胫骨结节移位的原因和位置:胫骨结节截骨术的指征和技术_髌骨形态的Wiberg分类（2019）

胫骨结节移位的原因和位置:胫骨结节截骨术的指征和技术_髌骨形态的Wiberg分类（2019）Why and Where to Move the Tibial Tubercle: Indications and Techniques for Tibial Tubercle Osteotomy

Middleton K K, Gruber S, Shubin S B. Why and Where to Move the Tibial Tubercle: Indications and Techniques for Tibial Tubercle Osteotomy[J]. Sports Med Arthrosc Rev, 2019,27(4): 154-160

转载文章的原链接1：

https://pubmed.ncbi.nlm.nih.gov/31688534/

转载文章的原链接2：

https://journals.lww.com/sportsmedarthro/abstract/2019/12000/why_and_where_to_move_the_tibial_tubercle_.6.aspx

Abstract

Patellofemoral disorders including pain and instability are common orthopedic problems, particularly in the adolescent population. Patellofemoral pain is usually anterior, poorly localized, and diffuse. Because of its multifactorial etiology, patellofemoral pain can be clinically challenging to diagnose and manage. With regards to instability, predisposing factors include trochlear dysplasia, patella alta, patellar tilt, and an elevated tibial tuberosity and trochlea groove distance. Initially, nonoperative management is recommended to treat patellofemoral maladies such as overload, maltracking, and acute first-time dislocations. However, tibial tubercle transfer (TTT) is commonly used to address cases of symptomatic malalignment and overload and recurrent patellar instability. The tubercle can be translated in multiplanar directions to correct patellar height, maltracking associated with instability, and to offload chondral defects. A thorough understanding of the anatomy and biomechanics of the patellofemoral joint is essential for optimizing results after TTT. Individualizing the direction and degree of tubercle transfer on the basis of patient parameters is critical to producing successful long-term results after surgery. This article will review the indications for performing a TTT and highlight the various techniques.

髌骨疾病包括疼痛和不稳定是常见的骨科问题，特别是在青少年人群中。髌股疼痛通常是前侧的，局限性差，弥漫性的。由于其多因素的病因，髌股疼痛可以在临床上具有挑战性的诊断和管理。至于不稳定性，诱发因素包括滑车发育不良、高位髌骨、髌骨倾斜、胫骨结节和滑车沟距离升高。最初，非手术治疗被推荐用于治疗髌骨疾病，如超载、错位和急性首次脱位。然而，胫骨结节转移（TTT）通常用于治疗症状性错位、超载和复发性髌骨不稳的病例。结节可以在多平面方向上平移，以纠正髌骨高度，与不稳定相关的畸形，并减轻软骨缺损。彻底了解髌股关节的解剖和生物力学对于优化TTT后的结果至关重要。在患者参数的基础上个性化tubercle转移的方向和程度对于术后产生成功的长期效果至关重要。本文将回顾执行TTT的适用证，并重点介绍各种技术。

Key Words: tibial tubercle transfer, osteotomy, patellofemoral instability, anteromedialization, tibial tubercle-trochlea groove (TT-TG) distance

Historically, tibial tubercle transfer (TTT) has been used in the treatment of a wide range of pathologies that affect the patellofemoral (PF) joint including patellar instability, focal chondral defects, overload syndromes, and arthritis. TTT can alter patellar tracking and subsequently improve patellar stability. In addition, it can be used to unload the patellar cartilage. In the setting of patellofemoral instability (PFI), a TTT can be performed as a stand-alone procedure for the aforementioned indications or, more commonly, in combination with soft tissue stabilizing procedures and cartilage restoration if necessary.

从历史上看，胫骨结节转移(TTT)已被广泛用于治疗影响髌骨股骨(PF)关节的各种病变，包括髌骨不稳定、局灶性软骨缺损、过载综合征和关节炎。TTT可以改变髌骨轨迹，进而改善髌骨稳定性。此外，它还可用于卸下髌骨软骨。在髌股不稳定(PFI)的情况下，TTT可以作为上述适应症的单独手术进行，或者更常见的是，必要时与软组织稳定手术和软骨修复手术联合进行。

The first reported TTT (medialization) was performed by Roux1 in 1888 for patellar instability. Subsequently, Hauser2 described a posterior and medial shift of the tubercle to reduce the risk of lateral dislocation; however, it resulted in increased constraint and deleterious effects on contact pressure. Though the short-term results were favorable with regard to stability, the Hauser procedure has become obsolete given the resultant increase in contact pressures and arthritis. For pain associated with arthritis, Maquet advocated straight anteriorization of the tibial tubercle.3 Later, Elmslie of the United Kingdom and A.G. Trillat of France promoted the concept of a pure medial transfer to treat lateral patellar contact pressures and patellar instability.4 Understanding the importance of minimizing joint reaction forces to prevent arthritis led to the modification of techniques for TTT. Most recently, Fulkerson popularized the anteromedialization (AMZ) of the tibial tuberosity through an oblique cut allowing a titratable shift in the sagittal and coronal planes.

Roux1于1888年首次报道了TTT(内侧化)治疗髌骨不稳。随后，Hauser2描述了结节的后侧和内侧移位，以减少外侧脱位的风险;然而，它会增加约束和对接触压力的有害影响。虽然短期结果在稳定性方面是有利的，但由于接触压力和关节炎的增加，Hauser手术已经过时了。对于与关节炎相关的疼痛，Maquet主张对胫骨结节进行直接前固定后来，英国的Elmslie和法国的A.G. Trillat提出了纯内侧移位的概念来治疗外侧髌骨接触压力和髌骨不稳了解最小化关节反作用力对预防关节炎的重要性导致了TTT技术的改进。最近，Fulkerson通过斜切口推广了胫骨结节的前内侧化(AMZ)，允许在矢状面和冠状面进行可titratable的移位。

This review article will focus on indications for TTT and surgical techniques for the treatment of PF disorders including patellar instability, malalignment, unloading of chondral defects, and arthritis. A brief review of the epidemiology, biomechanics, and relevant surgical anatomy will also be discussed.

这篇综述文章将重点介绍TTT的适应症和治疗PF疾病的手术技术，包括髌骨不稳定、排列不齐、软骨缺损卸载和关节炎。简要回顾流行病学，生物力学和相关的外科解剖也将讨论。

INCIDENCE OF PF DISORDERS

PF pain can be clinically challenging because of the multifactorial etiology of pain and derangement. Anterior knee pain has been reported in up to 30% of adolescents with ~75% of these patients reporting limited participation in athletics at midterm follow-up.5,6 A third of patients 13 to 19 years old have reported PF pain with 29 in 100,000 patients aged 10 to 17 years having PFI.6–8 Patellar instability has been divided into those sustaining a first-time dislocation or acute patellar dislocation and those with recurrent instability. The reported rate of recurrence after nonoperative management of first-time patellar dislocators is 33%.9 Lewallen et al10 identified multiple risk factors for recurrent instability including younger age, open physes, sports-related injuries, patella alta, and trochlear dysplasia. Authors reported that in the high-risk group, those younger than 25 years of age with trochlear dysplasia, the recurrence rate after nonoperative management was as high as 69%.10 In a recent article by Jaquith et al,11 using 4 significant risk factors for recurrent PFI after the first-time dislocation in children and adolescents, the authors developed a predictive risk model.11 The presence of all 4 risk factors including history of a contralateral patellar dislocation, patella alta, trochlear dysplasia, and skeletal immaturity conferred a predictive risk of recurrence as high as 88.4%.11

由于疼痛和紊乱的多因素病因，PF疼痛在临床上具有挑战性。据报道，高达30%的青少年出现前膝关节疼痛，其中约75%的患者在中期随访时报告运动受限5,6。13 - 19岁的患者中有三分之一报告了PF疼痛，10 - 17岁的患者中有29 / 10万患有PFI6 - 8。髌骨不稳定分为首次脱位或急性髌骨脱位和复发性不稳定。据报道，首次髌骨脱位非手术治疗后复发率为33%。Lewallen等人10确定了复发性不稳定的多种危险因素，包括年轻、open physes、运动相关损伤、高位髌骨和滑车发育不良。作者报道，在25岁以下的滑车发育不良高危人群中，非手术治疗后复发率高达69%。在Jaquith等人最近的一篇文章中，作者利用儿童和青少年首次脱位后复发性PFI的4个重要危险因素，建立了一个预测风险模型包括对侧髌骨脱位、高位髌骨、滑车发育不良和骨骼不成熟史在内的所有4种危险因素的存在使复发的预测风险高达88.4%。

Besides the risk of recurrence after a patellar dislocation, the frequency of resultant chondral injuries has been reported to be as high as 70%.12 In a study evaluating 39 consecutive knees with a first-time acute lateral patellar dislocation, Nomura et al13 observed that 95% of knees had articular cartilage injuries of the PF joint. After lateral dislocation, chondral injuries often exist on a spectrum ranging from fissures to focal defects to diffuse disease.

据报道，髌骨脱位除了有复发的风险外，导致软骨损伤的频率高达70%。在一项评估39例首次急性外侧髌骨脱位的连续膝关节的研究中，Nomura等13观察到95%的膝关节有PF关节软骨损伤。在外侧脱位后，软骨损伤通常存在于从裂缝到局灶性缺损到弥漫性疾病的范围内。

APPLIED SURGICAL ANATOMY AND BIOMECHANICS

Patients with symptomatic pathology associated with the PF joint will often have altered osseous anatomy and a combination of imbalanced axial, sagittal, and coronal plane forces acting at the level of the joint. An understanding of normal anatomy and biomechanics helps to appraise pathology associated with PFI to ensure the appropriate osteotomy for patients who have failed conservative treatment.

与PF关节相关的症状性病理患者通常会有骨解剖结构的改变，以及关节水平上的轴向、矢状面和冠状面力的不平衡组合。了解正常解剖和生物力学有助于评估与PFI相关的病理，以确保对保守治疗失败的患者进行适当的截骨。

The patella is a large sesamoid bone that articulates with the distal femoral sulcus through osseous and soft tissue restraints. The patellar cartilage is the thickest in the human body, measuring ~5 mm on average, though it has been reported up to 7-mm thick.14 The morphology of the patella can vary greatly between individuals with a constant medial and lateral facet divided by a vertical ridge along with an odd facet that engages in deep flexion. Patellar facets are concave in shape to accommodate the femoral surface; the lateral facet being wider to help maintain the patellar position in the trochlear groove. The medial facet may be flat or slightly convex according to the Wiberg15 classification described in 1941. It describes 3 different patellar types on the basis of the asymmetry between the medial and lateral facets on axial views of the patella (Fig. 1). Type 4, also known as the “Jaegerhut” patella, was later described by Baumgartl.16 It has no medial facet and consequently, no median ridge. The trochlea deepens distally with lateral deviation in regards to the axis of the femur17 and can demonstrate varying degrees of dysplasia as classified by Dejour et al.18

髌骨是一个大的籽状骨，通过骨和软组织约束与股骨远端沟相连14。.髌骨软骨是人体最厚的软骨，平均厚度约5毫米，但也有报道称其厚度可达7毫米。髌骨的形态在个体之间可以有很大的差异，恒定的内侧和外侧关节面由垂直的脊和一个参与深屈曲的奇数关节面分开。髌骨骨面呈凹形以容纳股骨表面;外侧小面更宽有助于维持滑车沟中髌骨的位置。根据Wiberg15在1941年的分类，内侧关节面可能是平的或微凸的。根据髌骨轴向视图中内侧和外侧关节面之间的不对称，它描述了三种不同的髌骨类型(图1)。4型，也被称为“Jaegerhut”髌骨，后来由baumgart16描述。滑车远端加深，与股骨轴相关的外侧偏移17，并可表现出Dejour等人分类的不同程度的发育不良18

FIGURE 1. Wiberg classification of patellar shape 髌骨形态的Wiberg分类

Type I: concave, symmetrical facets of equal size.

Type II: medial facet is slightly smaller than lateral facet and flat or slightly concave.

Type III: convex medial facet that is markedly smaller compared with the concave lateral facet. Note the angle between the medial and lateral facets is nearly 90 degrees.

Type IV: “Jaegerhut” patella with no medial facet (and no median ridge). Type IV was later described by Baumgartl.

The functional role of the patella is to enhance the lever arm of the extensor mechanism. During knee flexion and extension, very high loads transfer to the undersurface of the patella. As the contact point changes between the patella and trochlea throughout the knee range of motion, the joint reaction forces change because of altered force vectors in the lever system. The thick articular cartilage is believed to dissipate large joint reaction forces created during forceful contractions of the quadriceps muscle.

髌骨的功能作用是增强伸肌机制的杠杆臂。在膝关节屈伸时，非常高的负荷转移到髌骨下表面。在整个膝关节运动范围内，当髌骨和滑车之间的接触点发生变化时，由于杠杆系统中力矢量的改变，关节反作用力也会发生变化。厚实的关节软骨被认为可以消散股四头肌强力收缩时产生的巨大关节反作用力。

In knee extension, the patella sits proximal and lateral in the trochlear groove. Here, stability is afforded by soft tissue restraints alone. Consequently, the majority of dislocations occur in this position. In a patient with normal patellar height, the distal pole begins to engage in the trochlea at 20 to 30 degrees of flexion. As flexion progresses, joint reaction forces move distal to proximal and range from 385 N when walking to 6000 with jumping and landing.19 Throughout the arc of motion, static stability is offered by the patellar tendon, joint capsule, and ligamentous structures. The medial PF ligament is the primary stabilizer during the first 30 degrees of flexion providing nearly 60% of the restraint to lateral translation in this arc of motion, whereas the medial patellotibial ligament and medial patellomeniscal ligament compose the remaining medial patellar restraints and mainly function in greater degrees of flexion.20–22 The MPFL consist of 2 components: a transverse component arising between the adductor tubercle and the medial epicondyle, and an oblique decussation originating from the MCL,23 and appears as a thickening of the medial retinaculum between knee layers 2 and 3.24 The ligament itself has a broad insertion on the upper two thirds of the patella and into the quadriceps tendon25,26

在膝关节伸展时，髌骨位于滑车沟的近端和外侧。在这里，稳定性仅由软组织约束提供。因此，大多数位错发生在这个位置。在髌骨高度正常的患者中，远端极在屈曲20至30度时开始与滑车接合。随着屈曲的进展，关节反作用力从远端向近端移动，范围从步行时的385牛到跳跃和落地时的6000牛在整个运动弧线中，髌腱、关节囊和韧带结构提供静态稳定性。内侧髌韧带是前30度屈曲期间的主要稳定器，在该弧度运动中提供近60%的侧向平移约束，而髌胫骨内侧韧带和髌髌骨内侧韧带构成剩余的内侧髌韧带约束，主要在较大程度的屈曲中起作用20-22。强内收韧带由2个组成部分组成:一个是在内收肌结节和内上髁之间形成的横向部分，另一个是起源于MCL的斜韧带23，表现为膝关节层2和层3.24之间内侧支持带的增厚。韧带本身在髌骨的上三分之二处有一个广泛的插入，并进入股四头肌肌腱25,26

In a landmark anatomic study, Tanaka et al27 illustrated the anatomy of the medial PF complex, highlighting that the proximal fibers are directed into the distal portion of the quad tendon. It is because of this article that many have taken to reconstructing the medial quadriceps tendon-femoral ligament, which not only may more accurately reflect anatomy but also certainly decreases the risk of fracture with patellar tunnels.28

在一项具有里程碑意义的解剖研究中，Tanaka等人27阐述了内侧PF复合体的解剖结构，强调近端纤维指向股四头肌腱的远端部分。正是因为这篇文章，许多人开始重建股四头肌内侧肌腱-股韧带，这不仅可以更准确地反映解剖结构，而且肯定会降低髌骨隧道骨折的风险。28

Deviations of the normal articular relationship between the patella and the trochlea such as abnormal patellar height, malalignment, or excessive tilt, predispose to maltracking and PFI. A posteriorly directed force on the patella is generated by the respective pulls of the quadriceps tendon and patella tendon. Supraphysiological lateral force vectors can result from the aforementioned pathologies affecting the PF articulation.5 The Q-angle has historically served as an indicator of the lateral force vector with normal values reported to be between 14 and 17 degrees for men and women, respectively.29 It is the angle formed between the line of pull of the quadriceps (anterior superior iliac spine to mid-patella) and the line connecting the center of the patella with the tibial tuberosity measured at 20 degrees of knee flexion. A wide degree of interobserver and intraobserver reliabilities has been demonstrated in reporting this angle. For this reason, it is not used as frequently to determine the need for surgical treatment. However, the goal of TTT is aimed at decreasing this angle to allow for a more concentric pull of the extensor mechanism on the patella.30

髌骨与滑车之间正常关节关系的偏离，如髌骨高度异常、排列不当或过度倾斜，易导致轨迹不当和PFI。股四头肌肌腱和髌骨肌腱的拉力分别对髌骨产生后向力。生理上的侧向力矢量可由上述影响PF关节的病理引起Q角历来被用作横向力矢量的指标，据报道，男性和女性的正常值分别在14到17度之间它是股四头肌牵拉线(髂前上棘至髌骨中部)与髌骨中心与胫骨粗隆连接线之间形成的夹角，在膝关节屈曲20度时测量。在报告这个角度时，已经证明了观察者之间和观察者内部的广泛程度的可靠性。由于这个原因，它不常用来确定是否需要手术治疗。然而，TTT的目标是减小这个角度，使髌骨上的伸肌机构有一个更同心的拉力。

The distance between the center of the tibial tubercle and the trochlear groove (TT-TG) has essentially replaced the Q-angle as a proxy measure in the axial plane used to describe PF alignment. The TT-TG can be measured by super-imposing the 2 axial images on computed tomography (CT) or magnetic resonance imaging (MRI). The measurement begins at the center of the most proximal portion of the tibial tubercle and ends at the deepest portion of the trochlea groove (Fig. 2).31 Normal values on CT range from 10 to 13 mm with distances ＞ 15 mm associated with an increased risk of instability.18,31 Measurements of the TT-TG on MRI are reported to underestimate CT measurements by 3 to 4mm.32,33 Similar to the “Q” angle, the TT-TG measurement is also fraught with limitations as it can be influenced by the knee flexion angle and coronal alignment of the limb during imaging acquisition.34,35 Nonetheless, the TT-TG provides an excellent guide during preoperative evaluation to discern potential risks and benefits of performing a TTT.

胫骨结节中心与滑车沟之间的距离(TT-TG)基本上取代了Q角作为轴向平面上用于描述PF对准的替代测量。TT-TG可以通过在计算机断层扫描(CT)或磁共振成像(MRI)上叠加2轴图像来测量。测量从胫骨结节最近端的中心开始，到滑车沟最深的部分结束(图2)CT正常值范围为10 ~ 13mm，距离＞ 15mm与不稳定风险增加相关18,31。据报道，MRI上的TT-TG测量值比CT测量值低3至4mm32,33。与“Q”角相似，TT-TG测量也充满了局限性，因为它在成像采集过程中可能受到膝关节屈曲角度和肢体冠状排列的影响34,35。尽管如此，TT-TG为术前评估TTT的潜在风险和益处提供了很好的指导。

FIGURE 2. TT-TG distance is measured from the center of the tibial tubercle marked with an asterisk (A) to the center of the trochlea (B).The TT-TG measures 24.1 mm on superimposed MRI images (C). TT-TG indicates tibial tubercle-trochlear groove.

In the sagittal plane with the knee in slight flexion, the apex of the patella lies at or slightly proximal to the joint line. Changes in patellar height (alta or baja) affect the angle of flexion at which the patella engages the trochlea (Fig. 3). Patella alta results in patella engagement at deeper flexion angles with diminished contact area.36 Thus, the patella is at greater risk for subluxation. In addition, patella baja can lead to abnormal joint reactive forces. Numerous indices have been designed to assess patellar height, with the Caton-Deschamps index (CDI) being the senior authors preferred method because it can be measured in numerous imaging modalities (eg, x-ray, CT, and MRI) and it changes with surgeries that move the tubercle, whereas the Insall-Salvati does not. Patella alta measurements ＞ 1.3 and ＜0.8 have been traditionally used to help determine the need for surgical intervention; however, the evidence behind these values has not been fully elucidated.18

在矢状面，膝关节轻微屈曲时，髌骨尖端位于关节线或关节线的稍近端。髌骨高度(上或下)的变化会影响髌骨与滑车接合时的屈曲角度(图3)。上髌骨导致髌骨在更深的屈曲角度接合，接触面积减少因此，髌骨半脱位的风险更大。此外，膝盖骨下陷可导致关节反作用力异常。已经设计了许多指标来评估髌骨高度，其中Caton-Deschamps指数(CDI)是资深作者首选的方法，因为它可以通过多种成像方式(例如x射线，CT和MRI)测量，并且它会随着手术移动结节而变化，而Insall-Salvati则不会。髌骨上部测量值＞ 1.3和＜0.8传统上用于帮助确定是否需要手术干预;然而，这些价值背后的证据尚未得到充分阐明。

FIGURE 3. Patella alta (A) and baja (B) demonstrated on lateral radiographs.

In the transverse plane, the patella should lie horizontally such that the medial and lateral borders are equidistant from the femoral sulcus. The tilt of the patella can lead to abnormal forces across the PF joint and is typically a result of lateral retinacular tightness. Excessive overload and malalignment can predispose to chondral degeneration secondary to lateral PF compression syndrome,37 and can be accessed through the angle between the posterior femoral condyle and the transverse axis of the patella on an axial view of the knee (eg, Merchant x-ray, CT, or MRI).38

在横切面，髌骨应水平放置，使内侧和外侧边界与股沟等距。髌骨倾斜可导致PF关节异常受力，通常是侧支持带紧绷的结果。过度负荷和排列错位可诱发继发于外侧PF压迫综合征的软骨退行性变37，可在膝关节轴向视图(如Merchant x线、CT或MRI)上通过股骨后髁与髌骨横轴之间的夹角观察38

INDICATIONS AND PREOPERATIVE CONSIDERATIONS

Operative indications of TTT vary depending on the pathoanatomy of the patient. In general, surgical candidates will have persistent pain, swelling, and mechanical symptoms at the PF joint with knee flexion and extension that have failed to respond to conservative treatment.

Although ongoing studies are evaluating the role of surgical treatment after first-time dislocations, the current and still standard of care treatment for first-time dislocators is nonoperative with bracing and tailored physical therapy routines. Likewise, for patients with symptomatic overload syndrome, conservative management should be exhausted before surgical intervention.

After a second patellar dislocation, surgery is typically indicated for recurrent patellar instability including a proximal soft tissue reconstructive procedure possibly in conjunction with a TTT depending on the patient-specific clinical and radiographic parameters discussed in the last section.

In the setting of chondral injury relating to patellar overload, malalignment, or trauma, a TTT can be combined with cartilage restoration procedures to aid in unloading the joint. The direction and degree of tubercle translation depend on the patient’s radiographic parameters and the location of patellar chondral defects (when performing a TTT an unloading procedure). In the setting of an elevated TT-TG (certainly ≥ 20 mm), some degree of medicalization should be considered to correct the TT-TG closer to 10 mm. The amount of the desired distalization is calculated to result in a postoperative CDI of 1.1 to 1.2. Anteriorization is considered to unload the cartilage and or address any chondral lesions. The results of these unloading osteotomies are on the basis of the quality of the cartilage where the load is being shifted.39 Anteriorization of 2 cm can reduce the compressive forces across the joint by 50%; however, excessive elevation can result in skin problems and wound healing complications.40 Although long-term results are usually favorable following a Maquet procedure, the devastating complications reported have made this procedure less popular. Fulkerson and Edgar described an alternative surgery using a modified AMZ approach to avoid such complications. Yoshikazu O’Hara and Fulkerson (unpublished data) noted that steep, oblique osteotomies allow up to 17 mm of tibial tubercle anteriorization without using any bone graft. On the basis of in vitro load testing studies, the recommended amount of anteriorization typically between 10 and 15 mm.41,42

AUTHOR’SPREFERRED TECHNIQUE

As previously emphasized, the surgical technique should be tailored to each individual patient and must address the concomitant pathology within the knee. A myriad of TTT operative techniques have been described and guided systems have now been developed through the industry to help aid in the precision of the osteotomy cut and angle. The following described technique will focus on an isolated TTT excluding discussion of concomitant soft tissue, bony, and cartilage procedures

All procedures commence with a bilateral examination under anesthesia. Repeat examination with muscle relaxation allows us to confirm the overall range of motion, patellar mobility including the integrity of the MPFL, tightness of the lateral retinaculum and correctability of lateral tilt, and any other associated ligamentous injuries. Next, arthroscopy is used to carefully evaluate the articular surface of the patella (Fig. 4) and the location and grade of any articular lesions on the patella and trochlea, and remove any loose bodies secondary to recurrent patellar dislocations. Tracking is also evaluated on arthroscopy viewing from either the anterolateral or superolateral portal and visualizing the patellar tracking in the trochlea throughout a full range of motion. The lateral portion of the PF joint is also assessed for the overhang of the lateral facet in relation to the lateral trochlea, indicating how well (or poorly) the patella is centered (Fig. 5).

FIGURE 4. Undersurface of the patella (A) and an empty, dysplastic trochlea (B) viewing from the lateral portal. Asterisk marks the center of the trochlea.

FIGURE 5. An arthroscopic view from the lateral portal demonstrating lateral overhang of the patella over the lateral edge of the LFC. LFC indicates lateral femoral condyle.

The location of the incision for the TTT depends on the degree of anteriorization planned preoperatively. For steeper osteotomies, a more laterally based incision will help aid in visualizing the most posterior aspect of the cut to help protect the neurovascular structures. The incision is longitudinal and lateral to the edge of the tibial tuberosity if any degree of anteriorization is performed in addition to medicalization (Fig. 6). If a straight medialization is planned, the incision can lie more centrally over the tibial tubercle itself allowing protection of the skin for the flatter cut. Using sharp dissection, large full-thickness skin flaps are created down to the periosteum of the tubercle. Small parapatellar arthrotomies are made on either side of the patella tendon insertion. A Metzenbaum scissor is used to free the medial and lateral borders of the tendon so that it can be passed from medially to laterally, which ensures that the tendon is mobile so it can be protected during the transverse osteotomy cuts (Fig. 7).

FIGURE 6. An example of an incision for a left knee tibial tubercle osteotomy, longitudinal and lateral to the tibial tubercle. For steeper osteotomies, a more lateral incision will help aid in visu-

alizing the most posterior aspect of the tibial cut.

FIGURE 7. Metzenbaum scissors between the patella tendon distally and the anterior tibia.

FIGURE 8. Tibial shingle created with oscillating saw and osteotomes.

Next, the length and width of the shingle are marked medially using an electrocautery device. Laterally, the anterior compartment is subperiosteally elevated off the tibia and gently retracted using a periosteal elevator hugging the posterior cortex of the tibia. This protects the neurovascular structures. The desired shingle must be slightly wider than the patellar tendon proximally and at least 5 cm in length (Fig. 8). If a distalization is required, the shingle is extended to ~6 cm to allow for removal of distal bone (ostectomy) to normalize the CDI. Two single trocar short 0.045 inch K-wires are placed medially to lateral to serve as at emplate for the proposed trajectory and angle of the cut (Fig. 9). These should be angled in the anterior to posterior plan at either 30, 45, or 60 degrees depending on the amount of anteriorization desired. If only coronal plane correction is desired, then the K-wires would be placed parallel to the floor to achieve medialization alone.

FIGURE 9. Two K-wires mark the angle for tibial tubercle osteotomy. They serve as a template for the cut. Note the placement of a Cobb elevator retractor along the posterior cortex of the lateral tibia.

Broad periosteal elevators are gently placed around the postero-lateral edge of the tibia toretract the anterior compartment and periosteum. A 10-mm sagittal saw (40 mm in length) is then used to create a medially based cut between the 2 K-wires in the predetermined angle. The cut must progress in an anterior direction as it moves distally (as long as a distalization is not required) with care taken to maintain a periosteal hinge distally. The use of the saw is minimized to avoid the potential for heat necrosis, reducing the risk of delayed union or nonunion. An osteotome is used to complete the coronal cut and connect the cuts and then to make the transverse cut posterior and deep to the patella tendon just proximal to its distal insertion on the tibia. After completion of the cuts, the shingle should be free to toggle with the only remaining attachment being the distally based pedicle. A controlled Green stickfracture is invoked to free the distal portion of the pedicle.

The amount of medialization is determined preoperatively on the basis of the TT-TG. The distance of translation can be measured with an osteotome intraoperatively. The osteotome can be left in situ as a buttress to prevent loss of correction during tuberosity fixation or alternatively a K-wire can be used to provisionally secure the shingle while tracking is checked. Once the desired amount of translation has been determined, two 4.5 fully threaded compression screws are placed using the lag technique (3.2-mm drill bit for the threaded hole in the anterior cortex and 4.5-mm drill bit for the glide hole in the posterior cortex) in diverging directions (Fig. 10). This technique should achieve excellent compression of the shingle. The knee is then gently cycled to check patellar tracking. Care must be taken to preserve an adequate bone bridge between the 2 screws. Finally, fluoroscopy is used to check the length of both screws.

FIGURE 10. Ruler demonstrating translation of at least 12 mm after placement of 2 divergent screws.

COMPLICATIONS AND OUTCOMES

Though well described and touted for excellent results in the literature,5,43 the TTT procedure must be approached with caution. Minor complications include delayed wound healing, skin necrosis, superficial wound infections, skin irritation, and symptomatic hardware. More devastating complications include tibial fracture, fracture of the osteotomy shingle, osteotomy nonunion, overcorrection with resultant medial instability, and deep infection.44

CONCLUSIONS

TTT is a versatile operation that can be used to address amultitude of pathologies. The Maquet and the Elmslie-Trillat each correct only one plane. The AMZ procedure described by Fulkerson allows correction of both coronal plane malalignment and the unloading properties achieved by moving the tubercle anteriorly in the sagittal plane. The AMZ can be combined with a distalization in cases of severe patella alta to help address instability without increasing the PF contact forces (which is the result of a distalization if the tubercle is not anteriorized simultaneously).

TTT是一种多用途手术，可用于治疗多种病理。马克和埃尔姆斯利-特里亚各只对一个平面。Fulkerson描述的AMZ手术既可以矫正冠状面malalignment，也可以通过在矢状面向前移动结节来实现卸载。在严重高位髌骨的情况下，AMZ可与远端联合使用，以帮助解决不稳定问题，而不会增加PF接触力（如果结节未同时前化，这是远端操作的结果）。