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Eiji Takasawa, Naohiro Kawamura, Yoichi Iizuka, Junichi Ohya, Yuki Onishi, Junichi Kunogi, and Hirotaka Chikuda

OBJECTIVE

Proximal junctional kyphosis (PJK), which can worsen a patient’s quality of life, is a common complication following the surgical treatment of adult spinal deformity (ASD). Although various radiographic parameters have been proposed to predict the occurrence of PJK, the optimal method has not been established. The present study aimed to investigate the usefulness of the T1–L1 pelvic angle in the standing position (standing TLPA) for predicting the occurrence of PJK.

METHODS

The authors retrospectively extracted data for patients with ASD who underwent minimum 5-level fusion to the pelvis with upper instrumented vertebra between T8 and L1. In the present study, PJK was defined as ≥ 10° progression of the proximal junctional angle or reoperation due to progressive kyphosis during 1 year of follow-up. The following parameters were analyzed on whole-spine standing radiographs: the T1–pelvic angle, conventional thoracic kyphosis (TK; T4–12), whole-thoracic TK (T1–12), and the standing TLPA (defined as the angle formed by lines extending from the center of T1 and L1 to the femoral head axis). A logistic regression analysis and a receiver operating characteristic curve analysis were performed.

RESULTS

A total of 50 patients with ASD were enrolled (84% female; mean age 74.4 years). PJK occurred in 19 (38%) patients. Preoperatively, the PJK group showed significantly greater T1–pelvic angle (49.2° vs 34.4°), conventional TK (26.6° vs 17.6°), and standing-TLPA (30.0° vs 14.9°) values in comparison to the non-PJK group. There was no significant difference in the whole-thoracic TK between the two groups. A multivariate analysis showed that the standing TLPA and whole-thoracic TK were independent predictors of PJK. The standing TLPA had better accuracy than whole-thoracic TK (AUC 0.86 vs 0.64, p = 0.03). The optimal cutoff value of the standing TLPA was 23.0° (sensitivity 0.79, specificity 0.74). Using this cutoff value, the standing TLPA was the best predictor of PJK (OR 8.4, 95% CI 1.8–39, p = 0.007).

CONCLUSIONS

The preoperative standing TLPA was more closely associated with the occurrence of PJK than other radiographic parameters. These results suggest that this easily measured parameter is useful for the prediction of PJK.

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Shuhei Murase, Yasushi Oshima, Yujiro Takeshita, Kota Miyoshi, Kazuhito Soma, Naohiro Kawamura, Junichi Kunogi, Takashi Yamazaki, Dai Ariyoshi, Shigeo Sano, Hirohiko Inanami, Katsushi Takeshita, and Sakae Tanaka

OBJECTIVE

Interbody fusion cages are widely used to achieve initial fixation and secure spinal fusion; however, there are certain technique-related complications. Although anterior cage dislodgement can cause major vascular injury, the incidence is extremely rare. Here, the authors performed a review of anterior cage dislodgement following posterior lumbar interbody fusion (PLIF) surgery.

METHODS

The authors retrospectively reviewed the cases of 4625 patients who had undergone PLIF at 6 institutions between December 2007 and March 2015. They investigated the incidence and causes of surgery-related anterior cage dislodgement, salvage mechanisms, and postoperative courses.

RESULTS

Anterior cage dislodgement occurred in 12 cases (0.26%), all of which were caused by technical errors. In 9 cases, excessive cage impaction resulted in dislodgement. In 2 cases, when the cage on the ipsilateral side was inserted, it interacted and pushed out the other cage on the opposite side. In 1 case, the cage was positioned in an extreme lateral and anterior part of the intervertebral disc space, and it postoperatively dislodged. In 3 cases, the cage was removed in the same operative field. In the remaining 9 cases, CT angiography was performed postoperatively to assess the relationship between the dislodged cage and large vessels. Dislodged cages were conservatively observed in 2 cases. In 7 cases, the cage was removed because it was touching or compressing large vessels, and an additional anterior approach was selected. In 2 patients, there was significant bleeding from an injured inferior vena cava. There were no further complications or sequelae associated with the dislodged cages during the follow-up period.

CONCLUSIONS

Although rare, iatrogenic anterior cage dislodgement following a PLIF can occur. The authors found that technical errors made by experienced spine surgeons were the main causes of this complication. To prevent dislodgement, the surgeon should be cautious when inserting the cage, avoiding excessive cage impaction and ensuring cage control. Once dislodgement occurs, the surgeons must immediately address this difficult complication. First, the possibility of a large vessel injury should be considered. If the patient’s vital signs are stable, the surgeon should continue with the surgery without cage removal and perform CT angiography postoperatively to assess the cage location. Blind maneuvers should be avoided when the surgical site cannot be clearly viewed. When the cage compresses or touches the aortic artery or vena cava, it is better to remove the cage to avoid late-onset injury to major vessels. When the cage does not compress or touch vessels, its removal is controversial. The risk factors associated with performing another surgery should be evaluated on a case-by-case basis.