Hypothenar hammer syndrome: An expanded Kaji angiographic classification based on 91 cases

Hypothenar hammer syndrome (HHS) is characterized by ischemic symptoms of the hand related to a stenotic or occluded ulnar artery. The disease is considered rare, although there is evidence of underdiagnosis. Digital subtraction angiography (DSA) is the primary diagnostic tool, although staging is typically based on the Kaji classification, which captures most abnormalities, though some may be overlooked. This study proposes an all-encompassing angiographic classification system for HHS.

In this multicenter retrospective case series, electronic medical records were searched for patients with HHS based on vascular abnormalities and clinical symptoms in three hospitals. Among all HHS cases, clinical symptoms and DSAs were collected and classified using the Kaji classification system. This system only encompasses the pathology of the ulnar artery. We propose to augment the system with aneurysmatic deformation and radial artery disease.

A total of 80 patients with 91 affected hands were included. Most cases had stenotic and occlusive deformities, whereas 7 cases had an aneurysm in the ulnar artery. Three cases had concomitant occlusion of the radial artery. Overall, no significant associations were found between the type of stenosis and most prevalent symptoms, except for numbness (p = 0.009). A non-significant trend was observed of a higher prevalence of severe symptoms, such as necrosis, in patients with HHS with concomitant radial artery occlusion.

Expanding the Kaji classification with aneurysmatic deformation and concomitant radial artery disease offers a more accurate and comprehensive classification system for HHS.