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Biomechanical Evaluation of Flexor Tendon Repair Using Barbed Suture Material: A Comparative ex vivo Study
1565
LETTERS TO THE EDITOR
In Reply: The letter raises an important point, and I would like to make it clear to the readers and to all hand surgeons that one should not treat late granulomas of permanent fillers into the hand unless there is definite knowledge of the material injected. All my patients were asked to go back to the cosmetic clinic where they had the original injections to get the name of the
injected material. All patients reported in my article had Artecoll injections. Mohammad M. Al-Qattan, MBBS, FRCSC King Saud University Riyadh, Saudi Arabia doi:10.1016/j.jhsa.2011.07.004
Biomechanical Evaluation of Flexor Tendon Repair Using Barbed Suture Material: A Comparative ex vivo Study To the Editor: We read the article by Zeplin et al1 with great interest, evaluating barbed suture repair of an injured flexor tendon. Barbed sutures theoretically distribute loads throughout their intratendinous path. This is particularly appealing for resisting repair site gapping. Gap formation, preferably measured under dynamic conditions, is therefore an important end point when testing barbed suture tenorrhaphy. The use of load to failure measurements is less important with modern multistrand repairs. Nonethe-
less, we noted that the failure loads recorded by Zeplin et al1 were substantially higher than previously reported, especially considering that no circumferential suture was applied.2 This could be explained by their unconventional testing methodology, considering the tendons were repaired end-to-end, creating a loop. To examine this, we mechanically tested sheep forelimb deep flexor tendons repaired in 3 different configurations: (1) standard tendon repair (n ⫽ 2); (2) tendon loop with repair in 1 limb (n ⫽ 2)1; and (3) tendon loop with repair in both limbs
FIGURE 1: A Standard uniaxial tensile test. Tendons ends are secured in grips via compressive force and the repair is midway between clamps. B Looped configuration consists of 1 intact tendon limb and the repaired tendon limb. This is how we understood the study of Zeplin and co-workers1 performed mechanical testing. C Both limbs of the loop are repaired.
JHS 䉬 Vol A, September
1566
LETTERS TO THE EDITOR
(n ⫽ 2).3 We used 3-0 braided polyester suture (Ethibond Excel; Ethicon, Somerville, NJ) to perform a 4-strand cross-locked cruciate reconstruction. We performed uniaxial tensile tests with a standard 40-mm starting gauge length and 80-mm/min distraction rate. Figure 1 shows loads to failure. Looping a material increases the load to failure owing to load sharing between each side of the loop. The intact side is likely to be stiffer and load bear earlier than a repaired side that has been transected and reconstructed with suture. A loop with both sides repaired approximately doubles the ultimate load, but a loop with 1 intact limb is even stronger. Furthermore, looped configurations appose different flexor tendon zones that have different structural and biomechanical properties. By crossing defined zones and altering loading properties of tensile tests, tendon looping makes interpretation, comparison, and inferences based on the data more complex. Finally, these problems will cause even more confusion if necessary dynamic testing is conducted. Our small study presented here is limited in terms of sample size but a full study was not warranted because it was performed to illustrate a point related to the effect of testing technique. The work presented by Zeplin and co-workers1 as well as the study of Rees and co-workers3 demonstrate that testing techniques need to be carefully evaluated when comparing different studies, considering the differences be-
tween uniaxial-loaded, single-repair constructs versus various looped configurations. A direct comparison of loads between different studies should be made with caution and should consider the variables at play. The repair itself is the weakest link in the system when secure clamps are used. Barbed sutures may have appealing attributes for flexor tendon reconstruction, and further investigation is required to evaluate and optimize these materials for use in this context. Roger Haddad, MBBS, MS Tim S. Peltz, MD William R. Walsh, PhD Surgical and Orthopaedic Research Laboratories University of New South Wales Prince of Wales Hospital Sydney, New South Wales, Australia doi:10.1016/j.jhsa.2011.05.040 Editor’s Note: The authors of the original article chose not to respond to this letter.
REFERENCES 1. Zeplin PH, Zahn RK, Meffert RH, Schmidt K. Biomechanical evaluation of flexor tendon repair using barbed suture material: a comparative ex vivo study. J Hand Surg 2011;36A:446 – 449. 2. Viinikainen A, Göransson H, Ryhänen J. Primary flexor tendon repair techniques. Scand J Surg 2008;97:333–340. 3. Rees L, Matthews A, Masouros SD, Bull AM, Haywood R. Comparison of 1- and 2-knot, 4-strand, double-modified Kessler tendon repairs in a porcine model. J Hand Surg 2009;34A:705–709.
Caution Against Percutaneous Trigger Release in Patients on Anticoagulant To the Editor: Percutaneous trigger release is a safe and commonly performed procedure.1 When trying to avoid tendon laceration and neurovascular injury, it is easy to overlook bleeding as a potential complication. I report a cautionary case of postoperative hematoma in a patient who had this procedure while taking anticoagulants. A 72-year-old woman who was taking warfarin had her middle finger A1 pulley released percutaneously. Upon completion of the release, extra compression was applied to the site of release to secure hemostasis. I applied the dressing after ensuring that there was no bleeding from the puncture site or gross swelling. She returned to the office 2 days later with a grossly swollen and tender surgical site and blistering
of the volar skin overlying the proximal and middle phalanges (Fig. 1). Because there was no circulatory embarrassment, I prescribed a course of oral and topical antibiotics as prophylaxis against infection. To minimize stiffness, she had gentle mobilization of her hand. Over the course of 6 weeks, she recovered without infective complications. Her total active motion was 220°, and there was no triggering. Anticoagulants are not routinely withheld from patients having trigger release because the risk of aggravating stroke or coronary events outweighs the benefit. This case serves as a reminder that hematoma is a potential complication2,3 of percutaneous trigger release, despite its minimally invasive nature. Perhaps an open procedure is a safer
JHS 䉬 Vol A, September
LETTERS TO THE EDITOR
In Reply: The letter raises an important point, and I would like to make it clear to the readers and to all hand surgeons that one should not treat late granulomas of permanent fillers into the hand unless there is definite knowledge of the material injected. All my patients were asked to go back to the cosmetic clinic where they had the original injections to get the name of the
injected material. All patients reported in my article had Artecoll injections. Mohammad M. Al-Qattan, MBBS, FRCSC King Saud University Riyadh, Saudi Arabia doi:10.1016/j.jhsa.2011.07.004
Biomechanical Evaluation of Flexor Tendon Repair Using Barbed Suture Material: A Comparative ex vivo Study To the Editor: We read the article by Zeplin et al1 with great interest, evaluating barbed suture repair of an injured flexor tendon. Barbed sutures theoretically distribute loads throughout their intratendinous path. This is particularly appealing for resisting repair site gapping. Gap formation, preferably measured under dynamic conditions, is therefore an important end point when testing barbed suture tenorrhaphy. The use of load to failure measurements is less important with modern multistrand repairs. Nonethe-
less, we noted that the failure loads recorded by Zeplin et al1 were substantially higher than previously reported, especially considering that no circumferential suture was applied.2 This could be explained by their unconventional testing methodology, considering the tendons were repaired end-to-end, creating a loop. To examine this, we mechanically tested sheep forelimb deep flexor tendons repaired in 3 different configurations: (1) standard tendon repair (n ⫽ 2); (2) tendon loop with repair in 1 limb (n ⫽ 2)1; and (3) tendon loop with repair in both limbs
FIGURE 1: A Standard uniaxial tensile test. Tendons ends are secured in grips via compressive force and the repair is midway between clamps. B Looped configuration consists of 1 intact tendon limb and the repaired tendon limb. This is how we understood the study of Zeplin and co-workers1 performed mechanical testing. C Both limbs of the loop are repaired.
JHS 䉬 Vol A, September
1566
LETTERS TO THE EDITOR
(n ⫽ 2).3 We used 3-0 braided polyester suture (Ethibond Excel; Ethicon, Somerville, NJ) to perform a 4-strand cross-locked cruciate reconstruction. We performed uniaxial tensile tests with a standard 40-mm starting gauge length and 80-mm/min distraction rate. Figure 1 shows loads to failure. Looping a material increases the load to failure owing to load sharing between each side of the loop. The intact side is likely to be stiffer and load bear earlier than a repaired side that has been transected and reconstructed with suture. A loop with both sides repaired approximately doubles the ultimate load, but a loop with 1 intact limb is even stronger. Furthermore, looped configurations appose different flexor tendon zones that have different structural and biomechanical properties. By crossing defined zones and altering loading properties of tensile tests, tendon looping makes interpretation, comparison, and inferences based on the data more complex. Finally, these problems will cause even more confusion if necessary dynamic testing is conducted. Our small study presented here is limited in terms of sample size but a full study was not warranted because it was performed to illustrate a point related to the effect of testing technique. The work presented by Zeplin and co-workers1 as well as the study of Rees and co-workers3 demonstrate that testing techniques need to be carefully evaluated when comparing different studies, considering the differences be-
tween uniaxial-loaded, single-repair constructs versus various looped configurations. A direct comparison of loads between different studies should be made with caution and should consider the variables at play. The repair itself is the weakest link in the system when secure clamps are used. Barbed sutures may have appealing attributes for flexor tendon reconstruction, and further investigation is required to evaluate and optimize these materials for use in this context. Roger Haddad, MBBS, MS Tim S. Peltz, MD William R. Walsh, PhD Surgical and Orthopaedic Research Laboratories University of New South Wales Prince of Wales Hospital Sydney, New South Wales, Australia doi:10.1016/j.jhsa.2011.05.040 Editor’s Note: The authors of the original article chose not to respond to this letter.
REFERENCES 1. Zeplin PH, Zahn RK, Meffert RH, Schmidt K. Biomechanical evaluation of flexor tendon repair using barbed suture material: a comparative ex vivo study. J Hand Surg 2011;36A:446 – 449. 2. Viinikainen A, Göransson H, Ryhänen J. Primary flexor tendon repair techniques. Scand J Surg 2008;97:333–340. 3. Rees L, Matthews A, Masouros SD, Bull AM, Haywood R. Comparison of 1- and 2-knot, 4-strand, double-modified Kessler tendon repairs in a porcine model. J Hand Surg 2009;34A:705–709.
Caution Against Percutaneous Trigger Release in Patients on Anticoagulant To the Editor: Percutaneous trigger release is a safe and commonly performed procedure.1 When trying to avoid tendon laceration and neurovascular injury, it is easy to overlook bleeding as a potential complication. I report a cautionary case of postoperative hematoma in a patient who had this procedure while taking anticoagulants. A 72-year-old woman who was taking warfarin had her middle finger A1 pulley released percutaneously. Upon completion of the release, extra compression was applied to the site of release to secure hemostasis. I applied the dressing after ensuring that there was no bleeding from the puncture site or gross swelling. She returned to the office 2 days later with a grossly swollen and tender surgical site and blistering
of the volar skin overlying the proximal and middle phalanges (Fig. 1). Because there was no circulatory embarrassment, I prescribed a course of oral and topical antibiotics as prophylaxis against infection. To minimize stiffness, she had gentle mobilization of her hand. Over the course of 6 weeks, she recovered without infective complications. Her total active motion was 220°, and there was no triggering. Anticoagulants are not routinely withheld from patients having trigger release because the risk of aggravating stroke or coronary events outweighs the benefit. This case serves as a reminder that hematoma is a potential complication2,3 of percutaneous trigger release, despite its minimally invasive nature. Perhaps an open procedure is a safer
JHS 䉬 Vol A, September