Background: The use of autograft hamstring tendons for ACL reconstruction has increased due to measurable outcomes such as decreased donor site morbidity and improved fixation methods. Final graft diameter is effective in reducing the chance of graft re-tearing. Anthropometric parameters such as age, gender, height, weight, Body Mass Index (BMI) and thigh circumferencehave been reported to be of predictive value in a variety of studies but there is poor consensus agreement. MRI based radiologic assessments also needs radiologic workstation and special software. This study investigated the relationship between pre-operative semitendinosus tendon diameter measured by MRI   and intra-operative final  graftconstruct diameter.
Methods: Adult patientsconfirmed to have anterior cruciate ligament(ACL)rupture by positive physical test and 1.5 Tesla quality magnetic resonance imaging(MRI),who were candidates for autograft ACL reconstruction entered the study. Those with previous history of ACL surgery or candidates for allograft or bone patellar bone graft reconstruction were excluded. The MRI images of the patients were uploaded into Infinitesoftware. Joint level was determined first in coronal plane and then by using cross linking option the axial joint level was defined. Using cursor and ruler tools the maximum diameters of semitendinosus tendon was measured at the joint line,and two spaces (SPs) proximal and distal to it. Semitendinosus and final graft construct diameters were measured intraoperatively.SPSS software was used to analyze the data to find possible correlations.
Results:TheSemitendinosustendon graft diameter over 3.4 millimeters at two spaces distal to joint line on axial MRI cut well correlated to  intra-operative final graft  construct diameterof over 8 millimeters.
Conclusion: The proposed measurement techniqueis a reliable option to assist the surgeonsfor pre-operative prediction of graft size in hamstring autograft reconstruction.