A trochleoplasty is a surgical procedure to re-shape the walls of the trochlear groove.
If the groove is insufficiently deep or the walls too low, then the patella may flip out of the groove - this is called patellar dislocation.
Trochleoplasty may involve deepening the groove or elevating the wall (usually the lateral wall, which should be higher than the medial).
The procedure is known to have a relatively high failure rate, and more so in older patients, and there is also a high incidence of post-operative arthrofibrosis. It is not a procedure to be undertaken lightly and is only performed in centres with special expertise.
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