Abstract
Imaging techniques including MR scanning and ultrasound were discussed. However it was noted that for standard orthopaedic practice in the UK plain films were the initial imaging available. The importance of taking a skyline view was stressed.
The Dejour protocol was then outlined where the lateral Xray of the knee assesses the patellar height, the presence of dysplasia of the trochlear groove, and, if present, its boss height. A CT scan defines the patellar tilt angle, and with cuts through the tibial tubercle, the offset of the tibial tubercle from the trochlear groove (TTTG). The four abnormalities that can be defined are then corrected at operation. All patients undergo a lateral release. If the patellar tilt angle is greater than 20° then a medial reefing is performed. If the patellar height is greater than 1.2, a distalisation of the tibial tubercle to correct this to 1.0 is done. A MG of greater than 2Omm leads to a correction by an Elmsie medial tubercle transfer. A boss height of greater than 6mm suggests a trochleoplasty should be performed. However the Dejour protocol is yet to be validated.
It was concluded that imaging is essential for analysing patellofemoral instability. Plain films alone do not give enough information. Patterns of patellofemoral instability as assessed by CT scan (and MRI scan) are yet to be established. Postoperative imaging to confirm correction of abnormalities should be done. The measurements are worthwhile but their validation is awaited.
The abstracts were prepared by Mr Roger Smith. Correspondence should be addressed to him c/o British Orthopaedic Association, Royal College of Surgeons, 35-42 Lindoln’s Inn Fields, London WC2A 3PN.
