Development of an Innovative Quantitative Evaluation Method for Implant Loosening after Spinal Surgery Correlated with Clinical Symptoms

2021 Fiscal Year Final Research Report

• Project/Area Number: 20K20241
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 90140:Medical technology assessment-related
• Research Institution: University of Tsukuba
• Principal Investigator: Noguchi Hiroshi 筑波大学, 附属病院, 病院講師 (90783150)
• Project Period (FY): 2020-04-01 – 2022-03-31
• Keywords: トモシンセシス / 椎弓根スクリュー / インプラントゆるみ / 弛み定量評価

Outline of Final Research Achievements

We have developed an innovative laxity assessment method using tomosynthesis imaging to quantify the relative position of the spine and implants. Using this method, we conducted this study with the goal of analyzing the laxity of spinal screws after spinal fusion surgery in detail.
In clinical cases of lumbar spine surgery, implant laxity could be quantified by this method and a cutoff value could be found (1.7 degrees AUC = 0.98).
Next, we verified whether this method could be used for the cervical spine. A simulated bone experiment was performed to determine the appropriate reference point on the vertebral body side. The results of the verification in clinical cases showed that the angle of the screw centerline to the vertebral body could be measured in 16/21 cases (76%), and the angles under the two conditions of supine and upright positions were consistent. Although there was a problem with the reference point, this technique could be used for the cervical spine as well.

Free Research Field

整形外科　脊椎手術

Academic Significance and Societal Importance of the Research Achievements

近年、脊椎手術後のインプラントの弛みが高頻度に発生する事が臨床上の課題となっている。弛みにより腰背部痛や神経症状の再燃をきたすことも少なくなく、X線、CT画像等を用いたインプラントの術後画像評価が重要である。「スクリュー周囲での1mm以上の骨透亮像」が“弛み”と定義され、骨透亮像による定性的評価が標準的な検出法となっている。一方、我々が開発したトモシンセシスを用いた「脊椎とインプラントの相対的な位置関係」評価する画像解析手法は高精度の定量化が可能である。この新規手法に関して検証を進めることで、新たな知見を得ることができ、脊椎手術後の画像評価分野の発展に大きく貢献できると考えた。