Synovial folds of the lateral atlantoaxial joints: in vivo quantitative assessment using magnetic resonance imaging in healthy volunteers

Lateral atlantoaxial joint meniscoid volume in individuals with whiplash associated disorder: A case-control study

BACKGROUND

Lateral atlantoaxial (LAA) joints are established sources of nociceptive input in chronic whiplash associated disorder (WAD). These joints contain intra-articular meniscoids that may be damaged in whiplash trauma. LAA joint meniscoid morphology has not been investigated comprehensively in a chronic WAD population, and it is unclear whether morphological differences exist compared to a pain-free population.

OBJECTIVES

This study examined LAA joint meniscoid volume in individuals with chronic WAD who report pain in a distribution consistent with LAA joint pain.

DESIGN

Case-control study.

METHOD

Fourteen individuals with chronic WAD with pain in an LAA joint distribution (mean [SD] age 38.1 [10.8] years; six female) and 14 age- and sex-matched pain-free controls (38.0 [10.5] years) underwent cervical spine magnetic resonance imaging. LAA joint images were inspected for meniscoids; meniscoid volume was calculated in mm³ and as a percentage of articular cavity volume. Symptom duration, location and intensity were recorded. Data were analysed using paired t-tests, Wilcoxon signed-rank testing, Spearman's rank testing, linear and logistic regression (α < 0.05).

RESULTS

Ventral and dorsal meniscoids (n = 112) were found in each LAA joint. Greater dorsal meniscoid volume as a percentage of articular cavity volume was associated with higher pain intensity (odds ratio 1.48, p = 0.03; likelihood ratio test chi-square₂ = 6.64, p = 0.04), however no significant differences existed between meniscoid volumes of WAD and control participants.

CONCLUSIONS

Findings indicate a potential link between dorsal LAA joint meniscoid volume and pain, suggesting larger meniscoid size may have pathoanatomical significance in WAD.

Morphology and morphometry of lateral atlantoaxial joint meniscoids

The lateral atlantoaxial joints contain folds of synovium termed meniscoids that may potentially contribute to cervical spine pain; however, the anatomy of these structures has not been comprehensively investigated. The purpose of this study was to explore the morphology and morphometry of lateral atlantoaxial joint meniscoids. Twelve cadaveric hemi-spines (6 female; 6 left; mean 81.5 years, SD 7.3) were obtained for dissection and disarticulation of the lateral atlantoaxial joints. Meniscoids were identified and measurements made of surface area, length, and surrounding articular cartilage degeneration. Tissue was sectioned sagittally, stained with hematoxylin and eosin, and examined by light microscopy. Data were analyzed descriptively and using nonparametric techniques. Ventral and dorsal meniscoids (24 in total) were found in each joint, and could be classified histologically into adipose (32%), fibrous (41%), and fibroadipose (27%) meniscoids. No significant associations were found between meniscoid size and age, histology, cartilage degeneration, or joint position. Meniscoid length in males was significantly greater than in females (P = 0.04). Fibrous meniscoids were noted to be associated with articular cartilage degeneration, and adipose and fibroadipose meniscoids with intact cartilage (P = 0.05). Fibrous meniscoids tended to be located dorsally (78%), whereas adipose meniscoids were mostly located ventrally (86%). Distinct patterns in lateral atlantoaxial joint meniscoid morphology were observed, including the association of fibrous meniscoid composition with dorsal joint position and articular cartilage degeneration. The clinical significance of these patterns remains uncertain, and further research is needed to examine these structures across the lifespan and in cervical pathology.

Morphometry of the synovial folds of the lateral atlanto-axial joints: the anatomical basis for understanding their potential role in neck pain

PURPOSE

Intra-articular synovial folds of the cervical spine are considered to be a potential source of neck pain and disability. The purpose of the present study was to devise and validate a method to determine the normal morphometry of the synovial folds as a basis for understanding their functional and clinical significance.

METHODS

Nine cadaver cervical spines were sectioned in the sagittal plane. The presence of the synovial folds at the lateral atlanto-axial joints was determined and their morphology described. Depth of projection, cross-sectional area and volume of the ventral and dorsal synovial folds of the right and left lateral atlanto-axial joints were measured from sagittal sections and compared. The relationship between synovial fold dimensions and subject age and cartilage degeneration were determined. Repeat measurements were made for the calculation of method reliability, and the water displacement method was used to determine method validity.

RESULTS

There was a trend for ventral synovial folds to be larger than dorsal synovial folds. There was no correlation between synovial fold dimensions and age and extent of cartilage degeneration. Measurement reliability ranged from intraclass correlation coefficient 0.95-1.00 (intra-observer), 0.95-1.00 (test-retest) and 0.61-1.00 (inter-observer). Limits of agreement for the sectional and water displacement methods for the measurement of synovial fold volume were -1.04 ± 3.35 mm(3).

CONCLUSIONS

A reliable method for quantifying synovial fold dimensions was devised. The results of this study provide a basis for the determination and diagnosis of pathologies affecting the synovial folds.

Synovial folds - a pain in the neck?

The synovial folds of the cervical spine are regarded as a potential source of neck pain and headache, especially following whiplash injury. Damage to the synovial folds following motor vehicle trauma has been well documented in post-mortem studies. However, methods of identifying injury to the synovial folds in the survivors of motor vehicle trauma have proven elusive to date. Recently, it has been made possible to image the synovial folds in vivo using magnetic resonance imaging. This now makes it feasible to investigate the potential involvement of synovial folds in the generation of neck pain and headache and its relief using spinal manipulation. This paper reviews critically the morphology of the synovial folds of the cervical spine that underpins the hypotheses proposed to explain their functional and clinical significance and a new system of naming and classifying the synovial folds is presented. Although there is some evidence to support the contribution of the synovial folds to neck pain, several theories have little or no support and require investigation and further evaluation. These findings have implications for understanding the anatomical basis of neck pain and headache and the rationale for the use of spinal manipulation in their management.

The influence of age, anthropometrics and range of motion on the morphometry of the synovial folds of the lateral atlanto-axial joints: a pilot study

The purpose of this study was to investigate the effect of age, anthropometrics and cervical range of motion upon synovial fold volume. Ten healthy female subjects aged 20-40 years were included in the study. Age, height, body mass, dimensions of the head and neck and cervical range of motion of each subject were measured. Magnetic resonance (MR) images of the cervical spine were acquired; the volume of the ventral and dorsal synovial folds of the right and the left lateral atlanto-axial joints was measured using seed growing and thresholding methods. Using Spearman's correlation coefficient, it was determined that there was no correlation between synovial fold volume and age. Synovial fold volume was positively correlated with subject height and neck length but negatively correlated with body mass, body mass index and the circumference of the head and neck. The relationship between synovial fold volume and range of cervical motion varied with the plane of movement. The ability to image the synovial folds of the lateral atlanto-axial joints using MR imaging to determine their normal morphology provides the basis for investigating synovial fold pathology in patients with neck pain and headache.