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Surgical Techniques for Correction of Traumatic Hyperextension Instability of the Proximal Interphalangeal Joint: A Biomechanical Study
SCIENTIFIC ARTICLE
Surgical Techniques for Correction of Traumatic Hyperextension Instability of the Proximal Interphalangeal Joint: A Biomechanical Study Alan J. Micev, MD,* James M. Saucedo, MD, MBA,* David M. Kalainov, MD,* Liang Wang, PhD,* Madeleine Ma, MS,† Mark A. Yaffe, MD*
Purpose To compare the biomechanical strengths of 5 surgical techniques for treatment of traumatic hyperextension instability of the proximal interphalangeal (PIP) joint. Methods Thirty-six cadaveric fingers were randomly assigned to 6 groups: normal control, volar plate repair, flexor digitorum superficialis tenodesis (FDST), single lateral band transfer (SLBT), double lateral band transfer, and dual split lateral band transfer. For each experimental specimen, the volar plate and accessory collateral ligaments were transected, the PIP joint was hyperextended to 90 , and a PIP joint stabilizing procedure was completed. The ultimate strength of each procedure was ascertained by loading to failure, and the fingers were dissected to determine the pathoanatomy of failure. Force-displacement curves were used to estimate the stiffness of each group, and multiple pairwise statistical comparisons were performed. Results The mean PIP joint stiffness in the control group was significantly greater than the mean PIP joint stiffness in the FDST and SLBT groups, but not significantly different from the mean PIP joint stiffness in the other 3 groups. There were no significant differences in the mean PIP joint stiffness between the 5 joint stabilizing techniques. The SLBT, double lateral band transfer, and dual split lateral band transfer repairs all failed by massive disruption of the flexor tendon sheath, whereas the volar plate repairs and FDST repairs failed by either suture anchor pullout or suture breakage. Conclusions The stiffness of 5 surgical techniques to stabilize a traumatic hyperextensible PIP joint did not vary significantly. Clinical relevance The 5 described techniques to stabilize a posttraumatic PIP joint hyperextension deformity may provide for equal restraint to PIP joint hyperextension instability in the early postoperative period. The choice of procedure should take into consideration other factors not studied, including the potential for PIP joint flexion contracture and long-term durability. (J Hand Surg Am. 2015;-(-):-e-. Copyright Ó 2015 by the American Society for Surgery of the Hand. All rights reserved.) Key words Proximal interphalangeal joint, sprain, volar plate repair, flexor digitorum superficialis tenodesis, lateral band transfer. *Department of Orthopaedic Surgery, and the †Department of Preventative Medicine, Northwestern University, Feinberg School of Medicine, Chicago, IL. Received for publication March 17, 2015; accepted in revised form May 18, 2015. No benefits in any form have been received or will be received related directly or indirectly to the subject of this article. Corresponding author: Alan J. Micev, MD, Department of Orthopaedic Surgery, Northwestern University, 676 N. St. Clair, Suite 1350, Chicago, IL 60611; e-mail: ajmicev@ gmail.com. 0363-5023/15/---0001$36.00/0 http://dx.doi.org/10.1016/j.jhsa.2015.05.011
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proximal interphalangeal (PIP) joint may occur from a hyperextension injury to the finger. Treatment of closed dislocations, in the absence of gross postreduction PIP joint instability, consists of a period of protected finger motion with extension block splinting of the PIP joint and/or finger buddy taping.1 Despite general success with this treatment, a small number of patients may experience persistent dorsal instability of the PIP joint with ORSAL DISLOCATION OF THE
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pain, mechanical symptoms, and a swan-neck finger deformity.1e5 Surgical techniques to address chronic, posttraumatic PIP joint hyperextension instability have been designed to create a check-rein against PIP joint hyperextension.4,6 Investigators have reported satisfactory experiences with volar plate repair2,5,7e10 and PIP joint tenodesis using one or both slips of the flexor digitorum superficialis (FDS) tendon.5,9,11e13 Transferring one or both lateral bands volar to the PIP joint center of rotation will also provide a restraint to PIP joint hyperextension. Lateral band transfer techniques have been well-described for correction of PIP joint hyperextension and swan-neck deformities in patients with rheumatoid arthritis and cerebral palsy.1,14e20 In contrast, there is little information on the role of this approach for posttraumatic PIP joint hyperextension instability.21e24 In the absence of comparative clinical outcome data on the various techniques to restore traumatic PIP joint dorsal instability, understanding the biomechanical properties of the procedures may help guide the surgeon in determining the best treatment approach. The purpose of this study was to assess the biomechanical strengths of 5 surgical constructs for correction of traumatic PIP joint dorsal instability in order to determine if there is any superior technique. The 5 constructs that we tested were volar plate repair (VPR), flexor digitorum superficialis tenodesis (FDST), single lateral band transfer (SLBT), double lateral band transfer (DLBT), and dual split lateral band transfer (DSLBT).
randomly assigned 12 cards (representing each experimental procedure twice), and repeated with each subsequent finger (ie, middle finger followed by ring finger). In the end, the 6 experimental conditions were represented twice by each finger type. To ensure a minimum of freeze-thaw cycles, we adopted a strict process for preparing and testing the specimens. The specimens were stored at e30 Celsius and underwent a period of thawing at room temperature for 12 to 24 hours. After disarticulating and preparing each finger, the digit was either tested immediately or frozen again for testing on another day. No finger specimens were subjected to more than 2 freeze-thaw cycles before testing. When removing the central 3 fingers, the skin was left intact distal to the metacarpophalangeal joints; and the respective extensor, flexor, and intrinsic tendons were dissected free and tagged with sutures. Within each specimen, the flexor tendons were combined. In the index fingers, the extensor indicis proprius and extensor digitorum communis tendons were similarly combined as described by Husain et al.25 The intramedullary canal of each proximal phalanx was hand-reamed using a 3.5-mm drill bit, and a threaded bolt with a 3.7-mm outer diameter was inserted to a press fit. Thirty fingers assigned to the 5 surgical procedures underwent a simulated hyperextension injury to the PIP joint, whereas the PIP joints in the 6 control specimens were left undisturbed. In creating a PIP joint hyperextension injury, a volar approach to the joint was performed through a zig-zag skin incision. A small rectangular section of the flexor tendon sheath in between the A2 and the A4 pulleys was excised, the FDS and flexor digitorum profundus (FDP) tendons were retracted, and the volar plate and accessory collateral ligaments were released from the base of the middle phalanx.4,6 The PIP joint was then hyperextended to 90 and the assigned joint stabilizing technique was performed. A linear skin incision was made over the dorsum of the PIP joint, regardless of the designated procedure. The control finger specimens received volar and dorsal skin incisions only. All skin incisions were closed with 4-0 nylon monofilament sutures in a simple interrupted fashion.
MATERIALS AND METHODS Specimen preparation The index, middle, and ring fingers were harvested from 6 pairs of fresh-frozen matched forearms (5 male and 1 female specimens; age range, 45e67 y) with no known history of inflammatory arthritis or hand trauma. Radiographs were completed beforehand to ensure absence of skeletal deformity and interphalangeal arthrosis. Each finger was disarticulated from the hand at the base of the metacarpophalangeal joint. To ensure equal distribution of experimental conditions among the 36 fingers (ie, in order to avoid having a procedure represented by only index fingers, middle fingers, or ring fingers), we instituted the following randomization procedure. Cards for each of 6 tested conditions (5 surgical procedures and 1 control) were made for a total of 36 cards. We assigned a surgical procedure to each finger type in sequence. For example, we started with all 12 index fingers and J Hand Surg Am.
Surgical techniques Volar plate repair: The palmar incision used to create the PIP joint injury was opened. The FDS and FDP tendons were retracted, and the base of the middle phalanx was exposed. Two 1.3-mm holes were drilled into subchondral bone at the radial and ulnar base of the middle phalanx, and 2 Micro Mitek 1.3-mm r
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FIGURE 1: AeE, Schematic drawings of the 5 PIP joint stabilization procedures performed (the windows in the retinaculum between the A2 and the A4 pulleys are not depicted). A Volar plate repair with 2 suture anchors seated in the base of the middle phalanx. B Flexor digitorum superficialis tenodesis involving transfer of the ulnar slip of this tendon deep to the radial slip of this tendon and the FDP tendon and attachment to the distal-radial border of the proximal phalanx using 1 suture anchor. C Single lateral band transfer with central mobilization of the intact radial lateral band palmar to the PIP joint center of rotation and attachment to the flexor tendon sheath with sutures. D Double lateral band transfer with central mobilization of both intact lateral bands palmar to the PIP joint center of rotation and attachment to the flexor tendon sheath with sutures. E Dual split lateral band transfer involving mobilization of distally based, 2-mm-wide slips of lateral band tissue, transfer of the slips palmar to the PIP joint center of rotation, and attachment of the slips to the flexor tendon sheath with sutures (only 1 side shown).
QuickAnchor Plus anchors with attached 4-0 Ethibond sutures (DePuy Mitek, Raynham, MA) were seated. The volar plate and accessory collateral ligaments were reattached to the middle phalanx base by creating 2 mattress suture constructs, positioning the PIP joint in approximately 10 to 20 of flexion (Fig. 1A).8
and the A2 pulleys and creation of a potential stress riser in the bone distal to the intramedullary bolt. Single lateral band transfer: The extensor apparatus was exposed through the dorsal incision. The radial lateral band was dissected from the central tendon approximately 1 cm proximal and 1 cm distal to the PIP joint leaving the proximal and distal ends intact. The band was then mobilized to a point palmar to the PIP joint center of rotation and sutured to the remaining A3/C1 pulleys using 2 figure-of-eight constructs of 4-0 Ethibond suture (Ethicon, Cincinnati, OH) with the PIP joint in 10 to 20 of flexion (Fig. 1C).1,19
Flexor digitorum superficialis tenodesis: The volar incision was opened. The ulnar slip of the FDS tendon was isolated and dissected distally, preserving the insertion on the volar base of the middle phalanx. The ulnar slip was then cut as proximally as possible to ensure adequate length for transfer. The tendon slip was passed deep to both the FDP tendon and the radial slip of the FDS tendon. A 1.3-mm hole was drilled into the distal-radial aspect of the proximal phalanx and a Micro Mitek anchor with 4-0 Ethibond was seated. The FDS slip was secured to bone by creating a mattress suture construct with the PIP joint flexed 10 to 20 (Fig. 1B). This technique differed from the technique described by Catalano et al11 in which an FDS tendon slip was passed through a transverse tunnel in the proximal phalanx and stabilized to bone using an interference knot of tendon tissue and sutures. Harvesting a longer tendon slip for routing through a bone tunnel would have required supplementary dissection of tissue between the A1 J Hand Surg Am.
Double lateral band transfer: The extensor apparatus was exposed through the dorsal incision. The radial and ulnar lateral bands were dissected from the central tendon approximately 1 cm proximal and 1 cm distal to the PIP joint leaving the proximal and distal ends intact. Each band was then mobilized to a point palmar to the PIP joint center of rotation and sutured to the remaining A3/C1 pulleys using 2 figure-ofeight constructs of 4-0 Ethibond suture with the PIP joint in 10 to 20 of flexion (Fig. 1D). Dual split lateral band transfer: The extensor apparatus was exposed through the dorsal incision. Both lateral bands were isolated, and 2-mm wide, distally based r
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FIGURE 2: Finger specimen loaded onto the testing device for cyclical motion.
slips of lateral band tissue were fashioned. Two parallel vertical slits were then made on either side of the remaining A3/C1 pulleys, palmar to the PIP joint center of rotation leaving a small bridge of tissue in between the slits. The lateral bands were pulled through the slits proximally and reflected distally. The bands were secured to like tissue using 2 figureof-eight constructs of 4-0 Ethibond suture with the PIP joint in 10 to 20 of flexion (Fig. 1E).21
study (Fig. 3). The device produced an extension moment to the PIP joint to 90 , ultimately causing failure of the surgical construct. The force required to hyperextend each PIP joint was measured. Finally, the specimens were dissected to determine the mechanism of failure. Data analysis The median, SD, and 95% confidence interval of PIP joint stiffness with applied hyperextension moments were calculated for each group. A Kruskal-Wallis nonparametric test was used to assess for the mean differences between groups. The Wilcoxon-MannWhitney test with Bonferroni correction was used for multiple pairwise comparisons. The results were considered significant if the P value was less than .05, and a trend was defined by a P value of .05 to less than 1.0.
Biomechanical testing Each thawed finger specimen was mounted on a biomechanical testing device specifically designed for this project (Fig. 2). Weights were attached to the interosseous and lumbrical tendon insertions to balance their effects across the interphalangeal joints (1.0 N on the radial side and 0.5 N on the ulnar side), as described in earlier reports.25e32 The combined flexor and extensor tendons were then attached to motors that alternately pulled to produce flexion and extension at the PIP and distal interphalangeal joints. A 10 extension block was placed over the PIP joint in order to simulate a postoperative extension block orthosis. While mounted on the testing device, each finger was taken through 1,200 cycles of a full allowable arc of motion at 1 cycle/s. The number of cycles was selected based on a published report in which the authors estimated that 1,200 cycles simulated full flexion and extension of the fingers 5 times/h for 16 h/d for 2 weeks.25 Each specimen was grossly examined for failure of the surgical technique. The finger specimens were subsequently secured to another testing device specifically designed for this J Hand Surg Am.
Funding This study was internally funded through the Department of Orthopaedic Surgery at Northwestern University, Feinberg School of Medicine (the corresponding author’s institution). RESULTS None of the repairs failed during cyclic loading, and all specimens were successfully loaded to failure. The median stiffness values of the 6 groups are summarized in Figure 4. The control group had the highest median PIP joint stiffness at 76 N, and this was significantly greater than median stiffness in the FDST (P ¼ .033) and SLBT (P ¼ .033) groups, but r
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FIGURE 3: Finger specimen loaded onto the testing device before loading the PIP joint in extension to failure.
not significantly different from the VPR or DLBT groups (P > .1). In comparing the control group to the DSLBT group, there was a trend toward significantly increased stiffness in the control group (P ¼ .052). The SLBT, DLBT, and DSLBT reconstructions all failed by massive disruption of the flexor tendon sheath, whereas the VPR and FDST repairs failed by either suture anchor pullout or suture breakage. DISCUSSION In the acute or subacute setting, a hyperextension injury to the PIP joint may be managed effectively with dorsal extension block orthosis fabrication.1,33 However, the rare situation arises when orthosis fabrication fails and symptomatic hyperextension instability of the PIP joint develops.1,4,5,7,11,22 Bowers2 proposed that hyperextension instability of the PIP joint was most likely to occur in the absence of bone injury owing to poor vascularity of the volar plate and consequential adverse effects on soft tissue healing to bone. A swanneck deformity can develop and lead to difficulty initiating finger flexion with painful snapping as the lateral bands slide over the condyles of the proximal phalanx.1 If left untreated, the PIP joint may deteriorate over time. Various surgical techniques have been described to restore stability to the posttraumatic hyperextensible PIP joint and can be divided into 2 categories: volar articular and dorsal extra-articular.21 Volar articular J Hand Surg Am.
FIGURE 4: Box plots of each finger specimen group depict median stiffness, SD, and 95% confidence interval of PIP joint stiffness with applied hyperextension moments. C, control.
techniques, such as VPR and FDST, require a window in the flexor retinaculum, retraction of the flexor tendons, and manipulation of the PIP joint capsule. Dorsal extra-articular techniques do not require exposure of the PIP joint, but do necessitate manipulation of the extensor apparatus and binding of lateral band tissue to the flexor tendon sheath. Anticipated outcomes have been based on case reports and relatively small retrospective case series. Melone et al7 reported on 25 patients who underwent successful VPR for posttraumatic hyperextension deformity of the PIP joint and measured PIP joint r
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flexion contractures of 5 to 15 in an unspecified number of cases and more than 15 in 2 patients at a mean follow-up of 8 years. Catalano et al11 reported on 12 patients who were treated with an FDST for posttraumatic PIP joint dorsal instability and measured PIP joint flexion contractures of 5 to 10 in 5 patients and up to 60 in 2 other patients at a mean follow-up of 35 months. Other authors have reported varying degrees of PIP joint stiffness using comparable articularbased procedures with consistent restoration of PIP joint stability.5,8e10,13 The outcome data, however, are limited and preclude any meaningful comparisons between different techniques. Littler14,15 illustrated a dorsal, extra-articular lateral band transfer procedure for correction of a PIP joint hyperextension deformity. He sectioned the ulnar lateral band at the musculotendinous junction, leaving the distal insertion intact, and attached the free end to the flexor tendon sheath in a patient with rheumatoid arthritis. Zancolli and Zancolli20 adapted the lateral band transfer concept in the treatment of PIP joint hyperextension instability in association with cerebral palsy. They mobilized one lateral band, without disrupting the proximal or distal attachments, and stabilized the band in a sling created by suturing a slip of the FDS tendon to the volar plate (the socalled “Zancolli pulley”). Four publications describe lateral band transfer for treatment of posttraumatic PIP joint hyperextension instability.21e24 Ko et al21 successfully treated 2 patients with traumatic PIP joint hyperextension instability using a DSLBT repair technique. There was no recurrent instability in either case; however, one patient developed a 30 extensor lag of the PIP joint and a 15 extensor lag of the distal interphalangeal joint. Active extension of the terminal joint normalized with temporary splinting. Tonkin et al24 used an SLBT in 30 fingers with swan-neck deformities from trauma and other etiologies. There were no recurrences of PIP joint hyperextension instability, although patients did develop a mean PIP joint flexion contracture of 11 . Foucher et al23 reported 16 cases of SLBT to address traumatic PIP joint hyperextension instability and noted a flexion contracture of the PIP joint measuring greater than 20 in onehalf of their cases. Ahmed and Goldie22 described one case of an SLBT to treat concomitant hyperextension and lateral instability of the PIP joint and noted normal PIP joint motion after 5 years. Given the lack of comparative clinical outcome data on articular and extra-articular techniques to restore posttraumatic PIP joint dorsal instability, we planned our study to test the biomechanical strengths J Hand Surg Am.
of the different surgical constructs. We found essentially equivalent repair strengths of the 5 techniques tested. In addition, none of these interventions failed during cyclic loading with a 10 PIP joint dorsal extension block orthosis. This finding lends support to the practice of mobilizing fingers in the early postoperative period with a protective dorsal extension block orthosis.7,21 There were limitations with our study design that may have affected our findings and conclusions. Although the numbers of repair sutures were consistent within each procedural group, the suture numbers varied from 1 to 4 between groups and may have influenced the ultimate strength of each construct. Our FDS tenodesis technique used a suture anchor with a single suture rather than a bone tunnel as described by Catalano et al.11 Conceivably, suture anchor fixation would afford a weaker repair than bone tunnel fixation in the finger. We believed this variation necessary to avoid compromise of flexor tendon sheath integrity with added tissue dissection and to avert creation of a stress riser in the proximal phalanx from bone tunnel placement adjacent to the intramedullary bolt. Our testing devices only permitted measurements of PIP joint deformation in the sagittal plane. The stiffness values of the PIP joints in the specimens treated by VPR had more variability than the stiffness measurements obtained in the fingers treated with the other 4 surgical techniques. We suspect that the greater variability in PIP joint stiffness after VPR was due to a combination of factors, including slight variations in suture placement, imperceptible shifting of the suture anchors in bone, and small differences in mounting of the finger specimens to the testing device. Subtle and uncontrollable differences in suture placement and security, mounting of specimens to the testing devices, and attenuation of the repair constructs may have conceivably impacted all measurements. We propose that surgical decision making for posttraumatic PIP joint hyperextension instability be guided by surgeon preference in conjunction with patient education on the available techniques. Comparative clinical studies using consistent patient- and examiner-determined outcome tools are necessary to evaluate the safety and efficacy of the various stabilization procedures. ACKNOWLEDGMENT The authors would like to than Larry Zhang, PhD, for assistance in designing the experimental testing devices. r
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REFERENCES 1. Merrell G, Slade JF. Hand: dislocations and ligament injuries in the digits. In: Wolfe SW, Hotchkiss RN, Pederson WC, Kozin SW, eds. Green’s Operative Hand Surgery. 6th ed. Philadelphia, PA: Elsevier Churchill Livingstone; 2011:291e332. 2. Bowers WH. The proximal interphalangeal joint volar plate. II: a clinical study of hyperextension injury. J Hand Surg Am. 1981;6(1): 77e81. 3. Bowers WH, Wolf JW Jr, Nehil JL, Bittinger S. The proximal interphalangeal joint volar plate. I. An anatomical and biomechanical study. J Hand Surg Am. 1980;5(1):79e88. 4. Kleinert HE, Kasdan ML. Reconstruction of chronically subluxated proximal interphalangeal finger joint. J Bone Joint Surg Am. 1965;47(5):958e964. 5. McCue FC, Honner R, Marriott C, Johnson JR, Gleck JH. Athletic injuries of the proximal interphalangeal joint requiring surgical treatment. J Bone Joint Surg Am. 1970;52(5):937e956. 6. Kaplan EB. Extension deformities of the proximal interphalangeal joints of the fingers. An anatomical study. J Bone Joint Surg Am. 1936;18(3):781e783. 7. Melone CP Jr, Polatsch DB, Beldner S, Khorsandi M. Volar plate repair for posttraumatic hyperextension deformity of the proximal interphalangeal joint. Am J Orthop. 2010;39(4):190e194. 8. Onishi Y, Fujioka H, Doita M. Treatment of chronic post-traumatic hyperextension deformity of proximal interphalangeal joint using the suture anchor: a case report. Hand Surg. 2007;12(1):47e49. 9. Palmer AK, Linscheid RL. Chronic recurrent dislocation of the proximal interphalangeal joint of the finger. J Hand Surg Am. 1978;3(1):95e97. 10. Portis RB. Hyperextensibility of the proximal interphalangeal joint of the finger following trauma. J Bone Joint Surg Am. 1954;36(6): 1141e1146. 11. Catalano LW III, Skarparis AC, Glickel SZ, Barron OA, Malley D, Lane LB. Treatment of chronic, traumatic hyperextension deformities of the proximal interphalangeal joint with flexor digitorum superficialis tenodesis. J Hand Surg Am. 2003;28(3):448e452. 12. Lane CS. Reconstruction of the unstable proximal interphalangeal joint: the double superficialis tenodesis. J Hand Surg Am. 1978;3(4): 368e369. 13. Wiley AM. Instability of the proximal interphalangeal joint following dislocation and fracture dislocation: surgical repair. Hand (N Y). 1970;2(2):185e191. 14. Littler JW. The hand and wrist. In: Horworth MB, ed. A Textbook of Orthopedics. Stamford, CT: Dorman; 1959:284e285. 15. Littler JW. The finger extensor mechanism. Surg Clin North Am. 1967;47(2):415e432. 16. Nalebuff EA. The rheumatoid swan-neck deformity. Hand Clin. 1989;5(2):203e214. 17. Sirotakova M, Figus A, Jarrett P, Mishra A, Elliot D. Correction of swan neck deformity in rheumatoid arthritis using a new lateral
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extensor band technique. J Hand Surg Eur Vol. 2008;33(6): 712e716. Swanson AB. Surgery of the hand in cerebral palsy. Surg Clin North Am. 1964;44:1061e1070. de Bruin M, van Vliet DC, Smeulders MJ, Kreulen M. Long-term results of lateral band translocation for the correction of swan neck deformity in cerebral palsy. J Pediatr Orthop. 2010;30(1): 67e70. Zancolli EA, Zancolli EJ. Surgical rehabilitation of the spastic upper limb in cerebral palsy. In: Lamb DW, ed. The Paralyzed Hand. Edinburgh: Churchill Livingstone; 1987:153e167. Ko JH, Kalainov DM, Hsu LP, Fang RC, Mastey RD. Dual lateral band transfer for treatment of traumatic hyperextension instability of the proximal interphalangeal joint: a report of two cases. Hand (N Y). 2012;7(1):108e113. Ahmed HA, Goldie BS. Proximal interphalangeal joint instability: a dynamic technique for stabilization. J Hand Surg Br. 2002;27(4): 354e355. Foucher G, Tilquin B, Lenoble E. Treatment of post-traumatic swanneck deformities of the fingers. Apropos of a series of 43 patients. Rev Chir Orthop Reparatrice Appar Mot. 1992;78(8):505e511. Tonkin MA, Hughes J, Smith KL. Lateral band translocation for swan-neck deformity. J Hand Surg Am. 1992;17(2):260e267. Husain SN, Dietz JF, Kalainov DM, Lautenschlager EP. A biomechanical study of distal interphalangeal joint subluxation after mallet fracture injury. J Hand Surg Am. 2008;33(1):26e30. Chao EY, An KN, Cooney WP, Linscheid RL. Muscle and joint forces in the hand. In: Chao EYS, An K-N, Cooney WP III, Linscheid RL, eds. Biomechanics of the Hand. A Basic Research Study. Singapore: World Scientific; 1989:53e72. Fowler NK, Nicol AC. Interphalangeal joint and tendon forces: normal model and biomechanical consequences of surgical reconstruction. J Biomech. 2000;33(9):1055e1062. Dennerlein JT, Diao E, Mote CD Jr, Rempel DM. In vivo finger flexor tendon force while tapping on a keyswitch. J Orthop Res. 1999;17(2):178e184. Long C II, Conrad PW, Hall EA, Furler SL. Intrinsic-extrinsic muscle control of the hand in power grip and precision handling. An electromyographic study. J Bone Joint Surg Am. 1970;52(5):853e867. Schuind F, Garcia-Ellis M, Cooney WP III, An KN. Flexor tendon forces: in vivo measurements. J Hand Surg Am. 1992;17(2): 291e298. Elliot D, McGrouther DA. The excursions of the long extensor tendons of the hand. J Hand Surg Br. 1986;11(1):77e80. Wehbe MA, Hunter JH. Flexor tendon gliding in the hand. Part I. In vivo excursions. J Hand Surg Am. 1985;10(4):570e574. Werlinrud JC, Petersen K, Lauritsen J, Larsen S, Schroder H. A prospective randomized study of conservative versus surgical treatment of unstable palmar plate disruption of the proximal interphalangeal finger joint. Strategies Trauma Limb Reconstr. 2013;8(1): 21e24.
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Surgical Techniques for Correction of Traumatic Hyperextension Instability of the Proximal Interphalangeal Joint: A Biomechanical Study Alan J. Micev, MD,* James M. Saucedo, MD, MBA,* David M. Kalainov, MD,* Liang Wang, PhD,* Madeleine Ma, MS,† Mark A. Yaffe, MD*
Purpose To compare the biomechanical strengths of 5 surgical techniques for treatment of traumatic hyperextension instability of the proximal interphalangeal (PIP) joint. Methods Thirty-six cadaveric fingers were randomly assigned to 6 groups: normal control, volar plate repair, flexor digitorum superficialis tenodesis (FDST), single lateral band transfer (SLBT), double lateral band transfer, and dual split lateral band transfer. For each experimental specimen, the volar plate and accessory collateral ligaments were transected, the PIP joint was hyperextended to 90 , and a PIP joint stabilizing procedure was completed. The ultimate strength of each procedure was ascertained by loading to failure, and the fingers were dissected to determine the pathoanatomy of failure. Force-displacement curves were used to estimate the stiffness of each group, and multiple pairwise statistical comparisons were performed. Results The mean PIP joint stiffness in the control group was significantly greater than the mean PIP joint stiffness in the FDST and SLBT groups, but not significantly different from the mean PIP joint stiffness in the other 3 groups. There were no significant differences in the mean PIP joint stiffness between the 5 joint stabilizing techniques. The SLBT, double lateral band transfer, and dual split lateral band transfer repairs all failed by massive disruption of the flexor tendon sheath, whereas the volar plate repairs and FDST repairs failed by either suture anchor pullout or suture breakage. Conclusions The stiffness of 5 surgical techniques to stabilize a traumatic hyperextensible PIP joint did not vary significantly. Clinical relevance The 5 described techniques to stabilize a posttraumatic PIP joint hyperextension deformity may provide for equal restraint to PIP joint hyperextension instability in the early postoperative period. The choice of procedure should take into consideration other factors not studied, including the potential for PIP joint flexion contracture and long-term durability. (J Hand Surg Am. 2015;-(-):-e-. Copyright Ó 2015 by the American Society for Surgery of the Hand. All rights reserved.) Key words Proximal interphalangeal joint, sprain, volar plate repair, flexor digitorum superficialis tenodesis, lateral band transfer. *Department of Orthopaedic Surgery, and the †Department of Preventative Medicine, Northwestern University, Feinberg School of Medicine, Chicago, IL. Received for publication March 17, 2015; accepted in revised form May 18, 2015. No benefits in any form have been received or will be received related directly or indirectly to the subject of this article. Corresponding author: Alan J. Micev, MD, Department of Orthopaedic Surgery, Northwestern University, 676 N. St. Clair, Suite 1350, Chicago, IL 60611; e-mail: ajmicev@ gmail.com. 0363-5023/15/---0001$36.00/0 http://dx.doi.org/10.1016/j.jhsa.2015.05.011
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proximal interphalangeal (PIP) joint may occur from a hyperextension injury to the finger. Treatment of closed dislocations, in the absence of gross postreduction PIP joint instability, consists of a period of protected finger motion with extension block splinting of the PIP joint and/or finger buddy taping.1 Despite general success with this treatment, a small number of patients may experience persistent dorsal instability of the PIP joint with ORSAL DISLOCATION OF THE
Ó 2015 ASSH
r
Published by Elsevier, Inc. All rights reserved.
r
1
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CORRECTION OF PIP JOINT HYPEREXTENSION
pain, mechanical symptoms, and a swan-neck finger deformity.1e5 Surgical techniques to address chronic, posttraumatic PIP joint hyperextension instability have been designed to create a check-rein against PIP joint hyperextension.4,6 Investigators have reported satisfactory experiences with volar plate repair2,5,7e10 and PIP joint tenodesis using one or both slips of the flexor digitorum superficialis (FDS) tendon.5,9,11e13 Transferring one or both lateral bands volar to the PIP joint center of rotation will also provide a restraint to PIP joint hyperextension. Lateral band transfer techniques have been well-described for correction of PIP joint hyperextension and swan-neck deformities in patients with rheumatoid arthritis and cerebral palsy.1,14e20 In contrast, there is little information on the role of this approach for posttraumatic PIP joint hyperextension instability.21e24 In the absence of comparative clinical outcome data on the various techniques to restore traumatic PIP joint dorsal instability, understanding the biomechanical properties of the procedures may help guide the surgeon in determining the best treatment approach. The purpose of this study was to assess the biomechanical strengths of 5 surgical constructs for correction of traumatic PIP joint dorsal instability in order to determine if there is any superior technique. The 5 constructs that we tested were volar plate repair (VPR), flexor digitorum superficialis tenodesis (FDST), single lateral band transfer (SLBT), double lateral band transfer (DLBT), and dual split lateral band transfer (DSLBT).
randomly assigned 12 cards (representing each experimental procedure twice), and repeated with each subsequent finger (ie, middle finger followed by ring finger). In the end, the 6 experimental conditions were represented twice by each finger type. To ensure a minimum of freeze-thaw cycles, we adopted a strict process for preparing and testing the specimens. The specimens were stored at e30 Celsius and underwent a period of thawing at room temperature for 12 to 24 hours. After disarticulating and preparing each finger, the digit was either tested immediately or frozen again for testing on another day. No finger specimens were subjected to more than 2 freeze-thaw cycles before testing. When removing the central 3 fingers, the skin was left intact distal to the metacarpophalangeal joints; and the respective extensor, flexor, and intrinsic tendons were dissected free and tagged with sutures. Within each specimen, the flexor tendons were combined. In the index fingers, the extensor indicis proprius and extensor digitorum communis tendons were similarly combined as described by Husain et al.25 The intramedullary canal of each proximal phalanx was hand-reamed using a 3.5-mm drill bit, and a threaded bolt with a 3.7-mm outer diameter was inserted to a press fit. Thirty fingers assigned to the 5 surgical procedures underwent a simulated hyperextension injury to the PIP joint, whereas the PIP joints in the 6 control specimens were left undisturbed. In creating a PIP joint hyperextension injury, a volar approach to the joint was performed through a zig-zag skin incision. A small rectangular section of the flexor tendon sheath in between the A2 and the A4 pulleys was excised, the FDS and flexor digitorum profundus (FDP) tendons were retracted, and the volar plate and accessory collateral ligaments were released from the base of the middle phalanx.4,6 The PIP joint was then hyperextended to 90 and the assigned joint stabilizing technique was performed. A linear skin incision was made over the dorsum of the PIP joint, regardless of the designated procedure. The control finger specimens received volar and dorsal skin incisions only. All skin incisions were closed with 4-0 nylon monofilament sutures in a simple interrupted fashion.
MATERIALS AND METHODS Specimen preparation The index, middle, and ring fingers were harvested from 6 pairs of fresh-frozen matched forearms (5 male and 1 female specimens; age range, 45e67 y) with no known history of inflammatory arthritis or hand trauma. Radiographs were completed beforehand to ensure absence of skeletal deformity and interphalangeal arthrosis. Each finger was disarticulated from the hand at the base of the metacarpophalangeal joint. To ensure equal distribution of experimental conditions among the 36 fingers (ie, in order to avoid having a procedure represented by only index fingers, middle fingers, or ring fingers), we instituted the following randomization procedure. Cards for each of 6 tested conditions (5 surgical procedures and 1 control) were made for a total of 36 cards. We assigned a surgical procedure to each finger type in sequence. For example, we started with all 12 index fingers and J Hand Surg Am.
Surgical techniques Volar plate repair: The palmar incision used to create the PIP joint injury was opened. The FDS and FDP tendons were retracted, and the base of the middle phalanx was exposed. Two 1.3-mm holes were drilled into subchondral bone at the radial and ulnar base of the middle phalanx, and 2 Micro Mitek 1.3-mm r
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FIGURE 1: AeE, Schematic drawings of the 5 PIP joint stabilization procedures performed (the windows in the retinaculum between the A2 and the A4 pulleys are not depicted). A Volar plate repair with 2 suture anchors seated in the base of the middle phalanx. B Flexor digitorum superficialis tenodesis involving transfer of the ulnar slip of this tendon deep to the radial slip of this tendon and the FDP tendon and attachment to the distal-radial border of the proximal phalanx using 1 suture anchor. C Single lateral band transfer with central mobilization of the intact radial lateral band palmar to the PIP joint center of rotation and attachment to the flexor tendon sheath with sutures. D Double lateral band transfer with central mobilization of both intact lateral bands palmar to the PIP joint center of rotation and attachment to the flexor tendon sheath with sutures. E Dual split lateral band transfer involving mobilization of distally based, 2-mm-wide slips of lateral band tissue, transfer of the slips palmar to the PIP joint center of rotation, and attachment of the slips to the flexor tendon sheath with sutures (only 1 side shown).
QuickAnchor Plus anchors with attached 4-0 Ethibond sutures (DePuy Mitek, Raynham, MA) were seated. The volar plate and accessory collateral ligaments were reattached to the middle phalanx base by creating 2 mattress suture constructs, positioning the PIP joint in approximately 10 to 20 of flexion (Fig. 1A).8
and the A2 pulleys and creation of a potential stress riser in the bone distal to the intramedullary bolt. Single lateral band transfer: The extensor apparatus was exposed through the dorsal incision. The radial lateral band was dissected from the central tendon approximately 1 cm proximal and 1 cm distal to the PIP joint leaving the proximal and distal ends intact. The band was then mobilized to a point palmar to the PIP joint center of rotation and sutured to the remaining A3/C1 pulleys using 2 figure-of-eight constructs of 4-0 Ethibond suture (Ethicon, Cincinnati, OH) with the PIP joint in 10 to 20 of flexion (Fig. 1C).1,19
Flexor digitorum superficialis tenodesis: The volar incision was opened. The ulnar slip of the FDS tendon was isolated and dissected distally, preserving the insertion on the volar base of the middle phalanx. The ulnar slip was then cut as proximally as possible to ensure adequate length for transfer. The tendon slip was passed deep to both the FDP tendon and the radial slip of the FDS tendon. A 1.3-mm hole was drilled into the distal-radial aspect of the proximal phalanx and a Micro Mitek anchor with 4-0 Ethibond was seated. The FDS slip was secured to bone by creating a mattress suture construct with the PIP joint flexed 10 to 20 (Fig. 1B). This technique differed from the technique described by Catalano et al11 in which an FDS tendon slip was passed through a transverse tunnel in the proximal phalanx and stabilized to bone using an interference knot of tendon tissue and sutures. Harvesting a longer tendon slip for routing through a bone tunnel would have required supplementary dissection of tissue between the A1 J Hand Surg Am.
Double lateral band transfer: The extensor apparatus was exposed through the dorsal incision. The radial and ulnar lateral bands were dissected from the central tendon approximately 1 cm proximal and 1 cm distal to the PIP joint leaving the proximal and distal ends intact. Each band was then mobilized to a point palmar to the PIP joint center of rotation and sutured to the remaining A3/C1 pulleys using 2 figure-ofeight constructs of 4-0 Ethibond suture with the PIP joint in 10 to 20 of flexion (Fig. 1D). Dual split lateral band transfer: The extensor apparatus was exposed through the dorsal incision. Both lateral bands were isolated, and 2-mm wide, distally based r
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FIGURE 2: Finger specimen loaded onto the testing device for cyclical motion.
slips of lateral band tissue were fashioned. Two parallel vertical slits were then made on either side of the remaining A3/C1 pulleys, palmar to the PIP joint center of rotation leaving a small bridge of tissue in between the slits. The lateral bands were pulled through the slits proximally and reflected distally. The bands were secured to like tissue using 2 figureof-eight constructs of 4-0 Ethibond suture with the PIP joint in 10 to 20 of flexion (Fig. 1E).21
study (Fig. 3). The device produced an extension moment to the PIP joint to 90 , ultimately causing failure of the surgical construct. The force required to hyperextend each PIP joint was measured. Finally, the specimens were dissected to determine the mechanism of failure. Data analysis The median, SD, and 95% confidence interval of PIP joint stiffness with applied hyperextension moments were calculated for each group. A Kruskal-Wallis nonparametric test was used to assess for the mean differences between groups. The Wilcoxon-MannWhitney test with Bonferroni correction was used for multiple pairwise comparisons. The results were considered significant if the P value was less than .05, and a trend was defined by a P value of .05 to less than 1.0.
Biomechanical testing Each thawed finger specimen was mounted on a biomechanical testing device specifically designed for this project (Fig. 2). Weights were attached to the interosseous and lumbrical tendon insertions to balance their effects across the interphalangeal joints (1.0 N on the radial side and 0.5 N on the ulnar side), as described in earlier reports.25e32 The combined flexor and extensor tendons were then attached to motors that alternately pulled to produce flexion and extension at the PIP and distal interphalangeal joints. A 10 extension block was placed over the PIP joint in order to simulate a postoperative extension block orthosis. While mounted on the testing device, each finger was taken through 1,200 cycles of a full allowable arc of motion at 1 cycle/s. The number of cycles was selected based on a published report in which the authors estimated that 1,200 cycles simulated full flexion and extension of the fingers 5 times/h for 16 h/d for 2 weeks.25 Each specimen was grossly examined for failure of the surgical technique. The finger specimens were subsequently secured to another testing device specifically designed for this J Hand Surg Am.
Funding This study was internally funded through the Department of Orthopaedic Surgery at Northwestern University, Feinberg School of Medicine (the corresponding author’s institution). RESULTS None of the repairs failed during cyclic loading, and all specimens were successfully loaded to failure. The median stiffness values of the 6 groups are summarized in Figure 4. The control group had the highest median PIP joint stiffness at 76 N, and this was significantly greater than median stiffness in the FDST (P ¼ .033) and SLBT (P ¼ .033) groups, but r
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FIGURE 3: Finger specimen loaded onto the testing device before loading the PIP joint in extension to failure.
not significantly different from the VPR or DLBT groups (P > .1). In comparing the control group to the DSLBT group, there was a trend toward significantly increased stiffness in the control group (P ¼ .052). The SLBT, DLBT, and DSLBT reconstructions all failed by massive disruption of the flexor tendon sheath, whereas the VPR and FDST repairs failed by either suture anchor pullout or suture breakage. DISCUSSION In the acute or subacute setting, a hyperextension injury to the PIP joint may be managed effectively with dorsal extension block orthosis fabrication.1,33 However, the rare situation arises when orthosis fabrication fails and symptomatic hyperextension instability of the PIP joint develops.1,4,5,7,11,22 Bowers2 proposed that hyperextension instability of the PIP joint was most likely to occur in the absence of bone injury owing to poor vascularity of the volar plate and consequential adverse effects on soft tissue healing to bone. A swanneck deformity can develop and lead to difficulty initiating finger flexion with painful snapping as the lateral bands slide over the condyles of the proximal phalanx.1 If left untreated, the PIP joint may deteriorate over time. Various surgical techniques have been described to restore stability to the posttraumatic hyperextensible PIP joint and can be divided into 2 categories: volar articular and dorsal extra-articular.21 Volar articular J Hand Surg Am.
FIGURE 4: Box plots of each finger specimen group depict median stiffness, SD, and 95% confidence interval of PIP joint stiffness with applied hyperextension moments. C, control.
techniques, such as VPR and FDST, require a window in the flexor retinaculum, retraction of the flexor tendons, and manipulation of the PIP joint capsule. Dorsal extra-articular techniques do not require exposure of the PIP joint, but do necessitate manipulation of the extensor apparatus and binding of lateral band tissue to the flexor tendon sheath. Anticipated outcomes have been based on case reports and relatively small retrospective case series. Melone et al7 reported on 25 patients who underwent successful VPR for posttraumatic hyperextension deformity of the PIP joint and measured PIP joint r
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flexion contractures of 5 to 15 in an unspecified number of cases and more than 15 in 2 patients at a mean follow-up of 8 years. Catalano et al11 reported on 12 patients who were treated with an FDST for posttraumatic PIP joint dorsal instability and measured PIP joint flexion contractures of 5 to 10 in 5 patients and up to 60 in 2 other patients at a mean follow-up of 35 months. Other authors have reported varying degrees of PIP joint stiffness using comparable articularbased procedures with consistent restoration of PIP joint stability.5,8e10,13 The outcome data, however, are limited and preclude any meaningful comparisons between different techniques. Littler14,15 illustrated a dorsal, extra-articular lateral band transfer procedure for correction of a PIP joint hyperextension deformity. He sectioned the ulnar lateral band at the musculotendinous junction, leaving the distal insertion intact, and attached the free end to the flexor tendon sheath in a patient with rheumatoid arthritis. Zancolli and Zancolli20 adapted the lateral band transfer concept in the treatment of PIP joint hyperextension instability in association with cerebral palsy. They mobilized one lateral band, without disrupting the proximal or distal attachments, and stabilized the band in a sling created by suturing a slip of the FDS tendon to the volar plate (the socalled “Zancolli pulley”). Four publications describe lateral band transfer for treatment of posttraumatic PIP joint hyperextension instability.21e24 Ko et al21 successfully treated 2 patients with traumatic PIP joint hyperextension instability using a DSLBT repair technique. There was no recurrent instability in either case; however, one patient developed a 30 extensor lag of the PIP joint and a 15 extensor lag of the distal interphalangeal joint. Active extension of the terminal joint normalized with temporary splinting. Tonkin et al24 used an SLBT in 30 fingers with swan-neck deformities from trauma and other etiologies. There were no recurrences of PIP joint hyperextension instability, although patients did develop a mean PIP joint flexion contracture of 11 . Foucher et al23 reported 16 cases of SLBT to address traumatic PIP joint hyperextension instability and noted a flexion contracture of the PIP joint measuring greater than 20 in onehalf of their cases. Ahmed and Goldie22 described one case of an SLBT to treat concomitant hyperextension and lateral instability of the PIP joint and noted normal PIP joint motion after 5 years. Given the lack of comparative clinical outcome data on articular and extra-articular techniques to restore posttraumatic PIP joint dorsal instability, we planned our study to test the biomechanical strengths J Hand Surg Am.
of the different surgical constructs. We found essentially equivalent repair strengths of the 5 techniques tested. In addition, none of these interventions failed during cyclic loading with a 10 PIP joint dorsal extension block orthosis. This finding lends support to the practice of mobilizing fingers in the early postoperative period with a protective dorsal extension block orthosis.7,21 There were limitations with our study design that may have affected our findings and conclusions. Although the numbers of repair sutures were consistent within each procedural group, the suture numbers varied from 1 to 4 between groups and may have influenced the ultimate strength of each construct. Our FDS tenodesis technique used a suture anchor with a single suture rather than a bone tunnel as described by Catalano et al.11 Conceivably, suture anchor fixation would afford a weaker repair than bone tunnel fixation in the finger. We believed this variation necessary to avoid compromise of flexor tendon sheath integrity with added tissue dissection and to avert creation of a stress riser in the proximal phalanx from bone tunnel placement adjacent to the intramedullary bolt. Our testing devices only permitted measurements of PIP joint deformation in the sagittal plane. The stiffness values of the PIP joints in the specimens treated by VPR had more variability than the stiffness measurements obtained in the fingers treated with the other 4 surgical techniques. We suspect that the greater variability in PIP joint stiffness after VPR was due to a combination of factors, including slight variations in suture placement, imperceptible shifting of the suture anchors in bone, and small differences in mounting of the finger specimens to the testing device. Subtle and uncontrollable differences in suture placement and security, mounting of specimens to the testing devices, and attenuation of the repair constructs may have conceivably impacted all measurements. We propose that surgical decision making for posttraumatic PIP joint hyperextension instability be guided by surgeon preference in conjunction with patient education on the available techniques. Comparative clinical studies using consistent patient- and examiner-determined outcome tools are necessary to evaluate the safety and efficacy of the various stabilization procedures. ACKNOWLEDGMENT The authors would like to than Larry Zhang, PhD, for assistance in designing the experimental testing devices. r
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