The use of stereolithography for an unusual patellofemoral disorder.

A patient with habitual patellar dislocation which was not treated successfully by the Elmslie-Trillat procedure is described. In the knee, a unique morphologic feature of the patellofemoral joint was suspected as a cause, and a stereolithographic model was produced from the patient's computed tomography data to determine the pathologic features. Because the solid model confirmed the speculation, additional surgery was done to modify the geometry of the joint. In the surgery, cancellous bone was removed below the cartilage, and the geometry of the cartilage was modified with the subchondral bone, taking advantage of the elasticity of the bone and cartilage. The second surgery eliminated maltracking of the patella and a satisfactory result was obtained. Therefore, stereolithography is useful for the treatment of atypical patellofemoral disorders, allowing an understanding of the pathologic features and dynamic simulation of the surgery. The surgical procedure could be a promising method to alter the joint geometry without impairing the cartilage.