In the present study, the classical mode of termination (bifurcation of the sciatic nerve into tibial nerve and common peroneal nerve) was most frequently encountered with a prevalence of 82.43%. This is lower than the results of Amasiatu et al [4] who found, in their study in a Nigerian population, the bifurcation of the sciatic nerve in 86.52% of cases. Their results confirm with ours that bifurcation is the most frequent termination of the sciatic nerve.
In the present study, the trifurcation of sciatic nerve (sciatic nerve terminates in three branches) was the anatomical variation most frequently observed of the mode of termination of sciatic nerve. It was observed in 14.71% of cases. This prevalence observed in the present study is the highest in the literature. Amasiatu et al [4], in their study of 282 cases in a Nigerian population, noted trifurcation of the sciatic nerve in 37 cases (13.12%). It was observed in 3 out of 56 cases (5%) in the study by Berihu and Debeb [3] in an Ethiopian population, in 2 out of 50 cases (4%) in the study by Mallikarjun and Sangeetha [5], in 1 out of 50 cases (2%) in the study by Anbumani et al [6]. Sawant [7] reported a case of bilateral sciatic nerve trifurcation, It was reported in 1 case by Nayak [8] and Sharvari et al [9].
The terminal branches of the sciatic nerve in trifurcations according to the authors are summarized in Table 3.
Table 3: Terminal branches of the sciatic nerve in trifurcations according to the authors
Authors
|
Number of member
|
Number of trifurcations
|
Terminal branches of SN
|
Nayak [8]
|
-------
|
1
|
TN, CPN, lateral sural cutaneous nerve
|
Sawant [7]
|
2
|
2
|
TN, superficial and deep peroneal nerves
|
Mallikarjun and Sangeetha [5]
|
50
|
2
|
TN, CPN, soleus nerve
|
Berchus et Debeb [3]
|
56
|
3
|
TN, CPN, trunk to the lateral sural cutaneous nerve and CgPN (2 cases)
TN, superficial and deep peroneal nerves (1 case)
|
Sharvari et al [9]
|
2
|
1
|
TN, PN, sural nerve
|
Anbumani et al [6]
|
50
|
1
|
TN, CPN, sural nerve
|
Amasiatu et al [4]
|
282
|
37
|
TN, CPN, sural nerve
|
Present study
|
74
|
12
|
TN, CPN, trunk to the lateral sural cutaneous nerve and CgPN(5cases)
TN, CPN, CgPN (5 cases)
TN, CPN, sural nerve (2 cases)
|
CgPN=Communicating peroneal nerve, CPN=Common peroneal nerve, SN=Sciatic nerve, TN=Tibial nerve
In the present study, hexafurcation (six-branch termination) of the sciatic nerve was observed in 1 case in a male on the right. The sciatic nerve ended by giving the tibial, common peroneal, lateral sural cutaneous, medial sural cutaneous, communicating peroneal nerve and the soleus muscle nerve. This variation has not been noted in the literature. However, other variations have been reported in the literature, but were not observed in the present study. Amasiatu et al [4], in their study of 282 dissections, observed quadrifurcation (termination in four branches) of the sciatic nerve in 2 cases (0.71%) and quintufurcation (termination in five branches) of the sciatic nerve in 1 case (0.35%). Russa and Fabian [10] reported a case of sciatic nerve quadrifuraction.
In the present study, laterality was taken into account. The mode of termination of sciatic nerve showed a significant difference being more frequently bilateral than unilateral. In case of surgery on the two popliteal fossae of the same person, when the surgeon encounters a variation on one side, he must bear in mind that there is more chance of encountering the same variation of the other side.
Sciatic nerve trifurcation may be a boon to surgeons performing popliteal block for leg surgery, as the high endings of the sciatic nerve may be responsible for failure of popliteal block anesthesia [8].
Knowledge of the classic anatomy of the bifurcation as well as the possible variations of the sciatic nerve and its branches helps the radiologist and surgeons correctly interpret what they see and encounter when assessing and treating patients with sciatica and other nervous problems [3].