【专题文献】之人工髋关节置换——全髋关节置换术后髋关节脱位的处理

【专题文献】之人工髋关节置换

全髋翻修讲座之一：全髋关节置换疼痛的评估 By: 宋兵乙
全髋翻修讲座之二：髋关节翻修术中内植物的取出 By: 宋兵乙
全髋翻修讲座之三：髋关节翻修术中髋臼失败的重建和翻修 By: 宋兵乙
全髋翻修讲座之四：髋关节翻修术中股骨失败的重建和翻修 By: 宋兵乙
全髋翻修讲座之五：全髋关节置换术后髋关节脱位的处理 By: 飘洋过海
全髋翻修讲座之六：全髋关节置换术假体周围感染的处理 By: shiitake
全髋翻修讲座之七：下肢假体周围骨折的处理 By：宋兵乙

MINI-SYMPOSIUM: REVISION HIP SURGERY
小讲座：髋关节翻修术之五

The management of dislocation in hip arthroplasty
全髋关节置换术后髋关节脱位的处理

Abstract
Hip dislocation and the sequel of recurrent instability continues to be a problem following Total Hip Arthroplasty (THA), and is one of the leading causes of revision surgery. The cause of instability is often multi-factorial, including patient factors, surgeon factors, implant position and design, together with soft tissue related factors. Successful management of hip instability depends on an accurate assessment and, thereafter, addressing as many of these factors as possible. This article concentrates on the assessment and surgical management of hip instability following THA.
摘要 髋关节脱位以及不稳定是髋关节置换的主要问题，是髋关节置换术后翻修的首要原因。不稳定的原因包括多个因素，如患者自身的因素，外科医师的因素，植入物的位置和设计以及软组织相关的因素。对髋关节不稳成功的处理取决于准确的评估相关的可能因素。本文将重点评估全髋关节置换术后不稳定因素的处理。
Introduction
Dislocation occurs after 0.3% to 10% of primary total hip arthroplasty (THA) and after up to 28% of revision THA.1 Early dislocation, which has been defined as occurring within the first three months following THA, is more common but the cumulative risk of dislocation increases with the number of years following implant insertion. Half of those patients who dislocate suffer a single episode; however, for the other half recurrent instability and often further surgical intervention are required.2
引言 初次全髋关节置换术后发生脱位的概率为0.3%-10%，而翻修后的关节发生脱位的机率高达28% 。早期脱位指关节置换术后头三个月内发生的脱位，虽然早期脱位更为多见，但随着植入物在体内滞留时间的延长，脱位累计风险增加。有一半患者关节发生可位多是由于一次偶然事件引起，而另一半患者则是由于不存在不稳定因素所致，故常常需要外科手术干预 。
The patient with a dislocating THA is functionally impaired and this leads to patient apprehension and dissatisfaction.Clinical outcome scores and global outcome measures in patients who have had a dislocation of their hip are significantly worse than those without dislocation3 and do not improve despite successful revision surgery. The burden of revision surgery for instability to both patient and surgeon is considerable, in terms of both morbidity and cost. In North America instability is now the main reason for revision surgery, accounting for 22% of cases undergoing revision THA.4
关节脱位后引起患者功能受损，另一方面容易带来患者的不理解及不满意情绪。与那些没有发生脱位的关节相比较，发生脱位的关节功能评分统计学显示明显变差 ，即使翻修成功。就花费的费用及发病率而主，关节脱位翻修所带来的负担对医生或患者来说都是巨大的。在北美，不稳定因素是关节翻修有主要原因，占全髋翻修的22% 。
Instability following THA is most often multi-factorial and the underlying causes can be considered to fall into five major subgroups (Box 1). Prevention and avoidance of dislocation and instability in the first instance is obviously preferable and a recent Orthopaedics and Trauma article has addressed this topic (Volume 23:1 2009). By selecting the correct implant for each specific patient, ensuring that optimal component position is achieved and performing a thorough intra-operative trial reduction, subsequent instability should be minimised.
全髋关节术后不稳定常常是多因素的，表1列出了主要的五大因素（表1）。最近的骨科创伤文献表明，早期采取相关预防措施是第一位的。根据每个病人的情况选择其最适合的假体，术中确保假体的最佳位置，复位合仔细检查关节的稳定性，这些均有利于减少术后不稳定的发生。
Despite our best efforts, dislocations will occur, which serves to underline the multi-factorial nature of dislocation in THA. Therefore, when dislocation does occur following THA the cornerstone of subsequent successful management depends upon a detailed and accurate assessment, with the expectation that when as many of these factors are addressed as possible in the treatment strategy then a successful outcome should be more likely.
有时，尽管我们做出了最大努力，脱位仍可能会发生，这可能与我们强调的多因素不稳定有关。所以，当脱位出现后，我们应仔细对其评估，以便能作出成功的处理。

Assessment
Patient history
Deciding what factors caused a specific patient’s hip to dislocate requires a systematic approach, involving taking a targeted history, examination of the patient, gathering information from the notes and ordering appropriate investigations
When considering patient history in hip instability, details can be considered in three groups:
- History of events surrounding dislocation and details of any subsequent instability
- History of progress since index THA
- History and patient factors prior to index THA
Most of the patient factors for dislocation can be discovered in the clinical history. Questions relating to the dislocation include the number of dislocations and when they started. Dislocations that start to occur later in the life of the implant may be due wear of the articulating surfaces and change in the position of the implants. In the case of multiple dislocations, one should question what the original cause of the dislocation was. Was it associated with trauma or was it a positional event? The position in which the hip dislocates gives information on the direction of dislocation (i.e. anterior or posterior) and an idea of the primary arc of the implants.
临床评估
病史
要明确究竟是什么因素导致髋关节脱位，要求对患者资料行系统全面的分析，包括特定的病史，体格检查，收集患者治疗的相关记录以及适当的问卷调查等。
我们认为髋关节不稳定因素病史的采集，可从下面三人方面详细深入：
－ 脱位时的详细病史以及所发生的不稳定性
－ 关节置换术后的病史
－ 关节置换之前的详细病史
绝大多数患者脱位原因通过病史的询问均能发现。问卷调查的内容包括脱位的次数及什么时候开始。晚期的脱位可能是由于关节的磨损和假体位置的改变。对于多次脱位的患者，应该询问引起首次脱位的可能原因。脱位时是否和创伤或位置有关？脱位时的位置可以了解脱位的方向（前脱位或后脱位）以及假体最初的弧度。








Previous hip surgery, surgery for hip fractures and revision hip surgery all predispose a patient to the risk of dislocation. Compliance of the patient also needs to be assessed, as a lack of compliance could have compromised the original operation and will have to be taken into account for subsequent treatment.
之前的髋部手术史，既往有过髋部骨折及翻修手术均可出现脱位风险增加。需要对患者的医从性进行评估，医从性差对原来的手术有一定影响，在接下来的治疗也应将其考虑在内。
Patient-related factors involve the patient’s co-existing morbidities. Patients with a history of alcoholism, neurological conditions such as Parkinsonism, epilepsy and strokes are also at a higher risk of dislocation. Patients who are suffering from dementia and other psychiatric conditions may have issues surrounding compliance post hip surgery.
患者相关的因素涉及共存的相关疾病。有无饮酒精病史，神经系统方面疾病如柏金森氏病、癫痫或中风，是否存在痴呆及精神方面导致外科手术后医从性差的疾患等。
Woolson et al found that ‘‘cerebral dysfunction’’, which included a state of mental confusion during stay in hospital, a history of senile dementia/mental disorder and excessive alcohol consumption increased the risk of dislocation significantly. 5 Increasing age, especially patients over the age of 80, also carries a greater risk of dislocation; up to 12%.6 The notion that age itself is related to dislocation risk is controversial but it certainly may lead to increased risk of falls, decreased muscle control and degradation of cognitive ability; all of which can increase the risk of dislocation.
Woolson等发现，脑瘫（包括在住院期间精神混乱），老年痴呆/精神紊乱及酗酒均可导致脱位发生风险明显增加 。随着年龄的增大，尤其是当超过80岁时，脱位风险大为增加，可高达12% 。年龄本身因素引起脱位风险增加存在一定的争议，但年龄增加确实可导致跌倒风险增大，肌肉协调能力及认知能力下降，所有这些均可致脱位风险增大。
From the patient’s medical records it is important to gather information from the operation details such as the implants used and the size and type of the articulating surfaces. Information is also gathered regarding the operation itself, including the surgical approach used. The large majority of dislocations and therefore subsequent instability occur in the direction of the original surgical approach. Were any difficulties encountered during the procedure for any reason and was stability assessed intra-operatively? If the THA has previously dislocated and been treated with a closed reduced in theatre, was there an assessment of stability performed and in particular what was the safe arc of movement and status the soft tissue tension?
患者的医疗记录可获得与手术相关的详细信息，如假体的准确型号及尺寸、手术入路等。相当一大部分脱位的发生与原手术入路的方向有关。术中遇到的困难及稳定性如何评估？如果全髋置换术后以前曾有过脱位，后又经历了闭合复位，如何对其稳定性、髋关节的安全活动弧度以及软组织张力状态进行评估？
Clinical examination
On examination, as well as standard assessment, one must specifically inspect for leg length discrepancies and assess the
function of the abductor muscles. Look at the attitude of the limb; does it appear more internally or externally rotated than the opposite side? Assess the range of movement of the joint and whether is it excessive in any particular direction, and assess the rotational profile of the THA. The neurological status of the lower limb (in particular the superior gluteal and sciatic nerve function) should be assessed and documented, as damage from previous surgery or dislocation may have occurred.
体格检查
体检时，要严格按照标准执行，仔细比较双下肢长度差异，评估外展肌的功能。评估下肢的姿势，与对侧比较，它是更趋向于内旋还是外旋？检查关节的活动范围，是否存在某一方向的过度活动，对置换的全髋关节旋转活动进行评估。对肢体的神经状态进行检查并记录，确定损伤是来自以前或脱位引起。

Radiological investigations
Standardised radiographic views, including AP pelvis for hips and a lateral of the affected hip, can yield valuable information regarding the leg length, offset, and the implants used. Evidence of wear and loosening must be looked for. Varus or valgus alignment of the femoral component can affect the soft tissue tension. Component orientation is obviously important; although it can be difficult to comment on the cup anteversion, vital information can be gained from good quality AP (Figures 1 and 2) and lateral radiographs (Figures 1 and 2).
影像学检查
标准的放射片包括骨盆正位片及患髋侧位片，据此可找到有价值的信息，如肢体长度、偏心距及所用的内植物。仔细观察放射片上有无磨损及松动迹象。假体处于内翻或外翻可影响软组织张力。假体的方向很重要，虽然臼杯的前倾度很难判断，但从高质量的正、侧位片可获得重要的信息（图1，2）。

If infection is being considered clinically then blood tests for CRP and ESR should be performed and aspiration arthrogram performed if indicated. If there is concern about the alignment of the implants then CT scanning is an excellent way of gaining further information regarding the position of the implants (Figure 3). In particular, the acetabular component anteversion can be difficult to determine on plain radiographs and as this is frequently an issue resulting in instability, accurate assessment is required.7
当临床上考虑感染时，应抽血查以C反应蛋白、血沉及摄胸片检查。如需要进一步了解假体位置时，CT检查对于获得重要的信息是不错的选择（图3）。特别强调的是，髋臼假体的前倾在平片上难于评估，因此这往往是导致不稳定的潜在因素，精确的测量其角度是有必要的 。

Examination under anaesthetic and fluoroscopy screening can be a useful assessment tool in THA instability (Figure 4). The impingement free range of movement can be defined as well as the stable arc of movement. In particular, soft tissue tension can be assessed, which can be difficult to determine by other methods as it may well occur in a well-orientated THA with a functional primary arc of movement.
All of the information gathered helps formulate the plan for treatment and the further prevention of dislocation in the patient (Box 2).
术中，在麻醉及透视下对置换关节进行稳定性评估非常有用（图4）。不出现髋部撞击的自由活动范围界定为稳定的活动弧度。这种方法对软组织张力的评估特别适用，而其他的方法难以对此进行评估。假体位置良好的关节，其软组织张力一般都较好。
综合所有的患者资料信息有助于于制订治疗计划及进一步预防关节脱位的措施（表2）。

Treatment of dislocations following THA
Early post-operative first time dislocation
A first time dislocation is treated with a closed reduction. It is generally recommended that this be performed under anaesthesia in the operating theatre. It is important to ensure that the dynamic muscle stabilisers are overcome with the reduction manoeuvre and that potential damage to the components and patient’s own tissues is avoided. Both failed and successful reductions have been shown to cause bearing surface damage (Figure 5).
全髋关节置换术后脱位的治疗
术后早期首次脱位
首次脱位选择闭合复位，推荐在手术室麻醉后复位。保持足够的肌肉动力以克服复位时的阻力这一点很重要，潜在的假体及患者自身软组织的损害应该予以避免。无论是失败或成功的复位都关节面的磨损都有害（图5）。

The history, clinical examination and radiographs should allow the direction of the dislocation to be confirmed, as this will determine the reduction technique. Reduction techniques are similar to those manoeuvres for traumatic dislocations of the native hip. Radiographs should also be studied to appreciate both component fixation and indeed implant design as it is possible with loose or indeed certain implant designs to disturb the prosthesis during reduction (Figure 6). Intra-operative fluoroscopy can then be used to confirm reduction and assess the stability and status of the implants
病史，体检及影像资料可了解脱位的方向，由此可决定所采取的复位技术。复位方法与单纯髋关节创伤性脱位类似。复位前应对影像资料仔细研究，因为假体可能出现松动或某一部件阻挡复位可能（图6）。复位时透视有助于证实复位成功及假体的位置。

There is evidence to suggests that 2/3rds of patients with an early dislocation will not dislocate again as long as the implants are well positioned.1 It is therefore imperative to confirm that implants are well positioned and this may require further radiological imaging.
Although abduction braces and knee immobilizers are frequently used, their benefit in the peer-reviewed literature is of questionable value. Cesare et al braced 91 first time and 58 recurrent dislocations with no obvious mal-positioned implants and found bracing to be ineffective in preventing further dislocations when compared to a control group that was not braced.8 Physiotherapy with an emphasis on patient re-education may well be worthwhile.
The question then is how many dislocations one allows before treating the patient surgically? Although there is no specific evidence to support such a decision, generally most surgeons would intervene when more than two dislocations have occurred. The indications for operative intervention include recurrent instability, chronic dislocation, irreducible dislocations,mal-positioned implants and lack of adequate soft tissue tension leading to instability.
有证据表明，三分之二的早期脱位复位后，只要假体位置良好均不会发生再次脱位情况1。因此了解复位后假体的位置就显得尤为重要，故复位后应再次复查X线片。
虽然外展支具及膝关节制动经常被应用，但其文献综述资料上表明其真实价值仍存在商讨。Cesare等对91例首次关节脱位及58例反复关节脱位患者进行固定（所有患者复位后假体位置均无明显不良），与不固定的对照组比较，结果没有发现固定后对预防关节再次脱位存在好处 。理疗对于预防再次脱位有一定的价值。
那么问题是，究竟多少次脱位才考虑外科手术干预呢？虽然对这一问题目前没有明确的证据支持这一决定，但大多数外科医生认为两次以上的脱位考虑手术治疗。手术指征包括关节反复不稳，慢性脱位，不可复位的脱位，假体位置不良及外展肌力不足的患者。



Instability and component mal-position
Implant orientation obviously has a major effect on implant stability, and cup mal-position in particular is found to be a major cause of dislocation. Parvizi reported on their series of patients with recurrent instability that required revision surgery.9 Socket mal-position was identified as the major cause in 33 (35%) of 93 patients. Revision surgery was successful in preventing recurrence of instability in 91% in their series. Historically, however, the recurrence rates after component revision have been much higher (39e47%).10,11
If the components are mal-positioned then the implants should be revised to implants with the appropriate alignment. The recommended ‘‘safe zone’’ as described by Lewnineck for acetabular orientation is cup abduction of 40 t/_10 degrees and anterversion 15 +/-10 degrees.12 Exceeding the abovementioned measurements has been to show to increase the rates of dislocation from 1.5% to 6.1 %. The use of the transverse ligament has been shown to be a dependable landmark for the anteversion of the cup, as shown by Archbold and Beverland et al.13 By placing the cup parallel to the transverse ligament this prevents excessive anteversion or retroversion of the cup, thus placing the cup in the centre of the patient’s functional range, enhancing the joint’s stability. On the femoral side, the recommended anteversion angle is 10 to 25 degrees. An overall combined cup and stem anteversion of 45 degrees should be aimed for.14
不稳定与假体位置不良
植入物的方面对其稳定性作用是明显的，特别是臼杯位置不良被认为是一引起脱位的主要原因。Parvizi报告了一系列因反复不稳接受翻修手术的病例 ，99例患者，有33（35%）例臼的位置不良，91%的患者翻修手术成功。然而有研究表明，假体翻后其复发率更高（39－47%）10,11。
如果假体的位置不良，那么应采取翻修术以保持合适的假体位置。Lewnineck推荐安全值为：髋臼外展角40+/-10度，前倾角15+/-10度12。超过此界限值，脱位风险率将从1.5%增加6.1%不等。Archbold与Beverland等指出，髋臼横韧带是臼杯前倾角可靠的参考标志13。臼杯的放置与髋臼横韧带平行可避免其过度前倾或后倾，以保证其位置在关节功能活动范围中心，从而增强关节的稳定性。臼杯与股骨假体柄联合前倾45度是手术追求的目标14。


Instability and well-positioned components
The two principal reasons why well-positioned implants dislocate are because of either impingement or soft tissue (principally abductor) deficiency.
Dislocation may be due to impingement of bony or soft tissue, causing the hip to lever out. Occasionally a lump of scar tissue may be found to cause enough impingement to result in a dislocation. This tissue should be looked for at the time of revision and excised. Similarly, bony impingement can be caused by osteophytes around the acetabulum or a remnant of femoral neck not excised at the time of the primary surgery, and will require removal. Impingement can also be related to the implant characteristics or the patient’s femoral and pelvic anatomy.
If the natural femoral offset of the patient was not restored at the time of the index surgery, then poor soft tissue tension may be problematic; also the greater trochanter may impinge against the pelvis, effectively levering the hip out of joint. This can be addressed by restoring the offset at the time of the revision.
The two issues involving implant design and impingement are the primary arc and the excursion distance. The primary arc is the range of movement possible in the articulation before it impinges on the edge of the liner, which is followed by leveringout, and when the excursion or jump distance is exceeded dislocation occurs (generally the jump distance¼radius of the femoral head). The range of movement possible before impingement occurs is determined by the head:neck ratio. The larger the head is compared to the size of the neck, the further the hip has to travel before it impinges on the edge of the cup and thus the greater the primary arc of movement. Therefore, skirted femoral heads and elevated rim profile cups affect the primary arc and can cause impingement by virtue of their design.
Various implants have been used to optimise the head:neck ratio and the excursion distance of the revised implant. They include the use of large diameter femoral heads, modular component exchange and the use of bipolar and tri-polar articulations.
不稳定与假体位置良好的处理
假体位置良好而出现脱位的两大主要原因是撞击或软组织张力不足（主要是外展肌）。
脱位可能是由于骨性撞击或软组织的问题，偶尔也发现有软织疤痕包块形成足够的撞击力量导致关节脱位，翻修时应将这些组织予以切除。同样，骨性撞击也可能是由于髋臼周围的骨赘或初次全髋置换多残廇的股骨颈引发，手术时都就将其去除。撞击也可能与假体的特点或患者的股骨及骨盆解剖有关。
如果偏心距在手术时没有得到恢复，那接下来软组织张力将是一个问题；大粗隆将对关节形成撞击使其发生脱位。在关节翻修时应注意偏心距的恢复。
关节初始活动弧度与移动距离是涉及到假体设计与撞击的两个问题。初始活动弧度是关节与衬垫发生撞击前的活动范围，当移动距离或跳跃距离超过此范围时，标杆作用将使关节发生脱位（一般来讲，跳跃距离＝股骨头的半径）。撞击前的活动范围是由头颈率决定的，头与颈的比例越大，活动范围越大。因此有领的股骨假体柄与高边的髋臼影响关节的初始活动度，这是由于设计带来的撞击。
各种稳各样的假体设计被用来优化头颈比例与移动距离，包括应用大尺寸的股骨头，模具交配及应用双极、三极关节。






Large diameter femoral heads
Advances in manufacture, together with our knowledge of the wear of modern bearing surfaces, has resulted in the ability to use larger diameter femoral heads, thereby increasing THA stability. The larger diameter heads also allow for an increased neck length to be achieved without the incorporation of a skirt into the head design. Head sizes of 36mm and larger are now available for use with most bearing surfaces, including Highly Cross-linked UHMWPE, ceramic and metal articulations, each of which have their own advantages and disadvantages.

The use of jumbo-sized femoral heads is commonly employed in an attempt to prevent dislocation and is increasingly reported for management of recurrent instability. Beaule et al reported on 12 patients treated with large femoral heads (mean diameter 44 mm) for recurrent instability; in their series patients had an average of four previous operations and seven prior dislocations. At an average follow-up of 6.5 years, 10 patients had no further episodes of instability.15
大尺寸的股骨头 随着制造设计的不断改进与现代耐磨损理念的结合，产生的应用大股骨头的技术，以增加全髋关节的稳定性。大尺寸的股骨头允许应用相对长的股骨颈。目前36mm的头以及更大尺寸的头均可获得最大程度抗磨损，包括高分子聚乙烯，陶瓷对金属关节。当然，他们也各自有其自身的优、缺点。
利用大的股骨头来预防关节脱位的处理方法常有报道，Beaule等报道用大股骨头处理12例类似病人，股骨头平均直径44mm，这些病例中4例曾有过手术史，7例以前有过脱位，平均随访6.5年，10例患者情况良好。


Modular component exchange
Exchange of the modular components that comprise the THA can be undertaken as a method to improve stability (Figure 7). Modularity allows for alteration in neck length, acetabular offset and head diameter. Acetabular liners can be offset to improve soft tissue tension. Also, face-changing liners can re-direct the articulation interface by a limited amount. Elevated rim liners, whilst potentially increasing stability in a particular direction, will overall reduce the primary arc of movement of the articulation surface and may result in increased impingement in other positions. For the same reason, skirted femoral heads should be avoided.
Toomey et al reported a success rate of 92% at a mean of 5.8 years in a series of 13 hips using modular component exchange, and recommended the use of this technique only in selected cases.16 In general, the cup and stem have to be both well positioned and well fixed and the cup must also be of a sufficient size to allow for the use of a liner of sufficient thickness for the size of femoral head chosen. However, this technique is associated with complications, as reported by Barrack et al,17 including detachment of the femoral head, dislodgement of the polyethylene liner from the acetabular shell and asymmetrical rotation of the liner. In general, isolated modular exchange has had a relatively poor track record of success in treating recurrent instability in THA.
组配式假体翻修　组配式假体可用于全髋关节置换术后不稳定的翻修（图7），组配式假体使用灵活，股骨颈的长度、髋臼偏距及股骨头的直径均可调节。调节髋臼衬垫的偏距可改善软组织的张力。高边的衬垫同时可以增加某一特定方向的稳定性，但减少关节的活动弧度并增加撞击的发生。同样，带裙边的股骨头应尽量避免使用。
Toomey等报道了13例组配式假体使用的情况，平均随访5.8年，成功率92%，推荐根据病例选择性使用组配式假体16。一般来讲，臼杯与股骨假体柄都应该良好的固定，臼杯尺寸应足够大以容纳相应大的衬垫。然而，Barrack等报道这项技术也伴随有相关的并发症，包括股骨头分离，聚乙烯跑出髋臼之外及衬垫位置偏移。大体而言，组配式假体在治疗反复不稳定髋关节方面疗效相对较差。

Bi-polar and tri-polar arthroplasty
A bi-polar device is a small femoral head placed inside a polyethylene shell that is within a larger femoral head. The larger head then articulates with the native acetabulum. In theory, the movement occurs between the small head and the poly liner and also between the large head and the patient’s acetabulum. When the larger head articulates with an acetabular component it is called a tri-polar arthroplasty. Grigoris et al first described using tri-polar arthroplasty in a series
of 8 patients with no further dislocations at a mean of 4.2 years.18 Parvizi et al reported on a series of 27 recurrent dislocations treated with bipolar arthroplasties. At a mean of 5 years, 81 % had no further dislocations.19 However, there are problems associated with the use of bipolar arthroplasty. Not infrequently patients complain of groin pain and there is always potential for the implant to migrate, for what are modest gains in function. For these reasons, this should not be the first line of treatment for a dislocating arthroplasty and it is mainly indicated in salvage cases.
双极与三极关节置换 双极设计是一个小的股骨头在聚乙希鞘内活动，而聚乙希鞘在一更大的股骨头内运动，更大的股骨头与其自身髋臼相关节。理论上，运动发生在小头与极衬垫之间，也发生在大头与患者的髋臼之间。而当大头与髋臼假体之间发生运动时，则称作为三极人工关节。Grigoris等首先报道了用三极人工关节治疗8例患者的治疗报道，结果显示平均随访4.2年，均没有再脱位发生18。Parvizi等报道了用双极人工关节治疗27例反复脱位患者的情况，平均5年内，81%的患者没有发生再脱位19。然而双极人工关节的应用存在一些相关的问题。患者常常抱怨腹股沟区疼痛，另外存有潜在的内植物偏移风险。基于这些原因，决定了双极关节非一线治疗方法，它主要是失败病例手术指征。

Abductor function and soft tissue factors
A lack of soft tissue tension in THA can lead to instability. Certainly, failing to restore the offset of the hip can lead toinstability and this must be looked for in the radiographs in the investigations leading up to surgery. In such cases, the offset should be restored at the time of surgery. Non-union of the torchanteric osteotomy performed as part of the approach can lead to instability by defunctioning the abductors, reported to be as high as 17.6% when compared to 2.8% when the osteotomy healed.1 If present, the non-union should be treated with fixation at the time of surgery.

Trochanteric advancement has been suggested as a method of treating recurrent dislocators where neither component malpositioning nor impingement was the cause of the dislocations. Kaplan et al reported on 21 recurrent dislocators treated with an average of 16mm of trochanteric advancement.20 The surgery was successful in 17 of the patients. They noted that in the failures, two of the patients had non-union of the trochanter leading to a proximal migration of 1cm; these patients continued to dislocate repeatedly and thus it was suggested that proximal migration of the trochanter by 1 cm or more may result in an increased risk of dislocation.
外展肌功能与软组织因素  
髋关节置换软组织张力不足可导致不稳。当然，没有恢复髋关节的偏心矩也可致关节不稳，在影像资料查看时应仔细分析测量。对于偏心矩在外科手术时应该将其恢复，大粗隆截骨术后骨不连被认为是引起外展肌力不足的部分原因，不愈合与截骨术后骨愈合者相比较，关节不稳定风险比为17.6%:2.8%1。如果现在进行翻修，截骨不愈合应予以内固定。
大粗隆截骨术被推荐用于治疗非假体位置不良及非撞击引起的反复性关节脱位。Kaplan等报道了用大粗隆截骨术治疗21例反复关节脱位的患者，平均大粗隆前移16mm20，17例患者手术获得成功。他们注意到，2例失败病例出现了大粗隆骨不连，并向近端移位1cm，结果此2例患者术后发生反复脱位。因此他们指出，大粗隆向近端移位超过1cm，关节脱位风险增加。



Constrained acetabular liners
Constrained acetabular liners are a very powerful weapon in the armamentarium to treat THA instability. They are designed to resist dislocation of the femoral head by physically locking the head into the acetabular component, and their use is gaining in popularity. One potential reason for this may be their ease of use.
Two commonly used designs are a constrained UHMWPE liner with a metal reinforcement ring or a tri-polar constrained construct. Unfortunately, the advantage of increased stability of these systems can result in a decreased range of motion, increased wear, increased interface stresses and loosening, together with component failure of the constrained mechanism
(Figure 8).
The definitive indications for a constrained liner are recurrent dislocations with inadequate soft tissue, especially deficient abductor mechanism or neuromuscular disorders. Berend et al reported on 755 consecutive constrained acetabular components and reported a dislocation rate of 17.5% overall. When used for patients withrecurrent instability therewas a 29%dislocationrate.21

Certain patient factors cannot be changed. Lack of muscular control for any reason can, as mentioned, lead to instability of an arthroplasty. Similarly, lack of compliance is another issue that may not change. In such patients a constrained cup can be used.

Important to note with regard to the use of constrained liners is that any mal-alignment of the implants still needs to be corrected before using a constrained liner. The insertion of a constrained liner into a mal-positioned cup will increase impingement and will lead to early if not catastrophic failure. Although isolated case reports exist of successful closed reduction of constrained articulations, it is certainly the general rule that a dislocated constrained device cannot be reduced by closed means and requires an open reduction.22
限制性髋臼衬垫
限制性髋臼衬垫是非常强有力的治疗髋关节置换不稳的医疗器具。他们的设计原理是将股骨头锁定在髋臼假体内，从而达到抗脱位的作用。他们的应用正逐步变得流行。一个潜在的原因可能是由于他们的应用让术者放心。
两种常用的主要设计形势是一个限制性超高分子聚乙烯衬垫配备一金属增强环或者是一种三极限制性结构。不幸的是，在稳定性增强的同时，关节活动范围却减少，增加了关节磨损，增加了关节之间的压力并导致松动，从最终而导致假体固定失败（图8）。
因软组织张力不足导致的关节反复脱位，特别是外展肌力不足或神经肌肉状态紊乱是限制性髋臼衬垫使用的指征。Berend等报道了755例限制性髋臼衬垫使用的情况，脱位发生率为17.5%，应用于反复关节脱位患者的治疗时，其总的脱位发生率为29%21。
病人的某些因素可能是没法改变的，如肌肉缺乏控制力，同样，如果患者医从性差没法改善时，对于这样的病人也可以考虑使有限制性臼杯。
值得一提的是，在使用限制性臼杯衬垫时，臼杯的位置仍然要求良好。如果将限制性衬垫置入位置不良的臼杯内时，将会增加撞击的发生甚至灾难性的失败。虽然存在限制性臼杯脱位后有成功闭合复位的报道，但常规来讲应该采取切开复位22。

Other methods of treatment
In cemented acetabular cups, screw on lip augmentation devices have been used with some success.23 Although, just like elevated cementless acetabular liners, they effectively reduce the primary arc of movement, they can present a relatively conservative surgical option, particularly in elderly high-risk patients.

Other novel methods of treating recurrent dislocators are reported in the literature. These methods generally represent one centre, single surgeon series with small patient numbers. The use of Achilles tendon grafts24 and synthetic ligaments that act as check reigns to prevent dislocation have been described.
其他的治疗方法
骨水泥臼杯通过螺钉增强装置有一些成功的报道23，但是正如高边非骨水泥臼杯一样，他们均减少了关节的初始活动弧度，他们代表了相对较为保守的外科手术，特别是对风险较高的老年人来说。
其他的有关治疗关节反复脱位的病例在文献上有过报道。这些方法一般为一个中心或一部分外科医生对少量病例的治疗情况。通过跟腱移位及人工合成韧带作为预防脱位的装置也有过报道24。



Summary
Dislocation of a THA is both a common and a serious complication. It is usually caused by multiple factors. A systematic approach to both the diagnosis and treatment of dislocation is required for its management. The success of revision arthroplasty largely depends upon identifying the underlying aetiology. Implant position should be defined accurately and if sub-optimal, revised to the appropriate alignment. If the alignment is acceptable then impingement and soft tissue factors are a likely cause. Revision surgery should attempt to address all implant factors to maximise success rates. Many of the techniques that are described in this article can be used in combination, with a polymodal approach to a multi-factorial problem.
总结
髋关节置换术后关节脱位是常见且严重的一种并发症，它通常是由多因素所致，对脱位系统全面的诊断及治疗知识的撑握是必须的。要想成功翻修，就必须了解脱位的潜在病因学。了解假体的位置是否良好，如果位置良好，那撞击和软组织因素可能是脱位的原因。翻修时应对脱位原因仔细分析以求最大成功率。本文描述的各种处理方法可以联合应用来翻修因多因素导致的髋关节脱位。


参考文献
Woo RY, Morrey BF. Dislocations after total hip arthroplasty. J Bone Joint Surg Am 1982; 64: 1295e306.
Blom AW, Rogers M, Taylor AH, Pattison G, Whitehouse S,Bannister GC. Dislocation following total hip replacement: the AvonOrthopaedic Centre experience. Ann R Coll
Kotwal RS, Ganapathi M, John A, Maheson M, Jones S. Outcome of treatment for dislocation
after primary total hip replacement. J BoneJoint Surg Br 2009; 91-B: 321e6.
Bozic KJ, Kurtz SM, Lau E, et al. The epidemiology of revision totalhip arthroplasty in the
United States. J Bone Joint Surg Am 2009;91: 128-33.
Woolson ST, Rahimtoola ZO. Risk factors for dislocation during the first 3 months after
primary total hip replacement. J Arthroplasty 1999 Sept; 14: 662e8.
Newington DP, Bannister GC, Fordyce M. Primary total hip replacement in patients over 80
years of age. J Bone Joint Surgery Br 1990;72-B: 450-2.
Wines AP, McNicol. Computed tomography measurement of the accuracy of component
version in total hip arthroplasty. J Arthropalsty 2006; 21: 696e702.
DeWal H, Maurer SL, Tsai P, et al. Efficacy of abduction bracing in the management of total hip
arthroplasty dislocation. J Arthroplasty 2004; 19: 733-8.
Parvizi J, Kim KI, Goldberg G, et al. Recurrent Instability after Total Hip Arthroplasty: beware
of subtle component mal-positioning. Clin Orthop Relat Res 2006; 447: 60.
10 Morrey BF. Instability after total hip arthroplasty. Orthop Clin North Am 1992; 23: 237.
11 Lind M, Krarup N, Petersen LG, et al. Acetabular revision for recurrent dislocations: results in
14 cases after 3 years follow-up. Acta Orthop Scand 2002; 73: 291.
12 Lewinnek GE, Lewis JL, Tarr R, Compere CL, Zimmerman JR. Dislocations after total hip
replacement arthoplasties. J Bone Joint Surg Am 1978; 60: 217-20.
13 Archbold HAP, Mockford B, Molloy B, et al. The transverse acetabular ligament: an aid to
orientation of the acetabular component. J Bone Joint Surg Br 2006; 88-B: 883e6.
14 Ranawat CS, Rao RR, Rodriguez JA, Bhende HS. Correction of limblength inequality during
total hip arthroplasty. J Arthroplasty 2001; 16:717-20.
15 Beaule PE, Schmalzried TP, Udomkait P, Amstutz HC. Jumbo femoral heads for the treatment
of recurrent dislocation following total hip replacement. J Bone Joint Surg Am 2002; 84-A: 256.
16 Toomey SD, Hooper RH, McAuley JP, et al. Modular component exchange for treatment of
recurrent dislocation of total hip replacement in selected patients. J Bone Joint Surg Am 2001; 83: 1529.
17 Barack R. Dislocation after total hip arthroplasty: implant design and orientation. J Am Acad
Orthop Surg March/April 2003; 11(No 2): 89-99.
18 Grigoris P, Grecula MJ, Amstutz HC, et al. Tripolar hip replacement for recurrent prosthetic
dislocation. Clin Orth Related Res 1994 Jul; 304: 148-55.
19 Parvizi J, Morrey BF. Bipolar hip arthroplasty as a salvage treatment for instability of the hip. J Bone Joint Surg Am 2000; 8: 629.
20 Kaplan SJ, Thomas WH, Poss R. Trochanteric advancement for recurrent dislocation after total hip arthroplasty. J Arthroplasty 1987; 2: 119.
21 Berend KR, Lombardi A, Mallory T, et al. The long-term outcome of 755 consecutive
constrained acetabular components in total hip arthroplasty, examining the successes and the
failures. J Bone Joint Surg Am 2005; 20: 93.
22 Miller CW, Zura RD. Closed reduction of a dislocation of a constrained acetabular component. J Arthroplasty June 2001; 16: 504e5.
23 Campbell D. The posterior lip augmentation device for recurrent dislocation. J Bone Joint Surg Br 2002; 84-B: 154.
24 Lavigne M. Recurrent dislocation after total hip arthroplasty: Treatment with an achilles tendon allograft. J Arthroplasty 2001; 16:13-8.