Background:
In missed Monteggia fracture (MMF) cases, ulnar angulation and lengthening by osteotomy are required to reduce the dislocated radial head. This study aimed to clarify the abnormal discrepancy in length between the radius and ulna in MMF. We tested the hypothesis that the increase in the abnormal discrepancy in length between the radius and ulna relates with the duration of radial head dislocation.
Methods:
In total, 24 patients with MMF were studied and classified into 2 groups, according to the duration of radial head dislocation, including the early group (n=9, within 3 y) and the long-standing group (n=15, older than 3 y). The lengths of the radius (Lr) and ulna (Lu) were measured. The difference in length between the ulna and radius (DL=Lu−Lr) was calculated on both the affected (DLaff) and normal (DLnor) sides. DLnor−DLaff, which represented an abnormal discrepancy in both bones, was analyzed for correlation with the duration of radial head dislocation and the age at initial injury.
Results:
The affected and normal sides had no differences in the Lr of both the groups and in the Lu of the early group. However, in the long-standing group, Lu was significantly smaller in the affected side than in the normal side (P=0.001). In the long-standing group, DLaff was significantly smaller, owing to decreased length of the ulna, than DLnor (P=0.003). The DLnor−DLaff was positively correlated with the duration of radial head dislocation and was negatively correlated with the age at injury.
Conclusions:
In chronic MMF cases, the length of the ulna was shorter in the affected side than in the normal side. Therefore, ulnar lengthening is necessary to resolve this abnormal discrepancy and reduce the radial head. Because excessive ulnar lengthening has risks of postoperative complications, one of the surgical options is gradual ulnar lengthening or shortening osteotomy of the radius.
Level of Evidence:
Level III—Prognosis study.
This study aimed to reproduce and analyse the in vivo dynamic rotational motion of the forearm and to clarify the forearm motion involvement and anatomical function of the triangular fibrocartilage complex (TFCC). We analysed the in vivo dynamic forearm rotational motion of the radius and the ulna, using a novel image-matching method for intensity-based biplane two-dimensional–three-dimensional (2D–3D) registration. This study included 20 upper limbs of 10 healthy volunteers. The average range of forearm rotation was 69.8 ± 14.8° for pronation and 80.8 ± 13.4° for supination. The radius was most proximal to the maximum pronation, moved distally toward the neutral position, and again proximally toward supination. The average axial translation of the radius during forearm rotation was 0.98 mm. Length changes of four virtual ligaments of TFCC, palmar and dorsal superficial radioulnar ligaments (PSL and DSL) and palmar and dorsal deep radioulnar ligaments (PDL and DDL), were investigated. We found that the PSL and DSL were most tensed in mid-rotation, PDL in pronation, and DDL in supination. The sequential tension of the four ligaments during the forearm rotation motion was found to contribute to the stability of the DRUJ over a wide range of motion. In conclusion, we describe a method for detailed evaluation of in vivo dynamic forearm motion and provide new insight on forearm kinematics and the DRUJ.
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