Morphologic evaluation of chronic radial head dislocation: three-dimensional and quantitative analyses.
BACKGROUND
Treatment of chronic radial head dislocation is controversial, considering whether to reduce and reconstruct the proximal radioulnar joint. The anatomic alteration that influences the decision to reduce the dislocation is not completely understood.


OBJECTIVE
We attempted to clarify the changes of the proximal radioulnar joint that occur in chronic radial head dislocations to clarify how they might influence the decision to perform repair.


METHODS
We evaluated 15 patients with chronic radial head dislocations categorized by duration of "early" (< 3 years) (n = 8) and "longstanding" (> 3 years) (n = 7) groups. We measured the angle and depth of the radial notch of the proximal ulna and evaluated radial head deformity using 3-D bone models created from CT data.


RESULTS
For the early group, no differences were observed in the shape of the radial notch between affected and normal sides. For the longstanding group, the radial notch angle was greater on the affected side (mean +/- SD, 45.5 degrees +/- 9.7 degrees ) than on the normal side (29.7 degrees +/- 6.3 degrees ), and the radial notch depth was smaller on the affected side (0.2 +/- 1.6 mm) than on the normal side (2.3 +/- 1.3 mm). The shape of the radial head was nearly normal in the early group, whereas the longstanding group had a dome-shaped deformity.


CONCLUSIONS
In longstanding chronic radial head dislocation, deformation develops in the radial head and radial notch of the ulna, which is remodeled in a manner corresponding to the dislocated position of the radial head.


METHODS
Level III, prognostic study. See Guidelines for Authors for a complete description of levels of evidence.
Oka
Kunihiro
K
Department of Orthopaedic Surgery, Osaka University Graduate School of Medicine, 2-2 Yamada-oka, Suita, Osaka 565-0871, Japan. oka-kunihiro@umin.ac.jp
Murase
Tsuyoshi
T
Moritomo
Hisao
H
Sugamoto
Kazuomi
K
Yoshikawa
Hideki
H
D000293:Adolescent; D000328:Adult; D002648:Child; D002675:Child, Preschool; D002908:Chronic Disease; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional; D004204:Joint Dislocations / Q000000981:diagnostic imaging* / Q000209:etiology / Q000503:physiopathology; D008297:Male; D008953:Models, Anatomic; D011237:Predictive Value of Tests; D011857:Radiographic Image Interpretation, Computer-Assisted; D011884:Radius / Q000000981:diagnostic imaging*; D016059:Range of Motion, Articular; D013997:Time Factors; D014057:Tomography, X-Ray Computed; D014457:Ulna / Q000000981:diagnostic imaging*; D014955:Wrist Joint / Q000000981:diagnostic imaging* / Q000503:physiopathology; D055815:Young Adult