Sustainable Design of Structural and Functional Polymers for a Circular Economy.

To achieve a sustainable circular economy, polymer production must start transitioning to recycled and biobased feedstock and accomplish CO2 emission neutrality. This is not only true for structural polymers, such as in packaging or engineering applications, but also for functional polymers in liquid formulations, such as adhesives, lubricants, thickeners or dispersants. At their end of life, polymers must be either collected and recycled via a technical pathway, or be biodegradable if they are not collectable. Advances in polymer chemistry and applications, aided by computational material science, open the way to addressing these issues comprehensively by designing for recyclability and biodegradability. This Review explores how scientific progress, together with emerging regulatory frameworks, societal expectations and economic boundary conditions, paint pathways for the transformation towards a circular economy of polymers.

Off-axis view radiographs for assessing hallux valgus interphalangeus in hallux valgus deformity: A comparison with the traditional anteroposterior standing radiographs.

BACKGROUND: The newly described anteroposterior "off-axis view" (OAV) radiograph might help detect a hallux valgus interphalangeus (HVI) deformity more precisely compared to anteroposterior standing radiographs. METHODS: A radiographic assessment of HVI angles was performed using preoperative standing anteroposterior and OAV radiographs for 67 ft. Intra- and interobserver agreement for all angles and their correlation with HV severity were analyzed. RESULTS: The proximal-to-distal phalangeal articular angle showed less intra- and interobserver variance (intraclass correlation coefficient: 0.825) than did the other angles. OAV radiographs showed less interobserver reliability than did standing radiographs. HVI was underestimated significantly, by up to 5°, on standing radiographs compared to OAV radiographs (p < 0.001). The mean differences between OAV and standing radiographs were 3.7° and 5.0° for the proximal-to-distal phalangeal articular and hallux interphalangeal angles, respectively, and were more pronounced for moderate-to-severe HV deformities. CONCLUSION: Angular measurements of HVI on traditional anteroposterior standing radiographs are significantly smaller than on OAV radiographs. Furthermore, angular measurements on OAV radiographs are associated with higher interobserver reliability. The most precise angle representing an HVI deformity might be the proximal-to-distal phalangeal articular angle. CLINICAL RELEVANCE: Our findings may facilitate preoperative decision-making for additional akin osteotomy in HV correction. LEVEL OF EVIDENCE: Level II.

Need for concomitant Akin osteotomy in patients undergoing Chevron osteotomy can be determined preoperatively: a retrospective comparative study of 859 cases.

BACKGROUND: The Chevron osteotomy is a frequently used surgical method for hallux valgus correction. This method is often combined with an Akin osteotomy. To date, clear guidelines for the implementation of an additional Akin osteotomy are missing. The purpose of this study was to elucidate the impact of concomitant phalangeal correction on the outcome after hallux valgus surgery and to define indication criteria for an additional Akin osteotomy. METHODS: Patients (859 feet) undergoing distal Chevron osteotomy at our department were retrospectively grouped into group C (Chevron, 785 feet) and group AC (Chevron plus Akin, 74 ft). Radiological assessment including the intermetatarsal angle (IMA), the hallux valgus angle (HVA), the distal metatarsal articular angle (DMAA), and the proximal to distal phalangeal articular angle (PDPAA) was performed preoperatively, postoperatively, after 6 weeks, and after 3 months. Longer-term follow-up with a mean of 36.4 months was available for 248 cases (29%). RESULTS: A significant improvement of all parameters could be found to all points of survey (p < 0.001). Loss of correction was detected for HVA (p < 0.001) and IMA (p < 0.007) with higher levels in group C. Preoperative PDPAA exceeding 8° correlated significantly with loss of HVA correction in group C (p < 0.001). CONCLUSION: The combined Chevron and Akin osteotomy allowed for better correction of the hallux valgus deformity with better maintenance of the achieved correction. Recommendation for concomitant Akin osteotomy may be determined by a preoperative PDPAA exceeding 8°. TRIAL REGISTRATION: Retrospectively registered. UN5080 . LEVEL OF EVIDENCE: Therapeutic, Level III, retrospective comparative series.

Outcomes after scarf osteotomy with and without Akin osteotomy a retrospective comparative study.

BACKGROUND: The scarf osteotomy is a well-established surgical method for correcting a hallux valgus deformity. It is often combined with an Akin osteotomy. However, clear guidelines defining indication criteria are missing. The purpose of this study was to analyze the radiological outcome after scarf osteotomy in dependence of additional Akin osteotomy. METHODS: This study included 184 patients in whom a hallux valgus deformity was corrected with a scarf osteotomy (group S), and 63 patients in whom an additional Akin osteotomy was performed (group SA). Weight-bearing radiographs were evaluated preoperatively, postoperatively, after 6 weeks, after 3 months and at a follow-up with a mean of 45.4 months. Analysis was made for the following radiological parameters: the intermetatarsal angle (IMA), the hallux valgus angle (HVA), the distal metatarsal articular angle (DMAA), the proximal to distal phalangeal articular angle (PDPAA), and the position of the sesamoids as well as the joint congruity. RESULTS: Radiographic recurrence (HVA > 20°) was detected in 1 patient (1.6% of recurrence) in the SA group, and in 27 patients in the S group (14.7% of recurrence) at follow-up. Outcome between the two groups differed significantly showing reduced loss of HVA correction in the SA group (p < 0.001). The subgroup with a preoperative PDPAA above eight degrees showed significant inferiority of outcome for the S group compared to the SA group. CONCLUSION: Radiological outcome after scarf osteotomy is superior with concomitant Akin osteotomy. A preoperative PDPAA above eight degrees makes additional Akin osteotomy recommendable. LEVEL OF EVIDENCE: Therapeutic, Level III, retrospective comparative series.

Formation of a transient amorphous solid in low density aqueous charged sphere suspensions.

Colloidal glasses formed from hard spheres, nearly hard spheres, ellipsoids and platelets or their attractive variants, have been studied in great detail. Complementing and constraining theoretical approaches and simulations, the many different types of model systems have significantly advanced our understanding of the glass transition in general. Despite their early prediction, however, no experimental charged sphere glasses have been found at low density, where the competing process of crystallization prevails. We here report the formation of a transient amorphous solid formed from charged polymer spheres suspended in thoroughly deionized water at volume fractions of 0.0002-0.01. From optical experiments, we observe the presence of short-range order and an enhanced shear rigidity as compared to the stable polycrystalline solid of body centred cubic structure. On a density dependent time scale of hours to days, the amorphous solid transforms into this stable structure. We further present preliminary dynamic light scattering data showing the evolution of a second slow relaxation process possibly pointing to a dynamic heterogeneity known from other colloidal glasses and gels. We compare our findings to the predicted phase behaviour of charged sphere suspensions and discuss possible mechanisms for the formation of this peculiar type of colloidal glass.