Slight head extension: does it change the sagittal cervical curve?

It is commonly believed that slight flexion/extension of the head will reverse the cervical lordosis. The goal of the present study was to determine whether slight head extension could result in a cervical kyphosis changing into a lordosis. Forty consecutive volunteer subjects with a cervical kyphosis and with flexion in their resting head position had a neutral lateral cervical radiograph followed immediately by a lateral cervical view taken in an extended head position to level the bite line. Subjects were patients at a spine clinic in Elko, Nevada. All radiographs were digitized. Global and segmental angles of the cervical curve were compared for any change in angle due to slight extension of the head. The average extension of the head required to level the bite line was 13.9 degrees. This head extension was not substantially correlated with any segmental or global angle of lordosis. Subjects were categorized into those requiring slight head extension (0 degree-13.9 degrees) and those requiring a significant head extension (> 13.9 degrees). In the slight head extension group, the average change in global angle between posterior tangents on C2 and C7 was 6.9 degrees, and 80% of this change occurred in C1-C4. In the significant head extension group, the average change in global angle between posterior tangents on C2 and C7 was 11.0 degrees, and the major portion of this change occurred in C1-C4. Out of 40 subjects, only one subject, who was in the significant head extension group and had only a minor segmental kyphosis, changed from kyphosis to lordosis. The results show that slight extension of the head does not change a reversed cervical curve into a cervical lordosis as measured on lateral cervical radiographs. Only small extension angle changes (mean sum = 4.8 degrees) in the upper cervical segments (C2-C4) occur in head extension of 14 degrees or less.     

Which parameters are relevant in sagittal balance analysis of the cervical spine? A literature review

Introduction

Cervical spine is part of the spine with the most mobility in the sagittal plane. It is important for surgeons to have reliable, simple and reproducible parameters to analyse the cervical.

Material and method

This study is a systematic review and a critique of current parameters to help improve the study of cervical spinal balance. We conducted a systematic search of PUBMED/MEDLINE for literature published since January 2014. Only studies written in English and containing abstracts were considered for inclusion. The search performed was: «C7 slope» OR «T1 slope» OR «C2C7 offset» OR «C2C7 lordosis» OR «cervical SVA (sagittal vertical axis)» OR «TIA (thoracic inlet angle)» (Lee et al., J Spinal Disord Tech 25(2):E41–E47, 2012) OR «SCA (spino-cranial angle)». Exclusion criteria were purely post-operative and cadaveric analysis, studies performed with CT scan or MRI, studies on adolescent idiopathic scoliosis, traumatology studies and no standing analysis of the cervical spine. Relevance was confirmed by investigators if cervical parameters was a major criteria of the study.

Results

138 articles were found by the electronic search. After complete evaluation 20 articles were selected. The large majority of papers used the same parameters C2_C7 lordosis, C2–C7 SVA, T1 slope or C7 slope and T1 slope/cervical lordosis mismatch. Janusz reported a new parameter using a retrospective cohort of patient with cervical radiculopathy: the TIA (thoracic inlet angle). Le Huec reported an other new parameter based on a prospective study of asymptomatic volunteer: the spino-cranial angle (SCA). This parameter is highly correlated with the C7 slope and the cervical lordosis. Other studies reported parameters that are more global balance analysis including the cervical spine than cervical spine balance itself.

Conclusion

The most important parameters to analyse the cervical sagittal balance according to the literature available today for good clinical outcomes are the following: C7 or T1 slope, average value 20°, must not be higher than 40°. cSVA must not be less than 40°C (mean value 20 mm). SCA (spine cranial angle) must stay in a norm (83° ± 9°). Future studies should focus on those three parameters to analyse and compare pre and post op data and to correlate the results with the quality of life improvement.

     

Does the sagittal alignment of the cervical spine have an impact on disk degeneration? Minimum 10-year follow-up of asymptomatic volunteers

There have been few studies that investigated and clarified the relationships between progression of degenerative changes and sagittal alignment of the cervical spine. The objective of the study was to longitudinally evaluate the relationships among progression of degenerative changes of the cervical spine with age, the development of clinical symptoms and sagittal alignment of the cervical spine in healthy subjects. Out of 497 symptom-free volunteers who underwent MRI and plain radiography of the cervical spine between 1994 and 1996, 113 subjects (45 males and 68 females) who responded to our contacts were enrolled. All subjects underwent another MRI at an average of 11.3 years after the initial study. Their mean age at the time of the initial imaging was 36.6 ± 14.5 years (11–65 years). The items evaluated on MRI were (1) decrease in signal intensity of the intervertebral disks, (2) posterior disk protrusion, and (3) disk space narrowing. Each item was evaluated using a numerical grading system. The subjects were divided into four groups according to the age and sagittal alignment of the cervical spine, i.e., subjects under or over the age of 40 years, and subjects with the lordosis or non-lordosis type of sagittal alignment of the cervical spine. During the 10-year period, progression of decrease in signal intensity of the disk, posterior disk protrusion, and disk space narrowing were recognized in 64.6, 65.5, and 28.3% of the subjects, respectively. Progression of posterior disk protrusion was significantly more frequent in subjects over 40 years of age with non-lordosis type of sagittal alignment. Logistic regression analysis revealed that stiff shoulder was closely correlated with females (P = 0.001), and that numbness of the upper extremity was closely correlated with age (P = 0.030) and male (P = 0.038). However, no significant correlation between the sagittal alignment of the cervical spine and clinical symptoms was detected. Sagittal alignment of the cervical spine had some impact on the progression of degenerative changes of the cervical spine with aging; however, it had no correlation with the occurrence of future clinical symptoms.     

Spinal surgery in patients with Parkinson’s disease: experiences with the challenges posed by sagittal imbalance and the Parkinson’s spine

Only a few reports exist concerning biomechanical challenges spine surgeons face when treating Parkinson’s disease (PD) patients with spinal deformity. We recognized patients suffering from spinal deformity aggravated by the burden of PD to stress the principles of sagittal balance in surgical treatment. Treatment of sagittal imbalance in PD is difficult due to brittle bone and (the neuromuscular disorder) with postural dysfunction. We performed a retrospective review of 23 PD patients treated surgically for spinal disorders. Mean ASA score was 2.3 (2–3). Outcome analysis included review of medical records focusing on failure characteristics, complications, and radiographic analysis of balance parameters to characterize special risk factors or precautions to be considered in PD patients. The sample included 15 female and 8 male PD patients with mean age of 66.3 years (57–76) at index surgery and 67.9 years (59–76) at follow-up. 10 patients (43.5%) presented with the sequels of failed previous surgery. 18 patients (78.3%) underwent multilevel fusion (C3 level) with 16 patients (69.6%) having fusion to S1, S2 or the Ilium. At a mean follow-up of 14.5 months (1–59) we noted medical complications in 7 patients (30.4%) and surgical complications in 12 patients (52.2%). C7-sagittal center vertical line was 12.2 cm (8–57) preoperatively, 6.9 cm postoperatively, and 7.6 cm at follow-up. Detailed analysis of radiographs, sagittal spinal, and spino-pelvic balance, stressed a positive C7 off-set of 10 cm on average in 25% of patients at follow-up requiring revision surgery in 4 of them. Statistical analysis revealed that patients with a postoperative or follow-up sagittal imbalance (C7-SVL >10 cm) had a significantly increased rate of revision done or scheduled (p = 0.03). Patients with revision surgery as index procedure also were found more likely to suffer postoperative or final sagittal imbalance (C7-SPL, 10 cm; p = 0.008). At all, 33% of patients had any early or late revision performed. Nevertheless, 78% of patients were satisfied or very satisfied with their clinical outcome, while 22% were either not satisfied or uncertain regarding their outcome. The surgical history of PD patients treated for spinal disorders and the reasons necessitating redo surgery for recalcitrant global sagittal imbalance in our sample stressed the mainstays of spinal surgery in Parkinson’s: If spinal surgery is indicated, the reconstruction of spino-pelvic balance with focus on lumbar lordosis and global sagittal alignment is required.     

The standing and sitting sagittal spinopelvic alignment of Chinese young and elderly population: does age influence the differences between the two positions?

To investigate the characteristics of standing and sitting spinopelvic sagittal alignment among Chinese healthy population with different age groups. This cross-sectional, prospective study included a total of 235 volunteers aged 19 to 71 years. Volunteers were divided into two groups: group A (age ≤ 40 years; n = 140) and group B (age > 40 years, n = 95). Student’s t test was performed to compare the sagittal parameters including sagittal vertical axis (SVA), T1 pelvic angle (TPA), cervical lordosis (CL), thoracic kyphosis (TK), lumbar lordosis (LL) and pelvic tilt (PT) between standing and sitting positions of two groups. Multiple regression was performed to explore the influence factors of differences between two positions. In the standing position, group B had larger SVA, TK, PT and TPA than group A. When moving from standing to sitting position, increased SVA and PT were found in both groups, accompanied by decreased LL and TK. However, despite similar change in SVA, group B presented with lesser changes in LL, PT and TPA than group A in sitting position. Age and gender independently influenced the difference in PT and LL. In the standing position, the older volunteers showed larger SVA, TPA, TK, CL and PT than young population. Both groups showed similar changes when moving from standing to sitting, but the differences between the positions were smaller in older population. These characteristics in the standing and sitting positions of different age groups should be considered when planning surgical reconstruction of sagittal alignment. These slides can be retrieved under Electronic Supplementary Material.     

How do anterior/posterior translations of the thoracic cage affect the sagittal lumbar spine,pelvic tilt,and thoracic kyphosis?

Anterior and posterior thoracic cage translations in the sagittal plane have not been reported for their range of motion and effects on the lumbar spine and pelvis. Twenty subjects volunteered for full-spine radiography in neutral, anterior, and posterior thoracic cage translation postures in a standing position. While grasping an anterior vertical pole, with hands at elbow level, subjects were instructed on how to translate their thoracic cage without any flexion/extension, utilizing a full-length mirror. On the radiographs, all four vertebral body corners of T1 through S1 and the superior margin of the acetabulum were digitized. Segmental and global angles of thoracic kyphosis, sagittal lumbar curvature, and pelvic flexion/extension in translation postures were compared to alignment in the neutral posture. Using the femur heads as an origin, the mean range of thoracic cage translation, measured as horizontal movement of T12 from neutral posture, was found to be 85.1 mm anterior and 73 mm posterior. In anterior translation, the thoracic kyphosis is hypokyphotic (Cobb T1-T12 reduced by 16 degrees). In posterior translation, the segmental angles at T12-L1 and L1-L2 flexed, creating an "S" shape in the sagittal lumbar spine, while the thoracic kyphosis increased by 10 degrees. Using posterior tangents from L1 to L5 and T12 to S1, and Cobb angles at T12-S1, the lumbar curve reduced slightly (by less than 3.3 degrees for all global angle measurements) in anterior translation and reduced by 7.4 degrees, 5.7 degrees, and 8.1 degrees respectively in posterior thoracic translation. The angle of pelvic tilt (measured as the angle of intersection of a line through posterior-inferior S1 to the superior acetabulum and the horizontal) reduced by a mean of 15.9 degrees, and Ferguson's sacral base angle to horizontal reduced by a mean of 13.1 degrees in posterior translation. In anterior translation, pelvic tilt and Ferguson's sacral base angle increased by 15.1 degrees and 12.8 degrees, respectively. The findings of this study show that thoracic cage anterior/posterior translations cause significant changes in thoracic kyphosis (26 degrees ), lumbar curve, and pelvic tilt. An understanding of this main motion and consequent coupled movements might aid the understanding of spinal injury kinematics and spinal displacement analysis on full spine lateral radiographs of low back pain and spinal disorder populations.     

Does sagittal position of the CTDR-related centre of rotation influence functional outcome? Prospective 2-year follow-up analysis

Purpose

Recent studies describe significant rates of heterotopic ossification (HO) after cervical total disc replacement (CTDR). Little is known about the reasons, and one aspect that requires further in vivo investigation is the biomechanical alteration after CTDR and the role of the implant-related centre of rotation (CORi) in particular. The role of the sagittal position of the CORi on functional outcome in two versions of a semi-constrained disc prosthesis with sagittally different CORi is the topic of this study.

Methods

Patients were candidates for single-level CTDR between C3 and C7 who suffered from CDDD and received a standard or flat version of activ C? (Aesculap AG, Tuttlingen). Clinical and radiographic assessments were determined preoperatively, intraoperatively, at discharge and again at 6 weeks, 6 months, 1 and 2 years. Radiographic examinations were performed independently using specialized quantitative motion analysis software.

Results

Clinical outcome improved significantly regarding NDI as well as VAS on neck and arm pain with no differences in mean improvement by study group. Segmental angle measures show a significantly better lordotic alignment for both groups after surgery, but the degree of correction achieved is higher in the flat group. Correlation analysis proves that the more anterior the CORi is positioned, the higher the lordotic correction is achieved (Pearson rho ?0.385). Segmental ROM decreased in the standard group but was maintained for flat implants. At present, our data do not demonstrate a correlation between CORi and ROM at 2 years. Two years after surgery, severe HO grade III–IV was present in 31.6 % standard and 13.1 % flat cases with significant differences. Grouping according to HO severity showed comparable sagittal positions of CORi for flat implants but a more posterior position in the severe HO group for standard implants.

Conclusions

Our results confirm the influence of CORi location on segmental alignment, kinematics and HO for a semi-constrained CTDR, but it also indicates a multifactorial process.     

Does the asymmetry and extension function of the preoperative cervical paraspinal extensor predict postoperative cervical sagittal deformity in patients who undergo modified laminoplasty?

BACKGROUND CONTEXTA previous study found that the cross-sectional area (CSA) of the preoperative cervical paraspinal extensors (CPEs) was associated with loss of cervical lordosis after laminoplasty, while a recent study found that CPE asymmetry was associated with symptoms of degenerative cervical myelopathy. Whether preoperative CPE asymmetry can predict cervical sagittal deformity (CSD) after laminoplasty is unknown.PURPOSETo assess whether asymmetry, degree of degeneration, and extension function of the CPE can be used as predictors of postoperative CSD in patients who undergo laminoplasty.STUDY DESIGNA retrospective study.PATIENT SAMPLEFrom January 2017 to December 2019, 55 patients with multilevel cord compression and myelopathic symptoms were enrolled.OUTCOME MEASURESThe visual analog scale (VAS), neck disability index (NDI), and modified Japanese Orthopedic Association (mJOA) were used to assess cervical spinal function and quality of life.METHODSFrom January 2017 to December 2019, 55 patients undergoing modified laminoplasty were included. The following parameters were measured preoperatively and 24 months postoperatively on X-ray: (1) C0–C2 Cobb angle; (2) C2–C7 Cobb angle (CL); (3) T1 slope (T1S); (5) C2–C7 sagittal vertical axis (SVA); (6) T1S minus CL; (7) Preoperative extension function: Extension CL minus Neutral CL (EF). Preoperative global alignment parameters: (8) spino cranial angle, (9) C7-S1 sagittal vertical axis (C7 SVA), (10) pelvic incidence, (11) lumbar lordosis, (12) thoracic kyphosis. (13) Preoperative CPE parameters: Summation of bilateral total cross-sectional area (STCSA), summation of bilateral total cross-sectional area ratio (STCSAR), total cross-sectional area asymmetry, summation of bilateral functional cross-sectional area of muscle (SFCSA), summation of bilateral functional cross-sectional area of muscle ratio (FCSAR), and functional cross-sectional area of muscle asymmetry (FCSAA). The VAS, mJOA, and NDI were used to evaluate cervical spine function and quality of life. Patients were divided into the CSD group and the non-deformed group (N-CSD) group postoperatively, and the parameters between the two groups were compared. The Pearson correlation coefficient was used to evaluate the relationship between the parameters, and multiple regression analysis and ROC curve analysis were used to determine the predictors and key values.RESULTSCompared with functional scores, mJOA in the CSD group was significantly lower than that in the N-CSD group, while NDI and VAS were significantly higher. Postoperative CL was significantly correlated with EF, SFCSA/STCSA (C3–C6), SFCSAR (C4 and C6), STCSAR (C6), and FSCAA (C6). T1S minus CL was significantly correlated with EF, SFCSA/STCSA (C3–4 and C6), SFCSAR (C4 and C6), STCSAR (C6) and FSCAA (C6). C2–7 SVA was significantly correlated with EF, SFCSAR (C4 and C6), STCSAR (C6), and FSCAA (C6). Multiple regression analysis showed that FCSAA (C6), SFCSAR (C6), SFCSAR (C4), and EF were significant predictors of postoperative CSD. ROC curve analysis showed that the optimal cutoff points were 18.405, 2.95, 4.47, and 11.96.CONCLUSIONSThe present study found that preoperative extension dysfunction of CPEs, asymmetry at the C6 level cervical extensors, and cervical extensor CSAs without fatty infiltration at the C4 and C6 levels were associated with cervical sagittal imbalance after modified laminoplasty. These factors can be considered when future spine surgeons formulate surgical plans.     

C7棘突并C6下关节突骨折一例

1病例报告 患者,女性,33岁.因挥锨扭伤颈部10 d入院.入院前因用力挥锨扬麦糠,出现颈后部疼痛,活动时加重.查体:C7棘突压痛,局部隆起消失,可扪及C7棘突移动,颈部旋转受限,四肢感觉和肌力无异常.