Anatomic dimensions of the patella measured during total knee arthroplasty.

The anatomic measurements of 92 patellae with normal underlying bony structure were studied during total knee arthroplasty before and after resection of the articular surface. The articular surface of the patella was found to have an oval shape with a width-to-height ratio (46 x 36 mm) of 1.30. The dome was 4.8 mm high and displaced medially 3.6 mm. The medial facet was slightly thicker than the lateral facet (18 vs 17 mm). The lateral facet is 25% wider than the medial facet. Coverage provided by oval patellar prostheses was significantly better than with round prostheses. The patellae in women were significantly smaller than in men. Size differences and deformity need to be taken into account when the patella is prepared for resurfacing. It is recommended that the bony resection should be no greater than one third of the maximum patellar thickness to avoid alteration of normal bony structure. Key words: patella, total knee arthroplasty, anatomy.