* Study design: Monocentric, prospective, randomised study. Patients who need revision anterior cruciate ligament reconstruction and show a tunnel enlargement of >10mm will have a first operation filling the tibial/femoral tunnel either with bone graft substitute (Actifuse) or autologous spongiosa.~5 - 6 months after this first operation a CT will be performed to assess the bony consolidation of the former tibial/femoral tunnel. An MRI will be performed to assess vitality of the bone substitute.~An osseous biopsy will be taken from the tibial/femoral tunnel at the revision anterior cruciate ligament reconstruction approximately 6 months after bone grafting.~Clinical evaluation will be performed 6 weeks, 3 months and 6 months postoperative. At 6 months postoperative additional radiological evaluation and clinical assessment using the SF36 questionnaire will be performed.~Treatment: Either autologous spongiosa or Actifuse (MIS applicator) will be administered by the investigator as a bone graft substitute for tunnel enlargement in patients undergoing revision anterior cruciate ligament reconstruction.~Duration of Participation: The participation of each subject will be approximately 12 months.~Each subject will undergo revision anterior cruciate ligament reconstruction approximately 6 months after bone grafting. A biopsy will be taken at this operation. A clinical and radiological follow up is planned for further 6 months.~* Subjects: Male and female patients ≥ 18 years. Approximately 40 patients who undergo revision anterior cruciate ligament reconstruction will be included in the study.~Inclusion criteria: Patients in need of revision anterior cruciate ligament reconstruction Exclusion criteria: Infection, wound healing complications
The overall objective is the histological and radiological assessment of bony consolidation of the tibial/femoral tunnel using either bone graft substitute (Actifuse) or autologous spongiosa in patients undergoing revision anterior cruciate ligament reconstruction.~Clinical correlation with the histological and radiological results using the SF36 questionnaire.