Abrasion resistance of two types of nonabsorbable braided suture

Purpose: The purpose of this study was to compare the abrasion resistance of different types of non-absorbable braided sutures under varying in vitro conditions of cyclic loading. Type of Study: Biomechanical study. Methods: Two types of nonabsorbable braided sutures were used in this study, No. 2 Ethibond and No. 2 Fiberwire, combined with 5 different anchors: 5.0-mm Corkscrew anchor, 5.0-mm BioCorkscrew anchor, 3.0-mm BioFastak anchor, Panalok RC anchor, and 3.5-mm Panalok anchor. Twelve tests for each construct were performed. A custom-designed testing apparatus was constructed to evaluate the abrasion resistance of sutures through an anchor eyelet. The apparatus cycled the suture through the anchor eyelet at a rate of 84 revolutions per minute and a speed of 12.5 m/min. In addition to suture type, the effect of different suture-to-anchor angles and testing conditions (dry v wet testing) were evaluated. The number of cycles to failure and the mode of failure were recorded (suture breakage v eyelet breakage). Results: Results showed that under all testing conditions No. 2 Fiberwire displayed abrasion resistance superior to No. 2 Ethibond (P < .002 in all cases). The mean number of cycles to failure was 5 to 51 times greater when using No. 2 Fiberwire than when using No. 2 Ethibond. Altering the suture-to-anchor angle from 0° (in-line) to 45° decreased the abrasion resistance of both No. 2 Ethibond (69.8 cycles ± 26.5 cycles v 7.4 cycles ± 3.9 cycles; P < .000004) and No. 2 Fiberwire (918.3 cycles ± 417.4 cycles v 389.2 cycles ± 195.7 cycles; P = .001) when using the 5.0-mm Corkscrew anchor. Fiberwire performed equally well under both dry and wet conditions (P > .05) whereas Ethibond performed better under wet conditions (P = .0002) when using the 5.0-mm BioCorkscrew anchor. When using the Panalok RC anchor (mean failure, 11.2 cycles ± 1.3 cycles) or the 3.5-mm Panalok anchor (mean failure, 12.5 cycles ± 2.4 cycles), constructs failed at significantly lower cycles than other comparable anchor-suture constructs (P < .00007 in all cases). In addition, although the vast majority of failure modes for the other anchor-suture constructs was by suture breakage, the Panalok RC anchor and 3.5-mm Panalok anchor consistently failed by cutting of the suture through the biodegradable eyelet. Conclusions: (1) Suture abrasion differs according to the suture type, anchor type, and testing conditions. (2) No. 2 Fiberwire showed superior resistance to abrasion when compared with No. 2 Ethibond under all conditions tested in the study. (3) The abrasion resistance of No. 2 Fiberwire is sufficiently high to eliminate, clinically, the theoretical concerns over weakening of suture from the anchor eyelet. (4) Suture eyelets formed of biodegradable materials can fail at low numbers of cycles by cutting of the suture through the biodegradable eyelet during cyclic loading. Clinical Relevance: The study will help the surgeon to assess suture and suture anchor characteristics in order to optimize fixation of biologic tissues during surgical repair and reconstruction.     

Failure of suture material at suture anchor eyelets

Purpose: In the repair of soft tissue to bone using suture anchors, failure of the suture material can occur at the anchor eyelet. This study examines the load strength at which suture material fails with different metallic suture anchor eyelets. Type of study: Biomechanical study. Methods: Suture material (Ethibond No. 2, Ethicon, Norderstedt, Germany) was pulled out from 22 metallic suture anchor models at 60 mm/min, and tensile load at failure and failure mode were recorded. Tests were performed either by simultaneous pulling on 2 suture limbs in 3 different directions (straight, at 45°, and at 45° rotated by 90° to the suture anchor axis) or by pulling on 1 suture limb while measuring the resulting force on the second limb. All tests were performed until suture failure. Pulling was performed in single tests on an Instron materials testing machine (High Wycombe, UK), with the anchors held by a vise. Results: In all cases, the suture failed at the anchor eyelet. Failure load at straight loading ranged from 116 ± 5 N to 226 ± 5 N and from 69 ± 5 N to 193 ± 7 N when loaded at an angle of 45°. The best results were found with the Statak 5.2-mm (Zimmer, Warsaw, IN): 177 N; Corkscrew 6.5-mm anchor (Arthrex, Naples, FL): 174 N; and PeBA 4.0-mm anchor (OBL Orthopaedic Biosystems, Scottsdale, AZ): 169 N. With each eyelet, sutures failed preferentially in 1 direction, depending on the presence of sharp edges. Conclusions: Suture material can be cut at suture anchor eyelets. Failure load depends on sharp edges on the eyelet and occurs at forces up to 73% below the breaking strength of the suture material on a smooth hook. Anchors with suture-protecting channels are particularly sensitive to the orientation in which the sutures are loaded.     

Flexor tendon repairs: the impact of fiberwire on grasping and locking core sutures

PURPOSE: Immediate surgical repair and early mobilization are essential in preventing adhesion formation and finger stiffness. A new polyethylene-based, braided suture material, Fiberwire (Arthrex, Naples, FL), touting increased strength, presents the potential for stronger repairs and, therefore, earlier active motion after surgery with a greater safety margin. The purpose of this biomechanic study was to investigate the differences in gap formation, tensile strength, and mode of failure for 2 distinct repair techniques using nylon, Ethibond (Ethicon, Somerville, NJ), and Fiberwire. METHODS: Human cadaver flexor tendons were harvested and repaired in a randomized fashion with either the Strickland or Massachusetts General Hospital (MGH) repairs using either nylon, Ethibond, or Fiberwire. Twelve tendons per group were repaired for each combination of material and method. During load-to-failure testing, 2-mm gap force and maximum tensile strength were statistically analyzed. RESULTS: Strickland repairs failed by suture pull-out in 74% of repairs, whereas 99% of the MGH repairs failed by suture breakage. For MGH repairs, Fiberwire suture provided significantly more tensile strength than Ethibond and nylon. For Strickland repairs, where the mode of failure was more often by suture pull-out rather than breakage, differences between type of suture were not significant. When comparing repair techniques using Fiberwire, the MGH repair was significantly stronger than the Strickland repair. CONCLUSIONS: Biomechanic testing shows that Fiberwire outperforms both Ethibond and nylon suture when using a locked flexor tendon repair suture (MGH repair) but not when using a grasping-type, nonlocking repair (Strickland repair).     

The twist-lock concept of tissue transport and suture fixation without knots: observations along the Hong Kong skyline

Purpose:To evaluate the load to failure and the mode of failure of a novel suture anchor construct that does not require knots (the “twist-lock” construct) and to compare it with a standard suture anchor construct (Corkscrew; Arthrex, Naples, FL).Type of Study:Biomechanical single-pull load-to-failure study comparing the twist-lock construct to the Corkscrew suture anchor construct.Methods:The twist-lock construct is a suture anchor system that does not use knots, instead using 3 consecutive twists between suture limbs to enhance internal interference between the suture limbs. This system maximizes internal interference by 2 mechanically verifiable friction-multiplier mechanisms: the cable friction effect and the wedge effect. After theoretically verifying the strength characteristics of the twist-lock system, the authors tested and compared its strength in vitro to that of a standard screw-type suture anchor system (Corkscrew). Unicellular polyurethane, which has been shown to accurately mimic the properties of cancellous bone, was used for implantation of suture anchors for the purpose of comparing the load to failure of 10 identical constructs in each of the 2 anchor systems. Axial single-pull loading to failure was performed with an Instron 5565 testing machine (Instron, Canton, MA).Results:The average load to failure for the twist-lock group was 137.2 N, and the average for the Corkscrew group was 123.0 N, a difference of 14.2 N. This study shows that the twist-lock anchors failed at a load that was 12% higher than that of the Corkscrew group (P = .02).Conclusion:The twist-lock system is a suture anchor system that achieves suture fixation of soft tissue to bone without the need to tie knots. It shows single-pull loads to failure that are significantly higher than those of a standard suture anchor system.     

The effect of arthroscopic suture passing instruments on rotator cuff damage and repair strength

There are a variety of arthroscopic devices used to pass sutures through the rotator cuff for its repair. Because they vary in size and shape, it is possible that they could damage the cuff and affect the integrity of the repair. We chose four devices for assessment--SutureLasso (Arthrex, Naples, FL), straight BirdBeak (Arthrex, Naples, FL), Viper (Arthrex, Naples, FL), and a #7 tapered Mayo needle--and performed cuff reattachments in four paired shoulders using suture anchors. These repairs were cycled and tested to failure. The SutureLasso and Mayo needle repairs failed at approximately 285 N whereas the BirdBeak and Viper failed during cycling at 150 N. It appears that the devices, which made the bigger holes in the cuff, can compromise the integrity of the repair.     

The effect of suture anchor design and orientation on suture abrasion: An in vitro study

Purpose: To evaluate the effects of suture anchor design and orientation on suture abrasion in a cyclic model. Type of Study: In vitro. Methods: Biomechanical studies have shown suture breakage to be a predominant mode of failure in a suture anchor repair construct. It is possible that suture abrasion during knot tying or in vivo cyclic loading may contribute to early failure. This study specifically investigates suture abrasion caused by 17 commonly used suture anchors and demonstrates the effects of suture anchor angulation and rotation on suture abrasion. To eliminate target tissue as a source of failure, all anchors were implanted into a solid block of sawbones material and tested with No. 2 Ethibond Excel sutures (Ethicon, Somerville, NJ). The testing model focused on 3 variables: suture anchor type, suture pull angle (SA) and angle of anchor rotation (RA). Abrasion testing was then performed on a servohydraulic materials testing system by continually cycling the suture back and forth through each anchor with an excursion of 4 cm at a rate of 0.5 Hz under a load of 10 N until suture failure occurred. Results: Sutures performed significantly better when cycled in line with the anchor at 0° SA with 0° RA than they did at 45° SA with 0° RA or 45° SA with 90° RA. We found no significant difference between anchors tested at 45° SA with 0° RA and 45° SA with 90° RA. For tests performed using metallic suture anchors, all constructs failed by fraying of the suture. Constructs using biopolymer anchors and nonabsorbable polymeric anchors experienced a mixture of suture and anchor eyelet failures. Conclusions: In addition to the statistically significant detrimental effects of suture anchor angulation and rotation on suture abrasion, suture anchor eyelet design may also influence suture abrasion. Surgeons should be aware of the effects of anchor angulation, suture position in the eyelet, and design and composition of the eyelet to maximize the durability of the construct.Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 19, No 3 (March), 2003: pp 274–281     

Suture anchors, properties versus material and design: a biomechanical study in ovine model

The aim of our work was to compare the performance of suture anchors with various material and design that could be used in shoulder surgery. Three metallic and three bioabsorbable anchors mounted with stainless steel wire were tested. Their load to failure and mode of failure was determined in ex vivo ovine glenoids using Materials Testing Machine and attached load cell. Tensile load was applied at a rate of 60 mm/min, while load and displacement were recorded at a sampling rate of 100 Hz. Load to failure and failure mode was recorded. The mean load to failure for screw-type metallic anchors was Arthrex Fastak 678.3 N and Smith+Nephew Ti 3.5 499.7 N. Mitek GII (cylindrical with arcs) had a load to failure of 86.8 N. All bioabsorbable anchors exhibited lower load to failure comparing to screw-type metallic ones (P = 0.007), which was not statistically different between each other (P = 0.056): Arthrex BioFastak: 179.5 N; Mitek Panalok: 136.0 N; Smith+Nephew Bioraptor: 258.8 N. Metallic or bioabsorbable anchors had 30% eyelet failure (5/15 and 4/13, respectively). Our results suggest that metallic anchors have a better load to failure than bioabsorbable ones. Often the suture anchors’ weak point is their eyelet and needs further design improvement.     

The failure mode of two reabsorbable fixation systems: Swivelock with Fibertape versus Bio-Corkscrew with Fiberwire in bovine rotator cuff

BackgroundDespite technical advances in rotator cuff surgery, recurrent or persistent defects in the repaired tendon continue to occur. The improved strength of sutures and suture anchors has shown that the most common site of failure is the suture–tendon interface. The purpose of this study was to compare two different types of repair under both cyclic and load-to-failure conditions. The hypothesis is that the use of a fixation system with knotless anchor and taped suture results in better biomechanical performance, under both cyclic and load-to-failure conditions.MethodsThirty bovine shoulder specimens were randomly assigned to two group tests: the Swivelock 5-mm anchor with Fibertape (Group A) and the Bio-Corkscrew 5 mm with Fiberwire (Group B). We simulated the reconstruction of a rotator cuff tear with a single-row technique, performing a tenodesis with types A and B fixation. Each specimen underwent cyclic testing from 5 to 30 N for 30 cycles, followed by load-to-failure testing, in order to calculate the ultimate failure load (UFL).ResultsLoad-to-failure tests revealed a significantly higher UFL in Group A than in Group B. Wire fixing failed at the anchor loop whereas tape fixing failed at the sutures, suture–tendon interface, and anchors. Cyclic testing revealed no significantly greater slippage between the two groups. Stiffness values were not statistically significantly different. In all cases, tendons remained intact until the end of the cyclic testing.ConclusionsThe tape structure is biomechanically stronger than the wire structure.     

Primary fixation strength of rotator cuff repair techniques: a comparative study

Purpose:The goal of the study was to compare the primary fixation strength of transosseous suture, suture anchor, and hybrid repair techniques for rotator cuff repair.Type of Study:Animal model experiment.Methods:Thirty-two sheep shoulders were divided into 4 homogeneous groups, according to bone density and tendon dimensions. Infraspinatus tendons were transected from their insertions and reattached using 4 different techniques. Group 1 was repaired with a single Mason-Allen stitch and 2 transosseous tunnels for each end of the suture, knotted on the lateral cortex of proximal humerus; group 2 was repaired with double Mason-Allen stitches and 2 transosseous tunnels; group 3 was repaired with 2 Corkscrews (Arthrex, Germany); and group 4 was repaired with 2 Corkscrews combined with a single Mason-Allen transosseous suture. All specimens were tested for their fixation strengths with a material testing system.Results:The mode of failure in group 1 was mainly suture breakage. In groups 3 and 4, the tendons pulled out from the sutures. In group 2, sutures broke the bony bridge between the 2 tunnels. The mean load to failure value was 160.31 ± 34.59 N in group 1, 199.36 ± 11.73 N in group 2, 108.32 ± 15.98 N in group 3, and 214.24 ± 28.52 N in group 4. Anchor fixation was significantly weaker compared with other groups (P <.001). Combination of a transosseous suture and anchor fixation (group 4) was significantly stronger than the single transosseous suture (group 1) and double anchor techniques (group 3) (P <.001).Conclusions:Hybrid technique was the strongest among the tested rotator cuff repair techniques. With the addition of one transosseous suture to two anchors, the strength of the repair could be doubled.     

Mechanical testing of absorbable suture anchors

Purpose: Absorbable suture anchors offer great advantages but are made of mechanically weak material. The weakest link in the fixation of soft tissue to bone may therefore be the anchor itself. In this study, several commercially available anchors were mechanically tested in vitro. Type of study: Biomechanical bench study. Methods: Twelve absorbable suture anchor models were implanted into an artificial test bone according to the recommended technique. Testing temperature was 37°C ± 1°C. The anchors were loaded with an Instron testing machine with the suture material (USP No. 2, Ethibond, Ethicon, Somerville, NJ) in line with the anchor axis, with and without previous abrasion of the suture at the eyelet. Tensile load at failure and failure mode were recorded. To test creep behavior, a permanent load of 100 N was applied to the anchors, and time to failure was recorded. Suture anchor weight and crystallinity were analyzed. Results: Mean failure load on tensile testing using a cross-head speed of 60 mm/min ranged from 124 to 244 N. Failure modes were eyelet failure in 5 cases, suture failure in 6 cases, and anchor pullout in 1 case. In creep testing, eyelet failure occurred in 8 anchor models after a mean duration of 0.5 to 99 hours; 3 anchor models remained intact after 300 hours, and 1 anchor model failed by pullout of the test sample. Crystallinity ranged from 0% (amorphous) to 57.2%; anchor weight ranged from 0.036 to 0.161 g. Mechanical properties did not correlate with crystallinity but with anchor weight. Abrasion of the suture material at the eyelet had little effect on failure load. Conclusions: At 37°C, structural failure (breaking) of absorbable suture anchors may occur if loaded to the mechanical limit. Absorbable anchors are particularly sensitive to static, long-term loading.Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 19, No 2 (February), 2003: pp 188–193     

Initial fixation and cyclic loading stability of knotless suture anchors for rotator cuff repair

This study evaluated the resistance to gapping and the mode of failure for 2 knotless suture anchor systems used for rotator cuff repair compared with the performance of a conventional titanium anchor system. Eight matched pairs of fresh-frozen humeri were dissected free of all soft tissues and scanned to measure bone mineral density (BMD). The suture anchor systems tested were the TwinFix 5.0 Titanium (Smith & Nephew, Andover, MA), Bioknotless RC (DePuy Mitek, Norwood, MA), and Magnum (Opus Medical, San Juan Capistrano, CA), and each was inserted into each humerus. Cyclic, tensile loading was applied through the suture loop for 5000 cycles, or until failure, by using a servohydraulic testing machine. Gapping distances, defined as increasing elongation of the bone/anchor/suture system, were continuously measured. Total cycles to failure and mechanism of failure were documented. Mean initial (first cycle) and final (last cycle) gapping distances were 3.81 mm and 5.36 mm for the TwinFix 5.0, 4.02 mm and 5.34 mm for the Bioknotless RC, and 3.56 mm and 4.98 mm for the Magnum anchors. No significant difference was detected among mean gap openings (P > .05). However, the Bioknotless RC had more early failures (5) than the other 2 implants (1 each), approaching significance (P = .07). Trials of the Bioknotless RC that did not fail early were found to have significantly less gap opening than the other 2 systems for both initial (1.89 mm vs 3.82 mm for the TwinFix 5.0 and 3.56 mm for the Magnum) and final (2.00 mm vs 4.68 mm for the TwinFix 5.0 and 4.24 mm for the Magnum) gap opening. BMD was a significant predictor of initial (P = .029) and final (P = .008) gap opening, whereas the site of anchor insertion was a significant predictor of final displacement. The Opus Magnum was comparable with a conventional suture anchor, but the Mitek Bioknotless RC showed a trend toward early failure. Biomechanical analysis of knotless suture anchor systems can demonstrate trends among implants in an experimental setting. Knowledge of these trends could influence implant selection.     

Bearing area: A new indication for suture anchor pullout strength?

Studies performed to quantify the pullout strength of suture anchors have not adequately defined the basic device parameters that control monotonic pullout. The bearing area of a suture anchor can be used to understand and predict anchor pullout strength in a soft‐bone model. First, conical‐shaped test samples were varied in size and shape and tested for pullout in 5, 8, and 10 pcf sawbone models. Next, bearing area and pullout strength relationships developed from the test samples were validated against nine commercially available suture anchors, including the Mitek QuickAnchor and SpiraLok, Opus Magnum², ArthroCare ParaSorb, and Arthrex BioCorkscrew. The samples showed a direct correlation between bearing area and pullout strength. Increased insertion depth was a secondary condition that also increased pullout strength. The pullout strength for the suture anchors followed the predicted trends of conical devices based on their individual bearing areas. For the 5 and 8 pcf models, only two and three devices, respectively, fell outside the predicted pullout strength range by more than a standard deviation. The use of a synthetic sawbone model was validated against the pullout strength of an Arthrex Corkscrew in five fresh‐frozen cadaver humeral heads. The bearing area of a suture anchor can be used to predict the pullout strength independent of design in a soft‐bone model. This work helps provide a foundation to understand the principles that affect the pullout strength of suture anchors. © 2009 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 27: 1048–1054, 2009     

Rotator cuff repair with bioabsorbable screws: An in vivo and ex vivo investigation

Purpose: The purpose of this study was to evaluate in vivo the clinical outcomes of rotator cuff repairs with bioabsorbable screws compared with metal suture anchors, and to compare the ex vivo initial load to failure of rotator cuff repairs using 3 different bioabsorbable screws, suture anchors, and transosseous sutures. Type of Study: In vivo clinical outcomes investigation, and ex vivo biomechanical study. Methods: Three cohorts of patients with rotator cuff tears that measured less than 4 cm², were sequentially repaired with Mitek Rotator Cuff QuickAnchors (Mitek Surgical Products, Norwood, MA) (n = 9), Arthrex Headed Bio-Corkscrews (n = 9) (Arthrex, Naples, FL), and Mitek Rotator Cuff QuickAnchors (n = 9). Patients were systematically assessed with a specific shoulder questionnaire and 23 shoulder tests performed preoperatively and at 1 and 6 weeks, 3 and 6 months, and 1 year postoperatively. A correlative ex vivo biomechanical study was performed on 53 ovine shoulders to evaluate the initial failure load properties of bioabsorbable screws compared with fixation with suture anchors and transosseous sutures. Results: In the in vivo portion of the study, the cohort treated with the Headed Bio-Corkscrew demonstrated no improvement on any measured parameter until 1-year after rotator cuff repair. In contrast, shoulders repaired with Mitek Rotator Cuff QuickAnchors demonstrated improved overall shoulder function as early as 6 weeks postoperatively (P =.002), had a better constant score at 1-year after repair (88 ± 9 v 73 ± 17; P =.016), and a lower rate of revision rotator cuff repair (P =.029). In the ex vivo portion of the study, the bioabsorbable headed screws, Headed Bio-Corkscrew (100 ± 30 N) and BioTwist (76 ± 35 N), had inferior initial failure load properties compared with suture anchors (140 ± 36 N) and transosseous sutures (147 ± 68 N). In contrast, the BioCuff (190 ± 56 N), a bioabsorbable implant that used a screw and serrated washer design, had equivalent initial failure load properties as the suture repairs. Conclusions: This investigation had poorer early outcomes, a lower shoulder functional score 1-year after repair, and a higher rate of repeat surgery in patients who had their rotator cuff repaired with a bioabsorbable screw than in patients who had their shoulders repaired with a standard metal suture anchor. Furthermore, the biomechanical testing demonstrated a lower tensile load to failure in the tendons repaired with a simple screw design compared to suture anchors with a mattress stitch. Of note, the implant that used a screw and washer design demonstrated a greater ability to resist initial tensile load.Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 19, No 3 (March), 2003: pp 239–248     

Arthroscopic Bankart revision using all suture anchor in recurrent anterior shoulder dislocation: A case report

IntroductionArthroscopic Bankart revision after recurrent shoulder dislocation is still a matter of discussion. Several factors are contributing to this injury. Recently the development of all suture anchors has grown in popularity in arthroscopic stabilization. It was proven to preserve bone stock, smaller in size thus more anchors can be made.Presentation of caseWe presented a case of 27-year-old woman with recurrent anterior dislocation after seven years of arthroscopic Bankart repair. Seven years before, we performed Bankart repair using three 2.8 mm fiber-wire anchor (FASTak® (Arthrex, Karsfield Germany)). For the revision surgery we performed arthroscopic revision using four all suture anchor technique (Y-Knot® Flex All-Suture Anchor, 1.3 mm – One strand of #2 Hi-Fi® (Conmed, New York)).DiscussionFrom preoperative and intraoperative assessment, we found no anchor failure and no massive bony lesion. To preserve the bone stock we insert four all suture anchors between the old anchor. One year post-operative follow up showed that patient could gain normal range of movement. No early or late complications were observed.ConclusionCompared to the conventional metallic anchor, all suture anchor has the same biomechanical strength. Moreover due to its relatively small size, it can reserve bone stock and more anchors can be made thus adding more stability to the shoulder.     

The low-profile Roman bridge technique for knotless double-row repair of the rotator cuff

With advances in arthroscopic surgery, many techniques have been developed to increase the tendon–bone contact area, reconstituting a more anatomic configuration of the rotator cuff footprint and providing a better environment for tendon healing. We present a low-profile arthroscopic rotator cuff repair technique which uses suture bridges to optimize rotator cuff tendon–footprint contact area and mean pressure. A 5.5 mm Bio-Corkscrew suture anchor (Arthrex, Naples, FL, USA), double-loaded with No. 2 FiberWire sutures (Arthrex, Naples, FL, USA), is placed in the anteromedial aspect of the footprint. Two suture limbs from a single suture are both passed through a single anterior point in the rotator cuff. One suture limb is retrieved from the cannula. The second suture limb is passed through a single posterior point in the rotator cuff producing two points of fixation in the tendon, with a tendon bridge between them. The same suture limb is retrieved through the lateral portal, and then inserted into the bone by means of a Pushlock (Arthrex, Naples, FL, USA), placed approximately 1.5–2 cm posterior to the first anchor. This second suture is passed again in the posterior aspect of the cuff. The limbs of the first suture are pulled to compress the tendon in the medial aspect of the footprint. The two free suture limbs are used to produce suture bridges over the tendon by means of a Pushlock (Arthrex, Naples, FL, USA), placed 1 cm distal to the lateral edge of the footprint relative to the medially placed suture anchors anterior to posterior. This technique allows us to perform a low-profile (single pulley–suture bridges) repair for knotless double-row repair of the rotator cuff.     

A comparison of lateral ankle ligament suture anchor strength

BackgroundLateral ankle ligament repairs increasingly use suture anchors instead of bone tunnels. Our purpose was to compare the biomechanical properties of a knotted and knotless suture anchor appropriate for a lateral ankle ligament reconstruction.MethodsIn porcine distal fibulae, 10 samples of 2 different PEEK anchors were inserted. The attached sutures were cyclically loaded between 10 N and 60 N for 200 cycles. A destructive pull was performed and failure loads, cyclic displacement, stiffness, and failure mode recorded.ResultsPushLock 2.5 anchors failed before 200 cycles. PushLock 100 cycle displacement was less than Morphix 2.5 displacement (p < 0.001). Ultimate failure load for anchors completing 200 cycles was 86.5 N (PushLock) and 252.1 N (Morphix) (p < 0.05). The failure mode was suture breaking for all PushLocks while the Morphix failed equally by anchor breaking and suture breakage.ConclusionsThe knotted Morphix demonstrated more displacement and greater failure strength than the knotless PushLock. The PushLock failed consistently with suture breaking. The Morphix anchor failed both by anchor breaking and by suture breaking.     

Knot security in simple sliding knots and its relationship to rotator cuff repair: how secure must the knot be?

We sought to determine which simple sliding knot configurations would have adequate strength for rotator cuff repair. Four knot configurations were tied with both No. 1 polydioxanone suture and No. 2 Ethibond suture (Ethicon, Somerville, NJ) using 3 different tying techniques: hand-tie, standard knot pusher, and cannulated double-diameter knot pusher. The knots were then tested to failure on a materials testing system. The weakest standard knot configuration was S=S=S=S. The other 3 knot configurations (S//S//S//S, SxSxSxS, and S//xS//xS//xS) generally failed in the 35 to 50 N range. Ultimate strength in this range can be shown to be adequate to withstand, without suture failure, a maximal contraction of a repaired rotator cuff tear within the rotator crescent, assuming certain conditions are met (suture anchors placed 1 cm apart, 2 sutures per anchor). More complex knots are not necessary for adequate knot security. However, the same configuration with only 1 suture per anchor will not be strong enough because the suture will fail under maximum physiological load. This study shows that we can predict the adequacy of a given knot configuration under maximum physiological loading conditions.     

Suture anchor strength revisited

The rapid proliferation of suture anchors continues. Our prior report on the pullout strength of 14 different anchors is supplemented by a similar test conducted on 8 additional anchors. Comparative data on modes of failur and failure strengths (ultimate loads to failure) for these new devices are compared statistically with the previously tested anchors. In a fresh never-frozen porcine femur model, 10 samples of each of the additional anchors tested were threaded with stainless steel sutures and inserted into three different test areas (diaphyscal cortex, metaphyseal cortex, and a cancellous trough). Tensile stress parallel to the axis of insertion was applied at a rate of 12.5 mm/s by an Instron 1321 testing machine (Instron Corp., Canton, MA) until failure and mean anchor failure strengths calculated. The anchors tested were the MItek G2 as a control, miniMitek, Mitek Superanchor, Mitek Rotator Cuff anchor (Mitek Products, Westwood, MA), Innovasive Devices Radial Osteal Compression device (Innovasive Devices, Hopkinton, MA), Arthrex Fastak (Arthrex Inc, Naples, FL), Arthrotek miniHarpoon (Arthrotek, Warsaw, IN), Orthopedic Biosystems PeBA 3 and PeBA 5 (Orthopedic Biosystems, Scottsdale, AZ), and AME 5.5 screw (American Medical Electronics, Richardson, TX). Failure mode (anchor pullout, suture eyelet cut out, or wire breakage) was generally consistent for each anchor type. The size of insertion hole is clinically important and each anchor's performance was evaluated as a function of is minor diameter or drill hole. For screw anchors, the larger the minor diameter of the screw, the higher the mean failure strengthsin all three test areas (P = .001). However, larger drill holes for non-screw anchors resulted in lower mean failure strengths in cancellous bone (P = .03) and diaphyseal cortex (P < .005).     

Effect of core suture technique and type on the gliding resistance during cyclic motion following flexor tendon repair: A cadaveric study

We investigated the effects of two suture techniques using three suture types in a human model in vitro. We obtained 60 flexor digitorum profundus (FDP) tendons from cadavers and measured the gliding resistance during 1,000 cycles of simulated flexion–extension motion and load to failure of six groups: the modified Kessler (MK) repair using 3‐0 coated, braided polyester (Ethibond, Ethicon, Somerville, NJ), 3‐0 coated, braided polyester/monofilament polyethylene composite (FiberWire®; Arthrex, Naples, FL), or 4‐0 FiberWire; and the Massachusetts General Hospital (MGH) repair using 3‐0 Ethibond, 3‐0 FiberWire, or 4‐0 FiberWire. The 3‐0 Ethibond MGH suture had significantly higher ultimate load to failure than the 3‐0 or 4‐0 FiberWire MK suture. The 3‐0 and 4‐0 FiberWire MGH sutures had significantly higher load to failure than the three MK groups. The gliding resistances of the three MGH groups were significantly higher than that of the three corresponding MK groups. The MGH repair had more gliding resistance than an MK repair, even when comparing large diameter suture in the MK repair with smaller diameter suture in the MGH repair. In this study, suture technique was more important in predicting repair load to failure and gliding resistance than the nature or caliber of the suture material that was used. © 2010 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 28:1475–1481, 2010     

Tenodesis of the long head of biceps brachii: cyclic testing of five methods of fixation in a porcine model

For pathologies of the long head of the biceps brachii, various surgical treatment options have been described, ranging from tenotomy to different open and arthroscopic techniques for tenodesis. We analyzed the biomechanical properties of 5 widely used operative techniques for tenodesis of the long head of the biceps brachii: an interference screw (7 x 23-mm Arthrex BioTenodesis screw), a suture anchor (5 x 15-mm Arthrex BioCorkscrew), a ligament washer, the keyhole technique, and the bone tunnel technique. Ten porcine humeri for each technique were used to evaluate the ultimate failure load and cyclic displacement. Tenodesis with the interference screw showed a significantly greater ultimate failure load compared with every other technique (480.9 +/- 116.5 N, P < .005) and the least displacement after 200 cycles, significantly less in comparison to the keyhole and bone tunnel techniques (4.28 +/- 1.44 mm, P < .05). Interference screw fixation has superior biomechanical properties with respect to cyclic displacement and primary fixation strength.