Improved Orthopaedic Repairs through Mechanically Optimized, Adhesive Biomaterials

Despite countless surgical advances over the last several decades refining surgical approaches, repair techniques, and tools to treat tendon and tendon-to-bone injuries, we are still left with repair solutions that rely on fairly crude underlying mechanical principles. Musculoskeletal soft tissues have evolved to transfer high loads by optimizing stress distribution profiles across the tissue at each length scale. However, instead of mimicking these natural load transfer mechanisms, conventional suture approaches are limited by high load transfer across only a small number of anchor points within tissue. This leads to stress concentrations at anchor points that often cause repair failure as the sutures cut longitudinally through the fibrous tendon tissue like a wire cutting through cheese. Most tendon reconstruction ruptures occur within the first several weeks to months after repair, indicating that the initial strength of the repair is critical for its success. Over time under favorable conditions, the healing response can strengthen the repair sufficiently to function under typical physiologic forces. Here, we developed adhesive-based technologies to distribute load transfer more effectively across tendon and tendon-to-bone repairs, thus reducing peak stress and enabling repairs to sustain higher load before failure. First, we hypothesized that using the lateral surfaces along the length of suture to transfer load in shear would improve repair strength. We evaluated the mechanical principles of an adhesive-coated suture using a shear lag model to identify properties of suitable adhesives. Examination of the design space for an optimal adhesive demonstrated requirements for strong adhesion and low stiffness to maximize the strength of the adhesive-coated suture repair construct. When this design space was compared to real material properties in an Ashby plot, the model anticipated theoretical load transfer improvements of more than 7-fold over current tendon suture repairs using optimal elastomeric adhesives. We validated these model predictions experimentally using idealized single-strand pullout tests and clinically relevant flexor tendon repairs in cadaver canine flexor tendon. Clinically relevant repairs performed with Loctite 4903 cyanoacrylate-coated suture had significantly higher strength (17%) compared to standard repairs without adhesive. Notably, cyanoacrylate provided strong adhesion with high stiffness and brittle behavior, and was therefore not an ideal adhesive for enhancing suture repair. Nevertheless, the improvement in repair properties in a clinically relevant setting, even using a non-ideal adhesive, demonstrated the potential for the proposed approach to improve outcomes for treatments requiring suture fixation. We expanded this approach to assess the potential of adhesive films to increase the load tolerance of tendon-to-bone repairs. We hypothesized that adhesive films would redistribute load over the tendon footprint area where tendon inserts into bone, instead of focusing stress at just a few anchor points where suture from bone anchors punctures through tendon. Based on a shear lag model corroborated by a finite element model to establish the limits of the shear lag assumptions for thick or stiff adhesives, desirable adhesives again required compliance and high strength under shear loading. Models predicted an opportunity to increase transfer across tendon-to-bone repairs by over 10-fold. To rapidly evaluate adhesive mechanical properties for both applications using relevant tissue adherends, we developed a new method for consistent lap shear testing using tendon and bone planks. We validated shear lag predictions using this idealized test scenario and further assessed the ability of adhesives to provide additive benefit to rotator cuff repair strength using a clinically relevant human cadaver rotator cuff repair model with and without adhesive. Using this idealized adhesive testing platform, we demonstrated the potential of the proposed approach to improve outcomes in arthroscopic repair settings by applying a catechol-derived, marine mussel-mimetic adhesive with relevant mechanical properties that binds under water. Further study is needed to optimize adhesive binding properties and assess this approach in preclinical surgical tendon-to-bone repair scenarios. Finally, we developed a new approach to deliver adhesives and biofactors in tendon repairs using sutures with a porous outer sheath. These porous sutures were mechanically non-inferior to conventional sutures in single strand tests and clinically relevant tendon repairs. The porosity dramatically increased the suture surface area, which we conjectured would facilitate adhesive interdigitation and strong binding. Furthermore, this porous suture enabled growth factor or other bioactive factor addition to the inside of the suture for increased loading capacity and sustained release over the first 14 days, determined using connective tissue growth factor. In a clinically relevant canine in vivo injury and repair model, we assessed the effects of porous suture delivery of CTGF on the proliferative stage of repair at 14 days. This approach is hypothesized to act as a biological adhesive, increasing repair strength by modulating healing and encouraging tissue ingrowth into the suture pores. Taken together, these technologies represent dramatic departures from the traditional mechanical principles underlying tendon and tendon-to-bone repair, enabling large improvements in surgical repair strength without significantly changing the procedure in the operating room

Sustainability Planning as Paradigm Change

The theme of the next issue of Urban Planning will be Paradigm Shifts. To make the link between “sustainability” and “paradigm change,” the following commentary analyzes the former concept as a main example of the latter. Although it is often applied to rather modest planning initiatives, “sustainability” can be seen as requiring shifts in cognitive paradigm that are transformational, radical, and not yet fully appreciated by most of those who use the term. Specifically, this term implies a proactive, results-oriented approach (e.g. initiatives to actually meet GHG reduction targets), a long-term viewpoint (e.g. planning for 50 or 100+ years in the future), and a holistic or ecological mindset able to understand dynamic, evolving systems. This last change is the most difficult and requires thinking across scales of action, across time frames, across issue areas and goals (e.g. the “Three E’s” of environment, economy, and social equity), and across communities. It also means integrating different types of actions into a broader program of social change. Though challenging, these cognitive shifts can lead to radically different outcomes than past urban planning

Accessus ad auctores: Medieval Introductions to the Authors (Codex latinus monacensis 19475)

Medieval commentaries typically included an accessus, a standardized introduction to an author or book. In the twelfth century these introductions were anthologised, referred to now as Accessus ad auctores. They served as the first handbooks of literary criticism. The earliest and most comprehensive example, Bayerische Staatsbibliothek, Clm 19475, saec. XII, is presented here for the first time in a faithful critical edition, with a new translation and explanatory notes addressing different aspects of the text. This book\u27s aim is to present an accurate version of the text while respecting the arrangement and integrity of the anthology as a whole, and includes previously unpublished material from the anthology.https://scholarworks.wmich.edu/mip_teamssc/1002/thumbnail.jp

Transforming Livelihoods for Resilient Futures: How to Facilitate Graduation in Social Protection

It is frequently claimed that the most innovative feature of social protection, in contrast to safety nets, is that it has the potential to reduce the vulnerability of poor people to the extent that they can manage moderate risk without external support. This has led to an expansion of large-scale ‘productive safety net’ programmes. The potential to reduce vulnerability so that people can move off social protection provision is popularly termed ‘graduation’.1 However, the vision for graduation rests on the assumption of the existence of a large population of low-productivity, risk-prone and often poor households. Under this scenario, if risk can be underwritten through appropriate social protection then significant numbers of poor people have the potential to move out of vulnerability and extreme poverty into more productive and resilient livelihoods.The ambition of this paper is to map out the theory of change underpinning the notion of graduation and to set out, conceptually and empirically, the range of enabling and constraining factors that facilitate or undermine this change process.DfI

Cash Transfers and High Food Prices: Explaining Outcomes on Ethiopia’s Productive Safety Net Program

An ongoing and highly politicised debate concerns the relative efficacy of cash transfers versus food aid. This paper aims to shed light on this debate, drawing on new empirical evidence from Ethiopia’s Productive Safety Net Programme (PSNP). Our data derive from a two-wave panel survey conducted in 2006 and 2008. Ethiopia has experienced unprecedented rates of inflation since 2007, which have reduced the real purchasing power of PSNP cash payments. Our regression findings confirm that food transfers or ‘cash plus food’ packages are superior to cash transfers alone – they enable higher levels of income growth, livestock accumulation and self-reported food security. These results raise questions of fundamental importance to global humanitarian response and social protection policy. We draw out some implications for the design of social transfer programmes and describe some steps that could be taken to enable ‘predictable transfers to meet predictable needs’DfI

Transformative social protection

Social protection describes all public and private initiatives that provide income or consumption transfers to the poor, protect the vulnerable against livelihood risks, and enhance the social status and rights of the marginalised; with the overall objective of reducing the economic and social vulnerability of poor, vulnerable and marginalised groups. This paper argues against the popular perception of social protection as “social welfare programmes for poor countries”, consisting of costly targeted transfers to economically inactive or vulnerable groups. It also challenges the limited ambition of social protection policy in practice, which has moved little from its origins in the “social safety nets” discourse of the 1980s, and aims to provide “economic protection” against livelihood shocks, rather than “social protection” as broadly defined here. Instead, we argue that social protection can be affordable; it should extend to all of the population; it can contribute to the Millennium Development Goal of poverty reduction; and it can empower marginalised people and be socially “transformative”

Teaching Basic Transfer Pricing Inductively Using A Student Price-Negotiation Case

Students in an introductory management accounting course are given a brief introduction to the concept of transfer pricing and presented with a transfer pricing problem without any guidance on how to solve the problem. The problem requires groups of students to play the role of a selling(buying) division and determine an acceptable minimum(maximum) price for their group before negotiating with other groups. Students learn transfer pricing inductively as they work through the details of the case and arrive at a profit maximizing price for the product they are selling(buying)