Loss of cervical sagittal alignment worsens the cervical spinal lesions in patients with Hirayama disease.

OBJECTIVE: To quantify the cervical sagittal alignment in patients with Hirayama disease (HD) and to investigate the effect of loss of cervical sagittal alignment upon the cervical spinal lesions in HD. METHODS: Cervical sagittal alignments were measured in 253 HD patients and 63 healthy subjects by C2-C7 Cobb and a modified method of Toyama et al. Motor unit number estimation (MUNE) was performed in bilateral abductor pollicis brevis (APB) in all HD patients, and 31 patients further underwent cervical diffusion tensor imaging (DTI). RESULTS: Compared with healthy subjects, HD patients showed lower C2-C7 Cobb (P < 0.05), and 83.4% patients showed loss of cervical lordosis (cervical straight or kyphosis), which was greater than healthy subjects (55.6%, P < 0.05). Compared with lordotic/straight group, patients with cervical kyphosis showed lower MUNE values and greater single motor unit potential (SMUP) in bilateral APB, and higher apparent dispersion coefficient (ADC) and lower fractional anisotropy were observed at C4/C5 level in the latter than the former (P < 0.05). C2-C7 Cobb was associated with both C4/C5 ADC and bilateral SMUP (P < 0.05). CONCLUSIONS: Most HD patients showed loss of cervical sagittal alignments, and both MUNE and DTI detections demonstrated a positive correlation between loss of cervical sagittal alignments and cervical spinal lesions in HD. These findings supported that loss of cervical sagittal alignments may worsen motor impairments in HD. Therefore, it is necessary for clinicians to be aware of restoring cervical sagittal alignments during HD treatment.

Diffusion properties of asymptomatic lumbar intervertebral discs in a pediatric cohort: a preliminary study of apparent diffusion coefficient.

PURPOSE: To explore the apparent diffusion coefficients of intervertebral discs in an asymptomatic pediatric cohort. METHODS: We conducted a prospective MRI study of the lumbar spine from below the thoracolumbar junction to the lumbosacral junction on 12 subjects (mean age 13 y.o.) with no spinal pathology or spinal posture disorder. MRI was carried out using a 1.5 T machine with acquisitions realized both in sagittal and coronal planes. First, disc hydration was determined, and then, diffusion-weighted images were obtained using an SE single-shot echo-planar sequence. Apparent diffusion coefficients (ADC) of anterior annulus fibrosus (AAF), nucleus pulposus (NP) and posterior annulus fibrosus (PAF) were measured in the sagittal plane. RESULTS: Averaged hydration of 0.27 SD 0.03 confirmed the asymptomatic nature of discs. Average scaled values of ADC were 0.46 SD 0.01, 0.22 SD 0.09 and 0.18 SD 0.03 for NP, AAF and PAF, respectively. ADC of NP were almost constant along the spine; PAF values show a slight increase in the thorax-sacrum direction, while AAF values showed a pronounced decrease. Locally, ADC of AAF was higher compared to ADC PAF values below the thoracolumbar junction and it reversed for subjacent discs. CONCLUSIONS: In our knowledge, our study provided the first diffusive properties of asymptomatic intervertebral discs in an adolescent cohort. ADC of NP was slightly higher than adults'. ADC evolutions of AAF were correlated with lordosis concavity which pointed out the role of compressive strain on fluid transport properties. This study could furnish information about segment homeostasis for exploration of pediatric spinal pathologies.

Homozygous deletion of MYADML2 in cranial asymmetry, reduced bone maturation, multiple dislocations, lumbar lordosis, and prominent clavicles.

A null mutation in a patient can facilitate phenotype assignment and uncovers the function of that specific gene. We present five sibs of a consanguineous Pakistani family afflicted with a new syndrome with an unusual combination of skeletal anomalies including cranial asymmetry, fused sagittal sutures deviating from the medial axis, mandibular prognathia, maxillary hypoplasia, misaligned and crowded teeth, delayed bone age, multiple dislocations, hypoplastic and malpositioned patellae, humeral intracondylar fissures, scapular dyskinesis, long limbs, lumbar lordosis, protruding chest, prominent clavicles, short 5th digital rays, and ventral transverse digital creases plus features of cutis laxa. We mapped the disease gene locus to a 3.62-Mb region at 17q25.3 and identified a homozygous deletion of maximal 7.3 kb deduced to totally inactivate MYADML2 and downstream gene PYCR1, biallelic variants in which cause autosomal recessive cutis laxa (ARCL). All five affected sibs had the most common features of ARCL but not many of the less common ones. We attributed the anomalies not typical for ARCL to MYADML2 deficit, because no other genetic defect possibly a candidate to underlie the skeletal phenotype was found. MYADML2 is a gene of unknown function, has not been studied, and has not been associated with disease. Our findings present a possible phenotype for MYADML2 deficit that includes impaired bone patterning and maturation, definitely show that the gene is not essential for survival, and provide a start point for future studies on the function of MYADML2 protein. Detection of new patients is needed to confirm and delineate MYADML2-deficiency phenotype.

Earlier detection of hypochondroplasia: A large single-center UK case series and systematic review.

Hypochondroplasia (HCH) is a rare autosomal dominant skeletal dysplasia condition caused by FGFR3 mutations leading to disproportionate short stature. Classically HCH presents in toddlers or school-age children, as limb-to-trunk disproportion and is often mild and easily overlooked during infancy. We report experiences from a single-center UK HCH-cohort of 31 patients, the rate of antenatal HCH detection in our cohort (13/31, 41.9%) and describe relevant case-data for this subset of 13 patients. Inclusion criteria were patients with confirmed molecular HCH diagnosis (by age 3 years) and presenting with short long-bones or large head size on antenatal ultrasound scan. We then conducted a systematic literature review using PUBMED and MEDLINE, analyzing patients with HCH and related antenatal findings. Antenatally suspected (with subsequent molecular confirmation) HCH has been reported 15 times in the literature (2004-2019). Key markers (consistent in both groups) included reduced; femur length, humeral length and increased; biparietal diameter and head circumference. HCH is increasingly detected both antenatally and in infancy, contrary to previous descriptions. This is likely due to greater HCH awareness, improved imaging, and easier molecular testing. Thus, one should consider HCH outside the classical presenting period. Studying the natural history of younger patients with HCH is important with the advent of several targeted FGFR3 therapies currently in trials for Achondroplasia, that may soon be trialed in HCH.

Exercise-induced lordosis in zebrafish Danio rerio (Hamilton, 1822).

The anabolic effect of exercise on muscles and bones is well documented. In teleost fish, exercise has been shown to accelerate skeletogenesis, to increase bone volume, and to change the shape of vertebral bodies. Still, increased swimming has also been reported to induce malformations of the teleost vertebral column, particularly lordosis. This study examines whether zebrafish (Danio rerio) develops lordosis as a result of continuous physical exercise. Zebrafish were subjected, for 1 week, to an increased swimming exercise of 5.0, 6.5 or 8.0 total body lengths (TL) per second. Control and exercise group zebrafish were examined for the presence of vertebral abnormalities, by in vivo examination, whole mount staining for bone and cartilage and histology and micro-computed tomography (CT) scanning. Exercise zebrafish developed a significantly higher rate of lordosis in the haemal part of the vertebral column. At the end of the experiment, the frequency of lordosis in the control groups was 0.5 ± 1.3% and that in the exercise groups was 7.5 ± 10.6%, 47.5 ± 10.6% and 92.5 ± 6.0% of 5.0, 6.5 and 8.0 TL∙s-1 , respectively. Histological analysis and CT scanning revealed abnormal vertebrae with dorsal folding of the vertebral body end plates. Possible mechanisms that trigger lordotic spine malformations are discussed. This is the first study to report a quick, reliable and welfare-compatible method of inducing skeletal abnormalities in a vertebrate model during the post-embryonic period.

Correlation Between Parameters of Intervertebral Disc and Cervical Lordosis in Cervical Spondylotic Myelopathy.

BACKGROUND In cervical disc degeneration, cervical disc height (CDH) and cervical disc angle (CDA)have a certain but unidentified relationship with cervical lordosis (CL). This study aimed to reveal the relationship among CDH, CDA, and CL in patients diagnosed with cervical spondylotic myelopathy (CSM). MATERIAL AND METHODS A retrospective analysis was conducted using the data of 212 CSM patients (136 males and 76 females). According to CL angle, patients were classified into 2 groups: patients with CL ≤10° constituted Group 1 (n=102); patients with CL >10° constituted Group 2 (n=110). The CDH, CDA, and CL were measured using X-ray imaging. Pearson correlation analysis measured the correlation between CDH, CDA, and CL. Multiple linear regression was utilized to analyze the effects of CDH and CDA on CL. RESULTS The CDAs in every level were higher in Group 2 than those in Group 1 (P.

Correlation between the apex of lumbar lordosis and pelvic incidence in asymptomatic adult.

PURPOSE: The objective of this study was to test the correlation between the apex of lumbar lordosis (LLA) and pelvic incidence (PI) in asymptomatic adults, and to establish predictive formulae based on the PI to obtain the reference values of lumbar sagittal parameters. METHODS: A cohort of 183 asymptomatic volunteers older than 18 years was enrolled in this study between April 2017 and May 2019. A full-spine, standing X-ray was taken for each subject. The following parameters in the sagittal plane were measured: the LLA, the distance between the plumb line of the lumbar apex (LAPL) and gravity plumb line, lumbar lordosis (LL), the upper arc of lumbar lordosis (LLUA), the lower arc of lumbar lordosis (LLLA) and the PI. The correlations between lumbar parameters and PI were analysed, and simple linear regressions were simultaneously constructed. The statistical significance level was P < 0.05. RESULTS: The PI was statistically correlated with the LLA (rs = - 0.595, P < 0.001), LAPL (rs = 0.503, P < 0.001), LL (rs = 0.605, P < 0.001), LLUA (r = 0.354, P < 0.001) and the LLLA (r = 0.658, P < 0.001). The corresponding regression formulae were as follows: LLA = - 0.042*PI + 6.134 (R2 = 0.306), LAPL = 0.448*PI + 26.570 (R2 = 0.279), LL = 0.888*PI - 2.667 (R2 = 0.370), LLUA = 0.272*PI - 2.297 (R2 = 0.126) and LLLA = 0.607*PI + 0.177 (R2 = 0.433). CONCLUSION: The PI has strong correlations with the LLA, LAPL, LL, LLUA and LLLA, which demonstrates that the specific lumbar shape can be affected by the pelvic morphology. Moreover, predictive models for ideal lumbar sagittal parameters based on the PI have been developed, contributing to the design of precise and individualized preoperative plans. These slides can be retrieved under Electronic Supplementary Material.

Long-term impact of sagittal malalignment on hardware after posterior fixation of the thoracolumbar spine: a retrospective study.

BACKGROUND: The importance of sagittal alignment in healthy individuals and in reconstructive spinal surgery has been studied over the last 15 years. The aim of the present study was to assess the long-term effects of abnormal sagittal alignment on hardware after posterior thoracolumbar spinal fusion. METHODS: Patients who had undergone revision surgery (revision cohort, n = 34) due to breakage of their implants were compared retrospectively with patients who had intact implants at the final follow-up investigation after a long posterior thoracolumbar and/or lumbar spinal fusion (control cohort, n = 22). Clinical data and radiological parameters including the sagittal vertical axis (SVA), pelvic incidence (PI), lordosis gap (LG), pelvic tilt (PT), sacral slope (SS), lumbar lordosis (LL), thoracic kyphosis (TK), and the femoral obliquity angle (FOA) were assessed on full-spine lateral radiographs obtained in regular standing position. Data were analysed using descriptive statistics, parametric and non-parametric inferential statistics. RESULTS: Patients in the breakage group (female n = 21, male n = 9, mean age 60.9 ± 15.6 years) had a higher anterior shift of the C7 plumb line (SVA) (p = 0.02), retroversion of the pelvis (PT) (p < 0.001), PI-LL mismatch (LG) (p = 0.001), and PI (p = 0.002) than the intact group (female n = 10, male n = 12, mean age 65.7 ± 12.4 years). No significant difference was registered between groups in regard of SS, LL, TK, FOA, and the mean number of comorbidities. CONCLUSION: Failure of restoration of the SVA and the LG to the acceptable ranges, especially in patients with a high PI, may be regarded as a risk factor for the long-term failure of implants after posterior thoracolumbar spinal fusion.

Is intrinsic lumbar spine shape associated with lumbar disc degeneration? An exploratory study.

BACKGROUND: Lumbar disc degeneration (LDD) is a condition associated with recurrent low back pain (LBP). Knowledge regarding effective management is limited. As a step towards the identification of risk, prognostic or potentially modifiable factors in LDD patients, the aim of this study was to explore the hypothesis that intrinsic lumbar spine shape is associated with LDD and clinical outcomes in symptomatic adults. METHODS: 3 T MRI was used to acquire T2-weighted sagittal images (L1-S1) from 70 healthy controls and LDD patients (mean age 49 years, SD 11, range 31-71 years). Statistical Shape Modelling (SSM) was used to describe lumbar spine shape. SSM identified variations in lumbar shape as 'modes' of variation and quantified deviation from the mean. Intrinsic shape differences were determined between LDD groups using analysis of variance with post-hoc comparisons. The relationship between intrinsic shape and self-reported function, mental health and quality of life were also examined. RESULTS: The first 7 modes of variation explained 91% of variance in lumbar shape. Higher LDD sum scores correlated with a larger lumbar lordosis (Mode 1 (55% variance), P = 0.02), even lumbar curve distribution (Mode 2 (12% variance), P = 0.05), larger anterior-posterior (A-P) vertebral diameter (Mode 3 (10% variance), P = 0.007) and smaller L4-S1 disc spaces (Mode 7 (2% variance), P ≤ 0.001). In the presence of recurrent LBP, LDD was associated with a larger A-P vertebral diameter (Mode 3) and a more even lumbar curvature with smaller L5/S1 disc spaces (Mode 4), which was significantly associated with patient quality of life (P = 0.002-0.04, rp = 0.43-0.61)). CONCLUSIONS: This exploratory study provides new evidence that intrinsic shape phenotypes are associated with LDD and quality of life in patients. Longitudinal studies are required to establish the potential role of these risk or prognostic shape phenotypes.

Sarcopenia is related to spinal sagittal imbalance in patients with spinopelvic mismatch.

PURPOSE: To clarify the relationship between sarcopenia and spinopelvic parameters. METHODS: Among outpatients of spine surgery department, 126 patients (mean age 77.2 years. M/F = 71/55) were included. We diagnosed patients with sarcopenia using the diagnostic algorithm of the Asian Working Group for Sarcopenia. Spinopelvic parameters and the prevalence of spinopelvic mismatch (pelvic incidence minus lumbar lordosis ≥ 10°) were investigated and compared between patients with and without sarcopenia. Furthermore, we compared the spinopelvic parameters between the Sarcopenia and No Sarcopenia groups under each condition of spinopelvic match and mismatch. RESULTS: The prevalence of sarcopenia in this study was 21.4%. Overall, the spinopelvic parameters except thoracic kyphosis (TK) (Sarcopenia: 34.7°, No Sarcopenia: 24.3°, p < 0.01) were not significantly different between the Sarcopenia and No Sarcopenia groups. Prevalence of patients with spinopelvic mismatch was also not significantly different between the Sarcopenia and No Sarcopenia groups (37.0% vs. 42.4%, p = 0.66). Among patients without spinopelvic mismatch, there was no spinopelvic parameter with a significant difference between the 2 groups. However, among patients with spinopelvic mismatch, sagittal vertebral axis (SVA) (115.7 mm vs. 58.7 mm, p < 0.01) and TK (36.6° vs. 21.3°, p < 0.01) of the Sarcopenia group were significantly larger than those of the No Sarcopenia group. Moreover, sarcopenia was independently related to a significant increase in SVA (ß = 50.7, p < 0.01) and TK (ß = 14.0, p < 0.01) in patients with spinopelvic mismatch, after adjustment for age. CONCLUSIONS: Sarcopenia is related to spinal sagittal imbalance because of insufficient compensation by flattening thoracic kyphosis in patients with spinopelvic mismatch. These slides can be retrieved under Electronic Supplementary Material.

Comparison of cervical sagittal parameters among patients with neck pain and healthy controls: a comparative cross-sectional study.

INTRODUCTION: Previous studies have shown poor health-related outcomes among patients with spinal sagittal malalignment of the thoracolumbar or spinopelvic region, and less interest has been paid to the relationship between cervical sagittal balance and functional outcome of the patients. This study aims to compare the cervical sagittal parameters between patients with non-specific neck pain and asymptomatic controls. METHOD: Twenty-five patients (21 females/4 males) with non-specific neck pain and 25 age-, sex- and BMI-matched controls (18 females/7 males) participated in the study. Using a standard lateral cervical radiography, the Cobb angle between occiput-C2, C1-C2, C1-C7 and C2-C7 as well as the thoracic inlet angle (TIA) and C7 and T1 slope angles was measured. Also the spine cranial angle (SCA) and the C2-SVA (sacral vertical axis) and C1-SVA were measured. The primary outcome measure of the study was comparison of the sagittal balance variables between the patients and the healthy controls. Secondary outcome measures were correlation between pain intensity of the patients in neck pain group and their demographic and radiographic findings. Data analysis was performed using independent sample T test and Pearson's correlation for primary and secondary outcome measurements, respectively. RESULTS: There was no difference in cervical lordosis curvature (measured by C2-C7 and C1-C7 lordosis angle) between patients with non-specific NP and healthy controls (P value = 0.45 and 0.37, respectively). We found that T1 slope angle was significantly (P value = 0.02) lower in patients with neck pain. CONCLUSION: Our findings showed that the slope of the upper endplate of T1 vertebrae body (T1 slope) is significantly lower among patients with non-specific neck pain compared to controls. A compensatory mechanism to bring the center of head gravity back to the spinal axis might be the possible explanation for this difference. These slides can be retrieved under Electronic Supplementary Material.

Thoracolumbar junction orientation: its impact on thoracic kyphosis and sagittal alignment in both asymptomatic volunteers and symptomatic patients.

PURPOSE: The thoracolumbar junction (TLJ) has not been explored in regard to its contribution to global sagittal alignment. This study aims to define novel sagittal parameters of the TLJ and to assess their roles within global sagittal alignment. METHODS: Included for cross-sectional, retrospective analysis were asymptomatic volunteers and symptomatic patients who had undergone operation for adult spinal deformity. Unique sagittal parameters of the TLJ were measured using the midline of the T12-L1 disk space: The TLJ orientation [TLJO; thoracolumbar tilt (TLT) and slope (TLS)]. Thoracic kyphosis (TK; T5-12), C7-S1 sagittal vertical axis (SVA), lumbar lordosis (LL; L1-S1), sacral slope (SS), pelvic tilt (PT), and pelvic incidence (PI) were measured. Continuous variables were compared using the independent t test. Pearson correlations examined relationships between the parameters in each group. The asymptomatic TK was calculated using the measurement of the asymptomatic volunteer's TLJO by linear regression. RESULTS: One hundred fifteen asymptomatic volunteers and 127 symptomatic patients were included. Only LL among the lumbopelvic parameters correlated with TK (asymptomatic volunteers: r = - 0.42; symptomatic patients: r = - 0.40). All the pelvic parameters have no direct correlation with TK in both groups. TLJO had stronger correlation with TK [asymptomatic volunteers: r = - 0.68 (TLS), r = 0.41 (TLT); symptomatic patients: r = - 0.56 (TLS), r = 0.44 (TLT)] than the lumbopelvic parameters. TLS correlated with LL (asymptomatic volunteers: r = 0.78; symptomatic patients: r = 0.73). Most pelvic parameters correlated with TLJO except for PI. The asymptomatic TK was estimated by the derived formula: 20.847 + TLS × (- 1.198). CONCLUSION: The TLJO integrates the status of the lumbopelvic sagittal parameters and simultaneously correlates with thoracic and global sagittal alignment. These slides can be retrieved under Electronic Supplementary Material.

Sagittal balance of the spine.

The static sagittal balance of the normal spine is a physiological alignment of the spine in the most efficient manner by the muscular forces. During gait, this balance is constantly thwarted by single-foot support. This analysis involves the study of parameters which are now well defined. The pelvic incidence is constant, and the sacral slope and the pelvic tilt are positional. The cervical parameters are the upper (O-C2) and lower cervical curvatures (C2-C7), the C7 slope, the spino-cranial angle and the vertical cervical offset. At the thoracic and lumbar level, they are, respectively, kyphosis and lordosis. The OD-HA (odontoid hip axis) angle is the most efficient parameter to analyse the global balance. The average values of these parameters are reported with the new 3D measurements by Le Huec et al. The relationship between these different parameters was analysed, and Roussouly proposed his classification of the different spine shape. Ageing makes it possible to show compensation mechanisms at three levels: spinal, pelvic and lower limbs. Understanding these different data allows for better planning of the surgical management of the patients. Global evaluation of the entire spine and the measurement of the aforementioned parameters allow to determine the extent of the correction to be performed during surgery. Taking these parameters into account also enables us to understand the complications involved in this type of surgery: transitional syndromes or junctional syndromes. Integration of these parameters into the study of gait is an area still under investigation. These slides can be retrieved under Electronic Supplementary Material .

Effect of lordosis on adjacent levels after lumbar interbody fusion, before and after removal of the spinal fixator: a finite element analysis.

BACKGROUND: Literature indicates that adjacent-segment diseases after posterior lumbar interbody fusion with pedicle screw fixation accelerate degenerative changes at unfused adjacent segments due to the increased motion and intervertebral stress. Sagittal alignment of the spine is an important consideration as achieving proper lordosis could improve the outcome of spinal fusion and avoid the risk of adjacent segment diseases. Therefore, restoration of adequate lumbar lordosis is considered as a major factor in the long-term success of lumbar fusion. This study hypothesized that the removal of internal fixation devices in segments that have already fused together could reduce stress at the disc at adjacent segments, particularly in patients with inadequate lordosis. The purpose of this study was to analyze the biomechanical characteristics of a single fusion model (posterior lumbar interbody fusion with internal fixation) with different lordosis angles before and after removal of the internal fixation device. METHODS: Five finite element models were constructed for analysis; 1) Intact lumbar spine without any implants (INT), 2) Lumbar spine implanted with a spinal fixator and lordotic intervertebral cage at L4-L5 (FUS-f-5c), 3) Lumbar spine after removal of the spinal fixator (FUS-5c), 4) Lumbar spine implanted with a spinal fixator and non-lordotic intervertebral cage at L4-L5 (FUS-f-0c), and 5) Lumbar spine after removal of the spinal fixator from the FUS-f-0c model (FUS-0c). RESULTS: The ROM of adjacent segments in the FUS-f-0c model was found to be greater than in the FUS-f-5c model. After removing the fixator, the adjacent segments in the FUS-5c and FUS-0c models had a ROM that was similar to the intact spine under all loading conditions. Removing the fixator also reduced the contact forces on adjacent facet joints and reduced the peak stresses on the discs at adjacent levels. The greatest increase in stress on the discs was found in the FUS-f-0c model (at both L2/L3 and L3/L4), with intervertebral stress at L3/L4 increasing by 83% when placed in flexion. CONCLUSIONS: This study demonstrated how removing the spinal fixation construct after bone fusion could reduce intradiscal pressure and facet contact forces at adjacent segments, while retaining a suitable level of lumbar lordosis.

Comparison of Spinal Curvatures in the Sagittal Plane, as Well as Body Height and Mass in Polish Children and Adolescents Examined in the Late 1950s and in the Early 2000s.

BACKGROUND Humans are exposed to various stimuli which lead to somatic modifications and changes in body posture, negatively affecting many of its characteristics. The purpose of this study was to assess significant alterations which occurred in selected morphological features and spinal curvatures in children and adolescents over a period of 40 years. MATERIAL AND METHODS The total of 7041 subjects, aged 4-18 years (mean age 11.3 years) were included in the study, which was designed to compare measurements performed in year 1959 (Group 1, n=3235 individuals) and in year 2003 (Group 2, n=3806 individuals). The children were examined for body height, body mass, as well as thoracic and lumbar curvatures. In 1959, the measurements were carried out using a spherodorsimeter, while in 2003, the CQ System photogrammetry was used, producing corresponding results. The Mann-Whitney U test and the Student's t-test were used for statistical analysis. RESULTS The findings showed a significant decrease in the angle of lumbar lordosis and in sacral inclination as well as an increase in body height and mass, particularly in prepubertal children. On the other hand, the angle of thoracic kyphosis and the partial angles of physiological spinal curvatures changed only to a small degree over the 40-year period. CONCLUSIONS This study provides evidence related to changes which occurred during the relevant period of over 40 years, namely a decrease in both the angle of lumbar lordosis and the sacral inclination angle, as well as an increase in body height and mass. These changes should be taken into consideration in selecting norms and standards applied in healthcare services, and the findings suggest it is necessary to regularly update such standards.

K-line tilt as a novel radiographic parameter in cervical sagittal alignment.

OBJECTIVE: To investigate the relationship between the K-line tilt and classical cervical parameters such as the C2-C7 sagittal vertical axis (SVA), cervical lordosis, and the T1 slope in cervical sagittal alignment. We assessed whether the K-line tilt can be used as an excellent cervical parameter. METHODS: We reviewed 50 patients aged 60-89 years who visited the spine center outpatient clinic from May 2017 to September 2017 through cervical spine lateral radiography and checked the cervical spine parameters. All targeted patients were randomized without any prejudice. Radiographic measurements included the K-line tilt, C2-C7 lordosis, the C2-C7 SVA, the T1 slope, and T1 slope minus C2-C7 lordosis (T1S-CL). Pearson correlation coefficients were calculated between the K-line tilt and each cervical parameter. RESULTS: Of the 50 patients, 33 were men. The mean age of the patients was 70.84 ± 7.52 years. The mean K-line tilt was 11.28 ± 8.31°. The K-line tilt was correlated with the C2-C7 SVA (r = 0.813, P = 0.000) and T1S-CL (r = 0.315, P = 0.026). CONCLUSION: This study showed that the K-line tilt is also a useful parameter like the C2-C7 SVA and T1S-CL in cervical sagittal alignment. These slides can be retrieved under Electronic Supplementary Material.

Extremely high preoperative C7 slope limits compensatory cervical lordosis after muscle-preserving selective laminectomy.

PURPOSE: A high C7 slope induces C2-C7 lordosis to compensate for cervical sagittal balance adjustments. A muscle-preserving selective laminectomy (SL) can maintain this compensation postoperatively. This study evaluated the effect of an extremely high C7 slope on C2-C7 lordotic compensation following SL. METHODS: This study enrolled 151 cervical compressive myelopathy patients who underwent SL. Lateral cervical spine radiographs were taken before surgery and during final follow-up. Patients were divided into extremely high C7 slope (≥ 30°) (EH) and non-high C7 slope (< 30°) (NH) groups and the influence of a high C7 slope on radiological and surgical outcomes was examined. RESULTS: Mean age was higher in group EH (p < 0.001). Preoperatively, patients in group EH had a larger C2-C7 sagittal vertical axis (SVA) (p = 0.001) and greater cervical lordosis (p < 0.001). Although C2-C7 SVA increased after surgery, mean C2-C7 angle of group EH decreased. Mismatches between C7 slope and C2-C7 angle increased for group EH postoperatively (p = 0.015). Postoperative Japanese Orthopedic Association (JOA) score and recovery rate (RR) were slightly lower in group EH (p = 0.001 and p = 0.006, respectively). Multiple linear regression analyses revealed that extremely high C7 slope, not age, affected the RR of JOA score (p = 0.006). CONCLUSIONS: Patients in group EH were older and had highly compensated cervical sagittal alignment preoperatively. They demonstrated postoperative cervical sagittal balance mismatch increases and slightly worse functional recovery. An extremely high C7 slope limited compensatory cervical lordosis following SL. These slides can be retrieved under Electronic Supplementary Material.

Invariance of head-pelvis alignment and compensatory mechanisms for asymptomatic adults older than 49 years.

PURPOSE: The aim was to quantify the postural alignment of asymptomatic elderly, in comparison to a reference population, searching for possible invariants and compensatory mechanisms. METHODS: 41 volunteers (49-76 years old) underwent bi-planar X-rays with 3D reconstructions of the spine and pelvis. Alignment parameters were compared with those of a reference group of asymptomatic subjects younger than 40 years old, with a particular focus on center of acoustic meati (CAM) and odontoid (OD) with regard to hip axis (HA). Possible markers of compensation were also investigated. RESULTS: No significant difference among groups appeared for CAM-HA and OD-HA parameters. Twenty four percent of elders had an abnormally high SVA value and twenty seven percent had an abnormal global spine inclination. Increased pelvic tilt and cervical lordosis allowed maintaining the head above the pelvis. CONCLUSIONS: CAM-HA and OD-HA appeared quasi-invariant even in asymptomatic elderly. Some subjects exhibited alteration of spine alignment, compensated at the pelvis and cervical regions.

Classification of normal sagittal spine alignment: refounding the Roussouly classification.

PURPOSE: Although the Roussouly classification of common variants in spinal sagittal alignment is well accepted, no studies have implemented it in an asymptomatic adult population. In addition, no study investigated the radiographic features of asymptomatic patients with an anteverted pelvis. The aim of this prospective radiographic study of 296 asymptomatic adults without spinal pathology was to investigate how the Roussouly classification could include the anteverted pelvis concept. METHODS: Pelvic incidence (PI), sacral slope (SS), pelvic tilt (PT), and the lumbar parameters lumbar lordosis (Global LL), lordosis tilt angle (LTA), total number of lordotic vertebra (LL verteb), and C7 plumbline/sacrofemoral distance ratio (C7PL ratio) were evaluated in 296 healthy volunteers (126 males, 170 females; mean age, 27 years; range 18-48 years). Comparison between the five types of the Roussouly classification used Student, ANOVA, and Tukey tests for quantitative variables and χ 2, Fischer, and Holm tests for qualitative variables. RESULTS: Mean PI and PT were, respectively, (39°, 10°) for type 1, (41°, 10°) for type 2, (53°, 13°) for type 3, and (62°, 12°) for type 4 (p < 0.0001 and p < 0.01). A sizable portion (16%) of the population (type 3 AP) showed low-grade PI (mean, 48° ± 6°) despite having SS > 35°. PT was low or negative (mean 4° ± 3°). C7PL ratio was >1 (in front of the hip axis) in 13% of all cases, and between 0 and 1 (between sacrum and hip axis) in 49%. CONCLUSION: Although asymptomatic adults stood with stable global balance, the sagittal spinal alignment of healthy subjects, newly divided in 5 sagittal types, varied significantly. Type 3 AP appears as a new and unusual sagittal shape with low-grade PI, very low or negative PT, and hyperlordosis. Whereas most asymptomatic adults stood with C7PL behind the hip axis, a sizeable portion had C7 in front of the hip axis. This could be a new controversial aspect of ideal spinal balance.

An in vitro evaluation of sagittal alignment in the cervical spine after insertion of supraphysiologic lordotic implants.

PURPOSE: Cervical spine malalignment can develop as a consequence of degenerative disc disease or following spinal surgery. When normal sagittal alignment of the spine is disrupted, further degeneration may occur adjacent to the deformity. The purpose of this study was to investigate changes in lordosis and sagittal alignment in the cervical spine after insertion of supraphysiologic lordotic implants. METHODS: Eight cadaveric cervical spines (Occiput-T1) were tested. The occiput was free to translate horizontally and vertically but constrained from angular rotation. The T1 vertebra was rigidly fixed with a T1 tilt of 23°. Implants with varying degrees of lordosis were inserted starting with single-level constructs (C5-C6), followed by two (C5-C7), and three-level (C4-C7) constructs. Changes in sagittal alignment, Occ-C2 angle, cervical lordosis (C2-7), and segmental lordosis were measured. RESULTS: Increasing cage lordosis led to global increases in cervical lordosis. As implanted segmental lordosis increased, the axial levels compensated by decreasing in lordosis to maintain horizontal gaze. An increase in cage lordosis also corresponded with larger changes in SVA. CONCLUSION: Reciprocal compensation was observed in the axial and sub-axial cervical spine, with the Occ-C2 segment undergoing the largest compensation. Adding more implant lordosis led to larger reciprocal changes and changes in SVA. Implants with supraphysiologic lordosis may allow for additional capabilities in correcting cervical sagittal plane deformity, following further clinical evaluation.