Zur Bestimmung der Dysplasie des Femoro-Patellargelenkes

Abstract

On the basis of more than 1400 tangential X-rays made with Knutsson's technique, the author qims to demonstrate, employing optical and measurement criteria, the limits between normal conditions and dysplasias. Since there are no fixed boundaries, these two areas can only be delimited from each other with sufficient accuracy by means of an inter-mediate zone. The patella is differentiated according to its shape in euplasia, medial hypoplasia and dysplasia, corresponding to the trochlea in Types I-V. In relation to the knee joint in question, there is a high degree of correlation between the development of the patella and the trochlea. All in all, a dysplasia can be determined more easily and more accurately at the trochlea than at the patella, since the patella is subject to greater projectural changes and the points of measurement are more difficult to establish. Ficat and Bizou's condylar depth index and the condylar-joint surface angle of Brattström are recommended as especially suitable methods of measurement. Since the shape of the trochlea changes as a function of the extent to which the knee is bent, the latter must be cited in comparative investigations.

Increased Magnetic Resonance Imaging Signal of the Lateral Patellar Facet Cartilage: A Functional Marker for Patellar Instability?

“…1 Since we evaluated MRIs of the knee, we chose the values provided by Wittstein et al 44 as reference. With the majority of patients presenting with lower than trochlear Hepp type 3 after surgery, we also observed a normalization 23 of the trochlear shape resulting in restoration of femoropatellar articulation.…”

“…The tracking of the patella along the trochlear groove during knee flexion and extension is stabilized by the somewhat interlocking shapes of the patella and femur, as well as supporting soft tissue structures. 11,18,23,24,43 These soft tissue constraints include the patellar tendon as a continuation of the quadriceps femoris tendon, the medial and lateral retinaculum, and the medial patellofemoral ligament. 18,24 In addition, alignment of the tibial tuberosity relative to the extensor mechanism is important to confer stability at the patellofemoral articulation.…”

“…In the knee joint, predisposition for patellar instability can be assessed by abnormal patellar tilt, sulcus angle, Insall-Salvati ratio, 24 TTTG distance, 12,16 patellar shape (Wiberg types 3-5) 43 (Figure 1), and trochlear shape (Hepp types 3-5) 23 (Figure 2). Because we used MRI, we did not measure patellar tilt or sulcus angle.…”

“…The Insall-Salvati ratio is the ratio of the length of the patellar tendon and the craniocaudal extension of the patella: Normal values are 0.8 to 1.2. 23 In MRI, the TTTG distance is defined by the horizontal distance of the trochlear groove to the tibial tuberosity, with a normal value of 9.4 6 0.6 mm. 15 The Wiberg patellar shape is determined by the size of the medial and lateral facets ( Figure 1) and types 3 to 5 are considered abnormal, predisposing patients to early osteoarthrosis.…”

“…43 The trochlear shape is determined by the symmetry of elevation of the medial and lateral trochlear surfaces ( Figure 2) and type 3 to 5 are considered abnormal, also predisposing patients to early osteoarthrosis. 23 Acute lateral patellar dislocation results in a welldescribed pattern of injuries as sprain or rupture of the vastus medialis obliquus muscle, the medial retinaculum, the medial patellofemoral ligament, and the medial patellotibial ligament. 20,38,39 Cartilage injury at the medial facet of the patella 13,34 and a specific bone contusion pattern involving the lateral femoral condyle and the inferomedial patella are also described.…”