Intact Knee Research Articles

Development of a Porcine Model to Assess the Effect of In Situ Knee Joint Loading on Site-Specific Cartilage Gene Expression.

Cyclic mechanical loading of cartilage induces stresses and fluid flow, which are thought to modulate chondrocyte metabolism. The uneven surface, plus the heterogeneity of cartilage within a joint, makes stress and fluid pressure distribution in the tissue nonuniform, and gene expression may vary at different sites as a function of load magnitude, frequency, and time. In previous studies, cartilage explants were used for loading tests to investigate biological responses of the cartilage to mechanical loading. In contrast, we used loading tests on intact knee joints, to better reflect the loading conditions in a joint, and thus provide a more physiologically relevant mechanical environment. Gene expression levels in loaded samples for a selection of relevant genes were compared with those of the corresponding unloaded control samples to characterize potential differences. Furthermore, the effects of load magnitude and duration on gene expression levels were investigated. We observed differences in gene expression levels between samples from different sites in the same joint and between corresponding samples from the same site in loaded and unloaded joints. Consistent with previous findings, our results indicate that there is a critical upper and lower threshold of loading for triggering the expression of certain genes. Variations in gene expression levels may reflect the effect of local loading, topography, and structure of the cartilage in an intact joint on the metabolic activity of the associated cells.

Stress on the posteromedial region of the proximal tibia increased over time after anterior cruciate ligament injury.

Anterior cruciate ligament (ACL) injury induces anterior and rotatory instability of the knee. However, the effect of this instability on the stress distribution in the knee joint in living participants is not clear. The aim of this study was to compare the distribution pattern of subchondral bone density across the proximal tibia in the knees with and without ACL injury, and to investigate the correlation between the distribution patterns of the subchondral bone density and the duration of ACL-deficiency. Radiographic and computed tomography (CT) data pertaining to 20 patients with unilateral ACL injury without combined injury (ACL-deficient group) and 19 nontraumatic subjects (control group) were collected retrospectively. Subchondral bone density of the proximal tibia was assessed using CT-osteoabsorptiometry. Both the medial and lateral compartments of the proximal tibia were divided into three subregions of equal width in the sagittal direction. The percentage of high subchondral bone density areas (HDA%) in each subregion was quantitatively analyzed. HDA% of the posteromedial region was significantly higher in the ACL-deficient group (mean: 21.6%) than in the control group (14.7%) (p = 0.002). In contrast, HDA% of the anteromedial region was significantly lower in the ACL-deficient group (9.4%) than in the control group (15.3%) (p = 0.048). The logarithm of the time elapsed from ACL injury to CT examination showed a significant correlation with HDA% in the posteromedial region (p = 0.032). Subchondral bone density in the posteromedial region significantly increased after ACL injury and correlated with the duration of ACL-deficiency in semi-log manner in meniscus intact knees. The increase in stress on the posteromedial region after ACL injury, which induces a change in the subchondral bone density, justifies early ACL reconstruction after ACL injury.

Experimental validation of a new technique for the assessment of posterior tibial translation (ABC angle) after posterior cruciate ligament rupture

BackgroundThe aim of this cadaver study was to evaluate an original technique for measuring posterior tibial translation based on an angle value instead of a distance value, with and without posterior stress application. It was hypothesized that an angle measurement of the posterior tibial translation would confirm the presence of a PCL tear with the knee flexed and completely extended.MethodUsing fresh cadavers, a set of strict lateral views were taken by fluoroscopy with the knee at 0°, 45° and 90° flexion on the intact knee and after transecting the PCL. The primary endpoint was the change in the posterior translation measured using a new technique, the ABC angle. This measurement was compared to the conventional posterior translation distance measurement with and without a posterior stress placed on the knee.ResultsApplication of a posterior stress revealed clear changes in posterior translation after PCL transection with the knee at 0° for the angle technique and at 45° and 90° for the two techniques (p < 0.05). Contrary to the reference method, the ABC angle method found a statistically significant difference in posterior translation with the knee in extension.ConclusionOur technique provides a reliable radiographic measurement of posterior translation with the knee in extension, which should make it easier to acquire radiographs in patients who have pain with knee flexion. This angular measurement also has the advantage of not needing length calibration contrary to the reference technique.Level of evidenceIV

Bone bridge fixation has superior biomechanics on posterior knees to bone plug fixation after lateral meniscal allograft transplantation – A biomechanical study simulating partial weight-bearing conditions

BackgroundIt remains unknown how biomechanics change in posterior lateral knee using different fixation techniques in lateral meniscal allograft transplantation (MAT)during simulated toe-touch partial weight-bearing. This study aimed tocompare the biomechanical effects on posterior knee between bridgeand bone plug fixation in lateral MAT. MethodsIntact knee, bone bridge fixation, and bone plug fixation were tested with 500 N of axial load during knee flexion at 0°, 30°, and 60°, which simulated toe-touch partial weight-bearing. Contact area and peak pressure were assessed on posterior knee and the shift of peak pressure position were measured. ResultsOn the posterior lateral compartment, the contact mechanics of bone bridge fixation were similar to those of the intact knee (allP-values > 0.05), but its peak pressure was higher than that of intact knee at 60° (P = 0.002). For bone plug fixation, the contact area of the posterior lateral knee was significantly lower than those of intact knee and bone bridge fixation at 30° and 60° (allP-values < 0.05). The peak pressure of the posterior lateral knee was higher than that of the intact knee at all flexions and higher than that of bone bridge fixation at 30° and 60° (allP-values < 0.05). The peak pressure position of bone plug fixation shifted more laterally and posteriorly compared with intact knee and bone bridge fixation during knee flexion. ConclusionBone bridges could maintain posterior knee biomechanics better than bone plug fixation during knee bending during partial weight-bearing.

Anterolateral Structure Reconstruction Similarly Improves the Stability and Causes Less Overconstraint in Anterior Cruciate Ligament-Reconstructed Knees Compared With Modified Lemaire Lateral Extra-articular Tenodesis: A Biomechanical Study

To compare the kinematics of anterolateral structure (ALS) reconstruction (ALSR) and lateral extra-articular tenodesis (LET) in ACL-ALS-deficient knees with anterior cruciate ligament (ACL) reconstruction.Ten fresh-frozen cadaveric knees with the following conditions were tested: (1) intact, (2) ACL-ALS deficiency, (3) ACL reconstruction (ACLR), (4) ACLR combined with ALSR (ACL-ALSR) or LET (ACLR+LET). Anterior translation and tibial internal rotation were measured with 90-N anterior load and 5 N·m internal torque at 0°, 30°, 60°, and 90°. The anterolateral translation and internal rotation were also measured during a simulated pivot-shift test at 0°, 15°, 30°, and 45°. The knee kinematic changes in all reconstructions were compared with each other, with intact knees as the baseline.Isolated ACLR failed to restore native knee kinematics in ACL-ALS-deficient knees. Both ACL-ALSR and ACLR+LET procedures decreased the anterior instability of the ACLR. However, ACLR+LET caused overconstraints in internal rotation at 30° (-3.73° ± 2.60°, P = .023), 60° (-4.96° ± 2.22°, P = .001) and 90° (-6.14° ± 1.60°, P < .001). ACL-ALSR also overconstrained the knee at 60° (-3.65° ± 1.90°, P < .001) and 90° (-3.18° ± 2.53°, P < .001). For a simulated pivot-shift test, both combined procedures significantly reduced the ACLR instability, with anterolateral translation and internal rotation being overconstrained in ACLR+LET at 30° (-3.32 mm ± 3.89 mm, P = .005; -2.58° ± 1.61°, P < .001) and 45° (-3.02 mm ± 3.95 mm, P = .012; -3.44° ± 2.86°, P < .001). However, the ACL-ALSR overconstrained only the anterolateral translation at 30° (-1.51 mm ± 2.39 mm, P = .046) and internal rotation at 45° (-2.09° ± 1.70°, P < .001). There were no significant differences between the two combined procedures at most testing degrees in each testing state, except for the internal rotation at 30° (P = .007) and 90° (P = .032) in internal rotation torque.ACL reconstruction alone did not restore intact knee kinematics in knees with concurrent ACL tears and severe ALS injury (ACL-ALS-deficient status). Both ACL-ALSR and ACLR+LET procedures restored knee stability at some flexion degrees, with less overconstraints in internal rotation resulting from ACL-ALSR.For patients with combined ACL tears and severe ALS deficiency, isolated ACLR probably results in residual rotational and pivot-shift instability. Both ACL-ALSR and ACLR+LET show promise for the improvement of knee stability, whereas ACL-ALSR has less propensity for knee overconstraint.

Lateral Extra-articular Tenodesis Alters Lateral Compartment Contact Mechanics under Simulated Pivoting Maneuvers: An In Vitro Study

Background: There is concern that utilization of lateral extra-articular tenodesis (LET) in conjunction with anterior cruciate ligament (ACL) reconstruction (ACLR) may disturb lateral compartment contact mechanics and contribute to joint degeneration. Hypothesis: ACLR augmented with LET will alter lateral compartment contact mechanics in response to simulated pivoting maneuvers. Study Design: Controlled laboratory study. Methods: Loads simulating a pivot shift were applied to 7 cadaveric knees (4 male; mean age, 39 ± 12 years; range, 28-54 years) using a robotic manipulator. Each knee was tested with the ACL intact, sectioned, reconstructed (via patellar tendon autograft), and, finally, after augmenting ACLR with LET (using a modified Lemaire technique) in the presence of a sectioned anterolateral ligament and Kaplan fibers. Lateral compartment contact mechanics were measured using a contact stress transducer. Outcome measures were anteroposterior location of the center of contact stress (CCS), contact force from anterior to posterior, and peak and mean contact stress. Results: On average, augmenting ACLR with LET shifted the lateral compartment CCS anteriorly compared with the intact knee and compared with ACLR in isolation by a maximum of 5.4 ± 2.3 mm (P < .001) and 6.0 ± 2.6 mm (P < .001), respectively. ACLR augmented with LET also increased contact force anteriorly on the lateral tibial plateau compared with the intact knee and compared with isolated ACLR by a maximum of 12 ± 6 N (P = .001) and 17 ± 10 N (P = .002), respectively. Compared with ACLR in isolation, ACLR augmented with LET increased peak and mean lateral compartment contact stress by 0.7 ± 0.5 MPa (P = .005) and by 0.17 ± 0.12 (P = .006), respectively, at 15° of flexion. Conclusion: Under simulated pivoting loads, adding LET to ACLR anteriorized the CCS on the lateral tibial plateau, thereby increasing contact force anteriorly. Compared with ACLR in isolation, ACLR augmented with LET increased peak and mean lateral compartment contact stress at 15° of flexion. Clinical Relevance: The clinical and biological effect of increased anterior loading of the lateral compartment after LET merits further investigation. The ability of LET to anteriorize contact stress on the lateral compartment may be useful in knees with passive anterior subluxation of the lateral tibia.

Restricted Kinematic Alignment, the Fundamentals, and Clinical Applications.

Introduction: After a better understanding of normal knee anatomy and physiology, the Kinematic Alignment (KA) technique was introduced to improve clinical outcomes of total knee arthroplasty (TKA). The goal of the KA technique is to restore the pre-arthritic constitutional lower limb alignment of the patient. There is, however, a large range of normal knee anatomy. Unusual anatomies may be biomechanically inferior and affect TKA biomechanics and wear patterns. In 2011, the leading author proposed the restricted kinematic alignment (rKA) protocol, setting boundaries to KA for patients with an outlier or atypical knee anatomy.Material and Equipment: rKA aims to reproduce the constitutional knee anatomy of the patient within a safe range. Its fundamentals are based on sound comprehension of lower limb anatomy variation. There are five principles describing rKA: (1) Combined lower limb coronal orientation should be ± 3° of neutral; (2) Joint line orientation coronal alignment should be within ± 5° of neutral; (3) Natural knee's soft tissues tension/ laxities should be preserved/restored; (4) Femoral anatomy preservation is prioritized; (5) The unloaded/most intact knee compartment should be resurfaced and used as the pivot point when anatomical adjustment is required. An algorithm was developed to facilitate the decision-making.Methods: Since ~50% of patients will require anatomic modification to fit within rKA boundaries, rKA is ideally performed with patient-specific instrumentation (PSI), intra-operative computer navigation or robotic assistance. rKA surgical technique is presented in a stepwise manner, following the five principles in the algorithm.Results: rKA produced excellent mid-term clinical results in cemented or cementless TKA. Gait analysis showed that rKA TKA patients had gait patterns that were very close to a non-operated control group, and these kinematics differences translated into significantly better postoperative patient-reported scores than mechanical alignment (MA) TKA cases.Discussion: Aiming to improve the results of MA TKA, rKA protocol offers a satisfactory compromise that recreates patients' anatomy in most cases, omitting the need for extensive corrections and soft tissue releases that are often required with MA. Moreover, it precludes the reproduction of extreme anatomies seen with KA.

Efecto del Avance de la Tuberosidad Tibial (ATT) sobre la fuerza del tendon Patelar en Articulación de Rodilla Canina bajo Fuerza Femoral Caudal

The Tibial Tuberosity Advancement (TTA) surgical technique is used in veterinary surgery to limit cranial tibial translation during canine gait, lengthening the lever arm of the quadriceps in Anterior Cruciate Ligament-deficient (ACL-deficient) stifle joints. It is know that after TTA, the patellofemoral pressure decreases, but the Patellar Tendon (PT) behavior has not been observed experimentally yet. This study measures the PT force under caudal femoral drawer at knee flexion angles from 135° to 90° in intact and pathological knee to asses the effect of TTA on the tendon. Five fresh cadaveric adult canine stifle joint were tested in an apparatus in which muscle forces of the canine hind limb were simulated. Each knee was tested in three different conditions: intact, ACL-deficient and with TTA. PT force was measured using a electrical transducer. The greater the joint flexion angles, the greater the PT force. The knee average force of the five specimens in 90º flexion were 28.4 ± 3.2 Newtons (N) for the intact, 28.2 ± 3.4 N for the ACL-deficient and 24.9 ± 2 N for the TTA knee, which decreased compared to the healthy knee, so TTA generates a loosening of the PT force. The PT force showed a fast rate of change in the operated knee because of a shift in the pattern of knee flexion, so the biomechanics of the entire joint could be influenced by the TTA technique.

Arthroscopic Patellofemoral Measurements Can Reliably Assess Patellar Instability

To arthroscopically describe patellar position based on lateralization, tilt, and engagement, and compare measurements in normal, medial patellofemoral complex-(MPFC) deficient, and MPFC-reconstructed knees. In 10 cadaveric knees, arthroscopic patellar position was assessed by performing digital measurements on arthroscopic images obtained through a standard anterolateral portal. Lateralization was measured as millimeters overhang of the patella past the lateral edge of the lateral femoral condyle, viewing from the lateral gutter. Patellar tilt was calculated as the difference in medial and lateral distances from the patella to the trochlea, viewing from the sunrise view. Patellotrochlear distance was measured as the anteroposterior distance between the central trochlear groove and patella on the sunrise view. Measurements were obtained at 10° intervals of knee flexion from 0° to 90°, in intact knees (group 1), after arthroscopically transecting the MPFC fibers (group 2), and after MPFC reconstruction (group 3). Optimal cutoff values were identified to distinguish between intact versus MPFC-deficient states. When compared to group 1, group 2 demonstrated increased patellar lateralization by 22.5% at 0°-40° knee flexion (P= .006), which corrected to baseline in group 3 (P= .006). Patellar tilt measurements demonstrated no differences between groups. Patellotrochlear distance increased by 21.0% after MPFC transection (P= .031) at 0°-40° knee flexion, with correction to baseline after MPFC reconstruction (P= .031). More than 7 mm of lateral overhang at 20°-30° flexion and >6 mm of patellotrochlear distance at 10°-20° flexion were found to indicate MPFC deficiency. Utilizing standardized arthroscopic views, we identified significant increases in patellar lateralization and patellotrochlear distance in early knee flexion angles after MPFC transection, and these changes normalized after MPFC reconstruction. Arthroscopic assessments of patellar position may be useful in evaluating patellofemoral stability during patellar stabilization surgery.

Increased Rotatory Laxity after Anterolateral Ligament Lesion in Anterior Cruciate Ligament- (ACL-) Deficient Knees: A Cadaveric Study with Noninvasive Inertial Sensors.

The anterolateral ligament (ALL) has been suggested as an important secondary knee restrain on the dynamic laxity in anterior cruciate ligament- (ACL-) deficient knees. Nevertheless, its kinematical contribution to the pivot-shift (PS) phenomenon has not been clearly and objectively defined, and noninvasive sensor technology could give a crucial contribution in this direction. The aim of the present study was to quantify in vitro the PS phenomenon in order to investigate the differences between an ACL-deficient knee and an ACL+ALL-deficient knee. Ten fresh-frozen paired human cadaveric knees (n = 20) were included in this controlled laboratory study. Intact, ACL-deficient, and ACL+ALL-deficient knees were subjected to a manual PS test quantified by a noninvasive triaxial accelerometer (KiRA, OrthoKey). Kinematic data (i.e., posterior acceleration of the tibial lateral compartment) were recorded and compared among the three statuses. Pairwise Student's t-test was used to compare the single groups (p < 0.05). Intact knees, ACL-deficient knees, and ACL+ALL-deficient knees showed an acceleration of 5.3 ± 2.1 m/s2, 6.3 ± 2.3 m/s2, and 7.8 ± 2.1 m/s2, respectively. Combined sectioning of ACL and ALL resulted in a statistically significant acceleration increase compared to both the intact state (p < 0.01) and the ACL-deficient state (p < 0.01). The acceleration increase determined by isolated ACL resection compared to the intact state was not statistically significant (p > 0.05). The ALL sectioning increased the rotatory laxity during the PS after ACL sectioning as measured through a user-friendly, noninvasive triaxial accelerometer.

Design of a Semi-Active Prosthetic Knee for Transfemoral Amputees: Gait Symmetry Research by Simulation

The key technology of the prosthetic knee is to simulate the torque and angle of the biological knee. In this work, we proposed a novel prosthetic knee operated in semi-active mode. The structure with ball-screw driven by the motor and the passive hydraulic damping cylinder was presented. A four-bar linkage was adapted to track the instantaneous center motion of human knee. The mathematical models of hydraulic cylinder damping and active torque were established to simulate the knee torque and angle. The results show that the knee torque symmetry index is smaller than 10% in the whole gait. The knee angle symmetry index value is 34.7% in stance phase and 11.5% in swing phase. The angle in swing phase is closer to the intact knee. The semi-active prosthetic knee could provide similar torque and angle of the biological knee in the simulation. It has shown good potential in improving the gait symmetry of the transfemoral amputee.

Functional stability: an experimental knee joint cadaveric study on collateral ligaments tension

Applying proper tension to collateral ligaments during total knee arthroplasty surgery is fundamental to achieve optimal implant performance: low tension could lead to joint instability, over-tensioning leads to pain and stiffness. A "functional stability" must be defined and achieved during surgery to guarantee optimal results. In this study, an experimental cadaveric activity was performed to measure the minimum tension required to achieve knee functional stability. Ten knee specimens were investigated; femur and tibia were fixed in specifically designed fixtures and clamped to a loading frame; constant displacement rate was applied and resulting tension force was measured. Joint stability was determined as the slope change in the force/displacement curve, representing the activation of both collateral ligaments elastic region; the tension required to reach joint functional stability is then the span between ligaments toe region and this point. Intact, ACL (anterior cruciate ligament)-resected and ACL & PCL (posterior cruciate ligament)-resected knees were tested. The test was performed at different flexion angles; each configuration was analyzed three times. Results demonstrated an overall tension of 40-50N to be enough to reach stability in intact knees. Similar values are sufficient in ACL-resected knees, while significantly higher tension is required (up to 60N) after cruciate ligaments resection. The tension required was slightly higher at 60° of flexion. Results agree with other experimental studies, showing that the tensions required to stabilize a knee joint are lower than the ones applied nowadays via surgical tensioners. To reach functional stability, surgeons should consider such results intraoperatively and avoid ligament laxity or over-tension.

The Natural History of Medial Meniscal Tears in the ACL Deficient and ACL Reconstructed Rat Knee.

The process of anterior cruciate ligament (ACL) injury-induced meniscal tear formation is not fully understood. Clinical studies have shown that ACL reconstruction (ACLR) reduces the development of secondary meniscal tears, but it is difficult to gain insight into the protective effects of ACLR from clinical studies alone. Using rat ACL transection (ACLT) and ACLR models, we aimed to reveal (1) the formation process of meniscal tears secondary to ACLT and (2) the protective effects of ACLR on secondary meniscal tears. ACLT surgery alone or with ACLR was performed on the knees of rats. Histomorphological and histopathological changes were examined in the posteromedial region of the meniscus in intact rats and in rats that received ACLT or ACLR up to 12 weeks postsurgery. In addition, anterior-posterior joint laxity was measured using the universal testing machine to evaluate the effects of ACLT and ACLR on joint laxity. AAnterior-posterior laxity was significantly increased by ACLT compared to the intact knee. This ACLT-induced joint laxity was partially but significantly reduced by ACLR. Meniscal proliferation and hyaline cartilage-like tissue formation were detected in the medial meniscus at 4 weeks post-ACLT. At 12 weeks post-ACLT, hyaline cartilage-like tissue was replaced by ossicles and meniscal tears were observed. These ACLT-induced abnormalities were attenuated by ACLR. Our results suggest that ACLT-induced joint laxity induces secondary medial meniscal tears through meniscal proliferation and ossicle formation via endochondral ossification. Joint re-stabilization by ACLR suppresses meniscal proliferation and ossicle formation and consequently prevents secondary meniscal tears.

Relevance of the Tibial Slope on Functional Outcomes in ACL-Deficient and ACL Intact Fixed-Bearing Medial Unicompartmental Knee Arthroplasty

BackgroundExcessive posterior tibial slope in medial unicompartmental knee arthroplasty (UKA) has been implicated in early failure. The purpose of this study was to evaluate the relationship between preoperative posterior tibial slope and postoperative slope of the implant (PSI) on outcomes in patients with anterior cruciate ligament (ACL) intact and ACL-deficient knees after fixed-bearing medial UKA. MethodsPatients who underwent a medial UKA between 2002 and 2017 with a minimum 3-year follow-up were included. Preoperative posterior tibial slope and postoperative PSI were measured. Outcomes measures included Knee Injury and Osteoarthritis Outcomes Score (KOOS) subscales, Lysholm, and VR-12. Failure was defined as conversion to total knee arthroplasty. ResultsOf 241 knees undergoing UKA, 131 patients (70 women, 61 men; average age of 65 ± 10 years (average BMI of 27.9 ± 4) were included. For all patients, survivorship was 98% at 5 years and 96% at 10 years with a mean survival time for UKA was 15.2 years [95% CI: 14.6-15.7]. No failure had a PSI >7°. There were no superficial or deep infections. There were no significant differences in outcome scores between the ACL intact and the ACL-deficient group; therefore, the data were combined for analysis. At mean 8-year follow-up, KOOS pain scores were better in patients with PSI ≤7° (87 ± 16) than those with PSI >7° (81 ± 15). 76% of patients with PSI ≤7° reached the Patient Acceptable Symptom State for KOOS pain; whereas, 59% of patients with PSI >7° reached PASS for KOOS pain (P = .015). ConclusionPatients with postoperative posterior slope of the tibial implant >7° had significantly worse postoperative pain, without conversion to TKA, and with maintenance of high function. In ACL deficient and intact knees, nonrobotically-assisted, fixed-bearing medial UKA had a 96% survivorship at 10 years.

In Vivo Kinematic Analysis of Lateral Meniscal Allograft Transplantation With Soft Tissue Fixation.

Background:Lateral meniscal deficiency increases the pivot shift in the knee, and although meniscal allograft transplantation (MAT) is a well-established procedure with satisfactory clinical results, biomechanical studies have failed to show whether this procedure is able to restore knee kinematics.Purpose:To assess, in vivo, the kinematic effect of lateral MAT in anterior cruciate ligament–intact knees, with a particular focus on the pivot-shift maneuver.Study Design:Controlled laboratory study.Methods:Enrolled in this study were 10 consecutive patients undergoing lateral MAT. A surgical navigation system was used to acquire and quantify the following variables: anterior-posterior displacement at 30° of flexion (AP30) and 90° of flexion (AP90), varus-valgus rotation at 0° of flexion (VV0) and 30° of flexion, and dynamic laxity on the pivot-shift test, which was determined through anterior displacement of the lateral tibial compartment (APlat) and posterior acceleration of the lateral tibial compartment during tibial reduction (ACC). Data from before and after MAT were compared.Results:From pre- to postoperatively, there was a significant decrease in tibial translation of 2.8 mm (43%; P = .005) for AP30 and 1.9 mm (38%; P = .018) for AP90 as well as a significant difference of 3.6° (64%; P = .001) for VV0. There was also a significant pre- to postoperative reduction in the pivot shift of 7.4 mm (39%; P = .021) for APlat and 302.9 mm/s2 (75%; P = .005) for ACC.Conclusion:Lateral MAT improved knee kinematic parameters at time zero after surgery; the biomechanical effect of MAT was particularly evident during the pivot-shift maneuver.

The contralateral knee is a good predictor for determining normal knee stability: a cadaveric study.

The goal is to evaluate contralateral knee joint laxity and ascertain whether or not contralateral symmetry is observable. Secondary, a validation of a knee laxity testing rig is provided. Seven pairs of cadaveric knee specimens have been tested under passive conditions with and without external loads, involving a varus/valgus and an external/internal rotational torque and an anteroposterior shear force. Through the range of motion, the width of the varus/valgus laxity, internal/external laxity and anterior/posterior laxity for the medial and lateral compartment show no significant differences between left and right leg. These findings allow us to validate the setup, especially for relative values of laxity based on anatomical measures and knee joint biomechanics. A multidirectional laxity symmetry has been demonstrated for the intact knee and its contralateral knee in passive conditions as in an anesthetized patient. The passive laxity evaluation setup has been validated. Our work furthermore demonstrated a pronounced difference in anteroposterior mobility between the medial and lateral compartment of the knee, with a more stable medial side and more mobile lateral side. The contralateral knee can be used as reference for determining optimal knee laxity peri-operatively in total knee replacement and ligament reconstruction. Level IV, Case series.

Experimental and Finite Element Investigations on the Biomechanical Effects of Meniscal Tears in the Knee Joint: A Review

The knowledge of the complex biomechanical behaviour of the injured knee joints is of paramount importance in various clinical situations. A review of the biomechanical effects of meniscal tears based on experimental and finite element analysis has not been reported in the literature. The objective of this study is to present a review of experimental and finite element investigations on the consequences of meniscal tears such as longitudinal, radial, horizontal cleavage and root tears in the medial and lateral menisci. It is found that larger longitudinal tear in the medial meniscus has a significant impact on the magnitude of strain in the meniscus associated with a dramatic increase in CP in the tibial cartilage. Also, the untreated fragment of the torn meniscus leads to a significant rise in contact pressure in the cartilage resulting in the progressive degeneration of the cartilage surface. The radial tears in the lateral meniscus of more than 66% width and those in the medial meniscus of more than 75% width result in a substantial increase in the contact pressure in the cartilage compared to that in the intact knee joint. The root tears in the menisci demonstrate a significant influence on the biomechanical response of the knee joint. The results of finite element analysis studies are compared with experimental findings. Finally, some recommendations for future work are proposed to predict the realistic biomechanical response of the knee joints with meniscal tears. The results of this study present a rationale that could help surgeons in making clinical decisions when managing patients with meniscal tears.

The Influence of Load Carriage on Knee Joint Loading and Metabolic Cost on Walking with Lower-Limb Amputation: A Preliminary Modeling Study

ABSTRACT Introduction For able-bodied individuals, the mechanical output from the ankle muscles is modulated to meet the altered demands of load carriage. However, for individuals with a lower-limb amputation, the stiffness properties of standard-of-care prosthetic feet do not change with varying load conditions. Thus, individuals with amputation often develop gait asymmetries during load carriage that increase their risk for developing overuse injuries such as in the intact knee and increase the metabolic cost of walking relative to able-bodied individuals. The purpose of this preliminary study was to assess the influence of load carriage technique on knee joint loading and metabolic cost during gait of an individual with a below-knee amputation using a forward dynamics simulation framework. Methods Simulations were generated to track the experimental walking data of individuals with amputation for 3 loading conditions (unloaded, front load, and back load). Results These simulations showed that individuals with amputation rely on their intact limb as a compensatory strategy to meet the increased demands of carrying a load. Carrying a back load was found to increase intact knee joint loading relative to carrying a front load but reduced metabolic cost. Conclusion The tradeoff between joint loading and metabolic cost should be considered when determining the appropriate load carriage technique. Future work should focus on improving prosthetic foot designs to help reduce joint loading asymmetry and elevated metabolic cost during different loading conditions for individuals with lower-limb amputation.

Double-Bundle Anterior Cruciate Ligament Reconstruction With Lateral Extra-Articular Tenodesis Is Effective in Restoring Knee Stability in a Chronic, Complex Anterior Cruciate Ligament-Injured Knee Model: A Cadaveric Biomechanical Study

To compare knee stability after intra-articular isolated double-bundle (DB) anterior cruciate ligament reconstruction (ACLR) and single-bundle (SB) and DB ACLR combined with lateral extra-articular tenodesis (LET) in a chronic, complex anterior cruciate ligament (ACL)-injured knee model. In 10 fresh-frozen cadaveric knees, we measured knee laxity in the following order: (1) intact knee; (2) ACL-sectioned knee; (3) complex ACL-injured knee model with additional sectioning of the anterolateral complex and the posterior horns of the medial and lateral menisci; (4) SB ACLR plus LET; (5) DB ACLR; and (6) DB ACLR plus LET. In comparison with the intact knee, significantly increased internal rotation (IR) laxity persisted at 60° and 90° after DB ACLR (P= .002 and P= .003, respectively). SB ACLR plus LET and DB ACLR plus LET resulted in significant reductions in IR laxity at 90° (P= .003 and P= .037, respectively), representing overconstraint in IR. SB ACLR plus LET resulted in persistently increased external rotation (ER) laxity at 30°, 60°, and 90° (P= .001, P < .001, and P < .001, respectively). The DB ACLR condition persistently showed significant increases in anterior tibial translation laxity at 60° and 90° (P= .037 and P= .024, respectively). A greater increase in ER laxity was seen after SB ACLR plus LET versus DB ACLR plus LET at 30°, 60°, and 90° (P < .001, P < .001, and P < .001, respectively). DB ACLR plus LET restored intact knee stability in IR, ER, and anterior tibial translation laxity at 0°, 30°, 60°, and 90° of knee flexion except for overconstraint in IR at 90° in a chronic, complex ACL-injured knee model. This cadaveric study provides some biomechanical evidence to support performing DB ACLR combined with LET to restore knee stability after a complex, chronic knee injury involving an ACL tear combined with anterolateral complex injury and irreparable tears of the posterior horns of the medial and lateral menisci.

Effect of Percentage of Femoral Anterior Cruciate Ligament Insertion Site Reconstructed With Hamstring Tendon on Knee Kinematics and Graft Force

Background: Previous studies have stated that closely matching the size of the anterior cruciate ligament (ACL) insertion site footprint is important for biomechanical function and clinical stability after ACL reconstruction. However, the ACL varies widely regarding the area of femoral insertion, tibial insertion, and midsubstance of ACL, and reconstructing the insertion site area with a uniform diameter graft can result in a cross-sectional area that is greater than that of the midsubstance of the native ACL. Therefore, understanding the effect of relative graft size in ACL reconstruction on knee biomechanics is important for surgical planning. Purpose: To assess how the percentage of femoral insertion site affects knee biomechanics in single- and double-bundle ACL reconstruction. Study Design: Controlled laboratory study. Methods: A total of 14 human cadaveric knees were scanned with magnetic resonance imaging and tested using a robotic system under an anterior tibial load and a combined rotational load. In total, 7 knee states were evaluated: intact ACL; deficient ACL; single-bundle ACL reconstruction with approximate graft sizes 25% (small), 50% (medium), and 75% (large) of the femoral insertion site; and double-bundle reconstruction of approximately 50% (medium) and 75% (large) of the femoral insertion site, based on the ratio of the cross-sectional area of the graft to the area of the femoral ACL insertion site determined by magnetic resonance imaging. Results: Anterior tibial translation was not significantly larger than the intact state in single-bundle and double-bundle medium graft reconstructions (P > .05) and was significantly greater in the single-bundle small graft reconstruction (P < .05). Anterior knee translation in single-bundle medium graft and large graft reconstructions was not statistically different (P > .05). In contrast, the anterior tibial translation for double-bundle large graft reconstruction was significantly smaller than for double-bundle medium graft reconstruction at low flexion angles (P < .05). The single-bundle small graft force was significantly different from the intact ACL in situ force (P < .05). The graft force with double-bundle large reconstruction was significantly greater than that with the double-bundle medium reconstruction (P < .05) but was not significantly different from that of the intact ACL (P > .05). Conclusion: Knee biomechanics with a single-bundle small graft tended to be significantly different from those of the intact knee. In the kinematic and kinetic data for the single- and double-bundle medium graft reconstruction, only the anterior translation at full extension for the single-bundle reconstruction was significantly different (lower) from that of intact knee. This was a time zero study. Clinical Relevance: This study can provide surgeons with guidance in selecting the graft size for ACL reconstruction.