Observations of Rogue Seas in the Southern Ocean

We report direct observations of surface waves from a stereo camera system along with concurrent measurements of wind speed during an expedition across the Southern Ocean in the austral winter aboard the South African icebreaker S.A. Agulhas II. Records include water surface elevation across a range of wave conditions spanning from early stages of wave growth to full development. We give experimental evidence of rogue seas, i.e., sea states characterized by heavy tails of the probability density function well beyond the expectation based on bound mode theory. These conditions emerge during wave growth, where strong wind forcing and high nonlinearity drive wave dynamics. Quasiresonance wave-wave interactions, which are known to sustain the generation of large amplitude rogue waves, capture this behavior. Wave statistics return to normality as the wind forcing ceases and waves switch to a full developed condition.

Modelling attenuation of irregular wave fields by artificial ice floes in the laboratory

A summary is given on the utility of laboratory experiments for gaining understanding of wave attenuation in the marginal ice zone, as a complement to field observations, theory and numerical models. It is noted that most results to date are for regular incident waves, which, combined with the highly nonlinear wave-floe interaction phenomena observed and measured during experimental tests, implies that the attenuation of regular waves cannot necessarily be used to infer the attenuation of irregular waves. Two experiments are revisited in which irregular wave tests were conducted but not previously reported, one involving a single floe and the other a large number of floes, and the transmission coefficients for the irregular and regular wave tests are compared. The transmission spectra derived from the irregular wave tests agree with the regular wave data but are overpredicted by linear models due to nonlinear dissipative processes, regardless of floe configuration. This article is part of the theme issue 'Theory, modelling and observations of marginal ice zone dynamics: multidisciplinary perspectives and outlooks'.

Modelling attenuation of irregular wave fields by artificial ice floes in the laboratory

A summary is given on the utility of laboratory experiments for gaining understanding of wave attenuation in the marginal ice zone, as a complement to field observations, theory and numerical models. It is noted that most results to date are for regular incident waves, which, combined with the highly nonlinear wave-floe interaction phenomena observed and measured during experimental tests, implies that the attenuation of regular waves cannot necessarily be used to infer the attenuation of irregular waves. Two experiments are revisited in which irregular wave tests were conducted but not previously reported, one involving a single floe and the other a large number of floes, and the transmission coefficients for the irregular and regular wave tests are compared. The transmission spectra derived from the irregular wave tests agree with the regular wave data but are overpredicted by linear models due to nonlinear dissipative processes, regardless of floe configuration. This article is part of the theme issue 'Theory, modelling and observations of marginal ice zone dynamics: multidisciplinary perspectives and outlooks'.

Modelling attenuation of irregular wave fields by artificial ice floes in the laboratory

A summary is given on the utility of laboratory experiments for gaining understanding of wave attenuation in the marginal ice zone, as a complement to field observations, theory and numerical models. It is noted that most results to date are for regular incident waves, which, combined with the highly nonlinear wave-floe interaction phenomena observed and measured during experimental tests, implies that the attenuation of regular waves cannot necessarily be used to infer the attenuation of irregular waves. Two experiments are revisited in which irregular wave tests were conducted but not previously reported, one involving a single floe and the other a large number of floes, and the transmission coefficients for the irregular and regular wave tests are compared. The transmission spectra derived from the irregular wave tests agree with the regular wave data but are overpredicted by linear models due to nonlinear dissipative processes, regardless of floe configuration. This article is part of the theme issue 'Theory, modelling and observations of marginal ice zone dynamics: multidisciplinary perspectives and outlooks'.

The INCA® implant to treat isolated scaphotrapeziotrapezoid osteoarthritis: Preliminary results at a minimum 2 years' follow-up

We report results with the INCA® distal scaphoid pole resurfacing implant anchored within the scaphoid for isolated scaphotrapeziotrapezoid osteoarthritis. Thirty-five implants in 27 patients (mean age, 69 years) were retrospectively included with a minimum follow-up of 2 years. Outcome criteria were pain (VAS), PROMs (QuickDASH, PRWE and MMWS), wrist motion, pinch and grip strength, and radiographic assessment. The average follow-up was 4.6 years. There was a significant improvement in pain, PROMs, grip and pinch strength. Radial deviation and wrist extension showed slight but significant postoperative decrease (-4° for both). Dorsal intercalated segment instability (DISI) was significantly improved postoperatively (7 cases versus 21 preoperatively). There were 2 cases of implant loosening (6%) within the first 10 months: 1 keel malpositioning and 1 insufficient postoperative immobilization. These findings suggest that the INCA® implant is an effective and reliable medium-term solution for isolated scaphotrapeziotrapezoid osteoarthritis. By restoring scaphoid length and gliding on the trapeziotrapezoid surface, the implant contributes to restoring normal bone alignment of the wrist.

Spontaneous emergence of rogue waves in partially coherent waves: A quantitative experimental comparison between hydrodynamics and optics

Rogue waves are extreme and rare fluctuations of the wave field that have been discussed in many physical systems. Their presence substantially influences the statistical properties of a partially coherent wave field, i.e., a wave field characterized by a finite band spectrum with random Fourier phases. Their understanding is fundamental for the design of ships and offshore platforms. In many meteorological conditions waves in the ocean are characterized by the so-called Joint North Sea Wave Project (JONSWAP) spectrum. Here we compare two unique experimental results: the first one has been performed in a 270 m wave tank and the other in optical fibers. In both cases, waves characterized by a JONSWAP spectrum and random Fourier phases have been launched at the input of the experimental device. The quantitative comparison, based on an appropriate scaling of the two experiments, shows a very good agreement between the statistics in hydrodynamics and optics. Spontaneous emergence of heavy tails in the probability density function of the wave amplitude is observed in both systems. The results demonstrate the universal features of rogue waves and provide a fundamental and explicit bridge between two important fields of research. Numerical simulations are also compared with experimental results.

Coracoid bone block transfer procedure: Correlation between subscapularis volume below the bone graft and shoulder stability

INTRODUCTION

Coracoid bone graft transfer has become the gold standard in patients with recurrent anterior shoulder instability associated with bony defect. Several studies have shown that the main stabilizing component of this procedure is the sling effect by the conjoint tendon and the lower portion of subscapularis (SS). The purpose of this study was to determine whether a larger SS volume below the bone block was correlated to greater postoperative shoulder stability.

MATERIALS AND METHODS

This prospective study included a cohort of patients who underwent open coracoid bone graft transfer for post-traumatic recurrent anterior shoulder instability. Forty patients were reviewed at 2 years with a clinical and CT scan evaluation. A correlation analysis assessed the relation between the SS volume index (ratio of SS volume below the bone block to volume over the bone block) and Rowe and Walch-Duplay instability scores.

RESULTS

There exists a positive and significant correlation between SS volume index and postoperative Rowe score, r=0.37 (P=0.03). The same trend was observed for Walch-Duplay score without statistical significance. A larger inferior SS volume did not result in a limitation of external rotation, greater fatty infiltration, or malposition of the coracoid graft.

CONCLUSION

A larger SS volume below the bone block is related to greater postoperative shoulder stability. We recommend performing the split in the middle of the SS or higher instead of the junction of the superior two-thirds and inferior one-third as usually reported.

LEVEL OF EVIDENCE

III, prospective study.

Study of GSK3b inhibitors SB415286 and SB216763 to improve osteoblastic differentiation on microstructured titanium

Rough titanium surfaces enhance cell response to activation of Wnt canonical signalling, a pathway required for osteoblast differentiation. The present study investigated the effects of GSK3β-inhibitors SB216763 and SB415286 on osteoblastic differentiation on titanium surfaces with different topography and wettability. Osteoblastic MC3T3 cells were plated on smooth (Pickled), sand-blasted/acid-etched (SLA) or hyper hydrophilic SLA (modSLA) titanium discs and transfected with a reporter vector sys-tem for Wnt canonical signalling. Cells were also seeded in the presence or in the absence of GSK3b-inhibitors SB216763 or SB415286 and their viability, morphology and the expression of Wnt target and osteoblast specific genes was assessed by Real Time PCR. Inhibitors altered cell morphology and mostly reduced cell viability at high concentration. SB415286 markedly increased the expression of ALP in MC3T3 cells on rough surfaces at the concentration of 100 nM before decreasing its expression at higher concentrations. OCN expression was unaffected. Increasing concentrations of SB216763 increased the expression of ALP in MC3T3 cells on rough surfaces but OCN expression was not changed at any con-centration. SB216763 and SB415286 inhibitors should be further investigated as potential tools to improve cell differentiation on titanium surfaces for endosseous implants.

Clinical outcomes of proximal row carpectomy by preoperative midcarpal joint morphological classification: Viegas type I versus type II

The midcarpal joint can be classified into two anatomical types - Viegas type I and Viegas type II - based on the absence or presence of a medial facet for the hamate on the lunate (lunohamate facet). Type I is associated with a round capitate shape, which theoretically allows better congruence with the lunate fossa of the distal radius following proximal row carpectomy (PRC). This morphological feature has never been considered as a predictive factor of clinical outcome for this surgical procedure. This study aimed to compare the clinical and radiological outcomes of the two Viegas types following PRC. A retrospective single-center study was carried out on patients who underwent PRC for wrist osteoarthritis. Minimum follow-up was 2 years. Lunate type was determined based on preoperative CT arthrography. The clinical evaluation included range of motion (ROM) and strength as well as the functional DASH, Mayo Wrist scores and a VAS for pain. The outcome of radiocapitate osteoarthritis was assessed on plain radiographs. Forty patients were reviewed with a mean follow-up of 57 months. Twenty-one Viegas type I and 19 Viegas type II were identified on preoperative CT arthrography. The etiologies included 23 SLAC wrists (12 Viegas type I, 11 type II), 8 SNAC wrists (4 Viegas type I, 4 type II), 6 cases of Kienböck's disease (3 type IIIa, 3 type IIIb with 3 Viegas type I and 3 type II), 1 Preiser's disease and 2 cases of transscaphoid perilunate dislocation of the carpus. Patients with a Viegas type I lunate had significantly greater flexion-extension ROM: 83.5° vs. 71° (P=0.04) and radial deviation: 12° vs. 7° (P=0.013) than those with Viegas type II. However, three cases of complex regional pain syndrome (CRPS) were reported in the Viegas type II group vs. zero in the Viegas type I group. There were no differences between the two groups in terms of strength, functional scores or VAS pain. The outcome of radiocapitate osteoarthritis was similar in both groups. Considering the number of CRPS cases in the Viegas type II group and similar functional results in both groups, the worse outcomes of the Viegas type II patients in terms of ROM cannot be considered as clinically relevant. This comparative study does not provide a reasonable basis for concluding that Viegas type I patients are better candidates for PRC than Viegas type II patients.

Wind Generated Rogue Waves in an Annular Wave Flume

We investigate experimentally the statistical properties of a wind-generated wave field and the spontaneous formation of rogue waves in an annular flume. Unlike many experiments on rogue waves where waves are mechanically generated, here the wave field is forced naturally by wind as it is in the ocean. What is unique about the present experiment is that the annular geometry of the tank makes waves propagating circularly in an unlimited-fetch condition. Within this peculiar framework, we discuss the temporal evolution of the statistical properties of the surface elevation. We show that rogue waves and heavy-tail statistics may develop naturally during the growth of the waves just before the wave height reaches a stationary condition. Our results shed new light on the formation of rogue waves in a natural environment.

Excitation of rogue waves in a variable medium: an experimental study on the interaction of water waves and currents

We show experimentally that a stable wave propagating into a region characterized by an opposite current may become modulationally unstable. Experiments have been performed in two independent wave tank facilities; both of them are equipped with a wavemaker and a pump for generating a current propagating in the opposite direction with respect to the waves. The experimental results support a recent conjecture based on a current-modified nonlinear Schrödinger equation which establishes that rogue waves can be triggered by a nonhomogeneous current characterized by a negative horizontal velocity gradient.

Statistical properties of directional ocean waves: the role of the modulational instability in the formation of extreme events

We discuss two independent, large scale experiments performed in two wave basins of different dimensions in which the statistics of the surface wave elevation are addressed. Both facilities are equipped with a wave maker capable of generating waves with prescribed frequency and directional properties. The experimental results show that the probability of the formation of large amplitude waves strongly depends on the directional properties of the waves. Sea states characterized by long-crested and steep waves are more likely to be populated by freak waves with respect to those characterized by a large directional spreading.