Jeffrey C. Y. Chan

Tailoring the properties of cholecyst-derived extracellular matrix using carbodiimide cross-linking.

Modulation of properties of extracellular matrix (ECM) based scaffolds is key for their application in the clinical setting. In the present study, cross-linking was used as a tool for tailoring the properties of cholecyst-derived extracellular matrix (CEM). CEM was cross-linked with varying cross-linking concentrations of N,N-(3-dimethyl aminopropyl)-N′-ethyl carbodiimide (EDC) in the presence of N-hydroxysuccinimide (NHS). Shrink temperature measurements and ATR–FT-IR spectra were used to determine the degree of cross-linking. The effect of cross-linking on degradation was tested using the collagenase assay. Uniaxial tensile properties and the ability to support fibroblasts were also evaluated as a function of cross-linking. Shrink temperature increased from 59°C for non-cross-linked CEM to 78°C for the highest EDC cross-linking concentration, while IR peak area ratios for the free –NH2 group at 3290 cm−1 to that of the amide I band at 1635 cm−1 decreased with increasing EDC cross-linking concentration. Collagenase assay demonstrated that degradation rates for CEM can be tailored. EDC concentrations 0 to 0.0033 mmol/mg CEM were the cross-linking concentration range in which CEM showed varied susceptibility to collagenase degradation. Furthermore, cross-linking concentrations up to 0.1 mmol EDC/mg CEM did not have statistically significant effect on the uniaxial tensile strength, as well as morphology, viability and proliferation of fibroblasts on CEM. In conclusion, the degradation rates of CEM can be tailored using EDC-cross-linking, while maintaining the mechanical properties and the ability of CEM to support cells.

Efficacy of Crosslinking on Tailoring In Vivo Biodegradability of Fibro-Porous Decellularized Extracellular Matrix and Restoration of Native Tissue Structure: A Quantitative Study using Stereology Methods: Tailoring In Vivo Biodegradability of Decellularized ECM

Cholecyst-derived extracellular matrix (CEM) is a fibro-porous decellularized serosal layer of porcine gall-bladder. CEM loses 90% of its weight at 48 h of in vitro collagenase digestion, but takes two months to be completely resorbed in vivo. Carbodiimide (EDC) crosslinking helps tailoring CEMs in vitro collagenase susceptibility. Here, the efficacy of EDC crosslinking on tailoring in vivo biodegradability of CEM is reported. CEM crosslinked with 0.0005 and 0.0033 × 10(3) M of EDC/mg that lose 80% and 0% of their weight respectively to in vitro collagenase digestion, were present even after 180 days in vivo. Quantitative histopathology using stereology methods confirmed our qualitative observation that even a tiny degree of crosslinking can significantly prolong the rate of in vivo degradation and removal of CEM.

A Barbed Suture Repair For Flexor Tendons: A Novel Technique With No Exposed Barbs

Background: Barbed suture technology has shown promise in flexor tendon repairs, as there is an even distribution of load and the need for a knot is eliminated. We propose that a quick and simple, novel, barbed technique without any exposed barbs on the tendon surface has comparable strength and a smaller cross-sectional area at the repair site than traditional methods of repair. Methods: Forty porcine flexor tendons were randomized to polybutester 4-strand barbed repair or to 4-strand Adelaide monofilament repair. The cross-sectional area was measured before and after repair. Biomechanical testing was carried out and 2-mm gap formation force, ultimate strength of repair, and method of failure were recorded. Results: The mean ultimate strength of the barbed repairs was 54.51 ± 17.9 while that of the Adelaide repairs was 53.17 ± 16.35. The mean 2-mm gap formation force for the barbed group was 44.71 ± 17.86 whereas that of the Adelaide group was 20.25 ± 4.99. The postrepair percentage change in cross-sectional area at the repair site for the Adelaide group and barbed group was 12.0 ± 2.3 and 4.6 ± 2.8, respectively. Conclusions: We demonstrated that a 4-strand knotless, barbed method attained comparable strength to that of the traditional Adelaide repair technique. The barbed method had a significantly reduced cross-sectional area at the repair site compared with the Adelaide group. The 2-mm gap formation force was less in the barbed group than the Adelaide group. Barbed repairs show promise for tendon repairs; this simple method warrants further study in an animal model.

Surgical repair of central slip avulsion injuries with Mitek bone anchor--retrospective analysis of a case series.

The purpose of this study is to describe our technique of central slip repair using the Mitek bone anchor and to evaluate the treatment outcome. Eight digits in eight patients were reconstructed using the bone anchor: three little fingers, two middle fingers, two index fingers and one ring finger. There were two immediate and six delayed repairs (range from one day to eight months). Four patients had pre-operative intensive splinting and physiotherapy to restore passive extension of the proximal interphalangeal joint prior to central slip reconstruction. All patients have made good progress since surgery. No patient requires a second procedure and none of the bone anchors have dislodged or loosened. We conclude that the Mitek bone anchor is a reliable technique to achieve soft tissue to bone fixation in central slip avulsion injuries. We recommend that this technique be considered as a treatment option for patients requiring surgical repair.

A clinically relevant in vivo model for the assessment of scaffold efficacy in abdominal wall reconstruction

An animal model that allows for assessment of the degree of stretching or contraction of the implant area and the in vivo degradation properties of biological meshes is required to evaluate their performance in vivo. Adult New Zealand rabbits underwent full thickness subtotal unilateral rectus abdominis muscle excision and were reconstructed with the non-biodegradable Peri-Guard®, Prolene® or biodegradable Surgisis® meshes. Following 8 weeks of recovery, the anterior abdominal wall tissue samples were collected for measurement of the implant dimensions. The Peri-Guard and Prolene meshes showed a slight and obvious shrinkage, respectively, whereas the Surgisis mesh showed stretching, resulting in hernia formation. Surgisis meshes showed in vivo biodegradation and increased collagen formation. This surgical rabbit model for abdominal wall defects is advantageous for evaluating the in vivo behaviour of surgical meshes. Implant area stretching and shrinkage were detected corresponding to mesh properties, and histological analysis and stereological methods supported these findings.

Influence of clinical application on bioresorbability: Host response

Abstract This chapter begins by reviewing the host response pathways initiated by the implantation of a biomaterial and the mechanisms involved in restoring tissue stability and function. It then discusses both the host factors and material factors influencing the biodegradation of degradable biomaterials. In addition, the key mechanisms of in vivo biodegradation involved in the process of biomaterial elimination from the host are also presented.

Sea urchin spine arthritis of the proximal interphalangeal joint of the hand: radiological, intraoperative and histopathological findings.

Penetrating sea urchin spine injuries, can lead to devastating, irreversible consequences. Persistent inflammation, cutaneous granuloma, neuroma, tenosynovitis, arthritis and destructive arthritis, leading to permanent loss of function and digit amputation, can occur. We present a case of a patient who developed sea urchin spine arthritis of the proximal interphalangeal joint. Only 17 cases of sea urchin spine arthritis of the hand have been documented in the medical literature. However, in this case, the article also includes sequential radiographs, histopathological slides, and intra-operative photographs.

A CASE OF RECURRING MULTIFOCAL GIANT CELL TUMOUR OF THE TENDON SHEATH IN A CHILD

Giant cell tumour of the tendon sheath is rare in children. We present an unusual case of a recurring multifocal giant cell tumour of the tendon sheath in the hand and wrist of an 11-year-old boy. We are not aware of any similar report in the literature.

INTRAOPERATIVE FINDINGS OF NECROTIZING FASCIITIS OF THE HAND CAUSED BY STAPHYLOCOCCUS AUREUS INFECTION

A case of a 35-year-old male with necrotizing fasciitis of the hand is presented. Clinical manifestations of necrotizing fasciitis are discussed and intraoperative findings are highlighted to illustrate the disease process that initially affects the deep layer of the superficial fascia.