A Radiographic Classification of Capitate Morphology and Its Association With Kienböck Disease.

PURPOSE: Kienböck disease (KD), osteonecrosis of the lunate, has an unclear etiology. While there is a strong and clear association between KD and negative ulnar variance (UV), it is likely not the only mechanical factor. The capitate, which has a large joint surface with the lunate, may play a role in KD pathogenesis. This study investigated the association between capitate morphology and KD. We classified the capitate into three types based on the angle and length ratio of the capitotrapezoid (CT) and scaphocapitate joint lines: type I (short, vertical CT facet), type II (pentagonal with a large, oblique CT facet), and an intermediate type. We hypothesized that type II capitate increases capitate-lunate loading, leading to a higher incidence of KD.

METHODS

A case-control study was conducted, including 80 KD patients who underwent surgery between 2019 and 2024 and 467 controls with radiographs from suspected scaphoid fracture cases. Demographic data, UV, and capitate type were analyzed.

RESULTS

The prevalence of type II capitate in the control group was 18%. Patients with KD had considerably higher rates of negative UV (35% vs 7%) and type II capitate (30% vs 18%) compared to the control group. Among 488 non-negative UV patients and 59 negative UV patients, type II capitate remained more common in the KD group (42% vs 17%). Multivariable analysis confirmed negative UV (OR = 9.2, 95% CI: 4.8-17.4) and type II capitate (OR = 2.7, 95% CI: 1.5-5.0) as independent risk factors for KD.

CONCLUSIONS

Our study introduces a radiographic classification of capitate morphology and establishes its association with KD. These findings suggest that, beyond negative UV, type II capitate is an associated factor, warranting further research into its mechanical and vascular role in KD pathogenesis.

TYPE OF STUDY/LEVEL OF EVIDENCE: Diagnostic III.