Repair Strength Research Articles

Biomechanical study comparing Pulvertaft suture to step-cut suture

Tendon grafts are a component of the therapeutic arsenal for managing chronic flexor tendons injuries in the hand, especially during two-stage Hunter reconstruction. The purpose of this anatomical study was to compare the strength of the Pulvertaft weave versus the step-cut suture used for flexor tendon reconstruction to determine their role in early active mobilization. We performed a biomechanical study with cadaver specimens. Thirty-four hands were randomized and the tendons from both hands were equally assigned to each group. A comparison of the Pulvertaft weave (group 1) versus the step-cut suture (group 2) using the flexor digitorum profundus from the fourth finger and the longus palmaris was carried out. The main variable was the failure load in both repair groups. We also evaluated the cross-sectional area (CSA) and the tensile strength of the repairs. Thirty hands were included in our study. There was no significant difference in the failure load between the two groups (116N for group 1 versus 103N for group 2, P=0.2). The CSA was significantly smaller in the step-cut group compared to Pulvertaft group (19.8mm2 versus 35mm2, P<0.01). The tensile strength was significantly higher in the step-cut group than in the Pulvertaft group (5.3N/mm2 versus 3.4N/mm2, P<0.01). Early active mobilization requires a minimum repair strength of 75N. In our study, the step-cut suture appears strong enough and thin enough to decrease the fibrosis, which would lead to better functional results. No other study of this type has been published. The specimens in which the repair strength was less than 75N all involved a thin, weak longus palmaris. Other biomechanical studies should be done to define the anatomical criteria required for use of the palmaris longus tendon. The step-cut suture seems to be strong enough and thin enough to provide sufficient proximal attachment during flexor tendon reconstruction to allow early active mobilization.

Repair bond strength of nanohybrid composite resins with a universal adhesive

Objective: To investigate the repair bond strength of fresh and aged nanohybrid and hybrid composite resins using a universal adhesive (UA).Materials and methods: Fresh and aged substrates were prepared using two nanohybrid (Venus Pearl, Heraus Kulzer; Filtek Supreme XTE, 3 M ESPE) and one hybrid (Z100, 3 M ESPE) composite resin, and randomly assigned to different surface treatments: (1) no treatment (control), (2) surface roughening with 320-grit (SR), (3) SR + UA (iBOND, Heraus Kulzer), (4) SR + Silane (Signum, Ceramic Bond I, Heraeus Kulzer) + UA, (5) SR + Sandblasting (CoJet, 3 M ESPE) + Silane + UA. After surface treatment, fresh composite resin was added to the substrates at 2 mm layer increments to a height of 5 mm, and light cured. Restored specimens were water-stored for 24 h and sectioned to obtain 1.0 × 1.0 mm beams (n = 12), and were either water-stored for 24 h at 37 °C, or water-stored for 24 h, and then thermocycled for 6000 cycles before microtensile bond strength (µTBS) testing. Data were analyzed with ANOVA and Tukey’s HSD tests (p = .05).Results: Combined treatment of SR, sandblasting, silane and UA provided repair bond strength values comparable to the cohesive strength of each tested resin material (p < .05). Thermocycling significantly reduced the cohesive strength of the composite resins upto 65% (p < .05). Repair bond strengths of UA-treated groups were more stable under thermocycling.Conclusions: Universal adhesive application is a reliable method for composite repair. Sandblasting and silane application slightly increases the repair strength for all substrate types.

Fingertip Winding Suture: Pull-out Suture Technique for Flexor Tendon Repair in Zone I.

Injuries to flexor tendons in zone I has always been challenging during repair. Over the time several techniques were developed and modified to achieve the highest repair strength and thus the best functional outcome. These techniques vary from pull-out sutures with internal and external fixation to the use of bone anchors. All techniques were accompanied with advantages and disadvantages as well as postoperative morbidities related to certain techniques. In the present technique we introduce a subperiosteal pull-out suturing technique. It is a simple, strong, and cost-effective method for repair of flexor tendon injuries in zone I or in the context of tendon grafting.

Passive stiffness in the supraspinatus muscle after double-row and knotless transossous equivalent repair: A cadaveric study

Background Although various techniques for arthroscopic rotator cuff repair have been introduced, optimal technique is still controversial. Biomechanical studies have been performed to assess tendon-bone interface properties. However, few studies have focused on the effect of the rotator cuff muscle after repair. To determine a technique with improved cuff function, in addition to repair strength, other factors such as stiffness changes in the rotator cuff muscle should also be analyzed. The purpose of this study was to investigate passive stiffness in the supraspinatus (SSP) muscle using shear wave elastography (SWE) after double-row (DR) and knotless transosseous equivalent (KL-TOE) techniques. Methods Twelve fresh-frozen cadaveric shoulders with rotator cuff tear (tear size; small [6], medium-large [6]) were used. Passive stiffness of 4 anatomical regions in the SSP muscle was measured based on an established SWE method. Each specimen underwent 2 types of footprint repair (DR and KL-TOE, in a random order) with the arm at 30° abduction. SWE values, obtained with the arm at 0°, 30°, and 90° abduction, were compared in 3 different conditions: preoperative (torn) and postoperative conditions with the 2 techniques. Results In shoulders with medium-large size tears, SSP muscles showed increased stiffness values after rotator cuff repair with both techniques, and this was significantly observed at 0° abduction. In addition, stiffness of the SSP muscle was uniform among 4 regions after KL-TOE repair, whereas, DR repair caused significantly heterogeneous stiffness distribution within the muscle (P > 0.01). SSP muscles with small size tear did not show any significant differences in stiffness values between regions and repair technique. Conclusion KL-TOE technique for the medium-large size tear provided a more uniform stiffness distribution in repaired SSP muscles compared to the DR technique. Imbalanced muscular stiffness might cause limited functional recovery after the cuff repair. In addition to established evidences of biomechanical properties, the alteration of cuff muscle stiffness should be evaluated to determine the optimal technique.

Pullout strength of cement-augmented and wide-suture transosseous fixation in the greater tuberosity

BackgroundObtaining strong fixation in low-density bone is increasingly critical in surgical repair of rotator cuff tears because of the aging population. To evaluate two new methods of improving pullout strength of transosseous rotator cuff repair in low-density bone, we analyzed the effects of 1) using 2-mm suture tape instead of no. 2 suture and 2) augmenting the lateral tunnel with cement. MethodsEleven pairs of osteopenic or osteoporotic cadaveric humeri were identified by dual-energy x-ray absorptiometry. One bone tunnel and one suture were placed in the heads of 22 specimens. Five randomly selected pairs were repaired with no. 2 suture; the other six pairs were repaired with 2-mm suture tape. One side of each pair received lateral tunnel cement augmentation. Specimens were tested to suture pullout. Data were fitted to multivariate models that accounted for bone mineral density and other specimen characteristics. FindingsTwo specimens were excluded because of knot-slipping during testing. Use of suture tape versus no. 2 suture conferred a 75-N increase (95% CI: 37, 113) in pullout strength (P<0.001). Cement augmentation conferred a 42-N improvement (95% CI: 10, 75; P=0.011). Other significant predictors of pullout strength were age, sex, and bone mineral density. InterpretationWe show two methods of improving the fixation strength of transosseous rotator cuff repairs in low-density bone: using 2-mm suture tape instead of no. 2 suture and augmenting the lateral tunnel with cement. These methods may improve the feasibility of transosseous repairs in an aging patient population.

A Biomechanical Comparison of Limited Open Versus Krackow Repair for Achilles Tendon Rupture

Background: Soft tissue complications after Achilles tendon repair has led to increased interest in less invasive techniques. Various limited open techniques have gained popularity as an alternative to open operative repair. The purpose of this study was to biomechanically compare an open Krackow and limited open repair for Achilles tendon rupture. We hypothesized that there would be no statistical difference in load to failure, work to failure, and initial linear stiffness. Methods: A simulated Achilles tendon rupture was created 4 cm proximal to its insertion in 18 fresh-frozen cadaveric below-knee lower limbs. Specimens were randomized to open or limited open PARS Achilles Jig System repair. Repairs were loaded to failure at a rate of 25.4 mm/s to reflect loading during normal ankle range of motion. Load to failure, work to failure, and initial linear stiffness were compared between the 2 repair types. Results: The average load to failure (353.8 ± 88.8 N vs 313.3 ± 99.9 N; P = .38) and work to failure (6.4 ± 2.3 J vs 6.3 ± 3.5 J; P = .904) were not statistically different for Krackow and PARS repair, respectively. Mean initial linear stiffness of the Krackow repair (17.8 ± 5.4 N/mm) was significantly greater than PARS repair (11.8 ± 2.5 N/mm) ( P = .011). Conclusion: No significant difference in repair strength was seen, but higher initial linear stiffness for Krackow repair suggests superior resistance to gap formation, which may occur during postoperative rehabilitation. With equal repair strength, but less soft tissue devitalization, the PARS may be a favorable option for patients with risk factors for soft tissue complications.

Double-Layer Surface Modification of Polyamide Denture Base Material by Functionalized Sol-Gel Based Silica for Adhesion Improvement.

Limited surface treatments have been proposed to improve the bond strength between autopolymerizing resin and polyamide denture base materials. Still, the bond strength of autopolymerizing resins to nylon polymer is not strong enough to repair the fractured denture effectively. This study aimed to introduce a novel method to improve the adhesion of autopolymerizing resin to polyamide polymer by a double layer deposition of sol-gel silica and N-2-(aminoethyl)-3-aminopropyltrimethoxysilane (AE-APTMS). The silica sol was synthesized by acid-catalyzed hydrolysis of tetraethylorthosilicate (TEOS) as silica precursors. Polyamide specimens were dipped in TEOS-derived sol (TS group, n = 28), and exposed to ultraviolet (UV) light under O2 flow for 30 minutes. UV-treated specimens were immersed in AE-APTMS solution and left for 24 hours at room temperature. The other specimens were either immersed in AE-APTMS solution (AP group, n = 28) or left untreated (NT group, n = 28). Surface characterization was investigated by fourier transform infrared spectroscopy (FTIR) and atomic force microscopy (AFM). Two autopolymerizing resins (subgroups G and T, n = 14) were bonded to the specimens, thermocycled, and then tested for shear bond strength with a universal testing machine. Data were analyzed with one-way ANOVA followed by Tukey's HSD (α = 0.05). FTIR spectra of treated surfaces confirmed the chemical modification and appearance of functional groups on the polymer. One-way ANOVA revealed significant differences in shear bond strength among the study groups. Tukey's HSD showed that TST and TSG groups had significantly higher shear bond strength than control groups (p = 0.001 and p < 0.001, respectively). Moreover, bond strength values of APT were statistically significant compared to controls (p = 0.017). Amino functionalized TEOS-derived silica coating is a simple and cost-effective method for improving the bond strength between the autopolymerizing resin and polyamide denture base. Amino-functionalized silica coating could represent a more applicable and convenient option for improving the repair strength of autopolymerizing resin to polyamide polymer.

Effects of PDGF-BB delivery from heparinized collagen sutures on the healing of lacerated chicken flexor tendon in vivo.

A high strength aligned collagen suture was fabricated via linear electrocompaction and heparinized for prolonged delivery of PDFG-BB. When it was used to suture a complete lacerated flexor tendon in a chicken model controlled release of the PDGF-BB improved the strength of treated tendon after 12 weeks compared to tendon sutured with commercial nylon suture. Furthermore, Collagen suture with affinity bound PDGF-BB enhanced the vascularization and remodeling of lacerated tendon when it compare to synthetic nylon suture. Overall, electrocompacted collagen sutures holds potential to improve repair outcome in flexor tendon surgeries by improving repair strength and stiffness, vascularity, and remodeling via sustained delivery of the PDGF-BB. The bioinductive collagen suture introduces a platform for sustained delivery of other growth factors for a wide-array of applications.

A Biomechanical Comparison of a Limited Open and Standard Open Technique for Achilles Tendon Rupture Repair

Category: Basic Sciences/Biologics, Sports Introduction/Purpose: The drive to reduce soft tissue complications after Achilles tendon repair has led to increased interest in less invasive techniques. The PARS Achilles Jig System is one option that has gained popularity as an alternative to open repair. For many surgeons, standard open repair consists of a Krackow locking-loop technique. We compared the load to failure of a limited open and open Krackow technique for repair of Achilles tendon ruptures. Methods: Nine pairs of human cadaver lower limbs were randomized to undergo either a Krackow locking loop repair with epitendinous weave or a PARS Achilles Jig System Repair. Specimen were loaded to failure on a servo-hydraulic material testing machine. From load- displacement curves, initial linear stiffness, load to failure, and work to failure were calculated. Results: The average load to failure for Krackow repair (353.8 ± 88.8 N) and PARS repair (313.3 ± 99.9 N) was not statistically different (p = .38). The average work to failure for open repair (6.4 ± 2.3 J) and PARS repair (6.3 ± 3.5 J) was also not statistically different (p = .904). Mean initial linear stiffness of the Krackow repair (17.8 ± 5.4 N/mm) was significantly greater than the PARS repair (11.8 ± 2.5 N/mm) (p = .011). The predominant location of failure for Krackow repair was at the suture itself. In contrast, the PARS repair predominantly failed at the suture-tendon interface. Conclusion: The results suggest no difference between the Krackow and PARS repairs in terms of ultimate strength or work to failure. The Krackow repair demonstrated a higher initial linear stiffness than the PARS, which may imply a greater ability to withstand gap formation. With less devitalization to surrounding soft tissue and equal repair strength, the PARS system should be considered a favourable option for repair of ruptured Achilles tendons.

A Biomechanical Evaluation of a 2-Suture Anchor Repair Technique for Thumb Metacarpophalangeal Joint Ulnar Collateral Ligament Injuries.

A complete thumb ulnar collateral ligament (UCL) repaired with 1-suture anchor has been demonstrated to be significantly weaker compared with the intact UCL. The objective of this study is to test the biomechanical strength of a 2-anchor thumb UCL repair. Nine paired fresh-frozen hands were used for this biomechanical analysis. One thumb from each pair was randomized to the control group and one to the repair group. In the control group, the UCL was loaded to failure in tension. In the repair group, the UCL was dissected off of the proximal phalanx, subsequently repaired with a 2-anchor technique, and then tested to failure. The mean yield load was 342 N (95% confidence interval [CI], 215-470 N) in the control group and 68 N (95% CI, 45-91 N) in the repair group. The mean maximum load at failure was 379 N (95% CI, 246-513 N) in the control group and 84 N (95% CI, 62-105 N) in the repair group. The mean stiffness was 72 N/m (95% CI, 48-96 N/m) in the control group and 17 N/m (95% CI, 13-21 N) in the repair group. The mean displacement at failure was 7.8 mm (95% CI, 7-9 mm) in the control group and 7.8 mm (95% CI, 7-9 mm) in the repair group. The 2-anchor repair technique we tested does not acutely reestablish the strength of the insertion of the native insertion of the UCL with this technique.

Rotator cuff repair with a novel mesh suture: An ex vivo assessment of mechanical properties

Surgical repair is a common treatment for rotator cuff tear; however, the retear rate is high. A high degree of suture repair strength is important to ensure rotator cuff integrity for healing. The purpose of this study was to compare the mechanical performance of rotator cuffs repaired with a mesh suture versus traditional polydioxanone suture II and FiberWire sutures in a canine in vitro model. Seventy-two canine shoulders were harvested. An infraspinatus tendon tear was created in each shoulder. Two suture techniques-simple interrupted sutures and two-row suture bridge-were used to reconnect the infraspinatus tendon to the greater tuberosity, using three different suture types: Mesh suture, polydioxanone suture II, or FiberWire. Shoulders were loaded to failure under displacement control at a rate of 20 mm/min. Failure load was compared between suture types and techniques. Ultimate failure load was significantly higher in the specimens repaired with mesh suture than with polydioxanone suture II or FiberWire, regardless of suture technique. There was no significant difference in stiffness among the six groups, with the exception that FiberWire repairs were stiffer than polydioxanone suture II repairs with the simple interrupted technique. All specimens failed by suture pull-out from the tendon. Based on our biomechanical findings, rotator cuff repair with the mesh suture might provide superior initial strength against failure compared with the traditional polydioxanone suture II or FiberWire sutures. Use of the mesh suture may provide increased initial fixation strength and decrease gap formation, which could result in improved healing and lower re-tear rates following rotator cuff repair. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:987-992, 2018.

In-Vitro Quantification of Medial Collateral Ligament Tension in the Elbow.

The anterior bundle of the medial collateral ligament (AMCL) of the elbow is commonly injured in patients with elbow dislocations and in throwing athletes. This in-vitro study quantified tension in the native AMCL throughout elbow flexion for different arm positions. We conducted passive and simulated active elbow flexion in seven fresh-frozen cadaveric upper extremities using an established motion simulator. Motions were performed in the valgus and vertical positions from 20-120° while measuring AMCL tension using a custom transducer. Average AMCL tension was higher in the valgus compared to vertical position for both active (p = 0.03) and passive (p = 0.01) motion. Peak AMCL tension was higher in the valgus position for active (p = 0.02) and passive (p = 0.01) motion. There was no significant difference in AMCL tension between active and passive motion in the valgus (p = 0.15) or vertical (p = 0.39) positions. In the valgus position, tension increased with elbow flexion from 20-70° for both active (p = 0.04) and passive (p = 0.02) motion, but not from 70-120°. This in-vitro study demonstrated that AMCL tension increases with elbow flexion, and is greater in the valgus position relative to the vertical position. This information has important implications to the desired target strength of repair and reconstruction techniques.

Subacromial corticosteroid injections transiently decrease suture anchor pullout strength: biomechanical studies in rats

Arthroscopic rotator cuff (RC) repair incorporates suture anchors to secure torn RC tendons to the greater tuberosity (GT) bone. RC repair strength depends on the anchor-bone interface and on the quality of the GT. We evaluated the effect of single and multiple corticosteroid injections on the pullout strength of suture anchors. Fifty rats were divided into those receiving saline solution injection (control group), a single methylprednisolone acetate (MTA) injection (MTA1 group), or 3 once-weekly MTA injections (MTA3 group). Rats were killed humanely at 1 or 4 weeks after the last injection. A mini-suture anchor was inserted into the humeral head through the GT. Specimens were tested biomechanically. At 1 week after the last injection, the mean maximal pullout strength was significantly reduced in the MTA1 group (63.5%) and MTA3 group (56%) compared with the control group (P < .05 for both). Mean stiffness decreased significantly in both treatment groups compared with controls (P < .05). At 4 weeks after the last injection, there was a significant increase in the mean maximal pullout strength after single and triple MTA injections compared with values recorded at the 1-week time point (P < .05). At 4 weeks, the mean maximal pullout strength after a single MTA injection was 92.8% of the pullout strength measured in the control group. We showed a significant detrimental effect of corticosteroid exposure on the pullout strength of a suture anchor at 1 week. However, this effect was transient and resolved within a relatively short period. These findings indicate that a waiting period is required between subacromial corticosteroid injection and RC repair surgery that involves the use of suture anchors.

Effect of different surface treatment techniques on the repair strength of indirect composites.

Surface treatments of resin composite had little effect on the bond strength of the repaired composite.

Murine Supraspinatus Tendon Detachment and Repair Model Augmented With Tendon-Derived, Activated Endothelial Cells: A New Concept in Biologic Enhancement of Tendon-to-Bone Healing

Objectives:Biologic interventions are being increasingly used to improve outcome of rotator cuff repair. Individual growth factors and stem cell-based augmentations are among the most popular approaches. In this study we investigated a novel approach in which tendon-derived, activated endothelial cells (tAECs) are used as a source of tissue-specific growth factors to stimulate tendon intrinsic stem cell niche in our established murine model of microsurgical supraspinatus tendon (SST) detachment and repair.Methods:Study protocol was approved by the IACUC. In stage 1, 20 C57BL/6 mice underwent tendon harvest from fore- and hind limbs and endothelial cells isolation and transfection with adenoviral E4 ORF1 and red fluorescent protein labelling using a proprietary protocol. In stage 2, 158 C57BL/6 mice underwent the procedure with implantation of a 10μm fibrin glue bead (FGB) at the repair site and were randomly allocated to study group (SG) and control group (CG). Study mice received 100,000 tAECs suspended in the FGB. Control mice received the FGB only. 3 mice were sacrificed on post-operative day (POD) #3 and #7 for cell viability study. 96 mice were sacrificed at 1, 2, and 4 weeks, with 10 and 6 mice in each group and time point for biomechanical and histologic evaluations, respectively. 56 mice were sacrificed on POD 5, 10, 14, and 28 for gene expression analysis using qPCR, with 7 mice in each group and time point. Biomechanical evaluation consisted of determination of failure force and site. Histologic parameters were cell count (H&E), number of vessels (factor VIII-specific antibody), number of chondrocytes and proteoglycan content (Alcian Blue), and collagen organization (picrosirius red and polarized light microscopy). 12 evaluated genes were aggrecan (ACAN), collagen1α1 (COL1), collagen3α1 (COL3), MKX, MMP-3, 13, and 14, Runx2, scleraxis (Scx), SOX9, tenomodulin (TNM) and VEGFa.Results:Fluorescent microscopy revealed viable tAECs at the repair site on POD #3 with No fluorescent activity on POD #7. Failure force in the SG was 50% higher at 2 weeks (2.50 ± 0.55 N vs 1.86 ± 0.82 N, p = 0.012) with 65% of all failures occurring at SST mid-substance, whereas 90% of failures in the CG occurred at the repair site. There was no significant difference in failure force at 4 weeks. Cell count, number of vessels, and proteoglycan content (Figure 1) were significantly higher in the SG at all time points. The number of chondrocytes was higher in the SG at 1 week (Figure 1). Quantitative analysis showed significantly superior collagen organization in the SG (Figure 2). SCX, MKX, TNM and COL3 expression were up-regulated on POD #10 and decreased on day #28 in both groups. Expression of TNM and COL3 in the SG showed significance difference at 4 weeks. ACAN, SOX9, COL1, MMP14 expression exhibited an increase starting from POD 5, followed by a significant decline towards baseline by POD 28. In the SG, SOX9 peaked at day 14. Expression of VEGFa showed an uptrend at earlier time points (Figure 3).Conclusion:tAECs increased repair strength of SST. Histologic findings were suggestive of a more vigorous cellular and vascular response, higher proteoglycan content, and ultimately, superior collagen organization. A commensurate pattern was observed in expression of relevant genes. This approach opens a new avenue for cell-based biologic augmentation of SST repair with the goal of stimulating the intrinsic stem cell niche in tendon, as opposed to incorporating exogenous cell sources.

The Effect of Myostatin (GDF-8) on Proliferation and Tenocyte Differentiation of Rat Bone Marrow-Derived Mesenchymal Stem Cells.

The future in flexor tendon surgery involves tissue engineering approaches directed toward increasing early repair strength to accelerate tendon healing and to allow for earlier onset of rehabilitation. Previous work has shown that pluripotential mesenchymal stem cells may be successfully delivered to a tendon repair site using a suture carrier. The current work describes the use of Myostatin (GDF-8) to help guide these delivered pluripotential stem cells to differentiate down a tenocyte lineage to potentially maximize the reparative effects of these cells at the tendon repair site. Primary rat bone marrow mesenchymal stem cells isolated from the long bones of male Sprague-Dawley rats were treated with 500 ng/ml myostatin for 24 h, 48 h, and 72 h. Collagen 1 A, scleraxis (Scx), and tenomodulin (Tnmd) expression, indicative of tenogenesis, was analyzed using real time PCR and immunohistochemistry staining. A migration assay was performed to assess the functional activity of BMSCs after they were treated with myostatin. Compared to the control cells (without treatment), the cells treated with 500 ng/ml myostatin for 72 h exhibited higher expression of Col 1A, Scx, and Tnmd. The mRNA expression of Col1A, Scx, Tnmd increased 15.3, 13 and 7 times respectively. Immunohistochemistry staining showed Scx and Tnmd were expressed in the cellular cytoplasm. In response to myostatin, the cells also showed a tendency to proliferate and migrate more than the control cells. Myostatin (GDF-8) has the ability to increase rat bone marrow mesenchymal stem cell growth and differentiation toward a tenocyte lineage. This information could be useful for future studies regarding tendon repair.

Infection prevention using affinity polymer-coated, synthetic meshes in a pig hernia model

BackgroundGiven concern for hernia mesh infection, surgeons often use biologic mesh which may provide reduced risk of infection but at the cost of decreased repair durability. We evaluated mesh coating to provide sustained release of antibiotics to prevent prosthetic mesh infection and also allow a durable repair. Materials and methodsCyclodextrin-based polymer was crosslinked onto multifilament polyester mesh and loaded with vancomycin (1.75 mg/cm2). Pigs received modified meshes (n = 6) or normal, untreated meshes (n = 4), which were implanted into acute 10 × 5 cm ventral hernia, then directly inoculated with 106 colony-forming unit (CFU) of methicillin-resistant Staphylococcus aureus (MRSA). These were compared to animals receiving normal, uninfected mesh. All mesh was secured in an underlay bridge manner, and after 30 d, the abdominal wall was removed for quantitative bacterial culture and biomechanical analysis. ResultsAll animals survived 30 d. All six animals with coated mesh cleared MRSA infection. The four control animals did not clear MRSA (P = 0.005). Quantitative bacterial load was higher in standard mesh versus drug-delivery mesh group (2.34 × 104versus 80.9 CFU/gm). These data were log10-transformed and analyzed by Welch's t-test (P = 0.001). Minimum number of CFUs detectable by assay (300) was used instead of zero. Biomechanical analysis of controls (1.82 N/mm infected; 1.71 N/mm uninfected) showed no difference to the modified meshes (1.31 N/mm) in tissue integration (P = 0.15). ConclusionsWe successfully prevented synthetic mesh infection in a pig model using a cyclodextrin-based polymer to locally deliver vancomycin to the hernia repair site and clearing antibiotic-resistant bacteria. Polymer coating did not impact the strength of the hernia repair.

How should I fixate the subscapularis in total shoulder arthroplasty? A systematic review of pertinent subscapularis repair biomechanics.

The present study aimed to review the biomechanical outcomes of subscapularis repair techniques during total shoulder arthroplasty (TSA) to assist in clinical decision making. A systematic review of multiple databases was performed by searching PubMed, Scopus, Cochrane Library, Google Scholar, and all databases within EBSCOhost to find biomechanical studies of subscapularis repair techniques in cadaveric models of TSA. Nine studies met the inclusion criteria. In the majority of studies, lesser tuberosity osteotomy (LTO) techniques had greater load to failure and less cyclic displacement compared to subscapularis tenotomy or peel methods. LTO repairs with sutures wrapped around the humeral stem demonstrated superior biomechanical outcomes compared to techniques using only a tension band. In terms of load to failure, the strongest repair of any study was a dual-row fleck LTO using four sutures wrapped around the stem. Several cadaveric studies have shown superior biomechanical outcomes with LTO techniques compared to tenotomy. In the majority of studies, the strongest subscapularis repair technique in terms of biomechanical outcomes is a compression LTO. Using three or more sutures wrapped around the implant and the addition of a tension suture may increase the biomechanical strength of the LTO repair.

Effect of the Optimal Asymmetry on the Strength of Six-Strand Tendon Repair: An Ex Vivo Biomechanical Study

To evaluate the mechanical properties of a 6-strand core suture repair with asymmetric purchase in the 2 tendon ends, in comparison with a repair with symmetric suture purchases. Under cyclic loading of the tendons, we recorded the fatigue strength (Forces× Cycles) of a 6-strand flexor tendon repair with different symmetry in the lengths of suture purchase in 60 porcine tendons. The symmetric repair was made with 3 groups of parallel Kessler repairs of equal suture purchase (10 mm from the cut end) in the 2 tendon stumps. The asymmetric core suture repairs were then made with a Kessler repair of equal suture purchase (10 mm from the cut end) in the 2 tendon stumps, and shifting 2 other Kessler repairs by 1, 2, 3, 4, or 5 mm, respectively, along the longitudinal axis of the tendon in relation to the first (symmetric) Kessler repair. The core repairs with 2 mm or more asymmetry in suture purchases in 2 tendon ends showed significantly greater fatigue strength compared with those with symmetric suture placement. The core repairs with 3 mm or more asymmetry in suture purchases in 2 tendon ends showed significantly smaller gaps compared with those with symmetric suture placement. The core repairs with 3 mm or more asymmetry in suture purchases in 2 tendon ends generated increased fatigue strength and reduced gap sizes compared with those with symmetric suture placement in an exvivo porcine model. An asymmetric core suture repair with 3 mm or more difference in purchase length may allow for earlier rehabilitation and reduce the risk of postoperative complications.

Effect of different surface treatment techniques on the repair strength of indirect composites

ObjectivesComposite resin restorations present high survival rates and when a failure occurs repair is often possible. The aim of this study was to assess the effect of various repair techniques on indirect restorations. MethodsLAVA Ultimate (3M), and Clearfil Estenia blocks (Kuraray) were repaired with our without surface roughness treatments, silane application and artificial ageing. Micro-shear bond stress tests were performed, while cohesive strength served as positive control. ANOVA was used for cohesive strength and effect of ageing, and linear mixed models to evaluate the effect of treatment variables on repair strength. ResultsBoth materials reacted differently on surface treatments. Untreated (no treatment, no silane) repair strength was 16.3±6.3MPa for LAVA Ultimate and 19.0±4.3MPa for Estenia. Thermal cycling resulted in a 14–58% reduction of cohesive strength. Without cycling, all treatments resulted in a significant increase of bond strength in LAVA Ultimate (p<0.003). After cycling use of air-abrasion showed a positive trend for both substrates, significantly effective for LAVA Ultimate (p<0.04), and silane and CoJet for Estenia (p<0.024). The positive effect of HF treatment disappeared after cycling. ConclusionIt may be concluded that (1) the effect of surface treatment procedures on the repair bond strength of indirect composites is depended on the substrate and ageing. (2) Silane did not have a clear overall positive effect on bond strength and (3) artificial ageing had a strong negative influence on the stability of the adhesive interface and on the cohesive strength of one indirect composite resin material, but not the other.