Femoral tunnel placement in anterior cruciate ligament reconstruction: rationale of the two incision technique

Endoscopic anterior cruciate ligament (ACL) reconstruction can be performed through one-incision or two-incision technique. The current one-incision endoscopic ACL single bundle reconstruction techniques attempt to perform an isometric repair placing the graft along the roof of the intercondylar notch, anterior and superior to the native ACL insertion. However the ACL isometry is a theoretical condition, and has not stood up to detailed testing and investigation. Moreover this type of reconstruction results in a vertically oriented non-anatomic graft, which is able to control anterior tibial translation but not the rotational component of the instability. Femoral tunnel obliquity has a great effect on rotational stability. To improve the obliquity of graft, an anatomical ACL reconstruction should be attempt. Anatomical insertion of ACL on the femur lies very low in the notch, spreading between 11 and 9–8 o'clock position and the center lies lower than at 11 o'clock position. Femoral aiming devices through the tibial tunnel aim at an isometric placement, and they do not aim at an anatomic position of the graft. Also, a placement of tunnel in a position of 11 o'clock is unable to restore rotational stability. The two-incision technique, with the possibility to position femoral tunnel independently by tibial tunnel, allows us to place femoral tunnel entrance in a position of 10 'clock that can most accurately reproduce the anatomic behaviour of the ACL and can potentially improve the response of the graft to rotatory loads. This positioning results in a more oblique graft placement, avoiding problem related to PCL impingement during knee flexion. Further studies are required to understand if this kind of reconstruction can ameliorate proprioception as well as clinical outcome at a long-term follow-up.     

Biomechanical effects of medial-lateral tibial tunnel placement in posterior cruciate ligament reconstruction.

With most posterior cruciate (PCL) reconstruction techniques, the distal end of the graft is fixed within a tibial bone tunnel. Although a surgical goal is to locate this tunnel at the center of the PCL's tibial footprint, errors in medial-lateral tunnel placement of the tibial drill guide are possible because the position of the tip of the guide relative to the PCL's tibial footprint can be difficult to visualize from the standard arthroscopy portals. This study was designed to measure changes in knee laxity and graft forces resulting from mal-position of the tibial tunnel medial and lateral to the center of the PCL's tibial insertion. Bone-patellar tendon-bone allografts were inserted into three separate tibial tunnels drilled into each of 10 fresh-frozen knee specimens. Drilling the tibial tunnel 5 mm medial or lateral to the center of the PCL's tibial footprint had no significant effect on knee laxities; the graft pretension necessary to restore normal laxity at 90 degrees of knee flexion (laxity match pretension) with the medial tunnel was 13.8 N (29%) greater than with the central tunnel. During passive knee flexion-extension, graft forces with the medial tibial tunnel were significantly higher than those with the central tunnel for flexion angles greater than 65 degrees while graft forces with the central tibial tunnel were not significantly different than those with the lateral tibial tunnel. Graft forces with medial and lateral tunnels were not significantly different from those with a central tunnel for 100 N applied posterior tibial force, 5 Nm applied varus and valgus moment, and 5 Nm applied internal and external tibial torque. With the exception of slightly higher graft forces recorded with the medial tunnel beyond 65 degrees of passive knee flexion, errors in medial-lateral placement of the tibial tunnel would not appear to have important effects on the biomechanical characteristics of the reconstructed knee.     

Intraoperative Qualitätskontrolle bei der Bohrkanalplatzierung zum vorderen Kreuzbandersatz

The reconstruction of a ruptured anterior cruciate ligament (ACL) is a frequently performed operation, however technically demanding with a revision rate of approximately 10%. The correct placement of bone tunnels in femur and tibia is the most important variable to achieve a successful outcome. A distinct knowledge of the anatomic insertion sites is crucial. The ideal location for the femoral bone tunnel is achieved when a 1-2 mm posterior wall is left to the over-the-top position and when the entry to the bone tunnel is at 10 o'clock (right knees) or 14 o'clock (left knees) in the frontal plane. The femoral bone tunnel can be drilled through the tibial bone tunnel (transtibial technique) or through an anteromedial arthroscopic portal. According to recent studies the use of an anteromedial portal helps to reduce the risk of misplacement of the bone tunnel. The center of the tibial bone tunnel should be located on an imaginary line between medial border of the anterior horn of the lateral meniscus and the medial tibial spine. The position of the tibial guide wire has to be far enough posterior to avoid impingement of the graft with the roof of the intercondylar notch. Measures for quality control include the intraoperative use of an image intensifier (fluoroscopy), instrumented laxity measurements and a postoperative radiograph in 2 planes. The use of computer assisted surgery cannot routinely be recommended at present.     

Effects of notchplasty and femoral tunnel position on excursion patterns of an anterior cruciate ligament graft

Purpose: Errors in femoral tunnel placement in anterior cruciate ligament (ACL) reconstruction can cause excessive length changes in the graft during knee flexion and extension, resulting in graft elongation during the postoperative period. To improve the accuracy of tunnel placement and to avoid graft impingement, a notchplasty is commonly performed. The purpose of this study was to determine the effects of varying the position of the femoral tunnel and of performing a 2-mm notchplasty of the lateral femoral condyle and roof of the intercondylar notch on excursion patterns of a bone–patellar tendon–bone graft. Type of Study: Biomechanical cadaveric study. Methods: A cylindrical cap of bone, containing the tibial insertion of the ACL, was mechanically isolated in 15 fresh-frozen cadaveric specimens using a coring cutter. The bone cap was attached to an electronic isometer that recorded displacement of the bone cap relative to the tibia as the knee was taken through a 90° range of motion. After native ACL testing, the proximal end of a 10-mm bone–patella tendon–bone graft was fixed within femoral tunnels drilled at the 10-, 11-, and 12-o'clock (or 2-, 1-, and 12-o'clock) positions within the notch. The distal end of the graft was attached to the isometer. Testing was then completed at each tunnel position before and after notchplasty. Results: Before notchplasty, mean graft excursions at the 10- or 2-, 11- or 1-, and 12-o'clock tunnels were not significantly different from the excursions of the native ACL or each other. After a 2-mm notchplasty, mean graft excursions at the 3 tunnel locations were not sigificantly different from each other but were greater than mean graft excursions before notchplasty. After notchplasty, all grafts tightened during knee flexion. Conclusions: Although errors in placement along the arc of the intercondylar notch did not significantly affect graft excursion patterns, the apparent graft tightening with knee flexion that was observed for all 3 tunnel positions after notchplasty suggests that graft forces would increase with knee flexion over this range. This would indicate that as little amount of bone as possible should be removed from the posterior portion of the intercondylar notch in ACL reconstruction.Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 19, No 4 (April), 2003: pp 340–345     

Arthroscopic reconstruction of the anterior cruciate ligament using double anteromedial and posterolateral bundles

We propose a method for repairing the anterior cruciate ligament which takes advantage of the multifascular nature of the ligament to achieve better physiological anteroposterior and rotational stability compared with conventional methods. Arthroscopic reconstruction of the anteromedial and posterolateral bundles of the ligament closely reproduces normal anatomy. We have used this technique in 92 patients with anterior cruciate ligament laxity and present here the mid-term results. The hamstring tendons (gracilis and semitendinosus) are harvested carefully to obtain good quality grafts. Arthroscopic preparation of the notch allows careful cleaning of the axial aspect of the lateral condyle; it is crucial to well visualize the region over the top and delimit the 9 h-12 h zone for the right knee or the 12-15 h zone for the left knee. The femoral end of the anteromedial tunnel lies close to the floor of the intercondylar notch, 5 to 10 mm in front of the posterior border of the lateral condyle, at 13 h for the left knee and 11 h for the right knee. The femoral end of the posterolateral tunnel lies more anteriorly, at 14 h for the left knee and 10 h for the right knee. The tibial end of the posterolateral tunnel faces the anterolateral spike of the tibia. The tibial end of the anteromedial tunnel lies in front of the apex of the two tibial spikes half way between the anteromedial spike and the anterolateral spike, 8 mm in front of the protrusion of the posteriolateral pin. The posterolateral graft is run through the femoral and tibial tunnels first. A cortical fixation is used for the femoral end. The femoral end of the anteromedial graft is then fixed in the same way. The tibial fixation begins with the posterolateral graft with the knee close to full extension. The anteromedial graft is fixed with the knee in 90 degrees flexion. Thirty patients were reviewed at least six months after the procedure. Mean age was 28.2 years. Mean overall IKDC score was 86% (36% A and 50% B). Gain in laxity was significant: 6.53 preoperatively and 2.1 postoperatively. Most of the patients (86.6%) were able to resume their former occupation 2 months after the procedure. The different components of the anterior cruciate ligament and their respective functions have been the object of several studies. The anteromedial bundle maintains joint stability during extension and anteroposterior stability during flexion. The posterolateral bundle contributes to the action of the anteromedial bundle with an additional effect due to its position: rotational stability during flexion. In light of the multifascicular nature of the anterior cruciate ligament and the residual rotational laxity observed after conventional repair, our proposed method provides a more anatomic reconstruction which achieves better correction of anteroposterior and rotational stability. This technique should be validated with comparative trials against currently employed methods.     

SPECT/CT tracer uptake is influenced by tunnel orientation and position of the femoral and tibial ACL graft insertion site

Purpose

SPECT/CT is a hybrid imaging modality, which combines a 3D scintigraphy (SPECT) and a conventional computerised tomography (CT). SPECT/CT allows accurate anatomical localisation of metabolic tracer activity. It allows the correlation of surgical factors such as tunnel position and orientation with mechanical alignment, clinical outcome and biological factors. The purpose of this study was to investigate whether the SPECT/CT tracer uptake (intensity and distribution) correlates with the stability and laxity of the knee joint and the position and orientation of the tibial and femoral tunnels in patients after anterior cruciate ligament (ACL) reconstruction.

Methods

A consecutive series of knees (n = 66), with symptoms of pain and/or instability after ACL reconstruction were prospectively evaluated using clinical examination and 99mTc-HDP-SPECT/CT. Clinical laxity testing was performed using the Rolimeter (Ormed, Freiburg, Germany) including Lachman testing (0–2 mm, 3–5 mm, 6–10 mm, >10 mm), anterior drawer test (0–2 mm, 3–5 mm, 6–10 mm, >10 mm), pivot shift test (positive versus negative) and patient-based subjective instability (yes versus no).For analysis of SPECT/CT tracer uptake a previously validated SPECT/CT localisation scheme consisting of 17 tibial, nine femoral and four patellar regions on standardised axial, coronal, and sagittal slices was used. The tracer activity on SPECT/CT was localised and recorded using a 3D volumetric and quantitative analysis software.Mean, standard deviation, minimum and maximum of grading for each area of the localisation scheme were recorded. The position and orientation of the tibial and femoral tunnel was assessed using a previously published method on 3D-CT.

Results

Correlation of instability, pivot shift as well as clinical laxity testing with 99mTc-HDP-SPECT/CT tracer uptake intensity and distribution showed no significant correlation. 99mTc-HDP-SPECT/CT tracer uptake correlated significantly with the position and orientation of the ACL graft. A more horizontal femoral graft position showed significantly increased tracer uptake within the superior and posterior femoral regions. A more posteriorly-placed femoral insertion site showed significantly more tracer uptake within the femoral and tibial tunnel regions. A more vertical or a less medial tibial tunnel orientation showed significant increased uptake within the tibial and femoral tunnel regions. A more anterior tibial tunnel position showed significantly more tracer uptake in the femoral and tibial tunnel regions as well as the entire tibiofemoral joint.

Conclusions

SPECT/CT tracer uptake intensity and distribution showed a significant correlation with the femoral and tibial tunnel position and orientation in patients with symptomatic knees after ACL reconstruction. No correlation was found with stability or clinical laxity. SPECT/CT tracer uptake distribution has the potential to give us important information on joint homeostasis and remodelling after ACL reconstruction. It might help to predict ACL graft failure and improve our surgical ACL reconstruction technique in finding the optimal tunnel and graft position and orientation.     

Knee stability and graft function following anterior cruciate ligament reconstruction: Comparison between 11 o'clock and 10 o'clock femoral tunnel placement

Purpose: To study how well an anterior cruciate ligament (ACL) graft fixed at the 10 and 11 o'clock positions can restore knee function in response to both externally applied anterior tibial and combined rotatory loads by comparing the biomechanical results with each other and with the intact knee. Type of Study: Biomechanical experiment using human cadaveric specimens. Methods: Ten human cadaveric knees (age, 41±13 years) were reconstructed by placing a bone–patellar tendon–bone graft at the 10 and 11 o'clock positions, in a randomized order, and then tested using a robotic/universal force-moment sensor testing system. Two external loading conditions were applied: (1) 134 N anterior tibial load with the knee at full extension, 15°, 30°, 60°, and 90° of flexion, and (2) a combined rotatory load of 10 N-m valgus and 5 N-m internal tibial torque with the knee at 15° and 30° of flexion. The resulting kinematics of the reconstructed knee and in situ forces in the ACL graft were determined for each femoral tunnel position. Results: In response to a 134-N anterior tibial load, anterior tibial translation (ATT) for both femoral tunnel positions was not significantly different from the intact knee except at 90° of knee flexion as well as at 60° of knee flexion for the 10 o'clock position. There was no significant difference in the ATT between the 10 and 11 o'clock positions, except at 90° of knee flexion. Under a combined rotatory load, however, the coupled ATT for the 11 o'clock position was approximately 130% of that for the intact knee at 15° and 30° of flexion. For the 10 o'clock position, the coupled ATT was not significantly different from the intact knee at 15° of flexion and approximately 120% of that for the intact knee at 30° of flexion. Coupled ATT for the 10 o'clock position was significantly smaller than for the 11 o'clock position at 15° and 30° of flexion. The in situ force in the ACL graft was also significantly higher for the 10 o'clock position than the 11 o'clock position at 30° of flexion in response to the same loading condition (70 ± 18 N v 60 ± 15 N, respectively). Conclusions: The 10 o'clock position more effectively resists rotatory loads when compared with the 11 o'clock position as evidenced by smaller ATT and higher in situ force in the graft. Despite the fact that ACL grafts placed at the 10 or 11 o'clock positions are equally effective under an anterior tibial load, neither femoral tunnel position was able to fully restore knee stability to the level of the intact knee.Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 19, No 3 (March), 2003: pp 297–304     

Can suture repair of ACL transection restore normal anteroposterior laxity of the knee? An ex vivo study

Recent work has suggested the transected anterior cruciate ligament (ACL) can heal and support reasonable loads if repaired with sutures and a bioactive scaffold; however, use of a traditional suture configuration results in knees with increased anterior–posterior (AP) laxity. The objective was to determine whether one of five different suture repair constructs when performed at two different joint positions would restore normal AP knee laxity. AP laxity of the porcine knee at 60° of flexion was evaluated for five suture repair techniques. Femoral fixation for all repair techniques utilized a suture anchor. Primary repair was to either the tibial stump, one of three bony locations in the ACL footprint, or a hybrid bony fixation. All five repairs were tied with the knee in first 30° and then 60° of flexion for a total of 10 repair constructs. Suture repair to bony fixation points within the anterior half of the normal ACL footprint resulted in knee laxity values within 0.5 mm of the ACL‐intact joint when the sutures were tied with the knee at 60° flexion. Suture repair to the tibial stump, or with the knee at 30° of flexion, did not restore normal AP laxity of the knee. Three specific suture repair techniques for the transected porcine ACL restored the normal AP laxity of the knee at the time of surgery. Additional studies defining the changes in laxity with cyclic loading and in vivo healing are indicated. © 2008 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 26:1500–1505, 2008     

Radiographic evaluation of anterior cruciate ligament graft failure with special reference to tibial tunnel placement

Graft failure in anterior cruciate ligament (ACL) reconstruction can result from anterior placement of the tibial tunnel. Conventional radiographic evaluation of this problem does not take into account potential changes in tibio-femoral relationship caused by ACL instability. A retrospective radiographic evaluation of failed as well as successful ACL reconstructions was carried out. Both published radiographs as well as those obtained of patients treated by the authors were evaluated for tibial tunnel placement, roof impingement, and tibial position relative to the femur. In the second part of the study, the radiographs were obtained under standard conditions in both failed ACL reconstructions and normal knees. The results of both parts of the study indicate that lateral radiographs of the extended knee with ACL instability are likely to show subtle anterior tibial subluxation. The subluxation can give the impression of roof impingement on the graft. However, the majority of the failed knees had similar tibial tunnel placement compared with successful reconstructions and would appear unimpinged once corrected for subluxation. The diagnosis of graft impingement by the femoral intercondylar roof has to take into account potential tibial subluxation. Impingement as a cause graft failure may be less common than previously thought.Arthroscopy 1998 Mar;14(2):206-11     

Effect of the angle of the femoral and tibial tunnels in the coronal plane and incremental excision of the posterior cruciate ligament on tension of an anterior cruciate ligament graft: an in vitro study

BACKGROUND: High tension in an anterior cruciate ligament graft adversely affects both the graft and the knee; however, it is unknown why high graft tension in flexion occurs in association with a posterior femoral tunnel. The purpose of the present study was to determine the effect of the angle of the femoral and tibial tunnels in the coronal plane and incremental excision of the posterior cruciate ligament on the tension of an anterior cruciate ligament graft during passive flexion. METHODS: Eight cadaveric knees were tested. The angle of the tibial tunnel was varied to 60 degrees, 70 degrees, and 80 degrees in the coronal plane with use of three interchangeable, low-friction bushings. The femoral tunnel, with a 1-mm-thick posterior wall, was drilled through the tibial tunnel bushing with use of the transtibial technique. After the graft had been tested in all three tibial bushings with one femoral tunnel, the femoral tunnel was filled with bone cement and the tunnel combinations were tested. Lastly, the graft was replaced in the 80 degrees femoral and tibial tunnels, and the tests were repeated with excision of the lateral edge of the posterior cruciate ligament in 2-mm increments. Graft tension, the flexion angle, and anteroposterior laxity were recorded in a six-degrees-of-freedom load-application system that passively moved the knee from 0 degrees to 120 degrees of flexion. RESULTS: The graft tension at 120 degrees of flexion was affected by the angle of the femoral tunnel and by incremental excision of the posterior cruciate ligament. The highest graft tension at 120 degrees of flexion was 169 +/- 9 N, which was detected with the graft in the 80 degrees femoral and 80 degrees tibial tunnels. The lowest graft tension at 120 degrees of flexion was 76 +/- 8 N, which was detected with the graft in the 60 degrees femoral and 60 degrees tibial tunnels. The graft tension of 76 N at 120 degrees of flexion with the graft in the 60 degrees femoral and 60 degrees tibial tunnels was closer to the tension in the intact anterior cruciate ligament. Excision of the lateral edge of the posterior cruciate ligament in 2 and 4-mm increments significantly lowered the graft tension at 120 degrees of flexion without changing the anteroposterior position of the tibia. CONCLUSIONS: Placing the femoral tunnel at 60 degrees in the coronal plane lowers graft tension in flexion. Our results suggest that high graft tension in flexion is caused by impingement of the graft against the posterior cruciate ligament, which results from placing the femoral tunnel medially at the apex of the notch in the coronal plane.     

Factors affecting graft force in surgical reconstruction of the anterior cruciate ligament

The effect of the maximum unloaded graft length (Lo) and femoral fixation hole location on graft force with the knee under anteriorly directed tibial loads was measured in five fresh cadaver knees with a reconstruction of the anterior cruciate ligament (ACL). The reconstruction was performed using a composite graft consisting of the semitendinosus and gracilis tendons augmented with the Kennedy ligament augmentation device (LAD). Buckle transducers were used to measure ligament and graft forces. The total graft force was adjusted to match the intact ACL at 30 degrees flexion using a force-setting method so that a standardized reference configuration could be repeatedly obtained. The graft force was highly sensitive to Lo, typically changing by 50% with a change in Lo of 3 mm. Variation in femoral hole location of 5 mm anterior, posterior, proximal, and distal to the anatomic position produced changes in graft force, particularly at 60 degrees and 90 degrees flexion; however, these changes were not statistically significant. The effect of femoral hole location varied considerably between knees. This variability makes predicting proper hole placement difficult, and suggests the need to adjust each knee at surgery to account for this variable femoral hole position sensitivity.     

Comparisons of tunnel-graft angle and tunnel length and position between transtibial and transportal techniques in anterior cruciate ligament reconstruction

Purpose

Our aim was to evaluate tunnel-graft angle, tunnel length and position and change in graft length between transtibial (30 patients) and anteromedial (30 patients) portal techniques using 3D knee models after anterior cruciate ligament (ACL) reconstruction.

Methods

The 3D angle between femoral or tibial tunnels and graft at 0° and 90° flexion were compared between groups. We measured tunnel lengths and positions and evaluated the change in graft length from 0° to 90° flexion.

Results

The 3D angle at the femoral tunnel with graft showed a significant difference between groups at 0° flexion (p?=?0.01) but not at 90° flexion (p?=?0.12). The 3D angle of the tibial tunnel showed no significant differences between groups. Femoral tunnel length in the transtibial group was significantly longer than in the transportal group (40.7 vs 34.7 mm,), but tibial tunnel length was not. The relative height of the lateral femoral condyle was significantly lower in the transportal than the transtibial group (24.1 % vs 34.4 %). No significant differences were found between groups in terms of tibial tunnel position. The change in graft length also showed no significant difference between groups.

Conclusion

Even though the transportal technique in ACL reconstruction can place the femoral tunnel in a better anatomical position than the transtibial technique, it has risks of a short femoral tunnel and acute angle at the femoral tunnel. Moreover, there was also no difference in the change of the graft length between groups.     

Objective anterior cruciate ligament testing

We examined subjects with the Stryker knee laxity tester as part of the clinical examination to determine its usefulness in evaluating the anterior cruciate ligament. We measured 123 athletes with no history of knee injury, as well as 30 patients with ACL injury proven by arthroscopy, and 11 injured patients with intact ACL at arthroscopy. We recorded anterior and posterior tibial displacement at 20 degrees of knee flexion and 20 lbs force in each direction. Anterior laxity and side to side difference correlated with ACL injury; posterior and total AP laxity did not. In normal subjects, mean anterior laxity was 2.5 mm. Only 8% of normal knees had anterior laxity of 5 mm or more. Ten percent of normal subjects had a side to side difference of 2 mm or more. In ACL tears, mean laxity was 8.1 mm, with 94% measuring 5 mm or more. Of the subjects, 89% with unilateral ACL injury had an increase of 2 mm or more on the injured side. Ten of ten acute ACL tears were detected by these criteria, with no false positives. In injured knees with intact ACL, measurements did not differ significantly from normal. We found the objective knee laxity measurement to be a useful complement to clinical knee examination.     

Three-Dimensional Reconstruction Computed Tomography Evaluation of Tunnel Location during Single-Bundle Anterior Cruciate Ligament Reconstruction: A Comparison of Transtibial and 2-Incision Tibial Tunnel-Independent Techniques

Background

Anatomic tunnel positioning is important in anterior cruciate ligament (ACL) reconstructive surgery. Recent studies have suggested the limitations of a traditional transtibial technique to place the ACL graft within the anatomic tunnel position of the ACL on the femur. The purpose of this study is to determine if the 2-incision tibial tunnel-independent technique can place femoral tunnel to native ACL center when compared with the transtibial technique, as the placement with the tibial tunnel-independent technique is unconstrained by tibial tunnel.

Methods

In sixty-nine patients, single-bundle ACL reconstruction with preservation of remnant bundle using hamstring tendon autograft was performed. Femoral tunnel locations were measured with quadrant methods on the medial to lateral view of the lateral femoral condyle. Tibial tunnel locations were measured in the anatomical coordinates axis on the top view of the proximal tibia. These measurements were compared with reference data on anatomical tunnel position.

Results

With the quadrant method, the femoral tunnel centers of the transtibial technique and tibial tunnel-independent technique were located. The mean (± standard deviation) was 36.49% ± 7.65% and 24.71% ± 4.90%, respectively, from the over-the-top, along the notch roof (parallel to the Blumensaat line); and at 7.71% ± 7.25% and 27.08% ± 7.05%, from the notch roof (perpendicular to the Blumensaat line). The tibial tunnel centers of the transtibial technique and tibial tunnel-independent technique were located at 39.83% ± 8.20% and 36.32% ± 8.10%, respectively, of the anterior to posterior tibial plateau depth; and at 49.13% ± 4.02% and 47.75% ± 4.04%, of the medial to lateral tibial plateau width. There was no statistical difference between the two techniques in tibial tunnel position. The tibial tunnel-independent technique used in this study placed femoral tunnel closer to the anatomical ACL anteromedial bundle center. In contrast, the transtibial technique placed the femoral tunnel more shallow and higher from the anatomical position, resulting in more vertical grafts.

Conclusions

After single-bundle ACL reconstruction, three-dimensional computed tomography showed that the tibial tunnel-independent technique allows for the placement of the graft closer to the anatomical femoral tunnel position when compared with the traditional transtibial technique.     

Biomechanical effect of a two-segment anterior cruciate ligament graft with separate femoral attachments and differing levels of prescribed load sharing.

The objective of this study was to analyze the biomechanical effect of varying the level of prescribed load sharing between two segments of an anterior cruciate ligament (ACL) graft, and of separating the femoral attachments of these segments. Total anterior-posterior (AP) laxity was measured using an instrumented spatial linkage. Forces in graft segments were measured using buckle transducers. The two-segment graft was formed using the middle third of the patellar tendon with bone blocks and a synthetic augmentation device. Proximal fixation was obtained using a fixture which allowed changing the individual locations of the femoral attachments of the tendon and augmentation segments. Distal fixation was achieved using a force-setting device which allowed the loads in each segment to be set to prescribed levels. Total graft force, load sharing, and total AP laxity were recorded during the application of 100-N AP tibial loads at 0 degrees, 30 degrees, 60 degrees, 90 degrees, and 110 degrees flexion, for various combinations of load sharing set at extension and locations of femoral attachment sites. The load sharing, total graft force, and AP laxity during AP loading at the five test flexion angles were not significantly affected by changing the prescribed level of load sharing set at extension for a given femoral attachment configuration. However, varying the separate hole locations of the graft segments for a given level of load sharing significantly affected load sharing, total graft force, and AP laxity. If the tendon graft was located posteriorly (on the medial surface of the lateral femoral condyle) and the augmentation segment proximally, the augmentation carried a greater portion of the total force in flexion. If the augmentation segment was changed to a more posterosuperior location and the tendon posteroinferior, the tendon carried a higher percentage of the total force in flexion. AP laxity in most reconstruction states was significantly greater than in the normal joint with an intact ACL. The nature of the load sharing between the graft segments under AP tibial load over the flexion range can be controlled by the appropriate choice of the segments' femoral attachment locations.     

A new tibial coordinate system improves the precision of anterior-posterior knee laxity measurements: a cadaveric study using Roentgen stereophotogrammetric analysis.

Roentgen stereophotogrammetric analysis (RSA) can be used to measure changes in anterior-posterior (A-P) knee laxity after anterior cruciate ligament (ACL) reconstruction. Previous measurements of A-P knee laxity using RSA have employed a tibial coordinate system with the origin placed midway between the tips of the tibial-eminences. However, the precision in measuring A-P knee laxity might be improved if the origin was placed on the flexion-extension axis of rotation of the knee. The purpose of this study was to determine whether a center-of-rotation tibial coordinate system with the origin placed midway between the centers of the posterior femoral condyles, which closely approximates the flexion-extension center-of-rotation of the knee, improves the precision in measuring A-P knee laxity compared to the tibial-eminence-based coordinate system. A-P knee laxity was measured using each coordinate system six times in three human cadaveric knees implanted with 0.8-mm diameter tantalum markers. For each laxity measurement, the knee was placed in a custom loading apparatus and biplanar radiographs were obtained while the knee resisted a 44 N posterior shear force and 136 N anterior shear force. A-P knee laxity was determined from the change in position of the tibia, with respect to the femur, resulting from the posterior and anterior shear forces. The precision for each coordinate system was calculated as the pooled standard deviation of A-P knee laxity measurements. The precision of the center-of-rotation coordinate system was 0.33 mm, which was about a factor of 2 better than the 0.62 mm precision of the tibial-eminence coordinate system (p=0.006). The 0.33 mm precision with the center-of-rotation coordinate system suggests that an observed change of either 0.56 mm (i.e. 1.7 standard deviations) or greater in A-P knee laxity over time is a real change and not due to measurement error when the new tibial coordinate system is used and other factors contributing to variability are controlled as was done in this study. Accordingly, clinicians and researchers should consider the use of this alternate tibial coordinate system when making serial measurements of A-P knee laxity using RSA because the improved precision allows for the observation of smaller differences.     

The effects of tibial tunnel placement and roofplasty on reconstructed anterior cruciate ligament knees

Seventy-five anterior cruciate ligament (ACL) reconstructions augmented with the Kennedy Ligament Augmentation Device were evaluated according to classification of tibial drill-hole position on the basis of the anatomic landmarks of the ACL by two-dimensional radiographic imaging of the fully extended knee. The effects of roofplasty to avoid graft impingement were also assessed. The tibial drill-hole position was classified in relation to the medial intercondylar tubercle on anterior-posterior (AP) view, and in relation to Blumensaat's line (B-line) on lateral view. Arthroscopic evaluation of the ACL and incidence of chronic synovitis as well as Lysholm knee score, manual knee tests, knee extension and flexion angles, and knee tester measurements were performed. The results indicated that the knee joints in which the tibial drill hole was positioned laterally from the medial intercondylar tubercle or in which the tibial drill hole was positioned anteriorly to the B-line showed a tendency to develop more postoperative chronic synovitis. The knees in which the tibial drill hole was positioned anteriorly to the B-line also showed larger AP laxity. There was no difference between the non-roofplasty and roofplasty groups.     

Kniegelenklaxizität beim vorderen Kreuzbandersatz

Background

The use of interference screws for femoral graft fixation in anterior cruciate ligament (ACL) reconstruction with hamstring grafts can result in rotation of the graft around the screw leading to changes in the final position of the graft within the bone tunnel.

Material and methods

In a prospective study 107 patients (54 right and 53 left knees) underwent ACL reconstruction with a hamstring tendon autograft. Femoral fixation of the graft was performed with a standard right-thread screw in all cases. Patients were assessed at 6 months postoperatively with the international knee documentation committee (IKDC) standard evaluation including instrumented laxity measurements and the results were compared between right and left knees.

Results

A significantly higher postoperative anterior laxity was observed in left knees with a negative Lachman test in only 64 % of the cases compared with 87 % in the group of right knees. Accordingly, instrumented laxity measurements of the reconstructed knee compared with the contralateral knee revealed significant differences between left and right knees (left knees 1.8±1.2 mm and right knees 1.0±1.4 mm)

Conclusions

This study demonstrates the importance of femoral graft positioning and its sensitivity to multiple influencing factors. The use of standard right-thread interference screws for femoral graft fixation in the mirrored situation of right and left knees may produce a systematic error in ACL reconstruction. Due to a possible rotation of the graft around the screw, the final position of the transplant may vary thus leading to significant changes in anterior translation of the operated knee.     

保留并牵张残留纤维的前十字韧带双束重建术

目的 评估在亚急性期进行保留并牵张残留纤维的前十字韧带双束重建的临床效果.方法 2006年1月至2006年6月,对56例前十字韧带损伤患者在亚急性期进行保留并牵张残留纤维的前十字韧带双束重建.前十字韧带双束重建采用四隧道八股肌腱移植的方法.使用PDS缝线穿缝胫骨侧残留纤维,经深束股骨隧道牵张固定.使用IKDC及Lysholm评分标准评估疗效.结果 53例随访2年以上.末次随访时所有患者Lachman试验均为阴性.屈膝25°KT-1000检测结果显示双侧膝关节松弛度差值为(-0.44±1.53)mm,与术前(8.01±1.83)mm比较差异有统计学意义(t=37.03,P=0.0001).29例(54.7%)双侧膝关节松弛度差值小于0mm,提示患膝相对于健侧更为稳定或紧张.24例(45.3%)双侧膝关节松弛度差值为0～2mm.所有患者轴移试验均阴性.48例膝关节活动度正常,2例有5°屈曲受限,1例有小于5°屈曲受限,2例有5°过伸受限.根据IKDC评估标准,51例(96.2%)正常,2例(3.8%)接近正常.IKDC主观评分为(95.6±3.1)分,Lysholm评分为(94.8±2.9)分.受伤前Tegner评分平均为7.3分,末次随访时为7.1分.结论 根据2年以上随访结果,以IKDC为评估标准,保留并牵张残留纤维的前十字韧带双束重建能够使96.2%的患者恢复正常,3.8%的患者接近正常.     

Simulated graft recession in endoscopic ACL reconstruction: influence on graft strain

Eight fresh cadaveric knee specimens underwent arthroscopic-assisted ACL reconstruction to examine the influence of femoral graft recession on graft strain pattern. Length changes between tibial origin and femoral insertion (simulating graft strain or isometry pattern) were measured throughout knee motion (0 degrees-90 degrees) with a simulated ACL construct. Measurements were taken at the "endo" position (replicating the normal endoscopic position) and in progressive 1.5-mm increments proximally within the femoral tunnel (mimicking femoral graft recession). After recession up to a maximum of 15 mm, a block was placed anterior to the "recessed" graft construct (simulating placement of bone graft anterior to the recessed graft) and strain patterns were remeasured. Graft strain patterns were altered with as little as 1.5 mm recession in two of eight specimens. Compared to the "endo" position, all specimens showed a statistically significant decrease in strain by 3 mm of graft recession (P<.001 for 7 of 8, and P=.0138 for 1 of 8). A direct relationship exists between graft placement and ACL strain patterns, with more proximal graft "recession" adversely influencing normal graft strain. Bone graft placement anterior to the recessed graft restores strain patterns to those seen at the normal "endoscopic" position.