Sagittal Curvature Research Articles

Posterior three-column osteotomies for the treatment of rigid thoracic kyphosis – a case series

ObjectiveTo evaluate the results and complications of a series of patients who underwent three-column osteotomy using the posterior approach for correction of complex cases of rigid dorsal kyphotic deformity. MethodsReview of clinical records and images of 15 consecutive cases of pedicle subtraction osteotomies, bone-disk-bone osteotomies, or vertebral column resection, recording the etiology, type and level of osteotomy, extension of fixation, complications, and pre- and post-surgical measurements of the sagittal curves and pelvic parameters. ResultsSix pedicle subtraction osteotomies were performed, one of which in two adjacent vertebrae, as well as two bone-disk-bone osteotomies and seven vertebral column resection, two of which were performed in two adjacent vertebrae. The mean correction was 39.3° for the angular kyphosis and 33.9° for dorsal kyphosis. The corrections were similar regardless of the kind of osteotomy, the operated spinal segment, or the approach in one or two levels, but this may be a sample effect.Eight complications were observed in six patients (40% of cases): two medical complications, five early and one late surgical complication (over 90 days after surgery). There were three reoperations within less than one year from the initial surgery and one case of persistent paraparesis. Clinical complications were resolved without sequelae. There was no significant loss of correction during the segment, except in two cases of major mechanical failure due to a junctional segment fracture. ConclusionDespite being complex and aggressive procedures, prone to various complications, osteotomies with resection of the three columns are highly effective in the correction of rigid kyphotic deformities and safe enough to justify its use in selected cases.

Reproducibility of sagittal radiographic parameters in adolescent idiopathic scoliosis—a guide to reference values using serial imaging

Background ContextKnowledge of sagittal radiographic parameters in adolescent idiopathic scoliosis (AIS) patients has not yet caught up with our understanding of their roles in patients with adult spinal deformity. It is likely that more emphasis will be placed in restoring sagittal parameters for AIS patients in the future. Therefore, we need to understand how these parameters may vary in AIS to facilitate management plans. PurposeThis study aimed to determine the reproducibility of sagittal spinal parameters on lateral film radiographs in patients with AIS. Study Design/SettingThis was a retrospective, comparative study conducted in a tertiary health-care institution from January 2013 to February 2016 (3-year period). Patient SampleAll AIS patients who underwent deformity correction surgery from January 2013 to February 2016 and had two preoperative serial lateral radiographs taken within the time period of a month were included in the study. Outcome MeasuresRadiographic sagittal spinal parameters including sagittal vertical axis (SVA), cervical lordosis (CL), thoracic kyphosis (TK), thoracolumbar alignment (TL), lumbar lordosis (LL); standard spinopelvic measurements such as pelvic incidence (PI), pelvic tilt (PT), sacral slope (SS); as well as end and apical vertebrae of cervical, thoracic, and lumbar curves were the outcome measures. MethodsAll patient data were pooled from electronic medical records, and X-ray images were retrieved from Centricity Enterprise Web. Averaged X-ray measurements by two independent assessors were analyzed by comparing two radiographs of the same patients performed within a 1-month time period. Chi-squared and Wilcoxon signed-rank tests were used for categorical and continuous variables. ResultsThe study cohort comprised 138 patients, 28 men and 110 women, with a mean age of 15 years (range 11–20). Between the two lateral X-rays, there was a mean difference of 0.79 cm in SVA (p<.001), 0.70° in LL (p=.033), and 0.73° in PT (p=.010). In the combined Lenke 1 and 2 subgroup, there was a similar 0.77 cm (p=.002), 0.79° (p=.009), and 1.49° (p=.001) mean difference in SVA, LL, and PT, respectively. Additionally, there was also a 1.85° (p=.009) and 1.76° (p=.006) mean difference seen in TL and SS, respectively. The overall profile of the sagittal curves remained largely similar, with only the lumbar apex shifting from L3 to L4 during the first and the second X-rays, respectively (p<.001). This occurred for the combined Lenke 1 and 2 subgroup as well (p<.001). ConclusionMost radiographic sagittal spinal parameters in AIS patients are generally reproducible with some variations up to a maximum of 4°. This natural variation should be taken into account when interpreting these radiographic sagittal parameters so as to achieve the most accurate results in surgical planning.

Comparison of sagittal spinal curvatures and pelvic tilt in highly trained athletes from different sport disciplines

The aim of this study was to compare the thoracic and lumbar curvatures and pelvic tilt in relaxed standing and maximal trunk flexion among highly-trained young athletes from three different sports disciplines. Thirty-two male canoeists, 30 male kayakers and 24 male tennis players were recruited for the study. The Spinal Mouse® system was used to measure the thoracic and lumbar sagittal spinal curvatures and pelvic tilt in relaxed standing and maximal trunk flexion in sitting with flexed (McRae &amp;amp; Wright test) and extended knees (sit-and-reach test). Significant differences were found in maximal trunk flexion tests among athletes. Kayakers and canoeists showed increased anterior pelvic tilt compared to tennis players in the McRae &amp;amp; Wright (p&amp;lt;.01) and decreased posterior pelvic tilt in the sit-and-reach (p&amp;lt;.001) tests; however, canoeists had increased posterior pelvic tilt compared to kayakers in the sit-and-reach test (p&amp;lt;.01). Canoeists had increased thoracic kyphosis curvature compared to kayakers (p&amp;lt;.01) and tennis players (p&amp;lt;.001) in the sit-and-reach test. Spinal sagittal curvatures and pelvic tilt in relaxed standing did not show significant differences. In&amp;nbsp;conclusion, specific sport training may be associated with adaptations in the sagittal spinal curvatures and pelvic tilt when maximal trunk flexion positions are performed.

The Development of a Representative Porcine Early-Onset Scoliosis Model With a Standalone Posterior Spinal Tether

Study DesignIn vivo analysis in a porcine model. ObjectivesTo develop a porcine experimental scoliosis model representative of early-onset scoliosis (EOS) with the use of a radiopaque ultra-high molecular weight polyethylene (UHMWPE) posterior spinal tether. Summary of Background DataLarge animal experimental scoliosis models with substantial growth potential are needed to test new fusionless scoliosis correction techniques. Previously described scoliosis models involve rib procedures, which violate the thoracic cage and affect subsequent corrective procedures. Models omitting these rib procedures have experienced difficulties in producing persistent three-dimensional structural deformities representative of EOS. MethodsScoliosis was induced in 14 immature pigs using an asymmetric posterior radiopaque UHMWPE spinal tether fixated to an offset device at lumbar and thoracic levels. Radiographs were taken at 2-week intervals, and frontal and sagittal Cobb angles were measured. A tether release was performed at the 10-week follow-up, and the animals were observed for another 10 weeks. ResultsFour animals had complications (infections and/or screw breakout) and were excluded from the study. Eight animals developed progressive curves with a mean frontal Cobb angle of 62°. A thoracic lordosis (34°) and a thoracolumbar kyphosis (22°) formed. CT analysis, acquired prior to tether release, showed a mean vertebral rotation of 37° at the apex with a mean vertebral wedge angle of 10°. After tether release, the frontal Cobb angles decreased to 46° at the 20-week follow-up. Sagittal curvature was not substantially affected after tether release. ConclusionsWe describe a large animal scoliosis model, which exhibits a substantial deformity in three planes without the use of rib procedures additional to a posterior spinal tether. The created deformities showed persistence after tether release. With the management of infection and enhancement of instrumentation stability, the creation of a valid model for testing new devices in fusionless scoliosis surgery seems feasible. Level of EvidenceLevel V.

Predicting Cervical Alignment Required to Maintain Horizontal Gaze Based on Global Spinal Alignment.

A retrospective cohort. The aim of this study was to investigate the cervical alignment necessary for the maintenance of horizontal gaze that depends on underlying thoracolumbar alignment. Cervical Sagittal Curve (CC) is affected by thoracic and global alignment. Recent studies suggest large variability in normative CC ranging from lordotic to kyphotic alignment. No previous studies have assessed the effect of global spinal alignment on CC in maintenance of horizontal gaze. Patients without previous history of spinal surgery and able to maintain their horizontal gaze while undergoing full body imaging were included. Patients were stratified on the basis of thoracic kyphosis (TK) into (<30, 30-40, 40-50, and >50) and then by SRS-Schwab sagittal vertical axis (SVA) modifier into (posterior alignment SVA <0, aligned 0-50, and malaligned >50 mm). Cervical alignment was assessed among SVA grade in TK groups. Stepwise linear regression analysis was applied on random selection of 60% of the population. A simplified formula was developed and validated on the remaining 40%. In each TK group (n = 118, 137, 125, 197), lower CC (C2-C7) was significantly more lordotic by increased Schwab SVA grade. T1 slope and cervical SVA significantly increased with increased thoracolumbar (C7-S1) SVA. Upper CC (C0-C2) and mismatch between T1 slope and CC (T1-CL) were similar. Regression analysis revealed LL minus TK (LL-TK) as an independent predictor (r = 0.640, r = 0.410) with formula: CC = 10- (LL-TK)/2. Validation revealed that the absolute difference between the predicted CC and the actual CC was 8.5°. Moreover, 64.2% of patients had their predicted C2-C7 values within 10° of the actual CC. Cervical kyphosis may represent normal alignment in a significant number of patients. However, in patients with SVA >50 and greater thoracic kyphosis, cervical lordosis is needed to maintain the gaze. Cervical alignment can be predicted from underlying TK and lumbar lordosis, which may be clinically relevant when considering correction for thoracolumbar or cervical deformityLevel of Evidence: 3.

Intra and interrater reliability of spinal sagittal curves and mobility using pocket goniometer IncliMed® in healthy subjects

Radiographic examination is the gold standard to evaluate spine curves, but ionising radiations limit routine use. Non-invasive methods, such as skin-surface goniometer (IncliMed®) should be used instead. To evaluate intra- and interrater reliability to assess sagittal curves and mobility of the spine with IncliMed®. a reliability study on agonistic football players. Thoracic kyphosis, lumbar lordosis and mobility of the spine were assessed by IncliMed®. Measurements were repeated twice by each examiner during the same session with between-rater blinding. Intrarater and interrater reliability were measured by Intraclass Correlation Coefficient (ICC), 95% Confidence Interval (CI 95%) and Standard Error of Measurement (SEM). Thirty-four healthy female football players (19.17 ± 4.52 years) were enrolled. Statistical results showed high intrarater (0.805-0.923) and interrater (0.701-0.886) reliability (ICC > 0.8). The obtained intra- and interrater SEM were low, with overall absolute intrarater values between 1.39° and 2.76° and overall interrater values between 1.71° and 4.25°. IncliMed® provides high intra- and interrater reliability in healthy subjects, with limited Standard Error of Measurement. These results encourage its use in clinical practice and scientific research.

Effect of mono- or bisegmental lordosizing fusion on short-term global and index sagittal balance: a radiographic study.

Sagittal balance is widely recognized as an important outcome factor in reconstructive spinal surgery for lumbar degenerative conditions. However, its role in short segmental fixation is unknown. The aim of this study was to evaluate the preoperative and short-term postoperative spino-pelvic balance after short (1 or 2 levels) lordosizing lumbar fusion for degenerative disc disease (DDD). Twenty-six consecutive patients (13 males and 13 females) undergoing mono- or bisegmental lordosizing lumbar fusion (XLIF/TLIF) for lumbar DDD were included in the study. Clinical parameters were retrospectively collected from charts. Preoperative and early postoperative (6 weeks and 3 months) full-spine EOS X-rays were evaluated. Spinal parameters evaluating sagittal curvatures, pelvic orientation, global sagittal and coronal alignment, spino-pelvic balance, index level segmental lordosis and disc height were measured and statistically analyzed. A total of 16 TLIF and 10 XLIF procedures were performed. Eighteen were mono- and 8 were bisegmental fixations for a total of 34 fused segments. Seven patients (26.9%) showed a preoperative sagittal imbalance (defined as SVA>50 mm); 7 patients presented preoperative severe pelvic retroversion (defined as PT>20°) and 1 patient presented both. Disc height, intervertebral angle and segmental lordosis at the operated level significantly increased after surgery (P<0.01). No postoperative significant change in global sagittal alignment (SVA, TPA, T1SPi, T9SPi), pelvic orientation (SS, PT), coronal alignment, lumbar and L4-S1 lordosis and thoracic kyphosis have been observed. Mono- and bisegmental lordosizing fusion techniques, as XLIF and TLIF, are able to restore disc height and improve segmental lordosis. However they do not allow restoration of sagittal balance or improvement of compensatory mechanisms. A limited spinal reconstructive surgery on symptomatic levels can be reasonably proposed to patients with hidden or evident sagittal imbalance with any short-term radiographic impact.

Spino-pelvic coronal and sagittal alignment in Down's syndrome patients

Orthopedic conditions are common in subjects with Down's syndrome. Few studies have investigated spinal deformities in the frontal and sagittal planes but none have analyzed the pelvic parameters in relation to the spine. The aim was to describe the scoliotic deformities and sagittal spino-pelvic alignment in subjects with Down's syndrome. Forty-one subjects (13 F, 28 M, age 17.4 A 6.2 years) with Down's syndrome, without history of cardiac surgery, had undergone full body biplanar X rays with 3D reconstructions of their spine and pelvis. Subjects were age and gender-matched to 41 asymptomatic subjects (13 F, 28 M, age 17.7 A 5.4 years). Spinal and pelvic parameters were calculated: thoracic kyphosis (TK- T1–T12 and T4–T12), lumbar lordosis (LL- L1–L5 and L1–S1), coronal Cobb angle, axial rotation of the apical vertebra, pelvic incidence (PI), pelvic tilt (PT) and sacral slope (SS). Spino-pelvic parameters were compared between both groups using Student's or Mann-Whitney's tests. Since scoliosis can influence sagittal spinal curvatures, ANCOVA test was used to compare kyphosis and lordosis between groups while eliminating the frontal Cobb angle as a confounding factor. Significance level was set at 0.05. Significant differences on spino-pelvic parameters were found between the Down's syndrome and control group: pelvic incidence (53° vs. 45°, p = 0.01), sacral slope (48° vs 37°, p = 0.01), pelvic tilt (5° vs 8°, p = 0.009), L1–L5 (54° vs 44°, p = 0.001), L1–S1 (69° vs 57°, p = 0.01), T4–T12 (29° vs 38°, p = 0.001), number of patients where the Cobb angle was > 10° (20 subjects vs 8 subjects, p = 0.005), Cobb angle (11.5° vs 8°, p = 0.001), apical vertebral rotation (7° vs 4°, p = 0.001). After adjusting for Cobb angle, T1–T12, T4–T12, L1–L5 and L1–S1 remained significantly different between groups ( p

Quantitative morphometric study of the subaxial cervical vertebrae end plate

Background ContextCervical disc arthroplasty has been gradually adopted as an alternative for the treatment of cervical degenerative disease. However, there is a large discrepancy between footprints of currently available cervical disc prostheses and anatomic dimensions of cervical end plates. PurposeThis study aimed to accurately and comprehensively quantify the three-dimensional (3D) anatomic morphology of the cervical vertebral end plate and provide a theoretical basis for designing appropriate disc prostheses. Moreover, we introduced a novel geometric and mechanical model for 3D reconstruction techniques of the cervical end plate. Study DesignA descriptive study of the geometry of the middle and lower cervical vertebral end plates in cadaveric spines was carried out. MethodsA total of 138 cervical vertebral end plates were digitized using an optical 3D range scanning system, and then each end plate was reconstructed using the digitized image. For each end plate, the morphologic characteristics of six surface curves and the end plate concavity depth were symmetrically chosen and depicted. ResultsThe cranial end plates (relative to the disc) were concave and the caudal end plates were relatively flat at all disc levels, with mean concavity depths of 2.04 and 0.69 mm, respectively. For the caudal end plates, the end plate concavity apex was most often (81.42%) located in the posterior portion, whereas in the cranial end plates, the distribution was relatively even. For the sagittal curves, the foremost point and the rearmost point on the middle curve had a more forward position than those in the left curve and the right curve. Regarding the frontal plane curves, the length of the middle curve was longer than that of the anterior curve and posterior curve. For the cranial end plate, the maximal mean depth was the middle curve, whereas for the caudal end plate, the maximum depth was the posterior curve. ConclusionsThere is marked morphologic asymmetry, in that the cranial end plate is more concave than the corresponding caudal end plate. In the sagittal plane, the caudal end plates are aerofoil-shaped, whereas the cranial end plates are arc-shaped. In the transverse plane, the end plates are kidney-shaped. These morphologic characteristics of cervical vertebral end plates should be taken into consideration when designing cervical devices, such as artificial discs.

Preoperative and Postoperative Photographs and Surgical Outcomes of Patients With Kyphosis.

A retrospective clinical study was performed. The aim of the study was to show patients their pre- and postoperative body photographs, and determine the effect on postoperative patient satisfaction for thoracic and thoracolumbar sharp and round angular kyphosis. Previous studies have reported the normative values of pelvic sagittal parameters and the classification of normal patterns of sagittal curvature, but no study has investigated and compared the clinical photographs of sharp and round kyphosis. In patients who underwent surgery for thoracic and thoracolumbar sharp and round angular kyphosis, whole spine anteroposterior and lateral radiographs, and clinical photographs were obtained preoperatively and at the final follow-up. Pelvic and spinal parameters were measured, and the pre- and postoperative photographs were shown to patients. The Scoliosis Research Society 22r (SRS22r) and Short Form 36 surveys were administered to all patients, and the scores were analyzed. Thirty-eight patients diagnosed with kyphosis (mean age 19.6 yr, mean follow-up duration 26.4 mo) were divided into two groups: sharp (18 patients, mean age 20.1 yr) and round (20 patients, mean age 19.6 yr) kyphosis. There was no difference between values in the sharp and round groups in terms of age, follow-up duration, and Risser score (P > 0.05). In both groups, the subscores for pain, self-image, mental health, and satisfaction, except for the function/activity score, and the total score of the SRS22r survey were, however, significantly different between pre- and postoperative photographs. In addition, there was no significant difference between the two groups in any SRS22r domain and Short Form 36 scores. The surgical treatment of kyphosis was uniformly associated with improved quality of life, regardless of the kyphosis type. Thus, showing patients their pre- and postoperative photographs may enhance patient satisfaction, as measured by SRS22r scores. 4.

Two-staged Correction of Severe Congenital Scoliosis Associated With Intraspinal Abnormalities.

A retrospective study. To analyze the efficacy and safety of perioperative halo-gravity traction as an adjunct to posterior vertebral column resection (PVCR) in the treatment of patients with severe congenital scoliosis and coexisting asymptomatic intraspinal pathologies (diastematomyelia and/or tethered cord). Few reports to our knowledge review the use of perioperative halo-gravity traction and PVCR in this patient population. A total of 17 patients with a minimum 2-year follow-up who underwent PVCR using perioperative halo-gravity traction were analyzed. Patients were analyzed by age at date of examination (range, 11-23 y; mean, 14.4 y), sex (7 male, 10 female), major coronal curve magnitude (range, 108-149 degrees; average, 125 degrees), major sagittal curve magnitude (range, 72-118 degrees; average, 91 degrees). Complications related to halo traction and PVCR were reviewed. Radiographic outcomes demonstrated Cobb angle of major curve had an average correction of 28% after halo traction and it measured 53 degrees (range, 42-84 degrees) at the last follow-up, for a 58% correction. Maximal kyphosis improved to 58 degrees (range, 43-76 degrees) at ultimate follow-up. There were no permanent neurological deficits in this series. The study results suggested that surgical treatment for intraspinal abnormality may be unnecessary in asymptomatic patients with severe congenital scoliosis who are undergoing scoliosis corrective surgery. PVCR combined with perioperative traction is a safe and effective alternative for such patients.

Osteotomias posteriores de três colunas para tratamento de cifose dorsal rígida – Série de casos

ObjectiveTo evaluate the results and complications of a series of patients who underwent three‐column osteotomy using the posterior approach for correction of complex cases of rigid dorsal kyphotic deformity. MethodsReview of clinical records and images of 15 consecutive cases of pedicle subtraction osteotomies, bone‐disc‐bone osteotomies, or vertebral column resection, recording the etiology, type and level of osteotomy, extension of fixation, complications, and pre‐ and post‐surgical measurements of the sagittal curves and pelvic parameters. ResultsSix pedicle subtraction osteotomies were performed, one of which in two adjacent vertebrae, as well as two bone‐disc‐bone osteotomies and seven vertebral column resection, two of which were performed in two adjacent vertebrae. The mean correction was 39.3° for the angular kyphosis and 33.9° for dorsal kyphosis. The corrections were similar regardless of the kind of osteotomy, the operated spinal segment, or the approach in one or two levels, but this may be a sample effect.Eight complications were observed in six patients (40% of cases):two medical complications, five early and one late surgical complication (over 90 days after surgery). There were three reoperations within less than one year from the initial surgery and one case of persistent paraparesis. Clinical complications were resolved without sequelae. There was no significant loss of correction during the segment, except in two cases of major mechanical failure due to a junctional segment fracture. ConclusionDespite being complex and aggressive procedures, prone to various complications, osteotomies with resection of the three columns are highly effective in the correction of rigid kyphotic deformities and safe enough to justify its use in selected cases.

Three-dimensional reconstructions of Lenke 1A curves

Three-dimensional imaging was performed to identify if Lenke 1A curves could be reclassified in subgroups to improved orthopedic or surgical treatment of adolescent idiopathic scoliosis. It seems that multitude of 3D reconstructions can exist in Lenke 1A curves. With his classification Lenke introduces new parameters in radiographic analysis of idiopathic scoliosis like frontal lumbar and thoracic sagittal modifiers. Scoliosis is defined as a three dimensional deformity in frontal, sagittal and horizontal plane. The spine is considered as an heterogeneous beam, and is modeled as a deformable wire along which vertebrae are beads rotating about the wire. Each vertebra can rotate about the 3D spinal curve. 3D spinal curve is compound of plane regions connected together by zones of transition. The 3D spinal curve is uniquely flexed along the plane regions. The objective of this study was to identify if all Lenke 1A curves could have the same 3D representation. Biplanar radiographic examination with successive exposures (frontal and sagittal) or with EOS system, coupled with photogrammetric reconstructions, may be used for reconstructing the 3D spinal curve. In definitive, we obtain the 3D reconstruction and the regional plans with their parameters. To become familiar with the Lenke classification, we classified 223 antero-posterior radiographs and profile then compared our results: 4 independent readers (2 familiar with scoliosis and 2 no). Patient's characteristics, measurements (Cobb angles in the plan region, cervical, thoracic and lumbar sagittal curves, pelvic parameters and election planes characteristics) were recorded. A total of 63 consecutive Lenke 1A patients were included (mean age of 11.3 years for 47 girls and 16 boys). Thoracic Cobb angle was between 14° and 70° (mean 36.5°). Pelvic incidence was between 26° and 78° (mean 52.8°) and pelvic tilt between −6° and 29° (mean 9.8°). In most of cases, we find 4 torsion planes instead in 43% instead of 3 in asymptomatic subjects and the rotation of these was very disparate. Lenke 1A curves could be represented in a multitude of representations. The 3D representations of idiopathic scoliosis have to enter in our daily practice for the analysis and the orthopedic or chirurgical treatment of this one.

Does the type of sagittal spinal shape influence the clinical results of lumbar disc arthroplasty?

IntroductionIt has been suggested that the indication for lumbar total disc replacement (LTDR) takes into account the local parameters, such as the type of disc disease demonstrated on MRI and the presence or absence of facet joint osteoarthritis. The type of preoperative sagittal curvature could also be taken into account. This study reports the clinical results of LTDRs depending on the type of sagittal spinal alignment. Material and methodsEighty patients were included in this prospective study, with a mean age of 41.7years (range, 27–56years). The clinical analysis took into account the lumbar VAS, the Oswestry Disability Index (ODI), and the preoperative frequency of painkiller use, at 1year and at the last follow-up. The satisfaction index, return to work, and willingness to undergo the same treatment were also collected. The radiological study included the analysis of lumbar-pelvic parameters to distribute the patients according to the Roussouly classification. ResultsThe mean follow-up was 59.1months (range, 14–96months). The type 1 group included four cases. Reduction of the VAS, the ODI score, and the frequency of painkiller use at the last follow-up were significant in type 2 and 3 patients, and non-significant for type 4. Eighty-five percent of type 2 patients and 87.5% of type 3 patients were satisfied or very satisfied with the surgery versus only 68% of the type 4 patients. In addition, 63% of the type 4 patients declared they would be willing to undergo the same treatment again versus 85% of the type 2 patients and 82.5% of the type 3 patients. It should also be noted that 67% of the patients in this series returned to work. Discussion and conclusionThis study underscores the influence of the type of sagittal curvature on the clinical results of LTDR, with type 4 patients showing inferior clinical results because of a higher rate of residual lower back pain. The indication in LTDR should be reconsidered for discogenic lower back pain in type 4 patients.

Effects of inter-individual lumbar spine geometry variation on load-sharing: Geometrically personalized Finite Element study

There is a large, at times contradictory, body of research relating spinal curvature to Low Back Pain (LBP). Mechanical load is considered as important factor in LBP etiology. Geometry of the spinal structures and sagittal curvature of the lumbar spine govern its mechanical behavior. Thus, understanding how inter-individual geometry particularly sagittal curvature variation affects the spinal load-sharing becomes of high importance in LBP assessment. This study calculated and compared kinematics and load-sharing in three ligamentous lumbosacral spines: one hypo-lordotic (Hypo-L) with low lordosis, one normal-lordotic (Norm-L) with normal lordosis, and one hyper-lordotic (Hyper-L) with high lordosis in flexed and extended postures using 3D nonlinear Finite Element (FE) modeling. These postures were simulated by applying Follower Load (FL) combined with flexion or extension moment. The Hypo-L spine demonstrated stiffer behavior in flexion but more flexible response to extension compared to the Norm-L spine. The excessive lordosis stiffened response of the Hyper-L spine to extension but did not affect its resistance to flexion compared to the Norm-L spine. Despite the different resisting actions of the posterior ligaments to flexion moment, the increase of disc compression was similar in all the spines leading to similar load-sharing. However, resistance of the facet joints to extension was more important in the Norm- and Hyper-L spines which reduced the disc compression. The spinal curvature strongly influenced the magnitude and location of load on the spinal components and also altered the kinematics and load-sharing particularly in extension. Consideration of the subject-specific geometry and sagittal curvature should be an integral part of mechanical analysis of the lumbar spine.

Factors favoring regain of the lost vertical spinal height through posterior spinal fusion in adolescent idiopathic scoliosis.

Height gain is a common beneficial consequence following correction surgery in adolescent idiopathic scoliosis (AIS), yet little is known concerning factors favoring regain of the lost vertical spinal height (SH) through posterior spinal fusion. A consecutive series of AIS patients from February 2013 to August 2015 were reviewed. Surgical changes in SH (ΔSH), as well as the multiple coronal and sagittal deformity parameters were measured and correlated. Factors associated with ΔSH were identified through Pearson correlation analysis and multivariate regression analysis. A total of 172 single curve and 104 double curve patients were reviewed. The ΔSH averaged 2.5 ± 0.9 cm in single curve group and 2.9 ± 1.0 cm in double curve group. The multivariate regression analysis revealed the following pre-operative variables contributed significantly to ΔSH: pre-op Cobb angle, pre-op TK (single curve group only), pre-op GK (double curve group only) and pre-op LL (double curve group only) (p < 0.05). Thus change in height (in cm) = 0.044 × (pre-op Cobb angle) + 0.012 × (pre-op TK) (Single curve, adjusted R2 = 0.549) or 0.923 + 0.021 × (pre-op Cobb angle1) + 0.028 × (pre-op Cobb angle2) + 0.015 × (pre-op GK)-0.012 × (pre-op LL) (Double curve, adjusted R2 = 0.563). Severer pre-operative coronal Cobb angle and greater sagittal curves were beneficial factors favoring more contribution to the surgical lengthening effect in vertical spinal height in AIS.

Multi-objective analysis for assessing simultaneous changes in regional spinal curvatures under backpack carriage in young adults

Change in sagittal spinal curvature from the neutral upright stance is an important measure of the heaviness and correctness of backpack use. As current recommendations, with respect to spinal profile, of backpack load thresholds were based on the significant curvature change in individual spinal region only, this study investigated the most critical backpack load by assessing simultaneously the spinal curvature changes along the whole spine. A motion analysis system was used to measure the curvature changes in cervical, upper thoracic, lower thoracic and lumbar regions with backpack load at 0, 5, 10, 15 and 20% of body weight. A multi-objective goal programming model was adopted to determine the global critical load of maximum curvature change of the whole spine in accordance with the maximum curvature changes of the four spinal regions. Results suggested that the most critical backpack load was 13% of body weight for healthy male college students.Practitioner Summary: As current recommendations of backpack load thresholds were based on the significant curvature change in individual spinal region only, this study investigated the backpack load by considering simultaneously the spinal curvature changes along the whole spine. The recommendation, in terms of the global critical load, was 13% of body weight for healthy male college students.

Pelvic Incidence: The Great Biomechanical Effort.

Medical textbooks present the pelvis and the spine as distinct entities-an unfortunate practice that does not reflect the crucial and critical role that the pelvis plays in regulating spino-pelvic alignment. Researchers are working to delineate this role. Dubousset proposed the concept of the 3-dimensional pelvic vertebra, which suggested that the pelvis is just another caudal vertebra of the spine, and that analysis of the spine requires simultaneous analysis of pelvic morphology. To quantify pelvic morphology, Legaye introduced the pelvic incidence angle (PI) and espoused the theory that this angle regulates sagittal curvature of the spine. The PI is formed from 2 lines: line 1, perpendicular to the sacrum from the midline of the sacral plate, aims to quantify spatial orientation and dictate the lumbar curve; line 2, extending from the midline of the sacrum to the midpoint between femoral heads, illustrates the importance of sacral position inside the pelvis (SDC Figure 1, http://links.lww.com/BRS/B99).

Influence of Lumbar Lordosis Restoration on Clinical Outcome in Degenerative Lumbar Patients from the “Pre-Balance” Period: Ex Post Analysis of Spinal Parameters Restoration and Clinical Outcome in a Medium Follow-Up

Introduction Restoration of spinal balance is a widely accepted principle of spinal surgery planning. There is a huge amount of data supporting the correlation of clinical outcome and the restoration of theoretical physiological curves of the spine. Flat or hypolordotic fixations are rarely seen today, but there is someone who claims that spinal balance principles are too often pushed to extremes and, surprisingly, there is still some resistance to accept the routinary application of these concepts in the “simple” degenerative surgery, claiming that in short fixations for degenerative lumbar spinal disease it is not mandatory to be strict in the restoration of correct, theoretical spinal parameters to achieve satisfactory clinical results. In this study we present a homogeneous population of patients, operated by a single surgeon in a 3 years time, 7 to 10 years ago, with homogeneous degenerative pathology and similar constructs (2 to 4-level fixations). The peculiarity of this study is that all the patients have been operated regardless to spinal parameters restoration, because at the time of surgery the presurgical planning of spinal curves was not being sistematically adopted. The population is therefore a kind of spontaneous randomization, with patients with a good restoration of spinal theoretical curves and patient who didn't get any correction of sagittal curves. Material and Methods 36 patients with homogeneous diagnosis of degenerative spinal disease, operated by a single surgeon with a 2 to 4-level fixation until 2010 has been selected. ODI and Prolo scales has been used for direct clinical evaluation. The mean last follow-up was 4 years 4 months, with a minimum of 3 years. Radiological assessment has been performed by lumbar standing XRays AP and LL pre and postop, and PI-LL mismatch and the difference between theoretical lordosis and effective postoperative lordosis have been calculated. Statistical evaluation used Spearman correlation test between PI-LL mismatch and clinical scales values. Results Statistical correlation exists between clinical scale values and PI-LL mismatch. As a qualitative result, we observed that the higher is the difference between theoretical lordosis and effective postsurgical lordosis, the higher is the incidence of construct failure. Conclusion According to the results of this study, respect of the spinal balance principles seems to be helpful to achieve good clinical results in a medium follow-up for lumbar degenerative patients. These results come from a dataset that is not culturally influenced by spinal balance principles, coming from the past. Additionally, the single-surgeon, single-observer and single-center experience is somehow minimizing the confounding factors that usually affects this kind of studies.

Thoracic Volume Progressively Decreases in a Virtual Osteoporotic Vertebral Wedging Model with Increasing Severity of Kyphotic Deformity

Introduction Osteoporotic vertebral fractures commonly result in increased kyphotic angle. Several studies have shown that compared with controls increasing severity of osteoporotic kyphosis significantly decreases volumetric parameters of pulmonary function such as vital capacity. However the effect on the thoracic volume has been less fully studied. With the ability to accurately model thoracic volumes, we are now capable of virtually modeling the effect of increasing kyphosis on thoracic volume through the computer graphical software, Blender. We hypothesize the computed thoracic volume measured from a 3D virtual model decreases with progression of kyphosis from 50 to 100 degrees and the wedging fracture vertebrae only occur in sagittal plane. Methods Free opensource Blender software was used to create threedimensional thorax models with normal coronal and sagittal balance. By virtually wedging the vertebral bodies, the virtual osteoporotic models were progressively deformed by 10 degrees from 50100 degrees of kyphosis. Thoracic volume was simulated and measured via shrinkwrap modifier (Blender built-in function) applied to a sphere-shaped object within the virtual thoracic cavity. Results Virtual wedging of vertebral bodies was necessary to achieve virtual progression of sagittal curve. As kyphotic angle increased, more vertebral segments had to be virtually wedged. Thoracic volume in the virtual adult thorax with a 50 degrees kyphosis was 3643cc. The thoracic volumes approximately decreased in a linear fashion by means of 6.4% for every 10 degrees more of kyphosis. The final thoracic volume was 2472cc at 100 degrees of kyphosis, which was a 32.2% decrease in volume from baseline. Conclusion As the deformity progresses from 50 to 100 degrees, there is an overall 32.2% decrease in thoracic volumes. The decrease appears approximately linear. Although there is not a direct relationship between thoracic volume and pulmonary functions, adequate thoracic volume is a necessary condition for adequate pulmonary function. This study helps establish the relative magnitude of thoracicvolume decrease based on the sagittal Cobb angle.