The effect of graft tensioning in anatomic 2-bundle ACL reconstruction on knee joint kinematics

Tibial graft fixation methods and bone tunnel enlargement: A comparison between the TensionLoc implant system and the double-spike plate

Background/objective

TensionLoc (Arthrex, Naples, Florida, USA), a tibial graft fixation system for anterior cruciate ligament (ACL) reconstruction, is expected to apply the preoperatively determined level of graft tension and allow setting of lower initial tension. Considering its mechanism, we hypothesised that TensionLoc would prevent postoperative bone tunnel enlargement (TE) through fixation with lower initial tension. Therefore, the present study aimed to compare TE between ACL reconstructions using the double-spike plate (DSP; Smith and Nephew, Andover, Massachusetts) and TensionLoc implant system.

Methods

A total of 40 patients who underwent anatomical single-bundle ACL reconstruction with a hamstring tendon graft were retrospectively analysed. In the group in which DSP and screw were used, the initial graft tension was set to 40 N at 20° of knee flexion (group D). In the other group in which TensionLoc was used, the initial graft tension was set to 30 N at 20° of knee flexion (group T). Both groups included 20 patients each. Tunnel areas were measured using computed tomography images at one week and three months after surgery, and the TE ratio was calculated according to the following equation: TE ratio (%) = (tunnel area at three months after surgery - tunnel area at one week after surgery)/tunnel area at one week after surgery × 100.

Results

The femoral TE ratios were significantly higher in group T (80.5% ± 28.8%) than in group D (45.5% ± 34.6%) (p = 0.001). However, the tibial TE ratios did not significantly differ between the two groups.

Conclusion

Compared with ACL reconstruction using DSP and screw, ACL reconstruction using TensionLoc fixed the graft with lower initial tension but showed greater femoral TE and restricted knee extension in the early postoperative period.

Techniques for Femoral Socket Creation in ACL Reconstruction

Anterior cruciate ligament (ACL) injury is common and affects a wide variety of individuals. An ACL reconstruction is the treatment of choice for patients with subjective and objective symptoms of instability and is of particular importance to cutting or pivoting athletes. With many variables involved in ACL reconstruction, femoral tunnel placement has been found to affect clinical outcomes with nonanatomic placement being identified as the most common technical error. Traditionally the femoral tunnel was created through the tibial tunnel or transtibial with the use of a guide and a rigid reaming system. Because of proximal, nonanatomic tunnel placement using the transtibial technique, the use of the anteromedial portal and outside-in drilling techniques has allowed placement of the tunnel over the femoral footprint. In this paper, we discuss the difference between the 3 techniques and the advantages and disadvantages of each. The authors then explore the clinical differences and outcomes in techniques by reviewing the relevant literature.

A novel approach for optimal graft positioning and tensioning in anterior cruciate ligament reconstructive surgery based on the finite element modeling technique

BACKGROUND

In ACL-reconstructed patients the postoperative knee biomechanics may differ from the intact knee biomechanical behavior which can alter knee kinematics and kinetics, and as a result lead to the progression of knee osteoarthritis. The aim of this study was to demonstrate the potential of finite element models to define the optimal choices in surgical parameters in terms of optimal graft positioning in combination with graft type in order to restore the kinematic and kinetic behavior of the knee as best as possible.

METHODS

A workflow was proposed based on cadaveric experiments in order to restore the injured knee to a near normal physiological condition. Femoral and tibial graft insertion sites and graft fixation tension were optimized to obtain similar intact knee laxity, for three common single-bundle and one double-bundle reconstructions. To verify the success of the surgery with the variables calculated using the proposed workflow, a full walking cycle was simulated with the intact, ACL-ruptured, optimal ACL-reconstructed and non-optimal reconstructed knees.

RESULTS

Our results suggested that for patellar tendon and hamstring tendon grafts, anatomical positioning (fixation force: 40 N), and for quadriceps tendon graft, isometric positioning (fixation tension: 85 N) could recover the intact joint kinematics and kinetics. Also for double-bundle reconstruction, with the numerically calculated optimal insertion sites, both bundles needed 50-N fixation force.

CONCLUSIONS

With optimal graft positioning parameters, following the proposed workflow in this study, any of the single-bundle graft types and surgical techniques (single vs. double-bundle) may be used to acceptably recover the intact knee joint biomechanical behavior.

The Impact of ACL Laxity on a Bicondylar Robotic Knee and Implications in Human Joint Biomechanics

OBJECTIVE

Elucidating the role of structural mechanisms in the knee can improve joint surgeries, rehabilitation, and understanding of biped locomotion. Identification of key features, however, is challenging due to limitations in simulation and in-vivo studies. In particular the coupling of the patello-femoral and tibio-femoral joints with ligaments and its impact on joint mechanics and movement is not understood. We investigate this coupling experimentally through the design and testing of a robotic sagittal plane model.

METHODS

We constructed a sagittal plane robot comprised of: 1) elastic links representing cruciate ligaments; 2) a bi-condylar joint; 3) a patella; and 4) actuator hamstrings and quadriceps. Stiffness and geometry were derived from anthropometric data. [Formula: see text] squatting tests were executed at speeds of [Formula: see text] over a range of anterior cruciate ligament (ACL) slack lengths.

RESULTS

Increasing ACL length compromised joint stability, yet did not impact quadriceps mechanical advantage and force required for squat. The trend was consistent through varying condyle contact point and ligament force changes.

CONCLUSION

The geometry of the condyles allows the ratio of quadriceps to patella tendon force to compensate for contact point changes imparted by the removal of the ACL. Thus the system maintains a constant mechanical advantage.

SIGNIFICANCE

The investigation uncovers critical features of human knee biomechanics. Findings contribute to understanding of knee ligament damage, inform procedures for knee surgery and orthopaedic implant design, and support design of trans-femoral prosthetics and walking robots. Results further demonstrate the utility of robotics as a powerful means of studying human joint biomechanics.

The Anterolateral Structure of the Knee Does Not Affect Anterior and Dynamic Rotatory Stability in Anterior Cruciate Ligament Injury: Quantitative Evaluation With the Electromagnetic Measurement System

BACKGROUND

The biomechanical function of the anterolateral structure (ALS), which includes the anterolateral joint capsule and anterolateral ligament (ALL), remains a topic of debate.

HYPOTHESIS

The ALS contributes to knee joint stability during the Lachman test and the pivot-shift test in anterior cruciate ligament (ACL)-deficient knees.

STUDY DESIGN

Controlled laboratory study.

METHODS

Fourteen fresh-frozen hemipelvis lower limbs were used. For 7 specimens, the anterior one-third of the ALS and the residual ALS were cut intra-articularly with a radiofrequency device. Subsequently, the ACL was cut arthroscopically. For the other 7 specimens, the ACL was cut first, followed by the anterior one-third of the ALS and the residual ALS intra-articularly. During the procedures, the iliotibial band (ITB) was kept intact. At each condition, the anterior tibial translation (ATT) during the manual Lachman test and the acceleration of posterior tibial translation (APT) and the posterior tibial translation (PTT) during the manual pivot-shift test were measured quantitatively with an electromagnetic measurement system. The mean values of those parameters were compared among 6 groups (ACL intact, one-third ALS cut, all ALS cut, ACL cut, ACL/one-third ALS cut, and ACL/all ALS cut).

RESULTS

The mean ATTs during the Lachman test and the mean APTs and PTTs in the ACL-cut conditions (ACL cut, ACL/one-third ALS cut, and ACL/all ALS cut) were significantly larger than those under the ACL-intact conditions (ACL intact, one-third ALS cut, all ALS cut) (P < .01). However, no statistically significant differences were observed among the intact, one-third ALS-cut, and all ALS-cut conditions, within the ACL-intact or ACL-cut conditions.

CONCLUSION

Intra-articular dissection of the ALS did not increase the ATT during the Lachman test or the APT and PTT during the pivot-shift test under the intact condition of the ITB, regardless of the integrity of the ACL. When the ITB is intact, the ALS does not have a significant role in either anterior or dynamic rotatory knee stability, while the ACL does.

CLINICAL RELEVANCE

Recent growing interest about ALL reconstruction or ALS augmentation may not have a large role in controlling either anterior or dynamic rotatory knee instability in isolated ACL-deficient knees.

Stress distribution is deviated around the aperture of the femoral tunnel in the anatomic anterior cruciate ligament reconstruction

PURPOSE

Final tunnel location in the anterior cruciate ligament (ACL) reconstruction is unpredictable due to tunnel widening and/or transposition. The mechanical stress around the tunnel aperture seems to be a major factor but is not fully investigated. The purpose of this study was to measure the stress from the ACL graft around the tunnel aperture when the ACL graft tension reaches its peak.

METHODS

Six cadaveric knees were used. Single-bundle ACL reconstruction was performed using a hamstrings graft. Both femoral and tibial tunnels were created at the centre of the original ACL footprint. A 7-mm-internal-diameter aluminium cylinder with pressure sensors was placed in the femoral tunnel. Hamstrings graft with a microtension sensor was inserted. After fixation, passive extension-flexion was performed while monitoring the tunnel aperture pressure and the graft tension simultaneously. The pressure on the femoral tunnel aperture when the ACL graft tension reach its peak was compared between four directions.

RESULTS

The ACL graft tension peaked (67 ± 49 N) at full extension (-5.8 ± 4.1°). Pressure at the femoral tunnel aperture was different between different directions (p < 0.01). Distal part had significantly larger pressure (1.7 ± 1.3 MPa) than the other directions (p < 0.01). Second largest pressure was carried in the anterior part (0.6 ± 0.5 MPa), followed by proximal and posterior parts (0.4 ± 0.3, 0.2 ± 0.2 MPa respectively).

CONCLUSION

The stress distribution at the femoral tunnel aperture is not equal in different directions, while the distal part dominantly bears the stress from the ACL graft. Surgeons should pay close attention to the distal edge of the femoral tunnel which should be inside the anatomic ACL footprint eventually.

Effects of initial graft tension on femoral tunnel widening after anatomic anterior cruciate ligament reconstruction using a bone-patellar tendon-bone graft

INTRODUCTION

The effects of initial graft tension upon tunnel widening (TW) following anatomic anterior cruciate ligament (ACL) reconstruction have not been elucidated. The purpose of this study was to retrospectively investigate the effect of two different graft-tensioning protocols upon femoral TW following anatomic ACL reconstruction using a bone-patellar tendon-bone (BPTB) graft and a three-dimensional (3D) computed tomography (CT) model.

METHODS

Forty-three patients who underwent isolated ACL reconstruction using BPTB grafts were included in this study. In 18 out of the 43 patients, the graft was fixed at full knee extension with manual maximum pull (Group H). These patients were compared with 25 patients in whom the BPTB graft was fixed at full knee extension with 80-N pull (Group L). Tunnel aperture area was measured using 3D CT 1 week and 1 year postoperatively, thus enabling us to calculate the percentage change in the area of femoral tunnel aperture. Clinical assessment was performed 1 year postoperatively, corresponding to the time period of CT assessment, and involved the evaluation of Lysholm score, anterior knee stability using a KneeLax3 arthrometer, and the pivot-shift test.

RESULTS

When measured at 1 year postoperatively, the mean area of the femoral tunnel aperture had increased by 78.6 ± 36.8% in Group H when compared with at 1 week postoperatively, whereas that of Group L had increased by 27.7 ± 32.3%. Furthermore, TW (%) in Group H was significantly greater than that of Group L (P < 0.001). No significant differences were detected between the two groups with regard to any of the clinical outcomes evaluated.

CONCLUSION

High levels of initial graft tension resulted in greater TW of the femoral tunnel aperture following anatomical ACL reconstruction using BPTB grafts. However, such levels of graft tension did not affect clinical outcome.

Comparison Between Intra- and Extra-articular Tension of the Graft During Fixation in Anterior Cruciate Ligament Reconstruction

PURPOSE

To evaluate the tension deprivation through the tunnels with and without preconditioning at the time of fixation, and the influences of cyclic loading and pretensioning on graft tension in anatomic single bundle anterior cruciate ligament (ACL) reconstruction using a hamstring tendon.

METHODS

Nine fresh-frozen cadaveric knees underwent anatomic ACL reconstruction using hamstring grafts. Each specimen was examined to ensure that there was no severe osteoarthritic change, ligament insufficiency, or torn menisci by manual and arthroscopic evaluation. Applied graft tension was measured at the tibial tunnel outlet using a graft tensor with a load cell. Intra-articular graft tension was evaluated by using an originally developed microforce sensor, which was sutured into the graft. Both tensions were simultaneously measured just after initial tensioning under 3 different conditions: condition 1, just after initial tensioning of 20 N at 20° of knee flexion without preconditioning; condition 2, after the same initial tensioning following 5 rounds of passive cyclic flexion-extension movement; and condition 3, after the same initial tensioning following 5 minutes of static pretensioning of 20 N.

RESULTS

The intra-articular tension was 12.7 ± 5.3 N in condition 1, 12.0 ± 4.8 N in condition 2, and 13.5 ± 4.8 N in condition 3. In these 3 conditions, intra-articular graft tension was significantly lower than the applied tension of around 20 N (no pretension: P = .009, cyclic pretension: P = .004, static pretension: P = .008), with no difference among the 3 conditions (P = .82).

CONCLUSIONS

The intra-articular graft tension was significantly lower than the applied tension from the outside of the joint, even after cyclic loading and pretensioning.

CLINICAL RELEVANCE

It is difficult to evaluate the intra-articular graft tension precisely on the basis of the extra-articular tension at time zero in ACL reconstruction.

Effects of initial graft tension on clinical outcome after anatomic double-bundle anterior cruciate ligament reconstruction: comparison of two graft tension protocols

BACKGROUND

In anatomic double-bundle anterior cruciate ligament (ACL) reconstruction, there are great controversies concerning the ideal graft tension protocols. The purpose of this study was to clarify differences in the effect of two graft tension protocols on the clinical outcome after anatomic double-bundle anterior cruciate ligament (ACL) reconstruction by comparing the minimum 2-year clinical results.

METHODS

Ninety-seven patients with unilateral anatomic double-bundle ACL reconstruction were divided into two groups. In the first 44 patients (Group I), a 40-N tension was applied to each of the two hamstring autografts at 30° of knee flexion, and simultaneously fixed onto the tibia. In the remaining 53 patients (Group II), a 30-N tension was applied to each graft at 10° of knee flexion, and simultaneously fixed onto the tibia. Each patient was examined 2 years after surgery.

RESULTS

There wasn't a significant difference in the background of the two groups. There was no significant difference in the postoperative anterior laxity between the two groups. The average was 1.1 mm and 0.9 mm in Groups I and II, respectively. There wasn't any differences between the two groups in Lysholm knee score, International Knee Documentation Committee (IKDC) evaluation and muscle strength. Four patients had loss of knee extension in a range of 5° and 10° in Group I and none of the patients in Group II exhibited any loss in knee extension; which was statistically significant (p = 0.025).

CONCLUSION

The two initial graft tension protocols did not result in any significant differences in the Lysholm knee score and IKDC grade. However, it was noted that the 40-N tension applied to each graft at 30° of knee flexion more significantly induced loss of knee extension in comparison to the 30-N tension applied to each graft at 10°. From a clinical viewpoint, the loss of knee extension is one of the pathological conditions that should be absolutely avoided after ACL reconstruction. Therefore, the 30-N tension applied to each graft at 10° is preferable to the other graft tension protocol.

Experimental Execution of the Simulated Pivot-Shift Test: A Systematic Review of Techniques

PURPOSE

To conduct a systematic review to identify and summarize the various techniques that have been used to simulate the pivot-shift test in vitro.

METHODS

Medline, Embase, and the Cochrane Library were screened for studies involving the simulated pivot-shift test in human cadaveric knees published between 1946 and May 2014. Study parameters including sample size, study location, simulated pivot-shift technique, loads applied, knee flexion angles at which simulated pivot shift was tested, and kinematic evaluation tools were extracted and analyzed.

RESULTS

Forty-eight studies reporting simulated pivot-shift testing on 627 cadaveric knees fulfilled the criteria. Reviewer inter-rater agreement for study selection showed a κ score of 0.960 (full-text review). Twenty-seven studies described the use of internal rotation torque, with a mean of 5.3 Nm (range, 1 to 18 Nm). Forty-seven studies described the use of valgus torque, with a mean of 8.8 Nm (range, 1 to 25 Nm). Four studies described the use of iliotibial tract tension, ranging from 10 to 88 N. Regarding static simulated pivot-shift test techniques, 100% of the studies performed testing at 30° of knee flexion, and the most tested range of motion in the continuous tests was 0° to 90°. Anterior tibial translation was the most analyzed parameter during the simulated pivot-shift test, being used in 45 studies. In 22% of the studies, a robotic system was used to simulate the pivot-shift test. Robotic systems were shown to have better control of the loading system and higher tracking system accuracy.

CONCLUSIONS

This study provides a reference for investigators who desire to apply simulated pivot shift in their in vitro studies. It is recommended to simulate the pivot-shift test using a 10-Nm valgus torque and 5-Nm internal rotation torque. Knee flexion of 30° is mandatory for testing.

LEVEL OF EVIDENCE

Level IV, systematic review of basic science studies.

A Comparison of Ligament Tensions Between Intra- and Extra-Articular Measurement in Anterior Cruciate Ligament Reconstruction

Anterior cruciate ligament (ACL) reconstruction is one of the treatments of ACL injuries. In the surgery, the reconstructed ligament should be properly tensioned to provide a normal ligament behavior. However, the ligament tension has been measured with an extra-articular technique in past studies, while the intra-articular ligament tension is still unknown. The purpose of this study is to compare the ligament tensions between intra- and extra-articular measurements in the ACL reconstruction. Intra-articular measurement employs a micro-force sensor designed with a width and thickness same as those of the reconstructed ligament. This study performed two experiments (i.e., sensor accuracy and cadaveric study). In the sensor accuracy experiment, the accuracy of the sensor was about 3% until an applied force of 100 N. In the cadaveric study, the results of the intra- and extra-articular measurement tensions were 13.6±3.9 N and 18.7±1.3 N (n= 6), respectively. The significant difference in student t-test (p-value was 0.026) between the intra- and extra- articular measurements was observed. The bending angle and friction between the graft and bone tunnel, and the shape of the intra-articular edge of tibial bone tunnel affected the intra-articular measurement in ACL reconstruction.

Anteromedial versus transtibial tunnel drilling in anterior cruciate ligament reconstructions: a systematic review

PURPOSE

Failure to anatomically reconstruct the femoral footprint can lead to rotational instability and clinical failure. Thus we sought to compare femoral tunnel drilling techniques, specifically anteromedial (AM) and transtibial (TT) methods, with respect to rotational stability.

METHODS

In this study we evaluated available scientific support for the ability of both techniques to achieve rotational stability of the knee through a systematic review of the literature for directly comparative biomechanical and clinical studies.

RESULTS

We identified 9 studies (5 clinical Level II or III studies and 4 cadaveric studies) that directly compared AM and TT techniques. Three cadaveric and 2 clinical studies showed superior rotational stability with the AM technique as compared with the TT technique, whereas 2 cadaveric studies and 1 clinical study were unable to show any similar differences. Two studies showed superior clinical outcomes with the AM technique, whereas 3 studies were unable to show any difference.

CONCLUSIONS

In this systematic review of clinical and biomechanical studies directly comparing AM and TT techniques for anterior cruciate ligament reconstruction (ACLR) in the literature, there are mixed results, with some studies finding superior rotational stability and clinical outcomes with the AM technique and some finding no difference. No studies showed significantly better results with the TT technique. This study shows that the AM portal technique for ACLR may be more likely to produce improved clinical and biomechanical outcomes but that the TT technique is capable of producing similar outcomes.

LEVEL OF EVIDENCE

Level III, systematic review of Level II and III studies plus cadaver studies.

Standardized pivot shift test improves measurement accuracy

PURPOSE

The variability of the pivot shift test techniques greatly interferes with achieving a quantitative and generally comparable measurement. The purpose of this study was to compare the variation of the quantitative pivot shift measurements with different surgeons' preferred techniques to a standardized technique. The hypothesis was that standardizing the pivot shift test would improve consistency in the quantitative evaluation when compared with surgeon-specific techniques.

METHODS

A whole lower body cadaveric specimen was prepared to have a low-grade pivot shift on one side and high-grade pivot shift on the other side. Twelve expert surgeons performed the pivot shift test using (1) their preferred technique and (2) a standardized technique. Electromagnetic tracking was utilized to measure anterior tibial translation and acceleration of the reduction during the pivot shift test. The variation of the measurement was compared between the surgeons' preferred technique and the standardized technique.

RESULTS

The anterior tibial translation during pivot shift test was similar between using surgeons' preferred technique (left 24.0 ± 4.3 mm; right 15.5 ± 3.8 mm) and using standardized technique (left 25.1 ± 3.2 mm; right 15.6 ± 4.0 mm; n.s.). However, the variation in acceleration was significantly smaller with the standardized technique (left 3.0 ± 1.3 mm/s(2); right 2.5 ± 0.7 mm/s(2)) compared with the surgeons' preferred technique (left 4.3 ± 3.3 mm/s(2); right 3.4 ± 2.3 mm/s(2); both P < 0.01).

CONCLUSION

Standardizing the pivot shift test maneuver provides a more consistent quantitative evaluation and may be helpful in designing future multicenter clinical outcome trials.

LEVEL OF EVIDENCE

Diagnostic study, Level I.

The pivot shift: a global user guide

PURPOSE

The use of several different maneuvers for the pivot shift test has resulted in inconsistent quantitative measurements. The purpose of this study was to describe, analyze, and group several surgeon-specific techniques for the pivot shift test and to propose a standardized pivot shift test.

METHODS

Twelve expert surgeons examined a whole lower cadaveric extremity with their preferred technique and assigned a clinical grade, I-III. Anterior tibial translation and acceleration were measured using an electromagnetic system. The test was repeated after watching an instructional video focused on a standardized pivot shift technique. Measurements were repeated and compared with the preferred technique.

RESULTS

The expert surgeons utilized valgus stress unanimously in addition to fixed internal rotation (n = 5), fixed external rotation (n = 1), a motion-allowing technique (n = 3), a dislocation-type maneuver (n = 2), and a fixed anterior drawer type of maneuver in extension (n = 1). Anterior tibial translation measured was on average 15.9 ± 3.7 mm. Average tibial acceleration was 3.3 ± 2.1 mm/s(2). Average clinical grading was 2.3 ± 0.5. There were no differences in average clinical grading when using high stress (2.5 ± 0.6) versus low stress (2.3 ± 0.5, n.s.), or using fixed rotation (2.2 ± 0.5) versus a motion-allowing technique (2.3 ± 0.6; n.s.).

CONCLUSIONS

Clinical grading, tibial translation, and acceleration vary between examiners performing the pivot shift test. High forces and extremes of rotation are not necessary to produce a clinical detectable pivot shift. In the future, a standardized pivot shift test-which can be performed universally and utilizes only gentle forces allowing motion to occur-may be beneficial when assessing differences in outcome following ACL reconstruction.

Clinical grading of the pivot shift test correlates best with tibial acceleration

PURPOSE

Recently, different measurement systems have been developed to quantitatively measure the pivot shift in vivo. These systems lack validation and a large inter-examiner variability for the manually performed pivot shift test exists. The purpose of this study was to perform objective measurements of the pivot shift using three different measurement devices and to examine the correlation of the measurements with clinical grading of the pivot shift.

METHODS

A cadaver knee on a whole lower body specimen was prepared to display a high-grade pivot shift. The pivot shift tests were performed three times by 12 blinded expert surgeons using their preferred technique. Simultaneous data samplings were recorded using three different measurement devices: (1) electromagnetic tracking system using bone-attached and skin-fixed sensors, respectively, (2) triaxial accelerometer system, and (3) simple image analysis. The surgeons graded the knee clinically using pivot shift grades I-III. Correlations were calculated using the Spearman's rank correlation coefficient.

RESULTS

The expert surgeons average clinical grading was 2.3 (SD ± 0.5). Clinical grading displayed best correlation with the acceleration of reduction as measured by electromagnetic tracking system with bone-attached sensors (r = 0.67, P < 0.05). Similar correlation coefficient was found for the acceleration of reduction (r = 0.58, P = 0.05) and the "jerk" component of acceleration (r = 0.61, P < 0.05) measured by means of the triaxial accelerometer system.

CONCLUSION

The pivot shift can be quantified by several in vivo measurement devices. Best correlation with clinical grading was found with tibial acceleration parameters. Future studies will have to analyze how quantitative parameters can be utilized to standardize clinical grading of the pivot shift.

LEVEL OF EVIDENCE

Diagnostic study, Level II.

Comparison of three non-invasive quantitative measurement systems for the pivot shift test

PURPOSE

The purpose of this study was to evaluate three different non-invasive measuring devices for the pivot shift phenomenon with reference to direct bony movement measured by an electromagnetic device rigidly attached to the tibia and femur.

METHODS

A lower body cadaveric specimen was prepared to create a positive pivot shift in both knees. Twelve expert knee surgeons from worldwide performed their preferred pivot shift technique three times in each knee. After watching an instructional video, the examiners used a standardized technique to perform three additional pivot shift maneuvers in each knee. An electromagnetic tracking system, rigidly attached to femur and tibia, was used to provide reference measurements during the pivot shift test. Three different devices were correlated to the reference method and evaluated in this study: (1) Electromagnetic tracking system with skin sensors; (2) Triaxial accelerometer system; (3) Simple image analysis.

RESULTS

When results from both pivot shift techniques (preferred and standardized) were combined, the electromagnetic tracking system with skin sensors showed positive correlation with the reference measurement for acceleration and translation parameters (r = 0.88 and r = 0.67, respectively; both P < 0.01); The triaxial accelerometer system demonstrated good correlation with the reference measurement for acceleration (r = 0.75; P < 0.001). The image analysis system was poorly correlated to the translation of the reference measurement (r = 0.24; P < 0.01).

CONCLUSION

The electromagnetic tracking system with skin sensors provided the best correlation with the reference method. The triaxial accelerometer showed also a good correlation and the image analysis system showed a positive, but poor correlation with the reference method. More research is needed in order to validate simple and non-invasive devices for clinical application.

An image analysis method to quantify the lateral pivot shift test

PURPOSE

Although various kinematic measurements with advanced technology have been used for quantitative evaluation of the pivot shift test, there is no clinically available quantification method of the pivot shift test. The purpose was to describe a novel image analysis technique for quantitative assessment of the pivot shift test using universally available and affordable devices.

METHODS

Five ACL deficient knees were tested during examination under anesthesia. Three skin markers were attached to bony landmarks on the lateral side of the knee joint, (1) Gerdy's tubercle, (2) fibular head, and (3) lateral epicondyle. A standard digital video camera captured motion of the lateral aspect of the knee during the pivot shift test. The image was processed into a 2-dimensional (2-D) coordinate system with Image J software (National Institute of Health, USA) to trace the three landmarks. The anteroposterior (AP) position of the femur was calculated on consecutive still images extracted from the video recording. AP translation over time was reported.

RESULTS

The reduction phase of the pivot shift could be tracked consistently by a sudden anterior translation of the distal femur. The sudden anterior translation of the lateral epicondyle was on average 3.7 ± 2.1 mm and occurred within 0.2 ± 0.1 s from the start of this anterior translation till the end.

CONCLUSION

The sudden shift of the lateral compartment of the knee joint was successfully detected by this newly developed image analysis measurement method. This image analysis technique facilitates a simple and affordable method to evaluate the lateral pivot shift test.

LEVEL OF EVIDENCE

Diagnostic studies, Level IV.

Effects of different initial bundle tensioning strategies on the outcome of double-bundle ACL reconstruction: a cohort study

Background

This study was performed to investigate the effects of different strategies and initial tension applied to each one of the bundles, antero-medial (AM) and postero-lateral (PL), on clinical outcome in double bundle (DB) ACL reconstruction.

Methods

One hundred fifty-one primary unilateral DB ACL reconstructions performed by a single surgeon from 1994 through 2002 were included in the study with a follow-up of at least 24 months. They were divided in the following 3 groups: Group I - Higher initial tension applied manually in the AM bundle compared to PL. II - Higher tension applied in the PL bundle compared to AM. III - The 2 bundles were attempted to be equally tensioned. All fixations were performed in 30 degrees of flexion. Group I = 59 patients, group II = 53 patients and group III = 39 patients. The groups had no statistical differences concerning demographic distribution. Clinical outcome was retrospectively evaluated by use of knee range of motion, manual knee laxity tests, KT-1000, Lysholm knee scale, subjective recovery scale and sports performance recovery scale. The differences of data were analyzed among the three groups.

Results

Group I showed a significant extension deficit compared with groups II and III. ANOVA revealed a significant difference of anterior laxity measured by the KT-1000 (average KT difference of 2.1, 2.1 and 1.2 mm in Group I, II and III, respectively). A statistical difference was found among the three groups regarding subjective and sports performance recovery scales with Group II showing higher scores in recovery than Group I.

Conclusions

The current clinical study does not recommend manual maximum of initial tension applied to the anteromedial or posterolateral bundles with graft tension imbalance at 30 degrees of flexion in double-bundle ACL reconstruction to achieve a better clinical outcome.

The impact of tensioning device mal-positioning on strand tension during anterior cruciate ligament reconstruction

Background

In order to confer optimal strength and stiffness to the graft in Anterior Cruciate Ligament (ACL) reconstruction, the maintenance of equal strand tension prior to fixation, is desired; positioning of the tensioning device can significantly affect strand tension This study aimed to determine the effect of tensioning device mal-positioning on individual strand tension in simulated cadaveric ACL reconstructions.

Methods

Twenty cadaveric specimens, comprising bovine tibia and tendon harvested from sheep, were used to simulate ACL reconstruction with a looped four-strand tendon graft. A proprietary tensioning device was used to tension the graft during tibial component fixation with graft tension recorded using load cells. The effects of the tensioning device at extreme angles, and in various locking states, was evaluated.

Results

Strand tension varied significantly when the tensioning device was held at extreme angles (p < 0.001) or in 'locked' configurations of the tensioning device (p < 0.046). Tendon position also produced significant effects (p < 0.016) on the resultant strand tension.

Conclusion

An even distribution of tension among individual graft strands is obtained by maintaining the tensioning device in an unlocked state, aligned with the longitudinal axis of the tibial tunnel. If the maintenance of equal strand tension during tibial fixation of grafts is important, close attention must be paid to positioning of the tensioning device in order to optimize the resultant graft tension and, by implication, the strength and stiffness of the graft and ultimately, surgical outcome.

Anatomic double-bundle anterior crucial ligament reconstruction with G-ST

The anterior cruciate ligament (ACL) consists of two primal functional bundles, anteromedial bundle and posterolateral bundles. Those two bundles play different functional roles and contribute differently to knee stability throughout the range of motion. Recent advancement in studies of anatomy and biomechanics of ACL has led surgeons to perform double-bundle ACL reconstruction to obtain better stability and kinematics. Consequently, variable surgical techniques of double-bundle ACL reconstruction have been reported to replicate native ACL. In addition, various surgical key points and problems in double-bundle ACL reconstruction techniques have also been reported. There has been a trend to more anatomically replicate native ACL bundles, not simply creating two bundles. We summarize the basic knowledge and current concepts of anatomic double-bundle ACL reconstruction using hamstrings tendons.

Systematic review on cadaveric studies of anatomic anterior cruciate ligament reconstruction

PURPOSE

One of the templates in the development of "anatomic" anterior cruciate ligament (ACL) reconstruction has been basic science studies focusing on comparing various aspects of ACL reconstruction in order to optimize surgical technique. However, often such papers lack necessary data in the methods section to ascertain the proposed surgical technique as anatomic. The goal of this systematic review was to evaluate basic science studies on anatomic ACL reconstruction.

METHODS

A systematic electronic search was performed using the MEDLINE and EMBASE databases. Studies that were published from January 1995 to April 2009 were included. Only basic science studies on human cadavers that reported "anatomic" ACL reconstruction and written in English were included. Variation in surgical technique and reporting of surgical description were assessed.

RESULTS

Eighteen studies were included in this systematic review. Only the fixation method, graft type and tension pattern were reported in the majority studies. Notchplasty and radiographic documentation were grossly underreported. Other surgical data were reported at best in two-thirds of the studies. There was a large variation in the reported surgical techniques among the included studies. Due to the aforementioned, it was not deemed possible to pool data of the included studies.

CONCLUSION

For most variables in the surgical technique description, there was sizeable underreporting resulting in an inability to pool the outcomes. To provide literature that holds up to the current high level of medical research, authors are encouraged to report their surgical technique in a thorough manner, similar to high-level clinical trials.

Comparing stability of different single- and double-bundle anterior cruciate ligament reconstruction techniques: a cadaveric study using navigation

PURPOSE

The objective of this study was to analyze 2 different single-bundle anterior cruciate ligament (ACL) reconstruction procedures and compare their ability to reduce the pivot-shift phenomenon with an anatomic double-bundle (DB) technique.

METHODS

Twelve fresh-frozen cadaveric hip-to-toe lower extremity specimens were used. ACL reconstructions were performed by conventional single-bundle, anteromedial (AM) single-bundle, and DB techniques. Anterior tibial translation was measured in the intact knee, ACL-deficient knee, and the 3 ACL reconstructions in response to a Lachman test and a mechanized pivot-shift test. A surgical navigation system (Praxim Medivision, Grenoble, France) simultaneously tracked kinematics.

RESULTS

Intact knees were clinically graded as grade 0 (n = 12). ACL-deficient knees were graded as grade 1 (n = 10) and grade 2 (n = 2). With a mechanized pivot-shift test, anterior tibial translation was 1.7 +/- 3.0 mm, 9.7 +/- 3.8 mm, 4.4 +/- 1.0 mm, 1.8 +/- 1.5 mm, and -1.7 +/- 3.3 mm for intact knees, ACL-deficient knees, conventional technique, AM technique, and DB technique, respectively. There was a significant difference between the DB technique and both single-bundle techniques tested (P < .05).

CONCLUSIONS

The model used represents an isolated ACL injury without concomitant injury to the capsuloligamentous restraints or menisci. However, during the pivot shift, neither type of single-bundle ACL reconstruction stabilized the knee to the same degree as the DB ACL reconstruction.

CLINICAL RELEVANCE

In this cadaveric model a DB repair offers great anterior and rotational stability. Although this study suggests that the DB technique is biomechanically superior to a single-bundle technique using traditional transtibial tunnel positions, there appear to be minimal differences in knee kinematics during stability testing with the DB technique versus an AM graft position. Indeed, compared with the AM position alone, the DB technique "overconstrained" the kinematics of the knee during a pivoting maneuver at time zero in a cadaveric model with an isolated ACL injury.

Anatomic double-bundle anterior cruciate ligament reconstruction: kinematics and knee flexion angle-graft tension relation

PURPOSE

The purpose of this study was to compare the bundle tension curves and resultant knee kinematics between 2 tensioning protocols in anatomic double-bundle anterior cruciate ligament (ACL) reconstruction.

METHODS

Anatomic double-bundle ACL reconstruction was performed in 7 male cadaveric knees. Each graft was tensioned to 22 N under 2 conditions: (1) both bundles tensioned at 20 degrees of knee flexion (20/20 protocol) or (2) posterolateral (PL) bundle tensioned at 15 degrees and anteromedial (AM) bundle at 45 degrees (45/15 protocol). Knee kinematics were recorded in response to anterior and combined rotatory loads in the intact, ACL-deficient, and reconstructed states. Bundle tension was recorded dynamically with knee motion and during each loading test.

RESULTS

Tensioning both bundles at 20 degrees of knee flexion resulted in a reciprocal bundle tension pattern that was not statistically different; the PL bundle tension was greater than the AM bundle tension in full extension, and the AM bundle tension was greater than the PL bundle tension from 25 degrees to 120 degrees. In the second tensioning protocol, the AM bundle tension was significantly greater than the PL bundle tension at all flexion angles. Both tensioning protocols restored normal knee kinematics.

CONCLUSIONS

Bundle-tensioning protocol is a variable that has a significant effect on the bundle-loading patterns in double-bundle ACL reconstruction. The 20/20 protocol resulted in AM and PL bundle-loading patterns that were equivalent during dynamic testing, whereas the 45/15 protocol led to excessive tension in the AM bundle in full extension. We recommend equal tensioning of both bundles with the knee at 20 degrees of flexion to restore relatively normal tension curves in each bundle and to avoid excessive stress on the AM bundle.

CLINICAL RELEVANCE

In double-bundle ACL reconstruction, there is no consensus regarding bundle-tensioning protocols. This study provides data on the individual bundle tension curves that result from 2 commonly used tensioning protocols. These data will assist clinicians as the technique and application of double-bundle ACL reconstruction move forward.

Comparison between single-and double-bundle anterior cruciate ligament reconstruction: a prospective, randomized, single-blinded clinical trial

BACKGROUND

Double-bundle ACL reconstruction popularity is increasing with the aim to reproduce native ACL anatomy and improve ACL reconstruction outcome. However, to date, only a few randomized clinical studies have been published.

PURPOSE

The aim of this study was to prospectively compare the clinical results of single- and double-bundle ACL reconstruction.

STUDY DESIGN

Randomized controlled clinical trial; Level of evidence, 1.

METHODS

Seventy patients with a chronic unilateral ACL rupture who underwent arthroscopically assisted ACL reconstruction using a hamstring graft were randomized to receive a single- (SB) or double-bundle (DB) reconstruction. Both groups were comparable with regard to preoperative data. A double-incision surgical technique was adopted in both groups. The graft was fixed by looping the hamstring tendons around a bony (DB) or a metallic (SB) bridge on the tibial side and with interference screws reinforced with a staple on the femur. The same rehabilitation protocol was adopted. Outcome assessment was performed by a blinded, independent observer using the visual analog scale (VAS) score, the new International Knee Documentation Committee (IKDC) form, the Knee Injury and Osteoarthritis Outcome Score (KOOS), and KT-1000 arthrometer evaluation.

RESULTS

All the patients reached a minimum follow-up of 2 years. No differences between the 2 groups were observed in terms of KOOS and IKDC subjective score. A statistically significant difference in favor of the DB group was found with the VAS (P < .03). The objective IKDC final scores showed statistically significantly more "normal knees" in the DB group than in the SB group (P = .03). There was 1 stability failure in the DB group and 3 in the SB group. The KT-1000 arthrometer data showed a statistically significant decrease in the average anterior tibial translation in the DB group (1.2 mm DB vs 2.1 mm SB; P < .03). The incidence of a residual pivot-shift glide was 14% in DB and 26% in SB (P = .08).

CONCLUSION

In the 2-year minimum follow-up, DB ACL reconstructions showed better VAS, anterior knee laxity, and final objective IKDC scores than SB. However, longer follow-up and accurate instrumented in vivo rotational stability assessment are needed.

The effect of intra-operative knee flexion angle on determination of graft location in the anatomic double-bundle anterior cruciate ligament reconstruction

Graft tunnel placement is the factor with most influence on the outcome of double-bundle anterior cruciate ligament (ACL) reconstruction. However the final decision for the graft location has to be decided subjectively under arthroscopy, and can be misplaced due to the effect of the knee flexion angle. The displacement of the estimated placement by surgeons from the ACL anatomical attachment is due to the knee's differing knee flexion angle. Eight cadaveric knees and an electromagnetic position recording system were employed. After digitizing the anatomical location of AM and PL bundle center, four experienced surgeons estimated the graft placement repeatedly at 70 degrees , 90 degrees and 110 degrees of knee flexion. The displacements between these two positions were calculated and analyzed separately in antero-posterior and disto-proximal directions. The displacements of the estimated AM bundle placements were 4.7 +/- 3.4 mm at 70 degrees , 4.3 +/- 2.2 mm at 90 degrees , and 6.0 +/- 2.6 mm at 110 degrees , while those of the PL bundle were 4.0 +/- 2.2 mm at 70 degrees , 3.4 +/- 1.9 mm at 90 degrees , and 4.2 +/- 2.5 mm at 110 degrees . The best results were obtained at 90 degrees of knee flexion. Additionally, the estimated placements for both AM and PL bundle were located more distally as the flexion angle increased. Our results imply that the knee should be set at 90 degrees when determining the graft placement in double-bundle reconstruction to prevent misplacement of the graft usually in a disto-proximal direction.

Comparable results between lateralized single- and double-bundle ACL reconstructions

Patellar tendon autografts are not suitable for multibundle ACL reconstruction, a procedure that reportedly enhances postoperative knee stability. Biomechanical studies recommend lateral placement of the femoral tunnel for single-bundle reconstruction to improve postoperative knee kinematics. We asked whether a lateralized single-bundle patellar tendon graft (LSBP) would provide good short-term results of ACL reconstruction comparable to double-bundle hamstring tendon grafts (DBH). We prospectively followed 144 patients with unilateral ACL rupture treated with either LSBP or DBH in a nonrandomized fashion. Twenty-four female and 31 male patients with LSBP and 44 female and 26 male patients with DBH were followed for a minimum of 24 months (average, 38 months; range, 24-56 months). The patients with LSBP recovered knee extension better at 1 month compared with the patients with DBH, but extension was similar after 3 months. We observed no differences in the side-to-side difference of KT1000 measurement, pivot shift test, or anterior drawer test between LSBP and DBH. Although better recovery of hamstring strength in LSBP and better recovery of quadriceps strength in DBH were observed in the early postoperative period, these differences disappeared after 12 months. There was no difference in International Knee Documentation Committee objective evaluation between LSBP and DBH at the final followup.

LEVEL OF EVIDENCE

Level II, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.

Analysis of the graft bending angle at the femoral tunnel aperture in anatomic double bundle anterior cruciate ligament reconstruction: a comparison of the transtibial and the far anteromedial portal technique

The aim of this study is to investigate and compare the three dimensional bending angle of the graft at the femoral tunnel aperture in the transtibial and the far anteromedial portal technique. Seven fresh-frozen human cadaveric knees were used. Six degrees-of-freedom of knee kinematics and knee position data were measured using an electromagnetic device and the three dimensional bending angles of the each graft at the femoral tunnel aperture were calculated by computer simulation. Additionally, in order to assess the stress on the graft, the length change between the femoral and tibial attachment sites of the AM and PL bundle were calculated. The maximum length of each bundle was detected at full extension of the knee. The relative change of the length of the PL bundle in the range of 70 degrees -0 degrees of knee flexion was significantly larger than that of the AM bundle. (P < 0.05) Maximum graft bending angles in both techniques were obtained at full extension where the graft was fully stretched. The AM and PL graft bending angles in the transtibial technique were significantly larger than in the far anteromedial portal technique at low flexion angle (AM: 0 degrees -10 degrees , PL: 0 degrees -50 degrees ) (P < 0.01). This suggests use of the far anteromedial portal technique might result in lower stress on the graft at the femoral tunnel aperture and therefore might reduce graft damage.

An in vivo biomechanical study on the tension-versus-knee flexion angle curves of 2 grafts in anatomic double-bundle anterior cruciate ligament reconstruction: effects of initial tension and internal tibial rotation

PURPOSE

The purposes of this study were to determine the relation between the graft tension and the knee flexion angle in the anteromedial (AM) and posterolateral (PL) bundles of a clinically simulated anatomic double-bundle anterior cruciate ligament (ACL) reconstruction procedure and to clarify the effect of initial tension on the tension-versus-flexion curve of each graft, as well as the effect of internal rotation of the tibia on the tension of the 2 grafts.

METHODS

During ACL reconstruction in 30 patients, 2 suture anchors with a No. 1 polyester suture were firmly screwed into the center of the anatomic attachment of the AM and PL bundles on the femur, respectively, and each graft tension was measured with a strain gauge-type tensiometer attached at the end of the suture under 2 conditions of initial tension.

RESULTS

The averaged tension-versus-flexion curves were significantly different between the AM and PL grafts under each initial tension condition (P < .0001). The initial tension applied at 30 degrees of knee flexion significantly affected the absolute values of each graft tension at each knee flexion angle (P < .0001) but did not significantly affect the tension-versus-flexion curve pattern of each graft. The maximal internal rotation of the tibia significantly increased the tension on both the AM and PL grafts at knee flexion angles of less than 60 degrees under each initial tension condition (P < .0001).

CONCLUSIONS

The tension-versus-flexion curves of the 2 sutures, which mimicked the AM and PL grafts reconstructed clinically with the anatomic double-bundle ACL reconstruction procedure, were significantly different in the tension values. Differences in initial tension applied to the 2 grafts significantly affected the absolute values of each graft tension at each knee flexion angle but did not significantly affect the tension-versus-flexion curve pattern. The maximal internal rotation of the tibia significantly increased the tension on both the AM and PL suture grafts at knee flexion angles of less than 60 degrees .

LEVEL OF EVIDENCE

Level I, testing of previously developed diagnostic criteria in series of consecutive patients with universally applied gold standard.