The extensor apparatus of the knee joint and its peripheral vasti: anatomic investigation and clinical relevance.

Anatomic dissections of the vastus medialis m. in 115 fixed thigh specimens always demonstrated a clear separation between a long head of the muscle (VML) inserted at the base of the patella and a short head (VMO) inserted at its medial margin. The plane of separation was identified by a branch of the femoral n. in every case. In 17 instances, the localization of the nerve was superficial; in 57, it was in the areolar fascial plane; and in 41 instances in lay deeply between the muscles. The ramification of the branch of the femoral n. traversing the plane of separation showed 4 types of variation. Dissections of the vastus lateralis m. in 42 specimens always demonstrated a separation into 2 heads: a long head inserted at the base of the patella (VLL) and a short head inserted at its lateral margin (VLO). The directions of the individual heads of the quadriceps femoris m. were angulated in relation to the long axis of the femur. The deviations were between 10 degrees and 17 +/- 8 laterally for the vastus lateralis longus m. (VLL), between 26 degrees and 41 degrees laterally for the vastus lateralis obliquus m. (VLO), between 15 degrees and 18 degrees medially for the vastus medialis longus m. (VML), and between 46 degrees and 52 degrees medially for the vastus medialis obliquus m. (VMO). The results demonstrate great variation in the distal parts of the medial and lateral anterior thigh m.