A three-dimensional virtual morphometry study of the sigmoid notch of the distal radius

Intraoperative assessment of the dorso-ulnar fragment stability with stress fluoroscopy: An observational study

This study aims to investigate the effectiveness of intraoperative stress radiographs in evaluating the stability and fixation adequacy of the dorso-ulnar fragment (DUF) after volar plate application. Sixty-four patients who underwent open reduction and internal fixation due to comminuted distal radius fracture accompanied by DUF between May 2020 and February 2022 were reviewed retrospectively. Two groups were compared, with and without stress radiographs used in addition to routine fluoroscopic imaging during the surgical treatment of distal radius fractures. DUF sizes and fracture classifications were made according to preoperative computed tomography. Displacement of the DUF, dorsal cortex screw penetration, and the number of screws inserted into the DUF were evaluated on immediate postoperative CT scans and direct radiographs. DUF displacement at the patients' last follow-up was significantly higher in the control group (1.62 mm) than in the additional stress fluoroscopy applied group (0.53 mm). It was observed that the amount of displacement increased as the dorso-volar size of the DUF decreased. No significant difference was observed in dorsal cortex screw penetrations between the 2 groups. In the additional stress fluoroscopy applied group, stabilization rates with at least 1 screw over volar-locking plate for DUF were significantly higher (P < .001). Compared to the stress fluoroscopy group, the change in ulnar variance (P < .001) and volar tilt (P < .001) was significantly higher in the control group in the last follow-up radiography. No significant difference was observed between the implant removal rates of both groups. Evaluation of the stability of the DUF with stress radiographs after fixation is an effective method to reveal the need for additional fixation. Dorsal stress radiographs allow dynamic evaluation of fixation strength.

Midsectional Magnetic Resonance Imaging Analysis of the Sigmoid Notch of the Distal Radioulnar Joint

Purpose  This study describes the anatomy and analyzes the variations of the midsectional morphology of the sigmoid notch. Methods  The wrists of 50 patients with suspected scaphoid fracture were evaluated by magnetic resonance imaging (MRI). Sigmoid notch length, volar and dorsal rim heights, insertion length of the volar radioulnar ligament, and Tolat morphology classification were measured on T1-weighted axial plane MRI. Ulnar variance and distal radioulnar joint (DRUJ) inclination were assessed on anteroposterior radiographs. Results  The most common sigmoid notch shapes were types C (C-shaped, 60%) and B (ski-slope, 30%), followed by types D (S-shaped, 6%) and A (flat, 4%). Types A and B had a flat dorsal rim (mean 0.77 ± 1.09 mm, range 0.0-1.54 mm, and mean 0.22 ± 0.3 mm, range 0.0-0.76 mm, respectively). Types C and D had more prominent dorsal rims (means 1.47 ± 0.59 mm, range 0.66-2.57 mm, and mean 1.6 ± 0.97 mm, range 0.8-2.68 mm, respectively). The average volar lip length was 1.60 ± 1.11 mm (range, 0.0-4.10). The dorsovolar length of the radius was 18.4 ± 2.01 mm; the length of the sigmoid notch was 14.3 ± 1.73 mm. The type of sigmoid notch according to Tolat was significantly associated with volar lip length ( p  = 0.005). The type of sigmoid notch was not associated with ulnar variance or DRUJ inclination. The length of the sigmoid notch was significantly associated with the type of sigmoid notch ( p  = 0.005). The analysis demonstrated a negative association between the sigmoid notch length and the volar insertion of the radioulnar ligament ( p  = 0.019). Conclusions  The transversal morphology of the sigmoid notch was either flat with the least congruence (similar to type A of Tolat), with volar congruence only (similar to type B), or with volar and dorsal congruence (similar to types C and D). A shorter sigmoid notch may be compensated by a broader insertion of the volar radioulnar ligament. Clinical Relevance  The measurements and correlations demonstrated in this study can be a guide when considering reconstructive procedures or dealing with the instability of the DRUJ.

Morphologic Characteristics of the Sigmoid Notch of the Distal Radius for Patients With Peripheral Triangular Fibrocartilage Complex Tear

The distal radioulnar joint (DRUJ) is stabilized by the bony anatomy of the contact surfaces. The authors analyzed the morphologic characteristics and radiologic parameters at the sigmoid notch of patients with a peripheral triangular fibrocartilage complex (TFCC) tear compared with asymptomatic patients. Preoperative axial computed tomography scans were reviewed for 76 wrists with peripheral TFCC injuries, including foveal avulsion, and 76 wrists of age- and sex-matched control subjects. The authors used axial computed tomography scans of the DRUJ to classify the patients into 4 groups according to the type of sigmoid notch, namely, flat face, ski-slope, C-type, and S-type. They also measured the tilting angle, depth, width of the sigmoid notch, and radioulnar ratio (RUR). Statistical analyses were performed with the chi-square test or paired t test (P<.05). The mean proportions of flat face, ski-slope, C-type, and S-type sigmoid notches among patients with peripheral TFCC injuries were 42%, 22%, 29%, and 7%, respectively, whereas those for the control group were 33%, 1%, 65%, and 1%, respectively (P<.05). The tilting angle was lower (TFCC injury, 84.5°; control, 86.2°; P<.05) and the RUR was significantly higher (TFCC injury, 0.67; control, 0.56) in the TFCC group, particularly for men (P<.05). Depth (TFCC injury, 1.0 mm; control, 1.3 mm; P>.05) and width (TFCC injury, 14.8 mm; control, 14.5 mm; P>.05) were similar between the groups. Patients with ski-slope or dorsally tilted sigmoid notches may be at greater risk for peripheral TFCC injuries. [Orthopedics. 2021;44(6):e729-e734.].

The correlation between shape of the sigmoid notch of the distal radius and the risk of triangular fibrocartilage complex foveal tear

Aims

The aim of this study was to analyze the association between the shape of the distal radius sigmoid notch and triangular fibrocartilage complex (TFCC) foveal tear.

Methods

Between 2013 and 2018, patients were retrospectively recruited in two different groups. The patient group comprised individuals who underwent arthroscopic transosseous TFCC foveal repair for foveal tear of the wrist. The control group comprised individuals presenting with various diseases around wrist not affecting the TFCC. The study recruited 176 patients (58 patients, 118 controls). The sigmoid notch shape was classified into four types (flat-face, C-, S-, and ski-slope types) and three radiological parameters related to the sigmoid notch (namely, the radius curvature, depth, and version angle) were measured. The association of radiological parameters and sigmoid notch types with the TFCC foveal tear was investigated in univariate and multivariate analyses. Receiver operating characteristic curves were used to estimate a cut-off for any statistically significant variables.

Results

Univariate analysis showed that the flat-face type was more prevalent in the patients than in the control group (43% vs 21%; p = 0.002), while the C-type was lower in the patients than in the control group (3% vs 17%; p = 0.011). The depth and version angle of sigmoid notch showed a negative association with the TFCC foveal tear in the multivariate analysis (depth: odds ratio (OR) 0.380; p = 0.037; version angle: OR 0.896; p = 0.033). Estimated cut-off values were 1.34 mm for the depth (area under the curve (AUC) = 0.725) and 10.45° for the version angle (AUC = 0.726).

Conclusion

The proportion of flat-face sigmoid notch type was greater in the patient group than in the control group. The depth and version angle of sigmoid notch were negatively associated with TFCC foveal injury. Cite this article: Bone Joint J 2020;102-B(6):749–754.