In Vitro Cerclage Wiring Analysis

The ability of six different instruments to apply a cerclage wire under tension to a tension gage was compared. The loop knot produced greater final wire tension than the twist knot, both before and after bending. No significant difference in tension was found between the Swiss Osteo and A.S.I.F. instruments. The Rhinelander and Richards instruments gave approximately the same tension before the bend. The Rhinelander, Richards, and Vise Grip instruments showed no statistical difference in tension produced after the bend. The Bowen instrument developed the least amount of tension, both before and after bending the twist. All twist knots lost a significant amount of tension during the bending process. The twist-type knots that were twisted until breakage in the middle of the knot produced greater tension than those that were cut once they were tight. Cutting the twisted knot caused a significant decrease in wire tension. No correlation was found between operator pull and final cerclage wire tension.     

Evaluation of tension obtained by use of three knots for tying cerclage wires by surgeons of various abilities and experience

OBJECTIVE: To compare tension of 3 cerclage wire knots tied by surgeons of various abilities and experience. DESIGN: Cross-sectional study. SAMPLE POPULATION: Participants and faculty at a postgraduate course in veterinary orthopedics. PROCEDURE: Subjects tied a cerclage of their choice on an instrumented tying stand that displayed the tension on a computer. Mean tensions in cerclage wires tied with twist, single loop, or double loop knots were compared. The relationship between level of surgeon experience and tension achieved was examined. RESULTS: 29 twist, 30 single loop, and 16 double loop wires were analyzed. Mean +/- SD tension for twist knots was significantly less than for single loop knots (82.3+/-46.1 vs 166.6+/-42.2 N, respectively). Double loop knots achieved significantly greater tension (392.0+/-116.6 N) than twist and single loop knots did, even though few participants had ever tied this knot previously. There was no correlation with experience of the participant. For twist knots, wiggling the wire during cutting and pushing the twist over to flatten it to the bone further reduced tension. CONCLUSIONS AND CLINICAL RELEVANCE: Cerclage applied with a twist knot does not compress fracture fragments as effectively as cerclage applied with single loop or double loop techniques. Because greater compression of fragments will improve the stability of a fracture, a surgeon should strive to maximize the tension in the cerclage that they use. Experience and abilities of the surgeon are not associated with ability to tie cerclage wires tightly.     

Mechanical Characteristics and Comparisons of Cerclage Wires: Introduction of the Double-Wrap and Loop/Twist Tying Methods

Objective — Evaluate the mechanical properties of twist, loop, double loop, double-wrap and loop/twist cerclage.
Methods — The initial tension generated by 18 cerclage of each type was determined using a materials testing machine after tying around a testing jig. Six wires from each type were distracted and the initial stiffness and yield load were determined. Yield behavior was further investigated in six wires of each type by determining the load required to reduce cerclage tension below 30 Newton (N) following an incremental (50 N) stepwise load and unload regimen. The amount of collapse of the simulated bone fragments that resulted in the reduction of initial tension to 30 N was measured for the final six wires of each group. Data were analyzed by analysis of variance and a multiple comparison test.
Results — Twist type cerclage generated less tension than loop-type cerclage. The yield load of these two types was similar. Double-loop and double-wrap cerclage generated superior tension and resisted a greater load before loosening. Loop/twist cerclage had an intermediate initial tension but had the greatest resistance to loading. In the collapse test, the greater the initial tension, the more collapse could occur before the wire was loose. For all types of cerclage wire fixation, a reduction of diameter of the testing jig of more than 1% caused loosening.
Clinical Relevance — Double-loop and double-wrap cerclage provide greater compression of fragments and resist loads associated with weight-bearing better than the twist and loop methods. Loop/twist cerclage may have advantages because of their superior resistance to loading. All cerclage will loosen if fracture fragments collapse.     

Resistance of cerclage to knot failure

The comparative ability of loop-knotted and twist-knotted cerclage to withstand tensile forces was tested. Two twist-knot devices and one loop-knot device were used to apply cerclage wires to a 5-cm diameter split circular jaw mounted on a tensile testing machine. Twist-knot devices were tested with 0.8-, 1.0-, or 1.2-mm wire, and the loop-knot device was tested with 0.8-, 1.0-, or 1.25-mm wire. For all wire sizes, the twisted knot provided greater resistance to knot failure than did the loop-knot. Of the 2 twist-knot devices, the Rhinelander wire tightener-twister produced the greatest resistance to knot failure. Knot resistance increased with increase in wire size for all devices tested.     

Multiple Intramedullary Wire Fixation of a Radial Fracture in a Dog

Multiple intramedullary wire fixation infrequently can be used as an alternative technique to plating, transfixation devices, single intramedullary pinning, or external coaptation for some radius and ulna fractures.
This report describes a comminuted fracture of the radius and ulna with fissures and comminution extending too far into the proximal radius for effective application of a bone plate or Kirschner-Ehmer apparatus. Resulting fracture instability and collapse prohibited effective use of external coaptation as a primary means of fixation. The radial fracture was repaired and stabilized with full cerclage wires and multiple intramedullary Kirschner wires. The dog was using the leg normally 12 months following surgery.     

Median sternotomy closure in dogs: a mechanical comparison of technique stability

OBJECTIVE: To evaluate the mechanical properties of canine median sternotomy closure using double-loop cerclage compared with other commonly used cerclage sternotomy closure patterns. STUDY DESIGN: Experimental study. SAMPLE POPULATION: Forty canine cadaveric sternal segments. METHODS: Median sternotomy-wire constructs were loaded to failure in a materials testing machine. Each construct was radiographed before and after testing. Specific wire configurations tested were: 2 single twist cerclage centered on the sternebrae, single twist figure of 8 pattern centered on the sternal synchondrosis, double twist figure of 8 pattern centered on the sternal synchondrosis, 2 double-loop cerclage centered on the sternebrae, and 1 double-loop cerclage centered on the sternal synchondrosis. Wire configurations were compared by craniocaudal translation of sternabrae on pre-test radiographs, and displacement during loading, and mode of failure, based on analysis of test video, and post-test radiographs. RESULTS: Double-loop cerclage did not provide superior mechanical stabilization of median sternotomy. Both figure of 8 patterns had the least displacement at higher loads. Two single twists that were centered on sternebrae were least able to prevent displacement at higher loads, caused the most craniocaudal translation before testing, and fractured more often at loads < or = 200 N compared with other configurations. CONCLUSION: Sternal wiring techniques stabilizing sternal synchondroses had the least displacement. Overall, figure of 8 cerclage appeared most suitable because they minimized displacement at high loads and facilitated accurate reduction during tensioning. CLINICAL RELEVANCE: In closing canine sternotomy, figure of 8 cerclage may be most suitable. Double-loop cerclage centered on the sternal synchondrosis should be avoided because of wire failure at high loads.     

Influence of bolt tightening torque,wire size,and component reuse on wire fixation in circular external fixation

OBJECTIVES: To evaluate the effects of bolt torque, wire size, and component reuse on the ability to maintain wire tension in 3 external skeletal fixation systems. STUDY DESIGN: Biomechanical study. METHODS: Yield strength in tension of 1.0-, 1.2-, 1.5-, and 1.6-mm-diameter wires, and yield strength in torque of Hofmann Small Bone Fixation (SBF) cannulated and slotted bolts and IMEX regular and miniature bolts were determined on a testing machine. The minimum bolt tightening torque needed to prevent wire slippage at clinically recommended wire tensions was determined. Components were tested 10 times, and loads at slippage were recorded. RESULTS: The IMEX system required a mean of 8 Nm of bolt tightening torque to maintain 900 N (1.6-mm wires). The SBF system required a mean of 3 Nm bolt torque to maintain 300 N (1.0-mm wires) and 5 Nm to maintain 600 N (1.2-mm wires). The SBF cannulated bolt required 9 Nm of torque to maintain 900 N (1.5-mm wires). The SBF slotted bolts could only maintain 800 N before yield. The IMEX miniature system required a mean bolt torque of 1.1 Nm to maintain 300 N. The cannulated and slotted bolts from both manufacturers failed to maintain 70% of initial wire tension after 7 and 4 uses, respectively. CONCLUSIONS: The IMEX systems and the SBF system using 1.0- and 1.2-mm wires could maintain clinically recommended wire tension safely. Only the IMEX system could maintain clinically recommended wire tension safely using 1.5- or 1.6-mm wires. CLINICAL RELEVANCE: The SBF system using 1.0- and 1.2-mm wires and the IMEX system using all wire sizes can maintain clinically relevant wire tension. The SBF system using 1.5-mm wires could not. Cannulated and slotted bolts should not be used more than 6 and 3 times, respectively. Nuts should not be reused.     

Comparison of Alternate and Simultaneous Tensioning of Wires in a Single-Ring Fixator Construct

Objective— To measure and compare the strain of wires tensioned with alternate (ALT) and simultaneous (SIM) tensioning in a single-ring fixator construct and compare the stiffness of these constructs under axial loading.
Study Design— Experimental mechanical study.
Sample Population— Twenty-four, 84 mm diameter, single-ring constructs.
Methods— Twenty-four, 84 mm diameter, single-ring constructs were assembled using 2 1.6 mm wires placed at a 60° angle tensioned with either ALT or SIM technique to 90 kg tension. Voltage data from a strain gauge were recorded during the wire-tensioning process, cyclic axial loading, and load-to-failure testing. Wire strains were calculated for each wire and compared within constructs and between ALT and SIM groups. Construct stiffness was compared between groups.
Results— There was no difference between the tensioning methods in final wire strains after initial tensioning for both the wire below the ring (W1; P =.698) and the wire above the ring (W2; P =.233). There was also no difference in final wire strains within each tensioning method group (ALT, P =.289; SIM, P =.583). Loss of wire strain (3.5–5%) occurred after cyclic loading for both wires in both groups. There was no difference in construct stiffness between the ALT and SIM groups ( P =.126). Mode of failure was by wire breakage in all constructs and occurred most frequently in W1.
Conclusion— ALT tensioning of wires produced similar wire strains within a single-ring construct after initial tensioning to SIM tensioned wires. There was no difference in construct stiffness under axial loading between AIM and SIM tensioned constructs.
Clinical Relevance— ALT tensioning of wires in a single-ring fixator construct can be used as an alternative to SIM tensioning, as similar initial wire tensions are achieved.     

Effects of ring diameter and wire tension on the axial biomechanics of four-ring circular external skeletal fixator constructs.

OBJECTIVE: To determine relative effects of ring diameter and wire tension on axial biomechanical properties of 4-ring circular external skeletal fixator constructs. SAMPLE POPULATION: 4-ring circular external skeletal fixator constructs and artificial bone models. PROCEDURE: 4-ring constructs were assembled, using 50-, 66-, 84-, or 118-mm-diameter rings. Two 1.6-mm-diameter fixation wires were attached to opposing surfaces of each ring at intersection angles of 90 degrees and placed through a gap-fracture bone model. Three examples of each construct were loaded in axial compression at 7 N/s to a maximum load of 400 N at each of 4 wire tensions (0, 30, 60, and 90 kg). Response variables were determined from resulting load-displacement curves (construct stiffness, load at 1 mm of displacement, displacement at 400 N). RESULTS: Ring diameter and wire tension had a significant effect on all response variables and had a significant interaction for construct stiffness and displacement at 400 N. Significant differences within all response variables were seen among all 4 ring diameters and all 4 wire tensions. As ring diameter increased, effect of increasing wire tension on gap stiffness and gap displacement at 400 N decreased. Ring diameter had a greater effect than wire tension on all response variables. CONCLUSIONS AND CLINICAL RELEVANCE: Although effects of wire tension decrease as ring diameter increases, placing tension on wires in larger ring constructs is important because these constructs are inherently less stiff. The differential contribution of ring diameter, wire tension, and their interactions must be considered when using circular external skeletal fixators.     

Effect of Cerclage Wires on Periosteal Bone in Growing Dogs

Three diameters of wire were placed circumferentially around the femora of six 22 week old puppies. The wires were placed over the periosteum on one limb and under the periosteum on the other limb. The effect of the wires on actively growing bone was evaluated 3 and 8 weeks after placement. Diffuse growth of periosteal new bone occurred in immature dog femora in which cerclage were placed under the periosteum. This reaction corresponded with dramatically increased medullary and periosteal microvascularity coupled with histologic active trabecular bone formation. In femora in which wires were placed over the periosteum, even though the placement of the wires should supposedly have been the most detrimental, there were active vessels within the cortex directly under all wires. In both preparations, cerclage wires were becoming encased in the growing cortical bone 8 weeks after placement. Cerclage wires did not devitalize immature bone nor did it restrict adjacent appositional bone growth.     

A Mechanical Evaluation of the Resistance of Various Interfragmentary Wire Configurations to Torsion

Fourteen interfragmentary orthopedic wire configurations were tested in torsion using a transverse fracture polyvinylchloride pipe model. These models included single and double Kirschner pins with and without orthopedic wire added to the configuration. The orthopedic wire was applied in either an encircling, figure-of-eight (skewer pin), or cruciate pattern. Double Kirschner pins were applied in a mono- or biplanar fashion. An external fixator model was also tested. Stiffness, yield load, safe load, and energy of absorption were measured and calculated for each model. Orthopedic wire added to any configuration increased stiffness. All single pin configurations with orthopedic wire and the external fixator had the highest stiffness. Two Kirschner pins had a higher torsional yield load and safe load than single pin configurations with or without orthopedic wire. The external fixator model had the highest torsional yield load, safe load and energy of absorption of all configurations tested. However, the external fixator was only significantly different in safe load from the 90° biplanar configurations with wire and the cross pin configuration with encircling wire. The 90° biplanar configurations with wire and the cross pin configuration with encircling wire were equally as effective as the external fixator model in yield load and energy of absorption.     

Biomechanical comparison of dual interlocking single loop and double loop tension band techniques to the classic AO tension band technique for repair of olecranon osteotomies in dogs

OBJECTIVE: To compare olecranon fragment stability between the classic tension band wire (TBW) technique with the wire placed either in contact with (Arbeitsgemeinschaft für Osteosynthesefragen [AO]), or not in contact with, a Kirschner (K)-wire (AOW) to 2 novel wire patterns: a dual interlocking single loop (DISL) and a double loop (DL). STUDY DESIGN: Ex vivo mechanical evaluation on cadaveric bones. SAMPLE POPULATION: Canine ulnae (n=40) with olecranon osteotomies repaired with 2 K-wires and 1 of 4 TBW constructs. METHODS: Single load to failure applied through the triceps tendon. Displacement was measured from images captured from digital video. Techniques were compared based on the load resisted when the olecranon fragment was displaced 0.5, 1, and 2 mm. RESULTS: At 0.5 mm of displacement, the DISL construct resisted more load than the AOW construct (505 versus 350 N; P=.05). AO and DL constructs resisted an intermediate load (345 and 330 N, respectively). There was no significant difference between groups at 1 mm of displacement. At 2 mm of displacement, DL (785 N) resisted more load than AO (522 N, P=.01) and AOW (492 N, P=.03) groups. CONCLUSIONS: DISL constructs provided similar stability to classic TBW constructs whereas DL constructs were more stable at higher loads. CLINICAL RELEVANCE: The DL construct is easy to perform, less bulky, and provides comparable fragment stability to standard TBW techniques at functional loads. Surgical method is important for optimal performance of all TBW constructs.     

Biomechanical comparison of a circular external skeletal fixator construct to pin and tension band wire fixation for the stabilization of olecranon osteotomies in dogs: a cadaveric study

OBJECTIVE: To compare anatomic reduction and the biomechanical properties of a circular external skeletal fixator (CESF) construct to pin and tension band wire (PTBW) fixation for the stabilization of olecranon osteotomies in dogs. STUDY DESIGN: Cadaveric study. ANIMALS: Forelimbs from 12 skeletally mature mixed-breed dogs, weighing 23 to 28 kg. METHODS: An olecranon osteotomy was stabilized with either a CESF construct or PTBW fixation. A single distractive load to failure was applied to each specimen through the triceps tendon. Osteotomy reduction and biomechanical properties were compared between fixation groups. RESULTS: Reduction was not significantly different (gap: P =.171; malalignment: P =.558) between fixation groups. Osteotomies stabilized with the CESF had greater stiffness (P <.0001) and maximum load sustained (P <.0001) compared to PTBW fixation. There was no significant difference for yield load (P =.318) or for load at 1 mm of axial displacement (P =.997) between fixation groups. Failure of fixation occurred by bending of the intramedullary Steinmann pin and the fixation wires in the CESF specimens and by untwisting of the tension band wire knot with pullout and bending of the Kirschner wires in the PTBW specimens. CONCLUSIONS: Specimens stabilized with the CESF construct had similar reduction and yield load, greater stiffness and maximum load sustained, and less elastic deformation than specimens stabilized with PTBW fixation. CLINICAL RELEVANCE: The CESF construct may provide a biomechanically favorable alternative to PTBW fixation for stabilization of olecranon osteotomies in dogs, and its application warrants clinical investigation.     

Axial Characteristics of Circular External Skeletal Fixator Single Ring Constructs

OBJECTIVE: Evaluate the effects of varying ring diameter, wire tension, and wire-divergence angle on the axial stiffness characteristics of circular external skeletal fixator single-ring constructs. Study Design-Biomechanical evaluation using circular fixator components and a Delrin cylinder bone model. METHODS: Single ring constructs using two 1.6 mm diameter Kirschner wires to secure a 19 mm Delrin cylinder centered within the ring were examined. Component variables evaluated were ring diameter (50 mm, 66 mm, 84 mm, and 118 mm), wire-divergence angle (30 degrees, 60 degrees, and 90 degrees ), and wire tension (0 kg, 30 kg, 60 kg, and 90 kg). A total of 48 constructs were examined. Rings were rigidly mounted on a universal testing system and the cylinder loaded in axial compression (7.4 N/s) to 220 N. Load/displacement curves were analyzed to determine the following: the displacement (mm) that occurred before the slope of each load/displacement curve became linear, the stiffness (N/mm) of the linear portion of each load/deformation curve, and the total displacement (mm) produced at maximal load. Least-squares linear regression was used to model response variables as linear functions of ring diameter, wire divergence angle, and wire tension. Three-way interactions and 2-way interactions among independent component variables were evaluated first in the modeling process and included in a best model if response variables were found to have statistically significant regression coefficients. The regression coefficients and corresponding standard errors and covariances were used to estimate the maximal effect and standard error attributable to wire divergency angle (change from 30 degrees to 90 degrees ) and wire tension (change from 0 to 90 kg) for each ring diameter. RESULTS: All load/deformation curves had an initial exponential increase in stiffness, with the slope becoming linear at higher loads. The exponential phase was more pronounced in larger-diameter ring constructs and was mitigated by tensioning the wires. Ring diameter had the greatest influence on displacement that occurred before the curve became linear (semipartial r(2) [sp-r2] = .89), stiffness (sp-r2 = .94), and total displacement (sp-r2 = .93). Wire tension exerted a smaller influence on displacement that occurred before the curve became linear (sp-r2 =.06), stiffness (sp-r2 = .03), and total displacement (sp-r2 = .05). Wire divergence angle had a nominal effect on displacement that occurred before the curve became linear (sp-r2 = .0001), on stiffness (sp-r2 = .004), and on total displacement (sp-r2 =.003). CONCLUSIONS: Ring diameter had a profound effect on the axial stiffness characteristic of single ring constructs. Tensioning of the fixation wires can improve the axial stiffness characteristics of these constructs, particularly in larger diameter ring constructs, by mitigating the initial exponential phase of the load/deformation curve. Wire divergence angle had only a nominal differential effect on axial stability. CLINICAL RELEVANCE: Understanding how individual component variables and their interactions influence bone segment stability should help surgeons to optimize interfragmentary strain. Tensioning fixation wires is probably unnecessary in 50 mm diameter ring constructs, but assumes greater importance as ring diameter increases.     

Surgical repair of rib fractures in 14 neonatal foals: case selection, surgical technique and results

Reasons for performing study: Fractured ribs are encountered quite frequently in newborn Thoroughbred foals, often with fatal outcome. Surgical repair of fractures therefore requires consideration as a means of reducing mortality. Objectives: To evaluate the repair of rib fractures using internal fixation techniques in foals at 2 different equine hospitals following similar diagnostics and case selection. Methods: The records of 14 foals that underwent internal fixation of fracture ribs were reviewed. Subject details, clinical presentation, diagnosis, surgical technique, post operative care and complications were recorded. Follow-up information was obtained in 7 foals. Results: The fractured ribs were reduced and stabilised using reconstruction plate(s), self-tapping cortical screws and cerclage wire in 12 cases, Steinmann pins and cerclage wires in 1 case and both techniques in 1 case. Not every rib was reduced on each case. Surgical reduction was performed on an average of 2 ribs, range 1-3 ribs in each foal. At the time of writing, 4 foals had been sold, one age 2 years was in training and 2 others died from unrelated causes. Conclusions: Our data support the use of surgical stabilisation utilising reconstruction plates, self-tapping cortical screws and cerclage wire for selected cases of thoracic trauma in neonatal foals. The use of Steinmann pins may be suboptimal due to cyclic failure, implant migration and the potential for iatrogenic internal thoracic trauma. Potential relevance: Foals with existing extensive internal thoracic trauma resulting from rib fracture(s), or the potential for such trauma, previously considered to have a guarded to poor prognosis for survival, may be successfully managed with internal fixation of selected fracture sites.     

A comparison of ultra-high-molecular weight polyethylene cable and stainless steel wire using two fixation techniques for repair of equine midbody sesamoid fractures: an in vitro biomechanical study

OBJECTIVE: To compare the monotonic tensile and fatigue strength of 16-gauge stainless steel wire (SSW) to ultra-high-molecular weight polyethylene (UHMWPE) cable using a transfixed cerclage technique in an in vitro midbody sesamoid osteotomy model. Endoscopic modifications to Martins transfixed cerclage technique were developed. A new suture technique of fixation was compared with the transfixed cerclage technique by measuring gap formation after cyclic testing. STUDY DESIGN: An in vitro biomechanical paired equine cadaver limb study. SAMPLE POPULATION: Twenty-one paired cadaveric adult equine forelimbs. METHODS: Uniaxial medial midbody sesamoid osteotomies were created in paired adult equine forelimbs. Monotonic tensile strength was measured on 10 forelimbs repaired by a transfixed cerclage technique using wire or cable. Fatigue testing to failure was performed on 4 forelimbs repaired using the transfixed cerclage technique by cycling the limbs between 500 N and 2,000 N. The limbs were initially repaired with wire, cycled until the wire broke, then repaired with cable and cycled again to failure. Fatigue testing for gap displacement was performed on 8 limbs repaired with either the transfixed cerclage technique or the suture technique. Limbs were cycled between 500 N and 2,000 N for 10,000 cycles. The limbs were repaired with wire initially, tested, and then repaired with cable and tested again. Twenty-two limbs were used for mechanical testing. The remaining limbs (20) were used to develop and practice the endoscopic transfixed cerclage (10 limbs) and suture (10 limbs) techniques. RESULTS: Ultimate tensile strength (UTS) of UHMWPE cable constructs was 34% greater than the UTS of SSW constructs. Fatigue strength was 2 to 20 times greater for UHMWPE cable constructs than SSW constructs. Separation of fragments was 153% less for limbs repaired by the suture technique compared with those repaired by the transfixed cerclage technique. CONCLUSIONS: UHMWPE cable shows promise for this clinical application because of its greater tensile and fatigue strength. The newly described suture technique significantly reduced gap formation compared with the transfixed cerclage technique. Osteotomy gap formation occurred early in cycling, suggesting that rigid support in the form of a cast may be needed during the early postoperative period for wiring techniques. CLINICAL RELEVANCE: Clinical testing of UHMWPE cable should eliminate problems of wire breakage seen with SSW. The endoscopic transfixed cerclage technique can be used by surgeons familiar with arthroscopic surgery. However, the suture technique needs to be tested in vivo to determine whether there is a clinical advantage compared with the transfixed cerclage technique.     

Tension band wiring of canine and feline supracondylar epiphyseal femoral fractures (author's transl)

The present investigation describes the treatment of 27 cases of canine and feline supracondylar epiphyseal--metaphyseal femoral fractures with tension band wire. The wire was passed through transversal parallell drill holes, one in each fragment. The wires intercrossed dorsally. Stable fixation followed tightening of the wires. 20 out of 25 primarily successful cases were re-examined. 19 were completely well. One case showed a slight transient lameness following hard exercise.     

Fractures of the humerus.

A single or double bar, type I, unilateral external fixator can be used as primary or ancillary treatment for repair of many humeral fractures. Treatment of contaminated and comminuted fractures with external skeletal fixation provides rotational stability and axial alignment, access for wound management and bone grafting, and avoidance of vascular compromise by surgical invasion. In addition, the combination of external and internal (IM pins, cerclage wires, plates) fixation can provide greater initial fracture stability and subsequent dynamization or loading of bone (as the fixator is removed) than either of the systems used individually.     

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.     

Vascular Response of the Equine Radius to Cerclage Devices

The arterial blood supply to the diaphysis of the radius, and the vascular reaction when three cerclage devices (cerclage wire, Parham-Martin band, and a partially contacting band) were applied 2 cm apart, were studied in six adult ponies. The opposite radial diaphysis served as the control. Ponies were euthanatized at weeks 4 and 8. A centrifugal blood flow pattern was demonstrated by microangiography. Larger numbers of medullary arteries exist in equine than in canine and human long bones. Changes in centrifugal blood supply were not identified beneath any of the cerclage devices.