Tissue reactions to epoxy-crosslinked porcine heart valves post-treated with detergents or a dicarboxylic acid

Surgical reconstruction and mobilization therapy for a retracted extensor hallucis longus laceration and tendon defect repaired by split extensor hallucis longus tendon lengthening and dermal scaffold augmentation

A reconstructive technique and physical therapy protocol is presented for the treatment of extensor hallucis longus (EHL) lacerations with critical size defects caused by tendon retraction. The primary goal of treatment was to restore EHL structure and function without the use of a bridging allograft or tendon transfer. The technique is performed by split lengthening the distal segment of the lacerated EHL and rotating the lengthened segment proximally 180° to bridge the tendon defect. The lengthened tendon is then sutured to the proximal segment of the EHL. The EHL is then tubularized with an acellular dermal scaffold at the region of tendon rotation to improve tendon strength, minimize the probability of tendon overlengthening or re-rupture, and improve the tendon gliding motion, which can be compromised by the tendon irregularity caused by rotation of the tendon. Postoperative range of motion therapy should be initiated at 3 weeks postoperatively. A case report of this technique and postoperative mobilization protocol is presented. The American Orthopaedic Foot and Ankle Society midfoot score at 3 and 6 months postoperatively was 90 of 100. The patient regained active dorsiflexion motion of the hallux without functional limitations, deformity, or contracture of the hallux. The advantages of this technique include that a large cadaveric allograft is not needed to bridge a critical size tendon defect and tendon lengthening provides a biologically active tendon graft without the secondary comorbidities and dysfunction commonly associated with tendon transfer procedures.

Glycosaminoglycan-targeted fixation for improved bioprosthetic heart valve stabilization

Numerous crosslinking chemistries and methodologies have been investigated as alternative fixatives to glutaraldehyde (GLUT) for the stabilization of bioprosthetic heart valves (BHVs). Particular attention has been paid to valve leaflet collagen and elastin stability following fixation. However, the stability of glycosaminoglycans (GAGs), the primary component of the spongiosa layer of the BHV, has been largely overlooked despite recent evidence provided by our group illustrating their structural and functional importance. In the present study we investigate the ability of two different crosslinking chemistries: sodium metaperiodate (NaIO(4)) followed by GLUT (PG) and 1-Ethyl-3-(3 dimethylaminopropyl) carbodiimide/N-hydroxysuccinimide (EDC/NHS) followed by GLUT (ENG) to stabilize GAGs within BHV leaflets and compare resulting leaflet characteristics with that of GLUT-treated tissue. Incubation of fixed leaflets in GAG-degrading enzymes illustrated in vitro resistance of GAGs towards degradation in PG and ENG treated tissue while GLUT fixation alone was not effective in preventing GAG loss from BHV leaflets. Following subdermal implantation, significant amounts of GAGs were retained in leaflets in the ENG group in comparison to GLUT-treated tissue, although GAG loss was evident in all groups. Utilizing GAG-targeted fixation did not alter calcification potential of the leaflets while collagen stability was maintained at levels similar to that observed in conventional GLUT-treated tissue.

Bioscaffolds in tissue engineering: a rationale for use in the reconstruction of musculoskeletal soft tissues

Bioscaffolds derived from animal tissues can be an appealing substrate to induce the formation of functional tissue (histogenesis) within the context of tissue engineering. Bioscaffolds obtained from the extracellular matrix not only contain collagen, which can provide mechanical support, but also include the required biologically active molecules that provide a stimulus for active tissue remodeling. Manufacturing, processing, and the tissue source of the biological scaffold affect the biologic outcome and are important in predicting the clinical results. This article discusses the merits and limitations of using bioscaffolds in soft tissue engineering.

Calcification of Tissue Heart Valve Substitutes: Progress Toward Understanding and Prevention

Calcification plays a major role in the failure of bioprosthetic and other tissue heart valve substitutes. Tissue valve calcification is initiated primarily within residual cells that have been devitalized, usually by glutaraldehyde pretreatment. The mechanism involves reaction of calcium-containing extracellular fluid with membrane-associated phosphorus to yield calcium phosphate mineral deposits. Calcification is accelerated by young recipient age, valve factors such as glutaraldehyde fixation, and increased mechanical stress. Recent studies have suggested that pathologic calcification is regulated by inductive and inhibitory factors, similar to the physiologic mineralization of bone. The most promising preventive strategies have included binding of calcification inhibitors to glutaraldehyde fixed tissue, removal or modification of calcifiable components, modification of glutaraldehyde fixation, and use of tissue cross linking agents other than glutaraldehyde. This review summarizes current concepts in the pathophysiology of tissue valve calcification, including emerging concepts of endogenous regulation, progress toward prevention of calcification, and issues related to calcification of the aortic wall of stentless bioprosthetic valves.

Influence of surfactant molecules as air-entraining agent for bone cement macroporosity

Calcium phosphate bone cements (CPBCs) represent a potential synthetic alternative to bone-graft materials in bone surgery applications. CPBCs are biocompatible, bioresorbable, and slowly are replaced by new bone in vivo. However, CPBCs do not develop a macroporosity during setting that would allow fast bone ingrowth and good osteointegration of the implant. For this reason, recent research has approached the problem of inducing macroporosity inside the bone cement without influencing its normal setting. In this study, a new method for obtaining injectable macroporous CPBCs is proposed. It is based on the use of sodium dodecyl sulphate (SDS) as an air-entraining agent. The results have shown that the liquid-to-powder ratio and the SDS concentration, as well as the diameter and the interconnectivity of the macropores, can control the micro- and macroporosity. This new technology can be used to develop and optimize new commercial products for osteoporotic bone filling applications. Furthermore, the presented method also can be used at low temperatures before an operation to produce preformed implants to fit the particular needs of a patient.