Journal of Orthopaedics

The growing need of various orthopaedic procedure as a part of treatment of above pathologies demands accurate knowledge of measurements of the vertebra. The aim of our study is to determine the vertical and transversel diameters of pedicles and to have a morphological database of the vertebral pedicles,To compare and correlate this study with the available data,To discuss the various parameters with respect to applied anatomy. From our study we concluded that there is always an increase in width of lumbar pedicles proceeding from L1 to L5 levels and width being maximum at L5 level to enable in weight transmission.

Measurement of bone or any part of human body provides accurate knowledge about morphology of the structure which helps the clinicians, in diagnosing and treating various diseases. Due to present lifestyle and with its speed, it has resulted in increase in the incidence of assaults on the vertebral column in the form of different spinal pathologies such as prolapsed inter vertebral discs, spondylolisthesis, spondylosis, fractures. The growing need of various orthopaedic procedure as a part of treatment of above pathologies demands accurate knowledge of measurements of the vertebra. The present study was undertaken with the view to study lumbar region pedicles. Posterior spinal instrumentation is a time honored method of spinal fixation. Transpedicular fixation of the spine with pedicular screws is becoming increasingly popular as it is more stable and versatile because it provides three dimensional fixations. Several systems of internal fixation that uses the pedicle as a source of purchase for bone screws from posterior approach into the vertebral body are currently available. These systems depend on the ability of screws traversing the pedicles, the strongest part of vertebrae even in severe osteoporosis, to hold in until solid fusion occurs.

In several studies, researchers demonstrated fusion rates of 90% or greater with pedicle screw fixation. However along with this benefit a number of complications associated with pedicle screw fixation were reported. The most devasting complication related to pedicle screw is neurological injury secondary to misplaced screw abutting or transecting a nerve. So with the use of pedicle screw system it becomes imperative that a causal relationship between the screw and neurological complication be ruled out.

Morphometric study of pedicles of spine of dorsal and lumbar region is thus relevant and critical for proper placement of the traspedicular screw to avoid inadvertent penetration of pedicular wall. Accurate anatomical description of the shape and orientation of dorsal and lumbar pedicles are necessary for use of implantable devices and spinal instrumentation techniques.

Internal fixation methods are increasingly used for lateral fusion after a wide midline decompression, especially if articular processes have been scarified. Several studies have investigated the morphometry of thoracic pedicles with the use of various techniques such as direct measurements and on plain radiographs or computerized tomographic scans.

It is important to distinguish differences in the morphometry of dorsal and lumbar pedicles. Studies were conducted where data have been obtained from radiographs of spines and then compared with direct measurements. These data were then used to verify the accuracy of the technique that radiologist and surgeons must use for pre-operative evaluatio.

1. To determine the vertical and transversel diameters of pedicles and to have a morphological database of the vertebral pedicles.

Morphologic data base will help in the standardization of the dimensions of the pedicles of vertebrae in Indian population.

There has been growing interest in internal spinal fixation. Pedicle is important site for same .This anatomic database will definitely reduce the disparity between the pedicle screw size and the pedicle. Pedicle diameters are large enough in most cases to allow substantially larger screw diameter than currently used. This would improve the strength of transpedicle screw fixation. It will be helpful in designing of the spinal instruments.

Data can be useful while carrying out surgical procedures with the help of model vertebral column in the operation theatre.

The study was carried out in the Department of Orthopaedics and Department of Anatomy, Grant Medical College and Sir J.J. group of Hospitals, Mumbai.

For this study, 25 cadavers, ranging from 2 months to 24 months post embalmed were selected from the Department of Anatomy, Grant Medical College and Sir J.J. group of Hospitals, Mumbai.

Cadavers showing obvious deformity in the spine or a fractured spine were excluded from this study.

Cadavers were dissected using the midline posterior approach so as to expose the spine upto the sacrum. The facet joints and the vertical bony crest just below it were cleared of the soft tissue.

Direct measurements were taken on the vertebra with using a sliding vernier caliper and divider.

It was noted by a sliding vernier caliper and divider. The points just opposite each other on the upper and lower margins of pedicles, in the vertical plane on its lateral aspect, where the diameter was maximum were considered. First record was taken on right pedicle and then on left.

The deepest point on the lateral and medial aspect of each pedicle were chosen. The thickness was measured at these points, at right angles to the long axis of pedicle. First reading was taken for right pedicle and then for the left.

The cadavers showing obvious deformities in the spine or a fractured spine were excluded from this study.

Transverse pedicle diameter
The transverse diameter increased gradually from L1 to L5.
The maximum transverse diameter was found at L5 level.
The maximum mean transverse diameter was found at L5 (12.001 mm).
The range of maximum transverse diameter was from 9 to 20 mm at L5 level.
The minimum mean width of pedicle was found at L1 and was 7.242 mm.
The range of transverse diameter at L1 was from 5 to 11 mm.

Vertical pedicle diameter
The vertical pedicle diameter decreased marginally from L1 to L3 but again increased at L4 and abruptly increased at L5.
The minimum vertical pedicle diameter was noted at L3.
The range of vertical pedicle diameter atL3 was from 12 to 16 mm and mean at L3 level was 14.167 mm.
The maximum vertical pedicle diameter was recorded at L5.
Range of vertical pedicle diameter at L5 was from 14 to 25 mm and mean at L5 was 19.22 mm.

LEVEL		PDW
L1	MEAN	7.242
	S.ERROR	0.21
	RANGE	5 -11
	STD. DEVIATION	2.22
L2	MEAN	7.864
	S.ERROR	0.25
	RANGE	5 – 12
	STD. DEVIATION	2.66
L3	MEAN	9.106
	S.ERROR	0.26
	RANGE	6.5 – 14.5
	STD. DEVIATION	2.79
L4	MEAN	10.45
	S.ERROR	0.22
	RANGE	7.5 – 13
	STD. DEVIATION	2.35
L5	MEAN	12.001
	S.ERROR	0.41
	RANGE	9 – 20
	STD. DEVIATION	4.39

LEVEL		PDH
L1	MEAN	14.227
	S.ERROR	0.17
	RANGE	11 – 16.5
	STD. DEVIATION	1.86
L2	MEAN	14.227
	S.ERROR	0.17
	RANGE	12 - 18
	STD. DEVIATION	1.84
L3	MEAN	14.167
	S.ERROR	0.15
	RANGE	12 – 16
	STD. DEVIATION	1.57
L4	MEAN	14.909
	S.ERROR	0.23
	RANGE	12 – 19
	STD. DEVIATION	2.41
L5	MEAN	19.227
	S.ERROR	0.38
	RANGE	14 – 25
	STD. DEVIATION	4.03

Studies have been already conducted in white and a few non-whites population. However, only very few studies have been conducted in Indian population. Moreover, many studies have not reported all the morphometric dimensions related to pedicle screw placement.

If the dimensions of pedicles change at each vertebral level, information on this might help to prevent failure of fixation and injury to surrounding vital structures.

From above discussion, it is apparent that dimensions of pedicles of lumbar spine play a crucial role in success rate of pedicle screw fixation. The knowledge of pedicle morphology is essential for proper placement of the pedicle screws. Analysis of pedicle dimensions can be obtained from direct measurements, radiographs, computerized tomographic scans.

Berry-(1987) (1) - Studied selected thoracic and lumbar vertebrae. Total 30 vertebral columns were studied. He restricted his work to T2,T7, T12 and L1 to L5. He used the vernier caliper and the outside dimension Caliper and the angular measurements were recorded with a goniometer.

Zindrick(1987) - Study was carried out on the lumbar vertebrae from 170 vertebral columns. Total 2905 pedicles were measured. Measurements were made from the individual vertebral specimen roentrogram.

Krag (1988) – Mainly studied pedicles in the lower thoracic and lumbar region. This was actually a retrospective review of the C.T. Scans of the thoracic and the lumbar spines. Thus the X-ray imaging technique was used for the study.

Scoles(1988) – He employed the resources of the Hamman and Todd Osteological Collection at the Cleveland Museum of Natural History. They studied selected thoracic and lumbar vertebrae. The number of vertebral column studied was fifty. He observed that the posterior element morphology is highly variable and largely unpredictable. Linear measurements were made with the vernier caliper and the protractor. Angular measurements were taken with the goniometer. All the measurements were taken directly from the bony specimens. They calculated the mean, standard deviation, maximum and the minimum values for each. The linear regression analysis was used to search for co-relation between the measurements and also between the individual anthropometric data and the vertebral measurements.

Olsewski(1990) - Lumbosacral spines from 49 emblamed cadaver were used for the study. The pedicles of lumbar vertebrae were measured both directly and radiographically. The study was divided into 3 parts : -

2. The comparison of measurements on radiographs of lumbar pedicles in cadavera with direct measurements

3. The measurements of lumbar pedicles on radiographs and computerized tomographic scans of living young adults patients.

Panjabi (1991) - Study was carried out on the fresh autopsy specimens. He studied 144 thoracic vertebrae with the help of a three dimensional morphometer. The vertebra was secured in a morphometer stand and then subjected to the measurements, the linear as well as angular, by the three dimensional mophometer.

Amonoo –Kuofi(1995) – Has reported on his study of horizontal and vertical diameters of pedicle of lumbar verterbrae. Study was done on plain radiographs and measurements of lumbar pedicle were measured using a vernier caliper.

Sajal Mitra(2002) - Studied the morphometry of lumbar pedicle in Indian population as related to pedicle screw fixation. 20 cadavers were dissected and the measurements of lumbar pedicles were measured using a vernier caliper.

Singel T C(2004) – Study was conducted on 60 adult lumbar vertebrae. Direct measurements of horizontal and vertical diameter of pedicles of lumbar vertebrae were done on the preserved set of bones of individual dead bodies. Measurements were done by vernier caliper.

According to the above discussion, the present study concludes that there is always an increase in width of lumbar pedicles proceeding from L1 to L5 levels and width being maximum at L5 level to enable in weight transmission.

Referring to the above discussion, the present study concludes that the height of lumbar pedicles decreases as we move from L1 to L3 and again increases at L4 and maximum at L5.

The lordotic lumbar curvature of the vertebral column affects the pedicle which show a splaying effect. This is the result of the posterior shift of the weight transmission line.The splaying and tilting was obviously found in the pedicles of L4 and L5 vertebrae in present study. So one has to be aware of the misinterpretation of values of maximum and minimum pedicle diameters while reading computerized tomographic scans. So it is suggested that the patient should be given a proper position to get the exact minimum and maximum pedicle diameters at these levels.

Screw fixation of pedicle is safe method provided the transverse cortical diameter of the pedicle is accurately determined.

To avoid any untoward complication, a image intensifier should be used when inserting transpediclualr screws, particularly at L5.