前交叉韧带损伤膝关节侧副韧带长度的变化

背景:侧副韧带对膝关节的稳定性起着重要的作用,通过2D/3D图像配准技术可以实现膝关节的运动还原并获得前交叉韧带损伤后生理屈曲过程中内侧副韧带和外侧副韧带长度变化规律.目的:对前交叉韧带损伤膝关节侧副韧带长度变化进行运动还原体内稳定性研究.方法:选择单侧膝关节前交叉韧带断裂而对侧正常的8例患者,在生理负重屈曲采集0°,15°,30°,60°和90°时的相互垂直的2D图像,与CT(3D)图像在虚拟X射线投射系统进行2D/3D图像配准,还原膝关节不同角度时的股骨和胫骨相对3D位置关系,并通过韧带止点还原的方法对内侧副韧带、外侧副韧带进行韧带长度分析,并对比两侧.结果与结论:内侧副韧带损伤后在0°,15°和30°患膝内侧副韧带长度较健膝增加;内侧副韧带损伤后在0°、15°和30°患膝外侧副韧带长度较健膝减少,差异均有显著性意义(P＜0.05).结果提示,在0°、15°和30°,前交叉韧带损伤后患膝内侧副韧带长度较健膝增加,而外侧副韧带长度较健膝缩短.     

On the coupling between anterior and posterior cruciate ligaments,and knee joint response under anterior femoral drawer in flexion: a finite element study

OBJECTIVE: To investigate the extent of coupling between the anterior and posterior cruciate ligaments as well as the role of the posterior cruciate ligament in the knee joint response under anterior femoral force at different flexion angles. DESIGN: A developed finite element model of the tibiofemoral joint is used to perform non-linear elastostatic analyses. BACKGROUND: The structural properties of the posterior cruciate ligament subsequent to an injury (either left untreated or replaced by a graft) would likely change, an event that alters the function of not only the ligament itself but also the other intact cruciate ligament and the entire joint. METHODS: The model consists of two bony structures and their articular cartilage layers, menisci and four principal ligaments. Under 100 N anterior femoral load at different flexion angles from 0 degrees to 90 degrees, kinematics, forces in ligaments and contact forces in the fully unconstrained joint were computed in intact cases and following alterations in joint ligaments. RESULTS: Collateral ligaments were the primary structures to resist the force at full extension under 100 N anterior femoral load with a moderate contribution from the posterior cruciate ligament. With joint flexion up to 90 degrees, however, force in the posterior cruciate ligament substantially increased whereas that in collateral ligaments diminished. CONCLUSIONS: A remarkable coupling was found between the posterior cruciate ligament and the anterior cruciate ligament in flexion; a structural alteration in one of them significantly influenced the mechanical role of both ligaments and not just the one affected. A tauter or stiffer ligament increased the force in both ligaments while an excessive laxity or rupture in one diminished forces in both. RELEVANCE: Alterations in ligament stiffness or initial tautness during reconstruction surgery or following injuries markedly influence the normal role of both cruciate ligaments. Consideration of cruciate ligaments coupled together rather than in isolation should be the rule in the management of ligament injuries towards a successful long-term outcome.     

Effects of the posterior cruciate ligament reconstruction on the biomechanics of the knee joint: a finite element analysis

BACKGROUND: Previous experimental studies have been conducted to evaluate the biomechanical effects of posterior cruciate ligament reconstruction; but no consensus has been reached on the preferred method of reconstruction. METHODS: The 3D finite element mesh of a knee joint was reconstructed from computed tomography and magnetic resonance images. The ligaments were considered as hyperelastic materials. The tibiofemoral and patellofemoral joints were modeled with large sliding contact elements. The 3D model was used to simulate knee flexion from 0 degrees to 90 degrees in four cases: a knee with a "native" posterior cruciate ligament, a resected posterior cruciate ligament, a reconstructed single graft posterior cruciate ligament, and a reconstructed double graft posterior cruciate ligament. FINDINGS: A resected posterior cruciate ligament induced high compressive forces in the medial tibiofemoral and patellofemoral compartments. The pressures generated in the tibiofemoral and patellofemoral compartments were nearly the same for the two reconstruction techniques (single graft and double graft). The single graft resulted in lower tensile stresses inside the graft than for the double graft. INTERPRETATION: Firstly, a resected posterior cruciate ligament should be replaced to avoid excessive compressive forces, which are a source of cartilage degeneration. Secondly, the two types of posterior cruciate ligament reconstruction techniques partially restored the biomechanics of the knee in flexion, e.g. contact pressures were restored for pure flexion of the knee. The reconstruction techniques therefore partially restore the biomechanics of the knee in flexion. A double graft reconstruction is subjected to the highest tensile stresses.     

Dynamic in vitro measurement of posterior cruciate ligament load and tibiofemoral stress after TKA in dependence on tibiofemoral slope

BACKGROUND: To prevent excessive tension on the posterior cruciate ligament, some knee prosthesis-systems offer the option of creating a posterior tibiofemoral slope of the tibial component. The objective of this study was to investigate the effect of the amount of tibiofemoral slope on the posterior cruciate ligament load and tibiofemoral contact stress after total knee arthroplasty under isokinetic in vitro conditions. METHODS: Twelve fresh frozen knee specimens were tested in a knee simulator. After implantation of the Interax I.S.A. knee prosthesis-system with a mobile bearing inlay, a bow shaped load transducer was fixed in the medial fibres of the posterior cruciate ligament. A pressure sensitive film was fixed on the femoral inlay surface. The test cycle simulated an isokinetic extension cycle from 120 degrees of flexion to full extension. First, posterior cruciate ligament load and tibiofemoral peak contact stress were measured with the tibial component implanted with a neutral tibial slope and then with 10 degrees posterior slope. FINDINGS: After implantation of the tibial component without tibial slope, posterior cruciate ligament load reached a maximum load of 29.5 N (SD 17.1 N) at 97.8 degrees knee flexion. Tibiofemoral contact stress on the medial compartment reached a maximum of 11.9 MPa (SD 2.4 MPa) on the medial compartment and 15.0 MPa (SD 6.1 MPa) on the lateral compartment. With a tibial slope of 10 degrees , posterior cruciate ligament load reached a maximum of 14.5N (SD 4.9N, P = 0.04) at 100.5 degrees knee flexion and tibiofemoral stress increased to a maximum of 13.3 MPa (SD 4.7 MPa, P = 0.38) medial and 17.4 MPa (SD 8.2 MPa, P = 0.22) lateral in knee extension. INTERPRETATION: Maximum posterior cruciate ligament load was observed at high knee flexion angles, decreasing to full extension. The implantation of the tibial base plate with 10 degrees dorsal slope reduced posterior cruciate ligament load significantly in knee flexion above 50 degrees and slightly increased tibiofemoral contact stress in knee extension. Therefore a posterior tibial slope prevents an excessive load on the posterior cruciate ligament while having little effect on tibiofemoral stress at high knee flexion angles.     

Cruciate ligament forces in the human knee during rehabilitation exercises

OBJECTIVE: To determine the cruciate ligament forces occurring during typical rehabilitation exercises.Design. A combination of non-invasive measurements with mathematical modelling of the lower limb.Background. Direct measurement of ligament forces has not yet been successful in vivo in humans. A promising alternative is to calculate the forces mathematically. METHODS: Sixteen subjects performed isometric and isokinetic or squat exercises while the external forces and limb kinematics were measured. Internal forces were calculated using a geometrical model of the lower limb and the "dynamically determinate one-sided constraint" analysis procedure. RESULTS: During isokinetic/isometric extension, peak anterior cruciate ligament forces, occurring at knee angles of 35-40 degrees, may reach 0.55x body-weight. Peak posterior cruciate ligament forces are lower and occur around 90 degrees. During isokinetic/isometric flexion, peak posterior cruciate forces, which occur around 90 degrees, may exceed 4x body-weight; the anterior cruciate is not loaded. During squats, the anterior cruciate is lightly loaded at knee angles up to 50 degrees, after which the posterior cruciate is loaded. Peak posterior cruciate forces occur near the lowest point of the squat and may reach 3.5x body-weight. CONCLUSIONS: For anterior cruciate injuries, squats should be safer than isokinetic or isometric extension for quadriceps strengthening, though isokinetic or isometric flexion may safely be used for hamstrings strengthening. For posterior cruciate injuries, isokinetic extension at knee angles less than 70 degrees should be safe but isokinetic flexion and deep squats should be avoided until healing is well-advanced. RELEVANCE: Good rehabilitation is vital for a successful outcome to cruciate ligament injuries. Knowledge of ligament forces can aid the physician in the design of improved rehabilitation protocols.     

Knee joint biomechanics in open-kinetic-chain flexion exercises

BACKGROUND: Different rehabilitation exercises such as open-kinetic-chain flexion and extension exercises are currently employed in non-operative and post-operative managements of joint disorders. The challenge is to strengthen the muscles and to restore the near-normal function of the joint while protecting its components (e.g., the reconstructed ligament) from excessive stresses. METHODS: Using a validated 3D nonlinear finite element model, the detailed biomechanics of the entire joint in open-kinetic-chain flexion exercises are investigated at 0 degrees, 30 degrees, 60 degrees and 90 degrees joint angles. Two loading cases are simulated; one with only the weight of the leg and the foot while the second considers also a moderate resistant force of 30 N acting at the ankle perpendicular to the tibia. FINDINGS: The addition of 30 N resistant force substantially increased the required hamstrings forces, forces in posterior cruciate and lateral collateral ligaments and joint contact forces/areas/stresses. INTERPRETATION: At post-anterior cruciate ligament reconstruction or injury period, the exercise could safely be employed to strengthen the hamstrings muscles without a risk to the anterior cruciate ligament. In contrast, at post-posterior cruciate/lateral collateral ligaments reconstructions or injuries, the open-kinetic-chain flexion exercise should be avoided under moderate to large flexion angles and resistant forces.     

Biomechanical response of the passive human knee joint under anterior-posterior forces

Objective. To investigate the detailed biomechanics of the passive tibiofemoral knee joints in full extension under anterior/ posterior drawer forces of up to 400 N.

Design. A nonlinear three-dimensional finite element model of the entire human tibiofemoral joint consisting of bony structures, their articular cartilage layers, menisci, and four principal ligaments was utilized.

Background. The mechanics of the knee joint, specially under drawer forces, have extensively been investigated. Despite all these works, the detailed joint biomechanics, specially the role of boundary conditions, load transmission through menisci/ articular cartilage layers, and coupling between menisci and cruciate ligaments are not yet quantified.

Method. Nonlinear elastostatic analyses were carried out considering the tibiofemoral joint at full extension under anterior and posterior loads of up to 400 N applied either to the tibial or the femoral shaft. Cases with various boundary conditions, cruciate ligament deficiency (anterior or posterior), and total unilateral meniscectomy (medial or lateral) were analysed.

Results. In addition to the total primary anterior-posterior motion of about 9 mm at ± 400 N, significant coupled external tibial rotations of about 9 ° and 10 ° were computed under 400 N femoral posterior and anterior forces, respectively. The response was influenced by the manner of loading and boundary conditions. The anterior cruciate ligament and posterior cruciate ligament were the primary restraints to femoral posterior and anterior drawer forces, respectively. Section of either of these ligaments drastically increased the joint anterior-posterior motion. In the absence of cruciates, the collaterals became the primary restraints in both anterior-posterior forces. In this case, the tibial plateaus, specially the medial one in the anterior cruciate ligament-deficient joint, experienced much larger compressive forces. In addition to causing an increase in joint primary anterior-posterior laxity and anterior cruciate ligament forces, medial meniscectomy substantially increased coupled tibial external rotation, forces on the lateral plateau, and stresses in the articular cartilage of the lateral plateau.     

双能CT成像在显示膝关节韧带中的价值

目的 初步探讨双能CT成像在显示膝关节韧带中的价值.方法 对 12 例志愿者行膝关节双能CT 扫描,并均行容积显示(VRT)和多平面重建(MPR)等二维及三维图像后处理,用以显示膝关节的韧带.由2名有经验的放射科医生对图像进行分析.结果 膝关节部分韧带(膑韧带、前、后交叉韧带和腓侧副韧带)亦可清晰的显示;而较薄的韧带(胫侧副韧带)、横行的韧带(如膑内、外侧支持带)和后方的韧带(如恫斜韧带)显示欠佳.结论 双能CT是一种能够多方位、立体、直观地显示膝关节韧带的新方法,对临床应用具有一定的价值.     

Quantified kinematics of the injury to the posterior cruciate ligament: a computer-aided design simulation study

OBJECTIVE: To quantify the kinematics of the injury to the posterior cruciate and the other major knee ligaments as a function of the knee flexion angle at the moment of impact. DESIGN: Computer-aided design modelling was used to investigate the strain response of all major knee ligaments during antero-posterior abnormal tibio-femoral translation at 0-90 degrees knee flexion. BACKGROUND: It is generally believed that the likelihood of injury to the posterior cruciate ligament following anterior impact is higher in the flexed knee. However, there are no kinematical studies to quantify this clinical observation or investigate the role of the other knee ligaments in the above situation. METHODS: Computer calculations of the individual ligament strain were plotted against the magnitude of posterior tibial translation. Additionally, the strain rate for each ligament (defined as the ligament strain produced per mm of posterior tibial linear translation) was calculated as the slope of the strain-displacement curve for all tested degrees of knee flexion. RESULTS: The posterior cruciate ligament has been shown to be the primary restraint to posterior tibial translation in all degrees of knee flexion. However, at 90 degrees of knee flexion the strain rate of the posterior cruciate ligament is approximately half that in the fully extended knee and the posterior cruciate ligament is the only ligament to resist posterior tibial translation. CONCLUSIONS: The strain behaviour of the posterior cruciate ligament during injury is highly dependent on the knee flexion during the moment of impact. Forced posterior tibial translation in the 90 degrees flexed knee may result in isolated posterior cruciate ligament deficit rather than a complex ligament disruption. The strain rate of a ligament as introduced in the present study is a quantified parameter related to the resistance that the ligament imposes to an abnormal joint movement. Relevance. This study provides insight into the differential strain of the knee ligaments during impacts that result in posterior cruciate ligament injury. Studies that quantify the strain behaviour of individual knee ligaments are important to the understanding, diagnosis and prevention of injuries sustained during contact sports and high-energy road traffic accidents.     

The effect of an impulsive knee valgus moment on in vitro relative ACL strain during a simulated jump landing

BACKGROUND: We tested the hypothesis that impulsive compression, flexion and valgus knee moment loading during a simulated one-footed jump landing will significantly increase the peak relative strain in the anteromedial region of the anterior cruciate ligament compared with loading without the valgus moment. METHODS: Ten cadaveric knees [mean (SD) age: 67.9 (7.6) years; 5 males; 5 females] were mounted into a custom fixture to simulate a lower extremity impact loading of approximately 1600 N. Triaxial load cells monitored the 3D tibial and femoral impulsive force and moments at 2000 Hz, while 3D tibiofemoral kinematics were measured at 400 Hz. Pre-impact quadriceps, hamstring and gastrocnemius muscle forces were simulated using pretensioned steel cables. A differential variable reluctance transducer measured the relative strain in the anteromedial aspect of the anterior cruciate ligament. With the knee initially in 25 degrees flexion, 10 trials were conducted with the impulsive force directed 4 cm posterior to the knee joint center in the sagittal plane ("neutral" loading) to cause a flexion moment, 10 trials were conducted under a similar loading, but with the force directed 15 degrees lateral to the knee sagittal plane ("valgus" loading), and the 10 neutral loading trials were then repeated. A non-parametric Wilcoxon signed rank test was used to test the hypothesis using a P<0.05 significance level. FINDINGS: The peak normalized anterior cruciate ligament strain was 30% larger for the impulsive compression loading in valgus and flexion compared with an impulsive compression loading in isolated flexion (P<0.05). INTERPRETATION: Minimizing the abduction loading of the knee during a jump landing should help reduce anterior cruciate ligament strain during that maneuver.     

Distinctions of introarticular force distribution between genesis-II posterior stabilized and cruciate retaining total knee arthroplasty: An intraoperative comparative study of 45 patients

BackgroundAlthough both the posterior stabilized and cruciate retaining total knee arthroplasty have been proven to effectively relieve pain and restore basic functions, the joint gap width during flexion was reported to be different due to the presence or absence of posterior cruciate ligament, which may lead to different intra-articular force distribution. In this study, we investigated the distinctions in intra-articular force distribution between the two types of TKA designs in patients with varus knee osteoarthritis.MethodsForty five patients (50 knees) with varus knee osteoarthritis were prospectively included, with each 25 knees receiving cruciate retaining and posterior stabilized total knee arthroplasty, respectively. With an intra-articular force measurement system, the intra-articular force distribution with knee flexion at 0°, 30°, 45°, 60°, 90°, and 120° were recorded in all patients.FindingsThe total force was similar for posterior stabilized and cruciate retaining knees at all flexion degrees. However, force in the medial compartment accounted for 59.8% –84.0% of total force in posterior stabilized knees, while 27.4% –65.7% in cruciate retaining knees. In cruciate retaining knees, no significant difference was found between forces in the two compartments at 30° flexion (P = 0.444), but force was significantly concentrated in the lateral side during 45° –120° flexion (P = 0.000– 0.028).InterpretationAlthough the entire intra-articular forces were similar between CR and PS knees at different flexion angles, medial part had higher force than lateral part when PS knee was used. The posterior cruciate ligament do a role in soft balance, and make the force more evenly distributed.     

Komplexe Bandläsion des Kniegelenks

Combined injuries of the main knee ligaments have a broad spectrum, ranging from typical combinations like anterior cruciate ligament (ACL) and medial collateral ligament (MCL) ruptures up to knee luxations with severe combinations of both cruciate ligaments and at least one collateral ligament. Isolated injuries of the MCL and the posterior cruciate ligament (PCL) can be treated conservatively. Indications for surgical repair are mainly combined injuries of cruciate ligaments and ruptures of the lateral structures. Knee luxations are often complex injuries with neurovascular complications. Careful and early detection of these complications can avoid endangering the extremity and therefore prevent massive damage to the patient. Surgical repair of ligament injuries is superior to conservative treatment.     

The effect of functional knee brace design and hinge misalignment on lower limb joint mechanics

BACKGROUND: Knee bracing has been shown to alter lower limb joint mechanics, which may protect the anterior cruciate ligament. The effect of brace alignment and brace type, however, remains largely unknown. This study was conducted to determine whether the use of a functional knee brace, the type of brace used or its alignment relative to the knee causes biomechanical alterations to gait. METHODS: Ten healthy participants took part in two walking conditions (aligned brace and misaligned brace) for two different types of brace (sleeve brace with bilateral hinges and hinge-post-shell). A non-braced condition was included as a baseline measure. Three-dimensional kinematics and force platform data were used to calculate the joint intersegmental forces and net joint moments of the ankle, knee and hip. FINDINGS: In comparison to non-braced walking, the shell brace in its aligned position significantly reduced the peak ankle plantarflexor moment. There was a decreased peak knee flexion angle with both the aligned shell and sleeve braces. The shell brace in its aligned position significantly increased peak knee adduction and reduced peak knee internal rotation. INTERPRETATION: In this sample of healthy participants, functional knee bracing failed to alter lower limb mechanics in such a way that would reduce the force transmitted to the anterior cruciate ligament. In addition, although there were brace induced changes in lower limb kinematics with 2cm of distal hinge misalignment, it is unlikely that hinge misalignment of this magnitude is detrimental to an uninjured knee joint during walking.     

Influence of functional bracing on the kinetics of anterior cruciate ligament-injured knees during level walking

BACKGROUND: Use of functional knee braces has been suggested to provide protection and to improve kinetic performance of the knee in anterior cruciate ligament-injured patients. However, the efficacy of knee bracing in achieving these goals is still controversial. The purpose of this study was to examine the immediate effects of functional bracing on the three-dimensional kinetics of the knee in individuals with anterior cruciate ligament injuries during level walking. METHODS: Fifteen anterior cruciate ligament-deficient and 15 anterior cruciate ligament-reconstructed subjects were each fitted with a DonJoy Goldpoint brace and walked at a self-selected pace, first without and then with the brace. Kinematic and kinetic data were measured and three-dimensional joint moments and angular impulses at the knee were calculated and compared between bracing conditions and between limbs. FINDINGS: Functional knee bracing did not significantly affect the kinetics of the unaffected knees for either group. Bracing significantly increased the peak abductor moments in anterior cruciate ligament-deficient knees and reduced the bilateral kinetic asymmetry in the coronal plane. For the anterior cruciate ligament-reconstructed group, bracing increased peak moments and impulses of the abductors and extensors. It also reduced bilateral kinetic asymmetry in the sagittal and coronal planes. INTERPRETATION: Effects of the knee brace were apparent in the coronal plane for both anterior cruciate ligament-deficient and anterior cruciate ligament-reconstructed patients, and in the sagittal plane for anterior cruciate ligament-reconstructed patients. Functional bracing can be recommended for anterior cruciate ligament-reconstructed patients to assist in achieving better bilateral kinetic symmetry during gait. For anterior cruciate ligament-deficient patients, apart from bracing, additional emphasis on the rehabilitative training for better kinetic knee performance in the sagittal plane is needed.     

关节镜治疗部队训练所致的膝关节损伤

目的：探讨部队训练所致膝关节损伤的特点，提出治疗和预防的措施。方法：分析1985年以来我院收治的部队训练所致膝关节损伤的类型及治疗方法。结果：1985年以来共收治357例膝关节训练伤的患者。按各种损伤类型单独统计，半月板损伤321例，内侧副韧带损伤19例，外侧副韧带损伤3例，前交叉韧带损伤36例，后交叉韧带损伤7例，胫骨棘骨折11例。除内外侧副韧带损伤采用开放手术修复重建以外，均采用关节镜下的修复与重建，疗效满意，术后1年时随访优良率达92．43％。结论：膝关节损伤是部队训练伤的常见类型之一，特点主要是半月板和膝关节韧带的损伤。绝大多数膝关节损伤可采用关节镜微创技术治疗，术后进行康复锻练理疗。     

Relation between knee motion and ligament length patterns

Fifteen knee specimens were tested in a 6°-of-freedom test machine using quadriceps force to drive continuous flexion-extension motion. Ten of the knees were again tested following isolated transaction of the anterior cruciate ligament. From transducer outputs, three-dimensional motion was determined. Using biplanar radiography and bone sectioning, ligament insertion coordinates and joint surface geometry were determined and used to calculate ligament length ratios as a function of knee flexion. Consistent motion patterns were seen in all knees. The prominent aspects of motion were a 15° internal rotation and an 8.6 mm anterior displacement of the tibia with flexion from 0 to 120°. Anterior cruciate transaction resulted in abnormal and excessive anterior-posterior displacement in early flexion, but a return to normal in late flexion. The results indicated that under our test conditions the boundaries of anterior-posterior motion were determined primarily by the cruciate ligaments, but tibial rotation was not guided by the cruciate ligaments.     

Knee joint mechanics under quadriceps--hamstrings muscle forces are influenced by tibial restraint

BACKGROUND: To investigate the role of quadriceps and hamstrings muscle recruitments on knee joint mechanics, measurement studies constrain the tibial anterior-posterior translation at a point away from the joint. This generates a restraining force perpendicular to the tibia thus introducing an artefact shear force that likely alters joint mechanics and forces in cruciate ligaments. METHODS: A 3D nonlinear finite element model of the entire knee joint, including tibiofemoral and patellofemoral joints, was used to investigate joint mechanics in flexion (0 degrees -90 degrees ) under isolated and combined hamstrings and quadriceps activation. The effect of tibial restraint at two locations on results was studied and compared with the reference boundary condition of tibia constrained by pure moments. FINDINGS: Tibial restraint by a force rather than a pure moment substantially influences the joint response. For identical forces, hamstrings have much greater moment generating capacity at larger flexion angles while quadriceps are more effective at smaller angles. INTERPRETATION: Tibial constraint by a restraining force rather than a pure moment causes an artefact force on the joint that vary with muscle forces and restraining location. These artefact shear forces, especially when placed closer to the joint, considerably reduce forces in cruciate ligaments; in anterior cruciate ligament at near full extension and in posterior cruciate ligament at larger flexion angles. The beneficial effects of muscle co-contraction in reducing anterior cruciate ligament forces at near full extension and in posterior cruciate ligament forces at near 90 degrees , however, disappear as the restraint on the tibia approaches the joint. The artefact forces could distort results and their interpretations.     

Influence of the tunnel angle in ACL reconstructions on the biomechanics of the knee joint

BACKGROUND: A high tension in anterior cruciate ligament grafts affects both graft and knee functional performance. Clinical observations suggest that impingement of the graft against the posterior cruciate ligament might cause high graft tensions. Also, meniscal injury has been well documented in association with damage in the anterior cruciate ligament. METHODS: In this paper, we present the results obtained in a three-dimensional finite element model of the human knee, corresponding to different aspects of anterior cruciate ligament reconstruction with bone-patellar tendon-bone grafts. This model was used to investigate the effect of the angle in the coronal plane of femoral and tibial tunnels. Firstly, graft tension was computed in a knee moved from 0 degrees to 60 degrees of flexion and the results were compared with experimental ones obtained by other authors. Secondly, the resulting kinematics under an anterior load of 134 N was compared to that of the intact knee. FINDINGS: The obtained results showed that the closest anterior tibial translation to that of the intact knee was obtained with femoral and tibial tunnels with angles of 60 degrees. In this same case, a lower graft tension was also obtained. The results demonstrated noticeable increases in the meniscal stresses after anterior cruciate ligament reconstruction. INTERPRETATION: Our results showed that impingement only depends on the femoral tunnel angle. On the contrary, laxity principally depends on the tibial tunnel angle. The angle of the femoral tunnel affects the graft tension while the tibial tunnel affects laxity, meniscal stresses and strains.     

Assessment of functional knee bracing: an in vivo three-dimensional kinematic analysis of the anterior cruciate deficient knee

OBJECTIVE: To describe three-dimensional tibial and femoral movements in vivo and examine the effect of a brace on knee kinematics during moderate to intense activity. DESIGN: Skeletal kinematics of anterior cruciate ligament deficient knees was measured with and without braces during moderate to intense activity. BACKGROUND: Invasive markers implanted into the tibia and femur are the most accurate means to directly measure skeletal motion and may provide a more sensitive measure of the differences between brace conditions. METHODS: Steinmann traction pins were implanted into the femur and tibia of four subjects having a partial or complete anterior cruciate ligament rupture. Non-braced and braced conditions were randomly assigned and subjects jumped for maximal horizontal distance to sufficiently stress the anterior cruciate ligament. RESULTS: Intra-subject peak vertical force and posterior shear force were generally consistent between conditions. Intra-subject kinematics was repeatable but linear displacements between brace conditions were small. Differences in angular and linear skeletal motion were observed across subjects. Bracing the anterior cruciate ligament deficient knee resulted in only minor kinematic changes in tibiofemoral joint motion. CONCLUSION: In this study, no consistent reductions in anterior tibial translations were observed as a function of the knee brace tested. Relevance. Investigations have reported that knee braces fail when high loads are encountered or when load is applied in an unpredictable manner. Questions remain regarding tibiofemoral joint motion, in particular linear displacements. The pin technique is a means for direct skeletal measurement and may provide a more sensitive measure of the differences between brace conditions.     

The effect of graft stiffness on knee joint biomechanics after ACL reconstruction--a 3D computational simulation

OBJECTIVE: The objective was to determine the effect of varying graft stiffness and initial graft tension on knee kinematics and graft tension after anterior cruciate ligament reconstruction. DESIGN: A 3D computational knee model was used. BACKGROUND: Many factors influencing the biomechanical outcome of anterior cruciate ligament reconstruction have been investigated. However, there are no reports on the effect of variations in graft stiffness on knee behavior. METHODS: A 3D computational knee model was used to simulate anterior cruciate ligament reconstruction using three different grafts with stiffnesses similar to the anterior cruciate ligament (graft 1), a 10mm bone-patellar tendon-bone graft (graft 2), and a 14 mm bone-patellar tendon-bone graft (graft 3). The initial graft tension was set to 0 or 40 N with the knee at 30 degrees of flexion. A 134 N anterior tibial drawer load and a 400 N quadriceps load were applied to the knee, and kinematics and graft tension were calculated. RESULTS: When fixed with no initial tension, graft 1 was found to under-constrain the knee, while graft 2 slightly over-constrained the knee, and graft 3 over-constrained the knee when compared to the intact knee. When an initial graft tension of 40 N was used, all of the reconstructed knees were more constrained than when an initial tension of 0 N was used. CONCLUSIONS: This study suggests that graft stiffness has a direct impact on knee biomechanics after anterior cruciate ligament reconstruction. An optimal anterior cruciate ligament reconstruction can be achieved if the anterior cruciate ligament is replaced by a graft with similar structural stiffness. RELEVANCE: This study showed that if the graft material and fixation sites are selected such that the anterior cruciate ligament structural stiffness is retained, normal knee kinematics can be restored.