The role of MRI in diagnostic imaging of the injured knee

Clinical evaluation of the acutely injured knee is often supplemented by radiographic studies. Magnetic resonance imaging (MRI) is rapidly replacing other techniques as the study of choice for evaluating knee injuries. MRI can delineate meniscal tears, cruciate and collateral ligament injuries, and tendon, capsule and cartilage problems.     

Biomechanics of Multi-ligament Knee Injuries (MLKI) and Effects on Gait

Stability at the knee joint is provided by both the static structures, including the ligaments and joint capsule and the coordinated activation of dynamic structures surrounding the joint. These dual stabilizers allow for functional movements, such as gait, to occur safely, effectively, and efficiently. In the presence of a multi-ligament knee injury (MLKI) an absence of static stability can result in an increased reliance on the dynamic knee stabilizers. If sufficient stability is not provided, the potential for an increase in abnormal movements in the knee joint can result. These potential gait alterations that may be associated with a MLKI can result in abnormally high stresses on healing tissues and potentially high shearing forces on articular cartilage, resulting in early breakdown. Early recognition of gait abnormalities and an appropriate implementation of a gait re-training program to control abnormal forces in a patient following an MLKI or a surgical intervention for a MLKI are critical for successful long-term outcomes.     

Treatment of scapho-lunate instability

Scapho-lunate dissociation is one of the most frequent reasons of carpal instability. Diagnosis is mostly based on a careful physical examination where stability of the SL joint is specifically checked through different clinical maneuvers, followed by static and dynamic radiographic examination of the wrist in a variety of positions and loading conditions aiming at demonstrating the presence of a gap between the two dissociated bones. When in doubt, arthroscopy is used. In the treatment five factors are to be considered: integrity of the dorsal SL ligament, its healing potential, status of other scaphoid stabilizers, reducibility of malaligment and cartilage status. The staging classification of SLD is also presented. On this basis the possible treatment techniques both recent and past are described, including various methods of soft tissue repair and reconstruction procedures and bony stabilization.     

Cartilage mechanical tests: Evolution of current standards for cartilage repair and tissue engineering. A literature review

BackgroundRepair procedures and tissue engineering are solutions available in the clinical practice for the treatment of damaged articular cartilage. Regulatory bodies defined the requirements that any products, intended to regenerate cartilage, should have to be applied. In order to verify these requirements, the Food and Drug Administration (FDA, USA) and the International Standard Organization (ISO) indicated some Standard tests, which allow evaluating, in a reproducible way, the performances of scaffolds/treatments for cartilage tissue regeneration.MethodsA review of the literature about cartilage mechanical characterization found 394 studies, from 1970 to date. They were classified by material (simulated/animal/human cartilage) and method (theoretical/applied; static/dynamic; standard/non-standard study), and analyzed by nation and year of publication.FindingsWhile Standard methods for cartilage mechanical characterization still refer to studies developed in the eighties, expertise and interest on cartilage mechanics research are evolving continuously and internationally, with studies both in vitro – on human and animal tissues – and in silico, dealing with tissue function and modelling, using static and dynamic loading conditions.Interpretationthere is a consensus on the importance of mechanical characterization that should be considered to evaluate cartilage treatments. Still, relative Standards need to be updated to describe advanced constructs and procedures for cartilage regeneration in a more exhaustive way. The use of the more complex, fibre-reinforced biphasic model, instead of the standard simple biphasic model, to describe cartilage response to loading, and the standardisation of dynamic tests can represent a first step in this direction.     

Dynamic measurement of patellofemoral contact pressure following reconstruction of the medial patellofemoral ligament: an in vitro study

BACKGROUND: Surgical reconstruction of the medial patellofemoral ligament used to stabilize the patella against lateral dislocation may concomitantly produce alteration of the patellofemoral contact pressure distribution. Two different tendon transfer techniques of reconstructing the medial patellofemoral ligament, one dynamic and one static, as well as a proximal soft tissue realignment of the patella were investigated. METHODS: Eight human knee specimens were mounted in a kinematic knee simulator and isokinetic extension motion was simulated. Patellofemoral pressure was measured using a pressure sensitive film while a 100 N laterally directed dislocation load was applied to the patella. The specimens were evaluated in a physiologic state, as well as after dynamic reconstruction of the medial patellofemoral ligament using a distal transfer of the semitendinosus tendon, following static reconstruction using a semitendinosus autograft, and following proximal soft tissue realignment of the patella. FINDINGS: Following both reconstruction techniques of the medial patellofemoral ligament patellofemoral contact pressure was not significantly (P=0.49) altered. In contrast, after proximal realignment a trend (P=0.07) towards higher contact pressure near knee extension was observed. In the absence of a lateral dislocation load dynamic and static reconstruction resulted in a medialization (P=0.04) of the center of pressure, whereas under the application of a 100 N dislocation load the center of pressure showed no significant alteration. Following proximal realignment the center of pressure was significantly medialized without (P<0.01) and with a dislocation load (P=0.01) throughout the entire range of knee motion. INTERPRETATION: Static and dynamic ligament reconstruction of the medial patellofemoral ligament did not alter patellofemoral pressure. Proximal realignment, on the other hand, resulted in a constant medialization of the patellofemoral pressure. The data suggest that the reconstruction techniques would be associated with a low risk of causing premature cartilage degeneration due to excessive patellofemoral contact pressure, whereas proximal realignment could cause medial overload of the patellofemoral joint.     

Updates in biological therapies for knee injuries: full thickness cartilage defect

Full thickness cartilage defect might occur at different ages, but a focal defect is a major concern in the knee of young athletes. It causes impairment and does not heal by itself. Several techniques were described to treat symptomatic full thickness cartilage defect. Recently, several advances were described on the known techniques of microfracture, osteochondral allograft, cell therapy, and others. This article brings an update of current literature on these well-described techniques for full thickness cartilage defect.     

软骨修复材料在运动性膝关节软骨损伤修复中的作用膝关节

背景：评价软骨修复材料在膝关节软骨损伤修复中的效果,为医务、科研工作者的研究提供一定的借鉴。方法：采用电子检索的方式,在万方数据库（http：//www.wanfangdata.com.cn/）中检索2000-01/2011-03关于修复材料在膝关节软骨损伤研究的文章,关键词为＂生物材料;关节软骨;缺损;修复＂。排除重复研究、普通综述或Meta分析类文章,筛选纳入26篇文献进行评价。结果：膝关节软骨损伤在运动性损伤中较为常见,现在主要的治疗方法是自体骨软骨移植修复膝关节软骨缺损。新型的软骨替代材料研究仍处于动物试验阶段,且在动物体内长期疗效及远期的生物力学变化还未有进一步的证实,进入临床试验更需要一个过程。结论：关节软骨损伤修复的基础研究与临床治疗,虽仍存在许多重点和难点问题亟待探索,但关节软骨损伤修复正从生物材料移植向人工再造活性软骨的崭新阶段迈进。随着各种新型材料的研制和开发,关节软骨损伤修复研究将日益完善,并为临床奠定坚实的基础,应用前景十分广阔。     

Die varisierende schließende Femurosteotomie zur Behandlung der Valgusarthrose am Kniegelenk

Osteotomies around the knee have become more popular in recent years. The reasons are improved surgical techniques and new implants, which were specifically designed for these new methods. The goal of the closed-wedge distal femur osteotomy is to shift the mechanical load axis from the lateral to the medial compartment. This procedure unloads the lateral compartment and decreases the pressure on the cartilage. Various surgical methods were proposed for this osteotomy. Several authors recommended the lateral open-wedge technique. We observed pain related to the overstretched iliotibial tract and bone healing problems. The improved biplanar technique of closed-wedge distal femur osteotomy in combination with a new plate fixator [Tomofix MDF (medial distal femur)] can avoid these problems. Biomechanical tests have demonstrated favourable biomechanical data for this implant, allowing for a brace-free rehabilitation with partial weight bearing using two crutches. In our series of 46 cases, the described surgical technique proved to be an effective and safe treatment of the monocompartmental lateral osteoarthritis in combination with a valgus leg deformity.     

Changes in frontal plane dynamics and the loading response phase of the gait cycle are characteristic of severe knee osteoarthritis application of a multidimensional analysis technique

BACKGROUND: Osteoarthritis of the knee is related to many correlated mechanical factors that can be measured with gait analysis. Gait analysis results in large data sets. The analysis of these data is difficult due to the correlated, multidimensional nature of the measures. METHODS: A multidimensional model that uses two multivariate statistical techniques, principal component analysis and discriminant analysis, was used to discriminate between the gait patterns of the normal subject group and the osteoarthritis subject group. Nine time varying gait measures and eight discrete measures were included in the analysis. All interrelationships between and within the measures were retained in the analysis. FINDINGS: The multidimensional analysis technique successfully separated the gait patterns of normal and knee osteoarthritis subjects with a misclassification error rate of <6%. The most discriminatory feature described a static and dynamic alignment factor. The second most discriminatory feature described a gait pattern change during the loading response phase of the gait cycle. INTERPRETATION: The interrelationships between gait measures and between the time instants of the gait cycle can provide insight into the mechanical mechanisms of pathologies such as knee osteoarthritis. These results suggest that changes in frontal plane loading and alignment and the loading response phase of the gait cycle are characteristic of severe knee osteoarthritis gait patterns. Subsequent investigations earlier in the disease process may suggest the importance of these factors to the progression of knee osteoarthritis.     

Effect of manual therapy techniques on the stretch reflex in normal human quadriceps

The effect of four manual therapy techniques on the quadriceps stretch reflex amplitude (elicited by mechanical vibration) was studied in a randomized, controlled trial in 120 (20 in each of six groups) healthy human subjects aged 18–64 years. Passive and active techniques were studied; each under static and dynamic conditions. The passive procedures were massage (static) and knee oscillation (dynamic) for 5 min. Active techniques involved eight repetitions of isometric quadriceps contractions (static) and leg extension (dynamic). The two static techniques had no effect on the stretch reflex amplitude. Both dynamic techniques caused a reduction (active by 25%, p < 000001 and passive 12%, p < 005). Only the active, dynamic technique caused a greater change than in the control group (p < 0005). The effect lasted for less than 1 min. These data question the ability of such techniques to make clinically valid changes in motoneuron excitability. Further studies are required on those with neuromuscular pathology, who may respond differently to normal subjects.     

Static and dynamic correlates of the knee adduction moment in healthy knees ranging from normal to varus-aligned

Background

Individuals with medial knee osteoarthritis often present with varus knee alignment and ambulate with increased knee adduction moments. Understanding the factors that relate to the knee adduction moment in healthy individuals may provide insight into the development of this disease. Thus, this study aimed to examine the relationships of both static and dynamic lower extremity measures with the knee adduction moment. We hypothesized that the dynamic measures would be more closely related to this moment.

Methods

Arch height index, hip abduction strength and two static measures of knee alignment were recorded for 37 young asymptomatic knees that varied from normal to varus-aligned. Overground gait analyses were also performed. Correlation coefficients were used to assess the relationships between the static and dynamic variables to the knee adduction moment. Hierarchical regression analyses were then conducted using the static measures, the dynamic measures, and the static and dynamic measures together.

Results

Among the static measures, the tibial mechanical axis and the distance between the medial knee joint lines were correlated with the knee adduction moment. The best predictive static model (R² = 0.53) included only the tibial mechanical axis. Among the dynamic variables, knee adduction and rearfoot eversion angles were correlated with the knee adduction moment. Knee adduction and rearfoot eversion, together, were the best dynamic model (R² = 0.53). The static and dynamic measures together created the strongest of the three models (R² = 0.59).

Conclusions

These results suggest that dynamic measures slightly enhance the predictive strength of static measures when explaining variation in the knee adduction moment.     

Functional knee assessment with advanced imaging

The purpose of anterior cruciate ligament (ACL) reconstruction is to restore the native stability of the knee joint and to prevent further injury to meniscus and cartilage, yet studies have suggested that joint laxity remains prevalent in varying degrees after ACL reconstruction. Imaging can provide measurements of translational and rotational motions of the tibiofemoral joint that may be too small to detect in routine physical examinations. Various imaging modalities, including fluoroscopy, computed tomography (CT), and magnetic resonance imaging (MRI), have emerged as powerful methods in measuring the minute details involved in joint biomechanics. While each technique has its own strengths and limitations, they have all enhanced our understanding of the knee joint under various stresses and movements. Acquiring the knowledge of the complex and dynamic motions of the knee after surgery would help lead to improved surgical techniques and better patient outcomes.     

Autologe Knochen-Knorpel-Transplantation

In cases of chondral or osteochondral lesions, the autologous transfer of cartilage-bone cylinders is the only technique to provide hyaline cartilage at the defect site of weight-bearing joints such as the knee, ankle, hip, or even the elbow. The technique described is used for full-thickness cartilage defects or osteochondral lesions. Donor cylinders are harvested from knee areas in the anterolateral or medial trochlea with less contact pressure and transplanted to the lesion in the weight-bearing zone. Different technical approaches are described to achieve congruent joint surfaces by many small cylinders, the so-called mosaicplasty, or single cylinders of larger diameter. It has been shown that there is frequent and secure bony integration, but there is no ingrowth of cartilage itself. In some cases there are signs of cartilage degeneration in the graft. The clinical evaluation showed good to excellent results, especially at knee and ankle joints. Thus, the OATS is a reliable and reproducible technique for treatment of focal chondral and osteochondral lesions in weight-bearing joints.     

The use of spacers (static and mobile) in infection knee arthroplasty

Revision total knee arthroplasty (TKA) is the treatment of choice in patients with periprosthetic joint infection. It may be performed in either a single stage or two stages. In the latter option, between stages, an antibiotic-loaded spacer may be used to maintain a certain amount of joint stability and mobility after the infected implant is removed, adding an intra-articular concentration of antibiotics. There are two types of antibiotic-loaded cement spacers: static and dynamic. Static spacers basically create a temporary arthrodesis with antibiotic-loaded cement and usually are handmade within the surgical field. Dynamic spacers can be created intraoperatively by using different tools or may be prepackaged by the manufacturer; they allow range of motion between stages. In this article, the authors review the indications, surgical techniques, and results for static and dynamic spacers in two-stage revision TKA.     

Mikrofrakturierung und spezifische Rehabilitation zur Behandlung von Arthrose des Kniegelenks

Treatment of osteoarthritis in young and middle-aged patients, in whom joint replacement is usually not appropriate, is a challenge to orthopaedic surgeons. Arthroscopic techniques can help control patients’ symptoms. In particular, the microfracture procedure combined with management of the joint volume and a specific rehabilitation protocol shows good results in patients with osteoarthritis and cartilage defects by resurfacing the defect with a combination of types I and II cartilaginous tissue. Microfracture is a single-staged arthroscopic procedure that can be combined with any other arthroscopic treatment for osteoarthritis of the knee. With an appropriate rehabilitation protocol and techniques for controlling the joint volume, these treatments are very effective for pain relief and functional improvement. The described technique is our choice for initial surgical treatment of osteoarthritis of the knee.     

Objective measures on knee instability: dynamic tests: a review of devices for assessment of dynamic knee laxity through utilization of the pivot shift test

Current reconstructive methods used after anterior cruciate ligament (ACL) injury do not entirely restore native knee kinematics. Evaluation of dynamic knee laxity is important to accurately diagnose ACL deficiency, to evaluate reconstructive techniques, and to construct treatment algorithms for patients with ACL injury. The purpose of this study is to present recent progress in evaluation of dynamic knee laxity through utilization of the pivot shift test. A thorough electronic search was performed and relevant studies were assessed. Certain dynamic knee laxity measurement methods have been present for over 10 years (Navigation system, Electromagnetic sensor system) while other methods (Inertial sensor, Image analysis system) have been introduced recently. Methods to evaluate dynamic knee laxity through the pivot shift test are already potent. However, further refinement is warranted. In addition, to correctly quantify the pivot shift test, the involved forces need to be controlled through either standardization or mechanization of the pivot shift test.     

A review on the mechanical quality of articular cartilage - implications for the diagnosis of osteoarthritis

The functional behaviour of articular cartilage in diarthrodial joints is determined by its morphological and biomechanical properties. Whereas morphological changes are mainly detectable in the progressed stages of osteoarthritis, biomechanical properties seem to be more sensitive to early degenerative variations since they are determined by the biochemical composition and structural arrangement of the extracellular matrix. The objective of this paper is to review studies focussing on variations in the mechanical compressive properties during the early pre-osteoarthritic stage. The aim is to quantify the requirements to detect the early cartilage degeneration in pre-osteoarthritis based on the mechanical parameters and to create an updated basis for a better understanding of inherent relationships between characteristic parameters in articular cartilage.

Correlations between mechanical and biochemical parameters as well as magnetic resonance, ultrasonic, histological and structural parameters were observed. In early osteoarthritis, static moduli decrease below 80% of healthy controls and dynamic moduli below 30% of controls. To identify osteoarthritic changes of articular cartilage based on static or dynamic mechanical parameters in an early stage of the disease progression the accuracy of a mechanical testing method has to be adequate to detect changes of 10% in cartilage stiffness.     

Scratching the surface: articular cartilage disorders in the knee

Powerful techniques with MR imaging are being developed for evaluating articular cartilage. Pharmaceutical and biotechnology development is driven largely by the search for novel therapeutic solutions to the growing problem of arthritis in our aging society. Accordingly, imaging tools that will be used to direct patients to specific therapies and then to monitor treatment effectiveness and safety presently are being refined and validated in rigorous multicenter and multinational clinical trials aimed at gaining regulatory approval. As trials approach completion, radiologists can anticipate an increased demand for expertise and experience in evaluating articular cartilage disorders. This article reviews this novel mechanism for evolving imaging techniques for clinical use through clinical drug trials, lists the most promising MR imaging markers available for evaluating cartilage integrity, and speculates on how these techniques will find their way into clinical practice.     

Body motion during repetitive isodynamic lifting: a comparative study of normal subjects and low-back pain patients

To quantify performance differences between patients with low-back pain (LBP) and a control group during their performance of a repetitive isodynamic lifting task. Case-control study was done. LBP patients were recruited and tested at an outpatient ambulatory chronic pain rehabilitation program before treatment was begun. Fifty-three LBP patients who had prolonged back pain and 53 age and gender matched pain-free control subjects. Overall lifting performance measures included weight lifting and number of lifts completed; kinematic measures of hip and knee movements during lifting were described by hyperbolic tangent models, and included static measures of starting and ending angles, and dynamic measures of midpoint, falltime, and lift speed. Control subjects completed significantly more lifts and lifted more weight than patients. Starting hip flexion was greater for controls and starting knee flexion was greater for patients, indicating that patients used more of a leg lift. Patients and controls also differed significantly on dynamic measures, particularly lifting speed and hip and knee temporal midpoints. Major static and dynamic motion differences were found between LBP patients and controls as they performed repetitive lifting under a constant load. These findings indicate that body motion parameters, in addition to more common strength and endurance measures, are necessary to describe the impact of persistent LBP on a person's lifting abilities.