Traumatic posterior distal radioulnar joint instability treated with open versus arthroscopic methods: a retrospective cohort study
Article information
Abstract
Purpose
The distal radioulnar joint (DRUJ) at the wrist facilitates pronation and supination, and both bone structure and soft tissues contribute to its stability. This study analyzed the characteristics of patients with traumatic posterior DRUJ injuries and examined the clinical outcomes of open or arthroscopic treatment methods for these patients.
Methods
A retrospective cohort study was conducted on 14 patients with traumatic posterior DRUJ instability, excluding those with associated radius fractures. The study evaluated patient demographics, injury mechanisms, radiologic findings (DRUJ relationship in the coronal plane, sigmoid notch in the axial plane, the presence and location of an accompanying distal ulnar fracture, and ulnar variance in the opposite wrist), and clinical outcomes (visual analog scale, Disability of Arm, Shoulder, and Hand [DASH] score, and range of motion [ROM]). Patients were treated with either open repair or arthroscopic methods, and postoperative results were monitored over an average of 8.8 months.
Results
Ten patients had ulnar styloid fractures, with most occurring at the base or more proximally. The sigmoid notch was classified as the flat-face type in nine cases (64.3%) and the ski-slope type in five cases (35.7%). The clinical outcomes were favorable, with no significant differences between the open and arthroscopic groups regarding pain levels, DASH scores, and ROM.
Conclusion
Both treatment methods can achieve favorable clinical outcomes in managing traumatic posterior DRUJ instability.
Introduction
The distal radioulnar joint (DRUJ) at the wrist is where pronation and supination occur. The bone structure and soft tissues work in harmony to maintain joint stability [1,2]. The ulnar head articulates with the sigmoid notch of the radius account for approximately 20% of DRUJ stability [2,3]. The sigmoid notch, which forms a joint with the ulnar head, varies in shape among individuals: flat-face (42%), ski-slope (14%), C-type (30%), or S-type (14%) [3]. It also has a larger radius of rotation than the ulnar head, with a mean of 10 mm for the ulnar head and 15 mm for the radius [3]. The sigmoid notch has been described as having four shapes. During pronation, the ulnar head moves posteriorly, and during supination, it moves anteriorly.
Soft tissue structures, particularly the triangular fibrocartilage complex (TFCC), play a key role in DRUJ stability. The volar and dorsal radioulnar ligament, and foveal insertion within the TFCC are primary stabilizers [4,5], while the joint capsule, extensor carpi ulnaris (ECU), and interosseous ligament serve as secondary stabilizers [6,7]. Severe trauma to the DRUJ can cause TFCC rupture [2,8,9] and, rarely, subluxation or dislocation, often requiring surgical intervention [2,9]. Without proper diagnosis and treatment, such injuries can lead to significant wrist dysfunction, including stiffness, instability, and arthritis [10].
This study aims to analyze the characteristics of patients with DRUJ injuries accompanied by posterior subluxation or dislocation and to examine the clinical outcomes of open or arthroscopic treatment methods.
Methods
Ethics statement: The Institutional Review Boards of CHA Bundang Medical Center and National Health Insurance Service Ilsan Hospital approved the protocol of this study (No. CHAMC 2024-4-024/NHIMC 2024-04-014). Written informed consent was obtained from the patient for the publication of this study including all clinical images.
Two institutions and two orthopedic surgeons at each hospital participated in this retrospective cohort study. Patient data were collected between January 1, 2010, and December 31, 2023. We included only cases of traumatic posterior DRUJ instability. The patient presented with a notable history of trauma, and radiologic verification was achieved through the identification of DRUJ widening or a dorsal subluxation of ulnar head on X-ray. Diagnosis was further supported by physical examination findings, including dorsal prominence of the ulnar head, limitation in supination, snapping, and apprehension [3,10]. Additional imaging, such as computed tomography (CT), was performed to check for concurrent fractures, and magnetic resonance imaging was used to assess the condition of surrounding soft tissues. Cases involving a radius fracture such as Galeazzi fractures or Essex-Lopresti lesions, as well as other additional fractures or soft tissue injuries, were excluded. During the study period, we found only 14 patients who met the inclusion criteria.
1. Measurement of clinical and radiological parameters
We examined patient characteristics including age, sex, height, weight, and body mass index (BMI). We further examined injury mechanisms and the direction of the affected arm. For radiologic assessment, we assessed the distal radioulnar relationship in the coronal plane, the sigmoid notch in the axial plane, the presence and location of any accompanying distal ulnar fracture (DUF), and ulnar variance in the opposite wrist. The distal radioulnar relationship in the coronal plane was measured at the time of reduction by operation and categorized as parallel, oblique, or reverse oblique [3]. In the axial plane, the sigmoid notch was classified as flat-face, ski-slope, C-type, or S-type [3]. The DUF was divided into three types: type I (distal to base fracture), type II (base fracture), and type III (proximally located fracture from the styloid base) [11]. Operation-related factors included treatment methods (open or arthroscopic repair), additional procedures, and operation time.
After the operation, we examined the postoperative immobilization method and duration. As final outcomes, we assessed whether or not the ulnar styloid fracture united and the final ulnar variance. We evaluated the final pain levels using the visual analog scale (VAS), checked the Disability of Arm, Shoulder, and Hand (DASH) scores, and assessed the range of motion (ROM), including volar flexion, dorsiflexion, supination, and pronation.
Medical records were also reviewed to identify complications during the follow-up period, including infection, nerve injury, secondary ulnocarpal impaction, DRUJ arthritis, limitation of ROM, and whether or not revision surgery was needed.
2. Surgical procedures
For open repair, surgery proceeded as follows: a dorsal skin incision was made over the distal ulna between the ECU and extensor digiti minimi to gain access. The joint capsule, extensor retinaculum, and ECU sheath were found damaged, facilitating exposure of the dislocated area without the need for additional dissection. During the approach, relocation of structures obstructing the reduction of the ulnar head allows for relatively easy reduction. Once reduction is achieved, the damaged structures are then re-sutured. Tears of the distal radioulnar ligament were addressed with microanchor sutures for fixation at the ulnar insertion site. Additionally, capsular reinforcement was performed using the loop suture technique. Using loop sutures enables robust soft tissue repair; similar to tenorrhaphy, loop sutures are utilized to create a core suture to repair the torn capsule.
For arthroscopic repair, the approach is initiated using 3 to 4 (viewing) and 4 to 5 (working) portals. In most cases, reduction was achieved by pushing the ulnar head forward and supinating the wrist, and there were no instances where open reduction was necessary. Arthroscopy is performed to identify the damaged structures and confirm the TFCC tear using a probe. A targeting device through the portal is used to guide the tip to the ulnar fovea, creating a transosseous tunnel. TFCC repair is then conducted by passing sutures through the tunnel. Sutures are secured using an anchor, with slight traction released and the ulnar head pushed forward during tightening.
In both cases, additional distal radioulnar transaxial Kirschner wire (K-wire) fixation was performed based on the surgeon’s discretion for added stability.
3. Group categorization and outcome comparison
This study utilized data from two institutions, where one institution performed open repair for traumatic DRUJ instability surgeries, while the other institution performed arthroscopic repair. These choices reflected the surgical preferences of the respective institutions’ surgeons. We categorized the patients who underwent open repair as group 1 and those who underwent arthroscopic repair as group 2. We compared demographic variables between the two groups. As outcome measures, we compared the operation time, clinical outcomes, and complications.
4. Statistics
Due to the small sample size, we performed nonparametric comparisons. Continuous variables are presented as the mean and interquartile range. Categorical variables are expressed as numbers and percentages. Single comparisons of continuous variables were conducted using the Wilcoxon rank-sum test, while categorical variables were compared using the Fisher exact test. A significance level of p<0.05 was considered statistically significant. The statistical analysis was performed using IBM SPSS Statistics ver. 29.0 (IBM Corp., Armonk, NY, USA).
Results
1. Patient characteristics
The average age of the 14 patients was 24.8 years (range, 16–49 years). All patients presented with partial or complete impairment of wrist supination. There were 13 male patients and one female patient. The average height, weight, and BMI were 172 cm, 66.4 kg, and 22.3 kg/m2, respectively.
2. Injury mechanisms
Four patients fell from bicycles. Three fell on the ground while playing soccer. Two fell from the kickboards. One fell on the ground while running with a foot strap, and one fell on an icy road. One patient sustained a direct punch injury, and another was injured by a direct hit on a desk table.
The right wrist was affected in six patients, while the left wrist was affected in eight patients. However, in three patients, both wrists were injured, although the opposite wrist did not show significant DRUJ instability.
3. Radiologic evaluation
In 10 patients, ulnar styloid fractures occurred, with two type 1 fractures, five type 2 fractures, and three type 3 fractures. There were eight parallel distal radioulnar relationships in the coronal plane, followed by five oblique and one reverse-oblique relationships. In the axial evaluation of CT images, there were nine flat-face types (64.3%) and five ski-slope types (35.7%).
4. Treatment
The time interval between injury and operation ranged from 0 to 184 days, with an average of 32 days. Five patients had surgery over a month after the initial injury because other hospitals did not diagnose joint instability, opting for conservative treatment instead.
Open TFCC and capsular reinforcement were performed in nine patients (Fig. 1). One patient underwent arthroscopic synovectomy due to a missed diagnosis over 5 months. In five patients, arthroscopic transosseous one-tunnel TFCC repair was performed (Fig. 2). In eight patients who had an open repair, additional distal radioulnar K-wire fixation was done. Three patients who had arthroscopic repair also underwent additional distal radioulnar K-wire fixation. The average operation time, excluding one arthroscopic synovectomy combined in open repair, was 56 minutes (The average operation time for open repair was 50 minutes, while the average time for arthroscopic repair was 60 minutes.).
A patient who underwent open repair of the triangular fibrocartilage complex and capsular reinforcement. (A) Preoperative X-ray images, anteroposterior and lateral views. (B) Preoperative range of motion (ROM); the patient showed limited supination on the right wrist. (C–G) Intraoperative images. (C) The skin incision was made along the dorsal side of distal ulna. (D) The distal radioulnar ligament was torn with elongated scar tissue. (E) The distal radioulnar ligament was repaired using a microanchor. (F) Capsular reinforcement was performed using loop sutures. (G) Full ROM of supination and pronation was achieved immediately after surgery. (H) At the final follow-up, pictures of ROM show favorable clinical outcomes.
A patient who underwent arthroscopic triangular fibrocartilage complex (TFCC) repair. (A) Preoperative X-ray images, anteroposterior and lateral views. (B) Preoperative range of motion (ROM); the patient showed limited supination on the left wrist. (C) Preoperative magnetic resonance imaging findings of the TFCC injury. (D) Arthroscopic findings; transosseous one-tunnel TFCC repair was performed. (E) Postoperative X-ray image; additional distal radioulnar Kirschner wire fixation was performed. (F) At the final follow-up, pictures of ROM show favorable clinical outcomes.
Postoperatively, patients in the open repair group were immobilized with a short arm splint for 4 weeks. The K-wire was then removed, and wrist ROM exercises were allowed. In the arthroscopic group, if a K-wire was inserted, it was removed at 4 weeks postoperatively. For a total of 6 weeks postoperatively, patients wore a Munster cast or brace, allowing ROM after 6 weeks. Patients had outpatient follow-ups for an average of 8.8 months.
5. Outcomes
The ulnar styloid did not unite in six of the 10 patients. There was no significant difference observed in the distribution between the two groups (four of seven in group 1 and two of three in group 2, p=0.667). The final ulnar variance was –0.9, with only one patient presenting a 1-mm ulnar positive variance; the rest had neutral or negative variance.
The average pain VAS and DASH scores were 0.4 and 6.5, respectively. The average wrist ROM was 78.8° for volar flexion, 77.7° for dorsal flexion, 75.0° for pronation, and 78.6° for supination.
One patient required K-wire removal surgery because the wire could not be pulled out by force due to bending at the ulnar bone interface. There were no other complications.
6. Comparison
The results of the comparison between the two groups can be found in Table 1. The comparison revealed no statistically significant differences in patient characteristics (except for direction), operative time, or treatment outcomes, including pain VAS, DASH scores, and wrist ROM.
Comparison of the treatment groups
Discussion
We summarized our study results as follows. The traumatic posterior DRUJ instability mostly occurred in male patients with high-energy injury mechanisms. All of the patients noted partial and complete supination limitations prior to the operation. The shape of sigmoid notch were nine flat-face types (64.3%) and five ski-slope types (35.7%).
As noted in the results, the average operation time for open repair was 50 minutes, whereas the average time for arthroscopic repair was 60 minutes. Although open repair showed a shorter average operation time, statistical analysis revealed no significant difference in operation times between the two procedures (p=0.414). Not considerable case comparison, both open repair and arthroscopic TFCC transosseous fovea repair could obtain good clinical outcomes.
Since the ROM limitation, nine patients had operative treatment within postinjury 4 weeks. Other five patients missed explicit diagnosis, 33, 40, 45, 82, and even 184 days from the initial trauma. Eventually, the most delayed patients had open TFCC and capsular repair after arthroscopic synovectomy. Nonetheless, those patients also reported good clinical outcomes without complications of ROM limitation and arthritis in the final follow-up.
The TFCC proximal lamina inserts on the distal ulnar head foveal area [4,9]. Styloid base fractures, and even more proximal fractures, were assumed to indicate surgery due to concerns about DRUJ instability [12]. Despite having only four patients with traumatic posterior DRUJ instability, this condition occurred without an associated ulnar styloid fracture. Among patients with combined ulnar styloid fractures, the fractures occurred at the base or more proximally, except in one case. The ulnar styloid fractures resulted in a higher incidence of nonunion (six out of 10); however, ulnar styloid nonunion did not correlate with clinical outcomes. Several previous studies already reported whether this fracture heals or not has no impact on DRUJ stability [13-15].
Tsukuda et al. [16] reported that they conducted a quantitative analysis to determine the percentages of high-density areas on the articular surface of the sigmoid notch. They found that the C-type sigmoid has a regular curved shape, resulting in a wide contact area between the sigmoid notch and the ulnar head. In contrast, the ski-slope type sigmoid tilts toward the dorsal side and forms a straight line, leading to a narrow contact area between the sigmoid notch and the ulnar head. This reduced contact area increases joint incongruency and instability. A study by Jung et al. [17] found that the flat-face sigmoid notch type was more prevalent (43%) in patients with TFCC foveal tears compared to controls (21%). The C-type was less common in the patient group (3% vs. 17% in controls). Decreased sigmoid notch depth and version angle were associated with higher odds of TFCC foveal injury [17]. Other studies have also reported that chronic DRUJ instability can occur in patients with a flat sigmoid notch [18-20].
Many studies have similarly classified sigmoid notch shapes, correlating flatter or linear morphologies with reduced congruency at the DRUJ and an increased risk of instability. A flat-face or ski-slope type facilitates easier dorsal subluxation of the ulnar head from the shallow sigmoid notch. Interestingly, in our study, the sigmoid notch shape was either flat-face (nine patients, 64.3%) or ski-slope (five patients, 35.7%), with no C-type or S-type observed. These findings further confirm that sigmoid notches with a flat or linear morphology, such as flat-face or ski-slope types, are associated with a higher risk of instability.
In our study, the most common distal radioulnar relationship in the coronal plane was parallel in eight patients (57.1%), followed by oblique in five patients (35.7%), and reverse oblique in one patient (7.1%). There was no specific evidence of the parallel distal radioulnar relationship being associated with an increased risk of traumatic DRUJ instability in previous studies. In one study reviewing 1,000 radiographs of wrist [21], the most common cases were parallel (68%), oblique (26%), and reverse oblique (6%), and this study showed similar rates.
In the treatment of open repair, the primary procedure was capsular repair. In an experimental study, capsular incision did not cause DRUJ instability; however, the range of pronation and supination increased [22]. In a cadaveric study, capsular repair was important in restoring normal pronation and supination kinematics, highlighting its significance in treating traumatic DRUJ instability [23]. Conversely, arthroscopic foveal repair may focus primarily on DRUJ instability. Although the capsule was not directly repaired, the use of a transaxial K-wire and adequate immobilization time allowed for capsular healing, ultimately resulting in a good outcome. Gofton and Gordon [23] also claimed that preserving the TFCC provides sufficient stabilization when peripheral structures are damaged.
Since these injuries are rare, the subsequent small sample size was one of our critical limitations. The choice of repair technique can vary based on the surgeon’s knowledge and experience. Although both treatment methods presented good clinical outcomes, the fact that different surgeons performed the operations in our study was another limitation.
Conclusion
Although traumatic posterior DRUJ instability is not a common injury, it can result from high-energy trauma and is more prevalent in men. Adequate reduction and secure repair through open or arthroscopic procedures can achieve favorable clinical outcomes.
Notes
The authors have nothing to disclose.
Funding
None.