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Purpose: This paper aims at evaluating the effects of muscle load on knee kinematics and stability after TKA and second at evaluating the effect of TKA surgery on knee kinematics and stability; and third, at correlating the stability in passive conditions and the stability in active, muscle loaded conditions. Methods: Fourteen fresh frozen cadaveric knee specimens were tested under passive and active condition with and without external loads involving a varus/valgus and internal/external rotational torque before and after TKA surgery using two in-house developed and previously validated test setups. Results: Introduction of muscle force resulted in increased valgus (0.98°) and internal rotation of the femur (4.64°). TKA surgery also affected the neutral path kinematics, resulting in more varus (1.25°) and external rotation of the femur (5.22°). All laxities were significantly reduced by the introduction of the muscle load and after implantation of the TKA. The presence of the implant significantly affects the active varus/valgus laxity. This contrasts with the rotational laxity, in which case the passive laxity is the main determinant for the active laxity. For the varus/valgus laxity, the passive laxity is also a significant predictor of the active laxity. Conclusion: Knee stability is clearly affected by the presence of muscle load. This points to the relevance of appropriate rehabilitation with focus on avoiding muscular atrophy. At the same time, the functional, muscle loaded stability strongly relates to the passive, ligament-based stability. It remains therefore important to assess knee stability at the time of surgery, since the passive laxity is the only predictor for functional stability in the operating theatre. Level of evidence: Case series, Level IV. [ABSTRACT FROM AUTHOR]

Purpose: Revision constrained-condylar total knee arthroplasty (CCK-TKA) is often used to provide additional mechanical constraint after failure of a primary TKA. However, it is unknown how much this translates to a reliance on soft-tissue support. The aim of this study was therefore to compare the laxity of a native knee to the CCK-TKA implanted state and quantify how medial soft-tissues stabilise the knee following CCK-TKA.Methods: Ten intact cadaveric knees were tested in a robotic system at 0°, 30°, 60° and 90° flexion with ± 90  N anterior-posterior force, ± 8 Nm varus-valgus and ± 5 Nm internal-external torques. A fixed-bearing CCK-TKA was implanted and the laxity tests were repeated with the soft tissues intact and after sequential cutting. The deep and superficial medial collateral ligaments (dMCL, sMCL) and posteromedial capsule (PMC) were sequentially transected and the percentage contributions of each structure to restraining the applied loads were calculated.Results: Implanting a CCK-TKA did not alter anterior-posterior laxity from that of the original native knee, but it significantly decreased internal-external and varus-valgus rotational laxity (p < 0.05). Post CCK-TKA, the sMCL restrained 34% of the tibial displacing load in anterior drawer, 16% in internal rotation, 17% in external rotation and 53% in valgus, across the flexion angles tested. The dMCL restrained 11% of the valgus rotation moment.Conclusions: With a fully-competent sMCL in-vitro, a fixed-bearing CCK-TKA knee provided more rotational constraint than the native knee. The robotic test data showed that both the soft-tissues and the semi-constrained implant restrained rotational knee laxity. Therefore, in clinical practice, a fixed-bearing CCK-TKA knee could be indicated for use in a knee with lax, less-competent medial soft tissues.Level Of Evidence: Controlled laboratory study. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of the present study was to determine how the medial structures and ACL contribute to restraining anteromedial instability of the knee.Methods: Twenty-eight paired, fresh-frozen human cadaveric knees were tested in a six-degree of freedom robotic setup. After sequentially cutting the dMCL, sMCL, POL and ACL in four different cutting orders, the following simulated clinical laxity tests were applied at 0°, 30°, 60° and 90° of knee flexion: 4 Nm external tibial rotation (ER), 4 Nm internal tibial rotation (IR), 8 Nm valgus rotation (VR) and anteromedial rotation (AMR)-combined 89 N anterior tibial translation and 4 Nm ER. Knee kinematics were recorded in the intact state and after each cut using an optical tracking system. Differences in medial compartment translation (AMT) and tibial rotation (AMR, ER, IR, VR) from the intact state were then analyzed.Results: The sMCL was the most important restraint to AMR, ER and VR at all flexion angles. Release of the proximal tibial attachment of the sMCL caused no significant increase in laxity if the distal sMCL attachment remained intact. The dMCL was a minor restraint to AMT and ER. The POL controlled IR and was a minor restraint to AMT and ER near extension. The ACL contributed with the sMCL in restraining AMT and was a secondary restraint to ER and VR in the MCL deficient knee.Conclusion: The sMCL appears to be the most important restraint to anteromedial instability; the dMCL and POL play more minor roles. Based on the present data a new classification of anteromedial instability is proposed, which may support clinical examination and treatment decision. In higher grades of anteromedial instability an injury to the sMCL should be suspected and addressed if treated surgically. [ABSTRACT FROM AUTHOR]

Purpose: This study aimed to compare the intraoperative kinematics, especially for mid-flexion femorotibial anteroposterior (AP) stability, between newly developed medial congruent (MC) inserts and cruciate-retaining (CR) inserts in navigated cruciate-retaining total knee arthroplasty (CR-TKA).Methods: Thirty consecutive patients with varus osteoarthritis undergoing CR-TKA using an image-free navigation system were enrolled. AP kinematics, the AP translation under manual maximum stress to the knee joint at 45° flexion, rotational kinematics, and varus-valgus laxity were evaluated using a navigation system and statistically compared between the MC and CR inserts.Results: AP kinematic analysis showed that the femoral position with the CR insert was significantly anterior at a maximum extension to 45° flexion compared with the MC insert (p < 0.05). The amount of AP translation at 45° flexion with the MC insert was significantly smaller than that with the CR insert (p < 0.05). Rotational kinematics found that the tibial position at maximum extension was significantly externally rotated with the MC inserts than with the CR inserts. Varus-valgus laxity was comparable between the MC and CR inserts.Conclusion: The current results showed that greater mid-flexion AP stability was achieved with the MC inserts than with the CR inserts in CR-TKA. Intraoperative kinematics with the MC inserts more closely resembled those with preoperative conditions in CR-TKA.Level Of Evidence: III, prospective comparative study. [ABSTRACT FROM AUTHOR]

Purpose: The aim of this systematic review was to evaluate the evidence on the existence of midflexion instability in primary total knee arthroplasty and which factors might contribute to this condition.Methods: A comprehensive search of PubMed, Medline, Cochrane, CINAHL, and Embase databases was conducted since the inception of the database to July 2019. All relevant articles were retrieved, and their bibliographies were hand searched for further references on midflexion instability in primary total knee arthroplasty. The search strategy yielded 28 articles. After duplicate removal titles, abstracts and full text were reviewed. Fifteen studies were assessed for eligibility, 8 studies were excluded because they did not fully comply with the inclusion criteria. Seven articles were finally included in this systematic review. Anteroposterior translation, total knee arthroplasty design such as posterior-stabilized or posterior-cruciate-retaining total knee arthroplasty, joint line position with posterior condylar offset and joint gaps were considered to significantly influence midflexion stability.Results: Based on this systematic review anteroposterior translation of ≥ 7 mm was an independent risk factor for midflexion instability at 30° knee flexion. Joint line position can be altered by up to 5 mm without measurable changes in joint stability and both an increase and a decrease in posterior condylar offset led to 30° midflexion instability.Conclusion: Midflexion instability in primary total knee arthroplasty remains to be not entirely understood. Due to the low quality of available evidence, it is difficult to make any definitive conclusions. The factors which can lead to this condition were analyzed in this review, furthermore, we did not find exhaustive evidence on midflexion instability existence as an isolated entity. Nonetheless, this review will form a baseline for future research and creates awareness for the routine assessment of midflexion instability in primary total knee arthroplasty.Level Of Evidence: IV. [ABSTRACT FROM AUTHOR]

Purpose: Voluntary femoro-tibial subluxation is a rare entity predominantly found in pretoddlers. It presents as a dynamic phenomenon with uni- or bilateral audible snapping of the knee, often in a context of fatigue or irritation at the end of the day. The aim of the study was to observe the evolution and recovery in these patients.Methods: Ten children were included. Other causes of dislocating joints and pathologies with snapping of the lateral meniscus were excluded from this study. Six-week immobilisation with a splint at 70° of knee flexion was primarily recommended to all patients.Results: The mean age at onset of symptoms was 10 months. Forty percent of the patients presented with bilateral symptoms. Clinically, four patients were hyperlax. In all patients, subluxations could be reproduced passively by rotating the foot externally and advancing the internal tibial plateau anteriorly. Three of the patients were treated with a dorsal splint and experienced significantly less or cessation of symptoms. Two patients underwent surgery, one for a concomitant anterior cruciate ligament (ACL) rupture and meniscus tear that worsened the symptoms, another for concomitant patella dislocation and a meniscus tear. One patient's parents refused treatment and four patients experienced less symptoms at the time of consultation and were not immobilized. Except for the two patients undergoing surgeries, no sequelae were observed. In general, the symptoms got less frequent when the patient began to walk.Conclusion: Voluntary femoro-tibial subluxation in children is a rare and benign condition that often resolves spontaneously without sequelae. The risk of meniscus tear should, however, be considered if subluxations do not cease.Level Of Evidence: IV. [ABSTRACT FROM AUTHOR]

Purpose: Previous cadaver studies showed that the additional bone cuts in the distal and posterior femur and joint line elevation resulted in laxity at mid-flexion after total knee arthroplasty (TKA). However, these results are not always applicable to TKA candidates because the related studies used cadaver knees with no osteoarthritis. It was hypothesized that the joint line elevation results in mid-flexion laxity after TKA in patients with knee osteoarthritis. The purpose of this study was to analyze the relationship between joint line elevation and mid-flexion laxity in patients with knee osteoarthritis.Methods: 30 knees with varus osteoarthritis undergoing TKA were evaluated. Two femoral trial component models were prepared: (1) normal model with a thickness of the distal and posterior femoral components of 9 mm, and (2) 2-mm joint line elevation model with a thickness of the distal and posterior femoral components of 9 - 2 = 7 mm. This 2-mm joint line elevation model simulated an additional bone cut in the distal and posterior femur, and joint line elevation, without an additional bone cut. The femoral trial component models were set before implantation and measured the joint gap kinematics using a tensor device through the full knee range of motion.Results: The differences in joint gap change from 30° to 90° were not statistically significant between the two models. However, the joint line elevation model decreased the joint gap laxity at 120° (p = 0.02) and at 145° (p = 0.01).Conclusions: This study showed that a 2-mm joint line elevation was not associated with mid-flexion laxity in patients with varus osteoarthritis in the knee. The results of this study differed from the results in previous cadaver studies.Level Of Evidence: Therapeutic study, level II, prospective comparative study. [ABSTRACT FROM AUTHOR]

Purpose: Robot-assisted total knee arthroplasty (rTKA) remains in its infancy, is expensive but offers the promise of improved kinematic performance through precise bone cuts, with minimal soft tissue disruption, based on pre-resection soft tissue behaviour. This cadaveric study examined load transfer, soft tissue performance and radiographic indices for conventional (sTKA) versus rTKA. The null hypothesis was there would be no difference between the two modes of implantation.Methods: Whole (ten) cadaveric limbs were randomised to receive either robotic (rTKA, N = 5) or conventional measured resection (sTKA, N = 5) knee arthroplasty. Laxity patterns were established using validated fixed sensors (Verasense) with manual maximum displacement for six degrees of freedom. Tibiofemoral load and contact points were determined dynamically using remote sensor technology for medial and lateral compartments through a functional arc of motion (0-110 degrees of motion). Final component position was assessed using pre- and post-implantation CT.Results: No significant intergroup differences for laxity were found (n.s.). The rTKA group exhibited consistently balanced mediolateral load throughout the full arc with significantly reduced overall total load across the joint (for distinct points of measurement, p < 0.05). Despite using flexion-extension and mediolateral gap balancing with measured resection, the sTKA group failed to achieve balance in at least three points of the flexion arc. Post-operative CT confirmed satisfactory component alignment with no significant differences for positioning between the two groups.Conclusion: This work found improved load sharing for rTKA when compared to conventional surgery for same donor knees. Laxity and CT determined final component positioning was not significantly different. The work supports the contention that robot-assisted TKA delivers improved tibiofemoral load sharing in time zero studies under defined conditions but such offers the promise of improved clinical performance and reduced implant wear. [ABSTRACT FROM AUTHOR]

Purpose: Kinematically aligned (KA) TKA strives to restore native limb and knee alignments without ligament release with the premise that knee function likewise will be closely restored to native to the extent enabled by the components used. This study determined differences in anterior-posterior (AP) tibial contact locations of a KA TKA performed with asymmetric, fixed bearing, posterior cruciate-retaining (PCR) components from those of the native contralateral knee and also determined the incidence of posterior rim contact of the tibial insert during a deep knee bend and a step-up.Methods: Both knees were imaged using single-plane fluoroscopy for 25 patients with a calipered KA TKA and a native knee in the contralateral limb. AP tibial contact locations in each compartment were determined following 3D model-to-2D image registration. Differences in mean AP tibial contact locations in each compartment between the KA TKA knees and the native contralateral knees were analysed. Contact locations either on or beyond the most posterior point of the tibial insert determined the occurrence of posterior rim contact.Results: Mean AP tibial contact locations for both native and KA TKA knees remained relatively centred in the medial compartment but moved posterior in the lateral compartment during flexion. In both the medial and lateral compartments, differences in mean AP tibial contact locations between the KA TKA knees and the native contralateral knees were more posterior and greatest at 0° flexion for both activities (4 mm, p = 0.0009 and 7 mm, p < 0.0001 for deep knee bend and 6 mm, p < 0.0001 and 8 mm, p < 0.0001 for step-up in the medial and lateral compartments, respectively). The incidence of posterior rim contact of the tibial insert was 16% (4 of 25 patients) but the lowest Oxford Knee Score was 43 for these patients. The median Oxford Knee Score for all patients was 46 (out of 48).Conclusions: Calipered KA TKA with asymmetric, fixed bearing, PCR components resulted in mean AP tibial contact locations which were relatively centred in the compartments and differed at most from those of the native contralateral knee by approximately 15% of the AP dimension of a mid-sized tibial baseplate. Although posterior rim contact occurred in some patients, all such patients had high patient-reported outcome scores.Level Of Evidence: Therapeutic, Level III. [ABSTRACT FROM AUTHOR]

Purpose: Posterolateral rotatory instability (PLRI) of the elbow occurs from an insufficient lateral collateral ligament complex (LCLC). For subacute LCLC injuries, lateral ulnar collateral ligament (LUCL) internal bracing rather than reconstruction may be a viable option. The purpose of the study was to compare the stabilizing effects of LUCL internal bracing to triceps tendon graft reconstruction in simulated PLRI.Methods: Sixteen cadaveric elbows were assigned for either LUCL internal bracing (n = 8) or reconstruction with triceps tendon graft (n = 8). Specimen were mounted and a valgus rotational torque was applied to the ulna to test posterolateral rotatory stability. Posterolateral rotation was measured at 0°, 30°, 60°, 90° and 120° of elbow flexion. Cyclic loading was performed for 1000 cycles at 90° of elbow flexion. Three conditions were compared in each specimen: intact elbow, LUCL and radial collateral ligament (RCL) transected, and then either LUCL internal bracing or reconstruction with triceps tendon graft.Results: Transection of the LUCL and RCL significantly increased posterolateral rotation in all degrees of elbow flexion compared to the intact condition (P < 0.05). Both LUCL internal bracing and reconstruction restored posterolateral rotatory stability to the native state between 0° and 120° of elbow flexion, with no significant difference in improvement between groups. Similarly, LUCL internal bracing and reconstruction groups showed no significant difference in posterolateral rotation compared to the intact condition during cyclic loading.Conclusions: At time zero, both LUCL internal bracing and reconstruction with triceps tendon graft restored posterolateral rotatory stability. As such, this study supports the use of internal bracing as an adjunct to primary ligament repair in subacute PLRI. [ABSTRACT FROM AUTHOR]

Purpose: The aims of this study were (1) to study the biomechanics of single-bundle anatomic ACL reconstructed knees with and without notchplasty using a robotic testing system and (2) to determine if there would be a difference between performing a small or large notchplasty.Methods: Fifteen fresh-frozen specimens were used in this study. The ACL reconstruction (ACL-R) was performed using an anatomic single-bundle technique with the 8 mm soft tissue graft fixed at 30° with suspensory fixation on the femoral side and a screw and washer on the tibial side. The notchplasty was then created with a burr. The following knee states were compared: (1) ACL-R, (2) ACL-R with a small (3 mm) notchplasty, and (3) ACL-R with a large (6 mm) notchplasty. Four loading conditions were applied: (1) an anterior drawer with an 89 N anterior tibial load, (2) simulated pivot-shift loading, (3) a 5 Nm internal rotational moment, and (4) a 5 Nm external rotational moment.Results: Under anterior tibial loading, anterior tibial translation increased, and graft force decreased significantly after ACL-R + 3 mm notchplasty and ACLR + 6 mm notchplasty compared to ACL-R alone at FE, 15° and 30° of knee flexion. There were no changes in either anterior tibial translation or graft force under simulated pivot-shift loading, internal rotational moment, or external rotational moment.Conclusion: When added to anatomic ACL reconstruction, notchplasty increased anterior tibial translation and decreased graft forces during low knee flexion angles. There was no difference between a small and large notchplasty. The findings of this study are clinically relevant as the purpose of anatomic ACL reconstruction is to restore normal knee laxity, and while notchplasty may be helpful in avoiding graft impingement and improving visualization, removing even 3 mm of bone leads to biomechanical changes. [ABSTRACT FROM AUTHOR]

Purpose: To assess the impact on ankle stability after repairing the ATFL alone compared to repairing both the ATFL and CFL in a biomechanical cadaver model.Methods: Ten matched pairs of intact, fresh frozen human cadaver ankles (normal) were mounted to a test machine in 20.0° plantar flexion and 15.0° of internal rotation. Each ankle was loaded to body weight and then tested from 0.0° to 20.0° of inversion. The data recorded were torque at 20.0° and stiffness, peak pressure and contact area in the ankle joint using a Tekscan sensor, rotation of the talus and calcaneus, and translation of the calcaneus using a three-dimensional motion capture system. Ankles then underwent sectioning of the ATFL and CFL (injured), retested, then randomly assigned to ATFL-only Broström repair or combined ATFL and CFL repair. Testing was repeated after repair then loaded in inversion to failure (LTF).Results: The stiffness of the ankle was not significantly increased compared to the injured condition by repairing the ATFL only (n.s.) or the ATFL/CFL (n.s.). The calcaneus had significantly more rotation than the injured condition in the ATFL-only repair (p = 0.037) but not in the ATFL/CFL repair (n.s.). The ATFL failed at 40.3% higher torque than the CFL, at 17.4 ± 7.0 N m and 12.4 ± 4.1 N m, respectively, and 62.0% more rotation, at 43.9 ± 5.6° and 27.1 ± 6.8°, respectively.Conclusions: There was a greater increase in stiffness following combined ATFL/CFL repair compared to ATFL-only repair, although this did not reach statistical significance. The CFL fails before the ATFL, potentially indicating its vulnerability immediately following repair.Level Of Evidence: III, case-control therapeutic study. [ABSTRACT FROM AUTHOR]

Purpose: The acromioclavicular ligament complex (ACLC) is the primary stabilizer against horizontal translation with the superior ACLC providing the main contribution. The purpose of this study was to evaluate the specific regional contributions in the superior half of ACLC, where the surgeon can easily access and repair or reconstruct, for posterior translational and rotational stability.Methods: The superior half of ACLC was divided into three regions; Region A (0°-60°): an anterior 1/3 region of the superior half of ACLC, Region B (60°-120°): a superior 1/3 region of the superior half of ACLC, and Region C (120°-180°): a posterior 1/3 region of the superior half of ACLC. Fifteen fresh-frozen cadaveric shoulders were used. Biomechanical testing was performed to evaluate the resistance force against passive posterior translation (10 mm) and the resistance torque against passive posterior rotation (20°) during the following the four conditions. (1) Stability was tested on all specimens in their intact condition (n = 15). (2) The ACLC was dissected and stability was tested (n = 15). (3) Specimens were randomly divided into three groups by regions of suturing. Stability was tested after suturing Region A, Region B, or Region C (n = 5 per group). (4) Stability was tested after suturing additional regions: Region A + B (0°-120°), Region B + C (60°-180°), or Region A + C (0°-60°, 120°-180°, n = 5 per group).Results: The translational force increased after suturing Region A when compared with dissected ACLC (P = 0.025). The force after suturing Region A + B was significantly higher compared to the dissected ACLC (P < 0.001). The rotational torque increased after suturing Region A or Region B compared with dissected ACLC (P = 0.020, P = 0.045, respectively). The torque after suturing the Region A + C was significantly higher compared to the dissected ACLC (P < 0.001).Conclusion: The combined Region A + B contributed more to posterior translational stability than Region B + C or Region A + C. In contrast, combined Region A + C contributed more to posterior rotational stability than Region A + B or Region B + C. Based on these findings, surgical techniques restoring the entire superior ACLC are recommended to address both posterior translational and rotational stability of the AC joint. [ABSTRACT FROM AUTHOR]

Purpose: The aim of this study was to evaluate the effects of knee biomechanics with an irreparable lateral meniscus defect using the centralization capsular meniscus support procedure in the setting of the ACL-reconstructed knee in a porcine model. The hypothesis is the arthroscopic centralization will decrease the laxity and rotation of the ACL-reconstructed knee.Methods: Twelve fresh-frozen porcine knees were tested using a robotic testing system under the following loading conditions: (a) an 89.0 N anterior tibial load; (b) 4.0 N m internal and external rotational torques. Anatomic single-bundle ACL reconstruction with a 7 mm-diameter bovine extensor tendon graft was performed. A massive, middle segment, lateral meniscus defect was created via arthroscopy, and arthroscopic centralization was performed with a 1.4 mm anchor with a #2 suture. The LM states with ACL reconstruction evaluated were: intact, massive middle segment defect and with the lateral meniscus centralization procedure.Results: The rotation of the ACL reconstructed knee with the lateral meniscus defect was significantly higher than with the centralized lateral meniscus under an external rotational torque at 30° of knee flexion, and under an internal rotational torque at 30° and 45° of knee flexion. There were no systematic and consistent effects of LM centralization under anterior tibial translation.Conclusions: In this porcine model, the capsular support of middle segment of the lateral meniscus using arthroscopic centralization improved the residual rotational laxity of the ACL-reconstructed knee accompanied with lateral meniscus dysfunction due to massive meniscus defect. This study quantifies the benefit to knee kinematics of arthroscopic centralization by restoring the lateral meniscal function. [ABSTRACT FROM AUTHOR]

Purpose: Clinicians have different techniques and varying levels of experience with the pivot shift test, introducing variability into its performance. The purpose of this study was to evaluate the influence of teaching and repetition on the success rate and anterior translation of the lateral knee compartment during the pivot shift test in a cadaveric ACL injury model.Methods: Twenty-five participants (five each of medical students, orthopaedic surgery residents, physical therapists, athletic trainers, sports medicine fellows) were recruited and a senior orthopaedic surgeon served as gold standard examiner. Each participant performed 20 pivot shift tests on lower extremity cadaveric specimens with ACL deficiency and lateral meniscectomy: 5 prior to education (baseline), 10 after watching an instructional video (passive teaching), and 5 after an interactive education session (active teaching). The anterior translation of the lateral knee compartment was recorded during each pivot shift test using electromagnetic tracking system.Results: For medical students and orthopaedic surgery residents, significant improvement in success rate was found when compared to baseline (12% and 24%, respectively) after both passive (36% and 60%, respectively) and active teaching (52% and 72%, respectively) (p < 0.5). Medical students and residents were the only participants that independently achieved significant increases in anterior translation of the lateral knee compartment, each tripling the respective baseline value (p < 0.5). In the entire study population, significant increases in anterior translation of the lateral knee compartment and success rate of the pivot shift test were seen with continuous repetition (p < 0.5). However, the standard deviation of anterior translation of the lateral knee compartment was more than twice the gold standard examiner's standard deviation, indicating a high degree of variability.Conclusion: Teaching of the pivot shift test plays a major role in the development of a proper technique. However, variability persisted despite teaching and repetition. New methods may be needed to improve the teaching of the pivot shift test. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this study was to identify high-functioning anterior cruciate ligament-deficient patients and assess the effects of reconstruction on their self-reported functionality, muscle activations and biomechanical properties.Methods: Twenty young and active patients participated pre- (11.5 ± 14.3 months post-injury) and again 10.5 ± 1.7 months post-reconstruction and were individually matched to 20 healthy controls. Participants completed hop and side cut movements while patient-related outcome measures, lower limb electromyography, kinetic, and whole body kinematic data were collected. One-dimensional statistical parametric mapping was used to test for group differences (healthy vs deficient; deficient vs reconstructed; reconstructed vs healthy).Results: When comparing healthy to anterior cruciate ligament-deficient participants, all questionnaires indicated significant lower subjective function while the only substantial biomechanical difference between these participants was a decreased knee extensor moment in both the hop (peak difference: 0.63 Nm/kg, p < 0.001) and side cut (peak difference: 0.76 Nm/kg, p < 0.001). When comparing patients' pre- and post-reconstruction, no biomechanical differences were observed whereas only half of the questionnaires (Tegner, Lysholm, KNEES-ADL, KNEES-Slackness, KNEES-Looseness, KNEES-Sport Behaviour, IKDC, and KOOS-QoL) indicated higher function in the reconstructed state. When comparing the reconstructed patients to the healthy participants, all questionnaires were still significantly higher in the healthy controls. The reconstructed group also had a smaller flexion angle (peak difference: 14.5°, p = 0.007) and knee extensor moment (peak difference: 0.62 Nm/kg, p < 0.001) during the hop and a smaller knee extensor moment (peak difference: 0.90 Nm/kg, p < 0.001) during the side-cut task.Conclusion: At 10-months post-reconstruction, the current results indicate that in high-functioning anterior cruciate ligament-deficient patients, reconstruction had little impact on objective measures of functional ability during dynamic tasks although self-reported function was improved.Level Of Evidence: Therapeutic prospective cohort study, Level II. [ABSTRACT FROM AUTHOR]

Purpose: Concomitant meniscus injuries in the anterior cruciate ligament (ACL) have been suggested to exacerbate rotational laxity. However, the effect is supposed to be so small, if any, that some quantitative pivot-shift measurement is needed. The purpose of this prospective study was to determine the effect of meniscus tear on rotational laxity in ACL-deficient knees by an quantitative measurement. It was hypothesized that a concomitant meniscus tear, especially a lateral one, would induce greater pivot shift.Methods: Fifty-seven unilateral ACL-injured patients (26 men and 31 women, mean age: 24 ± 10 years) were included. The pivot-shift test was performed prior to ACL reconstruction, while a quantitative evaluation using an electromagnetic system to determine tibial acceleration and a clinical grading according to the IKDC were performed. Meniscus injuries were diagnosed arthroscopically, and concomitant meniscus tear was confirmed in 32 knees.Results: The clinical grade was not different between the ACL-injured knees of patients with and without meniscus tear (n.s.). Tibial acceleration did not show a statistical significant difference (meniscus-injured knees: 1.6 ± 1.1 m/s2 versus meniscus-intact knees: 1.2 ± 0.7 m/s2, n.s.). However, the subgroup analysis demonstrated that there was increased tibial acceleration in ACL-deficient knees with lateral meniscus tear (2.1 ± 1.1 m/s2, n = 13) compared with meniscus-intact knees (p < 0.05), whereas rotational laxity did not increase in the medial meniscus-injured and bilateral-injured knees (1.2 ± 0.9 m/s2, n = 12, n.s. and 1.4 ± 1.1 m/s2, n = 7, n.s., respectively).Conclusion: A concomitant meniscus tear, especially a lateral meniscus tear, has a significant impact on rotational laxity in ACL-injured knees. When a large pivot shift is observed in the ACL-injured knee, a concomitant meniscus tear should be suspected and an aggressive treatment would be considered. Meniscus injuries should be inspected carefully when substantial pivot shift is encountered in ACL-injured knees.Level Of Evidence: Diagnostic study, Level III. [ABSTRACT FROM AUTHOR]

Purpose: Individuals with impaired knee function after anterior cruciate ligament reconstruction (ACLR) may be at greater risk of developing knee osteoarthritis related to abnormal knee joint movement and loading. The aim of this study was to assess the association between knee biomechanics and knee laxity during hopping and clinically assessed knee function (i.e., patient-reported knee function and hop tests) following ACLR.Methods: Sixty-six participants (23 women, mean age 28 ± 6 years, mean 18 ± 3 months following ACLR) completed a standardized single-leg hopping task. Three-dimensional movement analysis was used to assess knee flexion excursion and body weight/height normalized knee flexion moments during landing for the involved limb. Anterior-posterior knee laxity was assessed with a KT-1000 knee arthrometer. Participants then completed a patient-reported knee function questionnaire and three separate hop tests (% of uninvolved limb) and were divided into poor and satisfactory knee function groups (satisfactory: ≥85% patient-reported knee function and ≥ 85% hop test symmetry). Associations between knee function and hop biomechanics/knee laxity were assessed using logistic regression and interquartile range scaled odds ratios (ORIQR).Results: Greater knee flexion excursion (ORIQR 2.9, 95%CI 1.1-7.8), greater knee flexion moment (ORIQR 4.9, 95%CI 1.6-14.3) and lesser knee laxity (ORIQR 4.7, 95%CI 1.5-14.9) were significantly associated with greater odds of having satisfactory knee function (≥ 85% patient-reported knee function and ≥ 85% hop test symmetry).Conclusion: Greater knee flexion excursion/moment during hop-landing and lesser knee laxity is associated with better patient-reported knee function and single-leg hop test performance following ACLR. Patients with lower levels of knee function following ACLR demonstrated hop-landing biomechanics previously associated with early patellofemoral osteoarthritis. Therefore, interventions aimed at improving hop landing biomechanics in people with poor knee function are likely required.Level Of Evidence: III, Cross-sectional study. [ABSTRACT FROM AUTHOR]

Purpose: The aim of this study was to determine patient and anatomic factors that influence anteroposterior and rotational laxity in knees with ACL tears. Based on the findings of biomechanical studies, we hypothesized that static and dynamic anterior tibial translation (ATT) as well as positive pivot shift would increase with female gender, tibial slope, and meniscal tears.Methods: The authors prospectively collected preoperative data and intraoperative findings of 417 patients that underwent ACL reconstruction. The exclusion criteria were: revision ACL procedures (n = 53), other surgical antecedents (n = 27), prior osteotomies (n = 7) or concomitant ligament tears on the ipsilateral knee (n = 34), and history of ACL tears in the contralateral knee (n = 45), leaving a study cohort of 251 patients. Their preoperative anteroposterior knee laxity was assessed objectively using 'static' monopodal weight-bearing radiographs and 'dynamic' instrumented differential measurements of ATT. Rotational laxity was assessed subjectively using the pivot shift test.Results: Multivariable regression showed that static ATT increases only with tibial slope (β = 0.30; p < 0.001), but dynamic ATT increases with tibial slope (β = 0.19; p = 0.041), medial meniscal tears (β = 1.27; p = 0.007), complete ACL tears (β = 2.06; p < 0.001), and to decrease with age (β = - 0.09; p < 0.001). Multivariable regression also indicated that high-grade pivot shift decreases with age (OR 0.94; p < 0.001) and for women (OR 0.25; p < 0.001), and to be higher for knees with complete ACL tears (OR 3.04; p = 0.002) or medial meniscal tears (OR 2.28; p = 0.010).Conclusion: Contrary to expectations based on biomechanical studies, static ATT was only affected by high posterior tibial slope, while dynamic ATT was affected by both high posterior tibial slopes and medial meniscal tears, but not by gender or lateral meniscal tears. Likewise, pivot shift was affected by gender and medial meniscal tears, but not lateral meniscal tears or posterior tibial slope. These findings are relevant to guide surgeons in optimizing their surgical procedures, such as conserving the menisci when possible, and rehabilitation protocols, by delaying full weight-bearing and return to sports in patients with anatomic and lesional risk factors.Level Of Evidence: Cohort study, Level IV. [ABSTRACT FROM AUTHOR]

Purpose: Valgus deformities of the lower extremity influence patellofemoral joint kinematics. However, studies examining the clinical outcome after treatment of patellar instability and maltracking due to valgus deformity are rare in recent literature. This study's purpose is to analyze the clinical results after combined distal femoral osteotomy (DFO) for treatment of patellar instability.Methods: From 2010 to 2016, 406 cases of patellofemoral instability and maltracking were treated. Twenty cases of recurring (≥ 2) patellar dislocations with genu valgum and unsuccessful conservative treatment were included in the study. A radiological analysis was performed, and anteroposterior (AP), lateral and long leg standing radiographs were analyzed, and the leg axis was pre- and postoperatively measured. At least 12 months postoperatively, the clinical leg axis, range of motion (ROM), apprehension sign, Zohlen sign, and J-sign were physically examined. Pain level and knee function were objectified on a visual analogue scale (VAS). The Lysholm, Kujala, and Tegner scores, re-dislocation rate, and patient satisfaction were also examined.Results: 20 combined DFOs on 18 patients with a median age of 23 years (15-55 years) were performed. The preoperative mechanical leg axis was 6.5° ± 2.0° valgus, and the mean tibial tuberosity to trochlear groove (TT-TG) distance was 19.1 ± 4.8 mm. All patients reported multiple dislocations. Intraoperatively, 71% presented III°-IV° cartilage lesions, located retropatellarly in 87% and correlating negatively with the postoperative Lysholm score (r = - 0.462, p = 0.040). The leg axis was corrected by 7.1° ± 2.6°, and in 17 cases, the tibial tubercle was additionally medialized by 10 ± 3.1 mm. All patellae were re-stabilized with medial patellofemoral ligament reconstruction. After a median period of 16 (12-64) months, the pain level decreased from 8.0 ± 1.4 to 2.3 ± 2.1 (VAS p ≤ 0.001) and knee function improved from 40.1 ± 17.9 to 78.5 ± 16.6 (Kujala p ≤ 0.001), 36.1 ± 19.5 to 81.6 ± 11.7 (Lysholm p ≤ 0.001), and 2.0 (1-5) to 4.0 (3-6) (median Tegner p ≤ 0.001). No re-dislocation was observed.Conclusion: Combined DFO is a suitable treatment for patellar instability and maltracking due to genu valgum, as it leads to very low re-dislocation rates, a significant reduction of pain, and a significant increase of knee function with good-to-excellent results in the short-term follow-up. However, a high prevalence of substantial cartilage lesions is observed, causing postoperative limitations of knee function.Level Of Evidence: IV, retrospective cohort study. [ABSTRACT FROM AUTHOR]

Purpose: To date, many radiographic parameters on patellar instability have their measurements taken statically, and have not been studied in various degrees of flexion according to the patellar tracking. There are also limited data regarding the use of these parameters in predicting recurrent patellar dislocation. The current study aims to review the radiographic parameters of the patellofemoral joint in different degrees of knee flexion and to correlate them with the presence of recurrent instability.Methods: A 10-year retrospective study was conducted on all patients who had computed tomography patellar-tracking scan done for patellar instability when aged 18 years or younger. The computed tomography patellar-tracking scans were performed with the knee in extension, 10° flexion, and 20° flexion. The axial radiographic parameters were evaluated at the patellar equator, roman arch, and distal patellar pole. Sagittal and coronal parameters were noted. Radiographic parameters were then correlated with recurrent patellar instability.Results: The femoral sulcus angle and trochlear groove depth at the distal patellar pole in 10° knee flexion (p value 0.04 and 0.03, respectively) and patellar equator in 20° knee flexion (p value 0.02 and 0.03, respectively) had the most significant clinical correlations with recurrent instability on multivariate analysis. Other radiographic parameters found to have significant clinical correlation on univariate analysis include the patellar tilt angle, congruence angle, femoral sulcus angle, trochlear groove depth, and Wiberg's classification.Conclusions: As per the knee dynamics, axial radiographic parameters had the most significant correlation with recurrent patellar instability when measured at the distal patellar pole in 10° knee flexion and at the patellar equator in 20° knee flexion. Future axial radiographic evaluation of patellofemoral instability should then be performed at these degrees of knee flexion and axial cuts. Trochlear dysplasia, as measured by the femoral sulcus angle and trochlear groove depth, was the most significant predictor of recurrent patellar instability in the skeletally immature. Wiberg's classification was also a novel factor found to have clinical correlation with patellofemoral instability.Level Of Evidence: III. [ABSTRACT FROM AUTHOR]

Purpose: To investigate intraoperative soft tissue balance with femoral component trial in place using a novel medial preserving gap technique, focusing on medial compartment stability and allowing lateral physiological laxity, with compared with using a measured resection technique in posterior-stabilized (PS) total knee arthroplasty (TKA).Methods: Primary PS TKA, using either medial preserving gap technique (n = 127) or measured resection technique (n = 148), was performed in 275 subjects with varus knee osteoarthritis. Intraoperative soft tissue balance with femoral component in place was assessed using Offset Repo-Tensor with 40 lbs. of joint distraction force throughout the range of motion, and medial and lateral compartment gaps (mm) were calculated. Medial and lateral joint gap changes (mm) were calculated by subtracting the medial/lateral compartment gap at 0° from the medial/lateral compartment gap at each knee flexion angle, respectively.Results: Medial and lateral joint gap changes in medial preserving gap technique were significantly smaller than measured resection technique respectively (mean difference between two procedures: medial; 0.9 ± 0.2 mm, lateral; 1.0 ± 0.3 mm). Medial and lateral joint gaps were significantly changed during knee flexion in measured resection technique, whereas medial and lateral joint gaps were not significantly changed during mid-to-deep knee flexion (30°-90° in medial, 30°-120° in lateral) in medial preserving gap technique.Conclusions: Medial preserving gap technique provided more consistent intraoperative soft tissue balance during knee flexion than the measured resection technique, suggesting that this novel technique can be utilized to obtain a more stable joint gap in PS TKA.Level Of Evidence: III. [ABSTRACT FROM AUTHOR]

Purpose: The purposes of this study were to quantify the increase in tibial force imbalance (i.e. magnitude of difference between medial and lateral tibial forces) and changes in laxities caused by 2° and 4° of varus-valgus (V-V) malalignment of the femoral component in kinematically aligned total knee arthroplasty (TKA) and use the results to detemine sensitivities to errors in making the distal femoral resections. Because V-V malalignment would introduce the greatest changes in the alignment of the articular surfaces at 0° flexion, the hypotheses were that the greatest increases in tibial force imbalance would occur at 0° flexion, that primarily V-V laxity would significantly change at this flexion angle, and that the tibial force imbalance would increase and laxities would change in proportion to the degree of V-V malalignment.Methods: Kinematically aligned TKA was performed on ten human cadaveric knee specimens using disposable manual instruments without soft tissue release. One 3D-printed reference femoral component, with unmodified geometry, was aligned to restore the native distal and posterior femoral joint lines. Four 3D-printed femoral components, with modified geometry, introduced V-V malalignments of 2° and 4° from the reference component. Medial and lateral tibial forces were measured during passive knee flexion-extension between 0° to 120° using a custom tibial force sensor. Eight laxities were measured from 0° to 120° flexion using a six degree-of-freedom load application system.Results: With the tibial component kinematically aligned, the increase in the tibial force imbalance from that of the reference component at 0° of flexion was sensitive to the degree of V-V malalignment of the femoral component. Sensitivities were 54 N/deg (medial tibial force increasing > lateral tibial force) (p < 0.0024) and 44 N/deg (lateral tibial force increasing > medial tibial force) (p < 0.0077) for varus and valgus malalignments, respectively. Varus-valgus malalignment did not significantly change varus, internal-external rotation, anterior-posterior, and compression-distraction laxities from 0° to 120° flexion. At only 30° of flexion, 4° of varus malalignment increased valgus laxity 1° (p = 0.0014).Conclusion: At 0° flexion, V-V malalignment of the femoral component caused the tibial force imbalance to increase significantly, whereas the laxities were relatively unaffected. Because tibial force imbalance has the potential to adversely affect patient-reported outcomes and satisfaction, surgeons should strive to limit errors in resecting the distal femoral condyles to within ± 0.5 mm which in turn limits the average increase in tibial force imbalance to 68 N. Because laxities were generally unaffected, instability resulting from large increases in laxity is not a clinical concern within the ± 4° range tested.Level Of Evidence: Therapeutic, Level II. [ABSTRACT FROM AUTHOR]

Purpose: Graft tensioning during medial patellofemoral ligament (MPFL) reconstruction typically allows for lateral patellar translation within the trochlear groove. Computational simulation was performed to relate the allowed patellar translation to patellofemoral kinematics and contact pressures.Methods: Multibody dynamic simulation models were developed to represent nine knees with patellar instability. Dual limb squatting was simulated representing the pre-operative condition and simulated MPFL reconstruction. The graft was tensioned to allow 10, 5, and 0 mm of patellar lateral translation at 30° of knee flexion. The patellofemoral contact pressure distribution was quantified using discrete element analysis.Results: For the 5 and 10 mm conditions, patellar lateral shift decreased significantly at 0° and 20°. The 0 mm condition significantly decreased lateral shift for nearly all flexion angles. All graft conditions significantly decreased lateral tilt at 0°, with additional significant decreases for the 5 and 0 mm conditions. The 0 mm condition significantly increased the maximum medial pressure at multiple flexion angles, increasing by 57% at 30°, but did not alter the maximum lateral pressure.Conclusions: Allowing 5 to 10 mm of patellar lateral translation limits lateral maltracking, thereby decreasing the risk of post-operative recurrent instability. Allowing no patellar translation during graft tensioning reduces maltracking further, but can overconstrain the patella, increasing the pressure applied to medial patellar cartilage already fibrillated or eroded from an instability episode. [ABSTRACT FROM AUTHOR]

Purpose: Several non-invasive devices have been developed to obtain quantitative assessment of the pivot-shift test in clinical setting using similar but diverse measurement parameters. However, the clinical usability of those measurements has yet to be closely investigated and compared. The purpose of this study was to compare the diagnostic accuracy of three non-invasive measurement devices for the pivot-shift test.Methods: Thirty patients with unilateral anterior cruciate ligament (ACL) injury were enrolled. The pivot-shift test was performed under general anaesthesia. Three devices, an accelerometer system (KiRA), an image analysis iPad application (iPad), and electromagnetic measurement system (EMS), were used simultaneously to provide two parameters, namely tibial acceleration monitored using KiRA and EMS, and tibial translation recorded using iPad and EMS. Side-to-side differences in each parameter and correlation between the measurements were tested, and a receiver-operating characteristic (ROC) curve analysis was conducted to compare their measurement accuracy.Results: Significant side-to-side differences were successfully detected using any of the measurements (all p < 0.01). KiRA demonstrated moderate correlation with the EMS for tibial acceleration (r = 0.54; p < 0.01), while poor correlation was observed between iPad and the EMS for the translation (r = 0.28; p < 0.01). The ROC curve analysis demonstrated better accuracy for the detection of ACL insufficiency in the EMS than KiRA and iPad for tibial acceleration and translation, respectively.Conclusions: Although all three measurements were similarly capable of detecting ACL deficiency, the EMS has the advantage of comprehensive evaluation of the pivot-shift test by evaluating both tibial acceleration and translation with higher accuracy than those of KiRA and iPad. It could be suggested that any of those measurement tools might improve the clinical diagnosis of ACL insufficiency.Level Of Evidence: Diagnostic study of consecutive patients with a universally applied gold standard, Level Ib. [ABSTRACT FROM AUTHOR]

Purpose: Notwithstanding the importance of the tibial slope (TS) for anterior tibial translation, little information is available regarding the implications on posterior laxity, particularly in healthy subjects. It was hypothesized that increased TS is associated with decreased posterior tibial translation (PTT) in healthy knees.Methods: A total of 124 stress radiographs of healthy knees were enrolled in this study. Tibial slope and the posterior tibial translation were evaluated using a Telos device with a 150-N force at 90° of knee flexion. Two blinded observers reviewed independently on two different occasions.Results: One hundred and twenty-four patients [35 females and 89 males; 41 (range 18-75) years] were enrolled in this study, with a mean PTT of 2.8 mm (±1.9 mm; range 0-8 mm) and a mean TS of 8.6° (±2.6°; range 1°-14°). Pearson correlation showed a significant correlation between the PTT and TS in the overall patient cohort (P < 0.0001) with r = 0.76 and R 2 = 0.58. There was no statistical difference between female and male patients regarding the PTT or the TS. Subgrouping of the patient cohort (four groups with n = 31) according to their TS (groups I < 7°; II = 7°-8.5°; III = 9°-10.5°; IV ≥ 11°) revealed significant differences between each subgroup, respectively. Furthermore, there was a weak but significant correlation between age and PTT (P = 0.004, r = 0.26).Conclusion: In addition to the substantial variance in tibial slope and posterior laxity among healthy knees, high tibial slope significantly correlates with increased posterior tibial translation. Increasing age is further associated with a greater magnitude of posterior tibial translation. Consequently, knowledge of the tibial slope facilitates simple estimation of posterior knee laxity, which is mandatory for PCL reconstruction and knee arthroplasty. [ABSTRACT FROM AUTHOR]

Purpose: This is a meta-analysis comparing biomechanical outcomes to determine whether an isolated posterior cruciate ligament (PCL) reconstruction can restore normal knee kinematics in a combined PCL/posterolateral complex (PLC) injury and whether double-bundle (DB) PCL reconstruction is superior in controlling posterior and rotational laxity compared with single-bundle (SB) PCL reconstruction in a PCL/PLC-deficient knee.Methods: A number of electronic databases were searched for relevant articles published through August 2016 that compared biomechanical outcomes of PCL reconstruction in patients who underwent reconstruction for combined PCL/PLC deficiencies. Data were searched, extracted, analysed, and assessed for quality according to Cochrane Collaboration guidelines, and biomechanical outcomes were evaluated using various outcome values. The results are presented as relative ratios for binary outcomes and standard mean differences for continuous outcomes with 95% confidence intervals.Results: Five biomechanical studies were included in this meta-analysis. There were significant differences in laxities such as posterior tibial translation (PTT), external rotation, varus rotation, and PTT coupled with external rotation in the isolated PCL reconstruction group compared with the native PCL group. Furthermore, there were no significant differences in laxities such as PTT, external rotation, or varus rotation between the SB and DB PCL reconstruction groups.Conclusion: Isolated PCL reconstruction, whether SB or DB, could not restore normal knee kinematics in the PCL/PLC-deficient knee. In such cases, residual laxity after isolated PCL reconstruction can be controlled successfully with PLC reconstruction. Therefore, simultaneous PCL and PLC reconstruction is recommended for patients with combined PCL/PLC injury. [ABSTRACT FROM AUTHOR]

Purpose: To investigate the stabilizing effect of a lateral meniscus posterior root repair in an ACL and root deficient knee.Methods: The hypothesis of the current study was that a sequential transection of the posterior root and the meniscofemoral ligaments in an ACL-deficient knee increases rotational instability, and conversely, a repair of the meniscus root reduces the internal tibial rotation. Therefore, eight human knee joints were tested in a robotic setup (5 N m internal torque, 50 N m anterior translation load). Five conditions were tested: intact, ACL cut, ACL cut + lateral meniscus posterior root tear (LMRT), ACL cut + LMRT + transection of the MFL and ACL cut + lateral meniscus root repair. The angles of internal tibial rotation as well as anterior tibial translation were recorded.Results: Transection of the lateral meniscus posterior root increased the internal tibial instability as compared to the ACL-insufficient state. A significant increase was detected in 60° and 90° of flextion. Sectioning of the meniscofemoral ligament further destabilized the knees significantly at all flexion angles as compared to the ACL-deficient state. Even in 30°, 60° and 90° a significant difference was detected as compared to the isolated root tear. A tibial fixation of the lateral meniscus root reduced the internal tibial rotation in all flexion angles and led to a significant decrease of internal tibial rotation in 30° and 90° as compared to the transection of the root and the MFL. The anterior tibial translation was increased in all conditions as compared to the native state.Conclusion: A lateral meniscus root repair can reduce internal tibial rotation in the ACL-deficient knee. To check the condition of the lateral posterior meniscus root attachment is clinical relevant as a lateral meniscus root repair might improve rotational stability. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this study was to evaluate the relationship between posterior tibial slope and knee kinematics in bi-cruciate stabilized (BCS) total knee arthroplasty (TKA), which has not been previously reported.Methods: This computer simulation study evaluated Journey 2 BCS components (Smith & Nephew, Inc., Memphis, TN, USA) implanted in a female patient to simulate weight-bearing stair climbing. Knee kinematics, patellofemoral contact forces, and quadriceps forces during stair climbing (from 86° to 6° of flexion) were computed in the simulation. Six different posterior tibial slope angles (0°-10°) were simulated to evaluate the effect of posterior tibial slope on knee kinematics and forces.Results: At 65° of knee flexion, no anterior sliding of the tibial component occurred if the posterior tibial slope was less than 10°. Anterior contact between the anterior aspect of the tibial post- and the femoral component was observed if the posterior tibial slope was 6° or more. An increase of 10° in posterior tibial slope (relative to 0°) led to a 4.8% decrease in maximum patellofemoral contact force and a 1.2% decrease in maximum quadriceps force.Conclusion: BCS TKA has a wide acceptable range of posterior tibial slope for avoiding knee instability if the posterior tibial slope is less than 10°. Surgeons should prioritize avoiding adverse effects over trying to achieve positive effects such as decreasing patellofemoral contact force and quadriceps force by increasing posterior tibial slope. Our study helps surgeons determine the optimal posterior tibial slope during surgery with BCS TKA; posterior tibial slope should not exceed 10° in routine clinical practice. [ABSTRACT FROM AUTHOR]

Purpose and Hypothesis: Correct femoral component rotation at knee arthroplasty influences patellar tracking and may determine function at extremes of movement. Additionally, such malrotation may deleteriously influence flexion/extension gap geometry and soft tissue balancing kinematics. Little is known about the effect of subtle rotational change upon load transfer across the tibiofemoral articulation. Our null hypothesis was that femoral component rotation would not influence load across this joint in predictable manner.Methods: A cadaveric study was performed to examine load transfer using the orthosensor device, respecting laxity patterns in 6° of motion, to examine load across the medial and lateral compartments across a full arc of motion. Mixed-effect modelling allowed for quantification of the effect upon load with internal and external femoral component rotation in relation to a datum in a modern single-radius cruciate-retaining primary knee design.Results: No significant change in maximal laxity was found between different femoral rotational states. Internal rotation of the femoral component resulted in significant increase in medial compartment load transfer for knee flexion including and beyond 60°. External rotation of the femoral component within the limits studied did not influence tibiofemoral load transfer.Conclusions: Internal rotation of the femoral component will adversely influence medial compartment load transfer and could lead to premature polyethylene wear on the medial side. [ABSTRACT FROM AUTHOR]

Purpose: In total knee arthroplasty (TKA), the posterior tibial slope is not always reconstructed correctly, and the knee ligaments may become too tight in flexion. To release a tight flexion gap, surgeons can increase the posterior tibial slope using two surgical resection techniques: the anterior tibial cortex (ACR) or the centre of tibial plateau (CPR) referencing. It is not known how this choice affects the knee laxity and function during activities of daily living. The aim of this study was to investigate the effect of tibial slope on knee laxity, kinematics and forces during a squatting activity using computer simulation techniques. We hypothesised that the effects depend on the referencing technique utilised.Methods: A validated musculoskeletal model of TKA was used. Knee laxity tests were simulated in flexion and extension. Then, a squat motion was simulated to calculate: movement of the tibiofemoral joint (TFJ) contact points and patello-femoral joint (PFJ) contact force. All analyses were repeated with more anterior (-3°), neutral (0°), and more posterior tibial slope (+3°, +6°, +9°), and with two referencing techniques (ACR, CPR).Results: Knee laxities increased dramatically with more posterior slope with the ACR technique (up to 400%), both in flexion and in extension. The CPR technique, instead, had much smaller effects (up to 42% variations). During squatting, more slope with the ACR technique resulted in larger movements of the TFJ contact point. The PFJ contact force decreased considerably with more slope with the CPR technique (12% body weight reduction every 3° more posterior slope), thanks to the preservation of the patellar height and quadriceps-femur load sharing.Conclusion: ACR technique alters considerably the knee laxity, both in flexion and extensions, and surgeons should be cautious about its use. More slope with CPR technique induces more favourable TFJ kinematics and loading of the knee extensor apparatus and does not substantially alter knee laxity. Preferably, the tibial slope resection should be pre-planned thoroughly and performed using CPR technique as accurately as possible. Surgeons can directly translate the results of this study into the clinical practice. [ABSTRACT FROM AUTHOR]

Purpose: One of the key factors responsible for altered kinematics and joint stability following contemporary total knee arthroplasty (TKA) is resection of the anterior cruciate ligament (ACL). However, ACL retention can present several technical challenges, and in some cases may not be viable due to an absent or nonfunctional ACL. Therefore, the goal of this research was to investigate whether substitution of the ACL through an anterior post mechanism could improve kinematic deficits of contemporary posterior cruciate ligament (PCL) retaining implants.Methods: Kinematic analysis of different implant types was done using KneeSIM, a previously established dynamic simulation tool. Walking, stair-ascent, chair-sit, and deep knee bend were simulated for an ACL-substituting (PCL-retaining) design, a bi-cruciate-retaining and ACL-sacrificing (PCL-retaining) implant, as well as the native knee. The motion of the femoral condyles relative to the tibia was recorded for kinematic comparisons.Results: The ACL-substituting and ACL-retaining implants provided similar kinematic improvements over the ACL-sacrificing implant, by reducing posterior femoral shift in extension and preventing paradoxical anterior sliding. During all simulated activities, the ACL-sacrificing implant showed between 7 and 8 mm of posterior shift in extension in contrast to the ACL-retaining implant and the ACL-substituting design, which showed overall kinematic trends similar to the native knee.Conclusion: The absence of ACL function has been linked to abnormal kinematics and joint stability in patients with contemporary TKA. ACL-substituting implants could be a valuable treatment option capable of overcoming the limitations of contemporary TKA, particularly when retaining the native ACL is not feasible or is challenging. [ABSTRACT FROM AUTHOR]

Purpose: Balancing mobile-bearing (MB) unicondylar knee arthroplasty (UKA) is challenging. If performed improperly, potential complications include pain, implant loosening, or progression of osteoarthritis in the preserved compartment. The purpose of this study was to document effects of improper balancing on knee kinematics and joint contact stress. It was hypothesized that over-stuffing would lead to more valgus and higher lateral contact force.Methods: Seven fresh-frozen cadaver legs were mounted in a kinematic rig that applied three motion patterns to the specimens: passive flexion-extension, open chain extension, and squatting. During testing, an infrared camera system recorded the trajectories of markers rigidly attached to femur and tibia, while a pressure sensor measured contact pressure in the lateral compartment. Prior computer tomography scans allowed identification of coordinate frames of the bones and calculations of anatomical rotations and translations. Collateral ligament strains were calculated, and quadriceps forces recorded. Following testing on the native knee, a medial MB UKA was implanted in each specimen and all motion trials were repeated. Three inlay thicknesses were tested to simulate optimal balancing as well as under- (1 mm thinner) and over-stuffing (1 mm thicker) of the medial compartment relative to the optimal thickness.Results: Under-stuffing of the medial compartment leads to kinematics closest to the native knee. Subjectively balanced and over-stuffed MB UKA knees were in more valgus. Lateral peak contact stress was higher from mid- to deep flexion following UKA in all three tested states; however, these results were not significant. Peak strain in the superficial medial collateral ligament (sMCL) was significantly higher in MB UKA, regardless of the inlay thickness mainly in mid-flexion. Inlay thickness had no significant impact on measured quadriceps force during squatting.Conclusion: The results underline the importance of optimal balancing. Over-stuffing should be avoided as it results in the largest kinematic changes relative to the native condition and induces higher strains in the sMCL. Based on the kinematic findings, it is advisable to use thinner inlays, as long as this is not compromising stability or risking inlay luxation. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate changes in midflexion rotational laxity before and after posterior-stabilized (PS)-total knee arthroplasty (TKA).Methods: Twenty-nine knees that underwent PS-TKA were evaluated. Manual mild passive rotational stress was applied to the knees, and the internal-external rotational angle was measured automatically by a navigation system at 30°, 45°, 60°, and 90° of knee flexion.Results: The post-operative internal rotational laxity was statistically significantly increased compared to the preoperative level at 30°, 45°, 60°, and 90° of flexion. The post-operative external rotational laxity was statistically significantly decreased compared to the preoperative level at 45° and 60° of flexion. The post-operative internal-external rotational laxity was statistically significantly increased compared to the preoperative level only at 30° of flexion. The preoperative and post-operative rotational laxity showed a significant correlation at 30°, 45°, 60°, and 90° of flexion.Conclusion: Internal-external rotational laxity increases at the initial flexion range due to resection of both the anterior or posterior cruciate ligaments and retention of the collateral ligaments in PS-TKA. Preoperative and post-operative rotational laxity indicated a significant correlation at the midflexion range. This study showed that a large preoperative rotational laxity increased the risk of a large post-operative laxity, especially at the initial flexion range in PS-TKA.Level Of Evidence: III. [ABSTRACT FROM AUTHOR]

Purpose: Abnormal knee motion under various conditions has been described after total knee arthroplasty (TKA). However, differences in kinematics and kinetics of knees with varus femoral versus varus tibial alignment have not been evaluated. It was hypothesized that varus femoral and tibial alignments have the same impact on knee motion.Methods: A musculoskeletal computer simulation was used. Femoral and tibial alignment in the coronal plane was each varied from neutral to 5° of varus in 1° increments. Lift-off, defined as an intercomponent distance of >2 mm, and tibiofemoral contact forces were evaluated during gait up to 60° of knee flexion. Knee kinematics and contact stresses were also examined during squat, with up to 130° of knee flexion.Results: During gait, lift-off occurred readily with more than 3° of varus tibial alignment and slight lateral joint laxity. In contrast, lift-off did not occur with varus femoral or tibial alignment of up to 5° during squat. Peak medial contact forces with varus femoral alignment were approximately twice those observed with varus tibial alignment. The lowest points of the femoral condyles moved internally with varus femoral alignment, contrary to the kinematics with neutral or varus tibial alignment. On the other hand, there was femoral medial sliding and edge loading against the tibia in mid-flexion with varus tibial alignment.Conclusion: Varus femoral alignment affects the non-physiological rotational movement of the tibiofemoral joint, whereas varus tibial alignment causes medial-lateral instability during mid-flexion. Varus femoral and tibial alignments might lead to post-TKA discomfort and unreliability. [ABSTRACT FROM AUTHOR]

Purpose: This study aims to objectively compare side-to-side differences of P-A laxity alone and coupled with rotatory laxity within magnetic resonance imaging, in patients with total anterior cruciate ligament (ACL) rupture.Methods: This prospective study enrolled sixty-one patients with signs and symptoms of unilateral total anterior cruciate ligament rupture, which were referred to magnetic resonance evaluation with simultaneous instrumented laxity measurements. Sixteen of those patients were randomly selected to also have the contralateral healthy knee laxity profile tested. Images were acquired for the medial and lateral tibial plateaus without pressure, with postero-anterior translation, and postero-anterior translation coupled with maximum internal and external rotation, respectively.Results: All parameters measured were significantly different between healthy and injured knees (P < 0.05), with exception of lateral plateau without stress. The difference between injured and healthy knees for medial and lateral tibial plateaus anterior displacement (P < 0.05) and rotation (P < 0.001) was statistically significant. It was found a significant correlation between the global rotation of the lateral tibial plateau (lateral plateau with internal + external rotation) with pivot-shift, and between the anterior global translation of both tibial plateaus (medial + lateral tibial plateau) with Lachman. The anterior global translation of both tibial plateaus was the most specific test with a cut-off point of 11.1 mm (93.8 %), and the global rotation of the lateral tibial plateau was the most sensitive test with a correspondent cut-off point of 15.1 mm (92.9 %).Conclusion: Objective laxity quantification of ACL-injured knees showed increased sagittal laxity, and simultaneously in sagittal and transversal planes, when compared to their healthy contralateral knee. Moreover, when measuring instability from anterior cruciate ligament ruptures, the anterior global translation of both tibial plateaus and global rotation of the lateral tibial plateau add diagnostic specificity and sensitivity. This work strengthens the evidence that the anterior cruciate ligament plays an important biomechanical role in controlling the anterior translation, but also both internal and external rotation. The high sensitivity and specificity of this device in objectively identifying and measuring the multiplanar instability clearly guides stability restoration clinical procedures. Level of evidence Cross-sectional study, Level III. [ABSTRACT FROM AUTHOR]

Purpose: Quantifying the effects of anterior cruciate ligament (ACL) deficiency on knee joint laxity is fundamental for understanding the outcomes of its reconstruction techniques. The general aim of this study was to determine intra-operatively the main modifications in knee laxity before and after standard isolated intra-articular and additional extra-articular anterolateral reinforcement. Our main hypothesis was that laxity abnormalities, particularly axial rotation, can still result from these ACL reconstruction techniques.Methods: Thirty-two patients with primary ACL deficiency were analysed by a navigation system immediately before and after each of the two reconstructions. Laxity measurements in terms of knee translations and rotations were taken during the anteroposterior drawer test, with internal-external rotation at 20° and 90° of flexion, and varus-valgus and pivot-shift tests. All these laxity measures were also taken originally from the contralateral healthy knee.Results: With respect to the contralateral healthy knee, in the ACL-deficient knee significantly increased laxity (expressed in %) was found in the medial compared with that of the lateral compartment, respectively, 115 and 68 % in the drawer test at 20° flexion, and 55 and 46 % at 90° flexion. In the medial compartment, a significant 35 % increment was also observed for the coupled tibial anteroposterior translation during axial knee rotation at 20° of flexion. After isolated intra-articular reconstruction, normal values of anteroposterior laxity were found restored in the pivot-shift and drawer tests in the lateral compartment, but not fully in the medial compartment. After the reinforcement, laxity in the medial compartment was also found restored in the axial rotation test at 20° flexion.Conclusion: In ACL reconstruction, with respect to the contralateral knee, intra-articular plus additional anterolateral reinforcement procedures do not restore normal joint laxity. This combined procedure over-constrained the lateral compartment, while excessive laxity still persists at the medial one.Level Of Evidence: III. [ABSTRACT FROM AUTHOR]

Purpose: Evaluating pivot shift phenomenon is difficult due to its subjectivity, wide variation of testing manoeuvres, and difficulty in evaluating patients while awake. The purpose of this study was to evaluate the pivot shift phenomenon using a triaxial accelerometer by two different manoeuvres, the pivot shift test as representative of flexion manoeuvre and N test as a representative of extension manoeuvre, and in two different conditions, awake and under anaesthesia.Methods: Twenty-nine patients with unilateral anterior cruciate ligament (ACL)-injured knee were included. Pivot shift test and N test were performed for both injured and uninjured legs while awake and under anaesthesia, with the acceleration measurements using a triaxial accelerometer (KiRA). The tests were also subjectively graded on a scale of 0-6 based on the modification of IKDC criteria.Results: Under anaesthesia, acceleration of ACL-injured knees was greater than that of uninjured knees in both pivot shift test (P < 0.001) and N test (P < 0.001) , whereas the acceleration value was greater in the N test. Furthermore, there were significant positive correlations between the acceleration and subjective grading in both tests, whereas the N test was more significant than the pivot shift test. On the other hand, there was no statistical significance in acceleration between ACL-injured and uninjured knees in either test while the patient was awake.Conclusion: The triaxial accelerometer was useful to objectively detect and quantitatively evaluate the pivot shift phenomenon by both the pivot shift test and N test under anaesthesia. The acceleration of ACL-injured knees was greater than that of uninjured knees, and the acceleration was correlated with the subjective manual grading, especially in the N test. On the other hand, its use while the patient was awake was likely limited.Levels Of Evidence: Diagnostic study of non-consecutive patients without a universally applied gold standard, Level III. [ABSTRACT FROM AUTHOR]

Purpose: The aim of this study was to quantify the medial soft tissue contributions to stability following constrained condylar (CC) total knee arthroplasty (TKA) and determine whether a medial reconstruction could restore stability to a soft tissue-deficient, CC-TKA knee.Methods: Eight cadaveric knees were mounted in a robotic system and tested at 0°, 30°, 60°, and 90° of flexion with ±50 N anterior-posterior force, ±8 Nm varus-valgus, and ±5 Nm internal-external torque. The deep and superficial medial collateral ligaments (dMCL, sMCL) and posteromedial capsule (PMC) were transected and their relative contributions to stabilising the applied loads were quantified. After complete medial soft tissue transection, a reconstruction using a semitendinosus tendon graft was performed, and the effect on kinematic behaviour under equivocal conditions was measured.Results: In the CC-TKA knee, the sMCL was the major medial restraint in anterior drawer, internal-external, and valgus rotation. No significant differences were found between the rotational laxities of the reconstructed knee to the pre-deficient state for the arc of motion examined. The relative contribution of the reconstruction was higher in valgus rotation at 60° than the sMCL; otherwise, the contribution of the reconstruction was similar to that of the sMCL.Conclusion: There is contention whether a CC-TKA can function with medial deficiency or more constraint is required. This work has shown that a CC-TKA may not provide enough stability with an absent sMCL. However, in such cases, combining the CC-TKA with a medial soft tissue reconstruction may be considered as an alternative to a hinged implant. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this study was to collect knee laxity data using a robotic testing device. The data collected were then compared to the results obtained from manual clinical examination.Methods: Two human cadavers were studied. A medial collateral ligament (MCL) tear was simulated in the left knee of cadaver 1, and a posterolateral corner (PLC) injury was simulated in the right knee of cadaver 2. Contralateral knees were left intact. Five blinded examiners carried out manual clinical examination on the knees. Laxity grades and a diagnosis were recorded. Using a robotic knee device which can measure knee laxity in three planes of motion: anterior-posterior, internal-external tibia rotation, and varus-valgus, quantitative data were obtained to document tibial motion relative to the femur.Results: One of the five examiners correctly diagnosed the MCL injury. Robotic testing showed a 1.7° larger valgus angle, 3° greater tibial internal rotation, and lower endpoint stiffness (11.1 vs. 24.6 Nm/°) in the MCL-injured knee during varus-valgus testing when compared to the intact knee and 4.9 mm greater medial tibial translation during rotational testing. Two of the five examiners correctly diagnosed the PLC injury, while the other examiners diagnosed an MCL tear. The PLC-injured knee demonstrated 4.1 mm more lateral tibial translation and 2.2 mm more posterior tibial translation during varus-valgus testing when compared to the intact knee.Conclusions: The robotic testing device was able to provide objective numerical data that reflected differences between the injured knees and the uninjured knees in both cadavers. The examiners that performed the manual clinical examination on the cadaver knees proved to be poor at diagnosing the injuries. Robotic testing could act as an adjunct to the manual clinical examination by supplying numbers that could improve diagnosis of knee injury.Level Of Evidence: Level II. [ABSTRACT FROM AUTHOR]

Purpose: Accurate soft tissue balance must be achieved to improve functional outcome after total knee arthroplasty (TKA). Sensor-integrated tibial trials have been introduced that allow real-time measurement of tibiofemoral kinematics during TKA. This study examined the interplay between tibiofemoral force and laxity, under defined intraoperative conditions, so as to quantify the kinematic behaviour of the CR femoral single-radius knee.Methods: TKA was undertaken in eight loaded cadaveric specimens. Computer navigation in combination with sensor data defined laxity and tibiofemoral contact force, respectively, during manual laxity testing. Fixed-effect linear modelling allowed quantification of the effect for flexion angle, direction of movement and TKA implantation upon the knee.Results: An inverse relationship between laxity and contact force was demonstrated. With flexion, laxity increased as contact force decreased under manual stress. Change in laxity was significant beyond 30° for coronal plane laxity and beyond 60° for rotatory laxity (p < 0.01). Rotational stress in mid-flexion demonstrated the greatest mismatch in inter-compartmental forces. Contact point position over the tibial sensor demonstrated paradoxical roll-forward with knee flexion.Conclusion: Traditional balancing techniques may not reliably equate to uniform laxity or contact forces across the tibiofemoral joint through a range of flexion and argue for the role of per-operative sensor use to aid final balancing of the knee. [ABSTRACT FROM AUTHOR]

Purpose: The recently reintroduced bicruciate-retaining Total Knee Arthroplasty (BCR TKA) is an interesting approach in the quest for close replication of knee joint biomechanics and kinematics closer to the native knee. Therefore, this study aimed at providing a detailed biomechanical view on the functional resemblance of BCR TKA to the native knee joint.Methods: Seven fresh-frozen full leg cadaver specimens (76 ± 10 year) were mounted in a 6 degrees-of-freedom kinematic rig that applied a dynamic squatting motion knee flexion. Two motion patterns were performed pre- and post-implantation of a fixed bearing BCR TKA: passive flexion-extension and squatting while an infrared camera system tracked the location of reflective markers attached to the tibia and femur. Additionally, specimen laxity was assessed using Lachman tests and varus/valgus stress tests in triplicate.Results: Overall, differences in tibiofemoral kinematics between native knee and BCR TKA were small. Some minor differences appeared under the load of a squat: less internal tibial rotation and some minor paradoxical anterior translation of the medial femoral condyle during mid-flexion. BCR TKA may slightly elevate the joint line. Knee laxity as measured by the Lachman and varus/valgus tests was not significantly influenced by BCR TKA implantation.Conclusion: As both cruciate ligaments are preserved with BCR TKA the unloaded knee closely resembles native knee kinematics including preserving the rollback mechanism. The loss of the conforming anatomy of menisci and tibial cartilage and replacement via a relatively flat polyethylene inlay may account for the loss of tibial internal rotation and the slight paradoxical AP motion of the medial femoral condyle with BCR TKA. This phenomenon reproduces findings made earlier with fixed bearing unicondylar knee arthroplasty. [ABSTRACT FROM AUTHOR]

Purpose: Adjustable cortical fixation has gained popularity recently for ACL reconstruction; however, one concern with these types of devices is the potential for laxity occurring post-operatively. An indicator of clinical laxity is cyclic displacement during bench-top mechanical testing. The hypothesis was that the cyclic displacement and maximum strength of different adjustable buttons currently on the market would vary depending on their mechanism of fixation.Methods: Three devices were studied: Biomet's ToggleLoc with ZipLoop Technology (ZL), Arthrex's TightRope RT (TR), and DePuy Mitek's RIGIDLOOP Adjustable (RLA). Each was tested in isolation on a servohydraulic test machine. The implants were pre-conditioned from 5 to 67 N for 10 cycles and then tested from 50 to 250 N for 1000 cycles at 1 Hz. Following cyclic loading, a load to failure test was conducted at a rate of 20 mm/min. Total displacement was calculated from the 1st to the 1000th cycle, and ultimate strength and failure mode were recorded.Results: Results showed that the RLA had significantly lower displacement versus both the TR (p = 0.012) and the ZL (p < 0.001). The TR also showed significantly lower displacement than the ZL (p < 0.001). The RLA and the ZL were both significantly stronger than the TR (p < 0.001).Conclusions: Both the RLA and TR showed clinically acceptable amounts of cyclic displacement and maximum strength. The clinical relevance of this study is that cyclic displacement results from bench-top tests may correlate with post-operative laxity, which ideally should be kept to a minimum. [ABSTRACT FROM AUTHOR]

The cruciate ligaments are components of the knee capsuloligamentous system providing vital neurosensory and biomechanical function. Since most historical primary ACL repair attempts were unsuccessful, reconstruction has become the preferred surgery. However, an increased understanding of the efficacy of lesion-site scaffolding, innovative suturing methods and materials, and evolving use of biological healing mediators such as platelet-rich plasma and stem cells has prompted reconsideration of what was once believed to be impossible. A growing number of in vivo animal studies and prospective clinical studies are providing increasing support for this intervention. The significance of ACL repair rather than reconstruction is that it more likely preserves the native neurosensory system, entheses, and ACL footprints. Tissue preservation combined with restored biomechanical function increases the likelihood for premorbid neuromuscular control system and dynamic knee stability recovery. This recovery should increase the potential for more patients to safely return to sports at their desired intensity and frequency. This current concepts paper revisits cruciate ligament neurosensory and neurovascular anatomy from the perspective of knee capsuloligamentous system function. Peripheral and central nerve pathways and central cortical representation mapping are also discussed. Surgical restoration of a more physiologically sound knee joint may be essential to solving the osteoarthritis dilemma. Innovative rehabilitative strategies and outcome measurement methodologies using more holistic and clinically relevant measurements that closely link biomechanical and neurosensory characteristics of physiological ACL function are discussed. Greater consideration of task-specific patient physical function and psychobehavioral links should better delineate the true efficacy of all ACL surgical and non-surgical interventions. Level of evidence IV. [ABSTRACT FROM AUTHOR]

Purpose: The aims of the study were (1) to evaluate the leg asymmetry assessed with ground reaction forces (GRFs) during unilateral and bilateral movements of different knee loads in anterior cruciate ligament (ACL) reconstructed patients and (2) to investigate differences in leg asymmetry depending on the International Knee Documentation Committee Subjective Form (IKDC) in order to identify potential compensation strategies.Methods: The knee function of 50 ACL reconstructed (patella tendon) patients was examined at 31 ± 7 months after the surgery. GRFs were quantified during the sit-to-stand and stand-to-sit test, the step-up and step-down test, and the two- and one-leg vertical jump. Further, the IKDC score, the anterior-posterior knee laxity, and the concentric torque of the quadriceps and hamstring muscles were evaluated.Results: Differences between the operated and non-operated leg were found in the knee laxity, the quadriceps torque, and GRFs. The patients with low IKDC scores demonstrated greater leg asymmetries in GRFs compared to the patients with high IKDC scores.Conclusions: ACL reconstructed patients showed GRF asymmetries during unilateral and bilateral movements of different knee loads. Three compensation strategies were found in patients with low subjective knee function: (1) a reduced eccentric load, (2) an inter-limb compensation during bilateral movements, and (3) the avoidance of high vertical impact forces. These compensation strategies may be indicative of a protective adaptation to avoid excessive ACL strain. GRF measurements are practicable and efficient tools to identify individual compensation strategies during early rehabilitation. [ABSTRACT FROM AUTHOR]

Purpose: Dynamic intraligamentary stabilization (DIS) has been introduced for the repair of acute anterior cruciate ligament (ACL) tears as an alternative to delayed reconstruction. The aim of the present study was to compare knee joint kinematics after DIS to those of the ACL-intact and ACL-deficient knee under simulated Lachman/KT-1000 and pivot-shift tests. We hypothesized that DIS provides knee joint kinematics equivalent to an intact ACL.Methods: With the use of a robotic knee simulator, knee kinematics were determined in simulated Lachman/KT-1000 and pivot-shift tests at 0°, 15°, 30°, 60°, and 90° of flexion in eight cadaveric knees under the following conditions: (1) intact ACL, (2) ACL deficiency, (3) DIS with a preload of 60 N, and (4) DIS with a preload of 80 N. Statistical analyses were performed using two-factor repeated-measures analysis of variance. The significance level was set at a p value of <0.05.Results: After DIS with a preload of either 60 N or 80 N, the anterior translation was significantly reduced in the simulated Lachman/KT-1000 and pivot-shift tests when compared to the ACL-deficient knee (p < 0.05). No significant differences were observed between the DIS reconstruction with a preload of 80 N and the intact ACL with regard to anterior laxity in either test. However, DIS with a preload of only 60 N was not able to restore knee joint kinematics to that of an intact knee in all degrees of flexion.Conclusion: DIS with a preload of 80 N restores knee joint kinematics comparable to that of an ACL-intact knee and is therefore capable of providing knee joint stability during ACL healing. DIS therefore provides a new technique for primary ACL repair with superior biomechanical properties in comparison with other techniques that have been described previously, although further clinical studies are required to determine its usefulness in clinical settings. [ABSTRACT FROM AUTHOR]

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

Purpose: The pivot shift test is performed in different techniques and the rotation of the tibia seems to have a significant impact on the amount of the pivot shift phenomenon. It has been hypothesised that external rotation will increase the phenomenon due to less tension at the iliotibial band in knee extension.Methods: Twenty-four patients with unilateral anterior cruciate ligament insufficiency were included prospectively. The pivot shift test was performed bilaterally in internal and external tibial rotation under general anaesthesia. Knee motion was captured using a femoral and a tibial inertial sensor. The difference between positive and negative peak values in Euclidean norm of acceleration was calculated to evaluate the amount of the pivot shift phenomenon.Results: The pivot shift phenomenon was significantly increased in patients with ACL insufficiency when the test was performed in external [mean 5.2 ms- 2 (95% CI 4.3-6.0)] compared to internal tibial rotation [mean 4.4 ms- 2 (95% CI 3.5-5.4)] (p = 0.002). In healthy, contralateral knees did not show any difference between external [mean 4.0 ms- 2 (95% CI 3.3-4.7)] and internal tibial rotation [mean 4.0 ms- 2 (95% CI 3.4-4.6)] (ns).Conclusions: The pivot shift phenomenon was increased with external rotation in ACL-insufficient knees, and therefore, one should perform the pivot shift test, rather, in external rotation to easily evoke the, sometimes difficult to detect, pivot shift phenomenon.Level Of Evidence: I (diagnostic study). [ABSTRACT FROM AUTHOR]

Injuries to the anterolateral complex of the knee can result in increased rotatory knee instability. However, to diagnose and treat patients with persistent instability properly, surgeons need to understand the multifactorial genesis as well as the complex anatomy of the anterolateral aspect of the knee in its entirety. While recent research focused primarily on one structure (anterolateral ligament-ALL), the purpose of this pictorial essay is to provide a detailed layer-by-layer description of the anterolateral complex of the knee, consisting of the iliotibial band with its superficial, middle, deep, and capsulo-osseous layer as well as the anterolateral joint capsule. This may help surgeons to not only understand the anatomy of this particular part of the knee, but may also provide guidance when performing extra-articular procedures in patients with rotatory knee instability. Level of evidence V. [ABSTRACT FROM AUTHOR]

Persistent rotatory knee laxity is increasingly recognized as a common finding after anterior cruciate ligament (ACL) reconstruction. While the reasons behind rotator knee laxity are multifactorial, the impact of the anterolateral knee structures is significant. As such, substantial focus has been directed toward better understanding these structures, including their anatomy, biomechanics, in vivo function, injury patterns, and the ideal procedures with which to address any rotatory knee laxity that results from damage to these structures. However, the complexity of lateral knee anatomy, varying dissection techniques, differing specimen preparation methods, inconsistent sectioning techniques in biomechanical studies, and confusing terminology have led to discrepancies in published studies on the topic. Furthermore, anatomical and functional descriptions have varied widely. As such, we have assembled a panel of expert surgeons and scientists to discuss the roles of the anterolateral structures in rotatory knee laxity, the healing potential of these structures, the most appropriate procedures to address rotatory knee laxity, and the indications for these procedures. In this round table discussion, KSSTA Editor-in-Chief Professor Jón Karlsson poses a variety of relevant and timely questions, and experts from around the world provide answers based on their personal experiences, scientific study, and interpretations of the literature. Level of evidence V. [ABSTRACT FROM AUTHOR]