This paper reports the angle between the EF and the horizontal (the extension facet angle- EFA) in normal knees and in knees with early AMOA.
A sagittal image at the midpoint of the femoral condyle was used to determine the EFA.
There is an association between an increased EFA (ie a steeper EF) and MRI evidence of AMOA. Although a causal link is not proven, we speculate that a steeper angle increases the duration of loading on the EF in stance and tibio-femoral interface shear. This may initiate cartilage breakdown.
This paper describes a simple new MRI measurement of the axial patellar tendon angle (APTA), and compares this angle in patients with and without patello-femoral instability.
In PFI, the patella is commonly tilted laterally. This is matched by the orientation of the patellar tendon. The increased tilt of the tendon is only partially normalized at its distal insertion with an abnormal angle of tibial attachment. When performing distal realignment procedures, angular correction as well as displacement may be appropriate.
Trochlear dysplasia is an important anatomical abnormality in symptomatic patellar instability. Our study assessed the mismatch between the bone and cartilaginous morphology in patients with a dysplastic trochlea compared with a control group. MRI scans of 25 knees in 23 patients with trochlear dysplasia and in 11 patients in a randomly selected control group were reviewed retrospectively, in order to assess the morphology of the cartilaginous and bony trochlea. Inter- and intra-observer error was assessed. In the dysplastic group there were 15 women and 8 men with a mean age of 20.4 years (14 to 30). The mean bony sulcus angle was 167.90 (1410 to 2030), whereas the mean cartilaginous sulcus angle was 186.50 (1520 to 2140; p <
0.001). In 74 of 75 axial images (98.7%) the cartilaginous contour was different from the osseous contour on subjective assessment; the cartilage exacerbated the abnormality. Our study shows that the morphology of the cartilaginous trochlea differs markedly from that of the underlying bony trochlea in patients with trochlear dysplasia. MRI is necessary in order to demonstrate the pathology and to facilitate surgical planning.
This paper reports the angle between the EF and the horizontal (the extension facet angle - EFA) in normal knees and in knees with early AMOA.
A sagittal image at the midpoint of the femoral condyle was used to determine the EFA. Repeat measurements were taken by two observers.
There is an association between an increased EFA (ie a steeper EF) and MRI evidence of AMOA. Although a causal link is not proven, we speculate that a steeper angle increases the duration of loading on the EF in stance and tibio-femoral interface shear. This may initiate cartilage breakdown.
Patello-femoral instability (PFI) and pain may be caused by anatomical abnormality. Many radiographic measurements have been used to describe the shape and position of the patella and femoral trochlea. This paper describes a simple new MRI measurement of the axial patellar tendon angle (APTA), and compares this angle in patients with and without patello-femoral instability.
In PFI, the patella is commonly tilted laterally. This is matched by the orientation of the patellar tendon. The increased tilt of the tendon is only partially normalized at its distal insertion with an abnormal angle of tibial attachment. When performing distal realignment procedures, angular correction as well as displacement may be appropriate.
Cartilaginous and bony sulcus angles. Cartilage thickness in the sulcus and on both condyles. Morphology of the bony and cartilaginous surface contour (flat, convex or concave). Horizontal distance of the bony and cartilaginous sulcus measured from the lateral epicondyle. Inter and intra observer error was recorded.
The average bony sulcus angle (SA) was 166.9 degrees (141 – 203) whereas the average cartilaginous SA was 184.8 degrees (152 – 222). In 74 of 75 axial images (98.6%) the cartilaginous SA was greater than the bony SA by an average of 17.6 degrees (3 45). The average cartilage thickness in the centre of the trochlea was 3.5 mm (1.4 – 5.2), and the thickness on the lateral and medial condyles were 2.2mm (1.8 3.5) and 1.9mm (0.6 3.3) respectively. In 74 of 75 axial images (98.6%) the cartilaginous contour was different to the osseous contour on subjective assessment. In 58 of 75 images (77.3%) the cartilaginous contour changed the bony morphology from concave to flat or convex, or from flat to convex. In 17 (22.6%) it reduced the concavity. The average horizontal distance of the bony sulcus from the lateral epicondyle was 33.7mm (24 42) and that of the cartilaginous sulcus 31.8mm (23 39).
The functional results are similar or better than those of a total knee replacement. Fourteen patients developed mal-alignment (4%) two of which required distal realignment. There have been no cases of deep infection, fracture, wear or loosening. Twenty seven knees (7%) developed evidence of disease progression, twenty two of which (6%) have required revision to a total knee replacement. Nineteen patients (5%) complained of some persistent anterior knee pain of uncertain cause.