Simone Bignozzi

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.

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

PurposeCombinations 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.MethodsThirty-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.ResultsSingle-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.ConclusionsBoth 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 designCase series.

An original clinical methodology for non-invasive assessment of pivot-shift test

Even if pivot-shift (PS) test has been clinically used to specifically detect anterior cruciate ligament (ACL) injury, the main problem in using this combined test has been yet associated with the difficulty of clearly quantifying its outcome. The goal of this study was to describe an original non-invasive methodology used to quantify PS test, highlighting its possible clinical reliability. The method was validated on 66 consecutive unilateral ACL-injured patients. A commercial triaxial accelerometer was non-invasively mounted on patients tibia, the corresponding 3D acceleration was acquired during PS test execution and a set of specific parameters were automatically identified on the signal to quantify the test. PS test was repeated three times on both injured and controlateral limbs. Reliability of the method was found to be good (mean intra-rater intraclass correlation coefficient was 0.79); moreover, we found that ACL-deficient knees presented statistically higher values for the identified parameters – than the controlateral healthy limbs, averagely reporting also large effect size.

Does ACL reconstruction restore knee stability in combined lesions? : An in vivo study

Treating anterior cruciate ligament (ACL) lesions combined with a torn medial collateral ligament (MCL) is controversial because residual laxity may lead to stretching of the ACL graft and eventual failure of the reconstruction. Few studies describe the in vivo translations of combined ACL and MCL injuries. We compared the preoperative and postoperative laxity between patients with combined ACL+MCL Grade II injuries and isolated ACL ruptures and tested whether an ACL reconstruction could restore all laxities in both groups. We evaluated knee kinematics during ACL reconstruction in 57 patients (37 ACL lesions and 20 ACL+MCL injury). Laxity tests were performed before and after graft fixation. Postoperatively, there was greater anteroposterior laxity and greater varus-valgus laxity in the group with MCL injury compared to the group with an ACL lesion only. This finding suggests residual laxities remain when ACL reconstruction is performed in patients with combined ACL+MCL lesion, and raises the question of addressing the MCL ligament when Grade II laxity is found.Level of Evidence: Level II, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Reliability of a navigation system for intra-operative evaluation of antero-posterior knee joint laxity

BACKGROUND The purpose of this study was to investigate about the reliability of measuring antero-posterior laxity within-subjects for in-vivo studies using a navigation system. METHODS The analysis was performed by enroling 60 patients undergoing anterior cruciate ligament ACL reconstruction, and assessing AP laxity during the Lachman and drawer tests. RESULTS For the navigation system standard deviation for intra-trial measures was 0.7 mm, thus the intra-trial repeatability coefficient was 2.2 mm; standard deviation for intra-trial measure was 1.2 mm, while the reference inter-trial repeatability coefficient between expert surgeons was 3.4 mm. CONCLUSIONS In conclusion, this study suggests that KIN-Nav may represent a new method to measure and document AP laxity intra-operatively with improved accuracy and test the effect of surgical treatment in-vivo with higher sensitivity than in the past and this study quantify its reliability for within-subjects studies performed by a single expert surgeon.

Description and validation of a navigation system for intra-operative evaluation of knee laxity.

This paper describes the features of KIN-nav, a navigation system specifically dedicated to intra-operative evaluation of knee laxity, and assesses the reliability of the system during surgery. The acquisition protocol for its intra-operative use, the original user interface, and the computational methods for elaboration of kinematic data are described in detail. Moreover, an extensive and specific validation of the system was performed in order to evaluate its intra-operative performance and usability. KIN-navs reliability and accuracy were analyzed in a series of 79 patients undergoing ACL reconstruction. The intra-surgeon repeatability computed for ACL-deficient and reconstructed knees at different flexion angles was less than 0.6 degrees for varus-valgus (VV) rotation, less than 1 mm for AP translation, and less than 1.6 degrees for IE rotation. The inter-surgeon repeatability is less than 2 degrees for VV rotation, 5 degrees for internal-external rotation, and less than 3 mm for AP translation. The proposed method was fast (requiring an additional 10 minutes of surgical time on average), required only a short learning period (5 cases), was minimally invasive, and was robust from the numerical perspective. Our system clearly shows that the use of navigation systems for kinematic evaluation provides useful and complete information on the knee state and test performance, and is simple and reliable to use. The good repeatability in manual kinematic tests is an improvement on the present ability to discriminate knee kinematics intra-operatively, and thus offers the possibility of better discrimination between knee pathologies and the prospect of new surgical applications.

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.

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° 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.

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

Abstract 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-Navs 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.

Does chronic medial collateral ligament laxity influence the outcome of anterior cruciate ligament reconstruction? A prospective evaluation with a minimum three-year follow-up

We have shown in a previous study that patients with combined lesions of the anterior cruciate (ACL) and medial collateral ligaments (MCL) had similar anteroposterior (AP) but greater valgus laxity at 30° after reconstruction of the ACL when compared with patients who had undergone reconstruction of an isolated ACL injury. The present study investigated the same cohort of patients after a minimum of three years to evaluate whether the residual valgus laxity led to a poorer clinical outcome. Each patient had undergone an arthroscopic double-bundle ACL reconstruction using a semitendinosus-gracilis graft. In the combined ACL/MCL injury group, the grade II medial collateral ligament injury was not treated. At follow-up, AP laxity was measured using a KT-2000 arthrometer, while valgus laxity was evaluated with Telos valgus stress radiographs and compared with the uninjured knee. We evaluated clinical outcome scores, muscle girth and time to return to activities for the two groups. Valgus stress radiographs showed statistically significant greater mean medial joint opening in the reconstructed compared with the uninjured knees (1.7 mm (SD 0.9) versus 0.9 mm (SD 0.7), respectively, p = 0.013), while no statistically significant difference was found between the AP laxity and the other clinical parameters. Our results show that the residual valgus laxity does not affect AP laxity significantly at a minimum follow up of three years, suggesting that no additional surgical procedure is needed for the medial collateral ligament in combined lesions.