***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: Objective : To assess the presence of tibial bone tunnel enlargement after surgical reconstruction of the anterior cruciate ligament using quadruple graft of the flexor tendons and correlate the functional results in their presence . Methods : The studied lasted six months and included 25 patients , with ages ranging from 18 to 43 years old . Assessment was based on radiographs taken immediately postoperatively and at the third and sixth month of follow up in the anterior cruciate ligament reconstruction .  Reconstruction of ligaments was performed with tendon grafts of the semitendinosus and gracilis muscle fixated in the femur with transverse metal screw and in the tibia with interference screws . Patients were evaluated objective ly by tests ligament , grade d from zero to four crosses and subjectively by the Lysholm method preoperative and after sixth month follow up . Results : Significant increase in the tunnels diameters were observed , 20.56 % for radiographs in the anteroposterior view , 26.48 % in profile view and 23.22 % in computed tomography . Descriptive statistics showed significant improvement in subjective and objective clinical parameters . Conclusions : The bone tunnel enlargement is a phenomenon found in the first months after surgical reconstruction of the anterior cruciate ligament and it has no implication s on clinical outcomes in the short term . Level of Evidence II , Prospect i ve Study BACKGROUND Bone tunnel enlargement after anterior cruciate ligament ( ACL ) reconstruction is well documented in the literature . The cause of this tunnel enlargement is unclear , but is thought to be multifactorial , with mechanical and biological factors playing a role . AIM The aim of this prospect i ve study was to evaluate how the different techniques may affect the bone tunnel enlargement and clinical outcome . PATIENTS AND METHODS Forty-five consecutive patients undergoing ACL reconstruction with autologous doubled semitendinosus and gracilis tendons  entered this study . They were r and omly assigned to enter group A ( In-Out technique , with cortical fixation and Interference screw ) and group B ( Out-In technique , metal cortical fixation on the femour and tibia ) . At a mean follow-up of 10 months , all the patients underwent CT scan exam to evaluate the post-operative diameters of both femoral and they underwent tibial tunnels clinical examination after 24 months . RESULTS The mean femoral tunnel diameter increased significantly from 9.05±0.3 mm to 10.01±2.3 mm in group A and from 9.04±0.8 mm to 9.3±1.12 mm in group B. The mean increase in femoral tunnel diameters observed in group A was significantly higher than that observed in group B ( p < 0.05 ) The mean tibial tunnel diameter increased significantly from 9.03±0.04 mm to 10.68±2.5 mm in group A and from 9.04±0.03 mm to 10.±0.78 mm in group B. The mean increase in tibial tunnel diameters observed in group A was significantly higher than that observed in group B ( p < 0.05 ) . No clinical differences were found between two groups and no correlations between clinical and radiological results were found in any patients of both groups . CONCLUSIONS Results of the study suggest that different mechanical fixation devices could influence tunnel widening . The lower stiffness of the fixation devices is probably responsible of the tunnel widening through the fixation devices 's micromotions in the femoral and tibial tunnels Background Several problems have been reported with use of allogenic grafts in anterior cruciate ligament reconstruction , including local immune response to allograft tendon within the synovial fluid , delayed maturation and ligamentization , and progressive tibial tunnel enlargement . Hypothesis There is a correlation between the use of allograft and tibial tunnel enlargement . Study Design Controlled laboratory study . Methods Twenty healthy adult female goats underwent allograft anterior cruciate ligament reconstruction  and were followed with serial radiographs at 6-week intervals . Animals were r and omly chosen for sacrifice between 18 and 36 weeks for histologic assessment . Results Significant radiographic increases in tunnel size were noted within the first 6 weeks of healing and remained up to 36 weeks with no further remodeling noted . Histologic analysis showed progressive ligamentization of the allografts with tendon-to-tunnel wall biologic fixation with dense connective tissue . Remodeling and incorporation of the bone plug was seen in all cases . The allograft tendon underwent early fibrous attachment within the tunnel and remodeled toward ligament histologic structure . Remodeling and incorporation of the bone plug was seen by 18 weeks . Conclusion Tibial tunnel enlargement , consistent with that seen in humans after  allograft anterior cruciate ligament reconstruction  , did not appear to affect the ultimate incorporation of the allograft on a histologic level BACKGROUND Femoral and  tibial tunnel widening ( TW ) after ACL reconstruction is a phenomenon increasing talk in the literature . It is underlying biological and mechanical causes . OBJECTIVE The aim of this study was to evaluate the relationship between bone tunnel enlargement and two different ACL fixation systems . PATIENTS AND METHODS 40 patient underwent ACL reconstruction with hamstring ; r and omly divided into group A with 20 patients treated with stiff systems ( femoral Rigidfix and tibial interference screw ) , and into group B , with 20 patients treated with morel elastic system ( femoral and tibial Tight-rope ) . Evaluated postoperatively with knee MRI at 40 days , 3 months , 6 months to measure bone tunnel diameters widening . RESULTS At 40 days tunnel widening between two groups shows no statistically difference . At 3 months postoperatively , femoral bone tunnel widening amounted on average to 1.84 mm in middle of tunnel and 1 mm at the mouth in joint in group A , and respectively 3.2 mm and 2.5 mm in group B ( p<0.05 ) . Tibial tunnel widening was 1.24 mm at the mouth in joint and 1.3 mm in middle in group A and respectively 2.26 mm and 2.43 mm in group B ( p<0.05 ) . At 6 months femoral tunnel widening amounted on average to 2.45 mm in middle and 1.35 mm at the mouth in joint in group A and respectively 3.5 mm and 2.7 mm in group B ( p<0.01 ) . Tibial tunnel widening amounted on average to 1.27 at mouth in joint and 1 mm in middle of tunnel in group A and respectively 2.6 mm and 2.3 mm in group B ( p<0.01 ) . CONCLUSIONS This study results suggest elastic fixation system increases bone tunnel enlargement after ACL reconstruction with hamstring without correlation with worse clinical performance . LEVEL OF EVIDENCE IV Anatomical observation and biomechanical studies have shown that the anterior cruciate ligament ( ACL ) mainly consists of two distinct bundles , the anteromedial ( AM ) bundle and posterolateral ( PL ) bundle . Conventional single-bundle ACL reconstruction techniques have focused on the restoration of the AM bundle while giving limited attention to the PL bundle . The purpose of this prospect i ve , r and omized clinical study is to compare the outcomes of ACL reconstruction when using either double-bundle or single-bundle technique and bioabsorbable interference screw fixation , and similar rehabilitation with both techniques . Sixty-five patients were r and omized into either double-bundle ( n = 35 ) or single-bundle ( n = 30 ) ACL reconstruction with hamstring tendons and bioabsorbable screw ( Hexalon , Inion Company , Tampere , Finl and ) fixation in both groups . The evaluation methods were clinical examination , KT-1000 arthrometer measurements , radiographic evaluation , as well as International Knee Documentation Committee and Lysholm knee scores . There were no differences between the study groups preoperatively . For an average of 14 months of follow-up ( range 12–20 months ) , 30 patients of the double-bundle group and 29 patients of the single-bundle group were available ( 91 % ) . At the follow-up , the rotational stability , as evaluated by pivot shift test , was significantly better in the double-bundle group than in the single-bundle group . However , in anterior stability of the knee , there was no significant difference between the groups . None of the patients in the double-bundle group had graft failure , while four patients in the single-bundle group had . In addition , knee scores were equal at the follow-up , and all the results were significantly better at the follow-up than preoperatively , in both groups PURPOSE The purpose of this study was to determine the time frame for tibial tunnel expansion in patients undergoing anterior cruciate ligament ( ACL ) reconstruction with hamstring autografts using an endoscopic technique . Does this expansion occur immediately after surgery or over the first 12 weeks of rehabilitation ? TYPE OF STUDY Observational study involving 10 patients . METHODS The single incision technique used a transtibial approach for drilling the femoral tunnel . Femoral fixation was accomplished with a closed-loop EndoButton ( Acufex , Smith & Nephew ; Mansfield , MA ) and tibial fixation with a soft tissue screw and washer augmented by a polylactic acid interference screw . Computed tomography ( CT ) scans were taken in a consistent manner at weeks 1 and 12 after surgery to measure tibial and femoral tunnel expansion . RESULTS The CT scans showed significant widening of the tibial tunnel between 1 and 12 weeks ( mean area of tibial tunnel increased from 82.5 to 112.7 mm2 ; P = .001 ) . Expansion of the femoral tunnel was also seen ; however , this change was not statistically significant ( P = .18 ) . CONCLUSIONS The expansion after surgery occurred over time , not immediately after surgery , and was probably caused by factors other than surgical technique . The significance of tibial tunnel expansion needs to be clinical ly correlated with a long-term study on the effect of tunnel expansion on graft survival Background : A long-term follow-up comparing double-bundle and single-bundle techniques for anterior cruciate ligament ( ACL ) reconstruction has not been reported before . Hypothesis : Double-bundle ACL reconstruction may have fewer graft ruptures , lower rates of osteoarthritis ( OA ) , and better stability than single-bundle reconstruction . Study Design : R and omized controlled trial ; Level of evidence , 2 . Methods : Ninety patients were r and omized for double-bundle ACL reconstruction with bioabsorbable screw fixation ( DB group ; n = 30 ) , single-bundle ACL reconstruction with bioabsorbable screw fixation ( SBB group ; n = 30 ) , and single-bundle ACL reconstruction with metallic screw fixation ( SBM group ; n = 30 ) . Evaluation methods consisted of a clinical examination , KT-1000 arthrometer measurements , International Knee Documentation Committee ( IKDC ) and Lysholm knee scores , and a radiographic examination of both the operated and contralateral knees . Results : Eighty-one patients ( 90 % ) were available at the 10-year follow-up . Eleven patients ( 1 in the DB group , 7 in the SBB group , and 3 in the SBM group ) had a graft failure during the follow-up and went on to undergo revision ACL surgery ( P = .043 ) . In the remaining 70 patients at 10 years , no significant group differences were found in the pivot-shift test findings , KT-1000 arthrometer measurements , or knee scores . The most OA findings were found in the medial compartment of the knee , with 38 % of the patients in the operated knee and 28 % of the patients in the contralateral nonoperated knee . However , no significant group difference was found . The most severe OA changes were in the patients who had the longest delay from the primary injury to ACL reconstruction ( P = .047 ) and in the patients who underwent partial meniscal resection at the time of ACL reconstruction ( P = .024 ) . Conclusion : Double-bundle ACL reconstruction result ed in significantly fewer graft failures than single-bundle ACL reconstruction during the follow-up . Knee stability and OA rates were similar at 10 years . The most severe OA changes were found in the patients who had the longest delay from the primary injury to ACL reconstruction and in the patients who underwent partial meniscal resection at the time of ACL reconstruction PURPOSE The purpose of this study was to determine the amount of tibial and femoral bone tunnel enlargement after double-bundle anterior cruciate ligament ( ACL ) reconstruction . METHODS Twenty-five consecutive patients undergoing primary double-bundle hamstring ACL reconstruction were included in a prospect i ve case series . Femoral fixation was performed by means of 2 EndoButton CL devices ( Smith & Nephew Endoscopy , And over , MA ) , and tibial fixation was done with 2 bioresorbable interference screws . Magnetic resonance imaging ( MRI ) was performed in all patients at a mean of 12.3 months postoperatively . Tunnel enlargement was determined by digitally measuring the widths perpendicular to the long axis of the anteromedial ( AM ) and posterolateral ( PL ) tunnels on an oblique coronal and axial plane . The MRI measurements were compared with the intraoperative drill diameter . RESULTS The mean tibial AM bone tunnel diameter increased from 0.74 to 1.06 cm , and the mean PL diameter increased from 0.60 to 0.89 cm . The mean femoral AM bone tunnel diameter increased from 0.71 to 0.97 cm , and the mean PL diameter increased from 0.58 to 0.85 cm . Bone tunnel enlargement was 43 % ( P = .001 ) for both tibial tunnels and 35 % ( P = .001 ) versus 48 % ( P < .001 ) for the femoral AM 
    Output:
    
Bone – patellar tendon – bone ( BPTB ) allograft had the largest average tunnel widening overall .
BPTB autograft had the lowest average tunnel widening overall .
Double-bundle hamstring graft configuration had a lower average tunnel widening than single-bundle configuration .
Rehabilitation protocol s after ACLR that used a full weight-bearing prescription in rehabilitation showed a greater average femoral tunnel widening than partial weight-bearing , and partial weight-bearing showed a greater average tibial tunnel widening than full weight-bearing .
With respect to graft types , double-bundle hamstring autografts reported lower average femoral and tibial TW than single-bundle hamstring autografts .
BPTB autografts reported the lowest average TW and BPTB allograft the largest average TW of all the grafts .