Original Article STUDY OF THE SPINAL CANAL OF UPPER CERVICAL SPINE Athar Maqbool1, Zubia Athar2, Owais Hameed1 ABSTRACT Background: The anteroposterior and transverse diameter of cervical spinal canal is reported to have some variability among different populations. Objective: To determine the midsagittal (antero posterior) diameter at the inlet & outlet and coronal (transverse) diameter of cervical spinal canal in first cervical (atlas) and second cervical (axis) vertebrae. Additionally review of literature was conducted to compare the findings with previous reported findings. Material and methods: This descriptive study was conducted in Anatomy department of Sheikh Zayed Medical College, Rahim Yar Khan & Wah Medical College, Wah Cantt. Rawalpindi, Pakistan. Measurement of midsagittal & coronal diameter of spinal canal of first & second cervical vertebrae was carried on dried human spinal columns of Pakistani origin. Results: In atlas vertebra mean midsagittal inlet & outlet diameter was 32.96 & 30.46 mm respectively whereas coronal diameter was 27.89 mm. In axis vertebra mean midsagittal inlet & outlet diameter was 20.74 & 15.80 mm respectively with a coronal diameter of 22.73 mm. Conclusion: Measurement of sagittal and coronal diameter of upper cervical spinal canal is of great clinical significance. Larger sagittal diameter of spinal canal has a protective effect with respect to injury of the spinal cord, so further studies are suggested to standardized the values of spinal canal. Key words: Atlas vertebra, axis vertebra , cervical spinal canal, midsagittal diameter, coronal diameter. INTRODUCTION amount (~7%) per level and is less in total than the The upper cervical spine is defined by cervical C1-2 lateral rotation.4 The morphology of vertebral vertebrae, C1 (the atlas) and C2 (the axis). This column is influenced externally by mechanical and region is distinct in anatomic shape and is more environmental factors and internally by genetic, mobile than the lower cervical spine, the subaxial hormonal and metabolic factors.5 Different cervical spine (C3 through C7). The atlas, or first measurements of the normal range of the cervical vertebra, is so named because it supports anteroposterior diameter of the spinal canal have the globe of the skull. Its appearance is quite been reported by authors.6-10 Certain amount of different from the other cervical vertebrae. Most discrepancy exists in these measurements that were notably it has no body or spinous process, but obtained from lateral radiographs of the cervical instead consists of a ring of bone made up of two spine. These discrepancies are described by Boijsen9 lateral masses joined at the front and back by the and are due to measurement differences caused by anterior arch and the posterior arch. The occipital different target distances, object-to-film distance, condyles of the skull rest upon the lateral masses and magnification errors common with radiographs. of C1. These articular facets allow most of the It has been suggested by the Lee et al11 that flexion and extension of the head on the neck as measurements made on the radiographic films could the occipital condyles articulate on the atlas.1-3 The not reveal the exact and true dimensions of the spinal axis is the second cervical vertebra. Its most canal diameters and, therefore, anatomical distinctive feature is a blunt tooth-like process, specimens were studied for accurate measurements. called the dens (Latin for "tooth") or odontoid There are few reports on the analysis of spinal canal process, which projects upward. The dens of upper cervical spines using the anatomical provides a kind of pivot and collar allowing the specimens; this study aims to evaluate: head and atlas to rotate around the dens. Most of The midsagittal inlet & outlet diameter of the spinal the lateral rotation of the neck actually occurs at canal in atlas and axis vertebrae and coronal or the C1-2 junction; the remaining motion of the transverse diameter of the spinal canal in both atlas cervical spine is distributed among the subaxial and axis vertebrae. spine vertebral motion segments as a fractional 1. Sheikh Zayed Medical College/Hospital, Rahim Yar Khan. MATERIAL & METHODS 2. Wah Medical College, Wah Cantt. The upper cervical vertebrae, C1 (atlas) and C2 (axis), of fifty sets of dried human spinal columns Correspondence: Professor of Anatomy, Sheikh Zayed Medical College, stored in the Anatomy department of Sheikh Zayed Rahim Yar Khan. Medical College, Rahim Yar Khan and Anatomy department of Wah Medical College, Wah Cantt, Email: [email protected] Mobile: 0300-5363985 Rawalpindi were used for this study. All subjects JSZMC Vol.3 No.3 351 Original Article were adults, age range was between 25 and 60 with a standard deviation of 2.23 (Table-I). years. Before taking the measurements, all the Measurements in midsagittal and coronal samples were inspected to ensure that the diameter of spinal canal in C2: vertebrae were intact and free from osteophytes or Midsagittal spinal canal inlet diameter was 17.55 any other vertebral abnormality. mm to 26.90 mm. The mean value was 20.74 mm In this descriptive study, the following parameters with a standard deviation 2.06. Midsagittal spinal were determined in the vertebrae: canal outlet diameter was 12.45 mm to 21.40 mm. 1. The midsagittal (anteroposterior) inlet, outlet, The mean value was 15.80 mm with a standard and coronal (transverse) diameters of the spinal deviation of 1.81. canal in C1. (Fig. I) Coronal (transverse) spinal canal diameter was 18.70 2. Coronal (transverse) diameter in C2. (Fig. II) mm to 25.40 mm. The mean value was 22.73 mm 3. In C2 vertebra, spinal canal inlet & spinal canal with a standard deviation of 1.60 (Table-I). outlet midsagittal diameters. (Fig. III) To carry out these linear measurements sliding Table I: Anatomic Parameters of C1 & C2 Spinal vernier caliper (Peacock Co., Tokyo, Japan) was Canal. used. The accuracy was 0.01 mm. Fig. I:( A). Midsagittal (anteroposterior) diameter of spinal C1 C2 canal inlet of Atlas (C1) Vertebra. Midsagittal Midsagittal Midsagittal Midsagittal Coronal Coronal Values Inlet Outlet Inlet Outlet (B).Midsagittal (anteroposterior) diameter of spinal canal Diameter Diameter Diameter Diameter Diameter Diameter (mm) (mm) outlet of Atlas (C1) Vertebra. (mm) (mm) (mm) (mm) (C).Coronal (transverse) diameter of spinal canal of Atlas Mean 32.96 30.46 27.89 20.74 15.80 22.73 (C1) Vertebra. Fig. II: (A). Midsagittal diameter of inlet of C2 and (B) Minimum 27.90 25.70 22.45 17.55 12.45 18.70 outlet Maximum 38. 25 35.35 32 .80 26.90 21 .40 25.40 Fig. III: Coronal diameter of C2 Standard 2.19 2.17 2.23 2.06 1.81 1.60 deviation DISCUSSION The spinal canal extends from the foramen magnum to the sacral hiatus. In the cervical and lumbar regions, which exhibit free mobility, it is large. Stenosis (narrowing) of the spinal canal may occur at single or multiple spinal levels and mainly affects the Fig. I cervical and lumbar regions. Severe spinal stenosis may compress the spinal cord and compromise its arterial supply. Localized stenosis may present with Fig. II the clinical features of spinal nerve compression or stretching of nerve roots over a prolapsed disc which cause ischemia and may provoke more damage to these structures.5 Fig. III Table II: Normal Range of Variations in Midsagittal RESULTS (Anteroposterior) Diameter of Spinal Canal of C1 (Atlas) & C2 (Axis) Vertebrae of Various Studies measured by Measurements in midsagittal and coronal Plain Radiographs diameter of spinal canal in C1: Focus- C1 C2 Number of Studies film Mean Range Mean Range Midsagittal (anteroposterior) inlet diameter of Cases distance (mm) (mm) (mm) (mm) Boijsen 1.5 m spinal canal, was 27.90 mm to 38.25 mm. The 200 ----- 19 - 32 ----- 16 - 27 (1954) (59 in.) mean value was 32.96 mm with a standard Wolf, Khilnani & 72 in. 200 ----- 16 - 30 ----- 15 - 27 deviation of 2.19. Midsagittal (anteroposterior) Malis (1956) outlet diameter was 25.70 mm to 35.35 mm. The Payne and Spillane 72 in. 90 ----- 16 - 26 ----- 15 - 23 mean value was 30.46 mm with a standard (1957) Burrows 72 in. 300 22.9 16 - 27 20.3 15 - 25 deviation of 2.17. Coronal (transverse) was 22.45 (1963) mm to 32.80 mm. The mean value was 27.89 mm Oon (1974) 72 in. 400 20.3 15 - 27 18.5 15 - 23.5 352 JSZMC Vol.3 No.3 Original Article Table III: Midsagittal (Anteroposterior) & Coronal (Transverse) Diameters of Spinal Canal for Atlas & Axis Vertebrae by Various Studies measured on Dried Bones No. of C1 C2 sets of Maximum Minimum Midsagittal Coronal Diameter Spinal Canal Coronal Diameter dried Midsagittal Spinal Canal Inlet (Outlet) Diameter (Canal Width) Outlet (Canal Width) Studies bones (Inlet) Diameter Mean Rang Range Mean Range Mean Range Mean Range Range Mean (mm) Mean (mm) (mm) (mm) (mm) (mm) (mm) (mm) (mm) (mm) (mm) (mm) Mazzara & 19.0 – Fielding 103 ----- ----- 30.1 25.5 -36.0 28.8 22.0 – 38.0 19.0 12.9 – 32.2 ----- ----- 22.8 26.5 (1988) Panjabi et al 12 ----- ----- ----- ----- ----- ----- 21.0 24.5 (1991) Xu et al 30 ----- ----- ----- ----- ----- ----- 18.0 15 – 22 15.3 13 – 19 21.9 18 – 26 (1995) Sengul & 38.2 – 20.7 – K adioglu 40 46.2 31 .4 23.7 – 46.3 28.7 25.2 – 33.5 20.8 11.5 – 28.9 17 .7 ----- 24. 5 77.5 28.3 (2006) Maqbool et al 27.90- 25.70 – 22.45 – 12.45 – 18.70 – ( Present 50 32.96 30.46 27.89 20.74 17.55 – 26.90 15.80 22.73 38.25 35.35 32.8 0 21.40 25.40 Study) Many researchers working in different areas of the 20 Xu et al measured the spinal canal of thirty dried world have been determining the mean diameter second cervical vertebrae of adult males and found Types and No of isolat es Antibiotics tested and sensitivity of the cervical spinal canal at different vertebral that the mean canal inlet (midsagittal) diameter was amikacin gentamicin ciprofloxacin ceftazidime ceftriaxone imipenem aztreonam levels in normal subjects, so that the clinicians 18.0 mm and mean canal outlet (midsagittal) Number(%) Number(%) Number(%) Number(%) Number(%) Number(%) Number(%) may be able to diagnose cervical spinal stenosis by diameter was 15.3 mm whereas mean spinal canal consulting these reference values.