Knowledge of variant anatomy of the sciatic nerve is important in avoiding
inadvertent injury during operations in the gluteal region and interpreting nondiscogenic
sciatica. This variant anatomy may cause piriformis syndrome and
failure of sciatic nerve block. The variations differ between populations but
data from Africans is scarce. This study, therefore, investigated variations of
sciatic nerve in a black Kenyan population.
One hundred and sixty-four sciatic nerves from 82 cadavers of black Kenyans
were exposed by dissection at the Department of Human Anatomy, University
of Nairobi, Kenya. The level of bifurcation, relationship to piriformis, and topographic
relations between the branches were studied. The results were analysed
by SPSS version 16.0 and are presented by macrographs.
In 33 (20.1%) cases division occurred in the pelvis, while in 131 (79.9%) it
occurred outside the pelvis. A single trunk sciatic nerve exited below the piriformis
muscle in 131 (79.9%) cases. In cases of pelvic division, the tibial nerve
was always infrapiriformic, while the common peroneal nerve passed below
piriformis in 16 (9.8%) cases, pierced the piriformis in 13 (7.9%), and passed
above it in 4 (2.4%). For those in which division was extrapelvic, 110 (67.1%)
were in the popliteal fossa, 17 (10.4%) in the middle third of the thigh, and
4 (2.4%) in the gluteal region. Where the division was pelvic, in 19 (11.6%) cases
they continued separately, in 8 (4.9%) the two nerves reunited, and in 6 (3.7%)
they were connected by a communicating nerve.
The sciatic nerve in the Kenyan population varies from the classical description
in over 30% of cases, with many high divisions, low incidence of piriformic
course of common peroneal nerve, reunion, and unusual connection between
common peroneal and tibial nerves. These variations may complicate surgery
and interpretation of sciatic neuropathy. Preoperative nerve imaging and extra
operative diligence in the gluteal region and the back of the thigh are recommended.
(Folia Morphol 2011; 70, 3: 175–179