Int J Anat Res 2016, 4(1):1859-63. ISSN 2321-4287 1859

Original Research Article

ANATOMICAL VARIATIONS OF SACRUM AND ITS CLINICALSIGNIFICANCEA.K.Manicka Vasuki *1, K.Kalyana Sundaram 2, M.Nirmaladevi 3, M.Jamuna 4,Deborah Joy Hebzibah 5, T.K.Aleyemma Fenn 6.

ABSTRACT

Address for Correspondence: Dr. A.K.Manicka Vasuki, Assistant Professor, Department Of Anatomy,PSG Institute of Medical Sciences and Research, Coimbatore-641004, Tamil Nadu, India.E-Mail: vasukikalyan01@gmail.com

Background and Aims: Sacrum is formed by the fusion of five sacral vertebrae and forms the lower part ofVertebral column. Anatomical variations, Morphology and Morphometry of Sacral hiatus are important clinicallyas well as surgically.Materials and Methods: This study was carried out on 75 dry human sacra of unknown sex to know Anatomicalvariations of sacrum. Results: Anatomical variations-failure of formation of superior articular process andlamina of left first sacral vertebra, incomplete development and fusion of second sacral vertebra, multipleforaminas on either side of spinous process above the sacral hiatus, multiple foraminas in the dorsal surfaceof base of the sacrum behind the auricular surface, incomplete median crest, Sacralisation of fifth lumbarvertebrae were identified.Conclusions: The knowledge of anatomical variations of Sacrum and variations of sacral hiatus are clinicallyimportant for caudal epidural block in Pediatric, Obstetric, Orthopedic, Urologic and Surgical practice.KEY WORDS: Sacrum, Lamina, Median crest, Sacralisation of lumbar vertebrae, Caudal epidural block.

INTRODUCTION

International Journal of Anatomy and Research,Int J Anat Res 2016, Vol 4(1):1859-63. ISSN 2321-4287

DOI: http://dx.doi.org/10.16965/ijar.2015.352

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Received: 30 Dec 2015 Accepted: 18 Jan 2016Peer Review: 30 Dec 2015 Published (O): 31 Jan 2016Revised: None Published (P): 31 Jan 2016

International Journal of Anatomy and ResearchISSN 2321-4287

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DOI: 10.16965/ijar.2015.352

*1,5 Assistant Professor, Department Of Anatomy, PSG Institute of Medical Sciences And Research,Coimbatore, Tamil Nadu, India.2 Associate Professor, Department of Anesthesiology, Coimbatore Medical College, Coimbatore,Tamil Nadu, India.3 Associate Professor, Department of Anatomy, PSG Institute of Medical Sciences And Research,Coimbatore, Tamil Nadu, India.4 Professor & HOD, Department of Anatomy, PSG Institute of Medical Sciences And Research,Coimbatore, Tamil Nadu, India.6 Former Professor & HOD, Department of Anatomy, PSG Institute of Medical Sciences AndResearch, Coimbatore, Tamil Nadu, India.

Sacrum is a large, triangular bone formed byfusion of five vertebrae present between the twohip (innominate) bones. It presents concave

anterior or pelvic surface and convex posteriorsurface. The broad base is directed above andthe apex is at the lower end. The base is dividedinto central part consisting of body of first sacral

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A.K.Manicka Vasuki et al.ANATOMICAL VARIATIONS OF SACRUM AND ITS CLINICAL SIGNIFICANCE.

vertebra and lateral mass or ala on either side.By its base the sacrum articulates with the fifthlumbar vertebra and by its apex it articulateswith the coccyx. The base presents the upperopening of sacral canal. The superolateralmargin of the body of first sacral vertebraprojects forwards as the sacral promontory,which is useful in measuring the diameters ofthe pelvis.The triangular sacral canal is formed by sacralvertebral foramina. The opening present at thecaudal end of sacral canal is known as sacralhiatus. The laminae and spinous process of thefifth and /or fourth sacral vertebrae fail to meetin the midline creating a deficiency known asthe hiatus in the posterior wall of the sacralcanal [1]. It is located inferior to the fourth orthird fused sacral spines or lower end of mediansacral crest. The remnants elongate downwardson both sides of sacral hiatus. These two bonyprocesses are called the sacral cornua anddefine important landmarks during caudalepidural block (CEB). Sacral hiatus is identifiedby palpation of sacral cornua. Sacral cornua arefelt at the upper end of natal cleft 5cm abovethe tip of coccyx. Structures emerge from sacralhiatus are the filum terminale, fifth sacral nervesand coccygeal nerves. The hiatus providesaccess to the extradural space in the sacralcanal.The anterior surface of Sacrum bears fouranterior sacral foramina which give passage toventral rami of upper four sacral spinal nervesand lateral sacral arteries. The dorsal surfaceof sacrum bears four posterior sacral foraminawhich give passage to posterior rami of the upperfour sacral spinal nerves.The upper surface of the lateral mass of Sacrumis termed the Ala of Sacrum.Sacral canal contains the cauda equina,duramater and arachnoid mater. At the lowermargin of second sacral vertebrae, thesubarachnoid space terminate. The fifth sacralroots, coccygeal roots and filum terminalepierce the blind end of the dural tube. Beyondthe dural tube, there is roomy extradural spacein the sacral canal.Reliability and success of Caudal epidural blockdepends on anatomical variations of sacral

MATERIALS AND METHODS

hiatus as observed by many authors.Caudalepidural block has been widely used fortreatment of chronic back pain.Sacral hiatusfunctions as a landmark when caudalanaesthesia is administered in Urology,Proctology,General surgery and Obsterics andGynaecology practice. The present study wasundertaken to find out the variations of Sacrum.

OBSERVATIONS

The materials for the present study consists ofSeventy five dry adult Sacra of unknown sexobtained from Anatomy department, PSG IMS &R, Coimbatore. If there is any anatomicalvariation of Sacrum, that was identified andnoted in each sacrum. The Variations of Sacrumwas compared with the Authors.

1. Failure of formation of right first sacral laminaand superior articular process with abnormalbony growth near the first dorsal foramina (Fig.1).2. Non-fusion of first sacral lamina (seen in foursacral vertebra) (Fig. 2 to Fig 5).3. Incomplete development and nonfusion oflaminae of second sacral vertebrae (seen in sixsacral vertebra) (Fig. 6 to Fig. 11).4. Absence of median crest with nonfusion oflaminas of first and second sacral vertebrae (Fig.12).5. Incomplete median crest (Fig. 13).6. A foramina in the right side of lamina ofsecond sacral vertebrae which indicatesincomplete development of right side of secondsacral vertebrae (seen in two sacral vertebra)(Fig. 14 and 15.7. Foraminas on either side below the firstspinous process and at the level of second andthird spinous process with absence of mediancrest (Fig. 16 and 17).8. Foramen just above the apex of sacralhiatus on either side (Fig. 18 and 19.9. Multiple foraminas in the dorsal surface ofbase of sacrum behind the auricular surface inthe ala for the attachment of Introsseousligament and dorsal sacroiliac ligament (Fig. 20).

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A.K.Manicka Vasuki et al.ANATOMICAL VARIATIONS OF SACRUM AND ITS CLINICAL SIGNIFICANCE.

Fig. 1 Fig. 2 Fig. 3 Fig. 4

Fig. 5 Fig. 6 Fig. 7 Fig. 8

Fig. 9 Fig. 10 Fig. 11 Fig. 12

Fig. 13 Fig. 14 Fig. 15 Fig. 16

Fig. 17 Fig. 18 Fig. 19 Fig. 20

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Fig. 21 Fig. 22 Fig. 23 Fig. 24

Fig. 25 Fig. 26

10. Complete dorsal wall agenesis (Fig. 21).

11. Sacralisation of fifth lumbar vertebrae (seenin four sacral vertebra) (Fig. 22 to Fig. 25).

12. High sacral hiatus (Fig. 26).

DISCUSSIONComplete non fusion of first sacral lamina wasobserved by Sushanth et al study [2]. Failure offormation of right first sacral lamina and superiorarticular process with abnormal bony growthnear the first dorsal foramina was observed inour study. High sacral hiatus with nonfusion oflamina of first sacral vertebrae was observedby Vishal.K et al [3]. This was also observed inour study.Incomplete development of second sacrallamina was found in Renu Chauhan et al study[4]. We found the same in six sacral vertebrae.Rare osseous growth on the Sacrum was foundon the ventral aspect of left side of first sacralvertebral body and the promontory by PujaChauhan et al5. But in our study, We observedabnormal bony mass near the right side of firstsacral foramina with failure of formation of firstand second sacral lamina with superior articularprocess.Complete dorsal wall agenesis of Sacrum wasobserved by Vanitha et al [6]. In our study, weobserved complete dorsal wall agenesis in onesacral vertebra.

Sacralisation of fifth lumbar vertebra wasobserved by Kubavat Dharati et al [7]. This wasalso observed in our study in four sacralvertebrae.The development of Sacrum resembles theossification of a typical vertebrae [8]. TheSacrum develops from fusion of five vertebrae.After puberty, the sacral vertebrae start fusingwith each other. The primary centres which formeach half of vertebral arch fuse posteriorly toform complete sacral canal. Complete fusion offive vertebrae as single piece of bone wasobserved after puberty. Any defect in formationleads to incomplete formation of Sacral canaland incomplete ossification of lamina.Spinabifida occulta or cystic can be accompanied andNeurological defects can be present in suchcases.The median crest is formed primarily from thespinous process of the upper three to four sacralvertebrae. The lamina of fifth sacral andsometimes fourth sacral vertebrae does not fusein the midline. As a result, the opening is termedsacral hiatus. If the laminae of the higher sacralvertebrae are not fused, then there will be a highsacral hiatus. This kind of anatomical variationin the sacral hiatus may lead to failure of caudalepidural analgesia, transpedicular and lateralmass screw placement failure.Lamina on the either side of median sacral crestforms sacral grooves. Number of muscleattachments-Multifidus, Sacrospinalis andErector spinae muscles originates from thesegrooves. If the second sacral lamina was notfused, the muscles would fail to get properattachment on the dorsal aspect of sacrum. Thedeficiency in the bony posterior wall of sacralcanal at the second sacral vertebrae level maypredispose the meninges protrusion whichresults in Spina bifida occulta.

A.K.Manicka Vasuki et al.ANATOMICAL VARIATIONS OF SACRUM AND ITS CLINICAL SIGNIFICANCE.

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CONCLUSION

Agenesis of dorsal wall is due to failure of fusionof sacral lamina. Maternal Diabetes duringpregnancy has been observed to cause sacralagenesis.The bony growth near the first dorsal foraminamay be explained that instead of a single primaryossification centre for the body, separate ventraland dorsal primary ossification centres appearfor the centrum which later fuse into single.Based on this, the growth is a developmentalanomaly because of the overgrowth of only thedorsal ossification centre overgrowth andincomplete fusion of this centre with first sacralbody could be an alternate explanation for thegrowth.In Sacralisation of fifth lumbar vertebrae, thetransverse process of last lumbar vertebraebecomes larger than normal on one side or boththe sides and fuses to the sacrum or ilium orboth. This is observed in 3.6 to 18% of peopleand is usually bilateral. In Sacralisation usuallyL5-S1 intervertebral disc becomes thin andnarrow, this abnormality is found by X-Ray. Theoccurrence of Lumbosacral transitional vertebra(LSTV)-Lumborisation or Sacralisation of fifthlumbar vertebra is linked to its embryologicaldevelopment and osteological defects.Embryologically, the vertebrae receivecontribution from caudal half of one sclerotomeand from the cranial half of succeedingsclerotome. Because of reduction of length ofvertebral column, the incidence of Sacralisationis higher than Lumborisation.Due to Sacralisation of fifth lumbar vertebra, thefusion of Lumbosacral joint might cause greatdifficulty during labour because of less mobilepelvis and may be the cause for low back pain.It is the one of the cause for lumbar discprolapse.

Clinicians need to be aware of such conditionsand their frequencies because the success ofcaudal epidural anaesthesia and analgesiadepends on the anatomical variations of Sacrumand the hiatus. Neurological symptoms may becaused due to such anomalies. The variationsof sacrum need to be known to theAnaesthetists, Radiologists, Surgeons,Orthopedicians and Gynaecologists.

Conflicts of Interests: None

REFERENCES

Knowledge of this type of variation may behelpful to the Radiologists in interpreting theradiographs of Sacral spine.This variation mayalso benefit Orthopedicians in diagnosing thecause of Low backpain. It is useful in diagnosingthe cause of neurological involvement ofbladder, rectum and lower limbs.In the present study, many variations of Sacrumlike incomplete formation of first Sacral laminaand superior articular process with bony growthnear the first dorsal foramina, nonfusion of firstsacral lamina with bony growth near the firstdorsal foramina, nonfusion of second sacrallamina, absence of median crest with nonfusionof lamina of first and second sacral lamina,complete dorsal wall agenesis, Sacralisation offifth lumbar vertebrae, elongated hiatus andnarrowing of Sacral canal at the apex of thehiatus were found in higher percentage. Thesevariations should be kept in mind while givingcaudal anaesthesia.

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How to cite this article: A.K.Manicka Vasuki,K.Kalyana Sundaram, M.Nirmaladevi, M.Jamuna,Deborah Joy Hebzibah, T.K.Aleyemma Fenn.ANATOMICAL VARIATIONS OF SACRUM AND ITSCLINICAL SIGNIFICANCE. Int J Anat Res 2016;4(1):1859-1863. DOI: 10.16965/ijar.2015.352

A.K.Manicka Vasuki et al.ANATOMICAL VARIATIONS OF SACRUM AND ITS CLINICAL SIGNIFICANCE.