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一次2レベルACDFのスクリューの長さは仮関節症リスクに影響するか？
Does Screw Length for Primary Two-level ACDF Influence Pseudarthrosis Risk?
PMID: 32673728 DOI: 10.1016/j.spinee.2020.07.002.
抄録
背景の文脈:
仮関節症は依然としてACDFを受ける患者の主要な合併症である（1年後の追跡調査では0％～15％）。潜在的に修正可能な危険因子は喫煙や骨粗鬆症などの文献で知られている。また、ネジの長さが長いほど引き抜き強度の向上と相関があることが知られているが、ネジの深さが深いほど術中合併症のリスクを高める可能性がある。本研究では、椎体に対するスクリューの深さが短いと、X線写真上の仮関節症のリスクが高まり、患者から報告されたアウトカム（PRO）が悪くなるという仮説を立てている。
BACKGROUND CONTEXT: Pseudarthrosis remains a major complication for patients undergoing ACDF (0%-15% at 1-year follow-up). Potentially modifiable risk factors are known in literature, such as smoking and osteoporosis. Biomechanical studies suggest that plates with locking screws can enhance the fixation rigidity and pull-out strength. Although longer screws are known to be correlated with increased pull-out strength, deeper screw depths can increase the risk for intraoperative complications. An important factor that has yet to be studied is the minimum screw length relative to the diameter of the vertebral body necessary to achieve successful fusion. In this study, we hypothesize that screws with shorter depths relative to the vertebral body will increase the risk for radiographic pseudarthrosis and result in poor patient reported outcomes (PROs).
目的:
ACDFスクリューの長さが仮関節症リスクに与える影響を調べる STUDY DESIGN::プロスペクティブに収集されたデータのレビュー PATIENT SAMPLE:: .合計85人の患者がこの研究に含まれた。平均年齢±標準偏差は58.9±10.3歳、患者の42.4%は女性であった。
PURPOSE: To examine the impact of ACDF screw length on pseudarthrosis risk STUDY DESIGN: : A review of prospectively collected data PATIENT SAMPLE: : A total of 85 patients were included in this study. The mean age ±standard deviation was 58.9±10.3 and 42.4% of patients were female. The mean follow-up was 21.6±8.3 months.
成果測定:
各ACDFレベルについて、スクリューの長さと椎体（VB）％（スクリューの長さ÷前後椎体の直径）を測定した。脊椎間運動(ISM)≧1mmを6週間、6ヶ月、1年で記録し、VB%のしきい値を変えてISM≧1mmの正負の予測値(PPV、NPV)を測定した。VB%が75%未満の場合、X線偽関節症の最高のPPV(93%)とNPV(70%)を有することが判明した。その後、この75%未満の閾値を二変量解析および多変量解析で評価した。
OUTCOME MEASURES: The neck disability index (NDI) was used to assess PROs up to 2-years after surgery. For each ACDF level, the screw length and vertebral body (VB) % (screw length divided by the anterior-posterior vertebral body diameter) were measured. Radiographic pseudarthrosis (interspinous motion (ISM) ≥1mm) was recorded at 6-weeks, 6-months, and 1-year for each patient. The positive and negative predictive values (PPV, NPV) for ISM ≥ 1mm were measured for different VB% thresholds. A VB% of <75% was found to have the highest PPV (93%) and NPV (70%) for radiographic pseudarthrosis. This threshold of <75% was then assessed in our bivariate and multivariate analyses.
方法:
冠動脈切除の有無にかかわらず、一次2レベルACDFを受けた成人（18歳以上）の患者のデータベース（2015～2018年）をレビューした。すべてのACDF構築物は固定アングルスクリューを使用した。多変量解析は、スクリューVB%がX線偽関節症の独立した危険因子であるかどうかを決定するために実施された。
METHODS: We reviewed a database (2015-2018) of adult (≥18 years-old) patients who underwent a primary two-level ACDF with or without corpectomy. All ACDF constructs involved fixed angle screws. The minimum follow-up period was 1 year. Multivariate analyses were performed to determine if screw VB% was an independent risk factor for radiographic pseudarthrosis.
結果:
1年後の再置換率は4.7%であった。1年後の再置換率は、VB%が75%未満の患者では、そうでない患者（98.6%）に比べて64.3%と大幅に悪化していた。他の時点と比較して、6週目にラジオグラフィ仮関節症を認めた患者は2年後までにNDIスコアが有意に悪化していた（p=0.047）。6週間後のラジオグラフィ仮関節症の独立した危険因子は、いずれかのスクリューVB％＜75％（OR77、p＜0.001）、喫煙者の既往・在宅（OR6.8、p＝0.024）、心筋梗塞の有無などであった。ISM≧1mmの患者では、1年後の再手術率が高い（5.9％対3.9％）が、統計的には有意ではなかった（p=0.656）。
RESULTS: By 1-year, overall fusion success was achieved in 92.9% of patients. The 1-year revision rate was 4.7%. Patients with any screw VB% <75% had substantially worse fusion success (64.3%) than those who did not (98.6%) at 1-year. The VB%<75% increased the risk for radiographic pseudarthrosis at every follow up period. In comparison to other time-points, patients with radiographic pseudarthrosis at 6 weeks had significantly worse NDI scores by 2-years (p=0.047). The independent risk factors for radiographic pseudarthrosis at 6-weeks included any screw VB%<75% (OR 77, p<0.001), prior/current smoker (OR 6.8, p=0.024), and corpectomy (OR 0.1, p=0.010). Patients with ISM≥1 mm had a higher rate of revision surgery at 1-year (5.9% vs. 3.9%), but this was not statistically significant (p=0.656).
結論:
一次2レベルACDFでは、VB%<75%は、本研究のすべての時点でISM（≥1mm）の増加と有意に関連していた。この閾値は術前および術中に簡単に測定することができ、術後初期のX線写真上の仮関節症と強い相関があることがわかっています。
CONCLUSIONS: In primary two-level ACDF, VB%<75% is significantly associated with increased ISM (≥1mm) at all time points for this study. As an intraoperative guide, spine surgeons can use the screw VB% threshold of <75% to avoid unnecessarily short screws. This threshold can be easily measured pre- and intra-operatively, and has been found to be strongly correlated to radiographic pseudarthrosis in the early postoperative period.
Copyright © 2020. Published by Elsevier Inc.