Wind-driven upwelling of iron sustains dense blooms and food webs in the eastern Weddell Gyre.

The Southern Ocean is a major sink of anthropogenic CO2 and an important foraging area for top trophic level consumers. However, iron limitation sets an upper limit to primary productivity. Here we report on a considerably dense late summer phytoplankton bloom spanning 9000 km2 in the open ocean of the eastern Weddell Gyre. Over its 2.5 months duration, the bloom accumulated up to 20 g C m-2 of organic matter, which is unusually high for Southern Ocean open waters. We show that, over 1997-2019, this open ocean bloom was likely driven by anomalies in easterly winds that push sea ice southwards and favor the upwelling of Warm Deep Water enriched in hydrothermal iron and, possibly, other iron sources. This recurring open ocean bloom likely facilitates enhanced carbon export and sustains high standing stocks of Antarctic krill, supporting feeding hot spots for marine birds and baleen whales.

Comparison of Different Bone Age Methods and Chronological Age in Prediction of Remaining Growth Around the Knee.

BACKGROUND: Bone age (BA) has been shown to be superior to chronological age (CA) when predicting remaining growth. However, it is not known whether the calculations are more accurate when BA is assessed by the Greulich and Pyle (GP) or the Sauvegrain (SG) methods. The aim of our study was to identify the method which gives an estimate closest to actual growth in the lower extremities. METHODS: Leg length radiographs, hand radiographs, and elbow radiographs were simultaneously obtained during the adolescent growth spurt (10 to 16 years) in 52 children treated for LLD, with radiographic follow-up of segmental length (femur, tibia, and foot) until skeletal maturity, were randomly selected from a local institutional register. BA, according to GP and SG, were manually rated, and BA based on the GP method was additionally assessed by the automated BoneXpert (BX) method. The remaining growth was calculated based on the White-Menelaus method for both BA methods (GP, SG), the combination of the 2 methods, GP by BX, CA, and the combination of CA and GP by BX. Estimated growth was compared with the actual growth in the distal femur and proximal tibia from the time of BA determination until skeletal maturity. RESULTS: For all included methods, the average calculated remaining growth was higher compared with the actual growth. The mean absolute difference between calculated remaining growth and actual growth in the femur and tibia was lowest using GP by BX [0.66 cm (SD 0.51 cm) and 0.43 cm (SD 0.34 cm)] and highest using CA [1.02 (SD 0.72) and 0.67 (SD 0.46)]. It was a significant association between calculated growth and the difference between actual and calculated growth for the SG method ( P =<0.001). CONCLUSION: During the adolescent growth spurt, the GP method compared with the SG method and CA gives the most accurate estimate of remaining growth around the knee according to our results. CLINICAL RELEVANCE: In calculations of remaining growth around the knee, BA assessment by the GP atlas or BX method should be used as the parameter of biological maturity.

Extreme snowstorms lead to large-scale seabird breeding failures in Antarctica.

Climate change increases the frequency and intensity of extreme weather events that negatively impact wildlife, from individuals to whole ecosystems1. In polar environments, such events include heat waves2, anomalous sea ice concentrations3 and storms4. Polar seabirds are adapted to withstand harsh conditions, and although extreme weather events affect their breeding success and other demographic rates, they are thought to affect only a part of the population. Complete breeding failure of an entire population due to extreme environmental conditions is rarely observed5. Here we report how exceptional storm activity in Dronning Maud Land (DML), Antarctica, in the austral summer of 2021/2022 caused almost complete and large-scale breeding failures of the area's three most common seabird species - Antarctic petrel (Thalassoica antarctica), Snow petrel (Pagodroma nivea) and South polar skua (Stercorarius maccormicki).

Angular deformities after percutaneous epiphysiodesis for leg length discrepancy.

Purpose: The purpose of this study was to systematically analyze the presence of secondary angular deformities after percutaneous epiphysiodesis based on long-standing radiographs, and to see if the occurrence and magnitude of angular deformities after percutaneous epiphysiodesis correlated with the amount of remaining growth at the time of surgery. Methods: From a local Health Register consisting of patients investigated using the Moseley Straight-Line Graph, we identified 269 patients who had undergone percutaneous epiphysiodesis from 2002 until 2020. Radiographic analysis included the measurement of mechanical axis and joint orientation angles on long-standing anterior-posterior radiographs. Remaining growth was analyzed based on the Menelaus method. Results: One hundred and forty epiphysiodeses (71 femurs and 69 tibiae) in 88 patients (39 girls and 49 boys) could be included in the study. Mean age at surgery was 13.2 (10-16.8) years, and mean skeletal age at surgery was 13.0 (9.8-15.7) years. A change of the MA (Mechanical axis) ≥10 mm was found in eight patients (9%). Secondary frontal plane deformities after percutaneous epiphysiodesis correlated significantly with the remaining growth at the time of surgery (p = 0.003). Conclusion: We found a high rate of secondary angular deformities after percutaneous epiphysiodesis, and the magnitude of the deformities correlated with the amount of remaining growth at the time of surgery. A modification of the original surgical method for percutaneous epiphysiodesis to also include ablation of central parts of the growth plate might be considered. Patients should be enrolled in a systematic follow-up scheme which allows for the early detection of possible angular deformities. Level of evidence: level III study.

A comparison of 3 different methods for assessment of skeletal age when treating leg-length discrepancies: an inter- and intra-observer study.

Background and purpose - Skeletal maturity is a crucial parameter when calculating remaining growth in children. We compared 3 different methods, 2 manual and 1 automated, in the radiological assessment of bone age with respect to precision and systematic difference. Material and methods - 66 simultaneous examinations of the left hand and left elbow from children treated for leg-length discrepancies were randomly selected for skeletal age assessment. The radiographs were anonymized and assessed twice with at least 3 weeks' interval according to the Greulich and Pyle (GP) and Sauvegrain (SG) methods by 5 radiologists with different levels of experience. The hand radiographs were also assessed for GP bone age by use of the automated BoneXpert (BX) method for comparison. Results - The inter-observer intraclass correlation coefficient (ICC) was 0.96 for the GP and 0.98 for the SG method. The inter- and intra-observer standard error of the measurement (SEm) was 0.41 and 0.32 years for the GP method and 0.27 and 0.21 years for the SG method with a significant difference (p < 0.001) between the methods and between the experienced and the less experienced radiologists for both methods (p = 0.003 and p < 0.001). In 25% of the assessments the discrepancy between the GP and the SG method was > 1 year. There was no systematic difference comparing either manual method with the automatic BX method. Interpretation - With respect to the precision of skeletal age determination, we recommend using the SG method or preferably the automated BX method based on GP assessments in the calculation of remaining growth.

Increased prefrontal cortical activation during challenging walking conditions in persons with lower limb amputation - an fNIRS observational study.

Background: Lower limb amputation (LLA) alters the sensorimotor control systems. Despite the self-reports of increased attention during mobility, the interaction between mobility and cognitive control mechanisms is not fully understood.Objective: Concurrently evaluate walking performance and prefrontal cortical (PFC) activity in persons with and without LLA during different walking conditions.Methods: Thirty-nine persons with LLA and thirty-three able-bodied controls participated. Walking performance was evaluated using the Figure-of 8-walk-test during three conditions: 1) UW (Usual walking with self-selected walking speed); 2) WCT (walking and carrying a tray with two cups filled with water); and 3) WUT (walking on uneven terrain). PFC activity was assessed using functional near-infrared spectroscopy (fNIRS). Linear mixed models were used to detect changes between groups and between walking conditions within each group.Results: Between-group comparisons showed increased PFC activity in persons with LLA during UW and WUT, and a significant decrease in walking performance during WCT and WUT compared to controls. Within-group comparisons showed increased PFC activity during WUT compared with UW and WCT and an overall difference in walking performance between the conditions (WU > WUT > WCT) in both groups. However, the effect of walking condition on PFC activity and walking performance was not modified by group (P > .1).Conclusion: The results suggest that persons with LLA have increased attentional demands during walking but choose the same cognitive-mobility strategy during challenging walking conditions as able-bodied persons. However, the attentional demands seem to depend on the complexity of the task.

Fine-scale spatial segregation in a pelagic seabird driven by differential use of tidewater glacier fronts.

In colonially breeding marine predators, individual movements and colonial segregation are influenced by seascape characteristics. Tidewater glacier fronts are important features of the Arctic seascape and are often described as foraging hotspots. Albeit their documented importance for wildlife, little is known about their structuring effect on Arctic predator movements and space use. In this study, we tested the hypothesis that tidewater glacier fronts can influence marine bird foraging patterns and drive spatial segregation among adjacent colonies. We analysed movements of black-legged kittiwakes (Rissa tridactyla) in a glacial fjord by tracking breeding individuals from five colonies. Although breeding kittiwakes were observed to travel up to ca. 280 km from the colony, individuals were more likely to use glacier fronts located closer to their colony and rarely used glacier fronts located farther away than 18 km. Such variation in the use of glacier fronts created fine-scale spatial segregation among the four closest (ca. 7 km distance on average) kittiwake colonies. Overall, our results support the hypothesis that spatially predictable foraging patches like glacier fronts can have strong structuring effects on predator movements and can modulate the magnitude of intercolonial spatial segregation in central-place foragers.

Postoperative changes in vertical ground reaction forces, walking barefoot and with ankle-foot orthoses in children with Cerebral Palsy.

BACKGROUND: Children with cerebral palsy often have problems to support the body centre of mass, seen as increased ratio between excessive vertical ground reaction forces during weight acceptance and decreased forces below bodyweight in late stance. We aimed to examine whether increasing ankle range of motion through surgery and restraining motion with ankle-foot orthoses postoperatively would have impact on the vertical ground reaction force in weight acceptance and late stance. METHODS: Ground reaction forces were recorded from 24 children with bilateral and 32 children with unilateral cerebral palsy, each measured walking barefoot before and after triceps surae lengthening. Postoperatively, the children were also measured walking with ankle-foot orthoses. Changes in vertical ground reaction forces between the three conditions were evaluated with functional curve and descriptive peak analyses; accounting for repeated measures and within-subject correlation. FINDINGS: After surgery, there were decreased vertical ground reaction forces in weight acceptance and increased forces in late stance. Additional significant changes with ankle-foot orthoses involved increased vertical forces in weight acceptance, and in late stance corresponding to bodyweight (bilateral, from 92% to 98% bodyweight; unilateral, from 94% to 103% bodyweight) postoperatively. INTERPRETATION: Our findings confirmed that surgery affected vertical ground reaction forces to approach more normative patterns. Additional changes with ankle-foot orthoses indicated further improved ability to support bodyweight and decelerate centre of mass in late stance.

Intermediate Dynamic Compression and Decreased Posterior Tilt With Interlocked Pins in Femoral Neck Fixation in Synthetic Bone.

Fixation failure with resulting non-union is the key complication after femoral neck fixation. It can be avoided by permitting dynamic compression and reducing rotation and posterior tilt of the femoral head. To achieve this, a novel implant that features an interlocking plate with three hook-pins (The Hansson Pinloc® System) was developed from the original two hook-pins. Only an enhanced torsional fixation by the implant modification is reported. The purpose was to compare the biomechanical compressive and bending stability of the original and modified implant in femoral neck fixation. To analyze the contribution of both modified components, three individual pins were included, although not in regular use. Forty-eight synthetic femurs with mid-cervical wedge osteotomies were fixated by two pins or identical triangular pin patterns with or without the plate. Eight specimens of each group were loaded cyclically in compression with an inferior wedge to simulate stance and anteroposterior bending with a posterior wedge to imitate sitting down. The clinically relevant stability measurements were stiffness and deformation. Fissure formation defined failure. The novel implant improved bending stability by 30% increased stiffness, 44% reduced deformation, and less frequent posterior neck fissure formation (p < 0.001) while increased compressive stability was only evident with 25% reduced deformation and less frequent inferior neck fissures (p < 0.001). These impacts were mainly mediated by the third pin, while the plate prevented a lateral fissure in compression (p < 0.001). The clinical stability was improved by dynamic compression and decreased posterior tilt by implant modification.

Femoral lengthening might impair physical function and lead to structural changes in adjacent joints: 10 patients with 27 to 34 years' follow-up.

Background and purpose - Literature describing long-term functional outcome and osteoarthritis (OA) in adjacent joints after femoral lengthening is rare. We evaluated physical function and the presence of radiographic OA in adjacent joints in 10 patients ≥ 27 years after femoral lengthening.Patients and methods - We conducted a cross-sectional study of 10 patients treated by unilateral femoral lengthening. Follow-up was between 27 and 34 years. Physical function was evaluated by the 30-second sit-to-stand (30sSTS) and a stair test and was compared with reference values. 4 single-legged hop tests were used to assess difference in physical function between the lengthened and contralateral limb. Radiographic OA was evaluated by joint space width (JSW) and Kellgren and Lawrence (KL) classification.Results - The patients scored worse compared with reference values on the 30sSTS and stair test, and worse on the lengthened limb on the single- and triple-hop test. Radiographic OA was found in the hip or knee in the lengthened limb in 3 of 10 patients based on JSW and 4 of 10 based on KL. No radiographic OA was found in unlengthened limbs.Interpretation - Our results showed impaired physical function both in general and of the lengthened limb. Additionally, we found a possible association between femoral lengthening and radiographic OA in adjacent joints in the long term. However, the sample size of the current study is small.

Assessing mobility for persons with lower limb amputation: the Figure-of-Eight Walk Test with the inclusion of two novel conditions.

PURPOSE: To investigate the internal consistency, convergent and known-groups construct validity of the Figure-of-Eight Walk Test with two novel conditions in persons with lower limb amputation, and to examine differences in walking performance between the three conditions within a group of persons with transtibial amputation and transfemoral amputation/knee disarticulation. MATERIALS AND METHODS: Fifty adults with unilateral amputation participated, 28 of whom had undergone a transtibial amputation and 22 a transfemoral amputation/knee disarticulation. Three Figure-of-Eight Walk Test conditions were investigated: 1) walking at a self-selected walking speed, 2) walking while carrying a tray with two cups of water, and 3) walking on uneven terrain. Internal consistency was evaluated using Cronbach's alpha. Convergent construct validity was examined by analysing the relationship between the Figure-of-Eight Walk Test parameters and performance-based parameters (Amputee Mobility Predictor, Ten-Meter Walk Test, Six-Minute Walk Test) and self-report measures (Prosthetic Limb Users Survey of Mobility, Activities-specific Balance Confidence Scale) using Spearman's rank-order correlations. Known-groups construct validity was assessed by comparing the Figure-of-Eight Walk Test parameters based on anatomical level of amputation. Friedman's test and post hoc analysis were used to examine differences between the walking conditions within each group. RESULTS: Cronbach's alpha coefficients of the Figure-of-Eight Walk Test parameters for all three conditions ranged from 0.89 to 0.99. The Figure-of-Eight Walk Test time and step parameters demonstrated moderate to good correlation (ρ = -0.50 to -0.77) for performance-based mobility measures. The correlations were stronger during Condition 3 in comparison with the original Figure-of-Eight Walk Test. The correlation was fair to good (ρ = -0.41 to -0.57) for the self-report mobility measures. Comparison between groups showed a difference between transtibial and transfemoral amputation/knee disarticulation participants when it comes to the Figure-of-Eight Walk Test time and smoothness parameters in Condition 2 (p < 0.05). Comparison between walking conditions within each group showed significant differences in the Figure-of-Eight Walk Test parameters in the two novel conditions in comparison with the original Figure-of-Eight Walk Test. The Figure-of-Eight Walk Test and the novel conditions demonstrated excellent internal consistency, good convergent construct validity, and evidence of known-groups construct validity. Future studies should further develop and standardise the smoothness scale to better quantify walking performance and assess the responsiveness and reliability (inter-rater and intra-rater) of the Figure-of-Eight Walk Test (time and steps) and the novel conditions, while studies on known-groups validity should include persons with a wider mobility range.IMPLICATIONS FOR REHABILITATIONFigure-of-Eight Walk Test with the two novel conditions, which include carrying a load and walking on uneven terrain, may help to provide meaningful information about walking ability in daily life.The two novel conditions pose different challenges to persons with lower limb amputation when compared to the original Figure-of-Eight Walk Test and underscore the relevance to assess mobility under challenging walking conditions.The Figure-of-Eight Walk Test and the two novel conditions demonstrated excellent internal consistency, good convergent construct validity, and evidence of known-groups construct validity.

Predictors for long-term curve progression after Boston brace treatment of idiopathic scoliosis.

BACKGROUND: Identifying factors that predict successful bracing in patients with idiopathic scoliosis may help planning treatment. AIM: To assess predictors for long-term curve progression and health-related quality of life after Boston brace treatment. DESIGN: Observational retrospective cohort study with analysis of brace treated patients followed from start until at least 10 years after treatment. SETTING: Patients recruited from the country's entire population consecutively treated at the National Hospital. POPULATION: 365 patients (339 girls/26 boys) with idiopathic scoliosis. Mean (SD) chronological age/bone age at start bracing was 13.2 (1.9)/12.6 (1.9) years. The primary major curve measured 33.2 (7.4°), and the major levels were thoracic (N.=248), thoracolumbar (N.=78) and lumbar (N.=39). Mean bracing time was 2.8 (1.5) years. Long-term follow-up was in average 23.3 (4.1) years after weaning with a mean major curve of 33.0 (13.1°). Successful treatment was defined as a stable primary curve with progression ≤5°, and secondary the SRS-22 questionnaire assessed quality of life. METHODS: We applied linear or logistic regression with backward elimination. Internal validation was assessed by bootstrapping. Twelve variables were included in the prediction models: age, bone age, scoliosis in close family, major curve size, level, shape, flexibility and in-brace redressement, compliance, curve magnitude after 1 year, treatment time and quality of life (SRS-22). RESULTS: 290 patients (79%) had rated good compliance using the brace >20 hours daily. Treatment failure was observed in 65 patients (18%), and 27 of them were operated. The best baseline predictors were age and brace redressement. During treatment compliance, major curve after 1 year, and treatment time were the best predictors, while thoracic major curve, curve size at start bracing and scoliosis in close family also contributed to the final model. The model's ability to predict quality of life was low. CONCLUSIONS: The best predictors for a long-term success were good redressement and compliance, unchanged or reduced major curve after one year and short treatment time. CLINICAL REHABILITATION IMPACT: Predictors at baseline and during early treatment can help identifying patients who benefit from bracing.

Increased stability by a novel femoral neck interlocking plate compared to conventional fixation methods. A biomechanical study in synthetic bone.

BACKGROUND: Stable fixation promotes union in the common femoral neck fractures, but high non-union rates due to fixation failure remain with traditional fixations. To enhance stability, a plate interlocking pins, but without further fixation to femur has been developed. To our knowledge, no comparison to other conventional fixation methods has been performed. We tested the hypothesis that the novel implant biomechanically leads to a more stable femoral neck fixation. METHODS: Fifty synthetic femurs with a cervical wedge osteotomy were allocated to intervention with three hook-pins interlocked in a plate (Hansson Pinloc® System) or standard fixations with a two-hole Dynamic Hip Screw® plate with an anti-rotational screw, three cannulated screws (ASNIS® III) or two screws (Olmed® or Cannulated Hip Screws®). Quasi-static non-destructive torsion around the neck, anteroposterior bending and vertical compression were tested to detect stiffness. The specimen's deformation was evaluated after cyclic compression simulating weight-bearing. Local deformation of implant channels was measured. Fixation failure was defined by fissure formation. FINDINGS: Compared to the conventional implants all together, the interlocked pins enhanced mean stiffness 130% in torsion and 33% in bending (P < 0.001), while compressive stability was increased by a reduced deformation of 62% in average of the global test specimen and 95% decreased local implant channel deformation after cycling (P < 0.001). In comparisons with each of the standard fixations the interlocking pins revealed no signs of adverse effects. INTERPRETATION: The novel femoral neck interlocking plate allowed dynamic compression and improved multi-directional stability compared to the traditional fixations.

Earlier colony arrival but no trend in hatching timing in two congeneric seabirds (Uria spp.) across the North Atlantic.

A global analysis recently showed that seabird breeding phenology (as the timing of egg-laying and hatching) does not, on average, respond to temperature changes or advance with time (Keogan et al. 2018 Nat. Clim. Change8, 313-318). This group, the most threatened of all birds, is therefore prone to spatio-temporal mismatches with their food resources. Yet, other aspects of the breeding phenology may also have a marked influence on breeding success, such as the arrival date of adults at the breeding site following winter migration. Here, we used a large tracking dataset of two congeneric seabirds breeding in 14 colonies across 18° latitudes, to show that arrival date at the colony was highly variable between colonies and species (ranging 80 days) and advanced 1.4 days/year while timing of egg-laying remained unchanged, resulting in an increasing pre-laying duration between 2009 and 2018. Thus, we demonstrate that potentially not all components of seabird breeding phenology are insensitive to changing environmental conditions.

Winter storms accelerate the demise of sea ice in the Atlantic sector of the Arctic Ocean.

A large retreat of sea-ice in the 'stormy' Atlantic Sector of the Arctic Ocean has become evident through a series of record minima for the winter maximum sea-ice extent since 2015. Results from the Norwegian young sea ICE (N-ICE2015) expedition, a five-month-long (Jan-Jun) drifting ice station in first and second year pack-ice north of Svalbard, showcase how sea-ice in this region is frequently affected by passing winter storms. Here we synthesise the interdisciplinary N-ICE2015 dataset, including independent observations of the atmosphere, snow, sea-ice, ocean, and ecosystem. We build upon recent results and illustrate the different mechanisms through which winter storms impact the coupled Arctic sea-ice system. These short-lived and episodic synoptic-scale events transport pulses of heat and moisture into the Arctic, which temporarily reduce radiative cooling and henceforth ice growth. Cumulative snowfall from each sequential storm deepens the snow pack and insulates the sea-ice, further inhibiting ice growth throughout the remaining winter season. Strong winds fracture the ice cover, enhance ocean-ice-atmosphere heat fluxes, and make the ice more susceptible to lateral melt. In conclusion, the legacy of Arctic winter storms for sea-ice and the ice-associated ecosystem in the Atlantic Sector lasts far beyond their short lifespan.

The stabilising effect by a novel cable cerclage configuration in long cephalomedullary nailing of subtrochanteric fractures with a posteromedial wedge.

BACKGROUND: Clinical studies suggest that an adjunctive cerclage in intramedullary nailing of subtrochanteric fractures improves the outcome. Despite this, to what extent various cerclage configurations influences the fixation strength, remains undocumented. We tested the hypothesis that the stability of subtrochanteric fractures with a posteromedial wedge treated with long cephalomedullary nail varies with cerclage configuration. METHODS: 40 composite femurs with a subtrochanteric osteotomy including a posteromedial-wedge were locked by cephalomedullary nailing (T2 recon, Stryker) and divided into 4 groups. In Group-A no cerclage was applied. The Group-B received a lateral tension-band (cerclage cable with crimp, Depuy-Synthes). Without any fixation, the wedge-component was removed in these groups. The Group-C was fixed with a cerclage encircling the wedge-component, while in the Group-D a novel figure-of-8 cerclage stabilised the wedge-component. Each femur was tested quasi-static in a material-testing-machine for stiffness calculation, first horizontally to simulate seated-position and then vertically to simulate standing-position. Finally, cyclic testing was performed in the upright-posture to measure deformation over time. FINDINGS: In Group-D the mean stiffness in the sitting-position was 6.4, 5.8 and 3.1 times higher than the Groups-A, B and C, respectively, and correspondingly 2.0, 2.1 and 1.7 times higher in the standing-position (p < 0.05). Over time, Group-D demonstrated less mean deformation than tension-band (p = 0.05), while the deformation was not significantly different from the other groups. INTERPRETATION: Additional use of cerclage enhances the stability of intramedullary nailed subtrochanteric fractures, and use of the figure-of-8 cerclage configuration, compressing the entire posteromedial-buttress, is the superior technique.

Impact of ankle-foot orthoses on gait 1 year after lower limb surgery in children with bilateral cerebral palsy.

BACKGROUND:: Different types of ankle-foot orthoses are commonly used following lower limb surgery in children with bilateral spastic cerebral palsy. After three-dimensional gait analysis 1 year postoperatively, many children are recommended continued use of ankle-foot orthoses. OBJECTIVES:: Our aims were to quantify the impact of ankle-foot orthoses on gait 1 year postoperatively and evaluate predictors for clinically important improvement. STUDY DESIGN:: Prospective cohort study. METHODS:: A total of 34 ambulating children with bilateral cerebral palsy, with mean age 11 years (range 6-17), comprising 12 girls and 22 boys, were measured with three-dimensional gait analysis preoperatively (barefoot) and 1 year postoperatively (barefoot and with ankle-foot orthoses). Outcome was evaluated using gait profile score, key kinematic, kinetic and temporal-spatial variables in paired sample comparisons. Logistic regression was used to evaluate predictors for clinically important improvement with orthoses (⩾1.6° change in gait profile score). RESULTS:: Walking barefoot 1 year postoperatively, major improvements were seen in gait profile score and key variables. With ankle-foot orthoses, there were significantly improved step length and velocity, additional moderate reduction/improvement in gait profile score and knee moments and decreased stance ankle dorsiflexion compared to barefoot. Children using ground reaction ankle-foot orthoses ( n = 14) decreased stance knee flexion from 13.9° walking barefoot to 8.2° with orthoses. High gait profile score and more gait dysfunction preoperatively were significant predictors of clinically important improvement walking with orthoses. CONCLUSION:: The results indicate improved gait function walking with ankle-foot orthoses versus barefoot 1 year after lower limb surgery. Stronger impact of ankle-foot orthoses was found in children with more pronounced gait dysfunction preoperatively. CLINICAL RELEVANCE: The 1-year postoperative three-dimensional gait analysis is a useful method to assess treatment outcome after lower limb surgery in children with bilateral cerebral palsy and could also guide clinicians whether further treatment with ankle-foot orthoses is indicated, using clinically important differences as thresholds to evaluate their impact on gait.

Limb lengthening and deformity correction with externally controlled motorized intramedullary nails: evaluation of 50 consecutive lengthenings.

Background and purpose - Limb lengthening with an intramedullary motorized nail is a relatively new method. We investigated if lengthening nails are reliable constructs for limb lengthening and deformity correction in the femur and the tibia. Patients and methods - 50 lengthenings (34 Precice and 16 Fitbone devices) in 47 patients (mean age 23 years [11-61]) with ≥12 months follow-up are included in this study. 30 lengthenings were done due to congenital and 20 because of posttraumatic deformity (21 antegrade femora, 23 retrograde femora, 6 tibiae). Initial deformities included a mean shortening of 42 mm (25-90). In 15 patients, simultaneous axial correction was done using the retrograde nailing technique. Results - The planned amount of lengthening was achieved in all but 2 patients. 5 patients who underwent simultaneous axial correction showed minor residual deformity; unintentionally induced minor deformities were found in the frontal and sagittal plane. The consolidation index was 1.2 months/cm (0.6-2.5) in the femur and 2.5 months/cm (1.6-4.0) in the tibia. 2 femoral fractures occurred in retrograde femoral lengthenings after consolidation due to substantial trauma. There were 8 complications, all of which were correctable by surgery, with no permanent sequelae. Interpretation - Controlled acute axial correction of angular deformities and limb lengthening can be achieved by a motorized intramedullary nail. A thorough preoperative planning and intraoperative control of alignment are required to avoid residual and unintentionally induced deformity. In the femur relatively fast consolidation could be observed, whereas healing was slower in the tibia.

High correlation between mechanical properties and bone mineral parameters in embalmed femurs after long-term storage.

BACKGROUND: Fresh frozen human femurs are considered "the gold standard" in biomechanical studies of hip fractures, resembling the in vivo situation mostly. A more readily available alternative is formalin embalmed femurs. However, to which extent formalin affects key features of bone; its mechanical properties, bone mineral content and their mutual relationship over time, remains unknown. Accordingly, we measured the mineral parameters and related them to the mechanical properties of formalin fixed femurs after long-term storage. METHODS: 36 paired femurs from human donors, fixed in formalin and stored for a mean period of 4.6 (3.5-6) years. Quantitative CT was performed to measure the bone mineral density and mass at the mainly cortical mid shaft and the center of the mainly cancellous condyles. Each pair was subjected to local tests by three-point bending and screw pullout of the shaft and lateral punch and metaphyseal cube compression of the condyles. FINDINGS: Neither mechanical nor bone mineral data were significantly correlated to storage time. Well-known associations for bone parameters with age and gender were retrieved. Maximum force of the cortical bone tests was highly correlated to the diaphyseal bone mass; (r = 0.80-0.87, p = 0.01), while maximum force of the cancellous bone tests correlated well to the density of the condylar bone; (r = 0.70, p = 0.01). INTERPRETATION: Our results indicate that mechanical and bone mineral data and their mutual relationship are conserved in formalin fixed femurs even after long-term storage. Formalin fixed femurs may serve as an alternative to fresh frozen femurs in biomechanical testing.

Increased torsional stability by a novel femoral neck locking plate. The role of plate design and pin configuration in a synthetic bone block model.

BACKGROUND: In undisplaced femoral neck fractures, internal fixation remains the main treatment, with mechanical failure as a frequent complication. As torsional stable fixation promotes femoral neck fracture healing, the Hansson Pinloc® System with a plate interlocking pins, was developed from the original hook pins. Since its effect on torsional stability is undocumented, the novel implant was compared with the original configurations. METHODS: Forty-two proximal femur models custom made of two blocks of polyurethane foam were tested. The medial block simulated the cancellous head, while the lateral was laminated with a glass fiber filled epoxy sheet simulating trochanteric cortical bone. Two hollow metal cylinders with a circumferential ball bearing in between mimicked the neck, with a perpendicular fracture in the middle. Fractures were fixated by two or three independent pins or by five configurations involving the interlocking plate (two pins with an optional peg in a small plate, or three pins in a small, medium or large plate). Six torsional tests were performed on each configuration to calculate torsional stiffness, torque at failure and failure energy. FINDINGS: The novel configurations improved parameters up to an average of 12.0 (stiffness), 19.3 (torque) and 19.9 (energy) times higher than the original two pins (P < 0.001). The plate, its size and its triangular configuration improved all parameters (P = 0.03), the plate being most effective, also preventing permanent failure (P < 0.001). INTERPRETATION: The novel plate design with its pin configuration enhanced torsional stability. To reveal clinical relevance a clinical study is planned.