Der Einfluss einer Ruptur des vorderen Kreuzbandes auf die posturale Kontrollfähigkeit

Background: Anterior cruciate ligament (ACL) rupture is one of the most serious sports-related injuries. It is associated with the loss of the stabilizing function of the ACL and considerable damage to intraligamentous receptors that provide proprioceptive feedback to the spinal cord and central nervous system. Purpose: It is unclear to what extent the loss of proprioceptive feedback affects postural control or, in other words, the ability to maintain an upright posture. We therefore investigated and qantified the influence of ACL rupture on postural control. Patients and Methods: We studied 58 patients (age: 25.9 ± 7.6 years, height: 175.8 ± 24.4 cm, weight: 81.9 ± 12.0 kg) with isolated unilateral ACL rupture using computerized dynamic posturography (CDP) and compared the stability of injured and uninjured legs. The presence of an ACL rupture had been confirmed by mechanical laxity testing, MRI and arthroscopy. Depending on their knee function, patients were classified as copers and non-copers and examined for their ability to control posture. Results: Mean overall stability index (OSI) scores were 3.7° ± 1.5° for injured legs and 3.0° ± 1.1° for uninjured legs (p < 0.001). A subgroup analysis revealed mean OSI scores of 3.4° ± 1.2° for copers and 4.0° ± 1.6° for non-copers (p = 0.11). Conclusions: During eyes-open testing, postural control was reduced by 23.3 % in patients with unilateral ACL rupture. This is a possible explanation for the subjective feeling of instability reported by many patients. The absence of a significant difference between copers and non-copers may be the result of an inadequate sample size, which had not been calculated for a comparison of these groups. Level of evidence: Prospective study level I

Piezoelectric coefficients and spontaneous polarization of ScAlN

We present a computational study of spontaneous polarization and piezoelectricity in ScxAl1?xN alloys in the compositional range from x = 0 to x = 0.5, obtained in the context of density functional theory and the Berry-phase theory of electric polarization using large periodic supercells. We report composition-dependent values of piezoelectric coefficients eij , piezoelectric moduli dij and elastic constants Cij . The theoretical findings are complemented with experimental measurement of e33 for a series of sputtered ScAlN films carried out with a piezoelectric resonator. The rapid increase with Sc content of the piezoelectric response reported in previous studies is confirmed for the available data. A detailed description of the full methodology required to calculate the piezoelectric properties of ScAlN, with application to other complex alloys, is presented. In particular, we find that the large amount of internal strain present in ScAlN and its intricate relation with electric polarization make configurational sampling and the use of large supercells at different compositions necessary in order to accurately derive the piezoelectric response of the material