Total Harmonic Distortion of a Piezoelectric MEMS Loudspeaker in an IEC 60318-4 Coupler Estimation Using Static Measurements and a Nonlinear State Space Model

We propose a method to evaluate the Total Harmonic Distortion generated by a cantilever-based PZT loudspeaker inside an IEC 60318-4 coupler. The model is validated using experimental data of a commercial loudspeaker. Using the time domain equations of the equivalent electrical circuit of the loudspeaker inside the coupler and a state space formulation, the acoustic pressure response is calculated and compared to the measurement of the manufacturer. Next, the stiffness, transduction and capacitance nonlinear functions are evaluated with a Double-Beam Laser Interferometer (DBLI) and a nanoindenter on test devices and on the commercial loudspeaker. By introducing the nonlinear functions into the model as amplitude-dependent parameters, the THD generated by the loudspeaker is calculated and compared to the value provided by the manufacturer. The good agreement between the measurement and the simulation could allow for a rather quick simulation of the performance of similarly designed loudspeakers at the early stage of the design, by only estimating the static linearity of the main nonlinearity sources.

The spanning plate as an internal fixator in complex distal radius fractures – a prospective cohort study

Objective

Minimal invasive temporary spanning plate (SP) fixation of the wrist has been described as an alternative treatment method in complex distal radius fractures (DRFs). The purpose of this study is to conduct an outcome analysis of all consecutive DRFs treated by SP fixation representing the so far largest published patient cohort outside the United States.

Methods

Indication for SP fixation included DRFs with severe metaphyseal comminution, radiocarpal luxation fractures with concomitant ligamentous injuries and very distal intra-articular fractures lacking the possibility of adequate plate anchoring. All consecutive patients undergoing SP fixation of DRFs were prospectively included in a single level I trauma centre between 01/01/2018 and 31/12/2020. Post-operative assessments included radiological, functional and patient-rated outcomes at a minimum of 12 months follow-up.

Results

In the mentioned timeframe, a total of 508 DRFs were treated operatively of which 28 underwent SP fixation. Average age was 58.1 years (range 22-95 years). The fracture type ranged from AO/OTA type B1.1 to C3.3 and included 8 fracture dislocations. SP removal was performed on average 3.7 months after the initial operation (range 1.4-6.5 months). The mean follow-up time was 14.5 months (range 12-24 months). Radiological evidence of fracture healing appeared on average 9.9 weeks (range 5-28 weeks) after the initial operation. One patient experienced oligosymptomatic non-union. Complications included 2 patients with tendon rupture and one patient with extensor tendon adhesions needing tenolysis at the time of plate removal leaving an overall complication rate of 12%. There was no implant failure and no infection. Mean satisfaction score was 8 (range 0-10) and mean visual analogue scale for resting pain was 0.9 (range 0-9). The mean PRWE score was 17.9 (range 0-59.5) and the mean DASH score was 16.6 (range 0-60.8). Grip strength averaged 23kg (range 4-74kg) amounting to 68% of the opposite side. Mean radial inclination, volar tilt and ulnar variance at 1 year were all within the acceptable limit predictive of symptomatic malunion.

Conclusion

The radiological, functional and patient-rated outcomes in this study are remarkably good considering the complexity of the included fractures. Therefore, this method represents a valuable alternative for the treatment of complex DRFs in selected patients.

Intramedullary screw fixation of metacarpal and phalangeal fractures - A systematic review of 837 patients

Intramedullary screw (IMS) fixation is increasingly used as an alternative treatment option in metacarpal and phalangeal fractures of the hand. However, this technique is currently the subject of controversy among hand surgeons. The aim of this systematic review was to gain insight on radiological, functional and patient-rated outcomes reported in literature. A comprehensive literature search of PubMed, Embase, CENTRAL and CINAHL databases was conducted on March 1st, 2021. All studies reporting on fracture union, complications, and functional and patient-rated outcome in IMS fixation of metacarpal and/or phalangeal fractures were selected. Two prospective and 16 retrospective cohort studies were included, encompassing a total of 837 patients with 958 fractures (693 metacarpal, 222 proximal phalangeal and 43 middle phalangeal). Mean surgery duration was 26.4 min (range 5-60 min). Union was ultimately achieved in all fractures in a mean of 5.7 weeks (range 2-12 weeks). The procedure-related complication rate was 3.2%. The most frequently reported complication was limitation of joint motion, occurring in 2.0% of cases. Incidence of other complications, including loss of reduction, infection and screw protrusion did not exceed 1%. Overall mean total active motion averaged 243° and grip strength reached 97.5% of the contralateral side. The Disabilities of the Arm, Shoulder and Hand (DASH) score averaged 3.7 points. Duration of sick leave was 7.3 weeks. According to the findings of this systematic review, IMS fixation is a time-saving and safe minimally invasive solution for both metacarpal and phalangeal fractures, with a low rate of complications and promising functional and patient-rated results.

[Therapy for ruptures of the rotator cuff of the shoulder (author's transl)]

The authors discuss the indication and various methods of repair of the rotator cuff tear. The results in 24 patients are evaluated with respect to postoperative pain and function.