Effect of chemotherapy and heat on biomechanical properties of absorbable sutures.

BACKGROUND: The quality of tissue repairs depends on tissue integrity, surgical technique, and material properties of the sutures used. Currently, there is no clear consensus on which is the best suture to use during cytoreductive surgery combined with hyperthermic intraperitoneal chemotherapy. The aim of this study was to evaluate the impact of heat and chemotherapy on sutures' biomechanical properties. METHODS: Six different 3.0 absorbable sutures (Biosyn, Dexon II, Maxon, Monocryl, PDS II, and Vicryl Plus) were tested. All suture strands were incubated for a 24-h period in saline, mitomycin-c, and oxaliplatin at 37 and 45°C. Suture loops were then loaded to failure using a servohydraulic testing machine. Data for tensile breaking force (TBF) and elongation rate were collected for all samples. RESULTS: Under basal condition, Maxon was the strongest of all sutures with a TBF of 59.6 ± 4.3 N (P < 0.01), and no significant difference in TBF was observed between other sutures. Heat alone had no impact on sutures' biomechanical parameters. Exposition to mitomycin-c at 45°C did not significantly affect sutures' basal tensile properties, with Maxon remaining the strongest suture. When incubated in oxaliplatin at 45°C, the six suture types had a similar TBF. In all experimental conditions, multifilament sutures had a significantly lower elongation rate than monofilament sutures, and no correlations were demonstrated between elongation rate and the TBF of sutures. CONCLUSIONS: This study showed that exposition to heated chemotherapy did not significantly affect absorbable sutures biomechanical properties.

The effect of six knotting methods on the biomechanical properties of three large diameter absorbable suture materials.

OBJECTIVE: To evaluate the effect of 6 different knotting methods on the mechanical properties of 3 large absorbable suture materials used in large animal surgery. STUDY DESIGN: In vitro mechanical study. Sample Population- Knotted suture loops (n=15 per group). METHODS: Suture loops were created between two low-friction pulleys with either 2 polydioxanone, 2 polyglactin 910 or 3 polyglactin 910. Strands were tied using 1 of 6 knotting technique: square knot, surgeon knot, clamped surgeon's knot, sliding half-hitch knot (HH), Delimar knot and self-locking knot (SLK). A single cycle to failure test was performed on each suture loop with a distraction rate of 100 mm/min. Failure modes were evaluated and breaking strength, elongation to failure and stiffness were compared. RESULTS: All loops except two HH failed at the knot by acute breaking. The double-stranded SLK was both stronger and stiffer than all other knots for each suture material. Clamping the first throw of the surgeon knot decreased load to failure significantly (143.11 +/- 8.64 N) compared with not clamping (159.21 +/- 6.14 N) for polydioxanone. Stiffness and elongation to failure were respectively lower and increased for 2 polydioxanone compared with both polyglactin 910 materials for all knotting techniques. CONCLUSIONS: Knotting techniques do influence structural properties of suture loops. The double strand loop conferred stiffer and stronger properties to the SLK CLINICAL RELEVANCE: Clamping the first throw of polydioxanone should be avoided when tying a suture under tension even using large diameter suture materials. Using a SLK might be considered as a useful alternative when excessive tension is present.

Combustion synthesis of porous biomaterials.

This article discusses the unique material manufacturing process of self-propagating high temperature synthesis (SHS) as applied to the making of porous biomaterials. Porous materials have long been considered as the first step toward in-vivo bone tissue engineering and the creation of patient life-time implants. The authors have approached this challenge by utilizing combustion synthesis, to create novel materials such as NiTi + TiC as well as porous forms of materials that are commonly accepted for biomedical applications such as tricalcium phosphate and hydroxyapatite. In the SHS product, physico-chemical properties are controlled by, but not limited to, reactant stoichiometry; green density; particle size of the reactant mix; use or presence of a gasifying agent; heating rate of the reactants and gravity. By balancing these parameters, the energy of the reaction is controlled to create the desired product stoichiometry, porosity, and mechanical properties. SHS provides a means to rapidly manufacture materials, saving time and production costs as well as enabling the synthesis of custom devices through the use of individual molds. Mold materials can range from graphite to paper or paper machete. Combustion synthesis offers a method for the rapid manufacture of affordable, individual biomedical devices that will reduce patient recovery time.

Biomechanical stability of a retrotubercle opening-wedge high tibial osteotomy.

In recent years, opening-wedge osteotomy has gained popularity. However, the complication rate reported is high. Opening-wedge osteotomy was modified to remedy the problems seen with the conventional technique including loss of correction, delayed healing, and patella infera. This biomechanical study evaluates the response of a new opening-wedge osteotomy in a static and dynamic mode of human cadavers. Results were compared to the stability of the conventional technique. Six preserved pairs of human cadaveric knees were tested. Specimens of the same pair were randomly assigned to either the modified or conventional osteotomy. Internal fixation was used to ensure precise correction and prevent bone collapse. Each tibia was loaded on a material testing system from 0 to 700 N for 10,000 cycles to simulate immediate full weight bearing in a walking individual. Specimens were then loaded to failure to determine ultimate load and stiffness of the construct. Displacement of the articular fragment and stiffness were measured during dynamic loading. Load to failure, displacement, and stiffness were measured during static testing. The modified osteotomy provided significantly greater stiffness (1392 N/mm) and smaller loss of correction (.68 mm) than the conventional osteotomy (741 N/mm; 1.76 mm) under cyclic loading conditions (P<.05). The modified retrotubercle osteotomy provides greater stiffness than the conventional osteotomy, increasing stability by 62% and minimizing loss of correction to <1 mm. The modified osteotomy eliminates the need for bone graft and provides additional strength to allow accelerated rehabilitation.

Biomechanical stability of high tibial opening wedge osteotomy: internal fixation versus external fixation.

PURPOSE: The goal of our study was to evaluate stability of internal fixation with a plate compared to external fixation in an opening wedge high tibial osteotomy model. Significance. To our knowledge, this is the only study to compare internal plate to external fixation in an opening wedge osteotomy model. The design of this cadaver study limits its direct application to clinical practice. MATERIAL AND METHOD: In each of the six pairs of fresh-frozen human cadaver knees one specimen was randomly assigned to internal plate fixation while the other was stabilized with an external fixation. The osteosynthesis plate incorporated a 12.5mm block that distracted the medial tibial cortices. Each knee was loaded on a mechanical testing machine to 700 N for 10,000 cycles to simulate immediate full weight bearing in a walking individual. SUMMARY OF RESULTS: The internal plate osteosynthesis provided significantly greater stiffness and smaller loss of correction (1.60mm) than the external fixation (3.22 mm) under cyclic loading condition (P<0.05). For static loading, the mean value of stiffness resulting in failure for the internal plate and external fixation, were respectively, 938 N/mm and 459 N/mm. Load to failure also showed two times greater stiffness in the plate osteosynthesis group. No hardware failure was observed in either construct. DISCUSSION AND CONCLUSION: Plate fixation was superior to external fixation in maintaining correction. However, progressive adjustment of the distraction with the external fixator allows precise "fine-tuning" during the healing process that is not possible with internal fixation.

Personalized implant for high tibial opening wedge: combination of solid freeform fabrication with combustion synthesis process.

In this work a new generation of bioceramic personalized implants were developed. This technique combines the processes of solid freeform fabrication (SFF) and combustion synthesis (CS) to create personalized bioceramic implants with tricalcium phosphate (TCP) and hydroxyapatite (HA). These porous bioceramics will be used to fill the tibial bone gap created by the opening wedge high tibial osteotomy (OWHTO). A freeform fabrication with three-dimensional printing (3DP) technique was used to fabricate a metallic mold with the same shape required to fill the gap in the opening wedge osteotomy. The mold was subsequently used in a CS process to fabricate the personalized ceramic implants with TCP and HA compositions. The mold geometry was designed on commercial 3D CAD software. The final personalized bioceramic implant was produced using a CS process. This technique was chosen because it exploits the exothermic reaction between P2O5 and CaO. Also, chemical composition and distribution of pores in the implant could be controlled. To determine the chemical composition, the microstructure, and the mechanical properties of the implant, cylindrical shapes were also fabricated using different fabrication parameters. Chemical composition was performed by X-ray diffraction. Pore size and pore interconnectivity was measured and analyzed using an electronic microscope system. Mechanical properties were determined by a mechanical testing system. The porous TCP and HA obtained have an open porous structure with an average 400 µm channel size. The mechanical behavior shows great stiffness and higher load to failure for both ceramics. Finally, this personalized ceramic implant facilitated the regeneration of new bone in the gap created by OWHTO and provides additional strength to allow accelerated rehabilitation.