Maximum load to failure and tensile displacement of an all-suture glenoid anchor compared with a screw-in glenoid anchor

All-suture anchor size and drill angle influence load to failure in a porcine model of subpectoral biceps tenodesis, a biomechanical study

BACKGROUND

Tenodesis of the long head of the biceps tendon is frequently performed in shoulder surgery, and all-suture anchors have become more popular as fixation methods. However, uncertainty still exists regarding the ultimate load to failure of all-suture anchors and the best insertion angle at a cortical humeral insertion point.

PURPOSE

The purpose of this study was to compare the biomechanical characteristics of three types of all-suture anchors frequently used for biceps tenodesis. In addition, the influence of two different insertion angles was observed in a porcine humeri model.

METHODS

The ultimate load to failure and failure mode of three types of all-suture anchors (1.6 FiberTak®, 1.9 FiberTak®, 2.6 FiberTak®, Arthrex®) applicable for subpectoral biceps tenodesis were evaluated at 90° and 45° insertion angles in 12 fresh-frozen porcine humeri. The anchors were inserted equally alternated in a randomized manner at three different insertion sites along the bicipital groove, and the suture tapes were knotted around a rod for pullout testing. In total, 36 anchors were evaluated in a universal testing machine (Zwick & Roell).

RESULTS

The 2.6 FiberTak® shows higher ultimate loads to failure with a 90° insertion angle (944.0 N ± 169.7 N; 537.0 N ± 308.8 N) compared to the 1.9 FiberTak® (677.8 N ± 57.7 N; 426.3 N ± 167.0 N, p-value: 0.0080) and 1.6 FiberTak® (733.0 N ± 67.6 N; 450.0 N ± 155.8 N, p-value: 0.0018). All anchor types show significantly higher ultimate loads to failure and smaller standard deviations at the 90° insertion angle than at the 45° insertion angle. The major failure mode was anchor pullout. Only the 2.6 FiberTak® anchors showed suture breakage as the major failure mode when placed with a 90° insertion angle.

CONCLUSIONS

All three all-suture anchors are suitable fixation methods for subpectoral biceps tenodesis. Regarding our data, we recommend 90° as the optimum insertion angle.

CLINICAL RELEVANCE

The influence of anchor size and insertion angle of an all-suture anchor should be known by the surgeon for optimizing ultimate loads to failure and for achieving a secure fixation.

A biomechanical study to optimize superior capsular reconstruction operative technique

Background

The goals of this study were to optimize superior capsular reconstruction by assessing the relative fixation strength of 4 suture anchors; evaluating 3 glenoid neck locations for fixation strength and bone mineral density (BMD); determining if there is a correlation between BMD and fixation strength; and determining which portal sites have optimal access to the posterosuperior and anterosuperior glenoid neck for anchor placement.

Methods

Twenty cadaveric specimens were randomized into 4 groups: all-suture anchor (FiberTak), conventional 3.0-mm knotless suture anchor (SutureTak), 3.9-mm knotless PEEK (polyetheretherketone) Corkscrew anchor, and 4.5-mm Bio-Corkscrew anchor. Each specimen was prepared with 3 anchors into the glenoid: an anterosuperior anchor, superior anchor, and posterosuperior anchor. All anchors were inserted into the superior glenoid neck 5 mm from the glenoid rim. A materials testing system performed cyclic testing (250 cycles) followed by load-to-failure testing at 12.5 mm/s. Cyclic elongation, first cycle excursion, maximum load, and stiffness were recorded. Using custom software, BMD was calculated at each anchor location. This software was also used to assess access to the posterosuperior and anterosuperior glenoid neck from standard arthroscopic portal positions.

Results

There was no significant difference in cyclic elongation (P = .546), first cycle excursion (P = .476), maximum load (P = .817), or stiffness (P = .309) among glenoid anchor positions. Cyclic elongation was significantly longer in the PEEK Corkscrew group relative to the other implants (P ≤ .002). First cycle excursion was significantly greater in the FiberTak group relative to all other implants (P ≤ .008). For load-to-failure testing, the Bio-Corkscrew group achieved the highest maximum load (P ≤ .001). No other differences in cyclic or failure testing were observed between the groups. No differences in stiffness testing were observed (P = .133). The superior glenoid rim had the greatest BMD (P = .003), but there was no correlation between BMD and cyclic/load outcomes. The posterior portal (80% of specimens) and the anterior portal (60% of specimens) demonstrated the best access to the posterosuperior and anterosuperior glenoid neck, respectively.

Conclusion

The 4.5-mm Bio-Corkscrew anchor provided the most robust fixation to the glenoid during superior capsular reconstruction as it demonstrated the strongest maximum load, had minimal elongation, had minimal first cycle excursion, and did not fail during cyclic testing. The superior glenoid neck had the highest BMD; however, there was no correlation between BMD or glenoid anchor location and biomechanical outcomes. The posterior portal and anterior portal provided optimal access to the posterosuperior glenoid neck and anterosuperior glenoid neck, respectively.

Retrospective Comparative Analysis of Clinical and Functional Outcome After Arthroscopic Bankart Repair using All-Suture Anchor and Metal Anchor

Introduction

Both knotted all suture anchors and metal anchors are used for arthroscopic Bankart repair. We retrospectively evaluated and compared clinical and functional outcomes after arthroscopic Bankart repair using the knotted all-suture anchors and knotted metal anchors.

Materials and methods

In a retrospective cohort analysis, patients who underwent arthroscopic Bankart repair without any concomitant additional lesion repair using either all-suture anchors or metal anchors, between January 2015 and May 2018 were identified. Their pre- and post-operative functional and clinical outcomes were compared using Rowe and WOSI scores. The recurrence rate in the two groups was also compared.

Results

A total of 41 patients in all suture anchors group and 47 in the metal anchors group were identified as per inclusion and exclusion criteria. The demographic profile of both groups was comparable. There was no significant difference in clinical and functional outcome between the two suture anchor groups as per Rowe (pre-operative 40.13+6.51 vs 38.09+6.24 and post-operative 2 years 93.28+7.09 vs 92.55+9.2) and WOSI (pre-operative 943.05+216.64 vs 977.55+165.46 and post-operative 2 years 278.21+227.56 vs 270.94+186.25) scores. There was a significant improvement in both the groups between preoperative and post-operative ROWE and WOSI scores at 6 months and 2 years follow-up as compared to pre-operative scores (p<0.001). Re-dislocation rates were also comparable (4.8% vs 6.3%).

Conclusion

All-suture anchors showed comparable clinical and functional results as the metal anchors for arthroscopic Bankart repair at two-year follow-up.

An additively manufactured titanium tilting suture anchor: a biomechanical assessment on human and ovine bone specimens

Introduction

A novel titanium tilting suture anchor was designed and fabricated using additive manufacturing. The anchor enjoyed a nonsymmetrical structure to facilitate its insertion procedure through a weight-induced tilt, a saw-teeth penetrating edge to provide a strong initial fixation into cancellous bones of various densities, and an appropriate surface texture to enhance the longterm fixation strength through bone ingrowth.

Methods

Biomechanical tests were performed on 10 ovine and 10 human cadaveric humeri to examine the insertion procedure and assess the initial fixation strength of the anchor, in comparison with a standard screw-type anchor as control.

Results

This study indicated a simple yet reliable insertion procedure for the tilting anchor. All anchors survived after 400 cycles of cyclic loadings and failed in the load-to-failure step. There were no significant differences between the displacements and fixation stiffnesses of the anchors in either group. The ultimate failure load was significantly smaller (p<0.05) for tilting anchors in ovine group (273.7 ± 129.72 N vs. 375.6 ± 106.36 N), but not different in human group (311.8 ± 82.55 N vs. 281.9 ± 88.35). Also, a larger number of tilting anchors were pulled out in ovine group (6 vs. 3) but a smaller number in human group (4 vs. 6).

Conclusion

It was concluded that the biomechanical performance of the designed tilting anchor is comparable with that of the standard screw-type anchors.

Fixation strength in arthroscopic labral repair of the hip: A head-to-head comparison of the biomechanical performance of a biocompatible vs. all-suture anchor in the setting of acetabuloplasty

Much is known about the biomechanical performance of various types of suture anchors commonly used for labral fixation in the shoulder; however, similar studies in the hip are less common. We sought to compare all-suture and polyether ether ketone small-diameter anchors in the setting of labral repair during hip arthroscopy, with and without acetabuloplasty. We hypothesized that the biomechanical properties of the all-suture group when compared to polyether ether ketone anchors would be similar amongst native acetabula and significantly less following acetabuloplasty and that pullout forces would be reduced in the anterior and inferior regions of the acetabulum compared to the superior region. Bone density was measured in nine matched pairs of fresh-frozen cadaveric acetabula in the superior, anterosuperior, and anterior regions. Acetabuloplasty was performed in all three regions, while the contralateral acetabulum was left in situ as a control. Suture anchors were placed such that one each of two different types was placed within each region. Specimens were tested in cyclic fatigue and loaded to failure. The all-suture group had significantly higher cyclic displacement compared to the polyether ether ketone, but there was no significant difference in ultimate load, regardless of acetabuloplasty. Amongst all non-resected specimens, the lowest bone density was observed consistently in the inferior region. Our results indicate that, with or without acetabuloplasty, a small-diameter polyether ether ketone anchor appears to be more stable than an all-suture anchor, which needs to be set first.

Clinical and radiological outcome of all-suture anchors in shoulder and elbow surgery

Background

All-suture anchors (ASAs) are noted to cause various bone reactions when used in upper limb surgery but clinical implications are unknown.

Methods

88 shoulders and 151 elbows with a mean follow-up of 47.1 ± 17.7 months were invited for follow-up including clinical examination, questionnaires and radiographs. The anchor drill holes were radiographically assessed.

Results

At final follow up, mean DASH was 12.9 ± 13.8 and mean VAS 2.2 ± 2.4 in the shoulder population. In the elbow group mean MEPS was 91.8 ± 12.7 and mean VAS 1.5 ± 1.9. Implant-specific complications were seen in 10 elbow cases but none in the shoulder group. The mean diameter of the 1.4 mm all-suture anchor drill hole was enlarged to 2.5 ± 1.4 mm in the shoulder group and to 2.9 ± 1.0 mm in the elbow group. 50% of the 1.4 mm anchor drill holes showed abnormal morphology but these morphologic changes did not correlate with clinical outcome, complications or reoperation rate.

Discussion

Satisfying clinical outcomes are found in upper limb surgery using ASAs. Various bone changes are seen after implantation of an ASA, but these are not clinically relevant. Long-term consecutive follow-up data is required.

All-Suture Suspensory Button Has Similar Biomechanical Performance to Metal Suspensory Button for Onlay Subpectoral Biceps Tenodesis

Purpose

To evaluate the maximal load at failure, cyclic displacement, and stiffness of onlay subpectoral biceps tenodesis (BT) with an intramedullary unicortical metal button (MB) versus a unicortical all-suture button (ASB).

Methods

Eighteen matched paired human cadaveric proximal humeri were randomly allocated for subpectoral BT with either ASB or MB using a high-strength suture. Specimens were tested on a servohydraulic mechanical testing apparatus under cyclic load for 1,000 cycles and then loaded to failure. The clamp was then adjusted to isolate the suture-anchor point interface and loaded to failure. Maximal load to failure, displacement, and stiffness were compared.

Results

There was no significant difference between groups in stiffness, displacement, or yield load. The maximal load to failure for the MB was greater than the ASB (347.6 ± 74.1N vs 266.5 ± 69.3N, P = .047). Eight specimens in each group failed by suture pull-through on the tendon. When the suture-anchor point interface was isolated, there was no significant difference in maximal load at failure (MB 586.5 ± 215.8N vs ASB 579.6 ± 255.9N, P = .957).

Conclusions

This study demonstrates that the MB and ASB have similar biomechanical performance when used in subpectoral BT. Although the MB showed statistically significant greater maximal load to failure, there was no difference between the MB and ASB when the suture-tendon interface was eliminated. Suture pull-through was the most common mode of failure for both implants, underscoring the importance of the suture-tendon interface.

Clinical Relevance

Fixation techniques for the treatment of long head of the biceps brachii tenodesis continue to evolve. The use of an all-suture suspensory button has advantages, but it is important to understand if this implant is a biomechanically suitable alternative to a metal suspensory button.

Single- and Double-Loaded All-Suture Anchor Repairs of Anteroinferior Labral Tears Are Biomechanically Similar in a Cadaveric Shoulder Model

Purpose

To compare the biomechanical strength of single- versus double-loaded all-suture constructs in an anteroinferior glenoid labral repair.

Methods

Anteroinferior labral lesions were created on 6 matched pairs of cadaveric shoulder specimens. Each shoulder in a matched pair was randomized to either receive capsulolabral repair with 3 single-loaded all-suture anchors or 3 double-loaded all-suture anchors. Immediately following capsulolabral repair, the specimens underwent mechanical testing, which included cyclic testing (5 N to 50 N for 500 cycles) and load-to-failure testing (rate of 15 mm/min). The gap formation between the repaired labrum and glenoid (measured at 1, 25, 100, and 500 cycles), the load at 2-mm gap formation, the maximum load at failure and the method of failure were recorded. Data were analyzed with paired Student t tests and Bonferroni correction factor.

Results

The single and double all-suture constructs did not differ significantly in gap formation at any number of cycles, load to 2-mm gap formation (P = .75), or maximum load to failure (P = .46) between the 2 groups.

Conclusions

In this study, single-loaded and double-loaded all-suture anchor constructs demonstrated comparable biomechanical performance and did not significantly differ in gap formation, load to 2-mm gap formation, or maximum load to failure when used in the capsulolabral repair of anteroinferior glenoid labral tears in human cadaveric specimens.

Clinical Relevance

Although studies have evaluated the biomechanical properties of various arthroscopic labral stabilization techniques, the biomechanical properties of all-suture anchors with regard to labral stabilization are not well understood.

Biomechanical Studies for Glenoid Based Labral Repairs With Suture Anchors Do Not Use Consistent Testing Methods: A Critical Systematic Review

PURPOSE

The purpose of this systematic review was to investigate variability in biomechanical testing protocols for laboratory-based studies using suture anchors for glenohumeral shoulder instability and SLAP lesion repair.

METHODS

A systematic review of Medline, Embase, Scopus, and Google Scholar using Covidence software was performed for all biomechanical studies investigating labral-based suture anchor repair for shoulder instability and SLAP lesions. Clinical studies, technical notes or surgical technique descriptions, or studies treating glenoid bone loss or capsulorrhaphy were excluded. Risk of bias (ROB) was assessed with the ROBINS-I tool. Study quality was assessed with the Quality Appraisal for Cadaveric Studies. Heterogeneity was assessed with the I² statistic.

RESULTS

A total of 41 studies were included. ROB was serious and critical in 27 studies, moderate in 13, and low in 1; 6 studies had high quality, 21 good quality, 10 moderate quality, 2 low quality, and 2 very low quality. Thirty-one studies used and 22 studies included cyclic loading. Angle of anchor insertion was reported by 33 studies. The force vector for displacement varied. The most common directions were perpendicular to the glenoid (n = 9), and anteroinferior or anterior (n = 8). The most common outcome measures were load to failure (n = 35), failure mode (n = 23), and stiffness (n = 21). Other outcome measures included load at displacement, displacement at failure, tensile load at displacement, translation, energy absorbed, cycles to failure, contact pressure, and elongation.

CONCLUSION

This systematic review demonstrated a clear lack of consistency in those cadaver studies that investigated biomechanical properties after surgical repair with suture anchors for shoulder instability and SLAP lesions. Testing methods between studies varied substantially with no universally applied standard for preloading, load to failure and cyclic loading protocols, insertion angles of suture anchors, or direction of loading. To allow comparability between studies standardization of testing protocols is strongly recommended.

All-Suture Anchors in Orthopaedic Surgery: Design, Rationale, Biomechanical Data, and Clinical Outcomes

All-suture anchors (ASAs) are a relatively new alternative to traditional suture anchors, comprised of sutures, suture tapes, or ribbons woven through a soft sleeve. These novel anchors are typically smaller than traditional anchors, allowing for more anchors to be used in the same amount of space or for use when bone stock is limited, for example, in revision settings. They can be inserted through curved guides to reach more challenging locations, and they have thus far had similar loads to failure during biomechanical testing as traditional anchors. However, these benefits must be weighed against new challenges. When using ASAs, care must be taken to fully deploy and seat the anchor against cortical bone for optimal fixation and to prevent gap formation. Furthermore, decortication, often performed to enhance the biologic environment for soft-tissue healing, may weaken the cortical bone on which ASA fixation depends on. The purpose of this article is to provide insight on the designs, advantages, and potential disadvantages associated with ASAs, as well as review the available biomechanical and clinical data.

Biomaterials Used for Suture Anchors in Orthopedic Surgery

Suture anchors are broadly used for attaching soft tissue (e.g., tendons, ligaments, and meniscus) to the bone and have become essential devices in sports medicine and during arthroscopic surgery. As the usage of suture anchors has increased, various material-specific advantages and challenges have been reported. As a result, suture anchors are continually changing to become safer and more efficient. In this ever-changing environment, it is clinically essential for the surgeon to understand the key characteristics of existing anchors sufficiently. This paper aims to summarize the current concepts on the characteristics of available suture anchors.

Editorial Commentary: All-Suture Anchors Are Small, Easier to Revise, and Biomechanically Equivalent to Conventional Implants: They Are the Way of the Future

All-suture anchors (ASAs) show biomechanical equivalence to conventional implants. The smaller size and easier ability to revise are important advantages of ASAs. A more vertical insertion angle increases ASA pullout strength. Proper depth of insertion is required to optimally seat ASAs on cortical bone. ASA pullout strength also results from compression of cancellous bone between the anchor and the cortex, and appropriately pretensioning the suture before loading is critical. A larger anchor (and a higher the number of sutures loaded per anchor) leads to a higher pullout strength of the anchor. Understanding the correct implantation technique is important to optimize the strength of ASAs.

Pullout Strength of All-Suture and Metallic Anchors in Repair of Lateral Collateral Ligament Injuries of the Elbow

PURPOSE

To compare the biomechanical properties of metallic anchor (MA) and all-suture anchor (ASA) constructs in the anatomic reattachment of the lateral ulnar collateral ligament complex to its humeral insertion.

METHODS

Twenty paired male human cadaveric elbows with a mean age of 46.3 years (range: 33-58 years) were used in this study. Each pair was randomly allocated across 2 groups of either MA or ASA. A single 3.5-mm MA or 2.6-mm ASA was then inserted flush into the lateral epicondyle. A dynamic tensile testing machine was used to perform cyclic loading followed by a load to failure test. During the cyclic loading phase, the anchors were sinusoidally tensioned from 10 N to 100 N for 1,000 cycles at a frequency of 0.5 Hz. In the load to failure test, the anchors were pulled at a rate of 3 mm/s. Load at 1-mm and 2-mm displacement, as well as load to ultimate failure were assessed. Clinical failure was defined as displacement of more than 2 mm. Normality of data was assessed with the Shapiro-Wilk test. Continuous data are presented as medians and compared with the Mann-Whitney U test and categorical data was compared with the χ² test or Fisher exact test.

RESULTS

Displacement was significantly greater for the ASA group during cyclic loading starting from the tenth cycle (P < .05). Displacement of more than 5 mm within the first 100 cycles was observed in 2 anchors in the ASA group. No difference was observed in loads required to displace 1 mm (MA: 146 N [6-169] vs ASA: 144 N [2-153]; P = .53) and 2 mm (MA: 171 N [13-202] vs ASA: 161 N [9-191]; P = .97), but there was a statistically significant difference between ultimate loads in favor of ASA in the load to failure test (MA: 297 N [84-343] vs 463 N [176-620]; P < .01).

CONCLUSIONS

In the cyclic test, no difference in clinical failure defined as pull-out of more than 2 mm was observed between 3.5 mm MAs and 2.6 mm ASAs. In the ultimate load to failure analysis, no difference was observed between groups in force causing 1 and 2 mm of displacement, but there was a significant difference in favor of ASA in the pull to ultimate failure test.

CLINICAL RELEVANCE

Potential benefits of all-suture anchors include preservation of bone stock, reduced radiographic artifacts, and easier revisions. Although their use has been investigated thoroughly in the shoulder, there remains a paucity of literature regarding displacement and pull-out strength in the elbow.

The Effect of Torque Differences for All-Suture Anchor Fixation Strength: A Biomechanical Analysis

Purpose

To investigate the biomechanical influence of differential loading of suture strands (torque) on the fixation strength of knotted and knotless all-suture anchors.

Methods

The biomechanical strength of 48 all-suture anchors was evaluated for 4 conditions in polyurethane foam blocks: (1) 12 knotted all-suture anchors loaded proportionately, (2) 12 knotted all-suture anchors with 1 suture strand bearing 50% of total force (partial torque), (3) 12 knotted all-suture anchors with 1 strand fixated and the other loaded (full torque), and (4) 12 knotless all-suture anchors with the loop kept open via a fixed rod. Force for 1 mm and 2 mm of displacement and ultimate failure load were assessed.

Results

For 1 mm of displacement, groups 2, 3, and 4 showed significantly lower forces than group 1 (all P < .001), with no statistically significant difference between groups 2 and 3 (P = .516); for 2 mm of displacement, all groups showed significantly lower forces than group 1 (P < .001), which positively correlated with applied torque. No differences in the mean ultimate loads observed between testing groups 1, 2, and 4 were noted, with 93.3 ± 3.8 N, 91.4 ± 4.7 N, and 92.6 ± 5.6 N, respectively; however, group 3 exhibited a significantly lower mean ultimate load (62.3 ± 1.7 N) than all other groups (P < .001).

Conclusions

The ultimate failure load of knotted and knotless all-suture anchor fixation was partially affected by loading differentials between strands in this validated foam block model. Differential loading of knotted all-suture anchor fixation presented greater initial displacement when compared with symmetrically loaded knotted all-suture anchors. Despite an initial increase in displacement, knotless all-suture anchors showed similar ultimate failure loads to knotted all-suture anchors with strands loaded equally.

Clinical Relevance

The role of suture strand loading imbalance on anchor fixation is variable and should be considered during placement and fixation of the repair constructs in a clinical setting.

Serial Changes in Perianchor Cysts Following Arthroscopic Labral Repair Using All-Suture Anchors

Backgroud

Changes in perianchor cysts around the all-suture anchors, which demonstrate distinguished features from the biocomposite anchors, have not been revealed sufficiently. The purpose of this study was to investigate serial changes of perianchor cysts according to the location of the inserted anchor in the glenoid in arthroscopic labral repair using all-suture anchors.

Methods

We enrolled 43 patients who underwent computed tomography (CT) immediately postoperatively and CT arthrogram (CTA) at 1 year or 2 years after arthroscopic labral repair using a 1.3-mm all-suture anchor for recurrent anterior shoulder dislocation with or without a superior labral tear from anterior to posterior and a posterior labral tear. The mean diameter and tissue density (HU) of perianchor cysts were measured depending on the location in the glenoid. Clinical outcomes, labral healing, and redislocation rate were evaluated at 2 years after surgery.

Results

On functional assessment, the mean American Shoulder and Elbow Surgeons score and Rowe score improved statistically significantly after surgery (from 47.9 ± 14.3 preoperatively to 90.1 ± 9.6 postoperatively and from 45.3 ± 12.4 preoperatively to 92.2 ± 10.1 postoperatively, respectively; p < 0.01). Postoperative redislocations were found in 2 patients (4.7%). In radiological evaluation, the mean diameter of perianchor cysts at postoperative 1 year (3.24 ± 0.65 mm) was significantly larger than the immediate postoperative diameter; however, there was no significant difference between postoperative 1 year and 2 years (3.23 ± 0.57 mm). Tissue density at the center of cysts demonstrated no significant difference between 1 and 2 year postoperatively (107.7 ± 29.8 HU [superior], 99.7 ± 31.7 HU [anteroinferior], and 105.1 ± 25.0 HU [posterior] vs. 109.1 ± 26.1 HU [superior], 106.4 ± 30.3 HU [anteroinferior], and 111.0 ± 32.9 HU [posterior]). The mean diameter of perianchor cysts in the anteroinferior position was largest compared with that in superior or posterior positions.

Conclusions

Perianchor cysts associated with all-suture anchors enlarged significantly within 1 year after arthroscopic labral repair regardless of the insertion location in the glenoid. However, the size and tissue density of perianchor cysts were similar at postoperative 1 and 2 years, and satisfactory stability and clinical outcomes were obtained.

Editorial Commentary: What is the Difference That Makes the Differences? The Practical Rationality of the All-Suture Anchor

Suture anchor technologies are constantly being innovated in the quest for improved stability, biological integration and clinical outcomes. However, the decision about the choice of suture-anchor materials remain elusive. There are some factors, including reliability, effectiveness, simplicity, familiarity, and cost, that affect a surgeon's preference. The relative weights placed on different factors by different surgeons play decisive roles in individual choice. But decisions and choices are not arbitrary or merely subjective. Alternative options can be warranted or contested by rational argumentation. At the end, there may be losses and gains in the change of 1 suture anchor for another, but science does progress.

Biomechanical Comparison of Knotless All-Suture Anchors and Knotted All-Suture Anchors in Type II SLAP Lesions: A Cadaveric Study

PURPOSE

To compare the biomechanical performance of knotless versus knotted all-suture anchors for the repair of type II SLAP lesions with a simulated peel-back mechanism.

METHODS

Twenty paired cadaveric shoulders were used. A standardized type II SLAP repair was performed using knotless (group A) or knotted (group B) all-suture anchors. The long head of the biceps (LHB) tendon was loaded in a posterior direction to simulate the peel-back mechanism. Cyclic loading was performed followed by load-to-failure testing. Stiffness, load at 1 and 2 mm of displacement, load to repair failure, load to ultimate failure, and failure modes were assessed.

RESULTS

The mean load to repair failure was similar in groups A (179.99 ± 58.42 N) and B (167.83 ± 44.27 N, P = .530). The mean load to ultimate failure was 230 ± 95.93 N in group A and 229.48 ± 78.45 N in group B and did not differ significantly (P = .958). Stiffness (P = .980), as well as load at 1 mm (P = .721) and 2 mm (P = .849) of displacement, did not differ significantly between groups. In 16 of the 20 specimens (7 in group A and 9 in group B), ultimate failure occurred at the proximal LHB tendon. Failed occurred through slippage of the labrum in 1 specimen in each group and through anchor pullout in 2 specimens in group A.

CONCLUSIONS

Knotless and knotted all-suture anchors displayed high initial fixation strength with no significant differences between groups in type II SLAP lesions. Ultimate failure occurred predominantly as tears of the proximal LHB tendon.

CLINICAL RELEVANCE

All-suture anchors have a smaller diameter than solid anchors, can be inserted through curved guides, preserve bone stock, and facilitate postoperative imaging. There is a paucity of literature investigating the biomechanical capacities of knotless versus knotted all-suture anchors in type II SLAP repair.

Pullout strength and failure mode of industrially manufactured and self-made all-suture anchors: a biomechanical analysis

BACKGROUND

This study presents a new technique for assembling an all-suture anchor from existing medical products. The biomechanical characteristics of this self-made anchor (SMA) are compared with those of an industrially manufactured all-suture anchor.

METHODS

The SMAs were made from established medical products (FiberWire #2 and 2-mm FiberTape; Arthrex, Naples, FL, USA). Pretesting was performed in biphasic polyurethane foam blocks. In the next step, 10 SMAs and 10 industrially made anchors (IMAs; 1.8-mm double-loaded Y-Knot Flex all-suture anchor; ConMed Linvatec, Largo, FL, USA) were applied with an insertion tool and tested in fresh porcine femora using a servohydraulic testing system, with a preload of 10 N and a displacement rate of 12.5 mm/s. Pullout strength and failure mode were recorded.

RESULTS

The mean load at failure in the foam blocks was 459 ± 124 N in the SMA group and 538 ± 83 N in the IMA group. In porcine bone, failure occurred at 461 ± 102 N in the SMA group and 431 ± 135 N in the IMA group. The differences in pullout strength between the 2 types of anchor were not statistically significant, either in the foam blocks (P = .17) or in porcine bone (P = .62).

CONCLUSION

A handmade all-suture anchor using 2 high-strength sutures woven into a 2-mm strip of high-strength tape did not show statistically different failure loads in polyurethane foam or in porcine metaphyseal bone in comparison with a commercially produced double-loaded all-suture anchor. The principal mode of failure in porcine bone in both groups was anchor pullout.

The Clinical and Biomechanical Performance of All-Suture Anchors: A Systematic Review

Purpose

This systematic review aimed to clarify the relative strengths and weaknesses of the all-suture anchors (ASAs) in both clinical and experimental studies. Our hypothesis was that there would be similar clinical and experimental data for ASAs regarding the biomechanical properties, clinical outcomes and complication rates.

Methods

A systematic review of MEDLINE and Embase databases was performed. The inclusion criteria for clinical studies were both retrospective or prospective study design and minimum 1-year follow-up; for biomechanical studies, the inclusion criteria were performance on either cadaver and animal bones or synthetic surfaces. Studies were excluded if the studies were not in English or if they were review articles, commentaries, letters, case reports, or technical notes. The risk of bias assessment was done using the Methodological Index for Non-randomized Studies (MINORS) tool.

Results

We included 13 experimental and 3 clinical studies. The least displacement under cyclic loading was recorded with Q-Fix. Failure mode was mostly by suture breaking for the Q-Fix, whereas anchor pullout was the most common for the others. Cadaver humerus’ greater tuberosity seemed to be less durable for the ASAs. Tests on cadaver glenoid showed similar biomechanical properties when compared to a control anchor. Studies investigating clinical and radiologic findings were very few, and only 3 case series were included in this review. Clinical findings of patients treated with ASAs for instability and rotator cuff repair showed satisfactory results and little increase in the complication rate (retear or revision surgery because of loose anchor).

Conclusions

ASAs have similar or better biomechanical properties compared to regular anchors. Low-profile design seems to be an important advantage. Case series can not distinguish between the possible clinical benefits and/or risks.

Clinical Relevance

ASAs have similar biomechanical properties when compared with other types of anchors. Their strength and performance vary with anatomic location, which may influence clinical success.

All-Suture Anchor Settling After Arthroscopic Repair of Small and Medium Rotator Cuff Tears

BACKGROUND

All-suture anchors are increasingly being used in rotator cuff repair. However, there are debates on the micromotion of all-suture anchors.

PURPOSE

To perform rotator cuff repair on patients with rotator cuff tears and different shoulder bone mineral densities (BMDs) and investigate (1) where the anchor is located under the cortex, (2) if there is any anchor migration settling during follow-up, and (3) if structural outcome differs according to shoulder BMD.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

We retrospectively investigated 88 patients who underwent arthroscopic single-row repair for small- to medium-sized rotator cuff tears (age [mean ± SD], 58.8 ± 7.1 years) from 712 cases of rotator cuff tendon repair between November 2015 and February 2018. Inclusion criteria were as follows: use of an all-suture anchor; preoperative shoulder BMD; and magnetic resonance imaging (MRI) conducted preoperatively, 2 days after surgery, and 10 months after surgery. Patients were excluded from the study if they underwent open rotator cuff repair (n = 118), got surgery with a double-row technique (n = 178), underwent surgery with anchors other than the all-suture type (n = 273), received anchor insertion in sites other than the greater tuberosity owing to concomitant procedures such as biceps tenodesis and subscapularis repair (n = 29), did not take preoperative shoulder BMD (n = 15), had more than a large-size tear (n = 6), and were lost to follow-up (n = 5). After compression of the all-suture anchor during surgery, the strands were pulled multiple times to ensure that the anchor was fixed onto the bone with appropriate tension. BMD was measured before surgery. Depth to anchor (DA), anchor settling, and repaired rotator cuff integrity were measured with MRI. Patients were categorized into 3 groups: group A (BMD, <0.4 g/cm²; n = 31), group B (BMD, 0.4-0.6 g/cm²; n = 32), and group C (BMD, >0.6 g/cm²; n = 25). A total of 65 patients had follow-up MRI. On the basis of rotator cuff tendon integrity, patients were categorized into either a sufficient thickness group (group S, Sugaya classification grade II or lower; n = 44) or an insufficient thickness group (group I, Sugaya classification grade III or higher; n = 21).

RESULTS

On time-zero MRI, the DA differed significantly among groups (group A, 3.62 ± 2.02 mm; group B, 5.18 ± 2.13 mm; group C, 6.30 ± 3.34 mm) (P = .001). The DA was deeper in patients with a higher BMD at time zero (r = 0.374; P = .001), but the DA did not differ at follow-up MRI (mean, 10.3 months after surgery). On follow-up MRI, anchor settling tended to increase with deeper time-zero DA (r = 0.769; P < .001). Anchor settling was significantly different among groups (group A, 1.33 ± 1.08 mm; group B, 2.78 ± 1.99 mm; group C, 3.81 ± 2.19 mm) (P = .001). The proportion of patients with sufficient thickness in each group did not show a statistical difference (group A, 70.8%; group B, 72.7%; group C, 57.9%) (P = .550).

CONCLUSION

In conclusion, this study confirmed that the postoperative site of anchor insertion in arthroscopic single-row rotator cuff repair with all-suture anchors was located farther from the cortex in patients with higher shoulder BMD and closer to the subcortical bone in patients with lower BMD. On follow-up MRI, no further settling occurred past a certain distance from the cortex, and there was no significant difference in anchor depth or integrity of the rotator cuff tendon based on shoulder BMD. Therefore, minimal settling in the all-suture anchor did not show clinical significance.

Biomechanical analysis of conventional anchor revision after all-suture anchor pullout: a human cadaveric shoulder model

HYPOTHESIS AND BACKGROUND

The possibility of implanting a conventional anchor at the pullout site following all-suture anchor failure was evaluated in a biomechanical cadaveric model. The hypothesis of the study was that anchor revision would yield equal biomechanical properties.

METHODS

Ten human humeri were obtained, and bone density was determined via computed tomography. After all-suture anchor (n = 5) and conventional 4.5-mm anchor (n = 5) insertion, biomechanical testing was conducted. Following all-suture anchor pullout, a conventional 5.5-mm anchor was inserted at the exact site of pullout (n = 5) and biomechanical testing was reinitiated. Testing was conducted using an initial preload of 20 N, followed by an unlimited cyclic protocol, with a stepwise increasing force of 0.05 N for each cycle at a rate of 1 Hz until system failure. The number of cycles, maximum load to failure, stiffness, displacement, and failure mode, as well as macroscopic observation at the failure site including diameter, shape, and cortical destruction, were registered.

RESULTS

The defect following all-suture pullout showed a mean diameter of 4 mm, and conventional revision was possible in each sample. There was no significant difference between the initial all-suture anchor implantation and the conventional anchor implantation or the conventional revision following all-suture failure regarding mean pullout strength, stiffness, displacement, or total number of cycles until failure.

CONCLUSION

Conventional anchor revision at the exact same site where all-suture anchor pullout occurred is possible and exhibits similar biomechanical properties.

Double on-lay fixation using all suture-type anchor for subpectoral biceps tenodesis has favorable functional outcomes and leads to less cosmetic deformities than single on-lay fixation

PURPOSE

This study aimed to compare the clinical outcomes between single on-lay and double on-lay subpectoral biceps tenodesis (SPBT) using all-suture type anchor in patients with concomitant long head of the biceps tendon (LHBT) lesions and rotator cuff tears.

METHODS

The study included 130 patients who underwent SPBT using all-suture type anchor and arthroscopic rotator cuff repair. Single and double anchor on-lay fixations were performed in 69 patients (group A) and 61 patients (group B), respectively. In 16 patients of group A and 36 patients of group B, a metallic wire was embedded at tenodesis site and difference of wire location pre-and postoperatively was measured using simple radiography.

RESULTS

In both groups, the mean visual analogue scale (VAS) score during motion, the mean UCLA and constant scores significantly improved at the last follow-up (all p < 0.001). These scores were not significantly different between two groups. However, postoperatively, a significant difference was observed in the incidence of cosmetic deformity between two groups (p = 0.019). The cosmetic deformity was noted in 9 (13.0%) patients (Popeye deformity 7.2% and biceps softening 5.8%) in group A and 1 (1.6%) patient (Popeye deformity) in group B. In the subgroup analysis on biceps migration after the surgery, the mean migration distance of metal wire was 2.5 ± 3.0 mm in group A and 1.9 ± 2.6 mm in group B (n.s.). No patient had migration of > 10 mm.

CONCLUSIONS

SPBT using all-suture type anchor was a favorable treatment option for lesions of the LHBT with rotator cuff tear. The clinical relevance of this study is the finding that double on-lay fixation with all-suture type anchor would result less cosmetic deformity than the single on-lay fixation for those who need subpectoral biceps tenodesis.

LEVEL OF EVIDENCE

III.

Conventional rotator cuff versus all-suture anchors-A biomechanical study focusing on the insertion angle in an unlimited cyclic model

PURPOSE

The purpose of this study was to compare the biomechanical properties of an all-suture anchor to a conventional anchor used commonly in rotator cuff repairs. Furthermore, the biomechanical influence of various implantation angles was evaluated in both anchor types in a human cadaveric model.

METHODS

30 humeri were allocated into three groups with a similar bone density. The two different anchor types were inserted at a predefined angle of 45°, 90° or 110°. Biomechanical testing included an initial preload of 20N followed by a cyclic protocol with a stepwise increasing force of 0,05N for each cycle at a rate of 1Hz until system failure. Number of cycles, maximum load to failure, stiffness, displacement and failure mode were determined.

RESULTS

27 anchors failed by pullout. There was no significant difference between the conventional and the all-suture anchor regarding mean pullout strength. No considerable discrepancy in stiffness or displacement could be perceived. Comparing the three implantation angles no significant difference could be observed for the all-suture or the conventional anchor.

CONCLUSION

All-suture anchors show similar biomechanical properties to conventional screw shaped anchors in an unlimited cyclic model. The exact insertion angle is not a significant predictor of failure.

Cyclic and Load-to-Failure Properties of All-Suture Anchors in Human Cadaveric Shoulder Glenoid Bone

PURPOSE

To evaluate the cyclic displacement and ultimate load to failure of 4 all-suture anchors in human cadaveric shoulder glenoid bone.

METHODS

Four all-suture anchors indicated for glenoid labral repair were tested in 14 matched pairs of human cadaveric fresh-frozen glenoids. Anchors were inserted at 4 different locations for a total of 112 tests (12-, 3-, 6-, and 9-o'clock positions for right glenoids). Cyclic loading (10 to 60 N at 1 Hz for 200 cycles) and single pull-to-failure testing (33 mm/s) were performed. A Kruskal-Wallis 1-way analysis of variance with the Dunn multiple-comparison post hoc test was used for statistical analysis.

RESULTS

One matched pair was excluded because of poor bone quality. Thus, 13 matched pairs were included in the study, and a total of 104 tests were performed. The Q-Fix anchors showed significantly less displacement after 100 cycles (mean ± standard deviation, 1.40 ± 0.97 mm; P < .001) and 200 cycles (1.53 ± 1.00 mm, P < .001) than all other anchors tested. The Q-Fix (191.3 ± 65.8 N), Suturefix (188.3 ± 61.4 N), and JuggerKnot (183.6 ± 63.5 N) anchors had significantly greater ultimate loads to failure than the Iconix anchors (143.5 ± 54.1 N) (P = .01, P = .012, and P = .021, respectively). Displacement greater than 5 mm occurred in 6 Iconix anchors (22.1%), 5 Suturefix anchors (19.2%), 4 JuggerKnot anchors (15.4%), and 0 Q-Fix anchors (0%).

CONCLUSIONS

The Q-Fix anchors showed less displacement with cyclic loading than the Iconix, JuggerKnot, and Suturefix anchors. The Iconix anchors had a lower ultimate load to failure than the Q-Fix, Suturefix, and JuggerKnot anchors. Only the Q-Fix group had no anchors displace greater than 5 mm with cyclic loading.

CLINICAL RELEVANCE

All-suture anchors vary in their deployment mechanism, which may alter their strength and performance. Operators must be aware of these anchors' propensity to displace while deploying them.

Editorial Commentary: All-Suture Shoulder Glenoid Anchors: Can We Adequately Tension Them or Knot?

All-suture anchors require smaller drill holes (often under 2.0 mm) than comparable solid glenoid anchors (e.g., Gryphon: 2.5-mm drill). A smaller drill allows closer anchor approximation, but there is no indication that this improves repair biomechanics. In fact closely associated multiple fixation points are associated with glenoid fractures, and the same multiple fixation points can be achieved with double- or triple-loaded conventional anchors. All-suture anchors require deployment immediately adjacent to intact cortical bone. Without this, slack and pistoning of the suture ball anchor occur during cyclic loading and have been associated with bone cavitation, repair loosening, and gap formation. A mechanical tensioning mechanism more effectively removes the slack than hand tensioning by the surgeon. Drill length is another concern. All-suture anchor drills measure between 20 and 24 mm long. This length is commonly associated with far cortex penetration and places the suprascapular nerve and axillary nerve at increased risk of contact damage. Maximizing all-suture anchor performance is associated with mechanical deployment systems rather than hand traction applied by the surgeon. Finally, no current all-suture anchor is biodegradable, osteoconductive, or replaced by bone.

Biomechanical Analysis of All-Suture Suture Anchor Fixation Compared With Conventional Suture Anchors and Interference Screws for Biceps Tenodesis

PURPOSE

To compare the biomechanical properties of all-suture suture anchors (ASSAs) with conventional interference screws (CISs) and conventional suture anchors (CSAs) for long head of the biceps tendon fixation during proximal biceps tenodesis (BT).

METHODS

We randomized 21 fresh-frozen human cadaveric shoulders into 3 subpectoral BT treatment groups: ASSA, CSA, and CIS. Each construct was cyclically loaded from 5 to 70 N for 500 cycles (1 Hz). All specimens that survived cyclic loading were then pulled to failure (1 mm/s). Elongation, maximum load, energy, and failure mode were recorded. The humerus was stripped of tissue and then subjected to torsional displacement at a rate of 1°/s until fracture occurred. Maximum load, displacement, stiffness, and energy were recorded.

RESULTS

During tendon testing, 3 specimens (43%) in the CIS group failed early during cyclic testing by the tendon tearing at the screw-tendon interface. All other specimens in the CIS group, as well as all specimens in the ASSA and CSA groups, survived cyclic testing and failed during pull-to-failure testing. Failure occurred at the tendon-anchor or -screw interface in all specimens (100%), with no anchor or screw pullout. The CIS group had significantly decreased elongation (8.9 ± 2.23 mm) at maximum load compared with the ASSA (19.2 ± 5.2 mm) and CSA (18.9 ± 2.23 mm) groups (P = .001). During torsional testing, the ASSA group was able to withstand significantly greater torsional displacement (9.22° ± 0.86°) before failure and had greater energy to failure (497.3 ± 45 Nmm-degrees) than the CIS group (6.13° ± 1.24° and 256.6 ± 70.3 Nmm-degrees, respectively; P = .005).

CONCLUSIONS

This study shows that the biomechanical properties of ASSA, CSA, and CIS constructs are similar. The interference screw group had lower tendon elongation at maximum load but had several early failures compared with the suture anchor groups. The use of suture anchors results in maximum tendon and torsional bone loads similar to interference screws for the long head of the biceps tendon. Torsional testing of the CIS resulted in spiral fractures traversing the screw tunnel in 100% of the specimens, which was not found in the suture anchor groups.

CLINICAL RELEVANCE

The ASSA is a viable fixation method for BT in comparison with the CSA and CIS.

Biomechanical Analysis of Medial-Row All-Suture Suture Anchor Fixation for Rotator Cuff Repair in a Pair-Matched Cadaveric Model

PURPOSE

To compare the biomechanical properties of all-suture suture anchors (ASSAs) with conventional suture anchors (CSAs) for double-row rotator cuff repair (RCR).

METHODS

Fourteen fresh-frozen human cadaveric shoulders were randomized into 2 RCR treatment groups: ASSA and CSA. All constructs received a double-row repair, with the lateral-row implants consisting of two 5.5-mm PEEK (polyether ether ketone) Footprint anchors. Each construct was loaded to a 10-N preload for 2 minutes, followed by cyclic loading from 10 to 160 N at a rate of 100 N/s for 100 cycles. Load-to-failure testing was performed immediately after cyclic loading testing at 1 mm/s from the zero position until failure. Cyclic creep, elongation amplitude, maximum load, stiffness, energy, and failure mode were recorded.

RESULTS

No significant difference in cyclic creep (P = .117) or elongation amplitude (P = .428) was found between the ASSA and CSA groups during cyclic testing. Three specimens in each group (43% in each) failed by the suture tearing through the tendon. The remaining specimens in each group failed by the anchor pulling out of the humeral head. The mean maximum load was 617.73 ± 177.77 N and 545.13 ± 212.98 N for the ASSA and CSA groups, respectively (P = .339). Maximum elongation before failure was not different between groups (P = .122). Mean energy and stiffness were not statistically different between the ASSA and CSA groups (P = .629 and P = .973, respectively).

CONCLUSIONS

In this cadaveric analysis with a simplified unidirectional experimental setup, failure mechanics and maximum load between the ASSA and CSA constructs were similar, with no difference in energy and stiffness. Although the ASSA group showed slightly larger elongation than the CSA group, these differences may not be clinically relevant.

CLINICAL RELEVANCE

This study provides a biomechanical head-to-head comparison of ASSAs and CSAs, indicating that ASSAs may be clinically equivalent to CSAs for use in an RCR.

Comparison of Clinical Outcomes and Computed Tomography Analysis for Tunnel Diameter After Arthroscopic Bankart Repair With the All-Suture Anchor and the Biodegradable Suture Anchor

PURPOSE

To compare the clinical outcomes and radiological findings at the anchor site after arthroscopic Bankart repair with all-suture anchors and biodegradable suture anchors in patients with recurrent anterior shoulder dislocation.

METHODS

The patients who underwent arthroscopic Bankart repair were divided into 2 groups depending on the type of the suture anchor used in different periods. Power analysis was designed based on the postoperative Rowe score. Clinical outcomes, including the Rowe score, American Shoulder and Elbow Surgeons score, subjective instability, and redislocation rates were evaluated. In all patients enrolled, the tunnel diameter of the anchor was assessed with computed tomography arthrogram at 1 year postoperatively. The Institutional Review Board of Ewha Womans University approved this study (no. EUMC 2017-05-058).

RESULTS

A total of 67 patients were enrolled: 33 underwent surgery with a 1.3-mm (single-loaded) or 1.8-mm (double-loaded) all-suture anchor (group A), and 34 underwent surgery with a 3.0-mm biodegradable anchor (10.8 mm in length, 30% 1,2,3-trichloropropane/70% poly-lactide-co-glycolic acid) (group B). There were no significant differences in clinical outcomes between groups A and B in the American Shoulder and Elbow Surgeons score (preoperatively, 51.2 ± 13.7 vs 47.7 ± 12.2; 2 years postoperatively, 88.5 ± 12.3 vs 89.7 ± 10.9; P = .667) and Rowe score (preoperatively, 41.4 ± 10.5 vs 41.3 ± 9.4; 2 years postoperatively, 87.9 ± 14.9 vs 88.5 ± 14.6; P = .857). Postoperative redislocation (6.1% vs 5.9%, P = .682) and subjective instability rate (12.2% vs 17.7%, P = .386) of both groups showed no significant difference. Average tunnel diameter increment was significantly greater with the 1.8-mm all-suture anchor (2.8 ± 0.9 mm) than the 1.3-mm all-suture anchor (1.2 ± 0.8 mm) and 3.0-mm biodegradable anchor (0.8 ± 1.2 mm) (P < .001).

CONCLUSIONS

Arthroscopic Bankart repair with the all-suture anchor showed comparable clinical outcomes and postoperative stability as the conventional biodegradable suture anchor at 2 years after surgery. Tunnel diameter increment of the all-suture anchor was significantly greater than that of the biodegradable suture anchor at the 1-year computed tomography analysis. Although tunnel diameter increment was greater with the all-suture anchor, it did not influence the clinical outcomes.

LEVEL OF EVIDENCE

Level III, retrospective comparative study.

Biomechanical effects of position and angle of insertion for all-suture anchors in arthroscopic Bankart repair

BACKGROUND

The biomechanical properties of all-suture anchor for labral repair depending on the insertion angle and location are lacking. The purpose of this study was to quantify the biomechanical fixation characteristics of the anchor position and insertion angle of all-suture anchors for arthroscopic Bankart repair.

METHODS

Twenty-four fresh frozen cadaveric glenoid were used. All-suture anchors with 1.5-mm diameter were randomly inserted at 2:30, 4:00, and 5:30 o'clock positions on the glenoid edge, with either 30°, 45° or 60° insertion angles to the mediolateral axis of the glenoid. Anchors were preloaded to 5 N and cyclically loaded from 5 N to 20 N for 10 cycles, followed by a load to failure test at 60 mm/min. Permanent, non-recoverable displacement was quantified at the end of the cyclic loading test to yield load.

FINDINGS

All-suture anchors implanted at the 2:30 o'clock position of the glenoid provided greater stiffness, yield load, and ultimate load than those inserted at the 4:00 and 5:30 o'clock positions, regardless of the insertion angle. Displacement at yield and ultimate load were similar among the positions and insertion angles (yield load, vs. 4:00, p = 0.01; vs. 5:30, p = 0.045; ultimate load, vs. 4:00, p < 0.01; vs. 5:30, p < 0.01). The insertion angles of 30°, 45° and 60° did not influence mechanical stability between the 4:00 and 5:30 o'clock positions.

INTERPRETATION

The insertion angle of all-suture anchors does not significantly affect the stability at antero-inferior quadrant of the glenoid.

Pullout Strength of All-Suture Anchors: Effect of the Insertion and Traction Angle-A Biomechanical Study

PURPOSE

To evaluate the pullout strength of the all-suture anchor (ASA), based on the angles of anchor insertion and traction.

METHODS

Synthetic saw bones of 2 densities (0.16 and 0.32 g/cm³) with 3 mm thick cortical bone models were used. ASAs were inserted at 45°, 60°, 75°, or 90° and pulled at 2 angles from the surface: 45° (simulating the physiological pull of the supraspinatus) and 90° (simulating pulling out during knot tying). Five consecutive pullout tests for each insertion and traction angle combination per saw bone were conducted to evaluate the ultimate load to failure and mode of failure (80 tests total). Thereafter, 9 matched pairs of human cadaveric humeri with 2 ASA types were used (insertion angles, 45°, 75°, 90°; traction angle, 90°). Nine consecutive tests were conducted for each insertion angle and anchor type (54 tests total).

RESULTS

The pullout strength was significantly higher for high density- than for low-density saw bones (all P < .05). The pullout strength was higher at the 45°than at the 90° traction angle (all P < .05) and was significantly higher at the 90° and 75° than at the 45° insertion angle in both high-density saw bones and cadaveric humeri (all P < .05). However, the pullout strength was not significantly different by ASA type (all P > .05).

CONCLUSIONS

ASA showed stronger pullout strength in higher density bones. Furthermore, it presented stronger pullout strength in the physiological traction direction of supraspinatus rather than in the knot-tying direction, consistent with the deadman theory. However, stronger pullout strength was observed in the vertically directed insertion angle, not 45°. Therefore, implanting the ASA vertically may be clinically more beneficial not only when performing knot tying during surgery, but also when the supraspinatus tendon loads the ASA postoperatively.

CLINICAL RELEVANCE

The study provides biomechanical evidence that the optimal insertion angle for an ASA is more vertical than the 45°.

Editorial Commentary: Biomechanics of All Suture Anchors: What We Know So Far

All suture anchors (ASAs) have proven valuable for soft tissue to bone fixation. They have a small footprint and can be inserted in tight spaces where little bone is available. Additionally, more ASAs can be inserted in the same amount of bone than their larger predecessors, and this may improve the overall biomechanics of the repair construct through load sharing at multiple points of fixation. ASAs are more dependent on the cortical bone than the cancellous bone where they are inserted for fixation. Decortication of this bone should be minimized or avoided, and deployed anchors should be seated to the cortical bone as much as possible at the time of insertion to avoid later settling with cyclic loading. In anchor biomechanical studies, it is important to look at gap formation with cyclic loading. This biomechanical property is clinically more significant than catastrophic failure because of anchor pullout or suture breakage, which is uncommon. Finally, regarding shoulder rotator cuff surgery, biological (healing) is our greatest challenge; in general, anchor fixation strength is adequate.

Biomechanical Evaluation of a Transtendinous All-Suture Anchor Technique Versus Interference Screw Technique for Suprapectoral Biceps Tenodesis in a Cadaveric Model

PURPOSE

To compare the biomechanical properties of an transtendinous all-suture anchor technique with the commonly-accepted interference screw technique in a cadaveric model.

METHODS

Sixteen fresh-frozen human cadaveric shoulders (mean age, 67.6 ± 5.8 years) were used and were randomly divided into 2 experimental long head of the biceps brachii (LHB) tenodesis groups (n = 8), namely transtendinous all-suture anchor technique and interference screw technique. The location of tenodesis was in the bicipital groove, 1 cm distal to the proximal border of the bicipital groove. Tensile force parallel to the longitudinal axis of the humerus was applied to each specimen. A preload of 5 N was applied for 2 minutes, followed by cyclic loading for 500 cycles from 5 to 70 N at 1 Hz; then, a load-to-failure test at 1 mm/s was performed. The ultimate failure load, stiffness, cyclic displacement, failure displacement, and failure modes were recorded.

RESULTS

The transtendinous all-suture anchor technique provided similar ultimate failure load and stiffness as the interference screw technique. However, the cyclic and failure displacements of the transtendinous all-suture anchor technique were significantly greater than the interference screw technique (P = .009 and .021, respectively). Six specimens in the transtendinous all-suture anchor group failed because of suture anchor pullout, while failure of the other 2 was caused by tendon tear; by contrast, all specimens in the interference screw group failed because of tendon tear.

CONCLUSIONS

The transtendinous all-suture anchor technique for LHB tenodesis offered equivalent ultimate failure load and stiffness but had significantly larger cyclic and failure displacement values when compared with the interference screw technique in this cadaveric biomechanical study.

CLINICAL RELEVANCE

The transtendinous all-suture anchor technique is an alternative technique for suprapectoral LHB tenodesis; however, care should be taken because only time zero biomechanical data are available.

Fixation methods and implants in shoulder stabilization: A historical perspective

BACKGROUND

Treatment for shoulder instability has changed significantly over the past decade from open procedures to arthroscopic procedures using a variety of different fixation methods and implants. The development of these implants has been highly influenced by the numerous complications that have arisen using early designs.

METHODS

A review of the literature was performed to describe the history of shoulder stabilization.

CONCLUSION

As biomedical technology improves, we should continue to see changes to implant design and manufacturing. Having an understanding of the history and evolution of these implants will provide us with context in which to guide future implant design and clinical use. This review article provides a comprehensive overview of the evolution of early shoulder stabilization techniques and implants to the modern implants being used today.

Slight Reduction in the Insertion Depth for an All-Suture Anchor Decreases Cyclic Displacement in the Shoulder Glenoid

PURPOSE

To determine if the depth of anchor insertion affects the biomechanical performance of a 1.5-mm all-suture anchor in glenoid bone.

METHODS

A 1.5-mm all-suture anchor was tested in 8 matched pairs of human cadaver fresh-frozen glenoids. Anchors were inserted at 6 different locations and tested at 3 different depths: 21 mm (preset drilling depth), 17 mm, and 13 mm. Cyclic loading and destructive testing was performed. Displacement after 100 and 200 cycles, along with ultimate failure strength, was determined.

RESULTS

After 100 and 200 cycles, anchors placed at 13 and 17 mm had undergone significantly less displacement than those at 21 mm (P < .05). No difference was observed in ultimate load to failure between anchors placed at 21 and 17 mm. However, the ultimate load to failure was significantly lower in anchors placed at 13 mm (P < .05). There were 5 clinical failures in anchors placed at 21 mm, one at 17 mm, and none at 13 mm.

CONCLUSIONS

The 1.5-mm all-suture anchor tested in this study has an optimal insertion depth of 17 mm, 4 mm shallower than the preset drill depth. At the optimal insertion depth of 17 mm, it underwent significantly less displacement after cyclic loading without a reduction in the ultimate load to failure.

CLINICAL RELEVANCE

Given the results of this study, the optimal insertion depth for this 1.5-mm all-suture anchor is 17 mm, 4 mm shallower than the preset drill depth.

Analysis of glenoid inter-anchor distance with an all-suture anchor system

Background

All-suture anchors used in arthroscopic shoulder stabilization employ small diameter anchors, which allow greater placement density on narrow surfaces such as the glenoid. There is no consensus in the literature about how close to one another two anchors may be implanted.

Purpose

The purpose of the present study is to compare the strength characteristics of two all-suture anchors placed in cadaveric human glenoid at variable distances to one another, in order to determine the minimum distance required for optimal strength.

Methods

Twelve fresh-frozen human cadaveric glenoids were implanted with 1.4 mm all-suture anchors at varying inter-anchor distances. Each glenoid was used for four tests, for a total of 48 tests. Anchors were implanted adjacent to one another or with 2, 3, or 5 mm bone bridges between pilot holes. The glenoids then underwent pullout testing using a test frame with a 5N preload followed by displacement of 12.5 mm/s. The primary outcomes were stiffness, failure strength, and ultimate strength.

Results

Stiffness was 13.52 ± 3.8, 17.97 ± 5.02, 17.59 ± 4.65 and 18.95 ± 4.67 N/mm for the adjacent, 2, 3, and 5 mm treatment groups, respectively. The adjacent group had a significantly lower stiffness compared to the other treatment groups. Failure strength was 48.68 ± 20.64, 76.16 ± 23.78, 73.19 ± 35.83 and 87.04 ± 34.67 N for the adjacent, 2, 3, and 5 mm treatment groups, respectively. The adjacent group had a significantly lower failure strength compared to the other treatment groups. Ultimate strength was also measured to be 190.59 ± 140.93, 268.7 ± 115.1, 283.23 ± 118.43, and 291.28 ± 118.24 for the adjacent, 2, 3, and 5 mm treatment groups, respectively.

Conclusions

This biomechanical study provides evidence that 1.4 mm all-suture anchors demonstrate similar strength characteristics when placed at least 2 mm or greater from one another. When 1.4 mm all-suture anchors were placed adjacent to one another, there was an observed decrease in failure strength and stiffness.

Clinical relevance

This study suggests that 1.4 mm all-suture anchors may be placed as close as 2 mm to one another while preserving strength characteristics.

Functional collagen conduits combined with human mesenchymal stem cells promote regeneration after sciatic nerve transection in dogs

Numerous studies have focused on the development of novel and innovative approaches for the treatment of peripheral nerve injury using artificial nerve guide conduits. In this study, we attempted to bridge 3.5-cm defects of the sciatic nerve with a longitudinally oriented collagen conduit (LOCC) loaded with human umbilical cord mesenchymal stem cells (hUC-MSCs). The LOCC contains a bundle of longitudinally aligned collagenous fibres enclosed in a hollow collagen tube. Our previous studies showed that an LOCC combined with neurotrophic factors enhances peripheral nerve regeneration. However, it remained unknown whether an LOCC seeded with hUC-MSCs could also promote regeneration. In this study, using various histological and electrophysiological analyses, we found that an LOCC provides mechanical support to newly growing nerves and functions as a structural scaffold for cells, thereby stimulating sciatic nerve regeneration. The LOCC and hUC-MSCs synergistically promoted regeneration and improved the functional recovery in a dog model of sciatic nerve injury. Therefore, the combined use of an LOCC and hUC-MSCs might have therapeutic potential for the treatment of peripheral nerve injury.

Arthroscopic Transtendinous Biceps Tenodesis With All-Suture Anchor

There are several methods for long head of the biceps (LHB) tenodesis, yet the optimal option is still debatable. Here we introduce a technique for arthroscopic suprapectoral biceps tenodesis with an all-suture anchor, the transtendinous biceps tenodesis technique. The LHB tenodesis is performed by using the Y-Knot anchor (1.3-mm). A standard suprapectoral approach is used for the tenodesis. A 1.3-mm drill bit is used to drill through the midportion of the biceps tendon and underlying bone to make a pilot hole. Next, the Y-Knot anchor is passed through the tendon and anchored on the underlying bone. A wrapping suture technique is then used to wrap around, tension, and secure the LHB tendon with the aid of a shuttling polydioxanone suture. The construct is fixed by tying down both suture limbs in a nonsliding fashion. This Technical Note describes an alternative method for all-arthroscopic suprapectoral biceps tenodesis using an all-suture anchor with a small diameter to minimize trauma to the tendon.

Editorial Commentary: All-Suture Anchors, Foam Blocks, and Biomechanical Testing

Barber's biomechanical work is well known to Arthroscopy's readers as thorough, comprehensive, and inclusive of new designs as they become available. In "All-Suture Anchors: Biomechanical Analysis of Pullout Strength, Displacement, and Failure Mode," the latest iteration, Barber and Herbert test all-suture anchors in both porcine femurs and biphasic foam. While we await in vivo clinical trials that compare all-suture anchors to currently used anchors, Barber and Herbert have provided data to inform anchor choice, and using their biomechanical data at time zero from all-suture anchor trials in an animal model, we can determine the anchors' feasibility for human clinical investigations.

All-Suture Anchors: Biomechanical Analysis of Pullout Strength, Displacement, and Failure Mode

PURPOSE

To evaluate the biomechanical and design characteristics of all-suture anchors.

METHODS

All-suture anchors were tested in fresh porcine cortical bone and biphasic polyurethane foam blocks by cyclic loading (10-100 N for 200 cycles), followed by destructive testing parallel to the insertion axis at 12.5 mm/s. Endpoints included ultimate failure load, displacement at 100 and 200 cycles, stiffness, and failure mode. Anchors tested included JuggerKnot (1.4, 1.5, and 2.8), Iconix (1, 2, and 3), Y-knot (1.3, 1.8, and 2.8), Q-Fix (1.8 and 2.8), and Draw Tight (1.8 and 3.2).

RESULTS

The mean ultimate failure strength of the triple-loaded anchors (564 ± 42 N) was significantly greater than the mean ultimate failure strength of the double-loaded anchors (465 ± 33 N) (P = .017), and the double-loaded anchors were stronger than the single-loaded anchors (256 ± 35 N) (P < .0001). No difference was found between the results in porcine bone and biphasic polyurethane foam. None of these anchors demonstrated 5 mm or 10 mm of displacement during cyclic loading. The Y-Knot demonstrated greater displacement than the JuggerKnot and Q-Fix (P = .025) but not the Iconix and Draw Tight (P > .05). The most common failure mode varied and was suture breaking for the Q-Fix (97%), JuggerKnot (81%), and Iconix anchors (58%), anchor pullout with the Draw Tight (76%), whereas the Y-Knot was 50% suture breaking and 50% anchor pullout.

CONCLUSIONS

The ultimate failure load of an all-suture anchor is correlated directly with its number of sutures. With cyclic loading, the Y-Knot demonstrated greater displacement than the JuggerKnot and Q-Fix but not the Iconix and Draw Tight. JuggerKnot (81%) and Q-Fix (97%) anchors failed by suture breaking, whereas the Draw Tight anchor failed by anchor pullout (76%).

CLINICAL RELEVANCE

All-suture anchors vary in strength and performance, and these factors may influence clinical success. Biphasic polyurethane foam is a validated model for suture anchor testing.

Biomechanical Comparison of All-Suture Anchor Fixation and Interference Screw Technique for Subpectoral Biceps Tenodesis

PURPOSE

To compare the biomechanical characteristics of the subpectoral Y-knot all-suture anchor fixation with those of the interference screw technique.

METHODS

Sixteen fresh-frozen human cadaveric shoulders with a mean age of 67.6 ± 5.8 years (range, 52 to 74 years) were studied. The specimens were randomly grouped into 2 experimental biceps tenodesis groups (n = 8): Y-knot all-suture anchor or interference screw. The specimens were cyclically tested to failure by applying tensile forces parallel to the longitudinal axis of the humerus. A preload of 5 N was applied for 2 minutes prior to cyclic loading for 500 cycles from 5 to 70 N at 1 Hz; subsequently, a load-to-failure test at 1 mm/s was performed. The ultimate failure load, stiffness, displacement at cyclic and failure loading, and mode of failure were recorded.

RESULTS

The all-suture anchor technique displayed values of ultimate failure load and stiffness comparable to that of the interference screw technique. The displacement at cyclic and failure loading of the all-suture anchor trials were significantly greater than the interference screw (P = .0002). The all-suture anchor specimens experienced anchor pullout and tendon tear equally during the trials, whereas the interference screw group experienced tendon tear in most of the cases and screw pullout in 2 trials.

CONCLUSIONS

The Y-knot all-suture anchor fixation provides equivalent ultimate failure load and stiffness when compared with the interference screw technique in tenodesis of the proximal biceps tendon from a subpectoral approach. However, the interference screw technique demonstrates significantly less displacement in response to cyclic and failure loading.

CLINICAL RELEVANCE

The all-suture anchor fixation is an alternative technique for subpectoral biceps tenodesis even at greater displacement when compared with the interference screw fixation during cyclic and failure loading.

Subpectoral biceps tenodesis: a new technique using an all-suture anchor fixation

There are several options for LHB tenodesis; yet, there is no standard of care. This technical note describes an extramedullary all-suture anchor technique for LHB tenodesis that is similar to the extramedullary cortical button technique. The LHB tenodesis is performed by using the Y-Knot (1.3-mm; ConMed Linvatec, Largo, FL).The biceps tenotomy is completed arthroscopically, and a standard subpectoral approach is used for the tenodesis. A reamer is first used to drill through the anterior cortex of the humerus; subsequently, a 1.3-mm drill bit is used to drill through the posterior cortex. The Y-Knot anchor is passed through the bone tunnel and secured on the posterior cortical bone. A modified rolling hitch suture is placed 10 mm distal to the end of the LHB tendon by using one suture limb of the Y-Knot anchor. The other suture limb is pulled to shuttle the LHB tendon into the humerus, and the construct is fixed by tying down one limb to the other. This technical note describes an alternative method for subpectoral biceps tenodesis and uses a small drill hole, conserves bone, and minimizes trauma to the tendon.

LEVEL OF EVIDENCE

V.