ANATOMIC ALIGNMENT OF THE PATELLAR GROOVE

The variability in alignment of the natural patellar groove was determ ined about various anatomic axes of the femur, using 3 plane radiograp hs and electronic digitization. After the patellar groove was identifi ed and marked on 15 anatomic specimen femurs, radiographs sere taken i n the coronal, sagittal, and transverse planes so that principal anato mic axes could be outlined. Through electronic digitization, a 3-dimen sional representation of the patellar groove was constructed about the distal anatomic axis, mechanical axis, transepicondylar axes, and tra nscondylar axes. Regarding these 4 principal anatomic axes, the variab ility in orientation of the patellar groove was profound in both coron al and transverse planes, typically involving a range of 11 degrees to 16 degrees about the mean. The average orientation most closely appro ximated the perpendicular to the transepicondylar axis in the coronal plane; however, the range varied extensively. None of the anatomic axe s tested proved reliable as a reference axis for proper position of th e patellar groove, and this study shows that the orientation of the na tural patellar groove is more variable than previously suspected. The failure of femoral components to accomodate this variability may expla in many complications associated with the patellar component in total knee arthroplasty.