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Kinematics of Thumb Ulnar Collateral Ligament Repair With Suture Tape Augmentation
SCIENTIFIC ARTICLE
Kinematics of Thumb Ulnar Collateral Ligament Repair With Suture Tape Augmentation Nilay A. Patel, MD,* Charles C. Lin, MD,*† Yasuo Itami, MD,*‡ Michelle H. McGarry, MS,*§ Steven S. Shin, MD,k Thay Q. Lee, PhD*§
Purpose Acute thumb ulnar collateral ligament (UCL) tears are common injuries of the thumb in athletes. Thumb UCL repair with suture tape augmentation is a novel procedure that may allow earlier return to play. The purpose of this study was to evaluate the biomechanical characteristics of the thumb after UCL repair with and without suture tape augmentation. Methods Eight cadaveric thumbs were tested in a custom hand testing system. Varusevalgus kinematics were measured at e10 , 0 , 15 , and 30 of thumb metacarpophalangeal flexion under the following conditions: (1) intact thumb UCL, (2) complete UCL tear (proper and accessory ligaments), (3) UCL repair, and (4) UCL repair with suture tape augmentation. Angular stiffness was also quantified after application of sequentially increasing valgus torque in the intact UCL repair and the UCL repair with suture tape augmentation conditions. Results Complete UCL tear increased total varusevalgus angulation at all degrees of thumb metacarpophalangeal flexion. Thumb UCL repair alone and repair with suture tape augmentation decreased total varusevalgus angulation relative to complete UCL tear at all flexion angles. Total varusevalgus angulation was not significantly different from intact results for either the repair alone or the repair with suture tape augmentation at all flexion angles. Repair with suture tape augmentation had significantly higher valgus angular stiffness compared with repair alone but not compared with intact. Conclusions Thumb UCL repair with suture tape augmentation is able to restore varusevalgus kinematics after complete UCL tear without over-constraining the joint. In addition, the higher angular stiffness afforded by the suture tape augmentation may allow for earlier rehabilitation after surgery. Clinical relevance Thumb UCL repair with suture tape augmentation may allow earlier return to sport in athletes than with repair alone. (J Hand Surg Am. 2019;-(-):1.e1-e6. Copyright Ó 2019 by the American Society for Surgery of the Hand. All rights reserved.) Key words collateral ligament repair, kinematics, return to play, return to sport, thumb ulnar collateral ligament.
From the *Orthopaedic Biomechanics Laboratory, Tibor Rubin VA Long Beach Healthcare System and University of California Irvine, Long Beach; the †Department of Orthopedic Surgery, NYU Langone Orthopedic Hospital, New York, NY; the ‡Department of Orthopedic Surgery, Osaka Medical College, Takatsuki, Osaka, Japan; the §Orthopaedic Biomechanics Laboratory, Congress Medical Foundation, Pasadena; and the kCedars-Sinai Kerlan-Jobe Institute, Los Angeles, CA.
This study was funded by Arthrex, Inc. who provided cadaveric specimens and implants for this study. The funding source did not play a role in the investigation. Corresponding author: Steven S. Shin MD, Cedars-Sinai Kerlan Jobe Institute, 6801 Park Terrace Drive #400, Los Angeles, CA 90045; e-mail: [email protected]. 0363-5023/19/---0001$36.00/0 https://doi.org/10.1016/j.jhsa.2019.09.005
Received for publication February 4, 2019; accepted in revised form September 25, 2019.
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ligament (UCL) injuries are the most common injuries to the thumb metacarpophalangeal (MCP) joint. First described by Campbell in 1955,1 the injury has an estimated incidence of 50,000 to 200,000/y.2 Acute UCL injuries are particularly common in downhill skiers and typically are caused by forced abduction and extension of the thumb MCP joint.3,4 Ulnar collateral ligament tears may be partial or complete and acute or chronic. Disruption of the thumb UCL has been associated with pain, instability, decreased pinch strength, and eventually osteoarthritis, likely caused by changes in kinematics from the loss of joint congruity and valgus stability.5 Partial tears are generally treated nonsurgically with MCP joint immobilization. Complete acute tears are treated with primary repair, whereas chronic tears are generally treated with UCL reconstruction. Numerous methods have been described for UCL repair including direct repair techniques and use of suture anchors.4,6e11 Return to sport of elite-level athletes after surgical repair of complete tears has been reported to be between 96% and 100% with an average of 49 days for collegiate football players and 56.2 days in Major League Baseball players.12,13 Recently, a novel technique for UCL repair with suture tape augmentation was described, which allows earlier return to play.14 In addition, biomechanical analysis of this technique demonstrated superior load to failure characteristics compared with repair alone.15 Suture tape, which is a flat-braided suture, provides protection to the repair during the initial revascularization and remodeling phase, theoretically allowing for a shorter period of immobilization, earlier range of motion (ROM) and return to play. Although the biomechanical strength of the thumb UCL repair with suture tape augmentation has been tested, to the authors' knowledge, no studies have been done to evaluate thumb MCP joint kinematics or construct stiffness. Good clinical outcomes rely on restoration of thumb MCP joint motion, stability, pinch strength, and grip strength.5 Therefore, kinematic analysis of the thumb MCP joint is important to understand the effects of suture tape augmentation on the repaired thumb UCL. It is also important to take into account initial construct stiffness, especially in elite athletes when considering early rehabilitation and return to play. The objective of this study was to evaluate the varusevalgus kinematics and valgus angular stiffness after thumb UCL repair with and without suture tape augmentation. We hypothesized that the thumb UCL HUMB ULNAR COLLATERAL
J Hand Surg Am.
FIGURE 1: Testing setup. Custom biomechanical thumb testing system allowing for measurement of varusevalgus kinematics of thumb MCP joint.
repair with suture tape augmentation would restore the varusevalgus kinematics of the thumb MCP joint and have higher construct stiffness compared with UCL repair alone. MATERIALS AND METHODS Specimen preparation Eight fresh-frozen male cadaveric specimens (mean age, 61 years; range, 52e69 years) were used for this study. Specimens were thawed overnight at room temperature before dissection. Thumbs were disarticulated at the thumb carpometacarpal joint, taking care to keep the extensor pollicis longus, extensor pollicis brevis, and flexor pollicis longus intact. The proximal portion of the proximal phalanx was stripped of all soft tissue for potting, and the soft tissues immediately around the MCP joint were retained. The adductor aponeurosis was gently freed from the underlying soft tissue and then cut and reflected to allow visualization of the proper and accessory UCLs. All specimens were evaluated before testing to assess for ligament injury or attenuation. The proximal aspect of the metacarpal was then cleared of any soft tissue and potted in 1.5 3-in polyvinyl chloride pipes in plaster of paris with straws to allow smooth tendon passage in anatomic directions. Testing setup We used a previously validated custom biomechanical thumb testing system for this study (Fig. 1).16 The testing system allowed for 6 degrees of freedom for the MCP joint, including varusevalgus motion, volaredorsal translation, and pronosupination. For this study, varusevalgus kinematics were r
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studied. The testing system had a motion arc that guided varusevalgus motion. A pin was placed into the thumb to guide varusevalgus motion. With the distal phalanx flexed to 30 , we inserted a 3.5 20cm pin through the proximal portion of the distal phalanx, across the interphalangeal joint, and into the medullary canal of the proximal phalanx to achieve stable fixation of the interphalangeal joint. Two loading lines were tied around the pin 80 mm distal to the MCP joint line to allow varusevalgus loading. These lines were kept in place with 2 rubber rings that prevented proximal or distal migration of the lines. The extensor pollicis longus and extensor pollicis brevis were sutured together using a Krakow stitch. The flexor pollicis longus was also sutured with a Krakow stich for loading. To replicate a pinch model,16,17 the neutral position for the specimen was loaded with 9.6 N for the extensors and 4.9 N for the flexors. These muscle loads were selected based on physiologic muscle cross-sectional area ratios.16,18e20 We placed 6 marking indentations to determine the movement of the proximal phalanx relative to the fixed position of the metacarpal. Three indentations were placed on the polyvinyl chloride pipe in which the metacarpal was firmly potted to track the metacarpal position. Three additional marking indentations were placed in the proximal phalanx to track its position in space. These markings were then digitized using a 3-dimensional digitizing system (Microscribe 3DLX System, Revware, Inc, Raleigh, NC).
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to prevent penetration of the articular cartilage. A 2.5-mm cannulated drill with a hard-stop guide was used to drill a 1-cm-deep hole into the proximal phalanx. A DX SwiveLock SL (Arthrex, Naples, FL) preloaded with SutureTape (Arthrex) and one 30 FiberWire (Arthrex) suture was inserted into the hole. A horizontal mattress suture configuration placed 2 mm from the distal edge of the ligament was used to repair the proper UCL. Ulnar collateral ligament repair with suture tape augmentation After kinematic testing of the repair condition, a small longitudinal slit was made in the proximal insertion of the UCL. A guide pin was placed through this slit perpendicular to the bony surface. We used a 2.5-mm cannulated drill to drill a 1-cm-deep hole into the metacarpal head. Both limbs of the SutureTape were then passed over the UCL and loaded onto a second DX SwiveLock SL anchor. With the MCP joint held at 30 flexion and the SutureTape limbs held taut, the SwiveLock was inserted into the metacarpal head to complete augmentation of the repair.
Complete UCL tear The complete tear model was created by distal detachment of the entire UCL, consisting of both the proper and accessory ligaments. This model is meant to simulate complete avulsion of the UCL without disrupting surrounding structures such as the dorsal capsule or volar plate.
Measurements Varus and valgus angulation were measured sequentially after application of 10 Ncm of varus and valgus torque at e10 , 0 , 15 , and 30 MCP joint flexion; total varusevalgus angulation was then calculated as the sum of the varus and valgus angulation. We selected load based on previously published data showing the maximal valgus torque that a repair model could withstand, which was 12 Ncm.15 After the intact condition, as well as the repair and repair with suture tape augmentation conditions, angular stiffness was tested at 30 MCP joint flexion by applying a sequentially increasing torque in the valgus direction. The increase in valgus angle was measured with each increase of 5 Ncm. The angular stiffness was calculated based on the increase in angle with an increase in valgus torque. A greater increase in valgus angle with the same fixed increase in valgus torque defines lower angular stiffness, whereas a smaller increase in valgus angle with the same fixed increase in valgus torque defines higher angular stiffness.
Ulnar collateral ligament repair technique The volar-ulnar aspect of the base of the proximal phalanx was cleared of remaining soft tissue. A drill guide pin was inserted to the laser line 1.5 mm away from the joint line at the insertion of the proper UCL
Calculations and statistical analysis Using the digitized points, we calculated the angle of the long axis of proximal phalanx relative to the long axis of the metacarpal. We then compared these measurements across conditions. Using pilot data, a
Testing conditions The following conditions were tested in each specimen for this study: (1) intact UCL; (2) complete UCL tear; (3) UCL repair; and (4) UCL repair with suture tape augmentation.
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FIGURE 2: Total varusevalgus angulation of thumb MCP joint at varying thumb MCP joint flexion angles: e10 , 0 , 15 , and 30 . Statistically significant at P < .05: *versus intact; †versus complete UCL tear.
sample size of 8 in each group was estimated to be sufficient to detect a 0.9 Ncm/degree difference in stiffness between repair and augmented repair with 80% power at a ¼ 0.05 and an SD of 1.3. One-way repeated-measures analysis of variance tests with Tukey post hoc tests were then used to compare kinematic parameters across testing conditions. Statistical significance was set at a < 0.05. RESULTS Total varusevalgus angulation increased at e10 , 0 , 15 , and 30 of thumb MCP joint flexion angles (P < .05) (Fig. 2). Thumb UCL repair alone and repair with suture tape augmentation decreased total varusevalgus angulation compared with the complete UCL tear at all flexion angles (P < .05). Total varusevalgus angulation was not significantly different from the intact condition for either the repair alone or the repair with suture tape augmentation at all flexion angles (Fig. 2). Repair with suture tape augmentation had significantly higher valgus angular stiffness compared with repair alone (P < .05) but not compared with intact. The intact UCL had a stiffness of 1.7 Ncm/degrees, the UCL repair alone had a stiffness of 1.5 Ncm/degrees, and the repair with suture tape augmentation had a stiffness of 2.3 Ncm/degrees (Fig. 3).
FIGURE 3: Average angular stiffness with sequential valgus loading of intact UCL, standard repair with suture anchor, and suture tape augmented repair. Statistically significant at P < .05: *versus repair.
demonstrated stiffness greater than the repair condition, which might allow for earlier rehabilitation. In this study, both the repair and the augmented repair were able to restore total varusevalgus of the MCP joint back to intact conditions. Thumb UCL tears have been implicated in weakness during pinching or grasping motions,17,21 and restoration of proper kinematics has been determined to be particularly important for performing precision and power grips.22 Therefore, it is important that the augmented repair recreated thumb kinematics not notably different from previous repair techniques or the intact condition. In addition, previous studies demonstrated that the repair technique can affect MCP joint motion.23 With the addition of a stiff, non-deformable suture in this construct, there was concern regarding possible over-constraint of the joint. However, we found that there was no major difference in kinematics between the augmented repair and intact
DISCUSSION The results suggest that suture tape augmentation of an anatomic thumb UCL repair is able to restore thumb valgus stability. In this study, augmentation resulted in varusevalgus kinematics similar to the intact thumb without over-constraint of the MCP joint. Furthermore, the augmented repair J Hand Surg Am.
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conditions. Therefore, this technique of augmenting an anatomic repair of the UCL is a viable method for restoring thumb stability. The time-0 angular stiffness of the suture tape augmented repair was significantly higher than standard repair in this study. Previous studies showed that direct repair alone may be unable to restore the original stiffness of the UCL. Firoozbakhsh et al24 found that joint rigidity of the repaired UCL was 2.3 times less than the intact ligament. Even with a 2anchor repair, Gil et al25 found that the stiffness of the construct was still significantly less than the intact ligament. For UCL reconstructions, Hogan et al26 compared the stiffness of 4 constructs and found that whereas construct stiffness varied, all of the reconstructions were less stiff than the intact UCL. Although the current results did not show a statistically significant decrease in angular stiffness in the repair-only group, possibly owing to testing at lower nondestructive loads, the added angular stiffness by the suture tape augmentation may allow for earlier, more aggressive rehabilitation and decreased immobilization by protecting the healing ligament. Greater and repeated loading might lead to suture cutout and early repair failure in the repair construct without the added stiffness provided by the suture tape. In this study, the angular stiffness against valgus stress in the UCL repair with suture tape augmentation was significantly higher than in the traditional UCL repair. After thumb UCL surgery, valgus stress to the thumb is limited to prevent postoperative laxity, especially in the early phase of postoperative programs. After traditional UCL repair with suture anchors, athletes are immobilized in a thumb spica cast for 4 weeks followed by 4 weeks of a removable thumb spica orthosis and therapy, with eventual return to play at an average of 7 weeks (range, 4e12 weeks) with supportive taping.27 In contrast, UCL repair with suture tape augmentation allowed a professional basketball player to begin rehabilitation 3 days after surgery and return to full play in 5 weeks without a brace or taping.14 The findings of this study may support suture tape augmentation of the thumb UCL repair to allow for a shorter period of immobilization, earlier initiation of therapy, and therefore faster return to play. However, because of the greater cost of suture tape augmentation, this technique may be cost-effective only in high-level athletes, although this has yet to be studied. There were several limitations of this study. First, this was a time-0 cadaveric study; therefore, we cannot account for the increased strength generated by biologic healing. However, time-0 stiffness and J Hand Surg Am.
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kinematics provide valuable information for the surgeon when determining proper rehabilitation protocols. Second, preparation of each specimen required division of the skin and the adductor aponeurosis. Previous studies did not demonstrate instability upon sectioning of these structures.28,29 Third, we did not assess contributions of supination deformity of the proximal phalanx to valgus kinematics after UCL tear. Fourth, the thumb flexion angles tested in this study were e10 , 0 , 15 , and 30 ; therefore, we are unable to provide conclusions for flexion angles greater than 30 . Fifth, although many techniques for thumb UCL repair have been described in the literature, we chose a simple horizontal mattress suture configuration. This was chosen because of the simplicity of the surgical technique as well as its broad applicability. Sixth, immobilization and rehabilitation protocols have not been standardized in the literature; therefore, our suggestion of earlier ROM may not generalize to surgeons who use shorter immobilization periods before ROM exercises for their repairs. Suture tape augmentation of the thumb UCL repair restores varusevalgus kinematics after complete UCL tear and demonstrates increased angular stiffness compared with repair alone. These results suggest that this technique may allow for earlier and more aggressive rehabilitation without significantly altering native thumb MCP joint kinematics. REFERENCES 1. Campbell CS. Gamekeeper’s thumb. J Bone Joint Surg Br. 1955;37(1):148e149. 2. Hinke DH, Erickson SJ, Chamoy L, Timins ME. Ulnar collateral ligament of the thumb: MR findings in cadavers, volunteers, and patients with ligamentous injury (gamekeeper’s thumb). 1994;163(6): 1431e1434. 3. Engkvist O, Balkfors B, Lindsjö U. Thumb injuries in downhill skiing. Int J Sport Med. 1982;3(1):50e55. 4. Derkash RS, Matyas JR, Weaver JK, et al. Acute surgical repair of the skier’s thumb. Clin Orthop Relat Res. 1987;216:29e33. 5. Samora J, Harris JD, Griesser MJ, Ruff ME, Awan HM. Outcomes after injury to the thumb ulnar collateral ligament—a systematic review. Clin J Sport Med. 2013;23(4):247e254. 6. Zeman C, Hunter RE, Freeman JR, Purnell ML, Mastrangelo J. Acute skier’s thumb repaired with a proximal phalanx suture anchor. Am J Sport Med. 1998;26(5):644e650. 7. Huber J, Bickert B, Germann G. The Mitek mini anchor in the treatment of the gamekeeper’s thumb. Eur J Plast Surg. 1997;20(5): 251e255. 8. Katolik LI, Friedrich J, Trumble TE. Repair of acute ulnar collateral ligament injuries of the thumb metacarpophalangeal joint: a retrospective comparison of pull-out sutures and bone anchor techniques. Plast Reconstr Surg. 2008;122(5):1451e1456. 9. Weiland AJ, Berner SH, Hotchkiss RN, R MR, Gerwin M. Repair of acute ulnar collateral ligament injuries of the thumb metacarpophalangeal joint with an intraosseous suture anchor. J Hand Surg Am. 1997;22(4):585e591.
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20. Wu JZ, Sinsel EW, Shroyer JF, et al. Analysis of the musculoskeletal loading of the thumb during pipetting—A pilot study. J Biomech. 2014;47(2):392e399. 21. Smith RJ. Post-traumatic instability of the metacarpophalangeal joint of the thumb. J Bone Joint Surg Am. 1977;59(1):14e21. 22. Bazanski T. Metacarpophalangeal joint kinematics during a grip of everyday objects using the three-dimensional motion analysis system. Acta Bioeng Biomech. 2010;12(2):79e85. 23. Bean C, Tencer AF, Trumble TE. The effect of thumb metacarpophalangeal ulnar collateral ligament attachment site on joint range of motion: an in vitro study. J Hand Surg Am. 1999;24(2):283e287. 24. Firoozbakhsh K, Yi I, Moneim MS, Umada Y. A study of ulnar collateral ligament of the thumb metacarpophalangeal joint. Clin Orthop Relat Res. 2002;403:240e247. 25. Gil JA, Chambers A, Shah KN, Crisco JJ, Got C, Akelman E. A biomechanical evaluation of a 2-suture anchor repair technique for thumb metacarpophalangeal joint ulnar collateral ligament injuries. Hand (N Y). 2018;13(5):581e585. 26. Hogan CJ, Ruland RT, Levin LS. Reconstruction of the ulnar collateral ligament of the thumb metacarpophalangeal joint: a cadaver study. J Hand Surg Am. 2005;30(2):394e399. 27. Werner BC, Hadeed MM, Lyons ML, Gluck JS, Diduch DR, Chhabra BA. Return to football and long-term clinical outcomes after thumb ulnar collateral ligament suture anchor repair in collegiate athletes. J Hand Surg Am. 2014;39(10):1992e1998. 28. Heyman P, Gelberman RH, Duncan K, Hipp JA. Injuries of the ulnar collateral ligament of the thumb metacarpophalangeal joint: biomechanical and prospective clinical studies on the usefulness of valgus stress testing. Clin Orthop Relat Res. 1993;(292):165e171. 29. Coonrad RW, Goldner JL. A study of the pathological findings and treatment in soft-tissue injury of the thumb metacarpophalangeal joint: with a clinical study of the normal range of motion in one thousand thumbs and a study of post mortem findings of ligamentous structures in relation to function. J Bone Joint Surg Am. 1968;50(3):439e451.
10. Ziegler C, Neshkova I, Schmidt K, Meffert R, Jakubietz M, Jakubietz R. Operative Behandlung der ulnaren Seitenbandläsion am Daumengrundgelenk. Oper Orthop Traumatol. 2015;28(2):111e127. 11. Moharram AN. Repair of ulnar collateral ligament injuries of thumb metacarpophalangeal joint with microanchors. Egypt Orthop J. 2014;49(1):34e37. 12. Jack RA II, Sochacki KR, Gagliano B, Lintner DM, Harris JD, McCullough PC. Performance and return to sport after thumb ulnar collateral ligament repair in Major League Baseball players. Orthop J Sport Med. 2018;6(1):2325967117747268. 13. Werner BC, Belkin NS, Kennelly S, et al. Injuries to the collateral ligaments of the metacarpophalangeal joint of the thumb, including simultaneous combined thumb ulnar and radial collateral ligament injuries, in National Football League athletes. 2017;45(1): 195e200. 14. Giacomo AF, Shin SS. Repair of the thumb ulnar collateral ligament with suture tape augmentation. Tech Hand Up Extrem Surg. 2017;21(4):164e166. 15. Shin SS, van Eck CF, Uquillas C. Suture tape augmentation of the thumbeulnar collateral ligament repair: a biomechanical study. J Hand Surg Am. 2018;43(9):868.e1e868.e6. 16. Kim B-S, Doermann A, Michelle M, Akeda M, Ihn H, Lee TQ. Dorsoradial instability of the thumb metacarpophalangeal joint: a biomechanical investigation. 2017;42(12):1029.e1e1029. e8. 17. Hsieh Y-F, Draganich LF, Mass DP. The effects of transection and reconstruction of the ulnar collateral ligament complex on the position of the proximal phalanx of the thumb during simulated tip pinch. J Hand Surg Am. 2000;25(2):313e321. 18. Doyle J. Surgical Anatomy of the Hand and Upper Extremity. Philadelphia, PA: Lippincott Williams & Wilkins; 2003. 19. Cooney WP, Chao EY. Biomechanical analysis of static forces in the thumb during hand function. J Bone Joint Surg Am. 1977;59(1): 27e36.
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Kinematics of Thumb Ulnar Collateral Ligament Repair With Suture Tape Augmentation Nilay A. Patel, MD,* Charles C. Lin, MD,*† Yasuo Itami, MD,*‡ Michelle H. McGarry, MS,*§ Steven S. Shin, MD,k Thay Q. Lee, PhD*§
Purpose Acute thumb ulnar collateral ligament (UCL) tears are common injuries of the thumb in athletes. Thumb UCL repair with suture tape augmentation is a novel procedure that may allow earlier return to play. The purpose of this study was to evaluate the biomechanical characteristics of the thumb after UCL repair with and without suture tape augmentation. Methods Eight cadaveric thumbs were tested in a custom hand testing system. Varusevalgus kinematics were measured at e10 , 0 , 15 , and 30 of thumb metacarpophalangeal flexion under the following conditions: (1) intact thumb UCL, (2) complete UCL tear (proper and accessory ligaments), (3) UCL repair, and (4) UCL repair with suture tape augmentation. Angular stiffness was also quantified after application of sequentially increasing valgus torque in the intact UCL repair and the UCL repair with suture tape augmentation conditions. Results Complete UCL tear increased total varusevalgus angulation at all degrees of thumb metacarpophalangeal flexion. Thumb UCL repair alone and repair with suture tape augmentation decreased total varusevalgus angulation relative to complete UCL tear at all flexion angles. Total varusevalgus angulation was not significantly different from intact results for either the repair alone or the repair with suture tape augmentation at all flexion angles. Repair with suture tape augmentation had significantly higher valgus angular stiffness compared with repair alone but not compared with intact. Conclusions Thumb UCL repair with suture tape augmentation is able to restore varusevalgus kinematics after complete UCL tear without over-constraining the joint. In addition, the higher angular stiffness afforded by the suture tape augmentation may allow for earlier rehabilitation after surgery. Clinical relevance Thumb UCL repair with suture tape augmentation may allow earlier return to sport in athletes than with repair alone. (J Hand Surg Am. 2019;-(-):1.e1-e6. Copyright Ó 2019 by the American Society for Surgery of the Hand. All rights reserved.) Key words collateral ligament repair, kinematics, return to play, return to sport, thumb ulnar collateral ligament.
From the *Orthopaedic Biomechanics Laboratory, Tibor Rubin VA Long Beach Healthcare System and University of California Irvine, Long Beach; the †Department of Orthopedic Surgery, NYU Langone Orthopedic Hospital, New York, NY; the ‡Department of Orthopedic Surgery, Osaka Medical College, Takatsuki, Osaka, Japan; the §Orthopaedic Biomechanics Laboratory, Congress Medical Foundation, Pasadena; and the kCedars-Sinai Kerlan-Jobe Institute, Los Angeles, CA.
This study was funded by Arthrex, Inc. who provided cadaveric specimens and implants for this study. The funding source did not play a role in the investigation. Corresponding author: Steven S. Shin MD, Cedars-Sinai Kerlan Jobe Institute, 6801 Park Terrace Drive #400, Los Angeles, CA 90045; e-mail: [email protected]. 0363-5023/19/---0001$36.00/0 https://doi.org/10.1016/j.jhsa.2019.09.005
Received for publication February 4, 2019; accepted in revised form September 25, 2019.
Ó 2019 ASSH
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ligament (UCL) injuries are the most common injuries to the thumb metacarpophalangeal (MCP) joint. First described by Campbell in 1955,1 the injury has an estimated incidence of 50,000 to 200,000/y.2 Acute UCL injuries are particularly common in downhill skiers and typically are caused by forced abduction and extension of the thumb MCP joint.3,4 Ulnar collateral ligament tears may be partial or complete and acute or chronic. Disruption of the thumb UCL has been associated with pain, instability, decreased pinch strength, and eventually osteoarthritis, likely caused by changes in kinematics from the loss of joint congruity and valgus stability.5 Partial tears are generally treated nonsurgically with MCP joint immobilization. Complete acute tears are treated with primary repair, whereas chronic tears are generally treated with UCL reconstruction. Numerous methods have been described for UCL repair including direct repair techniques and use of suture anchors.4,6e11 Return to sport of elite-level athletes after surgical repair of complete tears has been reported to be between 96% and 100% with an average of 49 days for collegiate football players and 56.2 days in Major League Baseball players.12,13 Recently, a novel technique for UCL repair with suture tape augmentation was described, which allows earlier return to play.14 In addition, biomechanical analysis of this technique demonstrated superior load to failure characteristics compared with repair alone.15 Suture tape, which is a flat-braided suture, provides protection to the repair during the initial revascularization and remodeling phase, theoretically allowing for a shorter period of immobilization, earlier range of motion (ROM) and return to play. Although the biomechanical strength of the thumb UCL repair with suture tape augmentation has been tested, to the authors' knowledge, no studies have been done to evaluate thumb MCP joint kinematics or construct stiffness. Good clinical outcomes rely on restoration of thumb MCP joint motion, stability, pinch strength, and grip strength.5 Therefore, kinematic analysis of the thumb MCP joint is important to understand the effects of suture tape augmentation on the repaired thumb UCL. It is also important to take into account initial construct stiffness, especially in elite athletes when considering early rehabilitation and return to play. The objective of this study was to evaluate the varusevalgus kinematics and valgus angular stiffness after thumb UCL repair with and without suture tape augmentation. We hypothesized that the thumb UCL HUMB ULNAR COLLATERAL
J Hand Surg Am.
FIGURE 1: Testing setup. Custom biomechanical thumb testing system allowing for measurement of varusevalgus kinematics of thumb MCP joint.
repair with suture tape augmentation would restore the varusevalgus kinematics of the thumb MCP joint and have higher construct stiffness compared with UCL repair alone. MATERIALS AND METHODS Specimen preparation Eight fresh-frozen male cadaveric specimens (mean age, 61 years; range, 52e69 years) were used for this study. Specimens were thawed overnight at room temperature before dissection. Thumbs were disarticulated at the thumb carpometacarpal joint, taking care to keep the extensor pollicis longus, extensor pollicis brevis, and flexor pollicis longus intact. The proximal portion of the proximal phalanx was stripped of all soft tissue for potting, and the soft tissues immediately around the MCP joint were retained. The adductor aponeurosis was gently freed from the underlying soft tissue and then cut and reflected to allow visualization of the proper and accessory UCLs. All specimens were evaluated before testing to assess for ligament injury or attenuation. The proximal aspect of the metacarpal was then cleared of any soft tissue and potted in 1.5 3-in polyvinyl chloride pipes in plaster of paris with straws to allow smooth tendon passage in anatomic directions. Testing setup We used a previously validated custom biomechanical thumb testing system for this study (Fig. 1).16 The testing system allowed for 6 degrees of freedom for the MCP joint, including varusevalgus motion, volaredorsal translation, and pronosupination. For this study, varusevalgus kinematics were r
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studied. The testing system had a motion arc that guided varusevalgus motion. A pin was placed into the thumb to guide varusevalgus motion. With the distal phalanx flexed to 30 , we inserted a 3.5 20cm pin through the proximal portion of the distal phalanx, across the interphalangeal joint, and into the medullary canal of the proximal phalanx to achieve stable fixation of the interphalangeal joint. Two loading lines were tied around the pin 80 mm distal to the MCP joint line to allow varusevalgus loading. These lines were kept in place with 2 rubber rings that prevented proximal or distal migration of the lines. The extensor pollicis longus and extensor pollicis brevis were sutured together using a Krakow stitch. The flexor pollicis longus was also sutured with a Krakow stich for loading. To replicate a pinch model,16,17 the neutral position for the specimen was loaded with 9.6 N for the extensors and 4.9 N for the flexors. These muscle loads were selected based on physiologic muscle cross-sectional area ratios.16,18e20 We placed 6 marking indentations to determine the movement of the proximal phalanx relative to the fixed position of the metacarpal. Three indentations were placed on the polyvinyl chloride pipe in which the metacarpal was firmly potted to track the metacarpal position. Three additional marking indentations were placed in the proximal phalanx to track its position in space. These markings were then digitized using a 3-dimensional digitizing system (Microscribe 3DLX System, Revware, Inc, Raleigh, NC).
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to prevent penetration of the articular cartilage. A 2.5-mm cannulated drill with a hard-stop guide was used to drill a 1-cm-deep hole into the proximal phalanx. A DX SwiveLock SL (Arthrex, Naples, FL) preloaded with SutureTape (Arthrex) and one 30 FiberWire (Arthrex) suture was inserted into the hole. A horizontal mattress suture configuration placed 2 mm from the distal edge of the ligament was used to repair the proper UCL. Ulnar collateral ligament repair with suture tape augmentation After kinematic testing of the repair condition, a small longitudinal slit was made in the proximal insertion of the UCL. A guide pin was placed through this slit perpendicular to the bony surface. We used a 2.5-mm cannulated drill to drill a 1-cm-deep hole into the metacarpal head. Both limbs of the SutureTape were then passed over the UCL and loaded onto a second DX SwiveLock SL anchor. With the MCP joint held at 30 flexion and the SutureTape limbs held taut, the SwiveLock was inserted into the metacarpal head to complete augmentation of the repair.
Complete UCL tear The complete tear model was created by distal detachment of the entire UCL, consisting of both the proper and accessory ligaments. This model is meant to simulate complete avulsion of the UCL without disrupting surrounding structures such as the dorsal capsule or volar plate.
Measurements Varus and valgus angulation were measured sequentially after application of 10 Ncm of varus and valgus torque at e10 , 0 , 15 , and 30 MCP joint flexion; total varusevalgus angulation was then calculated as the sum of the varus and valgus angulation. We selected load based on previously published data showing the maximal valgus torque that a repair model could withstand, which was 12 Ncm.15 After the intact condition, as well as the repair and repair with suture tape augmentation conditions, angular stiffness was tested at 30 MCP joint flexion by applying a sequentially increasing torque in the valgus direction. The increase in valgus angle was measured with each increase of 5 Ncm. The angular stiffness was calculated based on the increase in angle with an increase in valgus torque. A greater increase in valgus angle with the same fixed increase in valgus torque defines lower angular stiffness, whereas a smaller increase in valgus angle with the same fixed increase in valgus torque defines higher angular stiffness.
Ulnar collateral ligament repair technique The volar-ulnar aspect of the base of the proximal phalanx was cleared of remaining soft tissue. A drill guide pin was inserted to the laser line 1.5 mm away from the joint line at the insertion of the proper UCL
Calculations and statistical analysis Using the digitized points, we calculated the angle of the long axis of proximal phalanx relative to the long axis of the metacarpal. We then compared these measurements across conditions. Using pilot data, a
Testing conditions The following conditions were tested in each specimen for this study: (1) intact UCL; (2) complete UCL tear; (3) UCL repair; and (4) UCL repair with suture tape augmentation.
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FIGURE 2: Total varusevalgus angulation of thumb MCP joint at varying thumb MCP joint flexion angles: e10 , 0 , 15 , and 30 . Statistically significant at P < .05: *versus intact; †versus complete UCL tear.
sample size of 8 in each group was estimated to be sufficient to detect a 0.9 Ncm/degree difference in stiffness between repair and augmented repair with 80% power at a ¼ 0.05 and an SD of 1.3. One-way repeated-measures analysis of variance tests with Tukey post hoc tests were then used to compare kinematic parameters across testing conditions. Statistical significance was set at a < 0.05. RESULTS Total varusevalgus angulation increased at e10 , 0 , 15 , and 30 of thumb MCP joint flexion angles (P < .05) (Fig. 2). Thumb UCL repair alone and repair with suture tape augmentation decreased total varusevalgus angulation compared with the complete UCL tear at all flexion angles (P < .05). Total varusevalgus angulation was not significantly different from the intact condition for either the repair alone or the repair with suture tape augmentation at all flexion angles (Fig. 2). Repair with suture tape augmentation had significantly higher valgus angular stiffness compared with repair alone (P < .05) but not compared with intact. The intact UCL had a stiffness of 1.7 Ncm/degrees, the UCL repair alone had a stiffness of 1.5 Ncm/degrees, and the repair with suture tape augmentation had a stiffness of 2.3 Ncm/degrees (Fig. 3).
FIGURE 3: Average angular stiffness with sequential valgus loading of intact UCL, standard repair with suture anchor, and suture tape augmented repair. Statistically significant at P < .05: *versus repair.
demonstrated stiffness greater than the repair condition, which might allow for earlier rehabilitation. In this study, both the repair and the augmented repair were able to restore total varusevalgus of the MCP joint back to intact conditions. Thumb UCL tears have been implicated in weakness during pinching or grasping motions,17,21 and restoration of proper kinematics has been determined to be particularly important for performing precision and power grips.22 Therefore, it is important that the augmented repair recreated thumb kinematics not notably different from previous repair techniques or the intact condition. In addition, previous studies demonstrated that the repair technique can affect MCP joint motion.23 With the addition of a stiff, non-deformable suture in this construct, there was concern regarding possible over-constraint of the joint. However, we found that there was no major difference in kinematics between the augmented repair and intact
DISCUSSION The results suggest that suture tape augmentation of an anatomic thumb UCL repair is able to restore thumb valgus stability. In this study, augmentation resulted in varusevalgus kinematics similar to the intact thumb without over-constraint of the MCP joint. Furthermore, the augmented repair J Hand Surg Am.
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conditions. Therefore, this technique of augmenting an anatomic repair of the UCL is a viable method for restoring thumb stability. The time-0 angular stiffness of the suture tape augmented repair was significantly higher than standard repair in this study. Previous studies showed that direct repair alone may be unable to restore the original stiffness of the UCL. Firoozbakhsh et al24 found that joint rigidity of the repaired UCL was 2.3 times less than the intact ligament. Even with a 2anchor repair, Gil et al25 found that the stiffness of the construct was still significantly less than the intact ligament. For UCL reconstructions, Hogan et al26 compared the stiffness of 4 constructs and found that whereas construct stiffness varied, all of the reconstructions were less stiff than the intact UCL. Although the current results did not show a statistically significant decrease in angular stiffness in the repair-only group, possibly owing to testing at lower nondestructive loads, the added angular stiffness by the suture tape augmentation may allow for earlier, more aggressive rehabilitation and decreased immobilization by protecting the healing ligament. Greater and repeated loading might lead to suture cutout and early repair failure in the repair construct without the added stiffness provided by the suture tape. In this study, the angular stiffness against valgus stress in the UCL repair with suture tape augmentation was significantly higher than in the traditional UCL repair. After thumb UCL surgery, valgus stress to the thumb is limited to prevent postoperative laxity, especially in the early phase of postoperative programs. After traditional UCL repair with suture anchors, athletes are immobilized in a thumb spica cast for 4 weeks followed by 4 weeks of a removable thumb spica orthosis and therapy, with eventual return to play at an average of 7 weeks (range, 4e12 weeks) with supportive taping.27 In contrast, UCL repair with suture tape augmentation allowed a professional basketball player to begin rehabilitation 3 days after surgery and return to full play in 5 weeks without a brace or taping.14 The findings of this study may support suture tape augmentation of the thumb UCL repair to allow for a shorter period of immobilization, earlier initiation of therapy, and therefore faster return to play. However, because of the greater cost of suture tape augmentation, this technique may be cost-effective only in high-level athletes, although this has yet to be studied. There were several limitations of this study. First, this was a time-0 cadaveric study; therefore, we cannot account for the increased strength generated by biologic healing. However, time-0 stiffness and J Hand Surg Am.
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kinematics provide valuable information for the surgeon when determining proper rehabilitation protocols. Second, preparation of each specimen required division of the skin and the adductor aponeurosis. Previous studies did not demonstrate instability upon sectioning of these structures.28,29 Third, we did not assess contributions of supination deformity of the proximal phalanx to valgus kinematics after UCL tear. Fourth, the thumb flexion angles tested in this study were e10 , 0 , 15 , and 30 ; therefore, we are unable to provide conclusions for flexion angles greater than 30 . Fifth, although many techniques for thumb UCL repair have been described in the literature, we chose a simple horizontal mattress suture configuration. This was chosen because of the simplicity of the surgical technique as well as its broad applicability. Sixth, immobilization and rehabilitation protocols have not been standardized in the literature; therefore, our suggestion of earlier ROM may not generalize to surgeons who use shorter immobilization periods before ROM exercises for their repairs. Suture tape augmentation of the thumb UCL repair restores varusevalgus kinematics after complete UCL tear and demonstrates increased angular stiffness compared with repair alone. These results suggest that this technique may allow for earlier and more aggressive rehabilitation without significantly altering native thumb MCP joint kinematics. REFERENCES 1. Campbell CS. Gamekeeper’s thumb. J Bone Joint Surg Br. 1955;37(1):148e149. 2. Hinke DH, Erickson SJ, Chamoy L, Timins ME. Ulnar collateral ligament of the thumb: MR findings in cadavers, volunteers, and patients with ligamentous injury (gamekeeper’s thumb). 1994;163(6): 1431e1434. 3. Engkvist O, Balkfors B, Lindsjö U. Thumb injuries in downhill skiing. Int J Sport Med. 1982;3(1):50e55. 4. Derkash RS, Matyas JR, Weaver JK, et al. Acute surgical repair of the skier’s thumb. Clin Orthop Relat Res. 1987;216:29e33. 5. Samora J, Harris JD, Griesser MJ, Ruff ME, Awan HM. Outcomes after injury to the thumb ulnar collateral ligament—a systematic review. Clin J Sport Med. 2013;23(4):247e254. 6. Zeman C, Hunter RE, Freeman JR, Purnell ML, Mastrangelo J. Acute skier’s thumb repaired with a proximal phalanx suture anchor. Am J Sport Med. 1998;26(5):644e650. 7. Huber J, Bickert B, Germann G. The Mitek mini anchor in the treatment of the gamekeeper’s thumb. Eur J Plast Surg. 1997;20(5): 251e255. 8. Katolik LI, Friedrich J, Trumble TE. Repair of acute ulnar collateral ligament injuries of the thumb metacarpophalangeal joint: a retrospective comparison of pull-out sutures and bone anchor techniques. Plast Reconstr Surg. 2008;122(5):1451e1456. 9. Weiland AJ, Berner SH, Hotchkiss RN, R MR, Gerwin M. Repair of acute ulnar collateral ligament injuries of the thumb metacarpophalangeal joint with an intraosseous suture anchor. J Hand Surg Am. 1997;22(4):585e591.
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20. Wu JZ, Sinsel EW, Shroyer JF, et al. Analysis of the musculoskeletal loading of the thumb during pipetting—A pilot study. J Biomech. 2014;47(2):392e399. 21. Smith RJ. Post-traumatic instability of the metacarpophalangeal joint of the thumb. J Bone Joint Surg Am. 1977;59(1):14e21. 22. Bazanski T. Metacarpophalangeal joint kinematics during a grip of everyday objects using the three-dimensional motion analysis system. Acta Bioeng Biomech. 2010;12(2):79e85. 23. Bean C, Tencer AF, Trumble TE. The effect of thumb metacarpophalangeal ulnar collateral ligament attachment site on joint range of motion: an in vitro study. J Hand Surg Am. 1999;24(2):283e287. 24. Firoozbakhsh K, Yi I, Moneim MS, Umada Y. A study of ulnar collateral ligament of the thumb metacarpophalangeal joint. Clin Orthop Relat Res. 2002;403:240e247. 25. Gil JA, Chambers A, Shah KN, Crisco JJ, Got C, Akelman E. A biomechanical evaluation of a 2-suture anchor repair technique for thumb metacarpophalangeal joint ulnar collateral ligament injuries. Hand (N Y). 2018;13(5):581e585. 26. Hogan CJ, Ruland RT, Levin LS. Reconstruction of the ulnar collateral ligament of the thumb metacarpophalangeal joint: a cadaver study. J Hand Surg Am. 2005;30(2):394e399. 27. Werner BC, Hadeed MM, Lyons ML, Gluck JS, Diduch DR, Chhabra BA. Return to football and long-term clinical outcomes after thumb ulnar collateral ligament suture anchor repair in collegiate athletes. J Hand Surg Am. 2014;39(10):1992e1998. 28. Heyman P, Gelberman RH, Duncan K, Hipp JA. Injuries of the ulnar collateral ligament of the thumb metacarpophalangeal joint: biomechanical and prospective clinical studies on the usefulness of valgus stress testing. Clin Orthop Relat Res. 1993;(292):165e171. 29. Coonrad RW, Goldner JL. A study of the pathological findings and treatment in soft-tissue injury of the thumb metacarpophalangeal joint: with a clinical study of the normal range of motion in one thousand thumbs and a study of post mortem findings of ligamentous structures in relation to function. J Bone Joint Surg Am. 1968;50(3):439e451.
10. Ziegler C, Neshkova I, Schmidt K, Meffert R, Jakubietz M, Jakubietz R. Operative Behandlung der ulnaren Seitenbandläsion am Daumengrundgelenk. Oper Orthop Traumatol. 2015;28(2):111e127. 11. Moharram AN. Repair of ulnar collateral ligament injuries of thumb metacarpophalangeal joint with microanchors. Egypt Orthop J. 2014;49(1):34e37. 12. Jack RA II, Sochacki KR, Gagliano B, Lintner DM, Harris JD, McCullough PC. Performance and return to sport after thumb ulnar collateral ligament repair in Major League Baseball players. Orthop J Sport Med. 2018;6(1):2325967117747268. 13. Werner BC, Belkin NS, Kennelly S, et al. Injuries to the collateral ligaments of the metacarpophalangeal joint of the thumb, including simultaneous combined thumb ulnar and radial collateral ligament injuries, in National Football League athletes. 2017;45(1): 195e200. 14. Giacomo AF, Shin SS. Repair of the thumb ulnar collateral ligament with suture tape augmentation. Tech Hand Up Extrem Surg. 2017;21(4):164e166. 15. Shin SS, van Eck CF, Uquillas C. Suture tape augmentation of the thumbeulnar collateral ligament repair: a biomechanical study. J Hand Surg Am. 2018;43(9):868.e1e868.e6. 16. Kim B-S, Doermann A, Michelle M, Akeda M, Ihn H, Lee TQ. Dorsoradial instability of the thumb metacarpophalangeal joint: a biomechanical investigation. 2017;42(12):1029.e1e1029. e8. 17. Hsieh Y-F, Draganich LF, Mass DP. The effects of transection and reconstruction of the ulnar collateral ligament complex on the position of the proximal phalanx of the thumb during simulated tip pinch. J Hand Surg Am. 2000;25(2):313e321. 18. Doyle J. Surgical Anatomy of the Hand and Upper Extremity. Philadelphia, PA: Lippincott Williams & Wilkins; 2003. 19. Cooney WP, Chao EY. Biomechanical analysis of static forces in the thumb during hand function. J Bone Joint Surg Am. 1977;59(1): 27e36.
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