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Masashi Neo

Object. In this, the first of two articles regarding C1–2 transarticular screw fixation, the authors assessed the rate of fusion, surgery-related complications, and lessons learned after C1–2 transarticular screw fixation in an adult patient series.

Methods. The authors retrospectively reviewed 191 consecutive patients (107 women and 84 men; mean age 49.7 years, range 17–90 years) in whom at least one C1–2 transarticular screw was placed. Overall 353 transarticular screws were placed for trauma (85 patients), rheumatoid arthritis (63 patients), congenital anomaly (26 patients), os odontoideum (four patients), neoplasm (eight patients), and chronic cervical instability (five patients). Among these, 67 transarticular screws were placed in 36 patients as part of an occipitocervical construct. Seventeen patients had undergone 24 posterior C1–2 fusion attempts prior to referral. The mean follow-up period was 15.2 months (range 0.1–106.3 months).

Fusion was achieved in 98% of cases followed to commencement of fusion or for at least 24 months. The mean duration until fusion was 9.5 months (range 3–48 months). Complications occurred in 32 patients. Most were minor; however, five patients suffered vertebral artery (VA) injury. One bilateral VA injury resulted in patient death. The others did not result in any permanent neurological sequelae.

Conclusions. Based on this series, the authors have learned important lessons that can improve outcomes and safety. These include techniques to improve screw-related patient positioning, development of optimal instrumentation, improved screw materials and design, and defining the role for stereotactic navigation. Atlantoaxial transarticular screw fixation is highly effective in achieving fusion, and the complication rate is low when performed by properly trained surgeons.

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Shunsuke Fujibayashi, Masashi Neo and Takashi Nakamura

✓ Spinal fixation for destructive metastatic lesions at the lumbosacral junction is challenging because of the large and unique load-bearing characteristics present. In particular, caudal fixation is difficult in cases of sacral destruction because of insufficient S-1 pedicle screw anchorage. The authors describe their surgical technique for secure iliac screw placement and the clinical results obtained in five patients with metastatic spinal disease. All patients in this study underwent palliative operations with dual iliac screw fixation between April 1999 and October 2002, and the clinical and radiological findings were assessed. In all five patients, spinal metastases extended into the sacrum. The metastases were from renal cell carcinomas in two patients, lung cancer in two, and a paraganglioma in one patient.

Postoperative follow-up periods ranged from 3 months to 6 years (mean 28.4 months). Preoperatively, four patients could not walk due to severe pain or neurological compromise. Postoperatively, all patients reported a reduction in pain and regained the ability to walk. Complications included one case of early wound infection. In the patients with long survival after the operation, there was one case of iliac screw loosening and one case of rod breakage. The dual iliac screw fixation technique provided sufficient immediate stability for destructive lumbosacral metastasis.

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Masashi Neo, Mutsumi Matsushita, Tadashi Yasuda, Takeshi Sakamoto and Takashi Nakamura

✓ Posterior atlantoaxial transarticular screw fixation is an excellent procedure associated with high fusion rates. There is, however, the potential risk of vertebral artery (VA) injury. The authors designed a special aiming device that allows a cannulated screw to be inserted accurately in the most posterior part of the C1–2 joint via the most posterior and medial part of the isthmus of C-2; this screw pathway most safely avoids VA injury. The instruments include an aiming device and a flexible screw-inserting system. The tip of the aiming device is placed on the ridge of the C-2 isthmus just posterior to the atlantoaxial joint. The guide wire should then pass 1 mm below the device tip. The system consists of flexible guide wires, a drill, a tap, and a screwdriver, and the screw is inserted easily via a posterior approach in which the patient's back is not obstructive. Ten patients with atlantoaxial subluxation or osteoarthritis underwent surgery in which the device was used. In all cases, the screws were inserted safely without causing VA injury, although preoperative computerized tomography (CT) reconstructions revealed a high-risk high-riding unilateral VA in three patients. Postoperative CT reconstructions demonstrated that all screws but one were inserted as planned, and successfully cleared the vertebral groove.

In conclusion, this newly designed device is practical and useful for the accurate insertion of screws, thus avoiding VA injury during atlantoaxial transarticular screw fixation.

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Masashi Neo, Shunsuke Fujibayashi, Makoto Yoshida and Takashi Nakamura

✓The purpose of this retrospective review was to demonstrate the effectiveness of simple spinous process plate fixation as a salvage operation for failed anterior cervical fusion (ACF). In this technique, the spinous processes are securely sandwiched between a pair of plates with thorns, which are squeezed together by tightening screws that extend through the plates. The authors salvaged six failed ACFs (nonunion of bone graft, plate migration, or bone graft dislodgment) by conducting this fixation without bone grafting, or with an anterior or posterior local bone graft only. Anterior bone union was attained within 6 months in all cases. This technique is easy to perform and probably provides more mechanical strength than does conventional spinous process wiring, resulting in prompt fusion without the need for a new massive bone graft. This technique is a practical option in salvage operations for failed ACF.

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Masashi Neo, Takeshi Sakamoto, Shunsuke Fujibayashi and Takashi Nakamura

✓The authors describe a case of postoperative spinal epidural hematoma (PSEH) that developed in a patient 9 days after he underwent laminoplasty. A PSEH is a rare but critical complication of spinal surgery that usually occurs within a few days of the procedure. The authors draw attention to the possibility of delayed PSEH and its triggering mechanism. In this case, a 59-year-old man with no history of bleeding disorder underwent cervical laminoplasty for mild myelopathy. On the 7th postoperative day computed tomography demonstrated no abnormal findings in the operative field. On the 9th postoperative day, while straining to defecate, the patient suddenly felt neck and shoulder pain, and tetraplegia rapidly developed. Magnetic resonance imaging demonstrated a huge epidural hematoma. The clot was evacuated during emergency revision surgery, during which the arterial bleeding from a split muscle wall was confirmed. The postoperative course after the revision surgery was uneventful and the patient had none of the previous symptoms 1 year later.

A PSEH causing paralysis can occur even more than a week after surgery. The possibility of a delayed-onset PSEH should be kept in mind, and prompt diagnosis should be made when a patient presents with paresis or paralysis after an operation. The authors recommend advising patients that for a while after surgery they avoid strenuous activity.

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Shunsuke Fujibayashi, Masashi Neo and Takashi Nakamura

✓The authors report a rare case of surgically treated symptomatic thoracic kyphosis caused by dynamic compression in an elderly man. Myelopathy due to thoracic kyphosis has been reported in patients with congenital kyphosis, Scheuermann dorsal kyphosis, and Cushing disease, but to the authors’ knowledge this is the first report of dynamic kyphosis in an elderly person. This otherwise healthy 84-year-old man presented with a 2-year history of progressive difficulty in walking and bilateral leg dysesthesia. Despite several cervical and lumbar surgeries, his symptoms gradually worsened. A radiological examination revealed severe thoracic kyphosis, with a lateral Cobb angle of 59° from T-2 to T-12. On a dynamic computed tomography (CT) myelogram, severe thoracic spinal cord draping and stretching on flexion was demonstrated. On extension, however, imaging studies failed to show draping or stretching. Posterior corrective fusion was performed with instrumentation from T-2 to T-9. Postoperative CT myelography demonstrated no significant spinal cord compression with restoration of the cerebrospinal fluid space anterior to the spinal cord, and the successful correction of the kyphosis to 44°. The patient’s neurological sequelae gradually resolved throughout 6 months of follow up.

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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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Tsutomu Ohnishi, Masashi Neo, Mutsumi Matsushita, Masashi Komeda, Tadaaki Koyama and Takashi Nakamura

✓ The authors describe a case of delayed aortic rupture following the application of a smooth-rod Kaneda (SRK) instrument. This is a rare but critical complication of anterior spinal fusion in which instrumentation is placed, and the authors wish to draw attention to the possible complications arising from such surgery. A few cases of this complication were reported in 1986. No reports have been published since then; perhaps because techniques and implant design have improved. In this case, a 53-year-old man suffered a T-11 fracture and related paraparesis, and he underwent decompression and anterior fusion in which an iliac bone graft was placed using an SRK device. Although his neurological deficit resolved postoperatively, nonunion of the grafted bone caused progressive kyphosis of the thoracolumbar spine. Twenty months after surgery, he complained of progressive gastrointestinal symptoms, and a delayed aortic rupture with a pseudoaneurysm was found surrounding the implant. The aortic pseudoaneurysm was replaced with an artificial vessel, and the SRK device was removed immediately. Delayed aortic rupture associated with anterior instrumentation is extremely rare but can occur. Even if the design of the implants can be improved, the placement of implants near the aorta and subsequent changes in the close anatomical relationship between the aorta and the implant eventually may result in this life-threatening complication. Careful follow-up examination and early removal of the implant, if necessary, are important.

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Masahiko Miyata, Masashi Neo, Hiromu Ito, Makoto Yoshida, Shunsuke Fujibayashi and Takashi Nakamura

Object

Vertebral artery (VA) injury is a potentially serious complication of C-2 pedicle screw (PS) fixation. Although this surgery is frequently performed in patients with rheumatoid arthritis (RA), few studies have compared the risk of VA injury in patients with and without RA. In this study, the authors compare the morphological risk of VA injury relating to C-2 PS fixation in patients with and without RA.

Methods

A total of 110 3D CT images of the cervical spine including the axis were evaluated. Fifty patients with RA and 60 patients without RA were included in the study. The maximum PS diameter (MPSD) that could be used at C-2 without breaching the cortex was measured in 3D using a computer-assisted navigation system. A narrow-pedicle carrier was defined as a patient with an MPSD of 4 mm or less.

Results

In the RA group, 42 of 100 MPSDs were ≤ 4 mm, and 30 of 50 patients (60%) were narrow-pedicle carriers. In the non-RA group, 10 of 120 MPSDs (8%) were ≤ 4 mm, and 8 of 60 (13%) patients were narrow-pedicle carriers. The MPSD, the anteroposterior (AP) diameter of C-3, and the ratio of MPSD to the AP diameter of C-3 were significantly smaller in the RA group than in the non-RA group. Multiple logistic regression analysis showed that RA and narrow C-3 AP diameter were significant risk factors for a narrow-pedicle carrier.

Conclusions

Rheumatoid arthritis is a significant risk factor for a narrow C-2 pedicle. When performing PS placement at C-2, particularly in patients with RA, thorough preoperative evaluation of the bone architecture is very important for avoiding inadvertent injury to the VA.

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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.