**1. Introduction**

Distal-radius fracture (DRF), one of the most common fractures occurring in elderly people, accounts for approximately 18% of fractures in patients older than 65 years [1,2]. Triangular fibrocartilage complex (TFCC) tear, the injury most associated with unstable distal-radius fractures, has been reported in 39% to 84% of cases [2,3]. This concomitant injury may contribute to the development of chronic wrist pain, decreased grip strength, and restricted motion [4].

Better visualization and diagnosis of TFCC injury can be achieved by use of arthroscopic examination; however, it is not a standardized test for use in all patients with distal-radius fractures [5,6]. Although MRI scanning is used for diagnosis of TFCC injuries, MRI testing is not performed routinely in all patients with distal-radius fractures at the time of the injury [7]. Instead, the test is recommended for patients who have symptoms related to TFCC injury after the fracture treatment has ended, which can cause a delay in the treatment of the injury.

Some studies using MRI in patients with DRF have demonstrated the prevalence of TFCC injuries; however, studies on the pathomechanism of TFCC injuries concomitant to DRF have rarely been reported [7]. According to findings from previous studies, radiologic features such as the fracture pattern, the magnitude of displacement, and the presence

**Citation:** Kim, B.-S.; Cho, C.-H.; Lee, K.-J.; Lee, S.-W.; Byun, S.-H. Pathomechanism of Triangular Fibrocartilage Complex Injuries in Patients with Distal-Radius Fractures: A Magnetic-Resonance Imaging Study. *J. Clin. Med.* **2022**, *11*, 6168. https://doi.org/10.3390/jcm11206168

Academic Editor: Christian Carulli

Received: 5 September 2022 Accepted: 18 October 2022 Published: 19 October 2022

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**Copyright:** © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

of an ulnar styloid fracture may be independent predictors of TFCC injuries related to DRF [2,8,9]. This study hypothesized that performing an analysis of radiologic parameters in MRI studies of patients with DRF may foster an understanding of the pathomechanism of TFCC injuries.

The purpose of this study is to a conduct radiographic examination and MRI studies in order to determine the fracture mechanism of distal-radius fracture and the prevalence and the pathomechanism of TFCC injuries concomitant to fracture.

#### **2. Materials and Methods**

Sixty-three patients underwent surgical management for the treatment of distal-radius fracture in a single fellowship-training hospital between March 2020 and July 2021. Inclusion criteria were patients who underwent open reduction and internal fixation of the fracture. Patients younger than 18 years old and those who had previously occurring arthritis of the wrist or degenerative TFCC injuries on the affected wrist were excluded. Those patients underwent MRI scanning, and five patients who refused the test were excluded, so that 58 patients were finally included in this study (Figure 1).

**Figure 1.** Patient's flow chart. Patient profiles and the groups included in the study. MRI, magneticresonance imaging.

An analysis of simple radiographic parameters (the radial inclination, the radial length, the distal radioulnar joint (DRUJ) gap, the sagittal/radial transition ratio, the DRUJ gap on the unaffected wrist, and the presence of a distal ulnar fracture) and patterns of TFCC injury in the MRI scan was performed by two orthopedic surgeons using the Palmar classification. Regarding the classification of fractures, the Fernandez classification and the AO/OTA classification were used in defining the mechanism of injury and the fracture pattern, respectively. Other assessments included general demographics and underlying osteoporotic disease.

A standard 4 view x-ray of the injured wrist, and AP and lateral views of the uninjured side were obtained for all patients. Measurement of the DRUJ gap distance was performed on both sides in order to better evaluate widening of the DRUJ. The DRUJ distance was defined as the maximum distance between either the volar or dorsal cortical rim of the sigmoid notch of the radius and the ulnar head. The radial translation ratio was calculated as the fraction of the DRUJ gap distance relative to the radioulnar width of the proximal fracture fragment. On the lateral X-ray, the sagittal translation was defined as the distance between the volar cortex of the radius shaft and the volar cortical margin of the distal fracture fragment. The sagittal translation ratio was calculated as the fraction of the sagittal translation to the AP width of the proximal fracture fragment [2,8].

The articular involvement of the fracture and the presence of an ulnar styloid fracture, which was then classified as a tip, middle, or base fracture each separating 1/3 of the ulnar styloid, was evaluated in this study. In addition, ulnar styloid fracture was classified as type 1,2,3 each corresponding to distal to base where the superficial horizontal fibers of the TFCC are inserted, base fracture and proximal to the base fracture, respectively [9,10].

The radial length was defined as the distance between two lines drawn perpendicular to the long axis of the radius on the AP projection from the apex of the radial styloid and the level of the ulnar aspect of the articular surface. The radial length was measured on the uninjured wrist, and the radial length gap between both sides of the wrist was obtained for the evaluation of the pure radial shortening distance (Figure 2).

**Figure 2.** Radiologic parameter measurement technique. (**A**) Radial length. (**B**) Radial inclination. (**C**) DRUJ distance. (**D**) Fracture site width. (**E**) Dorsal angulation. (**F**) Sagittal translation. (**G**) Anteroposterior width. Radial translation ratio = C/D, Sagittal translation ratio = F/G. DRUJ, distal radioulnar joint.

An MRI examination of the injured wrist was performed on all patients using a 3.0 T MRI scanner (Magnetom 3.0 T, Siemens, Munich, Germany/Ingenia 3.0 T, Philip, Amsterdam, The Netherlands). Statistical analysis was performed using the SPSS statistical package (Version 22.0; IBM, Armonk, NY, USA). The Chi-square test was used for the evaluation of categorical variables, and the T-Test was used for the evaluation of continuous variables. The level of significance was set as *p* value < 0.05.
