Original Article
M ORPHOM ETRIC AND M ORPHOLOGICAL STUDY OF ARTICULAR
FACETS OF THE THORACOLUM BAR VERTEBRAL COLUM N IN
NORTH INDIAN POPULATION
Rimpi Gupta *
1, Rajan Singla
2, Gaurav Agnihotri
3, Reenu Kumari
4, Deepak Goyal
5.
ABSTRACT
Address for Correspondence: Dr. Rimpi Gupta, Assistant Professor, Depart ment of Anat omy, BPS GM C For Women, Khanpur Kalan, sonipat , Haryana, India. E-M ail: dr.rimpigupta15@gmail.com
Background: The art icular processes of t hor acolum bar vert ebral colum n play an im port ant role in w eight t ransm ission and det erm ining t he range and direct ion of m ovem ent s bet w een any t w o vert ebrae. Size of t hese facet s has been correlat ed w it h t he m agnit ude of st ress im posed on t hem .
Purpose of study: The present st udy has been conduct ed on t he art icular processes of 510 ver t ebrae (t horacic: 360; lum bar:150) w it h t he aim t o provide high qualit y dat a set s for const ruct ing t he m odels of spine t o st udy m echanics of spinal inst rum ent at ion. The lengt h , w idt h and t he dist ance bet w een t he r ight & left su perior & inferior ar t icular processes have been m easured w it h t he vernier callipers. The presence/ absence of m am illary t ubercle has been observed in t he present st udy.
Results:The lengt h of t horacic SAFs w as alm ost sam e at all levels w hereas t hat of t he lum bar SAFs increased gradually from L1-L5. However t he widt h show ed a variable t rend. In case of t horacic IAFs bot h t hese param et ers show ed a variable t rend. Whereas in lum bar region, t hese increased gradually from L1-L5. The dist ance bet w een t w o inferior art icular processes w as m ore t han t hat bet w een t w o super ior art icular processes at alm ost all levels except T1-T3 & L1-L4 w here reverse w as t rue. The m am illary t ubercle/ process w as alt oget her absent from T-1 t o T-8. From T-9 t o T-11, t he num ber of vert ebral colum n show ing m am illar y t ubercle increased from 4-19. How ever at T-12, it w as seen in 29 Vert ebral colum ns. In lum bar region, it w as w ell developed in all vert ebrae and t er m ed as m am illary process.
Conclusion: The m easur em ent s obt ained by present st udy r eveals t he im port ance of ar t icular facet s in underst anding basic spinal m echanics and it s applicat ion w it h respect t o w eight t ransm ission.
KEY W ORDS: Superior art icular facet , Infer ior art icular f acet , M am illar y pr ocess, w eight t ransm ission.
INTRODUCTION
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Received: 07 Aug 2015 Accept ed: 27 Aug 2015 Peer Review : 07 Aug 2015 Published (O): 30 Sep 2015 Revised: None Published (P): 30 Sep 2015
Int ernat ional Journal of Anat omy and Research ISSN 2321-4287
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DOI: 10.16965/ ijar.2015.236
* 1 Assistant Professor, Depart ment of Anat omy, BPS GM C For Women, sonipat , Haryana, India.
2 Addit ional Professor, Depart ment of Anat omy, Govt M edical College, Amrit sar, Punjab, India.
3 Associate Professor, Depart ment of Anat omy, Govt M edical College, Amrit sar, Punjab.
4 Demonst rat or, Anat omy, BPS GM C For Women, sonipat , Haryana, India.
5 M edical officer,HCM S-1, PHC Dubheta, Sonipat , Haryana, India.
The art icular processes of t horacic & lum bar vert ebrae not only play a pivot al role in w eight t ransmission t hrough vert ebral column but also
M ATERIALS AND M ETHODS
pediculolaminar junction directed post erolat era-l era-ly w h er eas i n era-l u m b ar r egi o n, t h ese b ear v er t ical co ncave ar t icu lar f acet s d i r ect ed posteromedially, w it h a rough mamillary process on t heir post erior borders. The inferior art icular processes, in t horacic region, bear oval & con-cave facet direct ed forw ards, slight ly downw ards & medially [1,2,3]. In lumbar region, t hese have convex art icular facet s facing ant erolat erally so t hat t hey look aw ay from each ot her [2]. In t horacic region, lack of upw ard inclinat ion of SAFs prohibit s much flexion & ext ension. How -ever, t he direct ion of art icular facet s allow free rot at ion, [4]. The lumbar ext ension is w ider in range t han flexion w hile t he rot at ion is limit ed by absence of common cent re of curvat ure for r i gh t & l ef t ar t i cul ar f acet s [ 5] . Th e zygapophyseal / f acet j oint s are ext r em ely im por t ant in t h e b iom echan ical & clin ical behaviour of t he spinal column [6]. These have been relat ed t o frequent source of low back pain [7,8,9]. Dhall (1984) [10] correlat ed t he size of art icular facet s w it h t he magnit ude of st ress imposed on t hem. Goel et al,1988 [11] used t he m odels of spine t o st udy t he m echanics of spi n al i n st r u m en t at i o n. Co n sid er in g t h e im por t an ce of t hor acic & lum bar ar t icular facet s in clinical set t ing and in underst anding basic spinal mechanics, t he present st udy w as designed t o provide high qualit y dat a set s of t hese art icular facet s.
The pr esent st udy w as conduct ed at Govt M edical college, Amrit sar aft er get ting approval f r o m In st it ut io nal Et hi cal Com m it t ee. The mat erial for t he st udy comprised of 30 adult human male t horacolumbar vert ebral columns i.e. a t ot al of 510 vert ebrae (t horacic:360 & lum bar : 150) obt ained from depart m ent of Anat omy, Govt M edical college, Amrit sar. The vertebrae w ere w it hout any gross abnormalit y. These w ere labelled from T1 t o L5 depending on t he vert ebra & bound in a w ire in t he correct sequence. Any part icular set of colum n w as belonging t o t he same body. Different param-et ers of superior (SAFs) & inferior art icular facet s (IAFs) (vide infra) w ere measured w it h t he help of a vernier calliper w it h least count of 0.02mm and mamillary tubercles were observed.
Length of SAF: It w as measured w it h vernier callipers on bot h sides as t he vert ical dist ance bet w een t he most superior point t o t he most inferior point on t he facet at t heir cent re. (CD in fig 1)
Fig. 1
AB: Widt h of superior art icular facet , CD: Lengt h of Superior art icular facet ,
EF: Dist ance bet w een t w o superior art icular pr ocesses.
W idth of SAF: It w as measured w it h vernier callipers on bot h sides as t he horizont al dist ance in t he cent re of t he facet . (AB in fig 1)
Distance betw een the tw o superior articular
p ro cesse s: It w as m easur ed w i t h ver n ier
callipers as t he dist ance bet w een t he medial borders of t he right and left superior art icular processes (EF in Fig1).
Length of the inferior articular facet: It w as
measured w it h vernier callipers as t he vert ical dist ance bet w een t he most superior t o most inferior point on t he facet almost at it s cent re on bot h sides. (AB in Fig.2).
Fig. 2
AB- Lengt h of t he art icular facet .
W idth of the inferior articular facet: It w as
measured w it h vernier callipers as t he horizontal dist ance on the facet almost in it s centre on bot h sides (AB in Fig3).
D ist a n ce b et w e en t w o in fe r ior a rt icula r
p ro cesse s: It w as m easur ed w i t h ver n ier
Fig. 3
AB-w idt h of inf erior art icular facet .
CD: Dist ance bet w een t w o infer ior art icular facet s.
M amillary tubercle/ process: The low er t ho-racic and all lumbar vert ebrae w ere examined for t he presence/ absence of a rough elevat ion on t he post erior border of t he superior art icular process called as m amillary t ubercle/ process on bot h t he sides [12].
RESULTS
Table 1 shows t he lengt h & w idt h of SAF on right & left sides and also t he dist ance bet w een t he tw o superior articular processes. It w as observed t hat t he lengt h of SAF w as almost same at all t horacic levels ranging bet w een 10-11mm on bot h t he sides. How ever, in lumbar region, it i ncr eased gr ad uall y f r o m L1 (R:12.32m m ; L: 12.42mm) t o L5 (R:15.31mm; L: 15.65mm). On comparing t he length on t w o sides, it w as found t o be m or e on right side by 0.02m m at all t horacic levels w hereas it w as more on left side by 0.04-0.34 mm at all lumbar levels. The w idt h, on right side, first decreased from 11.45mm at T1 (Range: 6.16-17.17m m ) t o 9.67m m at T8 (Range: 7.74- 13.10mm) w it h a slight crest seen at T5. Thereafter, it increased t o 15.43mm at L5 (Range: 8.40-21.76mm) w it h a dip seen at T12. On left side, it first decreased from 12.58mm at T1 (Range: 8.00-21.37m m ) t o 9.89m m at T3 (Range: 7.54-11.34mm). Thereafter, it increased t o 15.21mm at L5 (Range: 8.00-20.84mm) w it h almost same values seen in mid-t horacic region (T4-T8) and 2 dips seen at T11 & T12. When it w as compared on t w o sides, it w as found t o be m ore on lef t side at all levels by 0.01-1m m except T2-T5 & L5 (m or e on r i ght side by 0.07-0.6mm ). The dist ance bet w een t he t w o superior articular processes first decreased from 17.90m m at T1 (Range:12.25-27.02m m ) t o 10.98mm at T6 (Range:5.00-17.63mm). There
af t er, i t i n creased t o 20.90m m at L5 (Range:13.05-28.83mm) w it h a slight dip seen at T11. No comparat ive dat a w as available in t he accessible lit erat ure.
M am illary Tubercle/ process: In t he present
st udy, mamillary tubercle was absent alt ogether f r o m T1-T8 o n b o t h si des. As w e m ov ed caudally, at T9, it was encountered bilaterally in 4 (13.33%); at T10, in 15 (50%); at T11, in 19 (63.33%) and at T12, in 29 (96.67%) vert ebral col u m ns. Fr o m T9-T11 it w as d ir ect ed posterosuperiorly from the root of t he transverse process. How ever, at T12, it w as project ing superomedially. In lumbar region (L1-L5), t his t ubercle w as found t o be present bilat erally on t he post erior border of t he superior art icular pr ocess of all t he ver t ebr ae and w as m or e prominent and distinct being called as mamillary process.
lumbar region, it increased consist ent ly from L1 (R:10.86m m ; L:10.81mm ) t o L5 (R:14.09m m ; L:14.01mm) on bot h sides. When compared on t w o sides, it w as found t o be more on right side at most of t he levels by 0.01-0.4mm except T2, T5, T9, T11 & L2 w here it w as more on left side by 0.01-0.35mm . Lengt h w as also com pared w it h widt h of IAF & it follow ed t he same pat t ern as w as seen i n case o f SAF. Th e d i st ance bet w een t w o inferior art icular processes first decreased from 15.29mm at T1 (Range: 24.20m m ) t o 11.96m m at T7 (Range: 11.14-24.20mm) w it h a crest seen at T4. Thereafter, it increased t o 23.53m m at L5 (Range: 15.08-33.77mm) w it h a slight dip seen at L1. Dist ance betw een t w o superior art icular processes & t w o inferior articular processes w ere also compared. It w as seen t hat t he dist ance bet w een t w o inferior art icular processes w as more t han t hat bet w een t w o superior art icular processes at alm ost all levels. No com par at ive dat a w as available in t he accessible lit erat ure.
DISCUSSION
Table 1:Show ing The Lengt h And W idt h Of Superior Art icular Facet & Dist ance Bet w een Tw o Superior Ar t icular Processes.
M ean M ean M ean Range M ean M ean M ean Range M ean
R 12.6 9.3 10.15 5.44-15.00 12.3 13.3 11.45 6.16-17.17
L 12.6 9.67 10.13 7.11-14.81 14 13.41 12.58 8.00-21.37
R 12.2 9.85 10.87 8.07-15.83 11.7 10.48 11.39 8.12-19.25
L 13 10.22 10.81 8.77-14.15 12.1 10.52 11.15 7.56-14.77
R 10.8 9.52 10.62 8.20-13.58 10.8 9.8 10.41 7.39-16.03
L 11.7 10.48 10.5 7.86-12.93 10.6 9.56 9.89 7.54-11.34
R 10.8 14.71 10.85 7.47-14.71 10.5 9.5 10.14 8.15-13.03
L 11.5 9.25 9.92 6.73-12.06 10.3 9.17 10.07 8.02-12.56
R 12.1 8.96 11.05 8.64-14.32 10.6 9.44 10.58 8.80-14.26
L 10.9 9.24 10.2 6.68-13.37 9.8 8.64 9.97 8.31-12.85
R 11.7 9 10.49 8.05-13.23 9.6 8.96 9.88 7.54-14.21
L 11.8 9.15 10.33 7.14-13.36 10.1 8.58 9.99 8.30-12.33
R 11.9 8.78 10.72 7.75-15.68 9.6 8.56 9.98 6.22-15.74
L 11 9.11 10.31 6.83-13.56 9.9 8.74 10.06 8.18-15.91
R 11.5 8.63 10.29 7.68-14.00 10 8.74 9.67 7.74-13.10
L 11.7 9.07 10.22 5.87-11.24 10.3 8.78 10 7.54-12.78
R 12.1 8.62 11.17 8.13-16.54 11 9.04 10.36 5.65-15.63
L 11.7 9.12 10.67 7.36-14.68 10.7 8.5 10.56 7.35-14.73
R 12 8.76 11.26 8.50-14.12 11.5 9.68 11.21 8.20-15.02
L 12.4 9.16 11.13 8.77-14.24 12.9 9.52 11.57 8.33-16.71
R 12.5 9.32 11.1 8.99-13.72 11.4 10.08 11.24 7.84-16.46
L 12 9.52 10.98 7.00-13.40 11.3 9.88 11.4 8.55-14.98
R 13.4 9.42 11.61 7.23-15.10 11.2 9.29 10.88 7.89-14.74
L 12.5 9.84 11.19 6.72-15.27 10.5 9.16 10.89 7.91-14.50
R 12.7 10.33 12.32 7.02-17.38 10.2 10.25 11.63 6.62-15.68
L 12.2 11 12.42 9.22-15.96 10.5 11 11.82 7.62-15.54
R 14.6 11.85 13.82 8.42-22.02 11.1 13.04 12.69 6.71-18.92
L 14.6 12.46 13.91 9.95-20.29 11.4 13.31 12.85 7.81-18.20
R 16 12.69 14.62 8.40-20.79 13.8 13.85 14.21 7.26-19.43
L 15.9 12.77 14.66 11.0-19.99 13.9 13.92 14.44 8.43-18.68
R 16.1 12.77 15.22 10.4-22.73 14.1 15.04 14.73 9.10-20.45
L 17.3 12.85 15.46 10.9-22.67 15.3 14.96 14.82 9.23-19.12
R 17.4 12.85 15.31 10.6-21.53 16.3 15.2 15.43 8.40-21.76
L 17.5 13.2 15.65 9.84-22.71 14.9 15.1 15.21 8.00-20.84
Distance b/ w 2 superior articular processes A u th o r P a n ja b i e t a l. 1 9 9 3 [1 4 ] P a te l e t a l. 2 0 0 7 [ 1 5 ] W e st e rn In d ia n W e st e rn In d ia n P a n ja b i e t a l. 1 9 9 3 [1 4 ] P a te l e t a l. 2 0 0 7 [ 1 5 ]
Param eter Length of superior articular facet W idth of superior articular facet
T3 12.91 5.55-19.76
T4 12.6 5.50-20.54
(m m) Range
T1 17.9 12.25-27.02
T2 15.81 8.05-24.25
T7 11.04 5.1-16.6
T8 11.3 7.26-15.86
T5 12.09 5.61-19.14
T6 10.98 5.00-17.63
6.47-15.82
T12 14.62 8.48-19.04
T9 11.42 7.32-16.56
T10 11.51 7.09-15.5
L5 20.9 13.05-28.83
North Indian Present Study P re se n t S tu d y N o rt h In d ia n N o rt h In d ia n P re se n t st u d y P o p u la ti o n
L3 17.98 12.41-22.54
L4 18.9 13.70-24.50
L1 17.16 12.60-20.89
L2 17.65 12.84-21.21
T11 11.36
Table 2:Show ing The Lengt h, W idt h Of Inferior Ar t icular Facet And Dist ance Bet w een Tw o Infer ior Ar t icular Processes.
W estern Indian W estern Indian
M ean M ean M ean Range M ean M ean M ean Range M ean Range
R 12.5 9 10.91 7.72-14.42 11.9 9.71 11.46 8.68-18.26 L 13.3 9.31 11.46 7.45-15.34 13.2 9.88 11.09 8.25-15.16 R 11.2 9.09 10.89 8.54-13.80 11.1 9.22 10.38 7.87-14.73 L 11.8 9.09 11.26 8.76-14.68 11 9.28 10.53 9.00-11.82 R 11 8.67 10.53 8.21-12.72 9.9 8.96 9.97 7.87-12.42 L 10.7 8.63 10.53 8.17-12.69 10.4 8.85 9.96 8.29-11.59 R 11 8.77 10.85 7.95-15.20 10.4 8.73 10.04 8.06-12.81 L 11 8.67 10.82 8.67-14.60 9.8 8.57 9.63 8.20-11.77 R 10.9 8.31 10.4 8.30-13.70 9.7 8.16 9.89 8.02-14.46 L 11.2 8.28 10.77 8.28-15.03 9.7 8.13 10.23 7.94-15.86 R 10.3 8.21 10.31 7.98-13.87 9.6 8.21 9.94 8.21-13.85 L 11.1 8.33 10.7 8.33-14.82 9.7 8.18 9.87 7.83-13.68 R 10.6 8.26 10.57 8.26-13.02 9.8 8.24 10.4 8.24-15.03 L 11 8.24 10.84 8.24-13.11 10.3 8.18 10.39 8.18-13.71
R 10.9 8.18 10.73 8.18-14.50 10.4 8.33 10.33 7.94-14.32 L 11.6 8.39 11.09 8.39-14.68 10.7 8.36 10.28 8.16-14.00 R 12.3 9 11.78 9.00-16.21 11.9 9.36 11.64 7.99-15.28 L 12.5 9 12.09 8.51-16.18 12.6 9.48 11.7 7.73-15.53 R 12.4 9.5 11.63 8.55-14.46 11.9 9.63 11.83 9.01-16.38 L 11.7 9.6 12.28 9.15-17.29 11.4 9.67 11.64 9.58-15.70 R 13.3 9.5 12.44 8.14-15.69 11.4 9.4 10.33 5.81-14.37 L 12.5 9.63 11.73 8.35-15.12 10.9 9.43 10.42 7.31-16.38 R 12.5 9.97 12.32 8.88-15.59 9.5 9.5 9.58 6.53-12.66 L 12.7 9.93 12.02 8.77-17.25 9.8 9.47 9.58 7.28-12.70
R 15.3 11.27 14.17 8.34-21.35 12.4 10.6 10.86 7.61-14.26 L 15.2 11.37 14 9.19-19.87 10.7 10.77 10.81 7.60-13.72 R 16 12.47 15.01 11.70-22.14 12.7 10.63 11.51 7.35-14.10 L 16.3 12.53 14.39 11.10-21.10 12.2 11.81 11.52 6.81-15.51 R 15.7 12.77 15.24 10.56-20.16 13.8 12.33 11.87 6.90-15.66 L 16.4 12.9 15.57 10.83-20.48 13.4 12.43 11.85 7.00-15.00 R 16.2 12.83 15.38 11.48-22.61 14.7 12.97 13.07 7.28-18.45 L 15.6 12.9 15.43 11.00-20.93 14.1 12.83 12.9 7.10-17.94 R 18.4 13.13 16.42 11.94-22.66 15.6 13.61 14.09 7.04-19.76 L 17.3 13.23 16.24 11.32-21.86 16.1 13.58 14.01 7.40-18.21
Population (mm) North Indian North Indian North Indian
(mm)
Distance b/ w 2 inferior articular processes
Author Patel et al.
2007 [15] Present study
Patel et al. 2007 [15] Parameter
T3 12.57 8.25-16.4
T4 12.71 8.24-16.78
T1 15.29 11.16-24.20
T2 14 10.22-19.30
T7 11.96 8.95-15.00
T8 12.13 8.28-15.58
T5 12.39 8.64-16.62
T6 12.14 9.07-15.15
T12 15 10.00-18.65
T9 12.25 8.42-15.97
T10 12.31 8.00-17.45
L5 23.53 15.08-33.77
Length of inferior Articular facet W idth of inferior Articular facet
Panjabi et al. 1993 [14]
Panjabi et al.
1993 [14] Present Study Present Study
L3 16.09 10.88-19.86
L4 18.3 10.88-26.25
L1 14.93 11.60-19.36
L2 15.73 11.98-21.23
T11 13.93 9.90-18.51
lumbar region. How ever, in our st udy, t he SAFs w ere longer on right side in t horacic region and on lef t side in lum bar r egion w hich w as in cont rast w it h M asharaw i et al [13] w ho found it longer on left side in t horacic & on right side in lumbar region. When compared w it h w est ern populat ion [14] it w as found t o be less in Nort h Indians at all levels by 0.2-2.5mm w hich may be due t o t he f act t hat t he aver age height of w est er n pop ulat ion is gr eat er t han Indian populat ion. How ever, it was more in Nort h
0.16-1mm on bot h sides. This w as in consonance w it h Panjabi et al[ 14] and M asharaw i et al [13]. How ever, Patel et al [15] found t he w idt h t o be more as compared w it h height in upper t horacic & l u m bar r egi on s.. Si m i l ar v ar i at io n w as observed for t he IAFs. The lengt h of IAF w as found t o be less in Nort h Indians at all levels by 0.03-2mm as compared with Western population [14]. How ever, it was more in Nort h Indians at all levels by 1.8-3.3mm as compared w it h Indian populat ion of Gujrat st at e [15]. The w idt h of IAF w as found t o be less in Nort h Indians at all levels by 0.07-2.1m m as com pared w it h West er n populat ion [14]. How ever, it was more in Nort h In di an s at al l l ev el s b y 0.04-2.30m m as compared w it h Indian populat ion of Gujrat st at e [15]. The differences may be at tributed t o racial, regional & et hnic variat ions. No comparat ive dat a w as available in t he accessible lit erat ure for t he dist ance bet w een t w o superior art icular processes and t w o inferior art icular processes.
The morphology of mamillary t ubercle/ process w as in consonance w it h Pal & Rout al [16] w ho observed fusion t o a varied ext ent bet w een t he superior articular process and mamillary tubercle at T12 and L1. Pal & Rout al [16] revealed t hat due t o t he gradual rot at ion/ sagit t alisat ion, t he superior art icular process comes close t o t he mamillary t ubercle w hich fuses w it h it t o form t he lumbar like superior art icular process. This fusion st art s from below and proceeds upw ards, as a notch of varying dept h is observed bet ween t he 2 processes in a few vert ebrae. They furt her speculat ed t hat because of fusion, t he art icular sur face gr adually ext ends over t he m edial aspect of t he m am illary t uber cle. Thus, t he post erior m ost part of t he lum bar superior ar t i cul ar p r o cess i s f o r m ed b y t h e f u sed mamillary t ubercle w hich, morphologically, is an int egral part of t he t ransverse process.
Functional Significance: The art icular facet s play an import ant role in w eight t ransmission t hrough t he spinal column. According t o Pal & Rout al,1987[ 17] t he m echanism of w eight t ransmission in t he t horacic & lumbar region of vert ebral column depends upon t he follow ing t hree fact ors:
(i) Zygapophyseal joint s are involved in w eight bearing and a considerable proport ion of w eight is t ransmit t ed t hrough lumbar facet joint s.
Fig. 4: Diagram m at ic represent at ion of a t ypical t ho-racic vert ebr a seen from above. From t he lat eral part of art icular sur face forces are t ransm it t ed t o t he pedicle (a), w hereas from m edial part f orces are t ransm it t ed below t o t he lam ina (b)
(ii) Forces act at right angles t o t he plane of any art icular surface.
(i ii) Lin e of gr avit y passes an t er i or t o t he vert ebral bodies in t horacic region (because of t hor acic kyphosis) and post erior t o t hem in lum bar r egion (because of lum bar lordosis) crossing t he column at T11 and T12 vert ebral level.
As t he thoracic column is concave ant eriorly and the line of gravit y passes anterior t o the vert ebral bodies, t here is t endency for accent uat ion of load on t he vert ebral bodies. Hence t he w eight act in g at t he zygapo ph yseal j oi nt s is al so t ransmitted t owards t he vertebral body. This is support ed by t he fact t hat t he superior art icular surface faces post erolat erally and t hus w ould t ransmit t he w eight ant eromedially t o t he body t hrough it s pedicles (See Fig.4). In t he lumbar region t he line of gravit y passes post erior t o t he
The above mechanism of load t ransmission by t he lumbar facet joint s is also support ed by t he findings of Cihak [18], according t o w hom t he lumbar zygapophyseal joint s, at birt h, are all orient ed in the coronal plane, similar t o the joints of t horacic vert ebrae. How ever, dur ing t he post nat al grow t h t heir orient at ion st art s t o change fr om coronal t o sagit t al plane. The process of ‘sagit t alisat ion’ begins at t he 6t h
post nat al mont h and is complet ed by t he age of 18 m ont hs. Dur ing t his per iod t he art icular su r f ace gr adu all y r ot at es f r om co r on al t o sagit t al, becoming charact erist ically curved at t he same t ime. From t he above findings of Cihak [ 18] , it m ay b e said t h at t he p er i o d o f sagit t alisat ion corresponds t o t he development of lumbar curvat ure w hich is associat ed w it h the child learning t o st and erect and w alk. Thus t he p r o cess o f sagit t al isat i on of t h e ar t i cu lar processes in lumbar region is associat ed w it h l oad i ng o f t h e zy gap o ph y seal j o i n t s. Th e sagit t ally oriented curved articular processes are w ell adapt ed t o bear t he load act ing at t he lumbar zygapophyseal joint s. Furt her,t he fusion bet w een t he superior art icular & m am illary processes in t he lumbar region is an import ant funct ional adaptation to receive t he w eight from t he vert ebra above.
SUM M ARY & CONCLUSION
var iable t r end. The dist ance bet w een t w o superior articular processes first decreased from T-1 t o T-6 and t hen increased t o L-5 w it h a slight dip at T-11. The mamillary t ubercle/ process was alt oget her absent from 1 t o 8. From 9 t o T-11, t he number of vert ebral column show ing mamillary tubercle increased from 4-19. How ever at T-12, it was seen in 29 Vertebral columns & project ing superomedially. In lumbar region, it w as w ell developed in all vert ebrae know n as mamillary process.
In case of IAF, in t horacic region, neit her lengt h nor width of IAF depicted any t rend but in lumbar region, bot h t hese paramet ers increased from L1 t o L5. The dist ance bet w een t w o inferior art icular processes first decreased from T1 t o T7 w it h a crest seen at T4 and t hereaft er it increased t o L5 w it h a slight dip at L1.
The dist ance bet w een t w o inferior art icular processes w as m ore t han t hat bet w een t w o superior art icular processes at all levels except T1-T3 & L1-L4 w here reverse w as t rue.
To sum marise, in case of SAF, t he lengt h w as almost same at all t horacic levels but increased gradually from L1 t o L5. The w idt h depict ed a
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REFERENCES
Fig. 5: Diagram m at ic r epresent at ion of a t r ansverse sect i on p assi n g t h r o ugh a t yp ical l um b ar sup er io r art icular pr ocess. For ces act at right angle t o ar t icular sur face. The art icular sur face facing dorsally t r ansm it s t he load t o t he pedicle (a) and a lar ge surface facing m edially t ransm it s t he forces lat erally t o t he super ior art icular process (b). M P: m am illary Process. From t he super ior ar t icular pr ocess t he f or ces converge t o be t ransm it t ed t o t he inferior art icular process.
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