Case series of fluoroscopic findings and 3D reconstruction of human spinal MRIs of the space of Okada

Abstract

Objective To better understand the unexpected spread of contrast medium observed by conventional fluoroscopic X‐ray images during standard neuraxial techniques used in the treatment of pain. The support of 3D reconstruction of MRI images of structures within the lumbar spine was used to better understand the space of Okada. Methods Lumbar facet joint and epidural corticosteroid injections in five patients under fluoroscopic guidance with loss of resistance to air or saline to identify the facet joints or epidural space. Next, in a retrospective study, the authors examined the retrodural space of Okada and the neighboring tissues with 3D reconstruction of spinal MRIs of seven patients without any demonstrable spinal pathology to better understand the characteristics of the space of Okada. Results Contrast medium spread to the ipsilateral and contralateral sides was observed in five patients. The contralateral spread was thought to be through the retrodural space of Okada, which is a potential space between the anterior surface of the vertebral lamina and the posterior surface of the ligamentum flavum. It facilitates communication between the contralateral articular facet joints of the spine. Conclusions This study provides new evidence for the existence of the space of Okada where an unexpected contralateral spread occurred following facet joint and attempted epidural injection. The 3D reconstructions of MRIs may help us better understand the nature of the retrodural space of Okada and its clinical implications.

Unexpected injectate spread into the space of Okada during attempted epidural injection: Yet another case

“…Fluoroscopy revealed an unexpected spread of contrast medium into the interspinous region in addition to both L4-L5 facet joints. This spread was typical for the space of Okada (Lehman et al, 2015;Murthy et al, 2011;Okada, 1981;Reina et al, 2021); however, a less common feature, namely cranial contrast medium spread in a 'V' shape, was also seen in this patient (Figure 1a). The lateral fluoroscopic view showed the retrodural space without epidural spread (Figure 1b).…”

“…To the Editor, Our group previously presented a case series aided by a three-dimensional (3D) magnetic resonance imaging (MRI) reconstruction that described injection into the space of Okada as a possible cause of unsuccessful epidural analgesia or injection following the commonly used loss of resistance to air (LORA) technique (Reina et al, 2021). We proposed at the time that a possible cause of the epidural block or injection failure may have been that the epidural needle (or catheter) was placed inside the space of Okada rather than into the epidural space (Lehman et al, 2015;Murthy et al, 2011;Okada, 1981;Reina et al, 2021). This space was initially described at the cervical spine (Okada, 1981), but it was later also described at the lumbar region between the ligamentum flavum and the vertebral lamina (Iwanaga;et al, 2020;Reina et al, 2016).…”

“…Afterward, we again used 3D reconstruction of the MRI of the lumbar spine of another similar-sized healthy patient (Reina et al, 2021;Figure 2) and overlaid the fluoroscopic images at similar enlargements to demonstrate the spread in our patient. This reconstruction demonstrated the position of the space of Okada and its 'V' shape.…”

Fluoroscopic Findings of Extra-Cervical Facet Joint Flow and Its Incidence on Cervical Facet Joint Arthrograms

“…In 1981, Okada first described a space communicating with the bilateral CFJs at a single vertebral level, which was regarded as a potential pathway for the spread of injectants and infection [28,29]. This potential space is also present in the lumbar region [29][30][31]. It is located between the ligamentum flavum and the vertebral arch, possibly allowing further communication with the adjacent spaces, including the interspinous space [30].…”

“…It is located between the ligamentum flavum and the vertebral arch, possibly allowing further communication with the adjacent spaces, including the interspinous space [30]. Reina et al [31] reported that this potential space was difficult to identify anatomically because dissection could break the weak tissues included in the space, but they identified the space radiologically. Similarly, in our experience, this space has not been anatomically confirmed or detected during normal cadaveric dissection.…”