- Email: [email protected]
Biomechanical Study of the Digital Flexor Tendon Sliding Lengthening Technique
SCIENTIFIC ARTICLE
Biomechanical Study of the Digital Flexor Tendon Sliding Lengthening Technique Ken Hashimoto, MD, PhD,* Kazuki Kuniyoshi, MD, PhD,* Takane Suzuki, MD, PhD,† Ryo Hiwatari, MD, PhD,* Yusuke Matsuura, MD, PhD,* Kazuhisa Takahashi, MD, PhD*
Purpose To compare the mechanical properties of sliding lengthening (SL) and Z-lengthening (ZL) for flexor tendon elongation used for conditions such as Volkmann contracture, cerebral palsy, and poststroke spasticity. Methods We harvested 56 flexor tendons, including flexor pollicis longus tendons, flexor digitorum superficialis tendons (zones II to IV), and flexor digitorum profundus tendons (zones II to V) from 24 upper limbs of 12 fresh cadavers. Each tendon was harvested together with its homonymous tendon from the opposite side of the cadaver and paired. We used 28 pairs of tendons and divided them randomly into 4 groups depending on the lengthening distance (20 or 30 mm) and type of stitching (single or double mattress sutures). Then we divided each pair into either the SL or ZL group. Each group was composed of 7 specimens. The same surgeon lengthened all tendons and stitched them with 2-0 polyester sutures. We tested biomechanical tensile strength immediately after completing lengthening and suturing in each group. Results Ultimate tensile strengths were: 23 N for the SL 20-mm lengthening and single mattress suture and 7 N for the ZL; 25 N for the SL 20-mm lengthening and double mattress suture and 10 N for the ZL; 15 N for the SL 30-mm lengthening and single mattress suture and 8 N for the ZL; and 18 N for the SL 30-mm lengthening and double mattress suture and 10 N for the ZL. Conclusions The SL technique may be a good alternative to the ZL technique because it provides higher ultimate tensile strength. Clinical relevance Because of its higher ultimate tensile strength, the SL technique may allow for earlier rehabilitation and reduced risk of postoperative complications. (J Hand Surg Am. 2015;-(-):-e-. Copyright Ó 2015 by the American Society for Surgery of the Hand. All rights reserved.) Key words Flexor tendon lengthening, sliding lengthening, Z-lengthening.
L
ENGTHENING OF THE DIGITAL FLEXOR tendons in the forearm is a surgical technique used to correct flexion contracture of the wrist or fingers caused by such conditions as Volkmann contracture, cerebral
From the *Department of Orthopedic Surgery and the †Department of Environmental Health Science, Graduate School of Medicine, Chiba University, Chiba, Japan. Received for publication January 14, 2015; accepted in revised form June 30, 2015. No benefits in any form have been received or will be received related directly or indirectly to the subject of this article. Corresponding author: Ken Hashimoto, MD, PhD, Department of Orthopedic Surgery, Graduate School of Medicine, Chiba University, 1-8-1 Inohana, Chuo-ku, Chiba 260-8670, Japan; e-mail: [email protected]. 0363-5023/15/---0001$36.00/0 http://dx.doi.org/10.1016/j.jhsa.2015.06.120
palsy, and poststroke spasticity. Main methods used are sliding lengthening (SL),1 Z-lengthening (ZL),2,3 and fractional lengthening.4 The technique applied depends mainly on the severity of contracture and the amount of lengthening required.1 The purpose of this study was to compare the biomechanical properties of the commonly used SL and ZL techniques using freshfrozen cadaver material. MATERIALS AND METHODS We harvested 56 finger flexor tendons, including flexor pollicis longus tendons, flexor digitorum superficialis tendons (zones II to IV), and flexor digitorum profundus tendons (zone II to V) from the muscle-tendon junction
Ó 2015 ASSH
r
Published by Elsevier, Inc. All rights reserved.
r
1
2
DIGITAL FLEXOR TENDON SL TECHNIQUE
FIGURE 1: Sliding lengthening model groups. The yellow arrows indicate the amount of lengthening. The black arrow indicates the site of section for histology shown in Fig. 4.
The ZL model was produced by making a Z-shaped incision in the body of the tendon at an interval of 40 mm.
lengthening 20 mm
lengthening 30 mm
ZL 30 mm/1 suture ZL 30 mm/2 sutures ZL 20 mm/1 suture ZL 20 mm/2 sutures FIGURE 2: Z-Lengthening model groups.
to the tendon insertion point, from 24 upper limbs of 12 fresh-frozen cadavers, mean age 88 years (range, 76e105 years; 7 male and 5 female). We stored all specimens at e20 C and thawed them at room temperature for 24 hours before conducting the experiments at room temperature. A flexor tendon from one side of the cadaver and the homonymous tendon from the opposite side (for example, the flexor digitorum profundus [FDP] tendon from the right side and the FDP tendon from the left side of the cadaver) were harvested and paired. We obtained 28 pairs of tendons and randomly divided them into 4 groups depending on the lengthening distance (20 or 30 mm) and type of stitching J Hand Surg Am.
(single or double mattress sutures). Each pair was then divided into either the SL or ZL group. Therefore, 4 groups of the SL (Fig. 1) and 4 of the ZL (Fig. 2) each were composed of 7 tendons. We kept them moist with normal saline throughout the experiment. We produced the SL model by cutting the tendon halfway through on opposite sides at 40-mm intervals and applied traction on both ends to slide the central part of the tendon along its long axis until we achieved either 20 or 30 mm lengthening. We then secured the center of the area where the tendon fibers overlapped with single or double 2-0 polyester mattress sutures (Ethibond; Ethicon, Somerville, NJ). r
Vol. -, - 2015
DIGITAL FLEXOR TENDON SL TECHNIQUE
3
FIGURE 3: Ultimate tensile strength. Black bars represent the strength in the SL groups and grey bars represent the strength in the ZL groups.
FIGURE 4: Tendon fiber micrographs. The site of the section is indicated by the arrow in Figure 1. A Transverse section of tendon fibers showing narrowing of tendon diameter and deformation of tendon fibers. (Hematoxylin-eosin stain; magnification 4.) B Transverse section of tendon fibers showing fibers in the area where the tendon diameter was narrow. (Hematoxylin-eosin stain; magnification 10.) C Area of narrowed fibers. (Masson trichrome stain; magnification 10.)
We produced the ZL model by making a Z-shaped incision in the body of the tendon at 40-mm intervals to achieve either 20 or 30 mm lengthening. We secured the central part of the overlapping area with single or double 2-0 polyester mattress sutures as described above.
between the SL groups with different lengthening distances and considered differences significant at P < .05. Histology After we produced the SL model, we cut sections perpendicular to the long axis of the tendon and mounted them on slides for staining with hematoxylineosin or Masson trichrome stain. We examined the course of collagen fibers in the specimens with a light microscope.
Biomechanical evaluation We secured the cut ends of the tendon models in the clamp of a universal tester (AG-20 NXplus; Shimadzu, Kyoto, Japan). We then conducted traction experiments at 20 mm/min until failure. We calculated the ultimate tensile strength from the load-displacement curve. We also recorded the mode of failure for each test. We used the Wilcoxon signed-rank test to compare differences between the SL and ZL groups with the same lengthening distance and number of stitches. We used the Mann-Whitney U test to compare differences J Hand Surg Am.
RESULTS Biomechanical evaluation Ultimate failure load: The tensile strength of the SL was significantly higher than for the ZL in each group (P < .05) (Fig. 3). r
Vol. -, - 2015
4
DIGITAL FLEXOR TENDON SL TECHNIQUE
exercise can prevent adhesions and flexion contracture through contraction of the digital flexor muscles, forcing the tendon to glide and resulting in excursion.7 Our secondary question was whether the biomechanical tensile strength of SL was sufficient to enable early active mobilization. Shuind et al7 reported that early active flexion exercise requires a strength of 18.6 N or greater. Our SL model had a strength of 24.6 N (20 mm lengthening/double stitches) and 18.2 N (30 mm lengthening/double stitches). Our data might nearly meet their result. However, the use of early mobilization has recently become popular after flexor tendon repair8 and common methods of repair for early mobilization had higher mechanical strength of 29 N,9 60 N,10 and 97 N.11 Therefore, the strength achieved by our SL model may not be enough for early mobilization. Although we employed the conventional mattress suture for SL and ZL after the previous reports,1 in the current study the sutures pulled out as they cut or pulled through the fibers. Because the mattress suture is a side-to-side technique perpendicular to the tendon fibers, it effects a shearing force on the tendon. However, the biomechanical properties of the suture depend on the material and the number of strands crossing the repair site, and the suture caliber can improve the biomechanical properties of the lengthening model. Increasing the grasping strength of the suture on the tendon and the suture’s tensile strength, such as by adding supplementary sutures or locking sutures, may provide sufficient strength for early active exercise. In the SL groups with a single stitch, ultimate failure load was significantly higher in 20 mm lengthening than in 30 mm lengthening. Histology suggested that the reason for this difference in strength was that collagen fibers in the sliding surface exhibited partial continuity, which provided some inherent strength. Limitations of this investigation included its purely biomechanical nature, the lack of investigation of postoperative adhesions or gliding resistance, and the advanced age of the specimens. To determine differences in suture methods, the number of circumferential sutures, and the types of suture material, further experiments are required.
In the SL groups, ultimate failure load was significantly higher in the group with 20 mm lengthening and a single stitch than in the group with 30 mm lengthening and a single stitch (P ¼ .018) whereas there was no significant difference between the group with 20 mm lengthening and double stitches and the group with 30 mm lengthening with double stitches (P ¼ .055). A power analysis was also calculated to compare significant difference and was greater than .950 in all. Mode of failure: In the SL model, the sutures pulled out in most cases (79%). Suture breakage occurred at the site where the tendon was weakened after sliding in 0.40% of cases. Suture breakage occurred in 21% of cases. In the ZL model, the sutures pulled out before reaching the maximum tensile strength of the suture material in most cases (77%). We found no differences in the mode of failure between the SL and ZL groups. There was also no difference in the mode of failure between the group with a single suture and the one with double sutures in the SL and ZL groups, respectively. Histology We found that collagen fibers were split and displayed a cracked appearance, with smaller-diameter fibers present on the outside of the cracked area (Fig. 4). These findings confirmed the continuity of collagen fibers. DISCUSSION Tendon lengthening such as that of the Achilles tendon is commonly used in the lower extremity.2,5 In the forearm, methods of tendon lengthening are limited to SL and ZL, in which the tendon is lengthened, and fractional lengthening, in which the muscleetendon junction is lengthened. The maximum lengthening that can be achieved is 2 to 5 cm with the SL and ZL techniques and 1 to 3 cm with fractional lengthening.1 Therefore, surgeons choose the technique based on the severity of contracture and the amount of lengthening desired. Although SL and ZL techniques are both indicated for lengthening of almost the same distance, we wondered whether SL would have better biomechanical properties than ZL because some collagen fibers may be in continuity after SL. We confirmed the continuity of collagen fibers after SL and significantly better biomechanical properties than ZL for all groups (20 or 30 mm lengthening single or double stitches). Rupture and overlengthening frequently occur after lengthening, and postoperative external immobilization is required. As a consequence, adhesions and contracture may be problematic.6 Early active J Hand Surg Am.
REFERENCES 1. Matsuo T, Lai T, Tayama N. Combined flexor and extensor release for activation of voluntary movement of the fingers in patients with cerebral palsy. Clin Orthop Relat Res. 1990;(250):185e193. 2. White JW. Torsion of the Achilles tendon. Arch Surg. 1943;46:784. 3. Koman LA, Gelberman RH, Toby EB, Poehling GG. Cerebral palsy. Management of the upper extremity. Clin Orthop Relat Res. 1990;(253):62e74.
r
Vol. -, - 2015
DIGITAL FLEXOR TENDON SL TECHNIQUE
8. Maki Y, Yoshizu T, Tsubokawa N, Narisawa H, Maniwa K. Flexor tendon repair in zone II: the result of early active mobilization. Jpn Soc Surg Hand. 2009;25:763e765. 9. Angeles JG, Heminger H, Mass DP. Comparative biomechanical performances of 4-strand core suture repairs for zone II flexor tendon lacerations. J Hand Surg Am. 2002;27(3):508e517. 10. Choueka J, Heminger H, Mass DP. Cyclical testing of zone II flexor tendon repair. J Hand Surg Am. 2000;25(6):1127e1134. 11. Gan AW, Neo PY, He M, Yam AK, Chong AK, Tay SC. A biomechanical comparison of 3 loop suture materials in a 6-strand flexor tendon repair technique. J Hand Surg Am. 2012;37(9): 1830e1834.
4. Keenan MA, Abrams RA, Garland DE, Waters RL. Results of fractional lengthening of the finger flexors in adults with upper extremity spasticity. J Hand Surg Am. 1987;12(4):575e581. 5. Farshad M, Gerber C, Snedeker JG, Meyer DC. Helical cutting as a new method for tendon-lengthening in continuity. J Bone Joint Surg Am. 2011;93(8):733e738. 6. Aktas S, Ercan S, Candan L, Moralar U, Akata E. Early mobilization after sliding and Z-lengthening of heel cord: a preliminary experimental study in rabbits. Arch Orthop Traum Surg. 2001;121(1-2): 87e89. 7. Shuind F, Garcia-Elias M, Cooney WP III, An KN. Flexor tendon force: in vivo measurement. J Hand Surg Am. 1992;17(2):291e298.
J Hand Surg Am.
5
r
Vol. -, - 2015
Biomechanical Study of the Digital Flexor Tendon Sliding Lengthening Technique Ken Hashimoto, MD, PhD,* Kazuki Kuniyoshi, MD, PhD,* Takane Suzuki, MD, PhD,† Ryo Hiwatari, MD, PhD,* Yusuke Matsuura, MD, PhD,* Kazuhisa Takahashi, MD, PhD*
Purpose To compare the mechanical properties of sliding lengthening (SL) and Z-lengthening (ZL) for flexor tendon elongation used for conditions such as Volkmann contracture, cerebral palsy, and poststroke spasticity. Methods We harvested 56 flexor tendons, including flexor pollicis longus tendons, flexor digitorum superficialis tendons (zones II to IV), and flexor digitorum profundus tendons (zones II to V) from 24 upper limbs of 12 fresh cadavers. Each tendon was harvested together with its homonymous tendon from the opposite side of the cadaver and paired. We used 28 pairs of tendons and divided them randomly into 4 groups depending on the lengthening distance (20 or 30 mm) and type of stitching (single or double mattress sutures). Then we divided each pair into either the SL or ZL group. Each group was composed of 7 specimens. The same surgeon lengthened all tendons and stitched them with 2-0 polyester sutures. We tested biomechanical tensile strength immediately after completing lengthening and suturing in each group. Results Ultimate tensile strengths were: 23 N for the SL 20-mm lengthening and single mattress suture and 7 N for the ZL; 25 N for the SL 20-mm lengthening and double mattress suture and 10 N for the ZL; 15 N for the SL 30-mm lengthening and single mattress suture and 8 N for the ZL; and 18 N for the SL 30-mm lengthening and double mattress suture and 10 N for the ZL. Conclusions The SL technique may be a good alternative to the ZL technique because it provides higher ultimate tensile strength. Clinical relevance Because of its higher ultimate tensile strength, the SL technique may allow for earlier rehabilitation and reduced risk of postoperative complications. (J Hand Surg Am. 2015;-(-):-e-. Copyright Ó 2015 by the American Society for Surgery of the Hand. All rights reserved.) Key words Flexor tendon lengthening, sliding lengthening, Z-lengthening.
L
ENGTHENING OF THE DIGITAL FLEXOR tendons in the forearm is a surgical technique used to correct flexion contracture of the wrist or fingers caused by such conditions as Volkmann contracture, cerebral
From the *Department of Orthopedic Surgery and the †Department of Environmental Health Science, Graduate School of Medicine, Chiba University, Chiba, Japan. Received for publication January 14, 2015; accepted in revised form June 30, 2015. No benefits in any form have been received or will be received related directly or indirectly to the subject of this article. Corresponding author: Ken Hashimoto, MD, PhD, Department of Orthopedic Surgery, Graduate School of Medicine, Chiba University, 1-8-1 Inohana, Chuo-ku, Chiba 260-8670, Japan; e-mail: [email protected]. 0363-5023/15/---0001$36.00/0 http://dx.doi.org/10.1016/j.jhsa.2015.06.120
palsy, and poststroke spasticity. Main methods used are sliding lengthening (SL),1 Z-lengthening (ZL),2,3 and fractional lengthening.4 The technique applied depends mainly on the severity of contracture and the amount of lengthening required.1 The purpose of this study was to compare the biomechanical properties of the commonly used SL and ZL techniques using freshfrozen cadaver material. MATERIALS AND METHODS We harvested 56 finger flexor tendons, including flexor pollicis longus tendons, flexor digitorum superficialis tendons (zones II to IV), and flexor digitorum profundus tendons (zone II to V) from the muscle-tendon junction
Ó 2015 ASSH
r
Published by Elsevier, Inc. All rights reserved.
r
1
2
DIGITAL FLEXOR TENDON SL TECHNIQUE
FIGURE 1: Sliding lengthening model groups. The yellow arrows indicate the amount of lengthening. The black arrow indicates the site of section for histology shown in Fig. 4.
The ZL model was produced by making a Z-shaped incision in the body of the tendon at an interval of 40 mm.
lengthening 20 mm
lengthening 30 mm
ZL 30 mm/1 suture ZL 30 mm/2 sutures ZL 20 mm/1 suture ZL 20 mm/2 sutures FIGURE 2: Z-Lengthening model groups.
to the tendon insertion point, from 24 upper limbs of 12 fresh-frozen cadavers, mean age 88 years (range, 76e105 years; 7 male and 5 female). We stored all specimens at e20 C and thawed them at room temperature for 24 hours before conducting the experiments at room temperature. A flexor tendon from one side of the cadaver and the homonymous tendon from the opposite side (for example, the flexor digitorum profundus [FDP] tendon from the right side and the FDP tendon from the left side of the cadaver) were harvested and paired. We obtained 28 pairs of tendons and randomly divided them into 4 groups depending on the lengthening distance (20 or 30 mm) and type of stitching J Hand Surg Am.
(single or double mattress sutures). Each pair was then divided into either the SL or ZL group. Therefore, 4 groups of the SL (Fig. 1) and 4 of the ZL (Fig. 2) each were composed of 7 tendons. We kept them moist with normal saline throughout the experiment. We produced the SL model by cutting the tendon halfway through on opposite sides at 40-mm intervals and applied traction on both ends to slide the central part of the tendon along its long axis until we achieved either 20 or 30 mm lengthening. We then secured the center of the area where the tendon fibers overlapped with single or double 2-0 polyester mattress sutures (Ethibond; Ethicon, Somerville, NJ). r
Vol. -, - 2015
DIGITAL FLEXOR TENDON SL TECHNIQUE
3
FIGURE 3: Ultimate tensile strength. Black bars represent the strength in the SL groups and grey bars represent the strength in the ZL groups.
FIGURE 4: Tendon fiber micrographs. The site of the section is indicated by the arrow in Figure 1. A Transverse section of tendon fibers showing narrowing of tendon diameter and deformation of tendon fibers. (Hematoxylin-eosin stain; magnification 4.) B Transverse section of tendon fibers showing fibers in the area where the tendon diameter was narrow. (Hematoxylin-eosin stain; magnification 10.) C Area of narrowed fibers. (Masson trichrome stain; magnification 10.)
We produced the ZL model by making a Z-shaped incision in the body of the tendon at 40-mm intervals to achieve either 20 or 30 mm lengthening. We secured the central part of the overlapping area with single or double 2-0 polyester mattress sutures as described above.
between the SL groups with different lengthening distances and considered differences significant at P < .05. Histology After we produced the SL model, we cut sections perpendicular to the long axis of the tendon and mounted them on slides for staining with hematoxylineosin or Masson trichrome stain. We examined the course of collagen fibers in the specimens with a light microscope.
Biomechanical evaluation We secured the cut ends of the tendon models in the clamp of a universal tester (AG-20 NXplus; Shimadzu, Kyoto, Japan). We then conducted traction experiments at 20 mm/min until failure. We calculated the ultimate tensile strength from the load-displacement curve. We also recorded the mode of failure for each test. We used the Wilcoxon signed-rank test to compare differences between the SL and ZL groups with the same lengthening distance and number of stitches. We used the Mann-Whitney U test to compare differences J Hand Surg Am.
RESULTS Biomechanical evaluation Ultimate failure load: The tensile strength of the SL was significantly higher than for the ZL in each group (P < .05) (Fig. 3). r
Vol. -, - 2015
4
DIGITAL FLEXOR TENDON SL TECHNIQUE
exercise can prevent adhesions and flexion contracture through contraction of the digital flexor muscles, forcing the tendon to glide and resulting in excursion.7 Our secondary question was whether the biomechanical tensile strength of SL was sufficient to enable early active mobilization. Shuind et al7 reported that early active flexion exercise requires a strength of 18.6 N or greater. Our SL model had a strength of 24.6 N (20 mm lengthening/double stitches) and 18.2 N (30 mm lengthening/double stitches). Our data might nearly meet their result. However, the use of early mobilization has recently become popular after flexor tendon repair8 and common methods of repair for early mobilization had higher mechanical strength of 29 N,9 60 N,10 and 97 N.11 Therefore, the strength achieved by our SL model may not be enough for early mobilization. Although we employed the conventional mattress suture for SL and ZL after the previous reports,1 in the current study the sutures pulled out as they cut or pulled through the fibers. Because the mattress suture is a side-to-side technique perpendicular to the tendon fibers, it effects a shearing force on the tendon. However, the biomechanical properties of the suture depend on the material and the number of strands crossing the repair site, and the suture caliber can improve the biomechanical properties of the lengthening model. Increasing the grasping strength of the suture on the tendon and the suture’s tensile strength, such as by adding supplementary sutures or locking sutures, may provide sufficient strength for early active exercise. In the SL groups with a single stitch, ultimate failure load was significantly higher in 20 mm lengthening than in 30 mm lengthening. Histology suggested that the reason for this difference in strength was that collagen fibers in the sliding surface exhibited partial continuity, which provided some inherent strength. Limitations of this investigation included its purely biomechanical nature, the lack of investigation of postoperative adhesions or gliding resistance, and the advanced age of the specimens. To determine differences in suture methods, the number of circumferential sutures, and the types of suture material, further experiments are required.
In the SL groups, ultimate failure load was significantly higher in the group with 20 mm lengthening and a single stitch than in the group with 30 mm lengthening and a single stitch (P ¼ .018) whereas there was no significant difference between the group with 20 mm lengthening and double stitches and the group with 30 mm lengthening with double stitches (P ¼ .055). A power analysis was also calculated to compare significant difference and was greater than .950 in all. Mode of failure: In the SL model, the sutures pulled out in most cases (79%). Suture breakage occurred at the site where the tendon was weakened after sliding in 0.40% of cases. Suture breakage occurred in 21% of cases. In the ZL model, the sutures pulled out before reaching the maximum tensile strength of the suture material in most cases (77%). We found no differences in the mode of failure between the SL and ZL groups. There was also no difference in the mode of failure between the group with a single suture and the one with double sutures in the SL and ZL groups, respectively. Histology We found that collagen fibers were split and displayed a cracked appearance, with smaller-diameter fibers present on the outside of the cracked area (Fig. 4). These findings confirmed the continuity of collagen fibers. DISCUSSION Tendon lengthening such as that of the Achilles tendon is commonly used in the lower extremity.2,5 In the forearm, methods of tendon lengthening are limited to SL and ZL, in which the tendon is lengthened, and fractional lengthening, in which the muscleetendon junction is lengthened. The maximum lengthening that can be achieved is 2 to 5 cm with the SL and ZL techniques and 1 to 3 cm with fractional lengthening.1 Therefore, surgeons choose the technique based on the severity of contracture and the amount of lengthening desired. Although SL and ZL techniques are both indicated for lengthening of almost the same distance, we wondered whether SL would have better biomechanical properties than ZL because some collagen fibers may be in continuity after SL. We confirmed the continuity of collagen fibers after SL and significantly better biomechanical properties than ZL for all groups (20 or 30 mm lengthening single or double stitches). Rupture and overlengthening frequently occur after lengthening, and postoperative external immobilization is required. As a consequence, adhesions and contracture may be problematic.6 Early active J Hand Surg Am.
REFERENCES 1. Matsuo T, Lai T, Tayama N. Combined flexor and extensor release for activation of voluntary movement of the fingers in patients with cerebral palsy. Clin Orthop Relat Res. 1990;(250):185e193. 2. White JW. Torsion of the Achilles tendon. Arch Surg. 1943;46:784. 3. Koman LA, Gelberman RH, Toby EB, Poehling GG. Cerebral palsy. Management of the upper extremity. Clin Orthop Relat Res. 1990;(253):62e74.
r
Vol. -, - 2015
DIGITAL FLEXOR TENDON SL TECHNIQUE
8. Maki Y, Yoshizu T, Tsubokawa N, Narisawa H, Maniwa K. Flexor tendon repair in zone II: the result of early active mobilization. Jpn Soc Surg Hand. 2009;25:763e765. 9. Angeles JG, Heminger H, Mass DP. Comparative biomechanical performances of 4-strand core suture repairs for zone II flexor tendon lacerations. J Hand Surg Am. 2002;27(3):508e517. 10. Choueka J, Heminger H, Mass DP. Cyclical testing of zone II flexor tendon repair. J Hand Surg Am. 2000;25(6):1127e1134. 11. Gan AW, Neo PY, He M, Yam AK, Chong AK, Tay SC. A biomechanical comparison of 3 loop suture materials in a 6-strand flexor tendon repair technique. J Hand Surg Am. 2012;37(9): 1830e1834.
4. Keenan MA, Abrams RA, Garland DE, Waters RL. Results of fractional lengthening of the finger flexors in adults with upper extremity spasticity. J Hand Surg Am. 1987;12(4):575e581. 5. Farshad M, Gerber C, Snedeker JG, Meyer DC. Helical cutting as a new method for tendon-lengthening in continuity. J Bone Joint Surg Am. 2011;93(8):733e738. 6. Aktas S, Ercan S, Candan L, Moralar U, Akata E. Early mobilization after sliding and Z-lengthening of heel cord: a preliminary experimental study in rabbits. Arch Orthop Traum Surg. 2001;121(1-2): 87e89. 7. Shuind F, Garcia-Elias M, Cooney WP III, An KN. Flexor tendon force: in vivo measurement. J Hand Surg Am. 1992;17(2):291e298.
J Hand Surg Am.
5
r
Vol. -, - 2015