Superior Articular Facet Research Articles

Fusion of C2 and C3: embryological and clinical perspective

Skeletal abnormalities in the upper cervical region may result in severe neck ache, altered mobility, muscular weakness and sensory deficits. Fused cervical vertebrae (FCV) have been reported in literature, however cases with fused articular facets have scarcely been documented. During routine osteology demonstration, we came across fused axis and the 3rd cervical vertebra. There was complete fusion of the vertebral arch on the left side along with complete fusion between the inferior articular facet of C2 and superior articular facet of C3. There was partial fusion between the bodies of the vertebrae and the right half of the vertebral arch. Owing to the vital role of this region in various neck movements and spinal alignment, knowledge of such asymmetric variations in the upper cervical region, is of immense importance to orthopedicians, radiologists, neurosurgeons, anaesthetists, physiotherapists.Keywords: intubation, synostosis, axis, block vertebrae

Nutrient foramen location on the laminae provides a landmark for pedicle screw entry: a cadaveric study

BackgroundNutrient foramina are often encountered around the entry point of pedicle screws. Further, while probing the pedicle for pedicle screw insertion around the nutrient foramen, bleeding from the probe insertion hole is often observed. The purpose of this study was to investigate the frequency of occurrence of nutrient foramina, the association between the nutrient foramen and pedicle, and the safety and accuracy of cervical and thoracic pedicle screw placement using the nutrient foramen as the entry point.MethodsWe identified the location of the nutrient foramina for the dorsal branches of the segmental artery and their anatomical association to the pedicles and bony landmarks in the vertebrae for C3–T12 in seven cadavers. We also determined the frequency with which the nutrient foramina were present in 119 cadaveric vertebrae. We identified the pedicle location, base of the superior articular facet, and lateral border of laminae with respect to the nutrient foramen.ResultsThe overall presence of the nutrient foramina was 63% (150/238) in the specimens, with 60% (42/70) and 64% (108/168) identifiable in the cervical and thoracic vertebrae, respectively. In the cervical vertebrae, the nutrient foramen was located on the outer wall of the pedicle and was positioned between the cephalad and caudal walls. In the thoracic spine, 98% (106/108) nutrient foramina were located inside the pedicle walls.ConclusionsOur study findings confirm that the location of the nutrient foramen can be used for identifying the entry point for pedicle screws. In the cervical vertebrae, the nutrient foramina are located lateral to pedicle but within the cranial and caudal margins. In the thoracic vertebrae, the nutrient foramina are located in the medial and caudal regions of the pedicle. Thus, to decrease the risk of overshoot, the entry point for thoracic pedicle screws should be positioned a few millimeters cephalad and lateral to the nutrient foramen.

Friday, September 28, 2018 4:05 PM–5:05 PM abstracts: new concepts: cervical spine: 245. Risk of atlantooccipital joint injury during C1 pedicle screw insertion: a CT-based morphology study of atlas

BACKGROUND CONTEXT C1 pedicle screw technique is increasingly popular for atlantoaxial screw-rod fixation. Many authors have reported anatomic studies for C1 pedicle screw insertion. Most of them focused on whether the pedicle screw would injury transverse foramen, vertebral groove and spinal dura. No study evaluates the risk of atlantooccipital joint injury during C1 pedicle screw insertion yet. PURPOSE To evaluate the risk of atlantooccipital joint injury when inserting C1 pedicle screw and analyse the related anatomic factors. STUDY DESIGN/SETTING A CT-based morphology study. PATIENT SAMPLE Two hundred study units. OUTCOME MEASURES Atlantooccipital joint penetration by the pedicle screw was defined as atlantooccipital joint injury. METHODS One hundred thin-cut upper cervical spine computed tomography (CT) scans which met our inclusion criteria were acquired. The sagittal plane of the planned C1 pedicle screw trajectory was reconstructed. Each sagittal plane was considered as a single unit. And then a 3.5-mm-diameter cylinder was draw to simulate a 3.5-mm-diameter pedicle screw inserting into atlas on each sagittal plane. Atlantooccipital joint penetration by the pedicle screw was defined as atlantooccipital joint injury. Those sagittal planes with atlantooccipital joint injury were carefully studied and the morphology of the atlas was observed and analyzed. RESULTS Two hundred study units were obtained from one hundred upper cervical spine CT scans. Virtual C1 pedicle screw insertion showed that atlantooccipital joint injury occurred in thirty-two units (16%) with bilaterally in eleven patients and unilaterally in ten patients. Over-concave superior articular facet of atlas, high junction of C1 pedicle and C1 lateral mass, and over-cephalad incline of C1 pedicle were observed in units with atlantooccipital joint injury. CONCLUSIONS Two hundred study units were obtained from one hundred upper cervical spine CT scans. Virtual C1 pedicle screw insertion showed that atlantooccipital joint injury occurred in thirty-two units (16%) with bilaterally in eleven patients and unilaterally in ten patients. Over-concave superior articular facet of atlas, high junction of C1 pedicle and C1 lateral mass, and over-cephalad incline of C1 pedicle were observed in units with atlantooccipital joint injury.

Morphometric Study of Orientation of Superior Articular Facets of Thoracolumbar Vertebral Column in North Indian Population

Morphometric Study of Orientation of Superior Articular Facets of Thoracolumbar Vertebral Column in North Indian Population

Morphometric Study of Axis Vertebra in Subjects of Indian Origin

<p><strong>Background:</strong> The axis vertebra, exhibits complex and extensive variability in the morphology and there are vital neurovascular structures in its proximity. Knowledge of this variability is important for neurosurgeons, orthopaedicians, otorhynologists and other physicians who in everyday practice are in contact with disorders of the spine and their consequences.</p><p><strong>Objective:</strong> The aim was to evaluate various morphometric dimensions of axis vertebrae and to compare with the available data.</p><p><strong>Material and Methods:</strong> 50 dried human axis vertebrae of Indian origin, available in the Department of Anatomy, Dayanand Medical College and Hospital, Ludhiana were studied. Various dimensions were taken with vernier calipers, metric scale and graph paper. The dimensions were measured in millimetres and statistically analysed with paired t-test.</p><p><strong>Results:</strong> The mean of maximum anteroposterior diameter (max.APD) and maximum transverse diameter (max.TD) of Superior Articular Facet (SAF) was measured as 17.42mm±1.73 and 15.31mm±1.44 on the right side, 17.64mm±1.51 and 15.17mm±1.48 on left side. The mean Distance from Lateral most edge of SAF to Midline was measured as 22.56mm ± 2.37 and 22.40mm ± 2.16 on the right and left sides, respectively. The mean Distance from Tip of Transverse Process to Midline was 26.45mm ± 2.85 on the right and 26.03mm ± 2.64 on the left side. The mean Height of Dens was measured as 13.83mm ± 1.52, mean Width of Dens as 9.57mm ± 0.85. Width of Pedicle was measured as 10.52mm ± 1.99 and 10.61mm ± 1.67on right and left sides, respectively.</p><p><strong>Conclusion:</strong> The knowledge of these dimensions can provide useful information for safe planning of osseous fixation.</p>

Kinematics of the Cervical Spine After Unilateral Facet Fracture: An In Vitro Cadaver Study.

Biomechanical study utilizing human cadaveric cervical spines. To quantitatively assess the effects on intervertebral motion of isolated unilateral cervical facet fracture, and after disruption of the intervertebral disc at the same level. Clinical evidence has indirectly suggested that cervical facet fractures involving 40% of the height of the lateral mass can cause instability of the involved segment. No study to date has demonstrated the kinematic effects of such an injury in a cadaveric model of the cervical spine. Nine six-segment cervical spines were defrosted and fixated to a spine motion simulator capable to apply unconstrained bending moments in the three anatomical planes. The spines were subjected to a maximum torque of 2 N · m in flexion, extension, left and right lateral bending, and of 4 N · m in left and right axial rotation. Each spine was tested in the intact configuration (INTACT), and following two increasing degrees of injury at C4-C5: fracture of the facet (CF1), and CF1 with disruption of the intervertebral disc at the same level (CF2). Intervertebral kinematics was tracked via clusters of active markers fixated on each vertebra. Differences in kinematics between INTACT and the two injured configurations were assessed via one-way Analysis of Variance (P < 0.05). No significant differences were detected between INTACT and CF1 across all kinematic parameters (P > 0.05) at C4-C5. CF2, however, resulted in significant increase of flexion, left axial rotation, and left lateral bending with respect to INTACT (flexion at C4-C5: INTACT = 8.7° ± 3.5°; CF2 = 14.3 ± 5.7; P < 0.05). Our findings suggest that superior articular facet fractures alone involving 40% of the lateral mass may not necessarily result in intervertebral instability under physiologic loading conditions. The addition of partial injury to the intervertebral disc, however, resulted in statistically significant increase in angular displacement. N /A.

Spondylolysis in the past: A case study of hunter-gatherers from Southern Patagonia

Spondylolysis is a fracture of the pars interarticularis, the portion of the neural arch that lies between the superior articular facets and the inferior articular facets. Clinical evidence has suggested repetitive trauma to be the most probable cause, even though morphological weakness of the vertebra is probably also involved. Prevalence is between 3% and 8% in modern populations, while in archaeological samples it varies from 0% to 71.4%. Considering that very little data about this condition is available in past populations from the southern extreme of South America, the aim of this paper is to analyze the spondylolysis in a human skeletal sample from Southern Patagonia and, at the same time, to explore the prevalence of spondylolysis in archaeological contexts around the world to gain a better understanding of the results presented here. The Southern Patagonian skeletal series analyzed here showed a prevalence of 20%, with lower prevalence in the pre contact sample (11.1%) than in the contact period (23.1%). Skeletons from the Salesian Mission “Nuestra Señora de La Candelaria” showed a higher prevalence (25%) than the sample of skeletal remains recovered from outside the mission (20%), suggesting that changes in lifestyle of hunter-gatherers during contact could be implicated in the development of spondylolysis in this sample. A worldwide survey displays a wide range of prevalence figures in American and Asian samples and low diversity between African and European populations. Hunter-gatherers from Southern Patagonia showed similar values to those observed in other American samples.

A computed tomographic anatomical study of the upper sacrum. Application for a user guide of pelvic fixation with iliosacral screws in adult spinal deformity.

Widely used in traumatic pelvic ring fractures, the iliosacral (IS) screw technique for spino-pelvic fixation remains anecdotal in adult spinal deformity. The objective of this study was to assess anatomical variability of the adult upper sacrum and to provide a user guide of spino-pelvic fixation with IS screws in adult spinal deformity. Anatomical variability of the upper sacrum according to age, gender, height and weight was sought on 30 consecutive pelvic CT-scans. Thus, a user guide of spino-pelvic fixation with IS screws was modeled and assessed on ten CT-scans as described below. Two invariable landmarks usable during the surgical procedure were defined: point A (corresponding to the connector binding the IS screw to the spinal rod), equidistant from the first posterior sacral hole and the base of the S1 articular facet and 10mm-embedded into the sacrum; point B (corresponding to the tip of the IS screw) located at the junction of the anterior third and middle third of the sacral endplate in the sagittal plane and at the middle of the endplate in the coronal plane. Point C corresponded to the intersection between the A-B direction and the external facet of the iliac wing. Three-dimensional reconstructions modeling the IS screw optimal direction according to the A-B-C straight line were assessed. Age had no effect on the anatomy of the upper sacrum. The distance between the base of the S1 superior articular facet and the top of the first posterior sacral hole was correlated with weight (r=0.6; 95% CI [0.6-0.9]); p<0.001). Sacral end-plate thickness increased for male patients (p<0.001) and was strongly correlated with height (r=0.6; 95% CI [0.29-0.75]); p<0.001) and weight (r=0.8; 95% CI [0.6-0.9]); p<0.001). The thickness of the inferior part of the S1 vertebral body increased in male patients (p<0.001). Other measured parameters slightly varied according to gender, height and weight. Simulating the described technique of pelvic fixation, no misplaced IS screw was found whatever the age, gender and morphologic parameters. This user guide of spinopelvic fixation with IS screws seems to be reliable and reproducible independently of age, gender and morphologic characteristics but needs clinical assessment. Level IV.

Morphologic Evaluation of Lumbosacral Nerve Roots in the Vertebral Foramen: Measurement of Local Pressure of the Intervertebral Foramen.

The prospective cohort study. The objective was to evaluate the relationships between local pressure changes of the intervertebral foramen during lumbar spine extension and lumbar foraminal morphology. The physiological states of lumbosacral nerve roots in the vertebral foramen remain controversial. We evaluated 56 lumbosacral vertebral foramens in 21 patients with L4-degenerative spondylolisthesis. All patients underwent L4-5 posterolateral fusion (PLF). The local pressure of the intervertebral foramen was measured intraoperatively, and measurement was performed before and after L4-5 PLF. We defined the changes in the ratio of local pressure between lumbar flexion to extension as percent pressure. The sagittal angular motion, distance between the inferior cortex of the cranial pedicle and superior cortex of the caudal pedicle, posterosuperior margin of the superior vertebral body and superior articular facet, posteroinferior edge of the superior vertebral body and inferior articular facet, and the intervertebral disc height were measured using preoperative functional plain radiographs and CT images. The average local pressure of the intervertebral foramen significantly increased during lumbar extension. However, the L4-5 vertebral foraminal pressure after PLF were nearly identical. There was no significant correlation between percent pressure and lumbar range of motion. Furthermore, there were no significant correlations between percent pressure and each morphologic parameter of the lumbar foramen. There were no significant relationships between the lumbar foraminal morphology and intervertebral foraminal pressure changes during lumbar extension, and L4-5 vertebral foraminal pressure was not affected by the lumbar posture after L4-5 posterior fusion. On the basis of the results, the external dynamic stresses on the nerve roots in the vertebral foramen might be improved by lumbar posterior fusion using instrumentation without direct decompression of the vertebral foramen.

Accuracy of Percutaneous Pedicle Screw Placement: Does Training Level Matter?

In vitro human cadaveric surgical technique study. To assess the accuracy of percutaneous pedicle screw placement in a human cadaveric model using standard fluoroscopic guidance technique, compared across varying levels of experience. The current literature varies widely in the reported frequency of facet violation during placement of percutaneous pedicle screws. However, as of yet there are no studies examining the effect that training level has on accuracy of placement. Four surgeons with differing levels of training (PGY-2, PGY-4, fellow, attending) were evaluated on their accuracy of percutaneous placement of screws in a uniform manner. Each of the 10 cadavers was instrumented from L1 to S1 bilaterally, for a total of 120 screws. Specimens were dissected to evaluate for facet and pedicle wall violations. These were then recorded and analyzed to evaluate for correlation among participating surgeons, laterality, spinal level, and cadaver body mass index. Of 120 screws placed, there were 35 total violations [26 superior articular facet violations (21.7%), 5 intra-articular facet joint violations (4.2%), and 4 pedicle breaches (3.3%)]. Among the trainees there was no difference in the likelihood of causing a violation (P=0.8863) but there was a difference when compared with the attending surgeon (P=0.0175). Laterality (P=0.1598), spinal level (P=0.3536), and body mass index (P=0.8547) did not correlate with the likelihood of a violation. Surgeons of differing training levels are able to safely and accurately place lumbar pedicle screws in a percutaneous manner, with a low likelihood of facet and pedicle wall violations.

Shape change in the atlas with congenital midline non-union of its posterior arch: a morphometric geometric study

Background ContextThe congenital midline non-union of the posterior arch of the atlas is a developmental variant present at a frequency ranging from 0.7% to 3.9%. Most of the reported cases correspond to incidental findings during routine medical examination. In cases of posterior non-union, hypertrophy of the anterior arch and cortical bone thickening of the posterior arches have been observed and interpreted as adaptive responses of the atlas to increased mechanical stress. PurposeWe sought to determine if the congenital non-union of the posterior arch results in a change in the shape of the atlas. Study Design/SettingThis study is an analysis of the first cervical vertebrae from osteological collections through morphometric geometric techniques. MethodsA total of 21 vertebrae were scanned with a high-resolution three-dimensional scanner (Artec Space Spider, Artec Group, Luxembourg). To capture vertebral shape, 19 landmarks and 100 semilandmarks were placed on the vertebrae. Procrustes superimposition was applied to obtain size and shape data (MorphoJ 1.02; Klingenberg, 2011), which were analyzed through principal component analysis (PCA) and mean shape comparisons. ResultsThe PCA resulted in two components explaining 22.32% and 18.8% of the total shape variance. The graphic plotting of both components indicates a clear shape difference between the control atlas and the atlas with posterior non-union. This observation was supported by statistically significant differences in mean shape comparisons between both types of vertebra (p<.0001). Changes in shape were observed in the superior and inferior articular facets, the transverse processes, and the neural canal between the control and non-union vertebrae. ConclusionsNon-union of the posterior arch of the atlas is associated with significant changes in the shape of the vertebra.

Clinical effects of Dynesys system and transfacet decompression through Wiltse approach in the treatment of lumbar degenerative diseases

Objective: To investigate the early clinical effects of Dynesys system and transfacet decompression by Wiltse approach in the treatment of lumbar degenerative diseases. Methods: From January 2010 to December 2013, 48 patients suffering from lumbar degenerative diseases were treated with Dynesys system in addition to transfacet decompression through Wiltse approach.There were 28 males and 20 females with age of (51.8±6.8). The preoperative diagnosis included lumbar spinal stenosis(10 cases); lumber intervertebral disc herniation (38 cases). There were 23 cases in L4/5, 16 cases in L5/S1 and 9 cases in both of L4/5 and L5/S1.Posterolateral fixation with Dynesys pedicle screw through Wiltse approach.Unilateral resection of the inferior articular facet of the superior vertebra and the superior articular facet of the inferior vertebra.Decompression of the vertebral canal until the never root was decompressed satisfactorily.In the end, Dynesys was performed according to normal procedure.VAS, ODI evaluating standards were applied to evaluate the therapeutic effect.The intervertebral space and ROM of the lumbar were observed by X ray. Results: All patients underwent surgery safely without severe complications occurred.The average following up time was 33.5 (24-60) months.Compared with preoperative parameters (7.7±1.3, 70.8±13.5), the scores of VAS and ODI decreased significantly after surgery (2.3±1.5, 23.6±12.2) and at the final follow-up (2.2±1.4, 20.0±9.8) (P<0.05). There were significant difference in the height of intervertebral space and ROM at the stabilized segment (P<0.05), but no significant changes were seen at the adjacent segments (P>0.05). X-ray scan showed neither instability or internal fixation loosen, breakage or distortion in follow-up. Conclusion: Dynesys system in addition to transfacet decompression through Wiltse approach is a therapy option for mild lumbar degenerative disease.This method can retention the structure of lumbar posterior complex and the activity of the fixed segment, reduce the risk of low back pain together with nerve root decompressed.The early clinical results are satisfactory.

Functional analyses of the primate upper cervical vertebral column

Recent work has highlighted functional correlations between direct measures of head and neck posture and primate cervical bony morphology. Primates with more horizontal necks exhibit middle and lower cervical vertebral features that indicate increased mechanical advantage for deep nuchal musculature and mechanisms for column curvature formation and maintenance. How features of the C1 and C2 reflect quantified measures of posture have yet to be examined. This study incorporates bony morphology from the upper cervical levels from 20 extant primate species in order to investigate further how posture correlates with cervical vertebrae morphology. Results from phylogenetic generalized least-squares analyses indicate that few vertebral features exhibit a significant relationship with posture when accounting for differences in size. When size-adjusted traits were correlated with posture, vertebral variation had a stronger relationship with neck posture than head posture variables. Two C1 traits—relative posterior arch length and superior facet curvature—were correlated with neck posture variables. Relative posterior arch length exhibits a positive relationship with neck posture, while superior articular facet curvature demonstrates a negative relationship, such that as the neck becomes more horizontal, the greater the facet curvature. Four C2 features were also correlated with neck posture: relative pedicle and lamina lengths, relative superior facet orientation, and dens orientation. Relative pedicle and lamina lengths become craniocaudally longer as the neck becomes more horizontal. Relative C2 superior facet orientation and dens orientation exhibit negative correlations with posture, such that as the neck becomes more horizontal, the superior facet becomes more caudally inclined and the dens more dorsally inclined. These results produce a similar functional signal observed in the middle and lower cervical spine. Modeling the cervical vertebrae of more pronograde taxa within a sigmoidal spinal column model is further discussed and may prove useful in refining and testing future hypotheses of primate cervical mechanics.

Foramen arcuale: a rare morphological variation located in atlas vertebrae.

To investigate the incidence of foramen arcuale in dry atlas vertebrae which may cause clinical problems. Eighty-one dry human cervical vertebrae were examined. The evaluated parameters of two atlas vertebrae including foramen arcuale were as follows: maximum antero-posterior, transverse diameters and areas of the right and left superior articular facets and transverse foramina; maximum antero-posterior diameters, heights, areas and central sagittal thickness of bony arch forming roof of foramen arcuale, respectively. All parameters were measured with caliper in milimeters. Thirteen of eighty-one cervical vertebrae specimens (13/81, 16.05%) were atlas and the two of thirteen atlas vertebrae (2/13, 15.38%) had macroscopically complete foramen arcuale. Each of the two atlas vertebrae was including one foramen arcuale (one on the left and one on the right side). There was a statistically significant difference (p = 0.04) between the mean antero-posterior diameter of superior articular facet located on each side of atlas vertebrae, whereas not (p = 0.51) between mean antero-posterior diameter of transverse foramina. There was not any significant difference between the mean transverse diameters and areas of superior articular facets and transverse foramina located on each side of atlas vertebrae, respectively. Each of the areas of transverse foramina located on the same sides with foramen arcuale in two atlas vertebrae was less than the mean areas of transverse foramina located ipsilateral side with each foramen arcuale in thirteen atlas vertebrae. The present study provides additional information about the incidence and topography of the atlas vertebrae including foramen arcuale.

Sacralization of Fifth Lumbar Vertebra- A Case Report

During the osteology demonstration session for medical undergraduate students, we have observed a sacrum with sacralisation of fifth lumbar vertebra. The sacrum had six vertebrae with five pelvic sacral foramina. The body of fifth lumbar vertebra was completely fused with first sacral vertebra. The transverse process on the right side was broad and totally fused with ala of sacrum, whereas left side transverse process was not fused with ala. On the posterior aspect, the inferior articular facets of fifth lumbar vertebra were fused with superior articular facets of first sacral vertebra. From this observation, we conclude that, this is a unilateral sacralisation of fifth lumbar vertebra. Since sacralisation is strongly associated with low back pain, the present case is of high clinical value for medical personnel.

The role of allometry and posture in the evolution of the hominin subaxial cervical spine

Cervical vertebrae not only protect the spinal cord but also are the insertion and origin points for muscles related to the movement of the head, upper limb, and trunk, among others, and are thus important elements in primate evolution. While previous work has been undertaken on the first two cervical vertebrae, there is a dearth of studies on the subaxial cervical spine in hominines. In this paper, we provide detailed morphological information on two important aspects of the subaxial cervical vertebrae (C3 – C7): mid-sagittal morphology and superior facet orientation. We studied large samples of African apes including modern humans and the most complete fossil hominin subaxial cervical vertebrae using both traditional and geometric morphometrics. There are significant differences between extant hominoids related to the relative length and orientation of the spinous process as well as to the orientation of the articular facets, which are related to size, locomotion, and neck posture. In fact, fossil hominins do not completely conform to any of the extant groups. Our assessment of mid-sagittal morphology and superior articular facet orientation shows that australopiths have more Homo-like upper subaxial cervical vertebrae coupled with more “primitive” lower cervical vertebrae. Based on these results, we hypothesize that those changes, maybe related to postural changes derived from bipedalism, did not affect the entire subaxial cervical spine at once. From a methodological point of view, the combination of traditional and geometric morphometric data provides a more integrative perspective of morphological change and evolution, which is certainly useful in human evolutionary studies.

Morphometric Analysis of Human Second Cervical Vertebrae (Axis)

Possessing an odontoid process and unique superior articular facets, the axis vertebra morphometry significantly differs from morphometry of other cervical vertebrae. The fractures of axis, especially its dens, are very common and surgeries highly risky. Knowledge of the axis dimensions is essential not only for preclinical studies, diagnosis of spinal cord diseases, planning of the surgeries but also for correct selection and insertion of surgical instruments or vertebral implants design. Many quantitative studies of the second cervical vertebra have been performed, yet still lacking the area parameters determination and precision of three-dimension in vivo measurement. Vertebral dimensions are reported to vary among populations, although there are very little studies examining Caucasian specimen. This study aims to provide three-dimensional in vivo morphometric analysis of the axis vertebra as well as comparison to the previous studies. The clinically relevant vertebral dimensions were measured on the threedimensional model reconstruction of CT scans providing high accuracy. Five human second cervical vertebrae were investigated (Caucasian males) and linear, area and angular dimensions were measured. The data on vertebral body dimensions were best fitting Doherty and Naderi measurement. The vertebra body anterior height was established to be 26.2 mm and the posterior height 21.4 mm. The dens parameters were similar to those presented by Doherty. Doherty also reported large variation in the dens sagittal angle which was observed in the present study as well. The dens height was determined to be 17.8 mm which is significantly greater compared to the previous studies. The smallest height among specimens was reported to be 17.0 mm. The smallest anteroposterior or transverse diameter of the dens measured was the upper depth, 9.4 mm. The smallest and biggest areas of dens were measured to be 79.0 mm2 and 121.6 mm2. The superior articular facet area with mean value 211.2 mm2 was observed to be significantly bigger than the inferior area, 141.2 mm2. The mean sagittal angle of the inferior facet area was assessed to be 42.1° and the mean frontal angle of the superior articular facet 69.3°. The parameters of articular facets measured by Xu correspond to the present study. Due to the vertebral body enlargement in the inferior part of vertebra, the spinal canal superior depth,18.0 mm, was observed to be bigger than its inferior depth, 16.2 mm. In case of the spinal canal depth, Sengul measured values considerably greater than other studies. However, Singla, Gosavi and Xu presented the parameters very similar to the present study. Spinal canal width was measured to be 24.4 mm supporting the measurement done by Sengul which is 24.7 mm. The measured vertebral dimensions can be used either for development of instrumentation, preclinical planning of surgeries, implant design or as the reference values for evaluation and diagnosis of various clinical conditions.

Cervical Spine Deformity in Long-Standing, Untreated Congenital Muscular Torticollis.

Congenital muscular torticollis (CMT) is a benign condition. With early diagnosis and appropriate management, it can be cured completely, leaving no residual deformity. However, long-standing, untreated CMT can lead to permanent craniofacial deformities and asymmetry. Four adult patients presented to the author with long-standing, untreated CMT. Initial clinical assessment demonstrated tightness of the sternocleidomastoid muscle on the affected side. Investigation of cervical spine using 3-dimensional computed tomography scans with cervical segmentation allowed a 3-dimensional module to be separately created for each vertebra to detect any anatomical changes. A change in the axis of the vertebral column was noted when compared to that of the skull. Also, there were apparent anatomical changes affecting the vertebrae, which were most noticeable at the level of the atlas and axis vertebrae. These changes decreased gradually till reaching the seventh cervical vertebra, which appeared to be normal in all patients. The changes in the atlas vertebra were mostly due to its intimate relation with the skull base. The changes of the axis were the most significant, affecting mainly the superior articular facet, the lamina, and the body. There were seemingly permanent changes along the cervical spine region in the adult patients with long-standing, untreated CMT in the form of bending and rotation deformities that might result in residual torticollis postoperatively.

"Soft that molds the hard:" Geometric morphometry of lateral atlantoaxial joints focusing on the role of cartilage in changing the contour of bony articular surfaces.

Purpose:The existing literature on lateral atlantoaxial joints is predominantly on bony facets and is unable to explain various C1-2 motions observed. Geometric morphometry of facets would help us in understanding the role of cartilages in C1-2 biomechanics/kinematics.Objective:Anthropometric measurements (bone and cartilage) of the atlantoaxial joint and to assess the role of cartilages in joint biomechanics.Materials and Methods:The authors studied 10 cadaveric atlantoaxial lateral joints with the articular cartilage in situ and after removing it, using three-dimensional laser scanner. The data were compared using geometric morphometry with emphasis on surface contours of articulating surfaces.Results:The bony inferior articular facet of atlas is concave in both sagittal and coronal plane. The bony superior articular facet of axis is convex in sagittal plane and is concave (laterally) and convex medially in the coronal plane. The bony articulating surfaces were nonconcordant. The articular cartilages of both C1 and C2 are biconvex in both planes and are thicker than the concavities of bony articulating surfaces.Conclusion:The biconvex structure of cartilage converts the surface morphology of C1-C2 bony facets from concave on concavo-convex to convex on convex. This reduces the contact point making the six degrees of freedom of motion possible and also makes the joint gyroscopic.

Increased Pelvic Incidence is Associated With a More Coronal Facet Orientation in the Lower Lumbar Spine: A Cadaveric Study of 599 Lumbar Spines.

An anatomic study of facet angle orientation and morphology of the lumbar spine was performed. The aim of this study was to determine how age, gender, race, and pelvic incidence (PI) correlate with facet orientation in the lumbar spine. Lumbar facet orientation has important implications in the development of numerous pathologies of the spine, including arthritis, spondylolisthesis, and adult spinal deformity. Preliminary reports have suggested that sagittal balance of the spine may contribute to facet joint orientation. We therefore designed an anatomic study to investigate the relationship between PI and facet orientation, within the context of age, gender, and race. Five hundred ninety-nine cadaveric lumbar spines were obtained from the Hamann-Todd osteological collection. It was determined that facet angle was most reliably assessed by measuring the angle between the superior articular facet and the spinous process. Facet angles were measured bilaterally at each level from T12-L1 through L5-S1 in every specimen. Multivariate regression analysis was used to determine independent predictors of facet angle at each level. Facet angle increased rostrally to caudally, from 22.6 ± 8.3° at T12-L1 to 49.1 ± 12.4° at L5-S1. Cadaver age was an independent predictor of a more sagittal facet angle at lower spinal levels. Caucasian race was an independent predictor of increasing facet angle. Increased PI had no effect on facet angle at T12-L1, L1-L2, L2-L3, or L3-L4, although was a significant predictor of more coronally oriented facet joints at L4-L5 (standardized beta 0.096, P = 0.009) and L5-S1 (standardized beta 0.079, P = 0.032). The results of this study provide important data regarding differences in facet angle that exists between individuals. Moreover, the results of this study suggest that facet joints do possess the ability to remodel over time, perhaps in response to perturbations of sagittal balance, osteophyte formation, or other yet to be determined factors. N/A.