between december 2010 and october 2011 , 98 patients who were diagnosed with isolated acl ruptures underwent primary acl reconstruction using single bundle method with modified transtibial technique .
informed consent was obtained from all patients prior to receiving 3d - ct and radiograph for analyzing the femoral tunnel position after the operation . the patient pool consisted of 81 men and 17 women with a mean age of 27.3 years ( range , 15 to 60 years ) .
1c ) by two orthopedic surgeons on two separate occasions at an interval of 2 weeks to assess the interobserver and intraobserver reliability .
the quadrant method used to measure the postoperative femoral tunnel position by 3d - ct is as follows : 1 ) a true lateral view cutting at the middle of the intercondylar notch of the proximal femur by 3d - ct was attained through the picture of archiving and communication systems ( pacs , marotech , seoul , korea ) ( fig .
2 ) the image was enclosed with a rectangular measurement frame that was either parallel or perpendicular to the blumensaat line on power point ver .
2007 ( microsoft co. , redmond , wa , usa ) as shown in fig .
t calculated the deep to shallow distances from the center of the femoral tunnel parallel to the blumensaat line , and h calculated the high to low distances perpendicular to the blumensaat line .
in addition , the anatomical femoral attachment site of acl was shown on table 1 using the previous quadrant method .
after thorough arthroscopic evaluations of the acl , a 3 cm longitudinal skin incision at 2 cm medial to the tibial tuberosity was made .
the graft was cut in half and folded into half to produce a quadruple semitendinous graft .
if the harvested graft was shorter than 24 cm , a quadruple semitendinosus / gracilis graft was prepared by harvesting both the semitendinosus tendon and the gracilis tendon .
the intercondylar ridge of the lateral femoral condyle , and the bifurcate ridge that divides the am bundle and the posterolateral ( pl ) bundle were confirmed by removing the soft tissues at the femoral insertion of acl .
a bony mark at the anatomic center of acl footprint ( just posterior to the bifurcate ridge and center of anteroposterior [ ap ] width of footprint ) was made by passing a microfracture awl through the anteromedial portal as in fig .
2a . this center was deepened and widened to allow space for the guided pin through the tibial tunnel .
since the anatomical femoral tunnel is prepared by the trans - am portal , the transtibial guide pin tends to be located more to the anterior and proximal position of anatomic center than anticipated .
the ' triangular , funnel - shaped bony trough ' was employed to slip the eccentrically positioned guide into the anticipated anatomic center , which is part of our modified transtibial technique ( fig .
the starting point of the tibial edge / periphery was superior to the pes anserinus and the anterior margin of medial collateral ligament ( mcl ) ( fig .
the intra - articular site is positioned immediately lateral to the medial tibial spine and the extension of the inner margin of anterior horn of lateral meniscus .
the reference point of tibial tunnel is a little posterior region of the acl footprint .
the angle of the acl guide ( linvatec , largo , fl , usa ) was set at 47.5. the tibial tunnel was created using a reamer with diameter 1 mm smaller than the prepared acl graft . with a free hand technique , a guide pin was passed through the tibial tunnel towards the bony trough .
generally , the guide pin was located distal and anterior to the anatomical center , and extension of the knee nudged the guide pin towards the proximal and posterior region of the anatomic center , but was being bent at the intra - articular orifice of the tibial tunnel ( fig .
femoral reaming was performed with knee flexion which reduces the chances of blowing out the posterior wall and increases the femoral tunnel length .
when the reamer passes over the bending portion of the guide pin , the knee should be extended . after passing through the bending point
after the graft passage , femoral fixation was done with endobutton and bio - cross pin ( rigidfix system , mitek , johnson & johnson , norwood , ma , usa ) .
the graft was tensioned and fixed to the tibia by placing the ha screw ( bioscrew poly l - lactic acid , linvatec 
 linvatec ) .
we regularly performed follow - ups on the patients in the out - patient clinic and established a protocol for rehabilitation .
partial weight bearing with crutches for 6 weeks was mandated for patients who underwent meniscal repairs .
the treatment purpose of the patients was to gain a full range of motions at 2 to 6 weeks after surgery .
running and side - cutting activities were allowed at 3 months , with a return to sports activities at 6 months after surgery .
after thorough arthroscopic evaluations of the acl , a 3 cm longitudinal skin incision at 2 cm medial to the tibial tuberosity was made .
the graft was cut in half and folded into half to produce a quadruple semitendinous graft .
if the harvested graft was shorter than 24 cm , a quadruple semitendinosus / gracilis graft was prepared by harvesting both the semitendinosus tendon and the gracilis tendon .
the intercondylar ridge of the lateral femoral condyle , and the bifurcate ridge that divides the am bundle and the posterolateral ( pl ) bundle were confirmed by removing the soft tissues at the femoral insertion of acl .
a bony mark at the anatomic center of acl footprint ( just posterior to the bifurcate ridge and center of anteroposterior [ ap ] width of footprint ) was made by passing a microfracture awl through the anteromedial portal as in fig .
2a . this center was deepened and widened to allow space for the guided pin through the tibial tunnel .
since the anatomical femoral tunnel is prepared by the trans - am portal , the transtibial guide pin tends to be located more to the anterior and proximal position of anatomic center than anticipated .
the ' triangular , funnel - shaped bony trough ' was employed to slip the eccentrically positioned guide into the anticipated anatomic center , which is part of our modified transtibial technique ( fig .
the starting point of the tibial edge / periphery was superior to the pes anserinus and the anterior margin of medial collateral ligament ( mcl ) ( fig . 2c ) .
the intra - articular site is positioned immediately lateral to the medial tibial spine and the extension of the inner margin of anterior horn of lateral meniscus .
the reference point of tibial tunnel is a little posterior region of the acl footprint .
the angle of the acl guide ( linvatec , largo , fl , usa ) was set at 47.5. the tibial tunnel was created using a reamer with diameter 1 mm smaller than the prepared acl graft . with a free hand technique ,
generally , the guide pin was located distal and anterior to the anatomical center , and extension of the knee nudged the guide pin towards the proximal and posterior region of the anatomic center , but was being bent at the intra - articular orifice of the tibial tunnel ( fig .
femoral reaming was performed with knee flexion which reduces the chances of blowing out the posterior wall and increases the femoral tunnel length .
when the reamer passes over the bending portion of the guide pin , the knee should be extended . after passing through the bending point
after the graft passage , femoral fixation was done with endobutton and bio - cross pin ( rigidfix system , mitek , johnson & johnson , norwood , ma , usa ) . if femoral tunnel was short , the graft was press fitted with only endobutton .
the graft was tensioned and fixed to the tibia by placing the ha screw ( bioscrew poly l - lactic acid , linvatec 
 linvatec ) .
we regularly performed follow - ups on the patients in the out - patient clinic and established a protocol for rehabilitation .
partial weight bearing with crutches for 6 weeks was mandated for patients who underwent meniscal repairs .
the treatment purpose of the patients was to gain a full range of motions at 2 to 6 weeks after surgery .
a perturbation training program began at 6 weeks after surgery . running and side - cutting activities were allowed at 3 months , with a return to sports activities at 6 months after surgery .
the position of the femoral tunnel was measured using the quadrant method by 3d - ct,8 ) where t was 32.94%  5.16% , and h was 41.89%  5.58% ( fig .
these values were more distal and middle as compared with the previous data ( mean t , 29.85% ; h , 33.2% ) measured by quadrant method using cadaveric knees for validating anatomical acl footprints ( p < 0.05).9,10 ) the interobserver intraclass correlation coefficients ( iccs ) were 0.766 and 0.793 , whereas the intraobserver iccs were 0.875 and 0.893 .
the femoral tunnel angle on the ap view was 50.43  7.04 , for which the interobserver iccs were 0.783 and 0.795 , and the intraobserver iccs were 0.911 and 0.923 . on the process of optimizing this modified transtibial technique ,
mishaps such as breakage of the bended wire occurred on 3 occasions as the reamer passed through the tibial tunnel , and a shallow tibial tunnel was formed on another occasion , which all occurred during the initial series .
however , as the examiners became more experienced in executing this modified technique and when the safe zone of the bone stock was adjusted to the entry point of the tibia , these complications were avoided .
the purpose of this study is to describe a single bundle acl reconstruction performed with modified transtibial technique for positioning the femoral tunnel to anatomical footprint .
the femoral tunnel location was being evaluated with 3d - ct scan reconstructions with the quadrant method as described by bernard et al.,8 ) and the results of these scans were compared with those derived from arthroscopic identification . the results of this study showed that the t - value was 32.94%  5.16% , and the h - value was 41.89%  5.58% .
abebe et al.11 ) and kaseta et al.12 ) reported that the femoral tunnels were placed " deeper or more proximal " and " higher or more anterior " than the native acl insertions of the femur when the transtibial technique was used , which could result in increased laxity of the graft .
contrary to these results , the femoral tunnel in this study was located " shallower or more distal " and " lower or more posterior " than the mean value from multiple measurements of the anatomical acl footprints in cadaveric knees ( t , 29.85% ; h , 33.2% ) from previous studies that also used the quadrant method for calculation .
the mean values of the femoral tunnel created by the authors were placed between the am and pl bundle position , which were calculated as described by kopf et al.13 ) and tsukada et al.10 ) rue et al.6 ) reported that a laterally - oriented transtibial drilling femoral tunnel effectively overlapped approximately half the am bundle and half the pl bundle .
miller et al.14 ) proved that the intra - articular aperture of the femoral tunnel in all cases formed an ellipse , with the long and short axis averaging 13.9  1.6 mm and 9.4  0.8 mm in the trans - am method , and 12.1  0.8 mm and 10.6  0.6 mm respectively in the transtibial group .
accordingly , if the center of the femoral tunnel is relatively " distal " and " posterior , " the ellipse - shaped tunnel would allow the incorporation of original portions of the am and pl bundles leading to a more anatomical reconstruction .
hence , this modified transtibial technique has advantages over the traditional technique ( t , 37.2%  5.5% ; h , 11.3%  6.6% ) for being closer to its anatomical location.10,13 ) ferretti et al.15 ) reported the presence of a lateral intercondylar ridge in all patients who underwent acl reconstruction and the bifurcate ridge in 82% of 60 knees .
van eck et al.16 ) described 88% and 48% of these landmarks , respectively for their patients at arthroscopy .
however , to arthroscopically identify these landmarks on the medial wall of the lateral femoral condyle is difficult .
therefore , postoperative 3d - ct scans were used to validate whether this modified technique can reproducibly be used for the placement of the anatomic femoral tunnel .
our angle of the femoral tunnel in the coronal plane was on average 50.43  7.04 , when viewed by ap radiography , and it was lower than the results ( 61.7  5.5 , 58.8  8.3 ) from previous transtibial techniques , even when compared with the anteromedial portal technique ( 55.9  4.7 , 50.9  8.3 ) , which were measured by chang et al.17 ) and dargel et al.18 ) in addition , bedi et al.4 ) reported that the coronal angles of the oblique femoral tunnels from either the transtibial or the trans am portal techniques were 54.1  7.17 and 45.9  6.9 , respectively .
therefore , the rate of the posterior wall blowout was 50% with the latter technique .
thus , not only is the modified transtibial technique more reproducible , but it is also safer when such complications of the am portal technique is taken into consideration . there was no significant posterior wall blowout in our case series .
the entrance of the tibial tunnel is essential for the placement of the anatomic femoral tunnel when using the transtibial technique for acl reconstruction , especially if we want to prevent graft failures.19 ) recent studies have tried to accurately drill the tibial tunnel in relation to the native acl footprint of the femur , but without success.20,21 ) however , heming et al.7 ) reported the plausibility of the anatomical footprint using the transtibial technique , but commented that the starting point should be closer to the joint line , and the tibial tunnel length must be shortened for an accurately positioned footprint .
arnold et al.22 ) attempted to produce anatomical tunnels by transtibial drilling just proximal to the pes anserinus and ventral to the mcl , but in their case , the guide pin was projected too high in the notch and missed the femoral insertion . in this study ,
the authors followed arnold 's method to avoid creating shallow tibial tunnels , and furthermore , used a new modified method to prevent over - projecting the guide pin in the notch into a non - anatomical position .
there are some advantages of this modified transtibial technique in which the femoral tunnel is drilled appropriately through the tibial tunnel .
first , it is similar to the conventional method and easily replicated by surgeons who are familiar with the transtibial technique .
second , it is possible to create the femoral tunnel in an anatomic position through a relatively longer and deeper tibial tunnel with only a few additional and simple techniques ; triangular , funnel - shaped bony trough and by changing knee flexion angles during femoral tunneling .
third , it permits early rehabilitation through firm graft fixation resulting from tunnel length - graft length matching .
the limitations of the study may be that the authors used the mean values of the native acl insertions derived from multiple previous studies for comparison .
although the methods used in this paper are the same as those in previous studies , mean variations in the experimental instruments do not reflect the differences that arise , and , are therefore , a crude averaging of values . in addition , the icc was lower for the interobserver correlation coefficient in two observers , which may reflect the difficulty of selecting the true lateral view on the magnetic resonance imaging sagittal image , and measures the center of the femoral tunnel ( forming an ellipse interobservers ) . finally , there was a lack of full considerations for the length of the femoral tunnel and the characteristics of the tibial tunnel .
further studies to overcome these limitations are required , and essential evaluations of clinical outcomes for modified transtibial technique are necessary to prove its superiority over the traditional techniques . in conclusions ,
our modified transtibial technique is anticipated to provide a true anatomical placement of the femoral tunnel during acl reconstruction than the previous traditional transtibial techniques .
 backgroundthe purpose of this study is to report a modified transtibial technique to approach the center of anatomical femoral footprint in anterior cruciate ligament ( acl ) reconstruction and to investigate the accurate femoral tunnel position with 3-dimensional computed tomography ( 3d - ct ) and radiography after reconstruction.methodsfrom december 2010 to october 2011 , we evaluated 98 patients who underwent primary acl reconstruction using a modified transtibial technique to approach the center of anatomical femoral footprint in single bundle acl reconstruction with hamstring autograft . 
 their femoral tunnel positions were investigated with 3d - ct and radiography postoperatively . 
 femoral tunnel angle was measured on the postoperative anteroposterior ( ap ) radiograph and the center of the femoral tunnel aperture on the lateral femoral condyle was assessed with 3d - ct according to the quadrant method by two orthopedic surgeons.resultsaccording to the quadrant method with 3d - ct , the femoral tunnel was measured at a mean of 32.94%  5.16% from the proximal condylar surface ( parallel to the blumensaat line ) and 41.89%  5.58% from the notch roof ( perpendicular to the blumensaat line ) with good interobserver ( intraclass correlation coefficients [ icc ] , 0.766 and 0.793 , respectively ) and intraobserver reliability ( icc , 0.875 and 0.893 , respectively ) . according to the radiographic measurement on the ap view , the femoral tunnel angles averaged 50.43  7.04 ( icc , 0.783 and 0.911 , respectively).conclusionsour modified transtibial technique is anticipated to provide more anatomical placement of the femoral tunnel during acl reconstruction than the former traditional transtibial techniques . 
METHODS
Surgical Techniques
Postoperative Rehabilitation
RESULTS
DISCUSSION