The Sacroiliac Joint as a Cause of Pain – Review of the Sacroiliac Joint Morphology and Models for Pain Genesis

Introduction In recent years, the sacroiliac joint has become increasingly important as a generator of low back pain with and without pseudo-radicular pain in the legs. Up to 27% of reported back pain is generated by disorders in the sacroiliac joint. Method This review is based on a selective literature search of the sacroiliac joint (SIJ) as a possible pain generator. It also considers the anatomical structures and innervation of the sacroiliac joint. Results The SIJ is a complex joint in the region of the posterior pelvis and is formed by the sacrum and the ilium bones. The SIJ is very limited in movement in all three planes. Joint stability is ensured by the shape and especially by strong interosseous and extraosseous ligaments. Different anatomical variants of the sacroiliac joint, such as additional extra-articular secondary joints or ossification centres, can be regularly observed in CT scans. There is still controversy in the literature regarding innervation. However, there is agreement on dorsal innervation of the sacroiliac joint from lateral branches of the dorsal rami of the spinal nerves S I–S III with proportions of L III and L IV as well S IV. Nerve fibres and mechanoreceptors can also be detected in the surrounding ligaments. Conclusion A closer look at the anatomy and innervation of the SIJ shows that the SIJ is more than a simple joint. The complex interaction of the SIJ with its surrounding structures opens the possibility that pain arises from this area. The SIJ and its surrounding structures should be included in the diagnosis and treatment of back and leg pain. Published literature include a number of plausible models for the sacroiliac joint as pain generator. The knowledge of the special anatomy, the complex innervation as well as the special and sometimes very individual functionality of this joint, enhance our understanding of associated pathologies and complaints.

Anatomical study of the innervation of different parts of the posterior ligamentous region of the sacroiliac joint

Background and objectivesThe periarticular sacroiliac joint (SIJ) technique has become an important area of focus, and the quartering of the SIJ posterior ligamentous region has been proposed as a way to refine this technique. However, detailed nerve distribution combined with the division of the SIJ posterior ligamentous region is lacking. We aimed to explore the innervation of the SIJ posteriorly based on the quartering of the SIJ posterior ligamentous region.MethodsSixteen SIJs from eight embalmed cadavers were studied. Each SIJ posterior ligamentous region 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 identifiable terminal nerve branches in each area were examined.ResultsAreas 0–1 were innervated by the lateral branches of the dorsal rami of L4−L5 directly in all specimens. Areas 2–3 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 identifiable terminal nerve branches were significantly higher in areas 2–3 than in areas 0–1.ConclusionsThe inferior part of the SIJ posterior ligamentous region seems to be the main source of SIJ-related pain and is innervated by lumbar and sacral nerves via the PSN. However, the superior part directly innervated by lumbar nerves should not be neglected, and further clinical verification is needed.

Evaluating the extent of lumbar erector spinae plane block: an anatomical study

Background and objectivesThe erector spinae plane (ESP) block is a relatively new interfascial block technique. Previous cadaveric studies have shown extensive cephalocaudal spread with a single ESP injection at the thoracic level. However, little data exist for lumbar ESP block. The objective of this study was to examine the anatomical spread of dye following an ultrasound-guided lumbar ESP block in a human cadaveric model.MethodsAn ultrasound-guided ESP block was performed in unembalmed human cadavers using an in-plane approach with a curvilinear transducer oriented longitudinally. 20 mL of 0.166% methylene blue was injected into the plane between the distal end of the L4 transverse process and erector spinae muscle bilaterally in four specimens and unilaterally in one specimen (nine ESP blocks in total). The superficial and deep back muscles were dissected, and the extent of dye spread was documented in both cephalocaudal and medial–lateral directions.ResultsThere was cephalocaudal spread from L3 to L5 in all specimens with extension to L2 in four specimens. Medial–lateral spread was documented from the multifidus muscle to the lateral edge of the thoracolumbar fascia. There was extensive dye in and around the erector spinae musculature and spread to the dorsal rami in all specimens. There was no dye spread anteriorly into the dorsal root ganglion, ventral rami, or paravertebral space.ConclusionsA lumbar ESP injection has limited craniocaudal spread compared with injection in the thoracic region. It has consistent spread to dorsal rami, but no anterior spread to ventral rami or paravertebral space.

Efficacy of Erector Spinae Plane Block for Back Pain Referred from Visceral Pain in the Palliative Care Setting

Background: Erector spinae plane (ESP) block, an easy and safe interfascial plane block under ultrasound guidance, has an analgesic effect in various surgeries for chronic pain. However, no study has described the possible clinical efficacy of ESP block in palliative patients suffering from back pain referred from visceral pain. Case Report: Here we report three cases of successful ESP block at the middle to lower thoracic vertebras with 5–10 mL local anesthetic to relieve back pain referred from thoracic or abdominal visceral cancer pain. Back pain in these cases was derived from spinal extensor muscles supplied by the dorsal rami of the spinal nerve. Thoracic or abdominal visceral pain was suggested to stimulate the middle to lower thoracic dorsal rami of the spinal nerve. Conclusion: Despite the effect of ESP block on the ventral rami of the spinal nerve being uncertain, back pain accompanied by the lateral and medial branches of the dorsal rami of the spinal nerve, similar to that in these cases, can be relieved via ESP block. Therefore, ESP block can be easily and safely performed for relieving back pain referred from visceral pain in the palliative care setting. Further, to establish optimal volume, concentration of local anesthetic, and clinical efficacy, randomized control trials will be essential in the future. Key words: Erector spinae plane block, fascial plane block, referred pain, palliative care setting, dorsal rami of the spinal nerve, ventral rami of the spinal nerve, visceral pain, chronic pain

Neuroma of the Dorsal Rami in the Back and Its Surgical Treatment: A Case Report

A neuroma is a benign tumor caused by irregular or disorganized regeneration of nerve tissue after nerve injury. It sometimes causes severe symptoms and thus deteriorates the quality of life. There are few reports of truncal neuromas and its surgical treatment with the outcome. The authors report a case of a surgically improved traumatic neuroma in a 77-year-old man presented with dysesthesia of the back skin medial to the left scapula.

Mechanism of action of the erector spinae plane block: distribution of dye in a porcine model

This study aimed to describe the anatomical distribution of dye injected in the erector spinae plane (ESP) in a porcine living model, which could aid to reveal factors potentially relevant to the unexplained clinical effects of the ESP block. Six pigs received 0.6 mL/kg of 0.25% new methylene blue at the level of the sixth thoracic vertebra through either a cranial-to-caudal or a caudal-to-cranial in-plane ultrasound-guided bilateral ESP injection 20 min before euthanasia.Spread of dye evaluated through transverse cryosections (four injections) extended from T5 to T10 and from T5 to T8 when a cranial-to-caudal direction of injection was used, and from T5 to T9 and from T5 to T8 when the opposite direction of injection was used. A median of 4.5 medial and lateral branches of the dorsal rami was observed stained through anatomical dissection (eight injections), regardless of the direction of injection. No evidence of dye was found in the thoracic paravertebral or epidural spaces, where the dorsal root ganglia, ventral rami and rami communicantes are located. In all the cases, dye solution was found in the prevertebral thoracic lymph nodes.In this study, ESP injection resulted in a median spread over five spinal segments (12 injections), staining the lateral and medial branches of the dorsal rami of the spinal nerves, regardless of the direction of the needle used.

The Source and the Course of the Articular Branches to the T4-T8 Zygapophysial Joints

Objective To define the source and the course of the articular branches to the midthoracic zygapophysial (“z”) joints. Design Cadaveric dissection. Setting The Gross Anatomy Laboratory of the Duke University School of Medicine. Subjects Ten human cadaveric thoraces. Methods Gross and stereoscopic dissection of dorsal rami T4-T8 was performed bilaterally on 10 adult embalmed cadavers. The medial and lateral branches were traced to their origins from the dorsal rami, and the course of the articular nerves was documented through digital photography. Radio-opaque wire (20 gauge) was applied to the nerves. Fluoroscopic images were obtained to delineate their radiographic course with respect to osseous landmarks. Results Forty-eight inferior articular branches were identified. Three (6.3%) originated from the medial branch and 44 (91.7%) from the dorsal ramus. One was indeterminate. Fifty-one superior articular branches were identified. Eight (15.7%) originated from the medial branch and 43 (84.3%) from the dorsal ramus. In 12% of cases (6/50), there was side-to-side asymmetry in the origins of the articular branches. Nerves were commonly suspended in the intertransverse space. The articular branches contacted an osseous structure in only 39% of cases. As previously reported, a “descending branch” was not identified in any specimen. Conclusions Articular branches to the T4-T8 z-joints have substantial inter- and intraspecimen variability of origin. They typically arise from the dorsal ramus rather than the medial branch and frequently do not contact any osseous structure to allow percutaneous needle placement.

Comparing two posterior quadratus lumborum block approaches with low thoracic erector spinae plane block: an anatomic study

Background and objectivesBoth posterior quadratus lumborum (QL) and erector spinae plane (ESP) blocks have been described as new truncal interfascial plane blocks. Distribution of injectate is influenced by fascial anatomy; therefore, different injection sites may produce similar spread. This anatomic study was designed to test the hypothesis that a posteromedial QL block at L2 level will more closely resemble a low thoracic ESP block when compared with the posterolateral approach at L2 level.MethodsLeft-sided ESP blocks were performed in six cadavers at T10–11. Three of these cadavers received right-sided posteromedial QL block at L2, while the other three received right-sided posterolateral QL block at L2. All injections were composed of 20 mL methylcellulose 0.5 % mixed with India ink and 10 mL of Omnipaque (Iohexol) 240 mg/mL. CT 24 hours after injection and cadaver dissection were used to evaluate injectate spread.ResultsCephalocaudal spread of injectate by CT and cadaveric dissection was highly correlated (r=0.85 [95% CI 0.51 to 0.95]). Cadaver dissection showed ESP injectate spread deep to the muscle (mean [SD]) 11.7 (2.3) levels compared with 7.3 (1.2) levels for posterolateral QL and 9.7 (1.5) for posteromedial QL (p=0.04 overall, with a statistically significant pairwise difference between ESP and posterolateral QL only). The subcostal nerve and dorsal rami were commonly involved in most blocks, but the paravertebral space and ventral rami had inconsistent involvement. The lumbocostal ligament limited cranial spread from the posterlateral QL block approach.ConclusionsThe posteromedial QL block at L2 produces more cranial spread beyond the lumbocostal ligament than the posterolateral QL block, and this spread is comparable with a low thoracic ESP block. Both posterior QL and ESP blocks show unreliable spread of injectate to the paravertebral space and ventral rami, but the dorsal rami were frequently covered.