Examples of dramatic failures and their effectiveness in modern surgical disciplines: can we learn from our mistakes?

Bone adhesive materials: From bench to bedside

Biodegradable bone adhesives represent a highly sought-after type of biomaterial which would enable replacement of traditional metallic devices for fixation of bone. However, these biomaterials should fulfil an extremely large number of requirements. As a consequence, bone-adhesive biomaterials which meet all of these requirements are not yet commercially available. Therefore, this comprehensive review provides an extensive overview of the development of bone adhesives from a translational perspective. First, the definition, classification, and chemistry of various types of bone adhesives are highlighted to provide a detailed overview of this emerging class of biomaterials. In this review we particularly focused studies which describe the use of materials that are capable of gluing two pieces of bone together within a time frame of minutes to days. Second, this review critically reflects on i) the experimental conditions of commonly employed adhesion tests to assess bone adhesion and ii) the current state-of-the-art regarding their preclinical and clinical applicability.

Enhanced mechanical performance of mSLA-printed biopolymer nanocomposites due to phase functionalization

Functionalized phases can effectively increase the mechanical properties of nanocomposites through interfacial bonding. This work demonstrates masked stereolithography (mSLA) of biopolymer-based nanocomposites and the improvement of their mechanical properties by the functionalization of both polymer matrix and nanoparticles with methacrylate groups. 3D printable nanocomposite inks were prepared from plant-derived acrylated epoxidized soybean oil (AESO), polyethylene glycol diacrylate (PEGDA), and nano-hydroxyapatite (nHA). Both AESO and nHA were further functionalized with additional methacrylate groups. We hypothesized that the additional functionalization of AESO and surface functionalization of nHA would improve the tensile strength and fracture toughness of these nanocomposites by increasing the degree of crosslinking and the strength of the interface between the matrix and nanoparticles. Curing efficiency, rheology, and print-fidelity of the nanocomposites were evaluated. Mechanical test specimens were prepared by mSLA-based 3D printing. Tensile mechanical properties, Poisson's ratio, and Mode-I fracture toughness were measured by following ASTM standards. Fracture surfaces of the tested specimens were studied using scanning electron microscopy. Thermomechanical behavior, especially glass transition temperature (T_g), was studied using dynamic mechanical analysis (DMA). Functionalized AESO (mAESO) improved rheological, tensile, and fracture mechanical properties. For instance, by replacing AESO with mAESO, tensile strength, Young's modulus, fracture toughness (K_1c), and T_g increased by 33%, 53%, 40%, and 38% respectively. In addition, the combination of both functionalized nHA and mAESO improved the fracture toughness of the 10% volume fraction nHA nanocomposites but made them less extensible presumably due to reduced chain mobility due to greater crosslinking.

Semmelweis Reflex: An Age-Old Prejudice

BACKGROUND

Semmelweis reflex is a human behavioral tendency to stick to preexisting beliefs and to reject fresh ideas that contradict them (despite adequate evidence). We aim to familiarize the readers with the term that not only has a significant historical background but also grave clinical implications.

METHODS

A keyword search for "Semmelweis reflex," "Belief perseverance," "handwashing," and "Idea rejection" was conducted using PubMed Central, MEDLINE, and Google SCHOLAR. Literature published in paper-based journals and books was also searched. All manuscripts pertaining to these keywords were thoroughly analyzed for this review.

RESULTS

The first section of our paper briefs the story of Ignaz Semmelweis and brushes on the contributions of other intellectual researchers that were rebuffed initially. The discussion further explains the root cause of this dismissal, an inherent bias against uncertainty that may be at the core of our fear for new ideas. Finally, this review explores the means by which we can prevent ourselves from being a victim of rejection.

CONCLUSIONS

The age-old prejudice that is Semmelweis reflex is explored in this review. With careful and thorough study design, scientific rigor, and critical self-analysis of the manuscript, one can avoid being victimized by this reflex. The dual edged nature of this reflex lays unveiled when its importance is highlighted in the prematurely accepted medical failures. Understanding that any new idea goes through the grill of being critically analyzed and perceived encourages the scientist to hold on to the original thought as it may rather be practice changing.

Current State of Bone Adhesives-Necessities and Hurdles

The vision of gluing two bone fragments with biodegradable and biocompatible adhesives remains highly fascinating and attractive to orthopedic surgeons. Possibly shorter operation times, better stabilization, lower infection rates, and unnecessary removal make this approach very appealing. After 30 years of research in this field, the first adhesive systems are now appearing in scientific reports that may fulfill the comprehensive requirements of bioadhesives for bone. For a successful introduction into clinical application, special requirements of the musculoskeletal system, challenges in the production of a bone adhesive, as well as regulatory hurdles still need to be overcome. In this article, we will give an overview of existing synthetic polymers, biomimetic, and bio-based adhesive approaches, review the regulatory hurdles they face, and discuss perspectives of how bone adhesives could be efficiently introduced into clinical application, including legal regulations.

A biomechanical test model for evaluating osseous and osteochondral tissue adhesives

Background

Currently there are no standard models with which to evaluate the biomechanical performance of calcified tissue adhesives, in vivo. We present, herein, a pre-clinical murine distal femoral bone model for evaluating tissue adhesives intended for use in both osseous and osteochondral tissue reconstruction.

Results

Cylindrical cores (diameter (Ø) 2 mm (mm) × 2 mm depth), containing both cancellous and cortical bone, were fractured out from the distal femur and then reattached using one of two tissue adhesives. The adhesiveness of fibrin glue (Tisseel^tm), and a novel, biocompatible, calcium phosphate-based tissue adhesive (OsStic^tm) were evaluated by pullout testing, in which glued cores were extracted and the peak force at failure recorded. The results show that Tisseel weakly bonded the metaphyseal bone cores, while OsStic produced > 30-fold higher mean peak forces at failure (7.64 Newtons (N) vs. 0.21 N). The failure modes were consistently disparate, with Tisseel failing gradually, while OsStic failed abruptly, as would be expected with a calcium-based material. Imaging of the bone/adhesive interface with microcomputed tomography revealed that, for OsStic, failure occurred more often within cancellous bone (75% of tested samples) rather than at the adhesive interface.

Conclusions

Despite the challenges associated with biomechanical testing in small rodent models the preclinical ex-vivo test model presented herein is both sensitive and accurate. It enabled differences in tissue adhesive strength to be quantified even for very small osseous fragments (<Ø4mm). Importantly, this model can easily be scaled to larger animals and adapted to fracture fragment fixation in human bone. The present model is also compatible with other long-term in vivo evaluation methods (i.e. in vivo imaging, histological analysis, etc.).