AAOS:提高髋臼假体定位的准确性（2）

骨盆解剖标志Pelvic Landmarks
             Sotereanos et al. defined three osseous pelvic landmarks that establish a reference plane for determining acetabular component version and inclination. The line between the two inferior landmarks determines cup anteversion, and the amount of overhang from the most superior lateral point on the acetabu-lum is the amount of cup abduction. The authors devised a method that reproduces the templated amount of abduction and matches the patient’s native anteversion intraoperatively. Preoperative templating includes sizing the cup, posi-tioning it to restore the center of rotation, and measuring the amount of lateral overhang with the cup in 40  of abduction with use of angle guides. The measured amount of overhang is then used to ensure the accuracy of intraoperative cup place-ment; the cup is repositioned until the amount of overhang matches the intraoperative measurement. Overhanging lateral osteophytes can make it difficult to identify the true superior-lateral aspect of the acetabulum and mislead the surgeon into templating a cup position that is too horizontal. A technique to minimize component malpositioning resulting from these  lateral osteophytes involves assessment of the position of the rim of the socket relative to the acetabular notch inferiorly. If thereisexposureofthecomponent(too-verticalcupplace-ment) or of the bone (too-horizontal cup placement) relative to the acetabular notch inferiorly, there is malpositioning involving the abduction angle of the cup (Fig. 5).After a 360 view of the acetabulum is obtained, two distal points on the pelvis are identified (Fig. 6); together, these form an axis to establish a patient’s native anteversion.Point A in the figure marks the sulcus between the posterior rim of the ace-tabulum and the ischial tuberosity. This point is visualized by sliding a Cobb elevator over the posterior-inferior portion of the acetabular rim, along the ischium, and down to the sulcus. Point B, the second reference point on the pelvis, marks the confluence between the inferior aspect of the iliopectineal eminence and the lateral portion of the superior pubic ramus; this point is typically 5 mm from the anterior-inferior portion of the acetabulum. Next, the socket is reamed to the appropriate height and depth. The rim of the acetabular component should pass be-tween the two landmarks on the inner surface of the reamed acetabulum; otherwise, the center of rotation is too high. The rim of the prosthetic socket should pass through a line con-necting the two inferior landmarks and sit flush with the acetabular notch inferiorly.
            Sotereanos等介绍了骨盆上的三个骨性解剖标志，可建立髋臼假体的参照平面，确定前倾和外展角度。通过下方两个解剖标志的连线确定髋臼前倾角，臼杯与髋臼上外侧最高点的距离可评价臼杯的外展角。作者设计了一种新的方法，可以复制出模板上测得的外展角，并可在术中与患者本来的前倾角相匹配。术前模板测量包括臼杯的大小、恢复髋关节旋转中心的安装位置，并用角度导向器测量外展40°时臼杯超出髋臼外侧缘的距离。应用所测得的超出距离可在术中确定臼杯的准确位置，臼杯的位置应反复调整直至术中的超出距离与术前数值一致。外缘突出的骨赘会影响判断，而难以确定真正的髋臼上外侧缘，从而误导术者参照术前模板测量进行定位使髋臼的位置太过水平。为了避免外侧骨赘导致的臼杯定位错误，可以评估臼杯边缘相对于下方髋臼切迹的位置来判断。相对于下方的髋臼切迹，如果假体裸露（臼杯置入太过垂直）或骨质裸露（臼杯放置太过水平），提示臼杯的外展角存在异常（图5）。 对髋臼进行360°的观察以后，在骨盆的远端可以确定两个点（图6），通过两点的连线可以确定患者原始的前倾角。图中A点所示为髋臼后缘与坐骨结节之间的凹槽。直视下，用骨膜剥离器从髋臼后下缘向坐骨方向滑移，便可找到这一凹槽。B点是骨盆上的第二个参照点，为髂耻隆起下缘与耻骨上支外侧部分的交点，通常距离髋臼前下缘约5mm。接下来，将髋臼磨锉到合适的高度和深度，髋臼假体的边缘必须通过这两个参照点在髋臼内面相对应的位置。否则旋转中心就会太高。髋臼假体的边缘必须通过下方两个解剖标志点的连线，将下方的髋臼切迹完全填充。

图中A点所示为髋臼后缘与坐骨结节之间的凹槽。直视下，用骨膜剥离器（Cobb elevator）从髋臼后下缘向坐骨方向滑移，便可找到这一凹槽。B点是骨盆上的第二个参照点，为髂耻隆起下缘与耻骨上支外侧部分的交点，通常距离髋臼前下缘约5mm。图5 A，相对于下方的髋臼切迹，有骨质裸露提示臼杯放置得太水平；B，相对于下方的髋臼切迹，假体裸露提示臼杯放置得太垂直。

图6Points A and B form an axis to establish a patient’s native acetabular anteversion. Point A marks the sulcus between the posterior rim of the acetabulum and the ischial tuberosity. Point B marks the confluence of the inferior aspect of the iliopectineal eminence and the lateral portion of the superior ramus. Point C marks the most superior point on the ace-tabular rim.通过AB两点的连线可确定患者原始的髋臼前倾角。A点为髋臼后缘与坐骨结节之间的凹槽。B点为髂耻隆起下缘与耻骨上支外侧部分的交点，通常距离髋臼前下缘约5mm。C点是指髋臼边缘的最高点。
站立位侧位片 Standing Lateral Radiographs                McCollum and Gray developed a technique for positioning the acetabular component to maximize the functional impingement-free range of motion by anteverting the cup 30 and accounting for changes in pelvic tilt between the supine and standing positions. A routine preoperative standing lateral radiograph centered over the greater trochanter is obtained (Fig. 7). The angle subtended between a line drawn from the anterior superior iliac spine to the sciatic notch and a hor-izontal line is recorded (Fig. 8). This measurement is used intraoperatively to adjust the orientation of the cup to achieve positioning in 30  of anteversion and 30 to 50 of abduction.With the patient in the lateral recumbent position, the surgeon places a finger in the sciatic notch and another on the anterior superior iliac spine; a line connecting these two points is then drawn on the surgical drapes (Fig. 9).The goal of implanting the cup in 30 of anteversion in a standing position is accomplished intraoperatively by drawing a second line whose angle relative to the first line equals the measured difference between the angle templated from the preoperative standing lateral radiograph and 30  . The cup is then im-planted with the face parallel to the second line. A McKee cup positioner is oriented with the long end perpendicular to the second line on the drapes and the short handle parallel to that  line.        McCollum和Gray提出了一种定位髋臼假体的手术方法，可最大限度地获得无撞击的关节功能活动范围，该方法将臼杯前倾30°，以补偿站立位与仰卧位骨盆倾斜度的差异。术前常规拍摄以大转子为中心的站立位侧位片（图7）。在髂前上棘与坐骨大切迹之间连线，测量该线与水平线之间的夹角（图8）。这一测量结果有助于术中判断髋臼的方向，使髋臼获得30°的前倾以及30°-50°的外展。患者侧卧位时，术者可用手指触摸坐骨大切迹，另一手指置于髂前上棘，在手术巾表面上可以划出两点之间的连线（图9）。髋臼假体安装的目标位置是站立位前倾30°，为了获得这一位置，先计算术前站立位侧位片模板上第一条线的角度与30°之间的差值，再在手术巾上第一条线的位置加上这一差值，划出第二条线。在与第二条线平行的方向上置入臼杯。如应用McKee髋臼定位器，长柄的方向垂直于手术巾上的第二条线，短柄与之平行。图7 站立位侧位片显示骨盆倾斜度以及腰椎前凸对站立位髋臼的方向可产生明显的影响。在髂前上棘与坐骨大切迹之间连线，术前测量该线与水平线之间的夹角。结合这一信息以及术中的解剖标志，可以计算站立位和侧卧位髋臼方向的差异，有助于术者判断髋臼假体的位置（经Dr. James D’Antonio惠允）。图7-A 骨盆向后倾斜；图7-B，患者由于腰椎前凸，骨盆向前倾斜。图8 髂前上棘与前后上棘之间连线（上图），然后再在坐骨大切迹与髂前上棘之间连线（下图），术中可以通过两者之间的夹角判断髋臼的方向。图9 A-E髋臼定位的示意图。A，术者一根手指触摸到坐骨大切迹，另一手指在髂前上棘，确定第一条线。如果术前站立位侧位片上该线与水平面成角为20°，则以第一条为基准，增大10°（30°-20°）在手术巾上划出第二条线；B，打磨髋臼，髋臼锉的手柄垂直于第二条线，这样在站立位时髋臼杯相对水平面便可有30°的屈曲；C，应用Mckee髋臼定位器，短柄平行于手术巾上的直线，长柄与之垂直；D和E，假体置入以后测试稳定性，髋关节完全伸直外旋和完全屈曲内旋。
髋臼切迹角 Acetabular Notch Angle         Maruyama et al. defined the acetabular notch angle as forming a reference plane for assessing a patient’s natural acetabular anteversion. The acetabular notch angle is the angle sub-tended between a line extending from the greater sciatic notch to the posterior acetabular ridge and a line passing from the posterior acetabular ridge to the anterior acetabular ridge(Fig. 10). There is very little anatomic variation in the ace-tabular notch angle (89.0  ± 3.5 ), which is nearly a right angle in all patients. The patient is positioned laterally on the operating table, and the surgeon stands on the abdominal side of the patient to establish the acetabular notch angle. The surgeon palpates the greater sciatic notch and places his or her index finger across the posterior wall. A rod is positioned parallel to this line, and the point where it crosses the center of the acetabulum is marked on the superior portion of the ac-etabulum with use of electrocautery. The parallel surface of a hemispherical reamer placed perpendicular to this line de-notes anatomic anteversion. The surgeon then angles the reamer posteriorly to aim for the superior aspect of the greater sciatic notch in order to prepare the socket. This would usually result in an additional 10  to 15 of anteversion relative to the patient’s anatomic anteversion. D’Antonio re-ported a dislocation rate of 0.34% in 631 consecutive primary total hip arthroplasties performed with use of this technique, which relies on the acetabular notch angle and the sciatic notch to help guide acetabular component placement in place of external alignment guides。       Maruyama等提出了髋臼切迹角的概念，可确定一个基准平面，评价患者髋臼原始的前倾角。髋臼切迹角是指从坐骨大切迹到髋臼后壁的延长线与通过髋臼前后壁的直线之间的夹角（图10）。髋臼切迹角（89.0°±3.5°)的解剖变异很小，在所有患者中几乎都成直角。患者在手术台上取侧卧位，术者站在患者的腹侧，便于确定髋臼切迹角。触摸到坐骨大切迹后，将食指横过髋臼后壁。然后平行该线放置定位杆，找出穿过髋臼中心的平行线，在该线与髋臼上缘的交点上用电刀烧灼标记。半球形髋臼锉的杯口平面垂直于解剖前倾角的标志线放置，接下来术者可将髋臼锉向后调整，瞄准上方的坐骨大切迹依次打磨。这样通常可获得比解剖前倾角大10°-15°的前倾。D’Antonio报道，连续631例初次全髋关节置换均应用这一技术，参照髋臼切迹角和坐骨大切迹来安装髋臼假体，且没有应用其他外在的定位装置，最终脱位率仅0.34%。图10 骨盆从头侧向尾侧的视图。应用器械测量髋臼切迹角，通过髋臼后壁钩在坐骨大切迹处。线1和线2均平行于定位杆，线1通过髋臼后壁和坐骨大切迹的顶点（可用于定位）。线1平移至髋臼中心即为线2。线3通过髋臼的前后壁。线4是相对于解剖前倾增加的前倾角，该线指向坐骨大切迹的顶点，因此，平行于线2放置臼杯便是解剖前倾，如果参照线4安装髋臼，前倾角将比原始的解剖前倾角大10°-15°。
6、Benefits of Patient-Specific Morphology for Acetabular Component Placement 参照患者特异性的形态安装髋臼假体的优势           Patient-specific morphology is used to identify an individ-ualized target zone for each patient at the time of surgery this target zone guides accurate and precise acetabular com-ponent placement to minimize the risk of impingement and dislocation and optimize bearing surface wear (Table I).Placing the acetabular component in the traditional safe zone with use of conventional techniques is not the best currently available method to minimize the risk of dislocation and impingement. Evidence suggests that positioning the prosthetic acetabulum within an individualized, patient-specific, target zone that is defined by anatomic landmarks results in a lower rate of dislocation. Use of patient-specific morphology improves the ability of the surgeon to accurately and precisely implant the acetabular component in each patient’s target zone.The Lewinnek safe zone defines acceptable orientation of the acetabular component by the standards of many or-thopaedic surgeons. However, Lewinnek recognized that, al-though components placed within the safe zone have a lower rate of dislocation, the safe zone is still a very broad range within which dislocations have been reported. We advocate the concept of individualized target zones, defined by patient-specific morphology, that provide a more accurate and precise method of ensuring optimal acetabular component orientation.         在术中，可以通过患者特异性的形态特征确定不同个体的目标区域，参照该目标区域安装髋臼假体可获得精准的定位，使撞击和脱位的风险降至最低，最大限度地减少界面磨损。为了尽可能降低撞击和脱位的风险，从现在的角度看来，应用常规的技术将髋臼假体安装在传统的安全区并不是最好的方法。有证据显示，安装髋臼假体时通过解剖标志确定个体化的患者特异性的目标区域，可获得很低的脱位率。应用患者特异性的形态特征，可提高术者的手术技能，将髋臼假体精准地安装在不同患者各自的目标区域内。按照多数骨科医师的标准，通过Lewinnek安全区可将髋臼假体安装在尚可接受的位置上。然而，Lewinnek也认识到，虽然假体安装在安全区脱位率相对较低，但安全区仍然是一个相对宽泛的范围，在此范围内的脱位也有报道。我们主张通过患者特异性的形态特征，确定个体化的目标区域，可以更加精准地确定髋臼假体理想的位置。