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New Perspectives on Extensor Tendon Repair and Implications for Rehabilitation
New Perspectives on Extensor Tendon Repair and Implications for Rehabilitation Mary Lynn Newport, MD Department of Orthopaedic Surgery
Robert L. Tucker, OTR/L Department of Sports Medicine and Rehabilitation University of Connecticut Health Center Farmington, Connecticut
While flexor tendon injuries have received a great deal of attention concerning repair technique, repair healing, and postoperative therapy, extensor tendon injuries have received significantly less attention. However, these injuries are as problematic as their counterpart. Careful scrutiny of the quality of reported results demonstrates that not only do affected fingers lose extension, but that an even greater percentage lose flexion.1 Loss of digital flexion affecting grasp and power grip poses a greater functional loss than digital extensor lag.1–4 Because of these recognized postoperative complications, the surgical and therapeutic care of extensor tendon injuries should be as exacting and careful as for flexor tendon injuries.5 Extensor tendon rehabilitation utilizing some form of gliding technique, either dynamically assisted or actively mediated, has generally improved the quality of results when compared with postoperative immobilization.1–20 Protocols which utilize early controlled motion after repair have shown a greater than 90% good or excellent result rate for uncomplicated injuries in zones V to VIII compared with 54% to 95% good or excellent result rates for repairs treated with immobilization.1–20 Injuries in zones III and IV produce less favorable results than more proximal injuries1; however, these results have also
Correspondence and reprint requests to Dr. Mary Lynn Newport, Department of Orthopaedic Surgery, University of Connecticut Health Center, Farmington, CT 06034; e-mail:. doi:10.1197/j.jht.2005.01.006
ABSTRACT: This article reviews the available biomechanical and clinical studies on extensor tendon repair and postoperative management. Immobilization has been a foundation for the postoperative treatment of these injuries, with good or excellent results ranging between 54% and 95%. However, clinical outcomes have consistently improved when utilizing rehabilitation involving either dynamically assisted or active motion, with good or excellent results achieved in at least 90% of cases. In addition, available biomechanical studies concerning finger extension strength, tendon repair strength, tendon shortening, resultant loss of motion, and gliding capability have validated controlled motion as biomechanically sound utilizing contemporary repair techniques. J HAND THER. 2005;18:175–181.
been improved with techniques for early controlled motion.3,4,7,18,19 When compared with static splinting, some would argue these early controlled motion protocols can be cumbersome, time consuming, complicated, and expensive. In addition, there remains concern that such rehabilitation may place too much stress on the repair and may contribute to repair elongation or rupture. Repair rupture or failure, however, has not been of significant clinical consequence with the active or dynamic gliding techniques.2,8,10,19,20 In fact, all complications, including loss of motion, extensor lag, loss of grip strength, and incidence of tenolysis, decrease when early controlled motion is compared with immobilization.1,2,4–18 These protocols clearly improve the overall quality and reproducibility of result and should be utilized unless other contraindications such as associated injury or adverse patient profile exist.
REPAIR QUALITY Hand therapists should have a working knowledge of available extensor tendon repair techniques, their tensile strengths, and biomechanical implications. It is imperative that the therapist review the operative report and communicate with the surgeon to ascertain the number of tendons injured and zone of injury, realizing that injury in the distal zones (I–IV) tends to fare less well: zone V typically does best after injury, and zones VI to VIII are equivalent in prognosis—the area under the retinaculum does not scar more significantly or reduce the rate of good or April–June 2005 175
excellent results.1,3,10 It is also important the therapist obtain information on repair technique, suture material, quality of repair, and associated injury, including soft-tissue loss, periosteal damage, fracture, and joint capsule damage. All of these factors can alter splint design or controlled motion parameters for each individual patient. Contemporary extensor tendon repair techniques, because of anatomical differences, are less complicated in design and have less tensile strength compared with flexor tendon repair. The extensor is a much smaller tendon with a relatively flat cross section. Its collagen is longitudinally oriented, with little or no cross-linking. Because of this size differential and lack of surrounding paratenon (except in zone VII), extensors are not as amenable as flexor tendons to multiple-stranded, stronger repair techniques, especially in the more distal (III and IV) zones. The usual tendon biomechanical concerns of repair strength and failure mode have been investigated, but because of the intricate relationship between the intrinsic and extrinsic extensor mechanisms, several other variables come into play during extensor repair, including shortening, lost range of motion after repair, and increased force to obtain maximum flexion. Few studies have evaluated ultimate strength of extensor repair. The four-strand repair described by Howard et al.21 (‘‘MGH repair’’) has been shown to be strongest; however, other biomechanical features such as shortening or resultant loss of motion were not evaluated and their strength evaluation was performed somewhat differently than other studies (Table 1). Compared with the MGH or traditional modified Bunnell repair, a two-strand locked Bunnell repair has been shown to be intermediate in strength and has undergone further biomechanical evaluation (Table 1).22,23 The locked Bunnell showed an improved quality of strength (suture rupture rather than pullout) over the traditional Bunnell (17% versus 58% pullout) but less than the MGH repair (0% pullout), the four-strand Bunnell, or KrackowThomas (0% pullout) described by Howard et al.21–23 Surprisingly, the strength and quality of repair
comparing traditional two-stranded techniques is not significantly different in the smaller, thinner tendons of zone IV when compared with repair in zone VI.22,24 The ultimate strength requirement for extensor repair is not yet well understood. Urbaniak et al.’s25 work during carpal tunnel release on the direct measurement of flexor tendon forces by strain gauge has given us some understanding of the forces to which flexor tendons are subjected. Because similar access under local anesthesia is not presently possible, extensor strength has not been so directly measured in vivo. It has, however, has been measured indirectly. Ketchum et al.26 studied extension strength via a force transducer on the dorsum of the proximal phalanx and found that normal subjects could generate a force of 2.99 kg for the index finger, decreasing ulnarly to 1.97 kg for the small finger. Preliminary studies on maximum extension strength in our laboratory have shown similar findings, with the additional information that the long finger is the strongest and finger extension strength varies significantly according to wrist and metacarpophalangeal (MCP) position.27 Wrist extension of 40 degrees decreased possible extension force at the finger by approximately 25% (40 N versus 30 N or 4.08 kg force versus 3.06 kg). Wrist flexion increased possible extension force by similar amount. These results are expected because of the tenodesis effect wrist position has on the extensor tendon, but now the forces have been quantified so they can be compared with relative tendon repair strength. The implication for the treating therapist is obvious: a strong repair technique that can withstand significant force might be subjected to wrist flexion in rehabilitation, whereas a tenuous repair may require significant restriction in wrist range of motion. Repair strength versus extension force clearly requires further study, but other biomechanical factors such as shortening, pull-out strength, and ability to withstand cycling are also critically important in designing and choosing rehabilitation methods. Extensor repair in the cadaveric model produces a variable amount of tendon shortening that can
TABLE 1. Comparison Biomedical Characteristics Available Extensor Repair Techniques Repair* Mattress Bunnell (2 strand) Locked Bunnell Whipstitch (2 strand) *Bunnell (4 strand) *Krackow (4 strand) *MGH (4 strand)
Strength to gap (gm)
Average Shortening (mm)
Failure Mode (pullout)
Elongation after stress (mm)
Loss composite flexion (°)
488 1425 1780 1870 3200 3300 4800
7.6 6.8 5.8 13.5 NT NT NT
100% 58% 17% 0% 0% 0% 0%
NT 2.5 2.7 2.8 NT NT NT
43° 35° NT NT NT NT NT
NT = Not Tested. *This compares work by the senior author and by Howard et al.23 Howard et al. measured to 1 mm gap and all others were measured to 2 mm gap.
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significantly alter the biomechanics of the extensor mechanism, including loss of composite flexion and increasing force required to obtain full flexion (Table 1).22–24 Traditional repairs in zone VI such as the modified Bunnell technique produce an average of at least 7 mm of shortening (Table 1) and result in 35 degrees or more loss of composite flexion when the wrist is held in neutral position (Figure 1).22 The locked Bunnell produces less shortening (5.8 mm).23 A whipstitch repair, similar to a Krackow repair, was evaluated by Newport and Waters23 and found to shorten the tendon by over 13 mm, demonstrating that some repair techniques can produce significant shortening. In another biomechanical study, Minamikawa et al.28 showed there was a redundancy of 6.4 mm tendon over the metacarpal when the wrist was extended 45 degrees or more. They surmised this amount of tendon could be debrided without affecting digital motion or placing undue stress on the repair site, as long as the wrist was appropriately extended. While shortening with typical repair techniques and the amount which can be compensated for have been shown to be strikingly equivalent, it must be noted that these biomechanical experiments represent smooth tendon gliding in a cadaveric model without muscle tone, the increased friction of edema, adhesion formation, skin closure, or bulk of repair. Because of these postoperative factors, ability to compensate for tendon loss or shortening may be neutralized; repair strength and capacity to glide remain essential. When the extensor tendon, repaired with the locked Bunnell technique, is subjected to cycling through flexion and extension, there is elongation of 2.7 mm with the first cycle and 1.3 mm more over the next 100 cycles.23 Repair quality (suture pullout versus breakage) also degraded somewhat with cycling through the overall strength to 2 mm gap and failure did not. While elongation with cycling should produce concern if early controlled motion is considered as a rehabilitation option, it should be noted that the elongation was never greater than the
shortening produced by the repair itself and there was no repair gap evident during cycling. Wrist position beyond neutral was not evaluated in this study, but wrist extension and tendon redundancy as shown by Minamikawa et al.28 may afford some measure of stress relief to the repair site. Another biomechanical parameter that may affect the ultimate result after extensor repair is the increased amount of force that is required to pull the digit into maximum flexion. The average repair in zone VI shortens the tendon approximately 7 mm, requiring an increased force to maximum flexion of approximately 600 g (Figure 2).22 Repair in zone IV fares somewhat better, with tendon shortening of only 2 or 3 mm and force increase to full flexion of 350 to 400 g in the artificial tendon shortening model (Figure 3) and 0 to 180 g force with the modified Bunnell technique, which was the most biomechanically sound repair of those tested for zone IV.24 The multiple points of connection between the intrinsic and extrinsic extensor mechanism at this level prevent tendon shortening with repair. This decreases the resultant loss of proximal interphalangeal (PIP) motion (Figure 4) and consequently minimizes the increased force required to maximum flexion. These biomechanical findings show that intraoperative factors such as shortening may be less a cause for poor result in zone IV compared with zone VI and that adhesion formation because of the large surface area may be more significant in reducing the quality of result. Moving the tendon repair in these distal zones may be required to produce consistently good results.
FIGURE 1. Tendon shortening versus loss of MCP and PIP motion, zone VI.
FIGURE 2. Increase in force required to maximum digital flexion after tendon shortening, zone VI.
IMPLICATIONS FOR REHABILITATION There are many rehabilitation choices available for extensor tendon injury. The goals for each are the
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FIGURE 3. Increase in force required to maximum digital flexion after tendon shortening, zone IV. same: protect the repair, promote tendon healing and facilitate tendon gliding. Immobilization is the most traditional approach to extensor tendon injury. Theoretically, it is safest as the lack of joint motion should minimize tension on the healing tendon. While this philosophy relies on repair biology to increase the strength of the repaired tendon over time, it nonetheless requires a strong construct that must withstand tendon shortening, adhesion formation, and increased flexion forces from stiff digits when tendon gliding begins. Parameters for immobilization are dependent on level of injury relative to the juncturae tendinae, whether one or both lateral bands have been injured, possible injury to sagittal fibers, and associated ligamentous injury. These details will dictate inclusion of adjacent fingers and in what position to place each affected joint. Wound care and edema control are extremely important at this stage, though the role of the hand therapist may be limited until range of motion exercises are
FIGURE 4. Tendon shortening versus loss of motion, zone IV. 178
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begun. While immobilization would seem safest and requires the least amount of early rehabilitation effort, there are potential complications following this program, including tendon rupture, adhesion formation requiring tenolysis, extension lag, loss of flexion, and decreased grip strength.1,2,10,29 Over the last two decades, early motion protocols utilizing varying combinations of dynamic splinting and tendon gliding programs have become accepted as beneficial, effective methods of extensor tendon rehabilitation with significant improvement in results.2–4,6–8,10,13,15,18–20,30 Their focus has been to balance the tensile strength of the specific tendon repair with adequate joint motion and tendon gliding. Evans and Burkhalter10 have demonstrated through intraoperative measurement that 30-degree MCP flexion for the index/long fingers and 40-degree flexion for the ring/small fingers produce approximately 5 mm extensor digitorum communis excursion. This was felt to be sufficient for the extensor system, based on Duran and Houser’s31 work with flexor tendon excursion during dynamic splinting. Actual extensor excursion, however, has not been directly measured and, because an animal model for extensor repair has not yet proven practical, the excursion required to prevent adhesion formation can only be deduced through these indirect means. While most dynamic splint designs protect against full digital flexion with a fashioned flexion stop or by limiting the excursion of the outrigger, near-complete composite flexion may be tolerated within the confines of dynamic traction in the more proximal zones if the wrist is properly positioned. Browne and Ribik2 reported excellent clinical results with dynamic splinting and larger angles of digital flexion, and Minamikawa et al.’s28 work demonstrated that full composite flexion is possible without undue strain on the repair if the wrist is extended beyond 21 degrees. Excessive wrist extension, however, can cause the extensors to buckle in the more proximal zones, possibly decreasing functional gliding.28 The effect of tendon shortening after repair and its effect on joint position and rehabilitation protocol remains incompletely defined. However, biomechanical and clinical results support protocols that combine dynamic splinting with the wrist appropriately extended and near-full finger motion. Allowing increased digital motion while protecting the repair with wrist position may decrease complications of lost digital flexion. As mentioned previously, lost digital flexion has been a greater problem than extensor lag or adhesion formation, which requires tenolysis, though these complication rates have been lower for dynamic splinting than for static splinting.2,7,10,29 Most dynamic splints designed for extensor repair in the proximal zones (V–VII) leave the MCP joints free to rest at 0 degrees extension (Figure 5). During dynamic splinting for flexor tendon injury, Kleinert
FIGURE 5. Dynamic assist splint modeled after splints used for MCP joint replacement. The MCP joints are free to extend or hyperextend. et al.32 showed that flexor muscles were electrically silent during active extension and dynamically assisted flexion and consequently placed no active tension on the repair site. However, during electromyographic (EMG) testing in the usual dynamic extension splint, the extensor muscles are active during flexion and at rest in 84% of test subjects.33 For dynamic extension splinting, this inappropriate and potentially harmful electrical activity is reduced to 5% when a dorsal block hood is extended to the MCP joints to hold them in slight flexion (5–10 degrees) (Figure 6). This more closely resembles what Kleinert et al. demonstrated during dynamic flexor splinting. While inappropriate extensor elec-
trical activity has not been a significant clinical problem, use of a dorsal block to prevent MCP hyperextension may afford an additional safeguard to protect the repair from undue stress but still allow tendon gliding. Active motion after repair is the next logical step in improving extensor rehabilitation. This not only promotes tendon gliding, but should also physiologically stress the repair to enhance strength.34–36 Evans19 has shown improvement in results utilizing a short arc motion (SAM) protocol for injuries in zones III and IV, improving extension lag from 8 to 3 degrees and PIP motion from 72 to 88 degrees when compared with static splinting, without an
FIGURE 6. Dynamic assist splint with a dorsal block hood holding the MCP joints in slight flexion to prevent inappropriate EMG electrical activity. April–June 2005 179
increase in complications. In the more proximal zones, Evans and Thompson showed that minimal active muscle–tendon tension (MAMTT) also improves results.10 Recently, Keech et al.27 showed that wrist extension beyond neutral diminishes the extension force that can be generated at the proximal phalanx by almost one third (or approximately 1 kg force). This translates to approximately one half or more of overall extensor tendon repair strength; such wrist positioning, when combined with active muscle tensioning protocols, may protect the repair by decreasing the force across the repair site while permitting active tendon gliding. As with any treatment where choice exists, there are advantages and disadvantages to each of these rehabilitation protocols. With immobilization, patient responsibility is minimal, early cost is low, and there is a low danger of early repair failure from external forces, but the immobilization itself can contribute to undesirable edema, additional scar tissue, tendon adhesion, and late repair rupture or lack of motion. Factors such as age, suture type, associated injuries, and, most importantly, patient compliance, must be assessed to determine if immobilization is appropriate. Finally, the inconsistency of result reported in the literature after immobilization must be worrisome and efforts at early mobilization should be considered whenever feasible.1,5,9,11,12,17 Early controlled motion has proven to be a valuable advantage for the newly repaired extensor tendon.2,7,10,16,19,20,29,30 Early tendon gliding permits increased digital motion and, with careful application, complications such as repair rupture and tenolysis have diminished. Results reported by multiple authors have been very consistent and the advantage obvious, but the complexity of approach requires a compliant, motivated patient.
CONCLUSION Hand therapists and hand surgeons should have all available choices for extensor tendon repair and rehabilitation in their armamentarium. Immobilization may be the only option available if there is significant bony injury or there is a compliance issue. While some reports show that immobilization can yield excellent results, many others reveal significant concerns about the overall quality of result. Protocols that emphasize early controlled motion have significantly and consistently improved results, and biomechanical studies have shown that the repair can withstand the forces that may be placed upon them. Clinical studies of early controlled motion protocols have shown not only a consistently improved result, but also fewer complications. When feasible, it would appear that motion should be utilized to effectively 180
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maximize a patient’s final result after extensor tendon injury.
REFERENCES 1. Newport ML, Blair WF, Steyers CM. Long-term results of extensor tendon repair. J Hand Surg [Am]. 1990;15:961–6. 2. Browne EZ Jr, Ribik CA. Early dynamic splinting for extensor tendon injuries. J Hand Surg [Am]. 1989;14:72–6. 3. Hung LK, Chan A, Chang J, Tsang A, Leung PC. Early controlled active mobilization with dynamic splintage for treatment of extensor tendon injuries. J Hand Surg [Am]. 1990; 15:251–7. 4. Saldana MJ, Choban S, Westerbeck P, Schacherer TG. Results of acute zone III extensor tendon injuries treated with dynamic extension splinting. J Hand Surg [Am]. 1991;16: 1145–50. 5. Miller H. Repair of severed tendons of the hand and wrist. Surg Gynecol Obstet. 1942;75:693–8. 6. Allieau Y, Ascencio G, Fouzand JC. Protected passive mobilization after suturing of the extensor tendons of the hand. In: Tubiana R (ed). The Hand. Vol III. Philadelphia: WB Saunders, 1988, pp 157–66. 7. Chow JA, Dovelle S, Thomes LJ, Ho PK, Saldana MJ. A comparison of results of extensor tendon repair followed by early controlled mobilization versus static immobilization. J Hand Surg [Br]. 1989;14:18–20. 8. Crosby CA, Wehbe MA. Early protected motion after extensor tendon repair. J Hand Surg [Am]. 1999;24:1061–70. 9. Dargan EL. Management of extensor injuries of the hand. Surg Gynecol Obstet. 1969;128:1269–73. 10. Evans RB, Burkhalter WE. A study of the dynamic anatomy of extensor tendons and implications for treatment. J Hand Surg [Am]. 1986;11:74–9. 11. Flynn JE. Problems with trauma to the hand. J Bone Joint Surg Am. 1953;35:132–40. 12. Hauge MF. The results of tendon suture of the hands: a review of 500 patients. Acta Orthop Scand. 1954;24:258–70. 13. Ip WY, Chow SP. Results of dynamic splintage following extensor tendon repair. J Hand Surg [Br]. 1997;22:283–7. 14. Kelly AP Jr. Primary tendon repairs: a study of 789 consecutive tendon severances. J Bone Joint Surg Am. 1959;41:581–98. 15. Kerr CD, Burezak JR. Dynamic traction after extensor tendon repair in zones 6, 7, and 8: a retrospective study. J Hand Surg [Br]. 1989;14:21–2. 16. Khandwala AR, Webb J, Harris SB, Foster AJ, Elliot D. A comparison of dynamic extension splinting and controlled active mobilization of complete divisions of extensor tendons in zones 5 and 6. J Hand Surg [Br]. 2000;25:140–6. 17. Purcell T, Eadie PA, Murugan S, O’Donnell M, Lawless. Static splinting of extensor tendon repairs. J Hand Surg [Br]. 2000;25: 180–2. 18. Walsh MT, Rineheimer W, Muntzer E, Patel J, Sitler MR. Early controlled motion with dynamic splinting versus static splinting for zone II and IV extensor tendon lacerations. J Hand Ther. 1994;7:232–6. 19. Evans RB. Early active short arc motion for the repaired central slip. J Hand Surg [Am]. 1994;19A:991–7. 20. Evans RB, Thompson DE. The application of force to the healing tendon. J Hand Ther. 1993;6:266–84. 21. Howard RF, Ondrovic L, Greenwald DP. Biomechanical analysis of four-strand extensor tendon repair techniques. J Hand Surg [Am]. 1997;22:838–42. 22. Newport ML, Williams CD. Biomechanical characteristics of extensor tendon suture techniques. J Hand Surg [Am]. 1992;17: 1117–23. 23. Newport ML, Waters SM. Evaluation of new suture techniques for extensor tendon repair. J Hand Surg. In press. 24. Newport ML, Pollack GR, Williams CD. Biomechanical characteristics of suture techniques in extensor zone IV. J Hand Surg [Am]. 1995;20:650–6.
25. Urbaniak JR, Cahill JP, Mortenson RA. Tendon suturing methods: Analysis of tensile strength. In: American Academy of Orthopaedic Surgeons: Symposium on Tendon Surgery of the Hand. St. Louis: CV Mosby, 1975, pp 70–80. 26. Ketchum LD, Thompson D, Pocock G, Wallingford D. A clinical study of forces generated by the intrinsic muscles of the index finger and the extrinsic muscles of the hand. J Hand Surg. 1978;6:571–8. 27. Keech BM, Adams DJ, Diaz-Doran V, Newport ML. Extensor tendon tension in zone VI at maximal isometric contraction. Presented at the 2004 Annual Meeting of the Orthopaedic Research Society and the 2004 Annual Meeting of the American Academy of Orthopaedic Surgeons. 28. Minamikawa Y, Peimer CA, Yamaguchi T, Banasiak NA, Kambe K, Sherwin FS. Wrist position and extensor tendon amplitude following repair. J Hand Surg [Am]. 1992;17:268–71. 29. Bruner S, Wittemann M, Jester A, Blumental K, Germann G. Dynamic splinting after extensor repair in zones V to VII. J Hand Surg. 2003;28B:224–7. 30. Sylaidis P, Youatt M, Logan A. Early active mobilization for extensor tendon injuries: the Norwich regime. J Hand Surg [Br]. 1997;22:594–6.
31. Duran RJ, Houser RG. Controlled passive motion following flexor tendon repair in zones II and III. In: The American Academy of Orthopaedic Surgeons: Symposium on Tendon Surgery in the Hand. St. Louis: CV Mosby, 1975, p 105. 32. Kleinert HE, Kutz JE, Cohen MJ. Primary repair of zone 2 flexor tendon lacerations. In: American Academy of Orthopaedic Surgeons Symposium on Tendon Surgery of the Hand. St. Louis, MO: CV Mosby, 1975, pp 91–104. 33. Newport ML, Shukla A. Electrophysiologic basis of dynamic extensor splinting. J Hand Surg [Am]. 1992;17:272–7. 34. Freehan LM, Beauchene JG. Early tensile properties of healing chicken flexor tendons: early controlled passive motion versus postoperative immobilization. J Hand Surg [Am]. 1990;15: 63–8. 35. Gelberman RH, Vande Berg JS, Manske PR. The early stages of flexor tendon healing: a morphologic study of the first 14 days. J Hand Surg. 1985;10:776–84. 36. Hitchcock TF, Light TR, Bunch WH, et al. The effect of immediate constrained digital motion on the strength of flexor tendon repairs in chickens. J Hand Surg [Am]. 1987;12: 590–5.
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Robert L. Tucker, OTR/L Department of Sports Medicine and Rehabilitation University of Connecticut Health Center Farmington, Connecticut
While flexor tendon injuries have received a great deal of attention concerning repair technique, repair healing, and postoperative therapy, extensor tendon injuries have received significantly less attention. However, these injuries are as problematic as their counterpart. Careful scrutiny of the quality of reported results demonstrates that not only do affected fingers lose extension, but that an even greater percentage lose flexion.1 Loss of digital flexion affecting grasp and power grip poses a greater functional loss than digital extensor lag.1–4 Because of these recognized postoperative complications, the surgical and therapeutic care of extensor tendon injuries should be as exacting and careful as for flexor tendon injuries.5 Extensor tendon rehabilitation utilizing some form of gliding technique, either dynamically assisted or actively mediated, has generally improved the quality of results when compared with postoperative immobilization.1–20 Protocols which utilize early controlled motion after repair have shown a greater than 90% good or excellent result rate for uncomplicated injuries in zones V to VIII compared with 54% to 95% good or excellent result rates for repairs treated with immobilization.1–20 Injuries in zones III and IV produce less favorable results than more proximal injuries1; however, these results have also
Correspondence and reprint requests to Dr. Mary Lynn Newport, Department of Orthopaedic Surgery, University of Connecticut Health Center, Farmington, CT 06034; e-mail:
ABSTRACT: This article reviews the available biomechanical and clinical studies on extensor tendon repair and postoperative management. Immobilization has been a foundation for the postoperative treatment of these injuries, with good or excellent results ranging between 54% and 95%. However, clinical outcomes have consistently improved when utilizing rehabilitation involving either dynamically assisted or active motion, with good or excellent results achieved in at least 90% of cases. In addition, available biomechanical studies concerning finger extension strength, tendon repair strength, tendon shortening, resultant loss of motion, and gliding capability have validated controlled motion as biomechanically sound utilizing contemporary repair techniques. J HAND THER. 2005;18:175–181.
been improved with techniques for early controlled motion.3,4,7,18,19 When compared with static splinting, some would argue these early controlled motion protocols can be cumbersome, time consuming, complicated, and expensive. In addition, there remains concern that such rehabilitation may place too much stress on the repair and may contribute to repair elongation or rupture. Repair rupture or failure, however, has not been of significant clinical consequence with the active or dynamic gliding techniques.2,8,10,19,20 In fact, all complications, including loss of motion, extensor lag, loss of grip strength, and incidence of tenolysis, decrease when early controlled motion is compared with immobilization.1,2,4–18 These protocols clearly improve the overall quality and reproducibility of result and should be utilized unless other contraindications such as associated injury or adverse patient profile exist.
REPAIR QUALITY Hand therapists should have a working knowledge of available extensor tendon repair techniques, their tensile strengths, and biomechanical implications. It is imperative that the therapist review the operative report and communicate with the surgeon to ascertain the number of tendons injured and zone of injury, realizing that injury in the distal zones (I–IV) tends to fare less well: zone V typically does best after injury, and zones VI to VIII are equivalent in prognosis—the area under the retinaculum does not scar more significantly or reduce the rate of good or April–June 2005 175
excellent results.1,3,10 It is also important the therapist obtain information on repair technique, suture material, quality of repair, and associated injury, including soft-tissue loss, periosteal damage, fracture, and joint capsule damage. All of these factors can alter splint design or controlled motion parameters for each individual patient. Contemporary extensor tendon repair techniques, because of anatomical differences, are less complicated in design and have less tensile strength compared with flexor tendon repair. The extensor is a much smaller tendon with a relatively flat cross section. Its collagen is longitudinally oriented, with little or no cross-linking. Because of this size differential and lack of surrounding paratenon (except in zone VII), extensors are not as amenable as flexor tendons to multiple-stranded, stronger repair techniques, especially in the more distal (III and IV) zones. The usual tendon biomechanical concerns of repair strength and failure mode have been investigated, but because of the intricate relationship between the intrinsic and extrinsic extensor mechanisms, several other variables come into play during extensor repair, including shortening, lost range of motion after repair, and increased force to obtain maximum flexion. Few studies have evaluated ultimate strength of extensor repair. The four-strand repair described by Howard et al.21 (‘‘MGH repair’’) has been shown to be strongest; however, other biomechanical features such as shortening or resultant loss of motion were not evaluated and their strength evaluation was performed somewhat differently than other studies (Table 1). Compared with the MGH or traditional modified Bunnell repair, a two-strand locked Bunnell repair has been shown to be intermediate in strength and has undergone further biomechanical evaluation (Table 1).22,23 The locked Bunnell showed an improved quality of strength (suture rupture rather than pullout) over the traditional Bunnell (17% versus 58% pullout) but less than the MGH repair (0% pullout), the four-strand Bunnell, or KrackowThomas (0% pullout) described by Howard et al.21–23 Surprisingly, the strength and quality of repair
comparing traditional two-stranded techniques is not significantly different in the smaller, thinner tendons of zone IV when compared with repair in zone VI.22,24 The ultimate strength requirement for extensor repair is not yet well understood. Urbaniak et al.’s25 work during carpal tunnel release on the direct measurement of flexor tendon forces by strain gauge has given us some understanding of the forces to which flexor tendons are subjected. Because similar access under local anesthesia is not presently possible, extensor strength has not been so directly measured in vivo. It has, however, has been measured indirectly. Ketchum et al.26 studied extension strength via a force transducer on the dorsum of the proximal phalanx and found that normal subjects could generate a force of 2.99 kg for the index finger, decreasing ulnarly to 1.97 kg for the small finger. Preliminary studies on maximum extension strength in our laboratory have shown similar findings, with the additional information that the long finger is the strongest and finger extension strength varies significantly according to wrist and metacarpophalangeal (MCP) position.27 Wrist extension of 40 degrees decreased possible extension force at the finger by approximately 25% (40 N versus 30 N or 4.08 kg force versus 3.06 kg). Wrist flexion increased possible extension force by similar amount. These results are expected because of the tenodesis effect wrist position has on the extensor tendon, but now the forces have been quantified so they can be compared with relative tendon repair strength. The implication for the treating therapist is obvious: a strong repair technique that can withstand significant force might be subjected to wrist flexion in rehabilitation, whereas a tenuous repair may require significant restriction in wrist range of motion. Repair strength versus extension force clearly requires further study, but other biomechanical factors such as shortening, pull-out strength, and ability to withstand cycling are also critically important in designing and choosing rehabilitation methods. Extensor repair in the cadaveric model produces a variable amount of tendon shortening that can
TABLE 1. Comparison Biomedical Characteristics Available Extensor Repair Techniques Repair* Mattress Bunnell (2 strand) Locked Bunnell Whipstitch (2 strand) *Bunnell (4 strand) *Krackow (4 strand) *MGH (4 strand)
Strength to gap (gm)
Average Shortening (mm)
Failure Mode (pullout)
Elongation after stress (mm)
Loss composite flexion (°)
488 1425 1780 1870 3200 3300 4800
7.6 6.8 5.8 13.5 NT NT NT
100% 58% 17% 0% 0% 0% 0%
NT 2.5 2.7 2.8 NT NT NT
43° 35° NT NT NT NT NT
NT = Not Tested. *This compares work by the senior author and by Howard et al.23 Howard et al. measured to 1 mm gap and all others were measured to 2 mm gap.
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significantly alter the biomechanics of the extensor mechanism, including loss of composite flexion and increasing force required to obtain full flexion (Table 1).22–24 Traditional repairs in zone VI such as the modified Bunnell technique produce an average of at least 7 mm of shortening (Table 1) and result in 35 degrees or more loss of composite flexion when the wrist is held in neutral position (Figure 1).22 The locked Bunnell produces less shortening (5.8 mm).23 A whipstitch repair, similar to a Krackow repair, was evaluated by Newport and Waters23 and found to shorten the tendon by over 13 mm, demonstrating that some repair techniques can produce significant shortening. In another biomechanical study, Minamikawa et al.28 showed there was a redundancy of 6.4 mm tendon over the metacarpal when the wrist was extended 45 degrees or more. They surmised this amount of tendon could be debrided without affecting digital motion or placing undue stress on the repair site, as long as the wrist was appropriately extended. While shortening with typical repair techniques and the amount which can be compensated for have been shown to be strikingly equivalent, it must be noted that these biomechanical experiments represent smooth tendon gliding in a cadaveric model without muscle tone, the increased friction of edema, adhesion formation, skin closure, or bulk of repair. Because of these postoperative factors, ability to compensate for tendon loss or shortening may be neutralized; repair strength and capacity to glide remain essential. When the extensor tendon, repaired with the locked Bunnell technique, is subjected to cycling through flexion and extension, there is elongation of 2.7 mm with the first cycle and 1.3 mm more over the next 100 cycles.23 Repair quality (suture pullout versus breakage) also degraded somewhat with cycling through the overall strength to 2 mm gap and failure did not. While elongation with cycling should produce concern if early controlled motion is considered as a rehabilitation option, it should be noted that the elongation was never greater than the
shortening produced by the repair itself and there was no repair gap evident during cycling. Wrist position beyond neutral was not evaluated in this study, but wrist extension and tendon redundancy as shown by Minamikawa et al.28 may afford some measure of stress relief to the repair site. Another biomechanical parameter that may affect the ultimate result after extensor repair is the increased amount of force that is required to pull the digit into maximum flexion. The average repair in zone VI shortens the tendon approximately 7 mm, requiring an increased force to maximum flexion of approximately 600 g (Figure 2).22 Repair in zone IV fares somewhat better, with tendon shortening of only 2 or 3 mm and force increase to full flexion of 350 to 400 g in the artificial tendon shortening model (Figure 3) and 0 to 180 g force with the modified Bunnell technique, which was the most biomechanically sound repair of those tested for zone IV.24 The multiple points of connection between the intrinsic and extrinsic extensor mechanism at this level prevent tendon shortening with repair. This decreases the resultant loss of proximal interphalangeal (PIP) motion (Figure 4) and consequently minimizes the increased force required to maximum flexion. These biomechanical findings show that intraoperative factors such as shortening may be less a cause for poor result in zone IV compared with zone VI and that adhesion formation because of the large surface area may be more significant in reducing the quality of result. Moving the tendon repair in these distal zones may be required to produce consistently good results.
FIGURE 1. Tendon shortening versus loss of MCP and PIP motion, zone VI.
FIGURE 2. Increase in force required to maximum digital flexion after tendon shortening, zone VI.
IMPLICATIONS FOR REHABILITATION There are many rehabilitation choices available for extensor tendon injury. The goals for each are the
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FIGURE 3. Increase in force required to maximum digital flexion after tendon shortening, zone IV. same: protect the repair, promote tendon healing and facilitate tendon gliding. Immobilization is the most traditional approach to extensor tendon injury. Theoretically, it is safest as the lack of joint motion should minimize tension on the healing tendon. While this philosophy relies on repair biology to increase the strength of the repaired tendon over time, it nonetheless requires a strong construct that must withstand tendon shortening, adhesion formation, and increased flexion forces from stiff digits when tendon gliding begins. Parameters for immobilization are dependent on level of injury relative to the juncturae tendinae, whether one or both lateral bands have been injured, possible injury to sagittal fibers, and associated ligamentous injury. These details will dictate inclusion of adjacent fingers and in what position to place each affected joint. Wound care and edema control are extremely important at this stage, though the role of the hand therapist may be limited until range of motion exercises are
FIGURE 4. Tendon shortening versus loss of motion, zone IV. 178
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begun. While immobilization would seem safest and requires the least amount of early rehabilitation effort, there are potential complications following this program, including tendon rupture, adhesion formation requiring tenolysis, extension lag, loss of flexion, and decreased grip strength.1,2,10,29 Over the last two decades, early motion protocols utilizing varying combinations of dynamic splinting and tendon gliding programs have become accepted as beneficial, effective methods of extensor tendon rehabilitation with significant improvement in results.2–4,6–8,10,13,15,18–20,30 Their focus has been to balance the tensile strength of the specific tendon repair with adequate joint motion and tendon gliding. Evans and Burkhalter10 have demonstrated through intraoperative measurement that 30-degree MCP flexion for the index/long fingers and 40-degree flexion for the ring/small fingers produce approximately 5 mm extensor digitorum communis excursion. This was felt to be sufficient for the extensor system, based on Duran and Houser’s31 work with flexor tendon excursion during dynamic splinting. Actual extensor excursion, however, has not been directly measured and, because an animal model for extensor repair has not yet proven practical, the excursion required to prevent adhesion formation can only be deduced through these indirect means. While most dynamic splint designs protect against full digital flexion with a fashioned flexion stop or by limiting the excursion of the outrigger, near-complete composite flexion may be tolerated within the confines of dynamic traction in the more proximal zones if the wrist is properly positioned. Browne and Ribik2 reported excellent clinical results with dynamic splinting and larger angles of digital flexion, and Minamikawa et al.’s28 work demonstrated that full composite flexion is possible without undue strain on the repair if the wrist is extended beyond 21 degrees. Excessive wrist extension, however, can cause the extensors to buckle in the more proximal zones, possibly decreasing functional gliding.28 The effect of tendon shortening after repair and its effect on joint position and rehabilitation protocol remains incompletely defined. However, biomechanical and clinical results support protocols that combine dynamic splinting with the wrist appropriately extended and near-full finger motion. Allowing increased digital motion while protecting the repair with wrist position may decrease complications of lost digital flexion. As mentioned previously, lost digital flexion has been a greater problem than extensor lag or adhesion formation, which requires tenolysis, though these complication rates have been lower for dynamic splinting than for static splinting.2,7,10,29 Most dynamic splints designed for extensor repair in the proximal zones (V–VII) leave the MCP joints free to rest at 0 degrees extension (Figure 5). During dynamic splinting for flexor tendon injury, Kleinert
FIGURE 5. Dynamic assist splint modeled after splints used for MCP joint replacement. The MCP joints are free to extend or hyperextend. et al.32 showed that flexor muscles were electrically silent during active extension and dynamically assisted flexion and consequently placed no active tension on the repair site. However, during electromyographic (EMG) testing in the usual dynamic extension splint, the extensor muscles are active during flexion and at rest in 84% of test subjects.33 For dynamic extension splinting, this inappropriate and potentially harmful electrical activity is reduced to 5% when a dorsal block hood is extended to the MCP joints to hold them in slight flexion (5–10 degrees) (Figure 6). This more closely resembles what Kleinert et al. demonstrated during dynamic flexor splinting. While inappropriate extensor elec-
trical activity has not been a significant clinical problem, use of a dorsal block to prevent MCP hyperextension may afford an additional safeguard to protect the repair from undue stress but still allow tendon gliding. Active motion after repair is the next logical step in improving extensor rehabilitation. This not only promotes tendon gliding, but should also physiologically stress the repair to enhance strength.34–36 Evans19 has shown improvement in results utilizing a short arc motion (SAM) protocol for injuries in zones III and IV, improving extension lag from 8 to 3 degrees and PIP motion from 72 to 88 degrees when compared with static splinting, without an
FIGURE 6. Dynamic assist splint with a dorsal block hood holding the MCP joints in slight flexion to prevent inappropriate EMG electrical activity. April–June 2005 179
increase in complications. In the more proximal zones, Evans and Thompson showed that minimal active muscle–tendon tension (MAMTT) also improves results.10 Recently, Keech et al.27 showed that wrist extension beyond neutral diminishes the extension force that can be generated at the proximal phalanx by almost one third (or approximately 1 kg force). This translates to approximately one half or more of overall extensor tendon repair strength; such wrist positioning, when combined with active muscle tensioning protocols, may protect the repair by decreasing the force across the repair site while permitting active tendon gliding. As with any treatment where choice exists, there are advantages and disadvantages to each of these rehabilitation protocols. With immobilization, patient responsibility is minimal, early cost is low, and there is a low danger of early repair failure from external forces, but the immobilization itself can contribute to undesirable edema, additional scar tissue, tendon adhesion, and late repair rupture or lack of motion. Factors such as age, suture type, associated injuries, and, most importantly, patient compliance, must be assessed to determine if immobilization is appropriate. Finally, the inconsistency of result reported in the literature after immobilization must be worrisome and efforts at early mobilization should be considered whenever feasible.1,5,9,11,12,17 Early controlled motion has proven to be a valuable advantage for the newly repaired extensor tendon.2,7,10,16,19,20,29,30 Early tendon gliding permits increased digital motion and, with careful application, complications such as repair rupture and tenolysis have diminished. Results reported by multiple authors have been very consistent and the advantage obvious, but the complexity of approach requires a compliant, motivated patient.
CONCLUSION Hand therapists and hand surgeons should have all available choices for extensor tendon repair and rehabilitation in their armamentarium. Immobilization may be the only option available if there is significant bony injury or there is a compliance issue. While some reports show that immobilization can yield excellent results, many others reveal significant concerns about the overall quality of result. Protocols that emphasize early controlled motion have significantly and consistently improved results, and biomechanical studies have shown that the repair can withstand the forces that may be placed upon them. Clinical studies of early controlled motion protocols have shown not only a consistently improved result, but also fewer complications. When feasible, it would appear that motion should be utilized to effectively 180
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maximize a patient’s final result after extensor tendon injury.
REFERENCES 1. Newport ML, Blair WF, Steyers CM. Long-term results of extensor tendon repair. J Hand Surg [Am]. 1990;15:961–6. 2. Browne EZ Jr, Ribik CA. Early dynamic splinting for extensor tendon injuries. J Hand Surg [Am]. 1989;14:72–6. 3. Hung LK, Chan A, Chang J, Tsang A, Leung PC. Early controlled active mobilization with dynamic splintage for treatment of extensor tendon injuries. J Hand Surg [Am]. 1990; 15:251–7. 4. Saldana MJ, Choban S, Westerbeck P, Schacherer TG. Results of acute zone III extensor tendon injuries treated with dynamic extension splinting. J Hand Surg [Am]. 1991;16: 1145–50. 5. Miller H. Repair of severed tendons of the hand and wrist. Surg Gynecol Obstet. 1942;75:693–8. 6. Allieau Y, Ascencio G, Fouzand JC. Protected passive mobilization after suturing of the extensor tendons of the hand. In: Tubiana R (ed). The Hand. Vol III. Philadelphia: WB Saunders, 1988, pp 157–66. 7. Chow JA, Dovelle S, Thomes LJ, Ho PK, Saldana MJ. A comparison of results of extensor tendon repair followed by early controlled mobilization versus static immobilization. J Hand Surg [Br]. 1989;14:18–20. 8. Crosby CA, Wehbe MA. Early protected motion after extensor tendon repair. J Hand Surg [Am]. 1999;24:1061–70. 9. Dargan EL. Management of extensor injuries of the hand. Surg Gynecol Obstet. 1969;128:1269–73. 10. Evans RB, Burkhalter WE. A study of the dynamic anatomy of extensor tendons and implications for treatment. J Hand Surg [Am]. 1986;11:74–9. 11. Flynn JE. Problems with trauma to the hand. J Bone Joint Surg Am. 1953;35:132–40. 12. Hauge MF. The results of tendon suture of the hands: a review of 500 patients. Acta Orthop Scand. 1954;24:258–70. 13. Ip WY, Chow SP. Results of dynamic splintage following extensor tendon repair. J Hand Surg [Br]. 1997;22:283–7. 14. Kelly AP Jr. Primary tendon repairs: a study of 789 consecutive tendon severances. J Bone Joint Surg Am. 1959;41:581–98. 15. Kerr CD, Burezak JR. Dynamic traction after extensor tendon repair in zones 6, 7, and 8: a retrospective study. J Hand Surg [Br]. 1989;14:21–2. 16. Khandwala AR, Webb J, Harris SB, Foster AJ, Elliot D. A comparison of dynamic extension splinting and controlled active mobilization of complete divisions of extensor tendons in zones 5 and 6. J Hand Surg [Br]. 2000;25:140–6. 17. Purcell T, Eadie PA, Murugan S, O’Donnell M, Lawless. Static splinting of extensor tendon repairs. J Hand Surg [Br]. 2000;25: 180–2. 18. Walsh MT, Rineheimer W, Muntzer E, Patel J, Sitler MR. Early controlled motion with dynamic splinting versus static splinting for zone II and IV extensor tendon lacerations. J Hand Ther. 1994;7:232–6. 19. Evans RB. Early active short arc motion for the repaired central slip. J Hand Surg [Am]. 1994;19A:991–7. 20. Evans RB, Thompson DE. The application of force to the healing tendon. J Hand Ther. 1993;6:266–84. 21. Howard RF, Ondrovic L, Greenwald DP. Biomechanical analysis of four-strand extensor tendon repair techniques. J Hand Surg [Am]. 1997;22:838–42. 22. Newport ML, Williams CD. Biomechanical characteristics of extensor tendon suture techniques. J Hand Surg [Am]. 1992;17: 1117–23. 23. Newport ML, Waters SM. Evaluation of new suture techniques for extensor tendon repair. J Hand Surg. In press. 24. Newport ML, Pollack GR, Williams CD. Biomechanical characteristics of suture techniques in extensor zone IV. J Hand Surg [Am]. 1995;20:650–6.
25. Urbaniak JR, Cahill JP, Mortenson RA. Tendon suturing methods: Analysis of tensile strength. In: American Academy of Orthopaedic Surgeons: Symposium on Tendon Surgery of the Hand. St. Louis: CV Mosby, 1975, pp 70–80. 26. Ketchum LD, Thompson D, Pocock G, Wallingford D. A clinical study of forces generated by the intrinsic muscles of the index finger and the extrinsic muscles of the hand. J Hand Surg. 1978;6:571–8. 27. Keech BM, Adams DJ, Diaz-Doran V, Newport ML. Extensor tendon tension in zone VI at maximal isometric contraction. Presented at the 2004 Annual Meeting of the Orthopaedic Research Society and the 2004 Annual Meeting of the American Academy of Orthopaedic Surgeons. 28. Minamikawa Y, Peimer CA, Yamaguchi T, Banasiak NA, Kambe K, Sherwin FS. Wrist position and extensor tendon amplitude following repair. J Hand Surg [Am]. 1992;17:268–71. 29. Bruner S, Wittemann M, Jester A, Blumental K, Germann G. Dynamic splinting after extensor repair in zones V to VII. J Hand Surg. 2003;28B:224–7. 30. Sylaidis P, Youatt M, Logan A. Early active mobilization for extensor tendon injuries: the Norwich regime. J Hand Surg [Br]. 1997;22:594–6.
31. Duran RJ, Houser RG. Controlled passive motion following flexor tendon repair in zones II and III. In: The American Academy of Orthopaedic Surgeons: Symposium on Tendon Surgery in the Hand. St. Louis: CV Mosby, 1975, p 105. 32. Kleinert HE, Kutz JE, Cohen MJ. Primary repair of zone 2 flexor tendon lacerations. In: American Academy of Orthopaedic Surgeons Symposium on Tendon Surgery of the Hand. St. Louis, MO: CV Mosby, 1975, pp 91–104. 33. Newport ML, Shukla A. Electrophysiologic basis of dynamic extensor splinting. J Hand Surg [Am]. 1992;17:272–7. 34. Freehan LM, Beauchene JG. Early tensile properties of healing chicken flexor tendons: early controlled passive motion versus postoperative immobilization. J Hand Surg [Am]. 1990;15: 63–8. 35. Gelberman RH, Vande Berg JS, Manske PR. The early stages of flexor tendon healing: a morphologic study of the first 14 days. J Hand Surg. 1985;10:776–84. 36. Hitchcock TF, Light TR, Bunch WH, et al. The effect of immediate constrained digital motion on the strength of flexor tendon repairs in chickens. J Hand Surg [Am]. 1987;12: 590–5.
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