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A Biomechanical Comparison of 3 Different Arthroscopic Lateral Ankle Stabilization Techniques in 36 Cadaveric Ankles
The Journal of Foot & Ankle Surgery xxx (2016) 1–5
Contents lists available at ScienceDirect
The Journal of Foot & Ankle Surgery journal homepage: www.jfas.org
Original Research
A Biomechanical Comparison of 3 Different Arthroscopic Lateral Ankle Stabilization Techniques in 36 Cadaveric Ankles James M. Cottom, DPM, FACFAS 1, Joseph S. Baker, DPM, AACFAS 2, Phillip E. Richardson, DPM 2, Jared M. Maker, DPM 2 1 2
Director, Florida Orthopedic Foot and Ankle Center Fellowship, Sarasota, FL Fellow, Florida Orthopedic Foot and Ankle Center, Sarasota, FL
a r t i c l e i n f o
a b s t r a c t
Level of Clinical Evidence: 5
Arthroscopic lateral ankle stabilization has become an increasingly popular option among foot and ankle sur€ m-Gould procedure with the geons to address lateral ankle instability, because it combines a modified Brostro ability to address any intra-articular pathologic findings at the same session. The present study evaluated 3 different constructs in a cadaveric model. Thirty-six fresh frozen cadaver limbs were used, and the anterior talofibular ligament was identified and sectioned. The specimens were then placed into 1 of 3 groups. Group 1 received a repair with a single-row, 2-suture anchor construct; group 2 received repair with a novel, double-row, 4-anchor knotless construct; and group 3 received repair with a double-row, 3-anchor construct. Specimens were then tested for stiffness and load to ultimate failure using a customized jig. Stiffness was measured in each of the groups and was 12.10 5.43 (range 5.50 to 22.24) N/mm for group 1, 13.40 7.98 (range 6.71 to 36.28) N/ mm for group 2, and 12.55 4.00 (range 6.48 to 22.14) N/mm for group 3. No significant differences were found among the 3 groups in terms of stiffness (p ¼ .939, 1-way analysis of variance, ɑ ¼ 0.05). The groups were tested to failure, with observed force measurements of 156.43 30.39 (range 83.69 to 192.00) N for group 1, 206.62 55.62 (range 141.37 to 300.29) N for group 2, and 246.82 82.37 (range 164.26 to 384.93) N for group 3. Statistically significant differences were noted between groups 1 and 3 (p ¼ .006, 1-way analysis of variance, ɑ ¼ 0.05). The results of the present study have shown that a previously reported arthroscopic lateral ankle stabilization procedure, when modified with an additional proximal suture anchor into the fibula, results in a statistically significant increase in strength in terms of the maximum load to failure. Additionally, we have described a previously unreported, knotless technique for arthroscopic lateral ankle stabilization. Ó 2016 by the American College of Foot and Ankle Surgeons. All rights reserved.
Keywords: ankle instability arthroscopy lateral ankle stabilization load to failure stiffness
When nonoperative therapy fails in patients with chronic lateral ankle instability, surgical stabilization becomes an option for treatment. Lateral ankle stabilization procedures fall into 2 categories: anatomic and nonanatomic repairs (1). The anatomic approach was €m (2) in 1966. Gould et al (3) in 1980 first described by Brostro reported their modification of the procedure. More recently, several investigators have described arthroscopic and arthroscopically assisted procedures (4–7). However, few investigators have explored the biomechanical strength of these constructs in a laboratory setting. The present study explored 3 different constructs for lateral ankle stabilization performed using an arthroscopic approach. Additionally,
Financial Disclosure: None reported Conflict of Interest: James M. Cottom is a paid consultant for Arthrex and Stryker Corporations. Address correspondence to: James M. Cottom, DPM, FACFAS, Director, Florida Orthopedic Foot and Ankle Center Fellowship, 2030 Bee Ridge Road, Suite B, Sarasota, FL 34239. E-mail address: [email protected] (J.M. Cottom).
we introduced a novel, knotless approach to arthroscopic lateral ankle stabilization. Materials and Methods Thirty-six fresh-frozen cadaver limbs (18 matched pairs) were obtained and randomized into 1 of 3 groups, with 12 specimens in each group. The mean age of the specimens at limb loss or donation was 54 7.6 years. Of the 18 matched pairs, 6 (33.3%) were from male and 12 (66.7%) from female donors. Each of the specimens was free of any obvious foot or ankle pathologic findings. The cadavers were kept at 20 C and were thawed the day of the experiment. In each specimen, the anterior talofibular ligament (ATFL) was dissected and sectioned and then repaired with 1 of the 3 techniques of interest by the senior author (J.M.C.). Group 1 was repaired with a single-row construct using 2 bioabsorbable suture anchors (BioComposite SutureTakÔ; Arthrex, Naples, FL) attached to a no. 1 braided polyethylene/polyester multifilament suture (no. 1 FiberWireÔ, Arthrex). The repair was performed by inserting the first anchor 1 cm dorsal to the tip of the fibula, with care taken to ensure the anchor did not violate the medial and lateral cortices of the fibula. A second anchor was inserted in the same fashion but placed 1 cm proximal to the first anchor. Next, the 2 suture strands corresponding to each anchor were passed through the ATFL and inferior extensor retinaculum. The foot was dorsiflexed and everted by the assistant. Each suture strand was then tied down to its counterpart in the
1067-2516/$ - see front matter Ó 2016 by the American College of Foot and Ankle Surgeons. All rights reserved. http://dx.doi.org/10.1053/j.jfas.2016.07.025
2
J.M. Cottom et al. / The Journal of Foot & Ankle Surgery xxx (2016) 1–5
Fig. 1. Example of single-row repair with no. 1 FiberWireÔ performed in group 1.
same anchor using surgical knots to the appropriate tension (Fig. 1). The tails were then cut, completing the repair. Group 2 was repaired with a novel “knotless” construct, which, to the best of our knowledge, has not previously been described in published studies. The knotless construct consisted of a double-row, 4-anchor construct incorporating Labral TapeÔ (Arthrex) into the anchors. The first anchor was placed 1 cm dorsal to the tip of the fibula, with care taken to ensure the anchor did not violate the medial and lateral cortices of the fibula. A second anchor was inserted in the same fashion but placed 1 cm proximal to the first anchor. Next, the 2 tape strands corresponding to each anchor were passed through the ATFL and inferior extensor retinaculum. A separate 1- to 2-cm incision was made approximately 3 cm proximal to the distal fibula. The fibula was visualized, and, using the 2.9-mm suture anchor system, 2 drill holes were made into the fibula, with care taken to not violate the anterior and posterior cortices. At this point, an 18-gauge spinal needle was placed into each drill hole to maintain the visualized position. The foot was dorsiflexed and everted by the assistant. A strand from each anchor in the anterior fibula was then inserted into 1 of the lateral drill holes with a suture anchor. The last 2 strands were crossed and fixated into the fibula in the exact same fashion, creating a crossed suture anchor construct (Fig. 2). Group 3 was repaired with 2 bioabsorbable suture anchors (BioComposite SutureTakÔ; Arthrex) attached to a no. 1 braided polyethylene/polyester multifilament suture (no. 1 FiberWireÔ). The repair was performed by inserting the first anchor 1 cm dorsal to the tip of the fibula, with care taken to ensure the anchor did not violate the medial and lateral cortices of the fibula. A second anchor was inserted in the same fashion but placed 1 cm proximal to the first anchor. Next, the 2 suture strands
corresponding to each anchor were passed through the ATFL and inferior extensor retinaculum. The foot was dorsiflexed and everted by the assistant. Each suture strand was then tied down to its counterpart in the same anchor with surgical knots. A separate 1- to 2-cm incision was made approximately 3 cm proximal to the distal fibula. The fibula was visualized, and, using the 2.9-mm suture anchor system, a drill hole was made into the fibula. At this point, a needle was placed into the drill hole to maintain the visualized position. The strands were then secured into the fibula using the 2.9-mm bioabsorbable anchor (Fig. 3). The techniques are summarized in Table 1. After repair, each sample was secured to a 14-in. segment of 2-in. 8-in. wood using drywall screws. Two screws were driven through the dorsum of the foot and 2 through the calcaneus. The foot was then inspected for stability. If needed, an extra screw was driven through the talus for stability. A minimum of 4 screws were used in each foot. All specimens were then dissected, isolating the fibula, the repair, and all the tissue proximal to the repair. A medial to lateral hole was then drilled through the distal fibula, proximal to the lateral malleolus, using an 8-mm bone drill. A secured, dissected sample marked at the approximate distal fibular drill site is presented in Fig. 4. The fibula was then cut laterally, 5 cm proximal to the center of the drill hole using a bone saw (V600 Power System; Arthrex). The repairs were then isolated by cutting all remaining proximal tissue, taking care to not damage the repair. In the case of a repair being damaged during tissue release, the entire matched pair would be discarded and a new matched pair repaired and tested in its place. Mechanical testing was performed using an INSTRON E10 kN ElectroPuls Dynamic Testing System with a 10-kN load cell (Instron, Norwood, MA) secured to the crosshead. A clevis and pin fixture was secured to the cross-head, and a prepared sample was attached to the fixture by sliding the pin through the fibula drill hole. The sample was further C-clamped to a custom jig secured to the test platform that placed the foot in 20 of inversion and 10 of plantarflexion. The sample placement was adjusted such that the fibula was optimally centered below the load cell (Fig. 5). The constructs were preloaded to 5 N to remove any slack from the system and then loaded to 15 N over 10 seconds, held for 5 seconds, and then pulled to failure at a rate of 20 mm/min. The load and displacement data were recorded at 100 Hz, and the mode of failure was noted for each sample immediately after the pull to failure. The ultimate load was determined from the load versus displacement curves as the maximum load value reached during loading. The construct stiffness was also determined from the load versus displacement curve by calculating the slope of the linear portion during the pull to failure. Statistical analysis was then performed. The maximum load and stiffness measurements of the 3 sample groups were compared using 1-way analysis of variance, with the confidence level set at a ¼ 0.05. If either the equal variance or the ShapiroWilk normality test failed, a subsequent Kruskal-Wallis 1-way analysis of variance on ranks was performed.
Results A total of 36 specimens were used in the present investigation, and their mean average age was 54 7.6 years. None of the specimens were damaged during dissection of the repair site; therefore, it was not necessary to discard any of the repaired specimens. The results of the stiffness and load to failure tests are shown in Fig. 2 and presented in Table 2.
Fig. 2. (A) Example of double row, knotless repair performed with Labral TapeÔ in group 2. (B) Schematic of knotless technique with Labral TapeÔ in a patient who had received this type of repair.
J.M. Cottom et al. / The Journal of Foot & Ankle Surgery xxx (2016) 1–5
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Fig. 3. Example of double-row, 3-anchor technique with proximal suture anchor augmentation (group 3). Arrow is pointing to the proximal suture anchor site.
Fig. 4. A repaired, dissected, and secured specimen. The arrow marks the drill hole in the distal fibula where it attaches to the testing jig.
Group 1 underwent repair with the single-row construct, and the stiffness of the repair was 12.10 5.43 (range 5.50 to 22.24) N/mm. The maximum load to failure in group 1 was 156.43 30.39 (range 83.69 to 192.00) N. When the specimens were loaded to failure, 4 (33.3%) experienced anchor pullout, 4 (33.3%) experienced the suture knots being pulled through the tissues, and 4 (33.3%) experienced the tissues tearing from the talus. Group 2 underwent repair with the knotless technique. The stiffness of the repair in group 2 was 13.40 7.98 (range 6.71 to 36.28) N/mm. The maximum load to failure in group 2 was 206.62 55.62 (range 141.37 to 300.29) N. When the specimens were loaded to failure, 5 (41.7%) experienced anchor pullout, 6 (50%) experienced tissue tearing from the talus, and 1 (8.3%) experienced slippage of the Labral TapeÔ through the suture anchor. Group 3 underwent repair with the double-row, 3-anchor construct. The stiffness of the repair in group 3 was 12.55 4.00 (range 6.48 to 22.14) N/mm. The maximum load to failure was 246.82 82.37 (range 164.26 to 384.93) N. When the specimens were loaded to failure, 3 (25%) experienced anchor pullout and 9 (75%), tissue tearing from the talus. One-way analysis of variance testing was performed on the 3 sample groups for both stiffness and maximum load to failure. No statistically significant difference was found in terms of stiffness among the 3 groups (p ¼ .939). The maximum load to failure showed a trend toward an increase in strength among the 3 groups, with group 2 stronger than group 1 and group 3 stronger than group 2. However, only the difference in strength between groups 1 and 3 reached statistical significance (p ¼ .006).
to address a chronic attenuation or tear of the ATFL at the same time as addressing intra-articular pathologic features. The association of chronic lateral ankle instability and intra-articular pathologic findings has been well documented in published studies (8–10). With more attention given to arthroscopic lateral ankle stabilization procedures, some investigators have explored the biomechanical strength of these constructs. Drakos et al (11) compared the biome€m-Gould procedure chanical strength of a traditional, open Brostro with that of an arthroscopic repair in a cadaveric model. After
Discussion Arthroscopic and arthroscopically assisted lateral ankle stabilization procedures have gained popularity in recent years, with a number of investigators describing different techniques (4–7). The value of arthroscopic lateral ankle stabilization procedures lies in their ability Table 1 Summary of techniques used for repair in cadaveric specimens Test Group
Procedure
1 (n ¼ 12 specimens)
ArthroBrostromÒ: single-row, 2-anchor construct incorporating no. 1 suture to connect the ATFL and IER Knotless ArthroBrostromÒ: double-row, 4-anchor construct incorporating Labral TapeÔ to connect the ATFL and IER ArthroBrostromÒ with suture anchor modification: double-row, 3-anchor construct incorporating no. 1 suture to connect the ATFL and IER
2 (n ¼ 12 specimens) 3 (n ¼ 12 specimens)
Abbreviations: ATFL, anterior talofibular ligament; IER, inferior extensor retinaculum.
Fig. 5. A prepared specimen attached to the complete testing jig. The foot has been placed in a position of 10 of plantarflexion and 20 of plantarflexion.
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J.M. Cottom et al. / The Journal of Foot & Ankle Surgery xxx (2016) 1–5
Table 2 Summary of results in terms of stiffness and maximum load to failure Test Group
Maximum Load (N)
Stiffness (N/mm)
1 (n ¼ 12 specimens) 2 (n ¼ 12 specimens) 3 (n ¼ 12 specimens) P Value
156.43 30.39 206.62 55.62 246.82 82.37 .006
12.10 5.43 13.40 7.98 12.55 4.00 .939
Data presented as mean standard deviation.
sectioning the ATFL and calcaneofibular ligament, the specimens were repaired using either an open or arthroscopic approach and were then tested using a TelosÔ machine (Austin & Associates, Fallston, MD). The investigators found no significant differences between the 2 groups in terms of translation and motion during a talar tilt test (11). More recently, Giza et al (12) studied a modified arthroscopic € m procedure using a double-row construct with suture Brostro anchors. They tested a construct using the same bioabsorbable suture anchors as used in our present study but with no. 0 suture instead of no. 1 suture (12). They also used 2 anchors in the distal fibula placed through the arthroscopic portal, with an additional suture placed 3 cm proximal to the tip of the fibula. This was €m procedure prepared with compared to an arthroscopic Brostro the same technique but without proximal suture anchor augmentation. Their test results showed an average maximum load of € m repair group 154.4 60.3 N in the standard arthroscopic Brostro and 194.2 157.7 N in the group modified with a proximal anchor. They found that the additional suture anchor created a construct that showed a trend toward a stronger repair, but the difference did not reach statistical significance. Our study had results similar to those from Giza et al (12); however, the present study did show statistically significant differences between group 1 (single-row, 2-anchor construct) and group 3 (double-row, 3-anchor construct). When comparing the 2 studies side by side, the standard deviation in the group repaired with the double-row, 3-anchor construct might have some significance. In the report by Giza et al (12), the standard deviation of the double-row, 3-anchor construct was 157.7 N. In contrast, the standard deviation for group 3 in our study was 82.37 N. This might have led to a narrower sample group, which could potentially have increased the mean. This might account for why, despite using a similar protocol, our study found a statistically significant difference between these 2 groups and the study by Giza et al (12) did not. Another possible reason we found a significantly stronger repair with the additional suture anchor is that we used a slightly larger gauge suture material. We used no. 1 nonabsorbable suture (no. 1 FiberWireÔ), and Giza et al (12) used no. 0 suture. This could also account for the slightly stronger repair, which might have brought our comparison to reach statistical significance. In the present study, we also investigated a new construct, using 4 suture anchors in a knotless, double-row technique. This novel technique takes advantage of a very low profile, knotless construct and the use of stronger suture material. The suture material used, Labral TapeÔ has been described for use in shoulder reconstruction, mainly for use in labral tears and Bankart lesions associated with anterior glenohumeral instability (13). To the best of our knowledge, it has not been described previously in published studies in the context of lateral ankle instability. A white paper published by the Arthrex research and development department compared Labral TapeÔ to no. 2 FiberWireÔ in a cadaver shoulder model for glenohumeral instability and found a 37% increased resistance to tissue tear-through with the Labral TapeÔ (14). Although this finding does not directly correspond with the findings from the present study, it does set a foundation for exploration into this potentially stronger suture material for use in lateral ankle stabilization procedures.
Although the knotless, 4-anchor construct used in group 2 of the present study did show a trend toward a stronger repair than the single-row construct of group 1, the difference did not reach statistical significance. The group 2 construct was also slightly stiffer compared with the constructs of groups 1 and 3, but the difference was also not statistically significant. These results were fairly surprising, because we expected the knotless, 4-anchor construct to provide the strongest repair of the 3 groups. Several reasons could account for these results. First, the learning curve is increased with respect to the knotless technique, and the difference in suture material could have led to a difference in the “feel” for the anchors being placed. This might have played out in the laboratory, leading to a weaker repair than that of group 3. Second, the knotless technique might not be as strong as the double-row, 3-anchor repair used in group 3, because no knot is tied through the primary ATFL repair to resist the load placed through the foot. Thus, the construct used in group 3 would act more as a primary repair with a fail-safe mechanism in the additional suture anchor placed into the fibula, but the knotless technique in group 2 would still have a single point of failure. Clearly, further research is warranted in this area of study. The main drawbacks of the present study included the in vitro design, which by nature could not take into consideration the biologic healing of the lateral ankle ligaments. It is possible that the biomechanical properties of each of the different constructs changes during the healing process. This would certainly be a factor in choosing an appropriate construct for use in an actual patient population. Additionally, the weight of the patient and activity level were not considered when comparing these different constructs. This could also influence the choice of fixation used clinically. Finally, we did not undertake a power analysis when we chose to test 12 specimens in each treatment group; as such, it is possible that we could have made a type 2 statistical error wherein we failed to identify statistically significant differences when, perhaps, they actually existed. From the present study, we can draw several conclusions. First, we have shown that using a 3-anchor, double-row construct for arthroscopic lateral ankle stabilization was able to withstand a higher load to failure, which was stronger than the single-row construct using the same technique described by Cottom and Rigby (7). Second, we have shown that the use of Labral TapeÔ in arthroscopic lateral ankle stabilization in a knotless technique is reproducible but did not reach a statistically significant difference compared with a single-row technique in terms of the ultimate load to failure. Further research into the area of constructs used for arthroscopic lateral ankle stabilization is warranted and should focus on its use in the clinical setting. References 1. Colville M. Surgical treatment of the unstable ankle. J Am Acad Orthop Surg 6: 368–377, 1998. €m L. Sprained ankles, VI: surgical treatment of “chronic” ligament ruptures. 2. Brostro Acta Chir Scand 243:551–565, 1966. 3. Gould N, Seligson D, Gassman J. Early and late repair of the lateral ligaments of the ankle. Foot Ankle 1:84–89, 1980. 4. Acevedo J, Mangone P. Arthroscopic lateral ankle ligament reconstruction. Tech Foot Ankle Surg 10:111–116, 2011. 5. Corte-Real N, Moreira R. Arthroscopic repair of chronic lateral ankle instability. Foot Ankle Int 30:213–217, 2009. 6. Nery C, Raduan R, Del Buono A, Asaumi I, Cohen M, Maffulli N. Arthroscopic€m-Gould for chronic ankle instability: a long-term follow-up. Am J assisted Brostro Sports Med 39:2381–2388, 2011. € m procedure: a pro7. Cottom JM, Rigby RB. The “all inside” arthroscopic Brostro spective study of 40 consecutive patients. J Foot Ankle Surg 52:568–574, 2013. 8. Lee J, Hamilton G, Ford L. Associated intraarticular ankle pathologies associated with chronic lateral ankle instability. Foot Ankle Spec 4:284–289, 2011. 9. Hintermann B, Boss A, Schafer D. Arthroscopic findings in patients with chronic ankle instability. Am J Sports Med 30:402–409, 2002. 10. Ferkel R, Chams R. Chronic lateral instability: arthroscopic findings and long-term results. Foot Ankle Int 28:865–872, 2007.
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11. Drakos MC, Behrens SB, Paller D, Murphy C, DiGiovanni CW. Biomechanical comparison of an open vs arthroscopic approach for lateral ankle instability. Foot Ankle Int 35:809–815, 2014. 12. Giza E, Whitlow SR, Williams BT, Acevedo JI, Mangone PG, Haytmanek J, Curry EE, Turnbull TL, LaPrade RF, Wijdicks CA, Clanton TO. Biomechanical analysis of an € m ankle ligament repair and a suture anchor-augmented arthroscopic Brostro repair. Foot Ankle Int 36:836–841, 2015.
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13. Ostermann RC, Hofbauer M, Platzer P, Moen TC. The “labral bridge”: a novel technique for arthroscopic anatomic knotless Bankart repair. Arthrosc Tech 4: 91–95, 2015. 14. Arthrex. Biomechanical comparison of tissue tear through strength: Labral Tape and #2 FiberWire 2012. Available at: http://www.arthrex.com/resources/white-paper/ rl5gdqqCDECUZAE6UCg6kw/biomechanical-comparison-of-tissue-tear-throughrisk-labraltape-and-2-fiberwire. Accessed August 15, 2015.
Contents lists available at ScienceDirect
The Journal of Foot & Ankle Surgery journal homepage: www.jfas.org
Original Research
A Biomechanical Comparison of 3 Different Arthroscopic Lateral Ankle Stabilization Techniques in 36 Cadaveric Ankles James M. Cottom, DPM, FACFAS 1, Joseph S. Baker, DPM, AACFAS 2, Phillip E. Richardson, DPM 2, Jared M. Maker, DPM 2 1 2
Director, Florida Orthopedic Foot and Ankle Center Fellowship, Sarasota, FL Fellow, Florida Orthopedic Foot and Ankle Center, Sarasota, FL
a r t i c l e i n f o
a b s t r a c t
Level of Clinical Evidence: 5
Arthroscopic lateral ankle stabilization has become an increasingly popular option among foot and ankle sur€ m-Gould procedure with the geons to address lateral ankle instability, because it combines a modified Brostro ability to address any intra-articular pathologic findings at the same session. The present study evaluated 3 different constructs in a cadaveric model. Thirty-six fresh frozen cadaver limbs were used, and the anterior talofibular ligament was identified and sectioned. The specimens were then placed into 1 of 3 groups. Group 1 received a repair with a single-row, 2-suture anchor construct; group 2 received repair with a novel, double-row, 4-anchor knotless construct; and group 3 received repair with a double-row, 3-anchor construct. Specimens were then tested for stiffness and load to ultimate failure using a customized jig. Stiffness was measured in each of the groups and was 12.10 5.43 (range 5.50 to 22.24) N/mm for group 1, 13.40 7.98 (range 6.71 to 36.28) N/ mm for group 2, and 12.55 4.00 (range 6.48 to 22.14) N/mm for group 3. No significant differences were found among the 3 groups in terms of stiffness (p ¼ .939, 1-way analysis of variance, ɑ ¼ 0.05). The groups were tested to failure, with observed force measurements of 156.43 30.39 (range 83.69 to 192.00) N for group 1, 206.62 55.62 (range 141.37 to 300.29) N for group 2, and 246.82 82.37 (range 164.26 to 384.93) N for group 3. Statistically significant differences were noted between groups 1 and 3 (p ¼ .006, 1-way analysis of variance, ɑ ¼ 0.05). The results of the present study have shown that a previously reported arthroscopic lateral ankle stabilization procedure, when modified with an additional proximal suture anchor into the fibula, results in a statistically significant increase in strength in terms of the maximum load to failure. Additionally, we have described a previously unreported, knotless technique for arthroscopic lateral ankle stabilization. Ó 2016 by the American College of Foot and Ankle Surgeons. All rights reserved.
Keywords: ankle instability arthroscopy lateral ankle stabilization load to failure stiffness
When nonoperative therapy fails in patients with chronic lateral ankle instability, surgical stabilization becomes an option for treatment. Lateral ankle stabilization procedures fall into 2 categories: anatomic and nonanatomic repairs (1). The anatomic approach was €m (2) in 1966. Gould et al (3) in 1980 first described by Brostro reported their modification of the procedure. More recently, several investigators have described arthroscopic and arthroscopically assisted procedures (4–7). However, few investigators have explored the biomechanical strength of these constructs in a laboratory setting. The present study explored 3 different constructs for lateral ankle stabilization performed using an arthroscopic approach. Additionally,
Financial Disclosure: None reported Conflict of Interest: James M. Cottom is a paid consultant for Arthrex and Stryker Corporations. Address correspondence to: James M. Cottom, DPM, FACFAS, Director, Florida Orthopedic Foot and Ankle Center Fellowship, 2030 Bee Ridge Road, Suite B, Sarasota, FL 34239. E-mail address: [email protected] (J.M. Cottom).
we introduced a novel, knotless approach to arthroscopic lateral ankle stabilization. Materials and Methods Thirty-six fresh-frozen cadaver limbs (18 matched pairs) were obtained and randomized into 1 of 3 groups, with 12 specimens in each group. The mean age of the specimens at limb loss or donation was 54 7.6 years. Of the 18 matched pairs, 6 (33.3%) were from male and 12 (66.7%) from female donors. Each of the specimens was free of any obvious foot or ankle pathologic findings. The cadavers were kept at 20 C and were thawed the day of the experiment. In each specimen, the anterior talofibular ligament (ATFL) was dissected and sectioned and then repaired with 1 of the 3 techniques of interest by the senior author (J.M.C.). Group 1 was repaired with a single-row construct using 2 bioabsorbable suture anchors (BioComposite SutureTakÔ; Arthrex, Naples, FL) attached to a no. 1 braided polyethylene/polyester multifilament suture (no. 1 FiberWireÔ, Arthrex). The repair was performed by inserting the first anchor 1 cm dorsal to the tip of the fibula, with care taken to ensure the anchor did not violate the medial and lateral cortices of the fibula. A second anchor was inserted in the same fashion but placed 1 cm proximal to the first anchor. Next, the 2 suture strands corresponding to each anchor were passed through the ATFL and inferior extensor retinaculum. The foot was dorsiflexed and everted by the assistant. Each suture strand was then tied down to its counterpart in the
1067-2516/$ - see front matter Ó 2016 by the American College of Foot and Ankle Surgeons. All rights reserved. http://dx.doi.org/10.1053/j.jfas.2016.07.025
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J.M. Cottom et al. / The Journal of Foot & Ankle Surgery xxx (2016) 1–5
Fig. 1. Example of single-row repair with no. 1 FiberWireÔ performed in group 1.
same anchor using surgical knots to the appropriate tension (Fig. 1). The tails were then cut, completing the repair. Group 2 was repaired with a novel “knotless” construct, which, to the best of our knowledge, has not previously been described in published studies. The knotless construct consisted of a double-row, 4-anchor construct incorporating Labral TapeÔ (Arthrex) into the anchors. The first anchor was placed 1 cm dorsal to the tip of the fibula, with care taken to ensure the anchor did not violate the medial and lateral cortices of the fibula. A second anchor was inserted in the same fashion but placed 1 cm proximal to the first anchor. Next, the 2 tape strands corresponding to each anchor were passed through the ATFL and inferior extensor retinaculum. A separate 1- to 2-cm incision was made approximately 3 cm proximal to the distal fibula. The fibula was visualized, and, using the 2.9-mm suture anchor system, 2 drill holes were made into the fibula, with care taken to not violate the anterior and posterior cortices. At this point, an 18-gauge spinal needle was placed into each drill hole to maintain the visualized position. The foot was dorsiflexed and everted by the assistant. A strand from each anchor in the anterior fibula was then inserted into 1 of the lateral drill holes with a suture anchor. The last 2 strands were crossed and fixated into the fibula in the exact same fashion, creating a crossed suture anchor construct (Fig. 2). Group 3 was repaired with 2 bioabsorbable suture anchors (BioComposite SutureTakÔ; Arthrex) attached to a no. 1 braided polyethylene/polyester multifilament suture (no. 1 FiberWireÔ). The repair was performed by inserting the first anchor 1 cm dorsal to the tip of the fibula, with care taken to ensure the anchor did not violate the medial and lateral cortices of the fibula. A second anchor was inserted in the same fashion but placed 1 cm proximal to the first anchor. Next, the 2 suture strands
corresponding to each anchor were passed through the ATFL and inferior extensor retinaculum. The foot was dorsiflexed and everted by the assistant. Each suture strand was then tied down to its counterpart in the same anchor with surgical knots. A separate 1- to 2-cm incision was made approximately 3 cm proximal to the distal fibula. The fibula was visualized, and, using the 2.9-mm suture anchor system, a drill hole was made into the fibula. At this point, a needle was placed into the drill hole to maintain the visualized position. The strands were then secured into the fibula using the 2.9-mm bioabsorbable anchor (Fig. 3). The techniques are summarized in Table 1. After repair, each sample was secured to a 14-in. segment of 2-in. 8-in. wood using drywall screws. Two screws were driven through the dorsum of the foot and 2 through the calcaneus. The foot was then inspected for stability. If needed, an extra screw was driven through the talus for stability. A minimum of 4 screws were used in each foot. All specimens were then dissected, isolating the fibula, the repair, and all the tissue proximal to the repair. A medial to lateral hole was then drilled through the distal fibula, proximal to the lateral malleolus, using an 8-mm bone drill. A secured, dissected sample marked at the approximate distal fibular drill site is presented in Fig. 4. The fibula was then cut laterally, 5 cm proximal to the center of the drill hole using a bone saw (V600 Power System; Arthrex). The repairs were then isolated by cutting all remaining proximal tissue, taking care to not damage the repair. In the case of a repair being damaged during tissue release, the entire matched pair would be discarded and a new matched pair repaired and tested in its place. Mechanical testing was performed using an INSTRON E10 kN ElectroPuls Dynamic Testing System with a 10-kN load cell (Instron, Norwood, MA) secured to the crosshead. A clevis and pin fixture was secured to the cross-head, and a prepared sample was attached to the fixture by sliding the pin through the fibula drill hole. The sample was further C-clamped to a custom jig secured to the test platform that placed the foot in 20 of inversion and 10 of plantarflexion. The sample placement was adjusted such that the fibula was optimally centered below the load cell (Fig. 5). The constructs were preloaded to 5 N to remove any slack from the system and then loaded to 15 N over 10 seconds, held for 5 seconds, and then pulled to failure at a rate of 20 mm/min. The load and displacement data were recorded at 100 Hz, and the mode of failure was noted for each sample immediately after the pull to failure. The ultimate load was determined from the load versus displacement curves as the maximum load value reached during loading. The construct stiffness was also determined from the load versus displacement curve by calculating the slope of the linear portion during the pull to failure. Statistical analysis was then performed. The maximum load and stiffness measurements of the 3 sample groups were compared using 1-way analysis of variance, with the confidence level set at a ¼ 0.05. If either the equal variance or the ShapiroWilk normality test failed, a subsequent Kruskal-Wallis 1-way analysis of variance on ranks was performed.
Results A total of 36 specimens were used in the present investigation, and their mean average age was 54 7.6 years. None of the specimens were damaged during dissection of the repair site; therefore, it was not necessary to discard any of the repaired specimens. The results of the stiffness and load to failure tests are shown in Fig. 2 and presented in Table 2.
Fig. 2. (A) Example of double row, knotless repair performed with Labral TapeÔ in group 2. (B) Schematic of knotless technique with Labral TapeÔ in a patient who had received this type of repair.
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Fig. 3. Example of double-row, 3-anchor technique with proximal suture anchor augmentation (group 3). Arrow is pointing to the proximal suture anchor site.
Fig. 4. A repaired, dissected, and secured specimen. The arrow marks the drill hole in the distal fibula where it attaches to the testing jig.
Group 1 underwent repair with the single-row construct, and the stiffness of the repair was 12.10 5.43 (range 5.50 to 22.24) N/mm. The maximum load to failure in group 1 was 156.43 30.39 (range 83.69 to 192.00) N. When the specimens were loaded to failure, 4 (33.3%) experienced anchor pullout, 4 (33.3%) experienced the suture knots being pulled through the tissues, and 4 (33.3%) experienced the tissues tearing from the talus. Group 2 underwent repair with the knotless technique. The stiffness of the repair in group 2 was 13.40 7.98 (range 6.71 to 36.28) N/mm. The maximum load to failure in group 2 was 206.62 55.62 (range 141.37 to 300.29) N. When the specimens were loaded to failure, 5 (41.7%) experienced anchor pullout, 6 (50%) experienced tissue tearing from the talus, and 1 (8.3%) experienced slippage of the Labral TapeÔ through the suture anchor. Group 3 underwent repair with the double-row, 3-anchor construct. The stiffness of the repair in group 3 was 12.55 4.00 (range 6.48 to 22.14) N/mm. The maximum load to failure was 246.82 82.37 (range 164.26 to 384.93) N. When the specimens were loaded to failure, 3 (25%) experienced anchor pullout and 9 (75%), tissue tearing from the talus. One-way analysis of variance testing was performed on the 3 sample groups for both stiffness and maximum load to failure. No statistically significant difference was found in terms of stiffness among the 3 groups (p ¼ .939). The maximum load to failure showed a trend toward an increase in strength among the 3 groups, with group 2 stronger than group 1 and group 3 stronger than group 2. However, only the difference in strength between groups 1 and 3 reached statistical significance (p ¼ .006).
to address a chronic attenuation or tear of the ATFL at the same time as addressing intra-articular pathologic features. The association of chronic lateral ankle instability and intra-articular pathologic findings has been well documented in published studies (8–10). With more attention given to arthroscopic lateral ankle stabilization procedures, some investigators have explored the biomechanical strength of these constructs. Drakos et al (11) compared the biome€m-Gould procedure chanical strength of a traditional, open Brostro with that of an arthroscopic repair in a cadaveric model. After
Discussion Arthroscopic and arthroscopically assisted lateral ankle stabilization procedures have gained popularity in recent years, with a number of investigators describing different techniques (4–7). The value of arthroscopic lateral ankle stabilization procedures lies in their ability Table 1 Summary of techniques used for repair in cadaveric specimens Test Group
Procedure
1 (n ¼ 12 specimens)
ArthroBrostromÒ: single-row, 2-anchor construct incorporating no. 1 suture to connect the ATFL and IER Knotless ArthroBrostromÒ: double-row, 4-anchor construct incorporating Labral TapeÔ to connect the ATFL and IER ArthroBrostromÒ with suture anchor modification: double-row, 3-anchor construct incorporating no. 1 suture to connect the ATFL and IER
2 (n ¼ 12 specimens) 3 (n ¼ 12 specimens)
Abbreviations: ATFL, anterior talofibular ligament; IER, inferior extensor retinaculum.
Fig. 5. A prepared specimen attached to the complete testing jig. The foot has been placed in a position of 10 of plantarflexion and 20 of plantarflexion.
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Table 2 Summary of results in terms of stiffness and maximum load to failure Test Group
Maximum Load (N)
Stiffness (N/mm)
1 (n ¼ 12 specimens) 2 (n ¼ 12 specimens) 3 (n ¼ 12 specimens) P Value
156.43 30.39 206.62 55.62 246.82 82.37 .006
12.10 5.43 13.40 7.98 12.55 4.00 .939
Data presented as mean standard deviation.
sectioning the ATFL and calcaneofibular ligament, the specimens were repaired using either an open or arthroscopic approach and were then tested using a TelosÔ machine (Austin & Associates, Fallston, MD). The investigators found no significant differences between the 2 groups in terms of translation and motion during a talar tilt test (11). More recently, Giza et al (12) studied a modified arthroscopic € m procedure using a double-row construct with suture Brostro anchors. They tested a construct using the same bioabsorbable suture anchors as used in our present study but with no. 0 suture instead of no. 1 suture (12). They also used 2 anchors in the distal fibula placed through the arthroscopic portal, with an additional suture placed 3 cm proximal to the tip of the fibula. This was €m procedure prepared with compared to an arthroscopic Brostro the same technique but without proximal suture anchor augmentation. Their test results showed an average maximum load of € m repair group 154.4 60.3 N in the standard arthroscopic Brostro and 194.2 157.7 N in the group modified with a proximal anchor. They found that the additional suture anchor created a construct that showed a trend toward a stronger repair, but the difference did not reach statistical significance. Our study had results similar to those from Giza et al (12); however, the present study did show statistically significant differences between group 1 (single-row, 2-anchor construct) and group 3 (double-row, 3-anchor construct). When comparing the 2 studies side by side, the standard deviation in the group repaired with the double-row, 3-anchor construct might have some significance. In the report by Giza et al (12), the standard deviation of the double-row, 3-anchor construct was 157.7 N. In contrast, the standard deviation for group 3 in our study was 82.37 N. This might have led to a narrower sample group, which could potentially have increased the mean. This might account for why, despite using a similar protocol, our study found a statistically significant difference between these 2 groups and the study by Giza et al (12) did not. Another possible reason we found a significantly stronger repair with the additional suture anchor is that we used a slightly larger gauge suture material. We used no. 1 nonabsorbable suture (no. 1 FiberWireÔ), and Giza et al (12) used no. 0 suture. This could also account for the slightly stronger repair, which might have brought our comparison to reach statistical significance. In the present study, we also investigated a new construct, using 4 suture anchors in a knotless, double-row technique. This novel technique takes advantage of a very low profile, knotless construct and the use of stronger suture material. The suture material used, Labral TapeÔ has been described for use in shoulder reconstruction, mainly for use in labral tears and Bankart lesions associated with anterior glenohumeral instability (13). To the best of our knowledge, it has not been described previously in published studies in the context of lateral ankle instability. A white paper published by the Arthrex research and development department compared Labral TapeÔ to no. 2 FiberWireÔ in a cadaver shoulder model for glenohumeral instability and found a 37% increased resistance to tissue tear-through with the Labral TapeÔ (14). Although this finding does not directly correspond with the findings from the present study, it does set a foundation for exploration into this potentially stronger suture material for use in lateral ankle stabilization procedures.
Although the knotless, 4-anchor construct used in group 2 of the present study did show a trend toward a stronger repair than the single-row construct of group 1, the difference did not reach statistical significance. The group 2 construct was also slightly stiffer compared with the constructs of groups 1 and 3, but the difference was also not statistically significant. These results were fairly surprising, because we expected the knotless, 4-anchor construct to provide the strongest repair of the 3 groups. Several reasons could account for these results. First, the learning curve is increased with respect to the knotless technique, and the difference in suture material could have led to a difference in the “feel” for the anchors being placed. This might have played out in the laboratory, leading to a weaker repair than that of group 3. Second, the knotless technique might not be as strong as the double-row, 3-anchor repair used in group 3, because no knot is tied through the primary ATFL repair to resist the load placed through the foot. Thus, the construct used in group 3 would act more as a primary repair with a fail-safe mechanism in the additional suture anchor placed into the fibula, but the knotless technique in group 2 would still have a single point of failure. Clearly, further research is warranted in this area of study. The main drawbacks of the present study included the in vitro design, which by nature could not take into consideration the biologic healing of the lateral ankle ligaments. It is possible that the biomechanical properties of each of the different constructs changes during the healing process. This would certainly be a factor in choosing an appropriate construct for use in an actual patient population. Additionally, the weight of the patient and activity level were not considered when comparing these different constructs. This could also influence the choice of fixation used clinically. Finally, we did not undertake a power analysis when we chose to test 12 specimens in each treatment group; as such, it is possible that we could have made a type 2 statistical error wherein we failed to identify statistically significant differences when, perhaps, they actually existed. From the present study, we can draw several conclusions. First, we have shown that using a 3-anchor, double-row construct for arthroscopic lateral ankle stabilization was able to withstand a higher load to failure, which was stronger than the single-row construct using the same technique described by Cottom and Rigby (7). Second, we have shown that the use of Labral TapeÔ in arthroscopic lateral ankle stabilization in a knotless technique is reproducible but did not reach a statistically significant difference compared with a single-row technique in terms of the ultimate load to failure. Further research into the area of constructs used for arthroscopic lateral ankle stabilization is warranted and should focus on its use in the clinical setting. References 1. Colville M. Surgical treatment of the unstable ankle. J Am Acad Orthop Surg 6: 368–377, 1998. €m L. Sprained ankles, VI: surgical treatment of “chronic” ligament ruptures. 2. Brostro Acta Chir Scand 243:551–565, 1966. 3. Gould N, Seligson D, Gassman J. Early and late repair of the lateral ligaments of the ankle. Foot Ankle 1:84–89, 1980. 4. Acevedo J, Mangone P. Arthroscopic lateral ankle ligament reconstruction. Tech Foot Ankle Surg 10:111–116, 2011. 5. Corte-Real N, Moreira R. Arthroscopic repair of chronic lateral ankle instability. Foot Ankle Int 30:213–217, 2009. 6. Nery C, Raduan R, Del Buono A, Asaumi I, Cohen M, Maffulli N. Arthroscopic€m-Gould for chronic ankle instability: a long-term follow-up. Am J assisted Brostro Sports Med 39:2381–2388, 2011. € m procedure: a pro7. Cottom JM, Rigby RB. The “all inside” arthroscopic Brostro spective study of 40 consecutive patients. J Foot Ankle Surg 52:568–574, 2013. 8. Lee J, Hamilton G, Ford L. Associated intraarticular ankle pathologies associated with chronic lateral ankle instability. Foot Ankle Spec 4:284–289, 2011. 9. Hintermann B, Boss A, Schafer D. Arthroscopic findings in patients with chronic ankle instability. Am J Sports Med 30:402–409, 2002. 10. Ferkel R, Chams R. Chronic lateral instability: arthroscopic findings and long-term results. Foot Ankle Int 28:865–872, 2007.
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11. Drakos MC, Behrens SB, Paller D, Murphy C, DiGiovanni CW. Biomechanical comparison of an open vs arthroscopic approach for lateral ankle instability. Foot Ankle Int 35:809–815, 2014. 12. Giza E, Whitlow SR, Williams BT, Acevedo JI, Mangone PG, Haytmanek J, Curry EE, Turnbull TL, LaPrade RF, Wijdicks CA, Clanton TO. Biomechanical analysis of an € m ankle ligament repair and a suture anchor-augmented arthroscopic Brostro repair. Foot Ankle Int 36:836–841, 2015.
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13. Ostermann RC, Hofbauer M, Platzer P, Moen TC. The “labral bridge”: a novel technique for arthroscopic anatomic knotless Bankart repair. Arthrosc Tech 4: 91–95, 2015. 14. Arthrex. Biomechanical comparison of tissue tear through strength: Labral Tape and #2 FiberWire 2012. Available at: http://www.arthrex.com/resources/white-paper/ rl5gdqqCDECUZAE6UCg6kw/biomechanical-comparison-of-tissue-tear-throughrisk-labraltape-and-2-fiberwire. Accessed August 15, 2015.