胫骨旋转对髌股关节应力分布的影响

为探明胫骨旋转畸形对髌股关节应力分布的影响,本实验选取7个新鲜离体膝关节,在屈膝30°、60°、90°状态下,分别用压敏片测量胫骨中立位、内旋10°、20°、30°和外旋10°、20°、30°时的内、外侧髌股关节接触压力与峰值。结果显示外旋过程中,外侧髌股关节的接触压均值和接触压峰值呈非线性递增趋势,内侧呈非线性递减趋势;内旋过程中,外侧髌股关节的接触压均值和峰值逐渐减小,内侧则增加显著。上述变化在内旋20°到外旋20°的范围内较有规律。提示胫骨旋转畸形使髌股关节应力分布严重失衡,可能是引起髌股关节退变的重要因素。     

胫骨结节抬高内移术的生物力学研究

目的:探讨胫骨结节抬高内移术后膝关节在不同屈曲角度下髌股关节面接触面积和接触压力的变化.方法:选用8具新鲜离体膝关节标本,测量胫骨结节抬高术和胫骨结节抬高内移术前后膝关节Q角角度,并分别采用压敏片和染色法测试两种手术前后髌股关节接触面积、接触部位和应力分布的变化.结果:胫骨结节抬高内移(1.0cm)术后,Q角变小,接触面积减小,接触部位上移,腱股接触提早出现(54.6°),小屈膝角度(30°～60°)时接触压力明显减小,各屈膝角度下外侧关节面的接触压力均向内侧转移.以上变化与胫骨结节抬高术后的变化有明显差异.胫骨结节抬高内移0.5cm时,髌骨接触面积、部位、接触压力变化较小,无明显治疗意义.抬高内移达1.5cm时可造成髌骨内倾斜、髌骨不稳等严重的解剖关系紊乱.结论:胫骨结节抬高内移各1.0cm是较适宜的范围,可矫正髌骨外倾斜,改变髌股习惯接触部位,减轻髌股(尤其外侧关节面)接触压力,重新分布接触压力,腱股接触(55°左右)提早出现.以上变化可矫正髌股关节的解剖紊乱,对临床治疗髌骨软化症有一定意义.     

股骨髁髌股、胫股关节运动重叠接触区域及其生物力学测定

目的 :明确膝关节运动时胫骨、髌骨与股骨髁接触的重叠区域 ,测量并比较分析重叠区域内髌股、胫股关节各自接触压大小及分布特点 ,探讨髌股关节置换术中股骨滑车假体长度的设计。方法 :收集 8具新鲜膝关节尸体标本 ,在Instron 85 0 1生物力学测试仪上构建实验平台 ,模拟生理状态下膝关节站立到下蹲屈膝的过程 ,采用染色法描记重叠区域、压敏法测量髌股、胫股关节在该区域接触压。结果 :股骨髁关节面存在髌股、胫股关节运动重叠接触区域 ,范围大致相当股骨髁髌股关节接触区域内、始于屈膝 75°髌股接触部的后部分区域 ;重叠区域内髌股、胫股关节各自接触压测定显示 ,前者的接触压明显高于后者。结论 :股骨滑车假体的有效长度应涵盖髌股关节在股骨髁所有接触区域。     

CT在评估髌股关节排列中的应用

目的介绍和分析利用ＣＴ评估髌股关节排列的方法和价值。方法在屈膝３０°时用ＣＴ检测３２例５０侧膝髌股关节疼痛者（轴位Ｘ线片上髌股排列基本正常）和１５例２０侧膝无症状者的髌股关节,测量其髁间沟角、和谐角及外侧髌股角,观察病变在ＣＴ上的表现,分析髌股关节疼痛患者的髌股排列状况。结果髌股关节疼痛患者较无症状者具有较明显的髌股排列紊乱,单纯髌骨外置者１１侧膝,单纯髌骨倾斜者８侧膝,髌骨外置合并髌骨倾斜者１０侧膝。结论利用ＣＴ评估髌股关节排列较普通Ｘ线片有显著的优越性,可指导治疗的术式选择     

Q角对髌股关节接触力学的影响

本研究应用染色法和压敏片法,对8例新鲜尸体膝关节在不同Q角和屈膝角度时的髌股接触部位、面积和应力分布进行测试。结果表明:在生理Q角状态下,随着屈膝角度的增大,髌股接触从髌后关节面下极逐渐向上极移行,接触面积也逐渐增大,接触应力呈渐进缓慢增加:并在屈膝80°—90°时出现腱股接触现象,这种现象对保护关节软骨,避免局部软骨压力过高有重要意义。Q角改变后,接触区向内或向外侧偏移,接触面积无明显改变,但接触应力变化显著。作者认为异常的Q角是导致髌股疾病的一个潜在因素,无论是手术矫治还是运动员选材时都应予以重视。     

髌股关节CT测量参数的比较

目的探讨7个反映髌股关节排列关系参数的叠加法测量和单层法测量可信度.方法 15名前膝疼痛患者的30个膝关节,在屈膝0°和30°股肌松弛状态下,分别用CT图像叠加法和单层法测量髌股关节紊乱的7个参数,测量采用盲法重复,并应用组内相关系数(ICC)评价测量可重复性. 结果在屈膝0°和30°叠加测量法和单层测量法的外侧髌骨角(LPA)、髌骨倾斜角(PTA),以及叠加法的适合角(CA)、股骨滑车角(FTA)具有高可信度(ICC>0.9),单层法的CA在屈膝30°下可信度高(ICC>0.9).结论 CT图像叠加法测量LPA、PTA、CA、FTA有好的可重复性.     

髌骨不稳治疗的生物力学

髌骨不稳治疗的生物力学上海第二军医大学附属长征医院骨科（２００００３）范大鹏综述包聚良审校髌骨不稳指膝关节伸屈活动时髌骨外移程度加大。当伸直膝关节，髌骨波动外推超过自身宽度的１／２；屈膝３０°时，外推髌骨超过１ｃｍ，或轴位片上两侧髌股关节间隙相差超过...     

胫骨结构抬高术治疗髌股软骨病机理的研究

为客观评价胫骨结节抬高术治疗髌股软骨病的机理,采用Ｆｕｉｊ压敏片测压力和染色法测面积相结合,共测试８具新鲜离体膝关节标本,比较胫骨结节抬高术前后的髌股接触部位、面积和应力分布。发现胫骨结节抬高术后,髌骨的习惯性接触区位置向近端移行,这种现象有助于避开对软骨病灶区的挤压和应力集中,对缓解和消除髌股疼痛症状可能有利。因此,提出了“应力集中传导至软骨损伤区导致髌股疼痛”的设想。胫骨结节抬高术后,小屈膝角度（３０°－６０°）有一定的髌股减压作用,但随屈膝角度增加,髌股接触面积减小并出现压力分布不均或局部高压现象。胫骨结节抬高术后,“腱股接触”现象提早（６０°）出现,对髌股关节生物力学行为可能造成影响。     

人类髌股关节三维运动规律的研究

本实验通过精密机械式三维位移测量方法，采用１０条新鲜离体人膝关节标本定标加载，分析研究了屈膝过程中的髌股关切运动学及Ｑ角变化对髌股关节运动的影响。结果发现，人类髌股关切具有复杂而有规律性的三维运动特点，对传统认为“髌骨具二维运动”的观点提出了修正。同时发现，Ｑ角异常增大或减小，虽然对髌股运动趋势无显著影响，但可影响髌股运动幅度从而影响髌股稳定性。髌骨的许多特征运动均发生在屈膝３０°之前，髌骨此时也最不稳定，容易受到伤害提示临床手术治疗、护具设计及运动员选材时应予重视。     

髌骨位姿异常对髌股关节接触影响的研究

目的 深入研究髌骨位姿异常对髌股关节的接触影响.方法 通过正常膝关节MRI图像数据建立了髌股关节的正常和异常接触模型,基于正交试验对不同水平的髌股关节异常接触模型进行了有限元仿真模拟.结果 1)在膝关节屈曲过程中,髌股关节接触特性(Von Mises应力、接触压力和接触面积)对髌骨的屈曲和旋转参数最为敏感;2)髌股异常...     

The effect of bracing on patella alignment and patellofemoral joint contact area

PURPOSE: To examine the influence of two patellofemoral braces on pain response, patellar alignment, and patellofemoral joint contact area in persons with patellofemoral pain. METHODS: Fifteen women between the ages of 18 and 45 yr with a diagnosis of patellofemoral pain participated. After the assessment of pain response using a visual analog scale, subjects underwent axial plane magnetic resonance imaging of patellofemoral joint at 0 degrees, 20 degrees, 40 degrees, and 60 degrees of knee flexion. Imaging was done with the knee extensors contracted (25% body weight) under three conditions: 1) no brace, 2) On-Track brace, and 3) Patellar Tracking Orthosis (PTO). Measures of mediolateral patellar displacement and tilt and medial and lateral facet contact area were obtained from the magnetic resonance images. RESULTS: On average, the On-Track brace reduced symptoms by 50%, whereas the PTO reduced pain by 44%. When averaged across all knee flexion angles, the PTO and the On-Track brace significantly increased total patellofemoral joint contact area by 52.0 mm (21%) and 59.3 mm (24%), respectively, when compared with the no-brace condition. Bracing had no influence on lateral patellar tilt; however, small but significant changes in lateral patellar displacement were observed. CONCLUSION: Large changes in pain and contact area occurred without sizable changes in patellar alignment. The results of this study suggest that changes in patellar alignment by itself may not be responsible for pain alleviation after patellar bracing.     

Effect of bracing on patellar kinematics in patients with patellofemoral joint pain

PURPOSE: Bracing is commonly used to correct patellar malalignment syndromes. However, there are little objective data documenting the effect of such supports on patellofemoral joint relationships. The purpose of this study was to assess the effectiveness of an elastic patellofemoral sleeve brace in altering patellar tracking in subjects with patellofemoral pain. METHODS: Ten female subjects (12 patellofemoral joints) between the ages of 17 and 46 participated in this study. All subjects had a diagnosis of patellofemoral pain and demonstrated lateral patellar tracking based on magnetic resonance imaging (MRI) assessment. Each subject underwent kinematic MRI of the patellofemoral joint through a range of 45 to 0 degrees of knee flexion against a resistance of 15% body weight. Imaging was performed with and without a patellofemoral joint brace (Bauerfeind Genutrain P3 brace, Atlanta, GA). Measurement of medial/lateral patellar displacement, medial/lateral patellar tilt, and the depth of the trochlear groove (sulcus angle) were obtained with midpatellar image sections at 45, 36, 27, 18, 9 and 0 degrees of knee flexion. RESULTS: No statistically significant differences in medial/lateral patellar displacement or tilt were found between braced and unbraced trials across all knee flexion angles (P < 0.05). A small but statistically significant increase in sulcus angle was found across all knee flexion angles with the braced trials (P > 0.05). CONCLUSIONS: These results do not support the hypothesis that the brace used in this study corrects patellar tracking patterns in subjects with patellofemoral pain. However, the increased sulcus angle indicates a change in patella position within the trochlea. It is possible that the clinical improvements seen with bracing may be the result of subtle differences in joint mechanics and not gross changes in alignment.     

Axial and lateral radiographs in evaluating patellofemoral malalignment.

This is a prospective study of 431 patients (862 knees) with patellofemoral pain, patellar dislocation, or other abnormalities of the knee joint. There were 217 asymptomatic knees with no contralateral problems for comparison. All patients had a history and physical and radiographic examination of both knees. The radiographs included standard anteroposterior views, axial views at 30 degrees of knee flexion, and standing lateral views at 0 degree and 30 degrees of flexion. The presence of patellar tilt or subluxation was noted on the axial view. The lateral view of the patella, with precise overlap of the posterior femoral condyles, allowed determination of relationships between the patella's medial edge, median ridge, and lateral edge to assess patellar tilt. Sixty-two percent of patients with patellar dislocations demonstrated subluxation on the axial view, while 98% demonstrated an abnormal lateral view. Eighteen percent of the control knees revealed evidence of subluxation on the axial view while 35% demonstrated subluxation on the extended lateral view. The axial view demonstrated 62% sensitivity for dislocation, while the lateral view taken in full extension demonstrated 98% sensitivity. The specificity for previous dislocation was 82% for the axial view and 93% for the lateral flexed view. Given the high sensitivity of the lateral view for detecting prior patellar dislocation, a normal result on this view can virtually eliminate the question of previous dislocation. Also, with the high specificity of the axial view and lateral view with knee flexion, the two views combined can confirm a clinical impression of patellofemoral malalignment.     

Effect of patellar tendon shortening on tracking of the patella

BACKGROUND: Although 10% postoperative patellar tendon shortening after bone-patellar tendon-bone autograft reconstruction of the anterior cruciate ligament has been reported, there are no published studies assessing the effect of shortening on patellofemoral joint biomechanics under physiological loading conditions. PURPOSE: To investigate the influence of patellar tendon shortening on patellofemoral joint biomechanics. STUDY DESIGN: Controlled laboratory study. METHODS: The authors evaluated the patellofemoral contact area, the location of contact, and the patellofemoral joint reaction force and contact stresses in 7 cadaveric knees before and after 10% patellar tendon shortening. Shortening was achieved using a specially designed device. Experimental conditions simulating those occurring during level walking were employed: physiological quadriceps loads and corresponding angles of tibial rotation were applied at 15 degrees , 30 degrees , and 60 degrees flexion of the knee. Patellofemoral joint contact areas were measured before and after shortening using the silicone oil-carbon black powder suspension squeeze technique. RESULTS: After patellar tendon shortening, patellofemoral joint contact areas were displaced proximally on the patellar surface and distally on the femoral surface. Although the contact area increased by 18% at 15 degrees of knee flexion (P = .04), no significant change occurred at 30 degrees or 60 degrees of knee flexion (P > .05). Patellofemoral contact stress remained unchanged after patellar tendon shortening (P > .05) at each flexion angle. CONCLUSION: Our results suggest that a 10% shortening of the patellar tendon does not alter patellar contact stresses during locomotion. It is not clear whether apparent changes in contact location in all positions and contact area at 15 degrees would have clinical consequences.     

The effects of removal and reconstruction of the anterior cruciate ligament on the contact characteristics of the patellofemoral joint.

Seven cadaveric knees were used to investigate the effects of removal and reconstruction of the anterior cruciate ligament with a bone-patellar tendon-bone graft on contact characteristics of the patellofemoral joint during physiologic levels of quadriceps muscle loads at 30 degrees, 60 degrees, and 90 degrees of knee flexion. Loads were applied to the quadriceps tendon to equilibrate externally applied flexion moments equivalent to one-third of values for maximum isometric extension moments. Patellofemoral contact areas and pressures were measured using pressure-sensitive film. Excision of the anterior cruciate ligament resulted in significant decreases in the total patellofemoral contact area by as much as 94 mm2 (68%), the medial facet contact area by as much as 55 mm2 (93%), the combined average contact pressure by 0.7 MPa (21%), the medial facet average contact pressure by 2.3 MPa (70%), the combined peak contact pressure by 3.0 MPa (38%), and the medial facet peak contact pressure by 5.4 MPa (76%), all at 30 degrees of knee flexion. Excision of the anterior cruciate ligament also resulted in significant decreases in total, medial facet, and lateral facet patellofemoral contact areas at 60 degrees and 90 degrees of knee flexion. Intraarticular reconstruction returned these to levels not significantly different from those of the intact knee.     

Allowing one quadrant of patellar lateral translation during medial patellofemoral ligament reconstruction successfully limits maltracking without overconstraining the patella

Purpose

Graft tensioning during medial patellofemoral ligament (MPFL) reconstruction typically allows for lateral patellar translation within the trochlear groove. Computational simulation was performed to relate the allowed patellar translation to patellofemoral kinematics and contact pressures.

Methods

Multibody dynamic simulation models were developed to represent nine knees with patellar instability. Dual limb squatting was simulated representing the pre-operative condition and simulated MPFL reconstruction. The graft was tensioned to allow 10, 5, and 0 mm of patellar lateral translation at 30° of knee flexion. The patellofemoral contact pressure distribution was quantified using discrete element analysis.

Results

For the 5 and 10 mm conditions, patellar lateral shift decreased significantly at 0° and 20°. The 0 mm condition significantly decreased lateral shift for nearly all flexion angles. All graft conditions significantly decreased lateral tilt at 0°, with additional significant decreases for the 5 and 0 mm conditions. The 0 mm condition significantly increased the maximum medial pressure at multiple flexion angles, increasing by 57% at 30°, but did not alter the maximum lateral pressure.

Conclusions

Allowing 5 to 10 mm of patellar lateral translation limits lateral maltracking, thereby decreasing the risk of post-operative recurrent instability. Allowing no patellar translation during graft tensioning reduces maltracking further, but can overconstrain the patella, increasing the pressure applied to medial patellar cartilage already fibrillated or eroded from an instability episode.

     

Changes in patellar alignment after total knee arthroplasty

Although the results of total knee arthroplasty continue to improve, problems related to the patellofemoral joint remain significant. This study examined the factors affecting patellar alignment after total knee arthroplasty and subsequent changes in 56 knees during a postoperative period of 5.3 years. None of the knees examined displayed any clinical complications of the patellofemoral joint; no revision surgeries were necessary, with acceptable patellar alignment on average. The patellar resection angle had a strong influence on patellar alignment. Thinning of the patellar remnant on the medial side can increase postoperative lateral tilt, which leads to a need for lateral retinacular release. Although the changes in patellar alignment were minimal, the tendency that postoperative varus alignment resulted in patellar lateral tilt was observed. As postoperative femorotibial misalignment can lead to patellofemoral problems after total knee arthroplasty, surgeons need to pay scrupulous attention to femorotibial alignment and proper patellar preparation to decrease patellofemoral complications.     

Dynamic measurement of patellofemoral kinematics and contact pressure after lateral retinacular release: an in vitro study

The purpose of this study was to investigate the influence of lateral retinacular release and medial and lateral retinacular deficiency on patellofemoral position and retropatellar contact pressure. Human knee specimens (n = 8, mean age = 65 SD 7 years, all male) were tested in a kinematic knee-simulating machine. During simulation of an isokinetic knee extension cycle from 120° to full extension, a hydraulic cylinder applied sufficient force to the quadriceps tendon to produce an extension moment of 31 Nm. The position of the patella was measured using an ultrasound based motion analysis system (CMS 100^®, Zebris). The amount of patellofemoral contact pressure and its pressure distribution was measured using a pressure sensitive film (Tekscan^®, Boston). Patellar position and contact pressure were first investigated in intact knee conditions, after a lateral retinacular release and a release of the medial and lateral retinaculum. After lateral retinacular release the patella continuously moved from a significant medialised position at flexion (P = 0.01) to a lateralised position (P = 0.02) at full knee extension compared to intact conditions, the centre of patellofemoral contact pressure was significantly medialised (0.04) between 120° and 60° knee flexion. Patellofemoral contact pressure did not change significantly. In the deficient knee conditions the patella moved on a significant lateralised track (P = 0.04) through the entire extension cycle with a lateralised centre of patellofemoral pressure (P = 0.04) with a trend (P = 0.08) towards increased patellofemoral pressure. The results suggest that lateral retinacular release did not inevitably stabilise or medialise patellar tracking through the entire knee extension cycle, but could decrease pressure on the lateral patellar facet in knee flexion. Therefore lateral retinacular release should be considered carefully in cases of patellar instability.     

The effect of harvesting the central one-third of the patellar tendon on patellofemoral contact pressure.

This study assessed whether removing the central one-third of the patellar tendon, with or without side-to-side repair of the patellar tendon defect, would alter patellofemoral pressure. Patellofemoral pressure was assessed by testing five stable knees from five different cadaveric donors on a specially designed hydraulic knee machine. Patellofemoral joint pressures were measured by placing pressure-sensitive film into the patellofemoral articulation. The joint was loaded in a static fashion, with quadriceps forces consistent with walking (647 N) and stair climbing (1923 N), at 30 degrees, 60 degrees, and 90 degrees of knee flexion. Using the same knees, the central one-third of the patellar tendon was then sectioned, and patellofemoral joint pressure measurements were repeated at identical knee flexion angles and quadriceps-forces. Side-to-side repair of the patellar tendon defect was performed and patellofemoral joint pressure measurements were repeated. There were no statistically significant differences between the control and sectioned values or between the control and repaired defect values. These results suggest that harvesting the central one-third of the patellar tendon--with or without side-to-side repair of the patellar tendon defect--does not alter patellofemoral pressures.