograft were used. Radiographs showed that radiolucent lines were present in all cases. Two HA substitutes fractured without complications. One of them sank into the vertebral body. Some small beta-TCP fragments were found under the microscope. Histological study demonstrated only a few newly formed bones at the interface of the substitutes. The fragments of HA were encapsulated by fibrous tissue. The degradation process and bone regeneration were more active in beta-TCP than in HA. The intertrabecular spaces of bovine bone were filled with fibrous tissue. The results suggest that a porous calcium phosphate ceramic with special design might assure bone ingrowth and meet the mechanical requirements in cervical interbody fusion. The complications of these materials in the cervical spine should be highlighted.

Long-term results of Schollner costoplasty in patients with idiopathic scoliosis.

STUDY DESIGN: A retrospective analysis of patients with idiopathic scoliosis treated with Schollner costoplasty. OBJECTIVE: To evaluate the long-term effects of Schollner costoplasty on rib hump and respiratory function SUMMARY BACKGROUND DATA: Costoplasty is an established technique to improve chest wall deformity in patients with scoliosis. Concerns have been raised of the long-term effects of costoplasty on respiratory function in adults. No long-term studies of this procedure exist. METHODS: A total of 25 patients with idiopathic scoliosis rib hump deformity underwent Schollner costoplasty. There were 12 patients who underwent surgery on the convexity alone, and 13 underwent additional "concave surgery" (6 Silastic [Dow Corning Corp., Midland, MI] implants, 7 concave lengthenings). Five patients underwent simultaneous spinal arthrodesis. The remaining patients underwent delayed procedures (0.4 -19 years) following the index operation. Vital capacity (VC) and rib hump were measured before and after surgery, and at each attendance thereafter. RESULTS: Mean follow-up was 10.8 years. Average reduction in rib hump was 38 mm at 6 months and 29 mm at long-term. There was no significant difference in the preoperative and long-term VC (P = 0.4), although at 6 months after surgery, there was a significant reduction in VC of 5.1%(P = 0.03). Subgroup analysis (convex only, concave lengthening, concave Silastic) revealed a similar pattern for rib hump correction and maintenance of VC in the long-term for each group. There was no significant difference between adults and adolescents in terms of both the reduction in rib hump and the VC (P = 0.2 and 0.3) CONCLUSIONS: Rib hump correction and lung function are preserved in the long-term following Schollner costoplasty in both adults and adolescents.

Spondylolisthesis, pelvic incidence, and spinopelvic balance: a correlation study.

STUDY DESIGN: A retrospective study of the sagittal alignment in developmental spondylolisthesis. OBJECTIVES: To investigate the role of pelvic anatomy and its effect on the global balance of the trunk in developmental spondylolisthesis. SUMMARY OF BACKGROUND DATA: Pelvic incidence (PI) is a fundamental anatomic parameter that is specific and constant for each individual, and independent of the three-dimensional orientation of the pelvis. Recent studies have suggested an association between a high PI and patients with isthmic spondylolisthesis. METHODS: The lateral standing radiographs of the spine and pelvis of 214 subjects with developmental L5-S1 spondylolisthesis were analyzed with a dedicated software allowing the calculation of the following parameters: pelvic incidence (PI), sacral slope (SS), pelvic tilt (PT), lumbar lordosis (LL), thoracic kyphosis (TK), and grade of spondylolisthesis. All measurements were done by the same individual and compared to those of a cohort of 160 normal subjects. Student's tests were used to compare the parameters between the curve types and Pearson's correlation coefficients were used to investigate the association between all parameters (alpha = 0.01). RESULTS: PI, SS, PT, and LL are significantly greater (P < 0.01) in subjects with spondylolisthesis, while TK is significantly decreased. PI has a direct linear correlation (0.41-0.65) with SS, PT, and LL. Furthermore, the differences between the two populations increase in a direct linear fashion as the severity of the spondylolisthesis increases. CONCLUSIONS: Since PI is a constant anatomic pelvic variable specific to each individual and strongly determines SS, PT, and LL, which are position-dependent variables, this study suggests that pelvic anatomy has a direct influence on the development of a spondylolisthesis.Study participants with an increased pelvic incidence appear to be at higher risk of presenting a spondylolisthesis, and an increased PI may be an important factor predisposing to progression in developmental spondylolisthesis.

Kyphoplasty.

A variant of vertebroplasty known as "kyphoplasty" has been suggested for correcting vertebral compression fractures. A balloon placed inside the vertebral body is inflated to create a cavity, thereby restoring vertebral body height and allowing low-pressure cement injection. This procedure is gaining popularity in the United States. Over 1000 patients had been treated by the end of 2000. However, kyphoplasty is costly (chiefly because the balloon is disposable) and has not been evaluated in carefully designed studies. Although retrospective findings have been reported as highly promising, they are not sufficient to validate this procedure. The principle is innovative and the procedure deserves further investigation as a potentially effective means of correcting loss of vertebral height. Furthermore, use of a bone substitute instead of cement deserves investigation.

Instrumentación vertebral en animales

Presentamos el trabajo realizado en forma experimental en animales (ovejas), en los cuales hemos realizado una osteosíntesis vertebral por vía posterior, con un sistema Cotrel-Dubousset pediátrico. Trabajamos con un grupo de 20 ovejas, las cuales fueron divididas en dos grupos. Un primer grupo (10) fueron ovejas testigo, las cuales nos han permitido establecer criterios de normalidad en lo referido a la estructura de sus discos y articulaciones. El segundo grupo (10) fueron instrumentadas por vía posterior, siendo en este grupo, 5 de ellas, ovejas en crecimiento (3 meses de edad) y las otras 5 ovejas adultas, donde además de la instrumentación efectuamos la artrodesis con injerto autólogo. Se presenta en esta comunicación la metodología de trabajo empleada y las conclusiones a las que arribamos

Instrumentación vertebral en animales

Presentamos el trabajo realizado en forma experimental en animales (ovejas), en los cuales hemos realizado una osteosíntesis vertebral por vía posterior, con un sistema Cotrel-Dubousset pediátrico. Trabajamos con un grupo de 20 ovejas, las cuales fueron divididas en dos grupos. Un primer grupo (10) fueron ovejas testigo, las cuales nos han permitido establecer criterios de normalidad en lo referido a la estructura de sus discos y articulaciones. El segundo grupo (10) fueron instrumentadas por vía posterior, siendo en este grupo, 5 de ellas, ovejas en crecimiento (3 meses de edad) y las otras 5 ovejas adultas, donde además de la instrumentación efectuamos la artrodesis con injerto autólogo. Se presenta en esta comunicación la metodología de trabajo empleada y las conclusiones a las que arribamos