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Yasuchika Aoki, Masatsune Yamagata, Yoshikazu Ikeda, Fumitake Nakajima, Seiji Ohtori, Koichi Nakagawa, Arata Nakajima, Tomoaki Toyone, Sumihisa Orita, and Kazuhisa Takahashi


Many surgeons currently prefer to use transforaminal lumbar interbody fusion (TLIF), placing 1 unilateral pedicle screw (PS) and 1 cage. However, no study has examined whether unilateral fixation improves surgical outcome. The authors conducted a prospective randomized controlled trial with a minimum 2-year follow-up to analyze TLIF outcomes for 2 techniques: placement of a unilateral PS and a cage compared with placement of bilateral PSs and 2 cages.


Fifty patients with degenerative spondylolisthesis undergoing single-level TLIF were randomly assigned to receive either unilateral or bilateral fixation. Parameters compared between the groups were surgical invasiveness, severity of intermittent claudication, pre- and postoperative visual analog scale (VAS) scores (from 0 to 10 for back pain, lower-extremity pain, and lower-extremity numbness), postoperative disability scores for lumbar spinal disorders (Japanese Orthopaedic Association Back Pain Evaluation Questionnaire [JOABPEQ]), and fusion rates.


The mean operative time for TLIF was significantly (p = 0.05) shorter and mean estimated blood loss was significantly lower in the unilateral than in the bilateral group. Intermittent claudication improved in response to each technique, but there was no significant intergroup difference. The unilateral group had a nonsignificant tendency toward less improvement in VAS score for back pain (1.5 vs 3.7 for the bilateral group) and exhibited significantly less improvement in VAS score for lower-extremity pain (2.1 vs 5.1, respectively) and numbness (1.7 vs 4.4). There were no significant differences between the groups in postsurgical scores for all 5 items of the JOABPEQ. The fusion rates were 87.5% (21 of 24 patients) in the unilateral group and 95.7% (22 of 23) in the bilateral group.


Transforaminal lumbar interbody fusion involving unilateral PS fixation and a single-cage technique is less invasive than a 2-cage technique and bilateral fixation, and it improved patients' symptoms. However, it resulted in less improvement in back pain, lower-extremity pain, and lower-extremity numbness. When considering unilateral PS fixation and a single cage, the surgeon should be aware of the potential limitations of this technique. Clinical trial registration no.: UMIN000007833 (UMIN).

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Sei Yano, Yasuchika Aoki, Atsuya Watanabe, Takayuki Nakajima, Makoto Takazawa, Hiroyuki Hirasawa, Kazuhisa Takahashi, Koichi Nakagawa, Arata Nakajima, Hiroshi Takahashi, Sumihisa Orita, Yawara Eguchi, Takane Suzuki, and Seiji Ohtori

Pelvic ring fractures are defined as life-threatening injuries that can be treated surgically with external or internal fixation. The authors report on an 81-year-old woman with an unstable pelvic fracture accompanying multiple traumas that was successfully treated with a less invasive procedure. The patient was injured in a traffic accident and sustained a total of 20 fractures, including pelvic ring, bilateral rib, and lumbar transverse processes fractures, and multiple fractures of both upper and lower extremities. The pelvic ring fracture was unstable with fractures of the bilateral sacrum with right sacroiliac disruption, right superior and inferior pubic rami, left superior pubic ramus, and ischium. During emergency surgery, bilateral external fixation was applied to the iliac crest to stabilize the pelvic ring. Second and third surgeries were performed 11 and 18 days after the first emergency surgery, respectively, to treat the multiple fractures. At the third surgery, the pelvic ring fracture was stabilized surgically using a less invasive posterior fixation technique. In this technique, 2 iliac screws were inserted on each side following an 8-cm midline posterior incision from the S-1 to S-3 spinous process, with the subcutaneous tissue detached from the fascia of the paraspinal muscles. The S-2 spinous process was removed and 2 rods were connected to bilateral iliac screws to stabilize the bilateral ilium in a switchback fashion. A crosslink device was applied to connect the 2 rods at the base of the S-2 spinous process. Following pelvic fixation, percutaneous pedicle screws were inserted into L-4 and L-5 vertebral bodies on both sides, and connected to the cranial rod connecting the bilateral iliac screws, thus completing the lumbopelvic fixation. The postoperative course was favorable with no postoperative complications. At the 10-month follow-up, bone union had been achieved at the superior ramus of the pubis, the patient did not complain of pain, and her activities of daily life returned to preinjury status. Unstable pelvic ring fractures need to be sufficiently stabilized for good surgical outcome. However, to avoid postoperative complications, a less invasive treatment is preferred, particularly in cases with poor general condition. This procedure is less invasive and provides sufficient stabilization to the unstable pelvic ring fracture, and thus is the ideal surgical procedure for such cases.

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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


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.


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.


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.


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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Shiho Nakano, Masahiro Inoue, Hiroshi Takahashi, Go Kubota, Junya Saito, Masaki Norimoto, Keita Koyama, Atsuya Watanabe, Takayuki Nakajima, Yusuke Sato, Shuhei Ohyama, Sumihisa Orita, Yawara Eguchi, Kazuhide Inage, Yasuhiro Shiga, Masato Sonobe, Arata Nakajima, Seiji Ohtori, Koichi Nakagawa, and Yasuchika Aoki


The authors sought to evaluate the relationship between the difference in lumbar lordosis (DiLL) in the preoperative supine and standing positions and spinal sagittal alignment in patients with lumbar spinal stenosis (LSS) and to determine whether this difference affects the clinical outcome of laminectomy.


Sixty patients who underwent single-level unilateral laminectomy for bilateral decompression of LSS were evaluated. Spinopelvic parameters in the supine and standing positions were measured preoperatively and at 3 months and 2 years postoperatively. DiLL between the supine and standing positions was determined as follows: DiLL = supine LL − standing LL. On the basis of this determination patients were then categorized into DiLL(+) and DiLL(−) groups. The relationship between DiLL and preoperative spinopelvic parameters was evaluated using Pearson’s correlation coefficient. In addition, clinical outcomes such as visual analog scale (VAS) and Oswestry Disability Index (ODI) scores between the two groups were measured, and their relationship to DiLL was evaluated using two-group comparison and multivariate analysis.


There were 31 patients in the DiLL(+) group and 29 in the DiLL(−) group. DiLL was not associated with supine LL but was strongly correlated with standing LL and pelvic incidence (PI) − LL (PI − LL). In the preoperative spinopelvic alignment, LL and SS in the standing position were significantly smaller in the DiLL(+) group than in the DiLL(−) group, and PI − LL was significantly higher in the DiLL(+) group than in the DiLL(−) group. There was no difference in the clinical outcomes 3 months postoperatively, but low-back pain, especially in the sitting position, was significantly higher in the DiLL(+) group 2 years postoperatively. DiLL was associated with low-back pain in the sitting position, which was likely to persist in the DiLL(+) group postoperatively.


We evaluated the relationship between DiLL and spinal sagittal alignment and the influence of DiLL on postoperative outcomes in patients with LSS. DiLL was strongly correlated with PI − LL, and in the DiLL(+) group, postoperative low-back pain relapsed. DiLL can be useful as a new spinal alignment evaluation method that supports the conventional spinal sagittal alignment evaluation.