- Email: [email protected]
Restoration of Longitudinal Forearm Stability Using a Suture Button Construct
SCIENTIFIC ARTICLE
Restoration of Longitudinal Forearm Stability Using a Suture Button Construct Matthew L. Drake, MD, Gerald L. Farber, MD, Kacey L. White, BSc, Brent G. Parks, MSc, Keith A. Segalman, MD
Purpose This study proposed a method of restoring the longitudinal stability of the forearm provided by the central band of the interosseous membrane (IOM) by using a percutaneously placed suture button construct. We hypothesized that supporting the forearm IOM with a suture button construct would restore longitudinal stability in a cadaveric model of the Essex-Lopresti lesion. Methods We assessed 7 adult cadaver upper extremities radiographically for evidence of previous elbow, forearm, or wrist fracture. Each limb was mounted onto a materials testing system with the elbow held at 90° and the forearm in neutral. The intact specimen was loaded cyclically at 134 N to determine the native mobility of the forearm segment. Each specimen was tested after each of the following steps: radial head removal, transection of the IOM, and suture button construct reconstruction of the IOM. After the final reconstruction, each specimen was examined for forearm range of motion and evidence of neurovascular injury. Results Removal of the radial head and sectioning of the IOM sequentially increased average proximal migration of the radius by 3.6 and 7.1 mm, respectively. After reconstruction with the suture button construct, the IOM was restored to the intact state with only the radial head removed. Forearm rotation was not compromised by the reconstruction, and there was no evidence of neurovascular injury in any specimen. Conclusions A percutaneously placed suture button construct can restore the longitudinal stability provided by an IOM. The method described did not limit forearm rotation. We encountered no neurovascular injury in the specimens tested in this series. This construct may be an effective adjunct when combined with bony reconstruction to treat longitudinal forearm axis injuries. (J Hand Surg 2010;35A:1981–1985. Copyright © 2010 by the American Society for Surgery of the Hand. All rights reserved.) Key words Essex-Lopresti injury, interosseous membrane, suture button.
FromtheCurtisNationalHandCenter,UnionMemorialHospital,Baltimore,MD;andtheTriplerArmy Medical Center, Kailua, HI. Received for publication February 19, 2010; accepted in revised form September 13, 2010. Supported by a grant from the Raymond M. Curtis Research Foundation, Curtis National Hand Center, Baltimore, MD. No benefits in any form have been received or will be received related directly or indirectly to the subject of this article. Corresponding author: Keith Segalman, MD, c/o Anne Rupert Mattson, 3333 North Calvert Street, Suite M60, Baltimore, MD 21218; e-mail: [email protected]. 0363-5023/10/35A12-0010$36.00/0 doi:10.1016/j.jhsa.2010.09.009
HE INTEROSSEOUS MEMBRANE (IOM) has a critical role in providing longitudinal stability to the forearm. This becomes most apparent in the setting of an IOM tear along with a radial head fracture, leading to longitudinal radioulnar dissociation, or Essex-Lopresti injury. This injury is commonly treated with radial head repair or replacement; however, treatment of the IOM tear is controversial. Even with an intact radial head, abnormal load transfer occurs along the forearm in the absence of the IOM.1 A previous cadaver study showed that the central band of the IOM contributes 71% of the longitudinal stiffness of the forearm.2 Multiple authors have attempted to recon-
T
© ASSH 䉬 Published by Elsevier, Inc. All rights reserved. 䉬 1981
1982
RESTORING FOREARM LONGITUDINAL STABILITY
FIGURE 1: Test setup.
struct the IOM in cadavers using various materials and techniques with limited success in restoring the native longitudinal stiffness of the forearm.3– 8 We propose a method of reconstructing the central band of the IOM using a percutaneously placed suture button construct consisting of a completely internal implant that consists of two number-2 polyester sutures tensioned between 2 stainless-steel buttons. MATERIALS AND METHODS We used 7 fresh-frozen adult cadaver forearms for this study. The average specimen age was 74.4 years (range, 49 –95 y). Five specimens were male and 2 were female. All limbs were inspected for evidence of deformity or previous trauma. All limbs had unrestricted forearm pronation and supination. The specimens were radiographically inspected to ensure there was no previous fracture or arthrosis of the distal radioulnar joint, ulnar humeral, or radiocapitellar joint. We prepared each specimen by removing the phalanges through the metacarpophalangeal joints, as well as stripping the soft tissue from the humeral shaft. We measured the length from the radial styloid to radial head and ulnar styloid to
the tip of the olecranon. The trajectory of the suture button was planned with the drill hole entering the radius three fifths of its length proximal to the radial styloid and exiting the ulna one third of its length proximal to the ulnar styloid (Fig. 1). These bony entry points were chosen with respect to the anatomic parameters given by Chandler et al.9 We made a 4-cm incision over the radial border forearm to expose the radius and protect the superficial branch of the radial nerve and posterior interosseous nerve. A counter incision of 4 cm was made over the subcutaneous border of the ulna to allow manual palpation of the drill bit to ensure accurate placement. We passed a 2.8-mm drill from the radius to the ulna in an oblique fashion through the center of each bone. With the arm in the pronated position, the tunnels were created with a single pass of the drill bit entering the radial border of the radius and exiting the ulnar border of the ulna. The position of the forearm was pronation in 6 specimens and supination in 1. We chose the rotation of the forearm in each specimen based on the normal resting posture of the forearm. The Mini-Tightrope suture button (Arthrex, Naples, FL) is an internal implant consisting of two number-2
JHS 䉬 Vol A, December
RESTORING FOREARM LONGITUDINAL STABILITY
1983
FIGURE 2: Radial excursion as a function of condition.
polyester sutures that can be tensioned to the surgeon’s preference between 2 stainless-steel buttons. A 2.7-mm cannulated drill is included with the product; however, we used a 2.8-mm noncannulated drill because this facilitated preparing the drill holes. The suture button was then passed from the radius to ulna but not yet tightened. Each specimen was mounted vertically onto the testing apparatus (MTS Mini Bionix; MTS Systems, Eden Prairie, MN) with the hand secured to a wooden board with screws and washers through the intermetacarpal spaces. The elbow was placed at 90° with the forearm in neutral. The humeral shaft was secured to the base of the apparatus with metal clamps (Fig. 1). The suture button was placed before mounting on the testing apparatus because it was technically difficult to perform that maneuver with the elbow fixed at 90°.10 All specimens were loaded from 0 to 134 N longitudinally in uniaxial compression for 3 cycles at 1 mm/s using a triangular waveform. Load and actuator piston displacement data were recorded continuously at a rate of 10 Hz. We used the data from the third loading cycle for calculations. We used the linear variable differential transducer, built into the actuator of the materials testing system (MTS) load frame, to measure displacement. The intact specimen, with the suture button device in place, but not tensioned and tied, was loaded as outlined above. We then made a Kocher incision to expose the radial head, which was removed with a sagittal saw. The specimen was again loaded as previously described. The IOM was then divided from the radius along its entire length, taking care to not disrupt the
previously placed suture button; the specimen was again loaded and the data were recorded. Finally, we tightened the suture button maximally and tied it securely, performed a final loading of the specimen, and recorded a final dataset. The data from the third cycle of the 3 uniaxial cycles of loading were used to calculate average displacement values for each phase of testing. After completion of the load testing, each specimen was examined for pronation and supination range of motion. We carried out dissection to look specifically for evidence of nerve injury. We used a one-way, repeated measures analysis of variance with a Holm-Sidak post hoc analysis to determine whether any observed differences were significant (p ⱕ .05). RESULTS Figure 2 shows displacement data for each testing condition. With the IOM cut, suture button tied, and radial head out with IOM intact, displacement was significantly greater (p ⱕ .05) than for the intact specimen (12.7 ⫾ 6.8, 9.8 ⫾ 4.8, and 9.2 ⫾ 4.9 vs 5.6 ⫾ 2.4 mm, respectively; average ⫾ standard deviation). There was no statistically significant difference in displacement data between the radial head out with IOM intact versus the suture button tied. The group with the tied suture button was able to restore stability to the forearm consistent with the group with the radial head out. The suture button did not restore stability to the intact specimen. No specimen had loss of pronation or supination after the suture button was tensioned. Dissection of the specimens revealed no laceration or injury to the anterior interosseous nerve, posterior interosseous nerve, or
JHS 䉬 Vol A, December
1984
RESTORING FOREARM LONGITUDINAL STABILITY
superficial branch of the radial nerve. In the specimen in which the drill had been passed with the forearm in supination, the suture button was found to immediately overlie the anterior interosseous nerve. With tightening of the suture button, there was convergence of the proximal radius to the ulna; however, this did not appear to limit forearm rotation. DISCUSSION Our study demonstrates that a suture button construct can restore longitudinal stability to the forearm equal to the level provided by the native IOM. However, this construct alone does not restore the forearm stability to the native state. This finding is consistent with other previously reported techniques. Sellman et al. first reported reconstruction of the IOM with a synthetic material in 1995.3 In that cadaver study, the investigators attempted to restore stiffness of the forearm by using a nylon cord placed through drill tunnels in an open fashion and by replacing the radial head with a silicone and metallic implant. They found that the nylon cord alone restored 94% of forearm stiffness, the metal radial head restored 89%, and the combination of both restored stiffness to 145% of the intact state. The drawback of their described technique is that it required an extensive open dissection to place the nylon cord. Skahen et al. described a method of reconstructing the IOM using the entire flexor carpi radialis tendon.4 This technique prevented complete migration of the proximal radius to the capitellum; however, it did not restore longitudinal stability back to the intact state. Tejwani et al. compared 3 graft choices (palmaris longus, flexor carpi radialis, and bone patellar tendon bone) for IOM reconstruction with radial head replacement.7 None of the graft choices restored stability as effectively as the native IOM; however, all 3 limited proximal migration to some degree. Tejwani et al. also studied forces across the distal ulna in a cadaver model in which the IOM was reconstructed with palmaris longus in conjunction with a metallic radial head implant.6 They found that replacing the radial head alone did not restore distal ulna forces to the intact state, whereas adding a palmaris IOM graft lowered those forces to below the intact state. Pfaeffle and colleagues reported on a double bundle flexor carpi radialis reconstruction technique in 2006.8 Their findings were consistent with those of Tejwani et al.7 in that radial head replacement alone did not restore load forces across the wrist and elbow to the native state. Adams et al. proposed another method of addressing a chronic Essex-Lopresti lesion.11 In the technique, an
ulnar shortening osteotomy is performed, followed by radial head replacement and bone-patellar tendon-bone autograft reconstruction of the IOM. That case series of 16 patients showed promising results with good subjective outcomes, as well as improved radiographic parameters and grip strength.12 Our current study is novel in that we used a percutaneous technique that could be easily applied in a clinical setting. A major concern with the technique is that the suture button does not introduce biologic substrate into the forearm and may not provide long-term stability because the polyester suture would be expected to experience fatigue and can fail over time. In addition, there is the potential that the stainless-steel buttons may erode through the radius or ulna, causing the construct to loosen. We believe that the best application of the technique would be in the acute IOM tear, where there still may be potential for the membrane to heal; the implant would serve to hold the forearm reduced while this occurs. The current accepted technique for treating an acute Essex-Lopresti injury is to address the radial head through arthroplasty or repair and to percutaneously pin the distal radioulnar joint with the radius out to length.13 The concern is that the IOM may have limited healing potential and that the forearm may collapse after pin removal.14 The suture button is likely to function for much longer than the usual 6 weeks of stability provided by a distal radioulnar joint crosspin. This longer duration of stability may allow for biologic healing of the IOM, although this has not been proven. For the patient with a chronic injury, a construct that provides biologic material in addition to polyester suture may be more appropriate. A product that serves this purpose has been introduced subsequent to the design of our study. The AC Graft Rope (Arthrex, Naples, FL) allows allograft tendon to be inserted as well; however, a major drawback for the forearm would be the much larger drill holes through the radius and ulna that would be required, potentially increasing the risk of fracture. One weakness of the study is that we did not measure load transmission across the wrist or elbow. We measured longitudinal forearm motion by applying a constant 134 N compressive load and measured the resulting displacement of the radius. Further study should incorporate load transducers at the wrist and elbow to confirm that our migration data correspond to load directly. Another weakness of the study is that we did not add a radial head implant. It is likely that with the addition of a radial head implant, the displacement
JHS 䉬 Vol A, December
RESTORING FOREARM LONGITUDINAL STABILITY
would have been restored to the intact specimen state. However, previous cadaver studies have shown that load transmission across the elbow is not restored by simply replacing the radial head, without addressing the IOM deficiency.1,15 In addition, without a radial head implant we observed proximal radioulnar convergence, which could potentially be a clinical problem, although there was no loss of forearm rotation. This may be obviated by adding the use of a metallic implant. Another weakness of the study is that we were unable to quantitate the tension applied to the suture button before tying it securely. Maximum tension was applied because the tension would be present in a clinical setting, but this may not be reproducible in the laboratory setting. In addition, placing the implant before loading could have adversely affected the results, but technically it would have been too difficult to place the implant in the MTS machine and then place the implant. One specimen was positioned in supination while the suture button was passed. The reason for this variation was that this specimen was based on a normal resting posture, as opposed to the others in which pronation was the optimal position for handling. In the supination specimen, the anterior interosseous nerve was found to lie directly underneath the suture. This may have posed a clinical problem. We therefore recommend that the forearm be positioned in pronation and that an incision be made on the radius to prevent nerve injury. Our testing setup was designed to measure displacement of the cross-head of the MTS machine. We can extrapolate from our setup what was moving in the specimen, based on rigid fixation of the hand and elbow. The intact state demonstrated marked displacement of the MTS cross-head, averaging more than 5 mm. We believe that this displacement is attributed to initial compression of the carpus. Therefore, it was critical to obtain displacement data in the intact state to obtain a baseline. The hand and elbow were rigidly fixed to the testing apparatus, and subsequent increases in displacement after resection of the radial head and incision of the IOM are likely attributed to proximal migration of the radius. However, to firmly establish that radial motion is being measured, future studies should use a more precise method, such as a pin placed directly in the radius that can be tracked independently. A final weakness in our methodology stems from the lack of cyclical loading. If used in a clinical setting, the suture button construct would be subjected to numerous
1985
loading cycles in daily activities. Further study should attempt to test the durability of our construct to cyclical loading. A suture button construct is able to restore the stability to the forearm equal to that of the intact IOM with the radial head absent. This construct does not substitute for the intact radial head; nevertheless, the construct may be an effective adjunct to a radial head replacement or repair in treating acute longitudinal radioulnar dissociation to better restore normal forearm loading characteristics. REFERENCES 1. Tomaino MM, Pfaeffle J, Stabile K, Li ZM. Reconstruction of the interosseous ligament of the forearm reduces load on the radial head in cadavers. J Hand Surg 2003;28B:267–270. 2. Hotchkiss RN, An KN, Sowa DT, Basta S, Weiland AJ. An anatomic and mechanical study of the interosseous membrane of the forearm: pathomechanics of proximal migration of the radius. J Hand Surg 1989;14A:256 –261. 3. Sellman DC, Seitz WH Jr, Postak PD, Greenwald AS. Reconstructive strategies for radioulnar dissociation: a biomechanical study. J Orthop Trauma 1995;9:516 –522. 4. Skahen JR, Palmer AK, Werner FW, Fortino MD. Reconstruction of the interosseous membrane of the forearm in cadavers. J Hand Surg 1997;22A:986 –994. 5. Pfaeffle HJ, Stabile KJ, Li ZM, Tomaino MM. Reconstruction of the interosseous ligament restores normal forearm compressive load transfer in cadavers. J Hand Surg 2005;30A:319 –325. 6. Tejwani SG, Markolf KL, Benhaim P. Graft reconstruction of the interosseous membrane in conjunction with metallic radial head replacement: a cadaveric study. J Hand Surg 2005;30A:335–342. 7. Tejwani SG, Markolf KL, Benhaim P. Reconstruction of the interosseous membrane of the forearm with a graft substitute: a cadaveric study. J Hand Surg 2005;30A:326 –334. 8. Pfaeffle HJ, Stabile KJ, Li ZM, Tomaino MM. Reconstruction of the interosseous ligament unloads metallic radial head arthroplasty and the distal ulna in cadavers. J Hand Surg 2006;31A:269 –278. 9. Chandler JW, Stabile KJ, Pfaeffle HJ, Li ZM, Woo SL, Tomaino MM. Anatomic parameters for planning of interosseous ligament reconstruction using computer-assisted techniques. J Hand Surg 2003;28A:111–116. 10. Markolf KL, Lamey D, Yang S, Meals R, Hotchkiss R. Radioulnar load-sharing in the forearm. A study in cadavera. J Bone Joint Surg 1998;80A:879 – 888. 11. Adams JE, Culp RW, Osterman AL. Interosseous membrane reconstruction for the Essex-Lopresti injury. J Hand Surg 2010;35A:129 – 136. 12. Marcotte AL, Osterman AL. Longitudinal radioulnar dissociation: identification and treatment of acute and chronic injuries. Hand Clin 2007;23:195–208. 13. Hotchkiss RN. Injuries to the interosseous ligament of the forearm. Hand Clin 1994;10:391–398. 14. Knight DJ, Rymaszewski LA, Amis AA, Miller JH. Primary replacement of the fractured radial head with a metal prosthesis. J Bone Joint Surg 1993;75B:572–576. 15. Birkbeck DP, Failla JM, Hoshaw SJ, Fyhrie DP, Schaffler M. The interosseous membrane affects load distribution in the forearm. J Hand Surg 1997;22A:975–980.
JHS 䉬 Vol A, December
Restoration of Longitudinal Forearm Stability Using a Suture Button Construct Matthew L. Drake, MD, Gerald L. Farber, MD, Kacey L. White, BSc, Brent G. Parks, MSc, Keith A. Segalman, MD
Purpose This study proposed a method of restoring the longitudinal stability of the forearm provided by the central band of the interosseous membrane (IOM) by using a percutaneously placed suture button construct. We hypothesized that supporting the forearm IOM with a suture button construct would restore longitudinal stability in a cadaveric model of the Essex-Lopresti lesion. Methods We assessed 7 adult cadaver upper extremities radiographically for evidence of previous elbow, forearm, or wrist fracture. Each limb was mounted onto a materials testing system with the elbow held at 90° and the forearm in neutral. The intact specimen was loaded cyclically at 134 N to determine the native mobility of the forearm segment. Each specimen was tested after each of the following steps: radial head removal, transection of the IOM, and suture button construct reconstruction of the IOM. After the final reconstruction, each specimen was examined for forearm range of motion and evidence of neurovascular injury. Results Removal of the radial head and sectioning of the IOM sequentially increased average proximal migration of the radius by 3.6 and 7.1 mm, respectively. After reconstruction with the suture button construct, the IOM was restored to the intact state with only the radial head removed. Forearm rotation was not compromised by the reconstruction, and there was no evidence of neurovascular injury in any specimen. Conclusions A percutaneously placed suture button construct can restore the longitudinal stability provided by an IOM. The method described did not limit forearm rotation. We encountered no neurovascular injury in the specimens tested in this series. This construct may be an effective adjunct when combined with bony reconstruction to treat longitudinal forearm axis injuries. (J Hand Surg 2010;35A:1981–1985. Copyright © 2010 by the American Society for Surgery of the Hand. All rights reserved.) Key words Essex-Lopresti injury, interosseous membrane, suture button.
FromtheCurtisNationalHandCenter,UnionMemorialHospital,Baltimore,MD;andtheTriplerArmy Medical Center, Kailua, HI. Received for publication February 19, 2010; accepted in revised form September 13, 2010. Supported by a grant from the Raymond M. Curtis Research Foundation, Curtis National Hand Center, Baltimore, MD. No benefits in any form have been received or will be received related directly or indirectly to the subject of this article. Corresponding author: Keith Segalman, MD, c/o Anne Rupert Mattson, 3333 North Calvert Street, Suite M60, Baltimore, MD 21218; e-mail: [email protected]. 0363-5023/10/35A12-0010$36.00/0 doi:10.1016/j.jhsa.2010.09.009
HE INTEROSSEOUS MEMBRANE (IOM) has a critical role in providing longitudinal stability to the forearm. This becomes most apparent in the setting of an IOM tear along with a radial head fracture, leading to longitudinal radioulnar dissociation, or Essex-Lopresti injury. This injury is commonly treated with radial head repair or replacement; however, treatment of the IOM tear is controversial. Even with an intact radial head, abnormal load transfer occurs along the forearm in the absence of the IOM.1 A previous cadaver study showed that the central band of the IOM contributes 71% of the longitudinal stiffness of the forearm.2 Multiple authors have attempted to recon-
T
© ASSH 䉬 Published by Elsevier, Inc. All rights reserved. 䉬 1981
1982
RESTORING FOREARM LONGITUDINAL STABILITY
FIGURE 1: Test setup.
struct the IOM in cadavers using various materials and techniques with limited success in restoring the native longitudinal stiffness of the forearm.3– 8 We propose a method of reconstructing the central band of the IOM using a percutaneously placed suture button construct consisting of a completely internal implant that consists of two number-2 polyester sutures tensioned between 2 stainless-steel buttons. MATERIALS AND METHODS We used 7 fresh-frozen adult cadaver forearms for this study. The average specimen age was 74.4 years (range, 49 –95 y). Five specimens were male and 2 were female. All limbs were inspected for evidence of deformity or previous trauma. All limbs had unrestricted forearm pronation and supination. The specimens were radiographically inspected to ensure there was no previous fracture or arthrosis of the distal radioulnar joint, ulnar humeral, or radiocapitellar joint. We prepared each specimen by removing the phalanges through the metacarpophalangeal joints, as well as stripping the soft tissue from the humeral shaft. We measured the length from the radial styloid to radial head and ulnar styloid to
the tip of the olecranon. The trajectory of the suture button was planned with the drill hole entering the radius three fifths of its length proximal to the radial styloid and exiting the ulna one third of its length proximal to the ulnar styloid (Fig. 1). These bony entry points were chosen with respect to the anatomic parameters given by Chandler et al.9 We made a 4-cm incision over the radial border forearm to expose the radius and protect the superficial branch of the radial nerve and posterior interosseous nerve. A counter incision of 4 cm was made over the subcutaneous border of the ulna to allow manual palpation of the drill bit to ensure accurate placement. We passed a 2.8-mm drill from the radius to the ulna in an oblique fashion through the center of each bone. With the arm in the pronated position, the tunnels were created with a single pass of the drill bit entering the radial border of the radius and exiting the ulnar border of the ulna. The position of the forearm was pronation in 6 specimens and supination in 1. We chose the rotation of the forearm in each specimen based on the normal resting posture of the forearm. The Mini-Tightrope suture button (Arthrex, Naples, FL) is an internal implant consisting of two number-2
JHS 䉬 Vol A, December
RESTORING FOREARM LONGITUDINAL STABILITY
1983
FIGURE 2: Radial excursion as a function of condition.
polyester sutures that can be tensioned to the surgeon’s preference between 2 stainless-steel buttons. A 2.7-mm cannulated drill is included with the product; however, we used a 2.8-mm noncannulated drill because this facilitated preparing the drill holes. The suture button was then passed from the radius to ulna but not yet tightened. Each specimen was mounted vertically onto the testing apparatus (MTS Mini Bionix; MTS Systems, Eden Prairie, MN) with the hand secured to a wooden board with screws and washers through the intermetacarpal spaces. The elbow was placed at 90° with the forearm in neutral. The humeral shaft was secured to the base of the apparatus with metal clamps (Fig. 1). The suture button was placed before mounting on the testing apparatus because it was technically difficult to perform that maneuver with the elbow fixed at 90°.10 All specimens were loaded from 0 to 134 N longitudinally in uniaxial compression for 3 cycles at 1 mm/s using a triangular waveform. Load and actuator piston displacement data were recorded continuously at a rate of 10 Hz. We used the data from the third loading cycle for calculations. We used the linear variable differential transducer, built into the actuator of the materials testing system (MTS) load frame, to measure displacement. The intact specimen, with the suture button device in place, but not tensioned and tied, was loaded as outlined above. We then made a Kocher incision to expose the radial head, which was removed with a sagittal saw. The specimen was again loaded as previously described. The IOM was then divided from the radius along its entire length, taking care to not disrupt the
previously placed suture button; the specimen was again loaded and the data were recorded. Finally, we tightened the suture button maximally and tied it securely, performed a final loading of the specimen, and recorded a final dataset. The data from the third cycle of the 3 uniaxial cycles of loading were used to calculate average displacement values for each phase of testing. After completion of the load testing, each specimen was examined for pronation and supination range of motion. We carried out dissection to look specifically for evidence of nerve injury. We used a one-way, repeated measures analysis of variance with a Holm-Sidak post hoc analysis to determine whether any observed differences were significant (p ⱕ .05). RESULTS Figure 2 shows displacement data for each testing condition. With the IOM cut, suture button tied, and radial head out with IOM intact, displacement was significantly greater (p ⱕ .05) than for the intact specimen (12.7 ⫾ 6.8, 9.8 ⫾ 4.8, and 9.2 ⫾ 4.9 vs 5.6 ⫾ 2.4 mm, respectively; average ⫾ standard deviation). There was no statistically significant difference in displacement data between the radial head out with IOM intact versus the suture button tied. The group with the tied suture button was able to restore stability to the forearm consistent with the group with the radial head out. The suture button did not restore stability to the intact specimen. No specimen had loss of pronation or supination after the suture button was tensioned. Dissection of the specimens revealed no laceration or injury to the anterior interosseous nerve, posterior interosseous nerve, or
JHS 䉬 Vol A, December
1984
RESTORING FOREARM LONGITUDINAL STABILITY
superficial branch of the radial nerve. In the specimen in which the drill had been passed with the forearm in supination, the suture button was found to immediately overlie the anterior interosseous nerve. With tightening of the suture button, there was convergence of the proximal radius to the ulna; however, this did not appear to limit forearm rotation. DISCUSSION Our study demonstrates that a suture button construct can restore longitudinal stability to the forearm equal to the level provided by the native IOM. However, this construct alone does not restore the forearm stability to the native state. This finding is consistent with other previously reported techniques. Sellman et al. first reported reconstruction of the IOM with a synthetic material in 1995.3 In that cadaver study, the investigators attempted to restore stiffness of the forearm by using a nylon cord placed through drill tunnels in an open fashion and by replacing the radial head with a silicone and metallic implant. They found that the nylon cord alone restored 94% of forearm stiffness, the metal radial head restored 89%, and the combination of both restored stiffness to 145% of the intact state. The drawback of their described technique is that it required an extensive open dissection to place the nylon cord. Skahen et al. described a method of reconstructing the IOM using the entire flexor carpi radialis tendon.4 This technique prevented complete migration of the proximal radius to the capitellum; however, it did not restore longitudinal stability back to the intact state. Tejwani et al. compared 3 graft choices (palmaris longus, flexor carpi radialis, and bone patellar tendon bone) for IOM reconstruction with radial head replacement.7 None of the graft choices restored stability as effectively as the native IOM; however, all 3 limited proximal migration to some degree. Tejwani et al. also studied forces across the distal ulna in a cadaver model in which the IOM was reconstructed with palmaris longus in conjunction with a metallic radial head implant.6 They found that replacing the radial head alone did not restore distal ulna forces to the intact state, whereas adding a palmaris IOM graft lowered those forces to below the intact state. Pfaeffle and colleagues reported on a double bundle flexor carpi radialis reconstruction technique in 2006.8 Their findings were consistent with those of Tejwani et al.7 in that radial head replacement alone did not restore load forces across the wrist and elbow to the native state. Adams et al. proposed another method of addressing a chronic Essex-Lopresti lesion.11 In the technique, an
ulnar shortening osteotomy is performed, followed by radial head replacement and bone-patellar tendon-bone autograft reconstruction of the IOM. That case series of 16 patients showed promising results with good subjective outcomes, as well as improved radiographic parameters and grip strength.12 Our current study is novel in that we used a percutaneous technique that could be easily applied in a clinical setting. A major concern with the technique is that the suture button does not introduce biologic substrate into the forearm and may not provide long-term stability because the polyester suture would be expected to experience fatigue and can fail over time. In addition, there is the potential that the stainless-steel buttons may erode through the radius or ulna, causing the construct to loosen. We believe that the best application of the technique would be in the acute IOM tear, where there still may be potential for the membrane to heal; the implant would serve to hold the forearm reduced while this occurs. The current accepted technique for treating an acute Essex-Lopresti injury is to address the radial head through arthroplasty or repair and to percutaneously pin the distal radioulnar joint with the radius out to length.13 The concern is that the IOM may have limited healing potential and that the forearm may collapse after pin removal.14 The suture button is likely to function for much longer than the usual 6 weeks of stability provided by a distal radioulnar joint crosspin. This longer duration of stability may allow for biologic healing of the IOM, although this has not been proven. For the patient with a chronic injury, a construct that provides biologic material in addition to polyester suture may be more appropriate. A product that serves this purpose has been introduced subsequent to the design of our study. The AC Graft Rope (Arthrex, Naples, FL) allows allograft tendon to be inserted as well; however, a major drawback for the forearm would be the much larger drill holes through the radius and ulna that would be required, potentially increasing the risk of fracture. One weakness of the study is that we did not measure load transmission across the wrist or elbow. We measured longitudinal forearm motion by applying a constant 134 N compressive load and measured the resulting displacement of the radius. Further study should incorporate load transducers at the wrist and elbow to confirm that our migration data correspond to load directly. Another weakness of the study is that we did not add a radial head implant. It is likely that with the addition of a radial head implant, the displacement
JHS 䉬 Vol A, December
RESTORING FOREARM LONGITUDINAL STABILITY
would have been restored to the intact specimen state. However, previous cadaver studies have shown that load transmission across the elbow is not restored by simply replacing the radial head, without addressing the IOM deficiency.1,15 In addition, without a radial head implant we observed proximal radioulnar convergence, which could potentially be a clinical problem, although there was no loss of forearm rotation. This may be obviated by adding the use of a metallic implant. Another weakness of the study is that we were unable to quantitate the tension applied to the suture button before tying it securely. Maximum tension was applied because the tension would be present in a clinical setting, but this may not be reproducible in the laboratory setting. In addition, placing the implant before loading could have adversely affected the results, but technically it would have been too difficult to place the implant in the MTS machine and then place the implant. One specimen was positioned in supination while the suture button was passed. The reason for this variation was that this specimen was based on a normal resting posture, as opposed to the others in which pronation was the optimal position for handling. In the supination specimen, the anterior interosseous nerve was found to lie directly underneath the suture. This may have posed a clinical problem. We therefore recommend that the forearm be positioned in pronation and that an incision be made on the radius to prevent nerve injury. Our testing setup was designed to measure displacement of the cross-head of the MTS machine. We can extrapolate from our setup what was moving in the specimen, based on rigid fixation of the hand and elbow. The intact state demonstrated marked displacement of the MTS cross-head, averaging more than 5 mm. We believe that this displacement is attributed to initial compression of the carpus. Therefore, it was critical to obtain displacement data in the intact state to obtain a baseline. The hand and elbow were rigidly fixed to the testing apparatus, and subsequent increases in displacement after resection of the radial head and incision of the IOM are likely attributed to proximal migration of the radius. However, to firmly establish that radial motion is being measured, future studies should use a more precise method, such as a pin placed directly in the radius that can be tracked independently. A final weakness in our methodology stems from the lack of cyclical loading. If used in a clinical setting, the suture button construct would be subjected to numerous
1985
loading cycles in daily activities. Further study should attempt to test the durability of our construct to cyclical loading. A suture button construct is able to restore the stability to the forearm equal to that of the intact IOM with the radial head absent. This construct does not substitute for the intact radial head; nevertheless, the construct may be an effective adjunct to a radial head replacement or repair in treating acute longitudinal radioulnar dissociation to better restore normal forearm loading characteristics. REFERENCES 1. Tomaino MM, Pfaeffle J, Stabile K, Li ZM. Reconstruction of the interosseous ligament of the forearm reduces load on the radial head in cadavers. J Hand Surg 2003;28B:267–270. 2. Hotchkiss RN, An KN, Sowa DT, Basta S, Weiland AJ. An anatomic and mechanical study of the interosseous membrane of the forearm: pathomechanics of proximal migration of the radius. J Hand Surg 1989;14A:256 –261. 3. Sellman DC, Seitz WH Jr, Postak PD, Greenwald AS. Reconstructive strategies for radioulnar dissociation: a biomechanical study. J Orthop Trauma 1995;9:516 –522. 4. Skahen JR, Palmer AK, Werner FW, Fortino MD. Reconstruction of the interosseous membrane of the forearm in cadavers. J Hand Surg 1997;22A:986 –994. 5. Pfaeffle HJ, Stabile KJ, Li ZM, Tomaino MM. Reconstruction of the interosseous ligament restores normal forearm compressive load transfer in cadavers. J Hand Surg 2005;30A:319 –325. 6. Tejwani SG, Markolf KL, Benhaim P. Graft reconstruction of the interosseous membrane in conjunction with metallic radial head replacement: a cadaveric study. J Hand Surg 2005;30A:335–342. 7. Tejwani SG, Markolf KL, Benhaim P. Reconstruction of the interosseous membrane of the forearm with a graft substitute: a cadaveric study. J Hand Surg 2005;30A:326 –334. 8. Pfaeffle HJ, Stabile KJ, Li ZM, Tomaino MM. Reconstruction of the interosseous ligament unloads metallic radial head arthroplasty and the distal ulna in cadavers. J Hand Surg 2006;31A:269 –278. 9. Chandler JW, Stabile KJ, Pfaeffle HJ, Li ZM, Woo SL, Tomaino MM. Anatomic parameters for planning of interosseous ligament reconstruction using computer-assisted techniques. J Hand Surg 2003;28A:111–116. 10. Markolf KL, Lamey D, Yang S, Meals R, Hotchkiss R. Radioulnar load-sharing in the forearm. A study in cadavera. J Bone Joint Surg 1998;80A:879 – 888. 11. Adams JE, Culp RW, Osterman AL. Interosseous membrane reconstruction for the Essex-Lopresti injury. J Hand Surg 2010;35A:129 – 136. 12. Marcotte AL, Osterman AL. Longitudinal radioulnar dissociation: identification and treatment of acute and chronic injuries. Hand Clin 2007;23:195–208. 13. Hotchkiss RN. Injuries to the interosseous ligament of the forearm. Hand Clin 1994;10:391–398. 14. Knight DJ, Rymaszewski LA, Amis AA, Miller JH. Primary replacement of the fractured radial head with a metal prosthesis. J Bone Joint Surg 1993;75B:572–576. 15. Birkbeck DP, Failla JM, Hoshaw SJ, Fyhrie DP, Schaffler M. The interosseous membrane affects load distribution in the forearm. J Hand Surg 1997;22A:975–980.
JHS 䉬 Vol A, December