Lateral Translation Research Articles

Kinematic evaluation of isolated and combined medial patellofemoral and patellotibial ligament reconstruction to address lateral patellar instability

Objectives:The roles of the medial patellofemoral and patellotibial ligaments in patellofemoral kinematics have been previously reported. However, the effect of isolated and combined surgical reconstruction of these ligaments to restore native patellofemoral kinematics is not well understood. The purpose of this study was to determine the isolated and combined effects of medial patellofemoral and patellotibial ligament deficiency and reconstruction on patellofemoral kinematics.Methods:Sixteen matched-paired female, fresh-frozen, cadaveric knee specimens with a mean age of 53.5 years (range, 26-65) were used. Specimens were tested in five conditions; 1) intact, 2) MPFL or MPTL cut, 3) MPFL and MPTL combined cut, 4) MPFL or MPTL reconstruction, and 5) MPFL and MPTL combined reconstruction. Dynamic testing was performed by taking the knees through range of motion from 0° to 90° of knee flexion at 60 mm/min using a dynamic tensile testing machine by applying a force through the quadricep tendon. Following dynamic testing, knees were tested statically using a lateral load of 45 N applied to the patella at 0°, 30°, 60°, and 90° of flexion. In both dynamic and static loading tests, a motion capture system detected patellar position for each testing state to distinguish changes in patellar kinematics. Linear mixed effects modeling was performed to compare testing states.Results:Isolated MPFL deficiency created the greatest lateral translation of the patella at all knee flexion angles (p<0.001). MPTL deficiency alone did not create significant patella instability (p=0.68 or greater), but further increased instability when the MPFL was deficient (p<0.001). Isolated MPFL and combined MPFL and MPTL reconstruction decreased lateral patella translation (p<0.001). Native patella tracking was best recreated with combined ligament reconstruction while MPFL reconstruction alone over constrained the patella in extension and under constrained in flexion.Conclusions:The MPFL plays the greatest role in medial patellar stability, but the MPTL appears to have a large influence on patella tracking. The MPTL may be most important in preventing patellofemoral osteoarthritis following patella dislocation. Further investigation is needed to evaluate patellofemoral contact pressure following medial patellar ligament reconstruction.

Preoperative Complete Patellofemoral Dislocation in Extension Predicts an Inferior Clinical Outcome After Medial Patellofemoral Ligament Reconstruction in Patients With Recurrent Patellar Dislocation.

Background:Habitual patellar dislocation in extension (HPD-E) is a distinctive subtype of recurrent patellar dislocation (RPD); HPD-E represents the most severe type of patellar maltracking in RPD. It has been reported that the presence of preoperative patellar maltracking is associated with a worse clinical outcome after medial patellofemoral ligament (MPFL) reconstruction (MPFL-R).Purpose:To describe the radiological characteristics of HPD-E and to compare clinical outcomes after MPFL-R among patients with and without preoperative HPD-E.Study Design:Cohort study; Level of evidence, 3.Methods:From January 2012 to December 2015, a total of 230 consecutive patients (246 knees) with RPD were treated with MPFL-R alone or combined with tibial tubercle osteotomy. Among them, 28 patients diagnosed with HPD-E by preoperative 3-dimensional computed tomography (CT; HPD-E group) were matched in a 1:1 fashion to 28 control participants who did not show HPD-E (control group). Routine radiography and CT were performed to evaluate patellar height, trochlear dysplasia, tibial tubercle–trochlear groove distance, and torsional deformities. The mean patellar laxity index and lateral patellar translation assessed with stress radiography were measured preoperatively and postoperatively to quantify MPFL laxity. At minimum 2-year follow-up, patient-reported outcomes (Kujala, Lysholm, and Tegner scores), patellar maltracking, and redislocation rates were compared between the HPD-E and control groups.Results:The radiological characteristics of the HPD-E group were as follows: 89% (25/28) of patients had severe trochlear dysplasia (Dejour type B or D), and the mean femoral anteversion angle was 35.5° ± 4.7°. At the final follow-up, the HPD-E group had a significantly lower Kujala score (76.2 vs 84.5, respectively; P = .001), Lysholm score (75.4 vs 86.6, respectively; P < .001), and Tegner score (4.1 vs 5.8, respectively; P = .021) compared with the control group. The postoperative patellar laxity index (43% vs 19%, respectively; P < .001) and redislocation rate (25% vs 0%, respectively; P = .01) were significantly higher in the HPD-E group than in the control group.Conclusion:Preoperative 3-dimensional CT is a reliable method of identfying patients with HPD-E. Treatment of HPD-E by MPFL-R alone or combined with tibial tubercle osteotomy resulted in a higher redislocation rate, more severe MPFL residual laxity, and lower patient-reported outcome scores compared with patients without HPD-E who underwent MPFL-R.

Patient-Reported and Quantitative Outcomes of Anatomic Anterior Cruciate Ligament Reconstruction With Hamstring Tendon Autografts

Background:The pivot-shift test has become more consistent and reliable and is a meaningful outcome measurement after anterior cruciate ligament reconstruction (ACLR).Purpose/Hypothesis:The purpose of this investigation was to assess patient-reported outcomes (PROs) and the quantitative pivot shift (QPS) preoperatively, at time zero immediately after anatomic ACLR, and after 24 months as well as the relationship between PROs and the QPS. It was hypothesized that anatomic ACLR would restore rotatory stability measured by the pivot-shift test and that QPS measurements would be positively correlated with PROs.Study Design:Cohort study; Level of evidence, 2.Methods:The ACL-injured and contralateral uninjured knees from 89 of 107 (83.2%) enrolled patients at 4 international centers were evaluated using a standardized pivot-shift test. Tibial acceleration was assessed with an inertial sensor, and lateral compartment translation was measured using an image analysis system preoperatively, at time zero immediately postoperatively, and at follow-up after 2 years. PROs were assessed at 12 and 24 months postoperatively with the International Knee Documentation Committee (IKDC) subjective knee form, Cincinnati Knee Rating System (CKRS), Marx activity rating scale, and activity of daily living score (ADLS).Results:The mean patient age at surgery was 27 years (range, 15-45 years). A positive pivot shift preoperatively (side-to-side difference in tibial acceleration, 2.6 ± 4.0 m/s2; side-to-side difference in anterior tibial translation, 2.0 ± 2.0 mm) was reduced at time zero postoperatively (side-to-side difference in tibial acceleration, –0.5 ± 1.3 m/s2; side-to-side difference in anterior tibial translation, –0.1 ± 1.0 mm). All PROs improved from preoperatively to final follow-up at 24 months: from 56.5 to 85.5 points for the IKDC (P = .0001), from 28.8 to 32.4 points for the CKRS (P = .04), from 11.2 to 7.9 points for the Marx (P < .0001), and from 75.7 to 91.6 points for the ADLS (P < .0001). Neither preoperative nor time zero postoperative rotatory laxity assessed by the pivot-shift test correlated with PROs at 24-month follow-up. A graft retear was observed in 4 patients (4.5%) within 2 years of follow-up.Conclusion:Anatomic ACLR resulted in significantly improved and acceptable PROs at 2-year follow-up and a low failure rate. Anatomic ACLR restored QPS measurements of anterior tibial translation and tibial acceleration to those of the contralateral knee immediately after surgery while still under anesthesia, but there was no correlation between the QPS preoperatively or at time zero after ACLR and PROs at 2-year follow-up.

The Presence of Patellar Apprehension in Higher Degrees of Flexion Identifies Patients with Patella Alta and or Severe Trochlear Dysplasia

Objectives:Recurrent patellar instability is frequently treated surgically with reconstruction of the medial patellofemoral ligament (MPFL). Patients with significant patella alta, trochlear dysplasia, and/or an elevated tibial tubercle-trochlear groove (TT-TG) distance may benefit from a concurrent bony procedure such as a tibial tubercle osteotomy or trochleoplasty. The indications to include such procedures are traditionally based on imaging criteria, but remain controversial. Patellar apprehension is common in patients with patellar instability but typically resolves in higher degrees of knee flexion. We hypothesis that the persistence of patellar apprehension at greater than 60 degrees of knee flexion is associated with patella alta, increased TT-TG distance, and trochlear dysplasia.Methods:Seventy-six patients with recurrent patellar instability were prospectively identified in a sports medicine clinic. Patellar apprehension was evaluated in each patient. Apprehension was defined as the patient reporting that the patella felt unstable to lateral patellar translation. Apprehension was first assessed at full knee extension and repeated assessed as the knee was flexed in 10 degrees intervals as measured with a goniometer. The degree of flexion at which patellar apprehension disappeared was recorded. Plain films and MRI were obtained in all patients. Patellar height was assessed with the Caton-Deschamps (CD) index and trochlear morphology was assessed through measurement of the sulcus angle and depth on MRI and classification with the Dejour classification system. Imaging measurements of patients in which apprehension resolved by 60 degrees of knee flexion were compared with measures for those with apprehension that persisted deeper into flexion.Results:Apprehension resolved by 60 degrees of flexion in 55 patients and persisted into deeper flexion in 21 patients. The patients with delayed resolution of apprehension demonstrated a higher CD Index, elevated TT-TG distance, increased higher sulcus angle, decreased trochlear depth, and a higher incidence of Dejour B, C, or D dysplasia (all p < 0.05, Table 1). Of the 21 patients with delayed resolution of apprehension, 18 had either Dejour B, C, or D dysplasia or a Caton-Deschamps Index of at least 1.3. Delayed resolution of apprehension was present in 11 of the 16 patients with Dejour B, C, or D dysplasia.Conclusion:The presence of patellar apprehension in higher degrees of knee flexion is associated with patella alta, increased TT-TG distance, and more severe trochlear dysplasia. Further work is needed to evaluate utility of this exam finding to inform surgical decision-making in this population.

Translational Motion Estimation Using Kinect

Study on robot navigation has been progressing significantly. However, research of autonomous navigation is still lacking in environments with changing layout. For supporting robot navigation system, rotational and translational motion estimation need to be improved. Low cost sensor such as Kinect can be used as alternative to laser to percept changing in the vicinity of robot. There is still problem in developing motion estimation using Kinect. Narrowness in the sensor field of view limits its ability to track robot motion. This problem emerges specially in translational motion estimation. This paper aims to develop a simple approach based on RGB-D data for translational motion estimation of a Kinect sensor. RGB-D data consist of RGB and Depth images. In previous research, camera was positioned in the direction of longitudinal translational motion. This paper differs from previous works in terms of sensor setting that is placed in the direction of lateral translation movements. Point features are matched between pairs of RGB frame to get interesting pixels. Depth image provides distance information for these pixels in synchronization with feature tracking process. Law of cosines is then applied to these depth pixels to get position translation. Results show that our approach have decreased RMSE to 0.0382 meter better than previous works. In the future research, this translational motion estimation system will be implemented in mobile robot system to support navigation function.

Normal Kinematics of the Syndesmosis and Ankle Mortise During Dynamic Movements.

Background:Documenting the healthy articulation of the syndesmosis and talocrural joints, and measurement of 3D medial and lateral clear spaces may improve diagnostic and treatment guidelines for patients suffering from severe syndesmotic injury or chronic instability. This study aimed to define the range of motion (ROM) and displacement of the fibula and talus during static and dynamic activities, and measure the 3D movement in the tibiofibular (syndesmosis) and medial clear space.Methods:Six healthy volunteers performed dynamic weightbearing motions on a single-leg: heel-rise, squat, torso twist, and box jump. Participants posed in a nonweightbearing neutral stance as well as weightbearing neutral standing, plantarflexion, and dorsiflexion. High-speed stereoradiography measured 3D rotation and translation of the fibula and talus throughout each task. Medial clear space and tibiofibular gap distances were measured under each condition.Results:Total ROM for the fibula was greatest in internal-external rotation (9.3 ± 3.5 degrees), and anteroposterior (3.3 ± 2.2 mm) and superior-inferior (2.5 ± 0.9 mm) translation, rather than lateral widening (1.7 ± 1.0 mm). The total rotational ROM of the talus was greatest in dorsiflexion-plantarflexion (34.7 ± 12.9 degrees) and internal-external rotation (15.0 ± 3.4 degrees). Single-leg squatting increased the lateral clear space (P = .045) and widened the medial tibiofibular joint, whereas single-leg heel-rises decreased the lateral clear space (P = .001) and widened the tibiotalar space. Gap spaces in the tibiofibular and medial clear spaces did not exceed 2.3 ± 0.9 mm and 2.7 ± 1.2 mm, respectively.Conclusion:These data support a potential shift in the clinical understanding of fibula displacements during dynamic activities and how implant device constructs might be developed to restore physiologic mechanics.Clinical Relevance:Syndesmosis stabilization and rehabilitation should consider restoration of normal physiologic rotation and translation of the fibula and ankle mortise rather than focusing solely on the restriction of lateral translation.

Comparison of Patellofemoral Kinematics and Stability After Medial Patellofemoral Ligament and Medial Quadriceps Tendon–Femoral Ligament Reconstruction

Background: There is a lack of evidence regarding the optimum extensor-sided fixation method for medial patellofemoral ligament (MPFL) reconstruction. There is increased interest in avoiding patellar drilling via soft tissue–only fixation to the distal quadriceps, thus reconstructing the medial quadriceps tendon–femoral ligament (MQTFL). The biomechanical implications of differing extensor-sided fixation constructs remain unknown. Hypothesis: The null hypothesis was there would be no differences between traditional MPFL reconstruction and MQTFL reconstruction with respect to resistance to lateral translation, patellar position, or patellofemoral contact pressures. Study Design: Controlled laboratory study. Methods: Nine adult knee specimens were mounted on a jig that applied static, physiologic loads to the quadriceps tendons. Patellar position and orientation, knee flexion angle, and patellofemoral pressure were recorded at 8 different flexion angles between 0° and 110°. Additionally, a lateral patellar excursion test was conducted wherein a load was applied directly to the patella in the lateral direction with the knee at 30° of flexion and subjected to 2-N quadriceps loads. Testing was conducted under 4 conditions: intact, transected MPFL, MQTFL reconstruction, and MPFL reconstruction. For MQTFL reconstruction, the surgical technique established by Fulkerson was employed. For MPFL reconstruction, a traditional technique was utilized. Results: The patellar excursion test showed no significant difference between the MQTFL and intact states with respect to lateral translation. MPFL reconstruction led to significantly less lateral translation (P < .05) than all other states. There were no significant differences between MPFL and MQTFL reconstructions with respect to peak patellofemoral contact pressure. MPFL and MQTFL reconstructions both resulted in increased internal rotation of the patella with the knee in full extension. Conclusion: Soft tissue-only extensor-sided fixation to the distal quadriceps (MQTFL) during patella stabilization appears to re-create native stability in this time 0 cadaver model. Fixation to the patella (MPFL) was associated with increased resistance to lateral translation. Clinical Relevance: Evolving anatomic knowledge and concern for patellar fracture has led to increased interest in MQTFL reconstruction. Both MQTFL and MPFL reconstructions restored patellofemoral stability to lateral translation without increasing contact pressures under appropriate graft tensioning, with MQTFL more closely restoring native resistance to lateral translation at the time of surgery.

Combined medial patellofemoral and patellotibial reconstruction with soft tissue fixation in recurrent patellar dislocation

IntroductionThe medial patellofemoral and patellotibial ligaments (MPFL and MPTL) are the main passive restraints to lateral patellar translation. When nonoperative management of patellofemoral dislocations fails, surgical options can be considered to restore patellofemoral stability. Several reconstruction procedures of the MPFL with semitendinosus, gracilis, quadriceps tendon, and synthetic grafts have been described. No clear superiority of one surgical technique over another is evident. Materials and methodsPatients who suffered at least two documented episodes of unilateral patellar dislocation, confirmed radiographically and at clinical examination, underwent combined MPFL and MPTL reconstruction. Patients were regularly followed-up postoperatively at 2, 4, 8, 12, and 24 weeks, and then annually for a minimum of 2.5 years. Clinical and functional evaluations were performed using the modified Cincinnati rating system and the Kujala score, while anthropometry values including thigh volume and cross-sectional area of the thigh were measured before the operation and at the latest follow-up bilaterally. ResultsThere were 7 males and 27 females with a mean age of 26.5 ± 10.7 years (range, 13–39 years). The mean follow-up was 3.1 years (range, 2.5–4 years). The mean modified Cincinnati score Increased from 51 ± 22 preoperatively to 90 ± 19 (P = .001). The mean Kujala scores increased from 47 ± 17 preoperatively to 82 ± 17 (P = .02), with no significant differences between patients with or without osteochondral lesions (P ≥ .05), and between male and female patients (P ≥ .08). The Insall-Salvati index was 1.1 preoperatively and remained within normal range (P = .05) at the latest follow-up. ConclusionCombined reconstruction of MPFL and MPTL using an ipsilateral autologous gracilis tendon is satisfactory and effective and can be considered as suitable management option to treat recurrent dislocation of the patella. However, randomized studies are needed to compare different techniques. Study designCase series.

Experimental investigation of aerodynamic characteristics of bat carcasses after collision with a wind turbine

Abstract. A large number of bat fatalities have been reported in wind energy facilities in different regions globally. Wind farm operators are required to monitor bat fatalities by conducting carcass surveys at wind farms. A previous study implemented the ballistics model to characterize the carcass fall zone distributions after a bat is struck by turbine blades. The ballistics model considers the aerodynamic drag force term, which is dependent upon the carcass drag coefficient. The bat carcass drag coefficient is highly uncertain; no measurement of it is available. This paper introduces a methodology for bat carcass drag coefficient estimation. Field investigation at Macksburg wind farm resulted in the discovery of three bat species: the hoary bat (Lasiurus cinereus), eastern red bat (Lasiurus borealis), and evening bat (Nycticeius humeralis). Carcass drop experiments were performed from a dropping platform at finite height, and carcass position time series data were recorded using a high-speed camera. Falling carcasses were subjected to aerodynamic drag and gravitational forces. Carcasses were observed to undergo rotation, often rotating around multiple axes simultaneously, as well as lateral translation. The complex fall dynamics, along with drop from a limited height, prohibit the carcasses from attaining terminal velocity. Under this limitation, the drag coefficient is estimated by fitting a ballistics model to the measured velocity. Multivariable optimization was performed to fit the ballistics model to the measured velocity resulting, in an optimized estimate of the drag coefficient. A sensitivity analysis demonstrated significant variation in the drag coefficient with a small change in initial position, highlighting the chaotic nature of carcass fall dynamics. Based on the limited sample, the bat carcass drag coefficient and terminal velocity were found to be between 0.70–1.23 and 6.63–17.57 m s−1, respectively. The maximum distance carcasses are predicted to fall after impact with a typical utility-scale onshore wind turbine was computed using a 2-D ballistics model. Based on the range of drag coefficients found in this study, hoary and evening bats are estimated to fall within the rotor plane up to a maximum distance of 92 and 62 m, respectively, from the wind turbine tower. The ballistics model of carcasses after being struck by wind turbine blades can be used to obtain fall distributions for bats, guide carcass survey efforts, and correct survey data for limited or unsearched areas.

Treatment of non-united femoral neck fracture by a novel subtrochanteric angulation lateral translation valgus osteotomy (SALVA osteotomy)

The ideal treatment of non-united and neglected fracture neck femur in the young adult still remains unclear and is characterized by many biological and biomechanical challenges. Twenty-one patients with non-united or neglected fracture neck femur aged between 19 and 50years were treated by a novel subtrochanteric valgus osteotomy and were followed up for a mean of 26.7months. Patients were assessed by radiological parameters, the Harris Hip Score, Oxford Knee Score, and Askin Bryan Criteria to categorize the overall outcome of the patients at 24months. Other outcome measures included the occurrence of AVN, adductor lever arm, leg length discrepancy, and mechanical implant failure. All patients treated with the SALVA osteotomy consolidated and displayed a marked improvement of functional and radiological outcome measures. Nevertheless, there were 2 mechanical failures in patients with marked osteopenia and three developed AVN. In patients with un-united/neglected fracture neck femur, SALVA osteotomy appears to be reliable and reproducible. It also restores the abductor lever arm and improves the leg length discrepancy. Technically less demanding conversion to arthroplasty remains still possible prospectively.

Identifying Patients With Patella Alta and/or Severe Trochlear Dysplasia Through the Presence of Patellar Apprehension in Higher Degrees of Flexion.

Background:Recurrent patellar instability is frequently treated surgically with reconstruction of the medial patellofemoral ligament (MPFL). Patients with significant patella alta, trochlear dysplasia, and/or an elevated tibial tubercle–trochlear groove (TT-TG) distance may benefit from a concurrent bony procedure such as tibial tubercle osteotomy or trochleoplasty. The indications to perform such procedures are traditionally based on imaging criteria but remain controversial. Patellar apprehension is common in patients with patellar instability but typically resolves in higher degrees of knee flexion.Hypothesis:The persistence of patellar apprehension at greater than 60° of knee flexion is associated with patella alta, an increased TT-TG distance, and trochlear dysplasia.Study Design:Cross-sectional study; Level of evidence, 3.Methods:A total of 76 patients with recurrent patellar instability were prospectively identified in a sports medicine clinic. Patellar apprehension was evaluated in each patient. Apprehension was defined as the patient reporting that the patella felt unstable to lateral patellar translation. Apprehension was first assessed at full knee extension and repeatedly assessed as the knee was flexed in 10° intervals, as measured using a goniometer. The degree of flexion at which patellar apprehension disappeared was recorded. Plain radiographs and magnetic resonance imaging (MRI) scans were obtained for all patients. Patellar height was assessed with the Caton-Deschamps (CD) index, and trochlear morphology was assessed through measurements of the sulcus angle and depth on MRI and classified using the Dejour classification system. Imaging measurements of patients in whom apprehension resolved by 60° of knee flexion were compared with measurements for those with apprehension that persisted deeper into flexion.Results:Apprehension resolved by 60° of flexion in 56 patients and persisted into deeper flexion in 20 patients. The patients with a delayed resolution of apprehension demonstrated a higher CD index; elevated TT-TG distance; increased sulcus angle; decreased sulcus depth; and higher incidence of Dejour type B, C, or D dysplasia (all P < .05). Of the 20 patients with a delayed resolution of apprehension, 18 had either Dejour type B, C, or D dysplasia or a CD index of at least 1.30. A delayed resolution of apprehension was present in 11 of the 16 patients with Dejour type B, C, or D dysplasia.Conclusion:Overall, 90% of patients with significant patella alta and the majority of patients with high-grade trochlear dysplasia demonstrated patellar apprehension that persisted beyond 60° of knee flexion. Additionally, 90% of patients with persistent apprehension had significant patella alta and/or trochlear dysplasia. Further work is needed to evaluate the utility of these findings to inform surgical decision-making in this population.

Medial Patellotibial Ligament Reconstruction Improves Patella Tracking When Combined With Medial Patellofemoral Reconstruction: An In Vitro Kinematic Study

To investigate the isolated and combined effects of medial patellofemoral ligament (MPFL) and medial patellotibial ligament (MPTL) deficiency and reconstruction on patellofemoral kinematics. Sixteen matched-paired female cadaveric knee specimens with a mean age of 53.5 years (range, 26-65) were tested in 5 conditions: (1) intact, (2)MPFL or MPTL cut, (3) MPFL and MPTL combined cut, (4) MPFL or MPTL reconstruction, and (5) MPFL and MPTL combined reconstruction. Dynamic testing allowed continuous analysis of kinematics from 0° to 90° of knee flexion. Knees were also tested statically using a lateral load of 45 N at 0°, 30°, 60°, and 90° of flexion. In both dynamic and static loading tests, a motion capture system detected patellar position for each testing state to distinguish changes in patellar kinematics. Random-intercepts linear mixed-effects models were used to compare patellar kinematics. The MPFL is the primary restraint to lateral translation of the patella at all knee flexion angles. MPTL deficiency alone did not create significant patella instability, but further increased instability when the MPFL was deficient. Isolated MPFL and combined reconstruction provided improved stability. Through full range of motion native patella tracking was best recreated with combined ligament reconstruction. The MPFL plays the greatest role in medial patellar stability, but the MPTL appears to have an influence on patella tracking. This study provides further understanding to the impact of the MPFL and MPTL on patellofemoral motion with implications for reconstruction to improve stability and optimize patellofemoral tracking. This study provides further understanding of the role of the MPFL and MPTL on patellofemoral motion with implications for reconstruction to improve stability and optimize patellofemoral tracking.

Prediction of Knee Kinematics at the Time of Noncontact Anterior Cruciate Ligament Injuries Based on the Bone Bruises.

Biomechanical risk factors associated with the alignment and position of the knee for anterior cruciate ligament (ACL) injury are still not conclusive. As bone bruises identified on magnetic resonance imaging (MRI) following acute ACL injury could represent the impact footprint at the time of injury. To improve understanding of the ACL injury mechanism, we aimed to determine the knee kinematics during ACL injury based on the bone bruises. Knee MRI scans of patients who underwent acute noncontact ACL injuries were acquired. Numerical optimization was used to match the bone bruises of the femur and tibia and predict the knee positions during injury. Knee angles were compared between MRI measured position and predicted position. The knee flexion, abduction, and external tibial rotation angles were significantly greater in the predicted position than that in MRI measured position. Relative to MRI measured position, patients had a mean of 34.3mm of anterior tibial translation, 4.0mm of lateral tibial translation, and 16.0mm superior tibial translation in the predicted position. The results suggest that knee valgus and external tibial rotation accompanied by knee flexion are high-risk movement pattern for ACL injury in patients with lateral compartment bone bruising in conjunction with ACL injury.

Isolated MPTL reconstruction fails to restore lateral patellar stability when compared to MPFL reconstruction.

To biomechanically evaluate MPTL reconstruction and compare it with two techniques for MPFL reconstruction in regard to changes in patellofemoral contact pressures and restoration of patellar stability. This is an experimental laboratory study in eight human cadaveric knees. None had patellofemoral cartilage lesions or trochlear dysplasia as evaluated by conventional radiographs and MRI examinations. The specimens were secured in a testing apparatus, and the quadriceps was tensioned in line with the femoral shaft. Contact pressures were measured using the TekScan sensor at 30°, 60° and 90°. The sensor was placed in the patellofemoral joint through a proximal approach between femoral shaft and quadriceps tendon to not violate the medial and lateral patellofemoral complex. TekScan data were analysed to determine mean contact pressures on the medial and lateral patellar facets. Patellar lateral displacement was evaluated with the knee positioned at 30° of flexion and 9N of quadriceps load, then a lateral force of 22N was applied. The same protocol was used for each condition: native, medial patellofemoral complex lesion, medial patellofemoral ligament reconstruction (MPFL-R) using gracilis tendon, MPFL-R using quadriceps tendon transfer, and medial patellotibial ligament reconstruction (MPTL-R) using patellar tendon transfer. No statistical differences were found for mean and peak contact pressures, medial or lateral, among all three techniques. However, while both techniques of MPFL-R were able to restore the medial restraint, MPTL-R failed to restore resistance to lateral patellar translation to the native state (mean lateralization of the patella [mm]: native: 9.4; lesion: 22; gracilis MPFL-R: 8.1; quadriceps MPFL-R: 11.3; MPTL-R: 23.4 (p < 0.001). MPTL-R and both techniques for MPFL-R did not increase patellofemoral contact pressures; however, MPTL-R failed to provide a sufficient restraint against lateral patellar translation lateral translation in 30° of flexion. It, therefore, cannot be recommended as an isolated procedure for the treatment of patellar instability.

A novel device for a vertical rocking isolation system with uplift allowed for industrial equipment and structures

In this paper, a novel device called the “ISO3D-2G” is proposed for a three-dimensional vertical rocking isolation (VRI) system. The VRI system works by isolating critical vibration sources, e.g., earthquake events and operational high-frequency vibrations. In this work, only its performance as a seismic isolation system is studied. The ISO3D-2G is made of a steel structure and an elastomeric rubber system, offering improved properties as compared to previous versions of the device. The device is manufactured at a full scale and is experimentally tested. To represent the vertical non-linear hysteretic behavior of the device, a numerical model called the hyperelastic Bouc-Wen (HBW) model is developed. The HBW model combines a hyperelastic component (represented in this work by a third-order Ogden model) and a hysteretic component (represented by a modified BW model). The simply supported horizontal behavior of the device is represented through a non-linear 2D frictional hysteretic model. The HBW model is calibrated to fit the experimental data obtained in the test, and guidelines are provided for understanding and manually calibrating the model. The dynamic performance of the system is analyzed using time-history analyses with four records (three non-impulsive records and one impulsive record). Equations are presented for the motion of the system. For the three non-impulsive seismic records, the observed behavior was similar to that in conventional lateral isolation systems. Horizontal force reduction ratios between 7.4 and 10.9 were obtained. The maximum shear base remained below 23% of the total weight of the structure, even considering the three components of the ground motion. In addition, vertical force reduction ratios between 2 and 3.8 were obtained, demonstrating that the vertical isolation effect was satisfactory. However, for an impulsive seismic record, there was a significant change in the patterns of behavior, owing to the significant uplift of two of the four devices. Despite this, the structure remained stable, and the lateral isolation effect was preserved. Finally, it was concluded that using vertically flexible devices with high damping in the base of structures to generate a rocking isolation mechanism is an effective approach to reducing the seismic demand, even though the isolated modes of the structure do not take periods longer than 2.0 s. Although there was no lateral translation at the base, the VRI system isolated the structure by allowing lateral and vertical displacement of the center of mass.

Optimization of transmission and reconstruction parameters in angular displacement compounding using plane wave ultrasound

In ultrasound elastography, plane-wave acquisitions and angular displacement compounding (ADC) are often used and combined to allow high frame rates and to improve accuracy of lateral displacement estimates, respectively. This study investigates the performance of displacement and strain estimation for ADC as a function of; the main-to-grating-lobe-amplitude ratio which decreases as a function of steering angle; plane-wave acquisition and Delay-and-Sum (DaS)-related parameters; and grating-lobe filter cut-off frequency. Three experiments were conducted with a block phantom to test ADC performance for displacement fields of varying complexity: a lateral transducer shift, phantom rotation and phantom deformation. Experiments were repeated for four linear array transducers (pitch-to-lambda ratios between 0.6 and 1.4). Best ADC performance was found for steering angles that resulted in a theoretically derived main-to-grating-lobe-amplitude ratio of 1.7 dB for pure lateral translation and 6 dB for predominately lateral strain or rotation. Temporal filtering to reduce grating lobe signal or shifting of the receive aperture to receive angles below or above the optimal angle, as dictated by the main-to-grating-lobe-amplitude ratio, did not improve results. The accuracy of lateral displacement and strain estimates was improved by apodization in transmission and a dedicated F-number in DaS (0.75) allowing incidence angles within ± 33° in the active aperture. ADC with the optimized settings as found in this study improves the accuracy of displacements and strain estimates up to 80.7% compared to non-ADC. Compared to ADC settings described in current literature, our optimization improved the accuracy by 11.9% to 75.3% for lateral displacement and strain, and by 89.3% to 96.2% for rotation. The accuracy of ADC in rotation seemed to depend highly on plane-wave and DaS-related parameters which may explain the major improvement compared to settings in current literature. The overall improvement by optimized ADC was statistically significant compared to non-ADC (p = 0.003) and literature (p = 0.002).

Axial plane characteristics of thoracic scoliosis and their usefulness for determining the fusion levels and the correction technique.

There is insufficient information regarding axial plane characteristics of scoliosis despite its 3D nature. The posterior-anterior vertebral vector (VV) has been proposed to characterize the axial plane appearances of the thoracic scoliosis. This study aimed to highlight the importance of knowledge of axial plane features when determining fusion levels and correction techniques of thoracic curves. Altogether, 233 thoracic curves were analyzed using the VV after proving its usability instead of 3D angles to determine axial plane parameters such as apical vertebral (APV) axial rotations, APV lateral displacement, and intervertebral rotations (IVR). K-means clustering and regression analysis were used to identify axial plane curve patterns and determine the relationship between the coronal angles and axial plane characteristics, respectively. A close correlation was found between 3D angles and VV projected angles. Eight axial plane clusters were distinct, exhibiting different lateral APV displacement toward the interacetabular axis with relatively small axial rotations and a simultaneous decrease in sagittal curves. The regression analysis showed that the correlation of coronal curve magnitude was significantly stronger (r = 0.78) with APV lateral translation than with APV axial rotation (r = 0.65). Based on these findings, the primary goal of scoliosis correction should focus on minimizing lateral translation rather than eliminating axial rotation. Knowing the IVR in the axial plane helps accurately determine the limits of the structural curves. VV-based axial views can facilitate the accurate determination of the end vertebrae and selection of the appropriate correction technique of the curve. These slides can be retrieved under Electronic Supplementary Material.

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

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

Are Routine Follow-up Radiographs Necessary for Extra-articular Scapula Body Fractures Managed Conservatively?

Extra-articular scapula body fractures have been shown to have good outcomes with nonsurgical management. What is not known is whether routine postinjury imaging of these fractures is necessary for monitoring healing and alignment. As the shift toward providing cost-effective healthcare continues, we sought to evaluate if routine postinjury imaging of these fractures resulted in any change in management while secondarily evaluating the imaging for fracture patterns at risk of displacement. A retrospective review of all extra-articular scapula body fractures managed nonsurgically at our institution was performed from January 2013 to December 2017. We measured the glenopolar angle, lateral border offset, sagittal angulation, and translation on both injury CT scans and follow-up radiographs to evaluate if any displacement occurred. In fractures that displaced more than 10 mm or 10° in any measurement, we evaluated the fracture pattern to see if any particular pattern posed a risk for displacement. In addition, we evaluated the cost of imaging for all radiographs obtained in the follow-up period. A total of 139 patients with 147 extra-articular scapula body fractures were included in our analysis. No patient experienced a change in management based on postinjury radiographs. A total of 120 patients underwent postinjury imaging with a total of 204 radiographic series ordered, equating to $172,769.50 in radiograph expenses. Final radiographs were obtained at an average of 48.4 days postinjury, and overall, no significant difference was observed (P < 0.05) in any radiographic measurement when compared with the initial injury imaging; however, when looking at fractures that displaced, transverse fracture patterns of the scapula body represented a risk factor for displacement (relative risk = 6.5). Satisfactory outcomes have previously been demonstrated with nonsurgical management of scapula body fractures and for most of these injuries postinjury imaging may not be necessary or cost effective. Level IV.

Effects of transverse bodily movements of maxillary premolars on the surrounding hard tissue

This experimental study was designed to (1) produce buccal translation of maxillary premolars and (2) evaluate the effects on the buccal alveolar bone. A randomized split-mouth study was designed based on 7 adult male beagle dogs. The experimental side received a custom cantilever appliance fabricated to produce a translatory force through the maxillary second premolar's center of resistance. The contralateral second premolar received no appliance and served as the control. The premolars underwent 6-7weeks of buccal translation, followed by 3weeks of fixed retention. Biweekly tooth movements were evaluated using intraoral and radiographic measurements. Pretreatment and posttreatment models were measured to assess tipping. Three-dimensional microscopic tomography was used to quantify the amount and density of buccal bone. Bone formation and turnover were assessed using fluorescent labeling, hematoxylin and eosin staining, tartrate-resistant acid phosphatase staining, and bone sialoprotein immunostaining. The applied force (100g of force) translated (1.4mm) and minimally tipped (4°) the experimental teeth. Lateral translation produced dehiscences at the mesial and distal roots, with 2.0mm and 2.2mm loss of vertical bone height, respectively. Bone thickness decreased significantly (P<0.05) at the apical (∼0.4mm), midroot (∼0.4mm), and coronal (∼0.2mm) levels. Fluorescent imaging, hematoxylin and eosin staining, and immunostaining for bone sialoprotein all showed new bone formation extending along the entire periosteal surface of the second premolar's buccal plate. Tartrate-resistant acid phosphatase staining demonstrated greater osteoclastic activity on the experimental than that of control sections. New buccal bone forms on the periosteal surface during and after tooth translation, but the amount of bone that forms is less than the amount of bone loss, resulting in a net decrease in buccal bone thickness and a loss of crestal bone.