HAND SURGERY
Volar Stabilization of the Distal Radioulnar Joint for Chronic Instability Using the Pronator Quadratus Sang Ki Lee, MD, Jae Won Lee, MD, and Won Sik Choy, MD Abstract: In cases of chronic distal radioulnar joint (DRUJ) instability without DRUJ arthritis, reconstruction of the mechanical integrity of the radioulnar ligaments of the triangular fibrocartilage complex has been considered an ideal surgical treatment. However, reconstructive methods have several disadvantages. We evaluated volar stabilization of the DRUJ for chronic instability using the pronator quadratus (PQ) to determine whether it provided (1) proper stability, (2) restored wrist function, (3) was relatively convenient, and (4) was associated with a low complication rate. Altogether, 21 patients with chronic DRUJ instability (12 men, 9 women) with a mean age of 34 years (range, 17–65 years) were enrolled in the study. The diagnostic criteria were as follows: 3 months after the injury, greater than 8 mm of palmar-dorsal translation of the ulna relative to the radius, there was a lack of clear end point resistance compared with the contralateral side, and nonstressed computed tomographic scans provided supporting evidence. Follow-up was at least 12 months (range, 12–38 months). Palmar-dorsal translation of the ulna relative to the radius was decreased significantly from 10 to 4 mm (P = 0.028) and epicenter was increased significantly at the last follow-up [P = 0.015/0.026 (70 degrees of supination/neutral, respectively)]. Wrist range of motion was not significantly different, but grip strength had increased from 72% to 91%. Disabilities of the arm, shoulder, and hand and patient-rated wrist evaluation were also decreased compared with preoperative measurements [34.4 to 12.5/42.7 to 14.7 (disabilities of the arm, shoulder, and hand/patient-rated wrist evaluation, respectively)]. Pronator quadratus advancement volar stabilization provided proper stability, restored wrist function, was relatively convenient, and was associated with few complications. Our experience indicates that it is an acceptable, effective treatment option to reverse DRUJ instability in patients who did not have advanced DRUJ arthritis. Key Words: distal radioulnar joint, chronic instability, pronator quadratus (Ann Plast Surg 2016;76: 394–398)
D
isorders of the distal radioulnar joint (DRUJ), which are relatively common, may result from a developmental condition, trauma, or degenerative arthritis.1 The incidence of significant DRUJ injury is unknown.2 Stability of the DRUJ is provided by a bony architecture and soft tissues such as the triangular fibrocartilage complex (TFCC), the joint capsule, and surrounding muscles.3 Forearm and wrist function can be severely affected by a dysfunctional DRUJ. Even with its importance, surgeons tend to underestimate DRUJ function when making clinical assessments. The common reason for this underestimation is that it is difficult to assess DRUJ instability using plain radiography. Clinical examinations such as pain, wrist and forearm ROM, the piano key sign, and the shuck test are helpful but also have limitations in terms of providing an objective assessment of DRUJ function,4,5 and different variables to different examiners if Received March 24, 2014, and accepted for publication, after revision, August 17, 2014. From the Department of Orthopedic Surgery, Eulji University College of Medicine, Daejeon, South Korea. Conflicts of interest and sources of funding: none declared. Reprints: Sang Ki Lee, MD, Department of Orthopedic Surgery, Eulji University College of Medicine, 1306 Dunsan-dong, Seo-gu, Daejeon 302-799, South Korea. E-mail: [email protected]. Copyright © 2014 Wolters Kluwer Health, Inc. All rights reserved. ISSN: 0148-7043/16/7604–0394 DOI: 10.1097/SAP.0000000000000354
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ligamentous instability were assessed. In addition, it is easy to miss the diagnosis when DRUJ instability accompanies a fracture of wrist area (distal radius fracture, distal both forearm bone fracture, ulnar styloid base fracture) because of the pain associated with the fracture. If acute injuries are not diagnosed or treated properly, the problem may become chronic. Chronic DRUJ instability often results in substantial pain and disability, such as decreased grip strength, limited mobility, and mechanical symptoms (clicking or snapping with rotational movement of the forearm). This condition has been addressed surgically with numerous types of ligament reconstruction6–12 and salvage procedures, including the Darrach procedure,13 the Bowers hemiresection-interposition arthroplasty,14 the Suave-Kapandji procedures,15 the ulnar head replacement,16 and the hemiarthroplasty.17 Among these surgical options, a salvage procedure is indicated for DRUJ instability in patients with advanced DRUJ arthritis. In cases of chronic DRUJ instability without DRUJ arthritis, reconstruction of the mechanical integrity of the radioulnar ligaments of the TFCC has been considered ideal surgical treatment when primary repair of the TFCC is not feasible.1 These methods usually reconstruct an extrinsic or intrinsic ligament by passing harvested tendon through a drill hole. Several studies have reported successful results with those methods.18,19 Reconstructive methods have several disadvantages: They sacrifice normal soft tissue except using plantaris tendon allograft; cannot be applied to pediatric patients; the drill hole widens as time goes on (Fig. 1); and multiple incisions are required. Volar stabilization using pronator quadratus (PQ)20 could be an alternative surgical option to circumvent these problems. The PQ, a dynamic stabilizer of the DRUJ, is a strong muscle that makes the radius and ulna converge, particularly during a power grip.21 The PQ normally attaches to both the distal radius and ulna. The means of volar stabilization using PQ, the PQ is tightened by its normal origin point on the distal ulna was moved to a more medial and posterior origin (Fig. 2). The treatments using PQ were introduced as follows: salvage procedure22 or biomechanical effect on DRUJ stability as dynamic stabilizer.22,23 However, some advantages of using this treatment method include preservation of normal soft tissue, its application to pediatric patients (open physis), its small incision, and its relative convenience. Importantly,it also leaves room for another surgical treatment if it fails to achieve stability. We, therefore, assessed whether PQ advancement volar stabilization for chronic instability of the DRUJ could provide (1) proper stability, (2) restore wrist function, (3) be relatively convenient, and (4) produce a low complication rate.
MATERIALS AND METHODS Study Design This prospective study was performed from January 2009 to June 2012. A total of 27 patients were diagnosed with chronic DRUJ instability. The institutional review board approved this study, and all patients treated with the procedures during the study period were available for review. The diagnostic criteria were that it had been 3 months after the injury, there was greater than 8 mm of palmar-dorsal translation of the ulna relative to the radius,24 and/or there was a lack of clear end point resistance compared with the contralateral side.1 The physical Annals of Plastic Surgery • Volume 76, Number 4, April 2016
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Annals of Plastic Surgery • Volume 76, Number 4, April 2016
Volar Stabilization of DRUJ
TABLE 1. Demographic Data
FIGURE 1. A 25-year-old man was diagnosed as having DRUJ instability combined with a distal radius fracture 4 months after injury. He underwent reconstructive surgery. Anteroposterior plain radiography of his wrist at a 3-year postoperative follow-up visit revealed that drill holes in the radius (black arrow) and ulna (white arrows) were widening.
examination was the primary determinant of instability, nonstressed CT scans provided supporting evidence (grading by epicenter method25). Among those diagnosed as patients with chronic DRUJ who complained pain or discomfort with normal daily activities, the inclusion criteria for study enrollment were (1) chronic DRUJ instability without advanced DRUJ arthritis and (2) a history of unsuccessful conservative therapy (immobilization supination or neutral position for 6 weeks and physiotherapy in the form of strengthening the dynamic stabilizers). The exclusion criteria included (1) chronic DRUJ instability with advanced DRUJ arthritis and/or (2) ulnar impaction syndrome. On the basis of these criteria, 3 patients with advanced DRUJ arthritis and 3 with ulnar impaction syndrome were excluded. Therefore, 21 patients (12 men, 9 women) with a mean age of 34 years (range, 17–65 years) were enrolled in the study. The clinical pathway and randomization process were explained and obtained permission from the patients. The follow-up period was a minimum of 12 months (range, 12–38 months; average, 21 months) for all 21 patients (Table 1).
Surgical Technique The procedure, performed under tourniquet control, was done with the patient in a supine position on a radiolucent operating table. The elbow was flexed to 90 degrees. A longitudinal incision was made 1 fingerbreadth from the base of the ulnar styloid about 5 cm proximally along the ulnar border. The dorsal branch of the ulnar nerve was protected throughout the procedure. The ulnar neurovascular bundle was retracted, and the space immediately adjacent to the ulnar border of the PQ was identified. The periosteum of the ulnar aspect of the ulna
Variables
Patients
Total (n) Sex (M/F) Age, y Dominant side (n) Cause Distal radius fracture Radius diaphysis fracture Galeazzi fracture/dislocation Ulnar styloid base fracture TFCC injury Height, cm Weight, kg
21 12/9 34.2 (15) 14 10 3 2 4 2 168.7 (9) 64 (11)
Values are mean (SD).
was then incised, separating both the periosteum and the origin of the PQ using a periosteal elevator. It is important to include the fullthickness of the periosteum because it assists in suturing it to the distal ulna. Three or four paired holes are drilled into the ulna with 1.6-mm Kirschner wire (K-wire) in an anteroposterior direction along the more medial and posterior ulnar border separated by the periosteum and origin of the PQ for tying up the periosteum and the origin of the PQ. In the maximum supination state, the periosteum and origin of the PQ were tied using 2.0 Prolene passed through the paired drill hole. Next, the DRUJ was transfixed with 1.6-mm K-wire in wrist supination (Fig. 3). The wound was closed layer by layer. For postoperative rehabilitation, active finger motion was encouraged 1 day postoperatively. Patients were immobilized in a supinated sugar-tong splint for 4 weeks postoperatively and discontinued entirely. The K-wire was generally removed 4 weeks after surgery. Passive and active wrist ROM exercises were initiated. Strengthening exercises and stressful activities were delayed until near-painless motion was recovered.
Patient Assessment The results were assessed on the basis of achieving proper stability (palmar-dorsal translation of the ulna relative to the radius, anatomical relation of the ulna and radius during wrist rotation), restoration of day life wrist function—wrist ROM, the disabilities of the arm, shoulder, and hand (DASH),26 patient-rated wrist evaluation (PRWE),27 grip strength—operating time, and complications. The anatomical relation of the ulna and radius during wrist rotation was analyzed using nonstressed CT with the epicenter method25 (Fig. 4). Computed tomographic (CT) scans were obtained using 3-dimensional CT (Siemens, Forchheim, Germany). Both injured and contralateral wrists were
FIGURE 2. Schema for volar stabilization of the DRUJ for chronic instability using the PQ. Pronator quadratus is tighten by (A) its normal origin point on the distal ulna was moved to (B) a more medial and posterior origin. © 2014 Wolters Kluwer Health, Inc. All rights reserved.
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FIGURE 3. Procedures for volar stabilization of the DRUJ for chronic instability using the PQ. A, The periosteum of the ulnar aspect of the ulna was incised, separating both the periosteum and the origin of the PQ. Separating the full-thickness periosteum and the origin of the PQ was important because it assists when suturing them to the distal ulna. B, Three or four paired holes are drilled into the ulna along the more medial and posterior portions of ulnar border separating the periosteum and origin of the PQ. Then, 2.0 Prolene was passed through the paired drill hole. Periosteum and the origin of the PQ were tied up in a maximum supination state. C, DRUJ was transfixed with 1.6-mm K-wire in wrist supination.
scanned at 0.6-mm intervals in 3 positions—70 degrees of supination, neutral position, and 70 degrees of pronation—using a customdesigned positioning device (Fig. 5). Wrist ROM (extension, flexion, supination, and pronation) was measured using a goniometer. The DASH is a 30-item self-report questionnaire designed to evaluate the function and symptoms of the upper limb regardless of surgical site. Answers to questions about daily activities were scored from 0 (no impairment) to 100 (maximum impairment). The PRWE is a 15-item questionnaire used to assess wrist pain (5 items) and function (10 items: 6 for specific activities and 4 for usual activities). Each score ranges from 0 (no pain or difficulty during activity) to 100 (severe pain or being dysfunctional). Grip strength was measured using a JAMAR hand dynamometer (Therapeutic Equipment Corporation, Clayton, NJ). In accordance with the guidelines for the use of the JAMAR dynamometer, issued by the American Society for Surgery of the Hand, the second grip handle was used for all patients.28 The successive trials were used on both injured and uninjured hands. The results were recorded as a percentage of the unaffected side, as recommended by the American Society of
Hand Therapist. Grip strengths were adjusted by 10% for the nondominant hand for analysis. Each patient was assessed 3 times (preoperatively, at 6 months postoperatively, and at the last follow-up). Patients were questioned about the existence of complications throughout the follow-up period. To reduce measurement errors, all measurements were obtained twice by each author and average values calculated. Intraobserver reliability was considered the criteria of Winer (degree of bias and mean squared error).29 Reliability was classified, according to the intraclass correlation coefficient, as absent to poor (0–0.24), low (0.25–0.49), fair to moderate (0.50–0.69), good (0.70–0.89), or excellent (0.90–1.0). We achieved an interobserver reliability of 0.93. There were no missing data.
Statistical Analysis The differences between preoperative and postoperative values were analyzed using the Wilcoxon signed rank test for palmar-dorsal translation, anatomical relation, wrist ROM, DASH, PRWE, and grip strength. Significance was set at P < 0.05. We used SPSS version 20.0 software (IBM, Armonk, NY) for statistical analyses.
RESULTS The PQ advancement volar stabilization for chronic instability of the DRUJ provided proper stability. Palmar-dorsal translation of the ulna relative to the radius and epicenter (70 degrees of supination,
FIGURE 4. Epicenter method. A perpendicular line was drawn from the halfway point between the centers of the ulnar and the ulnar styloid to the sigmoid notch. The distance between this line and the midpoint of the sigmoid notch was measured (C-D), and the ratio of this distance to the length of the sigmoid notch (A-B) was calculated. 396
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FIGURE 5. Custom-designed positioning device. In prone position, the patient grips the goniometer handle. The forearm is fixed with a strap. Patient rotates the wrist to the targeted angle. © 2014 Wolters Kluwer Health, Inc. All rights reserved.
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Annals of Plastic Surgery • Volume 76, Number 4, April 2016
Volar Stabilization of DRUJ
TABLE 2. Outcome Measures for Stability Measurement
P/D translation, mm Epicenter 70-degree supination Neutral 70-degree pronation
Uninjured Wrist
4 (3–5) 0.10 (−0.06 to 0.19) 0.07 (−0.14 to 0.23) −0.01 (−0.19 to 0.24)
Preoperative
6 mo F/U
10 (9–12)
5 (4–6)
0.00 (−0.46 to 0.21) −0.01 (−0.49 to 0.33) −0.01 (−0.26 to 0.20)
P
Last F/U
4 (3–6)
0.09 (−0.05 to 0.20) 0.07 (−0.20 to 0.27) −0.01 (−0.23 to 0.22)
0.028*
0.10 (−0.05 to 0.18) 0.07 (−0.15 to 0.23) −0.01 (−0.20 to 0.23)
0.015* 0.026* 0.823
Values are mean (range) * Statistically significant F/U indicates follow-up; P/D, palmar-dorsal.
neutral) were decreased significantly at the last follow-up compared with the preoperative measurement [P = 0.028, 0.015/0.026 (70 degrees of supination/neutral, respectively)] (Table 2). Patients who underwent PQ advancement volar stabilization had restoration of acceptable wrist functions. At the last follow-up, wrist ROM was not significantly different, but grip strength had increased (P = 0.047). In addition, DASH and PRWE decreased (P = 0.037 and P = 0.027, respectively) compared with the preoperative measurements (Table 3). No intraoperative or postoperative complications were observed. No patients reported recurrent DRUJ instability, and no arthritic changes during follow-up period plain radiography or 24 months follow-up magnetic resonance images.
DISCUSSION Disorders of the DRUJ of diverse etiologies are relatively common.1 Forearm and wrist function can be severely affected by dysfunction of the DRUJ. Ideal management of DRUJ instability is controversial. If an acute injury to the DRUJ is not diagnosed or treated properly, it can become a chronic problem. Reconstruction of the mechanical integrity of the radioulnar ligaments6–11 was considered surgical treatment of chronic DRUJ instability if DRUJ arthritis was not present. Because current reconstructive treatment methods have several disadvantages, we suggest PQ advancement volar stabilization as an alternative surgical option. In the current study, we analyzed whether PQ advancement volar stabilization for chronic instability of the DRUJ could (1) provide proper stability, (2) restore wrist function, (3) be relatively convenient, and (4) produce a low complication rate. Several prior studies of ligament reconstruction of the DRUJ demonstrate stability in almost all patients18,19,30–34; however, stability was evaluated by physical examination and not quantified. Evaluation methods included the anteroposterior stress test performed at last follow-up and radiographic improvement of joint widening. In our study, we evaluated stability by physical examination and quantified it on nonstressed CT scans. Physical examination is an important diagnostic method but is limited by possible measurement errors by the tester. Computed tomographic scanning measuring the palmar-dorsal translation of the ulna and epicenter makes the evaluation more objective. These results demonstrated adequate stability in our series. We also achieved proper stability in the rotational state by performing volar side stabilization alone because we obtained satisfactory stability based on both neutral and 70 degrees of supination and pronation stability tests. Restoration of wrist function was evaluated by wrist ROM, functional scores (DASH, PRWE), and grip strength. The results of wrist ROM in previous studies indicated that ROM was not restricted following surgery but there was limited supination,32 no statistically significant difference between the preoperative and postoperative ROM,33 and no improvement in postoperative ROM.19 In this study, wrist © 2014 Wolters Kluwer Health, Inc. All rights reserved.
ROM was not significantly different after surgery either. The reason is that patients with chronic DRUJ instability and without advanced DRUJ arthritis were enrolled in our study, so almost all patients had normal wrist ROM. Other studies18,19,32,33 and ours have reported satisfactory results in regard to the functional score and grip strength. The tissues required for reconstructive surgery are usually harvested from the flexor carpi ulnaris tendon,8,9 extensor carpi ulnaris tendon,34 combined extensor carpi ulnaris/flexor carpi ulnaris tenodesis,35 or palmaris longus tendon.6 When harvesting tendon, it is necessary to remove adequate length and width for the reconstruction. Also, sufficient stability may not be achieved without determining the proper location of the hole through which to pass the harvested tendon. In contrast, PQ advancement volar stabilization is a 1-step procedure that simply medializes the origin of the PQ. It can reduce the number of practical errors during surgery and achieve steady outcomes with a smooth learning curve. Because of these conveniences, the average operating time in this study was a short 37 minutes. We performed only soft tissue procedures for bony alignment correction, and there were no DRUJ arthritic changes. In addition, there was no persistent or recurrent instability. However, if it had failed to achieve stability, these other avenues of surgical treatment remained viable options because normal tissues were preserved. If the ligament reconstruction of the DRUJ would fail to recover stability, soft tissue procedures would have difficulty in solving DRUJ instability. Thus, in a previous study, sigmoid notch osteotomy for persistent instability was performed.36 There were additional strengths of this method. First, it can be applied to pediatric patients. It is a soft tissue procedure that preserves normal tissue, so we could achieve proper stability and good outcomes without damaging a still-open physis (Fig. 6). Second, it could be done
TABLE 3. Outcome Measures for Wrist Functions Measurement
Preoperative
6-mo Follow-up
Last Follow-up
Wrist ROM, degree Flexion 66 (50–80) 68 (58–81) 72 (60–85) Extension 58 (48–75) 60 (50–75) 69 (65–80) Supination 75 (60–90) 78 (60–87) 82 (65–90) Pronation 70 (45–80) 72 (54–80) 77 (55–85) DASH 34.4 (5.8–56.7) 17.3 (0–54) 12.5 (0–52) PRWE 42.7 (5–79.5) 18.4 (0–60) 14.7 (0–58) Grip strength, % 72 (64–81) 86 (70–92) 91 (87–94)
P
0.210 0.058 0.178 0.089 0.037* 0.027* 0.047*
Values are mean (range). * Statistically significant.
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FIGURE 6. A, Postoperative anteroposterior wrist plain radiography of a 17-year-old male patient. The physis was still open. B, After 10 months of follow-up, the physis was still intact, with no physial arrest or arthritic changes.
with a small incision because it is a 1-step procedure. Third, we could initiate ROM exercises after 4 weeks postoperatively. It reduced the risk of ROM limitation, and patients had an early return to daily activity. This study has some limitations. First, although the study was designed as a prospective project, it was based on a single cohort so there was no control group for comparison such as group of patients with K-wire fixation alone. As ligamentous reconstructive surgery has been common, we referenced results of other studies for comparison data. Second, this series was relatively small. It was done in a single center, and we diagnosed only 27 chronic DRUJ instabilities during 3.5 years, selecting 21 patients after addressing inclusion and exclusion criteria. Thus, its size could be a cause of selection bias. However, no patients were lost to follow-up. We analyzed all enrolled patients and were therefore able to obtain precise, practical results. Third, our mean follow-up period was only 21 months. Early results for all patients were relatively good, but we could not analyze the long-term results. Although the early results are promising, longer-term monitoring and larger study populations are required to verify the presented data. The DRUJ instability remains a challenge. Instability may be treated with various remedies, although its ideal management is controversial. According to the results of this study, PQ advancement volar stabilization provides proper stability, restores wrist function, is relatively convenient, and is associated with a low complication rate. Our experience suggests that PQ advancement volar stabilization is an acceptable, effective treatment option for correcting DRUJ instability in patients who do not have advanced DRUJ arthritis. REFERENCES 1. Murray PM, Adams JE, Lam J, et al. Disorders of the distal radioulnar joint. Instr Course Lect. 2010;59:295–311. 2. Argintar E, Mantovani G, Pavan A. TFCC reattachment after traumatic DRUJ instability: a simple alternative to arthroscopic management. Tech Hand Up Extrem Surg. 2010;14:226–229. 3. af Ekenstam F, Hagert CG. Anatomical studies on the geometry and stability of the distal radio ulnar joint. Scand J Plast Reconstr Surg. 1985;19:17–25. 4. May MM, Lawton JN, Blazar PE. Ulnar styloid fractures associated with distal radius fractures: incidence and implications for distal radioulnar joint instability. J Hand Surg Am. 2002;27:965–971. 5. Szabo RM. Distal radioulnar joint instability. J Bone Joint Surg Am. 2006;88: 884–894. 6. Adams BD, Divelbiss BJ. Reconstruction of the posttraumatic unstable distal radioulnar joint. Orthop Clin North Am. 2001; 32:353–363,x.
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7. Fulkerson JP, Watson HK. Congenital anterior subluxation of the distal ulna. A case report. Clin Orthop Relat Res. 1978;131:179–182. 8. Hui FC, Linscheid RL. Ulnotriquetral augmentation tenodesis: a reconstructive procedure for dorsal subluxation of the distal radioulnar joint. J Hand Surg Am. 1982;7:230–236. 9. Petersen MS, Adams BD. Biomechanical evaluation of distal radioulnar reconstructions. J Hand Surg Am. 1993;18:328–334. 10. Scheker LR, Belliappa PP, Acosta R, et al. Reconstruction of the dorsal ligament of the triangular fibrocartilage complex. J Hand Surg Br. 1994;19:310–318. 11. Tsai TM, Stilwell JH. Repair of chronic subluxation of the distal radioulnar joint (ulnar dorsal) using flexor carpi ulnaris tendon. J Hand Surg Br. 1984;9:289–294. 12. Johnston Jones K, Sanders WE. Posttraumatic radioulnar instability: treatment by anatomic reconstruction of the volar and dorsal radioulnar ligaments. Orthop Trans. 1995–1996;19:832. 13. Bieber EJ, Linscheid RL, Dobyns JH, et al. Failed distal ulna resections. J Hand Surg [Am]. 1988;13:193–200. 14. Bowers WH. Distal radioulnar joint arthroplasty: the hemiresection-interposition technique. J Hand Surg [Am]. 1985;10:169–178. 15. Slater RR Jr, Szabo RM. The Sauve-Kapandji procedure. Tech Hand Up Extrem Surg. 1998;2:148–157. 16. Sauerbier M, Arsalan-Werner A, Enderle E, et al. Ulnar head replacement and related biomechanics. J Wrist Surg. 2013;2:27–32. 17. Sauder DJ, King GJ. Hemiarthroplasty of the distal ulna with an eccentric prosthesis. Tech Hand Up Extrem Surg. 2007;11:115–120. 18. Adams BD, Berger RA. An anatomic reconstruction of the distal radioulnar ligaments for posttraumatic distal radioulnar joint instability. J Hand Surg Am. 2002; 27:243–251. 19. Purisa H, Sezer I, Kabakas F, et al. Ligament reconstruction using the FulkersonWatson method to treat chronic isolated distal radioulnar joint instability: shortterm results. Acta Orthop Traumatol Turc. 2011;45:168–174. 20. Johnson RK. Stabilization of the distal ulna by transfer of the pronator quadrates origin. Clin Orthop Relat Res. 1992;275:130–132. 21. Bain GI, Heptinstall RJ, Webb JM, et al. Hemiresection of the distal ulna by means of pronator quadratus interposition and volar stabilization. Tech Hand Up Extrem Surg. 2007;11:83–86. 22. Gofton WT, Gordon KD, Dunning CE, et al. Soft-tissue stabilizers of the distal radioulnar joint: an in vitro kinematic study. J Hand Surg Am. 2004;29:423–431. 23. Gordon KD, Dunning CE, Johnson JA, et al. Influence of the pronator quadratus and supinator muscle load on DRUJ stability. J Hand Surg Am. 2003;28:943–950. 24. Haugstvedt JR, Berger RA, Berglund LJ, et al. An analysis of the constraint properties of the distal radioulnar ligament attachments to the ulna. J Hand Surg Am. 2002;27:61–67. 25. Wechsler RJ, Wehbe MA, Rifkin MD, et al. Computed tomography diagnosis of distal radioulnar subluxation. Skeletal Radiol. 1987;16:1–5. 26. Hudak PL, Amadio PC, Bombardier C. Development of an upper extremity outcome measure: the DASH (disabilities of the arm, shoulder and hand) [corrected]. The Upper Extremity Collaborative Group (UECG). Am J Ind Med. 1996;29: 602–608. 27. MacDermid JC, Turgeon T, Richards RS, et al. Patient rating of wrist pain and disability: a reliable and valid measurement tool. J Orthop Trauma. 1998;12: 577–586. 28. Bechtol CO. Grip test; the use of a dynamometer with adjustable handle spacings. J Bone Joint Surg Am. 1954;36-A:820–824; passim. 29. Winer BJ, Brown DR, Michels KM. Statistical Principles in Experimental Design. 3rd ed. New York, NY: McGraw-Hill, 1991. 30. Adams BD, Lawler E. Chronic instability of the distal radioulnar joint. J Am Acad Orthop Surg. 2007;15:571–575. 31. Lawler E, Adams BD. Reconstruction for DRUJ instability. Hand (N Y). 2007;2: 123–126. 32. Scheker LR, Ozer K. Ligamentous stabilization of the distal radioulnar joint. Tech Hand Up Extrem Surg. 2004;8:239–246. 33. Seo KN, Park MJ, Kang HJ. Anatomic reconstruction of the distal radioulnar ligament for posttraumatic distal radioulnar joint instability. Clin Orthop Surg. 2009; 1:138–145. 34. Shih JT, Lee HM. Functional results post-triangular fibrocartilage complex reconstruction with extensor carpi ulnaris with or without ulnar shortening in chronic distal radioulnar joint instability. Hand Surg. 2005;10:169–176. 35. Breen TF, Jupiter JB. Extensor carpi ulnaris and flexor carpi ulnaris tenodesis of the unstable distal ulna. J Hand Surg Am. 1989;14:612–617. 36. Kim BS, Song HS, Jung KH, et al. Distal radioulnar joint volar instability after ligament reconstruction failure treated with sigmoid notch osteotomy. Orthopedics. 2012;35:e984–987.
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Volar Stabilization of the Distal Radioulnar Joint for Chronic Instability Using the Pronator Quadratus Sang Ki Lee, MD, Jae Won Lee, MD, and Won Sik Choy, MD Abstract: In cases of chronic distal radioulnar joint (DRUJ) instability without DRUJ arthritis, reconstruction of the mechanical integrity of the radioulnar ligaments of the triangular fibrocartilage complex has been considered an ideal surgical treatment. However, reconstructive methods have several disadvantages. We evaluated volar stabilization of the DRUJ for chronic instability using the pronator quadratus (PQ) to determine whether it provided (1) proper stability, (2) restored wrist function, (3) was relatively convenient, and (4) was associated with a low complication rate. Altogether, 21 patients with chronic DRUJ instability (12 men, 9 women) with a mean age of 34 years (range, 17–65 years) were enrolled in the study. The diagnostic criteria were as follows: 3 months after the injury, greater than 8 mm of palmar-dorsal translation of the ulna relative to the radius, there was a lack of clear end point resistance compared with the contralateral side, and nonstressed computed tomographic scans provided supporting evidence. Follow-up was at least 12 months (range, 12–38 months). Palmar-dorsal translation of the ulna relative to the radius was decreased significantly from 10 to 4 mm (P = 0.028) and epicenter was increased significantly at the last follow-up [P = 0.015/0.026 (70 degrees of supination/neutral, respectively)]. Wrist range of motion was not significantly different, but grip strength had increased from 72% to 91%. Disabilities of the arm, shoulder, and hand and patient-rated wrist evaluation were also decreased compared with preoperative measurements [34.4 to 12.5/42.7 to 14.7 (disabilities of the arm, shoulder, and hand/patient-rated wrist evaluation, respectively)]. Pronator quadratus advancement volar stabilization provided proper stability, restored wrist function, was relatively convenient, and was associated with few complications. Our experience indicates that it is an acceptable, effective treatment option to reverse DRUJ instability in patients who did not have advanced DRUJ arthritis. Key Words: distal radioulnar joint, chronic instability, pronator quadratus (Ann Plast Surg 2016;76: 394–398)
D
isorders of the distal radioulnar joint (DRUJ), which are relatively common, may result from a developmental condition, trauma, or degenerative arthritis.1 The incidence of significant DRUJ injury is unknown.2 Stability of the DRUJ is provided by a bony architecture and soft tissues such as the triangular fibrocartilage complex (TFCC), the joint capsule, and surrounding muscles.3 Forearm and wrist function can be severely affected by a dysfunctional DRUJ. Even with its importance, surgeons tend to underestimate DRUJ function when making clinical assessments. The common reason for this underestimation is that it is difficult to assess DRUJ instability using plain radiography. Clinical examinations such as pain, wrist and forearm ROM, the piano key sign, and the shuck test are helpful but also have limitations in terms of providing an objective assessment of DRUJ function,4,5 and different variables to different examiners if Received March 24, 2014, and accepted for publication, after revision, August 17, 2014. From the Department of Orthopedic Surgery, Eulji University College of Medicine, Daejeon, South Korea. Conflicts of interest and sources of funding: none declared. Reprints: Sang Ki Lee, MD, Department of Orthopedic Surgery, Eulji University College of Medicine, 1306 Dunsan-dong, Seo-gu, Daejeon 302-799, South Korea. E-mail: [email protected]. Copyright © 2014 Wolters Kluwer Health, Inc. All rights reserved. ISSN: 0148-7043/16/7604–0394 DOI: 10.1097/SAP.0000000000000354
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ligamentous instability were assessed. In addition, it is easy to miss the diagnosis when DRUJ instability accompanies a fracture of wrist area (distal radius fracture, distal both forearm bone fracture, ulnar styloid base fracture) because of the pain associated with the fracture. If acute injuries are not diagnosed or treated properly, the problem may become chronic. Chronic DRUJ instability often results in substantial pain and disability, such as decreased grip strength, limited mobility, and mechanical symptoms (clicking or snapping with rotational movement of the forearm). This condition has been addressed surgically with numerous types of ligament reconstruction6–12 and salvage procedures, including the Darrach procedure,13 the Bowers hemiresection-interposition arthroplasty,14 the Suave-Kapandji procedures,15 the ulnar head replacement,16 and the hemiarthroplasty.17 Among these surgical options, a salvage procedure is indicated for DRUJ instability in patients with advanced DRUJ arthritis. In cases of chronic DRUJ instability without DRUJ arthritis, reconstruction of the mechanical integrity of the radioulnar ligaments of the TFCC has been considered ideal surgical treatment when primary repair of the TFCC is not feasible.1 These methods usually reconstruct an extrinsic or intrinsic ligament by passing harvested tendon through a drill hole. Several studies have reported successful results with those methods.18,19 Reconstructive methods have several disadvantages: They sacrifice normal soft tissue except using plantaris tendon allograft; cannot be applied to pediatric patients; the drill hole widens as time goes on (Fig. 1); and multiple incisions are required. Volar stabilization using pronator quadratus (PQ)20 could be an alternative surgical option to circumvent these problems. The PQ, a dynamic stabilizer of the DRUJ, is a strong muscle that makes the radius and ulna converge, particularly during a power grip.21 The PQ normally attaches to both the distal radius and ulna. The means of volar stabilization using PQ, the PQ is tightened by its normal origin point on the distal ulna was moved to a more medial and posterior origin (Fig. 2). The treatments using PQ were introduced as follows: salvage procedure22 or biomechanical effect on DRUJ stability as dynamic stabilizer.22,23 However, some advantages of using this treatment method include preservation of normal soft tissue, its application to pediatric patients (open physis), its small incision, and its relative convenience. Importantly,it also leaves room for another surgical treatment if it fails to achieve stability. We, therefore, assessed whether PQ advancement volar stabilization for chronic instability of the DRUJ could provide (1) proper stability, (2) restore wrist function, (3) be relatively convenient, and (4) produce a low complication rate.
MATERIALS AND METHODS Study Design This prospective study was performed from January 2009 to June 2012. A total of 27 patients were diagnosed with chronic DRUJ instability. The institutional review board approved this study, and all patients treated with the procedures during the study period were available for review. The diagnostic criteria were that it had been 3 months after the injury, there was greater than 8 mm of palmar-dorsal translation of the ulna relative to the radius,24 and/or there was a lack of clear end point resistance compared with the contralateral side.1 The physical Annals of Plastic Surgery • Volume 76, Number 4, April 2016
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Annals of Plastic Surgery • Volume 76, Number 4, April 2016
Volar Stabilization of DRUJ
TABLE 1. Demographic Data
FIGURE 1. A 25-year-old man was diagnosed as having DRUJ instability combined with a distal radius fracture 4 months after injury. He underwent reconstructive surgery. Anteroposterior plain radiography of his wrist at a 3-year postoperative follow-up visit revealed that drill holes in the radius (black arrow) and ulna (white arrows) were widening.
examination was the primary determinant of instability, nonstressed CT scans provided supporting evidence (grading by epicenter method25). Among those diagnosed as patients with chronic DRUJ who complained pain or discomfort with normal daily activities, the inclusion criteria for study enrollment were (1) chronic DRUJ instability without advanced DRUJ arthritis and (2) a history of unsuccessful conservative therapy (immobilization supination or neutral position for 6 weeks and physiotherapy in the form of strengthening the dynamic stabilizers). The exclusion criteria included (1) chronic DRUJ instability with advanced DRUJ arthritis and/or (2) ulnar impaction syndrome. On the basis of these criteria, 3 patients with advanced DRUJ arthritis and 3 with ulnar impaction syndrome were excluded. Therefore, 21 patients (12 men, 9 women) with a mean age of 34 years (range, 17–65 years) were enrolled in the study. The clinical pathway and randomization process were explained and obtained permission from the patients. The follow-up period was a minimum of 12 months (range, 12–38 months; average, 21 months) for all 21 patients (Table 1).
Surgical Technique The procedure, performed under tourniquet control, was done with the patient in a supine position on a radiolucent operating table. The elbow was flexed to 90 degrees. A longitudinal incision was made 1 fingerbreadth from the base of the ulnar styloid about 5 cm proximally along the ulnar border. The dorsal branch of the ulnar nerve was protected throughout the procedure. The ulnar neurovascular bundle was retracted, and the space immediately adjacent to the ulnar border of the PQ was identified. The periosteum of the ulnar aspect of the ulna
Variables
Patients
Total (n) Sex (M/F) Age, y Dominant side (n) Cause Distal radius fracture Radius diaphysis fracture Galeazzi fracture/dislocation Ulnar styloid base fracture TFCC injury Height, cm Weight, kg
21 12/9 34.2 (15) 14 10 3 2 4 2 168.7 (9) 64 (11)
Values are mean (SD).
was then incised, separating both the periosteum and the origin of the PQ using a periosteal elevator. It is important to include the fullthickness of the periosteum because it assists in suturing it to the distal ulna. Three or four paired holes are drilled into the ulna with 1.6-mm Kirschner wire (K-wire) in an anteroposterior direction along the more medial and posterior ulnar border separated by the periosteum and origin of the PQ for tying up the periosteum and the origin of the PQ. In the maximum supination state, the periosteum and origin of the PQ were tied using 2.0 Prolene passed through the paired drill hole. Next, the DRUJ was transfixed with 1.6-mm K-wire in wrist supination (Fig. 3). The wound was closed layer by layer. For postoperative rehabilitation, active finger motion was encouraged 1 day postoperatively. Patients were immobilized in a supinated sugar-tong splint for 4 weeks postoperatively and discontinued entirely. The K-wire was generally removed 4 weeks after surgery. Passive and active wrist ROM exercises were initiated. Strengthening exercises and stressful activities were delayed until near-painless motion was recovered.
Patient Assessment The results were assessed on the basis of achieving proper stability (palmar-dorsal translation of the ulna relative to the radius, anatomical relation of the ulna and radius during wrist rotation), restoration of day life wrist function—wrist ROM, the disabilities of the arm, shoulder, and hand (DASH),26 patient-rated wrist evaluation (PRWE),27 grip strength—operating time, and complications. The anatomical relation of the ulna and radius during wrist rotation was analyzed using nonstressed CT with the epicenter method25 (Fig. 4). Computed tomographic (CT) scans were obtained using 3-dimensional CT (Siemens, Forchheim, Germany). Both injured and contralateral wrists were
FIGURE 2. Schema for volar stabilization of the DRUJ for chronic instability using the PQ. Pronator quadratus is tighten by (A) its normal origin point on the distal ulna was moved to (B) a more medial and posterior origin. © 2014 Wolters Kluwer Health, Inc. All rights reserved.
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FIGURE 3. Procedures for volar stabilization of the DRUJ for chronic instability using the PQ. A, The periosteum of the ulnar aspect of the ulna was incised, separating both the periosteum and the origin of the PQ. Separating the full-thickness periosteum and the origin of the PQ was important because it assists when suturing them to the distal ulna. B, Three or four paired holes are drilled into the ulna along the more medial and posterior portions of ulnar border separating the periosteum and origin of the PQ. Then, 2.0 Prolene was passed through the paired drill hole. Periosteum and the origin of the PQ were tied up in a maximum supination state. C, DRUJ was transfixed with 1.6-mm K-wire in wrist supination.
scanned at 0.6-mm intervals in 3 positions—70 degrees of supination, neutral position, and 70 degrees of pronation—using a customdesigned positioning device (Fig. 5). Wrist ROM (extension, flexion, supination, and pronation) was measured using a goniometer. The DASH is a 30-item self-report questionnaire designed to evaluate the function and symptoms of the upper limb regardless of surgical site. Answers to questions about daily activities were scored from 0 (no impairment) to 100 (maximum impairment). The PRWE is a 15-item questionnaire used to assess wrist pain (5 items) and function (10 items: 6 for specific activities and 4 for usual activities). Each score ranges from 0 (no pain or difficulty during activity) to 100 (severe pain or being dysfunctional). Grip strength was measured using a JAMAR hand dynamometer (Therapeutic Equipment Corporation, Clayton, NJ). In accordance with the guidelines for the use of the JAMAR dynamometer, issued by the American Society for Surgery of the Hand, the second grip handle was used for all patients.28 The successive trials were used on both injured and uninjured hands. The results were recorded as a percentage of the unaffected side, as recommended by the American Society of
Hand Therapist. Grip strengths were adjusted by 10% for the nondominant hand for analysis. Each patient was assessed 3 times (preoperatively, at 6 months postoperatively, and at the last follow-up). Patients were questioned about the existence of complications throughout the follow-up period. To reduce measurement errors, all measurements were obtained twice by each author and average values calculated. Intraobserver reliability was considered the criteria of Winer (degree of bias and mean squared error).29 Reliability was classified, according to the intraclass correlation coefficient, as absent to poor (0–0.24), low (0.25–0.49), fair to moderate (0.50–0.69), good (0.70–0.89), or excellent (0.90–1.0). We achieved an interobserver reliability of 0.93. There were no missing data.
Statistical Analysis The differences between preoperative and postoperative values were analyzed using the Wilcoxon signed rank test for palmar-dorsal translation, anatomical relation, wrist ROM, DASH, PRWE, and grip strength. Significance was set at P < 0.05. We used SPSS version 20.0 software (IBM, Armonk, NY) for statistical analyses.
RESULTS The PQ advancement volar stabilization for chronic instability of the DRUJ provided proper stability. Palmar-dorsal translation of the ulna relative to the radius and epicenter (70 degrees of supination,
FIGURE 4. Epicenter method. A perpendicular line was drawn from the halfway point between the centers of the ulnar and the ulnar styloid to the sigmoid notch. The distance between this line and the midpoint of the sigmoid notch was measured (C-D), and the ratio of this distance to the length of the sigmoid notch (A-B) was calculated. 396
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FIGURE 5. Custom-designed positioning device. In prone position, the patient grips the goniometer handle. The forearm is fixed with a strap. Patient rotates the wrist to the targeted angle. © 2014 Wolters Kluwer Health, Inc. All rights reserved.
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Annals of Plastic Surgery • Volume 76, Number 4, April 2016
Volar Stabilization of DRUJ
TABLE 2. Outcome Measures for Stability Measurement
P/D translation, mm Epicenter 70-degree supination Neutral 70-degree pronation
Uninjured Wrist
4 (3–5) 0.10 (−0.06 to 0.19) 0.07 (−0.14 to 0.23) −0.01 (−0.19 to 0.24)
Preoperative
6 mo F/U
10 (9–12)
5 (4–6)
0.00 (−0.46 to 0.21) −0.01 (−0.49 to 0.33) −0.01 (−0.26 to 0.20)
P
Last F/U
4 (3–6)
0.09 (−0.05 to 0.20) 0.07 (−0.20 to 0.27) −0.01 (−0.23 to 0.22)
0.028*
0.10 (−0.05 to 0.18) 0.07 (−0.15 to 0.23) −0.01 (−0.20 to 0.23)
0.015* 0.026* 0.823
Values are mean (range) * Statistically significant F/U indicates follow-up; P/D, palmar-dorsal.
neutral) were decreased significantly at the last follow-up compared with the preoperative measurement [P = 0.028, 0.015/0.026 (70 degrees of supination/neutral, respectively)] (Table 2). Patients who underwent PQ advancement volar stabilization had restoration of acceptable wrist functions. At the last follow-up, wrist ROM was not significantly different, but grip strength had increased (P = 0.047). In addition, DASH and PRWE decreased (P = 0.037 and P = 0.027, respectively) compared with the preoperative measurements (Table 3). No intraoperative or postoperative complications were observed. No patients reported recurrent DRUJ instability, and no arthritic changes during follow-up period plain radiography or 24 months follow-up magnetic resonance images.
DISCUSSION Disorders of the DRUJ of diverse etiologies are relatively common.1 Forearm and wrist function can be severely affected by dysfunction of the DRUJ. Ideal management of DRUJ instability is controversial. If an acute injury to the DRUJ is not diagnosed or treated properly, it can become a chronic problem. Reconstruction of the mechanical integrity of the radioulnar ligaments6–11 was considered surgical treatment of chronic DRUJ instability if DRUJ arthritis was not present. Because current reconstructive treatment methods have several disadvantages, we suggest PQ advancement volar stabilization as an alternative surgical option. In the current study, we analyzed whether PQ advancement volar stabilization for chronic instability of the DRUJ could (1) provide proper stability, (2) restore wrist function, (3) be relatively convenient, and (4) produce a low complication rate. Several prior studies of ligament reconstruction of the DRUJ demonstrate stability in almost all patients18,19,30–34; however, stability was evaluated by physical examination and not quantified. Evaluation methods included the anteroposterior stress test performed at last follow-up and radiographic improvement of joint widening. In our study, we evaluated stability by physical examination and quantified it on nonstressed CT scans. Physical examination is an important diagnostic method but is limited by possible measurement errors by the tester. Computed tomographic scanning measuring the palmar-dorsal translation of the ulna and epicenter makes the evaluation more objective. These results demonstrated adequate stability in our series. We also achieved proper stability in the rotational state by performing volar side stabilization alone because we obtained satisfactory stability based on both neutral and 70 degrees of supination and pronation stability tests. Restoration of wrist function was evaluated by wrist ROM, functional scores (DASH, PRWE), and grip strength. The results of wrist ROM in previous studies indicated that ROM was not restricted following surgery but there was limited supination,32 no statistically significant difference between the preoperative and postoperative ROM,33 and no improvement in postoperative ROM.19 In this study, wrist © 2014 Wolters Kluwer Health, Inc. All rights reserved.
ROM was not significantly different after surgery either. The reason is that patients with chronic DRUJ instability and without advanced DRUJ arthritis were enrolled in our study, so almost all patients had normal wrist ROM. Other studies18,19,32,33 and ours have reported satisfactory results in regard to the functional score and grip strength. The tissues required for reconstructive surgery are usually harvested from the flexor carpi ulnaris tendon,8,9 extensor carpi ulnaris tendon,34 combined extensor carpi ulnaris/flexor carpi ulnaris tenodesis,35 or palmaris longus tendon.6 When harvesting tendon, it is necessary to remove adequate length and width for the reconstruction. Also, sufficient stability may not be achieved without determining the proper location of the hole through which to pass the harvested tendon. In contrast, PQ advancement volar stabilization is a 1-step procedure that simply medializes the origin of the PQ. It can reduce the number of practical errors during surgery and achieve steady outcomes with a smooth learning curve. Because of these conveniences, the average operating time in this study was a short 37 minutes. We performed only soft tissue procedures for bony alignment correction, and there were no DRUJ arthritic changes. In addition, there was no persistent or recurrent instability. However, if it had failed to achieve stability, these other avenues of surgical treatment remained viable options because normal tissues were preserved. If the ligament reconstruction of the DRUJ would fail to recover stability, soft tissue procedures would have difficulty in solving DRUJ instability. Thus, in a previous study, sigmoid notch osteotomy for persistent instability was performed.36 There were additional strengths of this method. First, it can be applied to pediatric patients. It is a soft tissue procedure that preserves normal tissue, so we could achieve proper stability and good outcomes without damaging a still-open physis (Fig. 6). Second, it could be done
TABLE 3. Outcome Measures for Wrist Functions Measurement
Preoperative
6-mo Follow-up
Last Follow-up
Wrist ROM, degree Flexion 66 (50–80) 68 (58–81) 72 (60–85) Extension 58 (48–75) 60 (50–75) 69 (65–80) Supination 75 (60–90) 78 (60–87) 82 (65–90) Pronation 70 (45–80) 72 (54–80) 77 (55–85) DASH 34.4 (5.8–56.7) 17.3 (0–54) 12.5 (0–52) PRWE 42.7 (5–79.5) 18.4 (0–60) 14.7 (0–58) Grip strength, % 72 (64–81) 86 (70–92) 91 (87–94)
P
0.210 0.058 0.178 0.089 0.037* 0.027* 0.047*
Values are mean (range). * Statistically significant.
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FIGURE 6. A, Postoperative anteroposterior wrist plain radiography of a 17-year-old male patient. The physis was still open. B, After 10 months of follow-up, the physis was still intact, with no physial arrest or arthritic changes.
with a small incision because it is a 1-step procedure. Third, we could initiate ROM exercises after 4 weeks postoperatively. It reduced the risk of ROM limitation, and patients had an early return to daily activity. This study has some limitations. First, although the study was designed as a prospective project, it was based on a single cohort so there was no control group for comparison such as group of patients with K-wire fixation alone. As ligamentous reconstructive surgery has been common, we referenced results of other studies for comparison data. Second, this series was relatively small. It was done in a single center, and we diagnosed only 27 chronic DRUJ instabilities during 3.5 years, selecting 21 patients after addressing inclusion and exclusion criteria. Thus, its size could be a cause of selection bias. However, no patients were lost to follow-up. We analyzed all enrolled patients and were therefore able to obtain precise, practical results. Third, our mean follow-up period was only 21 months. Early results for all patients were relatively good, but we could not analyze the long-term results. Although the early results are promising, longer-term monitoring and larger study populations are required to verify the presented data. The DRUJ instability remains a challenge. Instability may be treated with various remedies, although its ideal management is controversial. According to the results of this study, PQ advancement volar stabilization provides proper stability, restores wrist function, is relatively convenient, and is associated with a low complication rate. Our experience suggests that PQ advancement volar stabilization is an acceptable, effective treatment option for correcting DRUJ instability in patients who do not have advanced DRUJ arthritis. REFERENCES 1. Murray PM, Adams JE, Lam J, et al. Disorders of the distal radioulnar joint. Instr Course Lect. 2010;59:295–311. 2. Argintar E, Mantovani G, Pavan A. TFCC reattachment after traumatic DRUJ instability: a simple alternative to arthroscopic management. Tech Hand Up Extrem Surg. 2010;14:226–229. 3. af Ekenstam F, Hagert CG. Anatomical studies on the geometry and stability of the distal radio ulnar joint. Scand J Plast Reconstr Surg. 1985;19:17–25. 4. May MM, Lawton JN, Blazar PE. Ulnar styloid fractures associated with distal radius fractures: incidence and implications for distal radioulnar joint instability. J Hand Surg Am. 2002;27:965–971. 5. Szabo RM. Distal radioulnar joint instability. J Bone Joint Surg Am. 2006;88: 884–894. 6. Adams BD, Divelbiss BJ. Reconstruction of the posttraumatic unstable distal radioulnar joint. Orthop Clin North Am. 2001; 32:353–363,x.
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