Cartilage Pressure Research Articles

Functional Outcome of Traumatic Acetabulum Fractures : A 6 Months Comprehensive Follow Up Following Open Reduction Internal Fixation Surgery at Saiful Anwar General Hospital Malang

Acetabular fractures commonly occurred in young adult patient who suffered from high impact trauma which often associated with life threatening injuries. Displaced acetabular fractures lead to abnormal distribution on joint cartilage pressures. It produces early cartilage disruption and development of premature osteoarthritis at the hip. Anatomical reduction and fixation operation in acetabulum fractures still a major challenges due to its complications such as poor functional outcome after surgery. Despite its difficulty to predict the outcomes of acetabular fractures surgeries, functional outcomes scoring such as Oxford Hip Score (OHS) and Harris score may help surgeon to measure long term outcome following acetabular fractures.A total of 13 patients were treated over period of January 2018 until March 2019 in Saiful Anwar General Hospital Malang. The mean age of patients in this serial case is 37 years old and were operated within 2 weeks of injury. All the patients undergone an ORIF (Open Reduction Internal Fixation) operation and observed for the OHS and also Harris score 6 months following surgeries to measure functional outcome of the patients.The mean score of OHS in this serial case is 41 (satisfactory joint function) and the mean score of harris hip score is 91 (excellent). Some patients experience pain during activities, tingling sensation after standing in some periods of time, and heaviness when taking stairs 6 months after operation. This results conclude that the preoperative, operative and post operative management of patient with acetabular fracture in Saiful Anwar Hospital has satisfactory results.

The effect of a centralization procedure for extruded lateral meniscus on load distribution in porcine knee joints at different flexion angles

BackgroundMeniscal extrusion results in loss of the ability to resist hoop strain and biomechanical overload on the joint articular surface. A centralization technique has been developed to overcome these problems. In this study, we analyzed the biomechanics of the extruded and centralized lateral meniscus (LM) in porcine knee joints at different flexion angles.MethodsPorcine knee joints (n = 8) were set in the universal tester and each knee was tested under the following states: 1) intact; 2) extrusion—meniscal extrusion was created by resecting the posterior root of the LM and posterior synovial capsule; and 3) centralization—centralization was performed by two anchors inserted in the lateral tibial plateau. Deviation distance of the meniscus, contact pressure, and contact area in the anterior LM, middle LM, posterior LM, and the contact pressure of the tibial cartilage were evaluated with an axial compressive force of 200 N at knee flexion angles of 30°, 45°, 60°, and 90°.ResultsThe deviation distance of LM significantly increased in extrusion but was restored to the intact status after centralization at all angles. Both the contact pressure and area significantly decreased in extrusion and were restored after centralization close to the intact status in the anterior and middle LM; in the posterior LM, however, decreased contact pressure and area were not restored after centralization. The contact pressure of the tibial cartilage increased significantly in extrusion but decreased close to the intact status after centralization.ConclusionsThis centralization procedure could reduce extrusion of the LM and restore the load-distributing function of the anterior-middle LM. However, the procedure itself could not restore hoop function in cases where the defect lies in the posterior LM.

MPFL GRAFT TENSIONING TO TREAT PATELLAR INSTABILITY RELATED TO PATELLA ALTA: DYNAMIC SIMULATION

Background:Medial patellofemoral ligament (MPFL) reconstruction is a popular treatment for lateral patellar instability. For knees with patella alta, however, tibial tuberosity distalization is the most common approach due to concerns about graft tensioning. A MPFL graft is tensioned intra-operatively to prevent lateral subluxation without over-constraining the patella by allowing some translation.Purpose:To analyze the effects of MPFL reconstruction on lateral tracking and cartilage pressure for knees with patella alta using dynamic simulation of knee function.Methods:Knee function was simulated with 8 multibody dynamic simulation models (RecurDyn) constructed from 3.0 T MRI scans of subjects being treated for recurrent patellar instability. The models were validated in previous studies and included ligaments, tendons, and retinacular structures represented by tension-only springs (Fig1). Four models displayed patella alta; the remaining 4 models were made to reflect patella alta by lengthening the springs. Forces were applied to simulate a dual limb squat from 0º to 90º. Motion was simulated in a pre-operative condition and for three MPFL graft tensioning techniques (1.0, 0.5, and 0 patellar quadrants of lateral translation). The maximum bisect offset index during flexion was used as a measure of patellar instability and the maximum pressures applied to patellar cartilage (lateral, medial) as measures of the risk of overloading cartilage. Statistics were used to compare the parameters with significance set at p < 0.05. Post- and pre-operative maximum bisect offset index were also correlated.Results:MPFL reconstruction with 0.5 and 0 quadrants of allowed lateral translation significantly decreased the maximum bisect offset index compared to the pre-operative condition, but not for 1.0 quadrants (Table 1). MPFL reconstruction did not significantly influence the maximum pressure applied to medial or lateral cartilage. The maximum post-operative bisect offset index was significantly correlated with the pre-operative bisect offset index for 1.0 and 0.5 quadrants of lateral translation allowed (r2 = 0.80, 0.65, and 0.48 for grafts allowing 1, 0.5 and 0 quadrants of translation, respectively).Conclusion:For knees with patella alta, the influence of MPFL reconstruction on patellar tracking varied with the allowed patellar translation during graft tensioning. None of the graft tensioning conditions significantly decreased the maximum lateral pressure or increased the medial cartilage pressure.Significance:The graft tensioning process for MPFL reconstruction typically allows some lateral patellar translation to avoid overconstraining the knee. For knees with patella alta, reducing the allowed lateral translation seems to limit maltracking without overconstraining the knee.Table 1.Average (± standard deviation) output parameters (*p<0.05 compared to pre-op) Pre-opMPFL 1.0MPFL 0.5MPFL 0Maximum bisect offset0.92±0.180.86±0.170.81±0.14*0.74±0.13*Maximum lateral pressure4.2±0.93.9±0.93.7±0.93.8±1.0Maximum medial pressure3.0±1.73.4±1.23.4±1.43.7±1.2Fig1.Dynamic simulation of knee flexion and the patellofermoral pressure distribution.

Construction and analysis of finite element model of defected articular cartilage.

In order to construct a finite element model of defected articular cartilage, the mechanical behavior and degeneration of articular cartilage after injury were studied. The simplified analytical models of normal and defected articular cartilage and finite element models were established, respectively. Firstly, the analytical solution model and finite element model of hollow defect were constructed by using the elasticity theory of multi-hollow medium. Then, the analytical results of each model were calculated and programmed. The software MATLAB was used for programming calculation. Finally, a finite element solid model of defected articular cartilage was established by using human femoral joint. The solid model was analyzed and calculated by magnetic resonance imaging (MRI). The results showed that when the radius of articular cartilage defect r = 0, i.e. there was no defect in articular cartilage, the internal pore pressure of the defect cartilage was the largest, and its pore pressure value was pa. When the depth of articular cartilage defect r = 0, i.e. there was no defect in articular cartilage, the internal pore pressure of the defect cartilage was the largest, and its pore pressure value was pa, and it gradually decreased towards the outer boundary of cartilage. When the surface of femoral cartilage began to defect, with the increase of the depth of the defect (from shallow to deep), the maximum pore pressure in the defect cartilage gradually decreased, but the speed is slowly. With the increase of the defect radius, that is, the area of the defect, the maximum pore pressure in the defect cartilage gradually decreased. When there was no defect of articular cartilage, the internal pore pressure of the defect cartilage was the maximum, the value of pore pressure was pa, the value of pore pressure at the contact position of femoral cartilage was the largest, and it gradually decreased towards the outer boundary of cartilage. At the same location, the pore pressure of normal cartilage was significantly higher than that of defected cartilage. With the change of defect location, the pore pressure was reduced accordingly. Moreover, when the defect position moved from the outside to the inside, the corresponding pore pressure value was decreased gradually. To sum up, the finite element model of defected articular cartilage based on porous elasticity theory has better calculation ability, which proves the validity of the finite element software, and provides a strong basis for future model establishment and clinical treatment of articular cartilage.

A Comparison of the In Vivo Contact Pressure at the Tibiotalar Joint During Walking and Running

Category: Ankle Introduction/Purpose: Knowledge of cartilage pressure distribution in healthy ankle joints during gait is important for understanding the loading environment of articular cartilage and for providing a basis for comparison to evaluate how ankle pathology and surgical procedures affect cartilage loading. Finite element models of the ankle have been developed to examine in vitro loads at the tibiotalar joint during simulated standing in healthy and injured ankle joints [1, 2]. However, there are currently no in vivo studies of tibiotalar cartilage pressure during dynamic loading activities. The goal of this study was to develop a subject-specific finite element model of the tibiotalar joint to estimate contact pressure during walking and running. Methods: Informed consent was obtained from one healthy male, age 23 yrs., BMI 27 kg/m2). Synchronized biplane radiographs of the ankle were acquired at 100 and 150 frames per second during the support phase of overground walking and running, respectively, at a self-selected pace (1.5 m/s and 3.0 m/s, respectively). CT-based bone models of the tibia and talus were matched to the stereoradiographic images to precisely track the three-dimensional bone movement [3]. Six degrees-of-freedom joint kinematics were calculated for each bone model, and used to position bone models in the finite element analysis. Cartilage volumes for the distal tibia and proximal talus were created in Geomagic software by extruding the articulating bone surface. Bones were modeled as rigid bodies and cartilage was modeled as deformable bodies with uniform thickness of 1.3 mm [4-7]. Simulations were performed using FEBio software. The primary outcome parameter was peak cartilage pressure in the tibiotalar joint. Results: On average, peak tibiotalar cartilage pressure was approximately 25% greater during the midstance phase of running in comparison to walking (Figure 1). During walking, peak contact pressure occurred on the lateral-central region of the tibiotalar cartilage throughout the entire stance phase. During the early support phase of running, the location of peak contact pressure was also on the lateral-central region of the tibiotalar cartilage. During running push-off, pressure increased in the medial-central cartilage region and the overall peak cartilage pressure increased. Conclusion: A novel finding of this study is that the peak pressure in tibiotalar cartilage moves from the lateral to medial side of the joint during running, but remains on the lateral side throughout the support phase of walking. This suggests that the location and magnitude of the loads seen by tibiotalar joint cartilage are activity dependent, even in the healthy ankle joint. Future work will investigate cartilage loading in pathologic ankles before and after surgical intervention, as well as during other common athletic activities.

Simulation of surface strain in tibiofemoral cartilage during walking for the prediction of collagen fibre orientation

The collagen fibres in the superficial layer of tibiofemoral articular cartilage exhibit distinct patterns in orientation revealed by split lines. In this study, we introduce a simulation framework to predict cartilage surface loading during walking to investigate if split line orientations correspond with principal strain directions in the cartilage surface. The two-step framework uses a multibody musculoskeletal model to predict tibiofemoral kinematics which are then imposed on a deformable model to predict surface strains. The deformable model uses absolute nodal coordinate formulation (ANCF) shell elements to represent the articular surface and a system of spring-dampers and internal pressure to represent the underlying cartilage. Simulations were performed to predict surface strains due to internal pressure, loading induced by walking, and the combination of both loading due to pressure and walking. Peak femoral and tibial cartilage deflections were slightly greater than 1 mm during simulated walking. First principal strain magnitudes within the cartilage surface ranged up to 3%. Time-averaged first principal strains agreed best with split line maps from the literature when surface loading due to internal cartilage pressure was included. This result suggests there may be a connection between pressure-induced surface strain patterns and the collagen fibre orientation patterns that emerge.

Análise biomecânica da reconstrução do ligamento cruzado anterior

Introduction and objectiveReconstruction of the anterior cruciate ligament is recommended in athletes with high physical demands. Several techniques are used in reconstruction; however, the most relevant question still remains: what is the best biomechanical positioning for the graft. The aim of this study was to analyze the biomechanical effect of bone tunnels position on load distribution and joint kinetics, as well as the mid‐term functional results after anterior cruciate ligament reconstruction. MethodsA biomechanical study using finite element model of the original knee (without anterior cruciate ligament rupture) and reconstruction of the ACL (neo‐ACL) was performed in four combinations of bone tunnel positions (central femoral‐central tibial, anterior femoral‐central tibial, postero‐superior femoral‐anterior tibial, and central femoral‐anterior tibial), with the same type of graft. Each neo‐ACL model was compared with the original knee model regarding contact pressure in the cartilage, rotation, and translation of the femur, menisci, and deformation of the ligaments. ResultsNo neo‐ACL model was able to fully replicate the original knee model. When the femoral tunnel was positioned in the posterior position, 25% lower cartilage pressures were observed and the meniscus mobility was 12% to 30% higher compared to the original knee model. When the femoral tunnel was in the anterior position, an internal rotation 50% lower than the original knee model was observed. ConclusionThe results show that a location of the femoral tunnel more distant from the central position appears to be more suitable for a more distinct behavior regarding the intact joint. In the most anterior position, an increase in rotational instability is observed.

Serial Changes in the Joint Space Width and Joint Line Convergence Angle After Closed-Wedge High Tibial Osteotomy

Background: There have been little data concerning serial changes in the joint space width (JSW) and joint line convergence angle over the course of follow-up periods after closed-wedge high tibial osteotomy (CWHTO). Purpose: To evaluate serial changes in the JSW and joint line convergence angle after CWHTO. Study Design: Case series; Level of evidence, 4. Methods: A total of 100 computer-assisted CWHTOs with a minimum follow-up period of 3 years (mean, 4.4 years) were analyzed. Clinically, the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score was evaluated. Radiographically, the mechanical axis was measured preoperatively and postoperatively. The minimal JSW was measured as the shortest distance between the femur and the tibia. The convergence angle was measured as the angle between the tangent to the subchondral plates of the femoral condyle and the tibial plateau. Serial changes in these measurements were analyzed preoperatively; at 3 months, 6 months, 1 year, and 2 years postoperatively; and at the final follow-up. The intraclass correlation coefficients for all measurements were greater than 0.8. Results: The mean WOMAC score improved from 41.4 preoperatively to 14.9 at the final follow-up. The preoperative and postoperative mean mechanical axis was 8.1° varus and 1.6° valgus, respectively. The mean minimal JSW was 2.5, 2.9, 2.9, 3.1, 3.2, and 3.1 mm preoperatively and at 3 months, 6 months, 1 year, 2 years, and the final follow-up, respectively (P < .001). The mean convergence angle was 4.4°, 3.9°, 4.0°, 4.1°, 4.2°, and 4.3°, respectively, during the same time periods (P = .068). Conclusion: Cartilage healing, as indicated by the JSW, and clinical improvement were maintained over the minimum 3-year follow-up after CWHTO. Cartilage pressure, as indicated by the convergence angle, remained unchanged after CWHTO.

Relaxation of the MCL after an Open-Wedge High Tibial Osteotomy results in decreasing contact pressures of the knee over time

PurposeThe objective of this study was to investigate the effect of a medial open-wedge osteotomy (OWO) and the release of the superficial medial collateral ligament (MCL) on the tibiofemoral cartilage pressure, the MCL tension and the valgus laxity of the knee.MethodsSeven fresh-frozen, human cadaveric knees were used. Medial and lateral mean contact pressure (CP), peak contact pressure (peakCP), and contact area (CA) were measured using a pressure-sensitive film (I-Scan; Tekscan, Boston, MA). The MCL tension was measured using a custom-made device. These measurements were continuously recorded for 5 min after an OWO of 10°. After the osteotomy, the valgus laxity was measured with a handheld Newtonmeter. For one knee, the measurements were continued for 24 h. At the end, a complete release of the superficial MCL was performed and the measurements were repeated at 10°.ResultsThere was relaxation of the MCL after the osteotomy; the tension dropped in 5 min with 10.7% (mean difference 20.5 N (95% CI 16.1–24.9)), and in 24 h, the tension decreased by 24.2% (absolute difference 38.8 N) (one knee). After the osteotomy, the mean CP, peakCP and CA increased in the medial compartment (absolute difference 0.17 MPa (95% CI 0.14–0.20), 0.27 MPa (95% CI 0.24–0.30), 132.9mm2 (95% CI 67.7–198.2), respectively), and decreased in the lateral compartment (absolute difference 0.02 MPa (95% CI 0.03 –0.01), 0.08 MPa (95% CI 0.11 – 0.04), 47.0 mm2 (95% CI −105.8 to 11.8), respectively). Only after a release of the superficial MCL, the mean CP, peak CP and CA significantly decreased in the medial compartment (absolute difference 0.17, 0.27 MPa, 119.8 mm2, respectively), and increased in the lateral compartment (absolute difference 0.02, 0.11 MPa, 52.4 mm2, respectively). After the release of the superficial MCL, a mean increase of 7.9° [mean difference − 0.1° (95% CI −1.9 to 1.6)] of the valgus laxity was found.ConclusionsA release of the superficial MCL helps achieve the goal of reducing medial cartilage pressure in an OWO. There was considerable relaxation of the MCL after an OWO that resulted in a decrease of the mean CP in the medial and lateral compartments of the knee over time. However, cartilage pressure shifted from the medial to the lateral compartment only after release of the superficial MCL. The release of the superficial MCL caused a significant increase in the valgus laxity, which could influence stability after an OWO.Level of evidenceI.

A METHOD FOR COMPARISON OF RADIOCARPAL CARTILAGE T2 RELAXATION TIME MAPS AND CONTACT PRESSURE DISTRIBUTIONS IN NORMAL AND INJURED WRISTS

Objective: The goal of this study was to demonstrate a methodology to observe the relationship between joint contact pressure and cartilage T2 relaxation times in three-dimensional space. Methods: One subject diagnosed with unilateral scapholunate dissociation had both injured and uninjured wrists scanned using a Siemens 3T Skyra magnetic resonance imaging (MRI) scanner. Four time echo scans were performed with TE ranging 15–61[Formula: see text]ms with the hand relaxed. T2 maps were constructed using a custom Matlab code, and these maps were registered to anatomical images for the same subject. The anatomical images were used to construct surface contact models and calculate contact pressures for a simple grasp activity in a prior study. Contact pressures and T2 relaxation times were analyzed using regression analysis. Results and Conclusion: This study demonstrates the feasibility of comparing T2 relaxation times and contact pressure data. For this single demonstration subject, it is not surprising that no relationship was found between T2 relaxation times for the articular cartilage and contact pressures in the normal wrist, contact pressures in the wrist with injury, nor contact pressure changes due to injury. However, the method has been demonstrated and may be useful to evaluate the influence of joint injuries or other pathologies on T2 relaxation times in the context of changes in joint contact pressures with larger cohorts of subjects.

The use of t-tube cholangiocatheter stents in the treatment of pediatric tracheomalacia

Tracheomalacia is a common disorder in neonate and infants, which can lead to life-threatening airway occlusion, because of external pressure or intrinsic defect of tracheobroncial cartilage. Aortopexy and Stents are effective in relieving tracheomalacia in the latter patients. In this case we are to show how t-tube cholangiocatheter is effective and easy available in sever tracheomalacia neonates with intrinsic defect. It can be easily replaced and causes no infection, erosion, or sever complication in 9 months period.

The Effects of Surface Curvature on Cartilage Behaviour in Indentation Test: A Finite Element Study

Computational modeling of the behavior of articular cartilage is important in order to improve the understanding of disease processes such as arthritis, and the suitability of biomaterials in surgical treatment. In previous computational studies, the cartilage surface of axisymmetric models was assumed to be flat in order to evaluate the cartilage behavior. This assumption was inappropriate since the synovial joint possessed curvature geometrical shape and may contribute to inaccurate results. Therefore, this study aims to examine the effects of the cartilage surface curvature to the cartilage behavior in indentation test using finite element analysis. Axisymmetric biphasic poroelastic finite element models of flat and various cartilage surface radii, including both concave and convex shapes of the curve, were generated to simulate creep indentation test in order to investigate possible effect to the contact stress and pore pressure of the cartilage. Based on the results, the smaller cartilage surface of 10mm radius produced higher difference of the cartilage behavior where it generated 39% difference in pore pressure and 6% difference in contact stress, compared to the flat cartilage. This could indicate that the cartilage curvature does affect the cartilage behavior in indentation test particularly the pore pressure of cartilage.

Load-unloading response of intact and artificially degraded articular cartilage correlated with near infrared (NIR) absorption spectra

The conventional mechanical properties of articular cartilage, such as compressive stiffness, have been demonstrated to be limited in their capacity to distinguish intact (visually normal) from degraded cartilage samples. In this paper, we explore the correlation between a new mechanical parameter, namely the reswelling of articular cartilage following unloading from a given compressive load, and the near infrared (NIR) spectrum. The capacity to distinguish mechanically intact from proteoglycan-depleted tissue relative to the “reswelling” characteristic was first established, and the result was subsequently correlated with the NIR spectral data of the respective tissue samples. To achieve this, normal intact and enzymatically degraded samples were subjected to both NIR probing and mechanical compression based on a load-unload-reswelling protocol. The parameter δr, characteristic of the osmotic “reswelling” of the matrix after unloading to a constant small load in the order of the osmotic pressure of cartilage, was obtained for the different sample types. Multivariate statistics was employed to determine the degree of correlation between δr and the NIR absorption spectrum of relevant specimens using Partial Least Squared (PLS) regression. The results show a strong relationship (R2=95.89%, p<0.0001) between the spectral data and δr. This correlation of δr with NIR spectral data suggests the potential for determining the reswelling characteristics non-destructively. It was also observed that δr values bear a significant relationship with the cartilage matrix integrity, indicated by its proteoglycan content, and can therefore differentiate between normal and artificially degraded proteoglycan-depleted cartilage samples. It is therefore argued that the reswelling of cartilage, which is both biochemical (osmotic) and mechanical (hydrostatic pressure) in origin, could be a strong candidate for characterizing the tissue, especially in regions surrounding focal cartilage defects in joints.

Efficacy of Discoscope endoscope versus GlideScope video laryngoscope for difficult glottis exposure

Objective To compare the efficacy of Discoscope endoscope and GlideScope video laryngoscope for difficult glottis exposure.Methods Forty adult patients of both sexes scheduled for elective surgery under general anesthesia whose glottis was not visible at laryngoscopy (grade Ⅲ or Ⅳ according to Cormach-Lehane Grading of laryngoscopic view) were randomized into 2 groups (n =20 each):group GlideScope video laryngoscope (group G) and group Discoscope endoscope (group D).The glottis exposure time,intubating conditions,time from exposure of glottis to completion of tracheal intubation and incidence of postoperative sore throat and throat bleeding were recorded and compared between the 2 groups.Results Compared with group G,the glottis exposure time was significantly longer,the rate of backward pressure of cricoid cartilage lower,the time from exposure of glottis to completion of tracheal intubation shorter and the success rate of tracheal intubation at first attempt higher (P ＜ 0.05).There was no significant difference in the success rate of tracheal intubation at second attempt and postoperative incidence of sore throat and throat bleeding between the 2 groups(P ＞ 0.05).Conclusion DiscoScope endoscope is superior to GlideScope video laryngoscope in the management of difficult intubation in term of glottis exposure and success rate of tracheal intubation at first attempt. Key words: Endoscopy; Laryngoscopy ; Intubation, intratracheal ; Glottis

Partial Meniscectomy Changes Fluid Pressurization in Articular Cartilage in Human Knees

Partial meniscectomy is believed to change the biomechanics of the knee joint through alterations in the contact of articular cartilages and menisci. Although fluid pressure plays an important role in the load support mechanism of the knee, the fluid pressurization in the cartilages and menisci has been ignored in the finite element studies of the mechanics of meniscectomy. In the present study, a 3D fibril-reinforced poromechanical model of the knee joint was used to explore the fluid flow dependent changes in articular cartilage following partial medial and lateral meniscectomies. Six partial longitudinal meniscectomies were considered under relaxation, simple creep, and combined creep loading conditions. In comparison to the intact knee, partial meniscectomy not only caused a substantial increase in the maximum fluid pressure but also shifted the location of this pressure in the femoral cartilage. Furthermore, these changes were positively correlated to the size of meniscal resection. While in the intact joint, the location of the maximum fluid pressure was dependent on the loading conditions, in the meniscectomized joint the location was predominantly determined by the site of meniscal resection. The partial meniscectomy also reduced the rate of the pressure dissipation, resulting in even larger difference between creep and relaxation times as compared to the case of the intact knee. The knee joint became stiffer after meniscectomy because of higher fluid pressure at knee compression followed by slower pressure dissipation. The present study indicated the role of fluid pressurization in the altered mechanics of meniscectomized knees.

Hamstrings loading contributes to lateral patellofemoral malalignment and elevated cartilage pressures: An in vitro study

BackgroundHamstrings loading has previously been shown to increase tibiofemoral posterior translation and external rotation, which could contribute to patellofemoral malalignment and elevated patellofemoral pressures. The current study characterizes the influence of forces applied by the hamstrings on patellofemoral kinematics and the pressure applied to patellofemoral cartilage. MethodsTen knees were positioned at 40°, 60° and 80° of flexion in vitro, and loaded with 586N applied through the quadriceps, with and without an additional 200N applied through the hamstrings. Patellofemoral kinematics were characterized with magnetic sensors fixed to the patella and the femur, while the pressure applied to lateral and medial patellofemoral cartilage was measured with pressure sensors. A repeated measures ANOVA with three levels, combined with paired t-tests at each flexion angle, determined if loading the hamstrings significantly (P<0.05) influenced the output. FindingsLoading the hamstrings increased the average patellar flexion, lateral tilt and lateral shift by approximately 1°, 0.5° and 0.2mm, respectively. Each increase was significant for at least two flexion angles. Loading the hamstrings increased the percentage of the total contact force applied to lateral cartilage by approximately 5%, which was significant at each flexion angle, and the maximum lateral pressure by approximately 0.3MPa, which was significant at 40° and 60°. InterpretationThe increased lateral shift and tilt of the patella caused by loading the hamstrings can contribute to lateral malalignment and shifts pressure toward the lateral facet of the patella, which could contribute to overloading of lateral cartilage.

Cartilage Pressure Distributions Provide a Footprint to Define Female Anterior Cruciate Ligament Injury Mechanisms

Background Bone bruises located on the lateral femoral condyle and posterolateral tibia are commonly associated with anterior cruciate ligament (ACL) injuries and may contribute to the high risk for knee osteoarthritis after ACL injury. The resultant footprint (location) of a bone bruise after ACL injury provides evidence of the inciting injury mechanism. Purpose/Hypothesis (1) To analyze tibial and femoral articular cartilage pressure distributions during normal landing and injury simulations, and (2) to evaluate ACL strains for conditions that lead to articular cartilage pressure distributions similar to bone bruise patterns associated with ACL injury. The hypothesis was that combined knee abduction and anterior tibial translation injury simulations would demonstrate peak articular cartilage pressure distributions in the lateral femoral condyle and posterolateral tibia. The corollary hypothesis was that combined knee abduction and anterior tibial translation injury conditions would result in the highest ACL strains. Study Design Descriptive laboratory study. Methods Prospective biomechanical data from athletes who subsequently suffered ACL injuries after testing (n = 9) and uninjured teammates (n = 390) were used as baseline input data for finite element model comparisons. Results Peak articular pressures that occurred on the posterolateral tibia and lateral femoral condyle were demonstrated for injury conditions that had a baseline knee abduction angle of 5°. Combined planar injury conditions of abduction/anterior tibial translation, anterior tibial translation/internal tibial rotation, or anterior tibial translation/external tibial rotation or isolated anterior tibial translation, external tibial rotation, or internal tibial rotation resulted in peak pressures in the posterolateral tibia and lateral femur. The highest ACL strains occurred during the combined abduction/anterior tibial translation condition in the group that had a baseline knee abduction angle of 5°. Conclusion The results of this study support a valgus collapse as the major ACL injury mechanism that results from tibial abduction rotations combined with anterior tibial translation or external or internal tibial rotations. Clinical Relevance Reduction of large multiplanar knee motions that include abduction, anterior translation, and internal/external tibial motions may reduce the risk for ACL injuries and associated bone bruises. In particular, prevention of an abduction knee posture during initial contact of the foot with the ground may help prevent ACL injury.

Model predictions of increased knee joint loading in regions of thinner articular cartilage after patellar tendon adhesion

Patellar tendon adhesion is a complication from anterior cruciate ligament (ACL) reconstruction that may affect patellofemoral and tibiofemoral biomechanics. A computational model was used to investigate the changes in knee joint mechanics due to patellar tendon adhesion under normal physiological loading during gait. The calculations showed that patellar tendon adhesion up to the level of the anterior tibial plateau led to patellar infera, increased patellar flexion, and increased anterior tibial translation. These kinematic changes were associated with increased patellar contact force, a distal shift in peak patellar contact pressure, a posterior shift in peak tibial contact pressure, and increased peak tangential contact sliding distance over one gait cycle (i.e., contact slip). Postadhesion, patellar and tibial contact locations corresponded to regions of thinner cartilage. The predicted distal shift in patellar contact was in contrast to other patellar infera studies. Average patellar and tibial cartilage pressure did not change significantly following patellar tendon adhesion; however, peak medial tibial pressure increased. These results suggest that changes in peak tibial cartilage pressure, contact slip, and the migration of contact to regions of thinner cartilage are associated with patellar tendon adhesion and may be responsible for initiating patellofemoral pain and knee joint structural damage observed following ACL reconstruction.

The impact of ulnar collateral ligament tear and reconstruction on contact pressures in the lateral compartment of the elbow

Complete ulnar collateral ligament (UCL) injury increases articular pressure and reduces contact area compared with the normal intact UCL. UCL reconstruction restores the contact area and contact pressure observed in the native joint. Six male cadaveric elbows were mounted on a custom jig capable of simulating the 2 critical phases of the throwing motion during pitching. A contact sensor was placed through an anterior arthrotomy into the radiocapitellar joint. Each specimen then underwent valgus loading at 1.75 and 5.25 Nm of torque with the biceps, brachialis, and triceps under axial load in each testing condition. The average valgus laxity in the intact elbow at 90° was 3.7° ± 0.6° at the 5.25 Nm level of torque, which doubled after transection. The reconstruction group demonstrated less laxity (2.4° ± 0.4°) and reduced valgus angulation of the ulna at 5.25 Nm of torque. The transected UCL condition showed peak contact pressure 67% higher compared with the native ligament group at 5.25 Nm of torque. The reconstructed group increased peak articular cartilage pressures by 33% from the native ligament. At 5.25 Nm of torque for the 90° flexion phase, the transected UCL condition showed an average contact pressure of 84% greater than that of the native ligament group. Reconstruction of the UCL restored average articular pressures to within 20% of intact values at 90°. UCL injury increases radiocapitellar contact pressures and reduces resistance of the elbow to valgus loading. Contact pressures and valgus laxity can be improved with UCL reconstruction. Taken as a whole, the peak pressure data indicate that the reconstruction restores valgus stability and lateral contact pressures to nearly normal levels under the conditions tested. Because the 90 position is the clinically significant position, these laboratory data support the clinical success of the docking procedure.

A human knee joint model considering fluid pressure and fiber orientation in cartilages and menisci

Articular cartilages and menisci are generally considered to be elastic in the published human knee models, and thus the fluid-flow dependent response of the knee has not been explored using finite element analysis. In the present study, the fluid pressure and site-specific collagen fiber orientation in the cartilages and menisci were implemented into a finite element model of the knee using fibril-reinforced modeling previously proposed for articular cartilage. The geometry of the knee was obtained from magnetic resonance imaging of a healthy young male. The bones were considered to be elastic due to their greater stiffness compared to that of the cartilages and menisci. The displacements obtained for fast ramp compression were essentially same as those for instantaneous compression of equal magnitude with the fluid being trapped in the tissues, which was expected. However, a clearly different pattern of displacements was predicted by an elastic model using a greater Young's modulus and a Poisson's ratio for nearly incompressible material. The results indicated the influence of fluid pressure and fiber orientation on the deformation of articular cartilage in the knee. The fluid pressurization in the femoral cartilage was somehow affected by the site-specific fiber directions. The peak fluid pressure in the femoral condyles was reduced by three quarters when no fibril reinforcement was assumed. The present study indicates the necessity of implementing the fluid pressure and anisotropic fibril reinforcement in articular cartilage for a more accurate understanding of the mechanics of the knee.