Composite interference screws containing calcium phosphate for anterior cruciate ligament graft fixation could improve implant/bone integration and thereby reduced tunnelwidening and graft slippage. The present study investigated the effect of polylactate/hydroxyapatite interference screw (HA/PLLA) screw used for tibial graft fixation on tunnel widening and clinical outcomes compared with a metal interference screw. We hypothesized less tibial tunnelwidening with HA/PLLA screws compared to metal screws. Hundred patients with HA/PLLA screw tibial fixation was compared with 100 patients with metal screw tibial fixation. Tibial tunnel widening was measured on AP and lateral radiographs taken at 12 months follow-up. Clinical outcome was assessed by objective and subjective international Knee Documentation Committee (IKDC) scores, Noyes Sports Activity and Occupational Rating scores and KT-1000 knee laxity measurements. Tibial tunnel widening at the level of the metal screw group was 36% and 38% on AP and lateral radiographs respectively. Tunnel widening was lower in the HA/PLLA group with mean tunnel widening of 30% and 32% (p=0.012 and 0.018) on AP and lateral radiographs respectively. No differences were found for any of the clinical scores or for anterior knee laxity. The use of a polylactate/hydroxyapatite interference screw resulted in less tibial tunnel widening than a metal screw around the screw but did not affect clinical outcome or objective knee laxity.