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Yoshihisa Kotani, Manabu Ito, Kuniyoshi Abumi, Keigo Yasui and Akio Minami

The authors describe a case of a 52-year-old woman in whom tetraplegia developed with neurological respiratory failure due to POEMS syndrome associated with a solitary sacral plasmacytoma. Resection was finally performed after her condition proved resistant to radiation and chemotherapy. The patient showed a dramatic recovery and was ambulatory without tumor recurrence after 5 years and 6 months of follow-up. To the authors' knowledge, there are only 3 reported cases in the literature of bilateral phrenic nerve palsy leading to respiratory failure treated by chemotherapy. This is the first report describing neurological recovery after surgery for pentaplegia due to POEMS syndrome associated with solitary sacral plasmacytoma.

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Hirotaka Ito, Michiharu Morino, Manabu Niimura, Sachiko Takamizawa and Yoshie Shimizu

A 2-stage corpus callosotomy is accepted as a palliative procedure for patients older than 16 years with, in particular, medically intractable generalized epilepsy and drop attack seizures and is preferable for a lower risk of disconnection syndrome. Although the methods by which a previously performed craniotomy can be reopened for posterior callosotomy have already been reported, posterior corpus callosotomy using a parietooccipital interhemispheric approach with the patient in a semi-prone park-bench position has not been described in the literature. Here, the authors present a surgical technique for posterior callosotomy using a parietooccipital interhemispheric approach with a semi-prone park-bench position as a second surgery. Although this procedure requires an additional skin incision in the parietooccipital region, it makes the 2-stage callosotomy safer and easier to perform because of reduced intracranial adhesion, less bleeding, and an easier approach to the splenium of the corpus callosum.

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Yoshihisa Kotani, Kuniyoshi Abumi, Manabu Ito and Akio Minami

Object. The authors introduce a unique computer-assisted cervical pedicle screw (CPS) insertion technique used in conjunction with specially modified original pedicle screw insertion instruments. The accuracy of screw placement as well as surgery-related outcome and complication rates were compared between two groups of patients: those in whom a computer-assisted and those in whom a conventional manual insertion technique was used.

Methods. The screw insertion guiding system consisted of a modified awl, probe, tap and a screwdriver specially designed for a computer-assisted CPS insertion. Using this system, real-time instrument/screw tip information was three dimensionally identified in each step of screw insertion. Seventeen patients underwent CPS fixation in which a computer-assisted surgical navigation system was used. The cervical disorders consisted of spondylotic myelopathy with segmental instability or kyphosis, metastatic spinal tumor, rheumatoid spine, and postlaminectomy kyphosis. The rate of pedicle wall perforation was significantly lower in the computer-assisted group than that in the other group (1.2 and 6.7%, respectively; p < 0.05). The screw trajectory in the horizontal plane was significantly closer to the anatomical pedicle axis in the computer-assisted group compared with the manual insertion group (p < 0.05). This factor significantly reduced the incidence of screw perforation laterally. Complications such as neural damage or vascular injury were not demonstrated in the computer-assisted group (compared with 2% in the manual insertion treatment group). The overall surgery-related outcome was satisfactory.

Conclusions. In contrast to the previously reported computer-assisted technique, our CPS insertion technique provides real-time three-dimensional instrument/screw tip information. This serves as a powerful tool for safe and accurate pedicle screw placement in the cervical spine.

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Hideki Sudo, Kuniyoshi Abumi, Manabu Ito, Yoshihisa Kotani and Akio Minami

✓ The sublaminar wiring procedure has been commonly used for stabilizing the atlantoaxial complex. Multistrand braided cables were introduced in the early 1990s. In previous biomechanical studies these cables were demonstrated to be superior to monofilament wires in terms of their flexibility, mechanical strength, and fatigue-related characteristics. To the authors' knowledge, they are the first to describe clinically the occurrence of delayed spinal cord compression resulting from multistrand cables after the completion of rigid spinal arthrodesis in the upper cervical spine.

Three patients underwent posterior atlantoaxial fusion in which two sublaminar multistrand cables were placed. Between 15 and 48 months postoperatively, they suffered from upper- and lower-extremity numbness as well as gait disturbance. Plain radiography and computerized tomography myelography revealed spinal cord compression caused by the sublaminar cables, although fusion was complete and physiological alignment was maintained at the fused segment. The radiographs obtained immediately after surgery demonstrated that the initial cable placement had been properly performed. The shape of the cable at the initial surgery was oval and then gradually became circular. The anterior arc of the circular shape of the cable in fact led to the spinal cord compression.

Considering the mechanism of this late complication, a cable tends to spring open because of its high flexibility and becomes circular shaped even after the complete arthrodesis. When applying multistrand cables for intersegmental fixation at the atlantoaxial complex, delayed complications related to bowing of the cables is possible.

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Manabu Ito, Makoto Motomiya, Kuniyoshi Abumi, Osamu Shirado, Yoshihisa Kotani, Ken Kadoya, Eihiro Murota and Akio Minami

✓ Sarcoidosis is a systemic disease commonly affecting lung, skin, or eye. Sarcoidosis involved with osseous structures occurs in approximately 5% of patients, usually involving small bones. Spinal sarcoidosis is extremely rare. The authors report on a man in whom examination of a subclavicular lymph node biopsy specimen and its spinal involvement had established a diagnosis of sarcoidosis and who had undergone steroid therapy. Despite intensive conservative treatment, the authors observed progressive collapse of L-2 requiring spinal decompressive and reconstructive surgeries. Histological evaluation of the collapsed vertebra did not show the typical noncaseating granuloma; rather, the authors observed osteonecrosis of the entire L-2 structure without reactive cellular activities. Other potential diagnoses including infectious disease, metastatic spinal tumor, and osteoporotic vertebral collapse were excluded based on laboratory data, imaging studies, and pathological findings. Complete necrosis of the entire L-2 vertebra in this case can be considered as a rare clinical manifestation of spinal sarcoidosis. Because of osteopenia and systemic bone fragility, combined anterior—posterior spinal reconstructive surgery was performed to restabilize the severely damaged spine.

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Manabu Ito, Kuniyoshi Abumi, Yoshihisa Kotani, Masahiko Takahata, Hideki Sudo, Yoshihiro Hojo and Akio Minami

The authors present a new posterior correction technique consisting of simultaneous double-rod rotation using 2 contoured rods and polyaxial pedicle screws with or without Nesplon tapes. The purpose of this study is to introduce the basic principles and surgical procedures of this new posterior surgery for correction of adolescent idiopathic scoliosis. Through gradual rotation of the concave-side rod by 2 rod holders, the convex-side rod simultaneously rotates with the the concave-side rod. This procedure does not involve any force pushing down the spinal column around the apex. Since this procedure consists of upward pushing and lateral translation of the spinal column with simultaneous double-rod rotation maneuvers, it is simple and can obtain thoracic kyphosis as well as favorable scoliosis correction. This technique is applicable not only to a thoracic single curve but also to double major curves in cases of adolescent idiopathic scoliosis.

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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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Hideki Sudo, Itaru Oda, Kuniyoshi Abumi, Manabu Ito, Yoshihisa Kotani and Akio Minami

Object

The objectives of this study were to compare the biomechanical effects of five lumbar reconstruction models on the adjacent segment and to analyze the effects of three factors: construct stiffness, sagittal alignment, and the number of fused segments.

Methods

Nondestructive flexion–extension tests were performed by applying pure moments to 10 calf spinal (L3–S1) specimens. One-segment (L5–6) or two-segment (L5–S1) posterior fusion methods were simulated: 1) one-segment posterolateral fusion (PLF); 2) one-segment PLF with interbody fusion cages (one-segment PLIF/PLF); 3) two-segment PLF; 4) two-segment PLIF/PLF; and 5) two-segment PLF in kyphosis (two-segment kyphotic PLF). The range of motion (ROM) of the reconstructed segments, intradiscal pressure (IDP), and lamina strain in the upper (L4–5) adjacent segment were analyzed.

The ROM was significantly decreased in the PLIF/PLF models compared with that in the PLF alone models after both the one- and two-segment fusions. If the number of fused segments was increased, the pressure and strains were also increased in specimens subjected to the PLIF/PLF procedure, more so than the PLF-alone procedure. In the one-segment PLIF/PLF model the authors observed a reduced IDP and lamina strain compared with those in the kyphotic two-segment PLF model despite the latter’s higher levels of initial stiffness.

Conclusions

If the number of fused levels can be reduced by using PLIF to correct local kyphosis, then this procedure may be valuable for reducing adjacent-segment degenerative changes.

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Hideki Sudo, Manabu Ito, Kuniyoshi Abumi, Yoshihisa Kotani, Tatsuto Takeuchi, Keigo Yasui and Akio Minami

Object

As increasing numbers of patients receive long-term hemodialysis, the number of reports regarding hemodialysis-related cervical spine disorders has also increased. However, there have been few reports summarizing the surgical results in patients with these disorders. The objective of this study was to evaluate the long-term follow up and clinical results after surgical treatment of cervical disorders in patients undergoing hemodialysis.

Methods

Seventeen patients in whom surgery was performed for cervical spine disorders while they received long-term hemodialysis therapy were enrolled in this study. Of these, 15 underwent follow-up review for more than 3 years after surgery, and these represent the study population. The remaining two patients died of postoperative sepsis. The average follow-up period was 120 months. Five patients without spinal instability underwent spinal cord decompression in which bilateral open-door laminoplasty was performed. Ten patients with destructive spondyloarthropathy (DSA) underwent reconstructive surgery involving pedicle screw (PS) fixation. In eight patients in whom posterior instrumentation was placed, anterior strut bone grafting was performed with autologous iliac bone to treat anterior-column destruction. Marked neurological recovery was obtained in all patients after the initial surgery. In the mobile segments adjacent to the site of previous spinal fusion, the authors observed progressive destructive changes with significant instability in four patients (40%) who underwent circumferential spinal fusion. No patients required a second surgery after laminoplasty for spinal canal stenosis without DSA changes.

Conclusions

Cervical PS-assisted reconstruction provided an excellent fusion rate and good spinal alignment. During the long-term follow-up period, however, some cases required extension of the spinal fusion due to the destructive changes in the adjacent vertebral levels. Guidelines or recommendations to overcome these problems should be produced to further increase the survival rates of patients undergoing hemodialysis.

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Manabu Ito, Yoshihisa Kotani, Yoshihiro Hojo, Kuniyoshi Abumi, Tsuyoshi Kadosawa and Akio Minami

Object

The aim of this study was to evaluate the degree of bone ingrowth and bonding stiffness at the surface of hydroxyapatite ceramic (HAC) spacers with different porosities in an animal model and to discuss the ideal porous characteristics of these spacers for anterior spinal reconstruction.

Methods

Twenty-one adult sheep (age 1–2 years, mean weight 70 kg) were used in this experiment. Surgery consisted of anterior lumbar interbody fusion at L2–3 and L4–5, insertion of an HAC spacer (10 × 13 × 24 mm) with three different porosities (0, 3, and 15%), and single-rod anterior instrumentation. At 4 and 6 months postoperatively, the lumbar spines were harvested. Bonding conditions at the bone–HAC spacer interface were evaluated using neuroimages and biomechanically. A histological evaluation was also conducted to examine the state of bone ingrowth at the surface of the HAC spacer.

Biomechanical testing showed that the bonding strength of HAC at 6 months postoperatively was 0.047 MPa in 0% porosity spacers, 0.39 MPa in 3%, and 0.49 MPa in 15% porosity spacers. The histological study showed that there was a soft-tissue layer at the surface of the HAC spacer with 0% porosity. Direct bonding was observed between bone and spacers with 3 or 15% porosity. Micro–computed tomography scans showed direct bonding between the bone and HAC with 3 or 15% porosity. No direct bonding was observed in HAC with 0% porosity.

Conclusions

Dense (0%) HAC anterior vertebral spacers did not achieve direct bonding to the bone in the sheep model. The HAC vertebral spacers with 3 or 15% porosity showed proof of direct bonding to the bone at 6 months postoperatively. The higher porosity HAC spacer showed better bonding stiffness to the bone.