According to most literature, the quadriceps muscle is described as a four-bellied muscle; the rectus femoris and the three vasti muscles. This study provides a fifth muscle; the tensor VI (TVI).
During a dissection an additional muscle was found, that couldn’t be clearly assigned to the vastus lateralis or vastus intermedius. The aim of this study was therefor to clarify whether the TVI was an additional muscle.
In all 26 cadavers a separately innervated TVI muscle was found. It has its origin between the muscle fascias of the VL and VI. It continues distally into a flat and broad aponeurosis and has its insertion on the medial side of one of the deep layers of the quadriceps tendon.
In most cases, the TVI could easily be separated and distinguished from the VL and VI, all three between the intertrochanteric line and the greater trochantor. In some cases, the TVI was inseparable from the aponeurosis of the VI.
In previous literature, the VI is described as the deepest layer. The TVI can be described as the middle layer and the VL the superficial layer. The TVI could also be identified as a fascia layer and it is therefore important to have a good anatomical knowledge before dissection.
This is the first study to describe the TVI, however its specific function is not mentioned. Further research is necessary to identify any pathologies and its specific biomechanical function.
> From: Grob et al., Clin Anat 29 (2016) 256-263(Epub ahead of print)