A mechanical study of ligature security of commercially available pre-tied ligatures versus hand tied ligatures for use in equine laparoscopy

OBJECTIVE: To determine a hand-tied ligature knot configuration, suture size, and suture type that would be an acceptable substitute to commercially available ligature knots for use in equine laparoscopic surgery. STUDY DESIGN: Three-factor ANOVA with the fixed effects being suture type, suture size, and knot type. The dependent variable was ligature security (load to failure). METHODS: Commercially available Endoloop and 4 hand-tied slipknot ligatures were compared with a 4-layer square knot. The hand tied ligature knots tested were the 4S modified Roeder knot, the Brooks knot, the modified Roeder knot, and the Weston knot. Two suture sizes (0, 2) of each of 2 suture types (polydioxanone, polyglactin 910) were tested with each hand tied knot. Two types (polydioxanone, polyglactin 910) of size 0 Endoloop were tested. Twenty repetitions of each knot suture type were tested for force to yield on a materials testing machine. Statistical analysis consisted of a 3-way ANOVA with individual comparisons made using the Bonferroni method. Significance was P< or = .05. RESULTS: Only the 4S modified Roeder knot in 2 polydioxanone (103 N) was comparable with the breaking strength of the square knots (157 N). All other knot suture combinations tested were significantly weaker than the square knot (range, 2-18 N). CONCLUSION: For equine laparoscopy, a 2 polydioxanone 4S modified Roeder knot would be an acceptable alternative to the commercially available Endoloop. CLINICAL RELEVANCE: Laparoscopic slip knots are commonly used in equine laparoscopic surgery. Various knot configuration and suture size and type combinations will affect the security of the slip knot.     

A comparison of knot security of commonly used hand-tied laparoscopic slipknots

OBJECTIVE: To compare the peak force required for failure of hand-tied laparoscopic slipknot ligatures. STUDY DESIGN: In vitro mechanical evaluation of suture material/knot combinations. Sample POPULATION: Four hand-tied laparoscopic slipknots were studied. Three suture materials and 2 suture sizes were evaluated. Twenty samples of each group were tested, for a total of 400 samples. METHODS: The 4S modified Roeder, modified Roeder, and Weston and Brooks laparoscopic slipknots using 0 polyglyconate, 0 polyglycolic acid, 1 polyglyconate, and 1 polydioxanone (PDS) were tested. A vertical distracting force (5 mm/s) was applied until failure. Mean peak force to failure was obtained for each suture material, size, and knot combination. RESULTS: Mean (+/-SEM) peak force to failure of hand-tied ligatures ranged from 156.8+/-9.1 N to 4.8+/-.4 N. The 4S-modified Roeder had the highest mean peak force to failure. Ligatures tied with polyglyconate and size 1 suture had the highest mean peak force to failure. CONCLUSIONS: The 4S-modified Roeder was significantly and consistently stronger than the other slipknots. Polyglyconate was superior to other suture materials. The 1 polyglyconate had the highest mean peak force to failure followed by 0 polyglyconate that exceeded the 1PDS. CLINICAL RELEVANCE: The 4S-modified Roeder slipknot using 1 polyglyconate has the greatest breaking strength of sutures tested and should be considered when performing laparoscopic ligatures.     

The Effect of Six Knotting Methods on the Biomechanical Properties of Three Large Diameter Absorbable Suture Materials

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

An in vitro biomechanical comparison of the breaking strength and stiffness of polydioxanone (sizes 2, 7) and polyglactin 910 (sizes 3, 6) in the equine linea alba

OBJECTIVE: To determine failure strength, stiffness, and failure mode of 4 suture materials in equine linea alba. STUDY DESIGN: Randomized complete block design. SAMPLE POPULATION: Linea albas collected from 12 adult horses (mean weight, 475 kg; mean age, 10 years). METHODS: The ventral abdominal fascia, including the linea alba, was collected and bisected along the linea alba into right and left halves. Each half was divided into four, 5-cm sections extending from the umbilicus cranially, and randomly assigned to 1 of 4 suture materials: 2 polydioxanone (2 PD), 3 polyglactin 910 (3 PG), 6 polyglactin 910 (6 PG), and 7 polydioxanone (7 PD). A single cycle to failure test was performed on each specimen at a distraction rate of 100 mm/min. Differences in failure strength and stiffness for the materials were evaluated using a mixed linear model with significance set at P<.05. RESULTS: In 94 of 96 test sections, constructs failed by suture failure. There were significant differences in failure strength (P<.0001) and stiffness (P<.001) among the suture/tissue constructs. 7 PD had the highest breaking strength (316.8 N) followed by 6 PG (281.3 N), 3 PG (229.9 N), and 2 PD (193.0 N). Six PG had the largest stiffness (14 N/mm) followed by 3 PG (12.7 N/mm), 7 PD (10.1 N/mm), and 2 PD (7.2 N/mm). Suture breaking strength and stiffness were not affected by linea or fascia thickness, individual horse, half of the linea alba, or abdominal wall position. Eighty-five (90.4%) suture loops failed adjacent the knot. CONCLUSIONS: When tested in single cycle to failure, suture material was more likely to fail than the linea alba. Larger suture materials had higher breaking strengths than smaller suture materials and stiffness was also affected by suture material and size. CLINICAL RELEVANCE: Given its high initial breaking strength and its relatively longer in vivo strength retention, 7 PD seems an appropriate choice of suture material for closure of the equine linea alba when maximal short-term failure strength is desired.     

Evaluation of the tensile strengths of four monofilament absorbable suture materials after immersion in canine urine with or without bacteria

OBJECTIVE: To evaluate the tensile strength, elongation, and degradation of 4 monofilament absorbable suture materials that undergo degradation by hydrolysis in specimens of canine urine with various physical characteristics. SAMPLE POPULATION: 4 monofilament absorbable sutures (polydioxanone, poliglecaprone 25, polyglyconate, and glycomer 631). PROCEDURE: Voided urine was collected from 6 healthy dogs, pooled, filter-sterilized, and prepared to provide 5 media: sterile neutral (pH, 7.0), sterile acidic (pH, 6.2), sterile basic (pH, 8.8), Escherichia coli-inoculated, and Proteus mirabilis-inoculated urine. Ten strands of each suture material were immersed in each of the media for 0 to 28 days. Tensile strength and elongation of each suture material were evaluated by use of a texture analyzer on days 0, 1, 3, 7, 10, 14, 21, and 28. RESULTS: Reduction in tensile strength was detected for all materials in all urine specimens over time. Polyglyconate and polydioxanone had superior tensile strengths in sterile neutral and E. coli-inoculated urine, and polydioxanone retained the greatest tensile strength throughout the study period. All suture materials disintegrated before day 7 in P. mirabilis-inoculated urine. CONCLUSIONS AND CLINICAL RELEVANCE: Polydioxanone, polyglyconate, and glycomer 631 may be acceptable for urinary bladder closure in the presence of sterile neutral and E. coli-contaminated urine. Tensile strength of poliglecaprone 25 in urine may be unacceptable by the critical healing time for bladder tissue (14 to 21 days). During bladder surgery, exposure of suture material that degrades via hydrolysis to urine containing Proteus spp should be minimized.     

Evaluation of 5 Types of Fishing Material, 2 Sterilization Methods, and a Crimp-Clamp System for Extra-Articular Stabilization of the Canine Stifle Joint

OBJECTIVE: To evaluate the mechanical properties of 5 types of fishing material, 2 sterilization methods, and a commercially designed crimp-clamp system for the extra-articular repair of the canine stifle joint. STUDY DESIGN: Experimental study. SAMPLE POPULATION: Animals were not used in this study. METHODS: Two brands of monofilament nylon fishing line and 3 brands of monofilament nylon leader line were used to determine the effect of steam and ethylene oxide sterilization on strength and elongation of the material. A strand of 36-kg test monofilament nylon fishing material was wrapped around 2 rods or knotted to form a loop around 2 rods on a materials-testing machine. Ten trials of each brand of unsterilized, steam-sterilized, and ethylene oxide-sterilized fishing material were tested. A strand of each material was elongated to failure at a constant displacement of 1,000 mm/min to determine strength. A strand of each material was cycled 10 times to a load of 50 N to determine percent elongation. The brand of fishing material with the greatest strength and least elongation was crimped to form a loop around 2 rods on a materials-testing machine and tested as described above. ANOVA was used to determine the effect of sterilization method, brand of material, knot, wrap, and crimp on strength and elongation of the material, and a post-hoc t test was used when significant differences were found. A Student t test was used to compare fixation techniques (wrap, knot, and crimp). RESULTS: Sterilization by steam or ethylene oxide had no significant effect on the strength of the nylon fishing material. Steam sterilization resulted in significant increases (2- to 4-fold) in elongation of most nylon fishing material when compared with unsterilized material. Ethylene oxide sterilization had minimal effect on elongation of the fishing material. Mason leader line showed no significant change in strength or elongation regardless of sterilization method. Significantly less strength and significantly less elongation were demonstrated in Mason leader line that was crimped as compared with Mason leader line that was knotted. CONCLUSION: Ethlylene oxide was the preferred method of sterilization to preserve strength and minimize elongation of the fishing material. Of the materials tested, Mason leader line had the least elongation and the greatest preservation of strength when ethylene oxide was used as the sterilization method. Mason leader line and Sufix fishing line were comparable choices when steam was used as the sterilization method. Significantly less elongation was demonstrated in crimped Mason leader line as compared with knotted Mason leader line. CLINICAL RELEVANCE: Of the materials tested, Mason leader line and Sufix fishing line had the best mechanical properties for extracapsular stabilization of the canine stifle joint. Crimping is an attractive alternative to knotting and results in a reduction in elongation of the nylon fishing material.     

Knot Security of Suture Materials

The knot security of chromic gut, polyglycolic acid, polyglactin 910, polydioxanone, polypropylene, and monofilament nylon size 2-0 suture materials were tested biomechanically in vitro. Twenty reproducible knots were tied and incubated in canine serum at 37 degrees for 24 hours before testing. A "secure knot" was defined as a knot that, when tested to failure, broke rather than untied by slippage. The minimum number of throws necessary to make a secure, snug (1500 g tension) square knot was three for gut, polyglycolic acid, polyglactin 910, and polypropylene and four for polydioxanone and nylon. All throws including the first were counted. With all suture materials tested, surgeon's knots were as secure as square knots. Only gut, polyglycolic acid, and polydioxanone granny knots were as secure as square knots; no loosely tied (500 g tension) asymmetric square knots were as secure as snug square knots, and only polydioxanone and polypropylene loose square knots were as secure as snug square knots. Square knots used to start a continuous pattern required one additional throw with gut, polydioxanone, and nylon. Square knots used to end a continuous pattern required two to three additional throws with all materials tested.     

In vitro Comparison of Secure Aberdeen and Square Knots with Plasma‐ and Fat‐Coated Polydioxanone

Objective: To determine (1) the minimum number of throws to form secure Aberdeen (AB) and square knots to start (SS) and end (SE) continuous patterns, in fat‐ and plasma‐coated polydioxanone; and (2) compare relative knot security (RKS) and knot volumes of these secure SS, SE, and AB knots. Study Design: In vitro experimental materials testing. Sample Population: Polydioxanone suture material (3 metric). Methods: Each knot was tested 20 times, and throws incrementally added until secure SS, SE, and AB knots were found. RKS and knot volumes were calculated for SS, SE, and AB knots. Results: Secure SE knots needed 5 throws in plasma or fat. Secure SS knots needed 4 throws in plasma, but 5 in fat. The minimum AB configuration that was secure in plasma or fat was 3+1, however, the 4+1 AB knot was also secure in fat. Mean (SD) RKS of secure knots were: SE 59.69% (5.91), SS 67.92% (12.50), AB 81.08% (8.99). AB knots had significantly higher mean RKS than any SS or SE knot in plasma or fat (P<.001). Mean knot volume of 3+1 AB knot was significantly smaller than any secure SS or SE knots by 22.6–69.4% (P<.0001). Mean knot volume of 4+1 AB knots was significantly smaller than all fat secure SS and SE knots by 19.9–57.5% (P=.0001). Conclusion: The knot security of the SS knot was decreased by fat coating polydioxanone suture, requiring an additional throw to keep it secure. Secure AB knots had a higher breaking strength and smaller knot volume than secure SS and SE knots. Clinical Relevance: The AB may be preferable to square knots in continuous closures. As many body fluids contain lipid, surgeons should tie knot configurations considered secure in fat. We advise tying a 4+1 AB and placing a minimum of 5 throws to tie SS and SE knots using 3 metric polydioxanone.     

A secure Aberdeen knot: in vitro assessment of knot security in plasma and fat

O bjectives : To determine the minimum number of throws/turns to form a secure Aberdeen knot and the maximum ear slippage for these knots using three metric polydioxanone coated in fat or plasma. To compare plasma and novel canine liquefied fat as suture coating mediums for in vitro knot security testing.
M ethods : Throws/turns were incrementally added until a secure knot was found for plasma and fat. Knots were tensioned until failure and remaining ear length measured. A secure knot was defined as ear slippage 3 mm or less in 20 consecutively tested knots. Ear slippages were statistically analysed.
R esults : Minimum secure configuration was a 3+1 knot in plasma and fat, and its ear slipped a maximum of 2 mm in plasma and 2·5 mm in fat. A secure 4+1 knot had a maximum ear slippage of 0·5 mm, which was significantly less than that of the 3+1 knot (P<0·0001). Fat coating suture significantly decreases in vitro knot security compared with plasma (P=0·0035).
C linical S ignificance : The novel fat coating medium should be considered when testing in vitro knot security as it simulates a clinical knot tying environment. A 4+1 Aberdeen knot with a 3 mm ear is recommended to tie a secure Aberdeen knot in any body fluid environment.     

Biomechanical Evaluation of a Crimp Clamp System for Loop Fixation of Monofilament Nylon Leader Material Used for Stabilization of the Canine Stifle Joint

Objective —To test a crimp clamp system designed to secure monofilament nylon leader (MNL) material commonly used as lateral fabellotibial sutures (LFS) in extra-articular stabilization of the canine stifle joint.
Study Design — In vitro biomechanical tests of MNL loops secured with either the crimp clamp system or knots were performed. Suture loops (n = 94) were created from 27.3 kg tensile strength MNL and fastened with knots or crimp clamps. Tests were conducted on steam-sterilized, ethylene-oxide-sterilized, and nonsterilized MNL sutures. Loops were evaluated in single load tests and cycled tests. Values for load to failure, initial loop tension, loop elongation, mode of failure, and point of failure were determined.
Results —Crimp-clamped loops were superior to knotted loops in all parameters tested in both cycled and noncycled tests. Loop failure generally occurred by breaking within 3 mm of the fixation in both clamped and knotted tests. Loop elongation after cycling was greater in the knotted loops compared with clamped loops ( P < .001). Load to failure was greater in clamped tests than in knotted tests (P < .001), regardless of sterilization technique used. Significantly higher initial loop tension could be achieved with the clamp system compared with knot fixation ( P < .001).
Conclusions —The crimp clamp system provides superior in vitro loop fixation characteristics compared with knot fixation in 27.3 kg test MNL.
Clinical Relevance —Based on the results of biomechanical testing and the known biocompatibility of the system's implant components, clinical trials using the crimp clamp system are warranted.     

An in vitro comparison of two suture intervals using braided absorbable loop suture in the equine linea alba

OBJECTIVE: To compare bursting strength and failure modes of ventral median abdominal incisions closed with loop suture in a simple continuous pattern using two different suture-bite intervals. STUDY DESIGN: In vitro experiment. SAMPLE POPULATION: Equine cadavers (n=14; weighing >318 kg; postmortem interval <2 hours). METHODS: A template was used to make a 25 cm incision with suture interval and bite size of either 1.0 cm x 1.5 cm or 1.5 cm x 1.5 cm. A 200 L polyurethane bladder was inserted within the abdomen and insufflated to create abdominal wall tension. Celiotomies were closed with a #2 braided lactomer 9-1 continuous pattern with a loop suture. Deviation from the linea, closure time (minutes), total suture length (cm), suture length to wound ratio (SL:WL), bursting pressure (mm Hg), and failure modes (fascial or suture) were compared between groups using a Mann-Whitney U test. Significance was set at P<.05. RESULTS: No significant differences were identified between closing time, total suture length used, SL:WL, bursting pressure, or failure mode. Fascial failure was the main failure mode for both techniques; suture failure occurred rarely and knot failure did not occur. CONCLUSION: Based on the overall bursting pressure and failure mode, #2 braided lactomer loop suture placed in a continuous pattern should provide sufficient security for closure of the equine linea alba during recovery and the immediate postoperative period. CLINICAL RELEVANCE: Although there were no significant differences in the 2 patterns evaluated, the 1.5 cm x 1.5 cm pattern may have potential advantages for closure time, less total suture remaining in the wound, and strength.     

The Effect of Knotting Method on the Structural Properties of Large Diameter Nonabsorbable Monofilament Sutures

OBJECTIVE: To evaluate the effect of knotting method on the mechanical properties of large diameter nonabsorbable monofilament suture materials. STUDY DESIGN: In vitro mechanical evaluation. METHODS: A conventional square knot was compared with the surgeon's knot, sliding half-hitch, and clamped square knot. Knotted suture loops were created in a uniform manner and acutely tensioned to failure (20 mm/min loading rate; n = 20 per knot type for each material). Stiffness, yield, and failure characteristics of USP #2 nylon, #2 polybutester, #2 polypropylene, 27 kg test monofilament nylon fishing line, and 27 kg nylon leader material were evaluated. RESULTS: Compared with a conventional square knot, a surgeon's knot decreased stiffness for #2 polypropylene, 27 kg fishing line, and 27 kg leader (P < .05). A sliding half-hitch weakened all materials except 27 kg leader (P < .05). Clamping the first throw of a square knot increased the stiffness of 27 kg leader loops (P < .05). CONCLUSIONS: Based on clinically relevant parameters (stiffness and yield), knotting method had no effect on #2 nylon and #2 polybutester. The surgeon's knot is not recommended for #2 polypropylene and 27 kg fishing line and leader material. A sliding half-hitch decreased the yield of leader material. Clamping the first throw of a square knot had no adverse effects on acute properties of tested materials; it increased the stiffness for leader material. CLINICAL RELEVANCE: Knotting method does influence the structural properties of suture materials and should be considered when tying knots under tension.     

In Vitro Loss of Tensile Strength and Elasticity of Five Absorbable Suture Materials in Sterile and Infected Canine Urine

The loss of breaking strength and elasticity of five absorbable suture materials (polydioxanone [PDS-II], polyglycolic acid [PGA], polyglactin 910 [PG-910], polyglyconate [GTMC], and chromic gut) after in vitro incubation in sterile, Escherichia coli- and Proteus mirab/tfs-inoculated canine urine was studied. Biomechanical testing, in a controlled environment, was performed during the 28-day study period. Polydioxanone and chromic gut retained greater than 90% of their original strengths after 28 days of incubation in sterile urine and 87% of original strengths in E. co//-inoculated urine. Polyglyconate retained 24% and 18% of original strength, respectively, after incubation in sterile and E. co/i-inoculated urine for 28 days. Polyglycolic acid and PG-910 retained less than 30% of original strength in sterile urine and only 7% in E. co/i-inoculated urine after 21 days of incubation. In P. m/rabi/is-inoculated urine, loss of tensile strength and elongation was significant for all suture materials. Polyglycolic acid and PG-910 lost all strength after 24 hours of incubation. Polydioxanone lost all strength after 7 days of incubation, whereas GTMC retained 19% at day 7. Chromic gut retained 78% at day 7 and 16% after 21 days of incubation, however, the absence of normal phagocytic destruction of chromic gut in this in vitro study may have artificially elevated these values. In sterile urine with chemically modified pH, loss of strength and elongation was greater in alkaline urine than in neutral or acidic urine for all types of suture materials.     

In Vitro Biomechanical Evaluation and Comparison of FiberWire,FiberTape, OrthoFiber,and Nylon Leader Line for Potential Use During Extraarticular Stabilization Of Canine Cruciate Deficient Stifles

Objective— To compare biomechanical properties of 3 new generation polyethylene sutures (FiberTape [FT], FiberWire [FW], and OrthoFiber [OF]) with nylon leader line (NL) for use during extraarticular fixation of cranial cruciate deficient stifles. Study Design— In vitro biomechanical testing of suture loops under monotonic tensile and cyclical loading until failure. Sample Population— Constructs of FT, FW, OF, and NL. Methods— Twenty loops of each of 12 combinations of fixation and suture had monotonic tensile and cyclical loading. Two knotting techniques (square knot [SQ], slip knot [SL]) and a crimp clamp (CR) system were evaluated. Elongation, stiffness, and strength of constructs was tested. The main effects of group, loop material, and their interaction were evaluated. Results— Knotted FT, FW, and OF had less elongation than knotted NL under monotonic tensile and cyclical loading. Under monotonic tensile loading, knotted FT and OF were stiffer than knotted NL. CR FT, CR FW, and CR OF were stiffer than CR NL and CR FT, CR FW, and CR OF were stiffer than knotted FT, FW, and OF. FW and OF knotted loops were weaker than knotted NL. CR FT was stronger than CR NL. CR FT and CR OF were weaker than knotted FT and OF. Conclusions— Polyethylene sutures are stronger, stiffer and elongate less than nylon leader. Crimping suture alters the biomechanical properties of the loop. Clinical Relevance— FW, FT, and OF may perform better in reconstructive procedures, where increased strength and stiffness are considered to be beneficial.     

Mechanical comparison of two knots and two crimp systems for securing nylon line used for extra-articular stabilization of the canine stifle

OBJECTIVE: To compare mechanical properties of knotted and crimped nylon loops. STUDY DESIGN: In vitro mechanical evaluation. SAMPLE POPULATION: Loops of 27 kg-test nylon leader. Single strand-clamped square knot compared with 2 crimp systems. Two strand--self-locking knot compared with 2 crimped loops. METHODS: (a) Single pull to failure (n = 10) at 500 mm/min. Initial loop tension (N), peak load (N), peak elongation (mm), stiffness of the linear portion of the curve (N/mm), and failure mode were recorded. (b) Incremental cyclic loading to failure (n = 5)--each loop was cycled 5 times to 100 N at a loading rate of 200 mm/min. Cycling was repeated, with the load increased by 50 N after each set. Elongation (mm), tension remaining (N), and after permanent deformation was present, elongation at 10 N (mm) were measured. RESULTS: Initial tension and stiffness were greater for crimped loops when compared with knotted loops. There were no differences between crimped loops. The self-locking knot elongated more, and was less stiff, when compared with 2 crimped loops. With incremental loading, knotted loops elongated more than crimped loops. The tension remaining in the loop fell below 10 N more quickly for knotted loops compared with crimped loops. CONCLUSION: Crimped loops are stiffer, and resist both static and cyclic load more effectively before becoming permanently elongated, when compared with knotted loops. CLINICAL RELEVANCE: Stifle stability will be maintained more effectively by crimped nylon loops when compared with knotted loops.     

In vitro comparison of mechanical and degradation properties of equivalent absorbable suture materials from two different manufacturers

Objective: To compare the mechanical, knotting, and absorption properties of 3 synthetic absorbable suture materials (polyglactin 910, polydioxanone, poliglecaprone 25) from 2 different manufacturers (Huaiyin Medical Instruments Co. Ltd. and Ethicon Inc.). Sample Population: Suture material samples from the same manufacturing lot for each suture type and manufacturer. Methods: Part 1: 10 samples of each suture were incubated in bovine serum and tested for ultimate load and stiffness at days 0, 1, 7, 14, 21, and 28. Part 2: 10 knotted samples were similarly evaluated, without incubation. Results: Huaiyin polydioxanone had a greater (P<.001) ultimate load on days 0, 1, and 7; and a consistently greater stiffness for the duration of the study, compared with the Ethicon polydioxanone. Ethicon poliglecaprone 25 had a greater ultimate load on days 0, 1, 7 (P<.001); on day 21 Huaiyin had a greater ultimate load. Ethicon poliglecaprone had greater stiffness on days 0, 1, 7 (P<.001). Ethicon polyglactin 910 had a greater (P<.001) ultimate load at all times and a greater stiffness (P<.001) at days 0, 1, 7, and 14 compared with Huaiyin polyglactin 910. Huaiyin polydioxanone and polyglactin 910 had greater knot breaking strengths than Ethicon equivalents (P<.001). Conclusion: Differences in mechanical properties exist between nominally identical suture materials from different manufacturers.     

An Ex Vivo Biomechanical Study Comparing Strength Characteristics of a New Technique with the Three‐Loop Pulley for Equine Tenorrhaphy

Objective: To test single cycle to failure tensile strength characteristics of 6 suture material–pattern combinations in equine superficial digital flexor (SDF) tenorrhaphy, specifically to compare a 10‐strand modification of the Savage core suture technique with the 3‐loop pulley technique. Study Design: Ex vivo mechanical experiment comparing 3 different suture patterns with 2 different materials. Sample Population: Forelimb and hindlimb SDF tendons (n=48) harvested from adult Thoroughbred and Standardbred horses of mixed age and gender. Methods: Six suture material–pattern combinations were evaluated: (1) 10‐strand Savage, size 2 polydioxanone (PDS); (2) 10‐strand Savage, size 2 polyglactin 910 (PG910); (3) 10‐strand Savage, size 2 PDS with Lin‐locking epitenon suture, size 2–0 PDS; (4) 10‐strand Savage size 2 PG910 with Lin‐locking epitenon suture, size 2–0 PDS; (5) 3‐loop pulley, size 2 PDS; and (6) 3‐loop pulley, size 2 PG910. Maximum load at failure (N), gap at failure (mm), and mode of failure (suture breakage or pull through) were evaluated for each of the 6 suture material–pattern combinations and underwent statistical analysis to determine significance of differences and interactions of the measured data. Results: The 10‐strand Savage technique failed at a mean load of 872 N (804–939, 95% CI). The 10‐strand Savage with Lin‐locking failed at a significantly greater mean load of 998 N (930–1065, 95% CI). The 3‐loop pulley pattern failed with a mean load of 337 N (270–405, 95% CI). There were significant interactions between the technique and suture material used. Conclusion: The 10‐strand Savage technique for repair of transected cadaver SDF tendons has superior strength characteristics with or without the epitenon suture when compared to the 3‐loop pulley. Suture material and pattern interactions were observed with PG 910 conferring higher strength for the 10‐strand Savage whereas PDS did so for the 3‐loop pulley.     

Breaking strength and elasticity of synthetic absorbable suture materials incubated in phosphate-buffered saline solution, milk, and milk contaminated with Streptococcus agalactiae

OBJECTIVE: To determine in vitro effects of PBSS, milk, and bacteria-contaminated milk (BCM; contaminated by Streptococcus agalactiae) on properties of 3 synthetic absorbable suture materials. SAMPLE POPULATION: 3 types of synthetic absorbable suture materials (poliglecaprone 25, polyglycolic acid, and polydioxanone). PROCEDURES: Suture materials were tested to determine breaking strength and elasticity before (day 0) and after incubation in 3 media (PBSS, milk, and BCM) for 7, 14, and 21 days. A loop of suture material was elongated at a rate of 60 mm/min until it reached the breaking point. Tensile properties were statistically analyzed among media and incubation times. RESULTS: Incubation in milk and BCM significantly decreased breaking strength and elasticity of poliglecaprone 25, compared with results for incubation in PBSS. Incubation in BCM significantly decreased tensile properties of polyglycolic acid suture, compared with results for incubation in PBSS and milk. After incubation for 21 days, tensile properties of polydioxanone did not differ significantly among the media but were significantly decreased from values on day 0. CONCLUSIONS AND CLINICAL RELEVANCE: On the basis of this study, poliglecaprone 25 is an inappropriate suture material for use in teat surgery. Polyglycolic acid suture should be avoided in teats of cattle with mastitis. Of the suture materials tested, polydioxanone was best suited for use in teat surgery, as determined on the basis of material testing after incubation in milk, even when the milk was contaminated with bacteria.     

In vitro evaluation of the 18 and 36 kg Securos Cranial Cruciate Ligament Repair System

OBJECTIVE: To evaluate the mechanical properties of the 18 and 36 kg Securos Cranial Cruciate Ligament Repair System. STUDY DESIGN: In vitro mechanical evaluation. SAMPLE POPULATION: Loop constructs of 18, 27, and 36 kilogram test (kgt) nylon leader line (NLL) secured with Securos crimp-clamps (SCC, n=40 per NLL test weight) or by a clamped square knot (CSK; n=40/NLL test weight). METHODS: The 36 kg SCC were used for the 27 and 36 kgt NLL, and 18 kg SCC were used for the 18 kgt NLL. Loop constructs were mounted on a material testing machine, and distracted at 500 mm/min for static tests, and for cyclic tests at 500 mm/min to a distraction limit of 6 mm (18 kgt) or 7.5 mm (27 and 36 kgt) for 49 cycles, until failure. Constructs were tested at 20 degrees C except for 1 group of 27 kgt CSK loops tested at 40 degrees C. Load at failure, elongation, and stiffness was recorded and compared between groups under static or cyclic testing conditions. RESULTS: All 27 and 36 kgt loops failed by disruption of NLL contained within the knot or crimp-clamp, whereas 18 kgt SCC loops failed by the NLL pulling through the crimp-clamp. The 18 kg SCC loops had considerable variability in ultimate load and elongation (coefficient of variation 29.6% and 18.3%, respectively). There was no significant difference in elongation between 27.3 kgt CSK loops tested at 20 degrees C and 40 degrees C. Generally, in both static and cyclic testing, SCC constructs formed with 27.3 or 36.4 kgt NLL performed as well or better than CSK constructs, resulting in loops that were strong, underwent minimal elongation, and had high stiffness. CONCLUSION: The results support use of the 36 kg Securos system but not the 18 kg Securos system (with the clamp and crimping device used). The significantly lower load required for failure, slippage through the clamp, and substantial variability suggested that the crimp tube diameter or the crimping device tested may be inappropriate for use with 18 kgt NLL. CLINICAL RELEVANCE: Surgeons should be aware that crimp-clamp design is important in controlling suture slippage or breakage within the clamp, and that novel systems should undergo mechanical testing with the size suture material they are intended to secure before clinical use.     

In vitro bursting pressures of jejunal enterotomy closures in llamas

OBJECTIVE: To evaluate closure strength (in vitro bursting pressure) of jejunal enterotomies in llamas. STUDY DESIGN: In vitro experimental study. SAMPLE POPULATION: Jejunal specimens (n=72) from 6 llamas. METHODS: Differences in bursting pressures and luminal diameters were compared between 2 layer enterotomy closures with an initial full thickness simple continuous pattern oversewn with either a continuous Lembert or Cushing suture pattern using 3 sizes (2-0, 3-0, 4-0) of polyglactin 910 and polydioxanone. RESULTS: Bursting pressures were significantly higher for enterotomies closed with polydioxanone than polyglactin 910, independent of suture size, but there was no difference between Lembert and Cushing oversew patterns. Use of a Lembert pattern reduced intestinal diameter more than a Cushing pattern regardless of suture material or size. CONCLUSIONS: Although polydioxanone resisted higher bursting pressures than polyglactin 910, both suture materials should be considered satisfactory for jejunal enterotomy closure in llamas based on typical intraluminal pressures expected in clinical patients. The optimal oversew pattern may be continuous Cushing to maximize the luminal diameter in small intestinal enterotomy closures. CLINICAL RELEVANCE: In vitro bursting pressures may help to predict which enterotomy sites would leak post-operatively, although further studies are necessary to determine the outcome in clinical patients.