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Flexor Tendon Pulley V–Y Plasty: An alternative to Pulley Venting or Resection
ARTICLE IN PRESS FLEXOR TENDON PULLEY V–Y PLASTY: AN ALTERNATIVE TO PULLEY VENTING OR RESECTION E. DONA and W. R. WALSH From the Orthopaedic Research Laboratories, University of New South Wales, Prince of Wales Hospital, Sydney, Australia
Zone 2 flexor tendon repairs can require ‘‘venting’’ or partial resection of the A2 and/or A4 pulleys. We propose and biomechanically assess a technique used by the authors in which the A2 and A4 pulleys are divided and repaired using a V–Y plasty. Two groups of cadaveric fingers were used, one group for assessing the A2 pulley and the second for assessing the A4 pulley. Prepared fingers were mounted onto custom-made jigs, tested using a servohydraulic testing machine and assessed for load to failure. The loads obtained were 75N (SD ¼ 26N) and 234N (SD ¼ 73N) for the A4 and A2 pulleys, respectively. These loads are well in excess of those one would anticipate during a postoperative active mobilization protocol. Tendon pulley V–Y plasty creates a mechanically sound pulley and maintains sufficient cover of the underlying tendon. This technique provides access to perform a tendon repair and/or permits free tendon gliding post-repair, thus providing an attractive alternative to simply ‘‘venting’’, or resecting, an otherwise troublesome pulley. Journal of Hand Surgery (British and European Volume, 2006) 31B: 2: 133–137 Keywords: flexor tendon, repair, pulley, venting
Flexor tendon pulleys serve to maintain a constant relationship, or moment arm, between the flexor tendon and the joint axis. In doing so, they ensure maximum joint movement for any given amount of tendon excursion (Barton, 1969; Doyle and Blythe, 1974, 1975; Idler, 1985; Idler and Strickland, 1984; Lin et al., 1989; Peterson et al., 1986). Absence of the pulley system acts to increase the moment arm of the tendon with clinically apparent tendon bowstringing. The net effect is an increased amount of tendon excursion required to produce the same arc of motion, with a potentially decreased range of motion and power. The A2 and A4 pulleys are the strongest of the annular pulleys and are considered to be the most important (Bunnell, 1918; Doyle, 1988; Doyle and Blythe, 1974, 1975, 1989; Idler, 1985; Idler and Strickland, 1984; Lin et al., 1989, 1990; Manske and Lesker, 1977, 1983). Consequently, surgeons are careful to preserve their integrity during tendon repairs. Unfortunately, the pulley often restricts access to the tendon making it technically difficult to perform the repair (Kwai Ben and Elliot, 1998). They can also limit tendon excursion post-repair. As a result of this, surgeons have often been forced to partially or completely divide (‘‘vent’’) tendon pulleys (Kwai Ben and Elliot, 1998; Manske and Lesker, 1983; Strickland, 1986). It has been suggested that up to 75% resection of either of the A2 or A4 pulleys will provide ‘‘clinically acceptable’’ results (Mitsionis et al., 2000; Tomaino et al., 1998). This paper assesses V–Y plasty of flexor tendon pulleys as an alternative to venting or partial resection. This technique has been employed by the authors to gain adequate exposure to the flexor tendons and to allow unrestricted tendon gliding through the pulley after repair.
MATERIALS + METHODS Surgical technique The concept of V–Y plasty is not new to surgeons, although its application to tendon pulleys has not previously been described (Figs 1 and 2). V–Y plasty creates elongation of the tissue of interest with some small, but acceptable, narrowing. When this is applied to tendon pulleys, it creates increased length in the radial–ulnar axis, with shortening in the longitudinal axis. The end result is a pulley that has an increased circumference (Fig 3). Such a procedure can be performed for both the A2 and A4 pulleys. The A4 pulley requires a single V–Y plasty. However, because of its length, the A2 pulley requires two V–Y plasties side-by-side to increase the circumference along its whole length. In many clinical situations, only half of the A2 pulley requires an increase of circumference and a single V–Y plasty is sufficient. To maximize the benefit of the V–Y plasty, one needs to ensure that all three points of the ‘‘V’’ extend to the bony attachment of the pulley. The ‘‘V’’ is designed with each limb gently flared at the base and the apex of the V slightly rounded. This is done to increase the surface area of each of the tips of the three flaps created, thus maximising the suture purchase of each limb. After creating the ‘‘V’’, the clinical circumstances will dictate how far the apex of the ‘‘V’’ is advanced before repair. Generally, this would be several millimetres. If uncertain as to how far the apex needs to be advanced, a temporary holding stitch can be placed at the apex to create the vertical limb of the ‘‘Y’’. Once this has been performed, free gliding of the tendon beneath can be assessed. When satisfied with the length of the 133
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THE JOURNAL OF HAND SURGERY VOL. 31B No. 2 APRIL 2006
Fig 1 Diagrammatic illustrations of tendon pulley V–Y plasty. (a) A4 pulley showing the placement of the ‘‘V’’ incision; (b) closure in a ‘‘Y’’ fashion using a continuous suture. Note that the vertical limb of the Y does not require suturing.
vertical limb of the ‘‘Y’’, the pulley is formally repaired with a running 6/0 prolene suture. The vertical limb of the ‘‘Y’’ does not require suturing. Eighteen fingers, all ring, middle and index fingers, including the metacarpals, were harvested from six cadaveric hands. All palmar skin and subcutaneous tissues were excised. The tendon sheath was excised, preserving only the Al, A2 and A4 pulleys. Both the flexor digitorum profundus (FDP) and flexor digitorum superficialis (FDS) tendons were left intact. The fingers were randomly divided into two groups of nine for load to failure testing. Testing was performed for both the A2 and A4 pulleys after V–Y plasty to establish the force to failure. Failure of the pulley was defined as complete disruption of the V–Y plasty. A2 pulley The first group of fingers were used to assess the load to failure of A2 pulleys, each of which was enlarged with two V–Y plasties. Fingers were mounted on a custommade jig with the metacarpophalangeal joint (MCP) fixed at 901 and the proximal and distal interphalangeal (PIP and DIP) joints fixed in full extension (Fig 4). The FDP tendon was then gripped using non-slip custom grips, and pulled at a rate of 100 mm/minute. Testing was stopped when the A2 pulley failed. A4 pulley The second group of fingers were used to assess the load to failure in A4 pulleys, each of which was enlarged with a single V–Y plasty. Functional loading was performed differently to A2 testing. Fingers were mounted on a
Fig 2 Cadaveric specimens. (a) A4 pulley divided; (b) A4 pulley post V–Y plasty; (c) A2 pulley showing two side by side V–Y plasties.
custom-made jig with the MCP and PIP joints held in 451 flexion and the DIP joint in 301 of flexion (Fig 5). The FDP tendon was then gripped, using non-slip
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Fig 3 Cross-section of the A4 pulley showing the increase in circumference (broken line) generated by the V–Y plasty.
Fig 5 Testing of the A4 pulley. The digit is fixed in a clinically relevant position of flexion as shown. This increases the angle of the FDP tendon A4 pulley junction, thus increasing the perpendicular force acting on the pulley.
Fig 4 Testing of the A2 pulley. The digit is fixed with the MCP joint at 901 and the PIP and DIP joints fully extended. The tendon is pulled at a rate of 100 mm/minute. Note that the length of the A2 pulley means that it requires two side-by-side V–Y plasties.
custom grips, and pulled at a rate of 100 mm/minute. Testing was stopped when the A4 pulley failed.
RESULTS No specimen failed by FDP tendon avulsion from the distal phalanx. Failure in all tests was by the pulley under test giving way, with all pulleys failing by a
combination of suture breakage and suture pullout from the pulleys. For the A2 pulleys, either the proximal and distal V–Y plasties would fail simultaneously, or one would fail immediately after the other with no definite pattern existing. The mean load to failure of the A2 pulleys was 234N (SD ¼ 73N; range ¼ 155–331N). The mean load to failure of the A4 pulleys was 76N (SD ¼ 26N; range ¼ 46–114N).
DISCUSSION Although surgeons acknowledge the importance of tendon pulleys, they can impede the satisfactory repair of flexor tendons. This occurs by limiting access to the point of tendon division and repair and/or preventing satisfactory gliding of the tendon following repair (Kwai Ben and Elliot, 1998). To this end, surgeons have had to
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resort to either ‘‘venting’’, or partially excising, tendon pulleys. Venting refers to the partial or complete longitudinal division of the pulley. Strickland (1986) described and illustrated the technique of pulley venting. A prospective study by Kwai Ben and Elliot, (1998) looked at the incidence of pulley venting necessary to perform the repair and allow a full passive range of motion of the repaired flexor tendon(s) when performing tendon repairs in zones 2A and 2B. Of the 126 digits in the study, they found that the A4 pulley was vented in 56% of cases, with a mean length of pulley venting of 52%. They also found that 14 of the 126 digits (11%) required complete division of the A4 pulley to achieve these aims. Only 8% of the digits in this study had the A2 pulley partially vented. This was because the study did not include many tendons divided deep to this pulley, zone 2 injuries this far proximally being much less common than those more distally in the zone. Pulley resection is another option available to surgeons. A number of studies have looked at the decrease in total angular rotation and residual pulley strength after partial A2 and A4 pulley excision (Mitsionis et al., 1999, 2000; Tomaino et al., 1998). Mitsionis et al. (1999, 2000) assessed the effect of 75% excision of both the distal A2 pulley and proximal A4 pulley. These authors suggested that such radical excision still resulted in ‘‘clinically acceptable’’ decreases in total angular rotation and residual pulley strength. Other forms of pulley plasty have been advocated. Kapandji (1983) described a technique that was revisited in a more recent study (Paillard et al., 2002). It involves making a single oblique incision from one corner of the pulley to the contralateral corner, thus creating two triangular flaps which were then sutured together. Previous studies addressing the strength of tendon pulleys have employed direct pull-off testing methods (Manske and Lesker, 1977). This involves placing a loop of tendon or metal hook through the pulley and pulling in a perpendicular direction to the phalanx. Although such testing provides data on the overall strength of pulleys, the relevance of such data is questionable given that tendon pulleys are never subjected to that mechanism of distraction in vivo. Mitsionis et al. (2000) acknowledged this and employed both direct pull-off and ‘‘functional loading’’ testing protocols. For our A2 testing, we used the functional loading protocol used by Mitsionis et al. (2000). With this testing system, the A1 pulley buffers the vast majority of the forces acting through the flexor tendons. In clinical practice, if one were to employ an A2 V–Y pulley plasty, then the A1 pulley must be preserved. This is only a real consideration in those cases where one has to retrieve the tendon from the palm and, possibly, divide the A1 pulley in the process. For this reason, we felt that it was clinically correct to leave the A1 pulley intact for testing purposes. Unlike the A2 pulley, the A4 pulley does not have a significant annular pulley immediately adjacent to it to
THE JOURNAL OF HAND SURGERY VOL. 31B No. 2 APRIL 2006
buffer the flexor tendon forces. With this in mind, we tested the A4 pulleys using a position of flexion at all the joints. By doing this, the angle between the FDP tendon and pulley is increased, thus increasing the perpendicular force acting on the pulley. Although this should, theoretically, cause the pulleys to fail at lower loads, it does represent a clinically relevant position. Schuind et al. (1992) showed that the mean force acting along the FDP during active unresisted motion was 19N, with a maximum-recorded value of 29N. They also demonstrated that the mean forces acting along the FDP during grasp and tip pinch were 40N and 83N, respectively. Our study found the mean load to failure of the A2 pulley to be 234N (SD ¼ 73) and the A4 pulley to be 75N (SD ¼ 26), with the lowest value obtained being 46N. Additionally, the loads to failure in our study are likely to be an underestimate of those that would be obtained in vivo. This is because their biomechanical assessment was conducted without the support provided by the palmar soft tissues and any residual sheath, each of which would add to the failure load of the pulley. Despite this, the results obtained are well in excess of the forces acting along the FDP tendon during active unresisted motion, because of the buffering effect of the A1 pulley. As stated previously, this represents the likely situation that surgeons will encounter and therefore, we feel that this testing method and the results obtained are clinically relevant. Our findings would suggest that V–Y plasty of flexor tendon pulleys, protected by the presence of the other intact pulleys, would not compromise flexor tendon repairs undergoing active mobilization protocols after tendon repair. In conclusion, pulley V–Y plasty is a technique that can be used in flexor tendon repairs as it creates a mechanically sound pulley. This technique has been employed by the authors on a number of clinical occasions without the need to alter normal postoperative active mobilization protocols. However, we do not advocate its use as a technique to be routinely employed in flexor tendon repairs, but simply as an alternative to venting, or resecting, an otherwise troublesome flexor tendon pulley.
References Barton NJ (1969). Experimental study of optimal location of flexor tendon pulleys. Plastic and Reconstructive Surgery, 43: 125–129. Bunnell S (1918). Repair of tendons in the fingers and description of two new instruments. Surgery Gynecology and Obstetrics, 26: 103–110. Doyle JR (1988). Anatomy of the finger flexor sheath and pulley system. Journal of Hand Surgery, 13A: 473–484. Doyle JR, Blythe W (1974). Proceedings of the American Society for Surgery of the Hand – macroscopic and functional anatomy of the flexor sheath. Journal of Bone and Joint Surgery, 56A: 1094. Doyle JR, Blythe W. The finger flexor tendon sheath and pulleys: anatomy and reconstruction. In: AAOS symposium on tendon surgery in the hand. St Louis, CV Mosby Co., 1975: 81–87.
ARTICLE IN PRESS FLEXOR TENDON PULLEY V–Y PLASTY
Doyle JR, Blythe WF (1989). Anatomy of the flexor tendon sheath and pulley system: a current review. Journal of Hand Surgery, 14A: 349–351. Idler RS (1985). Anatomy and biomechanics of the digital flexor tendons. Hand Clinics, 1: 3–12. Idler RS, Strickland JW (1984). Proceedings of the American Society for Surgery of the Hand – effects of pulley resection on the biomechanics of the PIP joint. Journal of Hand Surgery, 9A: 595. Kapanji IA (1983). Reconstructive augmentation of the metacarpal tendons. Annales de Chirurgie de la Main, 2: 281–282. Kwai Ben I, Elliot D (1998). ‘‘Venting’’ or partial lateral release of the A2 and A4 pulleys after repair of zone 2 flexor tendon injuries. Journal of Hand Surgery, 23B: 649–654. Lin GT, Amadio P, An KN, Cooney WP (1989). Functional anatomy of the human digital flexor pulley system. Journal of Hand Surgery, 14A: 949–956. Lin GT, Cooney WP, Amadio P, An KN (1990). Mechanical properties of human pulleys. Journal of Hand Surgery, 15B: 429–434. Manske PR, Lesker PA (1977). Strength of human pulleys. Hand, 9: 147–152. Manske PR, Lesker PA (1983). Palmar aponeurosis pulley. Journal of Hand Surgery, 8A: 259–263. Mitsionis G, Bastidas JA, Grewal R, Pfaeffle HJ, Fischer KJ, Tomaino MM (1999). Feasibility of partial A2 and A4 pulley excision: effect on finger flexor tendon biomechanics. Journal of Hand Surgery, 24B: 310–314. Mitsionis G, Fischer KJ, Bastidas JA, Grewal R, Pfaeffle HJ, Tomaino MM (2000). Feasibility of partial A2 and A4 pulley
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excision: residual pulley strength. Journal of Hand Surgery, 25B: 90–94. Paillard PJ, Amadio PC, Zhao C, Zobitz ME, An KN (2002). Pulley plasty versus resection of one slip of the flexor digitorum superficialis after repair of both flexor tendons in zone II – a biomechanical study. Journal of Bone and Joint Surgery, 84A: 2039–2045. Peterson WW, Manske PR, Bollinger BA, Lesker PA, McCarthy JA (1986). Effect of pulley excision on flexor tendon biomechanics. Journal of Orthopaedic Research, 4: 96–101. Schuind F, Garcia-Elias M, Cooney WP, An KN (1992). Flexor tendon forces: in vivo measurements. Journal of Hand Surgery, 17A: 291–298. Strickland JW (1986). Flexor tendon injuries: Part 2 – Flexor tendon repair. Orthopaedic Review, 15: 49–69. Tomaino M, Mitsionis G, Basitidas J, Grewal R, Pfaeffle J (1998). The effect of partial excision of the A2 and A4 pulleys on the biomechanics of finger flexion. Journal of Hand Surgery, 23B: 50–52. Received: 10 April 2005 Accepted after revision: 28 September 2005 Dr Eddy Dona, Orthopaedic Research Laboratories, University of New South Wales, Prince of Wales Hospital, Randwick, 2031, Sydney, Australia. Tel.: 612 9382 2657; fax: 612 9382 2660. E-mail: [email protected]
r 2005 The British Society for Surgery of the Hand. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.jhsb.2005.09.024 available online at http://www.sciencedirect.com
Zone 2 flexor tendon repairs can require ‘‘venting’’ or partial resection of the A2 and/or A4 pulleys. We propose and biomechanically assess a technique used by the authors in which the A2 and A4 pulleys are divided and repaired using a V–Y plasty. Two groups of cadaveric fingers were used, one group for assessing the A2 pulley and the second for assessing the A4 pulley. Prepared fingers were mounted onto custom-made jigs, tested using a servohydraulic testing machine and assessed for load to failure. The loads obtained were 75N (SD ¼ 26N) and 234N (SD ¼ 73N) for the A4 and A2 pulleys, respectively. These loads are well in excess of those one would anticipate during a postoperative active mobilization protocol. Tendon pulley V–Y plasty creates a mechanically sound pulley and maintains sufficient cover of the underlying tendon. This technique provides access to perform a tendon repair and/or permits free tendon gliding post-repair, thus providing an attractive alternative to simply ‘‘venting’’, or resecting, an otherwise troublesome pulley. Journal of Hand Surgery (British and European Volume, 2006) 31B: 2: 133–137 Keywords: flexor tendon, repair, pulley, venting
Flexor tendon pulleys serve to maintain a constant relationship, or moment arm, between the flexor tendon and the joint axis. In doing so, they ensure maximum joint movement for any given amount of tendon excursion (Barton, 1969; Doyle and Blythe, 1974, 1975; Idler, 1985; Idler and Strickland, 1984; Lin et al., 1989; Peterson et al., 1986). Absence of the pulley system acts to increase the moment arm of the tendon with clinically apparent tendon bowstringing. The net effect is an increased amount of tendon excursion required to produce the same arc of motion, with a potentially decreased range of motion and power. The A2 and A4 pulleys are the strongest of the annular pulleys and are considered to be the most important (Bunnell, 1918; Doyle, 1988; Doyle and Blythe, 1974, 1975, 1989; Idler, 1985; Idler and Strickland, 1984; Lin et al., 1989, 1990; Manske and Lesker, 1977, 1983). Consequently, surgeons are careful to preserve their integrity during tendon repairs. Unfortunately, the pulley often restricts access to the tendon making it technically difficult to perform the repair (Kwai Ben and Elliot, 1998). They can also limit tendon excursion post-repair. As a result of this, surgeons have often been forced to partially or completely divide (‘‘vent’’) tendon pulleys (Kwai Ben and Elliot, 1998; Manske and Lesker, 1983; Strickland, 1986). It has been suggested that up to 75% resection of either of the A2 or A4 pulleys will provide ‘‘clinically acceptable’’ results (Mitsionis et al., 2000; Tomaino et al., 1998). This paper assesses V–Y plasty of flexor tendon pulleys as an alternative to venting or partial resection. This technique has been employed by the authors to gain adequate exposure to the flexor tendons and to allow unrestricted tendon gliding through the pulley after repair.
MATERIALS + METHODS Surgical technique The concept of V–Y plasty is not new to surgeons, although its application to tendon pulleys has not previously been described (Figs 1 and 2). V–Y plasty creates elongation of the tissue of interest with some small, but acceptable, narrowing. When this is applied to tendon pulleys, it creates increased length in the radial–ulnar axis, with shortening in the longitudinal axis. The end result is a pulley that has an increased circumference (Fig 3). Such a procedure can be performed for both the A2 and A4 pulleys. The A4 pulley requires a single V–Y plasty. However, because of its length, the A2 pulley requires two V–Y plasties side-by-side to increase the circumference along its whole length. In many clinical situations, only half of the A2 pulley requires an increase of circumference and a single V–Y plasty is sufficient. To maximize the benefit of the V–Y plasty, one needs to ensure that all three points of the ‘‘V’’ extend to the bony attachment of the pulley. The ‘‘V’’ is designed with each limb gently flared at the base and the apex of the V slightly rounded. This is done to increase the surface area of each of the tips of the three flaps created, thus maximising the suture purchase of each limb. After creating the ‘‘V’’, the clinical circumstances will dictate how far the apex of the ‘‘V’’ is advanced before repair. Generally, this would be several millimetres. If uncertain as to how far the apex needs to be advanced, a temporary holding stitch can be placed at the apex to create the vertical limb of the ‘‘Y’’. Once this has been performed, free gliding of the tendon beneath can be assessed. When satisfied with the length of the 133
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THE JOURNAL OF HAND SURGERY VOL. 31B No. 2 APRIL 2006
Fig 1 Diagrammatic illustrations of tendon pulley V–Y plasty. (a) A4 pulley showing the placement of the ‘‘V’’ incision; (b) closure in a ‘‘Y’’ fashion using a continuous suture. Note that the vertical limb of the Y does not require suturing.
vertical limb of the ‘‘Y’’, the pulley is formally repaired with a running 6/0 prolene suture. The vertical limb of the ‘‘Y’’ does not require suturing. Eighteen fingers, all ring, middle and index fingers, including the metacarpals, were harvested from six cadaveric hands. All palmar skin and subcutaneous tissues were excised. The tendon sheath was excised, preserving only the Al, A2 and A4 pulleys. Both the flexor digitorum profundus (FDP) and flexor digitorum superficialis (FDS) tendons were left intact. The fingers were randomly divided into two groups of nine for load to failure testing. Testing was performed for both the A2 and A4 pulleys after V–Y plasty to establish the force to failure. Failure of the pulley was defined as complete disruption of the V–Y plasty. A2 pulley The first group of fingers were used to assess the load to failure of A2 pulleys, each of which was enlarged with two V–Y plasties. Fingers were mounted on a custommade jig with the metacarpophalangeal joint (MCP) fixed at 901 and the proximal and distal interphalangeal (PIP and DIP) joints fixed in full extension (Fig 4). The FDP tendon was then gripped using non-slip custom grips, and pulled at a rate of 100 mm/minute. Testing was stopped when the A2 pulley failed. A4 pulley The second group of fingers were used to assess the load to failure in A4 pulleys, each of which was enlarged with a single V–Y plasty. Functional loading was performed differently to A2 testing. Fingers were mounted on a
Fig 2 Cadaveric specimens. (a) A4 pulley divided; (b) A4 pulley post V–Y plasty; (c) A2 pulley showing two side by side V–Y plasties.
custom-made jig with the MCP and PIP joints held in 451 flexion and the DIP joint in 301 of flexion (Fig 5). The FDP tendon was then gripped, using non-slip
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Fig 3 Cross-section of the A4 pulley showing the increase in circumference (broken line) generated by the V–Y plasty.
Fig 5 Testing of the A4 pulley. The digit is fixed in a clinically relevant position of flexion as shown. This increases the angle of the FDP tendon A4 pulley junction, thus increasing the perpendicular force acting on the pulley.
Fig 4 Testing of the A2 pulley. The digit is fixed with the MCP joint at 901 and the PIP and DIP joints fully extended. The tendon is pulled at a rate of 100 mm/minute. Note that the length of the A2 pulley means that it requires two side-by-side V–Y plasties.
custom grips, and pulled at a rate of 100 mm/minute. Testing was stopped when the A4 pulley failed.
RESULTS No specimen failed by FDP tendon avulsion from the distal phalanx. Failure in all tests was by the pulley under test giving way, with all pulleys failing by a
combination of suture breakage and suture pullout from the pulleys. For the A2 pulleys, either the proximal and distal V–Y plasties would fail simultaneously, or one would fail immediately after the other with no definite pattern existing. The mean load to failure of the A2 pulleys was 234N (SD ¼ 73N; range ¼ 155–331N). The mean load to failure of the A4 pulleys was 76N (SD ¼ 26N; range ¼ 46–114N).
DISCUSSION Although surgeons acknowledge the importance of tendon pulleys, they can impede the satisfactory repair of flexor tendons. This occurs by limiting access to the point of tendon division and repair and/or preventing satisfactory gliding of the tendon following repair (Kwai Ben and Elliot, 1998). To this end, surgeons have had to
ARTICLE IN PRESS 136
resort to either ‘‘venting’’, or partially excising, tendon pulleys. Venting refers to the partial or complete longitudinal division of the pulley. Strickland (1986) described and illustrated the technique of pulley venting. A prospective study by Kwai Ben and Elliot, (1998) looked at the incidence of pulley venting necessary to perform the repair and allow a full passive range of motion of the repaired flexor tendon(s) when performing tendon repairs in zones 2A and 2B. Of the 126 digits in the study, they found that the A4 pulley was vented in 56% of cases, with a mean length of pulley venting of 52%. They also found that 14 of the 126 digits (11%) required complete division of the A4 pulley to achieve these aims. Only 8% of the digits in this study had the A2 pulley partially vented. This was because the study did not include many tendons divided deep to this pulley, zone 2 injuries this far proximally being much less common than those more distally in the zone. Pulley resection is another option available to surgeons. A number of studies have looked at the decrease in total angular rotation and residual pulley strength after partial A2 and A4 pulley excision (Mitsionis et al., 1999, 2000; Tomaino et al., 1998). Mitsionis et al. (1999, 2000) assessed the effect of 75% excision of both the distal A2 pulley and proximal A4 pulley. These authors suggested that such radical excision still resulted in ‘‘clinically acceptable’’ decreases in total angular rotation and residual pulley strength. Other forms of pulley plasty have been advocated. Kapandji (1983) described a technique that was revisited in a more recent study (Paillard et al., 2002). It involves making a single oblique incision from one corner of the pulley to the contralateral corner, thus creating two triangular flaps which were then sutured together. Previous studies addressing the strength of tendon pulleys have employed direct pull-off testing methods (Manske and Lesker, 1977). This involves placing a loop of tendon or metal hook through the pulley and pulling in a perpendicular direction to the phalanx. Although such testing provides data on the overall strength of pulleys, the relevance of such data is questionable given that tendon pulleys are never subjected to that mechanism of distraction in vivo. Mitsionis et al. (2000) acknowledged this and employed both direct pull-off and ‘‘functional loading’’ testing protocols. For our A2 testing, we used the functional loading protocol used by Mitsionis et al. (2000). With this testing system, the A1 pulley buffers the vast majority of the forces acting through the flexor tendons. In clinical practice, if one were to employ an A2 V–Y pulley plasty, then the A1 pulley must be preserved. This is only a real consideration in those cases where one has to retrieve the tendon from the palm and, possibly, divide the A1 pulley in the process. For this reason, we felt that it was clinically correct to leave the A1 pulley intact for testing purposes. Unlike the A2 pulley, the A4 pulley does not have a significant annular pulley immediately adjacent to it to
THE JOURNAL OF HAND SURGERY VOL. 31B No. 2 APRIL 2006
buffer the flexor tendon forces. With this in mind, we tested the A4 pulleys using a position of flexion at all the joints. By doing this, the angle between the FDP tendon and pulley is increased, thus increasing the perpendicular force acting on the pulley. Although this should, theoretically, cause the pulleys to fail at lower loads, it does represent a clinically relevant position. Schuind et al. (1992) showed that the mean force acting along the FDP during active unresisted motion was 19N, with a maximum-recorded value of 29N. They also demonstrated that the mean forces acting along the FDP during grasp and tip pinch were 40N and 83N, respectively. Our study found the mean load to failure of the A2 pulley to be 234N (SD ¼ 73) and the A4 pulley to be 75N (SD ¼ 26), with the lowest value obtained being 46N. Additionally, the loads to failure in our study are likely to be an underestimate of those that would be obtained in vivo. This is because their biomechanical assessment was conducted without the support provided by the palmar soft tissues and any residual sheath, each of which would add to the failure load of the pulley. Despite this, the results obtained are well in excess of the forces acting along the FDP tendon during active unresisted motion, because of the buffering effect of the A1 pulley. As stated previously, this represents the likely situation that surgeons will encounter and therefore, we feel that this testing method and the results obtained are clinically relevant. Our findings would suggest that V–Y plasty of flexor tendon pulleys, protected by the presence of the other intact pulleys, would not compromise flexor tendon repairs undergoing active mobilization protocols after tendon repair. In conclusion, pulley V–Y plasty is a technique that can be used in flexor tendon repairs as it creates a mechanically sound pulley. This technique has been employed by the authors on a number of clinical occasions without the need to alter normal postoperative active mobilization protocols. However, we do not advocate its use as a technique to be routinely employed in flexor tendon repairs, but simply as an alternative to venting, or resecting, an otherwise troublesome flexor tendon pulley.
References Barton NJ (1969). Experimental study of optimal location of flexor tendon pulleys. Plastic and Reconstructive Surgery, 43: 125–129. Bunnell S (1918). Repair of tendons in the fingers and description of two new instruments. Surgery Gynecology and Obstetrics, 26: 103–110. Doyle JR (1988). Anatomy of the finger flexor sheath and pulley system. Journal of Hand Surgery, 13A: 473–484. Doyle JR, Blythe W (1974). Proceedings of the American Society for Surgery of the Hand – macroscopic and functional anatomy of the flexor sheath. Journal of Bone and Joint Surgery, 56A: 1094. Doyle JR, Blythe W. The finger flexor tendon sheath and pulleys: anatomy and reconstruction. In: AAOS symposium on tendon surgery in the hand. St Louis, CV Mosby Co., 1975: 81–87.
ARTICLE IN PRESS FLEXOR TENDON PULLEY V–Y PLASTY
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r 2005 The British Society for Surgery of the Hand. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.jhsb.2005.09.024 available online at http://www.sciencedirect.com