Orientation of the cruciate ligament in the sagittal plane. A method of predicting its length-change with flexion

A Novel Kinematic Model of the Tibiofemoral Joint Based on a Parallel Mechanism

This paper presents a complete kinematic model of the tibiofemoral joint (TFJ) based on a RRPP + 4-SPS parallel mechanism, where R, P, and S stand for revolute, prismatic, and spherical joints, respectively. The model accounts for the contact between tibia and femur, and the four major ligaments: anterior cruciate, posterior cruciate, medial collateral, and lateral collateral, with anatomical significance in their length variations. An experimental flexion passive motion task is performed, and the kinematic model is tested to determine its capability to reproduce the workspace of the motion task. In addition, an optimization process is performed to simulate prescribed ligament length variations during the motion task. The proposed kinematic model is capable to reproduce with high accuracy an experimental three-dimensional workspace, and at the same time, to simulate prescribed ligament length variation during the spatial flexion task. Prescribed ligament length variations are achieved through an optimization process of the ligament insertion points. This model can be used to improve the multibody kinematic optimization (MKO) process during gait analysis, and also in the design of rehabilitation devices as well as trajectories to accelerate the recovery of injured ligaments. The model shows potential to predict ligament length variations during different motion tasks, and can serve as a basis to develop complex models for kinetostatic and dynamic analyses without dealing with computationally expensive models.

Transtibial technique versus two incisions in anterior cruciate ligament reconstruction: tunnel positioning, isometricity and functional evaluation

OBJECTIVE

To compare the transtibial and two-incision techniques for anterior cruciate ligament (ACL) reconstruction using a single band.

METHODS

A prospective and randomized study was conducted in blocks. Patients underwent ACL reconstruction by means of two techniques: transtibial (group 1: 20 patients) or two incisions (group 2: 20 patients). The radiographic positioning of the tunnel, inclination of the graft, graft isometricity and functional results (IKDC and Lysholm) were evaluated.

RESULTS

The positioning of the femoral tunnel on the anteroposterior radiograph, expressed as a mean percentage relative to the medial border of the tibial plateau, was 54.6% in group 1 and 60.8% in group 2 (p < 0.05). The positioning of the femoral tunnel on the lateral radiograph, expressed as a mean percentage relative to the anterior border of Blumensaat's line, was 68.4% in group 1 and 58% in group 2 (p < 0.05). The mean inclination of the graft was 19° in group 1 and 27.2° in group 2 (p < 0.05). The mean graft isometricity was 0.96 mm in group 1 and 1.33 mm in group 2 (p > 0.05). Group 2 had better results from the pivot-shift maneuver (p < 0.05).

CONCLUSION

The technique of two incisions allowed positioning of the femoral tunnel that was more lateralized and anteriorized, such that the graft was more inclined and there was a clinically better result from the pivot-shift maneuver. There was no difference in isometricity and no final functional result over the short follow-up time evaluated.

Reconstruction of the anterior cruciate ligament by means of an anteromedial portal and femoral fixation using Rigidfix

Objective

To evaluate a series of patients who underwent surgery for reconstruction of the anterior cruciate ligament with flexor tendons, by means of the anteromedial transportal technique using Rigidfix for femoral fixation, and to analyze the positioning of the pins by means of tomography.

Methods

Thirty-two patients were included in the study. The clinical evaluation was done using the Lysholm, subjective IKDC and Rolimeter. All of them underwent computed tomography with 3D reconstruction in order to evaluate the entry point and positioning of the Rigidfix pins in relation to the joint cartilage of the lateral condyle of the femur.

Results

The mean Lysholm score obtained was 87.81 and the subjective IKDC was 83.72. Among the 32 patients evaluated, 43% returned to activities that were considered to be very vigorous, 9% vigorous, 37.5% moderate and 12.5% light. In 16 patients (50%), the distal entry point of the Rigidfix pin was located outside of the cartilage (extracartilage); in seven (21.87%), the distal pin injured the joint cartilage (intracartilage); and in nine (28.12%), it was at the border of the lateral condyle of the femur.

Conclusion

The patients who underwent ACL reconstruction by means of the anteromedial transportal using the Rigidfix system presented satisfactory clinical results over the length of follow-up evaluated. However, the risk of lesions of the joint cartilage from the distal Rigidfix pin needs to be taken into consideration when the technique via an anteromedial portal is used. Further studies with larger numbers of patients and longer follow-up times should be conducted for better evaluation.

Surgery for anterior cruciate ligament deficiency: a historical perspective

The anterior cruciate ligament (ACL) has entertained scientific minds since the Weber brothers provided biomechanical insight into the importance of the ACL in maintaining normal knee kinematics. Robert Adams described the first clinical case of ACL rupture in 1837 some 175 years to date, followed by Mayo-Robson of Leeds who performed the first ACL repair in 1895. At that time, most patients presented late and clinicians started to appreciate signs and symptoms and disabilities associated with such injuries. Hey Groves of Bristol provided the initial description of an ACL reconstruction with autologous tissue graft in 1917, almost as we know it today. His knowledge and achievements were, however, not uniformly appreciated during his life time. What followed was a period of startling ingenuity which created an amazing variety of different surgical procedures often based more on surgical fashion and the absence of a satisfactory alternative than any indication that continued refinements were leading to improved results. It is hence not surprising that real inventors were forgotten, good ideas discarded and untried surgical methods adopted with uncritical enthusiasm only to be set aside without further explanation. Over the past 100 years, surgeons have experimented with a variety of different graft sources including xenograft, and allografts, whilst autologous tissue has remained the most popular choice. Synthetic graft materials enjoyed temporary popularity in the 1980 and 1990s, in the misguided belief that artificial ligaments may be more durable and better equipped to withstand stresses and strains. Until the 1970s, ACL reconstructions were considered formidable procedures, often so complex and fraught with peril that they remained reserved for a chosen few, never gaining the level of popularity they are enjoying today. The increasing familiarity with arthroscopy, popularised through Jackson and Dandy, and enhancements in surgical technology firmly established ACL reconstruction as a common procedure within the realm of most surgeons' ability. More recently, the principle of anatomic ACL reconstruction, aiming at the functional restoration of native ACL dimensions and insertion sites, has been introduced, superseding the somewhat ill-advised concept of isometric graft placement. Double-bundle reconstruction is gaining in popularity, and combined extra- and intra-articular procedures are seeing a revival, but more accurate and reliable pre- and post-operative assessment tools are required to provide customised treatment options and appropriate evaluation and comparability of long-term results. Modern ACL surgery is united in the common goal of re-establishing joint homoeostasis with normal knee kinematics and function which may ultimately assist in reducing the prevalence of post-operative joint degeneration. This review hopes to provide an insight into the historical developments of ACL surgery and the various controversies surrounding its progress. Level of evidence V.

Correlation between the morphometric parameters of the anterior cruciate ligament and the intercondylar width: gender and age differences

The study was conducted on 50 cadavers (32 male and 18 female, aged 15-53 years; mean 34; SD 11) with intact anterior cruciate ligament (ACL), without diagnosed gonarthrosis of the knee joint. The following anatomical parameters of the ACL were measured: the length of anteromedial and posterolateral bundle, the mean length and the width of the ligament, the length and width of tibial insertion, the length and width of femoral insertion. The intercondylar width was measured at the level of popliteal groove. The width of male intercondylar notch (22 mm) was statistically significantly greater (P < 0.05) than the width of female intercondylar notch (18 mm). The width of the male ACL (12 mm) was significantly greater (P < 0.05) than the width of the female ACL (10 mm). The length of the male ACL femoral insertion (14 mm) was statistically significantly greater (P < 0.05) than in the female ACL femoral insertion (12 mm). Accordingly, with greater width of intercondylar notch, men have wider ACL than women. ACL width is in positive correlation with the male intercondylar notch width but it is not in correlation with the female intercondylar notch width. The width of male intercondylar notch correlates with the length and width of ACL femoral insertion. Taking into account the length and width of femoral insertion in examined cadaver knees, double bundle reconstruction would theoretically be possible in 76% of cases.

Differences in the placement of the tibial tunnel during reconstruction of the anterior cruciate ligament with and without computer-assisted navigation

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

Randomized 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 standard 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 standard 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.

Experimental evaluation of 3-dimensional kinematic behavior of the cruciate ligaments

PURPOSE

The purpose of this study was to evaluate a low-cost and easily reproducible technique for biomechanical studies in cadavers. In this kind of study, the natural effect of loading of the joint and shear forces are not taken into account. The objective is to describe the plastic deformation of the ligaments into 3-dimensional space.

METHOD

For 18 intact human cadaver knees, the cruciate ligaments were divided into 3 fiber bundles, the tibial or femoral fixation points were marked, and 2 perpendicular different x-ray exposures were performed, thus obtaining radiographs of spatial projections of the bundle in 3 anatomic planes (frontal, sagittal, and transversal). From the measurements made on the x-ray films, we obtained the average distance between the 2 fixation points of the cruciate ligaments on the tibia and the femur at 4 different flexion angles.

RESULTS

The distance between the fixation points of the medial and lateral fiber bundles of the cruciate ligaments did not change significantly during movement. There were, however, significant variations (P < .05) in the distance between the fixation points of the posterior fiber bundles of the anterior cruciate ligament and the anterior fiber bundles of the posterior cruciate ligament.

CONCLUSIONS

This technique was efficient for demonstrating the plastic deformability of the cruciate ligaments. The results proceeding from this type of study can assist in the planning of physical rehabilitation programs.

Femoral attachment of the anterior cruciate ligament

Endoscopic anterior cruciate ligament (ACL) reconstruction is one of the most popular orthopaedic procedures. Correct tunnel positioning is a prerequisite to success. Current surgical techniques are unable to duplicate the complex anatomy and function of the native ACL. Surgery mainly aims at restoring anteroposterior laxity. The ACL is not isometric and only a few fibers are nearly isometric over the full range of motion. However, a nearly isometric behaviour of the ACL graft is desirable. Isometry is mainly influenced by femoral attachment; thus the femoral tunnel position has a greater effect than the tibial on graft length changes. The purpose of this article is to describe the anatomy of the femoral ACL insertion and to discuss the surgical techniques used to replicate it.

A computational model of postoperative knee kinematics

A mathematical model for studying the passive kinematics of total knee prostheses can be useful in computer-aided planning and guidance of total joint replacement. If the insertion location and neutral length of knee ligaments is known, the passive kinematics of the knee can be calculated by minimizing the strain energy stored in the ligaments at any angular configuration of the knee. Insertions may be found intraoperatively, or may come from preoperative 3D medical images. The model considered here takes into consideration the geometry of the prosthesis and patient-specific information. This model can be used to study the kinematics of the knee joint of a patient after total joint replacement. The model may be useful in preoperative planning, computer-aided intraoperative guidance, and the design of new prosthetic joints.

Graft isometricity in unitunnel anterior cruciate ligament reconstruction: analysis of influential factors using a radiographic model

A radiographic model was developed to investigate the influence of three surgical variables on the change in attachment point distance (CAPD) of a hypothetical graft using the unitunnel technique of anterior cruciate ligament (ACL) reconstruction. Using three different femoral target points, we tested the hypothesis that varying the angle of knee flexion between 70 degrees and 110 degrees and varying the tibial starting point over a 4-cm range do not result in a significant variation in CAPD. We also tested the hypothesis that the CAPD from 0 degrees to 135 degrees is greater than the CAPD from 0 degrees to 90 degrees. There was a statistically significant correlation (r = 0.8465, P < 0.0001) between radiographically estimated and isometer-measured values of CAPD. The tibial starting point and the femoral target point were found to affect the CAPD significantly (P < 0.005). A more proximal tibial starting point was associated with a lower CAPD. Both the center of the anatomic femoral attachment of the ACL, and a point 1 mm medial to the junction of the roof and lateral wall of the femoral intercondylar notch and 6 mm anterior to its posterior margin, were associated with lower CAPD values than a target point 5 mm superior and posterior to the center of the femoral ACL attachment. The angle of knee flexion did not significantly affect the CAPD. The CAPD [0 degrees-135 degrees] was significantly greater than the CAPD [0 degree-90 degrees] for all combinations of variables (P < 0.0005).(ABSTRACT TRUNCATED AT 250 WORDS)

Femoral tunnel position in anterior cruciate ligament reconstruction using three techniques. A cadaver study

The possibility of achieving correct deep femoral tunnel positioning during anterior cruciate ligament (ACL) reconstruction with the double incision technique (DI), the transtibial technique (TT), and the anteromedial technique (AM) was evaluated in 30 cadaver knees. A reference hole was made just deep to the insertion of the anteromedial bundle of the ACL through an anteromedial arthrotomy. In the DI technique, a Kirshner wire was inserted outside-in using a rear entry C guide. In the TT and AM techniques, the K-wire was inserted inside-out through the tibial tunnel and through the arthrotomy, respectively. The reference hole could be achieved with each technique. Using lateral radiographs, the superficial aspect of the intra-articular exit of the femoral tunnel was found to be located on average at 36%, 36%, and 34% of the width of the condyles from the posterior margin (NS). None of the holes was more anterior than 40%. In conclusion, a deep femoral tunnel positioning could be achieved with each technique. The choice of technique must be based on the surgeon's preference and clinical results.

Knee joint motion: description and measurement

Knee joint motion has been described in various ways in the literature. These are explained and commented on. Two methods for describing knee joint motion with 6 degrees of freedom (DOF)--Euler angle and the helical axis of motion--are discussed. Techniques to measure joint motion which can either approximate the motion to less than 6 DOF or fully measure the spatial motion are identified. These include electrical linkage methods, radiographic and video techniques, fluoroscopic techniques and electromagnetic devices. In those cases where the full spatial motion is measured, the data are available to describe the motion in simpler terms (or with less DOF) than three rotations with three translations. This is necessary for clinical application and to facilitate communication between the clinician and the engineer.

Can an isometer predict the tensile behavior of a double-looped hamstring graft during anterior cruciate ligament reconstruction?

An isometer, a highly compliant spring-scale device for measuring suture displacement, has been used intraoperatively by surgeons to select the optimal placement of the femoral tunnel for an anterior cruciate ligament graft. The isometer measures the displacement of a suture centered in a tibial tunnel and attached to an intraarticular location on the femur before the femoral tunnel is drilled. Because the placement of the femoral tunnel strongly impacts the tensile behavior of an anterior cruciate ligament graft and because surgeons have used the amount of suture displacement to guide the placement of the femoral tunnel, the objective of this study was to determine the ability of an isometer to predict graft tension. In 14 patients undergoing reconstructive surgery of the anterior cruciate ligament, an isometer was used to measure suture displacement during passive knee motion for a provisional femoral tunnel location. An electrogoniometer recorded the flexion angle of the knee. The femoral tunnel was drilled. A double-looped semitendinosus and gracilis autograft was inserted around a post in the femoral tunnel, and the tension in the four limbs of the graft exiting the tibial tunnel was measured during passive knee motion. Graft-tension versus knee-flexion-angle curves revealed that each knee exhibited one of two distinct curve shapes: L-shaped, characterized by the maximum tension occurring at full extension and a nearly flat profile from 35 to 90 degrees of flexion, or U-shaped, with elevated tensions at 80-90 degrees of flexion (p < 0.001) reaching at least half of the tension in full extension. Because the shapes of the suture-displacement versus flexion-angle curves were more consistently L-shaped, the intraoperative measurement of suture displacement was not a useful predictor of either the increase in tension in the graft with flexion or the maximum tension in the graft.

ACL reconstruction by patellar tendon. A comparison of length by magnetic resonance imaging

In 50 knees the length of the anterior cruciate ligament (ACL), the patellar tendon, and the distance between the tibial tuberosity and the femoral origin of the ACL were evaluated by means of three-dimensional magnetic resonance imaging (MRI), which permits subsequent reconstruction of any sectional view. The measurements showed that the patellar tendon was always markedly longer than the ACL (mean 14.4 mm), but always shorter than the distance between the tibial tuberosity and the femoral insertion of the ACL (mean 19.2 mm). The mean lengths of the ACL and the patellar tendon were 38.2 mm and 52.6 mm, respectively. The mean distance between the femoral ACL origin and the tibial insertion of the patellar tendon was 71.8 mm. These results demonstrate that a distally based patellar tendon autograft alone (with the patellar bone block but without extension into the periosteum of the patella or the quadriceps tendon) cannot be placed anatomically correctly to the isometric femoral insertion of the ACL. When the patellar tendon is used for ACL reconstruction, it must be implanted as a free autograft. Nevertheless, considerable variations of length must be taken into account.

Posterior tibial tunnel placement to avoid anterior cruciate ligament graft impingement by the intercondylar roof. An in vitro and in vivo study

Recent recommendations to "customize" tibial tunnel placement based on the slope of the intercondylar roof and the amount knee hyperextension were derived from a series of cases with graft impingement by the intercondylar roof. We believe that this impingement is caused by anterior placement of the graft and not by variations of notch anatomy among individual patients. In Phase 1 of this study, we drilled tibial tunnels in the posteromedial aspect of the anterior cruciate ligament "footprint" after the ligament was excised in cadaveric knees. We then passed an impingement rod into the back of the knee joint. Lateral radiographs with the knee in hyperextension were taken of each specimen, and the distance between the superior border of the rod and intercondylar roof was measured. In Phase 2, we prospectively obtained lateral hyperextension radiographs of 75 consecutive knees with anterior cruciate ligament reconstructions and evaluated them for graft impingement based on recently published guidelines. In Phase 1, we found no cases of impingement and an average roof clearance of 8.3 mm. In Phase 2, we noted no cases of severe impingement, 3 cases of moderate impingement (4%), and 72 cases (96%) with no impingement. We conclude that posteromedial tibial tunnel placement alone is adequate to avoid graft impingement in almost all patients. Individualized tibial tunnel placement with specialized tibial guidance systems is not necessary.

Isometry measurements in the knee with the anterior cruciate ligament intact, sectioned, and reconstructed

When assessing isometry during anterior cruciate ligament surgery, it is assumed that points determined to be isometric remain so after reconstruction. We sought to evaluate if isometric measurements vary with the status of the anterior cruciate ligament. A computerized electronic isometer was used to measure the magnitude and pattern of change in separation distance between a constant point in the tibial insertion of the anterior cruciate ligament and five positions within the femoral insertion with the anterior cruciate ligament intact, sectioned, and reconstructed. For the center position, the magnitude and pattern of the change in separation distance was physiologically isometric in all conditions (maximal length change, 3.0 mm). For the posterior position, the isometry pattern remained physiologic in each condition, and the magnitude of the separation distance was nearly isometric in all conditions (maximal length change, 3.7 mm). The superior and inferior positions had similar isometric measurements in the intact and sectioned conditions but significantly different measurements after anterior cruciate ligament reconstruction. Intraoperative assessment of isometry at positions in the center or posterior portion of the anterior cruciate ligament's femoral insertion provides useful information that is not altered by reconstruction. For superior and inferior positions, however, points found to be isometric in the anterior cruciate ligament-deficient knee did not remain isometric after reconstruction.

Analytical study on the kinematic and dynamic behaviors of a knee joint

A knee model in the sagittal plane is established in this study. Specifically, the model is used to study the effects of inertia, articular surfaces of the knee joint, and patella on the behaviors of a knee joint. These behaviors include the joint surface contact point, ligament forces, instantaneous center and slide/roll ratio between the femur and tibia. Model results are compared to experimental cadaver studies available in the literature, as well as between the quasistatic and dynamic models. We found that inertia increases the sliding tendency in the latter part of flexion, and lengthens the cruciate ligaments. Decreasing the curvature of the femur surface geometry tends to reduce the ligament forces and moves the contact points towards the anterior positions. The introduction of the patellar ligament in the model seems to stabilize the behaviors of the knee joint as reflected by the behavior of the instant centers and the contact point pattern on the tibia surface. Furthermore, we found that different magnitudes of the external load applied to the tibia do not alter the qualitative behaviors of the knee joint.

A sagittal plane model of the knee and cruciate ligaments with application of a sensitivity analysis

In this investigation the complex multi-bundle structure of the cruciate ligaments and their interaction with the tibiofemoral joint was modeled analytically by representing the different regions of the cruciates with ligament elements. A sensitivity analysis was then performed to describe the effect that variations of the model input parameters had on the model variables (outputs). The effect that the cruciate ligament bundles had in controlling joint kinematics was dependent on knee flexion angle, and the load applied to the tibiofemoral joint. For passive range of knee motion with the thigh in the horizontal plane (a common rehabilitation activity), all cruciate ligament bundles were strained with the joint positioned between 0 and 10 deg of knee flexion, between 10 and 50 deg only the anterior bundle of the posterior cruciate ligament A-PCL was strained, and from 50 to 90 deg both the anteromedial portion of the anterior cruciate ligament A-ACL and the A-PCL were strained. This finding indicates that a strain distribution about a transverse cross section of the cruciates exists, and demonstrates the importance of differentiating between the strained and unstrained (unloaded) states of these ligaments. The strain value of a cruciate ligament bundle was an indication of how the bundle controls joint kinematics, while the unstrained values describe how much the ligament bundle must deform before it becomes strained and a restraint to tibiofemoral joint motion. In response to anterior and posterior directed loads, applied parallel to the tibial plateau, the respective, ACL and PCL load values were larger in magnitude. The sensitivity of the model outputs to the input parameters was highly dependent on knee flexion angle. The geometrical input parameters of the model (including the ligament insertion site locations and articular surface geometry) had the most pronounced effect on the model output quantities, while the stiffness and initial strain conditions of the ligament bundles had less of an effect on the model outputs. When loaded, the strain values of the ligament bundles were sensitive to the ligament insertion site position. The greatest sensitivity of the model outputs was the femoral insertion of the ACL; supporting clinical impressions and previous experimental findings. Changes in the anterior-posterior dimension of the femoral articular surface did not produce a substantial effect on the model outputs, while changes in the proximal-distal dimension created a large effect; similar results were found for the tibial surface dimensions. These findings indicate that rigid body contact between the articular surfaces may not be a realistic assumption particularly with application to the prediction of tibiofemoral compressive loading and the force/strain values of the cruciate ligament elements. This also has important implications for the design and clinical application of total knee replacements (that function as rigid bodies), particularly those that spare the PCL.

Radiographic evaluation of native anterior cruciate ligament attachments and graft placement for reconstruction. A cadaveric study

We examined seven cadaveric knees to determine the radiographic location of the native anterior cruciate ligament insertion sites as well as the location of tunnels used in anterior cruciate ligament reconstruction. Posteroanterior and lateral views at several flexion angles were taken with radiopaque markers around the insertions of the native anterior cruciate ligament and subsequent reconstruction tunnels. The femoral insertion was best seen on the 60 degrees notch view. On the lateral view, the femoral tunnel was easily seen as it crossed the roof of the intercondylar notch; however, because of the angle of the tunnel, the actual entrance into the knee may be well distal and anterior to this location. The tibial insertion and tunnel were easily seen at any flexion angle. The center of the insertion was 40% of the tibial diameter from the anterior margin. The lateral view in extension allowed determination of the tibial tunnel's location in relation to the intercondylar notch roof, but by itself did not allow accurate determination of the femoral tunnel's position. Notch and extension lateral radiographs together provided sufficient information for evaluation of anterior cruciate ligament graft position in a convenient, cost-effective format. Neither view by itself provides enough information to evaluate the position of the graft.

[Complications in 283 cruciate ligament replacement operations with free patellar tendon transplantation. Modification by surgical technique and surgery timing]

In our retrospective study we reviewed 283 patients who were operated on between 1984 and 1993 after an ACL-rupture. We used a free patellar tendon bone graft in all patients. The aim was to assess the complications such as infections, thrombosis, limitation of movement and graft failures. We also looked on the timing of operation and the technique. We saw an overall complication rate of 21.6%. The most common complication was a restricted range of motion in 10.9% which required surgery. In patients treated immediately after injury (within 7 days) we found an arthrofibrosis rate of 17.6%. In delayed surgery (more than 4 weeks after injury) this complication was only seen in 6.1%. The rate of infection was 4.6%, the rate of thrombosis 1.8% and in 4,2% we had to accept an ongoing instability. With these findings we now evaluate the needs and the social environment even more closely to find the best treatment protocol for each individual. In conclusion we favour secondary ACL-reconstruction.

In-vitro correlation between tension and length change in an anterior cruciate ligament substitute

The length change and tension patterns from multiple insertion locations of an anterior cruciate ligament substitute were studied in 10 cadaver knees. Length change was measured with a spring-loaded isometer of low stiffness, and tension was measured with a piezoelectric load cell. In both instances a thin Kevlar test ligament was positioned in five different femoral and two different tibial ligament insertion locations, that were all located within the normal attachments of the anterior cruciate ligament. Differences were found regarding length changes and tension patterns from a simulated active extension between the central, posterior, and anterior femoral locations. All locations showed larger length change and tension values in extension than in flexion. The anterior femoral ligament insertion location showed length change and tension patterns with increasing values in flexion compared to the other femoral locations. The anterior tibial ligament insertion location showed smaller excursions of both length and tension, than did the central one, but the patterns of the curves were similar. A statistically significant correlation was found between length change and tension patterns throughout a 130-0 degrees range of motion. A statistically significant correlation was also found between the maximum length and tension values. No fixed relationship was found between the magnitude of the length and tension values, when different intervals of the range of motion were studied. RELEVANCE: The intraoperative employment of length change measurements of a test ligament in anterior cruciate ligament reconstruction gives information on where high tension can be expected in the range of motion of the knee, and how this can differ depending on the angle of graft fixation. The information gained can also be used to improve drill channel location. However, no predictions on the magnitude of tension can be made, mainly due to large biological variability.

Graft failure in intra-articular anterior cruciate ligament reconstructions: a review of the literature

There exists a substantial group of patients with unsatisfactory results following anterior cruciate ligament (ACL) reconstructions. This may be attributable to graft failure. Revision surgery, for the correction of abnormal anterior translation of laxity, requires a careful analysis of the causes of failure to ensure the success of the salvage procedure. This review attempts to present an overview of some of the important studies in the literature pertaining to the intraoperative and postoperative factors that probably cause graft failure. It was done by initial identification of the articles from a Medline database followed by the use of cross references. It shows that failures can be minimised by adhering to the correct operative and post-operative techniques wherein proper attention to the factors, such as: adequate notchplasty, proper tunnel placements, proper tensioning, adequate fixation, optimal selection and harvest of the graft, and rehabilitation, are ensured.

Fiber orientation of posterior cruciate ligament: an experimental morphological and functional study, Part 2

The posterior cruciate ligament (PCL) can be anatomically divided into three bundles: anterolateral, posteromedial, and posterior oblique. The changes in distance between the femoral and tibial attachment sites of these three bundles were measured in 10 human knee specimens with intact ligamental structures. The femoral to tibial distance (and thus the length) of the posterior oblique bundle remained nearly the same throughout flexion between 0 degrees and 90 degrees. The femoral to tibial distance of the anterolateral and the posteromedial bundles distinctly changed throughout the same range of motion. For a truly functional replacement of the PCL, correct isometric placement of the transplant is especially important. Based on the results of the present study, an isometric reconstruction of the PCL is achieved by positioning the graft within the original attachment site of the posterior oblique bundle.

Sagittal knee stability after anterior cruciate ligament reconstruction with a patellar tendon strip. A two-year follow-up study

Tibial anteroposterior displacement after anterior cruciate ligament reconstruction with a patellar tendon graft was followed prospectively for 2 years in 24 patients with an arthrometer. The femoral ligament insertion location, in a lateral projection, and the change in intraarticular fixation distance, measured with an isometer, were documented intraoperatively. Two years after surgery, the overall mean injured-noninjured difference in anteroposterior displacement was 2.0 +/- 2.3 mm. All grafts were fixed during surgery at 20 degrees of knee flexion. Patients for whom this angle coincided with the angle of minimum intraarticular fixation distance (Group I), and patients who had a femoral ligament insertion location > 2 mm anterior to the center of the normal anterior cruciate ligament attachment (Group A) showed larger tibial displacement than the other patients. An injured-noninjured difference in tibial anteroposterior displacement > or = 3 mm was classified as failure. Groups I and A failure rates were higher than for the other patients. No correlation was found between anteroposterior displacement and magnitude of the change in intraarticular fixation distance. We conclude that anterior femoral locations lead to larger sagittal play after 2 years than central or posterior locations and that the magnitude of the fixation distance is less important than the pattern.

An in vivo comparison between intraoperative isometric measurement and local elongation of the graft after reconstruction of the anterior cruciate ligament

This study was designed to determine if isometric measurement can be used to predict the pattern of elongation (the change in length) of a bone-patellar ligament-bone graft during passive flexion-extension of the knee at the time of reconstruction of the anterior cruciate ligament in vivo. A standard operative reconstruction technique was performed on nine patients. The tunnel sites for the grafts were selected, and the change in the distance between these sites was measured, with use of a CA-5000 drill-guide isometer as the knee was subjected to passive flexion-extension. After the reconstruction was completed, a Hall-effect transducer was implanted in the graft to measure the local displacement in the mid-substance of the graft that was produced by passive flexion-extension of the knee. For comparison, the isometric measurements and the values for local displacement of the graft were normalized by calculation of the percentage change in the length. With the knee in 10 to 30 degrees of flexion, the average isometric measurements and the measurements of local displacement demonstrated a decrease in length; however, the two techniques of measurement deviated at angles of flexion of 40 degrees and more. On the average, the isometric measurement of elongation between the trial insertion sites predicted that the graft would increase in length in flexion relative to extension, in contrast to the response of the graft after fixation. There was no significant correlation between the isometric measurements and the local elongation of the graft (r2 = 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Tibial attachment area of the anterior cruciate ligament in the extended knee position. Anatomy and cryosections in vitro complemented by magnetic resonance arthrography in vivo

Knowledge of the anatomy of the anterior cruciate ligament (ACL), including its course and orientation in relation to the roof of the intercondylar fossa, is a prerequisite for successful intra-articular ACL reconstruction. To attain precision placement of the tibial attachment site and to avoid graft/roof conflict in the extended knee position, we assessed the anteroposterior tibial insertion of the ACL in the midsagittal plane of the extended knee. We measured the anterior-posterior (AP) limits and the center of the tibial attachment area of the ACL from the anterior tibial margin. The inclination angle of the intercondylar fossa roof was measured with respect to the shaft axis of the femur. The tibial attachment area of the ACL was determined in ten cadaveric knees. Using the cryoplaning technique, we determined the tibial attachment of the ACL in five knees. Using contrast magnetic resonance arthrography (MRA), we measured the tibial insertion of the ACL in 35 patients (23 male and 12 female) with intact ACLs. The total AP midsagittal diameter of the tibia averaged 51.0 +/- 5.8 mm in the cadaveric knees, 49 mm on cryosections, and 53.7 mm in men and 49.0 mm in women with MRA. The average anterior limit of the ACL, measured from the anterior tibial margin, was 14 +/- 4.2 mm in the cadaveric knees, 12.1 mm at cryosectional anatomy, and 15.2 mm in men and 13.4 mm in women with MRA.(ABSTRACT TRUNCATED AT 250 WORDS)

Roentgenographic and magnetic resonance imaging of anterior cruciate reconstruction using a patellar tendon graft--correlations with physical findings

The purpose of this study was to evaluate the influence of the graft positioning on the clinical outcome and magnetic resonance imaging (MRI) signal of the graft following anterior cruciate ligament (ACL) reconstruction using the central one-third of the patellar tendon. Twenty-two patients with a chronic anterior instability underwent a modified Marshall-MacIntosh procedure, while 27 with a subacute torn ACL had an ACL reconstruction using a free bone-patellar tendon-bone graft. The patients were retrospectively reviewed with a 1.8-year average follow-up (1-3 years). The clinical result was evaluated through the comparative range of motion and the residual laxity as measured with the KT 1,000 arthrometer. The roentgenographic analysis was performed from anteroposterior (AP) and mediolateral (ML) views, made first on one-leg standing with the knee at 30 degrees of flexion, and secondly at "zero" extension with active quadriceps contraction. Lines were drawn to visualise the location of the tibial and femoral tunnels in relation to the tibial plateaus and the intercondylar roof represented by Blumensaat's line. The analysis of the lateral MRI views of the graft allowed discrimination between homogenous and heterogenous graft signals. On lateral roentgenograms of normal knees, it was found that Blumensaat's line crossed the surface of the medial tibial plateau at 30% +/- 9% of its sagittal width (20%-40% range), demonstrating the variability of intercondylar roof inclination. The range of motion was normal in 34 patients (group I), 9 patients had a flexion deficit (group II), and 6 exhibited an extension deficit (group III). The residual laxity was similar in each group (P > 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Graft-tunnel mismatch in endoscopic anterior cruciate ligament reconstruction: a new technique of intraarticular measurement and modified graft harvesting

The purpose of this study was to determine the incidence of bitunnel interference fixation and accurate femoral insertion site targeting using a modified technique of endoscopic anterior cruciate ligament (ACL) reconstruction. Thirty-four consecutive central-third bone-patellar tendon-bone autograft modified endoscopic ACL reconstructions were prospectively studied. A new technique was used intraoperatively to directly measure (a) intraarticular (graft) distance (IAD) and (b) patellar tendon graft length, thereby allowing calculation of optimal tibial tunnel length for each case. Accuracy of guide pin placement through this tibial tunnel into the proposed femoral insertion site was assessed, as was the ability to achieve interference fixation in both tunnels (minimum of 20 mm bone interference fixation within the tibial tunnel). A new technique for patellar tendon-bone harvesting and proximal graft fixation to address graft mismatch is described. The average IAD from tibial origin to femoral ACL insertion measured 26.3 +/- 3.0 mm (range 21-33). The average patellar tendon length (LP) was 48.4 +/- 6.0 mm (range 40-63). The average calculated tibial tunnel length (TT) necessary to achieve bitunnel fixation (TT > or = LP + 20 - IAD) was 42.1 +/- 5.3 mm (range 36-57). Establishment of the calculated tibial tunnel length was achieved in 25 cases (74%) (no graft-tunnel mismatch). Graft-tunnel mismatch, in which the tibial tunnel could not be established to the length calculated necessary to accommodate a minimum of 20 mm of bone graft, occurred in nine cases (26%). Graft-tunnel mismatch occurred more frequently in patients whose patellar lengths were > or = 50 mm (p < 0.005), but was not found to correlate specifically to IAD. Recession of the graft up into the femoral tunnel allowed accommodation of the mismatched graft (bitunnel interference screw fixation) in these nine cases, averaging 22.0 +/- 2.98 mm (range 16-29 mm) of available distal bone block fixation. Tibial tunnel fixation of > or = 20 mm was achieved in 30 patients (88%), 18 mm in two, 17 mm in one, and 16 mm in one. Measurement error resulted in inadequate distal graft accommodation in four patients in whom error averaged 3 mm. Targeting of the femoral insertion site guide pin was achieved without requiring any knee manipulation for all cases. Patellar tendon graft protrusion through the tibial tunnel and potentially suboptimal graft fixation poses a frequent problem during endoscopic ACL reconstruction.(ABSTRACT TRUNCATED AT 400 WORDS)

The value of intraoperative isometry measurements in anterior cruciate ligament reconstruction: an in vivo correlation between substitute tension and length change

With the objective to evaluate an "isometry" measurement in an anterior cruciate ligament (ACL) substitute, in vivo measurements were taken on 10 patients undergoing reconstruction due to chronic ACL deficiency. Change in intraarticular length of a 1.2-mm test ligament, measured with an isometer, was correlated to the tension created in the same test ligament after fixation, measured with a piezoelectric load cell. The knee was passively moved through the 0-100 degrees range with the patient under general anaesthesia. Good statistical and visual correlations between length change and tension curves were found in individual knees. A correlation between total length change and maximum tension, for all knees grouped, was also found. Individual knees showed large variation in ability of the tissue to absorb load, resulting in a wide range of N/mm ratios between length and tension. Three knees with an isolated ACL injury all showed the least length change, implying a better restoration of kinematics in the absence of associated injuries. In nine of 10 knees the length change pattern could be used to identify the location of the femoral drill channel, as determined on an intraoperative lateral projection of the knee. Intraoperative isometry measurement can be used to predict the tension pattern in the reconstructed knee, but not the magnitude of tension. It will be useful to the surgeon in avoiding an anterior femoral ligament insertion site, which might threaten the integrity of the graft by tension rise in flexion.

A method for the kinematic evaluation of the knee following anterior cruciate ligament injury and reconstruction

A quantitative method for assessing the kinematics of the knee in the sagittal plane has been developed in order to evaluate the role of the anterior cruciate ligament following injury and reconstruction. Measurements were made on a series of lateral radiographs obtained at different angles of flexion with the limb weight-bearing and the foot and ankle rotated so that the condyles of the femur overlapped. The kinematics of the joint were then defined by recording the path of the tip of the medial tibial spine as flexion proceeded, using a coordinate system based on the femur. This method overcomes the problems inherent in quantifying knee kinematics by using the pathway of the centre of rotation. In an amputated knee, tibial positions could be specified to within approximately 1.2 mm. There were no significant differences between results obtained at the beginning and end of a six month period for the normal knees of two patients; the standard deviation of the measured tibial positions was approximately 1.6 mm.

Reconstruction of the anterior cruciate ligament with Achilles tendon autograft

The increasingly serious complications of artificial ligaments and allografts have brought them into disrepute. Recently, autografts have drawn more attention. A new type of autograft, the Achilles tendon autograft, has been developed and applied to anterior cruciate ligament reconstructions. This report describes the advantages of the Achilles tendon autograft used and presents the results of a prospective study of 21 patients with minimum 2 year follow up. Of the 21 cases, 16 patients (75%) had a rating of excellent; 2 (10%) good, 2 (10%) fair, and 1 (5%) poor. Preoperative knee scores of 56.7 were improved to 89.5 postoperatively. The authors removed less than half of the Achilles tendon with the calcaneal bone incorporated. Through magnetic resonance imaging we confirmed that the remaining Achilles tendon of the donor site regained its volume and strength within a year without significant complication. Achilles tendon autograft offers the advantages of length, elastic strain modulus, reproducibility in technique, and consistency of the result without significant complications.

Isometric versus tension measurements. A comparison for the reconstruction of the anterior cruciate ligament

This study was designed to compare the displacement patterns of an isometer, used to determine graft placement during reconstruction, with the actual tensions on an anterior cruciate ligament substitute. In cadaveric specimens, a Kevlar anterior cruciate ligament substitute was implanted in three separate femoral sites, each of which was subsequently fixed to two different tibial sites. The initial tension of the Kevlar substitute was set to 22 or 33 N at 20 degrees of knee flexion. The displacement patterns for each position were recorded during passive flexion-extension using the isometer. Using a custom-designed tensiometer, the tensile forces on the substitute after rigid fixation at the tibia and femur were measured. During passive flexion-extension, the maximum change in tension of the anterior cruciate ligament substitute, measured by the tensiometer, was correlated with the maximum change in displacement between attachment sites, measured by the isometer. The coefficient of determination was equal to 0.15, indicating that the isometer may not accurately predict the tensions developed in the substitute.

Arthroscopic anterior cruciate ligament reconstruction with patellar tendon

Anterior cruciate ligament reconstruction using a bone-patella tendon-bone free autologous graft was performed with an arthroscopic technique in 73 patients with chronic insufficiency. Sixty-nine (94.5%) were available for personal follow-up 3-5 years after the operation. Six patients (8%) had had postoperative difficulties in regaining a complete range of motion. Symptoms of giving-way were cured in 97% of the cases, and 89% had returned to vigorous activities. Residual anterior laxity (defined as pivot shift 2+, and/or Lachman 2+, and/or KT-1000 > 5 mm at the manual maximum) was found in 13% and was more frequent in patients with an uncorrected varus laxity. Patellofemoral crepitus was present in 17% of the knees and was associated with pain and/or swelling in a further 4%; it correlated with radiographic evidence of patellofemoral incongruence (p = 0.009). Comparison of the results with those of a previous series performed by arthrotomy revealed a decreased incidence of limited range of motion, severe patellar symptoms, and changes in patellar height. Stability was the same.

A model of human knee ligaments in the sagittal plane. Part 1: Response to passive flexion

The development of a mathematical model of the knee ligaments in the sagittal plane is presented. Essential features of the model are (a) the representation of selected cruciate ligament fibres as isometric links in a kinematic mechanism that controls passive knee flexion and (b) the mapping of all other ligament fibres between attachments on the tibia and femur. Fibres slacken and tighten as the ligament attachment areas on the bones move relative to each other. The model is used to study the shape and fibre length changes of the cruciate and collateral ligaments in response to passive flexion/extension of the knee. The model ligament shape and fibre length changes compare well qualitatively with experimental results reported in the literature. The results suggest that when designing and implanting a ligament replacement with the aim of reproducing the natural fibre strain patterns, the surgeon must not only implant through the natural attachment areas but must also maintain the natural fibre mapping and render all fibres just tight at the appropriate flexion angle.

The effect of tibial attachment site on graft impingement in an anterior cruciate ligament reconstruction

Anterior cruciate ligament reconstructions were performed in 14 cadaveric knee specimens using a 6-mm wide polypropylene graft. The graft was passed through a femoral tunnel at the attachment site of the anterior medial bundle of the anterior cruciate ligament. Seven tibial positions were evaluated as to the change in attachment site distance with passive range of motion and impingement on the intercondylar notch as the knee was passively ranged from 0 degree to 90 degrees of flexion. Impingement was also evaluated while the knee was extended by pulling through the quadriceps tendon. The tibial placement site affects the change in attachment site distance with passive range of motion and impingement on the intercondylar notch. Grafts passed through drill holes anterior and lateral to the insertion of the anterior fibers of the anterior cruciate ligament consistently produced impingement on the anterior outlet of the intercondylar notch. Knee extension with quadriceps tendon pull produced graft impingement in a greater arc of flexion than passive extension. Based on this study, optimum placement of the tibial hole should be at the insertion of the anterior medial fibers of the anterior cruciate ligament. Impingement recognized during surgery can be alleviated with notchplasty. With passive extension there should be a 3-mm clearance between the anterior portion of the intercondylar notch and the ligament graft to prevent the graft from impinging when the knee is actively extended.

A rationale for predicting anterior cruciate graft impingement by the intercondylar roof. A magnetic resonance imaging study

This study was designed to analyze how anterior tibial tunnel placement can result in graft impingement by the intercondylar roof. The relationship of the ACL to the intercondylar roof was studied using magnetic resonance scans. An attempt was made to predict the amount of bone that may need to be removed from the intercondylar roof to prevent impingement on a 10 mm thick ACL graft. Magnetic resonance scans of 19 normal ACLs were analyzed. The amount of bone removal required to correct roof impingement was determined for a graft placed either eccentrically or centrally within the ACL insertion, and within the bulk of the normal ACL fibers. An eccentric tibial tunnel placement required approximately 5 to 6 mm and a central placement required 2 to 3 mm of bone removal from the intercondylar roof to prevent impingement. Placing the graft within the bulk of the ACL fibers, just 3 mm posterior to the center of the ACL insertion, required little bone resection to prevent impingement. To prevent ACL graft impingement, roofplasties need to be performed in both acute and chronic ACL reconstructions if the presently accepted locations for positioning the tibial tunnel are used. A more anteriorly placed tibial tunnel requires more bone removal to prevent roof impingement than a more posteriorly positioned tibial tunnel.

Muscle-ligament interactions at the knee during walking

A two-dimensional mathematical model of the knee is used with gait analysis to calculate muscle, cruciate ligament and tibio-femoral contact forces developed at the knee during normal level walking. Ten normal adult subjects--four females and six males--participated. The knee model is based upon a four-bar linkage comprising the femur, tibia and two cruciate ligaments. It takes account of the rolling and sliding of the femur on the tibia during flexion/extension and the changes in direction of the ligaments and muscle tendons. We considered forces transmitted by six elements: quadriceps, hamstrings, gastrocnemius, anterior and posterior cruciate ligaments, and tibio-femoral contact. The equations of mechanics can be used to determine the absolute values of only three of the knee forces simultaneously, so that twenty limiting solutions of three of the six forces were considered. A limiting solution was rejected if any of the three forces were negative, corresponding to compressive muscle or ligament forces, or tensile contact forces. These constraints always reduced and at times removed the redundancy of the knee structures. The high incidence of predicted single muscle activity, supported by electromyography, suggested that the ligaments play a significant role in load transmission during gait. The temporal patterns of muscle and ligament activity and ligament force magnitudes were sensitive to the choice of model parameters. The analysis showed that each of four possible minimum principles of muscle selection--minimal muscle force, muscle stress, ligament force and contact force--was unlikely to be valid throughout the walking cycle.

Anterior cruciate ligament replacements: a mechanical study of femoral attachment location, flexion angle at tensioning, and initial tension

We examined three surgical variables that affect the ability of an anterior cruciate ligament replacement to restore the limit of anterior tibial translation. These were the placement site of the substitute on the femur, the initial tension applied to the replacement, and the flexion angle of the knee at the time of tensioning. An anterior load of 100 N was applied to the tibia. As the knee was flexed, we measured the tensile force in the substitute and the anteroposterior position of the femur relative to the tibia. Placement largely determined whether the force in the replacement increased or decreased with flexion. Placement also largely determined whether the tibia moved anteriorly or posteriorly with flexion compared to its position in the intact knee. The initial tension and the flexion angle at tensioning affected the magnitude of force in the substitute and the magnitude of the change in AP position. They did not affect how force and AP position changed with flexion. Greater increases in force and greater posterior shifts in tibial position were produced by changing the flexion angle at tensioning from 0 degrees to 30 degrees than by increasing the initial tension from 22 to 44 N.

The geometry of the knee in the sagittal plane

A geometric model of the tibio-femoral joint in the sagittal plane has been developed which demonstrates the relationship between the geometry of the cruciate ligaments and the geometry of the articular surfaces. The cruciate ligaments are represented as two inextensible fibres which, with the femur and the tibia, are analysed as a crossed four-bar linkage. The directions of the ligaments at each position of flexion are calculated. The instant centre, where the flexion axis crosses the parasagittal plane through the joint, lies at the intersection of the cruciates. It moves relative to each of the bones during flexion and extension. The successive positions of the flexion axis relative to a fixed femur and to a fixed tibia are deduced. The shapes of articular surfaces which would allow the bones to flex and extend while maintaining the ligaments each at constant length are calculated and are found to agree closely with the shapes of the natural articular surfaces. The calculated movements of the contact point between the femur and the tibia during flexion also agree well with measurements made on cadaver specimens. The outcome is a geometric simulation of the tibio-femoral joint in the sagittal plane which illustrates the central role played by the cruciate ligaments in the kinematics of the knee and which can be used for the analysis of ligament and contact forces.