Morphological variations of sciatic nerve and piriformis muscle in gluteal region during fetal period

SUMMARY Intramuscular drug injection in the gluteal region is often the most frequent cause of sciatic nerve injury in preterm newborns. Local anatomic variation is one of the predisposing causes of iatrogenic sciatic nerve injury . The aim of this morphological study was to assess the relationship of sciatic nerve with the piriformis muscle and to elucidate variations of fusion of piriformis with neighboring muscles in the gluteal region of Indian human preterm fetuses. Four types of relationship of the sciatic nerve with the piriformis muscle were observed in one hundred gluteal regions of fifty spontaneously aborted, formalin-fixed fetuses, aged 20 to 36 week (24 males and 26 females). In 85% of the gluteal regions, the classic pattern was found, in which the two components of the sciatic nerve fuse with each other proximal to the piriformis, and the fused sciatic nerve emerges at the lower border of the piriformis. In the remaining 15% of the gluteal regions, variations in relationship were found. The most common variation, characterized by the passage of the common peroneal component through the piriformis and the emergence of the tibial part at the lower border of the piriformis, was seen in 9% of the gluteal regions. Common peroneal and tibial components passed above and below the muscle respectively in 3%, and the unsplit sciatic nerve passed through the piriformis in 3% of the gluteal regions. Four types of fusion of the piriformis with the neighboring muscles were seen: namely, no fusion; fusion with superior gamellus; fusion with gluteus medius, or fusion with gluteus medius and obturator internus complex in 28%, 43%, 26% and 3% of the gluteal regions respectively. Anatomical variations of the sciatic nerve in relation to the piriformis muscle should be kept in mind while performing medical or surgical interventions in this region.

[1]  A. Akinremi,et al.  Injection-induced Sciatic Nerve Injury Among Children Managed in a Nigerian Physiotherapy Clinic: A Five-Year Review , 2011 .

[2]  N. Smoll.  Variations of the piriformis and sciatic nerve with clinical consequence: A review , 2010, Clinical anatomy.

[3]  S. Naderi,et al.  Variations in the high division of the sciatic nerve and relationship between the sciatic nerve and the piriformis. , 2009, Turkish neurosurgery.

[4]  S. Naderi,et al.  Anatomic considerations and the relationship between the piriformis muscle and the sciatic nerve , 2008, Surgical and Radiologic Anatomy.

[5]  G. Windisch,et al.  Piriformis muscle: clinical anatomy and consideration of the piriformis Syndrome , 2007, Surgical and Radiologic Anatomy.

[6]  M. A. Continenza,et al.  The ischiatic region: normal and MRI anatomy. , 2006, The Journal of sports medicine and physical fitness.

[7]  V. Pinskerova,et al.  Topographic variations of the relationship of the sciatic nerve and the piriformis muscle and its relevance to palsy after total hip arthroplasty , 2006, Surgical and Radiologic Anatomy.

[8]  A. Sosna,et al.  Sciatic nerve palsy after total hip replacement. , 2005, The Journal of bone and joint surgery. British volume.

[9]  O. Johansen,et al.  The internal obturator muscle may cause sciatic pain , 2003, Pain.

[10]  L. Favorito,et al.  VARIACIONES ANATÓMICAS ENTRE EL NERVIO ISQUIÁTICO Y EL MÚSCULO PIRIFORME DURANTE EL PERÍODO FETAL HUMANO , 2003 .

[11]  C. Giannakopoulou,et al.  Peroneal nerve palsy: a complication of umbilical artery catheterization in the full-term newborn of a mother with diabetes. , 2002, Pediatrics.

[12]  Z. Kurtoğlu,et al.  Variations of nerves located in deep gluteal region. , 1999, Okajimas folia anatomica Japonica.

[13]  T. Muro,et al.  Piriformis syndrome resulting from an anomalous relationship between the sciatic nerve and piriformis muscle. , 1999, Orthopedics.

[14]  J. Ducey,et al.  Sciatic entrapment neuropathy associated with an anomalous piriformis muscle , 1994, Pain.

[15]  Lee Cs,et al.  The relation of the sciatic nerve to the piriformis muscle , 1974 .

[16]  B. Anson,et al.  THE SCIATIC NERVE AND THE PIRIFORMIS MUSCLE: THEIR INTERRELATION A POSSIBLE CAUSE OF COCCYGODYNIA , 1938 .

[17]  B. Anson,et al.  The relation of the sciatic nerve and of its subdivisions to the piriformis muscle , 1937 .

[18]  F. Becchetti,et al.  Sciatic nerve injection palsy in the child: Early microsurgical treatment and long‐term results , 2009, Microsurgery.

[19]  V. Krstić,et al.  [The level of the sciatic nerve division and its relations to the piriform muscle]. , 2005, Vojnosanitetski pregled.

[20]  W. Hollinshead,et al.  The back and limbs , 1982 .

[21]  M. Pećina.  Contribution to the etiological explanation of the piriformis syndrome. , 1979, Acta anatomica.

[22]  C. S. Lee,et al.  [The relation of the sciatic nerve to the piriformis muscle]. , 1974, Taiwan yi xue hui za zhi. Journal of the Formosan Medical Association.