A novel, resorbable suture anchor: pullout strength from the human cadaver greater tuberosity.

The pullout strength of a collagen bone anchor that creates interference fixation as the result of radial swelling on hydration was compared with a Mitek rotator cuff anchor after insertion into the greater tuberosity of human cadaver humeri. Bones were fully hydrated at 37 degrees C. Stiffness, peak load, and the mode of failure were recorded. Real and apparent bone densities were measured. Peak load for the collagen anchor at 15 minutes (121.0N +/- 81.3N) was greater than at 2 minutes (60.5N +/- 38.5N) after insertion (P <.05). At between 5 and 60 minutes after insertion, peak loads for the Mitek and the collagen anchors did not differ. After 30 minutes from insertion, the mode of failure of the collagen anchor changed from pullout with minor body damage to pullout with major body damage. Peak load at pullout correlated with bone density for the Mitek (P <.05, r = 0.516) but for the collagen bone anchor appeared unaffected by bone density.     

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     

Bone suture anchors versus the pullout button for repair of distal profundus tendon injuries: a comparison of strength in human cadaveric hands.

Avulsion or distal tendon laceration of flexor digitorum profundus (FDP) is classically repaired to the base of the distal phalanx via a pullout suture over a button. Bone suture anchors, used extensively in other surgical areas, have recently been proposed for reattachment of the FDP to the distal phalanx. The FDP tendons of the index, long, and ring fingers in 9 fresh frozen cadeveric hands were randomized to 1 of 3 repair techniques after simulated distal avulsion injuries. These were the pullout button using 3-0 monofilament nylon in a 2-strand Bunnell suture pattern, the 1.8 mm Mini QuickAnchor (Mitek Products, Norwood, MA) using 3-0 braided polyester in a 2-strand Bunnell suture pattern, and the Mitek micro anchor using 3-0 braided polyester with a modified 4-strand Becker suture pattern. Nine specimens were loaded to failure, noting maximum load and mode of failure. The 1.3 mm Micro QuickAnchor (Mitek) technique (69.6 +/- 10.8 N) was significantly stronger than the pullout button (43.3 +/- 4.8 N) or the Mini anchor technique (44.6 +/- 12.7 N). The Micro bone suture anchor provides a stronger tendon to bone repair than the pullout button or the Mini anchor. Given the disadvantages of the pullout button, the Micro bone suture anchor with the modified Becker technique is worth consideration as an alternative method to repair distal FDP avulsions.     

Modes of failure of knotted and knotless suture anchors in an arthroscopic bankart repair model with the capsulolabral tissues intact

The purpose of this study was to assess failure modes of knotless and knotted anchors in a Bankart repair model with the capsulolabral soft tissues intact. Previous reports used a model stripped of soft tissues. In 8 matched pairs of cadaver shoulders, a Bankart lesion was repaired arthroscopically using either 2 Bio-SutureTak anchors (Arthrex, Naples, Florida) or 2 Bioknotless anchors (Mitek, Westwood, Massachusetts). The shoulders were mounted with the repaired capsulolabral tissues attached to a custom sinusoidal clamp, and were tested in cyclic loading (20-80 N, 100 cycles, 0.5 mm/s) and then load to failure (1.25 mm/s). Cut-through at the suture-tissue interface (23/32 anchors) was more common than pullout at the anchor-bone interface (9/32) as a mode of failure (P = .02). Failure at the suture-tissue interface occurred in 10/16 knotted and 13/16 knotless anchors. Mean (SD) ultimate load of knotted vs knotless anchors was 125.3 (67.4) N and 96.9 (95.1) N, respectively. Mean (SD) stiffness of knotted vs knotless anchors was 20.9 (6.4) N/mm and 19.8 (8.6)N/mm, respectively. We concluded that both knotted and knotless anchors fail most often at the suture-tissue interface. The tested model with the capsulolabral tissues intact is distinct from previous models, which tested the anchor-bone interface only.     

Biomechanical testing of a new knotless suture anchor compared with established anchors for rotator cuff repair

Various suture anchors are available for rotator cuff repair. For arthroscopic application, a knotless anchor was developed to simplify the intra-operative handling. We compared the new knotless anchor (BIOKNOTLESStrade mark RC; DePuy Mitek, Raynham, MA) with established absorbable and titanium suture anchors (UltraSorbtrade mark and Super Revo 5mmtrade mark; ConMed Linvatec, Utica, NY). Each anchor was tested on 6 human cadaveric shoulders. The anchors were inserted into the greater tuberosity. An incremental cyclic loading was performed. Ultimate failure loads, anchor displacement, and mode of failure were recorded. The anchor displacement of the BIOKNOTLESStrade mark RC (15.3 +/- 5.3 mm) after the first cycle with 75 N was significantly higher than with the two other anchors (Super Revo 2.1 +/- 1.6 mm, UltraSorb: 2.7 +/- 1.1 mm). There was no significant difference in the ultimate failure loads of the 3 anchors. Although the Bioknotlesstrade mark RC indicated comparable maximal pullout strength, it bares the risk of losing contact between the tendon-bone-interface due to a significantly higher system displacement. Therefore, gap formation between the bone and the soft tissue fixation jeopardizes the repair. Bioknotlesstrade mark RC should be used in the lateral row only when a double row technique for rotator cuff repair is performed, and is not appropriate for rotator cuff repair if used on its own.     

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).     

Fatigue properties of suture anchors in anterior shoulder reconstructions: Mitek GII

Suture anchors have simplified anterior capsule labral reconstruction. During rehabilitation the shoulder goes through many repetitions of range of motion exercises. These exercises will repetitively submaximally load the anchor and in theory should reduce the pullout strength of the suture anchor. No published reports exist on the fatigue strengths and properties of one of the most commonly used anchors: Mitek GII suture anchors. Fifty trials of cyclic submaximal load were done on 22 cadaveric glenoids with an average age of 66.8 years (range, 40 to 90 years). At two to three different sites on the same specimen, the anchors were inserted according to manufacturer's specifications. The anchors were tested to failure on a Instron 1331 servohydraulic mechanical testing system at 2 Hertz sinusoidal loading pattern using steel sutures and a predetermined load. There were 22 (44%) tests performed in the superior quadrant and 28 (56%) tests in the inferior quadrant. All anchors pulled out, and no wires broke. There were statistically significant differences between the superior and inferior portion of the glenoid with regard to number of cycles to failure at a given maximum load. The anchors underwent an average of 6,220 cycles before pullout at an average load of 162 N (SD = 73 N). In the superior quadrant, the average ultimate pullout strength was 237 N (SD = 42 N), whereas in the inferior quadrant the average ultimate pullout strength was 126 N (SD = 36 N). Hence, the ultimate pullout strength of the Mitek GII anchor was significantly higher (P < .002) in the superior quadrant than in the inferior quadrant. Using a least squares regression analysis, it was possible to predict the fatigue life of the superiorly and inferiorly placed suture anchors over a wide range of cycles. The R-squared values for trendlines showed good reliability (superior R² = 0.55; inferior R² = 0.28). The fatigue life curves for the two different quadrants were normalized using the ultimate pullout strength. This new, universal curve predicts the fatigue life of the Mitek GII anchor as a percentage of the ultimate pullout strength for any selected location. For a clinically relevant number of cycles, no more than approximately 40% to 50% of the ultimate pullout strength of the suture anchor can be cyclically applied to the anchor to guarantee a life for the duration of rehabilitation. For the entire system, the inferiorly placed anchors dictate the amount of cyclically applied load the system can experience without failing, and rehabilitation should be adjusted accordingly.     

In vitro comparison of standard and knotless metal suture anchors

Purpose: Clinical experience after failed Knotless suture anchor (Mitek, Westwood, MA) fixations suggested that the Knotless anchor provides considerably less fixation stability than a standard metal anchor. The purpose of this study was to analyze soft tissue fixation to bone comparing a standard and a Knotless metal suture anchor. Type of Study: In vitro study. Methods: The Mitek GII and Mitek Knotless suture anchors were tested on 7 human cadaveric fresh-frozen glenoids. The anchors were inserted into the glenoid rims, and the sutures of the anchors were fixed to a metal hook attached to the cross-head of a testing machine. Cyclic loading was performed. The gap formation between the metal hook and the glenoid rim, the ultimate failure loads and the modes of failure were determined. Results: The mean gap formation was significantly greater for the Knotless anchor (3.8 ± 1.4 mm) than for the GII anchor (2.4 ± 0.5 mm) after 25 cycles with 50 N repeated load (P = .04). The largest gap of a Knotless fixation was 5.3 mm compared with 3.0 mm for the GII. The ultimate failure load was not significantly different for the Knotless anchor (179 N) and for the GII anchor (129 N). Both anchors failed by either rupture of the suture material or by pullout of the anchors. Conclusions: The GII anchor allows significantly less displacement than the Knotless anchor. Ultimate tensile strength and mode of failure are similar. Greater displacement results in larger gap formation between the soft tissue and the bone. This might weaken and jeopardize the repair. Clincial Relevance: If reattached soft tissues are subjected to postoperative loading, gap formation may result when using the Knotless anchor. For these conditions, suture fixation with knots may be used instead.     

Reconstruction of the proximal interphalangeal joint collateral ligaments using the Mitek Micro Arc Anchor: an in vitro biomechanical assessment

Proximal interphalangeal joint (PIP) collateral ligament injuries are common and sometimes result in painful, stiff fingers. A number of techniques have been utilized in the past to reconstruct complete collateral ligament injuries. Recently, bone anchor systems have been described that allow collateral ligament reconstruction without the necessity of pull-out wires and other more cumbersome methods to reconstruct these ligaments. The Mitek bone anchor system has been used successfully in a variety of anatomic locations throughout the body to reattach soft tissues to bone. The current study was conducted to evaluate the biomechanical effects of the use of the Mitek Micro Arc Anchor in collateral ligament injuries of the PIP joint. In cadaveric PIP joints, the collateral ligament was isolated and then transsected in its mid substance. The authors compared suturing the ligament alone in standard fashion to repair of the ligament using a bone anchor inserted in the base of the middle phalanx. The joints were stressed to failure, with a lateral load applied at the distal end of the middle phalanx on a materials testing machine. The mean tensile failure loads of the two groups were the following: Mitek anchor, 16.4 +/- 3.7 N; suture repair, 19.3 +/- 7.6 N. The authors found no significant difference in the force required for failure of the repair or in the pattern of failure in the two groups. The Mitek Micro Arc Anchor appears to be adequate biomechanically to reconstruct the collateral ligaments of the finger PIP joint.     

Repair of central slip avulsions using Mitek Micro Arc bone anchors. An in vitro biomechanical assessment

In this study we evaluated the pullout strength of the Mitek Micro Arc anchor for the reconstruction of central slip avulsions at the proximal interphalangeal joint of the finger. Forty paired fresh frozen cadaver fingers were randomized into treatment (anchor) and control groups (horizontal mattress repair) and subjected to tensile loading to failure. The mean (SD) failure loads of the repairs were: Mitek repair group 22.3 (4.7) N, and control group 24.7 (5.5) N. There were no statistically significant differences between the failure loads or the failure mechanisms of the two repairs. The pullout strength of the isolated anchor-bone complex was evaluated by refitting five anchors with stainless steel wire. The mean failure load of the isolated anchor was 400% higher than the tendon-suture-anchor complex, indicating that the weakest link of the system is not the bone-anchor interface.     

Primärstabilität des Kapsel-Labrum-Komplexes nach Rekonstruktion mit Mitek-Bioknotless-Fadenankern am humanen Schulterkadavermodell

Background

This study examines the postoperative stability of the Mitek Bioknotless anchor system with biomechanical draw-out pulling in human cadaver shoulders.

Method

With simulation of anterior shoulder dislocation a test group (n=10, Ø 45 years) was tested against a native group (n=8, Ø 47 years). All shoulders were dissected up to the passive stabilizers. In the test group an artificial Bankart lesion was created and repaired with three Mitek Bioknotless anchors. The humeri of both groups were fixed in 60° glenohumeral abduction and 90° external rotation and then dislocated in a ventral direction. For evaluation purposes the ultimate draw-out strength, mode of failure, translation of humeral head, capsular slope, and bone density in the test group were measured.

Results

In the test group the ultimate strength was a median of 937 N (min. 554 N, max. 1,294 N) with 28 bony anchor dislocations, 1 suture rupture, and 1 capsular rupture, and in the native group with 6 Bankart and 2 HAGL lesions it was 1,214 N (708 N, 1,471 N). The bone density showed a positive correlation to the draw-out strength regarding cortical density and total density.

Conclusion

Regarding the high draw-out strength the Mitek Bioknotless anchor system provides enough stability for early functional treatment.     

Use of Mitek anchoring for Bankart repair: A comparative, randomized, prospective study with traditional bone sutures

The most common type of shoulder instability is posttraumatic anterior instability. Treatment is surgical. Of the several procedures used, the standard one is Bankart repair. However, this procedure is technically demanding. To simplify it a suture anchor such as Mitek anchors may be used. A prospective randomized study was conducted to compare Mitek anchors with bone sutures. The results showed that Mitek anchors shorten surgical time by making reattachment of the capsule easier. Shoulder muscle strength, range of motion, and frequency of recurrence were equally good in the anchor group and bone suture group. A roentgenographic method allowed exact measurement of placement of the anchors. This method showed at 2-year follow-up evaluation that the anchors were still in the anterior glenoid. No metal-related complications are found at the 2-year follow-up evaluation.     

Über die Primärfestigkeit konventioneller und alternativer Nahttechniken der RotatorenmanschetteEine biomechanische Untersuchung

The aim of this biomechanical study was to evaluate rotator cuff repair strength using different suture anchor techniques compared to conventional repair, taking into consideration the native strength of the supraspinatus tendon. Therefore, a defined defect of the supraspinatus was created in 50 freshly frozen cadaver specimen (group size n = 10; median age at death: 56 years). Five methods were employed for cuff repair: standard transosseous suture, modified transosseous suture with patch augmentation and three suture anchors (Acufex Wedge TAG, Acufex Rod TAG und Mitek GII). The maximum tensile load of the five techniques was: standard transosseous suture, 410 N; modified transosseous suture, 552 N; Wedge TAG, 207 N; Rod TAG, 217 N; Mitek GII, 186 N. The difference between the suture anchor and standard techniques were highly significant (P < 0.001). In this series, the Mitek Gll anchor showed the lowest anchor dislocation rate at 3% (n = 1). The Wedge TAG system had a dislocation rate of 27% (n = 8) and the Rod TAG system 43% (n = 13). Suture anchor techniques revealed about 20%, the standard technique 34% and its modification 60% of the hypothetically calculated native tendon strength. Compared to conventional transosseous suture techniques, the use of the suture anchors tested in this series does not significantly increase the primary fixation strength of rotator cuff repair. The metallic implant with two barbs (Mitek GII) seems to be superior to the polyacetal anchors when inserted into the spongiform bone of the greater tubercle. The considerably weaker repair strength needs to be taken into consideration in postoperative patient rehabilitation, especially after the use of suture anchors.     

Sutures and suture anchors: update 2003

Purpose:The purpose of this study was to evaluate recently introduced sutures and suture anchors for single-pull load-to-failure strength and failure mode.Type of Study:Experimental laboratory biomechanical study.Methods:Using an established protocol in fresh porcine femurs, anchors were tested in diaphyseal cortex, metaphyseal cortex, and cancellous troughs after threading them with either steel sutures or strong synthetic material to reduce the likelihood of suture breakage as a mode of failure. An Instron machine (Instron, Canton, MA) applied tensile loads parallel to the axis of insertion at a rate of 12.5 mm/second until failure, and mean anchor failure strengths were calculated. Mode of failure was recorded (anchor pullout, suture eyelet cutout, or wire breakage). Anchors tested included the RotorloC (Smith & Nephew Endoscopy, Andover, MA), TwinFix Ti 3.5, TwinFix Ti 5.0, and TwinFix AB (Smith & Nephew Endoscopy), Super Revo and UltraSorb (Linvatec, Largo, FL), Duet (Bionx Implants, Blue Bell, PA), AlloAnchor RC (Regeneration Technologies, Alachua, FL), Opus Magnum anchor (Opus Medical, San Juan Capistrano, CA), and the BioCorkscrew 5.0 and BioCorkscrew 6.5 (Arthrex, Naples, FL). Sutures tested were No.2 and No. 5 Ethibond (Ethicon, Somerville, NJ), No. 2 Panacryl (Mitek, a division of Ethicon, Somerville, NJ), and Nos. 2, 5, and 2–0 Fiberwire (Arthrex, Naples, FL).Results:The sutures all broke in the midpoint of their tested strand away from the grips. The No. 2 Ethibond failed at a mean of 21 lb (92 N); No. 5 Ethibond failed at a mean of 44 lb (193 N); No. 2, No. 5, and No. 2–0 Fiberwire at means of 44 lb (188 N), 112 lb (483N), and 19 lb (82 N), respectively; and No. 2 Panacryl at a mean of 22 lb (99 N). The suture anchors all failed at levels higher than the associated sutures.Conclusions:Screw anchors showed higher load to failure values than nonscrew designs, and the new biodegradable anchors showed failure loads lower than the anchors. All anchors were stronger than the suture for which they are designed.     

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.     

A Knotless Suture Anchor: Technique for use in arthroscopic Bankart repair

Arthroscopic Bankart repair performed using suture anchors most closely mimics open repair techniques. One of the challenges with the arthroscopic technique is tying consistent, good-quality arthroscopic knots. The unique Knotless Suture Anchor (Mitek Products, Westwood, MA) and method of use for arthroscopic Bankart repair is described. The Knotless Suture Anchor has a short loop of suture secured to the tail end of the anchor. A channel is located at the tip of the anchor that functions to capture the loop of suture after it has been passed through the ligament. The ligament is tensioned as the anchor is inserted into bone to the appropriate depth. The doubled suture configuration that is created with the loop increases the suture strength in the Knotless Suture Anchor compared with standard suture anchors with the same size suture. To my knowledge, this article describes the first knotless suture anchor. A secure, low-profile repair can be created without arthroscopic knot tying.Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 17, No 2 (February), 2001: pp 213–218     

Initial repair strengths of two methods for acute medial collateral ligament injuries of the elbow.

The purposes of this study were to compare the initial repair strength of the medial collateral ligament (MCL) of the elbow using trans-osseous sutures and suture anchor methods and to determine the effect of repair pretensioning. Twelve, fresh-frozen upper extremities (66 +/- 5 years) were mounted in a valgus-loading system. MCL repairs were performed using trans-osseous suture and suture anchor methods with 20 N or 40 N pretensioning. A cyclic (0.5 Hz), valgus 40 N load was applied 12 cm distal to the elbow axis of flexion. The load was increased by 10 N every 200 cycles until a length increase of 5 mm or catastrophic failure of the repair occurred. Repairs pretensioned with 40 N endured a significantly higher number of cycles and failed at higher loads than those pretensioned with 20 N (p < 0.05). No difference was found in the cycles or load to failure between trans-osseous sutures and suture anchors (p > 0.05). A higher magnitude of pretensioning of MCL repairs was found to increase initial repair strength suggesting that pretensioning should be performed clinically. Despite the comparable failure loads of the trans-osseous suture and suture anchor methods, the failure mechanism differed between the two techniques. The suture anchors usually failed catastrophically when the sutures broke as they passed through the anchor eyelet, while the trans-osseous sutures gradually elongated to the defined failure length by stretching and sliding through the ligament. The use of different suture anchors, suture sizes, or suture materials would likely influence the findings of this study and should be considered when applying these findings clinically.     

An in vitro study comparing the use of suture anchors and drill hole fixation for flexor digitorum longus transfer to the navicular

BACKGROUND: The surgical management of posterior tibial tendon dysfunction often includes transfer of the flexor digitorum longus (FDL) tendon through a tunnel in the navicular. Fixation often is obtained by sewing the tendon back onto itself. The purpose of this study was to compare this standard method of fixation with suture anchor fixation, a technique that may be associated with less surgical morbidity, because it requires the harvesting of less tendon length. METHODS: FDL tendon transfer to the navicular was done in 13 fresh-frozen cadaver specimens. In six feet comprising the standard group, the FDL tendon was transected distal to the master knot of Henry, placed through a drill hole into the navicular, and sutured back onto itself. In seven feet the FDL tendon was transected proximal to the master knot of Henry, placed into a drill hole into the navicular, and fixed with a suture anchor. Load was applied to the proximal FDL muscle and tendon using a materials testing system (MTS) machine and peak load to failure was measured. RESULTS: The mean load to failure was 142.48 N +/- 38.06 N for the standard group and 142.12 N +/- 59.26 N for the suture anchor group (p = 0.305 for the Student-t test and p = 0.945 for the Mann-Whitney test). CONCLUSION: Transfer of the FDL tendon to the navicular using suture anchor fixation requires less tendon length yet provides similar fixation strength as compared to sewing the tendon back onto itself. However, suture anchors are considerably more expensive than sutures. CLINICAL IMPLICATIONS: Suture anchors allow comparable fixation of FDL tendon transfer into a navicular without the need to disrupt the master knot of Henry. This technique may be associated with less morbidity including a shorter incision, decreased risk of medial plantar nerve injury, and decreased loss of lesser toe plantarflexion strength secondary to maintenance of the normal interconnections between the flexor hallucis longus (FHL) and FDL tendons.     

Revisability of polyetheretherketone suture anchors utilised in primary and revision Bankart repair

BackgroundPolyetheretherketone (PEEK) suture anchors are frequently used in Bankart shoulder stabilisation. This study analyzed the primary stability and revisability of PEEK anchors in-vitro in case of primary Bankart repair and revision Bankart repair after failed primary repair.MethodsTo simulate primary Bankart repair, 12 anchors (Arthrex PEEK PushLock® 3.5 mm) were implanted in 1, 3, 5, 7, 9 and 11 o'clock positions in cadaveric human glenoids and then cyclically tested. To simulate revision Bankart repair, 12 anchors were implanted in the same manner, over-drilled and 12 new anchors of the same diameter were implanted into the same bone socket as the primary anchors and then cyclically tested. The maximum failure loads (F_max), system displacements, force at clinical failure and modes of failure were recorded.ResultsOne primary anchor failed prematurely due to a technical problem. Three out of 12 revision anchors (25%) dislocated while setting the 25 N preload. The F_max, the displacement and clinical failure of the remaining 9 revision anchors were non-significant when compared to the 11 primary repair anchors. The main mode of failure in the primary and revision Bankart surgery group was suture slippage. Anchor dislocations were observed four times in the primary and once in the revision repair groups.ConclusionsRevision Bankart repair using PEEK anchors of the same diameter in a pre-existing bone socket is possible but bears high risk of premature anchor failure and can jeopardize the reconstruction. PEEK suture anchor in revision Bankart surgery should be implanted in a new bone socket if possible.     

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.