ANATOMICAL VARIATION OF THE SCIATIC NERVE

DIVISION

Author: GHERMAN IOANA-VASILICA

Coord.: Assistant lecturer dr. COŢOVANU ADRIANProfessor dr. PÁVAI ZOLTÁN

Coauthors: RÁDULY GERGŐAssistant lecturer dr. SZŐLLŐSI ATTILA ROMAN FLAVIA-CRISTINA

Anatomy of the sciatic

nerve

originates from the lumbosacral plexus

formed in the pelvis by joining anterior divisions of L4, L5, S1, S2 and S3 spinal nerves

leaves the lesser pelvis through greater sciatic foramen, inferior to piriformis muscle

usually separates into tibial nerve and common fibular nerve at the superior angle of popliteal fossa

the bifurcation may occur anywhere between the sacral plexus and popliteal space

variations of bifurcation carries clinical significance

Material and Method

the subject of this presentation is one formalin-fixed male cadaver from UMF Tg-Mureş

both lower extremities were dissected

gluteal muscles, piriformis m., obturator internus m., superior and inferior gemellus m., quadratus femoris m., vascular and nervous structures were exposed

Piriform m.

Common fibular n.

Tibial n.

ResultsBilateral variation: sciatic nerve divides into the

pelvis

the common fibular nerve passes superior to piriformis muscle

the tibial nerve passes inferior to piriformis muscle

lateral

medial

TN

CFN

Piriformis m.

CFN

CFN

TN

Results

TN

Biceps femoris m.

CFN

Gluteus maximus

m.

TN

CFN

Discussion

different studies show many forms of variations in sciatic nerve division

many authors have attempted classification of high divisions of sciatic nerve

Beaton & Anson classification considers six different types of higher divisions:

Type 1: Undivided sciatic nerve below undivided piriformis muscle

Type 2: Divisions of sciatic nerve between and below undivided piriformis muscle

Type 3: Divisions above and below undivided piriformis muscle

Type 4: Undivided sciatic nerve between heads

Type 5: Divisions between and above heads

Type 6: Undivided sciatic nerve above undivided piriformis muscle

Name of investigato

rs

Number of

cadavers

Type 1

Type 2

Type 3

Type 4

Type 5*

Type 6

Beaton & Anson (1937)

120 84.2%

11.7% 3.3% 0.8%

Beaton (1938)

240 90% 7.1% 2.1% 0.8%

Moore& Dalley

325 12.2% 0.5%

Ugrenovic et al.

100 fetuses

96% 2.5% 1.5%

Sayson et al.

1 One case

Pokorny et al.

91 79.1%

14.3% 4.4% 2.2%

*although mentioned as a division type, not described in any studies that we could acces

Findings of different studies according to Beaton & Anson classification

Conclusions

this presentation describes an anatomical variation of the sciatic nerve bifurcation and the relation between the common fibular nerve, tibial nerve and piriformis muscle

a bilateral variation found on a formalin-fixed cadaver from the Departament of Anatomy from the University of Medicine and Pharmacy of Tg-Mureş

type 3 of variation according to Beaton & Anson classification

anatomical variations of the sciatic nerve division are important for daily medical practice

ConclusionsPractical aspects

Sciatic nerve can be injured in: posterior dislocation of hip in fracture of hip jointduring total hip replacement surgery hemiarthroplasty of hip due to intramuscular injections

• Sciatic nerve has a long course it is vulnerable to nerve injury

The variation in the level of bifurcation of the sciatic nerve should be kept in consideration while performing surgical exploration

Possible failure of anesthesia during sciatic nerve block

Variations may cause nerve compressions under anatomic structures non discogenic sciatica, muscle atrophy

Bibliography SHAILESH PATEL, MITESH SHAH, RAKESH VORA, ANKUR ZALAWADIA, S. P. RATHOD, A variation in

the high division of the sciatic nerve and its relation with piriformis muscle, National journal of medical research, Vol 1 Issue 2 Oct – Dec 2011, pag.27-30

MUSTAFA GÜVENÇER, CIHAN IYEM, PINAR AKYER, SÜLEYMAN TETIK, SAIT NADERI, Variations in the High Division of the Sciatic Nerve and Relationship Between the Sciatic Nerve and the Piriformis, Turkish neurosurgery 2009, Vol 19, No 2, pag.139-144

MUTHU KUMAR T., SRIMATHI, ANANDA RANI, SUMATHI LATHA, A cadaveric study of sciatic nerve and it’s level of bifurcation, Journal of clinical and diagnostic research. 2011 December, Vol-5(8) pag.1502-1504

SARITHA S*, PRAVEEN KUMAR M , SUPRIYA G, Anatomical Variations in the Bifurcation of the Sciatic Nerve, A Cadaveric Study and its Clinical Implications, Anat Physio, Vol 2 • Issue 5

ENCIULESCU CONSTANTIN, Anatomy. Limbs 2013, Vol 6, pag.162-164

MOORE KL, DALLEY AF, Clinical oriented anatomy 7th edition, Baltimore Lippincott Williams & Wilkins, 2014, pag.575

Thank you!Which is Tibial

nerve path?

Piriformis hill

Gemellus

superior hill