Anatomical study of the medial patello-femoral ligament: landmarks for its surgical reconstruction

Purpose

The aim of this dissection study was to describe the anatomical insertions of the medial patello-femoral ligament (MPFL), and to assess its relationship with surrounding structures to improve its surgical reconstruction.

Methods

Twelve knees (7 cadavers) were included for the study. Measurements and general features of the MPFL were assessed: lengths, widths and insertions.

Results

The MPFL was found in all knees, presenting a triangular shape, and extending from the medial part of the patella to its femoral insertion (its length was of 59 ± 6.6 mm), distal to the adductor tubercle. The mean femoral insertion of the MPFL was 7.2 ± 2.7 mm proximal and 7.4 ± 4.0 mm posterior to the medial femoral epicondyle (MFE). It was also at a mean 11 ± 2.8 mm distal and 1.3 ± 2.1 mm posterior to the adductor tubercle, and 22 ± 6.4 mm anterior to the posterior condyle. We did not find any double-bundle organization on the patellar insertion. The width of the MPFL was 8.8 ± 2.9 mm at the femoral insertion, 27 ± 5.9 mm at the patellar insertion, and 12 ± 3.1 mm in the middle of the MPFL. The vastus medialis obliquus was found to be inserted on the superior part of the MPFL.

Conclusion

The adductor tubercle appeared to be a better landmark than the MFE for the femoral tunnel positioning during surgical reconstructions of the MPFL because it was easier to identify and its relationship with the femoral insertion of the MPFL was constant (10 mm below).     

The anterolateral ligament: Anatomic implications for its reconstruction

Background

The purpose of this study was to define the best anatomic parameters with which to perform an accurate anterolateral ligament (ALL) reconstruction. These parameters were anatomical insertions, allowing favorable isometry, length variation during flexion, and anthropometric predictors of ALL lengths.

Patellar resurfacing has minimal impact on in vitro tibiofemoral kinematics during deep knee flexion in total knee arthroplasty

BackgroundWhile patellar resurfacing can affect patellofemoral kinematics, the effect on tibiofemoral kinematics is unknown. We hypothesized that patellar resurfacing would affect tibiofemoral kinematics during deep knee flexion due to biomechanical alteration of the extensor mechanism.MethodsWe performed cruciate-retaining TKA in fresh-frozen human cadaveric knees (N = 5) and recorded fluoroscopic kinematics during deep knee flexion before and after the patellar resurfacing. To simulate deep knee flexion, cadaver knees were tested on a dynamic, quadriceps-driven, closed-kinetic chain simulator based on the Oxford knee rig design under loads equivalent to stair climbing. To measure knee kinematics, a 2-dimensional to 3-dimensional fluoroscopic registration technique was used. Component rotation, varus-valgus angle, and anteroposterior translation of medial and lateral contact points of the femoral component relative to the tibial component were calculated over the range of flexion.ResultsThere were no significant differences in femoral component external rotation (before patellar resurfacing: 6.6 ± 2.3°, after patellar resurfacing: 7.2 ± 1.8°, p = 0.36), and less than 1° difference in femorotibial varus-valgus angle between patellar resurfacing and non-resurfacing (p = 0.01). For both conditions, the medial and lateral femorotibial contact points moved posteriorly from 0° to 30° of flexion, but not beyond 30° of flexion. At 10° of flexion, after patellar resurfacing, the medial contact point was more anteriorly located than before patellar resurfacing.ConclusionDespite the potential for alteration of the knee extensor biomechanics, patellar resurfacing had minimal effect on tibiofemoral kinematics. Patellar resurfacing, if performed adequately, is unlikely to affect postoperative knee function.     

Femoral seating position of the EndoButton in single incision anterior cruciate ligament reconstruction: an anatomical study

Arthroscopic EndoButton fixation of anterior cruciate ligament (ACL) grafts over the femoral cortex has become popular in recent years. However, elongation of fixation materials has lead to tunnel enlargement, graft tunnel motion and instability. Synovial fluid passages along femoral tunnels following ACL reconstruction may result in destruction of tissues. The purpose of the present study was to identify the seating position of the EndoButton in regard to the boundaries of the knee capsule in single-incision arthroscopic ACL reconstruction. A total of 20 cadaveric knees were dissected and arthroscopic drill guides were used to create tibial and femoral tunnels. The distances between the exit points and boundaries of the suprapatellar bursa at three different degrees of knee flexion were measured. The average distances from the exit points to the superior boundaries of the suprapatellar bursa were 6.89 ± 5.40 mm (range, 16.87–1.21). However, in knee flexion of greater than 90°, tunnel exits were placed below the superior boundaries of the suprapatellar bursa (−7.08 ± 3.69 mm, range, −3.24 to −12.87). In order to place the EndoButton extraarticularly, a safe degree of knee flexion during femoral tunnel drilling was defined as 80°.     

Influence of knee flexion and femoral cross-pin insertion angle on posterolateral structures of the knee and lateral fixation lengths during ACL reconstruction

Purpose

Some studies have investigated knee flexion angle on the sagittal plane and insertion angle of the cross-pin on the coronal plane to evaluate proper femoral fixation. They evaluated the possibilities of injury to the posterolateral (PL) and neurovascular structures using several methods. The purposes of this study were to evaluate (1) the influence of knee flexion and femoral cross-pin insertion angles on knee PL structures and (2) the lateral fixation length of the cross-pin.

Methods

Ten fresh cadaveric knees with no previous surgeries around the knee were used. Transtibial femoral tunnels (1:30 or 10:30 o’clock position) were made at three different knee flexion angles (70°, 90°, and 110°). Two cross-pin guidewires (superior and inferior pins) were drilled at three different insertion angles [downward 30°, 0° (parallel to floor line), and upward 30°] for each knee flexion position. The distances from the insertion point of the two cross-pins to the lateral collateral ligament (LCL) and popliteus tendon (PT), and the distance from the lateral wall of the femoral tunnel to the lateral cortex of the femoral condyle were measured.

Results

No significant differences were observed in the superior and inferior pin depths (p?=?0.56 and 0.39). The distances from the superior pin to the LCL and from the inferior pin to the LCL were significantly shorter in all knee flexions with 0° and an upward 30° insertion angle than with 70° and 90° knee flexion with a downward 30° insertion angle, respectively (superior pin: p?=?0.02 and 0.03; inferior pin: p?=?0.03 and 0.03). No significant difference was observed in the distance between the superior pin and inferior pins and the PT (p?=?0.25).

Conclusions

The cross-pin was inserted close to the LCL and PT, and a downward 30° angle was the safest insertion angle. Lateral fixation length was sufficient for the cross-pin fixation in the 10:30- or 1:30-positioned femoral tunnel.     

髌骨沟的应用解剖

目的　为全膝关节成形术重建下肢正确力线提供解剖学基础。方法　在 40根干性股骨标本上用金属丝标记解剖轴、机械轴、髁上轴、经髁轴和髌骨沟全长 ,拍摄正位、侧位和轴位X线片 ,观测髌骨沟的弧长和弧度 ,髌骨沟与 4条基本轴线的角度。结果　髌骨沟的弧长和弧度变化幅度分别为 (2 0 .6± 1.8) (18.6～ 2 4.5 )mm和 115 .4°± 5 .6°(10 8.6°～ 118.4°) ;髌骨沟和股骨的 4条基本轴线的关系变化极大 ,变化范围在 10 .0°～ 16 .5°,髌骨沟最接近垂直干经上髁轴线。结论　在设计全膝人工关节股骨假体部分时 ,可参考髁上轴来确定髌骨沟的位置 ,使髌股关节能最大限度的匹配 ,减少术后并发症     

In-situ forces in the human posterior cruciate ligament in response to posterior tibial loading

Although some investigators have referred to the human posterior cruciate ligament (PCL) as the center of the knee, it has received less attention than the more frequently injured anterior cruciate ligament (ACL) and medial collateral ligament (MCL). Therefore, our understanding of the function of the PCL is limited. Our laboratory has developed a method of measuring thein-situ forces in a ligament without contacting that ligament by using a universal force-moment sensor (UFS). In this study, we attached a USF to the tibia and measuredin-situ forces of the human PCL as a function of knee flexion in response to tibial loading. At a 50-N posterior tibial load, the force in the PCL increased from 25±11 N (mean±SD) at 30° of knee flexion to 48±12 N at 90° of knee flexion. At 100 N, the corresponding increases were to 50±17 N and 95±17 N, respectively. Of note, at 30° knee flexion, approximately 45% of the resistance to posterior tibial loading was caused by contact between the tibia and the femoral condyles, whereas, at 90° of knee flexion, no resistance was caused by such contact. For direction of thein-situ force, the elevation angle from the tibial plateau was greater at 30° of knee flexion than at 90° of knee flexion. The data gathered on the magnitude and direction of thein-situ force of the PCL should help in our understanding of the dependence of knee flexion angle of the forces within the PCL.     

Modern femoral component design in total knee arthroplasty shows a lower patellar contact force during knee flexion compared with its predecessor

BackgroundThe relationship between the femoral component design in total knee arthroplasty (TKA) and the patellofemoral contact force, as well as the soft tissue balance, has not been well reported thus far.MethodsTwenty-eight mobile-bearing posterior-stabilized (PS) TKAs using the traditional model (PFC Sigma) and 27 mobile-bearing PS TKAs using the latest model (Attune) were included. Surgeries were performed using the measured resection technique assisted with the computed tomography (CT)-based free-hand navigation system. After all the trial components were placed, patellar contact forces on the medial and lateral sides were measured using two uniaxial ultrathin force transducers with the knee at 0°, 10°, 30°, 60°, 90°, 120°, and 135° of flexion. The joint component gap and the varus ligament balance of the femorotibial joint were also measured. The non-paired Student’s t-test was conducted to compare the values of the two groups.ResultsThe medial patellar contact force was significantly lower for Attune group than for PFC Sigma group at 120° of knee flexion (P = 0.0058). The lateral patellar contact force was also significantly lower for Attune group than PFC Sigma group at 120° and 135° of knee flexion (P = 0.0068 and P = 0.036). The joint component gap, as well as the varus ligament balance, showed no statistically significant difference between the two groups.ConclusionsReduced thickness and width of the anterior flange of the femoral component in the Attune may play a role in low patellar contact force.     

3T MRI-based anatomy of the anterolateral knee ligament in patients with and without an ACL-rupture: Implications for anatomical anterolateral ligament reconstruction

BackgroundAnterior cruciate ligament (ACL) rupture is often accompanied by an injury to the anterolateral ligament (ALL) of the knee. Detailed knowledge of the ALL attachments in ACL-ruptured patients is essential for an anatomical ALL reconstruction to avoid knee over-constraint and successfully treat the residual rotational instability. The aim of the present study was to investigate the three-dimensional (3D), topographic anatomy of the ALL attachment in both ACL-ruptured and ACL-intact patients using 3 Tesla magnetic resonance imaging (3T MRI).MethodsIn the present, retrospective case-control study, the magnetic resonance images of 90 knees with an ACL-rupture and 90 matched-controlled subjects, who suffered a non-contact knee injury without an ACL-rupture, were used to create 3D models of the knee. The femoral and tibial ALL footprints were outlined on each model, and their position was measured using an anatomical coordinate system.ResultsThe femoral origin of the ALL was located 4.9 ± 2.8 mm posterior and 3.8 ± 2.4 mm proximal to the lateral epicondyle in a non-isometric location in control subjects. In ACL-ruptured patients, it was located in a more posterior and distal, at 6.0 ± 1.9 mm posterior and 2.4 ± 1.7 mm proximal to the lateral epicondyle (p < 0.01), also in a non-isometric location. No difference was found in the tibial ALL insertion between groups.ConclusionThe femoral ALL origin was significantly different in ACL-ruptured patients compared to ACL-intact patients. The recommended femoral tunnel position for the anatomical ALL reconstruction, does not represent the femoral ALL origin in the ACL-ruptured knee.     

Interactive effect of femoral posterior condylar offset and tibial posterior slope on knee flexion in posterior cruciate ligament-substituting total knee arthroplasty

Background

This work aimed to evaluate the changes in the femoral posterior condylar offset (PCO) and tibial slope after posterior cruciate ligament (PCL)-substituting total knee arthroplasty (TKA), and to address the presence of any interactive effect between the two on knee flexion.

Anatomy and biomechanics of the medial patellofemoral ligament

The medial patellofemoral ligament (MPFL) is a band of retinacular tissue connecting the femoral medial epicondyle to the medial edge of the patella. The MPFL is approximately 55 mm long, and its width has been reported to range from 3 to 30 mm. The MPFL is overlaid by the distal part of vastus medialis obliquus to a variable extent, and fibres of MPFL merge into the deep aspect of the muscle. Despite the MPFL being very thin, it had a mean tensile strength of 208 N, and has been reported to be the primary passive restraint to patellar lateral displacement. Lateral patellar displacement tests in vitro showed that the patella subluxed most easily at 20 degrees knee flexion. The contribution of the MPFL to resisting patellar lateral subluxation was greatest in the extended knee. This finding was linked to the retinaculae being tightest in full knee extension, and slackening with flexion.     

改进Herbert螺钉修复髌韧带断裂的实验研究

目的　采用改进的Herbert螺钉修复髌韧带断裂,对其修复强度进行生物力学检测,明确该方法是否优于目前临床常用的骨钻孔修补法。方法　(1)22只新鲜羊膝关节标本在靠近胫骨结节6mm处切断髌韧带。分成两组,螺钉组和缝合组,分别对髌韧带进行修补缝合。测量缝合后髌韧带断裂时瞬间拉力和最大承受拉力。(2)11只活体狗手术切断双侧后腿髌韧带后,分别用螺钉和单纯缝合方法进行修补,4周后观察韧带愈合情况,并进行力学测试。结果　(1)螺钉组羊髌韧带缝合后断裂平均瞬间拉力为(71.13±14.23)N,缝合组为(46.09±8.41)N,两组间有显著差异(P<0.05)。螺钉组的平均最大拉力为(80.46±11.73)N,缝合组为(54.60±9.79)N,两组间亦有显著差异(P<0.05)。(2)活体狗螺钉组髌韧带完全愈合5例,缝合组2例。螺钉组平均断裂瞬间拉力为(202.99±12.17)N,缝合组为(162.41±15.80)N(P<0.05)。螺钉组最大拉力为(219.69±15.73)N,缝合组为(177.92±15.31)N(P<0.05)。结论　对于近止点的韧带断裂,改进的Herbert螺钉优于骨钻孔修补方法。     

The importance of femoral intramedullary entry point in knee arthroplasty

The purpose of this cadaveric study was to investigate how alignment of the femoral component in knee arthroplasty may be influenced by the entry site of the femoral intramedullary alignment rod. The angle between the rod and the distal femoral articular surface was measured in 20 non-arthritic cadaveric femurs using three different entry points. Entry points 10 mm anterior to the intercondylar notch and 8 mm medial to this point gave mean valgus angles of 8° (S.D. 1.0) and 10.2° (S.D. 1.0), respectively. Regression analysis showed no relationship between sex of the patient, body habitus, or leg length and valgus angulation of the distal femur. For total knee replacement in which the tibia is cut perpendicular to its axis in the coronal plane, thus eliminating 3° of tibial varus, we recommend using a femoral valgus angle of 5° with a hole anterior to the intercondylar notch and 7° with an anteromedial hole. Resecting the distal femur as recommended should enhance accuracy of component placement and survival of knee arthroplasties.     

股四头肌腱的临床应用解剖

目的　为临床应用股四头肌腱重建膝关节交叉韧带提供临床解剖学资料。 方法　在10具成人尸体标本上（20只膝关节）解剖观察股四头肌腱的形态和走行关系以及在髌骨附着点的解剖学特点,测量股直肌腱起止点宽度、长度以及髌骨上极的厚度。 结果　股直肌止点的宽度为（3.20±0.33）cm。起点的宽度为（1.28±0.25）cm。完全为腱性组织的长度为（6.96±0.80）cm。股直肌腱近侧端约4/5完全游离,远侧端约1/5与股外侧肌和股中间肌融合,共同构成股四头肌腱,附着于髌骨上极前方约3/4部分。髌上极的平均厚度为(2.22±0.14)cm。 结论　股四头肌腱的的解剖学特点,完全使其可以作为临床上行膝关节交叉韧带重建的供区之一。     

Influence of stem length on component flexion and posterior condylar offset in revision total knee arthroplasty

Background

Hyperextension of the femoral component and excessive slope of the tibial component may delay the cam–post engagement in semi-constrained revision total knee arthroplasty (TKA). Further, it may compromise the posterior condylar offset (PCO). No prior study has determined whether a short 50-mm stem, or longer stems (100 mm and 150 mm) lead to less hyperextension of the femoral component or excessive slope and its influence on the posterior condylar offset.

内侧髌股韧带重建治疗复发性髌骨脱位疗效观察

目的 探讨内侧髌股韧带重建治疗复发性髌骨脱位的临床效果.方法 回顾性分析湖北省荆州市中心医院2017年1月至2019年6月通过关节镜辅助下内侧髌股韧带双束重建治疗的29例复发性髌骨脱位患者的临床资料.其中,男10例,女19例,年龄14.0～29.5岁,平均19.4岁.测量TT-TG距离、髌骨倾斜角,计算Caton指数....     

Recutting the distal femur to increase maximal knee extension during TKA causes coronal plane laxity in mid-flexion

BackgroundThe aim of this study was to quantify the effects of distal femoral cut height on maximal knee extension and coronal plane knee laxity.MethodsSeven fresh-frozen cadaver legs from hip-to-toe underwent a posterior stabilized TKA using a measured resection technique with a computer navigation system equipped with a robotic cutting guide. After the initial femoral resections were performed, the posterior joint capsule was sutured until a 10° flexion contracture was obtained with the trial components in place. Two distal femoral recuts of + 2 mm each were then subsequently made and the trials were reinserted. The navigation system was used to measure the maximum extension angle achieved and overall coronal plane laxity [in degrees] at maximum extension, 30°, 60° and 90° of flexion, when applying a standardized varus/valgus load of 9.8 [Nm] across the knee.ResultsFor a 10 degree flexion contracture, performing the first distal recut of + 2 mm increased overall coronal plane laxity by approximately 4.0° at 30° of flexion (p = 0.002) and 1.9° at 60° of flexion (p = 0.126). Performing the second + 2 mm recut of the distal femur increased mid-flexion laxity by 6.4° (p < 0.0001) at 30° and 4.0° at 60° of flexion (p = 0.01), compared to the 9 mm baseline resection (control). Maximum knee extension increased from 10° of flexion to 6.4° (± 2.5° SD, p < 0.005) and to 1.4° (± 1.8° SD, p < 0.001) of flexion with each 2 mm recut of the distal femur.ConclusionsRecutting the distal femur not only increases the maximum knee extension achieved but also increases coronal plane laxity in midflexion.     

The effect of medial condylar bone loss of the knee on coronal plane stability--a cadaveric study

IntroductionThe quantitative effects of medial bone loss of the knee on both leg alignment and coronal plane stability are poorly understood.Materials and methodsUtilizing computer navigation, 5 mm bone defects of the medial distal femur (MDF), medial posterior femoral condyle (MPF), and medial tibial plateau (MT) were simulated in 10 cadaveric limbs, and alignment of the knee at various degrees of flexion were analyzed when applying standardized varus and valgus loads.ResultsThe 5 mm MPF defect significantly increased varus laxity at 90° of flexion by 3.3° ± 1.2° (p = 0.019), a 5 mm MDF defect resulted in a 2.2° ± 1.7° (p = 0.037) and a 2.1° ± 1.3° (p = 0.023) increase in laxity at 0° and 30° of flexion, respectively, and a 5 mm MT defect increased varus laxity at all flexion angles by 4.0° to 7.0°, but was only statistically significant at 30° (p = 0.026).DiscussionThis study confirms and quantifies the theories of flexion and extension gap balancing, and pseudolaxity of the medial collateral ligament in the varus knee, the results of which can be used in preoperative planning and intraoperative decision making for both total knee and unicondylar arthroplasty.     

Predictors of patellar alignment during weight bearing: An examination of patellar height and trochlear geometry

BackgroundPatellar malalignment is thought to be an etiological factor with respect to the development of patellofemoral pain. Although previous studies have suggested that the geometry of the femoral trochlea and the height of the patella play an important role in determining patellar alignment, no investigation has systematically examined these relationships during weight bearing. The aim of this study was to determine whether patellar height and/or trochlear geometry predicts patellar alignment (lateral patellar displacement and lateral patellar tilt) during weight bearing.MethodsMR images of the patellofemoral joint were acquired from 36 participants during weight bearing (25% of body weight) at 4 knee flexion angles (0°, 20°, 40° and 60°). Using the axial images, patellar alignment (lateral displacement and tilt) and femoral trochlear geometry (sulcus angle and inclination of the lateral femoral trochlea) were measured. Patellar height (Insall–Salvati ratio) was measured on reconstructed sagittal plane images.ResultsStepwise regression analysis revealed that at 0° of knee flexion, the height of the patella was the best predictor of lateral patellar tilt while the lateral trochlea inclination angle was the best predictor of lateral patellar displacement. Lateral trochlear inclination was the best predictor of patellar lateral displacement and tilt at 20°, 40° and 60° of knee flexion.ConclusionSimilar to a previous study performed under non-weight bearing condition, our findings suggest that lateral trochlear inclination is an important determinant of patellar alignment in weight bearing.Level of EvidenceLevel III     

Femoral articular geometry and patellofemoral stability

Background

Patellofemoral instability is a major cause of anterior knee pain. The aim of this study was to examine how the medial and lateral stability of the patellofemoral joint in the normal knee changes with knee flexion and measure its relationship to differences in femoral trochlear geometry.