Current Preclinical Testing of New Hip Arthroplasty Technologies Does Not Reflect Real-World Loadings: Capturing Patient-Specific and Activity-Related Variation in Hip Contact Forces

[An update on clinical gait analysis : Current developments and applications]

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.

Intra and inter-rater variability in the construction of patient-specific musculoskeletal model

BACKGROUND

Variations observed in biomechanical studies might be attributed to errors made by operators during the construction of musculoskeletal models, rather than being solely attributed to patient-specific geometry.

RESEARCH QUESTION

What is the impact of operator errors on the construction of musculoskeletal models, and how does it affect the estimation of muscle moment arms and hip joint reaction forces?

METHODS

Thirteen independent operators participated in defining the muscle model, while a single operator performed 13 repetitions to define the muscle model based on 3D bone geometry. For each model, the muscle moment arms relative to the hip joint center of rotation was evaluated. Additionally, the hip joint reaction force during one-legged stance was assessed using static inverse optimization.

RESULTS

The results indicated high levels of consistency, as evidenced by the intra- rater and inter-rater agreement measured by the Intraclass Correlation Coefficient (ICC), which yielded values of 0.95 and 0.99, respectively. However, the estimated muscle moment arms exhibited an error of up to 16 mm compared to the reference musculoskeletal model. It was found that muscles attached to prominent anatomical landmarks were specified with greater accuracy than those attached over larger areas. Furthermore, the variability in estimated moment arms contributed to variations of up to 12% in the hip joint reaction forces.

SIGNIFICANCE

Both moment arm and muscle force demonstrated significantly lower variability when assessed by a single operator, suggesting the preference for employing a single operator in the creation of musculoskeletal models for clinical biomechanical studies.

Design and manufacturing of biomimetic scaffolds for bone repair inspired by bone trabeculae

Porous scaffold (PorS) implants, particularly those that mimic the structural features of natural cancellous bone (NCanB), are increasingly essential for the treatment of large-area bone defects. However, the mechanical properties of NCanB-based bionic bone scaffold (BioS) and its performance as a bone repair material have not been fully explored. This study investigates the effect of bionic structure parameters on the mechanical properties and bone reconstruction performance of BioS. Using laser powder bed fusion (L-PBF) technology, different BioS with various structural parameters were created and evaluated using Micro-CT, compression testing, Finite Element (FE) Simulation, and computational fluid dynamics (CFD), and compared to commonly used clinical PorS. Assess the capacity of the BioS scaffold to support and enhance bone reconstruction following implantation through the evaluation of its mechanical properties, permeability, and fluid shear stress (FSS). BioS-85-90 and BioS-80-50 showed suitable mechanical properties, performed well in FE simulation of implantation, demonstrated outstanding abilities for osteoinductive ingrowth and bone tissue differentiation, and proved to be reliable materials for the reconstruction of bone defects. Therefore, BioS shows significant potential for clinical application as a bone reconstruction material, providing a solid foundation for the integration of tissue engineering and bionic design.

Validation of a musculoskeletal model to investigate hip joint mechanics in response to dynamic multiplanar tasks

Existing hip-focused musculoskeletal (MSK) models are limited by the hip range of motion, hip musculature detail, or have only been qualitatively validated. The purposes of this study were to: i) modify the existing 2396Hip MSK model to simulate dynamic tasks with multiplanar hip joint motion; and ii) validate the modified MSK model quantitatively against experimental data. Experimental data was collected from five healthy adults (age = 25 [6] years, two females) during eight movement tasks. The motion and ground reaction force data were input into the MSK modeling software OpenSim to calculate muscle activations and hip contact forces (HCFs). The HCFs were compared to experimental HCFs previously measured in total hip arthroplasty (THA) patients using instrumented hip prostheses. A gait simulation was performed using data from one THA patient to directly assess the model's accuracy in estimating HCFs. The young adults' modeled and experimental muscle activations for seven muscles were compared using a cross-correlation function. The model only overestimated the peak resultant HCFs by 0.06-0.08 N/BW compared to the experimentally measured HCFs of the THA patient. The young adults' HCFs were over two standard deviations higher than previously measured in the THA patients, which is likely a result of different movement patterns. The correlation coefficients indicated strong correlations between experimental and modeled muscle activations in 50 of the 56 comparisons. The results of this study suggest the new MSK model is an appropriate method to quantify HCFs and muscle activations in response to dynamic, multiplanar tasks among young, healthy adults.

Reverse dynamics analysis of contact force and muscle activities during the golf swing after total hip arthroplasty

There are no reports on hip kinetics including contact forces and muscle activities during the golf swing after total hip arthroplasty (THA). The aim of this study was to identify the characteristics of three-dimensional dynamics during the golf swing. Ten unilateral primary THA patients participated in motion capture test of their driver golf swing. The driver swing produced approximately 20-30° of rotation in both lead and trail replaced hips. The mean hip contact forces (HCFs) of lead and trail replaced hips were 5.1 and 6.6 × body weight, respectively. Left and right THAs showed similar HCFs of lead and trail hips. More than 60% of the Percent maximum voluntary isometric contraction was found in bilateral iliopsoas muscles in all unilateral THA. Three factors [female sex, lower modified Harris Hip Score, and higher HCF of surgical side] were associated with the golf-related replacement hip pain. Golf is an admissible sport after THA because driver swings do not contribute excessive rotation or contact forces to hip prostheses. HCF could be reduced through swing adjustments, which may allow patients with golf-related replacement hip pain to develop a comfortable golf game free from pain.

High tibial osteotomy effectively redistributes compressive knee loads during walking

The objectives of this study were to estimate pre- and postoperative lower limb kinematics and kinetics and knee intra-articular forces during gait using musculoskeletal modeling in a cohort of patients with knee osteoarthritis (OA) undergoing high tibial osteotomy (HTO), compare these to controls, and determine correlations between changes in these parameters and Knee Injury and Osteoarthritis Outcome Score (KOOS) subscores after HTO. Sixteen patients with isolated, symptomatic medial compartment knee OA completed pre- and postoperative gait analysis (mean follow-up time: 8.6 months). Sixteen age- and sex-matched asymptomatic volunteers participated as controls. Musculoskeletal modeling was used to evaluate lower limb joint moments and knee contact forces during gait. While HTO had limited influence on sagittal plane kinematics and moments, significant changes in the load distribution at the knee after HTO were observed with a lower postoperative compressive load on the medial compartment during midstance and a higher compressive load on the lateral compartment during early and late stance. Moreover, the lateral shear force in midstance was significantly lower after HTO. Changes in the external knee adduction moment (KAM) did not always coincide with reductions in the knee compressive force in the medial compartment. Biomechanical changes did not correlate with improvements in KOOS subscores. Hence, HTO effectively unloaded the medial compartment by redistributing part of the overall compressive force to the lateral compartment during gait with limited influence on gait function. The KAM may not adequately describe compartmental load magnitude or changes induced by interventions at the compartment level. Clinical trial registration: ClinicalTrials. gov Identifier-NCT02622204. Clinical significance: This study provides important evidence for changes in joint level loads after corrective osteotomy as joint preserving surgery and emphasizes the need for additional biomechanical outcomes of such interventions.

On the estimation of hip joint loads through musculoskeletal modeling

Noninvasive estimation of joint loads is still an open challenge in biomechanics. Although musculoskeletal modeling represents a solid resource, multiple improvements are still necessary to obtain accurate predictions of joint loads and to translate such potential into practical utility. The present study, focused on the hip joint, is aimed at reviewing the state-of-the-art literature on the estimation of hip joint reaction forces through musculoskeletal modeling. Our literature inspection, based on well-defined selection criteria, returned seventeen works, which were compared in terms of methods and results. Deviations between predicted and in vivo measured hip joint loads, taken from the OrthoLoad database, were assessed through quantitative deviation indices. Despite the numerous modeling and computational improvements made over the last two decades, predicted hip joint loads still deviate from their experimental counterparts and typically overestimate them. Several critical aspects have emerged that affect muscle force estimation, hence joint loads. Among them, the physical fidelity of the musculoskeletal model, with its parameters and geometry, plays a crucial role. Also, predicted joint loads are markedly affected by the selected muscle recruitment strategy, which reflects the underlying motor control policy. Practical guidelines for researchers interested in noninvasive estimation of hip joint loads are also provided.

Increased Femoral Anteversion Does Not Lead to Increased Joint Forces During Gait in a Cohort of Adolescent Patients

Orthopedic complications were previously reported for patients with increased femoral anteversion. A more comprehensive analysis of the influence of increased femoral anteversion on joint loading in these patients is required to better understand the pathology and its clinical management. Therefore, the aim was to investigate lower-limb kinematics, joint moments and forces during gait in adolescent patients with increased, isolated femoral anteversion compared to typically developing controls. Secondly, relationships between the joint loads experienced by the patients and different morphological and kinematic features were investigated. Patients with increased femoral anteversion (n = 42, 12.8 ± 1.9 years, femoral anteversion: 39.6 ± 6.9°) were compared to typically developing controls (n = 9, 12.0 ± 3.0 years, femoral anteversion: 18.7 ± 4.1°). Hip and knee joint kinematics and kinetics were calculated using subject-specific musculoskeletal models. Differences between patients and controls in the investigated outcome variables (joint kinematics, moments, and forces) were evaluated through statistical parametric mapping with Hotelling T2 and t-tests (α = 0.05). Canonical correlation analyses (CCAs) and regression analyses were used to evaluate within the patients’ cohort the effect of different morphological and kinematic predictors on the outcome variables. Predicted compressive proximo-distal loads in both hip and knee joints were significantly reduced in patients compared to controls. A gait pattern characterized by increased knee flexion during terminal stance (KneeFlex_tSt) was significantly correlated with hip and knee forces, as well as with the resultant force exerted by the quadriceps on the patella. On the other hand, hip internal rotation and in-toeing, did not affect the loads in the joints. Based on the finding of the CCAs and linear regression analyses, patients were further divided into two subgroups based KneeFlex_tSt. Patients with excessive KneeFlex_tSt presented a significantly higher femoral anteversion than those with normal KneeFlex_tSt. Patients with excessive KneeFlex_tSt presented significantly larger quadriceps forces on the patella and a larger posteriorly-oriented shear force at the knee, compared to patients with normal KneeFlex_tSt, but both patients’ subgroups presented only limited differences in terms of joint loading compared to controls. This study showed that an altered femoral morphology does not necessarily lead to an increased risk of joint overloading, but instead patient-specific kinematics should be considered.

Altered Muscle Contributions are Required to Support the Stance Limb During Voluntary Toe-Walking

Toe-walking characterizes several neuromuscular conditions and is associated with a reduction in gait stability and efficiency, as well as in life quality. The optimal choice of treatment depends on a correct understanding of the underlying pathology and on the individual biomechanics of walking. The objective of this study was to describe gait deviations occurring in a cohort of healthy adult subjects when mimicking a unilateral toe-walking pattern compared to their normal heel-to-toe gait pattern. The focus was to characterize the functional adaptations of the major lower-limb muscles which are required in order to toe walk. Musculoskeletal modeling was used to estimate the required muscle contributions to the joint sagittal moments. The support moment, defined as the sum of the sagittal extensive moments at the ankle, knee, and hip joints, was used to evaluate the overall muscular effort necessary to maintain stance limb stability and prevent the collapse of the knee. Compared to a normal heel-to-toe gait pattern, toe-walking was characterized by significantly different lower-limb kinematics and kinetics. The altered kinetic demands at each joint translated into different necessary moment contributions from most muscles. In particular, an earlier and prolonged ankle plantarflexion contribution was required from the soleus and gastrocnemius during most of the stance phase. The hip extensors had to provide a higher extensive moment during loading response, while a significantly higher knee extension contribution from the vasti was necessary during mid-stance. Compensatory muscular activations are therefore functionally required at every joint level in order to toe walk. A higher support moment during toe-walking indicates an overall higher muscular effort necessary to maintain stance limb stability and prevent the collapse of the knee. Higher muscular demands during gait may lead to fatigue, pain, and reduced quality of life. Toe-walking is indeed associated with significantly larger muscle forces exerted by the quadriceps to the patella and prolonged force transmission through the Achilles tendon during stance phase. Optimal treatment options should therefore account for muscular demands and potential overloads associated with specific compensatory mechanisms.

Multiscale biomechanics of the biphasic articular cartilage in the natural hip joint during routine activities

BACKGROUND AND OBJECTIVE

The investigation of the biomechanical behaviour of the articular cartilage (AC) under physiological loading is important to understand the joint function and onset of pathologies. This study aimed to develop a multiscale computational modelling approach and apply the approach to investigate the time-dependant biphasic behaviour of the AC in the natural hip joint under repetitive physiological loading over 80 cycles amongst six routine activities.

METHODS

A subject-specific musculoskeletal multibody dynamics (MBD) model was developed based on the anthropometry and motion capture data collected for a male subject. A corresponding FE model of the natural hip joint with biphasic AC was created based on the bone geometries exported from the MBD model. A multiscale computational modelling was then developed to couple the MBD model and the FE model and used to investigate the time-dependant biphasic behaviour of the AC under subject-specific physiological loading over 80 cycles amongst six routine activities.

RESULTS

The results showed that for all the activities considered, the interstitial fluid pressure in the AC supported over 80% of the loading. The maximum values of the peak contact pressure and peak fluid pressure for the whole cycle increased firstly and then remained stable over time from the 1st cycle to the 80th cycle. At these instants, the contact areas were located at the centre region of the AC. By contrast, when the contact area was located at the edge of the AC, these peak pressures were found to increase over time for some of the activities (squat, ascending stairs, descending stairs) but decrease for the other activities (normal walking, standing up, sitting down).

CONCLUSION

This study for the first time developed a multiscale computational modelling approach to couple a musculoskeletal MBD model of the body and a detailed FE model of the natural hip joint with biphasic AC, which enabled the evaluation of time-dependant biphasic behaviour of the AC under realistic physiological loading conditions. The study may have important implications in biomechanical studies of human cartilage to understand the joint function and biomechanical factors related to joint disease, and to support the development of cartilage substitution.

Contact force path in total hip arthroplasty: effect of cup medialisation in a whole-body simulation

BACKGROUND

Cup medialisation down to the true acetabular floor in total hip arthroplasty with a compensatory femoral offset increase seems to be mechanically advantageous for the abductor muscles due to the relocation of the lever arms (body weight lever arm decreased, abductor lever arm increased). However, limited information is currently available about the effects of this reconstruction type at the head cup interface, compared to an anatomical reconstruction that maintains the natural lever arms. Through a whole-body simulation analysis, we compared medialised versus anatomical reconstruction in THA to analyse the effects on: (1) contact force magnitude at the head cup interface; (2) contact force path in the cup; and (3) abductor activity.

METHODS

Musculoskeletal simulations were performed to calculate the above-mentioned parameters using inverse dynamics analysis. The differences between the virtually implanted THAs were calculated to compare the medialised versus anatomical reconstruction.

RESULTS

Cup medialisation with compensatory femoral offset increase led to: (1) a reduction in contact force magnitude at the head cup interface up to 6.6%; (2) a similar contact force path in the cup in terms of sliding distance and aspect ratio; and (3) a reduction in abductor activity up to 17.2% (gluteus medius).

CONCLUSIONS

In our opinion, these potential biomechanical gains do not generally justify a fully medialised reconstruction, especially in younger patients that are more likely to undergo revision surgery in their lifetime. Cup medialisation should be performed until sufficient press fit and bony coverage of a properly sized and oriented cup can be achieved.

Subject-Specific Modeling of Femoral Torsion Influences the Prediction of Hip Loading During Gait in Asymptomatic Adults

Hip osteoarthritis may be caused by increased or abnormal intra-articular forces, which are known to be related to structural articular cartilage damage. Femoral torsional deformities have previously been correlated with hip pain and labral damage, and they may contribute to the onset of hip osteoarthritis by exacerbating the effects of existing pathoanatomies, such as cam and pincer morphologies. A comprehensive understanding of the influence of femoral morphotypes on hip joint loading requires subject-specific morphometric and biomechanical data on the movement characteristics of individuals exhibiting varying degrees of femoral torsion. The aim of this study was to evaluate hip kinematics and kinetics as well as muscle and joint loads during gait in a group of adult subjects presenting a heterogeneous range of femoral torsion by means of personalized musculoskeletal models. Thirty-seven healthy volunteers underwent a 3D gait analysis at a self-selected walking speed. Femoral torsion was evaluated with low-dosage biplanar radiography. The collected motion capture data were used as input for an inverse dynamics analysis. Personalized musculoskeletal models were created by including femoral geometries that matched each subject’s radiographically measured femoral torsion. Correlations between femoral torsion and hip kinematics and kinetics, hip contact forces (HCFs), and muscle forces were analyzed. Within the investigated cohort, higher femoral antetorsion led to significantly higher anteromedial HCFs during gait (medial during loaded stance phase and anterior during swing phase). Most of the loads during gait are transmitted through the anterior/superolateral quadrant of the acetabulum. Correlations with hip kinematics and muscle forces were also observed. Femoral antetorsion, through altered kinematic strategies and different muscle activations and forces, may therefore lead to altered joint mechanics and pose a risk for articular damage. The method proposed in this study, which accounts for both morphological and kinematic characteristics, might help in identifying in a clinical setting patients who, as a consequence of altered femoral torsional alignment, present more severe functional impairments and altered joint mechanics and are therefore at a higher risk for cartilage damage and early onset of hip osteoarthritis.