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Journal of the Anatomical Society of India

Modification Of Protractor To Measure The Sagittal Angle Of Superior Articular Facets Of Vertebrae

Author(s): Patel, M.M. & Singel T.C.

Vol. 52, No. 1 (2003-01 - 2003-12)

Department of Anatomy, M.P. Shah Medical College, Jamnagar (Gujarat), INDIA.


The orientation of superior articular facets is an important phenomenon in the human spine. The present study was undertaken to develop a simple form of modified protractor to measure the sagittal angle of superior articular facets of vertebral column. With help of a simple protractor, long needle, 'U' shaped bent pin & rubberband, the protractor was modified for the purpose.

Key words: - Protractor, long needle, rubber band; superior articular facets, sagittal angle, vertebrae


The orientation of superior articular facets from C3 to S1 carries a functional and clinical significance in normal day-to-day activities of human body. Accurate information about the orientation of articular facets at all levels in human spinal column is not available in literature (Stewart, 1952; Comas, 1960; & Montagu, 1960).

According to the information obtained from the textbooks of anatomy & orthopedics, the articular facets in cervical region are oriented in coronal plane. The articular surfaces of superior facets face upwards & backwards & those of corresponding inferior facets face downwards & forwards. At the cervico-thoracic region and thoracic region, the superior articular facets face posterolaterally. In the thoraco-lumbar and lumbar region, superior articular facets face postero-medially. Similarly, superior articular facets of S1 are directed postero medially.

As part of our present study to measure the sagittal angle of superior articular facets; we searched for an appropriate instrument in various textbooks of anatomy, anthropometry and anthropology; but were not able to locate it. Therefore we decided to develop a simple form of the instrument to measure the sagittal angle of superior articular facets. It was found to be very handy & was successfully used to measure the sagittal angles of superior articular facets.

Material & Methods:

Materials consisted of the protractor, 'U' shaped bent pin, long needle & rubberband as shown in photograph (1). These form the modified type of protractor with 'U' shaped bent pin as shown in photograph (2). It was with the help of this modified protractor only that sagittal angles of both sides were measured.

The median sagittal line of the vertebra on its superior surface was determined by drawing a line passing through spinous process and mid point of the body of vertebra.

The mid point of the body of vertebra was obtained by another line running in the coronal plane to pass through widest portion of the body of the vertebra. Thus in photograph (3) median sagittal line is fixed & drawn with help of long needle & rubberband.

There after, the measurement of sagittal angle with the help of modified protractor becomes very easy & simple as shown in photograph (4). This insrument was successfully applied on 30 human vertebral columns from preserved sets of bones of individual dead bodies received at Anatomy department, M.P. Shah Medical College, Jamnagar as voluntary donations or the bodies being unclaimed.


Thus the modified protractor as described above is the simplest, cheapest & most easily used instrument in measuring orientation of superior articular facets with respect to sagittal plane successfully.


  1. Comas, J: Manual of Physical Anthropology, in : Craniology, osteology, somatology, general considerations, revised and enlarged English edition. Published by: Charles C Thomas, Springfield, Illinois, U.S.A. pp: 254-263,423 (1960).
  2. Montagu, M.F. A: An introduction to Physical Anthropology, In: A practical synopsis of methods of measurements in Physical Anthropology, 3rd edition. Published by : Charles C Thomas, Springfield, Illinois, U.S.A. pp: 555-635 (1960).
  3. Stewart, T.D.: Hardlicka's Practical Anthroprometry. In: Instruments, 4th edition. Published by: The Wistar institute of Anatomy and biology Philedelphia, pp: 25-40. (1952).

Missing Image

Photograph 1

Showing the various componenets of a modified protractor
P = protractor,
RB = Rubber band
N = Needle
BP = U shaped bent pin

Missing Image

Photograph 2

Showing the modified protractor
BP = U shaped bent pin

Missing Image

Photograph 3

Showing the medial Sagittal line ofvertebra
V = vertebra,
RB = rubber band,
N = Needle

Missing Image

Photograph 4

Showing the use of modified protractor to measure the sagittal angler of superior articlular facets of vertebra
MP = Modofied Protractor,
BP = U shaped bent pin,
N = needle, V = Vertebra, SA = Sagittal angle

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