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Yuichiro Abe, Shigenobu Sato, Koji Kato, Takahiko Hyakumachi, Yasushi Yanagibashi, Manabu Ito and Kuniyoshi Abumi

Augmented reality (AR) is an imaging technology by which virtual objects are overlaid onto images of real objects captured in real time by a tracking camera. This study aimed to introduce a novel AR guidance system called virtual protractor with augmented reality (VIPAR) to visualize a needle trajectory in 3D space during percutaneous vertebroplasty (PVP).

The AR system used for this study comprised a head-mount display (HMD) with a tracking camera and a marker sheet. An augmented scene was created by overlaying the preoperatively generated needle trajectory path onto a marker detected on the patient using AR software, thereby providing the surgeon with augmented views in real time through the HMD. The accuracy of the system was evaluated by using a computer-generated simulation model in a spine phantom and also evaluated clinically in 5 patients.

In the 40 spine phantom trials, the error of the insertion angle (EIA), defined as the difference between the attempted angle and the insertion angle, was evaluated using 3D CT scanning. Computed tomography analysis of the 40 spine phantom trials showed that the EIA in the axial plane significantly improved when VIPAR was used compared with when it was not used (0.96° ± 0.61° vs 4.34° ± 2.36°, respectively). The same held true for EIA in the sagittal plane (0.61° ± 0.70° vs 2.55° ± 1.93°, respectively).

In the clinical evaluation of the AR system, 5 patients with osteoporotic vertebral fractures underwent VIPAR-guided PVP from October 2011 to May 2012. The postoperative EIA was evaluated using CT. The clinical results of the 5 patients showed that the EIA in all 10 needle insertions was 2.09° ± 1.3° in the axial plane and 1.98° ± 1.8° in the sagittal plane. There was no pedicle breach or leakage of polymethylmethacrylate.

VIPAR was successfully used to assist in needle insertion during PVP by providing the surgeon with an ideal insertion point and needle trajectory through the HMD. The findings indicate that AR guidance technology can become a useful assistive device during spine surgeries requiring percutaneous procedures.

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Hisashi Yoshimoto, Shigenobu Sato, Izumi Nakagawa, Takahiko Hyakumachi, Yasushi Yanagibashi, Fumihito Nitta and Takeshi Masuda

✓The authors report the case of an 83-year-old woman with refractory sciatica attributable to isthmic spondylolisthesis at L-5. Her symptoms were successfully improved after posterior lumbar interbody fusion (PLIF) at L5–S1; however, notable swelling in her left leg suddenly developed 2 days postoperatively. Anterior migration of a fragment of bone graft was demonstrated on computed tomography scanning, and there was obvious occlusion of the left common iliac vein (CIV) on magnetic resonance venography. Ultrasonography revealed a thrombus in the left CIV at the site of compression. To prevent a pulmonary embolism during manipulation of the affected vein, an inferior vena cava filter was placed just before excision of the migrated bone fragment. The swelling in the patient’s leg subsided quickly after the surgery, and she was treated with heparin and warfarin to prevent recurrent deep vein thrombosis (DVT). Six months after the second surgery, complete restoration of blood flow to the left CIV and no recurrence of DVT were demonstrated on magnetic resonance venography. Especially in elderly patients with degenerative disc disease, excessive curettage and impaction of disc materials during the PLIF procedure may cause migration of bone graft fragments. Surgeons should be aware of the possible vascular complications of PLIF.

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Discal cysts of the lumbar spine

Report of five cases

Masaharu Nabeta, Hisashi Yoshimoto, Shigenobu Sato, Takahiko Hyakumachi, Yasushi Yanagibashi and Takeshi Masuda

✓Discal cysts are rare lesions that can result in refractory sciatica. Because they are so rare, their exact origin and details of the clinical manifestations are still unknown. The authors report on five men treated for discal cysts. The mean age of the patients at the time of the surgery was 32 years (range 25–38 years). All patients suffered from lower-extremity pain and the results of the straight leg–raising test were positive in all cases. Three patients reported motor weakness and four had sensory disturbance—symptoms similar to those found in patients with lumbar disc herniation. Magnetic resonance imaging demonstrated spherically shaped extradural lesions of various sizes with low and high signal intensities on T1- and T2-weighted images, respectively. Discography revealed obvious communication between the cyst and the intervertebral disc with reproducible leg pain in all patients. All patients underwent posterior decompression and excision of the cysts either with or without additional discectomy. The radicular symptoms were remarkably improved in all patients immediately after surgery, and no recurrent lesions were noted during follow up.

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Hisashi Yoshimoto, Shigenobu Sato, Takahiko Hyakumachi, Yasushi Yanagibashi and Takeshi Masuda

✓ The authors report the case of an 87-year-old woman who suffered from T1–2 pyogenic spondylitis resulting in progressive and severe paraplegia. Debridement and anterior manubrium-splitting fusion were difficult because a high-positioned aortic arch was very close to the infectious lesion. Because adequate intravenous antibiotic agents had nearly resolved the inflammation, the authors undertook anterior debridement and posterior fusion that involved costotransversectomy and the placement of a posterior cervical pedicle screw fixation system. At 1.5 years postoperatively, there were no signs of recurrent infection. Solid osseous union was documented, and the patient's paraplegia had improved.

A high-positioned aortic arch will likely interfere with an anterior approach to the cervicothoracic junction. If adequate antibiotic therapy has successfully controlled the spinal infection, anterior debridement and posterior fusion can be conducted in cases involving such anatomical limitations.