Kaum ein anderes Gelenk im menschlichen Körper gibt uns heute noch so viele Rätsel auf wie das Patellafemoralgelenk. So vielfältig die Diagnosen und Beschreibungen der Krankheitsbilder sind, so sehr unterscheiden sich die möglichen Therapieverfahren, ohne dass deren Sinn und Nutzen durch kontrollierte Studien nachgewiesen wurden. Um so mehr ist die Kenntnis der Grundlagen der Anatomie, Biomechanik sowie klinischen Herangehensweise Voraussetzung, um eine adäquate Therapie einleiten zu können. Teil 1 dieses Beitrags gibt eine differenzierte Übersicht über die Grundlagen mit Anamnese sowie klinischer und bildgebender Untersuchung der wichtigsten Krankheitsbilder. Im später veröffentlichten Teil 2 wird dann die Therapie der wichtigsten Krankheitsbilder dargestellt werden.

Die Kenntnis der Grundlagen der Anatomie, der Biomechanik sowie der klinischen Herangehensweise ist Voraussetzung bei allen orthopädisch/unfallchirurgischen Pathologien, um eine adäquate Therapie einleiten zu können. Aufgrund der Komplexität des patellofemoralen Gelenkabschnittes trifft dies beim vorderen Knieschmerzsyndrom in besonderem Maße zu. Nachdem Teil 1 dieses Beitrages eine differenzierte Übersicht über die Grundlagen mit Anamnese sowie klinischer und bildgebender Untersuchung der wichtigsten Krankheitsbilder lieferte, wird in diesem Teil 2 nun eine differenzierte Darstellung der operativen und konservativen Therapiemöglichkeiten gegeben.

Bis heute gehört die Therapie der isolierten patellofemoralen Arthrose (PFA) zu den komplexesten, da die Kinematik des patellofemoralen Gelenks (PFG) nicht nur durch das distale Femur direkt, sondern indirekt auch durch die Rotation der Hüfte, Achsdeformitäten, Fußstellung und passiven Weichteilfaktoren bestimmt wird. Während die primär traumatische Genese eher selten ist, führt die Kombination von akuter oder chronischer Instabilität und begleitender Druckerhöhung im PFG zu einer ausgeprägten PFA. Aus diesem Grund können nur Kombinationstherapien, die direkte und indirekte Ursachen gleichzeitig beheben, gute Erfolge vorweisen. Allerdings fehlen bis dato Studien und damit ein Goldstandard.

Prostheses with single radius SR design were supposed to be as good as the physiological kinematic and stability of the knee. This in-vitro biomechanical study compared SR to a multiple radius MR design on the one hand and seven left human knee specimens were used. The SR and MR knee prosthesis where implanted with a navigation system. We measured varus/valgus deviation of the mechanical axis and the deviation of the joint-line to the epicondyle-line in different knee flexion degrees 0°, 30°, 45°, 60° and 90° with and without 15 Nm of varus and valgus stress. Without varus/valgus-stress in all three groups physiological knee, SR and MR prosthesis the results were located on the varus-site. The variation of the SR was less than the MR, without being significant. Under varus and valgus stress varus/valgus axis deviation constantly grew. From 0--60° no significant deviation between the two prosthesis models was found. At 90° flexion varus/valgus deviation with the SR component was significantly p ≤ 0.05 smaller compared to the MR design. This in-vitro study showed that the SR prosthesis is significantly more stable in the coronal plane than the MR in higher flexion degrees. This could have an improved effect on biomechanical stability with a higher clinical function after SR-TKA.

The purpose of this study was to evaluate the results of a contoured focal articular femoral condyle resurfacing prosthetic in the treatment of full-thickness cartilage and osteochondral defects at the medial femoral condyle of the knee beyond 5 years.

Zur operativen Therapie einer patellaren Instabilität oder degenerativer patellofemoraler Veränderungen werden im klinischen Alltag häufig knöcherne Eingriffe mit Transfers der Tuberositas tibiae eingesetzt. Dieser Eingriff hat Auswirkungen auf die retropatellare Druckbelastung und auf die Kinematik der Patella. Je nachdem in welche Richtung dieser Transfer stattfindet, werden Bereiche der retropatellaren Knorpeloberfläche entlastet und andere belastet. Die populärste Kombination der Transferrichtungen aus Medialisierung und Ventralisierung führt zu einer Entlastung der lateralen Patellafacette und zu einer Stabilisierung der Patellakinematik gegen laterale Auslenkungen und Luxationen.

Hyaline articular cartilage consists mainly of water, which is reversibly transferred to the joint space under compression to reduce friction between the cartilage surfaces. This water content is regulated by proteoglycanes, which are produced by chondrocytes. Under excessive compression of the cartilage surface the collagen matrix ruptures and water is irreversibly transferred into the joint space, which reduces the elasticity of cartilage tissue. Power training should lead to a submaximal loading of cartilage below the rupture limit as the capacity of cartilage tissue to adapt to higher loads is limited. When the cartilage tissue shows osteoarthritic changes the loading capacity of the cartilage matrix is significantly reduced, which should be taken into consideration during power training.

Die Hüftarthroskopie hat in den vergangenen Jahren durch solide klinische Arbeiten, eine Weiterentwicklung der Operationstechnik und regelmäßige Operationskurse eine zunehmende Verbreitung gefunden. Gleichzeitig wird immer häufiger und insbesondere bei jungen und aktiven Patienten mit Koxarthrose der Wunsch nach einer gelenkerhaltenden Operationsmethode geäußert. Aktuelle retrospektive Arbeiten konnten zeigen, dass die klinischen Ergebnisse der Hüftarthroskopie bei einer manifesten Arthrose schlechter sind als bei einem intakten Gelenkknorpel. Trotzdem haben sich einige gute Indikationen zur Hüftarthroskopie bei Koxarthrose herausgestellt. Durch die Entfernung freier Gelenkkörper können Blockierungen beseitigt und persistierende Belastungsschmerzen häufig gebessert werden. Die Abtragung der femoralen Cam-Deformität und die gleichzeitig durchgeführte anterolaterale Kapsulotomie führen beim femoralen Impingement auch beim Arthrosepatienten in der Regel zu einer verbesserten Beweglichkeit des Hüftgelenks. Eine realistische Einstellung des Patienten auf eine eventuell nur geringfügige Verbesserung der Beschwerden ist die Voraussetzung des Behandlungserfolgs einer Hüftarthroskopie bei Koxarthrose.

Hyaliner Gelenkknorpel besteht zum größten Teil aus Wasser, welches unter Kompression in den Gelenkspalt reversibel abgegeben wird, sodass die Reibung zwischen den Knorpeloberflächen minimiert wird. Der Wassergehalt wird von durch Chondrozyten gebildeten Proteoglykanen reguliert. Bei einer übermäßigen Belastung des Knorpels finden sich Rupturen in der kollagenen Knorpelmatrix, die zu einem irreversiblen Wasserverlust führen, wodurch das Knorpelgewebe an Elastizität verliert. Krafttraining sollte zu einer Belastung des Knorpels unterhalb der Rupturgrenze der Kollagenmatrix führen, da die Anpassungsfähigkeit von hyalinem Knorpel an erhöhte Belastungen stark limitiert ist. Besteht eine arthrotische Vorschädigung des Knorpels, ist die Belastbarkeit der Knorpelmatrix signifikant herabgesetzt, was beim Krafttraining berücksichtigt werden sollte.

BACKGROUND:Salter innominate osteotomy of the pelvis is widely used to improve the coverage of the femoral head in developmental dysplasia of the hip, but the biomechanical and geometric changes after this osteotomy are not well understood.METHODS:A CT dataset of an 8-year-old child with severe dysplasia of both hips was used to create a polyamide model of the left hemipelvis and proximal femur. The hemipelvis was mounted to a holding device and the proximal femur attached to a sensor guided industrial robot. The robot was programmed to apply joint forces and torques based on single-leg stance. Two major muscles were represented by wires connected to hydraulic cylinders; muscle forces were adjusted to balance the joint moments. Resulting joint forces were measured using a pressure measuring sensor before and after Salter osteotomy of the hip. Geometric changes were recorded using a three-dimensional ultrasound measurement system.FINDINGS:The preoperative hip joint resultant force was 583N (270% body weight), while after the operation a mean force of 266N (120% body weight) was measured. Postoperative muscle forces were roughly half the preoperative values. The hip joint was translated medially and caudally. Postoperatively, the length of gluteus medius and maximus muscles increased.INTERPRETATION:The preoperative value of the resultant hip joint force is comparable to values reported in the literature. The results suggest that Salter innominate osteotomy leads to a reduction of hip joint and muscle forces in addition to increasing joint contact area.

The aim of adapted endoprostheses is to achieve at least the same percentage of negative elongation under the same stress in an implant-bone-combination. The negative elongation is like the downward deflexion of a spring under pressure. Due to the limitations mentioned above, the comparison of spring stiffness of bone and implant is the most promising way to achieve the adapted implant elasticity aimed at.

AIM:This biomechanical study was performed to evaluate the consequences of removing the central part of the patellar tendon on the kinematics and kinetics of the femoro-patellar joint. The tendonectomy was performed in the same manner as is frequently done during anterior cruciate ligament reconstructions. Of particular interest in this study was to identify potential factors of the patellar tendon resection which could result in anterior knee pain.METHOD:A simulated isokinetic knee extension from 120 degrees of flexion to full extension was performed on nine human knee cadaver specimens. Joint kinematics was evaluated with ultrasound sensors, and retropatellar contact pressure was measured using a thin-film resistive ink pressure measuring system. Data were taken before and after resection of the central third of the patellar tendon.RESULTS:Harvesting of the central third of the patellar tendon resulted in an elongation of the remaining patellar tendon by less then 0.5 mm. Furthermore, increases in patellar flexion lower than 1 degree were observed. Small changes in retropatellar pressure were also observed.CONCLUSION:The shortening of the patellar tendon due to tendon removal, as already suggested in several previous studies, is not attributed to the removal of the central portion of the tendon itself, but more likely due to secondary scarring contraction of the tissue. The changes of the patellarkinematics and the retropatellar pressure observed in this study are probably not of any clinical significance.

Studienziel: Methode: Ergebnisse: Schlussfolgerung: Aim: Method: Results: Conclusion:

The effects of the ZrO2 content and the particle size of ZrO2 powders on the microstructure, phase composition, physical and mechanical properties, and the abrasion wear resistance of advanced Al2O3 ceramics and zirconia-toughened alumina (ZTA) composites containing 0 to 30 mass% yttria-stabilised zirconia (YSZ) were investigated. The composite with a ZTA content of 30 mass% of ZrO2 exhibited the greatest resistance to abrasion wear. α-Al2O3 reflex broadening (hkl = 113) as a result of the microstresses in the Al2O3 crystal lattice during sandblasting decreased with increasing ZrO2 amount, where the ZrO2 particles located along the grain boundaries of Al2O3, hindering their growth and deformation. The use of nanodispersed ZrO2 powder produced by the plasma chemical technique led to a 1.5-fold increase in wear resistance in the resultant ZTA ceramic.

Background. To prevent excessive tension oil 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 oil the posterior cruciate ligament load and tibiofemoral contact stress after total knee arthroplasty tinder isokinetic in vitro conditions.Methods. Twelve fresh frozen knee specimens were tested in a knee simulator. After implantation of the Interax I.S.A.(R) 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 oil the femoral inlay surface. The test cycle simulated ail 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 14.5 N (SD 4.9 N, 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 oil tibiofemoral stress at high knee flexion angles. (c) 2006 Elsevier Ltd. All rights reserved.

Animal models are necessary for the development and analysis of surgical techniques in meniscal surgery because they are the only means of preclinically determining the influence of biological factors such as healing processes and joint remodeling. Furthermore, little is known about the biomechanical effect of meniscectomy in sheep. The aim of the study was thus to investigate the efficacy of using a resistive pressure measuring sensor to quantify the effect of chronic meniscectomy in an ovine model. Twelve sheep were divided into two groups (n = 6): a sham operated control group (A), and a medially meniscectomized group (B). After six months, lower limb specimens were loaded with a joint-compressive force of 500 N during which the pressure measuring sensor was positioned underneath the meniscus to determine contact area, mean and peak contact pressure. A significant reduction in contact area of about 55% was observed in the meniscectomized knees compared to the controls. Peak contact pressure of the meniscectomized knees significantly increased an average of 260.4% compared to the control knees. Based on the results of this study, we conclude that the resistive pressure measuring sensors provide a means to experimentally measure tibiofemoral contact mechanics even in this relatively small (compared to human) animal model.

High specific strength, low density and excellent corrosion resistance are three of the outstanding properties associated with titanium. Because of these properties, titanium has found a wide range of application.Because of their low density and high absorbance of kinetic energy cellular structures are increasingly finding application. Up to now especially foaming of complex devices shows the limitations of conventional foaming processes.Rapid manufacturing is used to build up individual objects for special applications. Because of the unique therapeutic demands individual patients, prostheses optimized to the requirements of the patient should be used to replace arthritic human joints.For a long survivability of the implants, it has been suggested that they be adapted macroscopically to the elasticity of human bone. To enable the manufacture of such prostheses, three innovative technologies have to be combined. In a laser cladding process a massive titanium structure will be built up to create a scaffold which is filled with titanium foam induced by laser beam. To foam the titanium by laser beam a foaming agent has to be added to the titanium powder. With the combination of laser cladding and laser-induced foaming in a rapid prototyping process, the goal of this work is to allow the rapid manufacturing of individual prostheses with adapted elasticity.

BACKGROUND:This study addresses work sharing during navigation-assisted total knee arthroplasty. Specifically, the concept is introduced of a "navigator" assistant who operates the navigation system during surgery while the surgeon concentrates on the primary steps of surgery.METHODS:In a prospective study of 40 total knee arthroplasties, one group of patients was treated using the navigator concept, a second group was treated using a conventional navigation setup, and a third group was treated with conventional internal and external alignment jigs. Surgery time and outcome parameters were compared.RESULTS:Results show a significant difference in surgery time between the three groups. The conventional and navigator concept groups showed similar surgery times; however, the navigation group without navigation concept exhibited longer surgery time.CONCLUSIONS:The navigator concept represents a highly effective principle to minimize surgery time needed during navigated total knee arthroplasty.