Morphological characteristics of the sigmoid notch of the distal radius affect the stress distribution patterns in the distal radioulnar joint

Surgical treatment of distal radius fractures: impact on forearm rotation in non-elderly patients

Forearm rotation restriction (FRR) is common after surgery for distal radius fractures (DRFs). The aim of the current study was to investigate the effect of DRFs on forearm rotation. This retrospective study reviewed patients with DRFs who underwent surgical treatment from January 2019 to December 2021. The patients' basic data and radiographic parameters were analyzed. Forearm rotation, including pronation and supination, was assessed using a standard goniometer. The Patient-Rated Wrist Evaluation (PRWE) score was evaluated, and the incidence of FRR at the 6-month follow-up was recorded. Univariate and multivariate logistic regression analyses were performed to identify risk factors correlated with FRR. A total of 127 patients with DRFs were included in this study. After surgery, 46 cases were considered to have FRR, with a rate of 36.2%, while the remaining 81 cases (63.8%) did not have FRR. The PRWE scores were 22.8 ± 5.2 and 17.9 ± 4.2 in the FRR group and non-FRR group, respectively, and the difference was statistically significant (P < 0.05). Multivariate analysis showed that the involvement of the sigmoid notch (OR, 2.88; 95% CI 1.49-5.56), post-operative volar tilt < 0° (OR, 2.16; 95% CI 1.34-3.50), and post-operative ulnar variance > 0 mm (OR, 1.37; 95% CI 1.06-1.78) were independently associated with the incidence of FRR. The FRR is associated with an increased PRWE score and may have had some impact on the patient's daily life. Fractures involving the sigmoid notch, dorsal angulation, and radial shortening deformity were found to be correlated with the incidence of FRR. Preoperative risk notification and intraoperative preventive measures are necessary for these patients.

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.

Influence of differences in bone morphology on the distribution patterns of subchondral bone density across the trapeziometacarpal joint

We aimed to clarify the effects of morphological patterns of the trapezium and first metacarpal on the distribution of subchondral bone density across the articular surface of the trapeziometacarpal (TMC) joint using computed tomography osteoabsorptiometry. Thirty-three patients with normal TMC joints were evaluated. The percentages of the high-density areas in the radial-dorsal and ulnar-volar regions of the trapezium were significantly higher than that in the ulnar-dorsal region, and that of the ulnar-dorsal region of the first metacarpal was significantly lower than in the other three regions. The percentage of the high-density area of the radial-dorsal region of the trapezium and trapezial inclination (TI) showed a significant positive correlation, and the percentages of the high-density areas in the ulnar-dorsal and ulnar-volar regions had significant negative correlations with TI at the articular surface of the first metacarpal. These results indicate that bony morphologic differences in the trapezium affect the distribution pattern of subchondral bone density through the TMC joint.

Stress distribution pattern in the distal radioulnar joint before and after ulnar shortening osteotomy in patients with ulnar impaction syndrome

Ulnar shortening osteotomy (USO) for ulnar impaction syndrome potentially leads to degenerative changes of the distal radioulnar joint (DRUJ). This study was performed to evaluate the effect of the sigmoid notch morphology on the stress distribution pattern of the DRUJ using computed tomography (CT) osteoabsorptiometry (CT-OAM). We reviewed the pre- and postoperative transverse CT images of 15 wrists that had undergone USO. The examined wrists were classified into two groups based on the sigmoid notch morphology: the linear-type notch (type L) and the curved-type notch (type C). We calculated and statistically compared the percentage of the high-density area (%HDA) in each divided region of the sigmoid notch. In type L, %HDA was significantly larger in the distal-dorsal region of the sigmoid notch before USO. Postoperatively, in type L, no specific regions showed a significantly different %HDA. In type C, %HDA was significantly larger in the distal-volar region of the sigmoid notch before USO. Postoperatively, %HDA of type C was significantly larger in the proximal-volar region. Our results suggest that in patients with ulnar impaction syndrome, morphological evaluation of the sigmoid notch can serve as a predictor of osteoarthritis in the DRUJ with or without USO.

Cartilage and subchondral bone distributions of the distal radius: a 3-dimensional analysis using cadavers

OBJECTIVE

To quantify the spatial distributions of cartilage and subchondral bone thickness of the distal radius.

DESIGN

Using 17 cadaveric wrists, three types of 3-dimensional models were created: a cartilage-bone model, obtained by laser scanning; a bone model, rescanned after dissolving the cartilage; and a subchondral bone model, obtained using computed tomography. By superimposing the bone model onto the cartilage-bone and the subchondral bone models, the cartilage and subchondral bone thickness were determined. Measurements along with the spatial distribution were made at fixed anatomic points including the scaphoid and lunate fossa, sigmoid notch and interfossal ridge, and compared at each of these four regions.

RESULTS

Cartilage thickness of the interfossal ridge (0.89 ± 0.23 mm) had a larger average thickness compared to that of the scaphoid fossa (0.70 ± 0.18 mm; p = 0.004), lunate fossa (0.75 ± 0.17 mm; p = 0.044) and sigmoid notch (0.64 ± 0.13 mm; p < 0.001). Subchondral bone was found to be thickest at the scaphoid (2.18 ± 0.72 mm) and lunate fossae (1.94 ± 0.93 mm), which were both thicker than that of sigmoid notch (1.63 ± 1.06 mm: vs scaphoid fossa, p = 0.020) or interfossal ridge (1.54 ± 0.84 mm: vs scaphoid fossa, p = 0.004; vs lunate fossa, p = 0.048). In the volar-ulnar sub-regions of the scaphoid and lunate fossa, the subchondral bone thickened.

CONCLUSIONS

Our data can be applied when treating distal radius fractures. Cartilage thickness was less than 1 mm across the articular surface, which may give an insight into threshold for an acceptable range of step-offs. The combined findings of subchondral bone appreciate the importance of the volar-ulnar corner of the distal radius in the volar locking plate fixation.

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.