Eine neuartige Knieendoprothese mit physiologischer Gelenkform

The natural tibiofemoral joint (TFJ) functions according to a roll-glide mechanism. In the stance phase (0–20° flexion), the femur rolls backwards over the tibia plateau, while further flexion causes increased gliding. This kinematics is based on the principle of a quadruple joint. The four morphological axes of rotation are the midpoints of the curvatures of the medial and lateral femoral condyles and the medial and lateral tibia plateau. In addition, the medial and lateral compartments are shifted a few millimetres in a sagittal direction, the medial tibia plateau being concave and the lateral plateau convex. In most knee arthroplasties, these factors are not taken into account; instead they are equipped with symmetrical medial and lateral joint surfaces. Thereby, the midpoints of the curvatures of the sagittal contours of the lateral and medial joint surfaces, on the femoral as well as on the tibial sides, create a common axis of rotation which does not allow a physiological roll-glide mechanism. The goal of this study was therefore to report on the biomechanical basis of the natural knee and to describe the development of a novel knee endoprosthesis based on a mathematical model. The design of the structurally new knee joint endoprosthesis has, on the lateral side, a convex shape of the tibial joint surface in a sagittal cross section. Furthermore, from a mathematical point of view, this knee endoprosthesis possesses essential kinematic and static properties similar to those of a physiological TFJ. Within the framework of the authorization tests, the endoprosthesis was examined according to ISO/WC 14243 in a knee simulator. The abrasion rates were, thereby, lower than or at least as good as those for conventional endoprostheses. The presented data demonstrate a novel concept in knee arthroplasty, which still has to be clinically confirmed by long term results.     

Die Bedeutung des dreidimensionalen Bewegungsablaufs des Femurotibialgelenks für die Ausrichtung von Knieführungsorthesen

Stimulated by investigations on the kinematics of the human knee joint conducted during the nineteenth and early twentieth centuries, we have determined the spatial motion of this articulation, describing it by means of the helical axis concept, as obtained with the assistance of modern tools. As expected, there are similarities with the results of other recent investigators. Some details of the photogrammetrical method employed are unique. We have now related our findings to unsolved problems in orthotics and prosthetics. The presentation also describes a technique to align the movement of a brace with that of the knee joint. This work serves as a basis on which criteria for the fitting of braces could be determined.     

Sinn oder Unsinn der „unloader braces“

Background

Unloader knee braces are a viable and cost-effective alternative in for treatment of medial osteoarthritis of the knee in selected patients. They provide the potential to predict which patients could benefit from a high tibial osteotomy (HTO) and which patients should better be treated which a unicondylar or bicondylar knee replacement.

Discussion

A direct clinical benefit in pain reduction as well as improved knee function has been shown in several clinical studies; however, the underlying mechanism remains uncertain. A potential reduction of the load in the medial compartment of the knee joint by reducing the varus or valgus deformity as well as a reduction of enhanced muscle contraction is discussed.

Conclusion

Despite the promising short-term results, possible long-term benefits of unloader braces are controversial. As possible reasons, natural progression of the underlying osteoarthritis as well as compliance of the patients to wear the braces diminishes significantly with time.     

Verletzungen des vorderen Kreuzbandes bei Sportlern

Anterior cruciate ligament ruptures represent serious injuries for athletes which are often associated with accompanying injuries and lead to relevant kinematic alterations in the femorotibial roll-glide mechanism of the knee joint. Instability resulting in recurrent giving way events, as well as instability-related meniscal and cartilage lesions can cause functional long-term impairment that may limit the athlete’s career. Anterior cruciate ligament replacement is therefore considered to be the gold standard for recovery of physical performance and to prevent secondary meniscal and cartilage damage. Continuous changes in the reconstruction of the anterior cruciate ligament have led to a variety of different methods, including graft choice, fixation devices and surgical techniques, which support the consideration of individual requirements of the athlete as well as sport-specific aspects. One of the main factors for restoring stability and the physiological kinematic roll-glide mechanism of the knee is an anatomical tunnel placement as well as a stable graft fixation in the tibia and femur. By achieving of these fundamental technical requirements an early functional rehabilitation and accelerated recovery of neuromuscular skills, strength and coordination can be achieved, so that an early return to sport activities is possible.     

Using real‐time MRI to quantify altered joint kinematics in subjects with patellofemoral pain and to evaluate the effects of a patellar brace or sleeve on joint motion

Abnormal patellofemoral joint motion is a possible cause of patellofemoral pain, and patellar braces are thought to alleviate pain by restoring normal joint kinematics. We evaluated whether females with patellofemoral pain exhibit abnormal patellofemoral joint kinematics during dynamic, weight‐bearing knee extension and assessed the effects of knee braces on patellofemoral motion. Real‐time magnetic resonance (MR) images of the patellofemoral joints of 36 female volunteers (13 pain‐free controls, 23 patellofemoral pain) were acquired during weight‐bearing knee extension. Pain subjects were also imaged while wearing a patellar‐stabilizing brace and a patellar sleeve. We measured axial‐plane kinematics from the images. Females with patellofemoral pain exhibited increased lateral translation of the patella for knee flexion angles between 0°and 50° (p = 0.03), and increased lateral tilt for knee flexion angles between 0° and 20° (p = 0.04). The brace and sleeve reduced the lateral translation of the patella; however, the brace reduced lateral displacement more than the sleeve (p = 0.006). The brace reduced patellar tilt near full extension (p = 0.001), while the sleeve had no effect on patellar tilt. Our results indicate that some subjects with patellofemoral pain exhibit abnormal weight‐bearing joint kinematics and that braces may be effective in reducing patellar maltracking in these subjects. Published by Wiley Periodicals, Inc. J Orthop Res 27: 571–577, 2009     

Knee braces

The preceding discussion has profiled the three different types of knee braces which are available on today's market. It also has attempted to discuss the controversies surrounding these braces and to analyze the scientific data presented to date. Prophylactic braces have been shown to be ineffective in preventing knee injuries in its present day design. Evidence also has shown that their use may even lead to increased knee injuries. Rehabilitative braces, on the other hand, do serve a useful purpose in regard to the operative and non-operative treatment of ligamentous knee injuries. With their ease of application and control of joint motion, they are an important addition to the surgeon's armamentarium. One must keep in mind, however, that these braces provide little static anterior/posterior control and the hinge settings may not actually affect true joint motion. Functional knee braces may play a role in the treatment of patients with pathological laxity due to an injury of the anterior cruciate ligament. Combined with an adequate rehabilitation program and activity modification, these braces do limit excessive anterior tibial translation under low loading conditions. However, under conditions of high loading these braces provide little or no resistance to anterior translation. Therefore, in most sporting activities, their efficacy is questionable. Knee bracing continues to be a complex and controversial topic in the field of orthopedic surgery.(ABSTRACT TRUNCATED AT 250 WORDS)     

Sense and nonsense of knee orthosis

The trend for early mobility after surgical treatment of knee joint ligament injuries has led to the production of a large number of different braces in recent years. To allow an approximation of the very complex motion of the human knee, the use of braces with so-called physiological hinges has been recommended in the last few years. The authors report on a group of 50 patients who had sustained injuries to the cruciate ligament and had received IOWA knee braces following surgical treatment, the fit being subsequently checked by X-ray. These checks clearly demonstrated that the hinge of the brace hardly coincides with the knee axes and that there were deviations ranging from 1 to 4 cm. The authors therefore come to the conclusion that brace-fit must be checked by X-ray in all cases and that incorrectly fitted braces should be corrected before use. There is so far no evidence that so-called physiological hinges are really superior to braces with single axes. The current trends and developments cannot really be justified as long as there is no guarantee that the axes of brace and human knee coincide both in motion and during weight-bearing.     

A computer-controlled contracture correction device with low-load and continuous torque: an animal experiment and prototype design for clinical use

The purpose of this study was to clarify the relationship between mechanical stress and tissue response of the contracted knee joint in rats and to propose a new design of contracture correction device for clinical use. Wistar rats were operated on to immobilize their knee joints with a procedure causing periarticular bleeding and were kept in flexed position for 40 days. At day 40, the immobilizing wire was removed, and after day 43, the contracted knee joint had been treated with tunable corrective devices secured by an external fixation method to the rear limb. These devices consisted of four types of motor-driving system which provided several different low-load and continuous stretch torques. Measuring the angle of maximum knee extension, its effectiveness was assessed comparing with a lower load and control group of natural recovery course. The device also had a cyclic joint movement within the acquired range of motion and an oval cam mechanism producing a small distraction force to the joint along its long axis. The results showed that an appropriate range of low-load continuous torque was more effective to correct joint contracture. On the basis of the animal experiment, a new computer-controlled, gas-driven contracture correction device was developed for clinical trial. It was concluded that mechanical application in a condition with low and continuous torque is a useful treatment for fixed joint contracture.     

A study of function and residual joint stiffness after functional bracing of tibial shaft fractures

Ninety-eight diaphyseal tibial fractures were treated with custom made functional braces in 97 patients older than 14 years of age. The average follow-up period was 1.86 years, and 53 patients had more than two years' evaluation (average, 2.83 years). The majority of the patients did not have full range of movement in the ankle and subtalar joints when the brace was removed after fracture healing. Although the stiffness decreased with time, a significant number of patients were left with residual joint stiffness. At an average follow-up period of 1.86 years, 68.4% of the patients had normal ankle motion and 60% had normal inversion and eversion of the hindfoot. In patients with more than two years' evaluation, 75.5% had normal ankle movement and 71.1% had normal inversion and eversion of the foot. In the knee joint, the incidence of residual joint stiffness was small and the amount of stiffness was clinically insignificant. Patients with an abnormal walking pattern after fracture healing had a high incidence of ankle and subtalar joint stiffness.     

Functional outcome after excision of heterotopic ossification about the knee in ICU patients

The objective of this study was to evaluate the degree of improvement in the range of movement in the knee joint, sitting ability, and overall ambulation in patients with heterotopic ossification of the knee joint who underwent surgical excision of ectopic bone. Between 1999 and 2006, 14 patients (23 joints) with significant heterotopic ossification of the knee joint that required surgery were evaluated. We compared the range of movement in the knee joint, sitting ability, and overall ambulation in the preoperative and postoperative periods using the Fuller and Keenan classification systems. Range of movement increased in 82% of cases (19 knee joints). Sitting ability improved in 13 patients (93%). Postoperatively, ambulation in eight patients (57%) was remarkably superior. In conclusion, resection of heterotopic ossification may significantly improve the range of movement in the knee joint, sitting ability, and overall ambulation.     

Kinematics of various joint mechanisms for the prosthetic substitution of the knee joint following knee exarticulation]

In the past, long amputation stumps of the thigh after knee disarticulation were difficult to fit with a knee prosthesis. Apart from other difficulties, one essential problem was caused by the fact that in preservation of the femoral length there was little or even no space to assemble a knee prosthesis at the level of the axis of the natural knee joint, that is to say at a position somewhere within the femoral condyles. In the meantime the number of knee disarticulations has increased and thus substituted the conventional above knee amputation. Consequently some new, partly polycentric knee joint mechanisms have been designed for the prosthetic fitting of knee disarticulation stumps as well as for long amputation stumps of the thigh. These mechanisms try to cope with the space problem in different ways and, moreover, some of them can also produce a moving centre of rotation at joint flexion similar to the natural knee joint. The motion pattern in current knee joint mechanisms is investigated by graphical construction of their centrodes and it is compared to the motion pattern of the natural knee joint.     

Three-dimensional knee motion before and after high tibial osteotomy for medial knee osteoarthritis

Background High tibial osteotomy (HTO) is an established surgical option for treating medial knee osteoarthritis. HTO moves the mechanical load on the knee joint from the medial compartment to the lateral compartment by changing the leg alignment, but the effects of the operation remain unclear. The purpose of this study was to evaluate the change in three-dimensional knee motion before and after HTO, focusing on lateral thrust and screw home movement, and to investigate the relationship between the change in knee motion and the clinical results. Methods A series of 19 patients with medial knee osteoarthritis who had undergone HTO were evaluated. We performed a clinical assessment, radiological evaluation, and motion analysis at 2.4 years postoperatively. The clinical assessment was performed using the Japanese Orthopaedic Association knee score. Results The score was significantly improved in all patients after operation. Motion analysis revealed that lateral thrust, which was observed in 18 of the 20 knees before operation, was reduced to 7 knees after operation. Regarding active terminal extension of the knee, three patterns of rotational movement were observed before operation: screw home movement (external rotation), reverse screw home movement (internal rotation), and no rotation. By contrast, after operation, only reverse screw home movement and no rotation were observed; the screw home movement disappeared in all patients. In the knees with reverse screw home movement after operation, the preoperative score was significantly lower than those in the knees with no rotation after operation. Conclusions Kinetically, HTO was useful for suppressing lateral thrust in medial knee osteoarthritis, although the rotational movement of the knee joint was unchanged.     

An in vivo analysis of the effectiveness of the osteoarthritic knee brace during heel-strike of gait.

The objective of this study was to analyze the effects of off-loading knee braces in patients diagnosed with symptomatic unicompartmental osteoarthritis. Under fluoroscopic surveillance, 15 patients were asked to perform normal gait on a treadmill. Each patient was asked initially to walk without using a knee brace and then to walk while wearing a brace. The fluoroscopic images of the patients at heel-strike were downloaded to a workstation computer. Condylar separation angle of the knee joint and the distances from the medial and lateral femoral condyles to the tibial plateau (condylar separation) were measured. Twelve of 15 patients (80%) reported relief of pain and demonstrated condylar separation of the degenerative compartment with the use of the off-loading brace. The 3 patients who did not demonstrate condylar separation were obese, making accurate brace fitting difficult. The average change in condylar separation and condylar separation angle was 1.2 mm (range, 0.0-4.5 mm) and 2.2 degrees (range, 0.0 degrees-7.8 degrees). This study demonstrated that condylar separation of a degenerative knee compartment can be achieved with off-loading braces with subsequent subjective relief of knee pain.     

Prophylactic knee braces and injury to the lower extremity

Five hundred and eighty high-school football players were studied over a period of two seasons to determine the effect of so-called prophylactic knee braces on the lower extremity. Two hundred and forty-seven athletes who wore single-hinged braces and eighty-three who wore double-hinged braces were paired for the same season of play with 250 athletes who were similar in height, weight, and playing position but who did not wear braces. The fifty-three injuries of the knee that occurred were significantly more frequent (p less than 0.001) in the group that wore single-hinged braces than in the matched, non-braced group. While there were more injuries of the knee in the participants who were double-hinged braces than in the matched controls, who did not wear braces, the increase in the number of injuries was not significant. There was also a dramatic increase (p less than 0.01) in the number of injuries of the ankle and foot in the athletes who wore braces. Our results question the efficacy of the braces that were studied and call attention to the potentially adverse effect of the braces on adjacent joints in the ipsilateral limb.     

Contralateral compensation with knee impairment

Knee motion of four healthy teenagers was unilaterally impaired by means of cast braces. Computerized analysis from video recording of walking was used to study the compensatory effects and to compare them with six patients. Restricted knee flexion caused little change in stance-phase knee motion on the restricted side. The unimpaired knee displayed exaggerated stance phase flexion and phase shifts, which in turn produced pelvic vaulting. The forces on the braces were high. Impairments to extension produced bilateral crouch without loss of flexion extension patterns within the limits of the impairment. Fatigue was more prominent than with blocks to flexion. Circumduction was found to be overrated as a compensation for stiff-leggedness. Lateral shift to the well side, combined with freezing of the well-side stance adduction, was a frequently used effective clearance mechanism. Phasic changes in motion of many body parts may combine to produce low-level pelvic displacement, especially when clinical weakness is present. Shortened stride length is the most sensitive indicator of this phenomenon. Graphs of individual joint motion do not easily convey the important phasic relationships that are fundamental to that motion and to the interpretation of its effects. Stick figures were better for analysis of this aspect of motion analysis, even though they are more subjective.     

Three-month efficacy of three knee braces in the treatment of medial knee osteoarthritis in a randomized crossover trial

Immediate biomechanical and functional effects of knee braces are often reported, however, the duration and type of knee brace treatment for knee osteoarthritis (KOA) remain unclear. The objective was to evaluate usage, comfort, pain, and knee adduction moment (KAM) of three knee braces each worn 3 months by patients. Twenty-four patients with KOA were assigned in a randomized crossover trial a valgus three-point bending system brace (V3P-brace), an unloader brace with valgus and external rotation functions (VER-brace) and a stabilizing brace used after ligament injuries (ACL-brace). Functional questionnaires and gait assessment were carried out before and after each brace wear period of 3 months. A Friedman test was applied between brace wear diary recordings. Repeated measures analyses of variance contrasted the factors brace type (ACL, V3P, and VER), time (pre and post) and wear (without and with) on comfort, pain, function, and KAM. Brace usage was similar, but the V3P-brace was slightly less worn. Discomfort was significantly lowered with the VER-brace. All knee braces relieved pain and symptoms from 10% to 40%. KAM angular impulse was reduced with the three braces, but the VER-brace obtained the lowest relative reduction of 9%. The interaction between time and wear indicated that part of the KAM reduction with brace wear was maintained post treatment. All three knee braces have great benefits for pain and function among the medial KOA population. The VER-brace offers additional advantages on daily use, comfort and KAM, which could improve compliance to brace treatment.     

Three dimensional kinematics of the knee joint

The study deals with 3 d-Kinematics and stability patterns according to a knee joint testing machine. During flexion the lateral femoral condyle displays near extension pure rolling, near flexion pure gliding, on the medial side this ratio is vice versa. 41 knee joint specimen provided internal-external transverse rotation during there whole range of motion. Additional varus rotation and medial translation occurred. In osteoarthritis the movement patterns were completely changed.     

Functional analysis of the effect of the posterior stabilising cam in two total knee replacements. A comparison of the Insall/Burstein and Bisurface prostheses

The Bisurface knee prosthesis (BP) has a posterior stabilising cam (ball-and-socket joint) in the mid-posterior region of the femorotibial joint in an attempt to improve the range of movement. Based on an in vitro weight-bearing study contact areas of the Insall/Burstein 2 (IB2) and the BP knee were compared using pressure-sensitive films. The stability afforded by the cam was evaluated by means of dislocation distances in the vertical and horizontal planes. Significant adverse anterior translation in mid-flexion was not observed with the BP knee since the cam was effective above 60 degrees of flexion. At flexion of 60 degrees or more, the total contact areas were larger, as the cam represented a weight-bearing surface. The dislocation distances for the BP knee compared favourably with those for the IB2 knee. We conclude that the cam of the BP knee allows good movement, stability and wear.     

The effectiveness of self-adjustable custom and off-the-shelf bracing in the treatment of varus gonarthrosis

BACKGROUND: A recent development in valgus-producing knee braces has been the adjustable "unloader" brace. The purpose of this study was to compare the effectiveness of off-the-shelf and custom-made patient-adjustable, valgus-producing knee unloader braces in relieving pain, reducing stiffness, and improving function and in reducing varus angulation and the peak adduction moments about the knee during gait and stair-stepping in patients with painful varus gonarthrosis of the knee. METHODS: Ten adult patients served as their own controls for the measurement of baseline values and then wore each of the two braces, one after the other, for four to five weeks in a random order. Pain, stiffness, and function were assessed with the Western Ontario and McMaster Universities Osteoarthritis Index. Gait and stair-stepping were evaluated with a three-dimensional motion analysis system and multicomponent force platform. Full-length (hip, knee, and ankle) standing anteroposterior radiographs were used to determine alignment of the knee. RESULTS: Both braces significantly reduced pain and stiffness (p<0.05), with the custom brace reducing stiffness significantly more than the off-the-shelf brace (p=0.030). The custom brace significantly improved function (p=0.010) and reduced the peak knee adduction moments during gait (p=0.033) and stair-stepping (p=0.002) compared with baseline values and compared with the off-the-shelf brace (p=0.029 and p=0.027, respectively). The custom brace significantly reduced varus angulation of the knee by 1.5 degrees compared with baseline (p=0.001) and by 1.3 degrees compared with the off-the-shelf brace (p=0.009). The off-the-shelf brace did not significantly reduce the varus angle. CONCLUSIONS: We investigated only the short-term effects of custom and off-the-shelf patient-adjustable valgus-producing knee "unloader" braces and found that patients with varus gonarthrosis of the knee may benefit significantly with respect to pain relief and reduced stiffness from use of either brace. However, such patients may experience additional significant benefit in improved function and reduced stiffness, varus angulation, and medial compartment loading of the knee from use of the custom-made patient-adjustable brace.     

Kinematische Analyse vor und nach bikondylärem Oberflächenersatz des Kniegelenks

Knee joint motion appears as a hinge movement around the flexion-extension axis. Corresponding to the rolling-sliding mechanism and alternative models of knee joint kinematics, an instant center pathway must be expected. The current photogrammetric investigation aimed to analyze these pathways when assessed in the sagittal plane in patients with preoperative varus or valgus deformity. A total of 40 patients either with varus or valgus deformity (20 in each group) were examined before and 6 months after implantation of PFC-SIGMA prostheses. Apart from the influence of knee joint deformity, a so-called soft tissue ratio was investigated. Therefore, the relation of thigh and femur as well as lower limb and tibia diameters was calculated and combined in one value. The investigation unit consisted of a standardized chair with passive knee joint movement (90-0 degrees flexion) supported by an electric motor. The position of predefined skin markers was assessed by digital camera with online transmission to a PC. The instant center pathway was then evaluated applying the Reuleaux technique based on the changes of skin marker positions. Results showed the following characteristics: small values of soft tissue ratio were represented by round or oval courses of the pathway whereas increasing ratios led to triangular and slightly increased dimensions of the courses. Varus deformity was primarily combined with an increase of the pathway's dimension and in contrast, valgus deformity showed decreased pathways. In each case, dimensions normalized after prosthesis implantation. The instant center pathway of knee joint motion showed for both patient groups characteristic phenomena. They were clearly associated with constitutional and clinical features of each patient.