Rotational laxity after anterior cruciate ligament injury by kinematic evaluation of clinical tests

Large Animal Models for Anterior Cruciate Ligament Research

Large animal (non-rodent mammal) models are commonly used in ACL research, but no species is currently considered the gold standard. Important considerations when selecting a large animal model include anatomical differences, the natural course of ACL pathology in that species, and biomechanical differences between humans and the chosen model. This article summarizes recent reports related to anatomy, pathology, and biomechanics of the ACL for large animal species (dog, goat, sheep, pig, and rabbit) commonly used in ACL research. Each species has unique features and benefits as well as potential drawbacks, which are highlighted in this review. This information may be useful in the selection process when designing future studies.

Use of a Computed Tomography Based Approach to Validate Noninvasive Devices to Measure Rotational Knee Laxity

The purpose of this study is to validate a noninvasive rotational knee laxity measuring device called “Rotameter P2” with an approach based on Computed Tomography (CT). This CT-approach using X-rays is hence invasive and can be regarded as a precise reference method that may also be applied to similar devices. An error due to imperfect femur fixation was observed but can be neglected for small torques. The most significant estimation error is due to the unavoidable soft tissues rotation and hence flexibility in the measurement chain. The error increases with the applied torque. The assessment showed that the rotational knee angle measured with the Rotameter is still overestimated because of thigh and femur displacement, soft tissues deformation, and measurement artefacts adding up to a maximum of 285% error at +15 Nm for the Internal Rotation of female volunteers. This may be questioned if such noninvasive devices for measuring the Tibia-Femoral Rotation (TFR) can help diagnosing knee pathologies and investigate ligament reconstructive surgery.

The role of static and dynamic rotatory laxity testing in evaluating ACL injury

In this article, we discuss current topics for rotatory knee laxity. All tests for knee laxity have a value. Static knee laxity tests reveal information for each individual patient's laxity status, especially compared to the contralateral side. Static knee laxity tests are simple to do, and some of them are instrumented, therefore quantifiable. Dynamic knee laxity tests are more complex. Dynamic stereo radiography (DSX) is considered the gold standard. Utilizing DSX, information can be gained on 3-D kinematics, functional joint space, and joint contact patterns. The disadvantage is that DSX is expensive and can only be performed in a laboratory environment. The pivot shift test is a unique test, because it is dynamic and easily performed in the office. However, it is subjective and only recently quantifiable. Future endeavors will attempt to improve the value of the pivot shift test by standardizing the test and improving measurement technologies, while keeping the pivot shift test simple and non-invasive.

Knee rotational laxity and proprioceptive function 2 years after partial ACL reconstruction

PURPOSE

The aim of our study was to evaluate knee rotational laxity and proprioceptive function 2 years after partial anterior cruciate ligament (ACL) reconstruction. According to our hypothesis, partial ACL reconstruction could restore knee laxity and function to the intact level.

METHODS

We conducted a study in fifteen consecutive patients undergoing partial ACL reconstruction. Fifteen anteromedial bundle tears were identified intraoperatively. Partial ACL reconstructions were performed by the same senior surgeon using a single-incision technique. A bone-patellar tendon-bone graft was used in 13 cases and a double-stranded semitendinosus graft in 2 cases of chronic patellar tendonitis. The mean age at surgery was 29 years. The time between ACL tear and surgery averaged 7.8 months (range 2.5-29.5 months). We developed an original device designed to assess knee proprioception (passive and active) and measure weight-bearing rotational laxity in full extension and at 30°, 60° and 90° of knee flexion. All measurements were taken on both the reconstructed and healthy knee.

RESULTS

The mean follow-up of the study was 3.4 years (range 2.6-4.4). No statistically significant difference in rotational laxity, active or passive proprioception could be observed between the reconstructed and healthy knee. External rotation was significantly greater than internal rotation in full extension and at 30° of flexion in the reconstructed and the healthy knee (P < 0.05). For each knee, active proprioception was found to be significantly different (higher) than passive proprioception (P < 0.05).

CONCLUSION

Our study did not detect any difference in rotational laxity and proprioception between the reconstructed and the healthy knee. Therefore, partial ACL reconstruction appears to restore satisfactory knee laxity and function in case of partial ACL tear.

LEVEL OF EVIDENCE

IV.

Application of robotic technology in biomechanics to study joint laxity

PRIMARY OBJECTIVE

To evaluate whether in vitro joint testing using a robot with six degrees of freedom is useful for evaluating changes in joint laxity as a result of chronic osteoarthritis (OA).

RESEARCH DESIGN

Repeated measures.

METHODS

Broyden's method of solving nonlinear systems of equations drove a hybrid method of load and position robotic control. Sheep stifles (knee joints) were loaded between 3 Nm of internal load through to 3 Nm of external load in 1 Nm increments. Kinematic and morphologic data from five healthy ovine stifles were compared to the chronic OA effects in four surgically destabilized stifles.

RESULTS

Stifles with chronic OA showed increases in stiffness while range of motion decreased. Gross morphologic changes included osteophytes and cartilage fibrillation.

DISCUSSION

Robotic testing proved useful for evaluating changes in joint mechanics as a result of chronic OA. We observed morphological changes and associated increases in joint stiffness and decreased laxity.

Anatomic double-bundle versus single-bundle ACL reconstruction: a comparative biomechanical study in rabbits

Thirty New Zealand white rabbits underwent anterior cruciate ligament (ACL) reconstruction in their right knees; 15 animals underwent a double-bundle anatomic ACL reconstruction using the medial third of the patellar tendon and the semitendinosus tendon. Additionally, 15 animals underwent ACL reconstruction, using a single-bundle semitendinosus tendon autograft. The knees of both groups were evaluated with a device similar to the KT1000 arthrometer onto which a dial indicator was attached (Mitutoyo dial indicator 2050) in 30 degrees and 90 degrees of flexion, preoperatively, after ACL resection and 3 months postoperatively. Statistical analysis of the results revealed that for 90 degrees of knee flexion, the mean estimated anterior shift for the double-bundle technique was 1.92 mm lesser than that of the single-bundle technique (P = 0.006). For 30 degrees of knee flexion, the mean anterior shift was again lesser than that of the single-bundle technique by 0.66 mm, but this difference was not statistically significant. The described double-bundle ACL reconstruction technique resulted in a more stable knee as far as the anterior tibial shift was concerned as compared to a single-bundle ACL reconstruction. This animal model may be potentially useful in the future for the study of other parameters influencing the outcome of the double-bundle ACL reconstruction.

Rotational knee laxity: reliability of a simple measurement device in vivo

Background

Double bundle ACL reconstruction has been demonstrated to decrease rotational knee laxity. However, there is no simple, commercially-available device to measure knee rotation. The investigators developed a simple, non-invasive device to measure knee rotation. In conjunction with a rigid boot to rotate the tibia and a force/moment sensor to allow precise determination of torque about the knee, a magnetic tracking system measures the axial rotation of the tibia with respect to the femur. This device has been shown to have acceptable levels of test re-test reliability to measure knee rotation in cadaveric knees.

Methods

The objective of this study was to determine reliability of the device in measuring knee rotation of human subjects. Specifically, the intra-tester reliability within a single testing session, test-retest reliability between two testing sessions, and inter-tester reliability were assessed for 11 male subjects with normal knees.

Results

The 95% confidence interval for rotation was less than 5° for intra-tester, test-retest, and inter-tester reliability, and the standard error of measurement for the differences between left and right knees was found to be less than 3°.

Conclusion

It was found that the knee rotation measurements obtained with this device have acceptable limits of reliability for clinical use and interpretation.

KIN-Nav navigation system for kinematic assessment in anterior cruciate ligament reconstruction: features, use, and perspectives

In this paper a new navigation system, KIN-Nav, developed for research and used during 80 anterior cruciate ligament (ACL) reconstructions is described. KIN-Nav is a user-friendly navigation system for flexible intraoperative acquisitions of anatomical and kinematic data, suitable for validation of biomechanical hypotheses. It performs real-time quantitative evaluation of antero-posterior, internal-external, and varus-valgus knee laxity at any degree of flexion and provides a new interface for this task, suitable also for comparison of pre-operative and post-operative knee laxity and surgical documentation. In this paper the concept and features of KIN-Nav, which represents a new approach to navigation and allows the investigation of new quantitative measurements in ACL reconstruction, are described. Two clinical studies are reported, as examples of clinical potentiality and correct use of this methodology. In this paper a preliminary analysis of KIN-Nav's reliability and clinical efficacy, performed during blinded repeated measures by three independent examiners, is also given. This analysis is the first assessment of the potential of navigation systems for evaluating knee kinematics.

Validation of a new protocol for navigated intraoperative assessment of knee kinematics

BACKGROUND

This study describes a novel method for accurate evaluations of knee kinematics during arthroscopic reconstructions of anterior cruciate ligament (ACL).

METHODS

Quantitative evaluation of knee stability was estimated by experimental validation on 30 volunteers and by statistical analysis of test repeatability.

RESULTS

Proposed method present short learning time, is minimally invasive and thus suitable for arthroscopic techniques. Computed laxity showed a repeatability of 1.5 degrees for varus-valgus, 3 degrees for internal-external, and 2mm for antero-posterior tests.

CONCLUSIONS

This method represents a reliable quantification of knee kinematics in surgery, able to improve present intra-operative assessment of knee stability.

Development and applications of a software tool for diarthrodial joint analysis

This paper describes a new software environment for advanced analysis of diarthrodial joints. The new tool provides a number of elaboration functions to investigate the joint kinematics, bone anatomy, and ligament and tendon properties. In particular, the shapes and the contact points of the articulating surfaces can be displayed and analysed through 2D user-defined sections and fittings (lines or conics). Ligament behaviour can be evaluated during joint movement, through the computation of elongations, orientations, and fiber strain. Motion trajectories can be also analysed through the calculation of helical axes, instantaneous rotations, and displacements in specific user-chosen coordinate reference frames. The software has an user-friendly graphical interface to display four-dimensional data (time-space data) obtained from medical images, navigation systems, spatial linkages or digitalizers, and can also generate printable reports and multiple graphs as well as ASCII files that can be imported to spreadsheet programs such as Microsoft Excel.

Validation of a new protocol for computer-assisted evaluation of kinematics of double-bundle ACL reconstruction

BACKGROUND

Computer-assisted surgery is useful to increase the precision of anterior cruciate ligament (ACL) surgical procedure, but could be even more important in evaluating the global performance of reconstructed ACL. This paper describes a new protocol for an accurate and extensive computer-assisted evaluation of single- and double-bundle reconstructions of ACL.

METHODS

The protocol consists of the acquisition of the leg axes, ACL and graft insertions by a navigation system, and tracking of the knee motion during the classical kinematic test of knee stability. These data are elaborated by computer software in order to compute graft biomechanical behaviour and the knee kinematics and estimate the performance of the intervention.

FINDINGS

The proposed protocol was validated on three cadaver knees. It resulted minimally invasive, effective to describe graft kinematic performance and able to provide a 3D reliable description of the reconstructed knee.

INTERPRETATION

The protocol is an extension of the present evaluation of computer-assisted packages and includes additional kinematic tests and computations. The scientist-reader can find important details on tested computations to implement a similar computer-assisted procedure for new applications in knee surgery, while the surgeon can find in this procedure a means to improve the evaluation of ACL reconstruction and identify the residual laxity.

Estimation of ACL forces by reproducing knee kinematics between sets of knees: A novel non-invasive methodology

In situ force in the anterior cruciate ligament (ACL) has been quantified both in vitro in response to relatively simple loads by means of robotic technology, as well as in vivo in response to more complex loads by means of force transducers and computational models. However, a methodology has been suggested to indirectly estimate the in situ forces in the ACL in a non-invasive, non-contact manner by reproducing six-degree of freedom (six-DOF) in vivo kinematics on cadaveric knees using a robotic/UFS testing system. Therefore, the objective of this study was to determine the feasibility of this approach. Kinematics from eight porcine knees (source knees) were collected at 30 degrees , 60 degrees , and 90 degrees of flexion in response to: (1) an anterior load of 100 N and (2) a valgus load of 5 N m. The average of each kinematic data set was reproduced on a separate set of eight knees (target knees). The in situ forces in the ACL were determined for both sets of knees and compared. Significant differences (rho<0.05) were found between the source knees and the target knees for all flexion angles in response to an anterior load. However, in response to valgus loads, there was no significant difference between the source knees and the target knees at 30 degrees and 90 degrees of flexion. It was noted that there was a correlation between anterior knee laxity (the distance along the displacement axis from the origin to the beginning of the linear region of the load-displacement curve) and internal-external rotation. These data suggest that in order to obtain reproducible results one needs to first match knees to knees with comparable anterior knee laxity. Thus, an estimate of the in situ forces in the ACL during in vivo activities might be obtainable using this novel methodology.

Experimental and Computational Modeling of Joint and Ligament Mechanics

Quantitative data on the mechanics of diarthrodial joints and the function of ligaments are needed to better understand injury mechanisms, improve surgical procedures, and develop improved rehabilitation protocols. Therefore, experimental and computational approaches have been developed to determine joint kinematics and the in-situ forces in ligaments and their replacement grafts using human cadaveric knee and shoulder joints. A robotic/universal force-moment sensor testing system is used in our research center for the evaluation of a wide variety of external loading conditions to study the function of ligaments and their replacements; it has the potential to reproduce in-vivo joint motions in a cadaver knee. Two types of computational models have also been developed: a rigid body spring model and a displacement controlled spring model. These computational models are designed to complement and enhance experimental studies so that more complex loading conditions can be examined and the stresses and strains in the soft tissues can be calculated. In the future, this combined approach will improve our understanding of these joints and soft tissues during in-vivo activities and serve as a tool to aid surgical planning and development of rehabilitation protocols.

Computer investigation of ACL orientation during passive range of motion

No quantitative data are reported in the literature regarding the orientation of anterior cruciate ligament (ACL) fibers during passive range of motion. In this study we performed an original qualitative and quantitative analysis in eight cadaver knees, examining ACL elongation and 3D orientation. Computer elaboration of anatomical and kinematic data obtained by a six degrees-of-freedom electrogoniometer enabled a mathematical and statistical evaluation of the 3D behavior of the ACL. Our data confirmed the isometric behavior of ACL. The inclination of ACL with respect to the tibial plateau decreases with flexion from 56 degrees to 33 degrees. Orientation of ACL with respect to the femoral notch increases with flexion from 4 degrees to 58 degrees. The ACL orientation in a medio-lateral direction changes from 24 degrees to 52 degrees. The postero-lateral and the antero-medial bundle have different angular variations, mainly with respect to the tibial plateau and medio-lateral direction. This quantitative and qualitative information not only increases the anatomical knowledge of the ACL, but could also be important in developing or improving the surgical strategy for ACL reconstruction.