VARIABILITIES IN ANATOMICAL ARRANGEMENT OF SACRAL PLEXUS ROOTS

Introduction. Branches of sacral plexus play an important role in the motor and sensory innervation of the lower limb. Various variations observed during the spinal operations have motivated us to start the study aimed on determination of the sacral plexus formation from its exit of particular roots from sacral foramina up to their formation into terminal branches. Material and method. One hundred sacral plexuses have been examined on 50 adult cadavers for a purpose to find out an incidence of its neural variations. We have considered also the course of their branches, the anatomoses and their thickness. We highlighted the motor innervation particularities in the relation to the diagnosis besides its anatomical complexity and variability. Results. Commonly were observed 3 sacral roots with the share of S4 and lumbosacral trunk of L4 and L5 and 4 sacral nerves. Doubled ascending course of S1 root was often observed, by the other sacral roots the doubled exit was not so frequent. Lumbosacral trunk was thickened in 19 cases. Very high division of the sciatic nerve (in the lesser pelvis) was observed in 2 cases. The branching off level of other nerves depended on the plexus type. Conclusion. Our study revealed a relatively frequent variabilities and described some extraordinary anatomical variations in the formation of nerve roots and branches of the sacral plexus. The detailed knowledge of these variabilities is useful for the proper diagnostics and surgical treatment of the sacral plexus injuries and unexplainable paient‘s complaints.

Introduction.Branches of sacral plexus play an important role in the motor and sensory innervation of the lower limb.Various variations observed during the spinal operations have motivated us to start the study aimed on determination of the sacral plexus formation from its exit of particular roots from sacral foramina up to their formation into terminal branches.Material and method.One hundred sacral plexuses have been examined on 50 adult cadavers for a purpose to find out an incidence of its neural variations.We have considered also the course of their branches, the anatomoses and their thickness.We highlighted the motor innervation particularities in the relation to the diagnosis besides its anatomical complexity and variability.Results.Commonly were observed 3 sacral roots with the share of S4 and lumbosacral trunk of L4 and L5 and 4 sacral nerves.Doubled ascending course of S1 root was often observed, by the other sacral roots the doubled exit was not so frequent.Lumbosacral trunk was thickened in 19 cases.Very high division of the sciatic nerve (in the lesser pelvis) was observed in 2 cases.The branching off level of other nerves depended on the plexus type.

Conclusion.
Our study revealed a relatively frequent variabilities and described some extraordinary anatomical variations in the formation of nerve roots and branches of the sacral plexus.The detailed knowledge of these variabilities is useful for the proper diagnostics and surgical treatment of the sacral plexus injuries and unexplainable paient's complaints.

INTRODUCTION
The sacral plexus is formed by the ventral branches of S1-S3 with a share of S4 and very important lumbosacral trunk formed of L4 and L5 roots.It extends above sacroiliac junction and consequently connects with the sacral nerves forming the sciatic nerve.The boundary root participating in the plexi formation is L4 root, which in some cases is largerly involved in the lumbar plexus formation and in the sacral by others.Its participation in that or the other plexus helps to characterize the whole plexus as cranial prefixed with a share or caudal postfixed without a share of T12.It is necessary to emphasize that L4 root does not always play the role of boundary root; sometimes it is L5 root (Chin and Chew, 1997).After the available literature, we have met only with the orphan works devoted to these problems (Erbil et al, 1998;Chin and Chew, 1997;Hope et al, 1985;Iczi et al, 2005;Urbanowitz, 1981;Williams et al, 1995;Wlliams and Warwick, 1985;Weber, 1961).

MATERIALS AND METHOD
The study was realized on 50 (fifty) fresh cadavers without innate or detected abnormalities, tumour diseases, orthopaedic deformities or spinal operations.The ethics committee approval was obtained prior to the study.However, to the best of our literature search, we could not come across any study performed by the use of those reference structures or points.Therefore, we were not able to discuss our findings on the topography of the lumbosacral plexus and roots with the results of others.The lumbosacral plexi were dissected and clarified in all of the 50 cadavers; bilaterally from the anterior access following evisceration.The sacral nerves (the sciatic nerve, superior and inferior gluteal nerves, posterior cutaneous nerve of the thigh and pudendal nerves) were identified bilaterally.The nerves of the sacral plexus are located on the anterior area of piriformis muscle.The branches of the iliac vessels are in the vicinity of S1, S2 and S3 roots.

RESULTS
As with the upper extremity, the neural trunks of lower extremity in high cranial form also receive more fascicles from above located nerves in comparison with low caudal form.

DISCUSSION
The lumbosacral plexus is an analogue of brachial one.Differences in lumbosacral plexus formation are demonstrated in that manner that segmental participation of certain nerves, as well as their participation in tissue innervation may be changed, as in brachial one on the periphery.Nevertheless, interest in details of both plexi formation is not the same.It is because injuries as well as variations of lumbosacral plexus formation are less frequent in comparison with brachial one.Indications for reconstructive operations of lumbosacral plexus are exceedingly rare.There are a lot of variations of standard pattern related to innervation from lumbosacral plexus, but innervation from the first two sacral nerves is quite constant.S2 root also innervates glutei and musculus biceps femoris.The superior gluteal nerve innervates gluteus medius muscle (so-called "deltoid" of coxal joint), gluteus minimus muscle and extends forward, innervating tensor fasciae latae muscle, while S3 root usually innervates flexors of big toe and only rarely other muscles on the lower extremity.S4 root innervates no muscles on the lower extremity.The L4 root contributes to lumbar and sacral plexi and therefore it is called branched or furcate "furcal nerve".With the exception of L4 root, in the literature we did not find any cases of root duplication or root fragmentation of lumbosacral plexus that could constitute real operational pitfalls for neurosurgeon and anaesthetist during the regional anaesthesia.Following Bergman et al. (1988), both plexilumbal and sacral-are connected with furcal nerve in 91.8%.The connection was not found in 7.4%.Iczi et al. (2005) has seen only one case of furcal nerve and had not observed any variation of the connection between lumbar and sacral plexus.Erbil et al. (1998) has described an occurence of prefixed type on one side and postfixed type on the other in the casuistics.These variations are very rare.Lumbar and sacral plexi play an important role in the regional

Anatomical variations of sacral plexus
Rev Arg de Anat Clin; 2010, 2 (3): 95-99 __________________________________________________________________________________________ Todos los derechos reservados.Reg.N°: 827274 anaesthesis, particularly in sacroiliac and pelvic surgery.For its surgical treatment is important to put attention to vessel structures.Inferior gluteal artery is the branch from the internal iliac artery and leads into numerous branches, damaging of which is necessary to have in mind in operation, because they may be retracted into pelvis and may bleed.The components of lumbosacral plexus spread on the lower extremity, similarly as the brachial plexus spread on the upper extremity.The sacral nerves spread similarly as the nerves from posterior fascicle of brachial plexus.Many variations of lumbosacral plexus formation are a source of diagnostic confusions besides atypical clinical and electromyographic findings.It is important to understand what neural functions are transferred in particular parts of the plexus.It is also necessary to bear in mind that muscle innervation may change independently on number of the root entering the plexus due to presence of various connections between plexus roots.Neural roots in prefixed type take more filaments from the above located spinal nerves.The injuries of highly located neural roots or nerves are accompanied with much more prevalent lesion on the periphery in comparison with the same injuries in postfixed type.The S3 root in postfixed type may have many filaments normally born by S2 root and the share of S4 may be greater.It is supposed that the deviations in lumbosacral plexus formation are caused by a deviation from normal development process, during the fourth week of foetal development (Marieb and Mallat, 2005;O'Rahilly et al, 1990).Anatomical organization of lumbosacral plexus has its particularities.Neuroanatomical variations are the cause of unexpected radicular patterns.It is necessary to take into account individual specific variants in formation of clinical picture, its diagnostics and surgical treatment.Injuries may be prevented or lessened to a minimum level through the detailed knowledge of the topographic features and variations.Understanding of the structure and course of sacral plexus is important during all interventions to these regions due to the potential damage on the nerve itself.Its importance raises by the introduction of the new procedures in spinal anaesthesia, spinal operations in spondylosurgery, endoscopic operations in retroperitoneal approach in laser discectomy, ozonotherapy, etc.

Figure 3 .
Figure 3. Plexiform exit of L5 root, left side, front view, in craniocaudal direction, from right to left
too.For other cases, truncus lumbosacralis and S1, S2, S3 roots were present.Changes in the sacral plexus on the level of neural roots were observed in 41 (forty-one) times.The double exit