The Relationship Between Superficial Lower Leg Length and Plantaris Tendon Length for Tendon Graft Availability: An Anatomical Morphometric Study in Cadavers

Background: The Plantaris tendon is a viable option for tendon grafting in various reconstructive procedures. This study aimed to develop a predictive model estimating plantaris tendon length (PTL) based on lower leg length (LL) to provide a preoperative baseline reference. Methods: An investigation was conducted on 238 lower limb sides from Thai cadavers to determine the prevalence and morphometry of the plantaris muscle. Measurements included PTL, tendon width (PTW), muscle belly length (PBL), total muscle length (PML), and LL. Results: The plantaris muscle was present in 88.24% of lower limb sides. A significant correlation was observed between PTL and LL (r = 0.581, p < 0.001). The predictive equation established was: PTL (mm) = 79.167 + [0.574 × LL (mm)], with a standard error of estimate of 20.06 mm. Testing on a separate sample showed no significant difference between predicted and actual PTL values (p = 0.206). Out of the 179 sides measured, 64.80% met the criteria for tendon graft suitability. Conclusions: These findings indicate that LL serves as a practical surface measurement providing an approximate preoperative estimate of PTL in a Thai population. Due to its moderate predictive power, it should be used as a supplementary assessment rather than a sole planning tool for surgical applications.