The Pivot-shift phenomenon (PS) is known to be one of the essential signs of functional insufficiency of the anterior cruciate ligament (ACL). To evaluate the dynamic knee laxity is very important to accurately diagnose ACL injury, to assess surgical reconstructive techniques, and to evaluate treatment approaches. However, the pivot-shift test remains a subjective clinical examination difficult to quantify. The aim of the present study is to validate the use of an innovative non-invasive device based on the use of an inertial sensor to quantify PS test. The validation was based on comparison with data acquired by a surgical navigation system.

The surgeon intraoperatively performed the PS tests on 15 patients just before fixing the graft required for the ACL reconstruction. A single accelerometer and a navigation system simultaneously acquired the joint kinematics. An additional optical tracker set to the accelerometer has allowed to quantify the movement of the sensor. The tibial anteroposterior acceleration obtained with the navigation system was compared with the acceleration acquired by the accelerometer. It is therefore estimated the presence of any artifacts due to the soft tissue as the test-retest repositioning error in the positioning of the sensor. It was also examined, the repeatability of the acceleration parameters necessary for the diagnosis of a possible ACL lesion and the waveform of the output signal obtained during the test. Finally it has been evaluated the correlation between the two acceleration measurements obtained by the two sensors.

The RMS (root mean square) of the error of test-retest positioning has reported a good value of 5.5 ± 2.9 mm. While the amounts related to the presence of soft tissue artifacts was equal to 4.9 ± 2.6 mm. It was also given a good intra-tester repeatability (Cronbach's alpha = 0.86). The inter-patient similarity analysis showed a high correlation in the acceleration waveform of 0.88 ± 0.14. Finally the measurements obtained between the two systems showed a good correlation (rs = 0.72, p<0.05).

This study showed good reliability of the proposed scheme and a good correlation with the results of the navigation system. The proposed device is therefore to be considered a valid method for evaluating dynamic joint laxity.

Anterior cruciate ligament (acl) reconstruction is one of the most commonly performed procedures in orthopedics for acl injury. While literature suggest short-term good-to-excellent functional results, a significant number of long-term studies report unexplained early oa development, regardless type of reconstruction. The present study reports the feasibility analysis and development of a clinical protocol, integrating different methodologies, able to determine which acl reconstruction technique could have the best chance to prevent oa. It gives also clinicians an effective tool to minimize the incidence of early oa.

A prospective clinical trial was defined to evaluate clinical outcome, biochemical changes in cartilage, biomechanical parameters and possible development of oa. The most common reconstruction techniques were selected for this study, including hamstring single-bundle, single-bundle with extraarticular tenodesis and anatomical double-bundle. Power analysis was performed in terms of changes at cartilage level measurable by mri with t2 mapping. A sample size of 42 patients with isolated traumatic acl injury were therefore identified, considering a possible 10% to follow-up. Subjects presenting skeletal immaturity, degenerative tear of acl, other potential risk factors of oa and previous knee surgery were excluded. Included patients were randomized and underwent one of the 3 specified reconstruction techniques. The patients were evaluated pre-operatively, intra-operatively and post-operatively at 4 and 18 months of follow-up. Clinical evaluation were performed at each time using subjective scores (koos) and generic health status (sf-12). The activity level were documented (marx) as well as objective function (ikdc).

Preliminary results allow to verify kinematic patterns during active tasks, including level walking, stair descending and squatting using dynamic roentgen sterephotogrammetric analysis (rsa) methodology before and after the injured ligament reconstruction. Intra-operative kinematics was also available by using a dedicated navigation system, thus to verify knee laxity at the time of surgery. Additionally, non-invasive assessment was possible both before the reconstruction and during the whole follow-up period by using inertial sensors. Integrating 3d models with kinematic data, estimation of contact areas of stress patterns on cartilage was also possible.

The presented integrate protocol allowed to acquired different types of information concerning clinical assessment, biochemical changes in cartilage and biomechanical parameters to identify which acl reconstruction could present the most chondroprotective behavior. Preliminary data showed all the potential of the proposed workflow. The study is on-going and final results will be shortly provided.

Introduction

Protective hard coatings are appealing for several technological applications and even for orthopaedic implants and prosthetic devices. For what concerns the application to prosthetic components, coating of the surface of the metallic part with low-friction and low-wear materials has been proposed [1, 2]; at the same time, concerning use of ceramic materials in joint arthroplasty, zirconia-toughned-alumina (ZTA) ceramic material has shown high strength, fracture toughness, elasticity, hardness, and wear resistance [3, 4]. The purpose of this study was to directly deposit ZTA coatings by using a novel sputter-based electron deposition technique, namely Pulsed Plasma Deposition (PPD) [5]. Preliminary characterization of realized coatings from the point of view of morphology, wettability, adhesion and friction coefficients was performed.

Introduction

Total joint arthroplasty is frequently necessary when a traumatic or degenerative disease leads to develop osteoarthritis (OA). Nowadays, the main reason for long term prosthesis failure is due to osteolysys and aseptic loosening of the implant itself, that are related to UHMWPE wear debris [1–3]. Different solutions to overcome this issue have been proposed, including different couplings like metal-on-metal and ceramic-on-ceramic. Our hypothesis was that a hard ceramic thin film realized on the plastic component (i.e. UHMWPE) could improve the friction and wear performance in a prosthetic coupling. The purpose of the presented study was therefore to characterize from the point of view of structure and mechanical performance of this ceramic-coated plastic component. The thin films were specifically realized by means of the novel Pulsed Plasma Deposition (PPD) technique [4].

Introduction

Providing proper rotational alignment of femoral component in total knee arthroplasty is mandatory to achieve correct kinematics, good ligament balance and proper patellar tracking. Recently functional references, like the function flexion axis (FFA), have been introduced to achieve this goal. Several studies reported the benefits of using the FFA but highlighted that further analyses are required to better verify the FFA applicability to the general clinical practice. Starting from the hypothesis that the FFA can thoroughly describe knee kinematics but that the joint kinematics itself can be different from flexion to extension movements, the purpose of this study was to analyse which factors could affect the FFA estimation by separately focusing on flexion and extension movements.

Introduction

Protective hard coatings are appealing for several technological applications like solar cells, organic electronics, fuel cells, cutting tools and even for orthopaedic implants and prosthetic devices. At present for what concerns the application to prosthetic components, the coating of the surface of the metallic part with low-friction and low-wear materials has been proposed [1]. Concerning the use of ceramic materials in joint arthroplasty, zirconia-toughned-alumina (ZTA) reported high strength, fracture toughness, elasticity, hardness, and wear resistance [2]. The main goal of this study was to directly deposit ZTA coating by using a novel sputter-based electron deposition technique, namely Pulsed Plasma Deposition (PPD) [3]. The realized coatings have been preliminary characterized from the point of view of morphology, wettability, adhesion and friction coefficients.

Introduction

Several methods, based on both functional and anatomical references, have been studied to reach the goal of a proper knee kinematics in total knee arthroplasty (TKA). However, at present, there is still a large debate about which is the most precise and accurate method to achieve the correct rotational implant positioning. One of the main methods already used in TKA to describe the tibiofemoral flexion-extension movement, based on a kinematic technique, thus not influenced by the typical variability related to the identification of anatomical references, is called “functional flexion axis” (FFA) method. The purpose of this study was to determine the repeatability in estimating knee functional flexion axis, thus evaluating the robustness of the method for navigated total knee arthroplasty.

Wear of the ultra-high molecular weight polyethylene (UHMWPE) insert is one of the major issue related to orthopaedic implants. In this study, the tribo-mechanical properties of zirconia-coated UHMWPE deposited by means of Pulsed Plasma Deposition (PPD) technique were analyzed. Specifically, strength to local plastic deformation, indentation work portioning and creep behavior were evaluated through nanoindentation and micro-scratch tests, whereas preliminary wear data were obtained by tribology tests. A strong reduction of plastic deformation and a drop of the creep phenomenon for the zirconia-coated UHMWPE were evidenced, whereas - in spite of similar wear data - different wear mechanism was also detected. This study supported the use of hard ceramic thin films to enhance the mechanical performance of the plastic inserts used in orthopaedics.

Introduction

The use of a surgical navigation system has been demonstrated to allow to intraoperatively analyze knee kinematics during total knee arthroplasty (TKA), thus providing the surgeon with a quantitative and reproducible estimation of the knee functional behaviour. Recently severak authors used the computer assisted surgery (CAS) for kinematic evaluations during TKA, in particular to evaluate the achievement of a correct joint biomechanics after the prosthesis implantation. The major concern related to CAS is that the movements are usually passively performed, thence without a real active task performed by the subject. Starting from the hypothesis that the passive kinematics may properly describe the biomechanic behaviour of the knee, the main goal of this work was to intra-operatively compare the active kinematics of the limb, analysing a flexion movement actively performed by the patient, and the passive kinematics, manually performed by the surgeon.

Introduction

When osteoarthritis occurs, joint replacement is the most frequent treatment. Currently, the mean survival rate for total joint arthroplasty is ∼90% after 10 years: the main reason for long-term implant failure, that generally required a revision surgery, are osteolysis and aseptic loosening of the implant, which are strongly correlated with wear debris formation from the UHMWPE insert [Ingham, 2005], as a consequence of the cyclic loading against the metallic or ceramic counterface [Dumbleton, 2002]. Wear debris bring to chronic inflammation of periprosthetic tissues causing an increase of bone reabsorption that finally provoke aseptic loosening, so implant failure[Holt, 2007]. Different solutions were proposed to reduce wear debris production but agreement has not been achieved yet. Our challenging approach prefigures the direct coating of the plastic component with a hard and well-adherent ceramic film, in order to drastically reduce wear debris formation from the plastic substrate while preserving its well-established bulk mechanical properties, especially under high local loads [Bianchi, 2013].

INTRODUCTION

This study aimed to intra-operatively quantify the improvements in knee stability given both by anatomic double-bundle (ADB) and single-bundle with additional lateral plasty (SBLP) ACL reconstruction using a navigation system.

Introduction

Several in vitro and in vivo studies have found correspondence between transepicondylar axis (TEA) and functional flexion axis (FFA) in healthy subjects. In addition some studies suggest that the use of FFA for rotational alignment of femoral implant may be more accurate than TEA. Ostheoarthritis (OA) may modify limb alignment and therefore flexion axis, introducing a bias at different flexion ranges during kinematic acquisition. In this study we want to understand whether OA affects somehow the FFA evaluation compared to TEA and whether the FFA could be considered a usable reference for implant positioning for osteoarthritic knees

Introduction

Patellar stability is an important component for a correct kinematic behaviour of the knee that depends on several factors such as joint geometry, muscles strength and soft tissues actions. Patellofemoral (PF) maltracking can results in many joint disorders which can cause pain and mobility alterations. The medial patellofemoral ligament (MPFL) is an important stabilizing structure for the patellofemoral joint. The aim of this study was to analyze patellofemoral kinematics with particular attention to the contribution of MPFL on patella stability.

Purpouse

We hypothesized that patients receiving a medial collagen meniscus implant (MCMI) would show better clinical, radiograpich and Magnetic Resonanace Imaging (MRI) outcomes than patients treated with partial medial meniscectomy (PMM) at minimum 10 year FU.

Introduction: Several in vitro and in vivo studies have found correspondence between transepicondylar axis (TEA) and mean helical axis (MHA) in healthy subjects. In addition some studies suggest that the use of MHA for rotational alignment of femoral implant may be more accurate than TEA. Ostheoarthritis (OA) may modify limb alignment and flexion axis, introducing a bias during kinematic acquisition. An in-vivo study comparing normal and osteoarthritic knees using MHA is still lacking. The purposes of this study were: to understand whether arthritis affects somehow the functional axis evaluation and then to assess whether the MHA could be considered as reference flexion axis also for osteoarthritic knees; starting from hypothesis that there is a correspondence between TEA and MHA, to evaluate whether in pathologic subjects there still is the same correspondence.

Material and Methods: We included a group of 15 OA patients undergoing TKA and, as control group, 60 patients that underwent ACL reconstruction, since in vivo studies reported small differences in kinematics between ACL reconstructed and uninjured limbs. With a surgical navigation system we recorded intraoperative kinematic data of different passive ranges of motion (PROM) and calculated the MHA applying a least square approach to the set of finite helical axes (FHA) obtained in three different ranges of motion (0°–120°; 35°–80°; 35°–120°). We compared the difference in orientation of MHA in the three ranges with respect to the TEA on frontal (XZ) and axial (XY) planes. The correlation of preoperative limb deformity with MHA-TEA angle was also performed.

Results: The results of difference of MHA-TEA angle between the OA and ACL groups for all the three ranges of flexion and in XZ and XY views showed no statistical difference (p=0.5188; p=0.7147 respectively). No statistical difference was found also about MHA-TEA angle between the three ranges in frontal and axial views (ANOVA p=0.6373; p=0.4183 respectively). There was no difference between the flexion and extension movements in the three ranges. We also found that correlation between limb alignment and MHA-TEA angle showed good correlation (r> 0.54, p< 0.001) in frontal view and fair correlation (r< 0.37, p< 0.05) in axial view for all ranges.

Conclusions: Our work has demonstrated that pathologic knees shows no differences in MHA orientation compared to nearly healthy subjects, moreover there is the same correspondence between TEA and MHA both in XZ and XY plane. We also found that preoperative limb alignment does not correlate with MHA-TEA angle. results are in agreement to studies on healthy subjects. Therefore the MHA may be considered a reliable reference for determining femoral flexion axis and a useful tool in the determination of femoral implant positioning on axial plane, even in surgical setup on osteoarthritic patients.

Introduction: The hip joint is usually considered a ball-in-socket. However, there have been few studies evaluating normal hip kinematics and the contribution coming from soft tissues. Capsular laxity is at the basis of injury to the acetabular labrum (most common pathological lesion seen during hip arthroscopy). The objectives of this study were to (1) assess hip kinematics with all the soft tissues intact using a surgical navigation system, (2) assess the relative contributions of the soft tissues to hip stability and (3) assess the relative contributions of periarticular soft tissues to hip range of motion.

Materials and Methods: We used 4 normal hemicorpse specimens for a total of 8 hips. A navigation system (KLEE, Orthokey) was used to acquire the kinematic data. The anatomical reference system was identified through the palpation of landmarks: (1) anterior superior iliac spines (ASIS) and (2) pelvic tubercles for the pelvis, (3) femoral head center and (4) epicondyles for femur. There were 12 passive kinematic tests repeated 3 times in 3 different limb conditions (‘intact’, ‘no-skin-muscle’, ‘labral tear’) to explore the whole kinematic range. We analysed the differences in flexion/extension, abduction/adduction, internal/external rotation ranges (Wilcoxon’s Signed Ranks Test).

Results: The kinematic analysis applied on the limbs highlighted the following range of motion: (1) the F/E was 115.7 ± 2.4° (12.9 ± 1.0° in extension/101.7 ± 3.0° in flexion) in ‘intact’ limb, 139.2 ± 10.8° (14.7 ± 2.7° in extension/120.7 ± 8.6° in flexion) in ‘no-skin no-muscle’ condition, and 174.3 ± 34.1° (25.3 ± 0.5° in extension/147.4 ± 35.4° in flexion) in ‘capsule cut’ condition; all the ranges were statistically different (p < 0.05); (2) the A/A was 44.5 ± 13.7° (35.4 ± 1.5° in abduction/10.1 ± 13.4° in adduction) in ‘intact’ limb, 59.2 ± 1.8° (38.5 ± 3.2° in abduction/21.7 ± 0.7° in adduction) in ‘no-skin no-muscle’ condition, and 82.0 ± 4.6° (57.4 ± 2.5° in abduction/25.6 ± 6.8° in adduction) in ‘capsule cut’ condition; all the ranges were statistically different (p < 0.05); (3) the IR/ER was 52.2 ± 10.5° (32.0 ± 11.9° in IR/21.5 ± 1.0° in ER) in ‘intact’ limb, 59.2 ± 1.8° (36.1 ± 14.1° in IR/26.5 ± 1.2° in ER) in ‘no-skin no-muscle’ condition, and 116.4 ± 54.4° (58.2 ± 16.1° in IR/55.6 ± 36.3° in ER) in the ‘capsule cut’ condition; all the ranges were statistically different (p < 0.05), except the ranges of ‘intact’ condition and ‘no-skin no-muscles’ one (p = 0.37).

Discussion: The study of the 3 different conditions highlighted the critical role of the soft tissues in hip stability and kinematics; the soft tissues do provide stability mainly in limiting hip range of motion. This study’s findings are a preliminary contribution in the understanding of the contribution of periarticular muscles, joint capsule and ligaments to hip kinematics.

Introduction: Anterior Cruciate Ligament (ACL) is primary constrain to anterior displacement of tibia with respect to the femur and secondary to internal/external (IE) and varus/valgus (VV) rotations; an ACL reconstruction should thus control not only AP but also IE and VV laxities. For this reasons, more attention has given to residual rotational instability. This study aims to verify if those subjects with high of pre-op knee laxities has also high post-op laxity after an ACL reconstruction.

Material and Methods: The study includes 115 patients, that underwent ACL reconstructions between January 2005 and September 2007. Patients with associated severe ligaments tears or severe chondral defects were excluded. The joint passive kinematics was intra-operatively assessed using the BLU-IGS system (Orthokey, Delaware). We evaluated, before and after the reconstruction, the manual maximum IE rotation at 30° and 90° of flexion, VV rotation at 0° and 30° of flexion and AP displacement at 30° and 90° of flexion. We used the k-means algorithm applied to pre-op values to create two groups among the patients: the GROUP H, with higher pre-op laxity and the GROUP L, with lower pre-op laxity. The pre-op groups were compared for each test using independent Student’s t-test (p=0.01) in order to assess their difference. Student’s t-test (p=0.01) was performed on the corresponding post-op values in order to verify if the difference between H and L was maintained after the reconstruction.

Results: Mean pre-op VV at 0° was 7.1±0.9° for group H and 4.7±0.8° for group L (p< 0.01), post-op was 3.2±0.8° for group H and 2.5±0.8° for group L (p< 0.01). Mean pre-op VV at 30° was 6.2±1.5° for group H and 3.4±0.7° for group L (p< 0.01), post-op was 3.4±1.3° for group H and 2.2± 0.9° for group L (p< 0.01). Mean pre-op IE at 30° was 28.3±3.5° for group H and 19.2±3.1° for group L (p< 0.01), post-op was 21.5±3.8° for group H and 14.7±3.7° for group L (p< 0.01). Mean pre-op IE at 90° was 31.3±2.8° for group H and 22.4±3.5° for group L (p< 0.01), post-op was 22.3±4.0° for group H and 17.0±4.4° for group L (p< 0.01). Mean pre-op AP at 30° was 14.5±2.1mm for group H and 8.9±1.6mm for group L (p< 0.01), post-op was 6.2±1.6mm for group H and 4.2±1.6mm for group L (p< 0.01). Mean pre-op AP at 90° was 11.2±1.7mm for group H and 6.7±1.4mm for group L (p< 0.01), post-op was 5.4±1.8mm for group H and 3.4±1.3mm for group L (p< 0.01).

Discussion: The comparison between group H and group L showed that those patients with higher pre-op laxity had maintained higher post-op values mainly for all the tests. This finding is probably correlated to the possible presence of different tears affecting soft structures of the joint and to the proper and specific anatomy of each patient.

Information on knee kinematics during surgery is currently lacking. The aim of this study is to describe intra-operative kinematics evaluations during uni-compartmental knee arthroplasty (UKA) and total knee arthroplasty (TKA) by mean of a navigation system. Anatomical and kinematic data were acquired by Kin-Nav navigation system and analysed by a dedicated elaboration software developed at our laboratory. The study was conducted on 20 patients: 10 patients undergoing mini-invasive UKA and 10 patients undergoing posterior-substituting-rotating-platform TKA. In both group of patients the surgeon performed passive knee flexion immediately before and immediately after the prosthetic implant. Pattern and amount of internal/external tibial rotation in function of flexion were computed and significant changes between before and after implant were evaluated adopting Student’s t-test (significant level p=0.05).

UKA implant did not significantly change the pattern of internal/external tibial rotation, nor the total magnitude of tibial rotation (15.75°±7.27°) during range of flexion (10°–110°), compared to pre-operative values (17.87°±7.34°, p=0.25). Magnitude of tibial rotation in TKA group before surgery (8.00°±3.67°) was significantly less compared to UKA patients and did not changed significantly after implant (5.96°±4.88°, p=0.09). Pattern of rotation before and after TKA implant were different between each other and between pattern in UKA patients both before and after implant.

Intra-operative evaluations on tibial rotation during knee flexion confirmed some assumptions on knee implants from post-operative methods and suggest a more extensive use of surgical navigation systems for kinematic studies.

Total knee arthroplasty (TKA) is actually a satisfactory technique to reduce pain and enhance mobility in osteoartritic pathologies (OA) of the knee. However, life of the implant is strictly dependent on restoration of correct knee kinematics, as alteration of motion pattern could led to abnormal wear in prosthetic components and also damage soft tissues. The aim of our study was to evaluate new kinematic tests to be performed during surgery in order to improve the standard intra-operative evaluation of the outcome on the individual case. We used Kin-Nav navigation system to acquire anatomic and kinematic data, which were analysed by a dedicated elaboration software developed at our laboratory. Ten patients undergoing rotating platform cruciate substituting TKA were considered for this study. Immediately before the implant and immediately after component positioning, the surgeon performed 3 complete knee flexion imposing internal tibial rotation (IPROM) and 3 complete knee flexion imposing external tibial rotation (EPROM). Tibial rotation during IPROM and EPROM tests was plotted in function of flexion (in the range 10°–110°). Repeatability of IPROM and EPROM was tested by calculating ICC (Intra-class Correlation Coefficient) between 3 repeated curves. Distance between IPROM curve and EPROM curve was computed at various degree of flexion. Maximum distance obtained during all range of flexion before and after the implant were compared by Student’s t-test (significant level p=0.05).

ICC for repeated motions were 0.99 for IPROM and 0.98 for EPROM. Maximum distance between tibial rotation in IPROM and EPROM was 27.82±6.98 before implant and significantly increased (p=0.001) to 40.09±6.92 after TKA. In one case we observed that the value remained similar before and after implant (from 33.11 to 33.98) while in one case we observed very large increase of rotation (from 30.56 to 50.01).

The proposed kinematic tests were able to quantify the increase of tibial rotation after TKA implant. Future development of the study are encouraging and will include a larger sample and reflections on individual findings.

Aims: This work describes a new intraoperative computer-assisted method for the evaluation of joint kinematics in both total (TKA) and uni-compartmental (UKA) knee arthroplasty. We report schematically the protocol and the preliminary in-vivo results we obtained on 11 patients (9 UKA – 2 TKA).

Methods: The system consists of an optoelectronic localizer, 2 reference arrays and a dedicated acquisition software, that permits the real-time control of limb position and allows the acquisition of joint motions. After a first phase of registration (anatomical landmarks identification) the surgeon executes, both before and after the reconstruction, a series of passive tests: range of motion (PROM) evaluation, varus-valgus (VV) stress at 0°, and VV at 30°. Furthermore the surgeon can acquire also anatomical surfaces (tibial plateaus, femoral condyles, prosthetic components, etc.). The 3D kinematic evaluations and anatomical data are recorded before and after the joint reconstruction. This new methodology has been used during 11 interventions fulfilled at our institute. We compare the PROM results with literature, and we also analyzed the interoperator repeatability in the execution of the tests (3 repetitions performed by a senior surgeon).

Results: The kinematic analysis of the PROM showed that there were no significant differences between per-operative and post-operative in all UKA cases. In the 2 TKR cases internal-external (IE) rotations appeared reduced after the implant, but further data are necessary to have a statistical evidence. The extension was improved both in UKA and TKA. The VV laxity at 0 ° was significantly reduced (p < 0.001), while at 30 ° stayed constant (p = 0.010). In all the TKR cases the evaluation of contact areas between femoral and tibial components showed normal pattern, and in UKA the contacts remain inside the prosthesis areas. Measured kinematic parameters (knee rotations, screw-home mechanism and alignment) were comparable with literature and manual estimation at surgical time.

Conclusions: The proposed protocol optimizes surgical times and minimizes invasiveness. The preliminary results showed that the system is able to quantify new kinematic parameters during intraoperative evaluations, provides data about alignments, gaps, stability and 3D motions of the individual knee and therefore can allow an accurate and real-time estimation of the passive knee function. Moreover the new 3D anatomical and kinematic data can improve the biomechanical understanding of the pathological and prosthetic knees.