Fixation technique of biodegradable magnesium alloy suture anchor in the rotator cuff repair of the shoulder in a goat model: a technical note.

BACKGROUND: Shoulder disorders, particularly rotator cuff tears, are prevalent musculoskeletal conditions related to aging. Although the widely used suture anchor technique provides strong mechanical support to the tendon, it is associated with a risk of postoperative tendon retearing. The conventionally used titanium alloys can affect the interpretation of magnetic resonance imaging. Degradable magnesium alloys possess excellent biocompatibility, similar mechanical property to the bone, and stimulating bone formation ability from Mg2+. The purpose of this experiment was to develop innovative magnesium-based suture anchors to enhance rotator cuff repair by improving fixation materials, and to evaluate their feasibility in a goat model. METHODS: We developed fluoridized ZK60 suture anchors as the implantation material for two goats, who underwent rotator cuff repair surgery on both shoulders. Computed tomography (CT) and histological analysis were performed at 12 weeks postoperatively, and the results were compared between the magnesium and titanium alloy groups. Additionally, a hematological examination was conducted, which included assessments of red blood cells, white blood cells, platelets, coagulation function, liver function, kidney function, and magnesium ion concentration. RESULTS: The 12-week postoperative CT images showed intact MgF2 ZK60 suture anchors, effectively reconnecting the infraspinatus tendon to the humeral head. The anchors became less visible on CT scans, indicating absorption by surrounding tissues. New bone formation in the MgF2 group surpassed that in the Ti group, demonstrating superior osseointegration. The similarity between cortical bone and magnesium reduced stress-shielding and promoted bone regeneration. Histological analysis revealed successful tendon healing with MgF2 anchors, while the Ti group showed discontinuous interfaces and reduced collagen secretion. Hematological examination showed stable liver, renal function, and magnesium ion levels. CONCLUSIONS: The findings indicate that MgF2-coated suture anchors are feasible for rotator cuff repair and potentially other orthopedic applications. We hope that magnesium alloy anchors can become the solution for rotator cuff tendon repair surgery.

Biomechanical comparison between various screw fixation angles for Latarjet procedure: a cadaveric biomechanical study.

BACKGROUND: The Latarjet procedure is a reliable treatment for the management of anterior glenohumeral instability with glenoid bone loss. However, the biomechanical properties of different fixation angles between screw and glenoid surface (α angle) have rarely been studied. The aim of the study was to investigate and compare the fixation stability, failure load, and failure mechanism between different α angles for Latarjet procedures, which were performed on cadaver specimens. METHODS: Twenty-four shoulder specimens (8 in each of 3 groups) were dissected free of all soft tissue, and a 25% glenoid defect was created. The coracoid process was osteomized and fixed with 2 screws at 3 different α angles: 0° (group A), 15° (group B), and 30° (group C). Specimens were mounted to a testing apparatus, and cyclic loading (100 cycles at 1 Hz) was applied with a staircase protocol (50, 100, 150, and 200 N). Gross graft displacement and interface displacement were measured. The ultimate failure loads and failure mechanisms were recorded. RESULTS: There was no significant difference in gross displacement under any cyclic load between 3 groups. However, a significant larger interface displacement was noted in group C than in group A in 150-N cyclic loading (P = .017). Under failure strength testing, all 24 specimens failed because of screw cutout from the glenoid, and the ultimate failure load was similar among the three groups. CONCLUSION: Compared with the 0° α angle, the displacement after cyclic loading did not significantly increase when the α angle was increased to 15° but significantly increased at 30° for Latarjet procedures, which were performed on cadaver specimens. The results suggest that surgeons should apply the screws as parallel as possible to the glenoid surface when performing the Latarjet procedure. Although mild deviation may not reduce fixation stability, α angles greater than 30° should be avoided.

Does posterior configuration have similar strength as parallel configuration for treating comminuted distal humerus fractures? A cadaveric biomechanical study.

BACKGROUND: The posterior plating technique could be used as a clinical alternative to parallel plating for treating comminuted distal humerus fractures (DHFs) successfully with good clinical results. However, the biomechanical characteristics for posterior fixation are still unclear. The purpose of this study is to evaluate the biomechanical properties of the posterior fixation and to make comparisons between the parallel and the posterior fixation systems. MATERIALS AND METHODS: We performed a cadaveric biomechanical testing with two posterior plating systems (a posterior two plating and a single posterior pre-contoured Y plating system) and one parallel two plating system to treat AO/OTA type-C2.3 DHFs. Among three groups, we compared construct stiffness, failure strength, and intercondylar width changes after 5000-cycle fatigue loading and failure loads and failure modes after destructive tests in both the axial compression and (sagittal) posterior bending directions. The correlations between construct failure loads and bone marrow density (BMD) were also compared. RESULTS: In axial direction, there were no significant differences in the stiffness and failure load between the posterior and the parallel constructs. However, in sagittal direction, the two-plate groups (posterior two plating and parallel plating group) had significant higher stiffness and failure loads than the one-plate group (single posterior Y plating). There was no fixation failure after 5000-cyclic loading in both directions for all groups. Positive correlation was noted between BMD and failure loads on parallel fixation. CONCLUSIONS: We found that when using two plates for treating comminuted DHFs, there were no significant differences in terms of most biomechanical measurements between posterior and parallel fixation. However, the single pre-contoured posterior Y plate construct was biomechanically weaker in the sagittal plane than the parallel and the posterior two-plate constructs, although there was no fixation failure after the fatigue test for all groups regardless of the fixation methods. LEVEL OF EVIDENCE: Biomechanical study.

Modified Superior Capsule Reconstruction Using the Long Head of the Biceps Tendon as Reinforcement to Rotator Cuff Repair Lowers Retear Rate in Large to Massive Reparable Rotator Cuff Tears.

PURPOSE: To retrospectively assess the clinical outcomes of the patients with large to massive reparable RCTs treated by arthroscopic rotator cuff repair (ARCR) combined with modified superior capsule reconstruction (mSCR) using the long head of biceps tendon (LHBT) as reinforcement with a minimum of 2 years of follow-up. METHODS: We retrospectively evaluated 40 patients with large to massive reparable RCTs who underwent ARCR and mSCR (group I) between February 2017 and June 2018 (18 patients) or underwent ARCR and tenotomy of LHBT performed at the insertion site (group II) between January 2015 and January 2017 (22 patients). The pain visual analog score (VAS) was assessed preoperatively and 1, 3, 6, 12, 24 months postoperatively. American Shoulder and Elbow Surgeons (ASES) scores, the University of California, Los Angeles (UCLA) shoulder rating scale, and active range of motion (AROM) were assessed before surgery and 6, 12, and 24 months after surgery. The integrity of the rotator cuff and mSCR was evaluated using magnetic resonance images at 12 months postoperatively. RESULTS: After surgery, both groups had significantly improved in VAS, ASES, UCLA and AROM scores in the final follow-up. There were no significant between-group differences in the characteristics of the patients before surgery. Group I had improved pain relief at 1 month (P < .001) and at 3 months (P < .01) after surgery. For the AROM, group I (flexion, external rotation, internal rotation) demonstrated better improvement than group II 6 months after surgery (all P < .05) and better internal rotation 12 and 24 months after surgery (all P < .05). The mSCR survival rate was 94.4% (17/18). The retear rate of repaired rotator cuffs for groups I and II was 16.7% (3/18) and 40.9% (9/22), respectively, and the differences were significant (P < .046). CONCLUSIONS: ARCR combined with mSCR using LHBT as reinforcement may lead to a lower retear rate and earlier functional recovery than conventional ARCR with tenotomy of LHBT for large to massive reparable RCTs. LEVEL OF EVIDENCE: Level III, retrospective therapeutic comparative trial.

Using Interconnected Knotless Anchor for Suprapectoral Biceps Tenodesis Could Offer Improved Biomechanical Properties in a Cadaveric Model.

PURPOSE: To compare the biomechanical characteristics of the interconnected knotless anchor (IKA) fixation with the double knotless anchor (DKA) and interference screw (IS) fixation in the suprapectoral biceps tenodesis. METHODS: In total, 24 fresh-frozen human cadaveric shoulders (mean age, 67.3 ± 6 years) were used for the study. All the specimens were randomly divided into 3 experimental biceps tenodesis groups (n = 8): IKA, DKA, and IS. After tenodesis, each specimen was preloaded at 5 N for 2 minutes, followed by a cyclic loading test from 5 to 70 N for 500 load cycles. Finally, a destructive axial load to failure test (1 mm/s) was performed. All the values, including ultimate failure load, stiffness, cyclic displacement, and mode of failure were evaluated. RESULTS: The IKA provided the highest construct stiffness (38.9 ± 7.7 N/mm) and ultimate failure load (288.3 ± 47.6 N), the results for which were statistically better than the corresponding results in the IS and DKA groups. In terms of cyclic displacement, there were no statistical differences among the 3 fixation constructs. The most common failure mode was biceps tendon tearing in IS group (7/8) and IKA group (8/8). In the contrast, suture slippage accounted for the most common failure mode in DKA. CONCLUSIONS: In suprapectoral bicep tenodesis, IKA fixation appears to offer improved construct stiffness and ultimate failure load while maintaining comparable suture slippage as compared with IS fixation or DKA fixation in the current biomechanical study. CLINICAL RELEVANCE: The IKA fixation compares favorably with other techniques and could be an alternative clinical option for suprapectoral biceps tenodesis.

The Double Krackow Suture Technique Does Not Offer a Significant Benefit Compared to the Krackow Suture Technique in Subpectoral Biceps Tenodesis Using a Double-Loaded Suture Anchor.

PURPOSE: To compare the biomechanical properties of the double simple suture (DSS) technique, Krackow suture (KS) technique, and double Krackow suture (DKS) technique in subpectoral biceps tenodesis using a double-loaded suture anchor in a porcine tendon model. METHODS: A total of 30 artificial composite (polymer and glass fiber) humeri and porcine flexor profundus tendons with diameter of 4.5 mm were used. The sample size was determined based on the results of the pilot study. Metallic suture anchors with double-loaded No. 2 braided sutures were inserted at the subpectoral tenodesis site, 5 cm from the superomedial corner of the greater tuberosity. Three suture techniques were used to fix the tendons: a DSS used as the control, a KS, and a DKS, which is an alternative tendon graft fixation technique. A preload of 5 N was applied for 2 minutes, followed by cyclic loading for 500 cycles ranging from 5 to 70 N; next, a load-to-failure test at 1 mm/s was performed. RESULTS: The KS (283.5 ± 57 N) and DKS (270.4 ± 50 N) groups had significantly greater ultimate failure loads as compared with the DSS group (84.1 ± 6.4 N) (P < .001). Meanwhile, the peak displacement at failure loads in the KS group (9.3 ± 2.2 mm) and DKS group (7.8 ± 1.7 mm) were significantly smaller than that of the DSS group (11.3 ± 2.9 mm) (P = .015). Stiffness in the DSS group (36.4 ± 3.0 N/mm), KS group (39.6 ± 2.5 N/mm), and DKS group (36.9 ± 4.6 N/mm) was not significantly different (P = .125). All DSS constructs and 6 KS constructs failed with tendons being cut through by the sutures, whereas the other 4 KS constructs and all DKS constructs failed resulting from suture breakage. CONCLUSIONS: In this subpectoral biceps tenodesis model, both the KS technique and the DKS technique had similar time 0 biomechanical properties that were better than those of the double simple suture technique. CLINICAL RELEVANCE: A sturdy suture-tendon structure could prevent clinical failure of a subpectoral biceps tenodesis using a suture anchor.

Intravenous Administration of Tranexamic Acid Significantly Improved Clarity of the Visual Field in Arthroscopic Shoulder Surgery. A Prospective, Double-Blind, and Randomized Controlled Trial.

PURPOSE: To determine whether intravenous administration of tranexamic acid (TXA) before shoulder arthroscopic rotator cuff repair surgery can improve arthroscopy visual clarity. METHODS: This was a prospective, double-blind, randomized, and placebo-controlled study. From May 2016 to April 2018, patients requiring arthroscopic rotator cuff repair were enrolled and randomly assigned to either the TXA group. receiving 1000 mg of TXA intravenously 10 minutes before surgery. or the placebo group. receiving the same volume of plain saline. Patients with pre-existing liver/renal disease, coagulopathy, or concurrent use of anticoagulation medications were excluded. Visual clarity was rated using a Numeric Rating Scale from grade 1 (poor) to grade 3 (clear) every 15 minutes throughout the surgery. Secondary outcomes included estimated perioperative blood loss, operative time, degree of shoulder swelling, postoperative subjective pain score, inpatient duration, and associated comorbidities were recorded. Both parametric and nonparametric methods were used for the statistical analysis. RESULTS: In total, 72 patients were enrolled, 37 in the TXA group and 35 in the placebo group. The demographic data were similar between the 2 groups. Visual clarity was found to be significantly better in the TXA group, with a greater percentage of grade 3 vision clarity (53.7 ± 18.9 % vs 40.5 ± 22.1%, P = .036). The average visual score in the TXA group (2.5 ± 0.2) also was better than that of the control group (2.3 ± 0.3) (P = .048). The postoperative subjective pain score was significantly lower in the TXA group (3.0 ± 1.5) than in the control group (4.3 ± 2.0) (P = .009). In addition, postoperative analgesic usage was significant lower in the TXA groups (9.6 ± 9.7 morphine milligram equivalent) than in the control group (14.7 ± 13.4 morphine milligram equivalent) (P = .037). Other parameters, such as operative time, estimated perioperative blood loss, degree of shoulder swelling, and duration of inpatient stay were similar between the 2 groups. None of the patients developed complications after surgery. CONCLUSIONS: Intravenous administration of TXA is an alternative way to improve visual clarity in arthroscopic shoulder surgery. It also reduces subjective pain and analgesic consumption in the early postoperative period without significant side effects. LEVEL OF EVIDENCE: Therapeutic studies level II.

Different suture anchor fixation techniques affect contact properties in humeral greater tuberosity fracture: a biomechanical study.

BACKGROUND: Suture anchor-based fixations of humeral greater tuberosity (GT) fractures have yielded good outcomes in both clinical and biomechanical studies. Be that as it may, the interface contact properties of these fixations have yet to be elaborated. In response, the contact characteristics of two double-row suture anchor fixations for the management of GT fracture were compared. METHODS: Two suture anchor-based fixation techniques, namely the Double-Row Suture Anchor Fixation (DR) and Suture-Bridge Technique (SB), were used to repair humeral GT fractures in 12 fresh-frozen human cadaveric shoulders. A Tekscan pressure sensor placed between the repaired tuberosity and humerus recorded continuous data points directly after repair and for 60 min at set time intervals. The constructs were then cyclically loaded until 100 N, and the shoulders tested at 0°, 30°, and 60° of abduction. Under an applied force, the contact pressure and contact area of the interface were determined. RESULTS: Although both fixation configurations showed decreased contact pressure and area over time, the SB group had higher contact pressure right after fixation and at all time points thereafter. In contrast, the DR group demonstrated significantly more contact pressure and area at each abduction position with the applied load. Nevertheless, contact pressure and area decreased in response to increasing abduction position for both fixation constructs. CONCLUSION: Findings suggest that despite the SB construct having superior interface contact immediately after fixation, the DR construct offered better contact performance at all abduction angles with applied force. LEVEL OF EVIDENCE: Basic Science, Biomechanics.

Intra-articular Injection of Platelet-Rich Plasma Is Superior to Hyaluronic Acid or Saline Solution in the Treatment of Mild to Moderate Knee Osteoarthritis: A Randomized, Double-Blind, Triple-Parallel, Placebo-Controlled Clinical Trial.

PURPOSE: To prospectively compare the efficacy of intra-articular injections of platelet-rich plasma (PRP) and hyaluronic acid (HA) with a sham control group (normal saline solution [NS]) for knee osteoarthritis in a randomized, dose-controlled, placebo-controlled, double-blind, triple-parallel clinical trial. METHODS: A total of 87 osteoarthritic knees (53 patients) were randomly assigned to 1 of 3 groups receiving 3 weekly injections of either leukocyte-poor PRP (31 knees), HA (29 knees), or NS (27 knees). The Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score and International Knee Documentation Committee (IKDC) subjective score were collected at baseline and at 1, 2, 6, and 12 months after treatment. Data were analyzed using generalized estimating equations. RESULTS: All 3 groups showed statistically significant improvements in both outcome measures at 1 month; however, only the PRP group sustained the significant improvement in both the WOMAC score (63.71 ± 20.67, increased by 21%) and IKDC score (49.93 ± 17.74, increased by 40%) at 12 months. For the intergroup comparison, except for the first month, there was a statistically significant difference between the PRP and NS groups in both scores throughout the study duration (regression coefficients of 8.72 [P = .0015], 7.94 [P = .0155], and 11.92 [P = .0014] at 2, 6, and 12 months, respectively, for WOMAC score, and 9.1 [P = .0001], 10.28 [P = .0002], and 13.97 [P < .0001], respectively, for IKDC score). There was no significant difference in both functional outcomes between the HA and NS groups at any time point. Only the PRP group reached the minimal clinically important difference in the WOMAC score at every evaluation (15%, 21%, 18%, and 21% at 1, 2, 6, and 12 months, respectively) and the minimal clinically important difference in the IKDC score at 6 months (improvement of 11.6). CONCLUSIONS: Intra-articular injections of leukocyte-poor PRP can provide clinically significant functional improvement for at least 1 year in patients with mild to moderate osteoarthritis of the knee. LEVEL OF EVIDENCE: Level I, randomized controlled single-center trial.

Continuous Passive Motion Promotes and Maintains Chondrogenesis in Autologous Endothelial Progenitor Cell-Loaded Porous PLGA Scaffolds during Osteochondral Defect Repair in a Rabbit Model.

Continuous passive motion (CPM) is widely used after total knee replacement. In this study, we investigated the effect of CPM combined with cell-based construct-transplantation in osteochondral tissue engineering. We created osteochondral defects (3 mm in diameter and 3 mm in depth) in the medial femoral condyle of 36 knees and randomized them into three groups: ED (empty defect), EPC/PLGA (endothelial progenitor cells (EPCs) seeded in the poly lactic-co-glycolic acid (PLGA) scaffold), or EPC/PLGA/CPM (EPC/PLGA scaffold complemented with CPM starting one day after transplantation). We investigated the effects of CPM and the EPC/PLGA constructs on tissue restoration in weight-bearing sites by histological observation and micro-computed tomography (micro-CT) evaluation 4 and 12 weeks after implantation. After CPM, the EPC/PLGA construct exhibited early osteochondral regeneration and prevention of subchondral bone overgrowth and cartilage degeneration. CPM did not alter the microenvironment created by the construct; it up-regulated the expression of the extracellular matrix components (glycosaminoglycan and collagen), down-regulated bone formation, and induced the biosynthesis of lubricin, which appeared in the EPC/PLGA/CPM group after 12 weeks. CPM can provide promoting signals during osteochondral tissue engineering and achieve a synergistic effect when combined with EPC/PLGA transplantation, so it should be considered a non-invasive treatment to be adopted in clinical practices.

Osteochondral Tissue Regeneration Using a Tyramine-Modified Bilayered PLGA Scaffold Combined with Articular Chondrocytes in a Porcine Model.

Repairing damaged articular cartilage is challenging due to the limited regenerative capacity of hyaline cartilage. In this study, we fabricated a bilayered poly (lactic-co-glycolic acid) (PLGA) scaffold with small (200⁻300 µm) and large (200⁻500 µm) pores by salt leaching to stimulate chondrocyte differentiation, cartilage formation, and endochondral ossification. The scaffold surface was treated with tyramine to promote scaffold integration into native tissue. Porcine chondrocytes retained a round shape during differentiation when grown on the small pore size scaffold, and had a fibroblast-like morphology during transdifferentiation in the large pore size scaffold after five days of culture. Tyramine-treated scaffolds with mixed pore sizes seeded with chondrocytes were pressed into three-mm porcine osteochondral defects; tyramine treatment enhanced the adhesion of the small pore size scaffold to osteochondral tissue and increased glycosaminoglycan and collagen type II (Col II) contents, while reducing collagen type X (Col X) production in the cartilage layer. Col X content was higher for scaffolds with a large pore size, which was accompanied by the enhanced generation of subchondral bone. Thus, chondrocytes seeded in tyramine-treated bilayered scaffolds with small and large pores in the upper and lower parts, respectively, can promote osteochondral regeneration and integration for articular cartilage repair.

A Biomechanical Evaluation of Various Double Krackow Suture Techniques for Soft-Tissue Graft Fixation.

PURPOSE: The purpose of this study was to compare the biomechanical properties among the different double Krackow suture techniques for tendon graft fixation. METHODS: Thirty porcine flexor profundus tendons were randomly divided into 3 groups of 10 specimens each. Three different double Krackow suture techniques were evaluated, namely, the McKeon's double Krackow (MDK) suture, Wilson's double Krackow (WDK) suture, and Ostrander's modified Krackow (OMK) suture. All suture configurations were completed with a braided nonabsorbable suture. Each suture-tendon construct was pretensioned to 100 N for 3 cycles, cyclically loaded from 50 to 200 N for 200 cycles, and then finally loaded to failure. Elongation after cyclic loading, ultimate load to failure, and the mode of failure were recorded for each specimen. RESULTS: There were significant differences in elongation after cyclic loading among the MDK suture (7.9 ± 3.6 mm, 14% ± 6%), WDK suture (11.6 ± 2.2 mm, 22% ± 3%), and OMK suture (9.6 ± 3.3 mm, 17% ± 6%; P = .018). In addition, although the post hoc analysis showed that elongation after cyclic loading in the MDK suture was significantly less than the WDK suture (P = .004), ultimate failure load and cross-sectional area were not significantly different across the 3 groups. CONCLUSIONS: In this porcine in vitro biomechanical study, the MDK suture had significantly smaller elongation after cyclic loading than the WDK suture; however, high elongation values may have a potential for risk of clinical laxity. The ultimate failure load was not different across the MDK, WDK, and OMK sutures. CLINICAL RELEVANCE: Smaller elongation during cyclic loading in a suture-tendon construct represents a lower possibility of tendon graft loosening after ligament reconstruction surgery. The double Krackow suture techniques are attractive options for tendon graft fixation in ligament reconstruction, and the MDK suture could possibly be the optimal choice among the double Krackow suture techniques.

Biomechanical Evaluation of a Transtendinous All-Suture Anchor Technique Versus Interference Screw Technique for Suprapectoral Biceps Tenodesis in a Cadaveric Model.

PURPOSE: To compare the biomechanical properties of an transtendinous all-suture anchor technique with the commonly-accepted interference screw technique in a cadaveric model. METHODS: Sixteen fresh-frozen human cadaveric shoulders (mean age, 67.6 ± 5.8 years) were used and were randomly divided into 2 experimental long head of the biceps brachii (LHB) tenodesis groups (n = 8), namely transtendinous all-suture anchor technique and interference screw technique. The location of tenodesis was in the bicipital groove, 1 cm distal to the proximal border of the bicipital groove. Tensile force parallel to the longitudinal axis of the humerus was applied to each specimen. A preload of 5 N was applied for 2 minutes, followed by cyclic loading for 500 cycles from 5 to 70 N at 1 Hz; then, a load-to-failure test at 1 mm/s was performed. The ultimate failure load, stiffness, cyclic displacement, failure displacement, and failure modes were recorded. RESULTS: The transtendinous all-suture anchor technique provided similar ultimate failure load and stiffness as the interference screw technique. However, the cyclic and failure displacements of the transtendinous all-suture anchor technique were significantly greater than the interference screw technique (P = .009 and .021, respectively). Six specimens in the transtendinous all-suture anchor group failed because of suture anchor pullout, while failure of the other 2 was caused by tendon tear; by contrast, all specimens in the interference screw group failed because of tendon tear. CONCLUSIONS: The transtendinous all-suture anchor technique for LHB tenodesis offered equivalent ultimate failure load and stiffness but had significantly larger cyclic and failure displacement values when compared with the interference screw technique in this cadaveric biomechanical study. CLINICAL RELEVANCE: The transtendinous all-suture anchor technique is an alternative technique for suprapectoral LHB tenodesis; however, care should be taken because only time zero biomechanical data are available.

The effect of humeral-fenestration diameter in Outerbridge-Kashiwagi arthroplasty on failure load of the distal humerus: a cadaveric biomechanical study.

INTRODUCTION: Outerbridge-Kashiwagi ulnohumeral arthroplasty is an effective method in treating elbow osteoarthritis; however, distal humerus fracture after surgery can become a critical issue. A previous biomechanical study has shown that the failure load of the distal humerus decreases after a fenestration, but the size of the fenestration hole has not yet been discussed. MATERIALS AND METHODS: 32 fresh-frozen cadaveric distal humeri were obtained. Two drill sizes were chosen for fenestration: 12 and 15 mm in diameter. Two directions of force were applied with a materials testing machine for biomechanical testing: 5° flexion for axial loading and 75° flexion for anterior-posterior (AP) loading. Each specimen randomly received one of the two fenestration sizes, and force directions. All specimens were loaded to failure at a rate of 2 mm/min. RESULTS: The failure loads of the 12 and 15 mm groups were not significantly different in either axial loading(3886 ± 1271 N vs 4286 ± 901 N) or AP loading(2303 ± 803 N vs 1897 ± 357 N). All specimens loaded with axial force failed via the fenestration holes; however, during AP loading, some specimens failed through the fenestration holes, while others at diaphysis (p = 0.28). CONCLUSIONS: The failure load of distal humeri did not differ significantly after fenestration of 12 or 15 mm. The clinical relevance is that as the risk of distal humerus fracture is not exacerbated, a larger-size fenestration hole could be of help to improve the effectiveness of this surgical procedure.

Correction to: Superior biomechanical properties and tying time with the modified Prusik knot and Wittstein suture loop to the Krackow stitch.

Due to an error during the production process, the legend.

Superior biomechanical properties and tying time with the modified Prusik knot and Wittstein suture loop to the Krackow stitch.

INTRODUCTION: The purposes of the study were to compare (1) the biomechanical properties of the modified Prusik knot, Wittstein suture loop, and Krackow stitch fixation, and (2) the knot tying times for tendon graft fixation among the Krackow stitch, modified rolling hitch, modified Prusik knot, and Wittstein suture loop. MATERIALS AND METHODS: First, 33 fresh-frozen porcine flexor profundus tendons were randomly divided into three groups of 11 specimens. The experimental procedure was designed to assess elongation of the suture-tendon construct across the modified Prusik knot, Wittstein suture loop, and the Krackow stitch. Multistranded nonabsorbable sutures were used. Each specimen was pre-tensioned to 100 N for three cycles, cyclically loaded to 200 N for 200 cycles, and finally loaded to failure. Elongation, load to failure, and failure mode of each specimen were recorded. Second, the knot tying times for modified rolling hitch, modified Prusik knot, Wittstein suture loop, and Krackow stitch were investigated. The measurements were taken on three different occasions to account for intraobserver repeatability and interobserver reproducibility. RESULTS: The elongation after cyclic loading of the modified Prusik knot (22 ± 6%), Wittstein suture loop (25 ± 2%) were significantly smaller than the Krackow stitch (31 ± 5%) (p = 0.001 and 0.003, respectively). The failure loads of three groups were not significantly from one another. Meanwhile, the Krackow stitch group (80.9 ± 16.7 s) had significantly longer average procedure time than the modified rolling hitch group (9.2. ± 1.9 s) (p < 0.001), modified Prusik knot group (9.1 ± 1.8 s) (p < 0.001), and Wittstein suture loop group (9.0 ± 2.2 s) (p < 0.001). CONCLUSIONS: Compared to the Krackow stitch, the modified Prusik knot and Wittstein suture loop had less elongation after cyclic loading and similar ultimate load to failure in this porcine in vitro biomechanical study. Shorter knot tying times were required to complete the modified rolling hitch, modified Prusik knot, and Wittstein suture loop than the Krackow stitch.

Exendin-4, a glucagon-like peptide-1 analogue, accelerates diabetic wound healing.

BACKGROUND: Diabetes disregulates inflammatory responses and impairs vascular function in wounds. Glucagon-like peptide-1 receptor (Glp-1R) agonists are hypoglycemic agents with pleiotropic vascular protective and anti-inflammatory effects. The therapeutic potential of a Glp-1 analogue in a diabetic rat model of excisional wound injury was investigated. MATERIALS AND METHODS: Excisional wounds were created on the dorsum of streptozotocin-induced diabetic rats, which received placebo or Glp-1 analogue exendin-4 (Ex4; 0.5 µg/kg/d, i.p.) for 2 wk. The final-to-initial wound area ratio was measured for 14 d. Levels of superoxide anions and proinflammatory cytokines in the wound were determined. Angiogenesis was assessed using the Matrigel assay. Expression levels of proangiogenic factors and extracellular matrix proteins were measured. RESULTS: Ex4 restored wound closure in diabetic rats and significantly suppressed the generation of superoxide anions and interleukin-6 in wounds. The number of circulating endothelial progenitor (CD34+/KDR+) cells increased significantly in Ex4-treated diabetic rats, which also showed increased capillary tube formation. Protein levels of vascular endothelial growth factor receptor-2, phosphorylated endothelial nitric oxide synthase, matrix metalloproteinase-2, and transforming growth factor-ß were increased in diabetic rats receiving Ex4 therapy. Ex4-enhanced vascularity, dermal regeneration, and epidermal regeneration, while it decreased hemorrhaging and increased the number of proliferative cells in the dermis. CONCLUSIONS: Ex4 accelerated excisional wound healing in subjects with diabetes. Glp-1R activation attenuates inflammatory response and enhances angiogenesis during the early proliferation phase of wound healing in diabetic subjects, while it enhances transforming growth factor-ß/matrix metalloproteinase-mediated regeneration during the maturation phase. These results suggest that Ex4 could be used as a standard hypoglycemic agent in diabetic patients with wound injury.

Do Needleless Knots have Similar Strength as the Krackow Suture? An In Vitro Porcine Tendon Study.

BACKGROUND: Numerous needleless techniques for tendon graft fixation that feature several advantages have been reported. However, there are few studies that have compared the holding strength between the needleless techniques (rolling hitch and modified rolling hitch) and traditional suture methods. QUESTIONS/PURPOSES: To compare the tendon graft-holding strength of the rolling hitch and modified rolling hitch with the Krackow stitch in an in vitro porcine biomechanical model. METHODS: Thirty fresh-frozen porcine flexor profundus tendons were randomly divided into three groups of 10 specimens. The experimental procedure was designed to assess elongation of the suture-tendon construct across the needleless tendon-grasping techniques and the Krackow stitch. All suture configurations were completed with a braided nonabsorbable suture. Each tendon was pretensioned to 100 N for three cycles, cyclically loaded from 50 to 200 N for 200 cycles, and then finally loaded to failure. Elongation, load to failure, and mode of failure were recorded for each specimen. RESULTS: Five of the 10 rolling hitch specimens failed during cyclic loading. With the numbers available, elongation after cyclic loading was not different among the successful rolling hitch specimens (19% [1.19 cm/6.17 cm] ± 6%), modified rolling hitch fixations (19% [1.11 cm/ 5.93 cm] ± 6%), and Krackow stitch fixations (26% [1.41 cm/5.43 cm] ± 6%); ultimate failure loads also were not different among the rolling hitch fixations (316 ± 35 N), modified rolling hitch fixations (342 ± 14 N), and Krackow stitches (327 ± 33 N) with the numbers available. CONCLUSIONS: With the numbers available, the rolling hitch, modified rolling hitch, and Krackow stitch techniques were not different in terms of elongation after cyclic loading and to failure in this in vitro biomechanical evaluation. CLINICAL RELEVANCE: Based on the biomechanical properties from this in vitro animal study, the modified rolling hitch may be an attractive alternative for tendon graft fixation in ligament-reconstruction surgery. Future studies might consider further evaluating these needleless techniques in a cadaver model, in an in vivo animal model, and in an intraarticular model in which the testing is performed in the presence of synovial fluid.

An in vivo study on endothelialized vascular grafts produced by autologous biotubes and adipose stem cells (ADSCs).

Currently, commercial synthetic vascular grafts made from Dacron and ePTFE for small-diameter, vascular applications (<6 mm) show limited reendothelization and are less compliant, often resulting in thrombosis and intimal hyperplasia. Although good blood compatibility can be achieved in autologous arteries and veins, the number of high quality harvest sites is limited, and the grafts are size-mismatched for use in the fistula or cardiovascular bypass surgery; thus, alternative small graft substitutes must be developed. A biotube is an in vivo, tissue-engineered approach for the growth of autologous grafts through the subcutaneous implantation of an inert rod through the inflammation process. In the present study, we embedded silicone rods with a diameter of 2 mm into the dorsal subcutaneous tissue of rabbits for 4 weeks to grow biotubes. The formation of functional endothelium cells aligned on the inner wall surface was achieved by seeding with adipose stem cells (ADSCs). The ADSCs-seeded biotubes were implanted into the carotid artery of rabbits for more than 1 month, and the patency rates and remodeling of endothelial cells were observed by angiography and fluorescence staining, respectively. Finally, the mechanical properties of the biotube were also evaluated. The fluorescence staining results showed that the ADSCs differentiated not only into endothelia cells but also into smooth muscle cells. Moreover, the patency of the ADSCs-seeded biotube remained high for at least 5 months. These small-sized ADSCs-seeded vascular biotubes may decrease the rate of intimal hyperplasia during longer implantation times and have potential clinical applications in the future.

Apparatus for Comparison of Pullout Forces for Various Thoracic Stent Grafts at Varying Neck Angulations and Oversizes.

BACKGROUND: The purpose of this study is to provide an apparatus for comparison of pullout forces for various thoracic stent grafts at varying neck angulations and oversizes. METHODS: An in vitro platform capable of performing pullout tests was used on stent grafts in angulated silicone tubes designed for this study (0°, 45°, 90°, and 135° with a 32-mm inner diameter) in a temperature-controlled chamber (37 ± 2°C). Three commercial stent grafts with sizes commonly used in Taiwan (Valiant: 34, 36, 38, and 40 mm; Zenith TX2: 34, 36, 38, and 40 mm; and TAG: 34, 37, and 40 mm) were used, and each size was tested 8 times for each angulation condition. RESULTS: The mean dislodgement forces (DFs) at 0° angulation within 10-20% oversize were approximately 22.7, 9.6, and 9.0 N for the Valiant, Zenith TX2, and TAG devices, respectively, whereas the mean DFs decreased by 46%, 38%, and 50% to 12.3, 5.9, and 4.5 N when the angulation reached 135°. Regression analysis shows that neck angulation was a significant factor for the Valiant and Zenith TX2 devices (P < 0.0001 and P < 0.0001, respectively) but not for the TAG device (P = 0.483). In addition, oversize and interactions between variables (angulation × oversize) exhibited significant effects on the DFs for all devices (P < 0.0001). CONCLUSIONS: We successfully built up an apparatus for comparison of pullout forces for various thoracic stent grafts at varying neck angulations and oversizes. With the empirical comparative data of different brand stent grafts under various conditions shown and compared, our findings suggest that aortic neck angulation has a negative correlation with stent-graft fixation. To have better stent-graft fixation and seal in the aortic arch for thoracic endovascular aortic repair, a longer landing zone with cautiously selected oversize is a more suitable selection.