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EXPERIMENTAL STUDY OF TWO NEW FLEXOR TENDON SUTURE TECHNIQUES FOR POSTOPERATIVE EARLY ACTIVE FLEXION EXERCISES
EXPERIMENTAL STUDY OF TWO NEW FLEXOR TENDON SUTURE TECHNIQUES FOR POSTOPERATIVE EARLY ACTIVE FLEXION EXERCISES N. KUSANO, T. YOSHIZU and Y. MAKI From the Niigata Hand Surgery Foundation, Niigata-shi, Japan
We used a rabbit model to test the postoperative mechanical strengths of two new tendon suture techniques. These were compared with the conventional modified Kessler and double looped suture techniques. For each technique, maximum load until 3 mm gap, load at 1 mm gap and ultimate load were measured at the time of operation and at weeks 1 and 3 after operation. Maximum load until 3 mm gap and load at 1 mm gap were significantly higher in the new techniques than in the conventional techniques at the time of operation and at 1 week; there was no statistical difference between the four techniques at 3 weeks. No technique resulted in a decrease in maximum load until 3 mm gap, load at 1 mm gap and ultimate load at 1 week. The new techniques reported here have the potential to withstand early active flexion exercises. Journal of Hand Surgery (British and European Volume, 1999) 24B: 2: 152–156 The results of flexor tendon surgery have improved greatly with the use of postoperative early passive mobilization protocols set down in the 1960s and 1970s (Duran and Houser, 1975; Kleinert et al., 1975; Lister et al., 1977; Young and Harmon, 1960). However, the results are still not perfect. Many authors have pointed out that the excursions of the flexor digitorum profundus (FDP) and flexor digitorum superficialis (FDS) tendons are limited during passive mobilization (McGrouther and Ahmed, 1981; Silfverskiöld et al., 1992; 1993). Therefore, early active flexion exercises were deemed necessary to achieve better results. To allow sufficient gliding of the repaired tendon during early active flexion exercises, a new suture technique, stronger than conventional techniques, is required. Mason and Allen (1941) and Urbaniak et al. (1975) noted that tensile strength decreases about 1 week after repair. Therefore, a suture technique has to be strong not only at the time of repair but also during the early postoperative period. We devised two new suture techniques and have applied the techniques in clinical practice since 1993 (Yoshizu et al., 1997). The purpose of this study was to evaluate the mechanical strength of the new suture techniques during the healing process in a rabbit model and to compare them with two conventional techniques: the modified Kessler technique and the double looped suture technique (Hayashi et al., 1984; 1986).
tendon was used because it is very similar in size to the human flexor tendon (4.5 mm compared to 5 mm in humans), and it is encircled with a fibro-osseous tunnel just as human flexor tendons are. In each of the four experimental groups, repaired tendons were harvested for mechanical testing at the time of tendon repair (n=8), at 1 week (n=8), and at 3 weeks (n=7). Operative procedures Each animal was anesthetized with intramuscular Ketaral (60 mg/kg) and intravenous pentobarbital (15 mg/kg). A tibial nerve block and peroneal nerve block were added with Lidocaine (1 mg/kg). A longitudinal skin incision was made on the tibial aspect of the ankle and extended proximally and distally. The flexor retinaculum and fibro-osseous tunnel were cut longitudinally to expose the flexor digitorum fibularis tendon (Fig 1). At this point tendons were transected at the level of the flexor retinaculum and repaired with one of four techniques (described below). The flexor retinaculum was
MATERIALS AND METHODS Experimental design All procedures were performed using sterile techniques and conducted in accordance with the guidelines of experimental animal care (Announcement Number 6, Prime Minister’s Office of Japan). We used the left flexor digitorum fibularis tendons (toe flexors) of 92 male rabbits weighing 2.5 to 3 kg. This
Fig 1
152
(a) Relevant anatomy of the rabbit hindlimb. (b) Immobilization.
FLEXOR TENDON TECHNIQUES
Fig 2
153
Kessler- Tsuge technique using double strand with two needles (Yoshizu #1 technique).
not repaired. Postoperatively, an above knee cast was applied with the knee in 30° flexion, the ankle in maximum plantar flexion, and the toes in maximum flexion. In this position the cast prevented the rabbits from weight bearing on the operated extremity.
Fig 3
Triple looped suture technique. (a,b) The first and second needles are inserted into the dorsoradial and dorsoulnar aspects of the tendon, while reflecting the tendon. The third needle is inserted into the flexor aspect of the tendon. (c) Sites of grasping.
Fig 4
Suture techniques in this study: (a) Pennington’s modified Kessler technique (b) Double looped suture technique. (c) Triple looped suture technique. (d) Kessler-Tsuge technique using double strand with two needles (Yoshizu #1 technique).
New suture techniques Kessler-Tsuge technique using double strand with two needles (Yoshizu #1 technique) The Yoshizu #1 technique is a combination of the Tsuge suture with a looped thread and the modified Kessler suture, using a double strand with two needles designed by one of us (TY) (Yoshizu et al., 1997) (Fig 2). We used 5/0 monofilament nylon sutures for core sutures. Four stitches of 6/0 monofilament nylon were used for the peripheral epitenous suture. Grasping sites of the modified Kessler suture were 8 mm apart from the tendon ends, and the grasping sites of the Tsuge suture were 9 mm from the tendon ends (Fig 4d). Triple looped suture technique Looped threads were inserted on the dorsoradial, dorsoulnar, and flexor aspects of the tendon so that the blood supply would not be disturbed. Each thread grasped one-sixth of the tendon circumference. The technique for making knots was identical to that described by Tsuchida et al. (1993) to reinforce the anchoring point (Fig 3). Three 5/0 monofilament looped nylon sutures were placed across the repair site. Four stitches of 6/0 monofilament nylon were used for the peripheral epitenous suture, and grasping sites were 8 mm from the tendon ends (Fig 4c). Conventional suture techniques Modified Kessler technique A 5/0 monofilament nylon core suture was placed across the site of division. Four stitches of 6/0 monofilament
nylon were used for the peripheral epitenous suture. A Pennington (1979) modification was employed, and grasping sites were 8 mm from the tendon ends (Fig 4a). Double looped suture technique In this group, two 5/0 monofilament looped nylon sutures were placed across the site of division. Four stitches of 6/0 monofilament nylon were used for the peripheral epitenous suture. Each thread of looped nylon grasped one-sixth of the tendon circumference; grasping sites were 8 mm a from the tendon ends (Fig 4b). Methods of evaluation The animals were humanely killed at the appropriate time period, and tendon specimens were dissected and mounted in nonslip jaws attached to a tensiometer.
154
Fig 5
THE JOURNAL OF HAND SURGERY VOL. 24B No. 2 APRIL 1999
Recording and measurement system.
Tendons were then stretched at a constant rate of 17 mm/min. We measured the maximum load until the appearance of a 3 mm gap. (Seradge [1983] showed in clinical work that flexor tendon repair deteriorates if a gap of 3 mm or more develops between the tendon ends). We also measured load at 1 mm gap and the ultimate load. The recorded values were compared to other reports in the medical literature. We used two video cameras during testing to record the condition of the suture site in the repaired tendons, a digital display of the load value, and the load curves on a computer monitor. Thus, evaluations could be made precisely and repeatedly (Fig 5). Statistical analysis was performed by one-way analysis of variance with Fisher’s multiple comparison test. A P value of <0.05 was accepted as statistically significant. RESULTS No specimen ruptured during immobilization. No specimens showed gap formation except for one that was repaired with double looped suture technique and tested at 1 week. This specimen showed 1 mm gap formation. In this specimen load at 1 mm gap was measured as 0 N. Maximum load until 3 mm gap We first analysed the suture techniques by comparing all four, then we analysed the individual suture techniques by load over time. The Yoshizu #1 technique and the triple looped suture technique were both significantly stronger than the modified Kessler and double looped suture techniques at the time of repair and at 1 week. At these same time periods there was no difference between the Yoshizu #1 technique and the triple looped suture technique. There was no statistical difference among the four techniques at 3 weeks (Fig 6). When we compared the maximum load for each suture technique until 3 mm gap formation at different times, no
Fig 6
< 3 mm). Comparison between sutures. Maximum load (gap = Mean (SD). (*) significantly greater than MK and DL techniques (P < 0.05). MK: modified Kessler. DL: double looped suture. TL: triple looped suture. Y1: Yoshizu #1.
statistical difference was found in any suture technique between strengths measured at the time of repair and at 1 week. However, in each suture technique, the load at 3 weeks after repair was significantly greater than that measured at the time of repair and at 1 week (Fig 7). Load at 1 mm gap The Yoshizu #1 technique and triple looped suture technique were significantly stronger than the modified Kessler and double looped suture techniques at the time of repair and at 1 week. No significant difference in load was found among the four techniques at 3 weeks (Fig 8). No statistical differences were noted in load between suture techniques at the time of repair and 1 week after repair. However, the loads at 3 weeks were significantly greater than at the time of repair and 1 week after repair in each suture technique (Fig 9). Ultimate load No significant difference was found among the four techniques in ultimate load between the time of repair and 1 week after repair. The loads at 3 weeks were significantly greater than at the time of repair and 1 week after repair in the modified Kessler technique and the Yoshizu #1 technique. The loads at 3 weeks were significantly greater than at 1 week in the double looped suture technique and the triple looped suture technique (Fig 10). DISCUSSION This study showed that the Yoshizu #1 technique and triple looped suture technique were significantly stronger
FLEXOR TENDON TECHNIQUES
155
Fig 7
< 3 mm) for each type of suture. Maximum load over time (gap = Mean (SD). (†) significantly significantly greater than at the time of repair and at 1 week (P < 0.05).
Fig 8
Fig 9
Load at 1 mm gap over time for each type of suture. Mean (SD). (†) significantly greater than at the time of repair and at 1 week (P < 0.05).
Fig 10 Ultimate load. Mean (SD). (†) significantly greater than at the time of repair and at 1 week (P < 0.05). (‡‡) significantly greater than at 1 week (P < 0.05).
than the conventional modified Kessler and double looped suture techniques. In addition, the data show that the Yoshizu #1 technique and the triple looped suture technique maintain their strengths at 1 week after surgery, an important consideration when choosing a postoperative flexor tendon rehabilitation program. Maximum load until 3 mm gap and load at 1 mm gap in both new techniques, were about 70% greater than the modified Kessler technique, not only at the time of repair but also 1 week after repair.
The strength requirements of the tendon during early active flexion exercise is still unknown. Schuind et al. (1992) reported that the FDP tendon load encountered clinically averaged 18.6 N (range, 1–28.4 N) during active unresisted flexion of the distal interphalangeal joint of the index finger in five patients operated on for treatment of carpal tunnel syndrome. Yoshizu et al. (1997) evaluated the mechanical strengths of the modified Kessler, double looped suture, Yoshizu #1, and triple looped suture techniques using fresh human flexor tendons with
Load at 1 mm gap. Comparison between sutures Mean (SD). (*) significantly greater than MK and DL techniques (P < 0.05).
156
4/0 suture. According to their report, the average values of maximum load until 3 mm gap formation were 20.4 N for the modified Kessler technique, 21.7 N for the double looped suture technique, 42.2 N for the Yoshizu #1 technique, and 37.4 N for the triple looped suture technique. The loads of the Yoshizu #1 technique and the triple looped suture technique did not decrease during the early phase of healing during the present study and so may be regarded to be over 37.4 N during all phases of healing. Because the loads of both new techniques in fresh human flexor tendons are about twice the amount of tendon force encountered clinically during active flexion (Schuind et al., 1992), the new techniques may be strong enough to withstand early active flexion exercise. Of course, resistance to motion as a result of oedema, haematoma, and suture bulk increases postoperatively. Moreover, the effect of repeated submaximal stress on suture strength is unknown; therefore, the exact suture strength needed for early active flexion exercise is unknown. However, because of the strength of these new techniques recorded in this study, we believe that they are able to withstand early active flexion exercises in a passive flexion active-hold technique, which was described by Cannon and Strickland (1985) for use after tenolysis and first applied to the postoperative flexor tendon rehabilitation program by Hagberg and Selvik (1991). Multi-strand flexor tendon suturing techniques have been introduced as a way of increasing repair strength (Lee, 1990; Savage, 1985), but they are very complicated. The two suture techniques reported in this study are not difficult to perform and so lend themselves to use in clinical practice. Tang et al. (1994) reported the clinical results of a multiple looped suture technique in which three threads of looped nylon were used. In their technique, all suture knots were placed on the flexor aspect of the tendon, which is different from the triple looped suture technique. Soejima et al. (1995) suggested there were biomechanical advantages to dorsal instead of palmar placement of the core suture in clinical tendon repair. Therefore, we believe the triple looped suture technique would be stronger than the multiple looped suture technique in the clinical situation. Mason and Allen (1941) and Urbaniak et al. (1975) reported a drop in tensile strength about 1 week after repair. In our study, none of the suturing techniques used showed a drop in the maximum load until 3 mm gap formation at 1 week and the ultimate load. This difference may be due to various factors. Mason and Allen used silk braid for suture material, which may cause inflammation and softening of the tendon. In the model used by Urbaniak et al., a peripheral suture was not added to the core suture, and stainless steel wire was used for suture material, which is now rarely used. Further investigations into these differences in results are necessary. In summary, the Kessler-Tsuge technique using a double strand with two needles (Yoshizu #1 technique) and the triple looped suture technique were significantly
THE JOURNAL OF HAND SURGERY VOL. 24B No. 2 APRIL 1999
stronger than the conventional techniques (modified Kessler and double looped suture techniques). Repair strengths, maintained 1 week after surgery, would allow early active flexion exercises in the clinical situation. Acknowledgement The authors thank H. Takahashi MD, Professor of the Department of Orthopaedic Surgery, Niigata University School of Medicine, for his suggestions.
References Cannon NM, Strickland JW (1985). Therapy following flexor tendon surgery. Hand Clinics, 1: 147–165. Duran R, Houser R. Controlled passive motion following flexor tendon repair in zones 2 and 3. In: Hunter JM, Schneider LH (Eds) AAOS symposium on tendon surgery in the hand. St Louis, Mosby, 1975: 105–114. Hagberg L, Selvik G (1991). Tendon excursion and dehiscence during early controlled mobilization after flexor tendon repair in zone II: an X-ray stereophotgrammetric analysis. Journal of Hand Surgery, 16A: 669–680. Hayashi J, Ikuta Y, Umeda S, Kojima S, Kanaujia R, Tsuge K (1984). Experimental study regarding tensile strength of tendon suturing methods. Journal of Japanese Society for Surgery of the Hand, 1: 58–61. Hayashi J, Tsuge K, Kanda T, Ikuta Y, Murozeki M (1986). Experimental study regarding tendon suturing methods. Part 3: gap formation and suture materials. Journal of Japanese Society for Surgery of the Hand, 3: 462–467. Kleinert HE, Kutz JE, Cohen MJ (1975). Primary repair of zone 2 flexor tendon lacerations. In: Hunter JM, Schneider LH (Eds) AAOS, symposium on tendon surgery in the hand. St Louis, Mosby, 1975: 91–104. Lee H (1990). Double loop locking suture: A technique of tendon repair for early active mobilization. Part I. Evolution of technique and experimental study. Journal of Hand Surgery, 15A: 945–952. Lister GD, Kleinert HE, Kutz JE, Atasoy E (1977). Primary flexor tendon repair followed by immediate controlled mobilization. Journal of Hand Surgery, 2: 441–451. Mason ML, Allen HS (1941). The rate of healing of tendons. An experiment study of tensile strength. Annals of Surgery, 113: 424–459. McGrouther DA, Ahmed MR (1981). Flexor tendon excursions in “no man’s land.” The Hand, 13: 129–141. Pennington DG (1979). The locking loop tendon suture. Plastic and Reconstructive Surgery, 63: 648–652. Savage R (1985). In vitro studies of a new method of flexor tendon repair. Journal of Hand Surgery, 10B: 135–141. Schuind F, Garcia-Elias M, Cooney WP, An K-N (1992). Flexor tendon forces: in vivo measurements. Journal of Hand Surgery, 17A: 291–298. Seradge H (1983). Elongation of the repair configuration following flexor tendon repair. Journal of Hand Surgery, 8: 182–185. Silfverskiöld K, May E, Törnvall A (1992). Flexor digitorum profundus tendon excursions during controlled motion after flexor tendon repair in zone II: a prospective clinical study. Journal of Hand Surgery, 17A: 122–131. Silfverskiöld K, May E, Törnvall A (1993). Tendon excursions after flexor tendon repair in zone II. results with a new controlled-motion program. Journal of Hand Surgery, 18A: 403–410. Soejima O, Diao E, Lotz JC, Hariharan JS (1995). Comparative mechanical analysis of dorsal versus palmar placement of core suture for flexor tendon repairs. Journal of hand Surgery, 20A: 801–807. Tang JB, Shi D, Gu YQ, Chen JC, Zhou B (1994). Double and multiple looped suture tendon repair. Journal of Hand Surgery, 19B: 699–703. Tsuchida H, Takayanagi M, Yoshizawa H, Sano F, Watanabe Y (1993). Experimental Study of the tendon repair: 3rd report – the tensile strength after tendon graft with dogs. Journal of Japanese Society for Surgery of the Hand, 10: 191–194. Urbaniak JR, Cahill JD, Mortenson RA. Tendon suturing methods: analysis of tensile strengths. In: Hunter JM, Schneider LH (Eds) AAOS symposium on tendon surgery in the hand. St Louis, Mosby, 1975: 70–80. Yoshizu T, Maki Y, Tajima T, Kusano N (1997). An in vitro evaluation of various new flexor repair techniques for early active motion exercise. Journal of Japanese Society for Surgery of the Hand, 13: 1135–1138. Young R, Harmon J (1960). Repair of the tendon injuries of the hand. Annals of Surgery, 151: 562–566. Received: 25 June 1998 Accepted after revision: 30 September 1998 N. Kusamo MD, Niigata Hand Surgery Foundation, Shinko-cho 1–18, Niigata-shi, 950–8556 Japan. E-mail: [email protected] ©1999 The British Society for Surgery of the Hand Article no. jhsb.1998.0174
We used a rabbit model to test the postoperative mechanical strengths of two new tendon suture techniques. These were compared with the conventional modified Kessler and double looped suture techniques. For each technique, maximum load until 3 mm gap, load at 1 mm gap and ultimate load were measured at the time of operation and at weeks 1 and 3 after operation. Maximum load until 3 mm gap and load at 1 mm gap were significantly higher in the new techniques than in the conventional techniques at the time of operation and at 1 week; there was no statistical difference between the four techniques at 3 weeks. No technique resulted in a decrease in maximum load until 3 mm gap, load at 1 mm gap and ultimate load at 1 week. The new techniques reported here have the potential to withstand early active flexion exercises. Journal of Hand Surgery (British and European Volume, 1999) 24B: 2: 152–156 The results of flexor tendon surgery have improved greatly with the use of postoperative early passive mobilization protocols set down in the 1960s and 1970s (Duran and Houser, 1975; Kleinert et al., 1975; Lister et al., 1977; Young and Harmon, 1960). However, the results are still not perfect. Many authors have pointed out that the excursions of the flexor digitorum profundus (FDP) and flexor digitorum superficialis (FDS) tendons are limited during passive mobilization (McGrouther and Ahmed, 1981; Silfverskiöld et al., 1992; 1993). Therefore, early active flexion exercises were deemed necessary to achieve better results. To allow sufficient gliding of the repaired tendon during early active flexion exercises, a new suture technique, stronger than conventional techniques, is required. Mason and Allen (1941) and Urbaniak et al. (1975) noted that tensile strength decreases about 1 week after repair. Therefore, a suture technique has to be strong not only at the time of repair but also during the early postoperative period. We devised two new suture techniques and have applied the techniques in clinical practice since 1993 (Yoshizu et al., 1997). The purpose of this study was to evaluate the mechanical strength of the new suture techniques during the healing process in a rabbit model and to compare them with two conventional techniques: the modified Kessler technique and the double looped suture technique (Hayashi et al., 1984; 1986).
tendon was used because it is very similar in size to the human flexor tendon (4.5 mm compared to 5 mm in humans), and it is encircled with a fibro-osseous tunnel just as human flexor tendons are. In each of the four experimental groups, repaired tendons were harvested for mechanical testing at the time of tendon repair (n=8), at 1 week (n=8), and at 3 weeks (n=7). Operative procedures Each animal was anesthetized with intramuscular Ketaral (60 mg/kg) and intravenous pentobarbital (15 mg/kg). A tibial nerve block and peroneal nerve block were added with Lidocaine (1 mg/kg). A longitudinal skin incision was made on the tibial aspect of the ankle and extended proximally and distally. The flexor retinaculum and fibro-osseous tunnel were cut longitudinally to expose the flexor digitorum fibularis tendon (Fig 1). At this point tendons were transected at the level of the flexor retinaculum and repaired with one of four techniques (described below). The flexor retinaculum was
MATERIALS AND METHODS Experimental design All procedures were performed using sterile techniques and conducted in accordance with the guidelines of experimental animal care (Announcement Number 6, Prime Minister’s Office of Japan). We used the left flexor digitorum fibularis tendons (toe flexors) of 92 male rabbits weighing 2.5 to 3 kg. This
Fig 1
152
(a) Relevant anatomy of the rabbit hindlimb. (b) Immobilization.
FLEXOR TENDON TECHNIQUES
Fig 2
153
Kessler- Tsuge technique using double strand with two needles (Yoshizu #1 technique).
not repaired. Postoperatively, an above knee cast was applied with the knee in 30° flexion, the ankle in maximum plantar flexion, and the toes in maximum flexion. In this position the cast prevented the rabbits from weight bearing on the operated extremity.
Fig 3
Triple looped suture technique. (a,b) The first and second needles are inserted into the dorsoradial and dorsoulnar aspects of the tendon, while reflecting the tendon. The third needle is inserted into the flexor aspect of the tendon. (c) Sites of grasping.
Fig 4
Suture techniques in this study: (a) Pennington’s modified Kessler technique (b) Double looped suture technique. (c) Triple looped suture technique. (d) Kessler-Tsuge technique using double strand with two needles (Yoshizu #1 technique).
New suture techniques Kessler-Tsuge technique using double strand with two needles (Yoshizu #1 technique) The Yoshizu #1 technique is a combination of the Tsuge suture with a looped thread and the modified Kessler suture, using a double strand with two needles designed by one of us (TY) (Yoshizu et al., 1997) (Fig 2). We used 5/0 monofilament nylon sutures for core sutures. Four stitches of 6/0 monofilament nylon were used for the peripheral epitenous suture. Grasping sites of the modified Kessler suture were 8 mm apart from the tendon ends, and the grasping sites of the Tsuge suture were 9 mm from the tendon ends (Fig 4d). Triple looped suture technique Looped threads were inserted on the dorsoradial, dorsoulnar, and flexor aspects of the tendon so that the blood supply would not be disturbed. Each thread grasped one-sixth of the tendon circumference. The technique for making knots was identical to that described by Tsuchida et al. (1993) to reinforce the anchoring point (Fig 3). Three 5/0 monofilament looped nylon sutures were placed across the repair site. Four stitches of 6/0 monofilament nylon were used for the peripheral epitenous suture, and grasping sites were 8 mm from the tendon ends (Fig 4c). Conventional suture techniques Modified Kessler technique A 5/0 monofilament nylon core suture was placed across the site of division. Four stitches of 6/0 monofilament
nylon were used for the peripheral epitenous suture. A Pennington (1979) modification was employed, and grasping sites were 8 mm from the tendon ends (Fig 4a). Double looped suture technique In this group, two 5/0 monofilament looped nylon sutures were placed across the site of division. Four stitches of 6/0 monofilament nylon were used for the peripheral epitenous suture. Each thread of looped nylon grasped one-sixth of the tendon circumference; grasping sites were 8 mm a from the tendon ends (Fig 4b). Methods of evaluation The animals were humanely killed at the appropriate time period, and tendon specimens were dissected and mounted in nonslip jaws attached to a tensiometer.
154
Fig 5
THE JOURNAL OF HAND SURGERY VOL. 24B No. 2 APRIL 1999
Recording and measurement system.
Tendons were then stretched at a constant rate of 17 mm/min. We measured the maximum load until the appearance of a 3 mm gap. (Seradge [1983] showed in clinical work that flexor tendon repair deteriorates if a gap of 3 mm or more develops between the tendon ends). We also measured load at 1 mm gap and the ultimate load. The recorded values were compared to other reports in the medical literature. We used two video cameras during testing to record the condition of the suture site in the repaired tendons, a digital display of the load value, and the load curves on a computer monitor. Thus, evaluations could be made precisely and repeatedly (Fig 5). Statistical analysis was performed by one-way analysis of variance with Fisher’s multiple comparison test. A P value of <0.05 was accepted as statistically significant. RESULTS No specimen ruptured during immobilization. No specimens showed gap formation except for one that was repaired with double looped suture technique and tested at 1 week. This specimen showed 1 mm gap formation. In this specimen load at 1 mm gap was measured as 0 N. Maximum load until 3 mm gap We first analysed the suture techniques by comparing all four, then we analysed the individual suture techniques by load over time. The Yoshizu #1 technique and the triple looped suture technique were both significantly stronger than the modified Kessler and double looped suture techniques at the time of repair and at 1 week. At these same time periods there was no difference between the Yoshizu #1 technique and the triple looped suture technique. There was no statistical difference among the four techniques at 3 weeks (Fig 6). When we compared the maximum load for each suture technique until 3 mm gap formation at different times, no
Fig 6
< 3 mm). Comparison between sutures. Maximum load (gap = Mean (SD). (*) significantly greater than MK and DL techniques (P < 0.05). MK: modified Kessler. DL: double looped suture. TL: triple looped suture. Y1: Yoshizu #1.
statistical difference was found in any suture technique between strengths measured at the time of repair and at 1 week. However, in each suture technique, the load at 3 weeks after repair was significantly greater than that measured at the time of repair and at 1 week (Fig 7). Load at 1 mm gap The Yoshizu #1 technique and triple looped suture technique were significantly stronger than the modified Kessler and double looped suture techniques at the time of repair and at 1 week. No significant difference in load was found among the four techniques at 3 weeks (Fig 8). No statistical differences were noted in load between suture techniques at the time of repair and 1 week after repair. However, the loads at 3 weeks were significantly greater than at the time of repair and 1 week after repair in each suture technique (Fig 9). Ultimate load No significant difference was found among the four techniques in ultimate load between the time of repair and 1 week after repair. The loads at 3 weeks were significantly greater than at the time of repair and 1 week after repair in the modified Kessler technique and the Yoshizu #1 technique. The loads at 3 weeks were significantly greater than at 1 week in the double looped suture technique and the triple looped suture technique (Fig 10). DISCUSSION This study showed that the Yoshizu #1 technique and triple looped suture technique were significantly stronger
FLEXOR TENDON TECHNIQUES
155
Fig 7
< 3 mm) for each type of suture. Maximum load over time (gap = Mean (SD). (†) significantly significantly greater than at the time of repair and at 1 week (P < 0.05).
Fig 8
Fig 9
Load at 1 mm gap over time for each type of suture. Mean (SD). (†) significantly greater than at the time of repair and at 1 week (P < 0.05).
Fig 10 Ultimate load. Mean (SD). (†) significantly greater than at the time of repair and at 1 week (P < 0.05). (‡‡) significantly greater than at 1 week (P < 0.05).
than the conventional modified Kessler and double looped suture techniques. In addition, the data show that the Yoshizu #1 technique and the triple looped suture technique maintain their strengths at 1 week after surgery, an important consideration when choosing a postoperative flexor tendon rehabilitation program. Maximum load until 3 mm gap and load at 1 mm gap in both new techniques, were about 70% greater than the modified Kessler technique, not only at the time of repair but also 1 week after repair.
The strength requirements of the tendon during early active flexion exercise is still unknown. Schuind et al. (1992) reported that the FDP tendon load encountered clinically averaged 18.6 N (range, 1–28.4 N) during active unresisted flexion of the distal interphalangeal joint of the index finger in five patients operated on for treatment of carpal tunnel syndrome. Yoshizu et al. (1997) evaluated the mechanical strengths of the modified Kessler, double looped suture, Yoshizu #1, and triple looped suture techniques using fresh human flexor tendons with
Load at 1 mm gap. Comparison between sutures Mean (SD). (*) significantly greater than MK and DL techniques (P < 0.05).
156
4/0 suture. According to their report, the average values of maximum load until 3 mm gap formation were 20.4 N for the modified Kessler technique, 21.7 N for the double looped suture technique, 42.2 N for the Yoshizu #1 technique, and 37.4 N for the triple looped suture technique. The loads of the Yoshizu #1 technique and the triple looped suture technique did not decrease during the early phase of healing during the present study and so may be regarded to be over 37.4 N during all phases of healing. Because the loads of both new techniques in fresh human flexor tendons are about twice the amount of tendon force encountered clinically during active flexion (Schuind et al., 1992), the new techniques may be strong enough to withstand early active flexion exercise. Of course, resistance to motion as a result of oedema, haematoma, and suture bulk increases postoperatively. Moreover, the effect of repeated submaximal stress on suture strength is unknown; therefore, the exact suture strength needed for early active flexion exercise is unknown. However, because of the strength of these new techniques recorded in this study, we believe that they are able to withstand early active flexion exercises in a passive flexion active-hold technique, which was described by Cannon and Strickland (1985) for use after tenolysis and first applied to the postoperative flexor tendon rehabilitation program by Hagberg and Selvik (1991). Multi-strand flexor tendon suturing techniques have been introduced as a way of increasing repair strength (Lee, 1990; Savage, 1985), but they are very complicated. The two suture techniques reported in this study are not difficult to perform and so lend themselves to use in clinical practice. Tang et al. (1994) reported the clinical results of a multiple looped suture technique in which three threads of looped nylon were used. In their technique, all suture knots were placed on the flexor aspect of the tendon, which is different from the triple looped suture technique. Soejima et al. (1995) suggested there were biomechanical advantages to dorsal instead of palmar placement of the core suture in clinical tendon repair. Therefore, we believe the triple looped suture technique would be stronger than the multiple looped suture technique in the clinical situation. Mason and Allen (1941) and Urbaniak et al. (1975) reported a drop in tensile strength about 1 week after repair. In our study, none of the suturing techniques used showed a drop in the maximum load until 3 mm gap formation at 1 week and the ultimate load. This difference may be due to various factors. Mason and Allen used silk braid for suture material, which may cause inflammation and softening of the tendon. In the model used by Urbaniak et al., a peripheral suture was not added to the core suture, and stainless steel wire was used for suture material, which is now rarely used. Further investigations into these differences in results are necessary. In summary, the Kessler-Tsuge technique using a double strand with two needles (Yoshizu #1 technique) and the triple looped suture technique were significantly
THE JOURNAL OF HAND SURGERY VOL. 24B No. 2 APRIL 1999
stronger than the conventional techniques (modified Kessler and double looped suture techniques). Repair strengths, maintained 1 week after surgery, would allow early active flexion exercises in the clinical situation. Acknowledgement The authors thank H. Takahashi MD, Professor of the Department of Orthopaedic Surgery, Niigata University School of Medicine, for his suggestions.
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