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Purpose: Lunate morphology has been postulated to play an integral role in the pathogenesis of Kienbock’s disease. The purpose of this study is to determine if the absence (type I) or presence (type II) of a medial (hamate) facet on the lunate will effect the radiographic characteristics and severity of Kienböck’s disease.

Methods: A retrospective review was performed on all patients evaluated and treated at our institution from 2002 to 2010 with a diagnosis of Kienböck’s disease which was confirmed on magnetic resonance imaging (MRI) and/or bone scan. Study groups consisted of type I versus type II lunates, as determined by MRI and/or computed tomography. Investigated variables included the modified Lichtman’s stage on presentation, radioscaphoid angle, presence of a coronal plane fracture of the lunate, modified carpal height, ulnar variance, and ulnar translocation of the carpus.

Results: A total of 106 wrists were included, 75 type I (71%) and 31 type II (29%) lunates. There was significantly more advanced disease (greater than stage 2) upon presentation in type I lunates (n=64, 86%) compared to type II lunates (n=19, 61%, p <0.05). Coronal fractures of the lunate were present in 76 wrists (72%) and were more likely in type I (n=58, 75%) compared to type II lunates (n=18, 58%, p=0.05). In the absence of a coronal fracture, radioscaphoid angles were greater in type I (53°) versus type II lunates (45°, p=0.04). There were no significant differences in modified carpal height, ulnar variance, or ulnar translocation of the carpus between both types of lunates.

Conclusion: Lunate morphology effects the severity of Kienböck’s disease at the time of initial staging. The incidence of coronal fractures of the lunate is 72% upon presentation, with type II lunates being protective against coronal fractures. The medial (hamate) facet of a type II lunate may prevent against scaphoid flexion deformity, thus limiting the progression of Kienbock’s disease.