On this page you will find selected and current projects of the Laboratory forBiomechanics and Biomaterials. If you have any questions about the individual projects or topics, you will find the contact person in the description.

DFG Forschergruppe

"FOR 2180: Graded Implants for Tendon-Bone Junctions (“Graded Implants”)"

Implant research recently focusses on functional tissue implants for homogenous tissues. Less well elaborated are implants for regions between tissues with strongly differing properties, e.g. tendon-bone junctions. Natural tissue junctions exhibit gradients: gradients in structure, composition, and resulting functionality which are reflected by alterations in biomechanical properties. This complex situation is addressed by the novel, graded cell-free implant presented by the re-search unit. Endogenous stem cells from the host shall be activated and instructed by the implant to rebuild a tendon-bone junction and to achieve a functional (“regenerated”) junction after degradation of the implant. Aim of the research unit is to demonstrate the principle feasibility and to generate a model of a graded implant for future applications at the tendon-bone junction of the rotator cuff.As basic material, electrospun fibre mats from biodegradable polymers (mainly based on polycaprolactone) with isotropic (“on the tendon side”) or anisotropic (“on the bone side”) fibre orientation will be used. The fibre mats will be equipped with appropriate porosity and permeability to allow for the survival and functionality of immigrating cells as well as the exchange of nutrients and products of metabolism. In addition, the mechanical properties will be tailored according to the in vivo-situation. Fibre surfaces will be modified and equipped with varying degrees of calcium phosphate, silica or polymeric nanoparticles. Silica- or polymeric nanoparticles will serve as release systems for biologically active proteins. Apart from Bone Morphogenetic Protein (BMP)2 and Transforming Growth Factor (TGF)-¿, Smad8 Linker region + Mad homology region 2 (Smad8 L+MH2) will be used. This is a modified transcription factor inducing differentiation of cells into tendon cells and tendon tissue. For controlled manipulation of the release kinetics the factors will be applied via nanoparticulate release systems in a graded manner. In order to achieve long-term release also amyloid variants of the proteins will be produced. Fixation of the implant on the bone side will by performed by commercially available bone anchors. At the tendon side, sutures will be used. The formation of a regenerated tissue junction after use of the implant will be verified in the research unit by use of small and large animal models.

Term since 2015

Contact person: Prof. Dr. rer. nat. Andrea Hoffmann

Homepage: https://www.gradierte-implantate.de/

EU Project

"Softpro - Synergy-based Open-source Foundations and Technologies for Prosthetics and Rehabilitation"

SoftPro project will study and design soft synergy-based robotics technologies to develop new prostheses, exoskeletons, and assistive devices for upper limb rehabilitation, which will greatly enhance the efficacy and accessibility to a greater number of users. Building on solid methodological bases, SoftPro will produce a significant social impact, promoting advanced robot prosthetic and assistive technology “from bench to bedside”; but it will also introduce disruptively new, admittedly risky but potentially high-impact ideas and paradigms.

Term since 2016

Contact person: Dr. Eike Jakubowitz

Homepage: http://www.softpro.eu/

DFG Research Grant

"Efficacy of dynamic load during walking on the prediction of rebound effects following guiding growth intervention in children with angular deformities"

Rationale: Malalignment of knee joints is predisposed to the development of unicompartmental degenerations because of the excessive load placed on one side of the knee. Therefore, guided growth in skeletally immature patients is recommended. However, a rebound effect (recurrence of the malalignment) after implant removal frequently occurs. Up to now, the reasons for this phenomenon are not well understood and standards for optimal timing for hardware removal do not exist. This timing is crucial for the long term success of the axial corrections. In addition, indication for hardware removal is based on static measures during standing that does not reflect the actual load situation and individual compensatory mechanisms during walking. Objectives: The aim of the study is to investigate the influence of the dynamic load during walking on the rebound effect following a guiding growth intervention using tension band plates. Methods: Gait analysis and standing radiographs will be captured the day before implantation and explantation of tension band plates. To analyse rebound effects, non-invasive gait analysis will be performed 6 and 12 months after explantation. To assess daily cumulative loadings mobile step trackers will be used. In order to predict the knee joint loading regime as a function of acting muscles, multi-body simulations will be applied and additionally compared with knee joint loading measures of gait analyses. Populations: 142 children with idiopathic varus or valgus leg malalignment and 60 typically developed age matched controls. Timeframe: The anticipated duration is 3 years. During the first six quarters patients and controls will be recruited. The expected time of axial correction through guiding growth is on average 12 month, the follow up time after removal is 6 and 12 months. Expected outcome: According to the current algorithm for hardware removal, which is based only on static measurements, a few patients may show a pathologic knee joint loading after explantation. Since the load situation affects bone remodelling, pathological loads may be related to higher rebound effects. The results of this study should give first time insights into the mechanical integrity of bones and muscles during and after guiding growth. This may improve the treatment algorithm.

Term since 2018

Contact person: Dr. Eike Jakubowitz

"Comparison of conventional socket attachment and osseointegrated prosthesis fixation for transfemoral amputees"

The conventional treatment for individuals with transfemoral amputation consists of the prosthesis being attached to the residual amputated limb by means of a socket. Despite advances in socket design complications such as skin problems still occur. In some cases, patients can not be mobilized with the socket technique. The osseointegrated prosthesis fixation offers an alternative. Whereby, an implant is inserted into the remaining femur and protrudes through the skin. The conventional socket is replaced by the osseointegrated prosthesis fixation and a direct connection between the prosthetic leg and the musculoskeletal system will be achieved.With amputation a part of the muscle volume will be lost and this leads to an imbalance of the musculature of the thigh. The loss is often compensated by a greater use of the contralateral side, which favors degenerative changes in the joints. Thus, a significant association between amputation and an increased risk of osteoarthritis of the contralateral leg are verified.Based on our preliminary work a patient-specific multi-body model will be developed representing the musculoskeletal system of transfemoral amputees, thereby different rehabilitation concepts of the socket technology and the osseointegrated prosthesis fixation will be considered. Furthermore, the model will consider patient specific bone and muscle loss whilst calculating joint loads and muscle forces during daily activities, such as level walking and stair climbing. The use of MRI, motion analysis and multi-body simulation is planned.The aim of the project is to investigate the effect of osseointegrated treatment compared to conventional socket technique on gait patterns and joint loads. Two working hypotheses will be proved:(1a) The gait pattern of patients, who are treated with a conventional socket, will lead to increased stress in the contralateral hip joint compared to the healthy subjects.(1b) The gait pattern of patients, who are treated with an osseointegrated prosthesis fixation, will lead to increased stress in the contralateral hip joint compared to the healthy subjects.(2) Patients, who are treated with an osseointegrated prosthesis fixation, have a more symmetrical gait pattern than patients who are treated with the conventional socket and have less stress in the hip joint.In addition, current methods for the socket design will be scrutinized and optimized together with the clinical partner. Hence, a stump of a transfemoral amputee will be developed from a biomechanical point of view with optimized muscle approaches to reduce energy consumption. Therefore, the quality of life of the affected patients could be reestablished and postoperatively improved reinforced, as the development of osteoarthritis caused by an increased load of the contralateral hip can be clarified.

Term since 2017

Contact person: Dr. Bastian Welke

"Optimization of Soft-Tissue Balancing for Total-Knee Arthroplasty"

The goal of this DFG-Proposal is to investigate the mechanisms and function of individual structures of the knee-joint with regards to soft-tissue balancing by means of in-vitro experiments supported by computer simulations. Using existing currently available data from the literature as a starting point, an optimized systematic sequence of soft-tissue release will be developed, and objective target parameters for soft-tissue balancing defined. The findings from the literature will be complemented by means of structured tissue resections on cadaveric knee specimens followed by stiffness investigations on the robot assisted test rig. Furthermore, the gathered data establisch a basis for the development of a extensive musculoskeletal multi-body model of the knee, which can be used to investigate further approaches for the soft tissue balancing. This project is the starting point for a model based, patient specific, simulation of the soft-tissue-balancing approach, which can be used to create a soft-tissue-planing tool for the knee-TKA in following projects.

Term since 2016

Contact persons:Dipl.-Ing. Dennis Nebel

"OMEGA - Optimization-based forward musculoskeletal simulation of pathological gait"

Knowledge of the motion and loading of the human body and its parts is essential in many fields of human medicine and in particular in orthopedic and trauma surgery. Modern numerical methods have advanced to the point that they are useful for estimating forces in the relevant structures based on a priori knowledge motion and external loading. However, their general usefulness is limited by their inability to predict motion and loading in response to changes in the body caused by disease or as a result of applying a given therapy to treat a disease. The aim of this project is to develop a new generation of forward simulator, based on the computation of most optimal motions, with the promise of predicting and thus improving therapeutic strategies for individual patients. Such simulator will help moving medicine away from a purely empirical approach which relies on the evolution of therapies based on evidence alone, to a point where guiding and predicting therapies is possible. An innovative forward musculoskeletal simulator (FMS) will be developed and implemented for this purpose. Although the simulator could in the future be applied to a wide range of musculoskeletal disorders it will first be tested and further evolved in three specially selected clinical situations: Knee and Ankle Bracing, Drop Foot Pathology, and Above Knee Amputation treated with a microprocessor-controlled knee-prosthesis. These three clinical situations were chosen because they are well characterized, treatments modalities can be altered non-invasively without undue risk to the patients, and sufficient numbers of patients are available. Although relatively simple, each of these pathologies represents a serious reduction in quality of life for the affected patients and general improvements in treatment approaches and in particular the adaptation of treatment modalities to the needs of individual patients will have a serious impact on quality of life. In all three cases a framework will be developed in the context of a clinical gait analysis laboratory, validated and further developed by using a combination of direct kinematic and kinetic measurements and inverse dynamic simulations as ground-truth data obtained from respective patient collectives.One of the most obvious areas of future application of the predictive capabilities of FMS is the treatment of advanced OA of the hip and knee, i.e. total hip (THA) and total knee arthroplasty (TKA). The cost of these procedures represents a significant and increasing economic challenge. This is a further indication of the significance of the basic-research to be performed in this project and demonstrates a major medical and economic impact: improving the treatment of, and providing powerful new methods for predicting the outcome of treatments in many contexts related to musculoskeletal diseases.

Term since 2016

Contact persons: Prof. Dr.-Ing. Christof Hurschler, M.Sc. Gilmar Fernades dos Santos

Partner organisation: Agence Nationale de la Recherche / The French National Research Agency

"Influence of musculotendinous stabilizers on the shoulder stability before and after implantation of a reverse shoulder prosthesis."

The implantation of a reverse shoulder joint prosthesis (ISP has been established as an effective surgical method for improving active shoulder joint mobility and pain reduction in patients with cuff tear arthropathy. However, due to the deficient muscular stabilizers in a substantial proportion of patients, the procedure leads to a postoperative luxation of the prosthesis. Influencing factors wich lead to an instability of the shoulder or an inadequate range of motion after implantation of an ISP, may be the orientation of the prosthetic components as well as the underlying pathology of the patient, a chronic rotator cuff. The key problem of the reverse shoulder arthroplasty treatment in patients with a residual rotator cuff is the lack of information regarding the damage pattern dependant risk of instability after the treatment. Although the surgical care of patients with an ISP provides good results, there is still a lack of information regarding the optimal soft tissue management for the treatment of a patient with a deficient rotator cuff in order to achieve maximum stability and range of motion. Therefore, the two main objectives of this research project are ,1. to investigate the role of the soft tissue tension and in particular the effect of individual musculotendinous stabilizers on the stability of the shoulder before and after implantation of a reverse shoulder joint prosthesis.2. to determine the optimum soft-tissue management, depending on the patient's individual pattern of damage of the musculotendinous stabilizers in order to achieve optimum stability of the joint and a maximum range of motion for a prosthetic restoration.

Term since 2016

Contact person: Dipl.-Ing. Dennis Nebel