New models of care and multidimensional solutions for oncological patients in the post-acute SARS-COV-2 period: a "Second Phase" also for cancer patients.

In Italy, SARS-CoV-2 outbreak registered a high transmission and disease rates. During the acute phase, oncologists provided to re-organize services and prioritize treatments, in order to limit viral spread and to protect cancer patients. The progressive reduction of the number of infections has prompted Italian government to gradually loosen the national confinement measures and to start the "Second phase" of measures to contain the pandemic. The issue on how to organize cancer care during this post-acute SARS-CoV-2 phase appears crucial and a reassessment of healthcare services is needed requiring new models of care for oncological patients. In order to address major challenges in cancer setting during post-acute SARS-CoV-2 phase, this work offers multidimensional solutions aimed to provide a new way to take care of cancer patients.

Advanced microscopy analysis of the micro-nanoscale architecture of human menisci.

The complex inhomogeneous architecture of the human meniscal tissue at the micro and nano scale in the absence of artefacts introduced by sample treatments has not yet been fully revealed. The knowledge of the internal structure organization is essential to understand the mechanical functionality of the meniscus and its relationship with the tissue's complex structure. In this work, we investigated human meniscal tissue structure using up-to-date non-invasive imaging techniques, based on multiphoton fluorescence and quantitative second harmonic generation microscopy complemented with Environmental Scanning Electron Microscopy measurements. Observations on 50 meniscal samples extracted from 6 human menisci (3 lateral and 3 medial) revealed fundamental features of structural morphology and allowed us to quantitatively describe the 3D organisation of elastin and collagen fibres bundles. 3D regular waves of collagen bundles are arranged in "honeycomb-like" cells that are comprised of pores surrounded by the collagen and elastin network at the micro-scale. This type of arrangement propagates from macro to the nanoscale.

Monitoring Caco-2 to enterocyte-like cells differentiation by means of electric impedance analysis on printed sensors.

BACKGROUND: Colorectal adenocarcinoma cells (Caco-2) are a widely used model of intestinal barrier to study cancer development, toxicological assessments, absorption and metabolism in food science or drug discovery. Caco-2 spontaneously differentiate into a monolayer expressing several specific characteristics, typically showed by mature enterocytes. For in vitro experiments, it is crucial to identify non-invasive and non-destructive techniques able to evaluate the integrity and differentiation of the cells monolayer. Thus, we aimed to assess these properties by analyzing electrical impedance measurements. METHODS: Caco-2 cells were differentiated for 21 days. The monolayer integrity and differentiation were primarily evaluated by means of morphological, biochemical and molecular data. Impedance measurements in a range of frequencies from 400 Hz to 50 kHz were performed using a dedicated set up, including customized Aerosol Jet Printed carbon-based sensors. RESULTS: The trends of RI observed at three different frequencies were able to describe cell growth and differentiation. In order to evaluate which frequencies better correlate with cell differentiation, Principal Component Analysis have been employed and the concordance analysis between RI magnitude and morphological, biochemical and molecular data, highlighted 40 kHz as the optimal frequency to assess Caco-2 cells differentiation process. CONCLUSION: We demonstrated the feasibility and reliability of applying impedance-based measurements not only to provide information about the monolayer status, but also for cell differentiation monitoring. GENERAL SIGNIFICANCE: This study underlined the possibility to use a dedicated sensor to assess the integrity and differentiation of Caco-2 monolayer, as a reliable non-destructive alternative to conventional approaches.

How cartilage status can be related to joint loads in anterior cruciate ligament reconstruction: a preliminary analysis including MRI t2 mapping and joint biomechanics.

The knee is the largest and most complex joint in the human body. Traumatic events, such as anterior cruciate ligament (ACL) tear, can lead to an alteration of joint tissues homeostasis. Literature reports an evident correlation between abnormal joint biomechanics and the status of articular tissues. These alterations, due to a sub-optimal ACL reconstruction, may result in an increasing risk of developing degenerative pathologies, such as osteoarthritis. Thus, the identification of the optimal surgical technique is a highly demanding issue in ACL reconstruction. The aim of this study was to analyze the correlation between joint cartilage conditions and knee biomechanics in ACL reconstructions, by integrating MRI T2 mapping investigations, radiostereophotogrammetry-based gait analysis and subject-specific musculoskeletal modelling.

Effects of working gas pressure on zirconium dioxide thin film prepared by pulsed plasma deposition: roughness, wettability, friction and wear characteristics.

In joint arthroplasty one of the main issues related to the failure of prosthetic implants is due to the wear of the ultra-high molecular weight polyethylene (UHMWPE) component. Surface treatments and coatings have been recognized as enhancing methods, able to improve the tribological properties of the implants. Therefore, the main objective of this work was to investigate the possibility to fabricate yttria-stabilized zirconia (YSZ) coatings on a metal (AISI 316-L) substrate by means of Pulsed Electron Deposition, in order to improve the tribological behavior of the polymer-metal coupling, by reducing the initial wear of the UHMWPE component. In order to optimize the coating characteristics, the effects of working gas pressure on both its morphological and tribological properties were analyzed. Morphological characterization of the films was evaluated by Atomic Force Microscopy (AFM). Coating wettability was also estimated by contact angle (CA) measurement. Tribological performance (coupling friction and wear of UHMWPE) was evaluated by using a ball-on-disc tribometer during highly-stressing tests in dry and lubricated (i.e. NaCl and serum) conditions; friction and wear were specifically evaluated at the initial sliding distances - to highlight the main effect of coating morphology - and after 100m - where the influence of the intrinsic materials properties prevails. AFM analysis highlighted that the working pressure heavily affected the morphological characteristics of the realized films. The wettability of the coating at the highest and lowest deposition pressures (CA ~ 60°, closed to substrate value) decreased for intermediate pressures, reaching a maximum CA of ~ 90°. Regarding tribological tests, a strong correlation was found in the initial steps between friction coefficient and wettability, which decreased as the distance increased. Concerning UHMWPE wear associated to coated counterpart, at 100m a reduction rate of about 7% in dry, 12% in NaCl and 5% in presence of serum was obtained compared to the uncoated counterpart. Differently from what highlighted for friction, no correlation was found between wear rate and morphological parameters. These findings, in agreement with literature, underlined the effect of the deposition pressure on the morphological properties, but suggested that physical characteristics are influenced too. Further research on the deposition process will be required in order to improve the tribological performance of the coating at long distances, addressing - above all - orthopedic applications.

Kinematics of ACL and anterolateral ligament. Part II: anterolateral and anterior cruciate ligament reconstruction.

PURPOSE: To quantify the influence of Single-Bundle with Lateral Plasty and Double-Bundle reconstruction on static and dynamic laxity in combined ACL- and ALL-deficient knees. METHODS: The study included 10 fresh-frozen human knees. The joints were analyzed in the following conditions: ACL + ALL resection, Single-Bundle with Lateral Plasty (SBLP) reconstruction, Double-Bundle (DB) reconstruction. Testing parameters were: anterior displacement at 30° and 90° of flexion (AP30, AP90) applying a manual maximum load; internal rotation at 30° and 90° of flexion (INT30, INT90) applying a 5 Nm torque and acceleration and internal rotation Pivot-Shift (PS) test. Kinematics was acquired by a navigation system. Paired Student's t test was conducted to assess statistical difference (P < 0.05). RESULTS: At both 30° and 90° of knee flexion, both SBLP and DB surgical techniques showed a significant reduction (P < 0.01) of anterior-posterior tibial displacement compared to the resection of ACL + ALL. At 30° on knee flexion it is the SBLP that allows the greatest reduction of internal rotational laxity when compared to DB reconstruction. Concerning the PS test, only SBPL procedure had a significant laxity decrease considering the acceleration reached by the joint when compared with the ACL + ALL state (P < 0.01). CONCLUSION: Clinical relevance of this study is that the internal rotation and PS test were more efficiently controlled by the SBLP technique than by the DB one at both 30° and 90° of flexion in case of ACL + ALL lesions.

Evaluation of the sealing function of the acetabular labrum: an in vitro biomechanical study.

PURPOSE: To quantitatively evaluate the biomechanical sealing function of an intact labrum and the effect of labral-chondral separation, cerclage suture labral repair, vertical mattress suture repair and partial labrectomy on distraction load and hip joint centre (HJC) displacement. METHODS: Eight fresh-frozen cadaveric hips were tested using a navigation system for intra-operative kinematic analysis. A six-axis load cell was used to measure the manually applied force when performing the tests: hip pivoting movement and distraction. The HJC displacement that occurred during the distraction test has been evaluated in correspondence of seven different values of applied force. During the pivoting motion, the maximum value of HJC displacement was evaluated. Five different conditions were tested: labrum intact, labral-chondral separation, vertical mattress suture repair, cerclage suture repair, and partial labrectomy. RESULTS: With regard to HJC displacement using at fixed value of force, the paired sample t test underscored the statistically significant differences (p < 0.05) for each of the five tested conditions among themselves. Only the comparison of intact versus labral-chondral separation was not significantly different. During pivoting motion, a statistically significantly greater displacement was identified after labrectomy when compared with the cerclage suture repair (p = 0.03) and vertical mattress repair (p < 0.01) in medial-lateral direction. Along proximal-distal direction, a significant lower displacement after labrectomy was identified when compared to the cerclage suture repair (p = 0.03). Performing the pivoting motion at the extreme ranges of motion demonstrated a higher value of displacement after labrectomy when compared with all the previously tested conditions. CONCLUSIONS: These results suggest that labral repair is important in the function of the hip and that the vertical mattress suture technique may be better than the cerclage suture repair.

Kinematics of ACL and anterolateral ligament. Part I: Combined lesion.

PURPOSE: To quantify the influence of ALL lesions on static and dynamic laxity in ACL-deficient knee. METHODS: The study was performed in 10 fresh-frozen knees. The joints were analysed in the following conditions: intact, ACL resection and ACL + ALL resection. Testing parameters were defined as: anterior displacement at 30° and 90° of flexion (AP30, AP90) applying a manual-maximum load; internal rotation at 30° and 90° of flexion (INT30, INT90) applying a 5 N m torque and internal rotation and acceleration during manual pivot-shift (PS) test. Kinematics was acquired by a navigation system; a testing rig and a torquemeter were used to control the limb position and the applied torque. Paired Student's t test was conducted to assess statistical difference, and significance was set at P < 0.05. RESULTS: The ALL resection determined a significant increase in terms of internal rotation (INT30 P = 0.02, INT90 P = 0.03), while AP30 (P n.s) and AP90 (P n.s) were not affected. ALL resection produced a significant increase in terms of acceleration during PS test (P < 0.01), but no significant change in PS internal rotation was observed. CONCLUSION: The ALL plays a significant role in controlling static internal rotation and acceleration during PS test. On the other hand, ALL resection did not produce any significant change in terms of anterior displacement. A trend was seen for the internal rotation during the pivot-shift test to increase after ALL resection was higher when compared to the intact and isolated ACL lesion states; however, the differences were not significant. The results highlight the clinical relevance of this structure that should be assessed before an ACL reconstruction in order to avoid residual laxity.

Technical variables of ACL surgical reconstruction: effect on post-operative static laxity and clinical implication.

PURPOSE: The hypothesis was that an alteration of different surgical variables of ACL reconstruction would produce significant changes in post-operative static laxity of knee joint. METHODS: Joint laxity was acquired by a surgical navigation system for 17 patients just after graft fixation during single-bundle reconstruction with extra-articular lateral tenodesis. The analysed laxity parameters were: internal/external rotation at 30° (IE30) and 90° (IE90) of flexion, varus/valgus rotation at 0° (VV0) and 30° (VV30) of flexion and anterior/posterior displacement at 30° (AP30) and 90° (AP90) of flexion. As surgical variables, the angles between the tibial tunnel and the three planes were defined as well as the lengths of the tunnel and the relationship between native footprints and tunnels. The same analysis was performed for the femoral side. All surgical variables were combined in a multivariate analysis to assess for predictive factors between them and post-operative laxities values. To quantify the performance of each multivariate model, the correlation ratio (η 2) and the corresponding P value (*P < 0.050) have been evaluated. RESULTS: Multivariate analysis underlined statistically significant models for the estimation of: AP30 (η 2 = 0.987; P = 0.014), IE30 (η 2 = 0.995; P = 0.005), IE90 (η 2 = 0.568; P = 0.010), VV0 (η 2 = 0.932; P = 0.003). The parameters that greatly affected the identified models were the orientation of the tibial tunnel with respect to the three anatomical planes. The estimation of AP30, IE30 and IE90 got lower value as the orientation of the tibial tunnel with respect to transverse plane decreases. Considering the orientation to sagittal ([Formula: see text]) and coronal ([Formula: see text]) plane, we found that their reduction provoked a decrease in the estimation of AP30, IE30 and IE90 (except [Formula: see text] that did not appear in the estimation of AP30). The estimation of VV0 got an increase of [Formula: see text], and [Formula: see text] which led to a laxity reduction. CONCLUSION: The main finding of the present in vivo study was the possibility to determine significant effects on post-operative static laxity level of different surgical variables of ACL reconstruction. In particular, the present study defined the conditions that minimize the different aspects of post-operative laxity at time-zero after surgery.

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.

Surface morphology, tribological properties and in vitro biocompatibility of nanostructured zirconia thin films.

Deposition of nanostructured and low-wear zirconia (ZrO2) thin films on the metallic component of a total joint implant is envisaged to reduce wear of the soft ultra-high molecular weight polyethylene (UHMWPE) counterpart. In this work, morphological surface features, wear resistance and in vitro-biocompatibility of zirconia thin films deposited by the novel Pulsed Plasma Deposition (PPD) method have been investigated. Film thickness, roughness and wettability were found to be strongly dependent on deposition gas pressure. Interestingly, wear rate of UHMWPE disks coupled to zirconia-coated titanium spheres was only poorly correlated to the contact angle values, while film roughness and thickness seemed not to affect it. Furthermore, wear of UHMWPE, when coupled with zirconia coated-titanium spheres, significantly decreased with respect to uncoated spheres under dry or NaCl-lubricated conditions; besides, when using bovine serum, similar results were obtained for coated and uncoated spheres. Finally, suitable mesenchymal stem and osteoblast cells adhesion, proliferation and viability were observed, suggesting good biocompatibility of the nanostructured zirconia films. Taken together, the results shown in this work indicate that zirconia thin films deposited by the PPD method deserve further investigations as low-wear materials for biomedical applications such as total joint replacement.

Tribological characterization of zirconia coatings deposited on Ti6Al4V components for orthopedic applications.

One of the most important issues leading to the failure of total joint arthroplasty is related to the wear of the plastic components, which are generally made of ultra high molecular weight polyethylene (UHMWPE). Therefore, the reduction of joint wear represents one of the main challenges the research in orthopedics is called to address nowadays. Surface treatments and coatings have been recognized as innovative methods to improve tribological properties, also in the orthopedic field. This work investigated the possibility to realize hard ceramic coatings on the metal component of a prosthesis, by means of Pulsed Plasma Deposition, in order to reduce friction and wear in the standard coupling against UHMWPE. Ti6Al4V substrates were coated with a 2 µm thick yttria-stabilized zirconia (YSZ) layer. The mechanical properties of the YSZ coatings were assessed by nanoindentation tests performed on flat Ti6Al4V substrates. Tribological performance was evaluated using a ball-on-disk tribometer in dry and lubricated (i.e. with fetal bovine serum) highly-stressing conditions, up to an overall distance of 10 km. Tribology was characterized in terms of coefficient of friction (CoF) and wear rate of the UHMWPE disk. After testing, specimens were analyzed through optical microscopy and SEM images, in order to check the wear degradation mechanisms. Progressive loading scratch tests were also performed in dry and wet conditions to determine the effects of the environment on the adhesion of the coating. Our results supported the beneficial effect of YSZ coating on metal components. In particular, the proposed solution significantly reduced UHMWPE wear rate and friction. At 10 km of sliding distance, a wear rate reduction of about 18% in dry configuration and of 4% in presence of serum, was obtained by the coated group compared to the uncoated group. As far as friction in dry condition is concerned, the coating allowed to maintain low CoF values until the end of the tests, with an overall difference of about 40% compared to the uncoated balls. In wet conditions, the friction values were found to be comparable between coated and uncoated materials, mainly due to a premature delamination of the coating. Scratch tests in wet showed in fact a reduction of the critical load required to a complete delamination due to a formation of blister, although no change or damage occurred at the coating during the soaking period. Although conditions of high values of contact pressure were considered, further analyses are however required to fully understand the behavior of YSZ coatings in wet environment and additional research on the deposition process will be mandatory in order to improve the coating tribological performance at long distances addressing orthopedic applications.

Optimizing thickness of ceramic coatings on plastic components for orthopedic applications: A finite element analysis.

Realizing hard ceramic coatings on the plastic component of a joint prosthesis can be strategic for the mechanical preservation of the whole implant and to extend its lifetime. Recently, thanks to the Plasma Pulsed Deposition (PPD) method, zirconia coatings on ultra-high molecular weight polyethylene (UHMWPE) substrates resulted in a feasible outcome. Focusing on both the highly specific requirements defined by the biomedical application and the effective possibilities given by the deposition method in the perspectives of technological transfer, it is mandatory to optimize the coating in terms of load bearing capacity. The main goal of this study was to identify through Finite Element Analysis (FEA) the optimal coating thickness that would be able to minimize UHMWPE strain, possible insurgence of cracks within the coating and stresses at coating-substrate interface. Simulations of nanoindentation and microindentation tests were specifically carried out. FEA findings demonstrated that, in general, thickening the zirconia coating strongly reduced the strains in the UHMWPE substrate, although the 1 µm thickness value was identified as critical for the presence of high stresses within the coating and at the interface with the substrate. Therefore, the optimal thickness resulted to be highly dependent on the specific loading condition and final applications.

Two different approaches for novel extracapsular cranial cruciate ligament reconstruction: an in vitro kinematics study.

OBJECTIVE: To analyse the best combination of isometric points with the best kinematic results between two different approaches of TightRope® cranial cruciate ligament reconstruction. MATERIALS AND METHODS: Cranial drawer, cranial tibial thrust, internal/external, range of motion and varus/valgus tests were passively performed in different stifle conditions: cranial cruciate ligament-intact/deficient, after F2-T2/F2-T3 TR reconstruction at 22-44-99 N of tension. Data were acquired by a custom-made navigation system. RESULTS: The cranial drawer test showed recovery of laxity only at 99 N in both approaches. Significant laxity reduction (cranial tibial thrust) was present at only the F2-T2 point. Differences were noted in internal/external and varus/valgus rotation between the cranial cruciate ligament-intact and TightRope® stifles at all of the implant tensions. The range of motion underlined significantly lower laxity values following the F2-T2/F2-T3 reconstruction at all of the evaluated implant tensions. CLINICAL SIGNIFICANCE: The best isometric site was at the F2-T2 point, however significant differences in the amount of laxity between the two techniques were limited to the cranial tibial thrust and internal/external test. The F2-T2 technique was the best consideration for clinical application because it is relatively easy to perform, repeatable and results in good stifle stability with low morbidity and complications.

Do pre-operative knee laxity values influence post-operative ones after anterior cruciate ligament reconstruction?

The objective of this study was to verify whether pre-reconstruction laxity condition effects post-reconstruction outcome. A total of 100 patients who underwent navigated Anterior Cruciate Ligament (ACL) reconstruction were included in the study and knee laxity analysed retrospectively. The knee was assessed in six different laxity tests before and after ACL reconstruction, namely antero-posterior (AP) and internal-external (IE) at 30° and 90°, and varus-valgus (VV) rotations at 0° and 30° of flexion. For each test, the least square (LS) fitting line based on pre-operative-to-post-operative laxity value was calculated. To what degree the post-operative laxity value is explainable by the corresponding pre-operative condition was evaluated by the LS line slope. Post-operatively, for each single patient, the grade of laxity decreased at any evaluated test. The strongest influence of pre-operative-to-post-operative laxity values was found during IE30 and IE90 tests. While AP30 and VV0 tests seem to be those in which the post-reconstruction laxity was barely affected by the pre-surgery condition. The analysis of the global laxity reduction confirms the previous results. Following this hypothesis, our study remarks on the importance of combined lesions to secondary restraints and the importance of fully understanding the residual laxity to optimize the surgical technique.

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.

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.

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.

Can the method of fixation influence the wear behaviour of ZrN coated unicompartmental mobile knee prostheses?

BACKGROUND: Modern unicompartmental knee prostheses represent a valid alternative to total knee replacement. It is known that variations in clinical alignment lead to altered biomechanics and abnormal wear. The aim of this study was to assess the influence, on wear behaviour, of two different cementing interfaces of the femoral components tested on a knee joint wear simulator. METHODS: The wear tests were run in a knee wear simulator at a frequency of 1.1 Hz for 3 million cycles in accordance with ISO 14243-3. Twelve commercial mobile GUR 1020 UHMWPE meniscus specimens articulated in between 12 cobalt-chromium-molybdenum alloy femoral and tibial components covered by a multi-layer of chromium nitride and a final layer of zirconium nitride ceramic coating to prevent ion release from the substrate. Two wear tests were performed: in the first test, each femoral component was cemented into a custom made metallic-block shaped to perfectly host it. In the second test, synthetic composite femurs received the femoral components on the basis of guidelines used in current surgery. FINDINGS: The two cementing interfaces showed a significantly different wear behaviour, quantified as mean weight loss (P<0.001). Scanning electron microscope examinations of new and tested metallic components showed macro- and micro-pores of few microns on both configurations. INTERPRETATION: The wear pattern observed at 3 million cycles showed differences between the two methods of fixation for the meniscus femoral components.