Evaluation of gap formation for different adhesive agents in primary teeth with optical coherence tomography.

Purpose: This study aimed to evaluate gap formation between the tooth surface and restorative material in terms of microleakage by using optical coherence tomography (OCT) for self-etch and selective-etch applications of two different universal and one self-etch adhesives. Materials and methods: Sixty non-caries, primary molar teeth were divided into six groups; self-etch and selective-etch application ways of two different universal and one self-etch adhesive systems (n:10). After Class-V cavities were prepared, every tooth was distributed randomly in groups to apply adhesion procedure and then, all cavities were restored with polyacid-modified composite resin. Microleakage was evaluated by measuring the gap between the tooth surface and restoration by a blind researcher with Image J Software from OCT images. During statistical analysis, the significance level was accepted as p<0.05. Results: According to the statistical analysis of the measurements obtained by Image J Software, selective-etch groups showed less gap formation than self-etch groups for each tested adhesive (p<0.05), and self-etch adhesive without etching showed significantly highest gap formation among all groups (p<0.05). Conclusion: Universal adhesives with a selective-etching step might be preferred over self-etch adhesives for long-lasting polyacid-modified composite resin restorations in primary teeth. However, obtained results should be considered with another prospective clinical study for long-term prognosis.

The Influence of Adhesive Strategy, Type of Dental Composite, and Polishing Time on Marginal Gap Formation in Class I-like Cavities.

Even after more than six decades of dental composite invention (1962), there is still controversial information about the time in which composite restorations should be polished in order to avoid marginal gap formation at the tooth-composite interface. The aim of the present study was to analyze the influence of adhesive strategy, the type of dental composite, and polishing time on marginal gap formation (%MG) at the tooth-composite interface. Class I-like cavities were hybridized with a universal adhesive system (Single Bond Universal) through two strategies: selective enamel etching (SEE) or self-etching mode (SEM). Cavities were filled with two types of dental composites: nanofilled (Z350) or bulk fill (Filtek One Bulk Fill-ONE), and polishing was performed immediately or delayed for 7 days (n = 5). %MG was evaluated by using a 3D laser confocal microscope. As flexural modulus (FM) and degree of conversion (DC%) are determinants of marginal integrity in dental composite restorations, these properties were evaluated for both composites. Data were analyzed by ANOVA and Tukey's HSD test (α = 0.05). Cavities hybridized following the SEE strategy presented lower %MG (p < 0.05). Z350 showed higher %MG than ONE (p < 0.05). There was no difference in %MG between the polishing times when the SEE strategy was used (p > 0.05). Z350 presented higher FM than ONE (p < 0.05). DC% was found to be not significant (p > 0.05). The results suggest that selective enamel etching (SEE) is a better strategy for producing less %MG in composite restorations with enamel margins irrespective of the time in which the restoration is polished.

Gap Resistance and Tensile Strength of a Q Suture Technique During Curved Loading: An Ex Vivo Porcine Flexor Tendon Study.

PURPOSE: This study aimed to determine the mechanical properties of the double Q suture technique in angular motion and to compare the gap formation associated with tendon repairs during curved and linear loading. METHODS: Eighty porcine flexor tendons were repaired with one of two 4-strand sutures: double Q suture or double modified Kessler plus peripheral running sutures. The repaired tendons were cyclically loaded sequentially against a pulley with a radius of 2.0, 1.5, and 1.0 cm or linearly without any pulleys. The number of tendons that formed an initial or 2-mm gap at the repair site during cyclic loading, the gap size between tendon ends when cyclic loading ended, and the ultimate strength were recorded. RESULTS: The gap at the repair site formed gradually from the dorsal to volar aspect during curved loading. No double Q repairs, but half of the double Kessler plus running suture repairs, formed an initial or 2-mm gap on the volar aspect during curved loading. The double Q group had a significantly smaller gap size on the dorsal aspect than the double Kessler plus running suture group at all three radii of curvature. The ultimate strength was similar between the two groups. There were no significant differences in linear motion between these two repairs. CONCLUSIONS: The double Q suture is superior to the conventional 4-strand tendon core suture plus running peripheral sutures in gap resistance in angular motion. This study provides insight into the formation of an unbalanced gap on the dorsal and volar aspects of tendon repair during curved loading. CLINICAL RELEVANCE: The double Q suture provides a simple and efficient option for flexor tendon repair considering the high risk of gap formation on the dorsal aspects of the tendon repair in angular motion.

Stabilization and Gap Formation of Adjustable Versus Fixed Primary ACL Repair With Internal Brace: An in Vitro Full-Construct Biomechanical Cadaveric Study.

Background: A knotless, tensionable primary anterior cruciate ligament (ACL) repair system preloaded with an internal brace has been released. Currently, there is no biomechanical data on the stabilization and gap formation behavior of the adjustable system when compared with fixed repairs in human ACL tissue. Hypothesis: That knotless adjustable suture repair with an internal brace would provide overall higher construct stability and greater load share on the ACL with less gap formation compared with fixed repair. Study Design: Controlled laboratory study. Methods: Human cadaveric knees were utilized for internal braced ACL repair constructs (each group n = 16). Two fixed groups consisting of a single-cinch loop (SCL), cortical button (SCL group), and knotless suture-anchor (anchor group) were compared with an SCL-adjustable loop device (SCL-ALD) group. Testing was performed at 4 different peak loads (50, 150, 250, 350 N) over 4000 cycles at 0.75 Hz including suture repair preconditioning (10 cycles at 0.5 Hz) for SCL-ALD. Specimens were ultimately pulled to failure with a cut internal brace. The final loading situation of the construct and ACL repair with gap formation and ultimate strength were evaluated. Results: Peak elongation at various peak loads showed a significantly higher (P < .001) stabilization of SCL-ALD when compared with both fixed groups. There was a significantly higher (P < .001) load share of SCL-ALD, especially at lower loads (48% of 50 N), and the gap formation remained restricted up to 250 N. With only a little load share on the fixed constructs (<6%) at lower loads (50, 150 N), gap formation in these groups started at a load of 150 N, leading to significantly higher gaps (P < .001). The ultimate failure load for SCL-ALD and anchor groups was significantly increased (P < .001) as compared with SCL. The stiffness of SCL-ALD (62.9 ± 10.6 N/mm) was significantly increased (P < .001). Conclusion: Internal braced knotless adjustable fixation for ACL repair with preconditioning of the suture repaired ligament increased the overall stabilization with higher load share on the ACL and restricted gap formation (<0.5 mm up to 350 N) compared with fixed suture repair. All internal braced repairs restored stability according to native ACL function. Clinical Relevance: Adjustable ACL repair improved the mechanical characteristics and reduced gap formation, but the overall clinical significance on healing remains unclear.

Time Course of Priming Effect of TF Inducers on Synergistic TF Expression and Intra-Cellular Gap Formation of Human Vascular Endothelial Cells via the Extrinsic Coagulation Cascade.

Chronic spontaneous urticaria (CSU) is characterized by daily recurring wheal and flare with itch for more than 6 weeks. The extrinsic coagulation system has been shown to be activated in correlation with CSU severity. We have reported that tissue factor (TF), a trigger of the extrinsic coagulation cascade, is synergistically expressed on vascular endothelial cells by simultaneous stimulation with TF inducers (TFI), followed by activation of the extrinsic coagulation cascade and hyper permeability in vitro. However, vascular endothelial cells are not likely to be simultaneously stimulated by multiple TFIs under physiological conditions. Therefore, in order to know whether sequential, rather than simultaneous, stimuli with interval may induce synergistic activation of TF, we investigated the time course of the priming effects of each TFI for synergistic TF expression in vascular endothelial cells (HUVECs). We stimulated HUVECs with a TFI (first stimulation) and then stimulated cells with another TFI at indicated time points (second stimulation) and detected TF expression and activity. The TF expression induced by simultaneous stimulation diminished in a few hours. However, both synergistic enhancement of TF expression and activation level of the coagulation cascade were detected even when the second stimulation was added 18 or 22 h after the first stimulation. Thus, the priming effect of TFI for synergistic TF expression may persist for a half day or longer.

Biomechanical Stability of Lateral Ulnar Collateral Ligament Reconstruction and Repair of the Elbow: The Role of Ligament Bracing on Gap Formation and Stabilization.

BACKGROUND: Augmented (internal braced) lateral ulnar collateral ligament (LUCL) repair has been biomechanically compared with reconstruction techniques in the elbow. However, LUCL repair alone has not yet been compared with augmented repair and reconstruction techniques. HYPOTHESIS: Internal bracing of LUCL repair would improve time-zero stabilization regarding gap formation, stiffness, and residual torque as compared with repair alone and reconstruction techniques to restore native elbow stability. STUDY DESIGN: Controlled laboratory study. METHODS: Overall, 24 cadaveric elbows were used for either internal braced LUCL repair (Repair-IB) or single- and double-strand ligament reconstruction with triceps (Recon-TR) and palmaris longus tendon graft (Recon-PL), respectively. Laxity testing in external rotation was consecutively performed at 90° of elbow flexion on the intact, dissected, and repaired conditions and with the previously assigned techniques. First, intact elbows were loaded to 7.0-N·m external torque to evaluate time-zero ligament rotations at 2.5, 4.0, 5.5, and 7.0 N·m. Rotation-controlled cycling was performed (total of 1000 cycles) for each surgical condition. Gapping, stiffness, and residual torque were analyzed. Finally, these and 8 additional intact elbows underwent torque-to-failure testing (30 deg/min). RESULTS: The dissected state showed the highest gap formation and lowest peak torques (P < .001). While gap formation of Repair-IB (P < .021) was significantly lower than that of repair without internal bracing at all rotation levels, gaps of Recon-PL were similar to and Recon-TR were significantly higher than those of Repair-IB except for the highest torsion level. Residual peak torques at specific rotation angles between native state and Recon-TR (α2.5), Recon-PL (α4.0), and Repair-IB (α5.5) were similar; all other comparisons were significantly different (P < .027). Torsional stiffness of Repair-IB was significantly higher at all rotation angles measured. Analysis of covariance showed significantly less gap formation over residual peak torques for Repair-IB (P < .001) as compared with all other groups. The native state failure load was significantly higher than Recon-PL and Recon-TR failure loads, with similar stiffness to all other groups. CONCLUSION: Repair-IB and Recon-PL of the LUCL showed increased rotational stiffness relative to the intact elbow for restoring posterolateral stability to the native state in a cadaveric model. Recon-TR demonstrated lower residual peak torques but provided near-native rotational stiffness. CLINICAL RELEVANCE: Internal bracing of LUCL repair may reduce suture-tearing effects through tissue and provide sufficient stabilization for healing throughout accelerated and reliable recovery without the need for a tendon graft.

Curing profile and marginal gap formation using a liner containing long-wavelength-absorbing photoinitiator: an in vitro study.

The aim was to evaluate the marginal-gap formation and curing profile of a new restorative technique using a liner with long-wavelength-absorbing photoinitiator (LWAP). Box-shaped preparations (6 mm × 4 mm × 4 mm) were made in third molars. All samples were treated with Clearfill SE Bond and divided into 4 groups (n = 5), according to restorative technique used: (1) incremental technique (INC-Technique); (2) camphorquinone-based liner (CQ-Liner) + bulk-fill resin composite; (3) LWAP-based liner (LWAP-Liner) + bulk-fill resin composite; and (4) bulk-fill technique without liner (BF-Technique). The marginal gaps (%) for all the samples were measured using micro-computed tomography. The restorations were cross-sectioned, and the degree of conversion (DC) and Knoop microhardness were evaluated at different depths (0.3, 1, 2, 3, and 4 mm). INC-Technique, CQ-Liner, and LWAP-Liner groups showed significantly fewer marginal gaps than those from the BF-Technique group. The BF-Technique specimens had the lowest DC and microhardness in depth. All the other techniques presented similar degree of conversion and microhardness at all the depths. The use of liners, regardless of the photoinitiator system, decreased the marginal-gap formation and improved the curing profile of bulk-filling restoration technique.

Influence of Matrix Type on Marginal Gap Formation of Deep Class II Bulk-Fill Composite Restorations.

Background: To test the hypothesis that transparent matrices result in more continuous margins of bulk-fill composite (BFC) restorations than metal matrices. Methods: Forty standardized MOD cavities in human molars with cervical margins in enamel and dentin were created and randomly assigned to four restorative treatment protocols: conventional nanohybrid composite (NANO) restoration (Tetric EvoCeram, Ivoclar Vivadent, Schaan, Liechtenstein) with a metal matrix (NANO-METAL) versus transparent matrix (NANO-TRANS), and bulk-fill composite restoration (Tetric EvoCeram Bulk Fill, Ivoclar Vivadent, Schaan, Liechtenstein) with a metal matrix (BFC-METAL) versus transparent matrix (BFC-TRANS). After artificial aging (2500 thermal cycles), marginal quality was evaluated by scanning electron microscopy using the replica technique. Statistical analyses were performed using the Mann−Whitney U-test and Wilcoxon test. The level of significance was p < 0.05. Results: Metal matrices yielded significantly (p = 0.0011) more continuous margins (46.211%) than transparent matrices (27.073%). Differences in continuous margins between NANO (34.482%) and BFC (38.802%) were not significant (p = 0.56). Matrix type did not influence marginal gap formation in BFC (p = 0.27) but did in NANO restorations (p = 0.001). Conclusion: Metal matrices positively influence the marginal quality of class II composite restorations, especially in deep cavity areas. The bulk-fill composite seems to be less sensitive to the influence of factors such as light polymerization and matrix type.

OCT Evaluation of Marginal and Internal Interface Integrity of Class V Composite Restorations after 36 to 48 Months.

PURPOSE: To compare a self-etch and a two-step etch-and-rinse adhesive in terms of internal and marginal composite-tooth bond failure separately on enamel and dentin/cement at 36-48 months after restoration placement using optical coherence tomography (OCT). MATERIALS AND METHODS: Twenty-seven patients with two or three class V composite restorations of noncarious cervical lesions 36-48 months after placement were included. The one-step self-etch adhesive Futurabond M ([Voco] group SE, n = 25) and the two-step etch-and-rinse adhesive Solobond M ([Voco] group ER, n = 20) combined with the nanohybrid composite Amaris (Voco) were evaluated. The four-step etch-and-rinse adhesive Syntac classic combined with Tetric EvoCeram (Ivoclar Vivadent) served as the control (n = 18). Spectral-domain OCT (SD-OCT, 1310-nm center wavelength) was applied. Marginal gaps and internal interfacial adhesive defects were quantified in cross-sectional OCT images. Groups were statistically compared using the Friedman/Wilcoxon test (α = 0.05). RESULTS: In enamel, nonsignificantly different percentages of marginal gap formation and internal interfacial adhesive defects were found between the groups (pi ≥ 0.258). In dentin/cement, SE showed significantly less marginal gap formation compared to ER (p < 0.001) and control (p = 0.001), and at the internal dentin-composite interface less adhesive defects were found compared to ER (p < 0.001) and control (p = 0.003). CONCLUSION: The self-etch adhesive used in the current study appears recommendable for restoration of noncarious cervical lesions with composite.

The effect of composite placement technique on the internal adaptation, gap formation and microshear bond strength.

Purpose: This study aimed to compare the efficiency of placement technique on internal adaptation, gap formation and microshear bond strength (SBS) of bulk-fill composite resin materials. Materials and methods: Standardized class V cavities were prepared for microcomputed tomography (mCT) test and divided into four groups (n=12) as follows: Group SDR: Smart Dentin Replacement system/bulk fill; Group SF2: Sonic-Fill system/bulk fill sonic-activated composite placement system; Group CHU: Herculite-XRV-Ultra composite resin inserted with Compothixo/sonic-vibrated composite resin placement system; Group HIT: Herculite-XRV-Ultra composite resin applied with incremental technique. Self-etch adhesive (Optibond-XTR) was used for bonding in all groups. After 10000 thermocycling, mCT scans were taken to reveal gap formation at the toothrestoration interface and universal testing machine was used to test microshear bond strength SBS values (n=10). ANOVA, post-hoc Bonferroni and Tukey HSD tests were used for evaluating the gap formation and SBS values p=0.05. Results: SF2 and CHU showed the best adaptability compared with both SDR and HIT. The difference between groups SDR and HIT was statistically significant (p<0.05).SBS values were found to be the highest for SF2, and the lowest for HIT groups (p>0.05). Conclusion: Bulk-fill composite resins placed either with sonic-activated or sonic-vibrated instrument demonstrated better adaptability, less gap formation and higher bond strength than both the bulk-fill flowable composite and conventional incremental techniques.

Can a New HEMA-free Two-step Self-etch Adhesive Improve Dentin Bonding Durability and Marginal Adaptation?

PURPOSE: A new two-step self-etch adhesive (2-SEA) free of hydrophilic monomers was evaluated. Its microtensile bond strength (µTBS) to dentin under various aging conditions, interfacial gap formation, water sorption/solubility, and formation of an acid-base resistant zone (ABRZ) were evaluated and compared with a gold-standard 2-SEA. MATERIALS AND METHODS: The new 2-SEA G2-Bond Universal (G2; GC) was compared to Clearfil SE Bond 2 (CSE2, Kuraray Noritake). Their µTBS to sound coronal dentin was tested after 1 week, 10,000 thermal cycles (TC), 20,000 TC, 6 months and 1 year. Failure mode was determined using scanning electron microscopy (SEM). Gap formation at the interface of 2-mm deep tapered cavities with an enamel border was observed using swept-source optical coherence tomography after 1 day, 1 week, 10,000 TC, and 20,000 TC. In addition, water sorption and solubility of the bonding agents was measured, and ABRZ formation was evaluated using SEM. RESULTS: There was no significant difference in µTBS between G2 and CSE2 (p > 0.05), and the aging conditions had no significant effect on µTBS (p > 0.05). In all groups, cohesive failures prevailed (55%-95%). Interfacial gap formation was initially similar for both adhesives (p > 0.05), but G2 exhibited a significantly lower gap formation than CSE2 after TC (p < 0.05). The water sorption of G2 was significantly lower compared to CSE2 (p < 0.05), and their solubility was statistically similar (p > 0.05). ABRZ of similar thickness was observed with both adhesives. CONCLUSION: The new 2-SEA exhibited stable dentin bonding and increased hydrophobicity resulting from the absence of hydrophilic monomers.

The impact of transverse components on resistance and ultimate strength of 6-strand tendon repairs.

We assessed the effects of tendon core sutures' transverse components on the tensile resistance of two commonly used 6-strand tendon repairs. Tang and Yoshizu #1 repairs (6-strand) were tested and compared with 4-strand rectangular and double Kessler sutures (4-strand). A total of 40 pig flexor tendons were tested under cyclic loading. We recorded the number of tendons that formed a 2-mm gap between two tendon ends during 20 cycles of cyclic loading test, stiffness at the 1st and 20th loading cycle, and gap distance at the repair site and the ultimate repair strength at the 20th cycles. We found that the Yoshizu #1 repairs were more prone to form gaps and their ultimate strength was significantly lower than that of the Tang repair. The transverse components in a 6-strand repair affect gap formation and failure strength.

Evaluation of low-viscosity bulk-fill composites regarding marginal and internal adaptation.

This study aimed at evaluating the marginal and internal adaptation of low-viscosity bulk-fill composites to enamel and dentin using a self-etch or an etch-and-rinse adhesive without and with artificial ageing. Hundred and twenty-eight MOD cavities in extracted molars were assigned to eight groups (n = 16), restored with the adhesives OptiBond FL (OFL) or Xeno V+ (X) and two low-viscosity bulk-fill composites SDR or x-tra base, covered with Premise. Tetric EvoCeram Bulk Fill and Premise served as a control. n = 8 per group were subjected to prolonged water storage (180 days) and thermocycling (2500×). Scanning electron microscopy was used to determine marginal gaps (MG) and interfacial adhesive defects (IAD). There were no significant differences between composite types in 44 out of 48 (MG) or 43/48 (IAD) comparisons. More MG were observed with X than with OFL (14 out of 16 comparisons, two significant), while in 16 of 16 comparisons with X more IAD were observed (14 significant). After artificial ageing, MG generally increased (9/16 significant), compared to IAD (one significant). The performance of the investigated composite types concerning the integrity of the tooth-composites interface was comparable. Compared to the 1-step self-etch system, the bond with the 3-step etch-and-rinse adhesive was raised.

Permeability of the Endothelial Barrier: Identifying and Reconciling Controversies.

Leakage from blood vessels into tissues is governed by mechanisms that control endothelial barrier function to maintain homeostasis. Dysregulated endothelial permeability contributes to many conditions and can influence disease morbidity and treatment. Diverse approaches used to study endothelial permeability have yielded a wealth of valuable insights. Yet, ongoing questions, technical challenges, and unresolved controversies relating to the mechanisms and relative contributions of barrier regulation, transendothelial sieving, and transport of fluid, solutes, and particulates complicate interpretations in the context of vascular physiology and pathophysiology. Here, we describe recent in vivo findings and other advances in understanding endothelial barrier function with the goal of identifying and reconciling controversies over cellular and molecular processes that regulate the vascular barrier in health and disease.

Tailored ablation index for pulmonary vein isolation according to wall thickness within the ablation circle.

BACKGROUND: Ablation index (AI), a novel lesion quality marker, includes contact force, time, and power of radiofrequency (RF) application, but not regional variation in wall thickness within the wide antral catheter ablation (WACA) circle. This study explored the relationships among AI target value, atrial wall thickness, and gap formation within the WACA circle in patients with paroxysmal atrial fibrillation (PAF). METHODS: We evaluated 102 consecutive patients (mean age, 65 ± 9 years) with PAF who underwent AI-guided WACA for ipsilateral pulmonary vein isolation (PVI). Each WACA circle was subdivided into eight segments, and overall 7143 RF applications were delivered, including 125 gaps in PVI ablation lines. For each RF tag within the ablation circle, we collected data on ablation lesion depth surrogates (time of application, delivery power, impedance drop, average contact force, force-time integral [FTI], and AI) and left atrial wall thickness measured by multidetector computer tomography scanning. RESULTS: The anterior and roof walls were the thickest segments of the ablation circle, in which 85.8% of gaps concentrated, while the posterior and inferior walls were the thinnest. Gap formation was significantly associated with FTI, AI, wall thickness, FTI/wall thickness, and AI/wall thickness. AI/wall thickness had the highest predictive value for gap formation, with a cutoff of 195.6 au/mm for effective ablation. CONCLUSIONS: In AI-guided PVI of PAF, AI/wall thickness by normalizing myocardial thickness variation along the WACA circle was a strong predictor of gap formation, with a target of 195.6 au/mm appearing suitable for effective ablation.

Evaluation of internal adaptation of flowable and bulk-fill resin-based composites

@#This study aimed to evaluate and compare the internal adaptation of bulk-fill resin-based composite restorative materials with flowable composites as lining materials using self-etch adhesive system. Class I cavities (2mmx4mm) were prepared on flattened occlusal surfaces of fifty extracted human premolars and randomly assigned into five groups (n=10) according to the materials used: Beautifil Bulk-fill Restorative (BR); Beautifil Bulk-fill Flowable (BF); Beautifil Flow Flowable F10 (BF10); and Self-etch adhesive (SEA). Group A: SEA+BR; Group B: SEA+BF10+BR; Group C: SEA+BF+BR; Group D: SEA+BF10+SEA+BR and Group E: SEA+BF+SEA+BR. The samples were thermocycled for 500 cycles, then sectioned mesiodistally, polished and pre-treated prior to scanning electron microscopy (SEM) evaluation. From SEM images, measurement of adhesive and cohesive adaptation failures was recorded at multiple sites of the pulpal floor and in between materials. Data were analysed using one-way ANOVA and post-hoc Tukey tests (p<0.05). Cohesive failure in SEA was observed at the pulpal floor with the lowest percentage in Group A (5.14%), and highest in Group C and E (>16%). However, there were no significant difference among all groups. Adhesive failure was seen at the pulpal floor between SEA+BF/BF10/BR and between SEA+dentine with the highest percentage of gaps formed in Group A between SEA+dentine (6.62%) and SEA+BR (5.30%). Nonetheless, no significant differences were observed among all groups with p=0.89 and p=0.70, respectively. With the use of BF/BF10 at the pulpal floor, adhesive failure was reduced but resulted in increased of cohesive failure. However, both adaptation failures were absent between materials (BF/BF10 and BR) regardless with or without application of SEA.

Biomechanical Functional Elbow Restoration of Acute Ulnar Collateral Ligament Tears: The Role of Internal Bracing on Gap Formation and Repair Stabilization.

BACKGROUND: Biomechanical studies have compared augmented primary repair with internal bracing versus reconstruction techniques of the anterior ulnar collateral ligament (aUCL) in the elbow. However, aUCL repair alone has not been compared with augmented repair or reconstruction techniques. HYPOTHESIS: Internal bracing of aUCL repair provides improved time-zero stabilization in terms of gap formation, torsional stiffness, and residual torque compared with both repair alone and the modified docking technique, with enhanced valgus stability restoration to that of the native ligament. STUDY DESIGN: Controlled laboratory study. METHODS: We randomized 8 matched pairs of cadaveric elbows to undergo either augmented aUCL repair or a modified docking technique through use of the palmaris longus tendon. Valgus laxity testing was consecutively performed at 90° of flexion on the intact, torn, and repaired conditions as well as the previously assigned techniques. First, intact elbows were loaded up to 10 N·m valgus torque to evaluate time-zero ligament rotations at valgus moments of 2.5, 5.0, 7.5, and 10 N·m. Rotation controlled cycling was performed (total 1000 cycles) for each surgical condition. Gap formation, stiffness, and residual torque were analyzed. Finally, these elbows and 8 additional intact elbows underwent torque to failure testing (30 deg/min). RESULTS: Repair alone revealed low torsional resistance and gapping, similar to the torn state. The augmented repair technique showed significantly higher torsional stiffness (P < .001) and residual torque (P < .001) compared with all other conditions and restored native function. Although reconstruction revealed similar initial stiffness and residual torque compared with an intact ligament, a steady decrease of torsional resistance led to a completely loose state at higher valgus rotations. Analysis of covariance between all groups showed significantly less gap formation for augmented repair (P < .001). The native failure load and stiffness were significantly higher and were similar to those of augmented repair (P = .766). CONCLUSION: Internal bracing of aUCL repair restored valgus stability to the native state with statistically improved torsional resistance, loading capability, and gap formation compared with reconstruction, especially at the upper load range of native aUCL function in the elbow. CLINICAL RELEVANCE: We found that aUCL repair with an internal brace effectively improves time-zero mechanical characteristics and may provide stabilized healing with accelerated and reliable recovery without the need for a tendon graft.

Treatment of Acute Proximal Anterior Cruciate Ligament Tears-Part 1: Gap Formation and Stabilization Potential of Repair Techniques.

BACKGROUND: Recently, there has been a resurgence of interest in primary repair of the anterior cruciate ligament (ACL), with fixation techniques evolving. However, to date, there have been no biomechanical studies comparing fixed to adjustable fixation repair techniques. HYPOTHESIS: Adjustable ACL repair provides for improved stabilization compared with fixed techniques with respect to both gap formation and residual load-bearing capability. STUDY DESIGN: Controlled laboratory study. METHODS: A total of 4 different ACL repair techniques (n = 5 per group), including single- and double-cinch loop (CL) cortical button fixation as well as knotless single-suture anchor fixation, were tested using a porcine model. For adjustable single-CL loop fixation, additional preconditioning (10 cycles at 0.5 Hz) was performed. The force after fixation and the actuator displacement to achieve a time-zero preload of 10 N were measured for fixed techniques. Incrementally increasing cycling (1 mm/500 cycles) from 1 to 8 mm was performed for 4000 cycles at 0.75 Hz before pull to failure (50 mm/min). The final residual peak load and gap formation for each test block were analyzed as well as ultimate strength. RESULTS: Knot tying of a single-CL over a button (mean ± SD, 0.66 ± 0.23 mm) and knotless anchor fixation (0.20 ± 0.12 mm) resulted in significant time-zero gaps (P < .001) and significantly higher overall gap formation at reduced residual loading (analysis of covariance, P < .001) compared with both the double-CL loop and adjustable fixation techniques. The adjustable group showed the highest failure load and stiffness, at 305.7 N and 117.1 N/mm, respectively. The failure load of the knotted single-CL group was significantly reduced compared with all other groups (P < .001). CONCLUSION: Adjustable single-CL cortical button fixation with intraoperative preconditioning optimized time-zero ACL tension and led to significantly improved stabilization and reduced gap formation, with the highest ultimate strength. Single-CL loop knot tying over the button and knotless anchor fixation resulted in time-zero gaps to achieve slight tension on the ACL and significantly higher gap formation at reduced load-bearing capability. CLINICAL RELEVANCE: Although the clinical relevance of gap formation is uncertain, a biomechanical understanding of the stabilization potential of current ACL repair techniques is pertinent to the continued evolution of surgical approaches to enable better clinical outcomes.

Treatment of Acute Proximal Anterior Cruciate Ligament Tears-Part 2: The Role of Internal Bracing on Gap Formation and Stabilization of Repair Techniques.

BACKGROUND: The latest biomechanical studies on some form of internal bracing have shown improved stabilization for anterior cruciate ligament (ACL) repair, but gap formation and load-sharing function have not yet been reported. HYPOTHESIS: Internal bracing of an adjustable ACL repair construct provides improved stabilization with reduced gap formation and higher residual loading on the ACL. STUDY DESIGN: Controlled laboratory study. METHODS: Internally braced ACL repair constructs with single- and double-cinch loop (CL) cortical buttons, a knotless suture anchor, and a single-CL cortical button with adjustable loop fixation (CLS-ALD) were tested (n = 20 each) in a porcine model at 4 different loads (n = 5 each) over 4000 cycles at 0.75 Hz (n = 80 total). The CLS-ALD technique allowed for additional preconditioning (10 cycles at 0.5 Hz). Test results of the isolated internal brace groups served as a baseline for comparison. Lastly, specimens were pulled to failure (50 mm/min) with a cut internal brace. Final loading and gap formation on the ACL repair construct as well as ultimate strength were analyzed. RESULTS: A statistical significance for peak loads over peak elongation was found between the CLS-ALD and all other reinforced groups (analysis of covariance, P < .001). Accordingly, the adjustable repair technique showed improved load-bearing capability with the internal brace compared with all other fixed repair groups and revealed significantly higher loads than the knotted single-CL group. Also, significantly reduced gap formation was found for the CLS-ALD compared with all other groups (P < .001), with no gap formation up to 150 N with a final gap of 0.85 ± 0.31 mm at 350 N. A significantly higher ultimate failure load (866.2 ± 104.0 N; P < .001) was found for the button-fixed internal brace group compared with all other groups. CONCLUSION: Internal bracing had a crucial role in improving the stabilization potential of ACL repair at loads occurring during normal daily activity. The added strength of the internal brace allowed for reducing peak loads on the ACL repair construct as well as restricting gap formation to below 3 mm at loads up to 350 N. CLINICAL RELEVANCE: Improvements in the mechanical characteristics of current ACL repair techniques that enable reduced gap formation and allow for early range of motion and accelerated rehabilitation may strengthen the self-healing response with the formation of stable scar tissue.

Effects of a Q Suture Technique on Resistance to Gap Formation and Tensile Strength of Repaired Tendons: An Ex Vivo Mechanical Study.

PURPOSE: The repair of digital flexor tendons following laceration should aim to prevent gapping at the repair site and restore the tensile strength of the tendons to facilitate postoperative movement. We present here a simple Q suture and test its effects on gap formation and tensile strength of the repaired tendons. METHODS: Sixty porcine tendons were repaired with 3 2-strand sutures (Kessler, Kessler plus 2Q, and Kessler plus running sutures) and 3 4-strand sutures (double Kessler, double Kessler plus 2Q, and double Kessler plus running sutures). The specimens were subjected to a cyclic loading. At each cycle, the number of tendons that initiated gapping or formed a 2-mm gap at the repair site was determined. After the cyclic load testing, the gap distance between tendon ends and the ultimate strength of the repaired tendons was measured. RESULTS: In both 2-strand and 4-strand tendon repairs, augmentation by insertion of the 2Q sutures reduced the number of tendons that showed 2-mm gaps ends during loading. Compared with the single Kessler and Kessler plus running sutures, Kessler plus 2Q suture significantly increased the ultimate strength of the tendon repair. Compared with the double Kessler and double Kessler plus running sutures, double Kessler plus 2Q suture significantly decreased the gap distance at the repair site after cyclic loading. CONCLUSIONS: The Q suture technique effectively enhances the resistance to gap formation of 2-strand and 4-stand tendon repair. It also improves the tensile strength of 2-strand Kessler repairs. CLINICAL RELEVANCE: The Q suture is a simple technique that can resist gap formation and strengthen the tensile strength of the repaired tendons in the laboratory setting.