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Comparison of Distal Radioulnar Joint Reconstructions Using an Active Joint Motion Simulator
Comparison of Distal Radioulnar Joint Reconstructions Using an Active Joint Motion Simulator Wade T. Gofton, MD, Karen D. Gordon, PhD, Cynthia E. Dunning, PhD, James A. Johnson, PhD, Graham J. W. King, MD, London, Ontario, Canada
Purpose: Distal radioulnar joint (DRUJ) instability can result in pain and functional disability. Numerous DRUJ reconstructive options have been described with minimal biomechanical analysis. The purpose of this study was to evaluate the ability of 4 well-described DRUJ reconstructions to restore joint kinematics using a dynamic, motion-controlled simulator. Methods: Eleven cadaveric upper extremities had computer-controlled simulated active forearm rotation. Joint kinematics were quantified by using an electromagnetic tracking system. We compared the passive and simulated active kinematics of the intact, unstable, and reconstructed DRUJ (capsular repair, 2 described radioulnar ligament reconstructions, and a radioulnar tethering procedure). Results: All reconstructions improved significantly the kinematics of the unstable DRUJ. The capsule repair restored simulated active joint kinematics closest to the intact DRUJ. Conclusions: All 4 reconstructions improved DRUJ stability significantly. The capsule repair most closely matched intact DRUJ kinematics and the radioulnar ligament reconstructions were found to be superior to a radioulnar tethering procedure. (J Hand Surg 2005;30A:733–742. Copyright © 2005 by the American Society for Surgery of the Hand.) Key words: Active, kinematics, joint, distal radioulnar, reconstruction.
Distal radioulnar joint (DRUJ) instability may occur secondary to injuries or chronic inflammatory conditions and can lead to progressive ulnar-sided wrist pain and dysfunction. The large range of motion required of the DRUJ for normal forearm rotation is From the Bioengineering Laboratory, Hand and Upper Limb Centre, St. Joseph’s Health Centre, Department of Surgery and Biomedical Engineering, University of Western Ontario. Received for publication November 10, 2003; accepted in revised form December 13, 2004. No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article. Corresponding author: Graham J. W. King, MD, Hand and Upper Limb Centre, St. Joseph’s Health Care London, 268 Grosvenor St, London, Ontario, Canada N6A 4L6;[email protected]. Copyright © 2005 by the American Society for Surgery of the Hand 0363-5023/05/30A04-0014$30.00/0 doi:10.1016/j.jhsa.2004.12.008
facilitated by minimal bony constraint and a greater dependence on soft-tissue and dynamic muscle stabilizers. Many reconstructive treatment options1–14 have been described to treat the chronically unstable DRUJ. These procedures reflect the limited intrinsic stability of the DRUJ and the difficulty in replicating the complex ligamentous anatomy that normally stabilizes it. The DRUJ capsule,15 the dorsal and palmar radioulnar ligaments,16 –22 the triangular fibrocartilage (TFC),23,24 the extensor carpi ulnaris (ECU) subsheath,25 the ulnocarpal ligaments (UCLs),26 the interosseous membrane,27–29 and the bony anatomy22 all contribute to DRUJ stability. The relative importance of each structure for stability, however, remains controversial. Treatment options for the chronically unstable DRUJ The Journal of Hand Surgery
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can be classified into 4 main categories as outlined by Adams and Divelbiss30: (1) a direct radioulnar link extrinsic to the joint, (2) an indirect radioulnar link through an ulnocarpal sling or a tenodesis, (3) a dynamic muscle transfer, or (4) a reconstruction of the radioulnar ligaments. The direct and indirect radioulnar links have been criticized for failing to provide adequate stability while restricting forearm motion.4,14,30 –32 Muscle transfers have been criticized for restricting forearm rotation and having unreliable outcomes.30 Current biomechanical data confirming the importance of the dorsal and palmar radioulnar ligaments in maintaining DRUJ stability has resulted in several recently described anatomic radioulnar reconstructions.4,30 Although initial clinical success has been reported with these and other reconstructions, currently only a limited appraisal of the clinical results is available.11,14 Biomechanical comparisons of these reconstructions also are limited.32 The purpose of this study was to evaluate the ability of several well-described DRUJ reconstructions to restore joint stability using a dynamic, motion-controlled simulator.
Materials and Methods Cadaver Specimen Preparation Eleven fresh frozen cadaveric upper extremities were tested using a previously described forearm joint simulator33,34 (mean age, 72 ⫾ 13 y; range, 38 –90 y; 7 male specimens, 7 left specimens). The tendons of the biceps, triceps, extensor carpi radialis longus, ECU, flexor carpi radialis, flexor carpi ulnaris, supinator, pronator teres, and pronator quadratus were exposed and sutured to stainless steel cables as described previously.33 Tissue desiccation was minimized by irrigation of the soft tissue and closure of the skin to prevent dehydration. The humerus was secured in the clamp of the simulator and each of the muscle cables was attached to a dedicated actuator (Fig. 1). A bar supported the proximal forearm to maintain the elbow position at 90° of flexion at all times. Receivers from an electromagnetic tracking device (Flock of Birds; Ascension Technology, Burlington, VT) were attached rigidly to pedestals on the radius and ulna to record the 3-dimensional (6 – df) motion of the radius and ulna relative to a transmitter (ie, fixed with respect to the humerus). Data were collected simultaneously from the electromagnetic tracking device and a customized in-line load cell was attached to the prime mover actuator (ie, biceps tendon during supination or pronator teres tendon during pronation). At the completion of the testing
Figure 1. Active-motion DRUJ simulator showing the specimen mounted in a clamp, attachment of cables from their respective muscles to the alignment pulleys and pneumatic actuators, and the electromagnetic tracking system.
protocol the joints were dissected and bony landmarks on the ulna and radius were digitized to allow construction of 3-dimensional bone coordinate systems and the transformation of the kinematic data.35 These bony landmarks included the radial styloid and the dorsal and palmar margins of the sigmoid notch on the distal radius, which also were necessary to establish the 2-dimensional kinematic method (see Data Analysis section later).
Testing Procedure The joint simulator34 was used to achieve active forearm rotation (pronation and supination) in the intact forearm and unstable forearm and after each of 4 separate DRUJ reconstructions. Computer-directed pneumatic actuators used either motion- (ie, velocity)
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or load-controlled tendon loading to produce active forearm rotation. Pronation was achieved by displacing the pronator teres tendon (ie, pronation prime mover) at a constant velocity of 5 mm/s (motion controlled) while applying load simultaneously to the pronator quadratus (80% of pronator teres load) using a load-controlled actuator. Supination was achieved by applying a similar motion-controlled load to the biceps (ie, supination prime mover) and load control to the supinator (50% of biceps load). The triceps tendon also was loaded (mean, 63.1 N; range, 50 –75 N) to a specimen-specific constant level to prevent elbow flexion off the support bar, and specimen-specific constant loads were applied to the flexor carpi ulnaris and radialis (wrist flexors mean, 10.1 N; range, 0 –20 N) and ECU and extensor carpi radialis longus (wrist extensors mean, 28.1 N; range, 10 – 60 N) to balance the wrist in the neutral position during active forearm rotation. A single investigator (W.T.G.) instigated passive motion by manually rotating the forearm through the full arc of pronation and supination.
Surgical Procedure Testing (consisting of both simulated active and passive trials) was performed initially on the intact forearm and these results were used as reference data for the subsequent surgical procedures. After intact testing an unstable DRUJ was created through sectioning of soft-tissue stabilizers. The DRUJ was approached through the floor of the fifth extensor compartment and the dorsal capsule was divided, leaving a cuff for later repair. The dorsal radioulnar ligament and the dorsal half of the TFC, the ECU subsheath, and the UCL also were released through this approach. A palmar approach to the DRUJ allowed division of the palmar capsule (leaving a cuff for later repair), the palmar radioulnar ligament and the palmar half of the TFC, the pronator quadratus, and the proximal and distal interosseous membrane. Data collection was repeated after sectioning and each reconstruction. Four separate reconstruction procedures were performed and tested in sequence (capsule repair, Adams36 reconstruction, modified Fulkerson-Watson reconstruction,37 Bowers4 reconstruction). The first consisted of a simple repair of the dorsal and palmar capsule using interrupted figure-of-eight sutures (no. 1 Ethibond; Ethicon, Cornelia, GA) to reapproximate the capsule (Fig. 2A). The other 3 reconstructions required tendon grafts. The flexor digitorum profundus tendons of the middle and ring fingers were used to provide donor tendons. Tendon fixation was achieved using custom-
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designed tendon clamps (Figs. 2B–D) to allow for multiple secure reconstructions. These clamps were found to be more effective in pilot studies than sutures, which often failed during kinematic testing. The clamps allowed the assessment of reconstruction kinematics rather than the strength of the early suture repair. The second reconstruction was modified from a technique described by Adams36 (Fig. 2B). An anteroposterior drill hole was created parallel and just radial to the sigmoid notch. A second drill hole was placed starting in the fovea at the base of the ulnar styloid and exiting proximal and medial on the ulnar shaft. The tendon was passed through the drill hole in the radius and both limbs then were passed through the ulnar drill hole at the base of the styloid, tensioned, and clamped on the medial ulna. This differs slightly from the original description, in which the repair was tensioned at the base of the ulnar styloid with a tendon clamp rather than tensioned after a circumferential pass around the ulnar shaft. This modification was required to allow the tendon clamp to achieve secure initial fixation for kinematic testing. The third reconstruction was a modified Fulkerson-Watson reconstruction37 (Fig. 2C). The tendon clamp anchored 1 limb of the tendon to the palmar aspect of the drill hole on the radius. The exiting limb on the dorsal side passed back to the palmar side of the wrist through the interosseous space, wrapped around the ulnar shaft to the dorsal side, and passed once again through the interosseous space to the palmar side in a figure-of-eight fashion. This limb passed through the drill hole on the radius and was tensioned and fixed on the dorsal radius with a second tendon clamp. This differs from the original technique in that a circumferential tendon does not pass around the ulna. This portion of the reconstruction was eliminated because biomechanical studies have shown that although figure-of-eight reconstructions improve stability simple loops can increase instability.32 The fourth reconstruction was a modification of the procedure described by Bowers4 (Fig. 2D). This reconstruction was described originally with an option to repair the UCLs by using a split from the palmar strand but this was not modeled in the current study. A drill hole was placed in the palmar portion of the sigmoid notch, meeting the previously drilled anteroposterior drill hole. A similar hole was placed in the dorsal portion of the sigmoid notch at the normal attachment of the dorsal marginal ligament, meeting the dorsal portion of the anteroposterior drill
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Figure 2. The DRUJ reconstructions. (A) Dorsal view of sectioned capsule and repair (with soft tissues shown). (B) Dorsal and axial views of Adams36 reconstruction with tendon graft and clamps (without soft tissues shown). (C) Dorsal and axial views of modified Fulkerson-Watson reconstruction with tendon graft and clamps (without soft tissues shown). (D) Dorsal and axial views of Bowers4 reconstruction with tendon graft and clamps (without soft tissues shown).
hole. One tendon limb was fixed to the palmar surface of the radius with a tendon clamp. The other limb passed through the radius anteroposterior drill hole, exiting the drill hole in the palmar portion of
the sigmoid notch. This limb crossed the ulnar head and was passed distal to proximal through the ulnar fovea drill hole, wrapped around the ulnar shaft, and passed once again through the ulnar drill hole prox-
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Figure 3. Schematic of variables used to quantify kinematics. A, palmar margin of sigmoid notch; B, dorsal margin of sigmoid notch; C, ulnar center; D, intersection of line AB with a perpendicular drawn from C; E, radial styloid.
imal to distal. This limb then passed through the dorsal sigmoid drill hole, exiting on the dorsal aspect of the radius where it was tensioned and fixed into position with a second tendon clamp.
Data Analysis The kinematic data were evaluated with a planar analysis to quantify DRUJ kinematics described previously.33 Traditional forearm kinematics also were calculated but are not reported here because we believe that the 2-dimensional analysis offers a clearer picture of the movement of the radius and ulna at the joint level. The plane of analysis (a transverse plane through the DRUJ) was defined using a customwritten, best-fit algorithm of the path of the distal tips of the dorsal and palmar margins of the sigmoid notch on the radius through 5 intact pronation and supination trials. An ulnar center was defined by the intersection of the average screw displacement axis with this plane. The average screw displacement axis was derived from 5 intact supination trials and was used subsequently as the ulnar center for all supination trials. A similar procedure was followed for pronation because the position of the average screw displacement axis varies slightly for supination and pronation.33 The distal radial styloid (Fig. 3, point E) and the palmar (Fig. 3, point A) and dorsal (Fig. 3, point B) radial points then were projected onto the plane of analysis through the joint. Three kinematic variables subsequently were calculated using these 4 points (Fig. 3). The first of these descriptors was the radioulnar ratio (RUR),38 a measure of the dorsal and
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palmar translations of the radius relative to the ulna. This ratio varies between 0.2 and 0.7 for normal DRUJ kinematics,38 with values near 0 signifying a dorsal translation of the radius relative to the ulna and values near 1 signifying palmar translation. The second descriptor was the dorsal-palmar angle (DPA or ␣) defined between the radius and ulna (Fig. 3, lines CF and DE), with positive values corresponding to palmar tilt of the radius and negative values corresponding to dorsal tilt. The third variable measured was radioulnar distance (RUD), or the perpendicular distance from the ulnar center to the line defined by the dorsal and palmar radial points. This variable was defined as negative for radioulnar convergence, or specifically when point D (in Fig. 3) migrated further medial than point C (in Fig. 3) (ulnar center). The RUD was defined as positive for diastasis values. These variables were calculated for the entire range of forearm rotation (pronation and supination), the angle of which was obtained through a fixed-axis angle analysis.
Statistical Analysis The RUD, DPA, and RUR were compared for all reconstructions at 5 angles of forearm rotation by using 1- and 2-way repeated measures analysis of variance with post hoc Student-Newman-Keuls tests (␣ was set to .05.)
Results Simulated Active Results The resection of the DRUJ stabilizers (dorsal and palmar capsule, dorsal and palmar radioulnar ligaments, TFC, ECU, UCL, pronator quadratus, and the interosseous membrane) produced significant changes in the RUD, DPA, and RUR. There was a significantly lower RUD (increase in radius and ulnar convergence) with active pronation (p ⬍ .01). During active supination significant increases in RUR (palmar translation of the radius, p ⬍ .01) and DPA (palmar tilt of the radius, p ⬍ .05) with a concomitant decrease in RUD (p ⬍ .05) were measured. Alterations in DRUJ kinematics generated by disruption of the soft-tissue stabilizers improved significantly after all soft-tissue reconstructions (Fig. 4). In most cases (exceptions are noted later) the kinematics after each reconstruction were not different from intact kinematics (p ⬎ .05), suggesting that the reconstruction procedures restored the altered kinematics seen in the unstable joint to those seen in the intact forearm. The capsule repair yielded significant improve-
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Figure 4. (A) Average RUR (n ⫽ 11). (B) Average DPA (n ⫽ 11). (C) Average RUD (n ⫽ 11). All are shown for active pronation (A/Pro) and supination (A/Sup) and passive pronation (P/Pro) and supination (P/Sup). Surgical stages include the intact forearm (Intact), a capsular repair (Capsule), Adams36 reconstruction (Adams), a modified Fulkerson-Watson (FW), a Bowers4 reconstruction (Bowers), and the completely sectioned forearm (unstable).
ment in kinematics (p ⬍ .05) compared with the unstable DRUJ and no significant differences (p ⬎ .05) from intact kinematics in any position. When
compared with the other reconstructions no significant differences in kinematics were observed. The reconstructions described by Adams36 and
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Bowers4 showed similar kinematics. In most positions significant improvements from unstable kinematics were observed. With simulated active supination, RUR and DPA for the reconstructions by both Adams36 and Bowers4 did not differ significantly (p ⬎ .05) from unstable values in pronation. In full pronation both reconstructions showed an increased RUR (palmar translation of the radius) and DPA (palmar tilt of the radius). This significant increase in RUR normalized by midpronation for the reconstruction described by Bowers4 and by the neutral-position reconstruction described by Adams36 and the increased DPA normalized by the neutral position for both reconstructions. With simulated active pronation the Adams36 reconstruction showed significant improvement from unstable kinematics in all positions (p ⬎ .05). The Bowers4 reconstruction, however, did not differ significantly from unstable RUD kinematics in the positions of full pronation and midpronation with a decrease in RUD relative to intact kinematics. The modified Fulkerson-Watson37 reconstruction also was unable to improve unstable simulated active supination kinematics in the pronated positions with increased RUR and DPA values significantly (p ⬍ .05). Although RUR kinematics normalized by the neutral position, unlike the radioulnar ligament reconstructions the DPA kinematics failed to normalize, showing an increased palmar tilt through the entire arc of motion.
Passive Results Significant differences between surgical procedures were seen during passive pronation only. When the forearm was positioned in midpronation and full pronation the modified Fulkerson-Watson technique generated lower RUR and DPA compared with the intact Adams36 and Bowers4 repairs (p ⬍ .05). When the forearm was positioned in full supination the unstable DRUJ displayed higher RUR and DPA compared with the intact forearm and all other reconstructions (p ⬍ .05).
Discussion All DRUJ reconstructions tested significantly improved simulated active DRUJ kinematics. The capsule reconstruction matched most closely the simulated active intact DRUJ kinematics, restoring the RUR, the RUD, and the DPA to normal ranges in all positions of simulated active or passive motion. The reconstructions described by Adams36 and Bowers4 showed similar kinematics, restoring the kinematics
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to the normal range in most positions of simulated active or passive motion. The modified FulkersonWatson37 reconstruction also stabilized the DRUJ but was not as effective at restoring kinematics with active supination and passive pronation. Distal radioulnar joint instability may be the result of an acute injury or a chronic degenerative process. After an acute injury the identification of DRUJ instability is essential to prevent further instability and dysfunction. Dorsal dislocation of the ulna often can be reduced with supination and palmar dislocation with pronation of the forearm.28,39,40 If the joint can be maintained congruently reduced in a long-arm cast or with radioulnar pinning for 6 weeks then ligament healing usually is sufficient to restore function.40 If a congruent reduction cannot be obtained and maintained then an open reduction is required. In association with a surgical reduction the repair of the TFC and associated radioulnar ligaments have been advocated.4,41 Until recently the role of the capsule as an additional DRUJ stabilizer has been underappreciated. Recent work shows the stabilizing effect of the capsule in the setting of an incompetent TFC.15,21 Our findings confirm that significant restoration of DRUJ kinematics can be achieved with a capsular repair alone. When compared with the intact state no significant differences between the intact DRUJ and that after capsular repair were evident in any position of active or passive rotation. These findings show that the capsule can provide significant support to the DRUJ and we would recommend a minimum of an acute capsule repair if a surgical approach is indicated. Capsular attenuation also may play a role in chronic instability. Therefore, with any reconstructive procedure for chronic instability care should be taken to preserve the remaining joint capsule; capsular imbrication or augmentation should be considered in an effort to support the underlying reconstruction. The DRUJ capsule, similar to the underlying radioulnar ligaments, is not a static structure during rotation and overtensioning may result in a limitation of rotation. The optimal tensioning and position of repair to ensure maximal rotation is beyond the scope of this study and requires further evaluation. In the setting of chronic instability, there usually is significant attenuation and/or loss of the local softtissue stabilizers such as the radioulnar ligaments, TFC, and DRUJ capsule. In the absence of forearm malunion, DRUJ incongruity, or significant DRUJ arthritis, soft-tissue reconstruction is a reasonable option for DRUJ stabilization in the symptomatic
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patient. Options as outlined by Adams and Divelbliss30 include (1) a direct radioulnar link extrinsic to the joint, (2) an indirect radioulnar link through an ulnocarpal sling or a tenodesis, (3) dynamic muscle transfer, or (4) reconstruction of the radioulnar ligaments. The Fulkerson-Watson reconstruction represents a direct radioulnar link, which has been criticized for failing to provide adequate stability and restricting forearm motion.30 –32 Previous biomechanical testing32 showed that the Fulkerson-Watson reconstruction improved static load stability; however, it failed to restore normal joint stability completely. The figure-of-eight–type construct was found to be important in restoring stability whereas the direct radioulnar links with simple loop reconstructions were found actually to increase instability relative to the unstable DRUJ.32 Our modification of the FulkersonWatson reconstruction37 preserved the figure-ofeight construct but removed the simple loop. With simulated active supination when the arm was in the pronated position, we found that stability was not improved relative to the unstable DRUJ and that the joint experienced increasing palmar tilt and translation of the radius relative to the ulna. With passive pronation the radius was translated significantly and tilted in a dorsal direction compared with the intact forearm. Significant differences in passive pronation kinematics also were observed between this reconstruction and the radioulnar reconstructions and capsule repair. In full to midpronation increased dorsal translation and tilt of the radius to the ulna were observed whereas increased palmar translation and tilt were observed in the fully supinated position when compared with the other reconstructions. Indirect radioulnar links through an ulnocarpal sling or tenodesis are ineffective.32 Muscle transfers have been criticized similarly for difficulty in optimizing the position of advancement and unreliable outcomes.30 These reconstruction methods were not studied in the current investigation. Several reconstructions of the distal radioulnar ligaments have been proposed recently. The advantage of these constructs is that theoretically the intraarticular reconstruction better duplicates the normal anatomy of the TFC complex. Scheker et al11 described a single intra-articular radioulnar ligament reconstruction to reconstruct either the dorsal or palmar ligament. It passed between the fovea and either the dorsal or palmar lip of the sigmoid notch, depending on the ligament reconstructed. All of their 15 patients seen in follow-up evaluations were satis-
fied, assumedly were stable, had improved grip strength, and had maintained their preoperative range except for an average 8° loss in supination. The reconstruction of both radioulnar ligaments could be accomplished only through an extensive dorsal and palmar incision. Bowers4 described a reconstruction recreating both the dorsal and palmar radioulnar ligaments with an option to reinforce the UCLs. This reconstruction also requires a dorsal and palmar approach and uses the rim of the sigmoid notch. He reported good clinical outcomes4 but, intuitively, joint kinematics must be altered as the size of the sigmoid notch is decreased because of placement of the graft through the dorsal and palmar articular margins. The Adams36 reconstruction is slightly more anatomic, inserting on the dorsal and palmar margins of the radius adjacent to the sigmoid notch and preserving the articular surface. In a review of clinical outcomes in 14 patients, Adams and Berger14 found it to be an effective treatment for radioulnar instability. Clinical stability was restored in 12 of 14 patients and the range of motion was at least 80% of the unaffected wrist. A more recent clinical review also showed restoration of radioulnar stability in 9 of 13 patients at the follow-up examination an average of 6 months later. Although there may be theoretical advantages of one over the other no significant kinematic differences between the Bowers4 reconstruction and the Adams36 reconstruction were observed in the current study. Both restored intact kinematics in the majority of positions although both resulted in greater deviations from normal kinematics in the pronated positions. This is consistent with findings in the static model28 and supports the concept of DRUJ rehabilitation in the supinated position. Both reconstructions resulted in increased palmar translation and palmar tilt of the radius in early simulated active supination. This normalized by midpronation for the Bowers4 reconstruction and the neutral position for the Adams36 reconstruction. The Bowers4 reconstruction also led to a decreased RUD in the pronated position during simulated active pronation. No significant differences between the radioulnar reconstructions or between the radioulnar reconstructions and capsular repair were observed. This study has limitations, as is the case in any in vitro study. Only a limited number of reconstructions could be performed in a single specimen to allow for a repeated-measures experimental design. Because the order of the reconstructions was not randomized
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for technical reasons there may have been a bias toward better results with the earlier reconstructions because of the known risk of desiccation and attenuation of soft-tissue stabilizers. The results of the later reconstructions in some instances, however, were superior to those performed earlier, suggesting that timing was not a critical issue in the current investigation. This 2-dimensional analysis is unable to identify changes in relative radioulnar height; however, these changes would be expected to be minimal with a preserved proximal radioulnar joint. The current study evaluated only the ability of the reconstructions to restore the kinematics of the intact DRUJ when subjected to passive and simulated active motion. The strength of the reconstructions and their performance against resisted rotation were not evaluated in the current investigation. Strengths of this study included using a novel biomechanical technique to better simulate in vivo forearm rotation with the incorporation of a motion-controlled simulator. A rigid clamping system was used to ensure that all tendon reconstructions remained secure throughout testing. In addition the hand, wrist, and surrounding anatomy of the DRUJ were retained. We found that after the disruption of all important forearm stabilizers DRUJ kinematics can be restored through a number of soft-tissue reconstructive procedures. The capsule repair was found to restore intact kinematics in all positions of passive and simulated active rotation. When surgical intervention is indicated for acute instability then the capsule should be considered for primary repair. In chronic instability in which capsule and ligament attenuation is often an issue, the capsule should be preserved in addition to performing a ligament reconstruction. A direct radioulnar link such as a Fulkerson-Watson–type reconstruction37 significantly improved kinematics but failed to reproduce normal kinematics in all forearm positions. The radioulnar ligament reconstructions better approximated intact kinematics and, considering recently published favorable short-term clinical results, should be considered in the setting of symptomatic DRUJ instability.
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The Journal of Hand Surgery / Vol. 30A No. 4 July 2005 ometry and stability of the distal radio ulnar joint. Scand J Plast Reconstr Surg 1985;19:17–25. Spinner M, Kaplan EB. Extensor carpi ulnaris. Its relationship to the stability of the distal radio-ulnar joint. Clin Orthop 1970;68:124 –129. Milch H. So-called dislocation of the lower end of the ulna. Ann Surg 1942;116:272–292. 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. King GJ, McMurtry RY, Rubenstein JD, Ogston NG. Computerized tomography of the distal radioulnar joint: correlation with ligamentous pathology in a cadaveric model. J Hand Surg 1986;11A:711–717. Pfaeffle HJ, Fischer KJ, Manson TT, Tomaino MM, Woo SL-Y, Herndon JH. Role of the forearm interosseous ligament: is it more than just longitudinal load transfer? J Hand Surg 2000;25A:683– 688. Adams BD, Divelbiss BJ. Reconstruction of the posttraumatic unstable distal radioulnar joint. Orthop Clin North Am 2001;32:353–363. Bowers WH. Instability of the distal radioulnar articulation. Hand Clin 1991;7:311–327. Petersen MS, Adams BD. Biomechanical evaluation of distal radioulnar reconstructions. J Hand Surg 1993;18A:327–334.
33. Gordon KD, Dunning CE, Johnson JA, King GJW. Influence of pronator quadratus and supinator muscle load on DRUJ stability. J Hand Surg 2003;28A:943–950. 34. Dunning CE, King GJW, Gordon KD, Johnson JA. Development of a motion-controlled in-vitro elbow testing system. J Orthop Res 2003;21:405– 411. 35. Johnson JA, Rath DA, Dunning CE, Roth SE, King GJW. Simulation of elbow and forearm motion in vitro using a load controlled testing apparatus. J Biomech 2000;33:635– 639. 36. Adams BD. Anatomic reconstruction of the distal radioulnar ligaments for DRUJ instability. Tech Upper Extremity Surg 2000;4:154 –160. 37. Fulkerson JP, Watson HK. Congenital anterior subluxation of the distal ulna: a case report. Clin Orthop 1978;131:179 – 182. 38. Lo IKY, MacDermid JC, Bennett JD, Bogoch E, King GJW. The radioulnar ratio: a new method of quantifying distal radioulnar joint subluxation. J Hand Surg 2001;26A:236 – 243. 39. Aulicino PL, Siegel JL. Acute injuries of the distal radioulnar joint. Hand Clin 1991;7:273–293. 40. Chidgey LK. Treatment of acute and chronic instability of the distal radio-ulnar joint. Hand Clin 1998;14:297–303. 41. Nicolaidis SC, Hildreth DH, Lichtman DM. Acute injuries of the distal radioulnar joint. Hand Clin 2000;16:449 – 459.
Purpose: Distal radioulnar joint (DRUJ) instability can result in pain and functional disability. Numerous DRUJ reconstructive options have been described with minimal biomechanical analysis. The purpose of this study was to evaluate the ability of 4 well-described DRUJ reconstructions to restore joint kinematics using a dynamic, motion-controlled simulator. Methods: Eleven cadaveric upper extremities had computer-controlled simulated active forearm rotation. Joint kinematics were quantified by using an electromagnetic tracking system. We compared the passive and simulated active kinematics of the intact, unstable, and reconstructed DRUJ (capsular repair, 2 described radioulnar ligament reconstructions, and a radioulnar tethering procedure). Results: All reconstructions improved significantly the kinematics of the unstable DRUJ. The capsule repair restored simulated active joint kinematics closest to the intact DRUJ. Conclusions: All 4 reconstructions improved DRUJ stability significantly. The capsule repair most closely matched intact DRUJ kinematics and the radioulnar ligament reconstructions were found to be superior to a radioulnar tethering procedure. (J Hand Surg 2005;30A:733–742. Copyright © 2005 by the American Society for Surgery of the Hand.) Key words: Active, kinematics, joint, distal radioulnar, reconstruction.
Distal radioulnar joint (DRUJ) instability may occur secondary to injuries or chronic inflammatory conditions and can lead to progressive ulnar-sided wrist pain and dysfunction. The large range of motion required of the DRUJ for normal forearm rotation is From the Bioengineering Laboratory, Hand and Upper Limb Centre, St. Joseph’s Health Centre, Department of Surgery and Biomedical Engineering, University of Western Ontario. Received for publication November 10, 2003; accepted in revised form December 13, 2004. No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article. Corresponding author: Graham J. W. King, MD, Hand and Upper Limb Centre, St. Joseph’s Health Care London, 268 Grosvenor St, London, Ontario, Canada N6A 4L6;[email protected]. Copyright © 2005 by the American Society for Surgery of the Hand 0363-5023/05/30A04-0014$30.00/0 doi:10.1016/j.jhsa.2004.12.008
facilitated by minimal bony constraint and a greater dependence on soft-tissue and dynamic muscle stabilizers. Many reconstructive treatment options1–14 have been described to treat the chronically unstable DRUJ. These procedures reflect the limited intrinsic stability of the DRUJ and the difficulty in replicating the complex ligamentous anatomy that normally stabilizes it. The DRUJ capsule,15 the dorsal and palmar radioulnar ligaments,16 –22 the triangular fibrocartilage (TFC),23,24 the extensor carpi ulnaris (ECU) subsheath,25 the ulnocarpal ligaments (UCLs),26 the interosseous membrane,27–29 and the bony anatomy22 all contribute to DRUJ stability. The relative importance of each structure for stability, however, remains controversial. Treatment options for the chronically unstable DRUJ The Journal of Hand Surgery
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can be classified into 4 main categories as outlined by Adams and Divelbiss30: (1) a direct radioulnar link extrinsic to the joint, (2) an indirect radioulnar link through an ulnocarpal sling or a tenodesis, (3) a dynamic muscle transfer, or (4) a reconstruction of the radioulnar ligaments. The direct and indirect radioulnar links have been criticized for failing to provide adequate stability while restricting forearm motion.4,14,30 –32 Muscle transfers have been criticized for restricting forearm rotation and having unreliable outcomes.30 Current biomechanical data confirming the importance of the dorsal and palmar radioulnar ligaments in maintaining DRUJ stability has resulted in several recently described anatomic radioulnar reconstructions.4,30 Although initial clinical success has been reported with these and other reconstructions, currently only a limited appraisal of the clinical results is available.11,14 Biomechanical comparisons of these reconstructions also are limited.32 The purpose of this study was to evaluate the ability of several well-described DRUJ reconstructions to restore joint stability using a dynamic, motion-controlled simulator.
Materials and Methods Cadaver Specimen Preparation Eleven fresh frozen cadaveric upper extremities were tested using a previously described forearm joint simulator33,34 (mean age, 72 ⫾ 13 y; range, 38 –90 y; 7 male specimens, 7 left specimens). The tendons of the biceps, triceps, extensor carpi radialis longus, ECU, flexor carpi radialis, flexor carpi ulnaris, supinator, pronator teres, and pronator quadratus were exposed and sutured to stainless steel cables as described previously.33 Tissue desiccation was minimized by irrigation of the soft tissue and closure of the skin to prevent dehydration. The humerus was secured in the clamp of the simulator and each of the muscle cables was attached to a dedicated actuator (Fig. 1). A bar supported the proximal forearm to maintain the elbow position at 90° of flexion at all times. Receivers from an electromagnetic tracking device (Flock of Birds; Ascension Technology, Burlington, VT) were attached rigidly to pedestals on the radius and ulna to record the 3-dimensional (6 – df) motion of the radius and ulna relative to a transmitter (ie, fixed with respect to the humerus). Data were collected simultaneously from the electromagnetic tracking device and a customized in-line load cell was attached to the prime mover actuator (ie, biceps tendon during supination or pronator teres tendon during pronation). At the completion of the testing
Figure 1. Active-motion DRUJ simulator showing the specimen mounted in a clamp, attachment of cables from their respective muscles to the alignment pulleys and pneumatic actuators, and the electromagnetic tracking system.
protocol the joints were dissected and bony landmarks on the ulna and radius were digitized to allow construction of 3-dimensional bone coordinate systems and the transformation of the kinematic data.35 These bony landmarks included the radial styloid and the dorsal and palmar margins of the sigmoid notch on the distal radius, which also were necessary to establish the 2-dimensional kinematic method (see Data Analysis section later).
Testing Procedure The joint simulator34 was used to achieve active forearm rotation (pronation and supination) in the intact forearm and unstable forearm and after each of 4 separate DRUJ reconstructions. Computer-directed pneumatic actuators used either motion- (ie, velocity)
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or load-controlled tendon loading to produce active forearm rotation. Pronation was achieved by displacing the pronator teres tendon (ie, pronation prime mover) at a constant velocity of 5 mm/s (motion controlled) while applying load simultaneously to the pronator quadratus (80% of pronator teres load) using a load-controlled actuator. Supination was achieved by applying a similar motion-controlled load to the biceps (ie, supination prime mover) and load control to the supinator (50% of biceps load). The triceps tendon also was loaded (mean, 63.1 N; range, 50 –75 N) to a specimen-specific constant level to prevent elbow flexion off the support bar, and specimen-specific constant loads were applied to the flexor carpi ulnaris and radialis (wrist flexors mean, 10.1 N; range, 0 –20 N) and ECU and extensor carpi radialis longus (wrist extensors mean, 28.1 N; range, 10 – 60 N) to balance the wrist in the neutral position during active forearm rotation. A single investigator (W.T.G.) instigated passive motion by manually rotating the forearm through the full arc of pronation and supination.
Surgical Procedure Testing (consisting of both simulated active and passive trials) was performed initially on the intact forearm and these results were used as reference data for the subsequent surgical procedures. After intact testing an unstable DRUJ was created through sectioning of soft-tissue stabilizers. The DRUJ was approached through the floor of the fifth extensor compartment and the dorsal capsule was divided, leaving a cuff for later repair. The dorsal radioulnar ligament and the dorsal half of the TFC, the ECU subsheath, and the UCL also were released through this approach. A palmar approach to the DRUJ allowed division of the palmar capsule (leaving a cuff for later repair), the palmar radioulnar ligament and the palmar half of the TFC, the pronator quadratus, and the proximal and distal interosseous membrane. Data collection was repeated after sectioning and each reconstruction. Four separate reconstruction procedures were performed and tested in sequence (capsule repair, Adams36 reconstruction, modified Fulkerson-Watson reconstruction,37 Bowers4 reconstruction). The first consisted of a simple repair of the dorsal and palmar capsule using interrupted figure-of-eight sutures (no. 1 Ethibond; Ethicon, Cornelia, GA) to reapproximate the capsule (Fig. 2A). The other 3 reconstructions required tendon grafts. The flexor digitorum profundus tendons of the middle and ring fingers were used to provide donor tendons. Tendon fixation was achieved using custom-
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designed tendon clamps (Figs. 2B–D) to allow for multiple secure reconstructions. These clamps were found to be more effective in pilot studies than sutures, which often failed during kinematic testing. The clamps allowed the assessment of reconstruction kinematics rather than the strength of the early suture repair. The second reconstruction was modified from a technique described by Adams36 (Fig. 2B). An anteroposterior drill hole was created parallel and just radial to the sigmoid notch. A second drill hole was placed starting in the fovea at the base of the ulnar styloid and exiting proximal and medial on the ulnar shaft. The tendon was passed through the drill hole in the radius and both limbs then were passed through the ulnar drill hole at the base of the styloid, tensioned, and clamped on the medial ulna. This differs slightly from the original description, in which the repair was tensioned at the base of the ulnar styloid with a tendon clamp rather than tensioned after a circumferential pass around the ulnar shaft. This modification was required to allow the tendon clamp to achieve secure initial fixation for kinematic testing. The third reconstruction was a modified Fulkerson-Watson reconstruction37 (Fig. 2C). The tendon clamp anchored 1 limb of the tendon to the palmar aspect of the drill hole on the radius. The exiting limb on the dorsal side passed back to the palmar side of the wrist through the interosseous space, wrapped around the ulnar shaft to the dorsal side, and passed once again through the interosseous space to the palmar side in a figure-of-eight fashion. This limb passed through the drill hole on the radius and was tensioned and fixed on the dorsal radius with a second tendon clamp. This differs from the original technique in that a circumferential tendon does not pass around the ulna. This portion of the reconstruction was eliminated because biomechanical studies have shown that although figure-of-eight reconstructions improve stability simple loops can increase instability.32 The fourth reconstruction was a modification of the procedure described by Bowers4 (Fig. 2D). This reconstruction was described originally with an option to repair the UCLs by using a split from the palmar strand but this was not modeled in the current study. A drill hole was placed in the palmar portion of the sigmoid notch, meeting the previously drilled anteroposterior drill hole. A similar hole was placed in the dorsal portion of the sigmoid notch at the normal attachment of the dorsal marginal ligament, meeting the dorsal portion of the anteroposterior drill
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Figure 2. The DRUJ reconstructions. (A) Dorsal view of sectioned capsule and repair (with soft tissues shown). (B) Dorsal and axial views of Adams36 reconstruction with tendon graft and clamps (without soft tissues shown). (C) Dorsal and axial views of modified Fulkerson-Watson reconstruction with tendon graft and clamps (without soft tissues shown). (D) Dorsal and axial views of Bowers4 reconstruction with tendon graft and clamps (without soft tissues shown).
hole. One tendon limb was fixed to the palmar surface of the radius with a tendon clamp. The other limb passed through the radius anteroposterior drill hole, exiting the drill hole in the palmar portion of
the sigmoid notch. This limb crossed the ulnar head and was passed distal to proximal through the ulnar fovea drill hole, wrapped around the ulnar shaft, and passed once again through the ulnar drill hole prox-
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Figure 3. Schematic of variables used to quantify kinematics. A, palmar margin of sigmoid notch; B, dorsal margin of sigmoid notch; C, ulnar center; D, intersection of line AB with a perpendicular drawn from C; E, radial styloid.
imal to distal. This limb then passed through the dorsal sigmoid drill hole, exiting on the dorsal aspect of the radius where it was tensioned and fixed into position with a second tendon clamp.
Data Analysis The kinematic data were evaluated with a planar analysis to quantify DRUJ kinematics described previously.33 Traditional forearm kinematics also were calculated but are not reported here because we believe that the 2-dimensional analysis offers a clearer picture of the movement of the radius and ulna at the joint level. The plane of analysis (a transverse plane through the DRUJ) was defined using a customwritten, best-fit algorithm of the path of the distal tips of the dorsal and palmar margins of the sigmoid notch on the radius through 5 intact pronation and supination trials. An ulnar center was defined by the intersection of the average screw displacement axis with this plane. The average screw displacement axis was derived from 5 intact supination trials and was used subsequently as the ulnar center for all supination trials. A similar procedure was followed for pronation because the position of the average screw displacement axis varies slightly for supination and pronation.33 The distal radial styloid (Fig. 3, point E) and the palmar (Fig. 3, point A) and dorsal (Fig. 3, point B) radial points then were projected onto the plane of analysis through the joint. Three kinematic variables subsequently were calculated using these 4 points (Fig. 3). The first of these descriptors was the radioulnar ratio (RUR),38 a measure of the dorsal and
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palmar translations of the radius relative to the ulna. This ratio varies between 0.2 and 0.7 for normal DRUJ kinematics,38 with values near 0 signifying a dorsal translation of the radius relative to the ulna and values near 1 signifying palmar translation. The second descriptor was the dorsal-palmar angle (DPA or ␣) defined between the radius and ulna (Fig. 3, lines CF and DE), with positive values corresponding to palmar tilt of the radius and negative values corresponding to dorsal tilt. The third variable measured was radioulnar distance (RUD), or the perpendicular distance from the ulnar center to the line defined by the dorsal and palmar radial points. This variable was defined as negative for radioulnar convergence, or specifically when point D (in Fig. 3) migrated further medial than point C (in Fig. 3) (ulnar center). The RUD was defined as positive for diastasis values. These variables were calculated for the entire range of forearm rotation (pronation and supination), the angle of which was obtained through a fixed-axis angle analysis.
Statistical Analysis The RUD, DPA, and RUR were compared for all reconstructions at 5 angles of forearm rotation by using 1- and 2-way repeated measures analysis of variance with post hoc Student-Newman-Keuls tests (␣ was set to .05.)
Results Simulated Active Results The resection of the DRUJ stabilizers (dorsal and palmar capsule, dorsal and palmar radioulnar ligaments, TFC, ECU, UCL, pronator quadratus, and the interosseous membrane) produced significant changes in the RUD, DPA, and RUR. There was a significantly lower RUD (increase in radius and ulnar convergence) with active pronation (p ⬍ .01). During active supination significant increases in RUR (palmar translation of the radius, p ⬍ .01) and DPA (palmar tilt of the radius, p ⬍ .05) with a concomitant decrease in RUD (p ⬍ .05) were measured. Alterations in DRUJ kinematics generated by disruption of the soft-tissue stabilizers improved significantly after all soft-tissue reconstructions (Fig. 4). In most cases (exceptions are noted later) the kinematics after each reconstruction were not different from intact kinematics (p ⬎ .05), suggesting that the reconstruction procedures restored the altered kinematics seen in the unstable joint to those seen in the intact forearm. The capsule repair yielded significant improve-
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Figure 4. (A) Average RUR (n ⫽ 11). (B) Average DPA (n ⫽ 11). (C) Average RUD (n ⫽ 11). All are shown for active pronation (A/Pro) and supination (A/Sup) and passive pronation (P/Pro) and supination (P/Sup). Surgical stages include the intact forearm (Intact), a capsular repair (Capsule), Adams36 reconstruction (Adams), a modified Fulkerson-Watson (FW), a Bowers4 reconstruction (Bowers), and the completely sectioned forearm (unstable).
ment in kinematics (p ⬍ .05) compared with the unstable DRUJ and no significant differences (p ⬎ .05) from intact kinematics in any position. When
compared with the other reconstructions no significant differences in kinematics were observed. The reconstructions described by Adams36 and
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Bowers4 showed similar kinematics. In most positions significant improvements from unstable kinematics were observed. With simulated active supination, RUR and DPA for the reconstructions by both Adams36 and Bowers4 did not differ significantly (p ⬎ .05) from unstable values in pronation. In full pronation both reconstructions showed an increased RUR (palmar translation of the radius) and DPA (palmar tilt of the radius). This significant increase in RUR normalized by midpronation for the reconstruction described by Bowers4 and by the neutral-position reconstruction described by Adams36 and the increased DPA normalized by the neutral position for both reconstructions. With simulated active pronation the Adams36 reconstruction showed significant improvement from unstable kinematics in all positions (p ⬎ .05). The Bowers4 reconstruction, however, did not differ significantly from unstable RUD kinematics in the positions of full pronation and midpronation with a decrease in RUD relative to intact kinematics. The modified Fulkerson-Watson37 reconstruction also was unable to improve unstable simulated active supination kinematics in the pronated positions with increased RUR and DPA values significantly (p ⬍ .05). Although RUR kinematics normalized by the neutral position, unlike the radioulnar ligament reconstructions the DPA kinematics failed to normalize, showing an increased palmar tilt through the entire arc of motion.
Passive Results Significant differences between surgical procedures were seen during passive pronation only. When the forearm was positioned in midpronation and full pronation the modified Fulkerson-Watson technique generated lower RUR and DPA compared with the intact Adams36 and Bowers4 repairs (p ⬍ .05). When the forearm was positioned in full supination the unstable DRUJ displayed higher RUR and DPA compared with the intact forearm and all other reconstructions (p ⬍ .05).
Discussion All DRUJ reconstructions tested significantly improved simulated active DRUJ kinematics. The capsule reconstruction matched most closely the simulated active intact DRUJ kinematics, restoring the RUR, the RUD, and the DPA to normal ranges in all positions of simulated active or passive motion. The reconstructions described by Adams36 and Bowers4 showed similar kinematics, restoring the kinematics
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to the normal range in most positions of simulated active or passive motion. The modified FulkersonWatson37 reconstruction also stabilized the DRUJ but was not as effective at restoring kinematics with active supination and passive pronation. Distal radioulnar joint instability may be the result of an acute injury or a chronic degenerative process. After an acute injury the identification of DRUJ instability is essential to prevent further instability and dysfunction. Dorsal dislocation of the ulna often can be reduced with supination and palmar dislocation with pronation of the forearm.28,39,40 If the joint can be maintained congruently reduced in a long-arm cast or with radioulnar pinning for 6 weeks then ligament healing usually is sufficient to restore function.40 If a congruent reduction cannot be obtained and maintained then an open reduction is required. In association with a surgical reduction the repair of the TFC and associated radioulnar ligaments have been advocated.4,41 Until recently the role of the capsule as an additional DRUJ stabilizer has been underappreciated. Recent work shows the stabilizing effect of the capsule in the setting of an incompetent TFC.15,21 Our findings confirm that significant restoration of DRUJ kinematics can be achieved with a capsular repair alone. When compared with the intact state no significant differences between the intact DRUJ and that after capsular repair were evident in any position of active or passive rotation. These findings show that the capsule can provide significant support to the DRUJ and we would recommend a minimum of an acute capsule repair if a surgical approach is indicated. Capsular attenuation also may play a role in chronic instability. Therefore, with any reconstructive procedure for chronic instability care should be taken to preserve the remaining joint capsule; capsular imbrication or augmentation should be considered in an effort to support the underlying reconstruction. The DRUJ capsule, similar to the underlying radioulnar ligaments, is not a static structure during rotation and overtensioning may result in a limitation of rotation. The optimal tensioning and position of repair to ensure maximal rotation is beyond the scope of this study and requires further evaluation. In the setting of chronic instability, there usually is significant attenuation and/or loss of the local softtissue stabilizers such as the radioulnar ligaments, TFC, and DRUJ capsule. In the absence of forearm malunion, DRUJ incongruity, or significant DRUJ arthritis, soft-tissue reconstruction is a reasonable option for DRUJ stabilization in the symptomatic
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patient. Options as outlined by Adams and Divelbliss30 include (1) a direct radioulnar link extrinsic to the joint, (2) an indirect radioulnar link through an ulnocarpal sling or a tenodesis, (3) dynamic muscle transfer, or (4) reconstruction of the radioulnar ligaments. The Fulkerson-Watson reconstruction represents a direct radioulnar link, which has been criticized for failing to provide adequate stability and restricting forearm motion.30 –32 Previous biomechanical testing32 showed that the Fulkerson-Watson reconstruction improved static load stability; however, it failed to restore normal joint stability completely. The figure-of-eight–type construct was found to be important in restoring stability whereas the direct radioulnar links with simple loop reconstructions were found actually to increase instability relative to the unstable DRUJ.32 Our modification of the FulkersonWatson reconstruction37 preserved the figure-ofeight construct but removed the simple loop. With simulated active supination when the arm was in the pronated position, we found that stability was not improved relative to the unstable DRUJ and that the joint experienced increasing palmar tilt and translation of the radius relative to the ulna. With passive pronation the radius was translated significantly and tilted in a dorsal direction compared with the intact forearm. Significant differences in passive pronation kinematics also were observed between this reconstruction and the radioulnar reconstructions and capsule repair. In full to midpronation increased dorsal translation and tilt of the radius to the ulna were observed whereas increased palmar translation and tilt were observed in the fully supinated position when compared with the other reconstructions. Indirect radioulnar links through an ulnocarpal sling or tenodesis are ineffective.32 Muscle transfers have been criticized similarly for difficulty in optimizing the position of advancement and unreliable outcomes.30 These reconstruction methods were not studied in the current investigation. Several reconstructions of the distal radioulnar ligaments have been proposed recently. The advantage of these constructs is that theoretically the intraarticular reconstruction better duplicates the normal anatomy of the TFC complex. Scheker et al11 described a single intra-articular radioulnar ligament reconstruction to reconstruct either the dorsal or palmar ligament. It passed between the fovea and either the dorsal or palmar lip of the sigmoid notch, depending on the ligament reconstructed. All of their 15 patients seen in follow-up evaluations were satis-
fied, assumedly were stable, had improved grip strength, and had maintained their preoperative range except for an average 8° loss in supination. The reconstruction of both radioulnar ligaments could be accomplished only through an extensive dorsal and palmar incision. Bowers4 described a reconstruction recreating both the dorsal and palmar radioulnar ligaments with an option to reinforce the UCLs. This reconstruction also requires a dorsal and palmar approach and uses the rim of the sigmoid notch. He reported good clinical outcomes4 but, intuitively, joint kinematics must be altered as the size of the sigmoid notch is decreased because of placement of the graft through the dorsal and palmar articular margins. The Adams36 reconstruction is slightly more anatomic, inserting on the dorsal and palmar margins of the radius adjacent to the sigmoid notch and preserving the articular surface. In a review of clinical outcomes in 14 patients, Adams and Berger14 found it to be an effective treatment for radioulnar instability. Clinical stability was restored in 12 of 14 patients and the range of motion was at least 80% of the unaffected wrist. A more recent clinical review also showed restoration of radioulnar stability in 9 of 13 patients at the follow-up examination an average of 6 months later. Although there may be theoretical advantages of one over the other no significant kinematic differences between the Bowers4 reconstruction and the Adams36 reconstruction were observed in the current study. Both restored intact kinematics in the majority of positions although both resulted in greater deviations from normal kinematics in the pronated positions. This is consistent with findings in the static model28 and supports the concept of DRUJ rehabilitation in the supinated position. Both reconstructions resulted in increased palmar translation and palmar tilt of the radius in early simulated active supination. This normalized by midpronation for the Bowers4 reconstruction and the neutral position for the Adams36 reconstruction. The Bowers4 reconstruction also led to a decreased RUD in the pronated position during simulated active pronation. No significant differences between the radioulnar reconstructions or between the radioulnar reconstructions and capsular repair were observed. This study has limitations, as is the case in any in vitro study. Only a limited number of reconstructions could be performed in a single specimen to allow for a repeated-measures experimental design. Because the order of the reconstructions was not randomized
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for technical reasons there may have been a bias toward better results with the earlier reconstructions because of the known risk of desiccation and attenuation of soft-tissue stabilizers. The results of the later reconstructions in some instances, however, were superior to those performed earlier, suggesting that timing was not a critical issue in the current investigation. This 2-dimensional analysis is unable to identify changes in relative radioulnar height; however, these changes would be expected to be minimal with a preserved proximal radioulnar joint. The current study evaluated only the ability of the reconstructions to restore the kinematics of the intact DRUJ when subjected to passive and simulated active motion. The strength of the reconstructions and their performance against resisted rotation were not evaluated in the current investigation. Strengths of this study included using a novel biomechanical technique to better simulate in vivo forearm rotation with the incorporation of a motion-controlled simulator. A rigid clamping system was used to ensure that all tendon reconstructions remained secure throughout testing. In addition the hand, wrist, and surrounding anatomy of the DRUJ were retained. We found that after the disruption of all important forearm stabilizers DRUJ kinematics can be restored through a number of soft-tissue reconstructive procedures. The capsule repair was found to restore intact kinematics in all positions of passive and simulated active rotation. When surgical intervention is indicated for acute instability then the capsule should be considered for primary repair. In chronic instability in which capsule and ligament attenuation is often an issue, the capsule should be preserved in addition to performing a ligament reconstruction. A direct radioulnar link such as a Fulkerson-Watson–type reconstruction37 significantly improved kinematics but failed to reproduce normal kinematics in all forearm positions. The radioulnar ligament reconstructions better approximated intact kinematics and, considering recently published favorable short-term clinical results, should be considered in the setting of symptomatic DRUJ instability.
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