Influence of implantation of a total hip endoprosthesis on the ipsilateral leg alignment: the effect of sex and dysplasia of the hip.

INTRODUCTION: Differences in leg and hip morphology exist between sexes and developmental hip dysplasia is known to alter proximal femoral morphology. The purpose of this study was to determine whether existing differences in leg alignment due to sex or developmental hip dysplasia have an effect on changes in leg alignment after total hip arthroplasty. MATERIALS AND METHODS: 30 hip osteoarthritis patients underwent biplanar full-length radiography in the standing position preoperatively and 3 months after total hip arthroplasty. Differences in leg alignment between men and women and between patients with primary hip osteoarthritis and patients with developmental dysplasia before and after surgery were tested using a general linear model for repeated measures. RESULTS: Implantation of a hip prosthesis had no differential effect on ipsilateral leg alignment in patients with hip osteoarthritis due to dysplasia and in patients with primary hip osteoarthritis. However, patients with hip osteoarthritis due to dysplasia had a 2.1° higher valgus both before and after surgery. After total hip arthroplasty, women had a significantly greater increase in varus angle (1.6° vs. 0°) and femoral offset (10.5 vs. 4.6 mm) compared with men. Because the change in acetabular offset was smaller (2.2 vs. 6.2 mm), the global femoral offset was only increased in women. Femoral torsion was constant for men (15.0° and 16.5°), whereas femoral torsion was significantly reduced in women (19.9° and 13.2°). CONCLUSIONS: Hip arthroplasty has a greater effect on leg axis in women than in men. The axial leg alignment of women could change from a natural valgus to a varus alignment. Therefore, surgeons should consider the effects of total hip arthroplasty on leg alignment in patients with hip osteoarthritis. Whether these changes in leg alignment are also clinically relevant and lead to premature medial or lateral knee osteoarthritis should be investigated in future work. TRIAL REGISTRATION: This study was registered with DRKS (German Clinical Trials Register) under the number DRKS00015053. Registered 1st of August 2018.

Effect of unplanned athletic movement on knee mechanics: a systematic review with multilevel meta-analysis.

OBJECTIVE: To compare the effects of pre-planned and unplanned movement tasks on knee biomechanics in uninjured individuals. DESIGN: Systematic review with meta-analysis. DATA SOURCES: Five databases (PubMed, Google Scholar, Cochrane Library, ScienceDirect and Web of Science) were searched from inception to November 2020. Cross-sectional, (randomised) controlled/non-controlled trials comparing knee angles/moments of pre-planned and unplanned single-leg landings/cuttings were included. Quality of evidence was assessed using the tool of the Grading of Recommendations Assessment, Development and Evaluation working group. METHODS: A multilevel meta-analysis with a robust random-effects meta-regression model was used to pool the standardised mean differences (SMD) of knee mechanics between pre-planned and unplanned tasks. The influence of possible effect modifiers (eg, competitive performance level) was examined in a moderator analysis. RESULTS: Twenty-five trials (485 participants) with good methodological quality (Downs and Black) were identified. Quality of evidence was downgraded due to potential risk of bias (eg, confounding). Moderate-quality evidence indicates that unplanned tasks evoked significantly higher external knee abduction (SMD: 0.34, 95% CI: 0.16 to 0.51, 14 studies) and tibial internal rotation moments (SMD: 0.51, 95% CI: 0.23 to 0.79, 11 studies). No significant between-condition differences were detected for sagittal plane mechanics (p>0.05). According to the moderator analysis, increased abduction moments particularly occurred in non-professional athletes (SMD: 0.55, 95% CI: 0.14 to 0.95, 5 studies). CONCLUSION: Unplanned movement entails higher knee abduction and tibial internal rotation moments, which could predispose for knee injury. Exercise professionals designing injury-prevention protocols, especially for non-elite athletes, should consider the implementation of assessments and exercises requiring time-constrained decision-making. PROSPERO REGISTRATION NUMBER: CRD42019140331.

Accuracy of Preoperative Templating in Total Hip Arthroplasty With Special Focus on Stem Morphology: A Randomized Comparison Between Common Digital and Three-Dimensional Planning Using Biplanar Radiographs.

BACKGROUND: Accurate preoperative planning is a key component of successful total hip arthroplasty (THA). The purpose of the present study was to compare the accuracy and reliability of three-dimensional (hipEOS) and common digital two-dimensional (TraumaCad) templating with special focus on stem morphology. METHODS: 51 patients undergoing THA were randomized to two groups. Preoperative planning was performed on 23 patients with hipEOS (3D) and on 28 patients with TraumaCad (2D) planning software. Planning results were compared with the implanted component size. Inter- and intraobserver reliability as well as planning accuracy of both planning methods with special focus on straight and short stem design were recorded. RESULTS: Intraobserver reliability of both planning methods was good for component planning (ICC2,1: 0.835-0.967). Interobserver ICC2,1 for stem and cup planning were higher for 3D templating (3D ICC2,1: 0.906-0.918 vs. 2D ICC2,1: 0.835-0.843). Total stem and cup size predictions were within 2 sizes for 3D and within 3 sizes for 2D planning. Comparing short stem planning accuracy of both planning methods, absolute difference between implanted and planned component size was significantly lower in 3D planning (P = .029). There was no significant difference in straight stem (P = .935) and cup (P = .954) planning accuracy. CONCLUSION: Our findings suggest that 3D templating with hipEOS software has a good overall reliability and may have a better planning accuracy of short stem prostheses than digital templating with TraumaCad software. Assuming that the number of implanted short stem prostheses will further increase in coming years, a more precise planning with 3D technique can contribute to improve surgery outcome.

[Axial deformities of the lower extremity in the frontal plane : From physiological development to pathological and possible long-term consequences]. / Achsdeformitäten der unteren Extremität in der Frontalebene : Von der physiologischen Entwicklung zum Pathologischen und zu möglichen Langzeitfolgen.

BACKGROUND: From birth to the end of growth, leg axes undergo physiological changes. Congenital, idiopathic or secondary deformities of the lower extremities are considered as a pre-arthrosis. A detailed clinical examination is of primary importance. On the basis of the established preventive examinations, predominantly asymptomatic deformities can be distinguished from age-typical physiological axis deviations at an early stage. THERAPY: There is a variety of conservative and surgical therapy options. In most cases, the spontaneous course of development can be waited for, depending on the deformity and the associated restrictions. It is important to recognize the right time for an intervention. Usually, surgical interventions are necessary, including guided growth by permanent and partial arrest of the growth plate or osteotomies. The aim is to restore the anatomical axial alignment and thus prevent the development of osteoarthritis. A missed intervention often leads to an early endoprosthetic replacement in adulthood.

[Dynamic analysis of joint loading due to leg axis deformity in the frontal plane : Relevance of instrumented gait analysis]. / Dynamische Analyse der Gelenkbelastung bei Beinachsendeformitäten in der Frontalebene : Stellenwert der instrumentellen Ganganalyse.

BACKGROUND: Instrumented 3D gait analysis (IGA) has been established for the functional evaluation of orthopedic diseases. It can provide valuable additional information beyond conventional static radiographic diagnostics and, thus, contributes to treatment decisions and a successful surgical outcome. Regarding the assessment of leg axis deformities IGA is currently only used in a few specialized centers. PRACTICE: This article describes the methods used by IGA and shows its benefit for the treatment of leg axis deformities of the knee in the frontal plane. In particular, the calculation of dynamic joint loads provides important insights regarding the development of degenerative joint deformities in the knee joint and, thus, complements the static assessment of the leg axis. A new treatment algorithm for guided growth intervention in children and adolescents by temporary epiphysiodesis is presented. IGA can be particularly useful for clinical decision-making in borderline cases. If there is a discrepancy between the static leg axis and dynamic knee joint loading, IGA can reveal potential compensatory mechanisms during walking.

[Prevalence and predictors of rebound deformity in the frontal plane : A literature review]. / Häufigkeit und Prädiktoren für einen Rebound nach operativer Achskorrektur in der Frontalebene : Eine Literaturübersicht.

The present literature review presents the current state of the art on the prevalence and causes of the rebound phenomenon after successful correction of leg axis deformity using temporary epiphysiodesis in children and adolescents. A total of 20 studies was included by three independent reviewers. The validity of most studies regarding the rebound incidence is limited by a non-standardized follow-up after plate removal, heterogeneous patient groups with a small number of cases, and missing information on the definition of rebound. The rebound incidence in studies without fundamental limitations in study design is on an average about 50% and underlines the clinical relevance of the topic. Only four studies reported reasons or risk factors for the occurrence of a rebound. In particular, a young age at the beginning of treatment with high residual growth potential after implant removal represents an increased rebound risk, which can be minimized by appropriate overcorrection of the leg axis.

Are changes in radiological leg alignment and femoral parameters after total hip replacement responsible for joint loading during gait?

BACKGROUND: Gait kinematics after total hip replacement only partly explain the differences in the joint moments in the frontal plane between hip osteoarthritis patients after hip replacement and healthy controls. The goal of this study was to determine if total hip replacement surgery affects radiological leg alignment (Hip-Knee-Shaft-Angle, femoral offset, Neck-Shaft-Angle and varus/valgus alignment) and which of these parameters can explain the joint moments, additionally to the gait kinematics. METHODS: 22 unilateral hip osteoarthritis patients who were scheduled for total hip replacement were included in the study. Preoperatively and 1 year postoperatively all patients had biplanar radiographic examinations and 3D gait analysis. RESULTS: The operated leg showed significantly (P < 0.05) more varus (1.1°) as well as a larger femoral offset (+ 8 mm) and a larger Hip-Knee-Shaft-Angle (+ 1.3°) after total hip replacement; however no significant differences in the joint moments in the frontal plane compared to healthy controls were found. The hip moment (first half of stance) and the knee moments (first and second half of stance) were mostly determined by the varus/valgus alignment (29% and respectively 36% and 35%). The combination with a kinematic parameter (knee range of motion, foot progression angle) increased the predictive value for the knee moments. CONCLUSION: In our patient group the joint moments after total hip replacement did not differ from healthy controls, whereas radiological leg alignment parameters changed significantly after the total hip replacement. A combination of these radiological leg parameters, especially the varus alignment, and the deviating kinematics explain the joint moments in the frontal plane during gait after total hip replacement surgery. For surgeons it is important not to create too much of a structural varus alignment by implanting the new hip joint as varus alignment can increase the knee adduction moment and the risk for osteoarthritis of the medial knee compartment. TRIAL REGISTRATION: This study was retrospectively registered with DRKS (German Clinical Trials Register) under the number DRKS00015053. Registered 1st of August 2018.

Influence of Hip Geometry Reconstruction on Frontal Plane Hip and Knee Joint Moments During Walking Following Primary Total Hip Replacement.

BACKGROUND: Following total hip replacement (THR), hip geometry reconstruction parameters such as the femoral offset (FO) correlate with hip stability and wear. The purpose of this study is to determine the relationship between hip geometry parameters and knee and hip joint loading during walking. METHODS: Forty-one patients were examined before and a minimum of 1 year after primary THR. Pearson correlation coefficient (r) was performed to identify relationships between radiographic parameters and gait data. In addition, we divided patients into 2 groups according to the restoration of the FO (within ±5 mm vs more than 5 mm increment). RESULTS: The FO and global offset (GO) showed a positive correlation with the first (r = 0.469, P = .002; r = 0.542, P < .001) and second (r = 0.365, P = .019; r = 0.484, P = .001) knee adduction moment (KAM). The neck-shaft angle revealed a negative correlation with the first hip adduction moment (r = -0.375, P = .047). The reconstruction of FO with an increment of more than 5 mm was associated with a significant higher first KAM (+16%, P = .045) compared to the restored group. CONCLUSION: Our findings suggest that abnormal hip and knee joint loading during walking after THR have a biomechanical background originating from hip geometry reconstruction. Patients with a high FO/GO were more likely to have an increased KAM during walking or vice versa. Surgeons need to be aware that an accurate control of FO, GO, and neck-shaft angle restoration in THR has an impact on hip and knee joint loading that may influence degenerative changes of the knee and higher wear of the artificial hip joint, respectively.

Differences in Gait Performance, Quadriceps Strength, and Physical Activity Between Fallers and Nonfallers in Women with Osteoporosis.

The present study should reveal differences in gait performance, quadriceps strength, and physical activity (PA) between fallers and nonfallers in women with osteoporosis. Forty-one women with osteoporosis (17 fallers, 24 nonfallers) participated. Gait analysis shows that fallers were walking with a slower walking speed (-9%, p = .033) and had a shorter stride length (-7%, p = .039). Moreover, fallers showed a decreased ankle power generation (-18%, p = .045). The quadriceps strength was decreased by 24% for fallers (p = .005) while PA showed no significant differences. Although a decrease in ankle power generation could have an effect on floor clearance for limb advancement in the swing phase, the causal relationship between spatiotemporal parameters (walking speed, stride length) and walking ankle joint power generation remains unknown and warrants further investigation. In conclusion, walking speed, stride length, ankle power generation, and quadriceps strength can be used to differentiate between fallers and nonfallers in women with osteoporosis.

Analysis of agreement between the German translation of the American Foot and Ankle Society's Ankle and Hindfoot Scale (AOFAS-AHS) and the Foot Function Index in its validated German translation by Naal et al. (FFI-D).

BACKGROUND: Despite its wide use in clinical outcome measurement, there is yet no validated German language version of the AOFAS-AHS available. After finishing cross-cultural adaption of the AOFAS-AHS according to the AAOS guidelines, an analysis of agreement was carried out. METHODS: This was done by means of the 18-item Foot Function Index in its validated German translation by Naal et al. (FFI-D). The results of 91 orthopedic patients as well as healthy persons in both scores were then compared intraindividually. The cohort consisted of 46 individuals with hindfoot disorders and 45 persons without any hindfoot complaints. The FFI-D-Score was linearly transformed in the range 0-100 points of the AOFAS. RESULTS: Encouraging correlation was then found for the patients with hindfoot disorders (Spearman's correlation 0.73 (95% CI 0.52-0.85); a median deviation of -2 points (interquartile range -13 points; +13 points) in patients with hindfoot disorders implied good median intraindividual score concordance. However, with 30 of these 46 patients showing score deviations beyond or below a pre-specified ±10 points range of clinically tolerable deviations, the scores cannot be considered exchangeable. CONCLUSION: Although the agreement analysis was performed for the German translation of the two questionnaires, analogous results can be expected also for other languages. It should be noted that the results do not allow for judging which of the scores is better suited to give a valid statement on patient outcome in treatment of hindfoot disorders. To verify which of these two scores is better suited to represent hindfoot-dysfunction a subsequent study using instrumental gait analysis and surface EMG is being carried out.

[An update on clinical gait analysis : Current developments and applications]. / Update klinische Ganganalyse : Aktuelle Entwicklungen und Einsatzmöglichkeiten.

The objective acquisition and assessment of joint movements and loads using instrumented gait analysis has become an established tool in clinical diagnostics. In particular, marker-based 3D gait analyses make use of an increasingly comprehensive database for the assessment of orthopaedic or neurological questions. Based on this data and medical-scientific experience, increasingly reliable approaches and evaluation strategies are emerging, which also draw on methods from artificial intelligence and musculoskeletal modelling. This article focusses on marker-based gait analyses of the lower extremity (hip, knee, foot) and how these can be used in a clinically relevant way using current methods, e.g. for determining indications or optimization of surgical planning. Finally, current developments and applications by using alternative methods from sensor technology and optical motion capture will be briefly discussed.

Subwavelength optical trapping with a fiber-based surface plasmonic lens.

We demonstrate three-dimensional (3D) optical trapping of subwavelength polystyrene beads and bacteria with a surface plasmonic lens fabricated on the endface of an optical fiber. To the best of our knowledge, this is the first demonstration of 3D trapping of subwavelength particles with single fiber optical tweezers. The optical power for achieving a stable 3D trap is smaller compared with conventional optical tweezers, indicating a stronger trap. Compared with surface plasmon tweezers, the trap enabled by our fiber tweezers is located ≈6 wavelengths away from the fiber endface, reducing thermal effects due to the metal absorption and preventing physical contact with the trapped objects.

Reliability and accuracy in three-dimensional gait analysis: a comparison of two lower body protocols.

The standard Plug-in-Gait (PiG) protocol used in three-dimensional gait analysis is prone to errors arising from inconsistent anatomical landmark identification and knee axis malalignment. The purpose of this study was to estimate the reliability and accuracy of a custom made lower body protocol (MA) compared with the PiG protocol. Twenty-five subjects volunteered to evaluate the intertrial reliability. In addition, intersession reliability was examined in 10 participants. An indirect indicator of accuracy according to the knee varus/valgus and flexion/extension range of motion (ROM) was used. Regarding frontal plane knee angles and moments as well as transverse plane motions in the knee and hip joint, the intersession errors were lower for the MA compared with the standard approach. In reference to the knee joint angle cross-talk, the MA produced 4.7° more knee flexion/extension ROM and resulted in 6.5° less knee varus/valgus ROM in the frontal plane. Therefore, the MA tested in this study produced a more accurate and reliable knee joint axis compared with the PiG protocol. These results are especially important for measuring frontal and transverse plane gait parameters.

Factors for Prolonged Pain and Restriction of Movement Following Hemiepiphysiodesis Plating for the Correction of Lower Limb Malalignment in the Frontal Plane: An Explorative Analysis.

The correction of valgus leg malalignment in children using implant-mediated growth guidance is widely used and effective. Despite the minimal invasive character of the procedure, a relevant number of patients sustain prolonged pain and limited mobility after temporary hemiepiphysiodesis. Our aim was to investigate implant-associated risk factors (such as implant position and screw angulation), surgical- or anesthesia-related risk factors (such as type of anesthesia, use, and duration), and pressure of tourniquet or duration of surgery for these complications. Thirty-four skeletally immature patients with idiopathic valgus deformities undergoing hemiepiphysiodesis plating from October 2018-July 2022 were enrolled in this retrospective study. Participants were divided into groups with and without prolonged complications (persistent pain, limited mobility of the operated knee between five weeks and six months) after surgery. Twenty-two patients (65%) had no notable complications, while twelve patients (35%) had prolonged complications. Both groups differed significantly in plate position relative to physis (p = 0.049). In addition, both groups showed significant differences in the distribution of implant location (p = 0.016). Group 1 had a shorter duration of surgery than group 2 (32 min vs. 38 min, p = 0.032) and a lower tourniquet pressure (250 mmHg vs. 270 mmHg, p = 0.019). In conclusion, simultaneous plate implantation at the femur and tibia and metaphyseal plate positioning resulted in prolonged pain and a delay of function. In addition, the amplitude of tourniquet pressure or duration of surgery could play a factor.

Intra- and interobserver reliability analysis of pediatric lower limb parameters on digital long leg radiographs.

BACKGROUND: Malalignments of the lower extremity are common reasons for orthopedic consultation because it may lead to osteoarthritis in adulthood. An accurate and reliable radiological assessment of lower limb alignment in children and adolescents is essential for clinical decision-making on treatment of limb deformities and for regular control after a surgical intervention. OBJECTIVE: First, does the analysis of full-length standing anteroposterior radiographs show a good intra- and interobserver reliability? Second, which parameter is most susceptible to observer-dependent errors? Third, what is the Standard Error of Measurement (SEM95%) of the absolute femoral and tibial length? METHODS: Two observers evaluated digital radiographs of 144 legs from 36 children and adolescents with pathological valgus alignment before a temporary hemiepiphysiodesis and before implant removal. Parameters included Mechanical Femorotibial Angle (MFA), Mechanical Axis Deviation (MAD), mechanical Lateral Distal Femoral Angle (mLDFA), mechanical Medial Proximal Tibial Angle (mMPTA), mechanical Lateral Proximal Femoral Angle (mLPFA), mechanical Lateral Distal Tibial Angle (mLDTA), Joint Line Convergence Angle (JLCA), femur length, tibial length. Intra- and interobserver reliability (ICC2,1), SEM95% and proportional errors were calculated. RESULTS: The intra- and interobserver reliability for almost all measurements was found to be good to excellent (Intra-ICC2,1: 0.849-0.999; Inter-ICC2,1: 0.864-0.996). The SEM95% of both observers was found to be ± 1.39° (MFA), ± 3.31 mm (MAD), ± 1.06° (mLDFA) and ± 1.29° (mMPTA). The proportional error of MAD and MFA is comparable (47.29% vs. 46.33%). The relevant knee joint surface angles show a lower proportional error for mLDFA (42.40%) than for mMPTA (51.60%). JLCA has a proportional error of 138%. Furthermore, the SEM95% for the absolute values of the femoral and tibial length was 4.53 mm for the femur and 3.12 mm for the tibia. CONCLUSIONS: In conclusion, a precise malalignment measurement and the knowledge about SEM95% of the respective parameters are crucial for correct surgical or nonsurgical treatment. The susceptibility to error must be considered when interpreting malalignment analysis and must be considered when planning a surgical intervention. The results of the present study elucidate that MAD and MFA are equally susceptible to observer-dependent errors. This study shows good to excellent intra- and interobserver ICCs for all leg alignment parameters and joint surface angles, except for JLCA. TRIAL REGISTRATION: This study was registered with DRKS (German Clinical Trials Register) under the number DRKS00015053. LEVEL OF EVIDENCE: I, Diagnostic Study.

Characterization of Postural Sway in Women with Osteoporosis and a Control Group by Means of Linear and Nonlinear Methods.

The mechanisms underlying the altered postural control and risk of falling in patients with osteoporosis are not yet fully understood. The aim of the present study was to investigate postural sway in women with osteoporosis and a control group. The postural sway of 41 women with osteoporosis (17 fallers and 24 non-fallers) and 19 healthy controls was measured in a static standing task with a force plate. The amount of sway was characterized by traditional (linear) center-of-pressure (COP) parameters. Structural (nonlinear) COP methods include spectral analysis by means of a 12-level wavelet transform and a regularity analysis via multiscale entropy (MSE) with determination of the complexity index. Patients showed increased body sway in the medial-lateral (ML) direction (standard deviation in mm: 2.63 ± 1.00 vs. 2.00 ± 0.58, p = 0.021; range of motion in mm: 15.33 ± 5.58 vs. 10.86 ± 3.14, p = 0.002) and more irregular sway in the anterior-posterior (AP) direction (complexity index: 13.75 ± 2.19 vs. 11.18 ± 4.44, p = 0.027) relative to controls. Fallers showed higher-frequency responses than non-fallers in the AP direction. Thus, postural sway is differently affected by osteoporosis in the ML and AP directions. Clinically, effective assessment and rehabilitation of balance disorders can benefit from an extended analysis of postural control with nonlinear methods, which may also contribute to the improvement of risk profiles or a screening tool for the identification of high-risk fallers, thereby prevent fractures in women with osteoporosis.

Validation of central peak height method for final adult height predictions on long leg radiographs.

Aims: Accurate skeletal age and final adult height prediction methods in paediatric orthopaedics are crucial for determining optimal timing of growth-guiding interventions and minimizing complications in treatments of various conditions. This study aimed to evaluate the accuracy of final adult height predictions using the central peak height (CPH) method with long leg X-rays and four different multiplier tables. Methods: This study included 31 patients who underwent temporary hemiepiphysiodesis for varus or valgus deformity of the leg between 2014 and 2020. The skeletal age at surgical intervention was evaluated using the CPH method with long leg radiographs. The true final adult height (FHTRUE) was determined when the growth plates were closed. The final height prediction accuracy of four different multiplier tables (1. Bayley and Pinneau; 2. Paley et al; 3. Sanders - Greulich and Pyle (SGP); and 4. Sanders - peak height velocity (PHV)) was then compared using either skeletal age or chronological age. Results: All final adult height predictions overestimated the FHTRUE, with the SGP multiplier table having the lowest overestimation and lowest absolute deviation when using both chronological age and skeletal age. There were no significant differences in final height prediction accuracy between using skeletal age and chronological age with PHV (p = 0.652) or SGP multiplier tables (p = 0.969). Adult height predictions with chronological age and SGP (r = 0.769; p ≤ 0.001), as well as chronological age and PHV (r = 0.822; p ≤ 0.001), showed higher correlations with FHTRUE than predictions with skeletal age and SGP (r = 0.657; p ≤ 0.001) or skeletal age and PHV (r = 0.707; p ≤ 0.001). Conclusion: There was no significant improvement in adult height prediction accuracy when using the CPH method compared to chronological age alone. The study concludes that there is no advantage in routinely using the CPH method for skeletal age determination over the simple use of chronological age. The findings highlight the need for more accurate methods to predict final adult height in contemporary patient populations.

Peak knee joint moments accurately predict medial and lateral knee contact forces in patients with valgus malalignment.

Compressive knee joint contact force during walking is thought to be related to initiation and progression of knee osteoarthritis. However, joint loading is often evaluated with surrogate measures, like the external knee adduction moment, due to the complexity of computing joint contact forces. Statistical models have shown promising correlations between medial knee joint contact forces and knee adduction moments in particularly in individuals with knee osteoarthritis or after total knee replacements (R2 = 0.44-0.60). The purpose of this study was to evaluate how accurately model-based predictions of peak medial and lateral knee joint contact forces during walking could be estimated by linear mixed-effects models including joint moments for children and adolescents with and without valgus malalignment. Peak knee joint moments were strongly correlated (R2 > 0.85, p < 0.001) with both peak medial and lateral knee joint contact forces. The knee flexion and adduction moments were significant covariates in the models, strengthening the understanding of the statistical relationship between both moments and medial and lateral knee joint contact forces. In the future, these models could be used to evaluate peak knee joint contact forces from musculoskeletal simulations using peak joint moments from motion capture software, obviating the need for time-consuming musculoskeletal simulations.

Influence of tension-band plates on the mechanical loading of the femoral growth plate during guided growth due to coronal plane deformities.

Introduction: Correction of knee malalignment by guided growth using a tension-band plate is a common therapy to prevent knee osteoarthritis among other things. This approach is based on the Hueter-Volkmann law stating that the length growth of bones is inhibited by compression and stimulated by tension. How the locally varying mechanical loading of the growth plate is influenced by the implant has not yet been investigated. This study combines load cases from the gait cycle with personalized geometry in order to investigate the mechanical influence of the tension-band plates. Methods: Personalized finite element models of four distal femoral epiphyses of three individuals, that had undergone guided growth, were generated. Load cases from the gait cycles and musculoskeletal modelling were simulated with and without implant. Morphological features of the growth plates were obtained from radiographs. 3D geometries were completed using non-individual Magnetic Resonance Images of age-matched individuals. Boundary conditions for the models were obtained from instrumented gait analyses. Results: The stress distribution in the growth plate was heterogenous and depended on the geometry. In the insertion region, the implants locally induced static stress and reduced the cyclic loading and unloading. Both factors that reduce the growth rate. On the contralateral side of the growth plate, increased tension stress was observed, which stimulates growth. Discussion: Personalized finite element models are able to estimate the changes of local static and cyclic loading of the growth plate induced by the implant. In future, this knowledge can help to better control growth modulation and avoid the return of the malalignment after the treatment. However, this requires models that are completely participant-specific in terms of load cases and 3D geometry.