Cold-Air Pool Processes in the Inn Valley During Föhn: A Comparison of Four Cases During the PIANO Campaign.

We present a comprehensive analysis of four south föhn events observed during the Penetration and Interruption of Alpine Foehn (PIANO) field campaign in the Inn Valley, Austria, in the vicinity of Innsbruck. The goal is to detect and quantify processes of cold-air pool (CAP) erosion by föhn as well as processes of föhn breakdown. Despite differences in föhn breakthrough and strength, the four cases exhibit similarities in CAP evolution: initially, the CAP experienced strongest warming in the centre of Innsbruck, where the föhn jet from the Wipp Valley interacted with the CAP in the Inn Valley. The resulting shear-flow instability at the föhn-CAP interface caused turbulent CAP erosion and, together with vertical warm-air advection, led to CAP depression over the city centre. This depression drove pre-föhn westerlies near the surface that caused cold-air advection inside the CAP west of the city centre and warm-air advection in the east. Ultimately, the latter contributed to stronger CAP erosion in the east than in the west. This stronger heating also explains the preferential initial föhn breakthrough at the valley floor east of Innsbruck. In two of the cases, subsequent westward propagation of the föhn-CAP boundary across the city accompanied by northerly (deflected) föhn winds led to a complete föhn breakthrough. Föhn breakdown occurred either by a backflow of the CAP remnant or by a cold-frontal passage. This study emphasizes the importance of both turbulence and advection in the CAP heat budget and reveal their large spatio-temporal variability. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s10546-021-00663-9.

The Impact of Three-Dimensional Effects on the Simulation of Turbulence Kinetic Energy in a Major Alpine Valley.

The correct simulation of the atmospheric boundary layer (ABL) is crucial for reliable weather forecasts in truly complex terrain. However, common assumptions for model parametrizations are only valid for horizontally homogeneous and flat terrain. Here, we evaluate the turbulence parametrization of the numerical weather prediction model COSMO with a horizontal grid spacing of Δ x = 1.1 km for the Inn Valley, Austria. The long-term, high-resolution turbulence measurements of the i-Box measurement sites provide a useful data pool of the ABL structure in the valley and on slopes. We focus on days and nights when ABL processes dominate and a thermally-driven circulation is present. Simulations are performed for case studies with both a one-dimensional turbulence parametrization, which only considers the vertical turbulent exchange, and a hybrid turbulence parametrization, also including horizontal shear production and advection in the budget of turbulence kinetic energy (TKE). We find a general underestimation of TKE by the model with the one-dimensional turbulence parametrization. In the simulations with the hybrid turbulence parametrization, the modelled TKE has a more realistic structure, especially in situations when the TKE production is dominated by shear related to the afternoon up-valley flow, and during nights, when a stable ABL is present. The model performance also improves for stations on the slopes. An estimation of the horizontal shear production from the observation network suggests that three-dimensional effects are a relevant part of TKE production in the valley.

Complication rate following high tibial open-wedge osteotomy with spacer plates for incipient osteoarthritis of the knee with varus malalignment.

PURPOSE: Medial open-wedge high tibial osteotomy (HTO) with spacer plates is recommended to correct varus malalignment of the knee with symptomatic overload of the medial compartment. METHODS: Fifty-five knees in 50 patients were assessed. Intra- and post-operative complications were recorded, and Tegner, Lysholm and IKDC scores were used to evaluate functional results. Radiological parameters consisted of medial proximal tibial angle (aMPTA), femorotibial angle (aFTA), posterior proximal tibial angle, lateral distal femur angle, mechanical axis deviation (MAD) and osteoarthritis score (Jäger and Wirth). RESULTS: Duration of follow-up was 5.0 ± 1.4 years. Overall and implant-related complication rates were 27.3 and 10.9 %, respectively. No statistical association could be detected between overall and implant-related complication rates and age, gender, wedge size, angle of correction or body mass index. Mean improvement in Lysholm score was 26.8. Overall IKDC scores at follow-up were A25, B26, C2 and D2. Post-operative correction of MPTA and FTA averaged to 89.6° and 173° and to 89° and 173.5° at follow-up, respectively. Initial MAD of 21.8 mm was corrected to 11.8 mm at follow-up. Osteoarthritis score increased from 1.4 ± 0.9 to 1.9 ± 0.9 points. CONCLUSIONS: HTO with spacer plates improves knee function and is an effective procedure in selected patients. Overall and implant-related complication rates should be considered and seem to be lower with a smaller angle of correction corresponding to incipient osteoarthritis and less varus deformity. LEVEL OF EVIDENCE: Retrospective case series, Level IV.

The effectiveness of skeletal imaging for quality assessment in posterior cruciate ligament reconstruction: reliability and validity of radiographs and computed tomography.

PURPOSE: For intra- and postoperative evaluation of precise and anatomic graft tunnel position, radiographs (XR) and computed tomography (CT) scans have been suggested. The purpose of this study was to evaluate the reliability and validity of XR and CT for quality assessment following PCL reconstruction. METHODS: Postoperative radiographs and CT scans were obtained in 45 consecutive patients following a standard single-bundle PCL reconstruction. Femoral and tibial tunnel apertures were correlated to femoral and tibial measurement grid systems. To assess the reliability and validity of XR and CT scans three independent observers evaluated radiographic and CT images for the position of femoral and tibial tunnel apertures. RESULTS: Almost perfect inter- and intra observer agreement (0.79-0.99) was found for all CT measurements except for the distance of the tunnel position to the previous physis line. Almost perfect and strong inter- and intraobserver agreement (0.70-0.98) was found for all tibial measurements on XR which tended to increase with repeated interpretation and to decrease with low levels of observer qualification. Femoral measurements yielded only poor-to-moderate reliability (0.02-0.5) between raters on XR but strong intraagreement within experienced observers (0.45-0.86). Specificity for XR was calculated with 75.7 % for P2 and P3 and with 71 % for femoral tunnel depth and height. CONCLUSION: XR and CT represent complementary imaging modalities and both offer considerable accuracy and precision for the determination of femoral and tibial tunnel apertures following PCL reconstruction and can be recommended for intra- and postoperative quality assessment.

Results of open reconstruction of anterior glenoid rim fractures following shoulder dislocation.

INTRODUCTION: The present study evaluates the clinical and radiological outcome following open reconstruction of avulsion fractures of the anterior glenoid rim in traumatic shoulder dislocation. MATERIAL AND METHODS: A total of 20 patients (mean age 49.4 years) were treated with open reduction and cannulated screw fixation. Eighteen patients were available for clinical and radiological follow-up after 3.1 (2.0-6.5) years. RESULTS: The average Constant Score was 78 and the average Rowe Score was 90 points. Documented complications were implant failure in one and neurological dysfunction in one patient. Radiographs revealed the bony fragment located in an unimproved displaced position in one patient and a progress in osteoarthritic changes in three patients. No recurrent subluxation or dislocation was observed. CONCLUSION: Open reconstruction of glenoid rim fractures is a valuable procedure regarding medium-term subjective and objective outcome measures. Recurrent dislocation, glenoid defects and early onset of osteoarthritic degeneration can be avoided.