The gracilis and semitendinosus muscles: a morphometric study on 18 specimens with clinical implications

The pes anserinus consists of the sartorius, semitendinosus, and gracilis muscles. They coalesce together with the leg fascia to form the anserine plate. The semitendinosus and gracilis both form the deep layer of this plate and are clinically relevant for ligament reconstruction. The aim of the study is to report a detailed morphometric evaluation of the semitendinosus and gracilis muscles and assess their clinical implications.

Using a rigorous dissection process on 18 cadaveric hips, measurements of both the semitendinosus and gracilis muscles with bone parameters were conducted. We measured the following: (a) total femur, femoral shaft, and neck lengths, (b) total muscle lengths, and (c) intra-muscular and extra-muscular (free) tendon lengths. Correlation values between bone variables, muscle variables, and in-between muscle variables were computed.

The total muscle and the distal intra-muscular tendon length of the St and Gr are correlated with the total femur length. When compared to gracilis, the total muscle and distal intra-muscular tendon lengths of the ST are much better correlated with the total femur length. The free distal tendon length for both muscles did not show a significant correlation with any of the femoral bone lengths.

The variability of tendon length of the ST/Gr poses a significant challenge to surgeons. This study reports a detailed morphometric evaluation of the ST/Gr hamstring muscle and tendons. It revealed a positive correlation between the femoral length and the ST/Gr graft lengths. This could help orthopedic surgeons in predicting the graft lengths pre-operatively and develop better planning for reconstructive surgeries.