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Work of flexion after tendon repair with various suture methods
W O R K OF F L E X I O N A F T E R T E N D O N R E P A I R W I T H V A R I O U S SUTURE METHODS A human cadaveric study M. AOKI, P. R. MANSKE, D. L. PRUITT and B. J. LARSON
From the Department of Orthopaedic Surgery, Washington UniversitySchool of Medicine, St Louis, USA After flexor tendon repair there is often increased resistance to tendon gliding at the repair site, which is greater for techniques using increased suture strands or suture material. This increased "friction" may be measured as the "work of flexion" in the laboratory setting. Tendon repairs performed in zone 2 in human cadaver hands using the two strand Kessler, the lateral Becker, the six strand Savage, internal and dorsal tendon splint, or the external mesh sleeve techniques, had "work of flexion" measurements made both before and after the laceration and repair. The average increase in work of flexion was 4.8% for Kessler; 6.5% for Becker; 10.9% for Savage; 19.3% for the internal tendon splint, 16.2% for the dorsal tendon splint and 44.3% for the external mesh sleeve. The work of flexion was found to increase in direct proportion to the amount of suture material at the repair site.
Journal of Hand Surgery (British and European Volume, 1995) 20B: 3:310-313 subsequently used by other authors (Peterson et al, 1986 a and b; 1990); it represents the summation of forces necessary to move the tendon along its excursion distance.
In order to increase the strength of flexor tendon repair and potentially allow early active motion, several authors have recommended alternative repair techniques to the standard methods (Bunnell, 1940; Kessler, 1973; Tsuge et al, 1975) which crosses the repair site with two strands of suture; most of the newer techniques use increased amounts of suture material. Becker and Davidoff (1977) placed running sutures along the two lateral margins of the tendon. Several authors have advocated increasing the number of suture strands to four (Ketchum et al, 1977; Lee, 1990; Robertson and A1-Qattan, 1992), and Savage (1985) has proposed a six-strand repair. Silfverski61d and Anderson (1993) supported the repair site with external nylon mesh sleeve. Recently, we incorporated a dacron tendon splint into the repair site which was placed either internally within the tendon substance or externally on the dorsal surface (Aoki et al, 1994). The Savage, external nylon mesh sleeve, and tendon splints are the strongest reported repair techniques, increasing the tensile strength of the repair site from 3.1 to 3.3 times that of the two strand Kessler technique in various cadaver studies. However, Noguchi et al (1993) raised concern about the effect of the increased suture material on the gliding properties of the tendon following repair. The purpose of this study was to measure the mechanical work of flexion (WOF) before and after tendon repair using six different repair techniques; these include the two strand modified Kessler (1973), the lateral margin Becker (Becker and Davidoff, 1977), the sixstrand Savage (1985), the external nylon mesh sleeve (SilfverskiNd and Anderson, 1993), and the tendon splint (both internal and dorsal; Aoki et al, 1994). Work of flexion is a mechanical measurement of tendon gliding which was initially proposed by Lane et al (1976) and
MATERIAL AND METHODS Experimental design
33 FDP tendons from nine fresh-frozen human cadaver hands were used in this study. The hands were fixed to a specially designed wooden frame using Kirchner wires through radius, carpal bones, and metacarpals, immobilizing the wrist in the neutral position. The FDP tendons were surgically exposed and the tendon sheath was opened between the A2 and A4 pulleys in each finger. All intrinsic muscles and synovium attached to the tendons proximal to A1 pulley were removed. The carpal tunnel was opened and the FDP tendon to each finger was identified and dissected free, completely separating each tendon. All skin incisions were closed without tendon sheath repair. The hand with the wooden frame was mounted on a Scott Tensile Testing Machine and a 25 g counterweight was attached to the finger distally to allow full finger extension. The work of flexion (see below) of each finger was then measured as the baseline control value. The hand was maintained in the test frame during the subsequent surgical procedures. The skin incision of each finger was opened and the profundus tendons again exposed between the A2 and A4 pulleys. Sharp lacerations were made in zone 2 and the tendons were repaired under magnification using one of the following techniques (Fig 1): modified Kessler (1973) (n=5); (2) Becker and Davidoff (1977) (n=5); Savage (1985; n =6); external mesh sleeve (Silfverski61d and Anderson, 1993; n=5); (5) internal tendon splint (Aoki et al, 1994; n = 6); and dorsal tendon splint (Aoki
N o benefits in any form have been or will be received from a commercial party related directly or indirectly to the subject of this article.
310
WORK
OF
FLEXION
AFTER
TENDON
REPAIR
311
Measurement o f work o f flexion
Modified Kessler
(
Savage
/
Mesh Sleeve Internal Tendon Splint
....... ,o
0
-~.x--.-:~ ×. ~
0
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Dorsal Tendon Splint Fig 1
Modified Kessler technique: A grasping suture with 4/0 Ethibond in which one knot is located outside tendon laceration site; there is a two-strand suture across the repair site. Becker technique: A beveled suture using 6/0 Prolene. Running sutures are placed along each lateral margin of the tendon; there are four strands and two knots located outside the tendon repair site. Savage technique: Using 4/0 Ethibond, three individual interrupted sutures are placed with two knots proximal to the tendon repair site and one knot distal. This is thus a six-strand suture. Each core suture has three grasps on each tendon end and a 6/0 Prolene epitenon suture is placed circumferentially. External mesh sleeve technique: A woven polyester material with 12 mm lengths, 0.23 mm thickness is used (Mersilene mesh, Ethicon Inc.; Silfverski61d and Anderson, 1993). The sleeve is rolled around the lacerated tendon ends to fix the size of each profundus tendon and fixed to the proximal and distal tendons using 6/0 Prolene cross stitch epitenon sutures. Internal tendon splint technique: A 1 cm horizontal slit is made transversely in each tendon end proximal and distal to the laceration site. A 5 x 18 x0.22mm Dacron splint is placed into this slit. Longitudinal sutures (4/0 Ethibond) placed along each lateral margin of the tendon close the 1 cm slit and incorporate the splint into the repair site. A 6/0 Prolene epitenon suture is placed circumferentially. Dorsal tendon splint technique: A two-strand Savage type core suture (4/0 Ethibond) is placed volarly aligning both tendon ends. A 5 x 18 x 0.22 mm Dacron splint is placed on the dorsal surface of tendon across laceration site and sutured to the tendon along each lateral margin. A 6/0 Prolene epitenon suture is placed circumferentially.
The specimens were m o u n t e d on a Scott Tensile Testing Machine (model JXL 101, Scott Testers, Inc., Providence, R I , U S A ) . T h e p r o x i m a l ends o f the F D P t e n d o n s were secured in t e n d o n clamps. A 25 g c o u n t e r weight was a t t a c h e d to the finger distally to allow full finger extension. T h e o v e r h e a d crossbar, secured to the c l a m p a t t a c h e d to the F D P t e n d o n , was a d v a n c e d at the rate o f 50 c m / m i n , which s i m u l a t e d active finger motion. A force versus t e n d o n excursion curve was p l o t t e d o n an X - Y c h a r t r e c o r d e r , r e c o r d i n g the entire excursion f r o m full extension until the fingertip t o u c h e d to the palm. W o r k o f flexion was c a l c u l a t e d as the a r e a u n d e r the force-excursion curve b y c o m p u t e r analysis a n d r e c o r d e d as k i l o g r a m f o r c e - m e t e r ( k g fm). This value reflects the b i o m e c h a n i c a l w o r k t h a t t e n d o n does d u r i n g finger flexion. T h e f o r c e - t e n d o n excursion curves o f all fingers showed a similar p a t t e r n a n d are quite r e p r o d u c i b l e d u r i n g r e p e a t e d trials ( F i g 3). T h e curve initially s h o w e d a g r a d u a l elevation as finger flexion was initiated, then reached p l a t e a u value t h r o u g h o u t m o s t o f the m i d - r a n g e o f finger flexion, a n d i n c r e a s e d in a l o g a r i t h m i c m a n n e r at t e r m i n a l flexion ( F i g 2). O n e o f the difficulties in using w o r k o f flexion m e a s u r e m e n t s in p r e v i o u s experim e n t s has been d e t e r m i n i n g when the e n d - p o i n t o f useful finger flexion h a s b e e n reached. I f one continues to pull on the t e n d o n after the finger touches the p a l m , the force continues to increase until the t e n d o n ruptures. In o r d e r to s t a n d a r d i z e w o r k o f flexion m e a s u r e m e n t s between specimen to the next, a specific r a n g e o f t e n d o n excursion over w h i c h w o r k o f flexion was m e a s u r e d was defined. O n the baseline ( c o n t r o l ) w o r k o f flexion m e a s u r e m e n t s , we d e s i g n a t e d the t e n d o n excursion f r o m when the finger first b e g a n to flex until the p o i n t when the force m e a s u r e d was twice (2 x ) the p l a t e a u value
AreaUnderCuwe (Work of F~x~n) U ~ III111111 [ill]llll ~ - ~ @ @ ~ t}t t I I I t I I I I Illlilllllllllllll r l I I t l I I I
et al, 1994; n = 6 ) . A 4/0 b r a i d e d p o l y e s t e r core suture ( E t h i b o n d ) a n d a 6/0 P r o l e n e circumferential e p i t e n o n suture were used for the Kessler a n d Savage techniques a n d to secure the t e n d o n splints. A 6/0 P r o l e n e suture was used for the Becker a n d D a v i d o f f (1977) m e t h o d as originally described, a n d also for a t t a c h i n g the external m e s h sleeve to the t e n d o n (Silfverski61d a n d A n d e r s o n , 1993). A l l skin incisions were closed w i t h o u t t e n d o n s h e a t h repair. A f t e r repair, the h a n d w i t h w o o d e n frame was r e m o u n t e d o n a Scott tensile testing m a c h i n e a n d the w o r k o f flexion o f each finger was o b t a i n e d a n d c o m p a r e d to the baseline values.
11 II II il
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I I t I2,.'h'~%4/VXA/F/A/VF/AAIVYXA/VYXXAAAA/l/tal I-.~t~'~A/A/VZ/VYXA/YAA/VYZAA/VYXA/VVVZAAAAA/~I
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Four force-tendon excursion curves were recorded on both pre-operative and post-operative conditions. The measured area under the curve represents the work of flexion. The average of values for each finger was determined. To standardize the tendon excursion for each finger, we designated the tendon excursion from when the finger first began to flex until the point when the force measured was twice the plateau value across the mid-range of finger flexion as the standard excursion.
T H E J O U R N A L OF H A N D SURGERY VOL. 20B No. 3 J U N E 1995
312
No visible trapping of sutured tendon in the proximal pulley was found on both Savage and internal/dorsal tendon splints during repetitive tendon gliding. However, there were apparent trappings of sutured tendons with external mesh sleeve technique as they passed through the proximal pulleys, but this did not limit excursion.
60-
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Kessler
Beeker
Savage
i
Mesh
Int. Splint
Dot. Sprint
Type of Suture
Fig 3
This showsthe increasein workof flexionwithvarioussuture methods. Savage vs Kessler, Becket, mesh sleeve, NS, NS, P<0.0057; internal splint vs Kessler, Becker, Savage, mesh sleeve,P<0.0017, P<0.0295, NS, P<0.0296; dorsal splintvs Kessler, Becker, Savage, mesh sleeve, P<0.0477, NS, NS, P < 0.0274.
than the tendon excursion (Fig 2). This sion was again identified on the repaired To determine the increase in the work to the suture repair of the tendon, we control and post-repair values using the mula:
defined excurspecimens. of flexion due compared the following for-
Post-repair W O F - Control WOF x 100 Control WOF This value can be considered as the increased mechanical drag caused by the tendon repair going through the fibro-osseous pulley system for each group. The average values were calculated and compared with each other using Student's t-test. RESULTS The increases in work of flexion values for each suture group are summarized in Figure 3. The average increase in work of flexion is lowest for the Kessler (4.8%) and Becker (6.5%), and the increase is intermediate for the Savage (10.9%), dorsal tendon splint (16.2%) and internal tendon splint (19.3%). It is greatest for the nylon mesh sleeve at 44.3% increase. There are statistically significant difference in the work of flexion between internal/dorsal tendon splint and Kessler suture techniques (P<0.0177; P<0.0477), but no significant difference is found between the Becker and dorsal tendon splint technique. There is also no significant difference between Kessler and Savage, and between Savage and both tendon splint suture techniques. The most notable feature of our data is that the increased work of flexion value of the external mesh sleeve repair technique is significantly greater than all of the other suture techniques (P< 0.00296 or less).
DISCUSSION The strength of a flexor tendon repair is directly related to the number of strands of suture which cross the repair site, the six-strand Savage technique being the strongest reported (Savage, 1985). Comparable repair site strength has also been obtained using an external mesh sleeve (Silfverski61d and Anderson, 1993) or tendon splint (Aoki et al, 1994). The tensile strength of the repair using the six-strand Savage, external mesh sleeve, and tendon splint in cadaver testing is greater than 6 kg force. Theoretically, this should allow early active tendon motion post-operatively (Schuind et al, 1992), thus potentially decreasing the likelihood of adhesion formation. However, these techniques all increase the amount of material at the repair site, probably increasing the bulk of the repair and the resistance to tendon gliding. The purpose of this study was to determine the relationship between the additional suture material of these newer techniques at the repair site and increased resistance to tendon gliding as measured by work of flexion. Most previous reports of new suture techniques have considered only the increased effect on tensile strength (Lee, 1990; Robertson and A1-Qattan, 1992; Silfverski61d and Anderson, 1993; Aoki et al, 1994). Although this is important, it is also essential to consider their effect on the resistance to tendon gliding. In this study we found increased resistance to tendon gliding after repair for all techniques tested. The Kessler increased 4%, the Becker 6%, the Savage 11%, the tendon splint 16% to 19%, and the mesh sleeve 44%. The increased "resistance" within the sheath was directly proportional to the amount of material used. Clinically, one would like to use a suture technique which has sufficient tensile strength to allow active motion, yet is not so bulky at the repair site as to significantly interfere with tendon excursion. Of the methods we tested, the Savage and tendon splint techniques provide initial tensile strength (8.1 to 8.4kgf; Aoki et al, 1994), yet increase resistance to gliding minimally by only 10 to 20%. Although the mesh sleeve also provides good tensile strength (10.3kgf; Silfverski61d and Anderson, 1993), the resistance to tendon gliding resulting from the external nylon mesh is significantly greater. It is important to note that this cadaver study did not consider the soft tissue swelling, oedema, and other factors associated with the healing process, which can also contribute to increased resistance to tendon gliding
WORK OF FLEXION AFTER TENDON REPAIR
(Peterson et al, 1986a). More complex repairs require more surgical manipulation of the tendon, which may also lead to more post-operative tendon oedema, thereby increasing the work of flexion in the healing period. Additional in vivo studies in experimental animals will be needed to address these questions. Acknowledgement This study has been supported in part by grant #15953 from the Shriner's Hospital for Crippled Children.
References AOKI, M., MANSKE, P. R., PRUITT, D. L. and LARSON, B. J. (1994). Tendon repair using flexor tendon splints: An experimental study. Journal of Hand Surgery, 19A: 6: 984-991. BECKER, H. and DAVIDOFF, M. (1977). Eliminating the gap in flexor tendon surgery: A new method of suture. The Hand, 9: 3:306-311. BUNNELL, S. (1940). Primary repair of severed tendons: The use of stainless steel wire. American Journal of Surgery, 47:502 516. KESSLER, 1. (1973). The "grasping" technique for tendon repair. The Hand, 5: 3:253 255. KETCHUM, L. D., MARTIN, N. L. and KAPPEL, D. A. (1977). Experimental evaluation of factors affecting the strength of tendon repairs. Plastic and Reconstructive Surgery, 59: 5: 708-719. LANE, J. M., BLACK, J. and BORA, F. W. (1976). Gliding function following flexor-tendon injury. Journal of Bone and Joint Surgery, 58A: 7:985 990. LEE, H. (1990). Double loop locking suture: A technique of tendon repair for early active mobilization. Journal of Hand Surgery, 15A: 6: 945-952.
313 NOGUCHI, M., SEILER, J. G., GELBERMAN, R. H., SOFRANKO, R. A. and WOO, S. L-Y. (1993). In vitro biomechanical analysis of suture methods for flexor tendon repair. Journal of Orthopaedic Research, 11: 4: 603-611. PETERSON, W. W., MANSKE, P. R., KAIN, C. C. and LESKER, P. A. (1986a). Effect of flexor sheath integrity on tendon gliding: A biomechanical and histologic study. Journal of Orthopaedic Research, 4: 4: 458-465. PETERSON, W. W., MANSKE, P. R., BOLLINGER, B. A., LESKER, P. A. and MCCARTHY, J. A. (1986b). Effect of pt~ey excision on flexor tendon biomechanics. Journal of Orthopaedic Research, 4: 1: 96-101. PETERSON,,W. W., MANSKE, P. R., DUNLAP, J , HORWITZ, D. S. and K A H N / B . (1990). Effect of various methods of restoring flexor sheath integrity on the formation of adhesions after tendon injury. Journal of Hand Surgery, 15A: 1: 48-56. ROBERTSON, G. A. and AL-QATTAN, M. M. (1992). A biomechanical analysis of a new interlock suture technique for flexor tendon repair. Journal of Hand Surgery, 17B: 1: 92-93. SAVAGE, R. (1985). In vitro studies of a new method of flexor tendon repair. Journal of Hand Surgery, 10B: 2: 135-141. SCHUIND, F., GARCIA-ELIAS, M., COONEY, W. P. and AN, K-N. (1992). Flexor tendon forces: In vivo measurements. Journal of Hand Surgery, 17A: 2: 291-298. SILFVERSKI(}LD, K. L. and ANDERSSON, C. H. (1993). Two new methods of tendon repair: An in vitro evaluation of tensile strength and gap formation. Journal of Hand Surgery, 18A: 1: 58-65. TSUGE, K., IKUTA, Y. and MATSUISHI, Y. (1975). Intra-tendinous tendon suture in the hand: A new technique. The Hand, 7: 3: 250-255.
Accepted: 21 September 1994 Paul R. Manske, MD, Department of Orthopaedic Surgery, Washington University School of Medicine, 11300West Pavilion, One Barnes Hospital Plaza, St Louis, MO 63110, USA. © 1995 The British Society for Surgery of the Hand
From the Department of Orthopaedic Surgery, Washington UniversitySchool of Medicine, St Louis, USA After flexor tendon repair there is often increased resistance to tendon gliding at the repair site, which is greater for techniques using increased suture strands or suture material. This increased "friction" may be measured as the "work of flexion" in the laboratory setting. Tendon repairs performed in zone 2 in human cadaver hands using the two strand Kessler, the lateral Becker, the six strand Savage, internal and dorsal tendon splint, or the external mesh sleeve techniques, had "work of flexion" measurements made both before and after the laceration and repair. The average increase in work of flexion was 4.8% for Kessler; 6.5% for Becker; 10.9% for Savage; 19.3% for the internal tendon splint, 16.2% for the dorsal tendon splint and 44.3% for the external mesh sleeve. The work of flexion was found to increase in direct proportion to the amount of suture material at the repair site.
Journal of Hand Surgery (British and European Volume, 1995) 20B: 3:310-313 subsequently used by other authors (Peterson et al, 1986 a and b; 1990); it represents the summation of forces necessary to move the tendon along its excursion distance.
In order to increase the strength of flexor tendon repair and potentially allow early active motion, several authors have recommended alternative repair techniques to the standard methods (Bunnell, 1940; Kessler, 1973; Tsuge et al, 1975) which crosses the repair site with two strands of suture; most of the newer techniques use increased amounts of suture material. Becker and Davidoff (1977) placed running sutures along the two lateral margins of the tendon. Several authors have advocated increasing the number of suture strands to four (Ketchum et al, 1977; Lee, 1990; Robertson and A1-Qattan, 1992), and Savage (1985) has proposed a six-strand repair. Silfverski61d and Anderson (1993) supported the repair site with external nylon mesh sleeve. Recently, we incorporated a dacron tendon splint into the repair site which was placed either internally within the tendon substance or externally on the dorsal surface (Aoki et al, 1994). The Savage, external nylon mesh sleeve, and tendon splints are the strongest reported repair techniques, increasing the tensile strength of the repair site from 3.1 to 3.3 times that of the two strand Kessler technique in various cadaver studies. However, Noguchi et al (1993) raised concern about the effect of the increased suture material on the gliding properties of the tendon following repair. The purpose of this study was to measure the mechanical work of flexion (WOF) before and after tendon repair using six different repair techniques; these include the two strand modified Kessler (1973), the lateral margin Becker (Becker and Davidoff, 1977), the sixstrand Savage (1985), the external nylon mesh sleeve (SilfverskiNd and Anderson, 1993), and the tendon splint (both internal and dorsal; Aoki et al, 1994). Work of flexion is a mechanical measurement of tendon gliding which was initially proposed by Lane et al (1976) and
MATERIAL AND METHODS Experimental design
33 FDP tendons from nine fresh-frozen human cadaver hands were used in this study. The hands were fixed to a specially designed wooden frame using Kirchner wires through radius, carpal bones, and metacarpals, immobilizing the wrist in the neutral position. The FDP tendons were surgically exposed and the tendon sheath was opened between the A2 and A4 pulleys in each finger. All intrinsic muscles and synovium attached to the tendons proximal to A1 pulley were removed. The carpal tunnel was opened and the FDP tendon to each finger was identified and dissected free, completely separating each tendon. All skin incisions were closed without tendon sheath repair. The hand with the wooden frame was mounted on a Scott Tensile Testing Machine and a 25 g counterweight was attached to the finger distally to allow full finger extension. The work of flexion (see below) of each finger was then measured as the baseline control value. The hand was maintained in the test frame during the subsequent surgical procedures. The skin incision of each finger was opened and the profundus tendons again exposed between the A2 and A4 pulleys. Sharp lacerations were made in zone 2 and the tendons were repaired under magnification using one of the following techniques (Fig 1): modified Kessler (1973) (n=5); (2) Becker and Davidoff (1977) (n=5); Savage (1985; n =6); external mesh sleeve (Silfverski61d and Anderson, 1993; n=5); (5) internal tendon splint (Aoki et al, 1994; n = 6); and dorsal tendon splint (Aoki
N o benefits in any form have been or will be received from a commercial party related directly or indirectly to the subject of this article.
310
WORK
OF
FLEXION
AFTER
TENDON
REPAIR
311
Measurement o f work o f flexion
Modified Kessler
(
Savage
/
Mesh Sleeve Internal Tendon Splint
....... ,o
0
-~.x--.-:~ ×. ~
0
,,~~,y_ """-""'
0
rv
Dorsal Tendon Splint Fig 1
Modified Kessler technique: A grasping suture with 4/0 Ethibond in which one knot is located outside tendon laceration site; there is a two-strand suture across the repair site. Becker technique: A beveled suture using 6/0 Prolene. Running sutures are placed along each lateral margin of the tendon; there are four strands and two knots located outside the tendon repair site. Savage technique: Using 4/0 Ethibond, three individual interrupted sutures are placed with two knots proximal to the tendon repair site and one knot distal. This is thus a six-strand suture. Each core suture has three grasps on each tendon end and a 6/0 Prolene epitenon suture is placed circumferentially. External mesh sleeve technique: A woven polyester material with 12 mm lengths, 0.23 mm thickness is used (Mersilene mesh, Ethicon Inc.; Silfverski61d and Anderson, 1993). The sleeve is rolled around the lacerated tendon ends to fix the size of each profundus tendon and fixed to the proximal and distal tendons using 6/0 Prolene cross stitch epitenon sutures. Internal tendon splint technique: A 1 cm horizontal slit is made transversely in each tendon end proximal and distal to the laceration site. A 5 x 18 x0.22mm Dacron splint is placed into this slit. Longitudinal sutures (4/0 Ethibond) placed along each lateral margin of the tendon close the 1 cm slit and incorporate the splint into the repair site. A 6/0 Prolene epitenon suture is placed circumferentially. Dorsal tendon splint technique: A two-strand Savage type core suture (4/0 Ethibond) is placed volarly aligning both tendon ends. A 5 x 18 x 0.22 mm Dacron splint is placed on the dorsal surface of tendon across laceration site and sutured to the tendon along each lateral margin. A 6/0 Prolene epitenon suture is placed circumferentially.
The specimens were m o u n t e d on a Scott Tensile Testing Machine (model JXL 101, Scott Testers, Inc., Providence, R I , U S A ) . T h e p r o x i m a l ends o f the F D P t e n d o n s were secured in t e n d o n clamps. A 25 g c o u n t e r weight was a t t a c h e d to the finger distally to allow full finger extension. T h e o v e r h e a d crossbar, secured to the c l a m p a t t a c h e d to the F D P t e n d o n , was a d v a n c e d at the rate o f 50 c m / m i n , which s i m u l a t e d active finger motion. A force versus t e n d o n excursion curve was p l o t t e d o n an X - Y c h a r t r e c o r d e r , r e c o r d i n g the entire excursion f r o m full extension until the fingertip t o u c h e d to the palm. W o r k o f flexion was c a l c u l a t e d as the a r e a u n d e r the force-excursion curve b y c o m p u t e r analysis a n d r e c o r d e d as k i l o g r a m f o r c e - m e t e r ( k g fm). This value reflects the b i o m e c h a n i c a l w o r k t h a t t e n d o n does d u r i n g finger flexion. T h e f o r c e - t e n d o n excursion curves o f all fingers showed a similar p a t t e r n a n d are quite r e p r o d u c i b l e d u r i n g r e p e a t e d trials ( F i g 3). T h e curve initially s h o w e d a g r a d u a l elevation as finger flexion was initiated, then reached p l a t e a u value t h r o u g h o u t m o s t o f the m i d - r a n g e o f finger flexion, a n d i n c r e a s e d in a l o g a r i t h m i c m a n n e r at t e r m i n a l flexion ( F i g 2). O n e o f the difficulties in using w o r k o f flexion m e a s u r e m e n t s in p r e v i o u s experim e n t s has been d e t e r m i n i n g when the e n d - p o i n t o f useful finger flexion h a s b e e n reached. I f one continues to pull on the t e n d o n after the finger touches the p a l m , the force continues to increase until the t e n d o n ruptures. In o r d e r to s t a n d a r d i z e w o r k o f flexion m e a s u r e m e n t s between specimen to the next, a specific r a n g e o f t e n d o n excursion over w h i c h w o r k o f flexion was m e a s u r e d was defined. O n the baseline ( c o n t r o l ) w o r k o f flexion m e a s u r e m e n t s , we d e s i g n a t e d the t e n d o n excursion f r o m when the finger first b e g a n to flex until the p o i n t when the force m e a s u r e d was twice (2 x ) the p l a t e a u value
AreaUnderCuwe (Work of F~x~n) U ~ III111111 [ill]llll ~ - ~ @ @ ~ t}t t I I I t I I I I Illlilllllllllllll r l I I t l I I I
et al, 1994; n = 6 ) . A 4/0 b r a i d e d p o l y e s t e r core suture ( E t h i b o n d ) a n d a 6/0 P r o l e n e circumferential e p i t e n o n suture were used for the Kessler a n d Savage techniques a n d to secure the t e n d o n splints. A 6/0 P r o l e n e suture was used for the Becker a n d D a v i d o f f (1977) m e t h o d as originally described, a n d also for a t t a c h i n g the external m e s h sleeve to the t e n d o n (Silfverski61d a n d A n d e r s o n , 1993). A l l skin incisions were closed w i t h o u t t e n d o n s h e a t h repair. A f t e r repair, the h a n d w i t h w o o d e n frame was r e m o u n t e d o n a Scott tensile testing m a c h i n e a n d the w o r k o f flexion o f each finger was o b t a i n e d a n d c o m p a r e d to the baseline values.
11 II II il
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Four force-tendon excursion curves were recorded on both pre-operative and post-operative conditions. The measured area under the curve represents the work of flexion. The average of values for each finger was determined. To standardize the tendon excursion for each finger, we designated the tendon excursion from when the finger first began to flex until the point when the force measured was twice the plateau value across the mid-range of finger flexion as the standard excursion.
T H E J O U R N A L OF H A N D SURGERY VOL. 20B No. 3 J U N E 1995
312
No visible trapping of sutured tendon in the proximal pulley was found on both Savage and internal/dorsal tendon splints during repetitive tendon gliding. However, there were apparent trappings of sutured tendons with external mesh sleeve technique as they passed through the proximal pulleys, but this did not limit excursion.
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Kessler
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i
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Int. Splint
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Fig 3
This showsthe increasein workof flexionwithvarioussuture methods. Savage vs Kessler, Becket, mesh sleeve, NS, NS, P<0.0057; internal splint vs Kessler, Becker, Savage, mesh sleeve,P<0.0017, P<0.0295, NS, P<0.0296; dorsal splintvs Kessler, Becker, Savage, mesh sleeve, P<0.0477, NS, NS, P < 0.0274.
than the tendon excursion (Fig 2). This sion was again identified on the repaired To determine the increase in the work to the suture repair of the tendon, we control and post-repair values using the mula:
defined excurspecimens. of flexion due compared the following for-
Post-repair W O F - Control WOF x 100 Control WOF This value can be considered as the increased mechanical drag caused by the tendon repair going through the fibro-osseous pulley system for each group. The average values were calculated and compared with each other using Student's t-test. RESULTS The increases in work of flexion values for each suture group are summarized in Figure 3. The average increase in work of flexion is lowest for the Kessler (4.8%) and Becker (6.5%), and the increase is intermediate for the Savage (10.9%), dorsal tendon splint (16.2%) and internal tendon splint (19.3%). It is greatest for the nylon mesh sleeve at 44.3% increase. There are statistically significant difference in the work of flexion between internal/dorsal tendon splint and Kessler suture techniques (P<0.0177; P<0.0477), but no significant difference is found between the Becker and dorsal tendon splint technique. There is also no significant difference between Kessler and Savage, and between Savage and both tendon splint suture techniques. The most notable feature of our data is that the increased work of flexion value of the external mesh sleeve repair technique is significantly greater than all of the other suture techniques (P< 0.00296 or less).
DISCUSSION The strength of a flexor tendon repair is directly related to the number of strands of suture which cross the repair site, the six-strand Savage technique being the strongest reported (Savage, 1985). Comparable repair site strength has also been obtained using an external mesh sleeve (Silfverski61d and Anderson, 1993) or tendon splint (Aoki et al, 1994). The tensile strength of the repair using the six-strand Savage, external mesh sleeve, and tendon splint in cadaver testing is greater than 6 kg force. Theoretically, this should allow early active tendon motion post-operatively (Schuind et al, 1992), thus potentially decreasing the likelihood of adhesion formation. However, these techniques all increase the amount of material at the repair site, probably increasing the bulk of the repair and the resistance to tendon gliding. The purpose of this study was to determine the relationship between the additional suture material of these newer techniques at the repair site and increased resistance to tendon gliding as measured by work of flexion. Most previous reports of new suture techniques have considered only the increased effect on tensile strength (Lee, 1990; Robertson and A1-Qattan, 1992; Silfverski61d and Anderson, 1993; Aoki et al, 1994). Although this is important, it is also essential to consider their effect on the resistance to tendon gliding. In this study we found increased resistance to tendon gliding after repair for all techniques tested. The Kessler increased 4%, the Becker 6%, the Savage 11%, the tendon splint 16% to 19%, and the mesh sleeve 44%. The increased "resistance" within the sheath was directly proportional to the amount of material used. Clinically, one would like to use a suture technique which has sufficient tensile strength to allow active motion, yet is not so bulky at the repair site as to significantly interfere with tendon excursion. Of the methods we tested, the Savage and tendon splint techniques provide initial tensile strength (8.1 to 8.4kgf; Aoki et al, 1994), yet increase resistance to gliding minimally by only 10 to 20%. Although the mesh sleeve also provides good tensile strength (10.3kgf; Silfverski61d and Anderson, 1993), the resistance to tendon gliding resulting from the external nylon mesh is significantly greater. It is important to note that this cadaver study did not consider the soft tissue swelling, oedema, and other factors associated with the healing process, which can also contribute to increased resistance to tendon gliding
WORK OF FLEXION AFTER TENDON REPAIR
(Peterson et al, 1986a). More complex repairs require more surgical manipulation of the tendon, which may also lead to more post-operative tendon oedema, thereby increasing the work of flexion in the healing period. Additional in vivo studies in experimental animals will be needed to address these questions. Acknowledgement This study has been supported in part by grant #15953 from the Shriner's Hospital for Crippled Children.
References AOKI, M., MANSKE, P. R., PRUITT, D. L. and LARSON, B. J. (1994). Tendon repair using flexor tendon splints: An experimental study. Journal of Hand Surgery, 19A: 6: 984-991. BECKER, H. and DAVIDOFF, M. (1977). Eliminating the gap in flexor tendon surgery: A new method of suture. The Hand, 9: 3:306-311. BUNNELL, S. (1940). Primary repair of severed tendons: The use of stainless steel wire. American Journal of Surgery, 47:502 516. KESSLER, 1. (1973). The "grasping" technique for tendon repair. The Hand, 5: 3:253 255. KETCHUM, L. D., MARTIN, N. L. and KAPPEL, D. A. (1977). Experimental evaluation of factors affecting the strength of tendon repairs. Plastic and Reconstructive Surgery, 59: 5: 708-719. LANE, J. M., BLACK, J. and BORA, F. W. (1976). Gliding function following flexor-tendon injury. Journal of Bone and Joint Surgery, 58A: 7:985 990. LEE, H. (1990). Double loop locking suture: A technique of tendon repair for early active mobilization. Journal of Hand Surgery, 15A: 6: 945-952.
313 NOGUCHI, M., SEILER, J. G., GELBERMAN, R. H., SOFRANKO, R. A. and WOO, S. L-Y. (1993). In vitro biomechanical analysis of suture methods for flexor tendon repair. Journal of Orthopaedic Research, 11: 4: 603-611. PETERSON, W. W., MANSKE, P. R., KAIN, C. C. and LESKER, P. A. (1986a). Effect of flexor sheath integrity on tendon gliding: A biomechanical and histologic study. Journal of Orthopaedic Research, 4: 4: 458-465. PETERSON, W. W., MANSKE, P. R., BOLLINGER, B. A., LESKER, P. A. and MCCARTHY, J. A. (1986b). Effect of pt~ey excision on flexor tendon biomechanics. Journal of Orthopaedic Research, 4: 1: 96-101. PETERSON,,W. W., MANSKE, P. R., DUNLAP, J , HORWITZ, D. S. and K A H N / B . (1990). Effect of various methods of restoring flexor sheath integrity on the formation of adhesions after tendon injury. Journal of Hand Surgery, 15A: 1: 48-56. ROBERTSON, G. A. and AL-QATTAN, M. M. (1992). A biomechanical analysis of a new interlock suture technique for flexor tendon repair. Journal of Hand Surgery, 17B: 1: 92-93. SAVAGE, R. (1985). In vitro studies of a new method of flexor tendon repair. Journal of Hand Surgery, 10B: 2: 135-141. SCHUIND, F., GARCIA-ELIAS, M., COONEY, W. P. and AN, K-N. (1992). Flexor tendon forces: In vivo measurements. Journal of Hand Surgery, 17A: 2: 291-298. SILFVERSKI(}LD, K. L. and ANDERSSON, C. H. (1993). Two new methods of tendon repair: An in vitro evaluation of tensile strength and gap formation. Journal of Hand Surgery, 18A: 1: 58-65. TSUGE, K., IKUTA, Y. and MATSUISHI, Y. (1975). Intra-tendinous tendon suture in the hand: A new technique. The Hand, 7: 3: 250-255.
Accepted: 21 September 1994 Paul R. Manske, MD, Department of Orthopaedic Surgery, Washington University School of Medicine, 11300West Pavilion, One Barnes Hospital Plaza, St Louis, MO 63110, USA. © 1995 The British Society for Surgery of the Hand