肺門作為軀干重心對強直性脊柱炎胸腰段后凸畸形矯形的意義

宋 凱 張永剛 李杰靜 余 文 唐翔宇 張國營 鄭國權 崔 賡 張雪松 毛克亞 王 征 王 巖

. 強直性脊柱炎 Ankylosing spondylitis .

肺門作為軀干重心對強直性脊柱炎胸腰段后凸畸形矯形的意義

宋 凱 張永剛 李杰靜 余 文 唐翔宇 張國營 鄭國權 崔 賡 張雪松 毛克亞 王 征 王 巖

目的探索能夠代表強直性脊柱炎 ( ankylosing spondylitis，AS ) 胸腰段后凸畸形軀干重心的影像學標記，進而設計 AS 胸腰段后凸畸形的截骨矯形方案。方法不規則物體的重心可通過兩個不同方向的懸吊或支撐力線獲得，通過手術前后髖軸的支撐力線可尋找 AS 胸腰段后凸畸形患者的軀干重心。38 例無脊髓神經癥狀體征、雙髖活動良好的 AS 胸腰段后凸畸形患者納入研究。比較 AS 矯形患者手術前后矢狀面平衡距離 ( sagittal vertical axis，SVA )、C7距髖軸中心水平距離 ( horizontal distance between hip axis and C7，HDHC )、T5距髖軸中心水平距離 ( horizontal distance between hip axis and T5，HDHT5)、T9距髖軸中水平距離 ( horizontal distance between hip axis and T9，HDHT9)、肺門距髖軸中心水平距離 ( horizontal distance between hip axis and hilus pulmonis，HDHH )，將矯形前后測量值做統計描述及配對 t 檢驗。采用組內相關系數 ( ICC ) 衡量 HDHH 的觀察者間信度 ( inter-observer reliability ) 及觀察者內復測信度 ( intra-observer reliability )。結果矯形前 SVA、HDHC、HDHT5、HDHT9、HDHH 分別為 21.1 cm、12.7 cm、3.5 cm、-3.8 cm、2.7 cm；矯形后分別為 9.1 cm、4.2 cm、-2.1 cm、-5.6 cm、0.9 cm。SVA、HDHC、HDHT5、HDHT9矯形前后變化有統計學意義，HDHH 矯形前后變化無統計學意義。HDHH 的觀察者間總體信度與觀察者內總體復測信度分別為 0.958、0.963 ( P＜0.001 )。結論矯形前后肺門垂線通?？偸锹湓隗y軸上，肺門可作為軀干重心的影像學標記應用于 AS 胸腰段后凸畸形的矯形設計。

脊柱炎，強直性；椎體后凸成形術；肺門；矯形外科手術；胸椎；腰椎

健康人群自然站立時，軀干重心落在髖軸上，此時骨盆處于中立位[1-4]。強直性脊柱炎 ( ankylosing spondylitis，AS ) 患者晚期易伴發僵硬固定的胸腰段后凸畸形，會導致患者軀干重心病理性前置，落在髖軸前方。此時，軀干在矢狀面上失平衡。由于AS 后凸患者脊柱強直失去代償能力，為重新取得平衡及最小的能量消耗，患者只能通過伸髖、屈膝，進而代償性后旋骨盆，試圖將軀干重心再次落在髖軸上 ，最終達到相對的平衡狀態[5-12]。因此，患者的骨盆旋轉狀態其實由軀干重心的位置變化決定，而軀干重心恢復至正常位置可確保矯形后骨盆中立位。

然而，人體軀干結構復雜，在矢狀面上，骨骼、肌肉、內臟等組織分布并不對稱。因此，尋找軀干重心的影像學標記并不容易。目前，國內外相關研究雖然證實 C7垂線并非重力線，但卻未能給出軀干重心的影像學標記[1-2,6,12]。本部分利用簡單的物理學原理，通過分析矯形前后不同影像學標記距離髖軸的水平距離，尋找并探討能夠代表 AS 后凸患者軀干重心的較好的影像學標記，并應用于截骨矯形的手術設計。

資料與方法

一、一般資料

2004 年 1 月至 2010 年 3 月，收治的 38 例無脊髓神經癥狀體征、雙髖活動良好的 AS 胸腰段后凸畸形患者。男 24 例，女 14 例；最小年齡 22 歲，最大年齡 57 歲，平均年齡 35 歲。

自然站立位拍攝外觀像及全脊柱側位 X 線像，測量矯形前后患者的矢狀面平衡距離 ( sagittal vertical axis，SVA )、C7距髖軸中心水平距離 ( horizontal distance between hip axis and C7，HDHC )、T5距髖軸中心水平距離 ( horizontal distance between hip axis and T5，HDHT5)、T9距髖軸中水平距離 ( horizontal distance between hip axis and T9，HDHT9)、肺門距髖軸中心水平距離 ( horizontal distance between hip axis and hilus pulmonis，HDHH ) ( 圖 1a )。

肺門側位像上主要由四部分組成：左主支氣管、中間支氣管、右肺動脈、左肺動脈。一般情況下，肺門各部分結構清晰可見 ( 圖 1b、c )，尤其是左主支氣管，一卵圓形高透亮影，一般位于肺門中心，也位于肺野中央。即便在胸廓形狀發生變化時，此影像學標志位置仍然相對固定[13-14]。本研究將左主支氣管作為肺門中心測量 HDHH。

圖1 a：全脊柱側位像 HA，髖軸；PSCS，骶骨后上角；HP，肺門；DHHC，C7距髖軸水平距離；DHHT5，T5距髖軸水平距離；HDHH，肺門距髖軸水平距離；DHHT9，T9距髖軸水平距離；SVA，矢狀面平衡距離，C7距骶骨后上角水平距離。b：肺門側位像大體觀。c：肺門側位像：A 左主支氣管；B 中間支氣管；C 右肺及葉間動脈；D 左肺動脈Fig.1 a: Lateral view of the whole spine. HA: hip axis; PSCS: Posterior superior corner of S1; HP: Hilus pulmonis; HDHC: Horizontal distance between hip axis and C7; HDHT5: Horizontal distance between hip axis and T5; HDHH: Horizontal distance between hip axis and hilus pulmonis; HDHT9: Horizontal distance between hip axis and T9; SVA: Sagittal vertical axis, or horizontal distance between the C7vertical line and the posterior superior corner of S1. b: Close-up view of the lateral hilus pulmonis. c: Lateral view of the hilus pulmonis; A Left main bronchus; B Bronchus intermedius; C Right pulmonary artery and interlobar artery; D Left pulmonary artery

二、手術方法

行后路經椎弓根單節段 ( L12 例，L214 例，L38 例 ) 或雙節段 ( T12與 L11 例，T12與 L23 例，T12與L32 例，L1與 L38 例 ) 楔形閉合截骨矯形椎弓根螺釘內固定術。

三、統計學分析

將矯形前后測量值做統計描述及配對 t 檢驗。采用組內相關系數 ( ICC ) 衡量 HDHH 的觀察者間信度 ( inter-observer reliability ) 及觀察者內復測信度( intra-observer reliability )。使用 SPSS 16.0 統計學軟件 ( SPSS 公司，美國 )，以 P＜0.05 為差異有統計學意義。

結 果

矯形前 SVA、HDHC、HDHT5、HDHT9、HDHH 分別為 21.1 cm、12.7 cm、3.5 cm、-3.8 cm、2.7 cm；矯形后分別為 9.1 cm、4.2 cm、-2.1 cm、-5.6 cm、0.9 cm。SVA、HDHC、HDHT5、HDHT9矯形前后均有統計學意義，HDHH 矯形前后無統計學意義 ( 表 1 )。

表1 矯形前后影像學參數統計描述及配對 t 檢驗 ( n=38，±s )Tab.1 Statistical description and paired t-test results of the preoperative and postoperative radiological parameters ( n=38,±s )

表1 矯形前后影像學參數統計描述及配對 t 檢驗 ( n=38，±s )Tab.1 Statistical description and paired t-test results of the preoperative and postoperative radiological parameters ( n=38,±s )

注：SVA：矢狀面平衡距離，HDHC：C7距髖軸中心水平距離，HDHT5：T5距髖軸中心水平距離，HDHT9：T9距髖軸中水平距離，HDHH：肺門距髖軸中心水平距離Notice: SVA: Sagittal vertical axis; HDHC: Horizontal distance between hip axis and C7; HDHT5: Horizontal distance between hip axis and T5; HDHT9: Horizontal distance between hip axis and T9; HDHH: Horizontal distance between hip axis and hilus pulmonis

項目 術前 術后 t 值 P 值SVA ( cm ) 21.1±9.0 ( 4.4～39.4 ) 9.1 ±5.0 ( 1.8～20.0 ) 13.3 ＜ 0.000 HDHC ( cm ) 12.7±8.1 ( -5.7～26.2 ) 4.2 ±5.0 ( -4.1～13.1 ) 8.3 ＜ 0.000 HDHT5( cm ) 3.5±7.3 ( -9.1～16.5 ) -2.1 ±3.9 ( -7.5～ 5.9 ) 6.2 ＜ 0.000 HDHT9( cm ) -3.8±6.1 ( -14.3～ 5.7 ) -5.6 ±3.3 ( -10.4～ 2.7 ) 2.7 0.010 HDHH ( cm ) 2.7±5.4 ( -6.6～16.1 ) 0.9 ±3.9 ( -7.7～ 8.5 ) 2.0 0.052

HDHH 的總體觀察者間總體信度與觀察者內總體復測信度分別為 0.958、0.963，P＜0.001。觀察者中，筆者得出最大的復測信度 ( ICC＝0.993，P＜0.001 )，而一非專業者得到最低的復測信度 ( ICC＝0.932，P＜0.001 )。

討 論

一、軀干重心的位置與骨盆旋轉的關系

健康成人自然站立位時，軀干重心落在髖軸中點上，而骶骨岬恰好也落在髖軸中點上[3,15]，軀干重心、骶骨岬、髖軸中點三點共線。我們可以將髖軸中點與骶骨岬的連線稱作為骨盆中立位線 ( pelvic neutral position line，PNP-line )，其位置狀態直接反映骨盆的旋轉情況。正常情況下，軀干重心在 PNP-line 上，而 PNP-line 也因此垂直地面，這個時候骨盆處于中立位狀態。

對矢狀面失衡的脊柱畸形患者而言，其軀干重心相對位置變化 ( 重心偏離 PNP-line，落在其前方或后方 )，但機體為再次獲得軀干平衡并節約能量消耗，骨盆會向相反的方向旋轉代償，仍然試圖將軀干重心落在髖軸中心之上。于是，骶骨岬會落在髖軸中心的前方或后方，而 PNP-line 則不再垂直地面，我們可以將 PNP-line 的垂線角 ( 也就是骶骨岬與髖軸中點連線的垂線角 ) 作為骨盆的旋轉角度( pelvic rotation angle，PRA )。

AS 后凸畸形患者骨盆處于后旋狀態，當矯形程度不同時，骨盆的旋轉狀態不同，可以通過軀干重心與 PNP-line ( 骶骨岬與髖軸連線 ) 的關系確定( 圖 2 )。

由此可以看出，AS 胸腰段后凸畸形矢狀面失平衡的實質就是：軀干重心偏離了骨盆中立位線。而矢狀位平衡重建的目標為：通過截骨矯形，將軀干重心重置于骨盆中立位線上。

二、軀干重心的影像學標記

人體軀干形狀、結構復雜，在矢狀面上，骨骼、肌肉、內臟等組織分布并非不對稱，如何尋找軀干重心點？力學原理告訴我們，對于不規則物體，可以通過懸吊法或支撐法尋找重心?；诖?，我們將可以將髖軸作為支點，通過矯形前后的兩條支撐線交點確定重心 ( 圖 3a、b )。

但是，同時應當指出，矯形前后的軀干形狀并不恒定。不過，如果我們以截骨節段將軀干分為近端、遠端兩部分。遠端軀干質量遠遠大于近端軀干質量，而且，遠端軀干相對髖軸的力臂同樣遠遠大于近端軀干[16]。通過力學、幾何學分析，我們可以近似的將遠端軀干的重心點看作整體軀干的重心點。而遠端軀干的形態及質量密度分布并無明顯變化 ( 圖 3c、d )。

結果顯示，矯形前后肺門垂線落在近髖軸上。因此，可將肺門作軀干重心的影像學標記。而矯形前肺門垂線落在髖軸稍前則說明患者骨盆后旋肌群及腰背肌群的張力作用與重心偏于髖軸支點的抵消現象。

圖2 矯形程度與骨盆旋態示意圖 a：代償機制 ( 1 ) 正常脊柱序列，重心落在髖軸上，PNP-line 垂直地面，骨盆位于中立位；( 2 ) AS胸腰段后凸畸形，骨盆中立位時，重心遠離 PNP-line，落在髖軸前方，此狀態不穩定；( 3 ) 為將重心再次落于髖軸上，骨盆后旋至旋后位，PNP-line 向后傾斜。b：矯形不足 ( 1 ) AS 后凸畸形，重心于 PNP-line 前方，骨盆位于旋后位；( 2 ) 矯形后，軀干重心后移，落在髖軸后方，但仍在 PNP-line 前方，此狀態不穩定。( 3 ) 為將重心再次落于髖軸上，骨盆前旋，PNP-line 后傾程度減小，骨盆仍位于旋后位。c：矯形過度 ( 1 ) AS 后凸畸形，重心于 PNP-line 前方，骨盆位于旋后位；( 2 ) 矯形后，軀干重心后移，遠遠落在髖軸后方，并落在PNP-line 后方，此狀態不穩定；( 3 ) 為將重心再次落于髖軸上，骨盆前旋，PNP-line 前傾，骨盆位于旋前位。d：矯形恰當 ( 1 ) AS 后凸畸形，重心于 PNP-line 前方，骨盆位于旋后位；( 2 ) 矯形后，軀干重心后移，落在髖軸后，但恰將重心重置于 PNP-line 上，即重心、骶骨岬、髖軸三點共線，此狀態不穩定；( 3 ) 為將重心再次落于髖軸上，骨盆前旋，PNP-line 再次垂直地面，骶骨岬恰落在髖軸上，骨盆位于中立位Fig.2 Diagram of correction degree and pelvic rotation a: Compensatory mechanism. ( 1 ) For a healthy adult, CG fell on HA. Pelvic neutral position line ( PNP-line ) was vertical to the ground, and the pelvis was located in neutral position; ( 2 ) In the patients with AS TLK, CG was anterior to HA and far from PNP-line when the pelvis was in neutral position. It was not a stable state; ( 3 ) In order to make CG fall on HA again, the pelvis was rotated backward and PNP-line tilted backwards. b: Insufficient pedicle subtraction osteotomy ( PSO ) angle. ( 1 ) Before the operation, CG was anterior to PNP-line and the pelvis was in supination position; ( 2 ) After PSO, CG was behind HA but still anterior to PNP-line, and it was not a stable state; ( 3 ) In order to make CG fall on HA again, the pelvis was rotated forward but still in supination position and the retroversion degree of PNP-line became less. c: Excess PSO angle. ( 1 ) Before the operation, CG was anterior to PNP-line and the pelvis was in backward rotation; ( 2 ) After PSO, CG was far behind HA and posterior to PNP-line. It was not a stable state; ( 3 ) In order to make CG fall on HA again, the pelvis was rotated forward but still in pronation position and PNP-line tilted forwards. d: Adequate PSO angle. ( 1 ) Before the operation, CG was anterior to PNP-line, and the pelvis was in backward rotation; ( 2 ) After PSO, CG was behind HA, and on PNP-line again. The 3 points of CG, sacral promontory ( SP ) and HA was on the same line. It was not a stable state; ( 3 ) In order to make CG fall on HA again, the pelvis was rotated forward and located in neutral position, with PNP-line vertical to the ground again and SP on HA

圖3 尋找重心示意圖 ( HA，髖軸中點；CG，整體軀干重心；CG1，遠端軀干重心；CG3，近端軀干重心；L1，遠端軀干力臂；L3，近端軀干力臂；S1，CG與 CG1 間距離；S3，CG 與 CG3 間距離 ) a：矯形前髖軸支撐線；b：矯形后髖軸支撐線，交點可近似認為是遠端軀干重心；c～d：矯形前后 CG1 ＞ CG3，L1＞L3，故 CG1 × L1＞＞ CG3 × L3，而 S1/ S3= CG3 × L3/ CG1 × L1，故 S1＜＜ S3。也就是說，遠端軀干重心位置非常接近整體軀干重心位置，因此可通過尋找遠端軀干重心來定位整體軀干重心Fig.3 Diagram of CG ( HA: Hip axis; CG: Center of gravity of the entire trunk; CG1: Center of gravity of the proximal part of the trunk; CG3: Center of gravity of the distal part of the trunk; L1: Distal end of the arm of force of the trunk; L3: Primary end of the arm of force of the trunk; S1: Distance between CG and CG1; S3: Distance between CG and CG3 ) a: Preoperative HA vertical line; b: Postoperative HA vertical line. The crossing point of the preoperative and postoperative vertical lines could be taken as CG3; c-d: Before and after the correction. CG1＞CG3 and L1＞L3, so CG1×L1＞＞CG3×L3. However, S1/S3=CG3×L3/CG1×L1, so S1＜＜S3. CG3 was far away from CG, so CG could be found once CG3 was confirmed

此外，本研究結果還提示：一般情況下，對 AS胸腰段后凸畸形，C7總是位于軀干重心之前 ( 術前12.7 cm，術后 4.2 cm )，其相對骶骨后上角更為靠前 ( 術前 SVA＝21.1 cm，術后 SVA＝9.1 cm )，傳統的矯形方案試圖將 C7重置于骶骨后上角 ( 即 SVA＝0 cm ) 其實是一個不可能實現的任務，Van Royen在其矯形設計中將 SVA 設定為 7.5 cm，其實在另一個方面同樣說明了 SVA＝0 cm 的不可能性[5-6]。T5矯形前位于重心之前 ( 3.5 cm )，矯形后位于重心后方 ( -2.1 cm )。T9總是位于軀干重心之后 ( 術前-3.8 cm，術后 -5.6 cm )。

三、矢狀面平衡的截骨矯形設計

既然肺門可以近似的看作重心的影像學標記，當以骶骨岬與髖軸作為骨盆中立位線時 ( PNP-line )作為骨盆中立位標準時，肺門、骶骨岬、髖軸三點共線可保證矯形后骨盆中立位 ( 圖 4 )。

圖4 截骨設計示意圖 ( HA，髖軸中點；SP，骶骨岬；HP，肺門；RP，截骨椎體前緣閉合點 ) a：連接 HA、SP 并做延長線 ( PNP-line )，以 RP 為圓心，RP-HP 為半徑作圓，交 HA-SP 與 HP’?！?HP-RP-HP’ = 32° 即為設計截骨角度；b：L3截骨 31°，術后骶骨岬再次落在髖軸上，PNP-line 垂直地面，骨盆處于中立位圖 5 單節段截骨設計實例 a：( 1 ) 測量術前 PI = 36°，則 tPT = 0.37 × PI-7 = 0.37 × 36-7 = 6°，通過理論 PT 做出直線 HA-HP’，我們將此線作為該患者骨盆中立位線；( 2 ) 選擇 L2作為截骨節段，將椎體皮質前緣閉合點標記為 RP，并作為圓心，RP-HP 為半徑作圓交骨盆中立位線于 HP’，也就是將肺門位置重置于骨盆中立位線上，則∠ HP-RP-HP’ = 50° 即為設計截骨角度。b：L2取得 40° + ( -10° ) = 50°的截骨角度，矯形后自然站立位實際 PT = 6°，骨盆處于中立位圖 6 雙節段截骨設計實例 a：( 1 ) 測量術前 PI = 52°，則 tPT = 0.37 × PI-7 = 0.37 × 52-7 = 12°，通過理論 PT 做直線 HA-HP’，我們將此線作為該患者骨盆中立位線。( 2 ) 選擇 L1、L3作為截骨節段，將椎體皮質前緣閉合點分別標記為 RP1、RP3。以 RP3 為圓心，RP1-RP3為半徑作圓，于圓周上取一點 O，∠ O-RP3-RP1 = 45? ( 自選角度 ) 即為 L3設計截骨角度；以 O 為圓心，RP1-HP 為半徑作圓交骨盆中立位線 于 HP’，將肺門位置再次重置于骨盆中立位線上?！?HP’-O-RP1-HP- ∠ O-RP3-RP1 = 75°-45° = 30° 為 L1截骨角度。b：L1取得15° + ( -15° ) =30° 的截骨角度，L3取得 40° + ( -5° ) = 45° 的截骨角度，矯形后患者自然站立位實際 PT = 12°，骨盆處于中立位Fig.4 Osteotomy design. ( HA: Hip axis; SP: Sacral promontory; HP: Hilus pulmonis; RP: Rotation point of the middle point at the front edge of PSO vertebra ) a: A straight line was deawn through SP and HA ( PNP-line ), and a circle was made with RP as the center and RP-HP as the radius. And then HP’ was the intersection with SP-HA. Theoretical osteotomy angle=∠HP’-RP-HP=31°; b: After a PSO=31°, CG and SP were on HA. PNP-line was vertical to the ground, and the pelvis was in neural positionFig.5 Personalized single-segment osteotomy design a: First, the preoperative PI was measured as 36°, and then tPT=0.37×PI-7=0.37×36-7=6°. Second, the theoretic PT was used to locate exact pelvic neutral positional line ( HA-HP’ ). Third, RP was marked, and a circle was made with RP as the center and RP-HP as the radius. At last, HP’ was the intersection with SP-HA. In conclusion, theoretical osteotomy angle=∠HP’-RP-HP=50°; b: After a PSO=40° ( postoperative lordosis ) +10° ( preoperative kyphosis ) =50°, the postoperative PT=6° and individual pelvic neutral positon was reconstructed successfullyFig.6 Personalized double-segment osteotomy design ( nunchuck design ) a: First, the preoperative PI was measured as 52°, and then tPT=0.37×PI-7=0.37×52-7=12°. Second, the theoretic PT was used to locate exact pelvic neutral positional line ( HA-HP’ ). Third, rotation point at L3: the middle point at the front edge of PSO vertebra ( RP3 ) and rotation point at L1: the middle point at the front edge of PSO vertebra ( RP1 ) were marked, and a circle was made with RP3 as the center and RP3-RP1 as the radius. And then, a little was made on the circle and marked as O, by which the osteotomy angle for L3was decided. Next, another circle was made with O as the center and RP1-HP as the radius. HP’ was the intersection with SP-HA. Theoretical osteotomy angle for L3=∠O-RP3-RP1=45°. Theoretical osteotomy angle for L1=∠HP’-O-RP1-HP-∠O-RP3-RP1=75°-45°=30°; b: After a PSO angle in L3of 45° ( 40° postoperative lordosis+5° preoperative kyphosis ), and a PSO angle in L1of 30° ( 15° postoperative lordosis+15° preoperative kyphosis ), for a total of 75°, the postoperative PT=12°, and individual pelvic neutral positon was reconstructed successfully

傳統的骨盆中立位標準多采取固定的骨盆傾斜角，骶骨傾斜角或者骶骨岬恰好落在髖軸上等，因此并不個性化[3,5-6]。近年來眾多研究證實了骨盆參數之間相關性，并通過骨盆形態學參數 ( PI，pelvic incidence，骨盆入射角 ) 預測骨盆體位性參數 ( PT，pelvic tilt，骨盆傾斜角 )，從而可使不同個體骨盆中立位的標準更為合理、科學[17-19]。手術設計方案：( 1 ) 通過 PI 預測理論 PT ( tPT＝0.37×PI-7 )[19]；( 2 )將肺門重置于 tPT ( theoretic PT，理論 PT ) 的骨盆中立位線上 ( 圖 5，6 )。

四、頜眉角的糾正 ( 圖 7 )

AS 胸腰段后凸畸形的矯形目標除了恢復脊柱－骨盆的矢狀面失衡外，最為關鍵的即矯正其頜眉角( chin-brow vertical angle，CBVA )。Suk 教授等認為，對于頸椎強直的 AS 患者，CBVA 在 -10°～10°時最為合理，但在標準的伸髖伸膝位測量頜眉角的方法，并不合理，因為 AS 后凸患者髖關節本身已處于過伸狀態[20]。因此，合理的頜眉角測量方式應為“自然站立位”，而其骨盆中立位時頜眉角則需要通過 X 線側位片追加骨盆后旋的角度“PT-tPT”，即：骨盆中立位時頜眉角＝外觀照自然站立位頜眉角＋X 線自然站立位 PT-tPT[21]。多數情況下，糾正頜眉角的理論截骨角度與重建矢狀面的理論截骨角度并不相同，基于截骨方法的幾何原理，我們可以調整截骨節段，當頜眉角糾正角度大于重建矢狀面平衡角度時，我們可以將截骨節段向頭端調整，反之則向尾端調整截骨節段[5,11]。術前評估患者頸椎屈伸活動度可為設計截骨角度提供了更大的可選擇空間。另外，截骨設計時應當考慮患者職業，手術預期等因素，最終在矢狀面重建及頜眉角糾正間找到一個最優平衡點。具體的介紹及設計方案我們將在專門文獻中詳細闡述。

圖7 胸部 X 線側位片 a：左主支氣管，右側支氣管；b：左主支氣管，左支氣管分支；c：藍色輪廓，左肺動脈；灰色輪廓，右肺及間葉動脈；左主支氣管，右主支氣管；d：近似當作左主支氣管，即肺門中心Fig.7 Lateral X-rays of the cervical vertebra a: Left main bronchus (); Right upper lobe bronchial orifice (). b: Left main bronchus ( asterisk ); Bronchus (). c: Left main bronchus (); Left pulmonary artery ( blue outline ); Right pulmonary artery and interlobar artery ( gray outline ). d: Left main bronchus () was supposed in the middle of the lung

五、本研究的不足

肺門由四部分組成：左主支氣管、中間支氣管、右肺動脈、左肺動脈。本研究將左主支氣管作為肺門中心，一般情況下，肺門各部分結構清晰可見，而左主支氣管為一卵圓形高透亮影，位于肺門中心，也位于肺野中央。即便在胸廓形狀發生變化時，此影像學標志位置仍然相對固定[13-14]。本研究的信度分析同樣證明了該影像學標志的可靠性 ( 觀察者間總體信度，ICC＝0.958；觀察者內總體復測信度，ICC＝0.963 )。

即便如此，在測量過程中，由于 X 線曝光情況的不確定性，在部分 X 線片上，尋找肺門依然是一個相對困難的事情。筆者之一作為研究者，經驗相對豐富，得出最大的復測信度 ( ICC＝0.993 )，而一非專業者得到最低的復測信度 ( ICC＝0.932 )。因此，經驗同樣成為更好尋找肺門的影響因素之一。圖 7 介紹了幾個容易誤讀的肺門圖片：a：示兩個軟圓形透亮影，上面一個為右主支氣管 ( 三角形 )，而下方為左主支氣管 ( 五角星 ) ，其更為接近肺野中央。b：中兩個更為透亮的區域 ( 箭頭 ) 是支氣管分支而非左主支氣管，左主支氣管 ( 五角星 ) 在其上方并發出支氣管分支，其同樣更靠近肺野中央。c：很難鑒別左主支氣管 ( 五角星 )，但左右肺動脈影相對清晰 ( 藍色及灰色輪廓 )，可根據其相對位置尋找左主支氣管。d：曝光顯影不清，在此狀態下，連接肺尖及肺底中點，連接肺前后壁中點，通過兩線交點近似確定肺野中心，將此點作為左主支氣管位置( 五角星 )，此法最為無奈但卻最為簡單方便。

本研究證明肺門近似為 AS 胸腰段后凸畸形的軀干重心，是通過多樣本統計后所得，絕非嚴格意義上的重心替代影像學標記，因此，在個案中，我們常發現，肺門垂線并未落在髖軸上方，而是或前或后。這與 SVA 評定矢狀面平衡類似，個案中的極少能能夠見到 C7恰落在骶骨后上角上。本研究所有入組患者均為雙髖活動良好患者，因此能夠在最大程度上代償后凸畸形，如將雙髖強直患者入組，則可能得出不一樣的結論。同樣，對于存在側凸的患者，由于雙肺冠狀面上的傾斜及嚴重不對稱性，肺門也很難被擴大應用。受限于實驗條件，本研究未能做更為深入的力學測試，因此也同樣遺憾。

綜上所述，AS 胸腰段后凸畸形矯形前后，自然站立位時，肺門垂線落在近髖軸上，因此可將肺門作為軀干重心的影像學標記應用于矯形設計。

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( 本文編輯：王永剛 )

Signifcance of the hilus pulmonis as the center of gravity of the trunk for deformity correction in thoracolumbar kyphosis secondary to ankylosing spondylitis

SONG Kai, ZHANG Yong-gang, LI Jie-jing, YU Wen, TANG Xiangyu, ZHANG Guo-ying, ZHENG Guo-quan, CUI Geng, ZHANG Xue-song, MAO Ke-ya, WANG Zheng, WANG Yan. Department of Orthopedics, Chinese PLA General Hospital, Beijing, 100853, PRC

ObjectiveTo investigate a radiological marker for the center of gravity ( CG ) of the trunk in the treatment of thoracolumbar kyphosis ( TLK ) secondary to ankylosing spondylitis ( AS ), so as to design deformity planning.MethodsThe CG of an irregular object could be obtained through hanging or supporting it in 2 different directions or points, and the CG of the trunk in the patients with AS TLK would be located by using the preoprative and postoperative hip axis vertical lines. A total of 38 patients with AS TLK were included in this study, who had good hips and no spinal cord injuries. The preoperarive and postoperative radiological parameters were measured, including sagittal vertical axis ( SVA ), horizontal distance between hip axis and C7( HDHC ), horizontal distance between hip axis and T5( HDHT5), horizontal distance between hip axis and T9( HDHT9) and horizontal distance between hip axis and hilus pulmonis ( HDHH ). The preoperative and postoperative measurement results were compared by statistical analysis and paired t-tests. The intraclass correlation coeffcient ( ICC ) was used to determine the intraobserver and interobserver reliabilities of HDHH.ResultsThe preoperative SVA, HDHC, HDHT5, HDHT9and HDHH values were 21.1 cm, 12.7 cm, 3.5 cm, -3.8 cm and 2.7 cm respectively, and the postoperative values were 9.1 cm, 4.2 cm, -2.1 cm, -5.6 cm and 0.9 cm respectively. The differences between the preoprative and postoperative values of SVA, HDHC, HDHT5and HDHT9were statistically significant, and while the differences between the preoprative and postoperative values of HDHH were not. The ICC for overall interobserver reliability was 0.958, and it was 0.963 for overall intraobserver reliability ( P＜0.001 ).ConclusionsThe hilus pulmonis falls approximately on the hip axis bothpreoperatively and postoperatively. It is a better radiological marker for the CG of the trunk for deformity planning in AS TLK.

Spondylitis, ankylosing; Kyphoplasty; Hilus pulmonis; Orthopedic procedures; Thoracic vertebrae; Lumbar vertebrae

10.3969/j.issn.2095-252X.2014.10.008

R681.5, R682.3

100853 北京，解放軍總醫院骨科

張永剛，Email: zhangyg301@hotmail.com

2014-07-17 )