Arthroscopic knee anatomy in young achondroplasia patients

Purpose Achondroplasia is the most common form of skeletal dysplasia, affecting more than 250 000 individuals worldwide. In these patients, the developing knee undergoes multiple anatomical changes. The purpose of this study was to characterise the intra-articular knee anatomy in children with achondroplasia who underwent knee arthroscopy.Methods Records of achondroplasia patients who underwent knee arthroscopy between 2009 and 2014 were reviewed. Demographic data, operative reports, follow-up notes, MRI and arthroscopy images were reviewed. Bony, cartilaginous and ligamentous changes were noted. The trochlea sulcus angle was measured from intra-operative arthroscopic images.Results A total of 12 knee arthroscopies in nine patients were performed. The mean age at surgery was 16.9 years (12 to 22). In all patients, the indication for surgery was knee pain and/or mechanical symptoms that were refractory to non-operative treatment. Three anatomical variations involving the distal femur were found in all knees: a deep femoral trochlea; a high A-shaped intercondylar notch; and a vertically oriented anterior cruciate ligament. The average trochlea sulcus angle measured 123°. Pathology included: synovial plica (one knee); chondral lesions (three knees); discoid lateral meniscus (11 knees); and meniscal tears (six knees). All patients were pain-free and returned to normal activity at final follow-up.Conclusion Children with achondroplasia have characteristic distal femur anatomy noted during knee arthroscopy. These variations should be considered normal during knee arthroscopy in these patients. Arthroscopic findings confirmed previous MRI findings within this specific population with the addition of a deep trochlear groove which was not previously reported.