Intraoperative conversion of a four-strand hamstring autograft to a five-strand configuration during an anterior cruciate ligament (ACL) reconstruction has been reported. However, the expected change in graft size and the dependence on patient characteristics are currently not well described. The purpose of this study was to determine the effective change in hamstring graft diameter and reliance on patient characteristics when intraoperatively converting a four-strand hamstring autograft into a five-strand configuration during an ACL reconstruction. A prospective, paired cohort study design was used to measure individual hamstring autograft diameter intraoperatively using traditional four-strand configuration followed by a five-strand configuration. All hamstring tendons included were long enough to consider a five-strand configuration. Five-strand hamstring autograft increased graft diameter in all patients. Hamstring tendon graft diameter increased by an average of 0.99mm (95% confidence interval [CI]: 0.84-1.11) in the five-strand configuration compared with the traditional four-strand configuration (mean: 7.8mm). There was no significant difference in the average increase in graft diameter between males (1.04mm) and females (0.92mm) ( p =0.323). Eighty-three percent (95% CI: 57.8-95.6) of average graft diameters <= 8mm in the four-strand configuration achieved an average graft diameter of >8mm in the five-strand configuration, and 70% (95% CI: 35.4- 91.9) of four-strand configuration average diameters<8mm achieved an average graft diameter>8.0mm in the five-strand configuration. Five-strand hamstring autograft reliably increased intraoperative hamstring tendon autograft diameter, with an average of 1mm, compared with traditional four-strand configuration. This increase in diameter is independent of sex and remained significant when controlling for age, laterality, body mass index, and semitendinosus length.
