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.     

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.     

Button Fixation Technique for Achilles Tendon Reinsertion: A Biomechanical Study

Chronic insertional tendinopathy of the Achilles tendon is a frequent and disabling pathologic entity. Operative treatment is indicated for patients for whom nonoperative management has failed. The treatment can consist of the complete detachment of the tendon insertion and extensive debridement. We biomechanically tested a new operative technique that uses buttons for fixation of the Achilles tendon insertion on the posterior calcaneal tuberosity and compared it with 2 standard bone anchor techniques. A total of 40 fresh-frozen cadaver specimens were used to compare 3 fixation techniques for reinserting the Achilles tendon: single row anchors, double row anchors, and buttons. The ultimate loads and failure mechanisms were recorded. The button assembly (median load 764 N, range 713 to 888) yielded a median fixation strength equal to 202% (range 137% to 251%) of that obtained with the double row anchors (median load 412 N, range 301 to 571) and 255% (range 213% to 317%) of that obtained with the single row anchors (median load 338 N, range 241 to 433N). The most common failure mechanisms were suture breakage with the buttons (55%) and pull out of the implant with the double row (70%) and single row (85%) anchors. The results of the present biomechanical cadaver study have shown that Achilles tendon reinsertion fixation using the button technique provides superior pull out strength than the bone anchors tested.     

Reattachment of the distal tendon of biceps: factors affecting the failure strength of the repair

Operative fixation is the treatment of choice for a rupture of the distal tendon of biceps. A variety of techniques have been described including transosseous sutures and suture anchors. The poor quality of the bone of the radial tuberosity might affect the load to failure of the tendon repair in early rehabilitation. The aim of this study was to determine the loads to failure of different techniques of fixation and to investigate their association with the bone mineral density of the radial tuberosity. Peripheral quantitative computed tomography was carried out to measure the trabecular and cortical bone mineral density of the radial tuberosity in 40 cadaver specimens. The loads to failure in four different techniques of fixation were determined. The Endobutton-based method showed the highest failure load at 270 N (sd 22) (p < 0.05). The mean failure load of the transosseous suture technique was 210 N (sd 66) and that of the TwinFix-QuickT 5.0 mm was 57 N (sd 22), significantly lower than those of all other repairs (p < 0.05). No significant correlation was seen between bone mineral density and loads to failure. The transosseous technique is an easy and cost-saving procedure for fixation of the distal biceps tendon. TwinFix-QuickT 5.0 mm had significantly lower failure loads, which might affect early rehabilitation, particularly in older patients.     

Transosseous tunnels versus suture anchors for the repair of acute quadriceps and patellar tendon ruptures: A systematic review and meta-analysis of biomechanical studies

BackgroundMultiple techniques have been developed for the repair of acute quadriceps and patellar tendon ruptures with the goal of optimizing clinical outcomes while minimizing complications and costs. The purpose of this study was to evaluate the biomechanical properties of transosseous tunnels and suture anchors for the repair of quadriceps and patellar tendon ruptures.MethodsA systematic review of the PubMed and Embase databases was performed based on the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines using specific search terms and eligibility criteria. Meta-analysis was performed by fixed-effects models for studies of low heterogeneity (I² <25%) and random-effects models for studies of moderate to high heterogeneity (I² ≥25%).ResultsA total of 392 studies were identified from the initial literature search with 7 studies meeting the eligibility criteria for quadriceps tendon repair and 8 studies meeting the eligibility criteria for patellar tendon repair. Based on the random-effects model for total gap formation and load to failure for quadriceps tendon repair, the mean difference was 8.88 mm (95% CI, −8.31 mm to 26.06 mm; p = 0.31) in favor of a larger gap with transosseous tunnels and −117.25N (95%CI, −242.73N to 8.23N; p = 0.07) in favor of a larger load to failure with suture anchors. A similar analysis for patellar tendon repair demonstrated a mean difference of 2.86 mm (95% CI, 1.08 mm to 4.64 mm; p = 0.002) in favor of a larger gap with transosseous tunnels and −56.34N (95% CI, −226.75 to 114.07N; p = 0.52) in favor of a larger load to failure with suture anchor repair.ConclusionsTransosseous tunnels are biomechanically similar to suture anchors for quadriceps tendon repair. Patellar tendon repair may benefit from reduced gap formation after cycling with suture anchor repair, but the load to failure for both techniques is biomechanically similar. Additional studies are necessary to evaluate these and alternative repair techniques.Level of evidenceSystematic review and meta-analysis of biomechanical studies, Level V.     

A biomechanical comparison of EndoButton versus suture anchor repair of distal biceps tendon injuries

The purpose of this study was to compare suture anchor and EndoButton repair of distal biceps injuries in a human bone-tendon model. Right and left arm repairs were alternately performed with either the EndoButton or 2 single-loaded 5-mm suture anchors. Each construct was cyclically loaded by use of a servohydraulic materials testing machine. Initial and final displacements were recorded. All repairs were then loaded to ultimate failure. Ten millimeters of displacement was designated the clinical failure point. The EndoButton group had more stiffness than the suture anchor group during initial cyclic loading (P = .01). There were no differences in final displacement measured after cyclic loading (2.06 mm for suture anchors and 2.58 mm for EndoButton). The EndoButton group had a 16% greater ultimate tensile load than the suture anchor group (274.77 N vs 230.06 N). The EndoButton group also had a 16% higher load to clinical failure (249.95 N vs 209.56 N). These differences were not statistically significant. The EndoButton and suture anchors provide comparable fixation strength for the repair and rehabilitation of distal biceps tendon ruptures.     

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.     

Cyclic loading of anchor-based rotator cuff repairs: Confirmation of the tension overload phenomenon and comparison of suture anchor fixation with transosseous fixation

Previous experimental studies of failure of rotator cuff repair have involved single pull to ultimate load. Such an experimental design does not represent the cyclic loading conditions experienced in vivo. We created 1 ×2 cm rotator cuff defects in 16 cadaver shoulders, repaired each defect with three MitekRC suture anchors (Mitek Surgical Products, Inc, Westwood, MA) using simple sutures of No. 2 Ethibond, and cyclically loaded the repairs by a servohydraulic materials test system actuator at physiological rates and loads (rate of 33 mm/s, load 180 N). A progressive gap was noted in each specimen, for a 100% rate of failure of the repairs. The central suture always failed first and by the largest magnitude, confirming tension overload centrally. One specimen exhibited combined bone and tendon failure, but the other 15 specimens failed through the tendon. Overall, the repairs failed to 5 mm and 10 mm at an average of 61 cycles and 285 cycles, respectively. Half the specimens were less than 45 years of age and had a 5-mm and 10-mm failure at an average of 107 and 478 cycles, respectively. The other half were over 45 years of age and failed to 5 mm and 10 mm at an average of 17 and 91 cycles, respectively, indicating more rapid failure of the rotator cuff tendons in the older group, and this was statistically significant (P ≤ .02). Comparison of suture anchor fixation in this study with transosseous bone tunnel fixation in a previous cyclic loading study at this institution indicates that bone fixation by suture anchors is significantly less prone to failure than bone fixation through bone tunnels (P = .0008). Changing the bone fixation from bone tunnels to suture anchors effectively transferred the weak link from bone to tendon.     

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.     

Suture anchor fixation strength in osteopenic versus non-osteopenic bone for rotator cuff repair

Introduction

Rotator cuff tears are increasing with age. Does osteopenic bone have an influence on the pullout strength of suture anchors?

Materials and methods

SPIRALOK 5.0 mm (DePuy Mitek), Super Revo 5 mm and UltraSorb (both ConMed Linvatec) suture anchors were tested in six osteopenic and six healthy human cadaveric humeri. Incremental cyclic loading was performed. The ultimate failure load, anchor displacement, and the mode of failure were recorded.

Results

In the non-osteopenic bone group, the absorbable SPIRALOK 5.0 mm achieved a significantly better pullout strength (274 N ± 29 N, mean ± SD) than the titanium anchor Super Revo 5 mm (188 N ± 34 N, mean ± SD), and the tilting anchor UltraSorb (192 N ± 34 N, mean ± SD). In the osteopenic bone group no significant difference in the pullout strength was found. The failure mechanisms, such as anchor pullout, rupture at eyelet, suture breakage and breakage of eyelet, varied between the anchors.

Conclusion

The present study demonstrates that, in osteopenic bone, absorbable suture anchors do not have lower pullout strengths than metal anchors. In normal bone, the bioabsorbable anchor in this study even outperformed the non-absorbable anchor.

     

Suture bridge transosseous equivalent repair is stronger than transosseous tied braided-tape

Background

This study biomechanically compares two methods of supraspinatus repair: single row transosseous braided-tape (BT) and suture bridge transosseous equivalent (SBTE) with 2 medial anchors and 2 lateral anchors. The purpose is to test the hypothesis that BT provides superior or equal biomechanical strength compared to SBTE.

A biomechanical comparison of repair techniques in posterior type II superior labral anterior and posterior (SLAP) lesions

The purpose of this study was to compare the 3 different fixation methods of posterior type superior labral anterior posterior (SLAP) II lesion. Fifteen cadavers were randomly divided into 3 groups to compare the initial strength of 3 different fixation methods in posterior type II SLAP lesions. Group I used 1 anchor for 1-point fixation with a conventional simple suture; group II used 1 anchor passing both limbs through the posterior-superior labrum in a mattress fashion; and group III used 2 anchors for 2-point fixation with conventional simple sutures. Repair failure (2 mm permanent displacement of repaired site) and ultimate failure were measured. The mean load to (clinical) failure was 156 +/- 22 N in group I, 117 +/- 33 N in group II, and 161 +/- 44 N in group III. The mean load to ultimate failure was 198 +/- 6 N in group I, 189 +/- 23 N in group II, and 179 +/- 22 N in group III. The specimen stiffness was equivalent among groups. In mode of failure, clinical failure (more than 2 mm separations) first occurred between the markers on the biceps tendon just above (A) and below (B) compared to other markers, and ultimate failure occurred at the labral-implant interface. A single simple suture anchor repair in posterior type II SLAP seems sufficient to withstand the initial load without clinical failure. A mattress suture, although it anchors the biceps root, seems to be inferior than simple suture technique.     

Evaluation of a New Knotless Suture Anchor Repair in Acute Achilles Tendon Ruptures: A Biomechanical Comparison of Three Techniques

Acute ruptures of the Achilles tendon are a common injury, and debate has continued in published studies on how best to treat these injuries. Specifically, controversy exists regarding the surgical approaches for Achilles tendon repair when one considers percutaneous versus open repair. The present study investigated the biomechanical strength of 3 different techniques for Achilles tendon repair in a cadaveric model. A total of 36 specimens were divided into 3 groups, each of which received a different construct. The first group received a traditional Krackow suture repair, the second group was repaired using a jig-assisted percutaneous suture, and the third group received a repair using a jig-assisted percutaneous repair modified with suture anchors placed into the calcaneus. The specimens were tested with cyclical loading and to ultimate failure. Cyclical loading showed a trend toward a stronger repair with the use of suture anchors after 10 cycles (p = .295), 500 cycles (p = .120), and 1000 cycles (p = .040). The ultimate load to failure was greatest in the group repaired with the modified knotless technique using the suture anchors (p = .098). The results of the present study show a clear trend toward a stronger construct in Achilles repair using a knotless suture anchor technique, which might translate to a faster return to activity and be more resistant to an early and aggressive rehabilitation protocol. Further clinical studies are warranted to evaluate this technique in a patient population.     

Biomechanical evaluation of biointegrable suture anchors composed of bovine compact bone in a pull-to-failure test in porcine tibial head specimens

AIM: Suture anchors of various designs have gained wide acceptance for securing soft tissues to bone. The biointegrable Tutofix CB anchors derived from bovine compact bone are available with diameters of 3 mm (CB3 anchor), 4 mm (CB4 anchor) and 5 mm (CB5 anchor). The CB anchors are push-in anchors and, from the biomechanical standpoint, they are a combination of press-fit and angulation anchors. The purpose of this study was to evaluate the CB anchors for singular pull load-to-failure strength using porcine tibial head specimens as a test model. METHODS: In all specimens, the joint surface was removed by performing a subchondral osteotomy. Axial PQ-CT scans of 12 specimens were obtained to determine the trabecular BMD. The anchors were implanted posteromedially and centrolaterally in the porcine tibial head specimens. After threading the anchors with a steel suture and predrilling of the anchor holes perpendicular to the osteotomy surface they were inserted 4 mm below the osteotomy surface. A universal testing machine applied tensile loads parallel to the axis of insertion at rates of 10 mm/min and 500 mm/min until pull-out failure or anchor breakage and mean anchor fixation strengths were calculated. RESULTS: The fixation strength of the CB anchors was found to be much higher at the dorsomedial implantation site than at the centrolateral implantation site. The CB4 anchors and CB5 anchors provided nearly the same fixation strength at a level much higher than that of the CB3 anchors. Bone mineral density had a strong influence on axial pull-out force of the anchors, especially the CB4 anchors and CB5 anchors. The overall correlation coefficient for bone mineral density with ultimate load-to-failure was 0.869 for the CB4 anchors and 0.716 for the CB5 anchors. Differences in failure strengths were also seen between the low and high extraction rates. With the high extraction rate much higher failure strengths were obtained than with the low extraction rate. The sudden pull eccentrically on the anchors caused a better fixation due to angulation of the anchor within the drill holes. CONCLUSION: In spite of the double worst-case scenario in the testing conditions, the CB anchors provided a high fixation strength in the trabecular bone of porcine tibial head specimens with the CB4 anchors and CB5 anchors being nearly equal and both being superior to the CB3 anchors. Bone mineral density had a strong influence on the axial pull-out force. Our results show that the CB anchors seem to be a reasonable alternative to metal and bioabsorbable suture anchors.     

Tissue fixation security in transosseous rotator cuff repairs: A mechanical comparison of simple versus mattress sutures

The primary purpose of this investigation was to compare tissue fixation security by simple sutures versus mattress sutures in transosseous rotator cuff repair. These two repair techniques were each performed in 17 human cadaver shoulders, with two bone tunnels being used for the repair by two simple sutures and two other bone tunnels being used for the repair by one mattress suture. The repairs were loaded to failure in a servohydraulic materials test system. Rotator cuff repair by simple sutures was found to be significantly stronger than repair by mattress sutures (P = .0007). The average ultimate load to failure for the simple suture construct (189.62 N) was 39.72% greater than that for the mattress suture construct (135.71 N). Most of the failures occurred by suture breakage at the knot. Load-sharing by multiple suture tails and multiple knots in the simple suture configuration likely contributed to its superior strength characteristics compared with the mattress suture configuration.     

Part II: Biomechanical assessment for a footprint-restoring transosseous-equivalent rotator cuff repair technique compared with a double-row repair technique

We hypothesized that a transosseous-equivalent repair would demonstrate improved tensile strength and gap formation between the tendon and tuberosity when compared with a double-row technique. In 6 fresh-frozen human shoulders, a transosseous-equivalent rotator cuff repair was performed: a suture limb from each of two medial anchors was bridged over the tendon and fixed laterally with an interference screw. In 6 contralateral matched-pair specimens, a double-row repair was performed. For all repairs, a materials testing machine was used to load each repair cyclically from 10 N to 180 N for 30 cycles; each repair underwent tensile testing to measure failure loads at a deformation rate of 1 mm/sec. Gap formation between the tendon edge and insertion was measured with a video digitizing system. The mean ultimate load to failure was significantly greater for the transosseous-equivalent technique (443.0 +/- 87.8 N) compared with the double-row technique (299.2 +/- 52.5 N) (P = .043). Gap formation during cyclic loading was not significantly different between the transosseous-equivalent and double-row techniques, with mean values of 3.74 +/- 1.51 mm and 3.79 +/- 0.68 mm, respectively (P = .95). Stiffness for all cycles was not statistically different between the two constructs (P > .40). The transosseous-equivalent rotator cuff repair technique improves ultimate failure loads when compared with a double-row technique. Gap formation is similar for both techniques. A transosseous-equivalent repair helps restore footprint dimensions and provides a stronger repair than the double-row technique, which may help optimize healing biology.     

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.     

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.     

Cyclic loading of rotator cuff repairs: A comparison of bioabsorbable tacks with metal suture anchors and transosseous sutures

Purpose: The purposes of the study were (1) to compare rotator cuff repair strengths after cyclic loading of 2 bioabsorbable nonsuture-based tack-type anchors, transosseous sutures, and a metal suture-based anchor, and (2) to correlate bone mineral density with mode of failure and cycles to failure. We hypothesized that specimens with a lower bone density would fail through bone at a lower number of cycles independent of the method of cuff fixation. Type of Study: Ex vivo biomechanical study. Methods: Standardized full-thickness rotator cuff defects were created in 30 fresh-frozen cadaveric shoulders that were randomized to 1 of 4 repair groups: transosseous sutures; Mitek Super suture anchors (Mitek Surgical Products, Westwood, MA); smooth bioabsorbable 8-mm Suretacs (Acufex, Smith & Nephew Endoscopy, Mansfield, MA); or spiked bioabsorbable 8-mm Suretacs (Acufex). All repairs were cyclically loaded from 10 to 180 N; the numbers of cycles to 50% (gap, 5 mm) and 100% (gap, 10 mm) failure were recorded. Results: In comparing the repair groups, we found only 1 significant difference: the number of cycles to 100% failure was significantly higher (P <.05) for the smooth bioabsorbable tack than for the transosseous suture group. There were no statistically significant (P ≤.05) differences in bone mineral densities with regard to each specimen’s mode of failure. Conclusions: Our results suggested that immediate postoperative fixation provided by bioabsorbable tacks was similar to that provided by Mitek anchors and more stable than that provided by transosseous sutures. Therefore, the immediate postoperative biomechanical strength of bioabsorbable tacks seems comparatively adequate for fixation of selected small rotator cuff tears. However, additional evaluation in an animal model to examine degradation characteristics and sustained strength of repair is recommended before clinical use.Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 17, No 4 (April), 2001: pp 360–364     

Suture anchor versus screw fixation for greater tuberosity fractures of the humerus—a biomechanical study

Suture anchors and screws are commonly used for fixation of humeral greater tuberosity (GT) fractures in either arthroscopic or open surgeries, but no biomechanical studies have been performed to compare the strength of fixation constructs using these two implants. This cadaveric study aimed to compare the biomechanical strength of three different fixation constructs in the management of GT fractures: Double‐Row Suture Anchor Fixation (DR); Suture‐Bridge Technique using suture anchors and knotless suture anchors (SB); and Two‐Screw Fixation (TS). The experimental procedure was designed to assess fracture displacement after cyclic loading, failure load, and failure mode of the fixation construct. Significant differences were found among the SB (321 N), DR (263 N), and TS (187 N) groups (SB > DR > TS, p < 0.05) in the mean force of cyclic loading to create 3 mm displacement. Regarding the mean force of cyclic loading to create 5 mm displacement and ultimate failure load, no significant difference was found between the DR (370 N, 480 N) and SB (399 N, 493 N) groups, but both groups achieved superior results compared with the TS group (249 N, 340 N) (p < 0.05). The results suggested that the suture anchor constructs would be stronger than the fixation construct using screws for the humeral GT fracture. © 2011 Orthopaedic Research Society Published by Wiley Periodicals, Inc. J Orthop Res 30:423–428, 2012