ABSTRACT
We present an experimental and theoretical study of the fragmentation of polymeric materials by impacting polypropylene particles of spherical shape against a hard wall. Experiments reveal a power law mass distribution of fragments with an exponent close to 1.2, which is significantly different from the known exponents of three-dimensional bulk materials. A 3D discrete element model is introduced which reproduces both the large permanent deformation of the polymer during impact and the novel value of the mass distribution exponent. We demonstrate that the dominance of shear in the crack formation and the plastic response of the material are the key features which give rise to the emergence of the novel universality class of fragmentation phenomena.
Subject(s)
Clavicle/injuries , Fractures, Bone/surgery , Adolescent , Adult , Aged , Casts, Surgical , Child , Child, Preschool , Clavicle/surgery , Female , Fracture Fixation, Internal/methods , Fractures, Bone/therapy , Humans , Male , Middle AgedABSTRACT
First experiences in allo-arthroplastics of the knee with 82 Guepar- and 28 sledge protheses are reported. The primary indication was painful osteoarthritis. The most important complication was the recurrent dislocation of the patella with following osteoarthritis, secondary vascular and infected tissue lesions.
Subject(s)
Joint Prosthesis/methods , Knee Joint/surgery , Aged , Arthroplasty/methods , Female , Humans , Joint Diseases/surgery , Joint Prosthesis/adverse effects , Joint Prosthesis/instrumentation , Middle Aged , Osteoarthritis/etiology , Time FactorsSubject(s)
Joint Prosthesis , Knee Joint/surgery , Adult , Bone Plates , Bone Screws , Female , Humans , Joint Diseases/surgery , Male , Middle AgedABSTRACT
In 27 beagles, 19 radius shaft pseudarthroses and 8 tibia were stimulated either by directly applied alternating current of low frequency and strength, delivered from an implanted battery source, or by a pulsing electromagnetic field inductively coupled to bone. Increase of periosteal callus was only found beneath parallel sling electrodes placed on pseudarthroses parallel to the radius shaft. Stimulation by transverse electrodes implanted into bone produced no significant increase of osteogenesis and bone healing, evaluated by x-rays, scintigrams, and morphometry when compared with contralateral leg controls.
