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

Total knee replacement: intraoperative and postoperative kinematic assessment

BACKGROUND AND AIM

The main goals of the total knee arthroplasty (TKA) is to reduce the perceived pain and  restore knee mobility and function in case of osteoarthritic knees joints. Literature shows how the three major causes of TKA failures are related to wear, loosening and instability and this is due to a problem of imbalance and malalignment. Intraoperative and postoperative kinematics analysis could be of benefit for improving surgery outcome. The aim of the present paper is to give an overview of the two set-up with the highest accuracy for intraoperative and postoperative TKA kinematics evaluation, currently in use at Istituto Ortopedico Rizzoli. Introperative and Postoperative Evaluation: For intraoperative evaluation it has been presented a navigation system with a specifically developed software, while for the postoperative it has been presented the roentgen stereophotogrammetric analysis (RSA). The navigation system consists in a laptop connected with an optoelectronic localizer (Polaris, Northern Digital Inc, Canada).  Two reference arrays with passive optical markers and a marked probe are used to localize the knee joint in the 3D space and track the joint kinematics. The RSA is a radiographic technique used in orthopaedic field for measuring micromotion at bone/prosthesis interface or for joint kinematics evaluation. The RSA uses two X-ray sources synchronized with two digital flat-panels.

CONCLUSIONS

The present paper shows that using the navigation system allows the surgeon to easily perform kinematic and alignment evaluation during TKA surgery while the RSA allows a quantitative evaluation of the joint kinematics during the recovery time.

Current use of navigation system in ACL surgery: a historical review

PURPOSE

The present review aims to analyse the available literature regarding the use of navigation systems in ACL reconstructive surgery underling the evolution during the years.

METHODS

A research of indexed scientific papers was performed on PubMed and Cochrane Library database. The research was performed in December 2015 with no publication year restriction. Only English-written papers and related to the terms ACL, NAVIGATION, CAOS and CAS were considered. Two reviewers independently selected only those manuscripts that presented at least the application of navigation system for ACL reconstructive surgery.

RESULTS

One hundred and forty-six of 394 articles were finally selected. In this analysis, it was possible to review the main uses of navigation system in ACL surgery including tunnel positioning for primary and revision surgery and kinematic assessment of knee laxity before and after different surgical procedures. In the early years, until 2006, navigation system was mainly used to improve tunnel positioning, but since the last decade, this tool has been principally used for kinematics evaluation. Increased accuracy of tunnel placement was observed using navigation surgery, especially, regarding femoral, 42 of 146 articles used navigation to guide tunnel positioning. During the following years, 82 of 146 articles have used navigation system to evaluate intraoperative knee kinematic. In particular, the importance of controlling rotatory laxity to achieve better surgical outcomes has been underlined.

CONLUSIONS

Several applications have been described and despite the contribution of navigation systems, its potential uses and theoretical advantages, there are still controversies about its clinical benefit. The present papers summarize the most relevant studies that have used navigation system in ACL reconstruction. In particular, the analysis identified four main applications of the navigation systems during ACL reconstructive surgery have been identified: (1) technical assistance for tunnel placement; (2) improvement in knowledge of the kinematic behaviour of ACL and other structures; (3) comparison of effectiveness of different surgical techniques in controlling laxities; (4) navigation system performance to improve the outcomes of ACL reconstruction and cost-effectiveness.

LEVEL OF EVIDENCE

IV.

Predictive mathematical modeling of knee static laxity after ACL reconstruction: in vivo analysis

Previous studies did not take into consideration such large variety of surgery variables which describe the performed anterior cruciate ligament (ACL) reconstruction and the interaction among them in the definition of postoperative outcome. Seventeen patients who underwent navigated Single Bundle plus Lateral Plasty ACL reconstruction were enrolled in the study. Static laxity was evaluated as the value of anterior/posterior displacement at 30° and at 90° of flexion, internal/external rotation at 30° and 90° of knee flexion, varus/valgus test at 0° and 30° of flexion. The evaluated surgical variables were analyzed through a multivariate analysis defining the following models: AP30estimate, AP90estimate, IE30estimate, IE90estimate, VV0estimate, VV30estimate. Surgical variables has been defined as the angles between the tibial tunnel and the three planes, the lengths of the tunnel and the relationship between native footprints and tunnels. An analogous characterization was performed for the femoral side. Performance and significance of the defined models have been quantified by the correlation ratio (η(2)) and the corresponding p-value (*p < 0.050). The analyzed models resulted to be statistically significant (p < 0.05) for prediction of postoperative static laxity values. The only exception was the AP90estimate model. The η(2) ranged from 0.568 (IE90estimate) to 0.995 (IE30estimate). The orientation of the tibial tunnel resulted to be the most important surgical variable for the performed laxity estimation. Mathematical models for postoperative knee laxity is a useful tool to evaluate the effects of different surgical variables on the postoperative outcome.

Computer-assisted anterior cruciate ligament reconstruction. Four generations of development and usage

The purpose of this paper is to review the literature about the contribution of navigation in anterior cruciate ligament (ACL) reconstruction. The evolution of computer-assisted surgery (CAS) for ACL reconstruction has undergone several steps. These steps were divided into 4 subsequent developments: (1) positioning of ACL graft placement; (2) laxity measurement of ACL reconstruction (quality control); (3) kinematic evaluation during ACL reconstruction (navigated pivot shift); (4) case-specific individual ACL reconstruction with adjustments and additional reconstruction options. CAS has shown to improve femoral tunnel positioning, even if clinical outcomes do not improve results of manual techniques. CAS technology has helped researchers better understand the effects of different ACL reconstruction techniques and bundles replacements on joint laxity and to describe tunnel positioning in relation to native ACL insertion. CAS in ACL surgery can improve results at time zero and can improve knowledge in this field.

In vivo kinematic evaluation of anatomic double-bundle anterior cruciate ligament reconstruction

BACKGROUND

There is controversy regarding the functional role of the posterolateral (PL) bundle of the anterior cruciate ligament (ACL).

PURPOSE

To evaluate the in vivo function of the PL and anteromedial (AM) bundles of the ACL during anatomic double-bundle (DB) ACL reconstruction for acute, isolated ACL tears utilizing a computer navigation system to track intraoperative knee kinematics.

STUDY DESIGN

Controlled laboratory study.

METHODS

Fifteen patients with acute, isolated ACL tears who underwent anatomic DB ACL reconstruction formed the sample for this study. During surgery, knees were examined by a clinician preoperatively, after fixation of the PL bundle, and after fixation of both the PL and AM bundles. An image-free computer navigation system with custom-made software recorded the data during kinematic tests. The examination consisted of the Lachman and anterior drawer tests, internal-external rotation at 30° of knee flexion, and varus-valgus rotation at 30° of knee flexion. Paired Wilcoxon tests were performed to evaluate the effects of each bundle. The comparisons included ACL-deficient to PL bundle-reconstructed knees, ACL-deficient to DB ACL-reconstructed knees, and PL bundle-reconstructed to DB ACL-reconstructed knees. Significance was set at P < .017 to account for the multiple comparisons.

RESULTS

Fixation of the PL bundle significantly improved knee laxity during the Lachman and anterior drawer tests as well as internal-external rotation at 30° of knee flexion (P < .017 for all tests). The addition of the AM bundle further improved knee laxity during the Lachman and anterior drawer tests compared with PL bundle fixation as well as during varus-valgus rotation at 30° of knee flexion compared with ACL-deficient knees (P < .017 for all tests).

CONCLUSION

This in vivo study demonstrates that isolated PL bundle reconstruction improves laxity in an ACL-deficient knee and that the addition of the AM bundle improves laxity parameters further.

CLINICAL RELEVANCE

Abnormal knee kinematics is known to be linked to the earlier onset of osteoarthritis and lower rates of return to sport. This study suggests that both the AM and PL bundles are important to stabilize ACL-deficient knees.

Does total knee arthroplasty modify flexion axis of the knee?

PURPOSE

To prospectively investigate whether preoperative functional flexion axis in patients with osteoarthritis- and varus-alignment changes after total knee arthroplasty and whether a correlation exists both between preoperative functional flexion axis and native limb deformity.

METHODS

A navigated total knee arthroplasty was performed in 108 patients using a specific software to acquire passive joint kinematics before and after implant positioning. The knee was cycled through three passive range of motions, from 0° to 120°. Functional flexion axis was computed using the mean helical axis algorithm. The angle between the functional flexion axis and the surgical transepicondylar axis was determined on frontal (α (F)) and axial (α (A)) plane. The pre- and postoperative hip-knee-ankle angle, related to femur mechanical axis, was determined.

RESULTS

Postoperative functional flexion axis was different from preoperative only on frontal plane, while no differences were found on axial plane. No correlation was found between preoperative α (A) and native limb deformity, while a poor correlation was found in frontal plane, between α (F) and preoperative hip-knee-ankle angle.

CONCLUSIONS

Total knee arthroplasty affects functional flexion axis only on frontal plane while has no effect on axial plane. Preoperative functional flexion axis is in a more varus position respect to the transepicondylar axis both in pre- and postoperative conditions. Moreover, the position of the functional axis on frontal plane in preoperative conditions is dependent on native limb alignment, while on axial plane is not dependent on the amount of preoperative varus deformity.

The posterior cruciate ligament: a study on its bony and soft tissue anatomy using novel 3D CT technology

PURPOSE

The bony insertion sites of the PCL have been studied and described extensively using 2D technology such as macroscopic images, plain radiograph, computerized tomography (CT) and MRI. The purpose of this study is to visualize both the tibial and the femoral bony insertion sites but also the soft tissue anatomy of the native PCL using novel 3D CT imaging. In addition, new concepts of best-fit cylinder and central axis are introduced and evaluated.

METHODS

Nine unpaired knees of embalmed cadavers were used in this study. Following the dissection process, the PCL was injected with a contrast medium for computed tomography (CT) imaging. The obtained CT images were segmented and rendered in 3D allowing morphological and morphometric analysis of PCL. Femoral and tibial footprint surface area, best-fit PCL-cylinder intersection area, best-fit PCL-cylinder/footprint coverage ratio, best-fit PCL-cylinder central axis projections at the tibial and femoral footprint were used to describe the anatomy of the PCL.

RESULTS

Mean footprint surface area of the tibial and femoral footprint were 189.1 and 293.3 mm², respectively. The mean diameter of the best-fit cylinder was 10.5 mm. The mean coverage of the best-fit cylinder on the tibial and femoral footprint was 76.5 and 46.5, respectively. The best-fit cylinder central axis was located in the anterolateral AL bundle footprint on the femur and more centrally in the PCL footprint on the tibia.

CONCLUSION

This study is the first to describe the detailed anatomy of the human PCL with respect to its course and footprints using a 3D approach. It confirms the large difference between the tibial and the femoral footprint area with the former being significantly smaller. In addition, a large inter-patient variability is observed. The best-fit cylinder and central axis concept offer additional insights into the optimal tunnel placement at the tibia and femoral footprint in order to cover the largest portion of the native PCL soft tissue.

ACCURACY CHARACTERIZATION OF AN INTEGRATED OPTICAL-BASED METHOD FOR LOADS MEASUREMENT IN COMPUTER AIDED SURGERY

Generally in the anterior cruciate ligament (ACL) injury assessment specific laxity tests (i.e., Lachman, drawer tests) are clinically performed to evaluate the presence of ligamentous lesion. At present these tests are qualitatively evaluated by the surgeon and some quantitative measurements can be performed only for Lachman/drawer tests by means of dedicated devices. This study aimed to characterize the accuracy of a novel integrated optical-based method that can be used both in intra-operative and in office assessment of ACL injuries; in particular this technology was addressed to measure the loads/torques applied during clinical laxity tests, extending the current possible quantitative evaluations. The system, based on a commercial optical localizer and common springs, was spatially characterized in order to verify displacement/rotation and corresponding applied load/torque measurements. Evaluated limits of agreement between measured and applied loads were from –0.541 to 1.781 N, with a bias of 0.621 N (P = 0.05) in a dedicated clinical-like setup. This approach reported an excellent accuracy in load measurements, showing its possible integration in computer-aided surgery (CAS).

Knee functional flexion axis in osteoarthritic patients: comparison in vivo with transepicondylar axis using a navigation system

PURPOSE

No study, up to now, has examined the effect of arthritis on pathologic subjects using functional flexion axis (FFA). The purpose of this study is to understand whether arthritis affects somehow the FFA evaluation and to assess whether the FFA could be considered a usable reference for implant positioning for osteoarthritic knees.

METHODS

Using a navigation system, FFA orientation was evaluated intraoperatively (computed with the mean helical axis method) in three different ranges of motion (0°-120°; 35°-80°; 35°-120°) and in two different planes (coronal and axial), for 111 osteoarthritis patients undergoing total knee arthroplasty. The results were compared with a control group of 60 patients that underwent ACL reconstruction. The angle between the transepicondylar axis (TEA) and FFA was computed.

RESULTS

Results showed in arthritic knees on frontal plane, an average difference between TEA and FFA of -2.8° ± 5.0° while on axial plane it was 0.6° ± 4.7°. No statistical difference was found between the three ranges in axial view, whereas some difference was found in frontal view (P < 0.0001). The TEA-FFA angle was not correlated with limb alignment on axial plane, while it was, even if poor, in frontal plane. In the control group, in frontal and in axial view, no statistical difference was found for the angle between TEA and FFA.

CONCLUSIONS

FFA can be used as reference for implant positioning in axial plane also in pathologic knees, while for the frontal plane further investigations are required.

Anatomic double-bundle and over-the-top single-bundle with additional extra-articular tenodesis: an in vivo quantitative assessment of knee laxity in two different ACL reconstructions

PURPOSE

Combinations of intra- and extra-articular procedures have been proposed for anterior cruciate ligament reconstruction with the aim of achieving an optimal control of translational and rotational knee laxities. Recently, the need for better reproducing the structural and functional behavior of the native anterior cruciate ligament led to the definition of anatomic double-bundle surgical approach. This study aimed to quantitatively verify whether the in vivo static and dynamic behavior obtained using over-the-top single-bundle with extra-articular tenodesis reconstruction was comparable to the results achieved by anatomic double-bundle approach.

METHODS

Thirty-five consecutive patients, with an isolated anterior cruciate ligament injury, were included in the study. Standard clinical laxities and pivot-shift test were quantified before and after anterior cruciate ligament reconstruction by means of a surgical navigation system dedicated to kinematic assessment; displacements of medial and lateral compartment during stress tests were also analyzed.

RESULTS

Single-bundle with extra-articular tenodesis approach presented statistically better laxity reduction in varus/valgus stress test at full extension and in internal/external rotation at 90° of flexion; lateral plasty controlled better the lateral compartment during drawer test and varus/valgus stress test both at 0° and 30° of flexion and both the compartments during internal/external rotation at 90° of flexion. On the other hand, pivot-shift phenomenon was better controlled by anatomic double-bundle reconstruction.

CONCLUSIONS

Both the reconstructions worked similarly for static knee laxity. The extra-articular procedure played an important role in better constraining the displacement of lateral tibial compartment, whereas the anatomic double-bundle reconstruction better restored the dynamic behavior of knee joint highlighted under pivot-shift stress test.

STUDY DESIGN

Case series.

Computer-assisted anterior cruciate ligament reconstruction: an evidence-based approach of the first 15 years

In the last 15 years, computer-assisted surgery (CAS) has been used for many purposes during anterior cruciate ligament (ACL) reconstruction, such as tunnel positioning, joint laxity evaluation, and biomechanical studies. This article is an evidence-based literature review of the contribution of such technology to ACL surgery. A search of the PubMed and Medline databases was performed. Articles were classified according to the study design and to the research topic: anatomy, laxity, kinematics, and comparison of surgical techniques. An evidence-based approach was used to verify the clinical usefulness of CAS to ACL surgery. The use of CAS for research purposes was also evaluated. CAS was shown to improve femoral tunnel positioning, even if clinical outcomes showed no differences compared with manual techniques. CAS technology was found to be useful for research purposes in terms of providing a better comprehension of the effect of different ACL reconstructions and of the different bundles on joint laxity, as well as describing tunnel positioning in relation to native ACL insertion. CAS in ACL surgery can improve results at time 0 and can improve knowledge about ACL anatomy and kinematics. Its application remains limited mostly to research purposes because of the invasiveness of the system and the absence of improved clinical results at follow-up.

Pivot-shift test: analysis and quantification of knee laxity parameters using a navigation system

Lachman, drawer, and pivot-shift (PS) tests are important in the assessment of ACL reconstruction. The goal of this work was to analyze the reliability of the PS test using a navigation system, identifying a set of new quantitative parameters and evaluating their clinical relevance. Eighteen patients that underwent anatomic double-bundle ACL reconstruction were included. The new dynamic parameters were: anteroposterior translation of the medial and lateral compartments and the joint center and internal/external and varus/valgus rotations of the joint. For each parameter we measured the peaks and the areas obtained during the test. Intratester repeatability, comparisons of pre- and postoperative laxities, and correlations between the PS peaks and the corresponding peaks obtained with standard static tests were evaluated. Areas, peaks, and static laxity outcomes were compared, grouping patients according to the preoperative International Knee Documentation Committee (IKDC) score. The PS test was reliable in identifying the surgical reconstruction. Correlation analysis showed good coefficients both for pre- and postoperative values. Patients with IKDC grade "D" had larger areas during the PS compared to patients with grade "C". Our analysis is helpful for characterizing patient-specific laxity and surgical performance, thus highlighting the clinical relevance of the PS test.

Clinical relevance of static and dynamic tests after anatomical double-bundle ACL reconstruction

A computer navigation system was used to collect kinematic data of 18 subjects undergoing ACL reconstruction. Surgical procedure was an anatomical four-tunnel hamstring double-bundle reconstruction. Static laxity and dynamic laxity were analyzed before and after graft passage and fixation. Correlations between static and dynamic laxities as well as with the preoperative IKDC score were determined. Static and dynamic laxities were significantly reduced after anatomic double-bundle ACL reconstruction (P < 0.05). There were no significant correlations between static and dynamic laxities (r < 0.4, P > 0.05). The preoperative IKDC score was only related to preoperative dynamic laxity (P < 0.01). The dynamic evaluation of pivot shift is able to better describe knee laxity, in particular rotational laxities and has no correlation with static laxity.

Intraoperative evaluation of total knee replacement: kinematic assessment with a navigation system

Interest in the kinematics of reconstructed knees has increased since it was shown that the alteration of knee motion could lead to abnormal wear and damage to soft tissues. We performed intraoperative kinematic measurements using a navigation system to study knee kinematics before and after posterior substituting rotating platform total knee arthroplasty (TKA). We verified intraoperatively (1) if varus/valgus (VV) laxity and anterior/posterior (AP) laxity were restored after TKA; (2) if TKA induced abnormal femoral rollback; and (3) how tibial axial rotation was influenced by TKA throughout the range of flexion. We found that TKA improved alignment in preoperative osteoarthritic varus knees which became neutral after surgery and maintained a neutral alignment in neutral knees. The VV stability at 0 degrees was restored while AP laxity at 90 degrees significantly increased after TKA. Following TKA, the femur had an abnormal anterior translation up to 60 degrees of flexion, followed by a small rollback of 12 +/- 5 mm. TKA influenced the tibia rotation pattern during flexion, but not the total amount of internal/external rotation throughout whole range of flexion, which was preserved after TKA (6 degrees +/- 5 degrees ). This study showed that the protocol proposed might be useful to adjust knee stability at time zero and that knee kinematic outcome during total knee replacement can be monitored by a navigation system.

Knee stability before and after total and unicondylar knee replacement: in vivo kinematic evaluation utilizing navigation

Surgical navigation systems are currently used to guide the surgeon in the correct alignment of the implant. The aim of this study was to expand the use of navigation systems by proposing a surgical protocol for intraoperative kinematics evaluations during knee arthroplasty. The protocol was evaluated on 20 patients, half undergoing unicondylar knee arthroplasty (UKA) and half undergoing posterior-substituting, rotating-platform total knee arthroplasty (TKA). The protocol includes a simple acquisition procedure and an original elaboration methodology. Kinematic tests were performed before and after surgery and included varus/valgus stress at 0 and 30 degrees and passive range of motion. Both UKA and TKA improved varus/valgus stability in extension and preserved the total magnitude of screw-home motion during flexion. Moreover, compared to preoperative conditions, values assumed by tibial axial rotation during flexion in TKA knees were more similar to the rotating patterns of UKA knees. The analysis of the anteroposterior displacement of the knee compartments confirmed that the two prostheses did not produce medial pivoting, but achieved a postoperative normal behavior. These results demonstrated that proposed intraoperative kinematics evaluations by a navigation system provided new information on the functional outcome of the reconstruction useful to restore knee kinematics during surgery.