The Influence of Natural Head Position on the Cervical Sagittal Alignment

Influence of cranium orientation on cervical sagittal alignment during radiographic examination: a radiographic analysis

BACKGROUND CONTEXT

During the radiographic examination, the cranium orientation varies not only individually but also within the same subject, in different imaging sessions. Knowing how changes in the orientation of the cranium influences cervical sagittal alignment during the radiographic examination of the cervical spine can aid clinicians in the accurate evaluation for cervical sagittal alignment in clinical practice.

PURPOSE

To radiographically examine the influence of cranium orientation on cervical sagittal alignment during radiographic examination in an asymptomatic cohort.

STUDY DESIGN

A prospective radiographic study.

PATIENT SAMPLE

Eighty asymptomatic volunteers (mean age, 40.4 years; 50.0% male) were enrolled.

OUTCOME MEASURES

Cervical sagittal parameters including the regional slope (C1 slope, C2 slope, C5 slope, C7 slope, and T1 slope), Cobb angle (O-C1 angle, C1-C2 angle, C2-C5 angle, C5-C7 angle, and C7-T1 angle), and cranial/cervical offset (sella turcica tilt [ST tilt] and C2 tilt).

METHODS

In all participants, standing lateral radiographs of the cervical spine were taken in three forward-gazing positions: anteverted-cranium (AC) position; neutral-cranium (NC) position; and retroverted-cranium (RC) position. Cervical sagittal parameters, including the regional slope, Cobb angle, and cranial/cervical offset, in these three positions were statistically compared.

RESULTS

The C1 and C2 slopes were anteverted and retroverted in the AC and RC positions, respectively, compared to those in the NC position. The C5 slope, C7 slope, and T1 slope were constant among the three positions. In O-C2 and C2-C5, statistically significant differences in the regional Cobb angles were identified among the three positions; however, there were no significant differences in the C5-C7 or C7-T1 segments. Cranial and cervical offsets of ST tilt and C2 tilt increased and decreased when the cranium was anteverted and retroverted, respectively.

CONCLUSIONS

The current study suggests that the adjustment of the cranium orientation when taking cervical spine radiographs is mainly controlled at the upper cervical spine of the O-C2 segment in an asymptomatic cohort. On radiograph, alignment in the upper cervical segment of O-C2 changes; accordingly, the middle cervical segment of C2-C5 can change during the adjustment of cranium orientation. However, alignment in the lower cervical segment of C5-C7 and the cervicothoracic junction of C7-T1 remains constant. Further, cranial/cervical offset increases and decreases when the cranium is anteverted and retroverted, respectively. Our results can help the accurate evaluation of cervical sagittal alignment on plain radiographs in clinical practice.

Analysis of sagittal spinal alignment at the adolescent age: for furniture design

Knowledge of the parameters of the human spine is essential in designing ergonomic furniture. The purpose of this study was to evaluate spinal alignment in adolescents of various ages. The lengths, curvatures, and concave-convex spacings of the spine were investigated in 268 participants aged 9-18 years. Ten ages were classified, and the rate of increase of parameters was calculated for each age and age group. The results showed that spinal parameters, except for cervical lordosis, increased with age. Adolescents were classified as 9-10, 11-12, 13-15, and 16-18 years old. A rapid increment of lengths and concave-convex spacings occurred at ages 13-15, while that of curvatures occurred at ages 16-18. Spinal parameters differed significantly among the age groups (p < 0.05). Concave-convex spacings reflected differences in the spine more clearly than the other parameters. This study suggests the necessity of designing spine-related furniture based on spinal parameters, thus providing adaptive support for the adolescent spine, particularly the lumbar spine. Practitioner summary: This study examined spinal lengths, curvatures, and concave-convex spacings in adolescents aged 9-8 years and then divided them into four age groups. Concave-convex spacings effectively reflected spinal differences between age groups, particularly the lumbar spine. These results can inform the ergonomic design of spine-related furniture.HIGHLIGHTSSpinal parameters increased progressively between 9 and 18 years. Regression analysis showed good linear correlations between TK, LL, SK, TS, and LS with age.Age classification of adolescents was Group I (9-10 years), Group II (11-12 years), Group III (13-15 years), and Group IV (16-18 years). The rapid increment of lengths and concave-convex spacings were in Group III while that of curvatures were in Group IV.Concave-convex spacings were vital parameters to evaluate the global balance of the spine.The lumbar spine is an essential segment for characterizing spinal alignment.

Evaluation of automated detection of head position on lateral cephalometric radiographs based on deep learning techniques

BACKGROUND

Lateral cephalometric radiograph (LCR) is crucial to diagnosis and treatment planning of maxillofacial diseases, but inappropriate head position, which reduces the accuracy of cephalometric measurements, can be challenging to detect for clinicians. This non-interventional retrospective study aims to develop two deep learning (DL) systems to efficiently, accurately, and instantly detect the head position on LCRs.

METHODS

LCRs from 13 centers were reviewed and a total of 3000 radiographs were collected and divided into 2400 cases (80.0 %) in the training set and 600 cases (20.0 %) in the validation set. Another 300 cases were selected independently as the test set. All the images were evaluated and landmarked by two board-certified orthodontists as references. The head position of the LCR was classified by the angle between the Frankfort Horizontal (FH) plane and the true horizontal (HOR) plane, and a value within - 3°- 3° was considered normal. The YOLOv3 model based on the traditional fixed-point method and the modified ResNet50 model featuring a non-linear mapping residual network were constructed and evaluated. Heatmap was generated to visualize the performances.

RESULTS

The modified ResNet50 model showed a superior classification accuracy of 96.0 %, higher than 93.5 % of the YOLOv3 model. The sensitivity&recall and specificity of the modified ResNet50 model were 0.959, 0.969, and those of the YOLOv3 model were 0.846, 0.916. The area under the curve (AUC) values of the modified ResNet50 and the YOLOv3 model were 0.985 ± 0.04 and 0.942 ± 0.042, respectively. Saliency maps demonstrated that the modified ResNet50 model considered the alignment of cervical vertebras, not just the periorbital and perinasal areas, as the YOLOv3 model did.

CONCLUSIONS

The modified ResNet50 model outperformed the YOLOv3 model in classifying head position on LCRs and showed promising potential in facilitating making accurate diagnoses and optimal treatment plans.

Comparison of spinal column alignment and autonomic nervous activity using the intersegmental tenderness test in the segment above

[Purpose] The thoracolumbar supraspinous intersegmental tenderness test (ITT) in the segment above was performed to compare spinal alignment and autonomic activity in the presence or absence of pain. [Participants and Methods] Thirty young males were grouped into Th1–4 (Cardiopulmonary visceral nerves), Th5–9 (Large visceral nerve), and Th10–12 (Small visceral nerve) by ITT for the presence of pain. Measurements of the spinal alignment and autonomic function were performed. [Results] Those with ITT pain had a significantly lower range of motion in the sagittal plane at Th12, Th12–L1, and L2–3 and in the frontal plane at Th1–2, Th4–5, Th6–7, and L3–4 than those in the no pain group. On autonomic function tests, the pain group had significantly lower Total Power, LF (Low Frequency), and CVRR (Coefficient of variation of R-R interval). [Conclusion] In ITT, patients with pain at Th5–9 have a mixture of reduced sagittal tilt angle and autonomic hypofunction of the adjacent upper and lower thoracic to lumbar vertebrae.

Correlation of supine MRI and standing radiographs for cervical sagittal balance in myelopathy patients: a cross-sectional study

PURPOSE

Cervical sagittal alignment is correlated with myelopathy severity and used by spinal surgeons for surgical planification. Magnetic resonance imaging (MRI) is the gold standard for the evaluation of cervical myelopathy but may not be for the assessment of cervical sagittal balance compared to X-rays. The objective of this study was to assess the correlation of cervical alignment between supine MRI and standing radiographs in patients with cervical spondylotic myelopathy (CSM).

METHODS

Cobb, Jackson and Harrison methods were used to measure cervical sagittal alignment on supine MRI and standing radiographs of CSM adults. Cervical alignment was divided based on Cobb angle values on lordotic (> 4°), kyphotic (< - 4°) and rectitude (- 4° to 4°). Correlations between radiographic and MRI measurements were determined. Intra- and interobserver reliability were assessed and MRI and X-Ray-measured angles were compared.

RESULTS

One hundred and thirty patients with CSM were reviewed. Correlations of cervical lordosis measures between radiographs and MRI were strong using the Cobb (0.65) and Jackson (0.63) methods, and moderate using the Harrison (0.37) method. Mean cervical lordosis angle was significantly lower on supine MRI compared to standing radiographs for all methods (Cobb 11.6 Rx vs. 9.2 MRI, Jackson 14.6 vs. 11.6, Harrison 23.5 vs. 19.9). Eighteen patients (15.4%) without lordosis on supine MRI presented lordosis on standing radiographs.

CONCLUSION

A substantial proportion of patients has sagittal alignment discrepancies between supine MRI and standing radiographs. Therefore, standing radiographs of the cervical spine should always be included in surgical planning of CSM patients.

Sagittal balance of the cervical spine: a systematic review and meta-analysis

PURPOSE

The purpose of this systematic review and meta-analysis was to compare the cervical sagittal parameters between patients with cervical spine disorder and asymptomatic controls.

METHODS

Two independent authors systematically searched online databases including Pubmed, Scopus, Cochrane library, and Web of Science up to June 2020. Cervical sagittal balance parameters, such as T1 slope, cervical SVA (cSVA), and spine cranial angle (SCA), were compared between the cervical spine in healthy, symptomatic, and pre-operative participants. Where possible, we pooled data using random-effects meta-analysis, by CMA software. Heterogeneity and publication bias were assessed using the I-squared statistic and funnel plots, respectively.

RESULTS

A total of 102 studies, comprising 13,802 cases (52.7% female), were included in this meta-analysis. We used the Newcastle-Ottawa Scale (NOS) to evaluate the quality of studies included in this review. Funnel plot and Begg's test did not indicate obvious publication bias. The pooled analysis reveals that the mean (SD) values were: T1 slope (degree), 24.5 (0.98), 25.7 (0.99), 25.4 (0.34); cSVA (mm), 18.7 (1.76), 22.7 (0.66), 22.4 (0.68) for healthy population, symptomatic, and pre-operative assessment, respectively. The mean value of the SCA (degree) was 79.5 (3.55) and 75.6 (10.3) for healthy and symptomatic groups, respectively. Statistical differences were observed between the groups (all P values < 0.001).

CONCLUSION

The findings showed that the T1 slope and the cSVA were significantly lower among patients with cervical spine disorder compared to controls and higher for the SCA. Further well-conducted studies are needed to complement our findings.

Cervical Extensor Muscles Play the Role on Malalignment of Cervical Spine: A Case Control Study With Surface Electromyography Assessment

STUDY DESIGN

A case control study.

OBJECTIVE

The aim of this study was to identify the potential impact of cervical spine malalignment on muscle parameters.

SUMMARY OF BACKGROUND DATA

Muscular factors are associated with cervical alignment. Nevertheless, only muscle dimensions or imaging changes have been evaluated, function of cervical muscles has scarcely been investigated.

METHODS

Thirty-four patients diagnosed as cervical spine degeneration associated with cervical malalignment and 32 control subjects were included in this case control study. Visual analogue scale (VAS) and the neck disability index (NDI) were used. The sagittal alignment parameters and cervical range of motion (ROM) were measured on cervical spine lateral radiographs, included C2-C7 lordosis, C2-C7 sagittal vertical axis (C2-C7 SVA), cervical gravity-sagittal vertical axis (CG-SVA), T1-Slope, and spinal canal angle (SCA). Surface electromyography (SEMG)-based flexion-relaxation ratio (FRR) was measured.

RESULTS

The result showed VAS score of the neck significantly lower in controls (P<0.05), C2-C7 lordosis, C2-C7 SVA, CG-SVA, T1-Slope and ROM showed significantly different (P<0.001) between malalignment group and control group, FRR of splenius capitis (FRRSpl) and upper trapezius (FRRUTr) of the malalignment group were lower than in the control group, which correlated well with NDI (rSpl = -0.181 rUTr = -0.275), FRRSpl correlated well with VAS (rSpl = -0.177). FRRSpl correlated strongly with C2-C7 SVA (r = 0.30), CG-SVA (r = 0.32), T1-Slope (r = 0.17), ROM (r = 0.19), FRRUTr correlated with C2-C7 lordosis (r = -0.23), CG-SVA (r = 0.19), T1-Slope (r = 0.28), ROM (r = 0.23).

CONCLUSION

Cervical malalignment patients had more tensional posterior cervical muscle and poor muscle functions. CG-SVA showed advantages in evaluating cervical malalignment.Level of Evidence: 3.