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Bungo Otsuki, Mitsuru Takemoto, Shunsuke Fujibayashi, Hiroaki Kimura, Kazutaka Masamoto and Shuichi Matsuda

Several articles have described the use of screw insertion guides during primary spine surgery; however, the use of such a guide during revision surgeries has not been described. The purpose of this study is to describe the utility of a custom screw insertion (CSI) guide assembled using a novel method and a full-scale, color-coded 3D plaster (FCTP) model for safe and accurate revision surgery.

The authors applied the CSI guide and the FCTP model in 3 cases. In the first case, a patient with multiple failed cervical spine surgeries underwent occipitocervicothoracic fusion. After a successful result for this patient, the authors applied the CSI guide in 2 other patients who underwent revision lumbar fusion surgeries to confirm the accuracy and the efficacy of the CSI guides in such cases. The models and guides were fabricated using rapid prototyping technology. The effectiveness of these methods was examined.

The FCTP model was designed using CT data. During model assembly, implants inserted during previous surgery were removed virtually, and for the cervical spine, vertebral arteries were colored red for planning. The CSI guide was designed with 5 or 6 arms to fit the bone surface precisely after removing artifacts. Surgery was performed by referring to the FCTP model. Because the actual structure of the bone surface was almost identical to that of the FCTP model, surgical exposure around the complex bone shape proceeded smoothly. The CSI guides were positioned accurately to aid the successful insertion of a pedicle screw into the C-2 vertebra in the case of cervical revision surgery, and 4 pedicle screws for lumbar vertebrae in the 2 other patients. Postoperative CT scans showed that all screw positions closely matched those predicted during the preoperative planning. In conclusion, the FCTP models and the novel CSI guides were effective for safe and accurate revision surgery of the spine.

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Minoru Ikenaga, Jitsuhiko Shikata, Mitsuru Takemoto and Chiaki Tanaka

Object

Many patient complications have been reported after the use of the pedicle subtraction osteotomy (PSO) technique. To the authors' knowledge, no previous reseachers have reported on the causes of complications after using the single-stage PSO technique with a posterior approach. The purpose of this study was to investigate complications after the procedure, to clarify the factors influencing the complications, and to identify ways to minimize complications.

Methods

Records for 67 patients treated with the PSO technique were examined retrospectively. All complications were recorded and analyzed in relation to the radiological and clinical outcomes.

No patient died or became paraplegic as a result of surgery. There were 48 surgery-related complications in 27 patients (40%): six intraoperative, four perioperative, and 38 late-onset postoperative complications. As the study progressed and more patients were treated, the rate of intraoperative complications decreased significantly. The incidence of late-onset complications associated with an adjacent-segment progression of kyphosis was lower in patients with a long fusion from a midthoracic vertebra to the sacrum or pelvis than in patients treated with a shorter fusion. The C-7 plumb line values and postoperative complications were closely correlated with clinical results.

Conclusions

Intraoperative complications can be prevented or the risks minimized with adequate surgical training. Most of the late-onset complications in these patients were related to the progression of kyphosis. The frequency of complications was closely correlated with patient satisfaction at follow up. Correcting the C-7 plumb line value with minimal complications appeared to lead to better clinical results.

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Shunsuke Fujibayashi, Masashi Neo, Mitsuru Takemoto, Masato Ota and Takashi Nakamura

Object

Foraminal stenosis is a common cause of lumbar radicular symptoms. Recognition of the dynamic pathology, as well as the static anatomical changes, is important to achieving successful surgical outcomes. Excessive facet and anulus removal leads to subsequent disc space narrowing and/or segmental instability, which can cause poor results after decompressive surgery. The objective of this study was to evaluate the efficacy of the paraspinalapproach transforaminal lumbar interbody fusion (TLIF) in the treatment of lumbar foraminal stenosis.

Methods

Twenty levels of lumbar foraminal stenosis in 16 patients were treated using an instrumented paraspinal-approach TLIF. There were 12 single-level and 4 two-level cases. Pathologies included foraminal stenosis at 13 levels and lateral disc herniation with disc space narrowing at 7.

Results

In all patients, preoperative radicular symptoms and mechanical low-back pain were resolved immediately after the operation and leg weakness improved gradually. The recovery rate using the Japanese Orthopaedic Association score was 89.1%. Bony union was achieved within 6 months after the operation in all cases. Postoperative MR imaging showed minimal changes in the paraspinal muscles in the single-level cases.

Conclusions

The paraspinal-approach TLIF is a minimally invasive, safe, and secure procedure for treating lumbar foraminal lesions. Direct visualization and decompression for the foraminal lesion, distraction of the collapsed disc space, and stabilization of the unstable segments can be achieved simultaneously through the paraspinal approach, which produces successful clinical and radiological results.

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Mitsuru Takemoto, Shunsuke Fujibayashi, Masashi Neo, Kazutaka So, Norihiro Akiyama, Tomiharu Matsushita, Tadashi Kokubo and Takashi Nakamura

Object

Porous biomaterials with adequate pore structure and appropriate mechanical properties are expected to provide a new generation of devices for spinal interbody fusion because of their potential to eliminate bone grafting. The purpose of this study was to evaluate the fusion characteristics of porous bioactive titanium implants using a canine anterior interbody fusion model.

Methods

Porous titanium implants sintered with volatile spacer particles (porosity 50%, average pore size 303 μm, compressive strength 116.3 MPa) were subjected to chemical and thermal treatments that give a bioactive microporous titania layer on the titanium surface (BT implant). Ten adult female beagle dogs underwent anterior lumbar interbody fusion at L6–7 using either BT implants or nontreated (NT) implants, followed by posterior spinous process wiring and facet screw fixation. Radiographic evaluations were performed at 1, 2, and 3 months postoperatively using X-ray fluoroscopy. Animals were killed 3 months postoperatively, and fusion status was evaluated by manual palpation and histological examination.

Results

Interbody fusion was confirmed in all five dogs in the BT group and three of five dogs in the NT group. Histological examination demonstrated a large amount of new bone formation with marrowlike tissue in the BT implants and primarily fibrous tissue formation in the NT implants.

Conclusions

Bioactive treatment effectively enhanced the fusion ability of the porous titanium implants. These findings, coupled with the appropriate mechanical properties in load-bearing conditions, indicate that these porous bioactive titanium implants represent a new generation of biomaterial for spinal interbody fusion.

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Kazuaki Morizane, Mitsuru Takemoto, Masashi Neo, Shunsuke Fujibayashi, Bungo Otsuki, Shimei Tanida, Takayoshi Shimizu, Hiromu Ito and Shuichi Matsuda

OBJECTIVE

Dyspnea and/or dysphagia is a life-threatening complication after occipitocervical fusion. The occiput-C2 angle (O-C2a) is useful for preventing dyspnea and/or dysphagia because O-C2a affects the oropharyngeal space. However, O-C2a is unreliable in atlantoaxial subluxation (AAS) because it does not reflect the translational motion of the cranium to C2, another factor affecting oropharyngeal area in patients with rheumatoid arthritis (RA) who have reducible AAS. The authors previously proposed the occipital and external acoustic meatus to axis angle (O-EAa; i.e., the angle made by McGregor’s line and a line joining the external auditory canal and the middle point of the endplate of the axis [EA line]) as a novel, useful, and powerful predictor of the anterior-posterior narrowest oropharyngeal airway space (nPAS) distance in healthy subjects. The aim of the present study was to elucidate the validity of O-EAa as an indicator of oropharyngeal airway space in RA patients with AAS.

METHODS

The authors investigated 64 patients with RA. The authors collected lateral cervical radiographs at neutral position, flexion, extension, protrusion, and retraction and measured the O-C2a, C2-C6, O-EAa, anterior atlantodental interval (AADI), and nPAS. Patients were classified into 2 groups according to the presence of AAS and its mobility: group N, patients without AAS; and group R, patients with reducible AAS during dynamic cervical movement.

RESULTS

Group N had a significantly lower AADI and O-EAa than group R in all but the extension position. The O-EAa was a better predictor for nPAS than O-C2a according to the mixed-effects models in both groups (marginal R2: 0.510 and 0.575 for the O-C2a and O-EAa models in group N, and 0.250 and 0.390 for the same models, respectively, in group R).

CONCLUSIONS

O-EAa was superior to O-C2a in predicting nPAS, especially in the case of AAS, because it affects both O-C2a and cranial translational motion. O-EAa would be a useful parameter for surgeons performing occipitocervical fusion in patients with AAS.