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1.  A modeling approach to compute modification of net joint forces caused by coping movements in obstetric brachial plexus palsy 
Many disorders of the musculoskeletal system are caused by modified net joint forces resulting from individual coping movement strategies of patients suffering from neuromuscular diseases. Purpose of this work is to introduce a personalized biomechanical model which allows the calculation of individual net joint forces via inverse dynamics based on anthropometry and kinematics of the upper extremity measured by 3D optoelectronical motion analysis.
The determined resulting net joint forces in the anatomical axis of movement may be used to explain the reason for possible malfunction of the musculoskeletal system, especially joint malformation. For example the resulting net joint forces in the humerothoracic joint from simulations are compared to a sample of children presenting obstetric brachial plexus palsy showing an internal shoulder rotation position and a sample of healthy children.
The results presented from the simulation show that an increased internal shoulder rotation position leads to increased net joint forces in the humerothoracic joint. A similar behavior is presented for the subjects suffering from brachial plexus palsy with an internal shoulder rotation position.
The increased net joint forces are a possible reason for joint malformation in the humerothoracic joint caused by coping movements resulting from neuromuscular dysfunction as stated in literature.
PMCID: PMC3816998  PMID: 24139445
Biomechanics; Kinematics; Kinetics; Internal shoulder rotation; Inverse dynamic; Joint malformation
2.  Perceiving One’s Own Limb Movements with Conflicting Sensory Feedback: The Role of Mode of Movement Control and Age 
Previous studies have demonstrated a great uncertainty in evaluating one’s own voluntary actions when visual feedback is suspended. We now compare these limitations in younger and older adults during active or passive limb movements. Participants put their dominant hand on a robot arm and performed movements actively or the relaxed limb was moved passively. Either a distorted visual feedback or no visual feedback at all was provided during the movement. Perception of limb movements was attenuated through visual feedback. This effect was more pronounced in older adults. However, no difference between active and passive movements was found. The results provide evidence for the limited awareness of body effects, even in the absence of voluntary actions.
PMCID: PMC3414862  PMID: 22908005
aging; visuomotor transformation; tool use; perception; action control; active and passive movement control; proprioception; vision
3.  Tension of knotted surgical sutures shows tissue specific rapid loss in a rodent model 
BMC Surgery  2011;11:36.
Every surgical suture compresses the enclosed tissue with a tension that depends from the knotting force and the resistance of the tissue. The aim of this study was to identify the dynamic change of applied suture tension with regard to the tissue specific cutting reaction.
In rabbits we placed single polypropylene sutures (3/0) in skin, muscle, liver, stomach and small intestine. Six measurements for each single organ were determined by tension sensors for 60 minutes. We collected tissue specimens to analyse the connective tissue stability by measuring the collagen/protein content.
We identified three phases in the process of suture loosening. The initial rapid loss of the first phase lasts only one minute. It can be regarded as cutting through damage of the tissue. The percentage of lost tension is closely related to the collagen content of the tissue (r = -0.424; p = 0.016). The second phase is characterized by a slower decrease of suture tension, reflecting a tissue specific plastic deformation. Phase 3 is characterized by a plateau representing the remaining structural stability of the tissue. The ratio of remaining tension to initial tension of phase 1 is closely related to the collagen content of the tissue (r = 0.392; p = 0.026).
Knotted non-elastic monofilament sutures rapidly loose tension. The initial phase of high tension may be narrowed by reduction of the surgeons' initial force of the sutures' elasticity to those of the tissue. Further studies have to confirm, whether reduced tissue compression and less local damage permits improved wound healing.
PMCID: PMC3275509  PMID: 22188826
suture tension; cutting reaction; collagen; suture material; polypropylene; tension sensor
4.  Introducing a feedback training system for guided home rehabilitation 
As the number of people requiring orthopaedic intervention is growing, individualized physiotherapeutic rehabilitation and adequate postoperative care becomes increasingly relevant. The chances of improvement in the patients condition is directly related to the performance and consistency of the physiotherapeutic exercises.
In this paper a smart, cost-effective and easy to use Feedback Training System for home rehabilitation based on standard resistive elements is introduced. This ensures high accuracy of the exercises performed and offers guidance and control to the patient by offering direct feedback about the performance of the movements.
46 patients were recruited and performed standard physiotherapeutic training to evaluate the system. The results show a significant increase in the patient's ability to reproduce even simple physiotherapeutic exercises when being supported by the Feedback Training System. Thus physiotherapeutic training can be extended into the home environment whilst ensuring a high quality of training.
PMCID: PMC2821380  PMID: 20078852
5.  Surgical Strategy in Obstetric Brachial Plexus Palsy: The Aachen Experience 
Seminars in Plastic Surgery  2004;18(4):285-299.
We present our personal experience with 650 children suffering from obstetric brachial plexus palsy. We describe the related surgery including early microsurgical nerve reconstruction and later tendon and muscle transfers. We discuss our clinical approach, the indications and timing for surgery, the technical details of primary and secondary surgery in our hands, and the possible outcome. We emphasize that both clinical work and research work need an interdisciplinary team approach and that diagnostic, therapeutic, and prognostic improvement is based on the refinements of our (micro)surgical skill and the continuous exchange of information between specialized centers.
PMCID: PMC2884798
Obstetric brachial plexus palsy; microsurgery; tendon/muscle transfers; cocontraction; movement analysis

Results 1-5 (5)