Background: There are few clinical studies evaluating the relationship between lunate cysts and symptomatic ulnar impaction syndrome (UIS). The purpose of this study was to investigate the prevalence and relationship between lunate cysts and UIS by comparing data from patients with UIS against those without.
Materials and methods: From March 2012 to January 2015, 375 patients who had undergone MRI or CT for reasons other than ulnar-sided wrist pain were classified into the 'asymptomatic group' (Group I). Thirty three patients who had been diagnosed with UIS were classified in the 'UIS group' (Group II). We determined whether any differences were present between the two groups and evaluated prognostic factors for lunate cysts.
Results: The prevalence of lunate cysts was significantly higher in Group II but only reached just above 50% (10.4% vs. 57.6%, p < 0.001]. Dorsal-side lunate cysts were more frequent than palmar side in Group I, while Group II had more cysts on the palmar side (74.4% vs. 52.6%, p = 0.001). Logistic regression analysis revealed that UIS and patient age was a significant factor for the presence of lunate cysts (odds ratio: 11.692, p < 0.001; odds ratio: 1.063, p < 0.001, respectively). However, positive ulnar variance or duration of symptom in Group II was not a predisposing factor for lunate cysts (odds ratio: 1.035, p = 0.598; odds ratio: 1.007, p = 0.877, respectively).
Conclusion: Since positive ulnar variance or duration of symptom did not affect the formation of the lunate cyst and only slightly more than 50% (57.6%) of patients with UIS had a lunate cyst, it seems unlikely that these cysts are a pathognomonic finding. Surgeons can obtain some evidence from lunate cysts on radiographic exams, but care must be taken that this diagnosis is not made hastily or without due consideration.
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