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Biomechanical Advantages of Triple-Loaded Suture Anchors Compared With Double-Row Rotator Cuff Repairs
Biomechanical Advantages of Triple-Loaded Suture Anchors Compared With Double-Row Rotator Cuff Repairs F. Alan Barber, M.D., Morley A. Herbert, Ph.D., F. Alexander Schroeder, M.D., Jorge Aziz-Jacobo, M.D., Matthew M. Mays, M.D., and Jay H. Rapley, M.D.
Purpose: To evaluate the strength and suture-tendon interface security of various suture anchors triply and doubly loaded with ultrahigh–molecular weight polyethylene– containing sutures and to evaluate the relative effectiveness of placing these anchors in a single-row or double-row arrangement by cyclic loading and then destructive testing. Methods: The infraspinatus muscle was reattached to the original humeral footprint by use of 1 of 5 different repair patterns in 40 bovine shoulders. Two single-row repairs and three double-row repairs were tested. High-strength sutures were used for all repairs. Five groups were studied: group 1, 2 triple-loaded screw suture anchors in a single row with simple stitches; group 2, 2 triple-loaded screw anchors in a single row with simple stitches over a fourth suture passed perpendicularly (“rip-stop” stitch); group 3, 2 medial and 2 lateral screw anchors with a single vertical mattress stitch passed from the medial anchors and 2 simple stitches passed from the lateral anchors; group 4, 2 medial double-loaded screw anchors tied in 2 mattress stitches and 2 push-in lateral anchors capturing the medial sutures in a “crisscross” spanning stitch; and group 5, 2 medial double-loaded screw anchors tied in 2 mattress stitches and 2 push-in lateral anchors creating a “suture-bridge” stitch. The specimens were cycled between 10 and 180 N at 1.0 Hz for 3,500 cycles or until failure. Endpoints were cyclic loading displacement (5 and 10 mm), total displacement, and ultimate failure load. Results: A single row of triply loaded anchors was more resistant to stretching to a 5- and 10-mm gap than the double-row repairs with or without the addition of a rip-stop suture (P ⬍ .05). The addition of a rip-stop stitch made the repair more resistant to gap formation than a double row repair (P ⬍ .05). The crisscross double row created by 2 medial double-loaded suture anchors and 2 lateral push-in anchors stretched more than any other group (P ⬍ .05). Conclusions: Double-row repairs with either crossing sutures or 4 separate anchor points were more likely to fail (5- or 10-mm gap) than a single-row repair loaded with 3 simple sutures. Clinical Relevance: The triple-loaded anchors with ultrahigh–molecular weight polyethylene– containing sutures placed in a single row were more resistant to stretching than the double-row groups.
T
he concept of double-row fixation has been advanced for arthroscopic rotator cuff repairs to attempt to provide a more secure repair with a broader
From the Plano Orthopedic Sports Medicine and Spine Center (F.A.B., J.A.-J., J.H.R.), Plano; Advanced Surgical Institutes, Medical City Dallas Hospital (M.A.H.), Dallas; Memorial Bone and Joint Clinic (F.A.S.), Houston; and Richmond Bone & Joint Clinic (M.M.M.), Sugar Land, Texas, U.S.A. Supported by ConMed Linvatec and DePuy Mitek. F.A.B. has received from ConMed Linvatec and DePuy Mitek something of value (exceeding the equivalent of US $500) related to this manuscript or research. Received December 15, 2008; accepted July 20, 2009. Address correspondence and reprint requests to F. Alan Barber, M.D., Plano Orthopedic and Sports Medicine Center, 5228 W Plano Pkwy, Plano, TX 75093, U.S.A. © 2010 by the Arthroscopy Association of North America 0749-8063/10/2603-8699$36.00/0 doi:10.1016/j.arthro.2009.07.019
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footprint on the greater tuberosity. Using new sutures with increased strength and new anchors, various repair combinations have been advocated to accomplish this.1 Clinically, single-row repairs of rotator cuff tendons have provided satisfactory long-term results2-5 and show no difference in clinical outcome when compared with double-row fixation.6 Some biomechanical studies suggest that double-row fixation of the supraspinatus tendon may offer higher failure loads,7-9 whereas others do not.10,11 These biomechanical tests do not maximize the suture placement or the number of sutures in what is called a single-row repair. The concept of suture bridges with crossing stitches is being used as a version of the double-row rotator cuff repair and has also been applied to other techniques.12-14 Suture management has been facilitated by newer passing devices. The single row may
Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 26, No 3 (March), 2010: pp 316-323
TRIPLE-LOADED SUTURE ANCHORS be more effective than the double-row model if a sufficiently strong construct can be achieved by use of multiple ultrahigh–molecular weight polyethylene (UHMWPE)– containing sutures and effective tissuecapturing stitch configurations to hold the tendon to bone. Changes in rotator cuff repair fixation techniques center around 2 major clinical concerns: improved healing and improved repair strength to enable more rapid mobilization. The purpose of this study was to evaluate the strength and suture-tendon interface security of various suture anchors triply and doubly loaded with UHMWPE-containing sutures, as well as to evaluate the relative effectiveness of placing these anchors in a single-row or double-row arrangement by cyclic loading and then destructive testing. The hypothesis of this study was that a single row of anchors, triple loaded with UHMWPE-containing sutures and tied by use of newer tissue-holding stitches, would show equivalent resistance to cyclic loading and destructive load-to-failure testing as double-row configurations. METHODS Forty bovine shoulders harvested from skeletally immature calves were obtained fresh from a local abattoir. This model has been shown to have a size and bone density similar to the proximal humerus in adult humans.11,15 The shoulders were prepared by removing all tissues except for the infraspinatus muscle and its tendon insertion from the proximal humerus. The infraspinatus tendon was then completely detached at its insertion to the humeral head, perpendicular to the collagen fibers, creating a “rotator cuff tendon tear” measuring approximately 4 cm in width. Any remaining soft tissue was removed from the insertion site. A non-elastic nylon mesh strap measuring approximately 2.5 cm wide was looped and sewn onto the front and back of the infraspinatus tendon near its muscletendon junction by use of multiple running and horizontal mattress stitches with No. 2 UHMWPE– containing suture. The tendon was then reattached to the original footprint on the humerus by use of 1 of 5 different repair patterns. Each of these 5 repair patterns used different suture anchor combinations creating either a singlerow or double-row repair. The anchors in each row were spaced approximately 2 cm apart and inserted at no greater than a 45° angle into the underlying bone surface at the original tendon insertion site. The an-
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chors were inserted under direct visualization to a constant depth as indicated by the appropriate depth mark on the anchor inserter. In those repairs using a double row, the medial row was placed first, immediately adjacent to the articular cartilage, followed by the lateral row. Both the simple and mattress stitches were passed 1 cm from each other and 1.5 cm deep into the tendon. Each suture strand was tied when appropriate by use of an open hand-tied square knot backed with 4 alternating half hitches. The different groups tested were as follows: ●
Group 1: Two triple-loaded Super Revo suture anchors (ThRevo anchor) (ConMed, Largo, FL) in a single row, tying the 3 simple UHMWPE sutures (Hi-Fi; ConMed) from each anchor with simple stitches (Fig 1). ● Group 2: Two triple-loaded Super Revo suture anchors in a single row, tying the 3 simple UHMWPE sutures (Hi-Fi; ConMed) from each anchor with simple stitches over separately passed horizontal mattress sutures (passed through the tendon approximately 1.5 cm from the tendon edge) perpendicularly to these simple stitches, creating a “rip-stop” combination stitch. This requires 3 simple stitches from each anchor over additional unthreaded separate sutures (Fig 2). ● Group 3: Four Super Revo suture anchors with UHMWPE sutures (Hi-Fi; ConMed) placed in 2 separate rows (2 anchors medial and 2 anchors lateral). A single vertical mattress stitch was passed
FIGURE 1. Single row of 2 screw anchors with triple simple sutures. © 2010 F. Alan Barber, used by permission.
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from each of the 2 medial-row anchors, and 2 simple stitches were passed from each of the 2 lateral-row anchors (traditional double-row configuration). ● Group 4: Two double-loaded Healix BR suture anchors (DePuy Mitek, Raynham, MA) medially tied in 2 mattress stitches using UHMWPE-containing sutures (Orthocord; DePuy Mitek) and 2 Versalok (DePuy Mitek) anchors laterally using the sutures from the medial mattress stitches creating a “crisscross” spanning stitch (Fig 3). ● Group 5: Two Bio-Corkscrew FT suture anchors (Arthrex, Naples, FL) double loaded with UHMWPEcontaining sutures (FiberWire; Arthrex) medially creating 2 mattress stitches and two PEEK (polyetheretherketone) PushLock suture anchors (Arthrex) laterally creating a “suture-bridge” stitch (Fig 4). After the repair construct was created, each specimen was mounted into a custom fixture in a materials testing machine (Instron model 1321; Instron, Canton, MA) and positioned to allow the tendon to be loaded in the physiologic direction perpendicular to the long axis of the humerus. A bar in the upper Instron fixture was passed through the nylon loop sutured to the infraspinatus tendon for testing. Load was measured in Newtons by use of the load cell of the materials
FIGURE 2. Single row with triple simple sutures from each anchor placed over independent horizontal sutures creating a rip-stop stitch. © 2010 F. Alan Barber, used by permission.
FIGURE 3. Two double-loaded Healix BR suture anchors (DePuy Mitek) medially tied in 2 mattress stitches using Orthocord sutures and 2 Versalok (DePuy Mitek) anchors laterally using sutures from medial mattress stitches creating crisscross spanning stitch. © 2010 F. Alan Barber, used by permission.
testing machine, and displacement at the repair site was measured in millimeters by the actuator movement on the materials testing machine. Data were sampled at 100 Hz.
FIGURE 4. Two Bio-Corkscrew FT suture anchors (Arthrex) double loaded with FiberWire sutures medially creating 2 mattress stitches and 2 PEEK (polyetheretherketone) PushLock suture anchors (Arthrex) laterally creating a suture-bridge stitch. © 2010 F. Alan Barber, used by permission.
TRIPLE-LOADED SUTURE ANCHORS TABLE 1. Group Group Group Group Group Group
1* 2 3 4 5
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Data for Stretching to at Least 5 mm During Testing
No. of Specimens
Stretched 5 mm
Did Not Stretch 5 mm
Mean No. of Cycles to Stretch 5 mm
Median No. of Cycles
Lower 95% CL for Mean
Upper 95% CL for Mean
8 8 8 10 8
7 7 7 10 7
1 1 1 0 1
650 ⫾ 777 386 ⫾ 251 62 ⫾ 31 47 ⫾ 22 91 ⫾ 58
296 391 54 48 76
⫺68 154 33 31 38
1,369 618 90 63 145
Abbreviation: CL, confidence limit. *Group 1 was statistically more resistant to stretching 5 mm than groups 3, 4, and 5 (P ⬍ .05).
The specimens were preloaded to 10 N for 5 seconds and then cycled between 10 and 180 N8,16-18 at 1.0 Hz for 3,500 cycles or until failure occurred. The gauge length after the initial cycle was used as the baseline. This cycle took any slack out of the system before data acquisition. Once the first cycle was completed, the number of cycles needed to reach both 5 mm and 10 mm of displacement was recorded. A higher number of cycles indicated greater resistance to stretch for the construct. The total amount of displacement was also recorded. After completion of 3,500 cycles, a single destructive test was applied until failure at a displacement rate of 12.5 mm/s. The total amount of displacement shown at the end of 3,500 cyclic loads, as well as the ultimate load to failure, was recorded. A total of 8 tests were run for each repair construct. Endpoints measured were displacement during cyclic loading (5-mm and 10-mm points16-19), total displacement observed during cycling, and final load to failure. The terms “crisscross” and “suture bridge” describe the same suture-knotting and suture-crossing configurations. Although these suture materials are different (Orthocord in group 4 and FiberWire in group 5), they have equivalent load-to-failure strengths.20,21 The proximal rows of groups 4 and 5 are held with 2 different screw-in anchors, both of which have been tested and have shown load-to-failure strengths (400 N for Healix22 and 260 N for Bio-Corkscrew FT20) greater than that applied during the cyclic loading phase of this test. The lateral anchors are also different. The PushLock anchor captures all the sutures through a distal “eyelet” with the sutures entering the eyelet in the same direction. This eyelet lies at the bottom of the anchor hole and, once deployed, impacts the larger main anchor body. The Versalok anchor fixes the sutures proximally by use of an expanding bolt construct, and the sutures enter the anchor body from 2 different directions.
Statistical analysis was performed by use of a 2-way analysis of variance with a Tukey post hoc test for multiple comparisons. Duncan multiple range tests were performed on the maximum stretching data. Statistical significance was set at P ⫽ .05. Medians and 95% confidence limits were calculated.
RESULTS The data from this test showed that the single-row constructs were more resistant to stretching to a 5-mm gap than the double-row groups (Table 1). The addition of the rip-stop horizontal stitch (group 2) did not seem to contribute any resistance to stretching of the construct. A statistical analysis of the 5-mm stretch data indicated that the relation between groups achieved statistical significance for group 1 versus groups 3, 4, and 5 (P ⬍ .05). All but 1 specimen from each group (except group 4) stretched at least 5 mm. All specimens in group 4 stretched at least 5 mm (Table 1). As the cyclic loading progressed, many of the specimens also showed 10 mm of gap formation (Table 2). Only 1 specimen from the single-row groups (groups 1 and 2) reached the 10-mm gap level, whereas more than half of the double-row constructs showed 10 mm of gap formation or more. A statistical analysis of this 10-mm endpoint data indicates that statistical significance was achieved (P ⫽ .02). A specific comparison of the relation between groups indicated that group 2 had statistically more resistance to the 10-mm gap formation than group 4 (P ⬍ .05). Although the simple stitches in group 1 required a mean of 650 cycles to stretch to a 5-mm gap in contrast to 386 cycles for the group 2 rip-stop configuration, the only group 1 sample that reached the 10-mm gap level required only 131 cycles beyond the 5-mm gap level, whereas the group 2 rip-stop repair required an additional 3,231 cycles to reach a 10-mm
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F. A. BARBER ET AL. TABLE 2.
Group Group Group Group Group Group
Data for Stretching to 10 mm or More During Testing
No. of Specimens
Stretched 10 mm
Did Not Stretch 10 mm
Mean No. of Cycles to Stretch 10 mm
Median No. of Cycles
Lower 95% CL for Mean
Upper 95% CL for Mean
8 8 8 10 8
1 1 5 8 5
7 7 3 2 3
131 3,231 1,523 ⫾ 879 589 ⫾ 561 1,767 ⫾ 1,033
131 3,231 2,004 474 1,903
— — 431 120 484
— — 2,615 1,058 3,050
1 2* 3 4 5
Abbreviation: CL, confidence limit. *Group 2 had statistically more resistance to 10-mm gap formation than group 4 (P ⬍ .05).
gap. Because only 1 sample in both groups reached the 10-mm gap, SDs are not given. The total amount of stretching during the 3,500 cycles was recorded and is listed in Table 3. Duncan multiple range testing showed that group 4 stretched significantly more than any other group (P ⬍ .05) and that the other groups were not different from each other in mean total gap formation. Finally, an analysis of the ultimate failure strength of the constructs that remained intact after 3,500 cycles, even if there was a noticeable gap present, was performed (Table 4). There was no statistical difference between groups (P ⫽ .15), although group 4 recorded the highest load-to-failure strength after cycling. DISCUSSION The purpose of this study was to evaluate the strength and suture-tendon-bone security of various suture anchors triply or doubly loaded with UHMWPE-containing sutures by use of various stitch patterns, as well as to evaluate the relative effectiveness of placing these anchors in a singlerow or double-row arrangement. Prior cyclic load studies have shown that most of the stretching during cyclic loading occurs during the initial 100 cycles, with less separation occurring between 100 and 500 cycles.23,24 In these tests the mean
TABLE 3. Group Group Group Group Group Group
1 2 3 4 5
number of cycles required to achieve a 5-mm gap was less than 100 for all double-row constructs, whereas the single-row constructs were markedly more resistant to gap formation and required several times as many cycles to reach that point. The number of cycles needed to increase the gap to 10 mm was significantly greater than the number required to reach 5 mm. It seems notable that only 1 sample of the 2 single-row constructs ultimately reached the 10-mm gap level, whereas 60% to 80% of the double-row constructs showed 10-mm gaps. Other cyclic loading studies have compared doublerow fixation with single-row fixation. One study using only 200 cycles (in contrast to the 3,500 cycles used here) reported greater gap formation in single rows than double rows.25 Although the double row tested was similar to group 3 in this test, the single row tested used only double-loaded suture anchors instead of triple-loaded anchors. Another 200 – cyclic load test compared our group 3 double-row construct with a single row of doubleloaded suture anchors placed at the lateral edge of the greater tuberosity8 and reported greater gap formation for the single row. In addition to only having 2 simple sutures, the single row tested was placed at the periphery of the greater tuberosity instead of the more clinically relevant location near the articular cartilage. It should be noted that trabecular, cortical, and total bone density declines as the insertion site moves lat-
Maximum Gap Formation After 3,500 Cycles
No. of Mean Median Minimum Maximum Specimens (mm) SD (mm) (mm) (mm) 8 7 7 10 8
8.2 8.4 11.5 15.6 9.8
3.2 2.4 1.9 5.9 3.5
7.9 7.9 11.2 15.6 10.5
3.9 6.4 9.2 7.3 3.4
14.9 13.2 14.7 25.6 15.7
TABLE 4. Group Group Group Group Group Group
1 2 3 4 5
Ultimate Failure Strength
No. of Specimens
Mean Force (N)
Median Force (N)
6 7 7 10 8
365.1 ⫾ 78.4 453.5 ⫾ 102.5 413.5 ⫾ 82.5 521.3 ⫾ 193.9 489.7 ⫾ 81.4
344.2 438.3 451.6 511.0 470.2
TRIPLE-LOADED SUTURE ANCHORS erally on the greater tuberosity (P ⬍ .01), making the lateral locations weaker anchor insertion sites and more likely to be associated with tendon-bone gap formation.26 The lateral row of suture anchors was the most common failure location in another study comparing different double-row constructs.1 This point is illustrated by a study comparing several double-row constructs with a double suture and single row placed closer to the articular margin than in the previously referenced study,8,19 which failed to show any difference in gap formation by use of UHMWPE-containing sutures and cyclic testing to 3,000 cycles. In fact, with loads up to 100 N (chosen because it simulated a passive early motion rehabilitation program), the maximum gap recorded for any single-row test was 2.5 mm, whereas the 3 double-row constructs had maximum gaps of 3.5, 4.6, and 3.7 mm. No statistically significant differences in load to failure and displacement with cyclic loading were shown in that test. The conclusion that single-row repairs are more susceptible to gap formation than double-row repairs is usually based on data generated from studies using only 1 or 2 sutures in an anchor rather than 3. The use of multiple sutures in a single anchor is common because of the costs associated with anchor devices. As arthroscopic skills improve, the ability to manage multiple sutures improves. It is certainly more efficient to insert 1 anchor with 3 sutures attached than to insert 3 anchors, each with a single suture. The number of sutures in 1 anchor and the suture configuration can significantly influence a repair. The addition of a third suture to a single anchor maximizes the strength of a suture anchor construct by significantly increasing the tissue-holding strength over that of 2 sutures.18,27 Ma et al.9 compared the elongation and failure loads of single- and double-row singleanchor repairs. A “massive cuff stitch” repair had cyclic and failure load characteristics similar to their double-row fixation. This massive cuff stitch was similar to our group 2 but had only 2 simple sutures passing over an independently place horizontal tissue stitch instead of the 3 used in our group 2. The stitch described by Ma et al.9 should not be confused with the one described by Sileo et al.,28 which had only a single simple stitch passing over a horizontal mattress stitch. The double-row repair tested in the study of Sileo et al. was similar to our group 3. This is further evidence that a single row with multiple sutures placed in the tissue either with or without a transverse rip-stop stitch will compare well with the classic double row for elongation and failure
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load. More anchor points, whether provided by more anchors or more sutures per anchor, provide a higher ultimate failure load.29 The type of suture also influences the repair performance. Stronger UHMWPE-containing sutures are becoming the norm, replacing braided polyester sutures. The UHMWPE-containing sutures have different properties,30 and an understanding of their properties and which arthroscopic knots are less likely to fail when tied using these sutures is important.31 The advantages advanced for double-row constructs include a larger footprint with more tissue coverage of the greater tuberosity, which is presumed to lead to better healing. Yet, healing over a larger footprint does not prevent rotator cuff failure medial to the double row,32 especially if too much tension has been forced into the system. A larger footprint may be “over-compressed” by crossing sutures (cross-stitch or suture-bridge technique) placing enough pressure on the tissue that blood flow is restricted. Studies have yet to show that these crossing sutures do not decrease blood flow and limit the healing potential of these already degenerative tendons. With these suturebridging techniques, a uniform footprint may not be easy to establish. Dog-ear or bird-beak deformities have been reported.13,33 Our hypothesis that a single row of triply loaded anchors and various double-row repairs would show equivalent resistance to cyclic loading was only partially supported by these data. The single row was more resistant to gap formation than the double-row constructs tested but showed no difference in ultimate load-to-failure strength. This study is a “time zero” study and does not address clinical healing. There is a lack of clinical evidence of any difference between single-row and double-row repairs,34 and this study does not address this issue. The postoperative rehabilitation protocol is an important factor influencing tissue healing. The amount of immobilization and repair protection needed is not addressed here. One possible implication of these data is that a single-row repair would be more resistant to gap formation at time zero than double-row constructs and may allow for earlier motion. A definitive answer on this question must await prospective randomized clinical data. Limitations of this study include the use of a bovine model, which does not reflect the precise biological performance of an in vivo rotator cuff repair, including determination of the rate or quality of healing, tendon tension, blood supply, and strength of the healing repair. The tendon tears tested were created
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rather than tears of degenerative tendons, and the chronic component of the pathology is a significant factor that affects cuff tendon healing. The variation in size, retraction, and tension in different rotator cuff tears makes uniform conclusions about a specific repair technique hard to draw. Other limitations include the fact that all other soft tissue was removed from the shoulder during the testing process. Clinically, the capsule and other rotator cuff tendons would have contributed to the strength of the repair. Some variation was introduced by using different anchor types for these repairs. The medial rows and single rows used different screw-in anchors. The medial row screw anchors were not the site of construct failure and because previous testing of these screw-in anchors showed that their load-to-failure strength was greater than that sustained during cyclic loading, this should not have an effect on these data. Finally, rotator cuff repairs vary depending on surgeon skill, repair technique, and the individual patient. These factors were eliminated to control the variables in this study. CONCLUSIONS This study showed that triple-loaded anchors with UHMWPE-containing sutures placed in a single-row construct were more resistant to stretching to a 5- and 10-mm gap than the double-row groups (P ⬍ .05). The triple-loaded single row with a rip-stop stitch was more resistant to gap formation than a double row repair (P ⬍ .05). The crisscross double row created by 2 medial double-loaded suture anchors and 2 lateral push-in anchors stretched more than any other group (P ⬍ .05). There was no difference between tripleloaded single-row and double-row constructs in ultimate failure strength.
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Acknowledgment: The authors appreciate the assistance of Jennifer Heldreth in data collection. 18.
REFERENCES 19. 1. Zheng N, Harris HW, Andrews JR. Failure analysis of rotator cuff repair: A comparison of three double-row techniques. J Bone Joint Surg Am 2008;90:1034-1042. 2. Adams CR, Schoolfield JD, Burkhart SS. The results of arthroscopic subscapularis tendon repairs. Arthroscopy 2008;24: 1381-1389. 3. Ko SH, Lee CC, Friedman D, Park KB, Warner JJ. Arthroscopic single-row supraspinatus tendon repair with a modified mattress locking stitch: A prospective, randomized controlled comparison with a simple stitch. Arthroscopy 2008;24:1005-1012. 4. Krishnan SG, Harkins DC, Schiffern SC, Pennington SD, Burkhead WZ. Arthroscopic repair of full-thickness tears of
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the rotator cuff in patients younger than 40 years. Arthroscopy 2008;24:324-328. Charousset C, Grimberg J, Duranthon LD, Bellaiche L, Petrover D, Kalra K. The time for functional recovery after arthroscopic rotator cuff repair: Correlation with tendon healing controlled by computed tomography arthrography. Arthroscopy 2008;24:25-33. Sugaya H, Maeda K, Matsuki K, Moriishi J. Functional and structural outcome after arthroscopic full-thickness rotator cuff repair: Single-row versus dual-row fixation. Arthroscopy 2005; 21:1307-1316. Meier SW, Meier JD. The effect of double-row fixation on initial repair strength in rotator cuff repair: A biomechanical study. Arthroscopy 2006;22:1168-1173. Kim DH, Elattrache NS, Tibone JE, et al. Biomechanical comparison of a single-row versus double-row suture anchor technique for rotator cuff repair. Am J Sports Med 2006;34: 407-414. Ma CB, Comerford L, Wilson J, Puttlitz CM. Biomechanical evaluation of arthroscopic rotator cuff repairs: Double-row compared with single-row fixation. J Bone Joint Surg Am 2006;88:403-410. Nelson CO, Sileo MJ, Grossman MG, Serra-Hsu F. Single-row modified Mason-Allen versus double-row arthroscopic rotator cuff repair: A biomechanical and surface area comparison. Arthroscopy 2008;24:941-948. Mahar A, Tamborlane J, Oka R, Esch J, Pedowitz RA. Singlerow suture anchor repair of the rotator cuff is biomechanically equivalent to double-row repair in a bovine model. Arthroscopy 2007;23:1265-1270. Song HS, Williams GR Jr. Arthroscopic reduction and fixation with suture-bridge technique for displaced or comminuted greater tuberosity fractures. Arthroscopy 2008;24:956-960. Kim KC, Rhee KJ, Shin HD. Deformities associated with the suture-bridge technique for full-thickness rotator cuff tears. Arthroscopy 2008;24:1251-1257. Ji JH, Kim WY, Ra KH. Arthroscopic double-row suture anchor fixation of minimally displaced greater tuberosity fractures. Arthroscopy 2007;23:1133.e1-1133.e4. Available online at www.arthroscopyjournal.org. Bynum CK, Lee S, Mahar A, Tasto J, Pedowitz R. Failure mode of suture anchors as a function of insertion depth. Am J Sports Med 2005;33:1030-1034. Burkhart SS, Diaz Pagan JL, Wirth MA, Athanasiou KA. Cyclic loading of anchor-based rotator cuff repairs: Confirmation of the tension overload phenomenon and comparison of suture anchor fixation with transosseous fixation. Arthroscopy 1997;13:720-724. Burkhart SS, Johnson TC, Wirth MA, Athanasiou KA. Cyclic loading of transosseous rotator cuff repairs: Tension overload as a possible cause of failure. Arthroscopy 1997; 13:172-176. Coons DA, Barber FA, Herbert MA. Triple-loaded singleanchor stitch configurations: An analysis of cyclically loaded suture-tendon interface security. Arthroscopy 2006;22:11541158. Mazzocca AD, Millett PJ, Guanche CA, Santangelo SA, Arciero RA. Arthroscopic single-row versus double-row suture anchor rotator cuff repair. Am J Sports Med 2005;33:18611868. Barber FA, Herbert MA, Coons DA, Boothby MH. Sutures and suture anchors—Update 2006. Arthroscopy 2006;22:10631069.e2. Available online at www.arthroscopyjournal.org. Barber FA, Herbert MA, Beavis RC. Cyclic load and failure behavior of arthroscopic knots and high strength sutures. Arthroscopy 2009;25:192-199. Barber FA, Herbert MA, Beavis RC, Barrera Oro F. Suture anchor materials, eyelets, and designs: Update 2008. Arthroscopy 2008;24:859-867.
TRIPLE-LOADED SUTURE ANCHORS 23. Barber FA, Coons DA, Ruiz-Suarez M. Cyclic load testing and ultimate failure strength of biodegradable glenoid anchors. Arthroscopy 2008;24:224-228. 24. Barber FA, Coons DA, Ruiz-Suarez M. Cyclic load testing of biodegradable suture anchors containing 2 high-strength sutures. Arthroscopy 2007;23:355-360. 25. Domb BG, Glousman RE, Brooks A, Hansen M, Lee TQ, ElAttrache NS. High-tension double-row footprint repair compared with reduced-tension single-row repair for massive rotator cuff tears. J Bone Joint Surg Am 2008;90:35-39 (Suppl 4). 26. Tingart MJ, Apreleva M, Zurakowski D, Warner JJ. Pullout strength of suture anchors used in rotator cuff repair. J Bone Joint Surg Am 2003;85:2190-2198. 27. Castagna A, Garofalo R, Conti M, Borroni M, Snyder SJ. Arthroscopic rotator cuff repair using a triple-loaded suture anchor and a modified Mason-Allen technique (Alex stitch). Arthroscopy 2007;23:440.e1-440.e4. Available online at www.arthroscopyjournal.org. 28. Sileo MJ, Ruotolo CR, Nelson CO, Serra-Hsu F, Panchal AP. A biomechanical comparison of the modified Mason-Allen stitch and massive cuff stitch in vitro. Arthroscopy 2007;23: 235-240.e2. Available online at www.arthroscopyjournal.org.
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29. Cummins CA, Appleyard RC, Strickland S, Haen PS, Chen S, Murrell GA. Rotator cuff repair: An ex vivo analysis of suture anchor repair techniques on initial load to failure. Arthroscopy 2005;21:1236-1241. 30. Kowalsky MS, Dellenbaugh SG, Erlichman DB, Gardner TR, Levine WN, Ahmad CS. Evaluation of suture abrasion against rotator cuff tendon and proximal humerus bone. Arthroscopy 2008;24:329-334. 31. Abbi G, Espinoza L, Odell T, Mahar A, Pedowitz R. Evaluation of 5 knots and 2 suture materials for arthroscopic rotator cuff repair: Very strong sutures can still slip. Arthroscopy 2006;22:38-43. 32. Trantalis JN, Boorman RS, Pletsch K, Lo IK. Medial rotator cuff failure after arthroscopic double-row rotator cuff repair. Arthroscopy 2008;24:727-731. 33. Kim KC, Rhee KJ, Shin HD, Kim YM. A modified suturebridge technique for a marginal dog-ear deformity caused during rotator cuff repair. Arthroscopy 2007;23:562.e1-562.e4. Available online at www.arthroscopyjournal.org. 34. Reardon DJ, Maffulli N. Clinical evidence shows no difference between single- and double-row repair for rotator cuff tears. Arthroscopy 2007;23:670-673.
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Purpose: To evaluate the strength and suture-tendon interface security of various suture anchors triply and doubly loaded with ultrahigh–molecular weight polyethylene– containing sutures and to evaluate the relative effectiveness of placing these anchors in a single-row or double-row arrangement by cyclic loading and then destructive testing. Methods: The infraspinatus muscle was reattached to the original humeral footprint by use of 1 of 5 different repair patterns in 40 bovine shoulders. Two single-row repairs and three double-row repairs were tested. High-strength sutures were used for all repairs. Five groups were studied: group 1, 2 triple-loaded screw suture anchors in a single row with simple stitches; group 2, 2 triple-loaded screw anchors in a single row with simple stitches over a fourth suture passed perpendicularly (“rip-stop” stitch); group 3, 2 medial and 2 lateral screw anchors with a single vertical mattress stitch passed from the medial anchors and 2 simple stitches passed from the lateral anchors; group 4, 2 medial double-loaded screw anchors tied in 2 mattress stitches and 2 push-in lateral anchors capturing the medial sutures in a “crisscross” spanning stitch; and group 5, 2 medial double-loaded screw anchors tied in 2 mattress stitches and 2 push-in lateral anchors creating a “suture-bridge” stitch. The specimens were cycled between 10 and 180 N at 1.0 Hz for 3,500 cycles or until failure. Endpoints were cyclic loading displacement (5 and 10 mm), total displacement, and ultimate failure load. Results: A single row of triply loaded anchors was more resistant to stretching to a 5- and 10-mm gap than the double-row repairs with or without the addition of a rip-stop suture (P ⬍ .05). The addition of a rip-stop stitch made the repair more resistant to gap formation than a double row repair (P ⬍ .05). The crisscross double row created by 2 medial double-loaded suture anchors and 2 lateral push-in anchors stretched more than any other group (P ⬍ .05). Conclusions: Double-row repairs with either crossing sutures or 4 separate anchor points were more likely to fail (5- or 10-mm gap) than a single-row repair loaded with 3 simple sutures. Clinical Relevance: The triple-loaded anchors with ultrahigh–molecular weight polyethylene– containing sutures placed in a single row were more resistant to stretching than the double-row groups.
T
he concept of double-row fixation has been advanced for arthroscopic rotator cuff repairs to attempt to provide a more secure repair with a broader
From the Plano Orthopedic Sports Medicine and Spine Center (F.A.B., J.A.-J., J.H.R.), Plano; Advanced Surgical Institutes, Medical City Dallas Hospital (M.A.H.), Dallas; Memorial Bone and Joint Clinic (F.A.S.), Houston; and Richmond Bone & Joint Clinic (M.M.M.), Sugar Land, Texas, U.S.A. Supported by ConMed Linvatec and DePuy Mitek. F.A.B. has received from ConMed Linvatec and DePuy Mitek something of value (exceeding the equivalent of US $500) related to this manuscript or research. Received December 15, 2008; accepted July 20, 2009. Address correspondence and reprint requests to F. Alan Barber, M.D., Plano Orthopedic and Sports Medicine Center, 5228 W Plano Pkwy, Plano, TX 75093, U.S.A. © 2010 by the Arthroscopy Association of North America 0749-8063/10/2603-8699$36.00/0 doi:10.1016/j.arthro.2009.07.019
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footprint on the greater tuberosity. Using new sutures with increased strength and new anchors, various repair combinations have been advocated to accomplish this.1 Clinically, single-row repairs of rotator cuff tendons have provided satisfactory long-term results2-5 and show no difference in clinical outcome when compared with double-row fixation.6 Some biomechanical studies suggest that double-row fixation of the supraspinatus tendon may offer higher failure loads,7-9 whereas others do not.10,11 These biomechanical tests do not maximize the suture placement or the number of sutures in what is called a single-row repair. The concept of suture bridges with crossing stitches is being used as a version of the double-row rotator cuff repair and has also been applied to other techniques.12-14 Suture management has been facilitated by newer passing devices. The single row may
Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 26, No 3 (March), 2010: pp 316-323
TRIPLE-LOADED SUTURE ANCHORS be more effective than the double-row model if a sufficiently strong construct can be achieved by use of multiple ultrahigh–molecular weight polyethylene (UHMWPE)– containing sutures and effective tissuecapturing stitch configurations to hold the tendon to bone. Changes in rotator cuff repair fixation techniques center around 2 major clinical concerns: improved healing and improved repair strength to enable more rapid mobilization. The purpose of this study was to evaluate the strength and suture-tendon interface security of various suture anchors triply and doubly loaded with UHMWPE-containing sutures, as well as to evaluate the relative effectiveness of placing these anchors in a single-row or double-row arrangement by cyclic loading and then destructive testing. The hypothesis of this study was that a single row of anchors, triple loaded with UHMWPE-containing sutures and tied by use of newer tissue-holding stitches, would show equivalent resistance to cyclic loading and destructive load-to-failure testing as double-row configurations. METHODS Forty bovine shoulders harvested from skeletally immature calves were obtained fresh from a local abattoir. This model has been shown to have a size and bone density similar to the proximal humerus in adult humans.11,15 The shoulders were prepared by removing all tissues except for the infraspinatus muscle and its tendon insertion from the proximal humerus. The infraspinatus tendon was then completely detached at its insertion to the humeral head, perpendicular to the collagen fibers, creating a “rotator cuff tendon tear” measuring approximately 4 cm in width. Any remaining soft tissue was removed from the insertion site. A non-elastic nylon mesh strap measuring approximately 2.5 cm wide was looped and sewn onto the front and back of the infraspinatus tendon near its muscletendon junction by use of multiple running and horizontal mattress stitches with No. 2 UHMWPE– containing suture. The tendon was then reattached to the original footprint on the humerus by use of 1 of 5 different repair patterns. Each of these 5 repair patterns used different suture anchor combinations creating either a singlerow or double-row repair. The anchors in each row were spaced approximately 2 cm apart and inserted at no greater than a 45° angle into the underlying bone surface at the original tendon insertion site. The an-
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chors were inserted under direct visualization to a constant depth as indicated by the appropriate depth mark on the anchor inserter. In those repairs using a double row, the medial row was placed first, immediately adjacent to the articular cartilage, followed by the lateral row. Both the simple and mattress stitches were passed 1 cm from each other and 1.5 cm deep into the tendon. Each suture strand was tied when appropriate by use of an open hand-tied square knot backed with 4 alternating half hitches. The different groups tested were as follows: ●
Group 1: Two triple-loaded Super Revo suture anchors (ThRevo anchor) (ConMed, Largo, FL) in a single row, tying the 3 simple UHMWPE sutures (Hi-Fi; ConMed) from each anchor with simple stitches (Fig 1). ● Group 2: Two triple-loaded Super Revo suture anchors in a single row, tying the 3 simple UHMWPE sutures (Hi-Fi; ConMed) from each anchor with simple stitches over separately passed horizontal mattress sutures (passed through the tendon approximately 1.5 cm from the tendon edge) perpendicularly to these simple stitches, creating a “rip-stop” combination stitch. This requires 3 simple stitches from each anchor over additional unthreaded separate sutures (Fig 2). ● Group 3: Four Super Revo suture anchors with UHMWPE sutures (Hi-Fi; ConMed) placed in 2 separate rows (2 anchors medial and 2 anchors lateral). A single vertical mattress stitch was passed
FIGURE 1. Single row of 2 screw anchors with triple simple sutures. © 2010 F. Alan Barber, used by permission.
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from each of the 2 medial-row anchors, and 2 simple stitches were passed from each of the 2 lateral-row anchors (traditional double-row configuration). ● Group 4: Two double-loaded Healix BR suture anchors (DePuy Mitek, Raynham, MA) medially tied in 2 mattress stitches using UHMWPE-containing sutures (Orthocord; DePuy Mitek) and 2 Versalok (DePuy Mitek) anchors laterally using the sutures from the medial mattress stitches creating a “crisscross” spanning stitch (Fig 3). ● Group 5: Two Bio-Corkscrew FT suture anchors (Arthrex, Naples, FL) double loaded with UHMWPEcontaining sutures (FiberWire; Arthrex) medially creating 2 mattress stitches and two PEEK (polyetheretherketone) PushLock suture anchors (Arthrex) laterally creating a “suture-bridge” stitch (Fig 4). After the repair construct was created, each specimen was mounted into a custom fixture in a materials testing machine (Instron model 1321; Instron, Canton, MA) and positioned to allow the tendon to be loaded in the physiologic direction perpendicular to the long axis of the humerus. A bar in the upper Instron fixture was passed through the nylon loop sutured to the infraspinatus tendon for testing. Load was measured in Newtons by use of the load cell of the materials
FIGURE 2. Single row with triple simple sutures from each anchor placed over independent horizontal sutures creating a rip-stop stitch. © 2010 F. Alan Barber, used by permission.
FIGURE 3. Two double-loaded Healix BR suture anchors (DePuy Mitek) medially tied in 2 mattress stitches using Orthocord sutures and 2 Versalok (DePuy Mitek) anchors laterally using sutures from medial mattress stitches creating crisscross spanning stitch. © 2010 F. Alan Barber, used by permission.
testing machine, and displacement at the repair site was measured in millimeters by the actuator movement on the materials testing machine. Data were sampled at 100 Hz.
FIGURE 4. Two Bio-Corkscrew FT suture anchors (Arthrex) double loaded with FiberWire sutures medially creating 2 mattress stitches and 2 PEEK (polyetheretherketone) PushLock suture anchors (Arthrex) laterally creating a suture-bridge stitch. © 2010 F. Alan Barber, used by permission.
TRIPLE-LOADED SUTURE ANCHORS TABLE 1. Group Group Group Group Group Group
1* 2 3 4 5
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Data for Stretching to at Least 5 mm During Testing
No. of Specimens
Stretched 5 mm
Did Not Stretch 5 mm
Mean No. of Cycles to Stretch 5 mm
Median No. of Cycles
Lower 95% CL for Mean
Upper 95% CL for Mean
8 8 8 10 8
7 7 7 10 7
1 1 1 0 1
650 ⫾ 777 386 ⫾ 251 62 ⫾ 31 47 ⫾ 22 91 ⫾ 58
296 391 54 48 76
⫺68 154 33 31 38
1,369 618 90 63 145
Abbreviation: CL, confidence limit. *Group 1 was statistically more resistant to stretching 5 mm than groups 3, 4, and 5 (P ⬍ .05).
The specimens were preloaded to 10 N for 5 seconds and then cycled between 10 and 180 N8,16-18 at 1.0 Hz for 3,500 cycles or until failure occurred. The gauge length after the initial cycle was used as the baseline. This cycle took any slack out of the system before data acquisition. Once the first cycle was completed, the number of cycles needed to reach both 5 mm and 10 mm of displacement was recorded. A higher number of cycles indicated greater resistance to stretch for the construct. The total amount of displacement was also recorded. After completion of 3,500 cycles, a single destructive test was applied until failure at a displacement rate of 12.5 mm/s. The total amount of displacement shown at the end of 3,500 cyclic loads, as well as the ultimate load to failure, was recorded. A total of 8 tests were run for each repair construct. Endpoints measured were displacement during cyclic loading (5-mm and 10-mm points16-19), total displacement observed during cycling, and final load to failure. The terms “crisscross” and “suture bridge” describe the same suture-knotting and suture-crossing configurations. Although these suture materials are different (Orthocord in group 4 and FiberWire in group 5), they have equivalent load-to-failure strengths.20,21 The proximal rows of groups 4 and 5 are held with 2 different screw-in anchors, both of which have been tested and have shown load-to-failure strengths (400 N for Healix22 and 260 N for Bio-Corkscrew FT20) greater than that applied during the cyclic loading phase of this test. The lateral anchors are also different. The PushLock anchor captures all the sutures through a distal “eyelet” with the sutures entering the eyelet in the same direction. This eyelet lies at the bottom of the anchor hole and, once deployed, impacts the larger main anchor body. The Versalok anchor fixes the sutures proximally by use of an expanding bolt construct, and the sutures enter the anchor body from 2 different directions.
Statistical analysis was performed by use of a 2-way analysis of variance with a Tukey post hoc test for multiple comparisons. Duncan multiple range tests were performed on the maximum stretching data. Statistical significance was set at P ⫽ .05. Medians and 95% confidence limits were calculated.
RESULTS The data from this test showed that the single-row constructs were more resistant to stretching to a 5-mm gap than the double-row groups (Table 1). The addition of the rip-stop horizontal stitch (group 2) did not seem to contribute any resistance to stretching of the construct. A statistical analysis of the 5-mm stretch data indicated that the relation between groups achieved statistical significance for group 1 versus groups 3, 4, and 5 (P ⬍ .05). All but 1 specimen from each group (except group 4) stretched at least 5 mm. All specimens in group 4 stretched at least 5 mm (Table 1). As the cyclic loading progressed, many of the specimens also showed 10 mm of gap formation (Table 2). Only 1 specimen from the single-row groups (groups 1 and 2) reached the 10-mm gap level, whereas more than half of the double-row constructs showed 10 mm of gap formation or more. A statistical analysis of this 10-mm endpoint data indicates that statistical significance was achieved (P ⫽ .02). A specific comparison of the relation between groups indicated that group 2 had statistically more resistance to the 10-mm gap formation than group 4 (P ⬍ .05). Although the simple stitches in group 1 required a mean of 650 cycles to stretch to a 5-mm gap in contrast to 386 cycles for the group 2 rip-stop configuration, the only group 1 sample that reached the 10-mm gap level required only 131 cycles beyond the 5-mm gap level, whereas the group 2 rip-stop repair required an additional 3,231 cycles to reach a 10-mm
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F. A. BARBER ET AL. TABLE 2.
Group Group Group Group Group Group
Data for Stretching to 10 mm or More During Testing
No. of Specimens
Stretched 10 mm
Did Not Stretch 10 mm
Mean No. of Cycles to Stretch 10 mm
Median No. of Cycles
Lower 95% CL for Mean
Upper 95% CL for Mean
8 8 8 10 8
1 1 5 8 5
7 7 3 2 3
131 3,231 1,523 ⫾ 879 589 ⫾ 561 1,767 ⫾ 1,033
131 3,231 2,004 474 1,903
— — 431 120 484
— — 2,615 1,058 3,050
1 2* 3 4 5
Abbreviation: CL, confidence limit. *Group 2 had statistically more resistance to 10-mm gap formation than group 4 (P ⬍ .05).
gap. Because only 1 sample in both groups reached the 10-mm gap, SDs are not given. The total amount of stretching during the 3,500 cycles was recorded and is listed in Table 3. Duncan multiple range testing showed that group 4 stretched significantly more than any other group (P ⬍ .05) and that the other groups were not different from each other in mean total gap formation. Finally, an analysis of the ultimate failure strength of the constructs that remained intact after 3,500 cycles, even if there was a noticeable gap present, was performed (Table 4). There was no statistical difference between groups (P ⫽ .15), although group 4 recorded the highest load-to-failure strength after cycling. DISCUSSION The purpose of this study was to evaluate the strength and suture-tendon-bone security of various suture anchors triply or doubly loaded with UHMWPE-containing sutures by use of various stitch patterns, as well as to evaluate the relative effectiveness of placing these anchors in a singlerow or double-row arrangement. Prior cyclic load studies have shown that most of the stretching during cyclic loading occurs during the initial 100 cycles, with less separation occurring between 100 and 500 cycles.23,24 In these tests the mean
TABLE 3. Group Group Group Group Group Group
1 2 3 4 5
number of cycles required to achieve a 5-mm gap was less than 100 for all double-row constructs, whereas the single-row constructs were markedly more resistant to gap formation and required several times as many cycles to reach that point. The number of cycles needed to increase the gap to 10 mm was significantly greater than the number required to reach 5 mm. It seems notable that only 1 sample of the 2 single-row constructs ultimately reached the 10-mm gap level, whereas 60% to 80% of the double-row constructs showed 10-mm gaps. Other cyclic loading studies have compared doublerow fixation with single-row fixation. One study using only 200 cycles (in contrast to the 3,500 cycles used here) reported greater gap formation in single rows than double rows.25 Although the double row tested was similar to group 3 in this test, the single row tested used only double-loaded suture anchors instead of triple-loaded anchors. Another 200 – cyclic load test compared our group 3 double-row construct with a single row of doubleloaded suture anchors placed at the lateral edge of the greater tuberosity8 and reported greater gap formation for the single row. In addition to only having 2 simple sutures, the single row tested was placed at the periphery of the greater tuberosity instead of the more clinically relevant location near the articular cartilage. It should be noted that trabecular, cortical, and total bone density declines as the insertion site moves lat-
Maximum Gap Formation After 3,500 Cycles
No. of Mean Median Minimum Maximum Specimens (mm) SD (mm) (mm) (mm) 8 7 7 10 8
8.2 8.4 11.5 15.6 9.8
3.2 2.4 1.9 5.9 3.5
7.9 7.9 11.2 15.6 10.5
3.9 6.4 9.2 7.3 3.4
14.9 13.2 14.7 25.6 15.7
TABLE 4. Group Group Group Group Group Group
1 2 3 4 5
Ultimate Failure Strength
No. of Specimens
Mean Force (N)
Median Force (N)
6 7 7 10 8
365.1 ⫾ 78.4 453.5 ⫾ 102.5 413.5 ⫾ 82.5 521.3 ⫾ 193.9 489.7 ⫾ 81.4
344.2 438.3 451.6 511.0 470.2
TRIPLE-LOADED SUTURE ANCHORS erally on the greater tuberosity (P ⬍ .01), making the lateral locations weaker anchor insertion sites and more likely to be associated with tendon-bone gap formation.26 The lateral row of suture anchors was the most common failure location in another study comparing different double-row constructs.1 This point is illustrated by a study comparing several double-row constructs with a double suture and single row placed closer to the articular margin than in the previously referenced study,8,19 which failed to show any difference in gap formation by use of UHMWPE-containing sutures and cyclic testing to 3,000 cycles. In fact, with loads up to 100 N (chosen because it simulated a passive early motion rehabilitation program), the maximum gap recorded for any single-row test was 2.5 mm, whereas the 3 double-row constructs had maximum gaps of 3.5, 4.6, and 3.7 mm. No statistically significant differences in load to failure and displacement with cyclic loading were shown in that test. The conclusion that single-row repairs are more susceptible to gap formation than double-row repairs is usually based on data generated from studies using only 1 or 2 sutures in an anchor rather than 3. The use of multiple sutures in a single anchor is common because of the costs associated with anchor devices. As arthroscopic skills improve, the ability to manage multiple sutures improves. It is certainly more efficient to insert 1 anchor with 3 sutures attached than to insert 3 anchors, each with a single suture. The number of sutures in 1 anchor and the suture configuration can significantly influence a repair. The addition of a third suture to a single anchor maximizes the strength of a suture anchor construct by significantly increasing the tissue-holding strength over that of 2 sutures.18,27 Ma et al.9 compared the elongation and failure loads of single- and double-row singleanchor repairs. A “massive cuff stitch” repair had cyclic and failure load characteristics similar to their double-row fixation. This massive cuff stitch was similar to our group 2 but had only 2 simple sutures passing over an independently place horizontal tissue stitch instead of the 3 used in our group 2. The stitch described by Ma et al.9 should not be confused with the one described by Sileo et al.,28 which had only a single simple stitch passing over a horizontal mattress stitch. The double-row repair tested in the study of Sileo et al. was similar to our group 3. This is further evidence that a single row with multiple sutures placed in the tissue either with or without a transverse rip-stop stitch will compare well with the classic double row for elongation and failure
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load. More anchor points, whether provided by more anchors or more sutures per anchor, provide a higher ultimate failure load.29 The type of suture also influences the repair performance. Stronger UHMWPE-containing sutures are becoming the norm, replacing braided polyester sutures. The UHMWPE-containing sutures have different properties,30 and an understanding of their properties and which arthroscopic knots are less likely to fail when tied using these sutures is important.31 The advantages advanced for double-row constructs include a larger footprint with more tissue coverage of the greater tuberosity, which is presumed to lead to better healing. Yet, healing over a larger footprint does not prevent rotator cuff failure medial to the double row,32 especially if too much tension has been forced into the system. A larger footprint may be “over-compressed” by crossing sutures (cross-stitch or suture-bridge technique) placing enough pressure on the tissue that blood flow is restricted. Studies have yet to show that these crossing sutures do not decrease blood flow and limit the healing potential of these already degenerative tendons. With these suturebridging techniques, a uniform footprint may not be easy to establish. Dog-ear or bird-beak deformities have been reported.13,33 Our hypothesis that a single row of triply loaded anchors and various double-row repairs would show equivalent resistance to cyclic loading was only partially supported by these data. The single row was more resistant to gap formation than the double-row constructs tested but showed no difference in ultimate load-to-failure strength. This study is a “time zero” study and does not address clinical healing. There is a lack of clinical evidence of any difference between single-row and double-row repairs,34 and this study does not address this issue. The postoperative rehabilitation protocol is an important factor influencing tissue healing. The amount of immobilization and repair protection needed is not addressed here. One possible implication of these data is that a single-row repair would be more resistant to gap formation at time zero than double-row constructs and may allow for earlier motion. A definitive answer on this question must await prospective randomized clinical data. Limitations of this study include the use of a bovine model, which does not reflect the precise biological performance of an in vivo rotator cuff repair, including determination of the rate or quality of healing, tendon tension, blood supply, and strength of the healing repair. The tendon tears tested were created
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rather than tears of degenerative tendons, and the chronic component of the pathology is a significant factor that affects cuff tendon healing. The variation in size, retraction, and tension in different rotator cuff tears makes uniform conclusions about a specific repair technique hard to draw. Other limitations include the fact that all other soft tissue was removed from the shoulder during the testing process. Clinically, the capsule and other rotator cuff tendons would have contributed to the strength of the repair. Some variation was introduced by using different anchor types for these repairs. The medial rows and single rows used different screw-in anchors. The medial row screw anchors were not the site of construct failure and because previous testing of these screw-in anchors showed that their load-to-failure strength was greater than that sustained during cyclic loading, this should not have an effect on these data. Finally, rotator cuff repairs vary depending on surgeon skill, repair technique, and the individual patient. These factors were eliminated to control the variables in this study. CONCLUSIONS This study showed that triple-loaded anchors with UHMWPE-containing sutures placed in a single-row construct were more resistant to stretching to a 5- and 10-mm gap than the double-row groups (P ⬍ .05). The triple-loaded single row with a rip-stop stitch was more resistant to gap formation than a double row repair (P ⬍ .05). The crisscross double row created by 2 medial double-loaded suture anchors and 2 lateral push-in anchors stretched more than any other group (P ⬍ .05). There was no difference between tripleloaded single-row and double-row constructs in ultimate failure strength.
5.
6.
7. 8.
9.
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12. 13. 14.
15. 16.
17.
Acknowledgment: The authors appreciate the assistance of Jennifer Heldreth in data collection. 18.
REFERENCES 19. 1. Zheng N, Harris HW, Andrews JR. Failure analysis of rotator cuff repair: A comparison of three double-row techniques. J Bone Joint Surg Am 2008;90:1034-1042. 2. Adams CR, Schoolfield JD, Burkhart SS. The results of arthroscopic subscapularis tendon repairs. Arthroscopy 2008;24: 1381-1389. 3. Ko SH, Lee CC, Friedman D, Park KB, Warner JJ. Arthroscopic single-row supraspinatus tendon repair with a modified mattress locking stitch: A prospective, randomized controlled comparison with a simple stitch. Arthroscopy 2008;24:1005-1012. 4. Krishnan SG, Harkins DC, Schiffern SC, Pennington SD, Burkhead WZ. Arthroscopic repair of full-thickness tears of
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the rotator cuff in patients younger than 40 years. Arthroscopy 2008;24:324-328. Charousset C, Grimberg J, Duranthon LD, Bellaiche L, Petrover D, Kalra K. The time for functional recovery after arthroscopic rotator cuff repair: Correlation with tendon healing controlled by computed tomography arthrography. Arthroscopy 2008;24:25-33. Sugaya H, Maeda K, Matsuki K, Moriishi J. Functional and structural outcome after arthroscopic full-thickness rotator cuff repair: Single-row versus dual-row fixation. Arthroscopy 2005; 21:1307-1316. Meier SW, Meier JD. The effect of double-row fixation on initial repair strength in rotator cuff repair: A biomechanical study. Arthroscopy 2006;22:1168-1173. Kim DH, Elattrache NS, Tibone JE, et al. Biomechanical comparison of a single-row versus double-row suture anchor technique for rotator cuff repair. Am J Sports Med 2006;34: 407-414. Ma CB, Comerford L, Wilson J, Puttlitz CM. Biomechanical evaluation of arthroscopic rotator cuff repairs: Double-row compared with single-row fixation. J Bone Joint Surg Am 2006;88:403-410. Nelson CO, Sileo MJ, Grossman MG, Serra-Hsu F. Single-row modified Mason-Allen versus double-row arthroscopic rotator cuff repair: A biomechanical and surface area comparison. Arthroscopy 2008;24:941-948. Mahar A, Tamborlane J, Oka R, Esch J, Pedowitz RA. Singlerow suture anchor repair of the rotator cuff is biomechanically equivalent to double-row repair in a bovine model. Arthroscopy 2007;23:1265-1270. Song HS, Williams GR Jr. Arthroscopic reduction and fixation with suture-bridge technique for displaced or comminuted greater tuberosity fractures. Arthroscopy 2008;24:956-960. Kim KC, Rhee KJ, Shin HD. Deformities associated with the suture-bridge technique for full-thickness rotator cuff tears. Arthroscopy 2008;24:1251-1257. Ji JH, Kim WY, Ra KH. Arthroscopic double-row suture anchor fixation of minimally displaced greater tuberosity fractures. Arthroscopy 2007;23:1133.e1-1133.e4. Available online at www.arthroscopyjournal.org. Bynum CK, Lee S, Mahar A, Tasto J, Pedowitz R. Failure mode of suture anchors as a function of insertion depth. Am J Sports Med 2005;33:1030-1034. Burkhart SS, Diaz Pagan JL, Wirth MA, Athanasiou KA. Cyclic loading of anchor-based rotator cuff repairs: Confirmation of the tension overload phenomenon and comparison of suture anchor fixation with transosseous fixation. Arthroscopy 1997;13:720-724. Burkhart SS, Johnson TC, Wirth MA, Athanasiou KA. Cyclic loading of transosseous rotator cuff repairs: Tension overload as a possible cause of failure. Arthroscopy 1997; 13:172-176. Coons DA, Barber FA, Herbert MA. Triple-loaded singleanchor stitch configurations: An analysis of cyclically loaded suture-tendon interface security. Arthroscopy 2006;22:11541158. Mazzocca AD, Millett PJ, Guanche CA, Santangelo SA, Arciero RA. Arthroscopic single-row versus double-row suture anchor rotator cuff repair. Am J Sports Med 2005;33:18611868. Barber FA, Herbert MA, Coons DA, Boothby MH. Sutures and suture anchors—Update 2006. Arthroscopy 2006;22:10631069.e2. Available online at www.arthroscopyjournal.org. Barber FA, Herbert MA, Beavis RC. Cyclic load and failure behavior of arthroscopic knots and high strength sutures. Arthroscopy 2009;25:192-199. Barber FA, Herbert MA, Beavis RC, Barrera Oro F. Suture anchor materials, eyelets, and designs: Update 2008. Arthroscopy 2008;24:859-867.
TRIPLE-LOADED SUTURE ANCHORS 23. Barber FA, Coons DA, Ruiz-Suarez M. Cyclic load testing and ultimate failure strength of biodegradable glenoid anchors. Arthroscopy 2008;24:224-228. 24. Barber FA, Coons DA, Ruiz-Suarez M. Cyclic load testing of biodegradable suture anchors containing 2 high-strength sutures. Arthroscopy 2007;23:355-360. 25. Domb BG, Glousman RE, Brooks A, Hansen M, Lee TQ, ElAttrache NS. High-tension double-row footprint repair compared with reduced-tension single-row repair for massive rotator cuff tears. J Bone Joint Surg Am 2008;90:35-39 (Suppl 4). 26. Tingart MJ, Apreleva M, Zurakowski D, Warner JJ. Pullout strength of suture anchors used in rotator cuff repair. J Bone Joint Surg Am 2003;85:2190-2198. 27. Castagna A, Garofalo R, Conti M, Borroni M, Snyder SJ. Arthroscopic rotator cuff repair using a triple-loaded suture anchor and a modified Mason-Allen technique (Alex stitch). Arthroscopy 2007;23:440.e1-440.e4. Available online at www.arthroscopyjournal.org. 28. Sileo MJ, Ruotolo CR, Nelson CO, Serra-Hsu F, Panchal AP. A biomechanical comparison of the modified Mason-Allen stitch and massive cuff stitch in vitro. Arthroscopy 2007;23: 235-240.e2. Available online at www.arthroscopyjournal.org.
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