Ensemble forecast experiments of summertime sea ice in the Arctic Ocean using the TOPAZ4 ice-ocean data assimilation system.

Precise information on sea ice thickness (SIT) and its prediction at medium-range (2-week) timescale is crucial for the safe maritime navigation in the Arctic Ocean. In this study, we investigate the sensitivity of medium-range prediction skill of summertime SIT distribution in the Arctic marginal seas to atmospheric forecast data, using the 51-member ECMWF operational ensemble prediction system (EPS). For a synoptic-scale cyclone event occurred in July 5-6, 2015, two-week probabilistic forecast experiments were conducted with the TOPAZ4 ice-ocean forecast system, starting on 1st July. The ensemble correlation analysis between the forecast SIT and the meteorological parameters shows that the forecast error of SIT distribution is sensitive to the sea ice drift speed until 1-week, indicating that realistic sea ice drift improves the sea ice thickness prediction. On the other hand, beyond 1 week lead, the forecast error of SIT distribution is more sensitive to surface heat flux rather than sea ice drift. The surface heat flux signal is confined to the sea ice edge region, where the shortwave radiation flux is related to the SIT change through the sea ice melting process. The shortwave radiation flux in the sea ice edge is mostly determined by the sea ice distribution, suggesting that the skillful prediction of sea ice distribution, which is largely affected by synoptic-scale disturbance, at shorter lead times indirectly affects the medium-range forecast skill. A comparison of different ensemble perturbation techniques shows that the prediction skill is better at shorter lead times (up to 1 week), when using an atmospheric EPS rather than the random perturbations used in the operational forecast system, but the random perturbations are advantageous beyond 1 week. Thus, the application of the EPS to an ice-ocean coupled forecast system leads to a more precise sea ice prediction on medium-range timescale, which we expect to become of practical use for the optimum shipping route in the Arctic Ocean.

The Sensitivity of Euro-Atlantic Regimes to Model Horizontal Resolution.

There is growing evidence that the atmospheric dynamics of the Euro-Atlantic sector during winter is driven in part by the presence of quasi-persistent regimes. However, general circulation models typically struggle to simulate these with, for example, an overly weakly persistent blocking regime. Previous studies have showed that increased horizontal resolution can improve the regime structure of a model but have so far only considered a single model with only one ensemble member at each resolution, leaving open the possibility that this may be either coincidental or model dependent. We show that the improvement in regime structure due to increased resolution is robust across multiple models with multiple ensemble members. However, while the high-resolution models have notably more tightly clustered data, other aspects of the regimes may not necessarily improve and are also subject to a large amount of sampling variability that typically requires at least three ensemble members to surmount.

Joint proprioception in the elderly with and without hip fracture.

OBJECTIVES: Decreased proprioception may contribute to the risk of falls in elderly patients. The purpose of this study is to determine whether patients with hip fractures have decreased hip proprioception compared with aged-matched controls, and whether hip proprioception differs in patients with repaired fractures compared with patients who have undergone prosthetic hip replacement after hip fracture. DESIGN: Retrospective. PATIENTS/PARTICIPANTS: Both hips of twenty-four hip fracture patients and age-matched patients without hip fractures were studied. Hip fracture patients were divided into osteosynthesis (twelve hips) and hemiarthroplasty (twelve hips) groups. INTERVENTION: Reproducibility of index angles (thirty hip flexion and thirty hip abduction) were compared with a six-degree-of-freedom electrogoniometer (instrumented spatial linkage; angular accuracy +/-0.5 degrees). RESULTS: There was no significant difference (flexion, p > 0.20; abduction, p > 0.67) in joint proprioception between fracture and no fracture groups. Likewise, there was no difference (flexion, p > 0.99, abduction; p > 0.74) in joint proprioception between osteosynthesis and hemiarthroplasty groups. CONCLUSIONS: Joint proprioception of hip fracture patients was not found to be diminished compared with age-matched normal controls. Additionally, replacement of the femoral head did not reduce joint proprioception compared with osteosynthesis with an intact femoral head. Maintenance of the femoral head does not seem to be necessary for the maintenance of joint proprioception in elderly hip fracture patients.

The relationship between dementia score and ambulatory level after hip fracture in the elderly.

Dementia or mental status has been considered a significant prognosticating factor for the outcome of hip fracture in the elderly; however, the relationship between dementia level and ambulatory level has not been investigated directly. This study was designed to investigate the relationship between ambulatory level and dementia level after hip fracture in the elderly. A retrospective study was performed of 162 hip fracture patients over 65 years old. We measured the dementia score (mini mental state test) of all patients and evaluated their ambulatory status (divided into three groups: dependent, partially dependent, and independent). We then investigated the relationship between ambulatory level and dementia level. Mean dementia score for each group was as follows: dependent group, 6.6 +/- 0.9; partially dependent group, 17.9 +/- 0.8; and independent group, 24.6 +/- 0.4 (+/- SE). There was a significant relationship between ambulatory level and dementia level (P< .0001).

Subvastus and medial parapatellar approaches in total knee arthroplasty.

This retrospective study compared the outcome of two consecutive groups of patients having primary total knee arthroplasty. The arthroplasties were performed in the first group (169 arthroplasties in 143 patients) from 1988 to 1992 using a medial parapatellar approach, and in the second group (167 arthroplasties in 148 patients) from 1992 to 1996 using a subvastus approach. The patient outcomes were evaluated at 6 months, and were based on clinical and radiographic measures, occurrence of intraoperative lateral retinacular release, and incidence of postoperative patellar subluxation. There were no significant differences between the two groups for range of motion, Knee Society knee and function scores, and stair climbing ability. The patella tracked centrally in significantly more knees with the subvastus approach (139 of 167 knees, 83%) than with the parapatellar approach (107 of 169 knees, 63%). There were significantly fewer knees in the subvastus group requiring a lateral retinacular release (62 of 167 knees, 37%), compared with the parapatellar group (113 of 169 knees, 67%). The authors concluded that the subvastus approach led to improved patellar tracking and stability. Although the surgical and rehabilitative protocols were identical for both groups, the results may have been affected by changing circumstances during the 9-year period of the study.

Postoperative ambulatory level after hip fracture in the elderly predicts survival rate.

The purpose of this study was to evaluate whether the ambulatory level premorbid or at discharge reflected the survival rate better. Ambulatory level was retrospectively evaluated as a postoperative indicator of survival rate following operative treatment in 301 consecutive patients over 65 years old. All of the patients were followed up for a mean of 62 months. The postoperative ambulatory level at discharge reliably reflected the survival rate in the elderly after hip fracture, better than the premorbid ambulatory level. It is confirmed that the planning of the operation and rehabilitation to maintain the premorbid ambulatory level after hip fracture might be critical.

Soft tissue release in total knee arthroplasty. Cadaver study using knees without deformities.

Soft tissue releases are performed to correct fixed deformities in total knee arthroplasty. The goal of this in vitro study was to investigate the relationship between the individual steps in a medial (eight anatomic specimen knees) or lateral (four anatomic specimen knees) soft tissue release sequence, the resulting change in the medial and lateral tibiofemoral gaps, and the change in coronal angulation caused by 10 Nm varus and valgus moments in extension and 90 degrees flexion. An optical encoder was used to measure the coronal angulation. The tibiofemoral gaps were measured with calipers with the knee distracted by a 53-N load. In the medial release sequence, a significant increase in coronal angulation and medial gap occurred after the release of the anteromedial sleeve 8 cm from the medial joint line. In the lateral release sequence, there was a significant increase in the coronal angle and lateral gap after the lateral collateral ligament and popliteus tendon were released from the femur. Release of the posterior cruciate ligament led to a significant increase in angle and gap in medial and lateral release sequences. These results are specific for the particular release sequences studied, with release of the posterior cruciate being the final step in each sequence.