***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: Introduction Correct placement of both tibial and femoral tunnels is one of the main factors for a favorable clinical outcome after anterior cruciate ligament ( ACL ) reconstruction . We used an original system of computer assisted surgery ( CAS ) . The system , based on fluoroscopic guidance combined with special graphical software of image analyzing , showed to the surgeon , before drilling , the recommended placement of tibial and femoral tunnel centers . We compared the first anatomical and clinical results of this procedure to the usual one single incision technique . Material s and methods We conducted a prospect i ve study on 73 patients ; 37 patients were operated on with CAS and 36 without CAS , by the same senior surgeon . The mean age was 27 years for both groups . Every patient was review ed at an average of 2.2 years ( range 1–4.5 ) by an independent observer , using IKDC scoring system , KT-1000 , and passive stress radiographs . Results Time between ACL rupture and reconstruction averaged 30 months for both groups . CAS needed 9.3 min extra surgery time . Clinical evaluation was grade d from A to C as per the IKDC scoring system : 67.6 % A , 29.7 % B , 2.7 % C with CAS ; and 60 % A , 37.1 % B , 2.9 % C without CAS . IKDC subjective knee evaluation score averaged 89.7 with CAS and 89.5 without CAS . Pre operative KT-1000 maxi manual differential laxity averaged 7 . At revision time , all the patients after CAS had a differential laxity less than 2 and 97.7 % without CAS . Stress X-rays differential laxity averaged 2.4 mm with CAS and 3 mm without CAS . The area of dispersion of the tunnels ’ center was smaller on the femoral side using the CAS method . There was no statistically significant difference between both groups using IKDC score , KT-1000 and passive stress radiographs . Conclusions The CAS method provided a more accurate and reproducible tunnels placement without clinical significant effect BACKGROUND Accurate and precise tunnel placement is critical to the success of anterior cruciate ligament ( ACL ) reconstruction . A new development , computer-assisted surgery , aids in placement of the ACL bone tunnels during surgery . Our hypothesis was that computer-assisted ACL reconstruction would allow more accurate and precise tunnel placement compared with conventional surgery . METHODS In a prospect i ve , double-blind , r and omized clinical study , 100 patients eligible for ACL reconstruction with a transtibial technique were stratified by surgeon and r and omized to either conventional or computer-assisted surgery . Measurement of femoral and tibial tunnel placement with use of three-dimensional computed tomography ( CT ) was used as the primary outcome to compare conventional ACL surgery with computer-assisted surgery . RESULTS The placement of the femoral tunnel did not differ between groups ( mean , 39.7 % of the proximal-distal distance on the intracondylar axis [ Blumensaat line ] in the conventional group compared with 39.0 % in the computer-assisted surgery group ; p = 0.70 ) . The anterior-posterior positioning of the tibial tunnel on the tibial plateau also did not differ significantly ( 38.9 % in the conventional group compared with 38.2 % in the computer-assisted surgery group ; p = 0.58 ) . There was no significant difference in the precision of either the femoral or the tibial tunnel placement between the two groups . CONCLUSIONS There was no significant difference in either the accuracy or the precision of tunnel placement between conventional and computer-assisted ACL reconstruction PURPOSE The purpose of this prospect i ve r and omized study was to assess biomechanical , radiographic , and functional results after single-bundle anterior cruciate ligament ( ACL ) reconstruction by use of a navigation system . METHODS ACL reconstruction was performed by use of the OrthoPilot navigation system ( B. Braun-Aesculap , Tuttlingen , Germany ) in 40 patients ( group 1 ) ; and in another 40 patients ,  surgery was done by the st and ard manual targeting technique  ( group 2 ) . The anterior laxity was measured with a KT-1000 arthrometer ( MEDmetric , San Diego , CA ) . Femoral and tibial tunnel position was evaluated radiologically according to the method described by Bernard and Hertel and by Harner et al. , respectively . The question naire-based Lysholm and International Knee Documentation Committee scales were included to compare the functional state in both groups . RESULTS The knees in group 1 were as stable as those in group 2 during the arthrometer testing , with a lower value of dispersion . The postoperative Lysholm and International Knee Documentation Committee scores had the same value in both groups . Statistical differences existed with regard to anterior-posterior femoral tunnel placement when the navigated and st and ard techniques were compared ; in the navigated group , more exact results were found . No significant complications were observed . CONCLUSIONS The only difference that we found between the navigated and st and ard groups was in radiographic tunnel position measurement . The computer-assisted navigation technique in our study result ed in more accurate tunnel placement in the femur ( but not the tibia ) than the traditional arthroscopic technique . However , the performed st and ard radiographic measurements are of limited precision in principle . Functional scales and stability tests gave similar results in both groups . LEVEL OF EVIDENCE Level I , therapeutic study PURPOSE The purpose of this study was to evaluate the benefits of computer navigation on tunnel placement during anterior cruciate ligament reconstruction . METHODS A prospect i ve , r and omized , controlled study comparing computer navigation with manual operation was performed between December 2003 and April 2004 . We assigned 20 patients to the computer navigation group and 20 patients to the manual navigation group .  Surgery was performed by use of a patellar tendon autograft with press-fit fixation . A lateral radiograph of the knee at maximum extension was used to determine the exact position of the tibial tunnel at 4 days postoperatively . Outcomes were evaluated with International Knee Documentation Committee 2000 , Tegner , and Lysholm scoring . There was an additional magnetic resonance imaging ( MRI ) evaluation of tunnel placement and graft quality at the most recent follow-up , approximately 24 months after surgery . RESULTS The postoperative radiographs and 2-year postoperative MRI scans showed no differences between groups for tibial or femoral tunnel placement . In both groups the mean tibial tunnel placement was 46 % of the maximal diameter of the tibia . There were no significant differences between groups for objective and subjective outcomes scoring . Although some qualitative differences existed between groups with respect to MRI graft appearance at 2 years , this had no correlation with overall results . CONCLUSIONS No significant differences were found between computer-assisted and manually navigated anterior cruciate ligament reconstruction with regard to tunnel placement and clinical results at a mean of 2 years postoperatively . LEVEL OF EVIDENCE Level I , r and omized , single-blinded , controlled trial Background Poor outcome in anterior cruciate ligament reconstruction is often related to tunnel position . Hypothesis Improving accuracy of the tunnel position will lead to improved outcome . Study Design R and omized controlled trial ; Level of evidence , 1 . Methods Sixty patients were r and omized to either st and ard instrumentation or computer-assisted guides to position the tibial and femoral tunnels . The results were evaluated on clinical outcome based on International Knee Documentation Committee form ( laxity ) and radiologic assessment : radiologic Lachman ( Telos at 150 and 200 N ) and analysis of the tunnel positions . Results International Knee Documentation Committee laxity was level A in 22 knees in the conventional group ( mean , 1.5 mm at 200 N ) compared with 26 navigated knees ( mean laxity , 1.3 mm ; P= .49 ) . Laxity was less than 2 mm in 96.7 % of the navigated group and 83 % of the conventional group ( P= .292 ) . The variability of laxity in the navigated group was significantly less than in the conventional group , with the st and ard deviation of the navigated group being smaller than that in the conventional group ( P= .0003 at 150 N and .0005 at 200 N Telos ) . A significant difference ( P= .03 ) was found between the groups in the ATB value ( distance between the projection of the Blumensaat line on the tibial plateau and the anterior edge of the tibial tunnel ) , characterizing the sagittal position of the tibial tunnel ( negative ATB values imply graft impingement in extension ) . In the conventional group , mean ATB was –0.2 ( –5 to + 4 ) , whereas it was 0.4 ( 0 to 3 ) in the navigated patients . There were no negative ATB values in the navigated group . Conclusion This study confirms that the accuracy and consistency of tibial tunnel position can be improved by the use of computer-assisted navigation and that the clinical result in terms of laxity is more reliable Background Next to graft fixation , correct positioning of the tibial and femoral tunnel is a deciding factor for the clinical result of anterior cruciate ligament reconstruction surgery .  Computer-assisted navigation has been proposed as a method to improve tunnel positioning . Purpose To examine the differences in tibial tunnel placement between cruciate ligament operations using manual and computer-assisted navigation . Study Design R and omized controlled trial ; Level of evidence , 1 . Methods Between December 2003 and April 2004 , 53 athletes underwent anterior cruciate ligament reconstruction surgery with arthroscopic press-fit technique .  The first group ( group N ; 24 athletes ) were operated on with the aid of a navigation system ( OrthoPilot , Aesculap AG & Co. KG , Braun ) , and the second group ( group M ; 29 athletes ) were “ manually ” operated on . A lateral radiograph of the knee at maximum extension was used to determine the exact position of the tibial tunnel four days postoperatively . In the measurements , the anterior and posterior boundaries of the tibial tunnel , as well as the center of the tibial tunnel in relation to the maximum tibia anteroposterior diameter were evaluated ( indicated in percent ) . An analysis of the tibial tunnel position proportional to the slope of the intercondylar roof was done to determine intercondylar impingement ( method according to Howell ) . The centers of the tibial tunnels were compared with the “ optimal ” position noted in previous studies . The st and ard deviation was determined for both groups to determine the variance of placement . Results The anterior tibial tunnel border was 19.4 mm in group M ( 29.7 % ) and 21.2 mm in group N ( 32.2 % ) ( P=.18 ) . The center of the tibial tunnel was located at 24.6 mm in group M ( 35.6 % ) and at 26.6 mm in group N ( 40.3 % ) ( P=.19 ) . In group M , the posterior tibial tunnel position was located at 30.2 mm ( 46.2 % ) , and in group N at 32.2 mm ( 49.1 % ) ( P=.21 ) . When comparing the centers of the tibial tunnels with the optimal 44 % found in previous studies , the value for group M ( 37.6 % ) varied significantly , while group N ( 40.5 % ) did not . However , there was no significant difference in the range variance for either group ; the st and ard deviation was 6.9 % ( 4.3 mm ) for group M and 5.9 % ( 3.5 mm ) for group N. One athlete showed moderate impingement in group N , and two athletes in group M. Conclusion Assisted navigation offers good support for correct placement of the tibial tunnel , although experienced surgeons can achieve essentially the same positioning as surgeons using computer-assisted navigation . Whether it is advisable to implement this procedure in daily surgical routine should be decided based on clinical results 
    Output:
    
From the available evidence , we are unable to demonstrate or refute a favourable effect of CAS for cruciate ligament reconstructions of the knee compared with conventional reconstructions .
However , the currently available evidence does not indicate that CAS in knee ligament reconstruction improves outcome .