- Email: [email protected]
Biomechanical Influence of the Vincula Tendinum on Digital Motion After Isolated Flexor Tendon Injury: A Cadaveric Study
Biomechanical Influence of the Vincula Tendinum on Digital Motion After Isolated Flexor Tendon Injury: A Cadaveric Study David A. Stewart, MBChB, Peter J. Smitham, LRCS, Mark P. Gianoutsos, MD, William R. Walsh, PhD From the Surgical and Orthopaedic Research Laboratories, University of New South Wales, Prince of Wales Hospital, Randwick, NSW, Australia; and the Plastic Surgery Department, Prince of Wales Hospital, Randwick, NSW, Australia.
Purpose: The vincula are specialized mesotendinous structures attaching to the flexor tendons of the hand. In addition to providing vascular supply to the tendons, the vincula can be mechanically important. The purpose of this study was to quantify the influence of intact vincula on digital flexion after flexor tendon laceration and to assess the ultimate strength and stiffness of the vincula. Methods: The index, middle, and ring fingers of 12 fresh-frozen cadaveric fingers were dissected free at the level of the metacarpophalangeal joint, preserving at least 10 cm of the flexor and extensor tendons. A 9.8-N load was applied to each flexor tendon, and using digital photography and image analysis software, the degree of flexion at the proximal and distal interphalangeal joints and excursion of tendons proximal to the metacarpophalangeal joint was recorded before and after division of the flexor digitorum profundus and flexor digitorum superficialis tendons at their insertions. Load to failure and stiffness of the vincula were measured via a uniaxial material testing apparatus. Analysis of means was performed with a paired t-test. Results: After division of the flexor digitorum superficialis tendon, proximal interphalangeal joint flexion secondary to the influence of the intact vincula was 93% of that compared with the uninjured digit. Distal interphalangeal joint flexion after flexor digitorum profundus transection was 69% of normal. The increased excursion of transected tendons compared with testing before division was 4 mm for flexor digitorum superficialis and 2 mm for flexor digitorum profundus. Load to failure was 27 N, and stiffness was 6 N/mm. Conclusions: The vincula breve can facilitate digital flexion after distal tendon transection, allowing tendons to act indirectly across the interphalangeal joints. The intact vincula breve can facilitate an almost normal range of motion across the interphalangeal joints, making the diagnosis of a flexor tendon injury difficult. In the immediate postinjury period, the vincula breve can hold a divided tendon within a few millimeters of its insertion. Testing against resistance is important to avoid missing the diagnosis of a tendon injury. (J Hand Surg 2007; 32A:1190 –1194. Copyright © 2007 by the American Society for Surgery of the Hand.) Key words: Interphalangeal joint, flexion, tendon, vincula.
he vincula are specialized mesotendinous structures that provide nutrition to the flexor tendons and support intrinsic tendon healing after injury.1–9 In addition to providing vascular supply to the flexor tendons, the vincula can in some circumstances affect the mechanics of digital flexion. It is recognized clinically that the intact vincula can minimize tendon retraction after flexor tendon
T 1190
The Journal of Hand Surgery
injuries. Anatomically, the vincula breve attach onto the volar plate of the interphalangeal joints10 and can therefore transmit the force of a divided flexor tendon across its respective joint (Fig. 1). For example, a divided flexor digitorum profundus (FDP) tendon at the level of the distal interphalangeal (DIP) joint could be missed on routine examination as flexion of the DIP joint may be facilitated by the indirect action
Stewart et al / Vincula Biomechanics
Figure 1. Diagrammatic representation of the connections of the flexor tendons across the interphalangeal joints after tendon transection. Red, volar plate; blue, vinculum.
of the flexor tendons on the volar plate via the vinculum breve. Case reports and cadaver dissections have shown that this is possible also at the proximal interphalangeal (PIP) joint of the fingers due to the vinculum breve of the flexor digitorum superficialis (FDS) tendon11 and at the interphalangeal (IP) joint of the thumb via the vinculum breve of the flexor pollicis longus (FPL) tendon.5 Although previous anatomic studies5,10,11 have explored the possibilities of flexion of the fingers via the vincula, there are no data available on the biomechanics of this system. The purpose of this study was to quantify the influence of intact vincula on digital flexion after flexor tendon laceration and to assess the ultimate strength and stiffness of the vincula.
1191
phalanx vertically. The finger was held in full extension by attaching a 500-g weight to the free tendon end, thus producing a 4.9-N load. Marker sutures of 4-0 polypropylene were placed on the flexor tendons at the level of the A1 pulley after preloading the flexor tendons with 0.98 N of force (by attaching a 100-g weight). The finger was flexed by applying a force of 9.8 N (1 kg) on the FDP tendon (Fig. 2). The amount of excursion of tendon from the A1 pulley was noted by movement of the marker suture, measured by digital calliper (Series 500 Digimatic Absolute Caliper; Mitutoyo UK Ltd., Andover, Hampshire, UK). A digital photograph was taken of the flexed digit and image analysis software (ImageJ; National Institutes of Health, Bethesda, MD) was used to calculate the angle of flexion at the PIPJ and DIPJ (Fig. 3A). After the load on the FDP tendon was released, the finger was extended again in the same fashion and then 9.8 N of traction was applied to the FDS tendon. Excursion of FDS tendon proximal to the A1 pulley and degree of flexion at the PIP
Materials and Methods Twelve fresh-frozen cadaveric fingers from 3 cadavers were used for the study. The average age was 76 years (range, 68 – 81 years). All dissection was performed by one of the authors (D.A.S.) using 3.5⫻ operating loupes. The index, middle, and ring fingers were dissected free at the level of the metacarpophalangeal joint (MCPJ) preserving at least 10 cm of the tendons of FDP, FDS, and extensor digitorum communis (EDC) proximal to the MCPJ. The skin was excised completely from the finger except for that overlying the dorsal aspect of the distal phalanx, which was left with the nail to preserve the extensor tendon insertion. Neurovascular bundles and subcutaneous tissues were removed to leave the flexor sheath exposed and intact. Two K-wires were inserted transversely through proximal and distal ends of the proximal phalanx to allow for mounting on the testing apparatus. The K-wires were held in a clamp to hold the proximal
Figure 2. Testing setup showing testing of intact FDP tendon.
1192
The Journal of Hand Surgery / Vol. 32A No. 8 October 2007
chanical testing was performed. A 1.6-mm (0.062in.) K-wire was placed anteroposteriorly through the tuft of the distal phalanx to allow mounting. This K-wire was held in a clamp, as was the flexor tendon of interest. Using a mini Bionix 858 MTS testing machine (MTS Systems Corp., Eden Prairie, MN), axial testing of the vincular attachments of individual divided flexor tendons was done at a rate of 1 mm/s, after preloading the tendons at 2 N. Six of the specimens were used to test FDP, and the other 6 were used to test FDS. Load to failure (via rupture of the vincula) was determined from the peak of the forcedisplacement curves generated, and stiffness of the vincula was calculated from the gradient of the curve. Mean excursion and interphalangeal joint flexion before and after tendon division were calculated and analyzed using a paired t-test and observational power analysis with SPSS for Windows (SPSS Inc., Chicago, IL).
Results
Figure 3. Digital flexion was observed before (A) and after (B) division of the FDP insertion. Note that flexion at the DIP joint is still possible with a divided tendon, due to the attachment of the vinculum.
Flexor tendon excursion and interphalangeal joint flexion were measured for each of the 12 digits both prior to and after selected tendon division (Table 1). Division of the insertion site of the flexor tendons resulted in a reduction in the degree of flexion at the interphalangeal joints and an increase in the excursion of the tendon required to achieve maximal flexion. The average degree of flexion possible at the DIP joint after FDP division was 31% less than that of the uninjured digit (p ⬍ .01). Flexion at the PIP joint by the divided FDS was reduced by only 7% (p ⬍ .01). The extra excursion of the tendons was 2 mm for FDP and 4 mm for FDS (p ⬍ .01). Average load to failure was 24 N for the vincula breve of FDS and
Table 1. Interphalangeal Flexion and Tendon Excursion Before and After Tendon Division
joint were determined again with the same methods. Once baseline data were obtained in this fashion, the FDP tendon was completely divided at the level of its insertion to the distal phalanx, and assessment of joint flexion and tendon excursion was performed again in the manner described above (Fig. 3). The FDS tendons were then divided just proximal to the A4 pulley and excursion and joint flexion assessed again. Tendons were divided with both joints in a neutral position. After the above studies, to identify the tensile strength and stiffness of the vincular system, me-
FDP acting on DIPJ
FDS acting on PIPJ
Before tendon division After tendon division Before tendon division After tendon division
Values are given as mean (SD).
Average Flexion
Average Tendon Excursion (mm)
74° (10.06)
31.5 (2.13)
50° (7.76)
33.2 (2.36)
120° (5.23)
20.1 (2.96)
112° (5.58)
23.8 (2.45)
Stewart et al / Vincula Biomechanics
27 N for the vincula breve of FDP. Average stiffness calculated from the gradient of the force-displacement curves was 6 N/mm. Observed power of the t-test for all variables was 1.00.
Discussion To ensure normal biomechanics of the flexor tendons in curvilinear testing, we preserved the flexor sheath, including all of the annular pulleys. As the A1 pulley was the most proximal part of the sheath left intact, this was used as the reference point for the excursion of the flexor tendons during testing of finger flexion. Although the A1 pulley is a strong structure, it attaches to the volar plate and is not a completely fixed point relative to the proximal phalanx and may be a source of error in our measurements. Likewise, although we preserved the flexor sheath, we removed other soft tissues, which may have had an effect on the mechanics of flexion of the fingers. Lastly, to make the greatest use of the cadaver tissue, the same fingers were used to test FDS tendons after the FDP tendons, and the interrelations of the flexor tendons may have altered some of the results had the FDP tendon been intact when FDS was tested. This study demonstrates the potential for clinically relevant interphalangeal joint flexion via the vincular structures despite flexor tendon transection. As a result, the clinician should be aware of the potential for active flexion of the PIP and DIP joints through the indirect action of the intact vinculum tendinum in the presence of a flexor tendon injury. Joint flexion was observed to be on average 93% of full flexion at the PIP joint and 69% of full flexion at the DIP joint. The average stiffness of the vincula was 6 N/mm; therefore the vincula are far less stiff and have far less mechanical strength than the tendons proper. In addition to highlighting the potential for clinical error in diagnosing a flexor tendon transaction, this study also demonstrates how one can avoid confusion in examining the finger with a potentially damaged tendon. In their case report of an unexpected finding of an FDP injury where a vinculum breve had preserved DIP joint movement, Sasaki11 and colleagues stress the importance of examining flexor function against resistance when a tendon injury is suspected. This study demonstrates the rationale for this method, as with only 6 N/mm of stiffness, the vinculum will provide much weaker flexion against resistance than an intact flexor tendon, which has a stiffness of around 118 N/mm as shown by Carlson et al.12 We measured an increased excursion of the FDS
1193
and FDP tendons at the level of the A1 pulley after division of their respective insertions into the middle and distal phalanges. This will correlate with a proportionate proximal movement of the divided tendon stumps. The strength of the vincula breve as measured by this study is comparable with that of suture anchors at 27 N13 and half to one-third the strength of conventionally used 2-strand flexor tendon repairs at 40 to 60 N as investigated by Brustein et al.14 This leads us to speculate that at least in the immediate postinjury period, the vincula can hold the tendon stumps within a few millimeters of the injury site. The implications for the natural history of the tendon injury and healing are beyond the scope of a cadaveric study. In vivo animal studies would be necessary to investigate the influence of the intact vinculum breve on potential flexor tendon healing in the absence of flexor tendon repair.13 Received for publication June 15, 2006; accepted in revised form May 16, 2007. No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article. Corresponding author: Dr. David A. Stewart, Surgical and Orthopaedic Research Laboratories, University of New South Wales, Prince of Wales Hospital, Randwick, NSW 2031, Australia; e-mail: [email protected] Copyright © 2007 by the American Society for Surgery of the Hand 0363-5023/07/32A08-0010$32.00/0 doi:10.1016/j.jhsa.2007.05.017
References 1. Lundborg G. The vascularization of the human flexor pollicis longus tendon. Hand 1979;11:28 –33. 2. Matsui T, Merklin RJ, Hunter JM. [A micro-vascular study of the human flexor tendons in the digital fibrous sheath– normal blood vessel arrangement of tendons and the effects of injuries of tendons and vincula on distribution of tendon blood vessels (author’s transl.).] Nippon Seikeigeka Gakkai Zasshi 1979;53:307–320. 3. Scharizer E. [Blood vessel supply of the flexor sinews (microanatomy) (author’s transl.).] Aktuelle Traumatol 1981; 11:109 –113. 4. Azar CA, Culver JE, Fleegler EJ. Blood supply of the flexor pollicis longus tendon. J Hand Surg 1983;8:471– 475. 5. Armenta E, Fisher J. Anatomy of flexor pollicis longus vinculum system. J Hand Surg 1984;9A:210 –212. 6. Poisel S, Gaber O. [Macroscopic blood supply of the tendons of the superficial and deep flexor muscles of the fingers in the palm.] Handchir Mikrochir Plast Chir 1985;17:314 –319. 7. Gelberman RH, Khabie V, Cahill CJ. The revascularization of healing flexor tendons in the digital sheath. A vascular injection study in dogs. J Bone Joint Surg 1991;73A:868 – 881. 8. Yalin A, Cavdar S, Ercan F. Vascularization of the long flexor tendon. Okajimas Folia Anat Jpn 1994;70:285–293. 9. Leversedge FJ, Ditsios K, Goldfarb CA, Silva MJ, Gelberman RH, Boyer MI. Vascular anatomy of the human flexor
1194
The Journal of Hand Surgery / Vol. 32A No. 8 October 2007
digitorum profundus tendon insertion. J Hand Surg 2002;27A:806 – 812. 10. Flindall E, McGrouther DA. Accessory roles of the vinculum breve of the flexor digitorum profundus and check-rein ligaments at the distal interphalangeal joint. J Hand Surg 1991;16B:305–310. 11. Sasaki Y, Nomura S. An unusual role of the vinculum after complete laceration of the flexor tendons. J Hand Surg 1987;12B:105–108. 12. Carlson GD, Botte MJ, Josephs MS, Newton PO, Davis JL,
Woo SL. Morphologic and biomechanical comparison of tendons used as free grafts. J Hand Surg 1993;18A:76 – 82. 13. Latendresse K, Dona E, Scougall PJ, Schreuder FB, Puchert E, Walsh WR. Cyclic testing of pullout sutures and micromitek suture anchors in flexor digitorum profundus tendon distal fixation. J Hand Surg 2005;30A:471– 478. 14. Brustein M, Pellegrini J, Choueka J, Heminger H, Mass D. Bone suture anchors versus the pullout button for repair of distal profundus tendon injuries: a comparison of strength in human cadaveric hands. J Hand Surg 2001;26A:489 – 496.
Purpose: The vincula are specialized mesotendinous structures attaching to the flexor tendons of the hand. In addition to providing vascular supply to the tendons, the vincula can be mechanically important. The purpose of this study was to quantify the influence of intact vincula on digital flexion after flexor tendon laceration and to assess the ultimate strength and stiffness of the vincula. Methods: The index, middle, and ring fingers of 12 fresh-frozen cadaveric fingers were dissected free at the level of the metacarpophalangeal joint, preserving at least 10 cm of the flexor and extensor tendons. A 9.8-N load was applied to each flexor tendon, and using digital photography and image analysis software, the degree of flexion at the proximal and distal interphalangeal joints and excursion of tendons proximal to the metacarpophalangeal joint was recorded before and after division of the flexor digitorum profundus and flexor digitorum superficialis tendons at their insertions. Load to failure and stiffness of the vincula were measured via a uniaxial material testing apparatus. Analysis of means was performed with a paired t-test. Results: After division of the flexor digitorum superficialis tendon, proximal interphalangeal joint flexion secondary to the influence of the intact vincula was 93% of that compared with the uninjured digit. Distal interphalangeal joint flexion after flexor digitorum profundus transection was 69% of normal. The increased excursion of transected tendons compared with testing before division was 4 mm for flexor digitorum superficialis and 2 mm for flexor digitorum profundus. Load to failure was 27 N, and stiffness was 6 N/mm. Conclusions: The vincula breve can facilitate digital flexion after distal tendon transection, allowing tendons to act indirectly across the interphalangeal joints. The intact vincula breve can facilitate an almost normal range of motion across the interphalangeal joints, making the diagnosis of a flexor tendon injury difficult. In the immediate postinjury period, the vincula breve can hold a divided tendon within a few millimeters of its insertion. Testing against resistance is important to avoid missing the diagnosis of a tendon injury. (J Hand Surg 2007; 32A:1190 –1194. Copyright © 2007 by the American Society for Surgery of the Hand.) Key words: Interphalangeal joint, flexion, tendon, vincula.
he vincula are specialized mesotendinous structures that provide nutrition to the flexor tendons and support intrinsic tendon healing after injury.1–9 In addition to providing vascular supply to the flexor tendons, the vincula can in some circumstances affect the mechanics of digital flexion. It is recognized clinically that the intact vincula can minimize tendon retraction after flexor tendon
T 1190
The Journal of Hand Surgery
injuries. Anatomically, the vincula breve attach onto the volar plate of the interphalangeal joints10 and can therefore transmit the force of a divided flexor tendon across its respective joint (Fig. 1). For example, a divided flexor digitorum profundus (FDP) tendon at the level of the distal interphalangeal (DIP) joint could be missed on routine examination as flexion of the DIP joint may be facilitated by the indirect action
Stewart et al / Vincula Biomechanics
Figure 1. Diagrammatic representation of the connections of the flexor tendons across the interphalangeal joints after tendon transection. Red, volar plate; blue, vinculum.
of the flexor tendons on the volar plate via the vinculum breve. Case reports and cadaver dissections have shown that this is possible also at the proximal interphalangeal (PIP) joint of the fingers due to the vinculum breve of the flexor digitorum superficialis (FDS) tendon11 and at the interphalangeal (IP) joint of the thumb via the vinculum breve of the flexor pollicis longus (FPL) tendon.5 Although previous anatomic studies5,10,11 have explored the possibilities of flexion of the fingers via the vincula, there are no data available on the biomechanics of this system. The purpose of this study was to quantify the influence of intact vincula on digital flexion after flexor tendon laceration and to assess the ultimate strength and stiffness of the vincula.
1191
phalanx vertically. The finger was held in full extension by attaching a 500-g weight to the free tendon end, thus producing a 4.9-N load. Marker sutures of 4-0 polypropylene were placed on the flexor tendons at the level of the A1 pulley after preloading the flexor tendons with 0.98 N of force (by attaching a 100-g weight). The finger was flexed by applying a force of 9.8 N (1 kg) on the FDP tendon (Fig. 2). The amount of excursion of tendon from the A1 pulley was noted by movement of the marker suture, measured by digital calliper (Series 500 Digimatic Absolute Caliper; Mitutoyo UK Ltd., Andover, Hampshire, UK). A digital photograph was taken of the flexed digit and image analysis software (ImageJ; National Institutes of Health, Bethesda, MD) was used to calculate the angle of flexion at the PIPJ and DIPJ (Fig. 3A). After the load on the FDP tendon was released, the finger was extended again in the same fashion and then 9.8 N of traction was applied to the FDS tendon. Excursion of FDS tendon proximal to the A1 pulley and degree of flexion at the PIP
Materials and Methods Twelve fresh-frozen cadaveric fingers from 3 cadavers were used for the study. The average age was 76 years (range, 68 – 81 years). All dissection was performed by one of the authors (D.A.S.) using 3.5⫻ operating loupes. The index, middle, and ring fingers were dissected free at the level of the metacarpophalangeal joint (MCPJ) preserving at least 10 cm of the tendons of FDP, FDS, and extensor digitorum communis (EDC) proximal to the MCPJ. The skin was excised completely from the finger except for that overlying the dorsal aspect of the distal phalanx, which was left with the nail to preserve the extensor tendon insertion. Neurovascular bundles and subcutaneous tissues were removed to leave the flexor sheath exposed and intact. Two K-wires were inserted transversely through proximal and distal ends of the proximal phalanx to allow for mounting on the testing apparatus. The K-wires were held in a clamp to hold the proximal
Figure 2. Testing setup showing testing of intact FDP tendon.
1192
The Journal of Hand Surgery / Vol. 32A No. 8 October 2007
chanical testing was performed. A 1.6-mm (0.062in.) K-wire was placed anteroposteriorly through the tuft of the distal phalanx to allow mounting. This K-wire was held in a clamp, as was the flexor tendon of interest. Using a mini Bionix 858 MTS testing machine (MTS Systems Corp., Eden Prairie, MN), axial testing of the vincular attachments of individual divided flexor tendons was done at a rate of 1 mm/s, after preloading the tendons at 2 N. Six of the specimens were used to test FDP, and the other 6 were used to test FDS. Load to failure (via rupture of the vincula) was determined from the peak of the forcedisplacement curves generated, and stiffness of the vincula was calculated from the gradient of the curve. Mean excursion and interphalangeal joint flexion before and after tendon division were calculated and analyzed using a paired t-test and observational power analysis with SPSS for Windows (SPSS Inc., Chicago, IL).
Results
Figure 3. Digital flexion was observed before (A) and after (B) division of the FDP insertion. Note that flexion at the DIP joint is still possible with a divided tendon, due to the attachment of the vinculum.
Flexor tendon excursion and interphalangeal joint flexion were measured for each of the 12 digits both prior to and after selected tendon division (Table 1). Division of the insertion site of the flexor tendons resulted in a reduction in the degree of flexion at the interphalangeal joints and an increase in the excursion of the tendon required to achieve maximal flexion. The average degree of flexion possible at the DIP joint after FDP division was 31% less than that of the uninjured digit (p ⬍ .01). Flexion at the PIP joint by the divided FDS was reduced by only 7% (p ⬍ .01). The extra excursion of the tendons was 2 mm for FDP and 4 mm for FDS (p ⬍ .01). Average load to failure was 24 N for the vincula breve of FDS and
Table 1. Interphalangeal Flexion and Tendon Excursion Before and After Tendon Division
joint were determined again with the same methods. Once baseline data were obtained in this fashion, the FDP tendon was completely divided at the level of its insertion to the distal phalanx, and assessment of joint flexion and tendon excursion was performed again in the manner described above (Fig. 3). The FDS tendons were then divided just proximal to the A4 pulley and excursion and joint flexion assessed again. Tendons were divided with both joints in a neutral position. After the above studies, to identify the tensile strength and stiffness of the vincular system, me-
FDP acting on DIPJ
FDS acting on PIPJ
Before tendon division After tendon division Before tendon division After tendon division
Values are given as mean (SD).
Average Flexion
Average Tendon Excursion (mm)
74° (10.06)
31.5 (2.13)
50° (7.76)
33.2 (2.36)
120° (5.23)
20.1 (2.96)
112° (5.58)
23.8 (2.45)
Stewart et al / Vincula Biomechanics
27 N for the vincula breve of FDP. Average stiffness calculated from the gradient of the force-displacement curves was 6 N/mm. Observed power of the t-test for all variables was 1.00.
Discussion To ensure normal biomechanics of the flexor tendons in curvilinear testing, we preserved the flexor sheath, including all of the annular pulleys. As the A1 pulley was the most proximal part of the sheath left intact, this was used as the reference point for the excursion of the flexor tendons during testing of finger flexion. Although the A1 pulley is a strong structure, it attaches to the volar plate and is not a completely fixed point relative to the proximal phalanx and may be a source of error in our measurements. Likewise, although we preserved the flexor sheath, we removed other soft tissues, which may have had an effect on the mechanics of flexion of the fingers. Lastly, to make the greatest use of the cadaver tissue, the same fingers were used to test FDS tendons after the FDP tendons, and the interrelations of the flexor tendons may have altered some of the results had the FDP tendon been intact when FDS was tested. This study demonstrates the potential for clinically relevant interphalangeal joint flexion via the vincular structures despite flexor tendon transection. As a result, the clinician should be aware of the potential for active flexion of the PIP and DIP joints through the indirect action of the intact vinculum tendinum in the presence of a flexor tendon injury. Joint flexion was observed to be on average 93% of full flexion at the PIP joint and 69% of full flexion at the DIP joint. The average stiffness of the vincula was 6 N/mm; therefore the vincula are far less stiff and have far less mechanical strength than the tendons proper. In addition to highlighting the potential for clinical error in diagnosing a flexor tendon transaction, this study also demonstrates how one can avoid confusion in examining the finger with a potentially damaged tendon. In their case report of an unexpected finding of an FDP injury where a vinculum breve had preserved DIP joint movement, Sasaki11 and colleagues stress the importance of examining flexor function against resistance when a tendon injury is suspected. This study demonstrates the rationale for this method, as with only 6 N/mm of stiffness, the vinculum will provide much weaker flexion against resistance than an intact flexor tendon, which has a stiffness of around 118 N/mm as shown by Carlson et al.12 We measured an increased excursion of the FDS
1193
and FDP tendons at the level of the A1 pulley after division of their respective insertions into the middle and distal phalanges. This will correlate with a proportionate proximal movement of the divided tendon stumps. The strength of the vincula breve as measured by this study is comparable with that of suture anchors at 27 N13 and half to one-third the strength of conventionally used 2-strand flexor tendon repairs at 40 to 60 N as investigated by Brustein et al.14 This leads us to speculate that at least in the immediate postinjury period, the vincula can hold the tendon stumps within a few millimeters of the injury site. The implications for the natural history of the tendon injury and healing are beyond the scope of a cadaveric study. In vivo animal studies would be necessary to investigate the influence of the intact vinculum breve on potential flexor tendon healing in the absence of flexor tendon repair.13 Received for publication June 15, 2006; accepted in revised form May 16, 2007. No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article. Corresponding author: Dr. David A. Stewart, Surgical and Orthopaedic Research Laboratories, University of New South Wales, Prince of Wales Hospital, Randwick, NSW 2031, Australia; e-mail: [email protected] Copyright © 2007 by the American Society for Surgery of the Hand 0363-5023/07/32A08-0010$32.00/0 doi:10.1016/j.jhsa.2007.05.017
References 1. Lundborg G. The vascularization of the human flexor pollicis longus tendon. Hand 1979;11:28 –33. 2. Matsui T, Merklin RJ, Hunter JM. [A micro-vascular study of the human flexor tendons in the digital fibrous sheath– normal blood vessel arrangement of tendons and the effects of injuries of tendons and vincula on distribution of tendon blood vessels (author’s transl.).] Nippon Seikeigeka Gakkai Zasshi 1979;53:307–320. 3. Scharizer E. [Blood vessel supply of the flexor sinews (microanatomy) (author’s transl.).] Aktuelle Traumatol 1981; 11:109 –113. 4. Azar CA, Culver JE, Fleegler EJ. Blood supply of the flexor pollicis longus tendon. J Hand Surg 1983;8:471– 475. 5. Armenta E, Fisher J. Anatomy of flexor pollicis longus vinculum system. J Hand Surg 1984;9A:210 –212. 6. Poisel S, Gaber O. [Macroscopic blood supply of the tendons of the superficial and deep flexor muscles of the fingers in the palm.] Handchir Mikrochir Plast Chir 1985;17:314 –319. 7. Gelberman RH, Khabie V, Cahill CJ. The revascularization of healing flexor tendons in the digital sheath. A vascular injection study in dogs. J Bone Joint Surg 1991;73A:868 – 881. 8. Yalin A, Cavdar S, Ercan F. Vascularization of the long flexor tendon. Okajimas Folia Anat Jpn 1994;70:285–293. 9. Leversedge FJ, Ditsios K, Goldfarb CA, Silva MJ, Gelberman RH, Boyer MI. Vascular anatomy of the human flexor
1194
The Journal of Hand Surgery / Vol. 32A No. 8 October 2007
digitorum profundus tendon insertion. J Hand Surg 2002;27A:806 – 812. 10. Flindall E, McGrouther DA. Accessory roles of the vinculum breve of the flexor digitorum profundus and check-rein ligaments at the distal interphalangeal joint. J Hand Surg 1991;16B:305–310. 11. Sasaki Y, Nomura S. An unusual role of the vinculum after complete laceration of the flexor tendons. J Hand Surg 1987;12B:105–108. 12. Carlson GD, Botte MJ, Josephs MS, Newton PO, Davis JL,
Woo SL. Morphologic and biomechanical comparison of tendons used as free grafts. J Hand Surg 1993;18A:76 – 82. 13. Latendresse K, Dona E, Scougall PJ, Schreuder FB, Puchert E, Walsh WR. Cyclic testing of pullout sutures and micromitek suture anchors in flexor digitorum profundus tendon distal fixation. J Hand Surg 2005;30A:471– 478. 14. Brustein M, Pellegrini J, Choueka J, Heminger H, Mass D. Bone suture anchors versus the pullout button for repair of distal profundus tendon injuries: a comparison of strength in human cadaveric hands. J Hand Surg 2001;26A:489 – 496.