The subcristal pelvic external fixator: technique, results, and rationale

Pelvic external fixators can be built in different grades of complexity starting from 3 basic frames (Fig. 1): anterosuperior,1,2 with pins inserted perpendicular to the iliaccrest in a superior to inferior direction (as in the Sla¨tis frame3); anteroinferior,1,2 with supra-acetabular pins inserted in ananterior to posterior direction4; and subcristal,2 with pinsinserted from the anterior superior iliac spine (ASIS) in thesubcortical bone of the iliac crest and parallel with the crest.
External fixation of the pelvis is one of the few pelvicoperations occasionally performed by surgeons who donot specialize in acetabular and pelvic ring fixations. Thesuperficial location of the iliac crest can easily misleadthe less-experienced surgeon who is attempting to use theanterosuperior configuration to control the pelvic volume inemergency situations, such that the pins are incorrectly placed.In our clinical practice, we have observed this predominantlyfor patients who have had their initial assessment andtreatment at peripheral health care centers. Others authorshave also acknowledged this problem.5 Most complicationsassociated with pelvic external fixators are related to thefailure to correctly place the pin between the inner and outertables of the ilium, interference of the pins with anatomicstructures located between skin and the bone entry point, orinjury at sites where bone penetration occurs.
After being faced with the complications and/or inconvenienceto the patients associated with the use of pelvicexternal fixators built on anterosuperior and anteroinferior pinplacement, we carefully analyzed the human pelvis anatomyand concluded that pin placement subcortical to the anteriorone fourth to one third of the iliac crest from the ASISprovided us with the best possible approach. We report on 20 patients where we used subcristal positioning of pins to provide pelvic ring fixation (Figs. 2, 3).

骨盆外固定器能够以三种不同的方式建立其复杂的固定支架（图1）：（a）前上固定，自前后方向垂直髂嵴置入固定针（称为Sla¨tis固定架）；（b）前下固定，固定针在髋臼上前后方向置入；（c）嵴下固定，固定针自髂前上棘（ASIS）平行髂嵴置入髂嵴的皮质下骨。

FIGURE 1. Pin position for the 3 types of pelvic external fixators: anterosuperior/Sla¨tis-type frame, anteroinferior/ supra-acetabular type frame, and subcristal-type frame.
图1 骨盆外固定器的三种置针类型：（a）前上/Sla¨tis固定架（b）前下/髋臼上固定架（c）嵴下固定架。

FIGURE 3. As illustrated in these pictures of an outpatient, the subcristal frame allows dressing, sitting, walking and full access to the abdominal wall for a laparotomy and subsequent management of a colostomy. A, Anterior view. B, Lateral view.
图3 此图是一例嵴下外固定后的出院患者，可进行穿衣，坐起和行走，完全胜任剖腹手术及结肠造瘘术后的后继处理。A,前面观B,侧面观。

FIGURE 2. The subcristal frame is well tolerated even in obese patients, as seen in this 140-kg female patient where the frame sits well under the abdominal apron.
图2 即使是肥胖患者也能良好的耐受嵴下骨外固定架，如图所见这一140kg的女性患者可在腹部围裙遮挡下带架坐起。

对于并不擅长髋臼和骨盆环固定手术的医生来说，骨盆外固定是其偶尔实施的手术之一。髂嵴的体表定位有时可能会对经验不足的医生造成误导，使其试图通过急诊前上固定去控制骨盆框，进而导致固定针的置入不当，在临床工作中，我们观察到了这一情况，主要发生在周边治疗中心的患者中，这些患者均有原始评估记录和最初的治疗情况。其他的一些作者也认同这种情况的存在。骨盆外固定器的并发症主要与以下因素相关：不能在体表内外正确地定位髂骨，解剖结构干扰皮肤与骨进针点间的定位或骨穿入部位存在损伤等。
前上和前下入针安装外固定器可导致多种并发症和/或对患者造成不便，我们历经这些情况之后仔细分析了人骨盆解剖，最终得出结论，从ASIS在髂嵴的前1/4到1/3皮质下骨置入固定针是最佳的固定方式。我们报道了应用皮质下固定骨盆环的20例患者的情况（图2、3）。

The patient is positioned supine on the operating table.The ASIS and the anterior aspect of the iliac crest’s contourare marked on the skin. A skin incision of approximately 2 cmis made in line with the iliac crest starting at the ASIS downtoward the subinguinal region (Fig. 4). Blunt dissection isused to expose the anterior aspect of the ASIS superficial to theinsertion of the inguinal ligament. A trocar–cannula set(trochar/drill sleeve/pin sleeve) is rolled mediolaterally andsuperoinferiorly over the ASIS to define the entry point.Because of the overhang of the iliac crest, the entry point liesmedial to the center of the palpable ASIS and allows placementof the threaded pin just lateral to the inner cortex of theilium. After defining the entry point, the trocar is removed withone hand, whereas the other hand stabilizes the drill sleeve.The external cortex is opened with a 4.0-mm drill orientatedparallel with the superior aspect of the iliac crest toward theiliac tuberosity (IT), whereas the contralateral hand guides thedirection by palpating the iliac crest between the thumb andindex fingers. While maintaining the pin sleeve in place, thedrill is removed and a 5-mm threaded pin (150–180 mm inlength) is inserted until all the threads of the pin are intraosseous.The pin is directed toward the IT between the2 cortices of the iliac crest. This is done at a low speed withthe power drill in the screw mode so that the blunt pin finds itsway between the 2 iliac cortices, without perforating them,before the change in direction of the iliac crest that occurs atthe IT. The position of the pin can be checked with an imageintensifier (Fig. 5) and then the procedure is repeated on theother side. The frame is completed with two 150- or 180-mmrods, 2 pin-to-rod clamps, and 1 rod-to-rod clamp (Figs. 2, 6).The procedure usually takes approximately 10 minutes.
If both anterior and posterior stabilization of the pelvicring are required, we routinely perform the posteriorstabilization first. At times, when we cannot reduce ormaintain the posterior reduction while we perform thepercutaneous sacroiliac screw fixation, we place the subcristalpins without mounting the frame and use them as ‘‘joy sticks’’to help manipulate and maintain the hemipelvis into thedesired position for sacroiliac screw fixation. The frame iscompleted only after the posterior ring has been stabilized.
患者仰卧于手术床台上，在皮肤上标记ASIS和髂嵴的前面轮廓。于腹股沟下区与髂嵴走行一致从髂前上棘髂嵴上做约2cm的皮肤切口（图4）。钝性剥离腹股沟韧带的附着点，暴露ASIS的前面。将穿刺套管装置（套管针/钻套/针套）于ASIS前后、上下拧入以确定进针点。由于髂嵴是悬突地，进针点可放在可触及的ASIS的中心内侧，允许将螺纹针置于髂骨内部皮质的外侧。进针点确定之后，一手移动套管针，另一手固定钻套。用4.0-mm钻头钻开外部皮质，方向与髂嵴的前面平行朝向髂骨粗隆（IT），对侧手通过拇指和食指固定于髂嵴上指导钻孔方向。保持套管针在适当的位置上，取下钻头，置入5-mm螺纹针（长150-180mm）直至螺纹针的螺纹全部置入骨质内。螺纹针要对准髂嵴内外皮质间的IT。这需要在低速钻模式下进行操作以便钝性的螺纹钉能沿着髂骨内外皮质之间的路径置入，在于髂嵴的IT上改变方向之前，不要将内外皮质钻透。置入针的位置可通过影像增强器进行检查核实（图5），然后以同样的方式置入另一侧的螺纹钉。用150或180mm的两根连接棒完成固定架的组装，两枚螺纹针与连接棒间用两枚夹钳固定，两根连接棒间用一枚夹钳固定（图2,6）。手术操作时间大约10分钟。

FIGURE 4. Superficial bony landmarks, skin incision, and drill/pin direction to build a subcristal frame. The surgeon’s left hand holds the iliac crest at the IT and guides the insertion of the pin.
图4 确立嵴下外固定架的体表骨性标志，皮肤切口及钻孔/入针方向。手术医生的左手固定在髂嵴的髂骨粗略上以指导固定针的置入。

FIGURE 5. Image intensifier intraoperative image confirming the intraosseous placement of the pin in the iliac crest in a subcristal-type pelvic external fixator.
图5 通过影像增强器术中证实嵴下型外固定器的固定针在髂嵴骨质内的位置。

FIGURE 6. Radiograph of a subcristal external fixator before its removal at 3 months.
图6 嵴下外固定器固定3个月，固定器取下之前的X线图像。

如果骨盆环前后均需要稳定，我们首先常规行后侧固定。有时我们不能复位或维持后侧复位，此时我们会实施经皮骶髂关节螺钉固定，然后置入固定针，但不安装固定架，将固定针作为“操纵杆（joy sticks）”以利于为骶髂关节螺钉固定控制和维持半骨盆到想要的位置，待后侧骨盆环稳定后再完成固定架的安装。

Postoperative Care
术后处理
After the operation, regular dry pin site dressings are applied until wound healing. The patients are mobilized as allowed by the stability of the posterior pelvic complex and associated injuries.
术后入钉部位辅料包盖，保持干燥直至伤口愈合。骨盆内相关复合损伤稳定后允许患者活动。

Patients
患者情况
Between 1992 and 2006, we applied 20 subcristal pelvicexternal fixators as the definitive method of fixation on theanterior pelvic complex for unstable pelvic ring disruptions.There were 6 females and 14 males with a mean age of39.2 years (range 19–66 years). The injuries of 18 patientswere classified as: 1 B1 injury, 3 B3 injuries, 5 C1-1 injuries,3 C1-2 injuries, 1 C1-3 injury, and 5 C2 injuries.6 We were notable to classify the injury in 2 of the patients due to lost x-rays. The patients were followed for a mean of 3.2 years (range2–7 years).
1992-2006年间，我们应用嵴下骨盆外固定器作为最终的固定方式固定于前骨盆复合体上治疗不稳定性骨盆环断裂共20例，其中女6例，男14例，平均年龄为39.2岁（范围19-66岁）。其中18例患者的骨折损伤分类为：B1型1例，B3型3例，C1-1型5例，C1-2型3例，C1-3型1例，C2型5例。2例患者由于X线片丢失不能进行骨折损伤分类。所有患者平均随访3.2年（范围2-7年）。
The fixators were maintained in place until the pelvicring injuries were deemed to be healed and/or stable, whichwas a mean of 10.7 weeks (range 4–22 weeks). The only exception was 1 patient where the subcristal external fixatorwas replaced after 4 weeks with plate fixation to correct gross pubic rami fracture displacement.
固定器维持固定直至术后平均10.7周（范围4-22周）考虑骨盆环损伤已愈合后/或稳定。唯一例外的是1例患者因需要纠正显著的耻骨支骨折移位，于4周后行钢板固定并重新安装外固定器。
All fixators were well tolerated by patients. After beingallowed to mobilize, all patients were able to dress, sit (Fig. 3),and walk. Four patients (20%) developed superficial pintrack infections, all of which were successfully treated withwound dressings and antibiotics. Three patients (2 infected with methicillin-sensitive Staphylococcus aureus and 1 with Pseudomonas aeruginosa) required antibiotics for 2 weeks,and the fourth case (infected with methicillin-resistant Staphylococcus aureus) required antibiotics for 5.5 weeks,until the removal of the frame. Infections were diagnosed at an average of 6 weeks after the fixator was applied (range 2.5–17weeks). The mean time from diagnosing the infection to removal of fixator was 5.4 weeks (range 3.5–5.5 weeks). None of these cases with infection had subsequent pin loosening,and the timing of frame removal was not affected by theinfection. There were no other complications, including lossof reduction, associated with the subcristal pelvic fixation.
所有外固定器均为患者所耐受，患者在允许活动后均能穿衣，做起（图3）和行走。外固定架取出之前，4例患者（20%）出现浅表的针道感染，通过局部伤口处理和应用抗生素后成功治愈，其中3例患者（2例患者存在甲氧西林敏感的金黄色葡萄球菌感染，1例存在绿脓杆菌感染）需要应用2周抗生素，第4例患者需要应用抗生素5.5周（耐甲氧西林的金黄色葡萄球菌感染）。在外固定应用后平均6周（平均2.5-17周）感染得以诊断。从诊断感染到外固定器移除的平均时间为5.4周（范围3.5-5.5周）。所有感染患者中无继发性固定针松动病例，固定器的移除时间不受感染的影响。未见复位丧失，嵴下骨盆固定相关的其他并发症发生。

The precise role of external fixators in the managementof pelvic ring fractures is still evolving, with periods of increased interest spurred on by potential improvements in the technique, followed by periods of less interest due to the complication rate and lack of desired stability associated with external fixation of the pelvis.7 In our clinical practice, were strict the use of pelvic external fixation to the management of some types of open pelvic fractures and pelvic injuries that require anterior stabilization but where internal fixation isconsidered inappropriate due to the pattern of associated pubic rami fractures.
骨盆外固定器在治疗骨盆环骨折中的确切作用还在不断发展，由于技术上的潜在改善激励医生们对该技术兴趣不断增加，后来，由于并发症的发生率以及骨盆外固定器固定骨盆后缺乏满意的稳定性使得人们对该技术的兴趣有所降低。在临床工作中，我们严格应用骨盆外固定器处理了一些类型的骨盆开放骨折和需要前侧稳定骨盆损伤，这些骨折类型由于其耻骨支的骨折模式考虑应用内固定是不恰当地。
Although numerous complications have been reportedafter pelvic external fixation,8 direct comparison of the typesand rates of complications is difficult as all studies have beenretrospective in nature and the method of diagnosing complicationswas inconsistent between studies. Nevertheless, thecomplications associated with anterosuperior frames includepin tract infection (which can lead to abscess formation,osteomyelitis, and the need for pin replacement8,9), asepticloosening, loss of reduction,9 incisional hernia,8 impingement,and nerve damage.9 For anteroinferior frames, intra-articularmalpositioning of the pins5,8 and suprapubic hernias10 havealso been reported.
尽管有大量骨盆外固定后发生并发症的报道，但由于各个研究间诊断并发症的性质和方法缺乏一致性，因此前瞻性的比较所有研究并发症的类型和发生率是十分困难地。尽管如此，前上固定架相关的并发症还是包括针道感染（可导致脓肿形成，骨髓炎以及需要更换固定针等），无菌性松动，复位丧失，切口疝，撞击以及神经损害等。对于前下固定架，固定针错位至关节内以及耻骨弓上疝也有报道。No significant anatomic structures are at risk when inserting a subcristal pin. Although the lateral cutaneous nerve of the thigh is in close vicinity, as this nerve passes deep to the inguinal ligament or through the ligament,11 it is not at risk aslong as the pin insertion technique is followed and the inguinal ligament/deep fascia layer are not violated.
嵴下固定针置入时无显著的解剖结构损伤风险。尽管在切口周围存在股外侧皮神经，然而该神经在腹股沟韧带的深处经过或穿过该韧带，只要遵循固定针置入技术，不侵扰腹股沟韧带/深筋膜层，就可避免该皮神经损伤的风险。
Correct pin placement is of utmost importance for optimizingmechanical stability and for preventing pin loosening,which in turn reduces the likelihood of pin tract infection.Correct placement of pins using the subcristal approach isfacilitated by the superficial location of the landmarks thatare used to guide pin positioning (ie, ASIS and IT). When wefirst started using this technique, we used an image intensifierduring the procedure but now only take in-theater postoperativex-rays to confirm correct pin placement. In contrastwith our experience using the subcristal approach, correct pinplacement using the anterosuperior approach is particularlydifficult for inexperienced surgeons, with Waikakul et al12reporting an 18% rate of incorrect pin placement. Althoughaiming devices have been described to improve pin placementduring the anterosuperior approach,12,13 these further increasethe complexity of the surgery. Supra-acetabular pin placementwhen using the anteroinferior approach is difficult due to thedeep location of the anterior superior iliac spine and the variableobliquity of the long axis of the ilium in the transverse plane.
对于优化机械稳定性和预防固定针松动，正确的放置固定针是最重要地，反过来，这也降低了针道感染的可能性。通过体表定位标志（即ASIS和IT）指导固定针定位使得嵴下固定针的正确放置变得十分便利。开始应用此项技术之初，术中我们需要应用影像增强器，但现在只采用普通术后X线就可确定固定针的正确位置。与我们应用嵴下固定方式的经验相反，采用前上方式固定针的正确放置对于经验不足的手术医生是十分困难地，Waikakul等报道固定针不正确的放置率为18%。尽管有报道称瞄准装置可改善前上固定方式的固定针放置的准确性，但这也进一步增加了手术的复杂性。由于需要髂前上棘的深部定位和髂骨长轴在横断面的倾斜变化，应用前下固定方式进行髋臼上置入固定针也是十分困难地。
Another consideration for the optimal approach to pelvicexternal fixation is the amount of soft tissue oppositionbetween the skin and bony insertion points. Pin insertion siteswhere the bony insertion point is closest to the skin will resultin less movement and better stability of soft tissue aroundthe pin, which in turn reduces the risk of pin tract infection.Solomon et al2 demonstrated that the amount of soft tissueinterposition at the pin insertion site was smallest with thesubcristal approach than the anterosuperior or anteroinferior approach.
对于骨盆外固定的最佳方式，另一项需要考虑的是皮肤和骨性置入点间的软组织对抗程度，固定针置入部位的骨性置入点距离皮肤越近会使松动越少发生且固定针周围软组织也越稳定，这反过来也减少了针道感染的风险。Solomon等研究证实，相比前上和前下固定方式，嵴下方式固定针置入部位（皮肤-骨）位置间的软组织量是最小地。
In terms of infection-related complications, in ourlimited patient series using the subcristal frame, our infectionrate of 20% compares favorably with the 24%–40% ratesreported with anterosuperior frames9,13,14 and also with the24% infection rate reported with anteroinferior frames.9 Furthermore, all the infections encountered in our patientswere successfully managed with wound care and antibioticsalone, without the need for pin replacement or frame removal,in contrast with previous reports associated where frameremoval has been necessary in some instances.8,9
在感染相关并发症等方面，在我们应用嵴下固定架治疗的有限患者系列中，感染的发生率为20%，情况好于前上固定架感染报道发生率的24%–40%，也优于前下固定架感染报道发生率的24%。此外，我们所遇到的所有感染患者经局部伤口处理和应用单一抗生素均获成功治愈，无需要更换固定针及移除固定架的病例。相反，在之前的报道中，这样的一些患者多需要移除外固定架。

Anatomic considerations suggest distinct advantages associated with the use of subcristal pin positioning for pelvic external fixation compared with the alternative pin positions currently employed. Subcristal pin positioning is the only technique that uses consistently and readily identifiable superficial bony landmarks (ASIS and IT) for pin insertion in a region with consistently adequate bone stock. Thus,the subcristal approach facilitates reliable pelvic external fixator that is easy to apply in a reproducible manner as a percutaneous procedure, without the need for an image intensifier or special jigs. The frame is well tolerated by patients for the extended periods of treatment that are often required. Furthermore, it allows dressing, sitting, and walking;full surgical access to the abdominal wall if required; and a lower overall complication rate.
基于解剖学的知识认为，相比目前普遍应用的其他固定针置入方式，骨盆外固定的嵴下入针方式具有其独特的优势。嵴下入针固定是容易确定入针始终如一部位的唯一方式，能准确地确定体表骨性标志（ASIS和IT），且这一区域始终存在足够的骨质以便置入固定针。因此，嵴下外固定方式使得外固定器的使用变得更为可靠和便利，经皮固定方式使固定器可重复利用，可不必应用图像增强器和特殊的导向尺。固定架能被需要长期治疗的患者多耐受。此外，也允许患者穿衣，做起和行走；患者可完全胜任必要的腹壁手术；并降低整体并发症的发生率。

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7. Tile M. Fractures of the Pelvis and Acetabulum. 1st ed. Baltimore, MD: Williams & Wilkins; 1984.
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9. Lindhal J, Hirvensalo E, Bo¨stman O, et al. Failure of reduction with an external fixator in the management of pelvic ring injuries. J Bone Joint Surg Br. 1999;81-B:955–962.
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知识补充
骨盆外固定技术是一项非常简便易行的骨盆固定方式，本文介绍了一种更为简单的骨盆外固定技术，尽管文章简短，但极为实用。水平有限，文献翻译错误之处难免， 望予指正！下面以图片的形式补充本文提到的骨盆相关解剖知识。