PONTICULI IN ATLAS VERTEBRAE AND ITS CLINICAL ASPECT

Address for Correspondence: Dr. Adil Bashir Shah, Registrar, Department of Orthopaedics, Government Medical College, Srinagar, Kashmir, India. E-Mail: adilshah111@gmail.com. Background: Atlas, the first cervical vertebra, has an oblique ligament which bridges the groove for vertebral artery. This ligament may ossify sometimes converting groove into foramen. These foramina are called as ponticulus posterior or arcuate foramen of the atlas. The ponticuli can distort vertebral artery. They have tendency to cause vertebra basic insufficiency. During any manipulation of cervical spine, these variations of atlas should be kept in mind. Objectives: To study the presence of ponticuli, their other features like whether complete or incomplete, unilateral or bilateral, sidednessright or left. Material and Methods: A total of 50 fully dried adult human atlas were collected from the Department of Anatomy, Government Medical College, Jammu and from the students of the first year MBBS, Government Medical College, Jammu. Bones were intact and free from osteophytes. The superior surface of posterior arch was observed carefully in each atlas for presence of ponticulus. Results: In the present study, 50 human atlas vertebrae were observed out of which 4 atlas (8%) had ponticuli. It was incomplete in 2 vertebrae (4%) and was complete in 2 atlas vertebrae (4%). It was unilateral in 3 atlas vertebrae (6%) and bilateral in 1 atlas vertebra (2%). 2 ponticuli were on the right side, 1 on left side and 2 were found on both sides. All were ponticuli posterior except one which was lateral ponticulus. Conclusion: The presence of ponticuli can cause cervical pain and pressurize vertebral artery leading to cerebrovascular accidents. Detailed knowledge about the variations in the cervical region is very helpful to neurosurgeons, orthopaedicians and otolaryngologists to avoid any mishap. Spinal surgeons must be fully aware about these ponticulus to prevent any complications during surgeries.

Article Information posterior arch.The posterior arch superiorly has a groove present behind the lateral mass of atlas which is being traversed by the vertebral artery (3 rd part), plexus of veins and C1 nerve (dorsal ramus) [3].There is an oblique ligament which bridges the groove for vertebral artery.This ligament may ossify sometimes converting groove into foramen [4].These foramina are First cervical vertebra, atlas is an atypical vertebra.According to Greek mythology, its name has been derived after "ATLAS" who supported earth on shoulders [1].Atlas is devoid of body and spine and is ring shaped [2].Globe of head is being stabilised by atlas.Atlas has two lateral masses being connected by anterior and called as ponticulus posterior or arcuate foramen of the atlas [5].Occassionally a bony bridge can extend from posterior root of transverse process to the lateral masses forming a foramen called ponticulus lateralis through which vertebral artery passes [6].The posterior ponticuli and lateral ponticuli can sometimes be present together and form posterolateral ponticuli.These ponticuli can distort vertebral artery [7].They have tendency to cause vertebra basic insufficiency [8,9].During any manipulation of cervical spine, these variations of atlas should be kept in mind [10].OBJECTIVES 1.To study incidence of ponticuli in atlas vertebrae.
2. To study if ponticuli in atlas are unilateral or bilateral.3. To find the presence of complete or incomplete ponticuli in atlas.4. To study if ponticuli are on right or left side of atlas vertebra.

MATERIALS AND METHODS
present study was done on 50 fully dried adult human atlas, which were collected from the Department of Anatomy, Government Medical College, Jammu and from the students of the first year MBBS, Government Medical College, Jammu.Bones were intact and free from osteophytes.The superior surface of posterior arch was observed carefully in each atlas for presence of ponticulus.

RESULTS
In the present study, 50 human atlas vertebrae were observed out of which 4 (8%) atlas had ponticuli.Ponticulus was incomplete in 2 (4%) vertebrae and was complete in 2 (4%) atlas vertebrae.It was unilateral in 6% and bilateral in 2%.Out of 5 ponticuli, 2 ponticuli were on the right side, 1 on left side and 2 were found on both the sides.All were ponticuli posterior except one which was lateral ponticulus.In total there were 5 ponticuli in 4 atlas vertebrae.(Fig: 1 to 4, Table:1-7)

DISCUSSION
Ponticuli of atlas is a clinical and anatomical variant [14].Vertebral artery tethering can occur due to ponticulus leading to its dissection due to trauma by the various head movements [15].Radiography of cervical spine is a valuable tool if there is suspicion of arcuate foramen especially if the patient complains of headache, temporal region pain, retro orbital pain, vertigo, periodic photophobia, pain in shoulders etc [16].
Detailed knowledge about the anatomy around the cervical region becomes necessary because various congenital, neoplastic and traumatic conditions continue to progress [11].The mechanism behind the ossification of ligament can be due to age.It can be due to external mechanical forces like heavy loads.Pulsations of the vertebral artery can also induce the ossification of ligament.Some suggest that they might be remnants of proatlas [5,8,12].The incomplete bony ponticuli was hypothesized a precursor of the complete bony ponticuli [13].Hasan et al [12] classified arcuate foramen into 6 groups: I -impression of vertebral artery.II -Distinct groove.III-Incomplete posterior ponticulus.IV-Complete posterior ponticulus.V-Lateral ponticulus extended from lateral mass to transverse process.VI-posterolateal ponticulus made by combination of complete posterior and lateral ponticulus [12].The presence of ponticulus was seen in 8% of atlas.Complete ponticulus was seen in 4% of vertebrae and incomplete ponticulus were observed in 4% of vertebrae.Their presence can cause cervical pain and pressurize vertebral artery leading to cerebrovascular accidents.Detailed knowledge about the variations in the cervical region is very helpful to neurosurgeons, orthopaedicians and otolaryngologists to avoid any mishap.Spinal surgeons must be fully aware about these ponticulus to prevent any complications during surgeries.

Table 1 :
Incidence of ponticuli in atlas.

Table 2 :
Percentage of complete and incomplete ponticuli.

Table 3 :
Percentage of unilateral and bilateral ponticuli.

Table 4 :
Percentage of right/left side of the ponticuli.

Table 5 :
Percentage of incomplete ring.

Table 6 :
Percentage of complete ring.

Table 7 :
Comparison of results of present study with previous studies.