Trochlear dysplasia is an important anatomical abnormality in symptomatic patellar instability. Our study assessed the mismatch between the bony 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 eight men with a mean age of 20.4 years (14 to 30). The mean bony sulcus angle was 167.9° (141° to 203°), whereas the mean cartilaginous sulcus angle was 186.5° (152° to 214°; 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.

We reviewed 34 knees in 24 children after a double-elevating osteotomy for late-presenting infantile Blount’s disease. The mean age of patients was 9.1 years (7 to 13.5).

All knees were in Langenskiöld stages IV to VI. The operative technique corrected the depression of the medial joint line by an elevating osteotomy, and the remaining tibial varus and internal torsion by an osteotomy just below the apophysis. In the more recent patients (19 knees), a proximal lateral tibial epiphysiodesis was performed at the same time.

The mean pre-operative angle of depression of the medial tibial plateau of 49° (40° to 60°) was corrected to a mean of 26° (20° to 30°), which was maintained at follow-up. The femoral deformity was too small to warrant femoral osteotomy in any of our patients. The mean pre-operative mechanical varus of 30.6° (14° to 66°) was corrected to 0° to 5° of mechanical valgus in 29 knees. In five knees, there was an undercorrection of 2° to 5° of mechanical varus. At follow-up a further eight knees, in which lateral epiphysiodesis was delayed beyond five months, developed recurrent tibial varus associated with fusion of the medial proximal tibial physis.

We have summarised the clinical and pathological changes in the knees of three patients in whom aqueous chlorhexidine 0.02% had been used as the irrigation solution during arthroscopically-assisted reconstruction of the anterior cruciate ligament. Even very dilute solutions of chlorhexidine can cause marked chondrolysis of articular cartilage leading to severe permanent damage to the knee. Irrigation solutions should be checked carefully to ensure that their composition is appropriate to the procedure being carried out. Exposure of articular cartilage to chlorhexidine should be avoided.