Critical analysis of causality between negative ulnar variance and Kienböck disease.
BACKGROUND
Negative ulnar variance has been associated with Kienböck disease, both supporting a causal link and providing a basis for therapeutic recommendations. The aim of this study was to determine whether there is a causal relationship between Kienböck disease and negative ulnar variance.


METHODS
The causal relationship between Kienböck disease and negative ulnar variance was assessed using three methodologies: (1) an analysis of the quantitative and qualitative distribution of ulnar variance in a case-control study of 81 patients with Kienböck disease and a control group of 212 healthy wrists; (2) a systematic literature review and meta-analysis of six case-control studies (including the case-control study presented in this article) to test for an association between Kienböck disease and negative ulnar variance; and (3) a determination of causal relationship by using the Bradford Hill criteria.


RESULTS
The case-control study indicated that when Kienböck disease is associated with negative ulnar variance (59 of 81), in 75 percent of the cases negative ulnar variance was equal (29 of 59) or less (15 of 59) pronounced on the contralateral healthy side. The odds ratio generated from the meta-analysis demonstrated a significant association between Kienböck disease and negative ulnar variance (OR, 3.58; 95 percent CI, 1.59 to 8.06; p = 0.002, random effects method). Six of nine Bradford Hill criteria do not support a causal relationship.


CONCLUSIONS
The significant association between Kienböck disease and negative ulnar variance can be well explained by selection bias because magnetic resonance imaging, which may detect and allow exclusion of a potential ulnar impaction syndrome, was performed in only the Kienböck disease group in all six case-control studies. The application of the Bradford Hill criteria does not provide sufficient scientific evidence to support a causal relationship between Kienböck disease and negative ulnar variance.


METHODS
Risk, III.
Tübingen and Stuttgart, Germany From the Department of Plastic, Hand and Reconstructive Surgery, Burn Center, BG-Trauma Center, the Institute for Clinical Epidemiology and Applied Biostatistics, and the University Department of Radiology, Eberhard-Karls-University Tübingen; and the Department for Plastic Surgery, Marienhospital Stuttgart.
Stéphane
S
Stahl
Adelana Santos
AS
Stahl
Christoph
C
Meisner
Pascal J H
PJH
Hentschel
Stephan
S
Valina
Oliver
O
Luz
Hans-Eberhard
HE
Schaller
Oliver
O
Lotter
D000328:Adult; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D010020:Osteonecrosis / Q000000981:diagnostic imaging / Q000453:epidemiology / Q000473:pathology*; D012307:Risk Factors; D014057:Tomography, X-Ray Computed; D014457:Ulna / Q000000981:diagnostic imaging / Q000473:pathology* / Q000502:physiology; D016474:Weight-Bearing / Q000502:physiology