In this randomized controlled trial the investigators will compare the results after primary anterior cruciate ligament (ACL) reconstruction using two different methods for femoral fixation of a bone-patellar tendon-bone (BPTB) autograft. Interference screws have been the standard method for fixing the femoral side of BPTB grafts; however, several pitfalls have been reported. Cortical fixation with the Endobutton CL BTB Fixation System has become available and the clinical results have been described as promising; however, no randomized controlled trials comparing these two femoral fixation methods have been conducted, and there is no published data that confirms that the bone block heals in the tunnel with the newer method.

The aim of our study is to compare the outcome after primary ACL reconstruction with BPTB autografts using the Endobutton CL BTB or metal interference screw for femoral fixation.

Primary anterior cruciate ligament (ACL) reconstructions with bone-patellar tendon-bone (BPTB) autografts have recently been found to have a lower risk of revision compared with hamstring tendon autografts, and BPTB has again become our graft of choice. Interference screws have been the standard method for fixing the femoral side of a BPTB graft; however problems such as damage of the graft and failure due to nonparallel screw placement have been reported. Cortical fixation using a suspensory system has been used for soft-tissue graft fixation for several years, and a corresponding device, the Endobutton CL BTB Fixation System (Smith & Nephew, Inc., Andover, MA, USA), has become available for fixation of bone-tendon-bone grafts. The clinical results after fixation with the Endobutton CL BTB have been described as promising; however, no randomized controlled trials comparing these two fixation methods have been conducted, and there is no published data that confirms that the bone block heals in the tunnel with the newer method.

In this randomized controlled trial, patients undergoing primary ACL reconstruction will be randomized into either an Endobutton group or an interference screw group. The primary aim of the study is to compare these two fixation methods, assessed by patient reported outcomes, laxity, range of motion and muscle strength. Knee related quality of life 2 years after surgery is the primary outcome, measured by the Knee injury and Osteoarthritis Outcome Score (KOOS) subscale "knee related Quality of life (QOL)". Other aims are to see if there is any difference in the integration of the bone block in the femoral tunnel assessed by CT scan, in the risk of developing osteoarthritis assessed by radiographs, or in the risk of a postoperative complication or revision. The patients will be followed up 6 weeks, 6 months, 2 years and 10 years after surgery. CT scan will be performed after 6 months, and radiographs after 2 years and 10 years. In addition details of the rehabilitation will be recorded. Patients undergoing a revision will be followed up but excluded from further comparisons in the study.

Our hypothesis is that there is no difference in the outcome after primary ACL reconstruction with BPTB autografts using the Endobutton CL BTB or metal interference screw for femoral fixation, both with a metal interference screw for the tibial fixation.

Inclusion Criteria:

• Primary reconstruction of ACL ruptures
• Surgery at least 6 weeks after injury
• The patient must accept and sign the informed consent form before surgery

Exclusion Criteria:

• Medical indication for using another graft than BPTB autograft (such as history of anterior knee pain or occupations etc. requiring frequent kneeling)
• Previous major surgical procedures in the same knee
• Major additional injuries in the knee (posterior cruciate ligament, lateral collateral ligament, medial collateral ligament, sutured meniscus lesions and major cartilage lesions undergoing cartilage repair)
• Contralateral ACL injury (treated or untreated)
• Present or former serious illness that makes follow-up or rehabilitation difficult (e.g. alcohol or drug abuse, psychiatric disease)