A 49-year-old woman presented with radicular pain in the right upper extremity of approximately 5 years. Spurling's sign was strongly positive to the right, and the deep tendon reflex (DTR) of the right triceps brachii was diminished (Table 1). The DTR of the right brachioradialis was slightly decreased. Moreover, sensory disturbance was present at the C6 and C7 dermatomal area (Table 1). Although manual muscle testing revealed no decreases in muscle strength, conservative treatment afforded no pain relief. Magnetic resonance imaging revealed foraminal stenosis at the C5/C6 and C6/C7 levels (Fig. 1A-C). Computed tomography myelography also revealed foraminal stenosis, caused by intervertebral disc herniation and osteophyte of the C6 and C7 vertebrae (Fig. 2A-D). The lateral edge of the right spinal foramen was congruous with the right vertebral artery at the C5/C6 level. Anterior decompression with foraminotomy and total disc replacement were performed. To adequately decompress the foraminal stenosis and avoid injuring the vertebral artery, intraoperative navigation and microscopic augmented reality (AR) support were planned. The patient was placed in a supine position and the skull was fixed with a carbon Mayfield clamp with a reference frame attached to the clamp. Subsequently, a transverse incision was made and an anterior approach to the cervical spine was used. After discectomy at the appropriate levels, an O-arm mobile intraoperative imaging system (O-armTM Surgical Imaging System, Medtronic Navigation Inc., Littleton, MA) was used to create an augmented image model in the navigation system (StealthStationTM Surgical Navigation System, Medtronic Navigation Inc.). Three-dimensional objects representing the surgical target were generated by applying anatomical mapping software (Stealth 3D Cranial SoftwareTM, Medtronic Navigation Inc. (Fig. 3A)) and were reconstructed on the 3D image. Regions of interest were transferred to the Zeiss OPMI Pentero microscope (Carl Zeiss Meditec AG, Oberkochen, Germany), and were visualized on demand in the AR microscope view immediately before decompression (Fig. 3B). During decompression, the location of the vertebral artery could be also confirmed under the AR microscope view. Anterior foraminotomy and uncinectomy were performed using an air drill and a curved curette (Fig. 3C), and complete decompression was confirmed (Fig. 3D). Sufficient decompression was confirmed postoperatively on coronal and axial computed tomography (Fig. 2E-H). Radicular pain in the right upper extremity was improved immediately after the operation.
Table 1.
Neurological Findings.
| Right upper extremity | Left upper extremity | ||
|---|---|---|---|
| MMT | Deltoid | 5 | 5 |
| Biceps brachii | 5 | 5 | |
| Brachioradialis | 5 | 5 | |
| Triceps brachii | 5 | 5 | |
| Wrist extensors | 5 | 5 | |
| Wrist flexors | 5 | 5 | |
| Digital extensors | 5 | 5 | |
| Digital flexors | 5 | 5 | |
| Abductor pollicis | 5 | 5 | |
| Abductor digiti minimi | 5 | 5 | |
| DTR | Deltoid | Normal | Normal |
| Biceps brachii | Normal | Normal | |
| Brachioradialis | Slightly decreased | Normal | |
| Triceps brachii | Diminished | Normal | |
| Abnormal sensation (pin prick) | Radial forearm 7/10 | Normal | |
| Back of the hand 6/10 | |||
| Painful area | Scapular region | No | |
| Radial overarm and forearm | |||
MMT, muscle manual test; DTR, deep tendon reflex
Figure 1.
T2-weighted magnetic resonance images: midsagittal image (A), axial images at C5/C6 (B), and C6/C7 intervertebral disc levels (C).
Figure 2.
Pre- and postoperative images: midsagittal reconstructive image (A), coronal reconstructive image (B), axial views at the C5/C6 (C), and C6/C7 intervertebral disc levels on preoperative computed tomography myelography (arrowheads, foraminal spur formation; broken line, right vertebral artery) (D). Midsagittal reconstructive image (E), coronal reconstructive image (F), and axial views at the C5/C6 (G) and C6/C7 (H) intervertebral disc levels on postoperative computed tomography myelography (arrowheads, decompressed foramen).
Figure 3.
Intraoperative microscopic views: regions of interest annotated on scans taken using an O-arm mobile intraoperative imaging system (A: red, vertebral artery; blue, spinal foramen). The annotated regions visualized on demand in the augmented reality microscope view (B). Anterior foraminotomy using a curved curette (C). Complete decompression confirmed (D).
AR technology was introduced clinically during the 1990s1) for the accurate placement of instruments in the spine, such as pedicle screw insertion, rod bending2), and percutaneous vertebroplasty3). Recently, microscopic AR has been used for minimally invasive and sufficient decompression. Onuma et al. applied a similar technique to anterior decompression for the treatment of cervical ossification of the longitudinal ligament and reported its usefulness in visualizing the ossification outline during decompression4). Umebayashi et al. used microscopic AR imaging in keyhole surgery to avoid excessive anatomical exposure5). Thus, AR technology can help with both accurate positioning and spatial recognition. As the Luschka joints show severe degenerative change in patients with unilateral foraminal stenosis, it is often difficult to determine how much decompression is needed6,7). Moreover, the vertebral artery is often present just adjacent to the foramen. We therefore applied microscopic AR to visualize the vertebral artery as a region of interest to avoid injuring the vessel. Since the present report shows a single case, it is necessary to verify the usefulness and strength of the technology based on future case series. Despite a preliminary information, using this technology also has educational advantages because it allows for images of the surgical area for decompression to be shared with medical supervisors/trainers and co-medical staff. AR technology is a promising means to provide intraoperative accuracy, safety, and education in the field of spine surgery.
Conflicts of Interest: The authors declare that there are no relevant conflicts of interest.
Sources of Funding: None.
Author Contributions: Takashi Hirai: study design, data acquisition, drafting of the manuscript, and critical revision of the manuscript.
Satoru Egawa: Software, drafting of the manuscript, and data acquisition.
Kenichiro Sakai: Software and data acquisition.
Hiroaki Onuma: Software and data acquisition.
Jun Hashimoto: Data acquisition and critical revision of the manuscript.
Kurando Utagawa: Software and data acquisition.
Shingo Morishita: Data acquisition and interpretation of the data.
Kentaro Yamada: Data acquisition and interpretation of the data.
Yu Matsukura: Data acquisition and drafting of the manuscript.
Yoshiyasu Arai: Drafting of the manuscript and data acquisition.
Toshitaka Yoshii: Supervision and critical revision of the manuscript.
Ethical Approval: Ethical approval was waived by the ethics committee as it is not required for case reports.
Informed Consent: Informed consent for publication was obtained by the patient described in this study.
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