Morphometric evaluation of the uncinate process and its importance in surgical approaches to the cervical spine: a cadaveric study.

INTRODUCTION: The uncinate process (UP) has an important role because of its relationship with the vertebral artery and spinal roots. Degenerative diseases cause osteophyte formation on the UP, leading to radiculopathy, myelopathy and vertebral vascular insufficiency, which may require surgical management. This study aimed to evaluate the morphometry of this region to shed light on the anatomy of the UP. METHODS: Morphometric data was obtained from 13 male formaldehyde-fixed cadavers. Direct measurements were obtained using a metal caliper. Computed tomography (CT) morphometry was performed with the cadavers in the supine position. RESULTS: Direct cadaveric measurements showed that the height of the UP increased from C3 (5.8 ± 1.0 mm) to C7 (6.6 ± 0.5 mm). On CT, the corresponding measurements were 5.9 ± 1.2 mm at C3 and 6.9 ± 0.6 mm at C7. The distance between the left and right apex of the UP from C3 to C7 also increased on both direct cadaveric and CT measurements (C3: 20.8 ± 1.0 mm and C7: 28.1 ± 2.4 mm vs. C3: 23.7 ± 3.4 mm and C7: 29.0 ± 3.0 mm, respectively). On CT, the distance between the UP and superior articular process at the C3 to C7 levels were 9.8 ± 1.7 mm, 7.9 ± 1.8 mm, 7.9 ± 1.6 mm, 7.8 ± 1.3 mm and 8.2 ± 1.7 mm, respectively. CONCLUSION: Direct cadaveric and CT measurements of the UP are useful for preoperative evaluation of the cervical spine and may lead to better surgical outcomes.

The importance of the greater occipital nerve in the occipital and the suboccipital region for nerve blockade and surgical approaches--an anatomic study on cadavers.

OBJECTIVE: Greater occipital nerve (GON) blockade is an effective method for treatment of occipital neuralgias. Occipital neuralgia or neuropraxis of this region may be seen particularly as a result of compression of the GON. This study shows the relationship between the GON and its external bone landmarks, in order to prevent complications and to perform nerve blockades safely. The study also defines the points where the GON pierces the semispinalis capitis (SSC) and the trapezius, and where the GON passes the obliquus capitis inferior (OCI), and identifies bone landmarks for places where the GON may be entrapped. MATERIALS AND METHODS: In the laboratories of Dokuz Eylül University, Faculty of Medicine Department of Anatomy, 12 GON's belonging to male adult cadavers fixed in formaldehyde were dissected. Colored silicone was injected to all cadavers and then microdissections were performed under a dissection microscope. The lesser occipital nerve, the GON, the greater auricular nerve, and the occipital artery (OA) were dissected. All measurements were made with a 0.1mm sensitive calipometer. RESULTS: The GON's diameter at the point where the GON pierces the SSC was found to be 2.5±0.3 mm. The distance between the point where the GON pierces the SSC and the external occipital protuberance (EOP) was 53.6±5.0 mm. The distance between this point and the midline was 9.0±1.9 mm, the distance between this point and the intermastoid line was 11.5±3.9 mm and the distance between this point and the mastoid process was 65.5±5.9 mm. The distance between the midline and the point where the GON pierces the aponeurosis of trapezius (AT) was 47.9±8.0 mm, the distance between this point and the EOP was 15.1±7.0 mm, the distance between this point and the intermastoid line was 17.1±2.8 mm, and the distance between this point and the mastoid process was 59.4±2.3 mm. We measured the distance between the OA and the intermastoid line to be 8.5±6.1 mm vertically and 32.3±3.9 mm horizontally to the midline. CONCLUSION: In this study, we define the GON's route in the suboccipital and the occipital region where the nerve pierces the SSC and the AT and where blockade or surgery can be performed. These data will help the surgeon and clinician to avoid complications in this region.

Location and incidence of the zygomaticofacial foramen: An anatomic study.

The location and incidence of the zygomaticofacial foramen (ZFF) was studied in 80 dry skulls (160 sides) of unsexed adult skulls of West Anatolian people. The average distances from the ZFF to the frontozygomatic suture, to the zygomaticomaxillary suture, and to the inferior orbital rim were found to be 26.2 +/- 3.2 mm, 18.6 +/- 3.14 mm, and 5.94 +/- 1.43 mm, respectively. The zygomas were evaluated for the number of foramina on their facial aspects. There was none in 25 (15.6%), one in 71 (44.4%), two in 45 (28.1%), three in 10 (6.3%), four in seven (4.4%), and five in two (1.3%) sides. The ZFF was also studied for its distribution around the zygoma by dividing the surface into four anatomical areas. There was no statistical difference between the morphometrical results on both sides. Data regarding the location and variation in the number of the ZFF is important in avoiding zygomatic nerve and vessel injury during surgery, but by virtue of the great variability found, ZFF is an unreliable landmark for maxillofacial surgery.

The human sacrum and safe approaches for screw placement.

The human sacrum is the target of lumbosacral instrumentation and decompression procedures. Such surgical interventions require detailed knowledge of the anatomy of the human sacrum. The aim of this study was to measure surgically relevant parameters. Several factors, including the one-piece composition of the sacrum, the angles of the sacral pedicles and the anteroposterior diameter of the sacral vertebral bodies distinguish the sacrum from other parts of spine. Thirty-two measurements of shape, angles and distances between parts were taken of the sacra of 100 adult West Anatolian people using a Vernier caliper accurate to 0.1 mm and goniometer. According to this morphometric study, when measured from the sagittal, the S1 facet angle was measured as 35.71 degrees +/-9.59 and 34.70 degrees +/-9.66, the sacral pedicle anteromedial screw trajectory angle was 35.65 degrees +/-4.73 and 31.95 degrees +/-3.95 and the anterolaterally oriented sacral wing screw trajectory angle was 32.65 degrees +/-3.51 and 29.10 degrees +/-3.14, on the right and left sides, respectively. The distance of the midline oriented S1 pedicle screw was 51.12 mm and 51.26 mm on the right and left side, respectively. The distance for sacral wing oriented screw placement was 50.13 mm and 50.46 mm on the right and left side, respectively. The anteroposterior and transverse diameter of the sacral spinal canal were 21.81 mm and 31.31 mm, respectively. Thus, this study describes anatomical specifications of the sacrum. These defined morphometric details should be taken into consideration during surgical procedures. This study also describes anatomical landmarks which will allow injury of the sacrum during surgery to be avoided.

Variations in the high division of the sciatic nerve and relationship between the sciatic nerve and the piriformis.

OBJECTIVE: The sciatic nerve (SN) separates into its branches, the tibial and common fibular nerves, outside the pelvis. However, it may rarely be separated within the pelvis. In such cases, the tibial nerve and the common fibular nerve may leave the pelvis through different routes. These variations may cause nerve compressions under other anatomic structures, resulting in non-discogenic sciatica. The aim of this study was to define the level of the SN exit and of the SN division. MATERIAL AND METHOD: 50 gluteal regions were examined in 25 formalin-fixed adult male cadavers. RESULTS: In 52% of the cases, the SN exited the pelvis as a whole nerve without any division, whereas in 48% a high division was observed. Branches of the SN left the pelvis through the infrapiriform foramen (IP) as two separate nerves In 24%. One branch of the SN left the pelvis through the IP and other through a different route in another 24%. CONCLUSION: The differences in the exit routes of these two nerves are important in clarifying the clinical etiology of nondiscogenic sciatica. These variations require reviewing the piriformis syndrome.

Surgical anatomy of the presacral area.

OBJECTIVE: L5-S1 instabilities can be fixated using minimally invasive presacral approach. The close relationship between the sacrum and neurovascular as well as intestinal structures may complicate the procedure during this approach. This requires knowledge regarding the normal anatomy of the presacral area to avoid the iatrogenic injuries. The aim of this study was to measure the distance between the sacrum and the structures anterior to it. MATERIALS AND METHODS: The measurements were performed on ten cadavers fixed with formaldehyde and ten MR imaging studies on individuals without any pathology in the presacral area. The distances between the sacrum and the presacral structures (i.e., middle and lateral sacral arteries, sympathetic trunks, internal iliac arteries and veins, and colon/rectum) were measured. RESULTS: Cadaver study showed that the middle sacral artery was located on the right side in 55.0%, on the left side in 31.7%, and on the midline in the 13.3% of cases. The distance between the sacral midline and middle sacral artery was found to be 8.0 +/- 5.4, 9.0 +/- 4.9, 8.7 +/- 6.0, 8.6 +/- 6.4, and 4.7 +/- 5.0 mm at the levels of S1-2, S2-3, S3-4, S4-5, and S5-coccyx, respectively. The distance between the sacral midline and the sympathetic trunk ranged between 22.4 +/- 5.8 and 9.5 +/- 3.2 mm in different levels between S1 and coccygeal level. The study also showed that the distance between the posterior wall of the intestine (colon/rectum) and the ventral surface of the sacrum can be as close as 11.44 +/- 7.69 mm on MR images. CONCLUSION: This study showed that there was close distance between the sacral midline and the structures anterior to it. The close relationships, as well as the potential for anatomical variations, require the use of sacral and presacral imaging before presacral approach.

Anatomic considerations and the relationship between the piriformis muscle and the sciatic nerve.

UNLABELLED: STATING BACKGROUND: The piriformis syndrome is one of the non-discogenics causes of sciatica. It results from the compression of the sciatic nerve (SN) by the piriformis muscle (PM) in the neutral and piriformis stretch test position. The evidence of the increase in pain in the test position requires a detailed anatomical study addressing the changes that occurred in the SN and PM anatomy during the test position. The aim of this study is to examine this relationship morphometrically. MATERIALS AND METHODS: A total of 20 right and left lower limbs of ten adult cadavers were examined. The SN and the PM were made visible. The location of the SN was evaluated with respect to the consistent bony landmarks, including the greater and the lesser trochanter of the femur, the ischial tuberosity, the ischial spine of the hip bone, the posterior inferior iliac spine of the hip bone and the posterior superior iliac spine of the hip bone. The study was done in both neutral and test positions (i.e., 30 degrees adduction 60 degrees flexion and approximately 10 degrees medial rotation position of the hip joint). RESULTS: The width of the greater sciatic notch was 63.09 +/- 13.59 mm. The length of the lower edge of the PM was 95.49 +/- 6.21 mm, and whereas the diameter of the SN where it emerged from the infrapiriforme was 17.00 +/- 3.70 mm, the diameter decreased to 11.03 +/- 2.52 mm at the level of the lesser trochanter of the femur. The SN intersected the PM most commonly in its medial second quarter anatomically. The vertical distance between the medial edge of the SN-PM intersection point and the ischial tuberosity was 85.62 +/- 17.23 and 72.28 +/- 7.56 mm (P < 0.05); the angle between the SN and the transverse plane was 66.36 degrees +/- 6.68 degrees and 71.90 +/- 8.48 degrees (P < 0.05); and the vertical distance between the medial edge of the SN and the apex of the ischial spine of the hip bone was 17.33 +/- 4.89 and 15.84 +/- 4.63 mm (P > 0.05), before and after the test position, respectively. CONCLUSION: This study provides helpful information regarding the course and the location of the SN. The presented morphometric data also revealed that after stretch test position, the infrapiriforme foramen becomes narrower; the SN becomes closer to the ischial spine of the hip bone, and the angle between the SN and the transverse plane increases. This study confirmed that the SN is prone to be trapped in the test position, and diagnosis of this situation requires dynamic MR and MR neurography study.

The relation between the lumbar vertebrae and the spinal nerves for far lateral lumbar spinal approaches.

The far lateral approaches to the lumbar spine require accurate knowledge of regional anatomy. The aim of this study is to evaluate the course of the lumbar nerve roots and their relation to important bony landmarks. Seven adult male cadavers fixed with formaldehyde were used. Morphometric parameters, including the lumbar nerve root diameters, the angle between the nerve roots and the midline, the transverse process length, the inter-transverse process height and width, and the relation between the nerve roots and the transverse processes of the caudal vertebrae were measured. It was observed that the diameter of the nerve roots, and the angle between the nerve roots and the midline, and the distance between the nerve roots and the lateral edge of the superior articular process increased gradually from L1 to L5. The diameter of the nerve root was 4.9+/-0.5mm for L1 and 7.5+/-1.0mm for L5. The midline nerve root angle was 36.1+/-1.6 degrees mm for L1 and 40.4+/-1.4 degrees mm for L5. The distance between the nerve root and the lateral edge of the superior articular process was 6.5+/-1.0mm for L1 and 11.4+/-1.6mm for L5. The nerve roots crossed the transverse processes of the caudal lumbar vertebrae. The nerve roots of L1 and L2 crossed the transverse processes in their first two quarters, the L3 nerve root crossed the transverse process in its second, third or fourth quarters, and the L4 nerve roots crossed the L5 transverse process in its third and fourth quarter or even external to it. Descending toward the lower lumbar vertebrae, the diameter of the lumbar nerve root increases and the nerve roots exit the intervertebral foramen with a larger angle. The special relation between the nerve roots and the caudal vertebra transverse process should be remembered during far lateral lumbar spine approaches.

Simulation of cerebrovascular circulation in the human cadaver for surgical neuroanatomy training.

OBJECTIVE: The current progress in diagnostic and screening methods and surgical equipment technologies facilitates the accessibility to numerous anatomic structures through various interventional approaches. Consequently, the exact knowledge of the anatomic locations of neurovascular structures and their interactions may ensure that the surgical intervention is planned in the most appropriate way and the structures are accessed with the least complication risk during the intervention. MATERIAL AND METHODS: A decapitated and formalin fixated whole-head of a male human cadaver kept for educational and research purposes in the Dokuz Eylul University Department of Anatomy was used in this study. Two separate reservoirs (for the arterial and the venous system) were connected to the Truno System 3 labeled perfusion pump. The reservoirs were filled with blue and red warm tap water. Colored tap water pumped on the right was emptied from the left. Continuous flow of the water in the closed-circuit arterial and venous systems was achieved. As the circulation was continuing, pterional craniotomy was performed and the dura mater was accessed and lifted under the Zeiss dissecting microscope. CONCLUSION: We believe that this model may contribute to neuroanatomy education and provide experience for the safe and ethical performance of surgical interventions during the intraoperative period.

The thickness and the lengths of the anterior wall of adult maxilla of the West Anatolian Turkish people.

The maxilla is the key structure on facial formation and stability. The knowledge about maxillary thickness and dimensions is crucial during facial reconstruction including this bone. In this study, anthropometric measurements of anterior wall of the maxilla on the dry human skulls were aimed. Sixty maxillae of 30 adult dry skulls of West Anatolian people were evaluated. Four vertical lines were drawn between the piriform aperture and lateral border of the bone and six horizontal lines between the infra-orbital margin and the inferior border of the piriform aperture. After establishing the lines, maxillary thicknesses on the intersection points of the vertical and horizontal lines and the lengths of the vertical lines from the infra-orbital margin to alveolar arch were measured by using a fine caliper. It was found that the thickest point of the anterior wall of the maxillae is on the lateral of the infra-orbital margin (5.17 +/- 2.27 mm), and thinnest one is on the inferior of the infra-orbital foramen (0.92 +/- 1.06 mm). The length of the vertical line tangent to piriform aperture (47.66 +/- 3.61 mm) is the longest. The corresponding data of the left and right maxillae were compared by Student's t test. There was no significant difference between both sides. After collecting the data, a thickness map of anterior wall of the maxilla was drawn. This data may be helpful in clinic during osteotomies, bone reconstructions, screw, or other reconstruction apparatus applications on the maxilla.

Thoracic duct variations may complicate the anterior spine procedures.

The aim of this study is to localize and document the anatomic features of the thoracic duct and its tributaries with special emphasis on the spinal surgery point of view. The thoracic ducts were dissected from nine formaldehyde-preserved male cadavers. The drainage patterns, diameter of the thoracic duct in upper, middle and lower thoracic segments, localization of main tributaries and morphologic features of cisterna chyli were determined. The thoracic duct was detected in all cadavers. The main tributaries were concentrated at upper thoracic (between third and fifth thoracic vertebrae) and lower thoracic segments (below the level of ninth thoracic vertebra) at the right side. However, the main lymphatic tributaries were drained into the thoracic duct only in the lower thoracic area (below the level of the tenth thoracic vertebra) at the left side. Two major anatomic variations were detected in the thoracic duct. In the first case, there were two different lymphatic drainage systems. In the second case, the thoracic duct was found as bifid at two different levels. In formaldehyde preservation, the dimensions of the soft tissues may change. For that reason, the dimensions were not discussed and they may not be a guide in surgery. Additionally, our study group is quite small. Larger series may be needed to define the anatomic variations. As a conclusion, anatomic variations of the thoracic duct are numerous and must be considered to avoid complications when doing surgery.

The V2 segment of the vertebral artery in anterior and anterolateral cervical spinal surgery: a cadaver angiographic study.

OBJECTIVE: The second segment of the vertebral artery is under the risk of injury during anterior and anterolateral cervical spine procedures. To avoid such a risk, one needs to be familiar with the regional anatomy. The aim of this study was to measure the distance between the vertebral artery and the uncinate process, midline, and the medial side of the longus colli muscle using vertebral artery angiograms at the level of C6, C5, C4, and C3 vertebrae. MATERIALS AND METHODS: In 12 human cadavers, the vertebral arteries were first irrigated with water. Then the arteries were filled with silicon and barium, and finally their angiographic images were obtained. RESULTS: The transverse diameter of the vertebral artery was measured at C6, C5, C4, C3, and C2 level. The values on the left were bigger than the values on the right (p>0.05). The distance between the vertebral artery and the midline decreased from C6 (17.2+/-5.6mm on the right, 17.2+/-2.3mm on the left) to C3 (15.8+/-5.3mm on the right, 13.8+/-2.1mm on the left) (p>0.05). The distance between the apex of the uncinate process and the medial side of the vertebral artery was found to be longer at C4 (2.7+/-1.0 mm on the right, 2.2+/-1.0mm on the left) and C5 (2.5+/-1.1mm on the right, 2.5+/-1.0mm on the left) vertebra levels on the right side (p=0.339 at C4, p=0.862 at C5). The distance between the medial side of the longus colli muscle and the medial side of the vertebral artery was measured as 9.7+/-2.7 mm (9.5+/-2.9 mm on the right, 9.8+/-2.6mm on the left) at C6 level, 9.2+/-2.6mm (8.6+/-2.4mm on the right, 9.8+/-3.1mm on the left) at C5, 9.4+/-1.9 mm (9.2+/-2.1mm on the right, 9.5+/-2.0mm on the left) at C4, and 10.4+/-2.7 mm (10.5+/-3.0mm on the right, 10.1+/-2.6mm on the left) at C3 vertebra level. No significant difference was found between the right and the left (p>0.05). The angle between the vertebral artery and the midline was measured as 4.0+/-1.9 degrees on the right and 2.2+/-1.4 degrees on the left side (p=0.030). CONCLUSION: It was considered that the values obtained could be useful in anterolateral and anterior cervical approaches in terms of evaluating the position of the vertebral artery and its relation to vertebral structures. It is also concluded that the risk of injury in upper subaxial cervical spine is higher than in the lower part of the subaxial cervical spine.

Morphometric analysis of human occipital condyle.

OBJECTIVE: The human occipital condyle is the unique bony structure connecting the cranium and the vertebral column. The progress in neuroimaging techniques has increased interest for aggressive craniovertebral surgery. Such surgery requires the knowledge regarding anatomical aspects of the craniovertebral junction. The aim of the present study is to analyze the occipital condyle morphometrically. MATERIAL AND METHODS: 404 occipital condyles of 202 dry skulls were used for this study. Twenty-seven parameters were measured, including length, width and height of occipital condyle, the distances between the occipital condyle and hypoglossal canal, as well as some important condyle-related angles. RESULTS: The length, width and the height of the occipital condyle were found to be 23.4, 10.6, and 9.2 mm, respectively. The anterior and posterior intercondylar distances are 21.0 and 41.6 mm, respectively. Sagittal intercondylar angle was 59.3 degrees. The intracranial orifice of the hypoglossal canal was found in the junction of the second and third quarter on the condyle in more than 55% of specimens. The shape of occipital condyles was classified into eight types as follows--type 1: oval-like condyle; type 2: kidney-like condyle; type 3: S-like condyle; type 4: eight-like condyle; type 5: triangle condyle; type 6: ring-like condyle; type 7: two-portioned condyle and type 8: deformed condyle. The most common type was type 1 (50%), whereas the most unusual type was type 7 (0.8%). CONCLUSION: It is concluded that the occipital condyle may present various shapes, length, width, and orientation, requiring a careful radiological analysis before craniovertebral junction surgery.

An anatomical study of the C-2 pedicle.

OBJECT: The C-2 pedicle plays an important role regarding screw purchase for spinal fixation. The aim of this study was to measure the C-2 pedicle-related linear and angular parameters. METHODS: Seven parameters in 160 C-2 pedicles (80 dry vertebrae) were measured using a Vernier caliper (accurate to 0.1 mm) and goniometer. The Student t-test was used to determine statistical significance. The authors found that the C-2 isthmus (pars interarticularis) and the C-2 pedicle are distinct structures. The C-2 isthmus covers the pedicle. The isthmus is present between the superior and inferior articular processes, and the pedicle is the structure beneath the C-2 isthmus. It connects the lateral mass-inferior articular process to the body of the axis. The heights of the right and the left C-2 pediculoisthmic components (PICs) were 10.3 +/- 1.6 and 9.9 +/- 1.5 mm, respectively. The posterior part of the superior aspect of the PIC was wider than the anterior portion. The widths of the posterosuperior aspect of the PIC were 11.1 +/- 2 and 11 +/- 1.7 mm on the right and left sides, whereas the widths of the anterosuperior aspect of the PIC were 7.9 +/- 1.7 and 8.5 +/- 1.6 mm, respectively. The inferior widths of this component were 6.0 +/- 1.5 and 5.5 +/- 1.3 mm on the right and left side, respectively. The lengths of the component were 28.8 +/- 2.9 mm on the right and 28.8 +/- 3.4 mm on the left side. The PIC exhibits a lateral-to-medial and an inferior-to-superior angle. Its axial angles were 28.4 +/- 2.5 and 28.6 +/- 2.2 degrees on the right and left sides, respectively; its sagittal angles were 18.8 +/- 2.1 and 18.8 +/- 1.7 degrees, respectively. CONCLUSIONS: The C-2 pedicle can be seen in the inferior aspect of the vertebra, and it connects posterior vertebral elements (that is, the lateral mass and inferior articular process) to the axial body. The isthmus drapes the pedicle. The authors suggest that this be termed "the pediculoisthmic component."

Iliolumbar veins have a high frequency of variations.

The spectrum of individual anatomic variations of the vascular structures are broad, however, the exact incidence of variations of the lumbosacral vein is obscure. In the current study, 38 iliolumbar veins were dissected from 19 formaldehyde-preserved male cadavers. The drainage pattern of the iliolumbar vein was determined. The diameter and the length of the iliolumbar vein were measured, and the relationships of the iliolumbar vein with the lumbosacral trunk, obturator nerve, and iliolumbar artery were ascertained. Means and standard deviations were used as descriptive measures to define variations among the cases. The iliolumbar vein or veins were detected in both sides of all 19 cadavers. Five drainage patterns were seen between the iliolumbar vein and the lumbosacral major veins. In only five cadavers, symmetric drainage patterns were seen on the left and the right sides. In our study, two drainage patterns were seen that were not previously reported. Anatomic variations of the iliolumbar vein are numerous and should be considered to avoid complications when doing surgery.