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Flexor Pulley System: Anatomy, Injury, and Management
CURRENT CONCEPTS
Flexor Pulley System: Anatomy, Injury, and Management Brian Zafonte, MD, Dora Rendulic, MD, Robert M. Szabo, MD CME INFORMATION AND DISCLOSURES The Review Section of JHS will contain at least 3 clinically relevant articles selected by the editor to be offered for CME in each issue. For CME credit, the participant must read the articles in print or online and correctly answer all related questions through an online examination. The questions on the test are designed to make the reader think and will occasionally require the reader to go back and scrutinize the article for details. The JHS CME Activity fee of $30.00 includes the exam questions/answers only and does not include access to the JHS articles referenced. Statement of Need: This CME activity was developed by the JHS review section editors and review article authors as a convenient education tool to help increase or affirm reader’s knowledge. The overall goal of the activity is for participants to evaluate the appropriateness of clinical data and apply it to their practice and the provision of patient care.
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Copyright ª 2014 by the American Society for Surgery of the Hand. All rights reserved.
Detail the anatomy and biomechanics of the flexor pulley system. Describe the epidemiology and etiology of flexor pulley system injuries. Recognize the clinical manifestations of closed pulley system rupture. Offer diagnostic strategies for various types of closed pulley system ruptures. Discuss treatment methods, outcomes, and complications of pulley system injuries.
From the Department of Orthopaedic Surgery, University of California, Davis, Sacramento, CA. Received for publication April 29, 2014; accepted in revised form June 3, 2014. No benefits in any form have been received or will be received related directly or indirectly to the subject of this article.
Corresponding author: Robert M. Szabo, MD, Department of Orthopaedic Surgery, Hand and Upper Extremity Service, University of California, Davis, School of Medicine, 4860 Y St., Suite 3800, Sacramento, CA 95817; e-mail: [email protected]. 0363-5023/14/3912-0033$36.00/0 http://dx.doi.org/10.1016/j.jhsa.2014.06.005
2014 ASSH
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Published by Elsevier, Inc. All rights reserved.
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Flexor pulley injuries are most commonly seen in avid rock climbers; however, reports of pulley ruptures in nonclimbers are increasing. In addition to traumatic disruption, corticosteroid-induced pulley rupture has been reported as a complication of treating stenosing tenosynovitis. Over the last decade, there have been 2 new developments in the way hand surgeons think about the flexor pulley system. First, the thumb pulley system has been shown
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to have 4 component constituents, in contrast to the classic teaching of 3 pulleys. Second, in cases of zone II flexor tendon injury, the intentional partial A2 and/or A4 pulley excision or venting is emerging as a component for successful treatment. This is challenging the onceheld dogma that preserving the integrity of the entire A2 and A4 pulleys is indispensable for normal digit function. (J Hand Surg Am. 2014;39(12):2525e2532. Copyright 2014 by the American Society for Surgery of the Hand. All rights reserved.) Key words Flexor pulley, annular pulley, rock climbing, pulley rupture, pulley reconstruction.
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ANATOMY AND BIOMECHANICS The digital flexor sheath-pulley system is a complex structure that permits normal and efficient flexor tendon function. This sheath-pulley system is composed of a deep synovial component and a superficial retinacular or pulley component. The pulleys are fibrous tissue condensations, which almost encircle the flexor tendons forming a fibro-osseous channel that functions to keep the tendons adjacent to the phalanges. This enables the transfer of a translational force generated from the muscle-tendon unit into a rotational moment on the phalanges. In the fingers, there are 5 annular (A1eA5) and 3 cruciate (C1eC3) pulleys running in descending order from proximal to distal (Fig. 1). The A2 and A4 pulleys insert directly into bone over the proximal and middle phalanges, respectively. In contrast, A1, A3, and A5 are narrower, more flexible, insert mostly into volar plate, and with the cruciate pulleys, permit compression without impingement and expansion during finger flexion and extension, respectively. A1, A3, and A5 pulleys are located over the metacarpophalangeal (MCP), proximal interphalangeal (PIP), and distal interphalangeal (DIP) joints, respectively. The cruciate pulleys comprise C1, C2, and C3, and lie between the A2eA3, the A3eA4, and the A4eA5 pulleys, respectively. Proximal to the A1 pulley lies the palmar aponeurotic (PA) pulley, which is composed of transverse ligament of the palmar aponeurosis that is attached to the underlying septa of Legueu and Juvara, thus forming an arch over the flexor tendons superficial and proximal to the A1 pulley. Biomechanical evaluation of the PA pulley demonstrated that isolated sectioning did not change work or load efficiency.1 However, the PA pulley has been implicated in the etiology of trigger finger.2 Traditionally, only 3 components of the thumb pulley system were described: A1, oblique, and A2 pulleys. The A1 pulley lies over the MCP joint, the oblique pulley runs from proximal ulnar to distal radial over the proximal phalanx, and the A2 pulley is located over the interphalangeal joint. A fourth thumb pulley, the variable annular pulley, has now been characterized (Fig. 2). First reported in J Hand Surg Am.
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2002,3 Schubert et al4 found this pulley to be present in 93% of cadaver specimens with 3 possible orientations: transverse, oblique, or continuous with the A1 pulley. The variable annular pulley can be an additional site of stenosis in trigger thumbs. Although the importance of a given pulley can be debated, the A2 and A4 pulleys have traditionally been deemed most important in preventing bowstringing.5,6 The A2 is bigger and considered more important; however, there is evidence that the A2 and A4 pulleys have similar biomechanical properties irrespective of differing digits or gender.7 Owing to this historic importance, most surgeons advocate their preservation, repair, or reconstruction. However, 2 lines of investigation have been challenging this dogma, particularly with respect to zone II flexor tendon injuries. First, biomechanical studies in cadavers examined the effects of partial pulley excision on finger function. Tomaino et al8 characterized partial distal excisions of the A2, A4, or A2 and A4 pulleys in combination and found that 25% of the A2 pulley, up to 75% of A4, and 25% of combined A2 and A4 can be excised without any significant effect on digit range of motion or work of flexion. Mitsionis et al9 reported similar findings. Both groups suggest that partial A2 and A4 pulleys excision (or incision called venting) may be used to facilitate tendon gliding after surgery, and that the modest decrease in digital range of motion may be clinically acceptable. In further examining the effects of partial distal versus partial proximal pulley excisions, results differ. Chow et al10 found significant decrease in overall finger motion with partial proximal incisions of either the A2 or the A4 pulley as compared with partial distal incisions. In contrast, Leeflang and Coert11 found that partial distal incisions of the A2 pulley led to greater bowstringing at the proximal phalanx as compared with partial proximal incisions. The A4 pulley was not assessed in that study. Although these data are limited by the use of different cadaver models employing nonphysiological loading forces, they provide the basis for the second line of investigation, in vivo analysis. Using a live chicken model to examine the effects of complete A2 incision on flexor tendon integrity Vol. 39, December 2014
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after tendon repair, Tang et al12 found no deleterious effects on flexor digitorum profundus (FDP) tendon function. In contrast, the data demonstrated improved tendon excursion and decreased work of flexion when compared with primary pulley repair. In a follow-up study using the same avian model, Cao and Tang13 measured the strength in flexor tendon repairs around the A2 pulley when it was preserved or completely incised and found that tendon repair strength was 30% to 60% greater after A2 division compared with the intact pulley. Consequently, they proposed that tendon repairs would be more successful with purposeful pulley disruption. The same group reported an increased tendon gliding resistance in the intact A2 pulley model, which led to significantly higher rates of postoperative tendon ruptures.14 Moreover, Tang15 has previously performed a detailed characterization of the area of the J Hand Surg Am.
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flexor sheath beneath the A2 pulley and suggested the FDP tendon gliding function may be improved after partial A2 excision. With respect to A4, Franko et al16 found a less than 3% increase in the work of flexion after partial distal or complete A4 pulley release and significantly less work of flexion when compared with FDP tendon repair with an intact A4 pulley. Collectively, this body of work, although done in cadaver and animal models, supports the rationale for considering intentional A2 and/or A4 pulley venting or excision during zone II flexor tendon repair. In contrast to available clinical and biomechanical data examining the pulley system in the fingers, much less progress has been made in characterizing the thumb pulley system. In a cadaver model, Zissimos et al17 studied the mechanical efficiency and angular joint displacement in the thumb. They found that isolated Vol. 39, December 2014
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FIGURE 1: A Sagittal and B coronal depictions of the finger flexor tendon pulley system. Black areas indicate the flexor tendon. Annular pulleys A1 to A5 and cruciate pulleys C1 to C3. Dotted lines represent the division of the flexor digitorum superficialis tendon. (Reproduced with permission Hauger O, Chung CB, Lektrakul N, et al. Pulley system in the fingers: normal anatomy and simulated lesions in cadavers at MR imaging, CT, and US with and without contrast material distention of the tendon sheath. Radiology 2000;217(1):201e212.26 Copyright 2000 Radiological Society of North America.)
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FIGURE 2: The flexor pulley system in the thumb. A Classic depiction of the 3-pulley system: A1, oblique, A2. BeD Updated illustrations to show the fourth pulley, the variable annular pulley (Av), which can be orientated transversely B, obliquely C, or in continuity with A1 D. (Reproduced with permission from Schubert MF, Shah VS, Craig CL, Zeller JL. Varied anatomy of the thumb pulley system: implications for successful trigger thumb release. J Hand Surg Am. 2012;37(11):2278e2285.4 Copyright 2012 Elsevier.)
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sectioning of either the A1 or the oblique pulley did not significantly alter thumb biomechanics. Only when both the A1 and the oblique pulleys were disrupted did significant tendon bowstringing occur. No differences were found with respect to intact versus sectioned A2 pulley. The authors concluded that either the A1 or the oblique pulley must be kept intact or reconstructed to maintain normal thumb kinematics and prevent bowstringing. CLINICAL PICTURE It is estimated that 75% of all rock climbers will suffer an upper extremity injury; 60% of those will involve the hand or wrist and 30% to 50% of those will involve closed injury to the flexor tendon-pulley system. In elite climbers, Logan et al18 reported a 33% incidence of finger tendon injuries, with an 8% incidence of A2 pulley rupture. Dy et al19 examined the rates of pulley J Hand Surg Am.
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reconstruction and reoperation in their retrospective study of all patients who had flexor pulley reconstruction from 1998 to 2009 in New York state. Six hundred and twenty-three patients underwent pulley reconstruction, with an overall incidence of 0.27 per 100,000 persons. They also found a 6% reoperation rate, the majority for tenolysis (64%). The infrequency of injury in the general population together with the paucity of clinical outcome data have made it challenging for hand surgeons to develop optimal treatment strategies for patients with pulley disruptions. Acute closed pulley rupture can be partial or complete and can occur in isolation or as part of multiple pulley disruptions. Frequently, patients complain of an audible pop or tearing sensation with only moderate pain over the injured pulley. Typically, there is no appreciable loss of grip strength. The most common physical examination findings in a single pulley rupture are swelling and pain over the affected pulley. However, Vol. 39, December 2014
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FIGURE 3: Biomechanics of the flexor tendon pulley system. The amount of finger flexion is proportional to tendon excursion and the moment arm (r). A The intact pulleys keep the flexor tendons close to the axis of rotation of the finger joints, thereby maximizing total finger flexion. B The moment arm (r) increases with pulley insufficiency leading to maximum tendon excursion before full finger flexion can be obtained. The flexor digitorum superficialis has been excluded for simplicity.
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pulley ruptures in nonclimbers are emerging. Lourie et al22 reported a case series of 4 professional baseball pitchers who sustained closed isolated A4 ruptures of the long finger. The injury was caused by a hyperextension force on the DIP joint while actively flexing the finger when throwing a fastball. Arora et al23 and Schoffl and Jungert24 described 14 cases of pulley rupture in patients who were lifting heavy objects using the crimp grip position. In all cases, rupture occurred when a sudden extension force was applied to an acutely flexed digit. Open pulley injuries are extremely rare, but iatrogenic pulley disruption can occur with aggressive trigger finger release or after tendon repair or tenolysis. The deleterious effect of repeated corticosteroid injections for trigger finger causing pulley rupture has been described,25 thus raising caution among hand surgeons in the treatment of this common hand problem. DIAGNOSIS The diagnosis of flexor pulley rupture is conventionally made by physical examination. X-rays are usually normal but may help rule out other injuries such as a palmar plate avulsion. Magnetic resonance imaging (MRI) and high-resolution ultrasound are the imaging modalities of choice when the physical examination remains equivocal. MRI helps characterize more complex injuries (eg, multiple pulley ruptures) and is useful to rule out other soft tissue pathology (eg, muscle or ligament injury). In cases of suspected pulley rupture, MRI provides excellent visualization of the entire pulley system and will show edema and increased tendon to bone distance secondary to anterior subluxation of the flexor tendons26 (Fig. 4). Vol. 39, December 2014
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local ecchymosis and hematoma formation can be seen as well. Clinically significant bowstringing is not appreciated unless sequential pulleys are ruptured, and they almost always include A2 and A4. Without these pulleys, the flexor tendon moment increases with finger flexion (Fig. 3). However, the resultant bowstringing causes an increased requirement in tendon excursion to produce the same amount of finger flexion. This results in an overall decrease in tendon excursion at maximum muscle contraction, which consequently precludes full finger flexion to the distal palmar crease. The bowstringing and loss of full flexion interferes with grip and alters the normal kinematics of the MCP and interphalangeal joints, which affects the normal equilibrium between the flexor and the extensor tendons. Long-term effects can be PIP joint flexion contractures in cases of multiple pulley ruptures and loss of strength, but the long-term sequelae of conservatively managed pulley ruptures remains to be reported. Closed pulley ruptures are most commonly seen in the ring finger followed by the middle finger. The A2 pulley is typically injured in isolation but A4 pulley disruption can also occur, either in isolation or as part of a complex injury. Severe panpulley ruptures can occur as well. The mechanism of injury causing pulley rupture is eccentric loading in the so called crimp position whereby the PIP joint is flexed 90 or more and the DIP joint is hyperextended. In this position, high tensile forces develop in the flexor digitorum superficialis and FDP tendons, which, together with the extreme PIP joint flexion, can generate up to 450 N of force on the pulleys.20 A2 can only withstand up to 400 N of force before rupturing.21 Shock loading of the fingers when a patient’s footing is lost can also cause pulley rupture in a similar fashion. Reports of
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FIGURE 4: MRI of intact and disrupted pulleys. A Sagittal and axial T1-weighted spin-echo images show the A2 and A4 pulleys as focal thickenings of low signal intensity (arrows and arrowheads in sagittal image) and the osseous insertion of the A2 pulley (arrows in axial image). (Reproduced with permission Hauger O, Chung CB, Lektrakul N, et al. Pulley system in the fingers: normal anatomy and simulated lesions in cadavers at MR imaging, CT, and US with and without contrast material distention of the tendon sheath. Radiology 2000;217(1):201e212.26 Copyright 2000 Radiological Society of North America.) B Sagittal fat-saturated proton density and nonefat-saturated axial T1-weighted images from a 50-year-old man with traumatic A2 through A4 ring finger pulley ruptures. The tendon-to-bone distance is increased (bowstringing). The axial image at the level of proximal phalanges demonstrates avulsion of A2 (white arrows) from bone.
More recently, ultrasound has become the mainstay for assessing flexor pulley injuries because it permits dynamic studies of the tendon-bone interface within the flexor pulley system at a significantly lower cost. A classification system for pulley injuries has been introduced.27 Grade I injuries represent pulley strains where imaging demonstrates no flexor tendon subluxation. Complete rupture of A4 or a partial rupture of A2 or A3 comprise the grade II injury, and grade III injury encompasses complete A2 or A3 pulley rupture. Grade IV injuries comprise multiple pulley ruptures or any single pulley rupture associated with a concomitant collateral ligament or lumbrical muscle rupture.
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TREATMENT Treatment for acute flexor pulley injuries is mostly conservative, especially for grades I, II, and III disruptions. Rest, ice packs, anti-inflammatory medication, and orthosis fabrication are first-line measures. External tape or rings have also been shown to reduce tendon bowstringing and limit flexion at the PIP joint, which consequently reduces pulley load and reinjury.28 Corticosteroid injections should be avoided in treating suspected pulley injuries because they may precipitate rupture or delay healing. In complex injuries (grade IV) in which multiple pulleys are concomitantly ruptured or there is an associated lumbrical muscle or collateral ligament injury, surgery J Hand Surg Am.
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is preferable. The goal of surgery is to prevent flexion contractures and decreased range of motion caused by flexor tendon bowstringing. For closed injuries, primary repair of pulley remnants has been noneffective; thus, efforts have focused on reconstructive strategies. Several variations of pulley reconstruction have been described, but all techniques follow the 2 basic principles of either a nonencircling or a loop method of reconstruction (Fig. 5). Weaving a tendon or fascial graft through the remnant pulley is an example of a nonencircling technique, and looping a graft circumferentially around the phalanx characterizes the encircling technique. With the encircling technique, the graft is placed deep to the extensor mechanism over the proximal phalanx and superficial to it over the middle phalanx during A2 and A4 reconstructions, respectively. Palmaris longus tendon and extensor retinaculum tissue are the grafts of choice, and regardless of graft type, good outcomes have been reported for both methods with similar return to preinjury levels of rock climbing.23,29,30 COMPLICATIONS Complications are not uncommon during flexor pulley reconstruction and include synovitis, stiffness, rerupture, infection, and phalanx fracture. Flexor tendon impingement can also compromise successful postoperative outcomes. Loss of flexion and stiffness can be Vol. 39, December 2014
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FIGURE 5: Two common techniques for reconstruction of the flexor pulleys. Nonencircling A and looped B reconstruction. (Reproduced with permission from Clark TA, Skeete K, Amadio PC. Flexor tendon pulley reconstruction. J Hand Surg Am. 2010;35(10):1685e1689.34 Copyright 2010 Elsevier.)
OUTCOMES Schoffl et al31 characterized outcomes in 21 avid rock climbers who were treated conservatively for closed pulley ruptures. The majority of injuries (82%) were grade II or III. At 3 years postinjury, they found no significant difference in finger strength between injured and healthy digits. In addition, repeat ultrasound examinations demonstrated no increase in flexor tendonebone distance over baseline examinations. The patients also reported excellent outcome scores, and all climbers returned to sport within one year of injury. There are numerous surgical techniques described for flexor pulley reconstruction, but few outcomes studies have been done, and available evidence is level 3 or 4. Arora et al.23 retrospectively compared 2 nonencircling techniques for A2 pulley reconstruction using autograft extensor retinaculum versus palmaris longus tendon. The study group included both climbers and nonclimbers with complete A2 pulley ruptures. At average follow-up of 4 years, results were excellent with respect to outcome scores, PIP joint flexion, and power grip and pinch strength. Moreover, both techniques yielded similar results and all patients returned to their preinjury level of activity. Moutet et al30 reported similar results in their series of 12 rock climbers who underwent nonencircling pulley reconstruction using J Hand Surg Am.
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extensor retinaculum grafts. In addition, Gabl et al29 published favorable results using extensor retinaculum in a nonencircling fashion. At final follow-up, patients reported decreased pain, increased finger PIP joint flexion, and improved pinch grip significantly. Furthermore, resolution of bowstringing was achieved in 5 out of 6 patients, with improvement seen in the sixth patient. The case report by Okutsu and colleagues32 provides the only outcome data using a loop reconstruction technique. The A2 pulley was reconstructed using a triple loop of palmaris longus, plantaris, or a strip of flexor carpi ulnaris tendon. At average follow-up of 21 months, they reported a 30 improvement in total active motion and a 1-cm improvement in tip-palm distance. With respect to intentional pulley disruption and immediate reconstruction after flexor tendon repair, Bunata33 reported encouraging results. In that study, patients underwent primary enlargement of the A2 or A4 pulley with an extensor retinaculum interposition graft to facilitate the repair of zone II flexor tendon lacerations. According to the Strickland criteria, 55% of fingers achieved excellent postoperative motion and there were no postoperative tendon ruptures or triggering. There were 5 postoperative flexion contractures seen; grip strength and quality of motion were not assessed. Additional clinical outcome studies are needed to characterize the effects and outcomes of intentional pulley excision or venting during flexor tendon repair. DISCUSSION Most pulley ruptures can be successfully treated conservatively with full return to preinjury activity. When surgery is necessary, pulley reconstruction, not repair, results in the best outcomes. In stenosing tenosynovitis, repeat corticosteroid injections should be used with caution because they may precipitate a pulley rupture. The variable thumb annular pulley Vol. 39, December 2014
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caused by graft overtightening, whereas poor tensioning results in no clinical improvement in bowstringing and loss of motion. In addition, adhesions requiring reoperation are a common complication after pulley reconstruction.19 Postoperative infection is rare and more commonly associated with 2-stage flexor tendon reconstructions. Rerupture is also not commonly seen but can be treated with a secondary reconstruction. A phalanx fracture can adversely compromise results but is diagnosed with imaging and is treated based on fracture pattern.
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may represent an additional area of stenosis in trigger thumbs. At times, intentional excision or venting of A2 and/or A4 during repair of zone II flexor tendon injuries may lead to improved outcomes. Therefore, when confronted with the situation in which the repaired tendon does not pass smoothly under a pulley, current evidence suggests it may be better to perform a partial pulley excision than to preserve A2 or A4 pulleys at all costs. Additional studies are needed before clinical practice guidelines can be advocated. REFERENCES
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1. Phillips C, Mass D. Mechanical analysis of the palmar aponeurosis pulley in human cadavers. J Hand Surg Am. 1996;21(2):240e244. 2. Sherman PJ, Lane LB. The palmar aponeurosis pulley as a cause of trigger finger. A report of two cases. J Bone Joint Surg Am. 1996;78(11):1753e1754. 3. Bayat A, Shaaban H, Giakas G, Lees VC. The pulley system of the thumb: anatomic and biomechanical study. J Hand Surg Am. 2002;27(4):628e635. 4. Schubert MF, Shah VS, Craig CL, Zeller JL. Varied anatomy of the thumb pulley system: implications for successful trigger thumb release. J Hand Surg Am. 2012;37(11):2278e2285. 5. Doyle JR. Anatomy of the flexor tendon sheath and pulley system: a current review. J Hand Surg Am. 1989;14(2 Pt 2):349e351. 6. Peterson WW, Manske PR, Bollinger BA, Lesker PA, McCarthy JA. Effect of pulley excision on flexor tendon biomechanics. J Orthop Res. 1986;4(1):96e101. 7. Mallo GC, Sless Y, Hurst L, Wilson K. A2 and A4 flexor pulley biomechanical analysis: comparison among gender and digit. Hand (N Y). 2008;3(1):13e16. 8. Tomaino M, Mitsionis G, Basitidas J, Grewal R, Pfaeffle J. The effect of partial excision of the A2 and A4 pulleys on the biomechanics of finger flexion. J Hand Surg Br. 1998;23(1):50e52. 9. Mitsionis G, Bastidas JA, Grewal R, Pfaeffle HJ, Fischer KJ, Tomaino MM. Feasibility of partial A2 and A4 pulley excision: effect on finger flexor tendon biomechanics. J Hand Surg Am. 1999;24(2): 310e314. 10. Chow JC, Sensinger J, McNeal D, Chow B, Amirouche F, Gonzalez M. Importance of proximal A2 and A4 pulleys to maintaining kinematics in the hand: a biomechanical study. Hand (N Y). 2014;9(1):105e111. 11. Leeflang S, Coert JH. The role of proximal pulleys in preventing tendon bowstringing: Pulley rupture and tendon bowstringing. J Plast Reconstr Aesthet Surg. 2014;67(6):822e827. 12. Tang JB, Xie RG, Cao Y, Ke ZS, Xu Y. A2 pulley incision or one slip of the superficialis improves flexor tendon repairs. Clin Orthop Relat Res. 2007;456:121e127. 13. Cao Y, Tang JB. Strength of tendon repair decreases in the presence of an intact A2 pulley: biomechanical study in a chicken model. J Hand Surg Am. 2009;34(10):1763e1770.
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14. Tang JB, Cao Y, Wu YF, Wang GH. Effect of A2 pulley release on repaired tendon gliding resistance and rupture in a chicken model. J Hand Surg Am. 2009;34(6):1080e1087. 15. Tang JB. The double sheath system and tendon gliding in zone 2C. J Hand Surg Br. 1995;20(3):281e285. 16. Franko OI, Lee NM, Finneran JJ, et al. Quantification of partial or complete A4 pulley release with FDP repair in cadaveric tendons. J Hand Surg Am. 2011;36(3):439e445. 17. Zissimos AG, Szabo RM, Yinger KE, Sharkey NA. Biomechanics of the thumb flexor pulley system. J Hand Surg Am. 1994;19(3):475e479. 18. Logan AJ, Makwana N, Mason G, Dias J. Acute hand and wrist injuries in experienced rock climbers. Br J Sports Med. 2004;38(5):545e548. 19. Dy CJ, Lyman S, Schreiber JJ, Do HT, Daluiski A. The epidemiology of reoperation after flexor pulley reconstruction. J Hand Surg Am. 2013;38(9):1705e1711. 20. Bollen SR. Injury to the A2 pulley in rock climbers. J Hand Surg Br. 1990;15(2):268e270. 21. Lin GT, Cooney WP, Amadio PC, An KN. Mechanical properties of human pulleys. J Hand Surg Br. 1990;15(4):429e434. 22. Lourie GM, Hamby Z, Raasch WG, Chandler JB, Porter JL. Annular flexor pulley injuries in professional baseball pitchers: a case series. Am J Sports Med. 2011;39(2):421e424. 23. Arora R, Fritz D, Zimmermann R, et al. Reconstruction of the digital flexor pulley system: a retrospective comparison of two methods of treatment. J Hand Surg Eur Vol. 2007;32(1):60e66. 24. Schoffl VR, Jungert J. Closed flexor pulley injuries in nonclimbing activities. J Hand Surg Am. 2006;31(5):806e810. 25. Hamano H, Motomiya M, Iwasaki N. Adverse effect of repeated corticosteroid injections for trigger finger on flexor pulley system. J Hand Surg Eur Vol. 2013;38(3):326e327. 26. Hauger O, Chung CB, Lektrakul N, et al. Pulley system in the fingers: normal anatomy and simulated lesions in cadavers at MR imaging, CT, and US with and without contrast material distention of the tendon sheath. Radiology. 2000;217(1):201e212. 27. Schoffl V, Hochholzer T, Winkelmann HP, Strecker W. Pulley injuries in rock climbers. Wilderness Environ Med. 2003;14(2):94e100. 28. Schoffl I, Einwag F, Strecker W, Hennig F, Schoffl V. Impact of taping after finger flexor tendon pulley ruptures in rock climbers. J Appl Biomech. 2007;23(1):52e62. 29. Gabl M, Reinhart C, Lutz M, Bodner G, Angermann P, Pechlaner S. The use of a graft from the second extensor compartment to reconstruct the A2 flexor pulley in the long finger. J Hand Surg Br. 2000;25(1):98e101. 30. Moutet F, Forli A, Voulliaume D. Pulley rupture and reconstruction in rock climbers. Tech Hand Up Extrem Surg. 2004;8(3):149e155. 31. Schoffl VR, Einwag F, Strecker W, Schoffl I. Strength measurement and clinical outcome after pulley ruptures in climbers. Med Sci Sports Exerc. 2006;38(4):637e643. 32. Okutsu I, Ninomiya S, Hiraki S, Inanami H, Kuroshima N. Threeloop technique for A2 pulley reconstruction. J Hand Surg Am. 1987;12(5 Pt 1):790e794. 33. Bunata RE. Primary pulley enlargement in zone 2 by incision and repair with an extensor retinaculum graft. J Hand Surg Am. 2010;35(5):785e790. 34. Clark TA, Skeete K, Amadio PC. Flexor tendon pulley reconstruction. J Hand Surg Am. 2010;35(10):1685e1689.
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Flexor Pulley System: Anatomy, Injury, and Management Brian Zafonte, MD, Dora Rendulic, MD, Robert M. Szabo, MD CME INFORMATION AND DISCLOSURES The Review Section of JHS will contain at least 3 clinically relevant articles selected by the editor to be offered for CME in each issue. For CME credit, the participant must read the articles in print or online and correctly answer all related questions through an online examination. The questions on the test are designed to make the reader think and will occasionally require the reader to go back and scrutinize the article for details. The JHS CME Activity fee of $30.00 includes the exam questions/answers only and does not include access to the JHS articles referenced. Statement of Need: This CME activity was developed by the JHS review section editors and review article authors as a convenient education tool to help increase or affirm reader’s knowledge. The overall goal of the activity is for participants to evaluate the appropriateness of clinical data and apply it to their practice and the provision of patient care.
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Copyright ª 2014 by the American Society for Surgery of the Hand. All rights reserved.
Detail the anatomy and biomechanics of the flexor pulley system. Describe the epidemiology and etiology of flexor pulley system injuries. Recognize the clinical manifestations of closed pulley system rupture. Offer diagnostic strategies for various types of closed pulley system ruptures. Discuss treatment methods, outcomes, and complications of pulley system injuries.
From the Department of Orthopaedic Surgery, University of California, Davis, Sacramento, CA. Received for publication April 29, 2014; accepted in revised form June 3, 2014. No benefits in any form have been received or will be received related directly or indirectly to the subject of this article.
Corresponding author: Robert M. Szabo, MD, Department of Orthopaedic Surgery, Hand and Upper Extremity Service, University of California, Davis, School of Medicine, 4860 Y St., Suite 3800, Sacramento, CA 95817; e-mail: [email protected]. 0363-5023/14/3912-0033$36.00/0 http://dx.doi.org/10.1016/j.jhsa.2014.06.005
2014 ASSH
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Flexor pulley injuries are most commonly seen in avid rock climbers; however, reports of pulley ruptures in nonclimbers are increasing. In addition to traumatic disruption, corticosteroid-induced pulley rupture has been reported as a complication of treating stenosing tenosynovitis. Over the last decade, there have been 2 new developments in the way hand surgeons think about the flexor pulley system. First, the thumb pulley system has been shown
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to have 4 component constituents, in contrast to the classic teaching of 3 pulleys. Second, in cases of zone II flexor tendon injury, the intentional partial A2 and/or A4 pulley excision or venting is emerging as a component for successful treatment. This is challenging the onceheld dogma that preserving the integrity of the entire A2 and A4 pulleys is indispensable for normal digit function. (J Hand Surg Am. 2014;39(12):2525e2532. Copyright 2014 by the American Society for Surgery of the Hand. All rights reserved.) Key words Flexor pulley, annular pulley, rock climbing, pulley rupture, pulley reconstruction.
Current Concepts
ANATOMY AND BIOMECHANICS The digital flexor sheath-pulley system is a complex structure that permits normal and efficient flexor tendon function. This sheath-pulley system is composed of a deep synovial component and a superficial retinacular or pulley component. The pulleys are fibrous tissue condensations, which almost encircle the flexor tendons forming a fibro-osseous channel that functions to keep the tendons adjacent to the phalanges. This enables the transfer of a translational force generated from the muscle-tendon unit into a rotational moment on the phalanges. In the fingers, there are 5 annular (A1eA5) and 3 cruciate (C1eC3) pulleys running in descending order from proximal to distal (Fig. 1). The A2 and A4 pulleys insert directly into bone over the proximal and middle phalanges, respectively. In contrast, A1, A3, and A5 are narrower, more flexible, insert mostly into volar plate, and with the cruciate pulleys, permit compression without impingement and expansion during finger flexion and extension, respectively. A1, A3, and A5 pulleys are located over the metacarpophalangeal (MCP), proximal interphalangeal (PIP), and distal interphalangeal (DIP) joints, respectively. The cruciate pulleys comprise C1, C2, and C3, and lie between the A2eA3, the A3eA4, and the A4eA5 pulleys, respectively. Proximal to the A1 pulley lies the palmar aponeurotic (PA) pulley, which is composed of transverse ligament of the palmar aponeurosis that is attached to the underlying septa of Legueu and Juvara, thus forming an arch over the flexor tendons superficial and proximal to the A1 pulley. Biomechanical evaluation of the PA pulley demonstrated that isolated sectioning did not change work or load efficiency.1 However, the PA pulley has been implicated in the etiology of trigger finger.2 Traditionally, only 3 components of the thumb pulley system were described: A1, oblique, and A2 pulleys. The A1 pulley lies over the MCP joint, the oblique pulley runs from proximal ulnar to distal radial over the proximal phalanx, and the A2 pulley is located over the interphalangeal joint. A fourth thumb pulley, the variable annular pulley, has now been characterized (Fig. 2). First reported in J Hand Surg Am.
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2002,3 Schubert et al4 found this pulley to be present in 93% of cadaver specimens with 3 possible orientations: transverse, oblique, or continuous with the A1 pulley. The variable annular pulley can be an additional site of stenosis in trigger thumbs. Although the importance of a given pulley can be debated, the A2 and A4 pulleys have traditionally been deemed most important in preventing bowstringing.5,6 The A2 is bigger and considered more important; however, there is evidence that the A2 and A4 pulleys have similar biomechanical properties irrespective of differing digits or gender.7 Owing to this historic importance, most surgeons advocate their preservation, repair, or reconstruction. However, 2 lines of investigation have been challenging this dogma, particularly with respect to zone II flexor tendon injuries. First, biomechanical studies in cadavers examined the effects of partial pulley excision on finger function. Tomaino et al8 characterized partial distal excisions of the A2, A4, or A2 and A4 pulleys in combination and found that 25% of the A2 pulley, up to 75% of A4, and 25% of combined A2 and A4 can be excised without any significant effect on digit range of motion or work of flexion. Mitsionis et al9 reported similar findings. Both groups suggest that partial A2 and A4 pulleys excision (or incision called venting) may be used to facilitate tendon gliding after surgery, and that the modest decrease in digital range of motion may be clinically acceptable. In further examining the effects of partial distal versus partial proximal pulley excisions, results differ. Chow et al10 found significant decrease in overall finger motion with partial proximal incisions of either the A2 or the A4 pulley as compared with partial distal incisions. In contrast, Leeflang and Coert11 found that partial distal incisions of the A2 pulley led to greater bowstringing at the proximal phalanx as compared with partial proximal incisions. The A4 pulley was not assessed in that study. Although these data are limited by the use of different cadaver models employing nonphysiological loading forces, they provide the basis for the second line of investigation, in vivo analysis. Using a live chicken model to examine the effects of complete A2 incision on flexor tendon integrity Vol. 39, December 2014
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after tendon repair, Tang et al12 found no deleterious effects on flexor digitorum profundus (FDP) tendon function. In contrast, the data demonstrated improved tendon excursion and decreased work of flexion when compared with primary pulley repair. In a follow-up study using the same avian model, Cao and Tang13 measured the strength in flexor tendon repairs around the A2 pulley when it was preserved or completely incised and found that tendon repair strength was 30% to 60% greater after A2 division compared with the intact pulley. Consequently, they proposed that tendon repairs would be more successful with purposeful pulley disruption. The same group reported an increased tendon gliding resistance in the intact A2 pulley model, which led to significantly higher rates of postoperative tendon ruptures.14 Moreover, Tang15 has previously performed a detailed characterization of the area of the J Hand Surg Am.
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flexor sheath beneath the A2 pulley and suggested the FDP tendon gliding function may be improved after partial A2 excision. With respect to A4, Franko et al16 found a less than 3% increase in the work of flexion after partial distal or complete A4 pulley release and significantly less work of flexion when compared with FDP tendon repair with an intact A4 pulley. Collectively, this body of work, although done in cadaver and animal models, supports the rationale for considering intentional A2 and/or A4 pulley venting or excision during zone II flexor tendon repair. In contrast to available clinical and biomechanical data examining the pulley system in the fingers, much less progress has been made in characterizing the thumb pulley system. In a cadaver model, Zissimos et al17 studied the mechanical efficiency and angular joint displacement in the thumb. They found that isolated Vol. 39, December 2014
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FIGURE 1: A Sagittal and B coronal depictions of the finger flexor tendon pulley system. Black areas indicate the flexor tendon. Annular pulleys A1 to A5 and cruciate pulleys C1 to C3. Dotted lines represent the division of the flexor digitorum superficialis tendon. (Reproduced with permission Hauger O, Chung CB, Lektrakul N, et al. Pulley system in the fingers: normal anatomy and simulated lesions in cadavers at MR imaging, CT, and US with and without contrast material distention of the tendon sheath. Radiology 2000;217(1):201e212.26 Copyright 2000 Radiological Society of North America.)
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FIGURE 2: The flexor pulley system in the thumb. A Classic depiction of the 3-pulley system: A1, oblique, A2. BeD Updated illustrations to show the fourth pulley, the variable annular pulley (Av), which can be orientated transversely B, obliquely C, or in continuity with A1 D. (Reproduced with permission from Schubert MF, Shah VS, Craig CL, Zeller JL. Varied anatomy of the thumb pulley system: implications for successful trigger thumb release. J Hand Surg Am. 2012;37(11):2278e2285.4 Copyright 2012 Elsevier.)
Current Concepts
sectioning of either the A1 or the oblique pulley did not significantly alter thumb biomechanics. Only when both the A1 and the oblique pulleys were disrupted did significant tendon bowstringing occur. No differences were found with respect to intact versus sectioned A2 pulley. The authors concluded that either the A1 or the oblique pulley must be kept intact or reconstructed to maintain normal thumb kinematics and prevent bowstringing. CLINICAL PICTURE It is estimated that 75% of all rock climbers will suffer an upper extremity injury; 60% of those will involve the hand or wrist and 30% to 50% of those will involve closed injury to the flexor tendon-pulley system. In elite climbers, Logan et al18 reported a 33% incidence of finger tendon injuries, with an 8% incidence of A2 pulley rupture. Dy et al19 examined the rates of pulley J Hand Surg Am.
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reconstruction and reoperation in their retrospective study of all patients who had flexor pulley reconstruction from 1998 to 2009 in New York state. Six hundred and twenty-three patients underwent pulley reconstruction, with an overall incidence of 0.27 per 100,000 persons. They also found a 6% reoperation rate, the majority for tenolysis (64%). The infrequency of injury in the general population together with the paucity of clinical outcome data have made it challenging for hand surgeons to develop optimal treatment strategies for patients with pulley disruptions. Acute closed pulley rupture can be partial or complete and can occur in isolation or as part of multiple pulley disruptions. Frequently, patients complain of an audible pop or tearing sensation with only moderate pain over the injured pulley. Typically, there is no appreciable loss of grip strength. The most common physical examination findings in a single pulley rupture are swelling and pain over the affected pulley. However, Vol. 39, December 2014
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FIGURE 3: Biomechanics of the flexor tendon pulley system. The amount of finger flexion is proportional to tendon excursion and the moment arm (r). A The intact pulleys keep the flexor tendons close to the axis of rotation of the finger joints, thereby maximizing total finger flexion. B The moment arm (r) increases with pulley insufficiency leading to maximum tendon excursion before full finger flexion can be obtained. The flexor digitorum superficialis has been excluded for simplicity.
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pulley ruptures in nonclimbers are emerging. Lourie et al22 reported a case series of 4 professional baseball pitchers who sustained closed isolated A4 ruptures of the long finger. The injury was caused by a hyperextension force on the DIP joint while actively flexing the finger when throwing a fastball. Arora et al23 and Schoffl and Jungert24 described 14 cases of pulley rupture in patients who were lifting heavy objects using the crimp grip position. In all cases, rupture occurred when a sudden extension force was applied to an acutely flexed digit. Open pulley injuries are extremely rare, but iatrogenic pulley disruption can occur with aggressive trigger finger release or after tendon repair or tenolysis. The deleterious effect of repeated corticosteroid injections for trigger finger causing pulley rupture has been described,25 thus raising caution among hand surgeons in the treatment of this common hand problem. DIAGNOSIS The diagnosis of flexor pulley rupture is conventionally made by physical examination. X-rays are usually normal but may help rule out other injuries such as a palmar plate avulsion. Magnetic resonance imaging (MRI) and high-resolution ultrasound are the imaging modalities of choice when the physical examination remains equivocal. MRI helps characterize more complex injuries (eg, multiple pulley ruptures) and is useful to rule out other soft tissue pathology (eg, muscle or ligament injury). In cases of suspected pulley rupture, MRI provides excellent visualization of the entire pulley system and will show edema and increased tendon to bone distance secondary to anterior subluxation of the flexor tendons26 (Fig. 4). Vol. 39, December 2014
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local ecchymosis and hematoma formation can be seen as well. Clinically significant bowstringing is not appreciated unless sequential pulleys are ruptured, and they almost always include A2 and A4. Without these pulleys, the flexor tendon moment increases with finger flexion (Fig. 3). However, the resultant bowstringing causes an increased requirement in tendon excursion to produce the same amount of finger flexion. This results in an overall decrease in tendon excursion at maximum muscle contraction, which consequently precludes full finger flexion to the distal palmar crease. The bowstringing and loss of full flexion interferes with grip and alters the normal kinematics of the MCP and interphalangeal joints, which affects the normal equilibrium between the flexor and the extensor tendons. Long-term effects can be PIP joint flexion contractures in cases of multiple pulley ruptures and loss of strength, but the long-term sequelae of conservatively managed pulley ruptures remains to be reported. Closed pulley ruptures are most commonly seen in the ring finger followed by the middle finger. The A2 pulley is typically injured in isolation but A4 pulley disruption can also occur, either in isolation or as part of a complex injury. Severe panpulley ruptures can occur as well. The mechanism of injury causing pulley rupture is eccentric loading in the so called crimp position whereby the PIP joint is flexed 90 or more and the DIP joint is hyperextended. In this position, high tensile forces develop in the flexor digitorum superficialis and FDP tendons, which, together with the extreme PIP joint flexion, can generate up to 450 N of force on the pulleys.20 A2 can only withstand up to 400 N of force before rupturing.21 Shock loading of the fingers when a patient’s footing is lost can also cause pulley rupture in a similar fashion. Reports of
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FIGURE 4: MRI of intact and disrupted pulleys. A Sagittal and axial T1-weighted spin-echo images show the A2 and A4 pulleys as focal thickenings of low signal intensity (arrows and arrowheads in sagittal image) and the osseous insertion of the A2 pulley (arrows in axial image). (Reproduced with permission Hauger O, Chung CB, Lektrakul N, et al. Pulley system in the fingers: normal anatomy and simulated lesions in cadavers at MR imaging, CT, and US with and without contrast material distention of the tendon sheath. Radiology 2000;217(1):201e212.26 Copyright 2000 Radiological Society of North America.) B Sagittal fat-saturated proton density and nonefat-saturated axial T1-weighted images from a 50-year-old man with traumatic A2 through A4 ring finger pulley ruptures. The tendon-to-bone distance is increased (bowstringing). The axial image at the level of proximal phalanges demonstrates avulsion of A2 (white arrows) from bone.
More recently, ultrasound has become the mainstay for assessing flexor pulley injuries because it permits dynamic studies of the tendon-bone interface within the flexor pulley system at a significantly lower cost. A classification system for pulley injuries has been introduced.27 Grade I injuries represent pulley strains where imaging demonstrates no flexor tendon subluxation. Complete rupture of A4 or a partial rupture of A2 or A3 comprise the grade II injury, and grade III injury encompasses complete A2 or A3 pulley rupture. Grade IV injuries comprise multiple pulley ruptures or any single pulley rupture associated with a concomitant collateral ligament or lumbrical muscle rupture.
Current Concepts
TREATMENT Treatment for acute flexor pulley injuries is mostly conservative, especially for grades I, II, and III disruptions. Rest, ice packs, anti-inflammatory medication, and orthosis fabrication are first-line measures. External tape or rings have also been shown to reduce tendon bowstringing and limit flexion at the PIP joint, which consequently reduces pulley load and reinjury.28 Corticosteroid injections should be avoided in treating suspected pulley injuries because they may precipitate rupture or delay healing. In complex injuries (grade IV) in which multiple pulleys are concomitantly ruptured or there is an associated lumbrical muscle or collateral ligament injury, surgery J Hand Surg Am.
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is preferable. The goal of surgery is to prevent flexion contractures and decreased range of motion caused by flexor tendon bowstringing. For closed injuries, primary repair of pulley remnants has been noneffective; thus, efforts have focused on reconstructive strategies. Several variations of pulley reconstruction have been described, but all techniques follow the 2 basic principles of either a nonencircling or a loop method of reconstruction (Fig. 5). Weaving a tendon or fascial graft through the remnant pulley is an example of a nonencircling technique, and looping a graft circumferentially around the phalanx characterizes the encircling technique. With the encircling technique, the graft is placed deep to the extensor mechanism over the proximal phalanx and superficial to it over the middle phalanx during A2 and A4 reconstructions, respectively. Palmaris longus tendon and extensor retinaculum tissue are the grafts of choice, and regardless of graft type, good outcomes have been reported for both methods with similar return to preinjury levels of rock climbing.23,29,30 COMPLICATIONS Complications are not uncommon during flexor pulley reconstruction and include synovitis, stiffness, rerupture, infection, and phalanx fracture. Flexor tendon impingement can also compromise successful postoperative outcomes. Loss of flexion and stiffness can be Vol. 39, December 2014
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FIGURE 5: Two common techniques for reconstruction of the flexor pulleys. Nonencircling A and looped B reconstruction. (Reproduced with permission from Clark TA, Skeete K, Amadio PC. Flexor tendon pulley reconstruction. J Hand Surg Am. 2010;35(10):1685e1689.34 Copyright 2010 Elsevier.)
OUTCOMES Schoffl et al31 characterized outcomes in 21 avid rock climbers who were treated conservatively for closed pulley ruptures. The majority of injuries (82%) were grade II or III. At 3 years postinjury, they found no significant difference in finger strength between injured and healthy digits. In addition, repeat ultrasound examinations demonstrated no increase in flexor tendonebone distance over baseline examinations. The patients also reported excellent outcome scores, and all climbers returned to sport within one year of injury. There are numerous surgical techniques described for flexor pulley reconstruction, but few outcomes studies have been done, and available evidence is level 3 or 4. Arora et al.23 retrospectively compared 2 nonencircling techniques for A2 pulley reconstruction using autograft extensor retinaculum versus palmaris longus tendon. The study group included both climbers and nonclimbers with complete A2 pulley ruptures. At average follow-up of 4 years, results were excellent with respect to outcome scores, PIP joint flexion, and power grip and pinch strength. Moreover, both techniques yielded similar results and all patients returned to their preinjury level of activity. Moutet et al30 reported similar results in their series of 12 rock climbers who underwent nonencircling pulley reconstruction using J Hand Surg Am.
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extensor retinaculum grafts. In addition, Gabl et al29 published favorable results using extensor retinaculum in a nonencircling fashion. At final follow-up, patients reported decreased pain, increased finger PIP joint flexion, and improved pinch grip significantly. Furthermore, resolution of bowstringing was achieved in 5 out of 6 patients, with improvement seen in the sixth patient. The case report by Okutsu and colleagues32 provides the only outcome data using a loop reconstruction technique. The A2 pulley was reconstructed using a triple loop of palmaris longus, plantaris, or a strip of flexor carpi ulnaris tendon. At average follow-up of 21 months, they reported a 30 improvement in total active motion and a 1-cm improvement in tip-palm distance. With respect to intentional pulley disruption and immediate reconstruction after flexor tendon repair, Bunata33 reported encouraging results. In that study, patients underwent primary enlargement of the A2 or A4 pulley with an extensor retinaculum interposition graft to facilitate the repair of zone II flexor tendon lacerations. According to the Strickland criteria, 55% of fingers achieved excellent postoperative motion and there were no postoperative tendon ruptures or triggering. There were 5 postoperative flexion contractures seen; grip strength and quality of motion were not assessed. Additional clinical outcome studies are needed to characterize the effects and outcomes of intentional pulley excision or venting during flexor tendon repair. DISCUSSION Most pulley ruptures can be successfully treated conservatively with full return to preinjury activity. When surgery is necessary, pulley reconstruction, not repair, results in the best outcomes. In stenosing tenosynovitis, repeat corticosteroid injections should be used with caution because they may precipitate a pulley rupture. The variable thumb annular pulley Vol. 39, December 2014
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caused by graft overtightening, whereas poor tensioning results in no clinical improvement in bowstringing and loss of motion. In addition, adhesions requiring reoperation are a common complication after pulley reconstruction.19 Postoperative infection is rare and more commonly associated with 2-stage flexor tendon reconstructions. Rerupture is also not commonly seen but can be treated with a secondary reconstruction. A phalanx fracture can adversely compromise results but is diagnosed with imaging and is treated based on fracture pattern.
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may represent an additional area of stenosis in trigger thumbs. At times, intentional excision or venting of A2 and/or A4 during repair of zone II flexor tendon injuries may lead to improved outcomes. Therefore, when confronted with the situation in which the repaired tendon does not pass smoothly under a pulley, current evidence suggests it may be better to perform a partial pulley excision than to preserve A2 or A4 pulleys at all costs. Additional studies are needed before clinical practice guidelines can be advocated. REFERENCES
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1. Phillips C, Mass D. Mechanical analysis of the palmar aponeurosis pulley in human cadavers. J Hand Surg Am. 1996;21(2):240e244. 2. Sherman PJ, Lane LB. The palmar aponeurosis pulley as a cause of trigger finger. A report of two cases. J Bone Joint Surg Am. 1996;78(11):1753e1754. 3. Bayat A, Shaaban H, Giakas G, Lees VC. The pulley system of the thumb: anatomic and biomechanical study. J Hand Surg Am. 2002;27(4):628e635. 4. Schubert MF, Shah VS, Craig CL, Zeller JL. Varied anatomy of the thumb pulley system: implications for successful trigger thumb release. J Hand Surg Am. 2012;37(11):2278e2285. 5. Doyle JR. Anatomy of the flexor tendon sheath and pulley system: a current review. J Hand Surg Am. 1989;14(2 Pt 2):349e351. 6. Peterson WW, Manske PR, Bollinger BA, Lesker PA, McCarthy JA. Effect of pulley excision on flexor tendon biomechanics. J Orthop Res. 1986;4(1):96e101. 7. Mallo GC, Sless Y, Hurst L, Wilson K. A2 and A4 flexor pulley biomechanical analysis: comparison among gender and digit. Hand (N Y). 2008;3(1):13e16. 8. Tomaino M, Mitsionis G, Basitidas J, Grewal R, Pfaeffle J. The effect of partial excision of the A2 and A4 pulleys on the biomechanics of finger flexion. J Hand Surg Br. 1998;23(1):50e52. 9. Mitsionis G, Bastidas JA, Grewal R, Pfaeffle HJ, Fischer KJ, Tomaino MM. Feasibility of partial A2 and A4 pulley excision: effect on finger flexor tendon biomechanics. J Hand Surg Am. 1999;24(2): 310e314. 10. Chow JC, Sensinger J, McNeal D, Chow B, Amirouche F, Gonzalez M. Importance of proximal A2 and A4 pulleys to maintaining kinematics in the hand: a biomechanical study. Hand (N Y). 2014;9(1):105e111. 11. Leeflang S, Coert JH. The role of proximal pulleys in preventing tendon bowstringing: Pulley rupture and tendon bowstringing. J Plast Reconstr Aesthet Surg. 2014;67(6):822e827. 12. Tang JB, Xie RG, Cao Y, Ke ZS, Xu Y. A2 pulley incision or one slip of the superficialis improves flexor tendon repairs. Clin Orthop Relat Res. 2007;456:121e127. 13. Cao Y, Tang JB. Strength of tendon repair decreases in the presence of an intact A2 pulley: biomechanical study in a chicken model. J Hand Surg Am. 2009;34(10):1763e1770.
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14. Tang JB, Cao Y, Wu YF, Wang GH. Effect of A2 pulley release on repaired tendon gliding resistance and rupture in a chicken model. J Hand Surg Am. 2009;34(6):1080e1087. 15. Tang JB. The double sheath system and tendon gliding in zone 2C. J Hand Surg Br. 1995;20(3):281e285. 16. Franko OI, Lee NM, Finneran JJ, et al. Quantification of partial or complete A4 pulley release with FDP repair in cadaveric tendons. J Hand Surg Am. 2011;36(3):439e445. 17. Zissimos AG, Szabo RM, Yinger KE, Sharkey NA. Biomechanics of the thumb flexor pulley system. J Hand Surg Am. 1994;19(3):475e479. 18. Logan AJ, Makwana N, Mason G, Dias J. Acute hand and wrist injuries in experienced rock climbers. Br J Sports Med. 2004;38(5):545e548. 19. Dy CJ, Lyman S, Schreiber JJ, Do HT, Daluiski A. The epidemiology of reoperation after flexor pulley reconstruction. J Hand Surg Am. 2013;38(9):1705e1711. 20. Bollen SR. Injury to the A2 pulley in rock climbers. J Hand Surg Br. 1990;15(2):268e270. 21. Lin GT, Cooney WP, Amadio PC, An KN. Mechanical properties of human pulleys. J Hand Surg Br. 1990;15(4):429e434. 22. Lourie GM, Hamby Z, Raasch WG, Chandler JB, Porter JL. Annular flexor pulley injuries in professional baseball pitchers: a case series. Am J Sports Med. 2011;39(2):421e424. 23. Arora R, Fritz D, Zimmermann R, et al. Reconstruction of the digital flexor pulley system: a retrospective comparison of two methods of treatment. J Hand Surg Eur Vol. 2007;32(1):60e66. 24. Schoffl VR, Jungert J. Closed flexor pulley injuries in nonclimbing activities. J Hand Surg Am. 2006;31(5):806e810. 25. Hamano H, Motomiya M, Iwasaki N. Adverse effect of repeated corticosteroid injections for trigger finger on flexor pulley system. J Hand Surg Eur Vol. 2013;38(3):326e327. 26. Hauger O, Chung CB, Lektrakul N, et al. Pulley system in the fingers: normal anatomy and simulated lesions in cadavers at MR imaging, CT, and US with and without contrast material distention of the tendon sheath. Radiology. 2000;217(1):201e212. 27. Schoffl V, Hochholzer T, Winkelmann HP, Strecker W. Pulley injuries in rock climbers. Wilderness Environ Med. 2003;14(2):94e100. 28. Schoffl I, Einwag F, Strecker W, Hennig F, Schoffl V. Impact of taping after finger flexor tendon pulley ruptures in rock climbers. J Appl Biomech. 2007;23(1):52e62. 29. Gabl M, Reinhart C, Lutz M, Bodner G, Angermann P, Pechlaner S. The use of a graft from the second extensor compartment to reconstruct the A2 flexor pulley in the long finger. J Hand Surg Br. 2000;25(1):98e101. 30. Moutet F, Forli A, Voulliaume D. Pulley rupture and reconstruction in rock climbers. Tech Hand Up Extrem Surg. 2004;8(3):149e155. 31. Schoffl VR, Einwag F, Strecker W, Schoffl I. Strength measurement and clinical outcome after pulley ruptures in climbers. Med Sci Sports Exerc. 2006;38(4):637e643. 32. Okutsu I, Ninomiya S, Hiraki S, Inanami H, Kuroshima N. Threeloop technique for A2 pulley reconstruction. J Hand Surg Am. 1987;12(5 Pt 1):790e794. 33. Bunata RE. Primary pulley enlargement in zone 2 by incision and repair with an extensor retinaculum graft. J Hand Surg Am. 2010;35(5):785e790. 34. Clark TA, Skeete K, Amadio PC. Flexor tendon pulley reconstruction. J Hand Surg Am. 2010;35(10):1685e1689.
Vol. 39, December 2014