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Naoya Kikuchi, Masafumi Uesugi, Masao Koda, Tomoaki Shimizu, Kohei Murakami, Mamoru Kono, Haruka Tanaka, and Masashi Yamazaki

The use of methotrexate (MTX) to treat rheumatoid arthritis (RA) is increasing. Recently, MTX-associated lymphoproliferative disorder (MTX-LPD) has been frequently reported as lymphoma occurring during MTX therapy. The authors report their experience with a relatively rare case of MTX-LPD presenting in the lumbar spine. The patient, a 73-year-old woman who experienced low-back pain while receiving MTX therapy for RA, was suspected of having developed MTX-LPD based on her medical history, images of the L1 vertebra, and transpedicular biopsy results. One week after discontinuing MTX, the patient’s low-back pain reportedly improved. The woman was diagnosed with MTX-LPD based on histopathological findings. MTX discontinuation alone coincided with spontaneous tumor regression. Because MTX-LPD can occur in tissues other than lymph nodes, such as in bones and joints, it is a disease that should be considered when diagnosing spinal tumors in patients receiving MTX therapy.

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Yasuchika Aoki, Masatsune Yamagata, Fumitake Nakajima, Yoshikazu Ikeda, Koh Shimizu, Masakazu Yoshihara, Junichi Iwasaki, Tomoaki Toyone, Koichi Nakagawa, Arata Nakajima, Kazuhisa Takahashi, and Seiji Ohtori

Object

Because the authors encountered 4 cases of hardware migration following transforaminal lumbar interbody fusion, a retrospective study was conducted to identify factors influencing the posterior migration of fusion cages.

Methods

Patients with lumbar degenerative disc disease (125 individuals; 144 disc levels) were treated using transforaminal lumbar interbody fusion and followed for 12–33 months. Medical records and pre- and postoperative radiographs were reviewed, and factors influencing the incidence of cage migration were analyzed.

Results

Postoperative cage migration was found in 4 patients at or before 3 months. Because all the cages that migrated postoperatively were bullet-shaped (Capstone), only these cages were analyzed. The analysis of preoperative radiographs revealed that higher posterior disc height ([PDH] ≥ 6 mm) significantly increased the incidence of postoperative cage migration, but percent slippage, translation, range of motion, and Cobb angle did not. The incidence of cage migration in patients with unilateral fixation (3 [8.3%] of 36) was not significantly different from that in patients with bilateral fixation (1 [2.1%] of 48). Patients who had scoliotic curvature with a Cobb angle > 10° when treated with unilateral fixation demonstrated a tendency to have more frequent postoperative cage migration than patients treated with bilateral fixation.

To examine the influence of the height of fusion cages, a value obtained by subtracting preoperative anterior disc height (ADH) or PDH from cage height was defined as “Cage height – ADH” (or “Cage height –PDH”). The analysis revealed that the value for “Cage height –ADH” as well as “Cage height –PDH” was significantly lower in migrated levels than in nonmigrated levels, suggesting that the choice of undersized cages may increase the incidence of cage migration.

Conclusions

The results suggest that the use of a bullet-shaped cage, higher PDH, the presence of scoliotic curvature, and undersized fusion cages are possible risk factors for cage migration. One patient with postoperative cage migration following bilateral screw fixation underwent revision surgery, and the pedicle screw fixation was found to be disrupted. Other than in this patient, cage migration occurred only in those treated by unilateral fixation. The potential for postoperative cage migration and limitations of unilateral fixation should be considered by spine surgeons.

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Tomoaki Shimizu, Masao Koda, Tetsuya Abe, Tomoyuki Asada, Kosuke Sato, Yosuke Shibao, Mamoru Kono, Fumihiko Eto, Kousei Miura, Kentaro Mataki, Hiroshi Noguchi, Hiroshi Takahashi, Toru Funayama, and Masashi Yamazaki

OBJECTIVE

The goal of this study was to clarify the clinical utility of paravertebral foramen screws (PVFSs) and to determine intraoperative indicators for appropriate screw placement during posterior cervical fusion surgery to improve its safety.

METHODS

The authors included data from 46 patients (29 men and 17 women, mean age 61.7 years) who underwent posterior cervical spine surgery with 94 PVFSs. Of the 94 PVFSs, 77 were used in C6, 9 in C3, 5 in C4, and 3 in C5. According to the cervical lateral radiographic view, the authors divided the 94 PVFSs into 3 groups as follows: a longer group, in which the tip of PVFS was located anteriorly from the line of the posterior wall of the vertebral body (> +0 mm); an intermediate group, in which the screw tip was located up to 2 mm posteriorly to the posterior wall of the vertebral body (–2 to 0 mm); and a shorter group, in which the screw tip was located more than 2 mm posteriorly (< –2 mm). The accuracy of screw placement was assessed using CT imaging in the axial plane, and the proportion of screws penetrating a vertebral foramen or a transverse foramen was compared between the 3 groups. Screw loosening was defined as a lucent zone around the screw evaluated on cervical radiography at 1 year after surgery. Complications related to PVFS insertion and revision surgery related to PVFS were evaluated.

RESULTS

The authors classified 25 PVFSs into the longer group, 43 into the intermediate group, and 26 into the shorter group. The proportion of screws penetrating a vertebral foramen was largest in the shorter group, and the proportion penetrating a transverse foramen was largest in the longer group. Screw loosening was confirmed for 3 of 94 PVFSs. One PVFS inserted in C6 unilaterally within a long construct from C2 to C7 showed loosening, but it did not cause clinical symptoms. Revision surgery was required for 2 PVFSs inserted in C3 bilaterally as the lower instrumented vertebra in occiput–cervical fusion because they pulled out. There was no neurovascular complication related to PVFS insertion.

CONCLUSIONS

PVFSs are useful for posterior cervical fusion surgery as alternative anchor screws, and the line of the posterior wall of the cervical body on lateral fluoroscopic images is a potential intraoperative reference to indicate an appropriate trajectory for PVFSs.