An Anatomical Study Of The Innervation Of Different Parts Of The Posterior Ligamentous Complex Of The Sacroiliac Joint

Background and objective:Sacroiliac joint(SIJ)related pain is one of the most common causes of chronic low back pain,various techniques have been proposed to diagnose or treat SIJ related pain,but these techniques still need to be improved.Among them,extra-articular SIJ injection targeting on the nervous structure in the posterior ligamentous complex of SIJ is an important technique for the diagnosis and treatment of SIJ related pain.Some literature reported the quartering of the posterior ligamentous complex of SIJ as a way to refine extra-articular SIJ injection;however,detailed description of nerve distribution in each area is lacking.Therefore,this study aimed to explore the innervation and nerve distribution in each area of the posterior ligamentous complex of SIJ,and provide help with a view to the exploration and improvement of the diagnosis and treatment for SIJ related pain.Methods:Eight embalmed cadavers were studied.Each posterior ligamentous complex of SIJ was equally divided into areas 0-3 from top to bottom.The origin,distribution,quantity,transverse diameter,spatial orientation,relation with bony structures,and the number of terminal nerve branches in each area were examined and recorded.Results:Areas 0-1(corresponding to the superior part of the posterior ligamentous complex of SIJ)were innervated by the lateral branches of the dorsal rami of L4-5 directly in all specimens.Areas 2-3(corresponding to the inferior part of the posterior ligamentous complex of SIJ)were innervated by that of both lumbar and sacral nerves via the posterior sacral network(PSN),with L5 contributing to the PSN in all specimens and L4 in 68.75%.The number of terminal nerve branches were significantly higher in areas 2-3 than in areas 0-1.Conclusions:The nerve distribution of the posterior ligamentous complex of SIJ is mainly located at the inferior part,and is transmitted by the lateral branches of lumbar and sacral nerves via the PSN.Although the nerve distribution in the upper part directly originated from the lateral branches of lumbar nerves is relatively sparse,it should not be neglected.Further clinical verification is needed.