Indications and early to mid-term results of ulnar head replacement.

INTRODUCTION: The aim of this study was to explore the indications and show the early to mid-term results of ulnar head replacement for the treatment of pathological conditions of the distal radioulnar joint. METHODS: Our study group comprised 52 patients with a mean age of 64 years who had 56 ulnar head replacements. Seven were implanted to salvage an unstable deletive procedure; the rest were for primary treatment of osteoarthritis, rheumatoid arthritis and trauma. Concomitant procedures along with the ulnar head replacement included wrist arthrodesis, joint replacement and tendon transfers. RESULTS: The follow-up duration ranged from 1 year to 11 years (mean: 60 months, median: 60 months). In almost all of the patients, pain improved with a median visual analogue scale score of 2 (mean: 2.2, range: 0-8) and a median DASH (Disabilities of the Arm, Shoulder and Hand) score of 12.5 (mean: 17.9, range: 0-56). Of the 52 patients, 47 reported they would have the same procedure again. CONCLUSIONS: Ulnar head replacement appears to be a reliable and effective procedure solving several pathological problems of the distal radioulnar joint. We present a large patient group with a short to medium-term follow-up duration.

Microdamage evaluation in human trabecular bone based on nonlinear ultrasound vibro-modulation (NUVM).

The primary aim of this work is to investigate the potential of nonlinear ultrasound for microdamage detection in human bone. Microdamage evaluation in human bone is of great importance, because it is considered a significant parameter for characterizing fracture risk. Experiments employing nonlinear acoustic vibro-modulation were carried out in human femoral trabecular specimens removed during surgery. A frequency mixing (inter-modulation) was observed between an ultrasound wave, propagating in the bone, and a low-frequency vibration applied directly to the bone specimens. The appearance of side frequencies, which are related to the vibrational excitation, around the fundamental ultrasound frequency manifests the modulation nonlinear phenomenon. Instead of inducing microdamage by mechanical fatigue loading, specimens with different degree of osteoporosis were used. The experiments demonstrated that osteoporotic bone exhibits stronger nonlinearity compared to healthy bone presenting significant increase of the modulation amplitude with increasing degree of osteoporosis. The obtained results indicate that, in contrast to conventional hysteretic nonlinearity, dissipative acoustic nonlinearity can be of significance in the generation of nonlinear modulation effects. In the proposed technique the size and the shape of samples are not crucial compared to nonlinear resonant ultrasound spectroscopy (NRUS). Furthermore, the method is sensitive to the presence of microdamage, non-invasive, easy to implement and most important, it can be proved valuable tool for in vivo bone damage characterization.