IJCRR

IJCRR - 5(21), November, 2013

Pages: 50-55

Date of Publication: 21-Nov-2013

STUDY OF TRANSVERSE AND SAGITTAL DIAMETERS OF LUMBAR PEDICLES IN RELATION TO TRANS-PEDICULAR SCREW FIXATION USING MRI IN RAJASTHAN POPULATION

Author: Meghna Bhaumik, Neelam Bapna, Uday Bhaumik, K. Prabhakaran

Category: Healthcare

Abstract:Introduction: The technique of inter-pedicular screw fixation for the purpose of spinal fixation has gained enormous importance in the recent years. The choice of screw for the procedure is determined by the minimum (transverse) diameter of the pedicle .Morphometric data on the diameters of the pedicles are therefore useful in preoperative planning and in designing pedicle screws.Most of the previous study of the morphometry of pedicle is based on white population using x-rays and CT scans. Therefore the present study was conducted in the Western region of India in state of Rajasthan to measure the morphometry of pedicles in relation to trans-pedicular screw fixations as well as to distinguish differences in the morphometry of pedicles in men and women of different age groups using MRI technique. Aims and Objectives: To evaluate the sexual differences in transverse and Sagittal diameters of lumbar vertebral pedicle. Also to determine the difference of diameter in the pedicles of different age groups and finally to determine the morphometry of pedicles in relation to trans- pedicular screw fixation in the region of Rajasthan. Materials And Methods: MRI scan of 1000 patients (both males and females) between the age group of 20 to 60 years, with the history of low back pain reporting to the outpatient department of Neurosurgery, Orthopedics, Rehabilitation and inpatients admitted in various wards for complaints of disc protrusion, disc extrusion, spondolysthesis (not associated with gross vertebral body collapse) of S.M.S. hospitals, Jaipur formed the material for the current study. Results: There is a cranio\?caudal increase of transverse and sagittal diameters from L1 toL5 vertebrae. Dimensions of male population are significantly higher than female population with respect transverse diameter and sagittal diameter. With the above parameters the size of the screw for transpedicular screw fixation can be derived.

Keywords: lumbar vertebra, lumbar pedicle, trans-pedicular screw fixation

Full Text:

INTRODUCTION

The technique of inter-pedicular screw fixation for the purpose of spinal fixation has gained enormous importance in the recent years.

Stefee et al¹ and Zindric² described the screw fixation procedure as the method of choice for stabilization of the lumbo-sacral spine. Many types of pedicle screw systems have been  developed; basically  they  all  entail  the  insertion  of  screws through  the  pedicle  from  the  posterior  aspect  into  the  vertebral bodies. The success of the technique depends upon the ability of the screws to obtain and maintain balance within the vertebral body² .This is determined among other factors by the accuracy of choice of screw, size of the pedicle and the quality of the bone of the pedicle.

The   choice   of   screw   for the procedure is determined by the minimum (horizontal) diameter of the pedicle^3,4 .Morphometric data   on   the   diameters   of   the   pedicles   are therefore useful in preoperative planning and in designing pedicle screws.

Most  of  the  previous  study  of  the  morphometry  of  pedicle  is based on white population^5-10         

Almost  all  the  previous  workers  have  reported  the  data  on morphometry  of  the  pedicle  based  on  a  common  pool  of  vertebrae where male and female vertebrae were pooled together^5,6,2,7. However, recently Amonoo Kuofi¹⁰ has reported statistically significant sex differences in pedicle morphometry.

Thus according to Kragman³, as the racial variations in skeleton are well known the morphometry  of  pedicle  may vary population  to  population,  even  within  the  same  population,  the anatomical  variations  have  been  reported  in  the  shape,  size  and angulations of the pedicles by Weinstein et al⁴.

C.T. scans or M.R.I. sections represent a new approach to    vertebral morphometry allowing certain measurements to be measured for the first time.

Morphometric studies of the pedicles have demonstrated variations in pedicle shape, size and angulations. Carefully taken routine radiographs, CT scans and MRI scans can help in determine about the diameter, length and angulations of the pedicle.  This  is  critically important,  particularly  in  placing  screws  in  rotated  vertebrae  and deformed spines like in patient with scoliosis or spondylolisthesis.

Anatomic variations may prevent placing a screw in a particular pedicle or necessitate using a smaller screw than originally planned.

Risks of neural damage can be minimized by thorough knowledge of the anatomy of vertebral column as well as practicing on anatomical  specimens.  Therefore  the  present  study  was  conducted  in  the  Western region of India in state of Rajasthan to measure the morphometry of pedicles  in  relation  to  trans-pedicular  screw  fixations  as  well  as  to distinguish  differences  in  the  morphometry  of  pedicles  in  men  and women of different age groups.

AIMS AND OBJECTIVES

1. To evaluate the sexual differences in transverse and
2. Sagittal diameters of lumbar vertebral pedicle.
3. To  determine  the  difference  of  diameter  in  the  pedicles  of  different age groups.
4. To determine the morphometry of pedicles in relation to trans- pedicular screw fixation in the region of Rajasthan.

MATERIALS AND METHODS

MRI scan of 1000 patients (both males and females) between the age group of 20 to 60 years, with the history of low back pain reporting to the outpatient department of Neurosurgery, Orthopedics, Rehabilitation and inpatients admitted in various wards for complaints of disc protrusion, disc extrusion, spondolysthesis (not associated with gross vertebral body collapse) of S.M.S. hospitals, Jaipur formed the material for the current study. Only Patients who were natives of Rajasthan State (born and brought up in Rajasthan) were included in the study.

Whereas Patients suffering from congenital spinal deformities like Achondroplasia, Tethered cord syndrome, spinal dysraphism, spilt cord malformation etc. and Patients affected with spinal tuberculosis, spinal meningitis and even Patients coming with spinal trauma along with bony injuries, were excluded from the study. Also Patients below 20 years of 

Transverse  diameter  of  pedicle  –  The  transverse  diameter  of pedicles  are  showing  a  steady  increase  from  first  to  fifth  lumbar vertebrae. The value of transverse diameter of pedicle is 9.01 mm at L1  vertebra  and  18.00  mm  at  vertebra  L5,  while  in  females  the minimum value is 8.10 mm at L1 vertebra and the maximum value is 16.01 mm at L5 vertebra. P value is highly significant for L1, L3, L4 and L5 vertebrae (P<0.001), between male and female population and significant changes are noted at L2 vertebra in both sexes. With advancing   age   this   diameter   also   follows   a   steady   increase   in dimensions.

Sagittal diameter of pedicle – This parameter is showing increase in  dimensions  of  pedicles  in  cranio  -caudal  directions  with  the minimum  values  of  16.40  mm  in  males  at  L1  vertebra  to  the maximum  value  of  18.25  mm  at  L5  vertebra,  while  in  females  the minimum value of sagittal diameter is 15.45 mm at L1 vertebra and the maximum value of sagittal diameter is 17.53 mm at L5 vertebra. Significant changes (P<0.01) are recorded between male and female populations,  while  non  significant  changes  are  noted  at  L4  and  L5 vertebrae  in  both  sexes.  Sagittal diameter also  undergoes  linear increase in dimensions as the age progresses.

The studies conducted  by  H.S.  Amonoo  Kuofi¹⁰,  Mitra et  al¹¹  on  horizontal  and  vertical  diameters  of  pedicles stated,  that  the  values  of  sagittal  diameter  followed  an  increasing trend  from  above  downwards  (from  vertebra  L1  to  L5),  the  highest value for sagittal   diameter was found at L5 vertebra and the lowest value  was  for  vertebra  L1.  The  values  of  sagittal  diameters of pedicles in males were 17.1 at L1 vertebra and in females it was 16.2 mm¹⁰ and  the  sagittal  diameter  was  18.6  mm  in males  and  in  females  it  was  17.65  mm  at  vertebra  L5¹⁰.

In present study we have also noted, values regarding sagittal diameters of pedicles similar to Amonoo Kuofi¹⁰. In present study the sagittal diameter of pedicles in males is 16.40 mm and in females it is 15.45 mm for vertebra LI. At vertebra L5 the sagittal diameters of pedicles  in  males  is  18.25  mm  and  in  females  it  is  17.53  mm.  In present  study  the  values  of  sagittal  diameters  are  lower  in  females than male subjects.

CONCLUSION

From the present study following conclusions are derived –

1. There is a cranio–caudal increase of transverse and Sagittal diameters from L1 toL5 vertebrae.
2. Dimensions of male population are significantly higher than female population with respect transverse diameter and Sagittal diameter.
3. With the above parameters the size of the screw for transpedicular screw fixation can be derived.

The large sample size of the study reiterates and establishes the  observations,  that  there  are  significant  differences  in  pedicular morphology  in  Indian  population,  when  compared  with  Western counterparts.  Although  the  trends  are  similar  with  few  exceptions but  the, values  are  consistently  lower  for  various Morphometric Measurements in Indian population. The difference in values may be on account of ethnic related morphologic differences as Indians have noticeably smaller build than their Western counterparts. Ethnicity with its diverse cultural, dietary and genetic factors and not just the body size or height, has the potential to influence the overall pedicle morphometry.

Thus,  this  study  strengthens  the  case  for  customizing  the existing           range of  spine pedicle implants according to ethnic characteristics  or  developing  ethnic  specific  implants.  Further,  this study indicates that computer            software           aided    pedicular morphometery  data  are  quite  reliable  and  comparable  to  other published studies with other methods, but has advantages like being much  simpler,  more  user  friendly,  unbiased  and  patient  specific. Therefore, the need for preoperative computer aided M.R.I/C.T. base morphometrics

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