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Journal of the Anatomical Society of India

Orientation of Superior Articular Facets from C3 to S1 Vertebrae

Author(s): Patel M M, Gohil D V, Singel T C

Vol. 53, No. 2 (2004-07 - 2004-12)

M. P. Shah Medical College, Jam nagar, Gujarat

Abstract:

A study was conducted on 50 adult dry human vertebral columns from the collection of Anatomy Department of MP Shah Medical College, Jamnagar to know the orientation of superior articular facets of 3rd cervical to 1st sacral vertebra in respect to the sagittal plane. The aim was to evaluate the change in orientation of superior articular facets at various levels in the vertebral column and to observe the pattern of changes.

In the present study the inclination of superior articular facets at C3 vertebra was observed as posteromedial and gradually changed to posterolateral at thoracic level. In the lumbar region the superior articular facets faced posteromedially.

A gradual change in orientation of superior articular facets was observed in cervico-thoracic region in 80% of vertebral columns while in thoraco-lumbar region, gradual change was observed only in 6% vertebral columns.

In the cervico-thoracic region, a sudden change of orientation of superior articular facets was seen in 20% vertebral columns most commonly occurring at C4-C5 and C5-C6 levels, while in the thoraco-lumbar region 94% vertebral columns showed a sudden change in orientation of superior articular facets, most commonly at T12-L1 level followed by T11-T12 level. Asymmetry of orientation of superior articular facets was observed in few C4 to T1 and T12 veretebrae. Knowledge of change of orientation of superior articular facets of vertebrae helps in understanding of movements and clinical conditions of the vertebral column.

Key words: Superior articular facets, orientation, vertebrae, sagittal angle

Introduction:

The orientation of superior articular facets of vertebrae at various levels changes according to the functional and mechanical requirement of the vertebral column, Peter L William (2000). This change is either sudden, at one vertebral level or gradual, over two or more than two vertebral levels, Davis (1955), Singer et al (1988), Shinohara (1997), Pal and Routal (2001).

Articular facets guide the extent and direction of vertebral movements. In the cervical region the upward inclination of superior articular facets allows free flexion and extension. Cervical lateral flexion and rotation are always combined. Superomedial inclination of superior articular facets imparts rotation during lateral flexion. In the thoracic region lack of upward inclination of superior articular facets prohibits much flexion and extension. However, the direction of articular facets allows free lateral rotation, Davis (1955). The lumbar extension is wider in range than flexion; rotation is limited by absence of common center of curvature for right & left articular facets, Putz (1985).

Superior articular facets of typical cervical vertebrae are directed supero-posteriorly. In the thoracic region they face posteriorly and are directed a little superolaterally. The superior articular facets of lumbar vertebrae face posteromedially, Peter L William (2000). There is a change of orientation of superior articular facets from cervical to lumbar vertebrae. The level of change in orientation in cervico-thoracic region can occur any where between C4 and T1 vertebrae, the C6 vertebra being the most common site of transition, Pal and Routal ( 2001). The change in orientation of superior articular facets from thoracic to lumbar type usually occurs at 11th thoracic vertebra, sometimes 12th or 10th, Davis (1955), Shinohara (1997), Singer et al, (1988). The present study was undertaken to know the orientation of superior articular facets of C3 to S1 vertebrae in a sequence.

Material and Methods:

50 dry adult human vertebral columns from the collection in the Anatomy Department, MP Shah Medical College, Jamnagar were included in the study. All belonged to the male sex and were ossified completely. They were free from any congenital anomaly or pathological change. The sagittal angle of both superior articular facets of each vertebra was measured with the help of a modified protactor, Patel and Singel (2003) and the method adopted by Tulsi and Hermanis (1993). The sequential change of sagittal angle from C3 to S1 vertebral levels was noted in each vertebral column. The range, mean and standard deviation was calculated for each vertebral level. When there was a change in orientation of superior articular facets between two adjacent vertebrae it was called sudden change and when it occurred over two or more vertebral levels it was named gradual. The difference of orientation of right and left superior articular facets if any, was also noted.

Fig. 1: Measurement of Sagittal angle of superior articular facet.

Missing Image

Table - I: Range, Mean & Standard Deviation of Sagittal angles of superior articular facets of right and left sides from C3 to S1 vertebrae.

Vertebra Left Right
Range Mean S.D. Range Mean S.D.
C3 62-85 70.2 7.03 54-85 69.5 7.7
C4 60-104 82 10.16 68-112 81.4 9.56
C5 70-118 91 11.78 75-120 91 10.95
C6 76-120 95.93 10.06 75-118 95.56 10.45
C7 72-104 93.9 7.4 78-105 94.23 6.64
T1 86-110 99.03 5.38 85-114 99.58 5.49
T2 95-115 105.2 5.07 96-118 106.89 6.58
T3 102-120 109.5 5.22 96-118 107.42 5.95
T4 98-120 106 5.75 94-117 105 5.35
T5 92-118 106 5.5 93-117 107 6.2
T6 99-117 107 4.3 95-116 107 4.8
T7 97-117 106 4.6 99-115 106 4.2
T8 91-113 105 4.4 96-115 106 4.13
T9 97-110 103 3.3 91-115 105 5
T10 91-111 105 4.6 95-120 106 4.7
T11 65-115 106 8.2 75-115 105 6.6
T12 30-120 87 24.5 29-123 87 27.3
L1 15-102 36 18.4 10-86 37 16.33
L2 10-40 29 0.21 10-43 26 7.7
L3 5-45 29 10.33 5-46 25 10.4
L4 12-57 35 11.12 7-50 40 14
L5 7-70 44 13.39 7-63 41 12.9
S1 20-79 55 14.8 30-75 36 17

Observation and Results:

In all 50 vertebral columns the superior articular facets of C3 vertebrae were facing posteromedially(mean sagittal angle 70.2 degree). The orientation changed from posteromedial to posterolateral from C4 to C7 vertebrae (mean sagittal angle varied from 60 to 120°). At the thoracic level the superior articular facets in all 50 vertebral columns from T1 to T10 were facing posterolaterally (mean sagittal angle varied from 105.0 to 109.5°). At T11 and T12 vertebra the orientation of superior articular facets was found to be variable from posterolateral to posteromedial. At T11 level in 48 vertebral columns the direction of superior articular facets was posterolateral (mean sagittal angle 106°) while at T12 level in only 25 vertebral columns the direction was posterolateral (mean sagittal angle 87°). In all all 50 vertebral columns the superior articular facets of lumbar vertebrae were facing posteromedially (mean sagittal angle varied from 29 to 55°) (Table 1).

Discussion:

Movements of vertebral column mainly occur at the intervertebral discs. Zygapophyseal joints, formed between superior and inferior articular facets of adjacent vertebrae, contribute to the extent and direction of movement of vertebral column. The direction of superior articular facets of cervical vertebrae is Postero-superior, Peter William (2000). In present study, the orientation of superior articular facets in the cervical region was variable. At the level of C3 the orientation was posteromedial in 100% while at C4 level the orientation was postero-medial in 74% vertebral columns (Table - 2). Pal and Routal (2000) found the same in their study on 30 vertebral columns. In the present study a gradual change from postero-medial orientation to postero-lateral orientation occurred from C4 to C7 vertebrae. At C5, 30% vertebrae had postero-lateral superior articular facets while at C6, 56% and at C7, 76% vertebrae had postero-lateral superior articular facets. In thoracic region, the superior articular facets faced posterolaterally in all vertebral columns from T2 to T10 vertebrae. At T1 level this direction was seen in 94% vertebral columns (Table -2). This is the typical orientation given by Peter William (2000) and Davis (1965). The orientation of superior articular facets in lumbar region was posteromedial, seen in 100% vertebral columns (Table-2), which is same as mentioned by Peter William (2000).

The pattern of change of the orientation of superior articular facets from C3 to S1 vertebral levels revealed that the change from postero-medial inclination at C3 level to postero-lateral inclination at T1 level was predominantly gradual occurring over C4 to C7 levels seen in 80% vertebral columns. In only 20% columns the change in orientation was sudden (over two adjacent vertebra) usually at C4/C5 and C5/C6 levels. The same has only been reported earlier by Pal et al (2003) in their study of 30 vertebral columns.

Table 2: The orientation of superior articular facets from C3 TO S1 vertebrae

Vertebra Posteromedial Posterolateral Transitional
C3 50 0 0
C4 37 3 10
C5 15 15 20
C6 4 28 18
C7 4 38 8
T1 0 47 3
T2 0 50 0
T3 0 50 0
T4 0 50 0
T5 0 50 0
T6 0 50 0
T7 0 50 0
T8 0 50 0
T9 0 50 0
T10 0 50 0
T11 2 48 0
T12 22 25 3
L1 50 0 0
L2 50 0 0
L3 50 0 0
L4 50 0 0
L5 50 0 0
S1 50 0 0

On the other hand, the present study noted that the change from thoracic type postero-lateral superior articular facets to lumbar type postero-medial superior articular facets was sudden in 94% vertebral columns, occurring most commonly at T12-L1 vertebra in 54%.

Table 3: Pattern of sudden change in orientation of superior articular facets

Region Level
Cervicothoracic C3/C4 C4/C5 C5/C6 C6/C7 C7/T1 Total
  1 4 4 0 1 10
Thoraco lumbar T10/T11 T11/T12 T12/L11      
1 9 27     47

Fig. 2

Missing Image

On the right side - Sudden change of superior articular facets from postero-laterally facing facets to postero- medially facing facets in thoracolumbar region.
On the left side - Vertebrae C4, C5, C6, C7 & T1 having gradual change in orientation of superior articular facets.
Arrows on C4 shows the facets pointing posteriorly.
Arrows on C5 to C7 shows gradual change of direction to Postero-lateral.
Arrows on T1 shows the facets changing their direction and facing postero-laterally.

It was seen at T11-T12 vertebra in 38% vertebral columns while at T10 vertebral level in only 2% cases (Table-3). Shinohara et al, 1997 also reported a change in orientation of superior articular facets from the thoracic to lumbar type to occur over two vertebral segments in 66% and the most common site of change in their study was at T12-L1 level (in 44%) followed by T11-T12 level (in 22%), which is similar to present study. In remaining 34% transition was gradual over three vertebrae. However, it is in contrast to that reported by Peter William (2000), according to whom the transition most commonly occurs at T11 vertebral level and occasionally at T12 or T10 levels.

Asymmetry of superior articular facets in cervicothoracic region was noted in C4 (20%), C5 (40%), C6 (36%), C7 (16%), T1 (6%) vertebrae. Since there is a gradual change of orientation of superior articular facets from C4 to T1 level these vertebrae would be where the transition is occurring.

Asymmetry of superior articular facets in thoracolumbar region was rare, noted in only 6% T12 vertebrae. This could be because the transition from thoracic to lumbar type superior articular facets was predominantly sudden. A study by Singer KP et al, 1988 however, noted that articular tropism of more than 20 degrees was seen in 21% of T11-T12 joints and 9% T12-L1 joints.

Conclusion:

There was a gradual change of orientation of superior articular facets from cervical to thoracic region and sudden change from thoracic to lumbar region. It may have significant role in movement and clinical conditions of vertebral column.

References:

  1. Davis PR. The thoraco lumbar mortice joint. Journal of Anatomy. 1955; 89: 370-377.
  2. Pal GP, Routal RV. The orientation of articular facets of the zygapophyseal joints at the cervical and upper thoracic region. Journal of Anatomy. 2001; 198: 431-441.
  3. Patel MM, Singel TC. Modification of protractor to measure the sagittal angle of superior articular facets of vertebrae. J. Anat. Sor. India. 2003; 52 (1): 15.
  4. Peter L William. Gray's Anatomy. Churchill Livingstone, Edinburgh, London.. 2000; 38th Ed; 5, 515-527.
  5. Putz R. The functional morphology of the superior articular processes of the lumbar vertebrae. Journal of Anatomy 1985; 143: 181-187.
  6. Shinohara H. Changes in the surface of the superior articular joint from the lower thoracic to the upper lumbar vertebrae, J. Anat. 1997; 190: 461-465.
  7. Singer KP, Brcidahl PD, Day RE. Variations in the zygapophyseal joint orientation and the level of transition at the thoracolumbar junction. Preliminary survey using computed tomography. Surg. Radiol. Anat. 1998; 10: 291295.
  8. Tulsi RS, Hermanis GM. A study of the angle of inclination and facet curvature of superior lumbar zygapophyseal facets. Spine. 1993; 18: 1311-13
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