Biplane video X-ray (BVX) – with models segmented from magnetic resonance imaging (MRI) – is used to directly track bones during dynamic activities. Investigating tibiofemoral kinematics helps to understand effects of disease, injury, and possible interventions. Develop a protocol and compare in-vivo kinematics during loaded dynamic activities using BVX and MRI. BVX (60 FPS) was captured whilst three healthy volunteers performed three repeats of lunge, stair ascent and gait. MRI scans were performed (Magnetom 3T Prisma, Siemens). 3D bone models of the tibia and femur were segmented (Simpleware Scan IP, Synopsis). Bone poses were obtained by manually matching bone models to X-rays (DSX Suite, C-Motion Inc.). Mean range of motion (ROM) of the contact points on the medial and lateral tibial plateau were calculated using custom MATLAB code (MathWorks). Results were filtered using an adaptive low pass Butterworth filter (Frequency range: 5-29Hz). Gait and Stair ascent activities from one participant's data showed increased ROM for medial-lateral (ML) translation in the medial compartment but decreased ROM in anterior-posterior (AP) translation when comparing against the same translations on the lateral compartment of the tibial plateau. Lunge activity showed increased ROM for both ML and AP translation in the medial compartment when compared with the lateral compartment. These results highlight the variability in condylar translations between different activities. Understanding healthy in-vivo kinematics across different activities allows the determination of suitable activities to best investigate the kinematic changes due to disease or injury and assess the efficacy of different interventions. Acknowledgements: This research was supported by the Engineering and Physical Sciences Research Council (EPSRC) doctoral training grant (EP/T517951/1)

Numerous papers present in-vivo knee kinematics data following total knee arthroplasty (TKA) from fluoroscopic testing. Comparing data is challenging given the large number of factors that potentially affect the reported kinematics. This paper aims at understanding the effect of following three different factors: implant geometry, performed activity and analysis method. A total of 30 patients who underwent TKA were included in this study. This group was subdivided in three equal groups: each group receiving a different type of posterior stabilized total knee prosthesis. During single-plane fluoroscopic analysis, each patient performed three activities: open chain flexion extension, closed chain squatting and chair-rising. The 2D fluoroscopic data were subsequently converted to 3D implant positions and used to evaluate the tibiofemoral contact points and landmark-based kinematic parameters. Significantly different anteroposterior translations and internal-external rotations were observed between the considered implants. In the lateral compartment, these differences only appeared after post-cam engagement. Comparing the activities, a significant more posterior position was observed for both the medial and lateral compartment in the closed chain activities during mid-flexion. A strong and significant correlation was found between the contact-points and landmarks-based analyses method. However, large individual variations were also observed, yielding a difference of up to 25% in anteroposterior position between both methods. In conclusion, all three evaluated factors significantly affect the obtained tibiofemoral kinematics. The individual implant design significantly affects the anteroposterior tibiofemoral position, internal-external rotation and timing of post-cam engagement. Both kinematics and post-cam engagement additionally depend on the activity investigated, with a more posterior position and associated higher patella lever arm for the closed chain activities. Attention should also be paid to the considered analysis method and associated kinematics definition: analyzing the tibiofemoral contact points potentially yields significantly different results compared to a landmark-based approach

Introduction and Objective. Malunion after trauma can lead to coronal plane malalignment in the lower limb. The mechanical hypothesis suggests that this alters the load distribution in the knee joint and that that this increased load may predispose to compartmental arthritis. This is generally accepted in the orthopaedic community and serves as the basis guiding deformity correction after malunion as well as congenital or insidious onset malalignment. Much of the literature surrounding the contribution of lower limb alignment to arthritis comes from cohort studies of incident osteoarthritis. There has been a causation dilemma perpetuated in a number of studies - suggesting malalignment does not contribute to, but is instead a consequence of, compartmental arthritis. In this investigation the relationship between compartmental (medial or lateral) arthritis and coronal plane malalignment (varus or valgus) in patients with post traumatic unilateral limb deformity was examined. This represents a specific niche cohort of patients in which worsened compartmental knee arthritis after extra-articular injury must rationally be attributed to malalignment. Materials and Methods. The picture archiving system was searched to identify all 1160 long leg x ray films available at a major metropolitan trauma center over a 12-year period. Images were screened for inclusion and exclusion criteria, namely patients >10 years after traumatic long bone fracture without contralateral injury or arthroplasty to give 39 cases. Alignment was measured according to established surgical standards on long leg films by 3 independent reviewers, and arthritis scores Osteoarthritis Research Society International (OARSI) and Kellegren-Lawrence (KL) were recorded independently for each compartment of both knees. Malalignment was defined conservatively as mechanical axis deviation outside of 0–20 mm medial from centre of the knee, to give 27 patients. Comparison of mean compartmental arthritis score was performed for patients with varus and valgus malalignment, using Analysis of Variance and linear regression. Results. In knees with varus malalignment there was a greater mean arthritis score in the medial compartment compared to the contralateral knee, with OARSI scores 5.69 vs 3.86 (0.32, 3.35 95% CI; p<0.05) and KL 2.92 vs 1.92 (0.38, 1.62; p<0.005). There was a similar trend in valgus knees for the lateral compartment OARSI 2.98 vs 1.84 (CI −0.16, 2.42; p=0.1) and KL 1.76 vs 1.31 (CI −0.12, 1.01; p=0.17), but the evidence was not conclusive. OARSI arthritis score was significantly associated with absolute MAD (0.7/10mm MAD, p<0.0005) and Time (0.6/decade, p=0.01) in a linear regression model. Conclusions. Malalignment in the coronal plane is correlated with worsened arthritis scores in the medial compartment for varus deformity and may similarly result in worsened lateral compartment arthritis in valgus knees. These findings support the mechanical hypothesis that arthritis may be related to altered stress distribution at the knee, larger studies may provide further conclusive evidence

A correct ligament loading following TKA surgery is believed to minimize instability and improve patient satisfaction. The evaluation of the ligament stress or strain is however impractical in a surgical setting. Alternatively, tibial trial components containing force sensors have the potential to indirectly assess the ligament loading. These instrumented components quantify the medial and lateral forces in the tibiofemoral joint. Although this method finds clinical application already, the target values for both the force magnitude and medial / lateral force ratio under surgical conditions remain uncertain. A total of eight non-arthritic cadaveric knees have been tested mimicking surgical conditions. Therefore, the specimens are mounted in a custom knee simulator. This simulator allows to test full lower limb specimens, providing kinematic freedom throughout the range of motion. Knee flexion is obtained by lifting the femur (thigh pull). Knee kinematics are simultaneously recorded by means of a navigation system and based on the mechanical axis of the femur and tibia. In addition, the load transferred through the medial and lateral compartment of the knee is monitored. Therefore, a 2.4 mm thick sawing blade is used to machine a slot in the tibia perpendicular to the mechanical axis, at the location of the tibial cut in TKA surgery. A complete disconnection was thereby assured between the tibial plateau and the distal tibia. To fill the created gap, custom 3D printed shims were inserted. Through their specific geometry, these shims create a load deviation between two Tekscan pressure pads on the medial and lateral side. Following the insertion of the shims, the knee was closed before performing the kinematic and kinetic tests. Seven specimens showed a limited varus throughout the range of motion (ranging from 1° to 7° varus). The other knee was in valgus (4° valgus). Amongst varus knees, the results were very consistent, indicating high loads in full extension. Subsequently, the loads decrease as the knee flexes and eventually vanishes on the lateral side. This leads to consistently high compartmental load ratios (medial load / total load) in flexion. In full extension the screw-home mechanism results in increased loads, both medially and laterally. Upon flexion, the lateral loads disappear. This is attributed to slackening of the lateral collateral ligament, in turn linked to the femoral rollback and slope of the lateral compartment. The isometry of the medial collateral ligament contributes on the other hand to the near-constant load in the medial compartment. The above particularly applies for varus knees. The single valgus knee tested indicated a higher load transmission by the lateral compartment, potentially attributed to a contracture of the lateral structures. With respect to TKA surgery, these findings are particularly relevant when considering anatomically designed implants. For those implants, this study concludes that a tighter medial compartment reflects that of healthy varus knees. Be aware however that in full extension, higher and up to equal loads can be acceptable for the medial and lateral compartment

Trochlear dysplasia is a specific morphotype of the knee, characterized by but not limited to a specific anatomy of the trochlea. The notch, posterior femur and tibial plateau also seem to be involved. In our study we conducted a semi-automated landmark-based 3D analysis on the distal femur, tibial plateau and patella. The knee morphology of a study population (n=20), diagnosed with trochlear dysplasia and a history of recurrent patellar dislocation was compared to a gender- and age-matched control group (n=20). The arthro-CT scan-based 3D-models were isotropically scaled and landmark-based reference planes were created for quantification of the morphometry. Statistical analysis was performed to detect shape differences between the femur, tibia and patella as individual bone models (Mann-Whitney U test) and to detect differences in size agreement between femur and tibia (Pearson's correlation test). The size of the femur did not differ significantly between the two groups, but the maximum size difference (scaling factor) over all cases was 35%. Significant differences were observed in the trochlear dysplasia (TD) versus control group for all conventional parameters. Morphometrical measurements showed also significant differences in the three directions (anteroposterior (AP), mediolateral (ML), proximodistal (PD)) for the distal femur, tibia and patella. Correlation tests between the width of the distal femur and the tibial plateau revealed that TD knees show less agreement between femur and tibia than the control knees; this was observed for the overall width (TD: r=0.172; p=0.494 - control group: r=0.636; p=0.003) and the medial compartment (TD: r=0.164; p=0.516 - control group: r=0.679; p=0.001), but not for the lateral compartment (TD: r=0.512; p=0.029 - control: r=0.683; p=0.001). In both groups the intercondylar eminence width was strongly correlated with the notch width (TD: r=0.791; p=0.001 - control: r=0.643; p=0.002). The morphology of the trochleodysplastic knee differs significantly from the normal knee by means of an increased ratio of AP/ML width for both femur and tibia, a smaller femoral notch and a lack of correspondence in mediolateral width between the femur and tibia. More specifically, the medial femoral condyle shows no correlation with the medial tibial plateau

Background. Some models of knee osteoarthritis (OA) suggest that the properties of knee tissues are adapted in healthy joints, and that OA development is due to a breakdown in the equilibrium among tissue properties. Cartilage thickness and bone density are particularly important properties in this regard because both are related to the mechanical environment. This study tested the hypothesis that locations of thickest cartilage are associated with locations where bone density is the highest in non-OA tibias. Method. CT-arthrography was performed on six non-OA subjects (2 males; 58± 15 years old). Images were segmented to build 3D models of the bone and cartilage structures. Maps of cartilage thickness were calculated for the medial and lateral subchondral bone areas by measuring the distance between bone and cartilage structures. Bone density maps were calculated based on the intensity of the CT-arthrography signal in the first 3mm of bone. The location of thickest cartilage and most dense bone were measured in the medial and lateral compartments. These locations were then normalised, and paired t-tests and linear regressions were performed to compare the thickness and density locations. Results. In the medial compartment, the location of highest bone density was significantly more medial than the location of thickest cartilage (p=0.03). Additionally, the location of both features were highly correlated along the anterior-posterior direction (R⁁2=0.92). In the lateral compartment, the location of highest bone density was correlated with the location of thickest cartilage along the medial-lateral direction (R⁁2 =0.64). Conclusion. This study showed that the location of highest bone density is correlated with the location of thickest cartilage in non-OA tibias, thus supporting the idea that knee tissues are adapted in healthy knees

Background. Osteoarthritis (OA) is a degenerative, chronic disease of the articular cartilage that affects more than 150 million people [1]. In the knee, OA can begin as either isolated medial OA or isolated lateral OA. Previous research [2,3] shows medial OA and lateral OA have characteristic cartilage lesion locations and progression patterns as well as flexion angles associated with lesion development, indicating strong involvement of mechanical factors in disease initiation. Therefore, it is important to investigate these mechanical factors. Previous studies combined data sets (geometry, motion, load) from separate sources. The aim of the current work was to use a consistent multi-modal approach. Method. A finite element (FE) model of a healthy knee in full extension was created using magnetic resonance imaging (MRI) and motion analysis data from the same subject (female, 24 yrs). MRI data was obtained using a 3T MRI scanner (Philips Medical Systems/Achieva). Surface geometries of the tibia, femur, and associated cartilage were then semi-automatically segmented and processed (Mimics 12.5; Geomagic Studio 11; SolidWorks 2009). Motion data was collected at 100 Hz (Vicon 612) during level walking and subsequently applied to a lower limb model (AnyBody Version 3.0) to calculate muscle forces. Both sets of data were then combined to create a subject-specific FE model (ANSYS 11.0) which was solved to determine relative contact areas, pressures, and deformations in the medial and lateral tibiofemoral compartments. Results. Contact area in the medial tibiofemoral compartment was approximately twice as large as in the lateral compartment. Medially, tibiofemoral contact occurred anteriorly and centrally; maximum cartilage deformation also occurred in these regions. Laterally, contact occurred centrally in both the anterior-posterior and medial-lateral directions with maximum deformation gradients occurring anteriorly and posteriorly. Overall, cartilage deformation was larger in the medial (1.73 mm) than in the lateral compartment (1.50 mm). Contact pressure was also larger medially (111 kN) than laterally (83 kN) with equal pressure gradients extending in all directions from the centre of medial tibiofemoral contact but concentrated posterior to the lateral compartment's contact area. Discussion. The current results match previous literature. Contact areas for tibiofemoral cartilage at full extension correlate well with lesion locations described in medial OA, commonly associated with small flexion angles. Concentrated pressure gradient locations also agree with cartilage lesion progression directions cited in the literature. Future work will involve creating more subject-specific models and including higher flexion angles. J Boyd was funded by the Clarendon Fund, National Science Foundation and Whitaker International Fellowship

Physiological kinematics is very difficult to restore after total knee arthroplasty (TKA). A new model of medial stabilized (MS) TKA prosthesis has a high spherical congruence of the internal compartment, which guarantees anteroposterior (AP) stability associated with a flat surface of the insert in the lateral compartment, that allows a greater AP translation of the external condyle during knee flexion. The aim of our study is to evaluate, by dynamic radiostereometric analysis (RSA), the knee in vivo kinematics after the implantation of a MS prosthesis during sit to stand and lunge movements. To describe the in vivo kinematics of the knee after MS Fixed Bearing TKA (GMK Sphere (TM) Medacta International AG, Castel San Pietro, Switzerland) using Model Based dynamic RSA. A cohort of 18 patients (72.1 ± 7.4 years old) was evaluated by dynamic RSA 9 months after TKA. The kinematic evaluation was carried out using the dynamic RSA tool (BI-STAND DRX 2), developed at our Institute, during the execution of sit to stand and lunge movements. The kinematic data were processed using the Grood and Suntay decomposition and the Low Point method. The patients performed two motor tasks: a sit-to-stand and a lunge. Data were related to the flexion angle versus internal-external, varus-valgus rotations and antero-posterior translations of the femur with respect to the tibia. During the sit to stand, the kinematic analysis showed the presence of a medial pivot, with a significantly greater (p=0.0216) anterior translation of the lateral condyle (3.9 ± 0.8 mm) than the medial one (1.6 ± 0.8 mm) associated with a femoral internal rotation (4.5 ± 0.9 deg). During the lunge, in the flexion phase, the lateral condyle showed a larger posterior translation than the medial one (6.2 ± 0.8 mm vs 5.3 ± 0.8 mm) associated with a femoral external rotation (3.1 ± 0.9 deg). In the extension phase, there is a larger anterior translation of the lateral condyle than the medial one (5.8 ± 0.8 mm vs 4.6 ± 0.8 mm) associated with femoral internal rotation (6.2 ± 0.9 deg). Analysing individual kinematics, we also found a negative correlation between clinical scores and VV laxity during sit to stand (R= −0.61) and that the higher femoral extra-rotation, the poorer clinical scores (R= 0.65). The finding of outliers in the VV and IE rotations analysis highlights the importance of a correct soft tissue balancing in order to allow the prosthetic design to manifest its innovative features

Knee ligament injury is one of the most frequent sport injuries and ligament reconstruction has been used to restore the structural stability of the joint. Cycling exercises have been shown to be safe for anterior cruciate ligament (ACL) reconstruction and are thus often prescribed in the rehabilitation of patients after ligament reconstruction. However, whether it is safe for posterior cruciate ligament (PCL) reconstruction remains unclear. Considering the structural roles of the PCL, backward cycling may be more suitable for rehabilitation in PCL reconstruction. However, no study has documented the differences in the effects on the knee kinematics between forward and backward pedaling. Therefore, the current study aimed to measure and compare the arthrokinematics of the tibiofemoral joint between forward and backward pedaling using a biplane fluoroscope-to- computed tomography (CT) registration method. Eight healthy young adults participated in the current study with informed written consent. Each subject performed forward and backward pedaling with an average resistance of 20 Nm, while the motion of the left knee was monitored simultaneously by a biplane fluoroscope (ALLURA XPER FD, Philips) at 30 fps and a 14-camera stereophotogrammetry system (Vicon, OMG, UK) at 120 Hz. Before the motion experiment, the knee was CT and magnetic resonance scanned, which enabled the reconstruction of the bones and articular cartilage. The bone models were registered to the fluoroscopic images using a volumetric model-based fluoroscopy-to-CT registration method, giving the 3-D poses of the bones. The bone poses were then used to calculate the rigid-body kinematics of the joint and the arthrokinematics of the articular cartilage. In this study, the top dead center of the crank was defined as 0° so forward pedaling sequence would begin from 0° to 360°. Compared with forward pedaling, for crank angles from 0° to 180°, backward pedaling showed significantly more tibial external rotation. Moreover, both the joint center and contact positions in the lateral compartment were more anterior while the contact positions in the medial compartment was more posterior, during backward pedaling. For crank angles from 180° to 360°, the above-observed phenomena were generally reversed, except for the anterior-posterior component of the contact positions in the medial compartment. Forward and backward pedaling displayed significant differences in the internal/external rotations while the rotations in the sagittal and frontal planes were similar. Compared with forward cycling, the greater tibial external rotation for crank angles from 0° to 180° during backward pedaling appeared to be the main reason for the more anterior contact positions in the lateral compartment and more posterior contact positions in the medial compartment. Even though knee angular motions during forward and backward pedaling were largely similar in the sagittal and frontal planes, significant differences existed in the other components with different contact patterns. The current results suggest that different pedaling direction may be used in rehabilitation programs for better treatment outcome in future clinical applications

Summary. In a rabbit model of early osteoarthritis, structural changes in femoral condyle cartilage were severer in the lateral compartment and preceded alterations in the underlying bone. In the medial compartment, altered bone properties occurred together with structural changes in cartilage. Introduction. Early osteoarthritic changes in cartilage have been previously studied through anterior cruciate ligament transection (ACLT) in rabbits. However, parallel changes in the structure of subchondral and trabecular bone at 4 weeks after ACLT are not known. Methods. Skeletally mature 14-month old New Zealand white rabbits (n=8) underwent ACLT in the left knee, while right knees were used as controls (CTRL). Femoral condyles (FCs) were harvested at 4 weeks after ACLT. INDENTATION TESTING. Stepwise stress-relaxation tests were performed on medial and lateral FC cartilage (100%/s ramp rate, 3×5% step, 15 min relaxation time). Sinusoidal loading was then applied (amplitude 4% of thickness, 1Hz, 4 cycles). Equilibrium (Eeq) and dynamic (Ed) moduli were derived from stress-relaxation and sinusoidal tests, respectively. STRUCTURAL ANALYSIS OF CARTILAGE. Polarised light microscopy (PLM) and digital densitometry (DD) were used to analyze the collagen orientation angle (COA) and proteoglycan content in the cartilage samples. STRUCTURAL ANALYSIS OF BONE. Distal compartments of FCs were scanned using a high-resolution µCT scanner (Skyscan 1172, Belgium) with an isotropic voxel size of 25 µm. µCT data were imported into Mimics (Materialise, Belgium) for segmentation. 2×2×4 mm. 3. volumes of interest (VOIs) were placed in weight-bearing regions of medial and lateral FCs. Subchondral bone plate thickness (Pt.Th), trabecular volume fraction (BV/TV), trabecular thickness (Tb.Th), structural model index (SMI) and trabecular separation (Tb.Sp) were calculated using the CTAnalyzer software (Skyscan) from the VOIs. STATISTICAL TESTS. Mixed linear model for cartilage parameters and Wilcoxon signed-rank test for bone parameters were used to compare ACLT and CTRL groups (p < 0.05). Results. In both lateral and medial FC compartments, Eeq was significantly smaller in ACLT than in CTRL cartilage. In the medial compartment, also Ed was significantly smaller in ACLT than in CTRL cartilage. As a result of ACLT, significant alterations in the COA extended deeper into cartilage in the lateral than medial compartment, while proteoglycan content was reduced significantly and similarly in both lateral and medial FC cartilages. After ACLT, Pt.Th was significantly reduced in the medial compartment, while no changes were observed in the lateral compartment. Furthermore, only in the medial compartment, both BV/TV and Tb.Th were significantly smaller in the ACLT compared to the CTRL group. Discussion. The study showed that disruption of the collagen architecture in the ACLT joint cartilage extended into the middle zone only in the lateral FC compartment. Instead, thinning of the subchondral bone plate combined with resorption of trabecular bone was observed only in the medial FC compartment. The former finding reflects early osteoarthritic changes, while the latter finding may be indicative of a diminished loading in the medial FC compartment, as caused by ACLT

Osteoarthritis (OA) is a common, debilitating joint disease involving degeneration of cartilage and bone. It has been suggested that subtle changes in the molecular structure of subchondral bone may precede cartilaginous changes in the osteoarthritic joint. To explore these changes Raman spectroscopy was employed as a diagnostic tool. Raman spectroscopy measures inelastic scattered laser light produced when photons interact with chemical materials. Resultant changes in wavelength form spectra relative to the chemical composition of the given sample: with bone this includes the mineral and matrix components, unlike conventional X-rays. The aim of our study is to explore the hypothesis: Changes in matrix composition of osteoarthritic subchondral bone can be detected with Raman spectroscopy. pQCT and Raman spectroscopy were employed to determine the bone mineral density (BMD) and bone quality, respectively. Ten medial compartment OA and five control (non-OA) tibial plateaus were interrogated and analysis performed to compare OA to control, and medial to lateral compartments. The subchondral bone of the medial OA compartments had higher BMD (p=0.05) and thickness compared to lateral and control samples. Spectral analysis revealed there is no difference between the medial and lateral compartments within either cohort. However, there is a statistically significant (p=0.02) spectral difference between the OA and control specimens. The detection of bone matrix changes in osteoarthritis using Raman spectroscopy contributes to the understanding of the biochemical signature of subchondral bone across diseased and control tibial plateaus. This technique has potential to shed light on the role of bone in osteoarthritis

Study of failed Oxford medial unicompartmental knee replacements at the Royal Cornwall Hospital. Objective. we set up a retrospective study to identify the various reasons for failure of oxford medial unicompartmental knee replacements and to assess their outcome following revision. Materials and Method. Over 5 years (2006- 2010) we identified 26 failed unicompartmental knee replacements, which were revised at the Royal Cornwall hospital. We retrospectively analysed the data to include pre-operative and post-operative Oxford score, range of movement, patient satisfaction and the type of implant used. Results. There were 9 males and 17 females in our series with an average age of 65 years (49 to 80). The average follow up was 2.6 years (1 - 4.6 years). The pre-revision Oxford score was 21.3 (12 to 35), which improved to 41.7 (18 to 47) following surgery. Almost all patients benefited with increase in the range of movement. The implants were revised at an average duration of 4 years and 8 months (1 to 17 yrs) following the index operation. The commonest cause of failure was progression of arthritis in the lateral compartment 50 % (13/26), revision for unexplained pain 23 % (6/26) and aseptic loosening 23 % (6/26). There was one case of sepsis 4 % (1/26). We did not come across dislocation of the bearing. The implants were revised using primary or complex primary knee systems. The infected knee was revised using a two-stage technique. Conclusion. Unicompartmental knee replacement is a successful procedure for treating isolated medial compartment arthritis. Commonest indication for revision in our study was progression of arthritis in the lateral compartment. Revision is relatively easy and results of revision are good with high patient satisfaction. Our results are comparable to published data from larger centres

Focal cartilage defects (FCDs) found in medial and lateral compartments of the knee are accompanied with patient-reported pain and loss of joint function. There is a deficit of evidence to explain why they occur. We hypothesise that aberrant knee joint loading may be partially responsible for FCD pathology, therefore this study aims to use 3-dimensional motion capture (MoCap) analysis methods to investigate differences in gait biomechanics of subjects with symptomatic FCDs. 11 subjects with Outerbridge grade II FCDs of the tibiofemoral joint (5 medial compartment, 6 lateral compartment) and 10 non-pathological controls underwent level-gait MoCap analysis using an infra-red camera (Qualisys) and force-plate (Bertec) passive marker system. 6-degree of freedom models were generated and used to calculate spatio-temporal measures, and frontal and sagittal plane knee, hip and ankle rotation and moment waveforms (Visual 3D). Principle component analysis (PCA) was used to score subjects based on common waveform features, and PC scores were tested for differences using Mann-Whitney tests (SPSS). No group differences were found in BMI, age or spatio-temporal measures. Medial-knee FCD subjects experienced higher (p=0.05) overall knee adduction moments (KAMs) compared to controls. Conversely, lateral-knee FCD subjects found lower (p=0.031) overall KAMs. Knee flexion and extension moments (KFMs/KEMs) were relatively reduced (p=0.013), but only in medial FCD subjects. This was accompanied by a significantly (p=0.019) higher knee flexion angle (KFA) during late-stance. KAMs have been shown to be predictive of frontal plane joint contact forces, and therefore our results may be reflective of FCD subjects overloading their respective diseased knee condyles. The differences in knee sagittal plane knee moments (KFMs/KEMs) and angles (KFA) seen in medial FCD subjects are suggestive of gait adaptations to pain. Overall these results suggest treatments of FCDs should consider offloading the respective affected condyle for better surgical outcomes

Compartment syndrome of the foot requires urgent surgical treatment. Currently, there is still no agreement on the number and location of the myofascial compartments of the foot. The aim of this cadaver study was to provide an anatomical basis for surgical decompression in the event of compartment syndrome. We found that there were three tough vertical fascial septae that extended from the hindfoot to the midfoot on the plantar aspect of the foot. These septae separated the posterior half of the foot into three compartments. The medial compartment containing the abductor hallucis was surrounded medially by skin and subcutaneous fat and laterally by the medial septum. The intermediate compartment, containing the flexor digitorum brevis and the quadratus plantae more deeply, was surrounded by the medial septum medially, the intermediate septum laterally and the main plantar aponeurosis on its plantar aspect. The lateral compartment containing the abductor digiti minimi was surrounded medially by the intermediate septum, laterally by the lateral septum and on its plantar aspect by the lateral band of the main plantar aponeurosis. No distinct myofascial compartments exist in the forefoot. Based on our findings, in theory, fasciotomy of the hindfoot compartments through a modified medial incision would be sufficient to decompress the foot

Background. Finite element (FE) models are frequently used in biomechanics to predict the behaviour of new implant designs. To increase the stability after severe bone loss tibial components with long stems are used in revision total knee replacements (TKR). A clinically reported complication after revision surgery is the occurrence of pain in the stem-end region. The aim of this analysis was the development of a validated FE-model of a fully cemented implant and to evaluate the effect of different tibial stem orientations. Methods. A scanned 4th generation synthetic left tibia (Sawbones) was used to develop the FE-model with a virtually implanted fully cemented tibial component. The 500 N load was applied with medial:lateral compartment distributions of 60:40 and 80:20. Different stem positons were simulated by modifying the resection surface angle posterior to the tibias shaft axis. The results were compared with an experimental study which used strain gauges on Sawbones tibias with an implanted tibial TKR component. The locations of the experimental strain gauges were modelled in the FE study. Results. Similar patterns and magnitudes of the predicted and experimentally measured strains were observed which validated the FE-model. An increase of strain at the most distal gauge locations were measured with the stem-end in contact to the posterior cortical bone. More uniform strain distributions were observed with the stem aligned to the intramedullary canal axis. The load distribution of 80:20 shifts the strains to tensile laterally and a large increase of compressive strain in the medial distal tibia. Conclusions. A contributory factor of the clinically reported stem-end pain is possibly the direct effect of contact of the tibial stem-end to the posterior region of the cortical bone. The increased load to the medial tibial compartment is more critical for the development of pain

Knee osteoarthritis (OA) affects an estimated 250 million people worldwide, with a cure yet to be found. Consequently, there is an urgent need to improve our understanding of OA physiopathology. While knee OA has long been mostly described as a loss of cartilage thickness (CTh) and research has focused on this characteristic, the role of bone alterations is rapidly gaining in interest. Analyzing subchondral bone mineral density (sBMD) is particularly interesting because this could inform on the mechanical environment at the knee. However, there is a paucity of data on sBMD in literature mainly because of the lack of prior methods to measure this parameter. A method for 3D sBMD assessment based on computed tomography (CT) scans was recently proposed, thus allowing testing for sBMD differences in knee OA. This study aimed at comparing non-OA and medial OA knees in terms of tibial sBMD and CTh. Specifically, it was hypothesized that sBMD and CTh differ with OA. Ten knees with severe medial OA and 10 matched non-OA knees were analyzed after ethical approval (50% male; 60 ± 3 years old). The arthro-CT scans of the 20 knees were segmented using custom software to build 3D mesh models of the tibial bone and cartilage. CTh maps were obtained by calculating the distance between cartilage and bone meshes, while sBMD maps were calculated based on the intensity of the CT in the first 3mm of bone. For each knee, the average CTh and sBMD values over the entire medial and lateral compartments were calculated and used to determine the medial-to-lateral (M/L) CTh and sBMD ratios. Unpaired t-tests and receiver operating characteristic (ROC) were used for statistical analysis. The M/L sBMD ratio was significantly higher in OA compared to non-OA knees (1.14 ± 0.04 vs. 1.08 ± 0.03; p<0.01), whereas the CTh ratio was not significantly different between groups (0.70 ± 0.21 vs. 0.85 ± 0.10; p=0.06). No significant differences were found between OA and non-OA knees for the average medial CTh and sBMD (p>0.4). High classification performance was obtained for the sBMD ratio and low performance for the average sBMD in the medial compartment (areas under the ROC curve of 0.9 and 0.6, respectively). CTh ratio and medial compartment average provided medium classification performances (areas under the curve of 0.7). This study showed that sBMD differed between non-OA and severe medial OA knees and that sBMD M/L ratio was more sensitive to OA severity than CTh variables. These results brought new insights into the pathogenesis of knee OA, by supporting the idea that sBMD is altered with OA and suggesting that sBMD could play a role in disease development. Indeed, the mechanical stresses on the cartilages are related to the mechanical characteristics of the bones. Indirectly, this study also demonstrated the value of arthro-CT scans to simultaneously assess sBMD and CTh. Additional studies with larger cohorts of patients at different stages of the disease are necessary to better understand when changes in sBMD occur

Introduction. Ostochondral lesion of the knee is a common cause of chronic knee pain. Arthroscopic treatment with subcondral microfracture is a widespread technique leading to noticeable improvement of knee function and pain. To improve the effectiveness of this treatment options, we thought to add intra (PRF) or post-operative (PRP) growth factors. Platelet rich plasma (PRP) is obtained by centrifugation of the blood to produce a plasma with high concentration of platelets and growth factors. This latter represents a promising method to manage degenerative cartilage lesion and can be used postoperatively to improve clinical results of patients treated arthroscopically. Platelet Rich Fibrin (PRF) has been presented as a second-generation platelet concentrate, and it is used intraoperatively to cover the microfracuteres’ holes. No literature was found about using of PRF intraoperative in association with arthroscopic microfracture technique. The aim of this study is to compare clinical outcomes of the treatment of knee osteochondral lesion using arthroscopic microfracture technique alone or in association with PRF Intraoperative application using “Vivostat” system or with PRP “ReGen Lab” postoperative injection. Patients & Methods. 90 patients with clinical and radiographic evidence of osteochondral lesion of the medial or lateral compartment of the knee were enrolled. All patients received arthroscopic debridement and Microfractures and were randomised into 3 groups: 30 patients received microfractures and intraoperative PRF “Vivostat” injection(Group A), 30 patients received microfracture and 3 intra-articular injections of 5.5 mL PRP “Regen”(Group B), 30 patients received microfracture only. IKDC, KOOS and VAS score were administered to all patients before starting the treatment, at 1, 6 and 12 months from the end of the management. Results. Patients who received microfracture and PRF intraoperative application provided the best outcomes, showing a significant higher clinical scores (P<0.001) compared to the other two groups. Patients underwent PRP postoperative administration reported significant higher score than those undergoing arthroscopic microfracture alone (P<0.005), but lesser than Intraoperative PRF group at 6 months and 1 year follow up. Discussion/Conclusion. Treatment of osteochondral lesions of the knee using microfracture technique significantly improved functional and pain scores from the pre- to postoperatively time in the overall cohort. Intraoperative application of PRF shows significantly better outcome than postoperative PRP injections. However, additional treatment with intra-articular PRP injection as an adjunct to microfracture technique may offer better clinical outcomes over microfracture technique alone

Bone marrow lesions (BMLs) have been extensively linked to the osteoarthritis (OA) disease pathway in the knee. Semi-quantitative evaluation has been unable to effectively study the spatial and temporal distribution of BMLs and consequently little is understood about their natural history. This study used a novel statistical model to precisely locate the BMLs within the subchondral bone and compare BML distribution with the distribution of denuded cartilage. MR images from individuals (n=88) with radiographic evidence of OA were selected from the Osteoarthritis Initiative. Slice-by-slice, subvoxel delineation of the lesions was performed across the paired images using the criteria laid out by Roemer (2009). A statistical bone model was fitted to each image across the cohort, creating a dense set of anatomically corresponded points which allowed BML depth, position and volume to be calculated. The association between BML and denudation was also measured semi-quantitatively by visually scoring the lesions as either overlapping or adjacent to denuded AC, or not. At baseline 75 subjects had BMLs present in at least one compartment. Of the 188 compartments with BMLs 46% demonstrated change greater than 727mm cubed, the calculated smallest detectable difference. The majority of lesions were found in medial compartments compared to lateral compartments and the patella (Figure 1A). Furthermore, in the baseline images 76.9% of all BMLs either overlapped or were adjacent to denuded bone. The closeness of this relationship in four individuals is shown in Figure 1B. The distribution of lesions follows a clear trend with the majority found in the patellofemoral joint, medial femoro-tibial joint and medial tibial compartment. Moreover the novel method of measurement and display of BMLs demonstrates that there is a striking similarity between the spatial distribution of BMLs and denuded cartilage in subjects with OA. This co-location infers the lesions have a mechanical origin much like the lesions that occur in healthy patients as a direct result of trauma. It is therefore suggested that OA associated BMLs are in fact no different from the BMLs caused by mechanical damage, but occur as a result of localised disruption to the joint mechanics, a common feature of OA

Summary Statement. An MRI-derived subject-specific finite element model of a knee joint was loaded with subject-specific kinetic data to investigate stress and strain distribution in knee cartilage during the stance phase of gait in-vivo. Introduction. Finite element analysis (FEA) has been widely used to predict the local stress and strain distribution at the tibiofemoral joint to study the effects of ligament injury, meniscus injury and cartilage defects on soft tissue loading under different loading conditions. Previous studies have focused on static FEA of the tibiofemoral joint, with few attempts to conduct subject-specific FEA on the knee during physical activity. In one FEA study utilising subject-specific loading during gait, the knee was simplified by using linear springs to represent ligaments. To address the gap that no studies have performed subject-specific FEA at the tibiofemoral joint with detailed structures, the present study aims to develop a highly detailed subject-specific FE model of knee joint to precisely simulate the stress distribution at knee cartilage during the stance phase of the gait cycle. Method. A detailed three-dimensional model of a healthy human knee was developed from MRI images of a living subject, including the main anatomical structures (bones, all principal ligaments, menisci and articular cartilages). The femur, tibia and fibula were considered as rigid bodies, while the menisci and articular cartilage were modelled as linearly elastic, isotropic and homogeneous while the ligaments were considered to be hyperelastic. Loading and boundary condition assignment was based on the kinematic and kinetic data recorded during gait analysis. Ten time intervals during the stance phase of gait were separately simulated to quantify the time–dependent stress distribution throughout the cycle from heel-strike to toe-off. Loading condition of the tibiofemoral joint varys during the gait cycle since the joint angle changes from extension to flextion, therefore different joint angles at relative time interval were determined to accurately simulate the varing loading condition. Results. The compressive stress and tensile strain distributions in the femoral cartilage, tibia cartilage and menisci of each selected time interval during the stance phase of gait cycle were quantified and corresponded to specific amount of varus/valgus knee moment obtained by inverse dynamics analysis of the kinematic and kinetic data from gait analysis. Therefore a correlation between stress/strain and the frontal movement was established and analysed. For example, at 10% of stance phase, the stress concentration was observed on the lateral compartment due to the valgus moment created at heel strike. At the next interval, the stress concentration shifted to the medial side as the frontal knee moment shifted to a varus orientation. Discussion. The results suggest that the stress distribution of tibiofemoral articular cartilage is qualitatively consistent with the valgus and varus moment observed during the stance phase of gait. The methods described could be applied to investigate the effects of injury and reconstruction on stress distribution within the tibiofemoral joint

We report a study of the shapes of the tibial and femoral articular surfaces in sagittal, frontal and coronal planes which was performed on cadaver knees using two techniques, MRI and computer interpolation of sections of the articular surfaces acquired by a three-dimensional digitiser. The findings using MRI, confirmed in a previous study by dissection, were the same as those using the digitiser. Thus both methods appear to be valid anatomical tools. The tibial and femoral articular surfaces can be divided into anterior segments, contacting from 0° to 20 ± 10° of flexion, and posterior segments, contacting from 20 ± 10° to 120° of flexion. The medial and lateral compartments are asymmetrical, particularly anteriorly. Posteromedially, the femur is spherical and is located in a conforming, but partly deficient, tibial socket. Posterolaterally, it is circular only in the sagittal section and the tibia is flat centrally, sloping downwards both anteriorly and posteriorly to receive the meniscal horns. Anteromedially, the femur is convex with a sagittal radius larger than that posteriorly, while the tibia is flat sloping upwards and forwards. Anterolaterally, both the femoral and tibial surfaces are largely deficient. These shapes suggest that medially the femur can rotate on the tibia through three axes intersecting in the middle of the femoral sphere, but that the sphere can only translate anteroposteriorly and even then to a limited extent. Laterally, the femur can freely translate anteroposteriorly, but can only rotate around a transverse axis for that part of the arc, i.e., near extension, during which it comes into contact with the tibia through its flattened distal/medial surface as against its spherical posterior surface