Clinical scores and motion-capturing gait analysis are today’s gold standard for outcome measurement after knee arthroplasty, although they are criticized for bias and their ability to reflect patients’ actual quality of life has been questioned. In this context, mobile gait analysis systems have been introduced to overcome some of these limitations. This study used a previously developed mobile gait analysis system comprising three inertial sensor units to evaluate daily activities and sports. The sensors were taped to the lumbosacral junction and the thigh and shank of the affected limb. The annotated raw data was evaluated using our validated proprietary software. Six patients undergoing knee arthroplasty were examined the day before and 12 months after surgery. All patients reported a satisfactory outcome, although four patients still had limitations in their desired activities. In this context, feasible running speed demonstrated a good correlation with reported impairments in sports-related activities. Notably, knee flexion angle while descending stairs and the ability to stop abruptly when running exhibited good correlation with the clinical stability and proprioception of the knee. Moreover, fatigue effects were displayed in some patients. The introduced system appears to be suitable for outcome measurement after knee arthroplasty and has the potential to overcome some of the limitations of stationary gait labs while gathering additional meaningful parameters regarding the force limits of the knee.

The clinical implementation of percutaneous implants is still limited owing to infections at the side of the stoma. In our concept, this issue is addressed by designing copolymer surface coatings possessing biocompatibility and antimicrobial activity to improve the maintenance of a physiological skin seal at the skin-implant interface. Different copolymers with surface-active phosphonate and antimicrobial cationic groups were designed. Thus, coated titanium samples were cultured with bacterial strains or fibroblasts, respectively. Antimicrobial impact was evaluated by imaging the reduction of bacterial adherence. Biocompatibility was displayed by fibroblast proliferation and morphology. A variety of copolymers of 4-vinylpyridine with vinylbenzylphosphonate or dimethyl(2-methacryloyloxy-ethyl) phosphonate were prepared by free radical polymerization. The optimized polymer coating (copolymer D) showed a reduction of adherent bacteria up to 95%, with only a slight reduction in the adherence of human fibroblasts compared with blank titanium controls. In this study, we demonstrate in vitro that polymer surface coatings can be simultaneously antimicrobial and biocompatible. We consider this to be a promising technology for the realization of a permanent aseptic percutaneous passage as needed for the advancement of osseointegrated limb prosthesis.

Techniques for the skeletal attachment of amputation-prostheses have been developed over recent decades. This type of attachment has only been performed on a small number of patients. It poses various potential advantages compared to conventional treatment with a socket, but is also associated with an increased risk of bone or implant-bone interface fracture in the case of a fall. We therefore investigated the bending stiffness and ultimate bending moment of such devices implanted in human and synthetic bones. Eight human specimens and 16 synthetic models of the proximal femora were implanted with lower extremity prostheses and eight human specimens and six synthetic humeri were implanted with upper extremity prostheses. They were dissected according to typical amputation levels and underwent loading in a material testing machine in a four-point bending setup. Bending stiffness, ultimate bending moment and fracture modes were determined in a load to failure experiment. Additionally, axial pull-out was performed on eight synthetic specimens of the lower extremity. Maximum bending moment of the synthetic femora was 160.6±27.5 Nm, the flexural rigidity of the synthetic femora was 189.0±22.6 Nm². Maximum bending moment of the human femora was 100.4±38.5 Nm, and the flexural rigidity was 137.8±29.4 Nm². The maximum bending moment of the six synthetic humeri was 104.9±19.0 Nm, and the flexural rigidity was 63.7±3.6 Nm². For the human humeri the maximum bending moment was 36.7±11.0 Nm, and the flexural rigidity at was 43.7±10.5 Nm². The maximum pull-out force for the eight synthetic femora was 3571±919 N. Significant differences were found between human and synthetic specimens of the lower and upper extremity regarding maximum bending moment, bending displacement and flexural rigidity. The results of this study are relevant with respect to previous finding regarding the load at the interfaces of osseointegrated prosthesis fixation devices and are crucial for the development of safety devices intended to protect the bone-implant interface from damaging loadings.