SCIENTIFIC ARTICLE
Distal Radioulnar Joint Kinematics in Simulated Dorsally Angulated Distal Radius Fractures Masao Nishiwaki, MD, PhD, Mark Welsh, BScE, Braden Gammon, MD, Louis M. Ferreira, PhD, James A. Johnson, PhD, Graham J. W. King, MD, MSc
Purpose To examine the effects of dorsal angulation deformities of the distal radius with and without triangular fibrocartilage complex (TFCC) rupture on the 3-dimensional kinematics of the distal radioulnar joint (DRUJ) during simulated active motion. Methods Nine fresh-frozen cadaveric specimens were tested in a forearm simulator that produced active forearm rotation. Dorsal angulation deformities of the distal radius with 10 , 20 , and 30 angulation were created. Changes in the position of the ulna relative to the radius at the DRUJ as a consequence of each dorsal angulation deformity were quantified during simulated active supination in terms of volar, ulnar, and distal displacement of the ulna. Testing was performed initially with the TFCC intact and repeated after complete sectioning of the TFCC at its ulnar insertion. Results Increasing dorsal angulation deformities of the distal radius significantly increased volar, ulnar, and distal displacement of the ulna when the TFCC was intact. Sectioning of the TFCC significantly increased volar displacement of the ulna in dorsal angulation deformities. As little as 10 of dorsal angulation significantly increased distal displacement of the ulna with the TFCC intact and resulted in a significant increase in volar, ulnar, and distal displacement of the ulna with sectioned TFCC. Conclusions Dorsal angulation deformities of the distal radius affect the 3-dimensional kinematics of the DRUJ, especially with the TFCC sectioned. Clinical relevance The progressive change in DRUJ kinematics with increasing dorsal angulation may partially explain the relationship between the magnitude of dorsal angulation of distal radius fractures and functional outcomes in younger patients. The status of the TFCC should be evaluated carefully, as well as the magnitude of osseous deformity in patients with distal radius fractures and malunions, because changes in DRUJ kinematics caused by dorsal angulation are greater when the TFCC is ruptured. (J Hand Surg Am. 2014;39(4):656e663. Copyright Ó 2014 by the American Society for Surgery of the Hand. All rights reserved.) Key words Distal radioulnar joint, distal radius fracture, dorsal angulation, kinematics, triangular fibrocartilage complex.
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radius is the most commonly reported complication of treatment for distal radius fractures and is correlated with weakness, stiffness, ulnar-sided wrist pain, ALUNION OF THE DISTAL
median nerve dysfunction, and carpal or distal radioulnar joint (DRUJ) instability.1,2 Although many authors have reported that malalignment is not necessarily associated with worse functional outcomes in elderly
From the Hand and Upper Limb Centre, Bioengineering Laboratory, St Joseph’s Health Care, London, Ontario, Canada.
No benefits in any form have been received or will be received related directly or indirectly to the subject of this article.
Received for publication September 4, 2013; accepted in revised form January 10, 2014.
Corresponding author: Masao Nishiwaki, MD, PhD, Department of Orthopaedic Surgery, Keio University, 35 Shinanomachi, Shinjuku-ku, Tokyo 160-8582, Japan; e-mail: [email protected].
This study was supported by Canadian Institutes for Health Research Grant R0598A13.
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variance averaged 0 1 mm (range, e1 to þ1 mm). The specimens were thawed completely at room temperature. The fingers were disarticulated at the metacarpophalangeal joints. The tendons of the biceps, pronator teres, flexor carpi ulnaris, flexor carpi radialis, extensor carpi ulnaris, and extensor carpi radialis longus were exposed and sutured using sutures (Ethicon, Somerville, NJ). The sutures for the pronator teres, flexor carpi ulnaris, and flexor carpi radialis were routed through custom plastic sleeves attached to the medial epicondyle of the humerus to recreate the muscle lines of action. The sutures for the extensor carpi ulnaris and extensor carpi radialis longus were routed through sleeves on the lateral epicondyle of the humerus. To simulate the supinator, a suture anchor was placed at the radial attachment, and the suture was routed through a plastic sleeve placed at the ulnar attachment. The humerus was rigidly secured in the clamp on the simulator (Fig. 1). The ulna was secured with 2 threaded pins to the simulator with the elbow in 90 flexion to allow the forearm to rotate freely. A rod was inserted longitudinally into the third metacarpal shaft and placed through a ring mounted on the motion simulator to avoid wrist extreme positions. The biceps suture terminated at a servomotor (SM2315D; Animatic, Santa Clara, CA). The sutures to the other tendons were routed through an alignment system mounted on the testing apparatus and were attached to individual pneumatic actuators (Airpot Corporation, Norwalk, CT). Optical tracking markers (Optotrak Certus; Northern Digital, Waterloo, Ontario, Canada) were attached rigidly to pedestals on the shaft of the radius and ulna to capture the continuous forearm motion throughout testing.
patients,3e9 the degree of dorsal angulation has a significant influence on functional outcomes in younger patients.1,3,10e12 Previous biomechanical studies examined various factors that were affected by dorsal angulation deformities.13e21 Short et al13 showed that increased dorsal tilt increased the load through the ulna and the load became concentrated along the dorsal rim of the ulnocarpal and radioscaphoid articulations. Pogue et al14 also demonstrated a dorsal shift and greater concentration of the loads in the scaphoid and lunate fossae in dorsal angulation deformities. The effects of dorsal angulation deformities on the DRUJ have been also examined in terms of the forearm rotation axis,15,16 joint congruency,17 range of forearm rotation,17e19 triangular fibrocartilage complex (TFCC) strain,15,20 interbone joint spacing,20 and joint stiffness.21 However, the conclusions vary widely owing to the difficulties of evaluating DRUJ motion. The DRUJ kinematics has been analyzed only in static conditions, whereas dynamic conditions would allow for a more physiologic assessment. In addition, 3-dimensional changes in DRUJ kinematics have not been well quantified, which is essential to gain a better understanding of the implications of distal radial deformities on the DRUJ. Furthermore, TFCC rupture is often associated with distal radius fractures with and without ulnar styloid fractures.22,23 However, it is unclear whether a TFCC injury accompanying a distal radius fracture has any effects on the 3-dimensional kinematics of the DRUJ. The purpose of this study was to quantify the effects of dorsal angulation deformities of the distal radius with and without TFCC rupture on the 3-dimensional kinematics of the DRUJ using an active motion simulator. We hypothesized that dorsal angulation deformities of the distal radius would alter the 3-dimensional kinematics of the DRUJ and the changes in DRUJ kinematics caused by dorsal angulation would be greater when the TFCC was ruptured.
Simulation of distal radial deformities A 3-degree-of-freedom adjustable implant described previously19 was employed to create dorsal angulation deformities of the distal radius (Fig. 2). To install the implant, a 20-mm segment of the volar radius was removed 2 mm proximal to the DRUJ using an oscillating saw and leaving the dorsal cortex intact. The distal and proximal components of the implant were rigidly fixed to the distal and proximal radial fragment using screws, which were augmented with polymethylmethacrylate to ensure that the device did not loosen during testing. The dorsal bone bridge was removed after implant installation to ensure that the normal alignment of the radius was maintained. Dorsal angulation deformities of the distal radius with 10 , 20 , and 30 angulation from the original volar tilt were created with their apex at the proximal end of the volar surface of the distal radial fragment, by
MATERIALS AND METHODS Specimen preparation Nine fresh-frozen left upper extremities (mean age, 62 y; range, 29e77 y; 7 men and 2 women) amputated at the midportion of the humerus were used. There was no history of wrist disease or trauma in any specimen. Specimens with marked limitation of motion or DRUJ arthritic changes on pretesting computed tomography scans were excluded from this study. Volar tilt averaged 10 3 (range, 7 to 14 ), radial inclination averaged 24 1 (range, 22 to 25 ), and ulnar J Hand Surg Am.
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FIGURE 1: Forearm motion simulator. Active supination was achieved by displacing the cable sutured to the biceps tendon (red line) at a constant velocity using a servomotor, while simultaneously applying load to the cable sutured to the supinator muscle (yellow line) using a load-controlled actuator. Constant loads were applied by pneumatic actuators to cables sutured to 5 tendons (green lines). Optical tracking markers attached to pedestals on the shaft of the radius and ulna were used to capture the continuous forearm motion.
switching the removable central appliance of the implant to an angulated version.
each distal radial deformity. These tests were performed initially with the TFCC intact and were repeated after complete sectioning of the TFCC at its ulnar insertion. The specimen was not removed from the testing system while sectioning the TFCC. At the completion of the testing protocol, the joints were dissected, and landmarks on the ulna, radius, and radial implant were digitized to allow for construction of 3-dimensional bone coordinate systems and transformation of the kinematic data. The specimens were kept moist using saline irrigation of the soft tissues and by closure of the skin throughout the test.
Testing protocol Before we created the distal radius deformities, we recorded kinematic data continuously during simulated active supination to create a control. Active supination was simulated by displacing the biceps tendon at a constant velocity of 5 mm/s using a servomotor while applying 33% of this load simultaneously to the supinator using a load-controlled actuator. This load distribution was based on physiologic cross-sectional areas and electromyographic data.24 A constant resistive muscle load of 20 N was applied to the pronator teres. Constant tone loads of 10 N were applied to the flexor carpi ulnaris, flexor carpi radialis, extensor carpi ulnaris, and extensor carpi radialis longus. Distal radial deformities with 10 , 20 , and 30 of dorsal angulation from the original volar tilt were created, and kinematic data were collected continuously during simulated active supination with J Hand Surg Am.
Outcome variables and data analysis To quantify the effects of dorsal angulation deformities of the distal radius on DRUJ kinematics 3-dimensionally, we evaluated changes in the position of the ulna relative to the radius at the DRUJ as a consequence of dorsal angulation deformities at each forearm rotation angle using clinically relevant joint coordinate systems. The ulnar coordinate system was r
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FIGURE 2: The 3-degree-of-freedom adjustable implant employed to simulate distal radius fracture deformities in vitro. A The condition without distal radial deformities. B Thirty degrees of dorsal angulation deformity of the distal radius. Dorsal angulation deformities were created with their apex at the proximal end of the volar surface of the distal radial fragment by switching the removable central appliance to the angulated one.
located at the circle center of the ulna head. The distal radius coordinate system was located at the center of the sigmoid notch of the radius (Fig. 3). The volar, ulnar, and proximal axes of the distal radius coordinate system were produced from digitizing landmarks on the radius and radial implant. When the distal radius deformities were created, the distal radius coordinate system was transformed to be still located at the center of the sigmoid notch of the radius and parallel to the original orientation. Changes of the position of the circle center of the ulnar head along the volar axis in the distal radius coordinate system as a consequence of distal radial deformities from the intact radius were defined as volar displacement of the ulna. Changes on the ulnar axis were defined as ulnar displacement of the ulna. Negative changes along the proximal axis were defined as distal displacement of the ulna. These 3 kinematic descriptors (volar, ulnar, and distal displacement of the ulna) were calculated both in TFCC intact and sectioned conditions from 40 pronation to 60 supination at 10 increments, which was the maximum range of forearm rotation common to all specimens. Because the position of the ulna in the distal radius coordinate system moved by sectioning the TFCC and during forearm rotation, J Hand Surg Am.
these kinematic descriptors were defined as the differences from the intact radius in each TFCC condition at each forearm rotation angle. Statistical methods A 2-way repeated measures analysis of variance with GreenhouseeGeisser correction was performed for each of the 3 kinematic descriptors separately in TFCC intact and sectioned conditions, with the independent variables of dorsal angulation deformity and forearm rotation angle. The effects of the TFCC condition on these kinematic descriptors were analyzed using a 3-way repeated measures analysis of variance with GreenhouseeGeisser correction for the independent variables of the TFCC condition, dorsal angulation deformity, and forearm rotation angle. Statistical significance was set at P < .050. RESULTS Volar displacement of the ulna Volar displacement of the ulna significantly increased with increasing dorsal angulation of the distal radius when the TFCC was intact (P < .001) (Fig. 4A). We found a significant increase in volar displacement r
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FIGURE 3: A distal radius coordinate system was established to describe the relationship between the ulna and radius at the DRUJ. This coordinate system was located at the center of the sigmoid notch of the radius. The volar axis was produced by the line, directed volarly, connecting 2 dimples on the radial side of the proximal component of the radial implant. The ulnar axis was produced by the line, directed ulnarly, connecting 2 dimples on the volar side of the proximal component. The proximal axis was produced by the crossproduct of these 2 axes, which guaranteed that the proximal axis was orthogonal to the volar and ulnar axes. The dimples on the implant were physically designed so that the volar and ulnar axes were orthogonal; however, to ensure orthogonality with mathematical precision, a second cross-product of the proximal and ulnar axes was made to produce a new volar axis. For each distal radial deformity, this coordinate system was mathematically transformed to remain located at the center of the sigmoid notch and parallel to its original (neutral) orientation. This was intended to mimic a clinical radiographic transverse-view plane slicing through the center of the distal radius and consistently perpendicular to the long axis.
at 30 dorsal angulation (1.2 0.8 mm; P ¼ .007), but not at 10 (0.5 0.5 mm; P ¼ .131) or 20 (0.5 0.6 mm; P ¼ .325), compared with the intact radius. Volar displacement was significantly larger with the forearm in supination (P ¼ .017). Sectioning of the TFCC significantly increased volar displacement of the ulna with dorsal angulation deformities (P ¼ .011). After sectioning the TFCC, we found a significant increase in volar displacement with dorsal angulation deformities of 10 (0.7 0.6 mm; P ¼ .049), 20 (1.0 0.8 mm; P ¼ .040), and 30 (2.7 0.7 mm; P < .001), compared with the intact radius (Fig. 4B). Forearm rotation angle had no significant effect on volar displacement with sectioned TFCC (P ¼ .084).
a significant increase in ulnar displacement at 20 of dorsal angulation (0.5 0.4 mm; P ¼ .043), but not at 10 (0.2 0.2 mm; P ¼ .202) or 30 (0.5 0.6 mm; P ¼ .151), compared with the intact radius. The TFCC condition had no significant effect on ulnar displacement with dorsal angulation deformities (P ¼ .084). After sectioning the TFCC, we found a significant increase in ulnar displacement with dorsal angulation deformities of 10 (0.3 0.2 mm; P ¼ .017), 20 (0.7 0.3 mm; P ¼ .001), and 30 (1.0 0.4 mm; P < .001), compared with the intact radius (Fig. 5B). Forearm rotation angle had no significant effect on ulnar displacement both in the TFCC intact (P ¼ .107) and sectioned (P ¼ .080) conditions.
Ulnar displacement of the ulna Ulnar displacement of the ulna significantly increased as the dorsal angulation of the distal radius increased with an intact TFCC (P ¼ .015) (Fig. 5A). We found
Distal displacement of the ulna Distal displacement of the ulna significantly increased with increasing dorsal angulation deformities in the intact TFCC (P < .001) (Fig. 6A). We found a
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FIGURE 4: Volar displacement of the ulna from the intact radius as a result of 10 (10DA), 20 (20DA), and 30 (30DA) of dorsal angulation deformities of the distal radius in the A intact and B sectioned TFCC at each forearm rotation angle. The abscissa represents the forearm rotation angle, and the ordinate represents the mean volar displacement of the ulna. The error bars indicate the standard deviation.
FIGURE 5: Ulnar displacement of the ulna from the intact radius as a result of 10 (10DA), 20 (20DA), and 30 (30DA) of dorsal angulation deformities of the distal radius in the A intact and B sectioned TFCC at each forearm rotation angle. The abscissa represents the forearm rotation angle, and the ordinate represents the mean ulnar displacement of the ulna. The error bars indicate the standard deviation.
DISCUSSION The current study confirmed that increasing dorsal angulation deformities of the distal radius significantly increased volar, ulnar, and distal displacement of the ulna both in TFCC intact and sectioned conditions. These findings are consistent with previous biomechanical studies that examined the changes of the DRUJ kinematics after distal radius fractures.15,17 Kihara et al17 showed that the alignment of the DRUJ worsened with increasing dorsal tilt of the distal radius. This was noticed especially with more than 20 of dorsal angulation from the original tilt. Adams15 reported that 15 of dorsally angulated distal radius produced 3.5 mm of shift in the axis of forearm rotation. In our study, statistically significant increases
significant increase in distal displacement with dorsal angulation deformities of 10 (0.5 0.4 mm; P ¼ .030), 20 (1.1 0.7 mm; P ¼ .006), and 30 (2.0 1.0 mm; P ¼ .002), compared with the intact radius. Distal displacement was significantly greater in supination (P < .001). There was no significant difference in distal displacement of the ulna between TFCC intact and sectioned conditions (P ¼ .242). After sectioning the TFCC, we found a significant increase in distal displacement with dorsal angulation deformities of 10 (0.4 0.3 mm; P ¼ .014), 20 (1.2 0.6 mm; P ¼ .002), and 30 (2.4 0.8 mm; P < .001), compared with the intact radius (Fig. 6B). Forearm rotation angle had no significant effect on distal displacement with sectioned TFCC (P ¼ .216). J Hand Surg Am.
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FIGURE 6: Distal displacement of the ulna from the intact radius as a result of 10 (10DA), 20 (20DA), and 30 (30DA) of dorsal angulation deformities of the distal radius in the A intact and B sectioned TFCC at each forearm rotation angle. The abscissa represents the forearm rotation angle, and the ordinate represents the mean distal displacement of the ulna. The error bars indicate the standard deviation.
compared with the intact radius were found with 10 or more of dorsal angulation in distal displacement of the ulna, 20 in ulnar displacement, and 30 in volar displacement when the TFCC was intact. This study showed that volar displacement of the ulna caused by dorsal angulation deformities was significantly larger with the sectioned TFCC rather than the intact TFCC. As little as 10 of dorsal angulation deformity increased volar, ulnar, and distal displacement of the ulna compared with the intact radius when the TFCC was sectioned. Because the TFCC connects the distal radius and ulna to stabilize the DRUJ,25e28 the intact TFCC restricts the displacement of the ulna with respect to the distal radius. Therefore, when the dorsal angulation deformities of the distal radius are created with an intact TFCC, the proximal radius shaft moves volarly with respect to the ulna to minimize the displacement at the distal end of the DRUJ while tension in the TFCC increases. Once the TFCC is sectioned, dorsal angulation deformities move the ulna more volarly with respect to the distal radius because the sectioned TFCC no longer restricts the displacement at the DRUJ. These findings are supported by the biomechanical study of Adams,15 which showed that 15 of dorsally angulated distal radius increased strains in the dorsal radioulnar ligament by 9%. Conversely, our results are contradictory to the findings of Kihara et al17 showing that sectioning of the TFCC did not cause a significant change in dorsal or volar displacement of the radius with respect to the ulna with dorsally angulated distal radius deformities. They analyzed the 2-dimensional changes of the DRUJ kinematics after dorsal angulation deformities of the distal radius in the transverse plane. Their J Hand Surg Am.
kinematic data were collected in the static position by weights applied to the biceps or pronator teres, whereas our study employed simulated active supination, which may produce more physiologic loading and motion. In addition, they simulated distal radius fractures using an external fixator, whereas we used an adjustable implant. These factors may explain the difference in the findings between the studies. A number of investigators have agreed that there is a close relationship between the magnitude of dorsal angulation and functional outcomes in younger patients.1,3,10e12 This may be partially explained by progressive changes in the DRUJ kinematics with increasing dorsal angulation demonstrated here. The altered kinematics could produce abnormal contact and loading patterns, which cause pain and degenerative changes at the DRUJ. Conversely, changes in the DRUJ kinematics may not affect the functional outcomes in elderly patients with low demands on the upper extremity. This study also showed that changes in the DRUJ kinematics caused by dorsal angulation deformities were larger in sectioned TFCC than those in intact TFCC. This emphasizes the clinical importance of evaluating the integrity of the TFCC as well as the magnitude of osseous deformities when managing acute or healed displaced fractures of the distal radius. We examined only simple dorsal angulation deformities because dorsal/volar tilt has been shown to be the most valid and reliable radiographic predictor of functional outcomes.1,10,12 However, dorsal angulation deformities are often combined with dorsal translation, radial translation or angulation, shortening, and rotation.13,20,29 Fraser et al19 demonstrated that combined deformities had a greater effect on forearm rotation than isolated malpositions. Combined r
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deformities may also affect the 3-dimensional kinematics of the DRUJ and should be assessed in future studies. We examined DRUJ kinematics during active supination and not pronation. We performed a pilot study for both active supination and pronation. The pilot study showed the same trends for both motions, but active pronation produced a smaller range of motion than active supination owing to the limitations of our testing simulator. Therefore, we decided to investigate only active supination. This study has limitations. First, we analyzed the DRUJ kinematics during active supination from 40 pronation to 60 supination because it was the maximum range of forearm rotation common to all specimens. The data at the maximum supination and pronation were not included, although some patients with distal radial deformities have symptoms at the maximum forearm rotation. We were unable to analyze this data statistically because of the variable magnitudes of rotation seen across different specimens. In addition, this study was performed in vitro, which had no potential for soft tissue adaptation. Moore et al16 showed that malunion did not alter the location or orientation of the prosupination rotation axes, by an in vivo analysis of the DRUJ kinematics in patients with malunion at an average of 10 months after injury. In their patients, soft tissues may have adapted to compensate for the radial deformities to restore the normal DRUJ kinematics, or the errors in the measurement technique may have prevented small differences in DRUJ kinematics from being quantified. However, our cadaveric study isolated and clarified the effect of dorsal angulation deformities on DRUJ kinematics, which is difficult to achieve in an in vivo study.
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in an elderly cohort with conservatively treated distal radius fractures. J Hand Surg Am. 2004;29(6):1121e1127. Egol KA, Walsh M, Romo-Cardoso S, Dorsky S, Paksima N. Distal radial fractures in the elderly: operative compared with nonoperative treatment. J Bone Joint Surg Am. 2010;92(9):1851e1857. Roumen RM, Hesp WL, Bruggink ED. Unstable Colles’ fractures in elderly patients: a randomized trial of external fixation for redisplacement. J Bone Joint Surg Br. 1991;73(2):307e311. Wong TC, Chiu Y, Tsang WL, Leung WY, Yam SK, Yeung SH. Casting versus percutaneous pinning for extra-articular fractures of the distal radius in an elderly Chinese population: a prospective randomised controlled trial. J Hand Surg Eur Vol. 2010;35(3):202e208. Gartland JJ Jr, Werley CW. Evaluation of healed Colles’ fractures. J Bone Joint Surg Am. 1951;33(4):895e907. Fernandez DL. Correction of post-traumatic wrist deformity in adults by osteotomy, bone-grafting, and internal fixation. J Bone Joint Surg Am. 1982;64(8):1164e1178. McQueen M, Caspers J. Colles fracture: does the anatomical result affect the final function? J Bone Joint Surg Br. 1988;70(4):649e651. Short WH, Palmer AK, Werner FW, Murphy DJ. A biomechanical study of distal radial fractures. J Hand Surg Am. 1987;12(4):529e534. Pogue DJ, Viegas SF, Patterson RM, et al. Effects of distal radius fracture malunion on wrist joint mechanics. J Hand Surg Am. 1990;15(5):721e727. Adams BD. Effects of radial deformity on distal radioulnar joint mechanics. J Hand Surg Am. 1993;18(3):492e498. Moore DC, Hogan KA, Crisco JJ III, Akelman E, Dasilva MF, Weiss AP. Three-dimensional in vivo kinematics of the distal radioulnar joint in malunited distal radius fractures. J Hand Surg Am. 2002;27(2):233e242. Kihara H, Palmer AK, Werner FW, Short WH, Fortino MD. The effect of dorsally angulated distal radius fractures on distal radioulnar joint congruency and forearm rotation. J Hand Surg Am. 1996;21(1):40e47. Bronstein AJ, Trumble TE, Tencer AF. The effects of distal radius fracture malalignment on forearm rotation: a cadaveric study. J Hand Surg Am. 1997;22(2):258e262. Fraser GS, Ferreira LM, Johnson JA, King GJ. The effect of multiplanar distal radius fractures on forearm rotation: in vitro biomechanical study. J Hand Surg Am. 2009;34(5):838e848. Crisco JJ, Moore DC, Marai GE, et al. Effects of distal radius malunion on distal radioulnar joint mechanics—an in vivo study. J Orthop Res. 2007;25(4):547e555. Saito T, Nakamura T, Nagura T, Nishiwaki M, Sato K, Toyama Y. The effects of dorsally angulated distal radius fractures on distal radioulnar joint stability: a biomechanical study. J Hand Surg Eur Vol. 2013;38(7):739e745. Mrkonjic A, Geijer M, Lindau T, Tagil M. The natural course of traumatic triangular fibrocartilage complex tears in distal radial fractures: a 13-15 year follow-up of arthroscopically diagnosed but untreated injuries. J Hand Surg Am. 2012;37(8):1555e1560. Lindau T, Hagberg L, Adlercreutz C, Jonsson K, Aspenberg P. Distal radioulnar instability is an independent worsening factor in distal radial fractures. Clin Orthop Relat Res. 2000;376:229e235. Gordon KD, Dunning CE, Johnson JA, King GJ. Influence of the pronator quadratus and supinator muscle load on DRUJ stability. J Hand Surg Am. 2003;28(6):943e950. Palmer AK, Werner FW. The triangular fibrocartilage complex of the wrist—anatomy and function. J Hand Surg Am. 1981;6(2):153e162. Stuart PR, Berger RA, Linscheid RL, An KN. The dorsopalmar stability of the distal radioulnar joint. J Hand Surg Am. 2000;25(4):689e699. Nakamura T, Yabe Y, Horiuchi Y. Functional anatomy of the triangular fibrocartilage complex. J Hand Surg Br. 1996;21(5):581e586. Schuind F, An KN, Berglund L, et al. The distal radioulnar ligaments: a biomechanical study. J Hand Surg Am. 1991;16(6):1106e1114. Miyake J, Murase T, Yamanaka Y, Moritomo H, Sugamoto K, Yoshikawa H. Three-dimensional deformity analysis of malunited distal radius fractures and their influence on wrist and forearm motion. J Hand Surg Eur Vol. 2012;37(6):506e512.
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Distal Radioulnar Joint Kinematics in Simulated Dorsally Angulated Distal Radius Fractures Masao Nishiwaki, MD, PhD, Mark Welsh, BScE, Braden Gammon, MD, Louis M. Ferreira, PhD, James A. Johnson, PhD, Graham J. W. King, MD, MSc
Purpose To examine the effects of dorsal angulation deformities of the distal radius with and without triangular fibrocartilage complex (TFCC) rupture on the 3-dimensional kinematics of the distal radioulnar joint (DRUJ) during simulated active motion. Methods Nine fresh-frozen cadaveric specimens were tested in a forearm simulator that produced active forearm rotation. Dorsal angulation deformities of the distal radius with 10 , 20 , and 30 angulation were created. Changes in the position of the ulna relative to the radius at the DRUJ as a consequence of each dorsal angulation deformity were quantified during simulated active supination in terms of volar, ulnar, and distal displacement of the ulna. Testing was performed initially with the TFCC intact and repeated after complete sectioning of the TFCC at its ulnar insertion. Results Increasing dorsal angulation deformities of the distal radius significantly increased volar, ulnar, and distal displacement of the ulna when the TFCC was intact. Sectioning of the TFCC significantly increased volar displacement of the ulna in dorsal angulation deformities. As little as 10 of dorsal angulation significantly increased distal displacement of the ulna with the TFCC intact and resulted in a significant increase in volar, ulnar, and distal displacement of the ulna with sectioned TFCC. Conclusions Dorsal angulation deformities of the distal radius affect the 3-dimensional kinematics of the DRUJ, especially with the TFCC sectioned. Clinical relevance The progressive change in DRUJ kinematics with increasing dorsal angulation may partially explain the relationship between the magnitude of dorsal angulation of distal radius fractures and functional outcomes in younger patients. The status of the TFCC should be evaluated carefully, as well as the magnitude of osseous deformity in patients with distal radius fractures and malunions, because changes in DRUJ kinematics caused by dorsal angulation are greater when the TFCC is ruptured. (J Hand Surg Am. 2014;39(4):656e663. Copyright Ó 2014 by the American Society for Surgery of the Hand. All rights reserved.) Key words Distal radioulnar joint, distal radius fracture, dorsal angulation, kinematics, triangular fibrocartilage complex.
M
radius is the most commonly reported complication of treatment for distal radius fractures and is correlated with weakness, stiffness, ulnar-sided wrist pain, ALUNION OF THE DISTAL
median nerve dysfunction, and carpal or distal radioulnar joint (DRUJ) instability.1,2 Although many authors have reported that malalignment is not necessarily associated with worse functional outcomes in elderly
From the Hand and Upper Limb Centre, Bioengineering Laboratory, St Joseph’s Health Care, London, Ontario, Canada.
No benefits in any form have been received or will be received related directly or indirectly to the subject of this article.
Received for publication September 4, 2013; accepted in revised form January 10, 2014.
Corresponding author: Masao Nishiwaki, MD, PhD, Department of Orthopaedic Surgery, Keio University, 35 Shinanomachi, Shinjuku-ku, Tokyo 160-8582, Japan; e-mail: [email protected].
This study was supported by Canadian Institutes for Health Research Grant R0598A13.
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DRUJ KINEMATICS IN DISTAL RADIUS FRACTURES
variance averaged 0 1 mm (range, e1 to þ1 mm). The specimens were thawed completely at room temperature. The fingers were disarticulated at the metacarpophalangeal joints. The tendons of the biceps, pronator teres, flexor carpi ulnaris, flexor carpi radialis, extensor carpi ulnaris, and extensor carpi radialis longus were exposed and sutured using sutures (Ethicon, Somerville, NJ). The sutures for the pronator teres, flexor carpi ulnaris, and flexor carpi radialis were routed through custom plastic sleeves attached to the medial epicondyle of the humerus to recreate the muscle lines of action. The sutures for the extensor carpi ulnaris and extensor carpi radialis longus were routed through sleeves on the lateral epicondyle of the humerus. To simulate the supinator, a suture anchor was placed at the radial attachment, and the suture was routed through a plastic sleeve placed at the ulnar attachment. The humerus was rigidly secured in the clamp on the simulator (Fig. 1). The ulna was secured with 2 threaded pins to the simulator with the elbow in 90 flexion to allow the forearm to rotate freely. A rod was inserted longitudinally into the third metacarpal shaft and placed through a ring mounted on the motion simulator to avoid wrist extreme positions. The biceps suture terminated at a servomotor (SM2315D; Animatic, Santa Clara, CA). The sutures to the other tendons were routed through an alignment system mounted on the testing apparatus and were attached to individual pneumatic actuators (Airpot Corporation, Norwalk, CT). Optical tracking markers (Optotrak Certus; Northern Digital, Waterloo, Ontario, Canada) were attached rigidly to pedestals on the shaft of the radius and ulna to capture the continuous forearm motion throughout testing.
patients,3e9 the degree of dorsal angulation has a significant influence on functional outcomes in younger patients.1,3,10e12 Previous biomechanical studies examined various factors that were affected by dorsal angulation deformities.13e21 Short et al13 showed that increased dorsal tilt increased the load through the ulna and the load became concentrated along the dorsal rim of the ulnocarpal and radioscaphoid articulations. Pogue et al14 also demonstrated a dorsal shift and greater concentration of the loads in the scaphoid and lunate fossae in dorsal angulation deformities. The effects of dorsal angulation deformities on the DRUJ have been also examined in terms of the forearm rotation axis,15,16 joint congruency,17 range of forearm rotation,17e19 triangular fibrocartilage complex (TFCC) strain,15,20 interbone joint spacing,20 and joint stiffness.21 However, the conclusions vary widely owing to the difficulties of evaluating DRUJ motion. The DRUJ kinematics has been analyzed only in static conditions, whereas dynamic conditions would allow for a more physiologic assessment. In addition, 3-dimensional changes in DRUJ kinematics have not been well quantified, which is essential to gain a better understanding of the implications of distal radial deformities on the DRUJ. Furthermore, TFCC rupture is often associated with distal radius fractures with and without ulnar styloid fractures.22,23 However, it is unclear whether a TFCC injury accompanying a distal radius fracture has any effects on the 3-dimensional kinematics of the DRUJ. The purpose of this study was to quantify the effects of dorsal angulation deformities of the distal radius with and without TFCC rupture on the 3-dimensional kinematics of the DRUJ using an active motion simulator. We hypothesized that dorsal angulation deformities of the distal radius would alter the 3-dimensional kinematics of the DRUJ and the changes in DRUJ kinematics caused by dorsal angulation would be greater when the TFCC was ruptured.
Simulation of distal radial deformities A 3-degree-of-freedom adjustable implant described previously19 was employed to create dorsal angulation deformities of the distal radius (Fig. 2). To install the implant, a 20-mm segment of the volar radius was removed 2 mm proximal to the DRUJ using an oscillating saw and leaving the dorsal cortex intact. The distal and proximal components of the implant were rigidly fixed to the distal and proximal radial fragment using screws, which were augmented with polymethylmethacrylate to ensure that the device did not loosen during testing. The dorsal bone bridge was removed after implant installation to ensure that the normal alignment of the radius was maintained. Dorsal angulation deformities of the distal radius with 10 , 20 , and 30 angulation from the original volar tilt were created with their apex at the proximal end of the volar surface of the distal radial fragment, by
MATERIALS AND METHODS Specimen preparation Nine fresh-frozen left upper extremities (mean age, 62 y; range, 29e77 y; 7 men and 2 women) amputated at the midportion of the humerus were used. There was no history of wrist disease or trauma in any specimen. Specimens with marked limitation of motion or DRUJ arthritic changes on pretesting computed tomography scans were excluded from this study. Volar tilt averaged 10 3 (range, 7 to 14 ), radial inclination averaged 24 1 (range, 22 to 25 ), and ulnar J Hand Surg Am.
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FIGURE 1: Forearm motion simulator. Active supination was achieved by displacing the cable sutured to the biceps tendon (red line) at a constant velocity using a servomotor, while simultaneously applying load to the cable sutured to the supinator muscle (yellow line) using a load-controlled actuator. Constant loads were applied by pneumatic actuators to cables sutured to 5 tendons (green lines). Optical tracking markers attached to pedestals on the shaft of the radius and ulna were used to capture the continuous forearm motion.
switching the removable central appliance of the implant to an angulated version.
each distal radial deformity. These tests were performed initially with the TFCC intact and were repeated after complete sectioning of the TFCC at its ulnar insertion. The specimen was not removed from the testing system while sectioning the TFCC. At the completion of the testing protocol, the joints were dissected, and landmarks on the ulna, radius, and radial implant were digitized to allow for construction of 3-dimensional bone coordinate systems and transformation of the kinematic data. The specimens were kept moist using saline irrigation of the soft tissues and by closure of the skin throughout the test.
Testing protocol Before we created the distal radius deformities, we recorded kinematic data continuously during simulated active supination to create a control. Active supination was simulated by displacing the biceps tendon at a constant velocity of 5 mm/s using a servomotor while applying 33% of this load simultaneously to the supinator using a load-controlled actuator. This load distribution was based on physiologic cross-sectional areas and electromyographic data.24 A constant resistive muscle load of 20 N was applied to the pronator teres. Constant tone loads of 10 N were applied to the flexor carpi ulnaris, flexor carpi radialis, extensor carpi ulnaris, and extensor carpi radialis longus. Distal radial deformities with 10 , 20 , and 30 of dorsal angulation from the original volar tilt were created, and kinematic data were collected continuously during simulated active supination with J Hand Surg Am.
Outcome variables and data analysis To quantify the effects of dorsal angulation deformities of the distal radius on DRUJ kinematics 3-dimensionally, we evaluated changes in the position of the ulna relative to the radius at the DRUJ as a consequence of dorsal angulation deformities at each forearm rotation angle using clinically relevant joint coordinate systems. The ulnar coordinate system was r
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FIGURE 2: The 3-degree-of-freedom adjustable implant employed to simulate distal radius fracture deformities in vitro. A The condition without distal radial deformities. B Thirty degrees of dorsal angulation deformity of the distal radius. Dorsal angulation deformities were created with their apex at the proximal end of the volar surface of the distal radial fragment by switching the removable central appliance to the angulated one.
located at the circle center of the ulna head. The distal radius coordinate system was located at the center of the sigmoid notch of the radius (Fig. 3). The volar, ulnar, and proximal axes of the distal radius coordinate system were produced from digitizing landmarks on the radius and radial implant. When the distal radius deformities were created, the distal radius coordinate system was transformed to be still located at the center of the sigmoid notch of the radius and parallel to the original orientation. Changes of the position of the circle center of the ulnar head along the volar axis in the distal radius coordinate system as a consequence of distal radial deformities from the intact radius were defined as volar displacement of the ulna. Changes on the ulnar axis were defined as ulnar displacement of the ulna. Negative changes along the proximal axis were defined as distal displacement of the ulna. These 3 kinematic descriptors (volar, ulnar, and distal displacement of the ulna) were calculated both in TFCC intact and sectioned conditions from 40 pronation to 60 supination at 10 increments, which was the maximum range of forearm rotation common to all specimens. Because the position of the ulna in the distal radius coordinate system moved by sectioning the TFCC and during forearm rotation, J Hand Surg Am.
these kinematic descriptors were defined as the differences from the intact radius in each TFCC condition at each forearm rotation angle. Statistical methods A 2-way repeated measures analysis of variance with GreenhouseeGeisser correction was performed for each of the 3 kinematic descriptors separately in TFCC intact and sectioned conditions, with the independent variables of dorsal angulation deformity and forearm rotation angle. The effects of the TFCC condition on these kinematic descriptors were analyzed using a 3-way repeated measures analysis of variance with GreenhouseeGeisser correction for the independent variables of the TFCC condition, dorsal angulation deformity, and forearm rotation angle. Statistical significance was set at P < .050. RESULTS Volar displacement of the ulna Volar displacement of the ulna significantly increased with increasing dorsal angulation of the distal radius when the TFCC was intact (P < .001) (Fig. 4A). We found a significant increase in volar displacement r
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FIGURE 3: A distal radius coordinate system was established to describe the relationship between the ulna and radius at the DRUJ. This coordinate system was located at the center of the sigmoid notch of the radius. The volar axis was produced by the line, directed volarly, connecting 2 dimples on the radial side of the proximal component of the radial implant. The ulnar axis was produced by the line, directed ulnarly, connecting 2 dimples on the volar side of the proximal component. The proximal axis was produced by the crossproduct of these 2 axes, which guaranteed that the proximal axis was orthogonal to the volar and ulnar axes. The dimples on the implant were physically designed so that the volar and ulnar axes were orthogonal; however, to ensure orthogonality with mathematical precision, a second cross-product of the proximal and ulnar axes was made to produce a new volar axis. For each distal radial deformity, this coordinate system was mathematically transformed to remain located at the center of the sigmoid notch and parallel to its original (neutral) orientation. This was intended to mimic a clinical radiographic transverse-view plane slicing through the center of the distal radius and consistently perpendicular to the long axis.
at 30 dorsal angulation (1.2 0.8 mm; P ¼ .007), but not at 10 (0.5 0.5 mm; P ¼ .131) or 20 (0.5 0.6 mm; P ¼ .325), compared with the intact radius. Volar displacement was significantly larger with the forearm in supination (P ¼ .017). Sectioning of the TFCC significantly increased volar displacement of the ulna with dorsal angulation deformities (P ¼ .011). After sectioning the TFCC, we found a significant increase in volar displacement with dorsal angulation deformities of 10 (0.7 0.6 mm; P ¼ .049), 20 (1.0 0.8 mm; P ¼ .040), and 30 (2.7 0.7 mm; P < .001), compared with the intact radius (Fig. 4B). Forearm rotation angle had no significant effect on volar displacement with sectioned TFCC (P ¼ .084).
a significant increase in ulnar displacement at 20 of dorsal angulation (0.5 0.4 mm; P ¼ .043), but not at 10 (0.2 0.2 mm; P ¼ .202) or 30 (0.5 0.6 mm; P ¼ .151), compared with the intact radius. The TFCC condition had no significant effect on ulnar displacement with dorsal angulation deformities (P ¼ .084). After sectioning the TFCC, we found a significant increase in ulnar displacement with dorsal angulation deformities of 10 (0.3 0.2 mm; P ¼ .017), 20 (0.7 0.3 mm; P ¼ .001), and 30 (1.0 0.4 mm; P < .001), compared with the intact radius (Fig. 5B). Forearm rotation angle had no significant effect on ulnar displacement both in the TFCC intact (P ¼ .107) and sectioned (P ¼ .080) conditions.
Ulnar displacement of the ulna Ulnar displacement of the ulna significantly increased as the dorsal angulation of the distal radius increased with an intact TFCC (P ¼ .015) (Fig. 5A). We found
Distal displacement of the ulna Distal displacement of the ulna significantly increased with increasing dorsal angulation deformities in the intact TFCC (P < .001) (Fig. 6A). We found a
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FIGURE 4: Volar displacement of the ulna from the intact radius as a result of 10 (10DA), 20 (20DA), and 30 (30DA) of dorsal angulation deformities of the distal radius in the A intact and B sectioned TFCC at each forearm rotation angle. The abscissa represents the forearm rotation angle, and the ordinate represents the mean volar displacement of the ulna. The error bars indicate the standard deviation.
FIGURE 5: Ulnar displacement of the ulna from the intact radius as a result of 10 (10DA), 20 (20DA), and 30 (30DA) of dorsal angulation deformities of the distal radius in the A intact and B sectioned TFCC at each forearm rotation angle. The abscissa represents the forearm rotation angle, and the ordinate represents the mean ulnar displacement of the ulna. The error bars indicate the standard deviation.
DISCUSSION The current study confirmed that increasing dorsal angulation deformities of the distal radius significantly increased volar, ulnar, and distal displacement of the ulna both in TFCC intact and sectioned conditions. These findings are consistent with previous biomechanical studies that examined the changes of the DRUJ kinematics after distal radius fractures.15,17 Kihara et al17 showed that the alignment of the DRUJ worsened with increasing dorsal tilt of the distal radius. This was noticed especially with more than 20 of dorsal angulation from the original tilt. Adams15 reported that 15 of dorsally angulated distal radius produced 3.5 mm of shift in the axis of forearm rotation. In our study, statistically significant increases
significant increase in distal displacement with dorsal angulation deformities of 10 (0.5 0.4 mm; P ¼ .030), 20 (1.1 0.7 mm; P ¼ .006), and 30 (2.0 1.0 mm; P ¼ .002), compared with the intact radius. Distal displacement was significantly greater in supination (P < .001). There was no significant difference in distal displacement of the ulna between TFCC intact and sectioned conditions (P ¼ .242). After sectioning the TFCC, we found a significant increase in distal displacement with dorsal angulation deformities of 10 (0.4 0.3 mm; P ¼ .014), 20 (1.2 0.6 mm; P ¼ .002), and 30 (2.4 0.8 mm; P < .001), compared with the intact radius (Fig. 6B). Forearm rotation angle had no significant effect on distal displacement with sectioned TFCC (P ¼ .216). J Hand Surg Am.
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FIGURE 6: Distal displacement of the ulna from the intact radius as a result of 10 (10DA), 20 (20DA), and 30 (30DA) of dorsal angulation deformities of the distal radius in the A intact and B sectioned TFCC at each forearm rotation angle. The abscissa represents the forearm rotation angle, and the ordinate represents the mean distal displacement of the ulna. The error bars indicate the standard deviation.
compared with the intact radius were found with 10 or more of dorsal angulation in distal displacement of the ulna, 20 in ulnar displacement, and 30 in volar displacement when the TFCC was intact. This study showed that volar displacement of the ulna caused by dorsal angulation deformities was significantly larger with the sectioned TFCC rather than the intact TFCC. As little as 10 of dorsal angulation deformity increased volar, ulnar, and distal displacement of the ulna compared with the intact radius when the TFCC was sectioned. Because the TFCC connects the distal radius and ulna to stabilize the DRUJ,25e28 the intact TFCC restricts the displacement of the ulna with respect to the distal radius. Therefore, when the dorsal angulation deformities of the distal radius are created with an intact TFCC, the proximal radius shaft moves volarly with respect to the ulna to minimize the displacement at the distal end of the DRUJ while tension in the TFCC increases. Once the TFCC is sectioned, dorsal angulation deformities move the ulna more volarly with respect to the distal radius because the sectioned TFCC no longer restricts the displacement at the DRUJ. These findings are supported by the biomechanical study of Adams,15 which showed that 15 of dorsally angulated distal radius increased strains in the dorsal radioulnar ligament by 9%. Conversely, our results are contradictory to the findings of Kihara et al17 showing that sectioning of the TFCC did not cause a significant change in dorsal or volar displacement of the radius with respect to the ulna with dorsally angulated distal radius deformities. They analyzed the 2-dimensional changes of the DRUJ kinematics after dorsal angulation deformities of the distal radius in the transverse plane. Their J Hand Surg Am.
kinematic data were collected in the static position by weights applied to the biceps or pronator teres, whereas our study employed simulated active supination, which may produce more physiologic loading and motion. In addition, they simulated distal radius fractures using an external fixator, whereas we used an adjustable implant. These factors may explain the difference in the findings between the studies. A number of investigators have agreed that there is a close relationship between the magnitude of dorsal angulation and functional outcomes in younger patients.1,3,10e12 This may be partially explained by progressive changes in the DRUJ kinematics with increasing dorsal angulation demonstrated here. The altered kinematics could produce abnormal contact and loading patterns, which cause pain and degenerative changes at the DRUJ. Conversely, changes in the DRUJ kinematics may not affect the functional outcomes in elderly patients with low demands on the upper extremity. This study also showed that changes in the DRUJ kinematics caused by dorsal angulation deformities were larger in sectioned TFCC than those in intact TFCC. This emphasizes the clinical importance of evaluating the integrity of the TFCC as well as the magnitude of osseous deformities when managing acute or healed displaced fractures of the distal radius. We examined only simple dorsal angulation deformities because dorsal/volar tilt has been shown to be the most valid and reliable radiographic predictor of functional outcomes.1,10,12 However, dorsal angulation deformities are often combined with dorsal translation, radial translation or angulation, shortening, and rotation.13,20,29 Fraser et al19 demonstrated that combined deformities had a greater effect on forearm rotation than isolated malpositions. Combined r
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deformities may also affect the 3-dimensional kinematics of the DRUJ and should be assessed in future studies. We examined DRUJ kinematics during active supination and not pronation. We performed a pilot study for both active supination and pronation. The pilot study showed the same trends for both motions, but active pronation produced a smaller range of motion than active supination owing to the limitations of our testing simulator. Therefore, we decided to investigate only active supination. This study has limitations. First, we analyzed the DRUJ kinematics during active supination from 40 pronation to 60 supination because it was the maximum range of forearm rotation common to all specimens. The data at the maximum supination and pronation were not included, although some patients with distal radial deformities have symptoms at the maximum forearm rotation. We were unable to analyze this data statistically because of the variable magnitudes of rotation seen across different specimens. In addition, this study was performed in vitro, which had no potential for soft tissue adaptation. Moore et al16 showed that malunion did not alter the location or orientation of the prosupination rotation axes, by an in vivo analysis of the DRUJ kinematics in patients with malunion at an average of 10 months after injury. In their patients, soft tissues may have adapted to compensate for the radial deformities to restore the normal DRUJ kinematics, or the errors in the measurement technique may have prevented small differences in DRUJ kinematics from being quantified. However, our cadaveric study isolated and clarified the effect of dorsal angulation deformities on DRUJ kinematics, which is difficult to achieve in an in vivo study.
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